JP5247627B2 - Image processing apparatus and method, and image display apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus and method for enlarging a digitized image, and an image display apparatus and method, and generates a high frequency component when enlarging an image, thereby providing a high resolution feeling. An enlarged image is obtained.

  In general, when the number of pixels of the output image is larger than the number of pixels of the input image, the image processing apparatus must enlarge the image. In a conventional image processing apparatus, an image is enlarged by weighting and adding pixel values of pixels in the vicinity of the pixel of interest.

  For example, in the image processing apparatus described in Patent Document 1, five adjacent pixel data in the main scanning direction output from each shift register are multiplied by a predetermined weighting constant, and the multiplication result in each pixel data is obtained. An arithmetic circuit for adding is provided, and when image data enlargement processing is performed, the arithmetic result in the arithmetic circuit is selected and output by the selector as pixel data at the center of these pixel data.

JP-A-6-31346 (FIG. 1)

  Weighting and adding pixel values of pixels in the vicinity of the target pixel is a low-pass filter process that passes only the low-frequency component of the input image. Therefore, the above-described conventional technique has a problem that the resolution of the enlarged image is lost because a high-frequency component cannot be sufficiently applied to the enlarged image.

The present invention has been made to solve the above-described problems, and the image processing apparatus of the present invention includes:
In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
First correction component generation means including second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Second correction component generation means including non-linear processing image generation means for outputting a second intermediate image obtained by performing processing including non-linear processing on the second enlarged image;
A second addition means for adding the output of the first correction component generation means and the output of the second correction component generation means;
The result of the addition in the second addition means is used as the output of the high frequency component image processing means,
The first correction component generation means outputs a third intermediate image obtained by amplifying each pixel value of the first intermediate image with a first amplification factor obtained according to the pixel value of the first enlarged image. Further comprising first high frequency component image correcting means
The third intermediate image is used as an output of the first correction component generation means.

  According to the present invention, a high-frequency component can be sufficiently provided without causing excessive overshoot, and an enlarged image with a sense of resolution can be obtained.

It is a block diagram which shows the structure of the image processing apparatus of Embodiment 1 of this invention. 1 is a block diagram illustrating a configuration example of an image display device using the image processing device according to a first embodiment. It is a block diagram which shows the structure of the image processing apparatus of FIG. 1 in detail. (A)-(d) is a pixel arrangement | positioning figure which shows operation | movement of the image expansion means 2A. It is a block diagram which shows the structural example of 2 A of image expansion means. It is a block diagram which shows the structural example of the image expansion means 2B. It is a block diagram which shows the structural example of the horizontal direction nonlinear processing means 31h. It is a block diagram which shows the structural example of the vertical direction nonlinear processing means 31v. It is a block diagram which shows the structural example of 33 A of high frequency component process means. (A) And (b) is a figure which shows the relationship between the pixel value of amplification factor calculation means 3MA, and amplification factor. It is a block diagram which shows the structural example of the high frequency component process means 33B. (A) And (b) is a figure which shows the relationship between the pixel value of amplification factor calculation means 3HA, and amplification factor. (A)-(d) is a figure which shows the frequency spectrum and frequency response for demonstrating the process of obtaining enlarged image D2A. (A)-(f) is a figure which shows the frequency spectrum and frequency response for demonstrating the process of obtaining intermediate | middle image D32A. (A)-(c) is a figure which shows the frequency spectrum and frequency response for demonstrating the process of obtaining intermediate image D32B. (A)-(e) is a figure which shows the signal intensity | strength obtained when a step edge signal and a step edge signal are sampled with a different sampling frequency, and the signal strength of the high frequency component. (A)-(f) is a figure which shows the signal strength for demonstrating operation | movement of the nonlinear processing means 31 and the high frequency component image generation means 32B. (A)-(d) is a figure which shows the signal strength for demonstrating the effect which adds intermediate image D32A, D32B. (A) And (b) is a figure which shows the signal strength for demonstrating the effect and malfunction which add intermediate | middle image D32A, D32B. It is a figure which shows the relationship between the pixel value of amplification factor calculation means 3MA, 3HA, and amplification factor. It is explanatory drawing of the frequency spectrum of the expansion image Dout. (A)-(e) is a figure which shows the signal intensity | strength obtained when a step edge signal and a step edge signal are sampled with a different sampling frequency, and the signal strength of the high frequency component. (A)-(f) is a figure which shows the strength of the signal for demonstrating operation | movement of the nonlinear processing means 31 and the high frequency component image generation means 32B. It is a block diagram which shows the structural example of the image processing apparatus of Embodiment 2 of this invention. 10 is a flowchart illustrating an image processing method according to Embodiment 2. FIG. It is a flowchart which shows high frequency component image generation step ST1. It is a flowchart which shows image expansion step ST2B. It is a flowchart which shows high frequency component image processing step ST3. It is a flowchart which shows horizontal direction nonlinear process step ST31h. It is a flowchart which shows vertical direction nonlinear processing step ST31v. It is a flowchart which shows high frequency component image correction step ST33A. It is a flowchart which shows high frequency component image correction step ST33B. It is a block diagram which shows the structure of the image processing apparatus of Embodiment 3 of this invention. It is a flowchart which shows the image processing method of Embodiment 4 of this invention. FIG. 6 is a block diagram illustrating a modification of the image processing apparatus according to the first embodiment. FIG. 10 is a flowchart showing a modification of the high frequency component image processing step ST3 of the second embodiment. FIG. 10 is a block diagram illustrating a modification of the image processing apparatus according to the third embodiment. FIG. 10 is a flowchart showing a modification of the image processing method according to the fourth embodiment.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an image processing apparatus according to Embodiment 1 of the present invention, and can be used as a part of the image display apparatus shown in FIG. 2, for example. Here, the image display apparatus shown in FIG. 2 includes an image processing apparatus U1 including the image processing apparatus shown in FIG. 1 and a display unit 9, and an image DU1 obtained as an output for the image DORG in the image processing apparatus U1. It is displayed on the display unit 9.

The image processing apparatus according to Embodiment 1 includes an image enlarging means 2A, a high frequency component image generating means 1, an image enlarging means 2B, a high frequency component image processing means 3, and an adding means 4.
The image enlarging means 2A enlarges the input image Din and generates an enlarged image D2A.
The high frequency component image generation means 1 extracts only the high frequency component of the input image Din and generates a high frequency component image D1.

The image enlarging means 2B enlarges the high frequency component image D1 output from the high frequency component image generating means 1 to generate an enlarged image (high frequency component enlarged image) D2B.
The high frequency component image processing means 3 performs a process described later on the enlarged image D2B output from the image enlargement means 2B, and generates a high frequency component image (high frequency component processed image) D3.

  The adding means 4 adds the high frequency component image D3 output from the high frequency component image processing means 3 to the enlarged image D2A output from the image enlarging means 2A, and the result is the final enlarged image, that is, the output Output as an image Dout. The output of the adding means 4 is supplied as, for example, an image DU1 to the display unit 9 of the image display device shown in FIG.

  In this specification, it is described that processing such as enlargement, high-frequency component generation, and high-frequency component processing is performed on an “image”. Specifically, it is performed on digital data representing an image. Is called. In addition, the description of “image” may specifically mean “image data”.

  Detailed operations of the image enlarging unit 2A, the high frequency component image generating unit 1, the image enlarging unit 2B, and the high frequency component image processing unit 3 will be described later. The frequency component of the high frequency component image D3 is obtained by the enlarged image D2A. The frequency component is higher than the frequency component. Therefore, by adding the high frequency component image D3 to the enlarged image D2A in the adding means 4, an enlarged image Dout containing a large amount of high frequency components can be obtained.

  FIG. 3 is a diagram showing details of the configuration of the image processing apparatus according to the first embodiment shown in FIG. Hereinafter, the configuration of the image enlarging means 2A, the high frequency component image generating means 1, the image enlarging means 2B, and the high frequency component image processing means 3 will be described in more detail with reference to FIG.

  The image enlarging means 2A enlarges the image in at least one of the horizontal direction and the vertical direction. For example, the image enlarging means 2A enlarges the image in the horizontal direction and the vertical direction at the same magnification, but instead, the magnifications differ in the horizontal direction and the vertical direction. It is also possible to perform enlargement with. Further, enlargement may be performed only in one of the horizontal direction and the vertical direction. For example, when the display screen is horizontally long with respect to the input image, enlargement may be performed only in the horizontal direction.

  The high frequency component image generation means 1 extracts a high frequency component (a component higher than the predetermined frequency Fb) of the input image Din and generates a high frequency component image D1. A horizontal high-frequency component image generating unit 1h and a vertical high-frequency component image generating unit 1v that generate a frequency component image D1h and a vertical high-frequency component image D1v are provided. The high frequency component image D1 is composed of the horizontal high frequency component image D1h and the vertical high frequency component image D1v.

  The image enlarging means 2B includes an image enlarging means 2Bh that generates an enlarged image D2Bh obtained by enlarging the horizontal high-frequency component image D1h, and an image enlarging means 2Bv that generates an enlarged image D2Bv obtained by enlarging the vertical high-frequency component image D1v. The enlarged image D2B is composed of the enlarged image D2Bh and the enlarged image D2Bv.

  When the image enlarging means 2A enlarges in both the horizontal and vertical directions, the image enlarging means 2Bh enlarges the horizontal high frequency component image D1h in both the horizontal and vertical directions, and the image enlarging means 2Bv The direction high frequency component image D1v is enlarged in both the horizontal direction and the vertical direction. The enlargement of the horizontal high-frequency component image D1h and the vertical high-frequency component image D1v by the image enlargement means 2Bh and 2Bv is performed at the same magnification for each of the enlargement by the image enlargement means 2A and the horizontal and vertical directions.

  The high frequency component image processing means 3 includes a first correction component generation means 3A, a second correction component generation means 3B, and an addition means 34. The first correction component generation unit 3A includes a high frequency component image generation unit 32A and a high frequency component image correction unit 33A, and the second correction component generation unit 3B includes a nonlinear processing image generation unit 30 and a high frequency component. Component image correcting means 33B.

  The high frequency component image generating means 32A extracts the high frequency component (component higher than the predetermined frequency Fd) of the enlarged image D2B and outputs an intermediate image (high frequency component image) D32A, which is included in the enlarged image D2Bh. A horizontal high-frequency component image generating unit 32Ah that generates a horizontal intermediate image D32Ah that extracts only the high-frequency component in the horizontal direction, and a vertical intermediate image D32Av that extracts only the high-frequency component in the vertical direction of the enlarged image D2Bv. A vertical high-frequency component image generating unit 32Av is generated, and an intermediate image D32A composed of a horizontal intermediate image D32Ah and a vertical intermediate image D32Av is output from the high-frequency component image generating unit 32A.

The nonlinear processed image generating means (edge sharpened image generating means) 30 outputs an intermediate image (edge sharpened image) D32B obtained by performing processing including nonlinear processing on the enlarged image D2B. And high frequency component image generation means 32B.
The nonlinear processing means 31 generates a nonlinear processed image D31 obtained by performing nonlinear processing for edge sharpening, which will be described later, on the enlarged image D2B.
The high frequency component image generating unit 32B outputs an intermediate image D32B obtained by extracting only the high frequency component (component higher than the predetermined frequency Ff) included in the nonlinear processed image D31.

  The non-linear processing means 31 generates a non-linear processed image D31h that is non-linearly processed with respect to the enlarged image D2Bh, and a vertical non-linear process that generates a non-linearly processed image D31v that is non-linearly processed with respect to the enlarged image D2Bv. Means 31v is provided, and the nonlinear processed image D31 is composed of a nonlinear processed image D31h and a nonlinear processed image D31v.

  The high frequency component image generation unit 32B extracts the high frequency component from the nonlinear processed image D31h, extracts the high frequency component from the horizontal processed high frequency component image generation unit 32Bh that generates the horizontal intermediate image D32Bh, and the nonlinear processed image D31v, A vertical high frequency component image generating means 32Bv for generating a vertical intermediate image D32Bv is provided, and the intermediate image D32B is composed of a horizontal intermediate image D32Bh and a vertical intermediate image D32Bv.

  The high frequency component image correcting unit 33A receives the enlarged image D2A and the intermediate image D32A, and outputs an intermediate image (corrected image) D33A obtained by amplifying the intermediate image D32A with an amplification factor determined according to the pixel value of the enlarged image D2A. The correction processing is performed on the horizontal intermediate image D32Ah to generate the horizontal intermediate image D33Ah, and the correction processing is performed on the vertical high-frequency component image correction means 33Ah and the vertical intermediate image D32Av. And a vertical high frequency component image correcting means 33Av for generating a vertical intermediate image D33Av. An intermediate image D33A is configured by the horizontal intermediate image D33Ah and the vertical intermediate image D33Av.

  The high frequency component image correcting unit 33B receives the enlarged image D2A and the intermediate image D32B, and outputs an intermediate image (corrected image) D33B obtained by amplifying the intermediate image D32B with an amplification factor determined according to the pixel value of the enlarged image D2A. The horizontal intermediate image D32Bh is corrected, and the horizontal high-frequency component image correcting unit 33Bh for generating the horizontal intermediate image D33Bh and the vertical intermediate image D32Bv are corrected. And a vertical high frequency component image correcting means 33Bv for generating the vertical intermediate image D33Bv. The intermediate image D33B is configured by the horizontal intermediate image D33Bh and the vertical intermediate image D33Bv.

  The adding means 34 adds the intermediate image D33A and the intermediate image D33B, and outputs the addition result as a high frequency component image D3.

  Hereinafter, the operation of each component will be described in more detail by taking as an example the case of generating an enlarged image Dout in which the input image Din is doubled in both the horizontal direction and the vertical direction. Through this description, the operation and effect of the present invention will become clearer.

  First, the operation of the image enlarging means 2A will be described. The image enlarging means 2A generates an enlarged image D2A obtained by enlarging the input image Din twice in both the horizontal direction and the vertical direction. FIGS. 4A to 4D are diagrams schematically showing an example of a procedure for generating the enlarged image D2A in the image enlarging unit 2A, and FIG. 5 is a diagram showing an example of the image enlarging unit 2A.

  The image enlarging unit 2A includes a zero insertion unit 21A and a low frequency component passing unit 22A. Hereinafter, the operations of the zero insertion means 21A and the low frequency component passing means 22A will be described with reference to FIGS. 4A shows the input image Din (particularly, the arrangement of pixels constituting a part of the image), FIG. 4B shows the zero insertion image D21A generated by the zero insertion means 21A, and FIG. FIG. 4D shows the filter coefficient used when the enlarged image D2A is generated by the low frequency component passing means 22A, and FIG. 4D shows the enlarged image D2A generated by the low frequency component passing means 22A. 4A, 4B, and 4D show horizontal coordinates X and vertical coordinates Y corresponding to the positions of the pixels.

In the zero insertion means 21A, one pixel per pixel (in the input image Din) having a pixel value 0 with respect to the input image Din (one between two adjacent pixels) in the horizontal direction, and one in the vertical direction A zero-inserted image D21A is generated in which one (one between two adjacent lines) is inserted per line (of the input image Din).
If “PXY” represents the pixel value of the pixel at the coordinates (X, Y) of the input image Din, and “P′XY” represents the pixel value of the pixel at the coordinates (X, Y) of the zero-inserted image D21A, then zero. The pixel value represented by P ′ (2X−1) (2Y−1) in the insertion image D21A is equal to PXY in the input image Din, and P ′ (2X−1) (2Y), P ′ (2X) (2Y). ), P ′ (2X) (2Y−1), the pixel value is equal to zero.

The low frequency component passing means 22A performs the filter operation represented by the filter coefficient shown in FIG. 4C on the zero insertion image D21A, thereby generating the enlarged image D2A shown in FIG. .
For example, the pixel value QXY of the pixel at coordinates (X, Y) included in the enlarged image D2A is calculated as in the following equation (1).

QXY = (4/16) ×
{P ′ (X−1) (Y−1) + 2P′X (Y−1) + P ′ (X + 1) (Y−1)
+ 2P ′ (X−1) Y + 4P′XY + 2P ′ (X + 1) Y
+ P ′ (X−1) (Y + 1) + 2P′X (Y + 1) + P ′ (X + 1) (Y + 1)}
... (1)

  Since the filter coefficient represented in FIG. 4C represents a low-pass filter, the processing in the low-frequency component passing unit 22A represented by the equation (1) is performed by the low-frequency component (predetermined frequency Fa) of the zero insertion image D21A. This corresponds to taking out the following components).

In the formula (1), P ′ (X−1) (Y−1), 2P′X (Y−1), P ′ (X + 1) (Y−1), 2P ′ (X−1) Y, P 'XY, 2P' (X + 1) Y, P '(X-1) (Y + 1), P'X (Y + 1), P' (X + 1) (Y + 1)
Some of them have a value of 0, and the others have pixel values themselves of the input image Din. Therefore, the enlargement process is the same as the process of appropriately weighting and adding pixel values near the pixel of interest in the input image Din.

Next, operations of the horizontal direction high frequency component image generating unit 1h and the vertical direction high frequency component image generating unit 1v will be described.
The horizontal high-frequency component image generating means 1h applies a high-pass filter using, for example, a predetermined number of pixels in the vicinity of each pixel of the input image Din and the horizontal direction to the input image Din, and applies the horizontal high-frequency component image. D1h is generated.
On the other hand, the vertical high frequency component image generation unit 1v applies a high pass filter to the input image Din by applying a high pass filter using, for example, a predetermined number of pixels in the vicinity of each pixel of the input image Din and the vertical direction. A component image D1v is generated.

  Applying a high-pass filter corresponds to extracting a high-frequency component, and the horizontal high-frequency component image D1h includes a high-frequency component in the horizontal direction of the input image Din (consisting of a component higher than a predetermined horizontal frequency). The vertical high frequency component image D1v includes a high frequency component in the vertical direction of the input image Din (consisting of a component higher than a predetermined vertical frequency).

As a process for applying a high-pass filter performed by the horizontal high-frequency component image generating unit 1h, for example, a low-frequency component in the horizontal direction (or a predetermined line aligned in the horizontal direction with respect to each pixel) from the input signal to the unit 1h By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a number of pixels, it is possible to perform processing for extracting a high frequency component.
Similarly, as a process of applying a high-pass filter performed by the vertical high frequency component image generating means 1v, for example, from the input signal to the means 1v, the vertical low frequency component (or the vertical direction for each pixel). By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of aligned pixels, it is possible to perform processing for extracting a high frequency component.

  Next, the operation of the image enlarging means 2Bh and 2Bv will be described. The image enlarging means 2Bh generates an enlarged image D2Bh obtained by enlarging the horizontal high-frequency component image D1h twice in both the horizontal and vertical directions, and the image enlarging means 2Bv converts the vertical high-frequency component image D1v in both the horizontal and vertical directions. An enlarged image D2Bv enlarged twice is generated.

Each of the image enlarging means 2Bh and the image enlarging means 2Bv can be configured in the same manner as the image enlarging means 2A described with reference to FIG. Therefore, the image enlarging means 2B composed of the image enlarging means 2Bh and the image enlarging means 2Bv can be shown as shown in FIG.
The input of the image enlarging means 2Bh is a horizontal high frequency component image D1h, and the output is an enlarged image D2Bh. The input of the image enlarging means 2Bv is a vertical high frequency component image D1v, and the output is an enlarged image D2Bv.

The image enlarging unit 2Bh includes a zero insertion unit 21Bh and a low frequency component passing unit 22Bh, and the image enlarging unit 2Bv includes a zero insertion unit 21Bv and a low frequency component passing unit 22Bv.
Each of the zero insertion means 21Bh and the zero insertion means 21Bv is the same as the zero insertion means 21A of FIG. 5, and each of the low frequency component passage means 22Bh and the low frequency component passage means 22Bv is a low frequency component of FIG. This is the same as the passing means 22A.

The zero insertion image D21B as the output of the zero insertion means 21B is composed of the zero insertion image D21Bh output from the zero insertion means 21Bh and the zero insertion image D21Bv output from the zero insertion means 21Bv.
The enlarged image D2B as the output of the low frequency component passing means 22B is composed of the enlarged image D2Bh outputted from the low frequency component passing means 22Bh and the enlarged image D2Bv outputted from the low frequency component passing means 22Bv. The output of the low frequency component passing means 22B is obtained by extracting the low frequency component (component below Fc) of the zero insertion image D21B.

Next, the operation of the high frequency component image generating means 32A will be described.
The horizontal high-frequency component image generating means 32Ah applies a horizontal high-pass filter to the enlarged image D2Bh to extract only high-frequency components composed of components of a predetermined horizontal frequency or more, and generates a horizontal intermediate image D32Ah.
On the other hand, the vertical high-frequency component image generation means 32Av applies a high-pass filter in the vertical direction to the enlarged image D2Bv to extract only the high-frequency components composed of components having a frequency equal to or higher than a predetermined vertical frequency, and generates a vertical intermediate image D32Av. To do.
Then, an intermediate image D32A composed of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av is output from the high frequency component image generating means 32A.

The high-pass filter processing performed by the horizontal high-frequency component image generation unit 32Ah is performed in the same manner as the horizontal high-frequency component image generation unit 1h, and the high-pass filter performed by the vertical high-frequency component image generation unit 32Av. The processing to be applied can be performed in the same manner as the processing in the vertical high frequency component image generation means 1v.
That is, the processing for applying the high-pass filter performed by the horizontal high-frequency component image generation means 32Ah is, for example, from the input signal to the means 32Ah in the horizontal direction, as in the processing by the horizontal high-frequency component image generation means 1h. To extract a high frequency component by subtracting the low frequency component of (or a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of pixels aligned in the horizontal direction with respect to each pixel). it can.

  Similarly, as a process for applying a high-pass filter performed by the vertical high frequency component image generating means 32Av, for example, from the input signal to the means 32Av, a low frequency component in the vertical direction (or in a direction perpendicular to each pixel). By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of aligned pixels, it is possible to perform processing for extracting a high frequency component.

  Next, the operation of the nonlinear processing means 31 will be described. The nonlinear processing means 31 includes a horizontal nonlinear processing means 31h and a vertical nonlinear processing means 31v. The horizontal non-linear processing means 31h and the vertical non-linear processing means 31v are configured in the same manner. However, the horizontal non-linear processing means 31h performs horizontal processing, and the vertical non-linear processing means 31v performs vertical processing.

  FIG. 7 is a diagram showing the internal configuration of the horizontal nonlinear processing means 31h. The illustrated horizontal non-linear processing means 31h includes a zero-cross determining means 311h and a signal amplifying means 312h.

The zero cross determination means 311h confirms the change in the pixel value in the inputted enlarged image D2Bh along the horizontal direction. Then, a point where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels before and after the zero cross point by the signal D311h (in the illustrated example, each of the pixels immediately before and after 1 pixel) is transmitted to the signal amplifying means 312h.
In the horizontal non-linear processing means 31h, pixels located on the left and right of the zero cross point are recognized as pixels before and after the zero cross point.

The horizontal direction signal amplifying unit 312h amplifies the pixel value of the third enlarged image D2Bh with an amplification factor determined according to the determination result of the horizontal direction zero cross determining unit 311h. Specifically, the signal amplifying unit 312h specifies pixels before and after the zero cross point (pixels existing in a predetermined region including the zero cross point) based on the signal D311h, and regarding the pixels before and after the zero cross point. Only the pixel value is amplified (the absolute value is increased) to generate a nonlinear processed image D31h. That is, the amplification factor for the pixel values of the pixels before and after the zero cross point is set to a value larger than 1, and the amplification factors for the pixel values of the other pixels are set to 1.
By such processing, edge sharpening including stepwise changes in signal values of pixels arranged in the horizontal direction is performed.

  FIG. 8 is a diagram showing the internal configuration of the vertical nonlinear processing means 31v. The illustrated vertical non-linear processing means 31v includes a zero-cross determining means 311v and a signal amplifying means 312v.

The zero-cross determining unit 311v confirms the change of the pixel value in the input enlarged image D2Bv along the vertical direction. A point where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels before and after the zero cross point by the signal D311v (in the illustrated example, the respective pixels immediately before and after 1 pixel) is transmitted to the signal amplifying means 312v.
The vertical nonlinear processing means 31v recognizes pixels located above and below the zero cross point as pixels before and after the zero cross point.

The vertical direction signal amplifying unit 312v amplifies the pixel value of the fourth enlarged image D2Bv with an amplification factor determined according to the determination result of the vertical direction zero cross determining unit 311v. Specifically, the signal amplifying unit 312v identifies pixels (pixels existing within a predetermined region including the zero cross point) before and after the zero cross point based on the signal D311v, and detects the pixels before and after the zero cross point. Only the pixel value is amplified (the absolute value is increased) to generate a nonlinear processed image D31v. That is, the amplification factor for the pixel values of the pixels before and after the zero cross point is set to a value larger than 1, and the amplification factors for the pixel values of the other pixels are set to 1.
By such processing, edge sharpening including step-like changes in signal values of pixels arranged in the vertical direction is performed.

  In the example shown in the figure, the pixel value is amplified only for each one pixel immediately before and after the zero cross point, but a predetermined number of pixels before and after the zero cross point, in other words, the zero cross point is determined. It is also possible to amplify the pixel value for a pixel that exists in a predetermined region. Alternatively, the size of the “predetermined area” (the number of pixels included in the predetermined area) may be changed according to the image enlargement ratio in the image enlargement unit 2B (set to an appropriate value for the enlargement ratio). good.

Next, the operation of the high frequency component image generating means 32B will be described.
The horizontal high-frequency component image generating means 32Bh applies a high-pass filter in the horizontal direction to the non-linearly processed image D31h to extract only high-frequency components composed of components having a frequency equal to or higher than a predetermined horizontal frequency, and generates a horizontal intermediate image D32Bh. . On the other hand, the vertical high-frequency component image generation means 32Bv applies a high-pass filter in the vertical direction to the nonlinear processed image D31v to extract only the high-frequency component composed of components having a frequency equal to or higher than a predetermined vertical frequency, and outputs the vertical intermediate image D32Bv. Generate. An intermediate image D32B composed of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv generated in this way is output from the high frequency component image generating means 32B.

The high-pass filter processing performed by the horizontal high-frequency component image generation unit 32Bh is performed in the same manner as the processing by the horizontal high-frequency component image generation unit 1h, and the high-pass filter performed by the vertical high-frequency component image generation unit 32Bv. The processing to be applied can be performed in the same manner as the processing in the vertical high frequency component image generation means 1v.
That is, as a process for applying a high-pass filter performed by the horizontal high-frequency component image generating means 32Bh, for example, the horizontal low-frequency component (or the horizontal alignment for each pixel) from the input signal to the means 32Bh. By subtracting the simple average value or the weighted average value of the pixel values in the local area composed of the predetermined number of pixels, it is possible to perform processing for extracting the high frequency component.

  Similarly, as a process for applying a high-pass filter performed by the vertical high frequency component image generating means 32Bv, for example, from the input signal to the means 32Bv, the vertical low frequency component (or the vertical direction for each pixel). By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of aligned pixels, it is possible to perform processing for extracting a high frequency component.

Next, the detailed operation of the high frequency component image correcting unit 33A will be described.
FIG. 9 is a diagram showing the internal configuration of the high frequency component image correcting means 33A. The high frequency component image correcting means 33A shown in FIG.
It has amplification factor calculation means 3MA and pixel value amplification means 3MB.

The amplification factor calculation means 3MA determines the amplification factor D3MA based on the pixel value of the enlarged image D2A.
The pixel value amplification unit 3MB amplifies the pixel value of the intermediate image D32A with the amplification factor D3MA determined by the amplification factor determination unit 3MA, and outputs the result as the intermediate image D3MB. The intermediate image D3MB is output as the intermediate image D33A from the high frequency component image correcting means 33A.
As described above, the pixel value of the intermediate image D32A is amplified by the amplification factor D3MA. This operation is performed for each pixel. That is, the amplification factor calculation means 3MA calculates the amplification factor D3MA for each pixel value of the intermediate image D32A. That is, the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the intermediate image D32A is calculated using the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the enlarged image D2A. Amplified with the amplified gain D3MA.

  As described above, the pixel value of the intermediate image D32A is amplified based on the amplification factor D3MA. The intermediate image D32A is composed of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av. An amplification factor D3MAh for the horizontal intermediate image D32Ah and an amplification factor D3MAv for the vertical intermediate image D32Av are determined. That is, the horizontal direction gain calculation means 3MAh in the gain determination means 3MA determines the gain D3MAh based on the pixel value of the enlarged image D2A, and the vertical direction gain calculation means 3MAv has the pixel value of the enlarged image D2A. Then, the amplification factor D3MAv is determined, and the amplification factor calculation means 3MA outputs the amplification factor D3MAh and the amplification factor D3MAv as the amplification factor D3MA.

The operation of the amplification factor calculation means 3MA will be described in more detail with reference to FIGS. 10 (a) and 10 (b). The amplification factor calculation means 3MA calculates the amplification factor D3MA based on the pixel value of the enlarged image D2A.
This amplification factor is calculated to be a small value when the pixel value of the enlarged image D2A is large. FIGS. 10A and 10B show an example of the amplification factor D3MA calculated by the amplification factor determination unit 3MA. FIG. 10A shows the amplification factor D3MAh calculated by the horizontal direction amplification factor determination unit 3MAh. FIG. 10B shows the amplification factor D3MAv calculated by the vertical direction amplification factor determination means 3MAv.

  As shown in FIG. 10A, the amplification factor D3MAh takes a small value when the pixel value of the enlarged image D2A is large. As an example, assuming that the slopes kMh1, kMh2, and kMh3 are all negative numbers, a predetermined value GMhb is taken when the pixel value of the enlarged image D2A is 0, and the slope kMh1 is between the pixel value 0 and a certain value AMh1. It is conceivable that the pixel value decreases with a slope kMh2 between AMh1 and a certain value AMh2, and decreases with a slope kMh3 when the pixel value is greater than AMh2. Obviously, it is better that the amplification factor is 0 or more. Therefore, when the amplification factor becomes a negative value in the above determination, the value is set to 0.

と表される。 When this relationship is expressed as G for the amplification factor D3MAh and L for the pixel value of the enlarged image D2A,

It is expressed.

  The amplification factor D3MAh is intended to be controlled so as to be small when the pixel value of the enlarged image D2A is large. Therefore, the slopes kMh1, kMh2, and kMh3 do not have to be negative numbers as described above. For example, only the slope kMh3 may be negative as long as it can be controlled. Furthermore, if the pixel value of the enlarged image D2A is large, the amplification factor D3MAh can be controlled to have a small value as long as each coefficient in Expression (2) takes any value. Further, the method for obtaining the amplification factor D3MAh is not limited to the equation (2).

  As illustrated in FIG. 10B, the amplification factor D3MAv takes a small value when the pixel value of the enlarged image D2A is large. As an example, assuming that the slopes kMv1, kMv2, and kMv3 are all negative numbers, a predetermined value GMvb is taken when the pixel value of the enlarged image D2A is 0, and the slope kMv1 is between the pixel value 0 and a value AMv1. It is conceivable that the pixel value decreases with a slope kMv2 when the pixel value is between AMv1 and a certain value AMv2, and decreases with the slope kMv3 when the pixel value is greater than or equal to AMv2. Obviously, it is better that the amplification factor is 0 or more. Therefore, when the amplification factor becomes a negative value in the above determination, the value is set to 0.

と表される。 This relationship can be expressed as G for the amplification factor D3MAv and L for the pixel value of the enlarged image D2A.

It is expressed.

Note that the amplification factor D3MAv is intended to be controlled to be a small value when the pixel value of the enlarged image D2A is large. Therefore, the slopes kMv1, kMv2, and kMv3 do not have to be negative numbers as described above. For example, only the slope kMv3 may be negative as long as it can be controlled. Furthermore, if the pixel value of the enlarged image D2A is large, the amplification factor D3MAv can be set to a small value as long as it can be controlled to be a small value. Further, the method for obtaining the amplification factor D3MAv is not limited to the expression (3).
The above is the operation of the amplification factor calculation means 3MA.

  Next, the pixel value amplifying unit 3MB amplifies the pixel value of the intermediate image D32A based on the amplification factor D3MA. Since the intermediate image D32A includes a horizontal intermediate image D32Ah and a vertical intermediate image D32Av, the pixel value amplifying unit 3MB includes a horizontal pixel value amplifying unit 3MBh for amplifying the pixel value of the horizontal intermediate image D32Ah, and a vertical value. Vertical direction pixel value amplifying means 3MBv for amplifying the pixel value of the direction intermediate image D32Av.

  The horizontal pixel value amplifying unit 3MBh outputs an image D3MBh obtained by amplifying the pixel value of the horizontal intermediate image D32Ah based on the amplification factor D3MAh, and the vertical pixel value amplifying unit 3MBv is based on the amplification factor D3MAv. An image D3MBv obtained by amplifying the pixel value of the image D32Av is output. As described above, this operation is performed for each pixel. That is, the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the horizontal intermediate image D32Ah is the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the enlarged image D2A. The pixel value of the pixel amplified by the amplification factor D3MAh calculated in the above and represented by the horizontal coordinate x and the vertical coordinate y in the vertical intermediate image D32Av is the horizontal coordinate x and the vertical coordinate y in the enlarged image D2A. Is amplified with the amplification factor D3MAv calculated using the pixel value of the pixel represented by Then, the image value D3MBh and the image D3MBv are output as the image D3MB from the pixel value amplifying unit 3MB.

Then, the image D3MB is output from the high frequency component image correcting means 33A as the intermediate image D33A. The intermediate image D33A includes a horizontal intermediate image D33Ah corresponding to the image D3MBh and a vertical intermediate image D33Av corresponding to the image D3MBv.
The above is the operation of the pixel value amplification factor means 3MB.

  The above is the operation of the high frequency component correction unit 33A. In the high frequency component image correction unit 33A, the intermediate image D32A is corrected by the amplification factor (or gain, gain) determined according to the pixel value of the enlarged image D2A. It is done.

Next, a detailed operation of the high frequency component image correcting unit 33B will be described.
FIG. 11 is a diagram showing an internal configuration of the high frequency component image correcting unit 33B. The high frequency component image correcting unit 33B shown in the figure includes an amplification factor calculating unit 3HA and a pixel value amplifying unit 3HB.

The amplification factor determination means 3HA determines the amplification factor D3HA based on the pixel value of the enlarged image D2A. The pixel value amplifying unit 3HB amplifies the pixel value of the intermediate image D32B with the amplification factor D3HA determined by the amplification factor calculating unit 3HA, and outputs the result as the intermediate image D3HB. An intermediate image D3HB is output as an intermediate image D33B from the high frequency component image correcting means 33B.
As described above, the pixel value of the intermediate image D32B is amplified by the amplification factor D3HA. This operation is performed for each pixel. That is, the amplification factor determining means 3HA calculates the amplification factor D3HA for each pixel value of the intermediate image D32B. That is, the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the intermediate image D32B is calculated using the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the enlarged image D2A. Amplified with the amplification factor D3HA.

  As described above, the pixel value of the intermediate image D32B is amplified based on the amplification factor D3HA. Since the intermediate image D32B is composed of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv, the amplification factor D3HA is: An amplification factor D3HAh for the horizontal intermediate image D32Bh and an amplification factor D3HAv for the vertical intermediate image D32Bv are determined. That is, the horizontal direction amplification factor determination unit 3HAh in the amplification factor calculation unit 3HA determines the amplification factor D3HAh based on the pixel value of the enlarged image D2A, and the vertical direction amplification factor determination unit 3HAv uses the pixel value of the enlarged image D2A. Then, the amplification factor D3HAv is determined, and the amplification factor determination unit 3HA outputs the amplification factor D3HAh and the amplification factor D3HAv as the amplification factor D3HA.

  The operation of the amplification factor determining means 3HA will be described in more detail with reference to FIGS. 12 (a) and 12 (b). The amplification factor calculation means 3HA calculates the amplification factor D3HA based on the pixel value of the enlarged image D2A. This amplification factor is calculated to be a small value when the pixel value of the enlarged image D2A is large. 12A and 12B show an example of the amplification factor D3HA calculated by the amplification factor determination unit 3HA, and FIG. 12A shows the amplification factor D3HAh calculated by the horizontal direction amplification factor determination unit 3HAh. FIG. 12B shows the amplification factor D3HAv calculated by the vertical direction amplification factor determination means 3HAv.

  As shown in FIG. 12A, the amplification factor D3HAh takes a small value when the pixel value of the enlarged image D2A is large. As an example, assuming that the slopes kHh1, kHh2, and kHh3 are all negative numbers, a predetermined value GHhb is taken when the pixel value of the enlarged image D2A is 0, and the slope kHh1 is between 0 and a value AHh1. It is conceivable that the pixel value decreases with a slope kHh2 between AHh1 and a certain value AHh2, and decreases with a slope kHh3 when the pixel value is greater than or equal to AHh2. Obviously, it is better that the amplification factor is 0 or more. Therefore, when the amplification factor becomes a negative value in the above determination, the value is set to 0.

と表される。 When this relationship is expressed as G for the amplification factor D3HAh and L for the pixel value of the enlarged image D2A,

It is expressed.

  Note that the amplification factor D3HAh is intended to be controlled to be a small value when the pixel value of the enlarged image D2A is large. Therefore, the slopes kHh1, kHh2, and kHh3 do not have to be negative numbers as described above. For example, only the slope kHh3 may be negative as long as it can be controlled. Furthermore, if the pixel value of the enlarged image D2A is large, the amplification factor D3HAh can be controlled to have a small value as long as each coefficient in Expression (4) takes any value. Further, the method for obtaining the amplification factor D3HAh is not limited to the equation (4).

  As shown in FIG. 12B, the amplification factor D3HAv takes a small value when the pixel value of the enlarged image D2A is large. As an example, assuming that the slopes kHv1, kHv2, and kHv3 are all negative numbers, a predetermined value GHvb is taken when the pixel value of the enlarged image D2A is 0, and the slope kHv1 is between 0 and a value AHv1. It can be considered that the pixel value decreases with a slope kHv2 between AHv1 and a certain value AHv2, and decreases with a slope kHv3 when the pixel value is greater than or equal to AHv2. Obviously, it is better that the amplification factor is 0 or more. Therefore, when the amplification factor becomes a negative value in the above determination, the value is set to 0.

と表される。 This relationship can be expressed as G for the amplification factor D3HAv and L for the pixel value of the enlarged image D2A.

It is expressed.

Note that the amplification factor D3HAv is intended to be controlled to be a small value when the pixel value of the enlarged image D2A is large. Therefore, the slopes kHv1, kHv2, and kHv3 do not have to be negative numbers as described above. For example, only the slope kHv3 may be negative as long as it can be controlled. Furthermore, if the pixel value of the enlarged image D2A is large, the gain D3HAv can be set to a small value as long as it can be controlled to be a small value. Further, the method for obtaining the amplification factor D3HAv is not limited to the equation (5).
The above is the operation of the amplification factor calculation means 3HA.

  Next, the pixel value amplifying unit 3HB amplifies the pixel value of the intermediate image D32B based on the amplification factor D3HA. Since the intermediate image D32B includes a horizontal intermediate image D32Bh and a vertical intermediate image D32Bv, the pixel value amplifying unit 3HB and a horizontal pixel value amplifying unit 3HBh for amplifying the pixel value of the horizontal intermediate image D32Bh Vertical direction pixel value amplification means 3HBv for amplifying the pixel value of the direction intermediate image D32Bv.

  The horizontal pixel value amplifying unit 3HBh outputs an image D3HBh obtained by amplifying the pixel value of the horizontal intermediate image D32Bh based on the amplification factor D3HAh, and the vertical pixel value amplifying unit 3HBv is based on the amplification factor D3HAv. An image D3HBv obtained by amplifying the pixel value of the image D32Bv is output. As described above, this operation is performed for each pixel. That is, the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the horizontal intermediate image D32Bh is the pixel value of the pixel represented by the horizontal coordinate x and the vertical coordinate y in the enlarged image D2A. The pixel value of the pixel that is amplified by the amplification factor D3HAh calculated in the above and represented by the horizontal coordinate x and the vertical coordinate y in the vertical intermediate image D32Av is the horizontal coordinate x and the vertical coordinate y in the enlarged image D2A. Is amplified with the amplification factor D3HAv calculated using the pixel value of the pixel represented by The pixel value amplifying unit 3HB outputs an image D3HBh and an image D3HBv as an image D3HB.

The image D3HB is output from the high frequency component image processing means 33B as the intermediate image D33B. The intermediate image D33B includes a horizontal intermediate image D33Bh corresponding to the image D3HBh and a vertical intermediate image D33Bv corresponding to the image D3HBv.
The above is the operation of the pixel value amplification factor means 3HB.

  The above is the operation of the high frequency component correction unit 33B. In the high frequency component image correction unit 33B, the intermediate image D32B is corrected according to the amplification factor (or gain or gain) determined according to the pixel value of the enlarged image D2A. It is done.

  Next, the operation of the adding means 34 will be described. The adding means 34 outputs the result of adding the intermediate image D33A and the intermediate image D33B as a high frequency component image D3.

  Here, since the intermediate image D33A is composed of the horizontal intermediate image D33Ah and the vertical intermediate image D33Av, and the intermediate image D33B is composed of the horizontal intermediate image D33Bh and the vertical intermediate image D33Bv, the intermediate image D33A and the intermediate image D33B are added together. , Horizontal intermediate image D33Ah, vertical intermediate image D33Av, horizontal intermediate image D33Bh, and vertical intermediate image D33Bv. The addition process here is not limited to simple addition, and may be a process of adding each image with an individual weight.

  Finally, the operation of the adding means 4 will be described. The adding means 4 adds the enlarged image D2A and the high frequency component image D3. Then, an image obtained as a result of adding the enlarged image D2A and the high frequency component image D3 in the adding means 4 is output from the image processing apparatus as a final enlarged image Dout. The addition process here is not limited to simple addition, and may be a process of adding each image with an individual weight.

The operation and effect of the image processing apparatus according to the present invention will be described below.
In the embodiment of the present invention, the intermediate images D32A and D32B are not added as they are, but the high frequency component image D3 is generated and added to the enlarged image D2A. The intermediate images D32A and D32B are not added to the high frequency component image correcting unit 33A. Are added to the enlarged image D2A by adding after correcting at 33B, and hereinafter, the intermediate images D32A and D32B are added as they are to generate the high frequency component image D3. Then, the effect obtained when adding to the enlarged image D2A will be described, and then the effect obtained by adding the intermediate images D33A and D33B instead of the intermediate images D32A and D32B will be described.

  The enlarged image D2A includes a frequency component corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din, and the high frequency component image D3 includes a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din. Therefore, the magnified image Dout generated by adding the magnified image D2A and the high frequency component image D3 has frequency components over all frequency regions that reach the Nyquist frequency after the image is magnified.

  First, it will be described that the enlarged image D2A has a frequency component corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din.

  FIGS. 13A to 13D are diagrams schematically showing the action when the enlarged image D2A is generated from the input image Din. FIG. 13A shows the frequency spectrum of the input image Din. b) shows the frequency spectrum of the zero insertion image D21A, FIG. 13 (c) shows the frequency response of the low-frequency component passing means 22A, and FIG. 13 (d) shows the frequency spectrum of the enlarged image D2A.

  The frequency spectrum of the input image Din will be described. Normally, natural images and the like are input from the input image Din, but the spectral intensities of these images are concentrated around the origin of the frequency space. Therefore, the frequency spectrum of the input image Din can be expressed as shown in FIG. Here, the vertical axis in FIG. 13A represents the spectral intensity, the horizontal axis represents the spatial frequency, and Fn represents the Nyquist frequency of the input image Din.

  Since the normal input image Din is a two-dimensional image, its frequency spectrum is also represented in a two-dimensional frequency space, but its shape is isotropic with the frequency spectrum shown in FIG. It will spread to. Therefore, in order to describe the frequency spectrum, it is only necessary to show the shape of one dimension at a minimum. In the future, unless otherwise specified, the shape of the frequency space will be described by showing only one dimension.

  Next, the frequency spectrum of the zero insertion image D21A will be described. By inserting one pixel per pixel (of the input image Din) and a pixel value of 0 with respect to the input image Din by the zero insertion means 21A, folding around the frequency Fn occurs in the frequency space. As a result, the frequency spectrum of the zero insertion image D21A is as shown in FIG.

  Next, the frequency response of the low frequency component passing means 22A will be described. As described above, since the calculation in the low frequency component passing means 22A is low pass filter processing, the frequency response of the low frequency component passing means 22A becomes lower as the frequency becomes higher as shown in FIG. . In the example shown in the figure, the low frequency component passing means 22A mainly passes the frequency component equal to or lower than the first frequency Fa (= Fn).

  Finally, the frequency spectrum of the enlarged image D2A will be described. An enlarged image D2A is generated by passing the zero insertion image D21A having the frequency spectrum shown in FIG. 13B through the low frequency component passing means 22A having the frequency response shown in FIG. 13C. Therefore, the frequency spectrum of the enlarged image D2A is obtained by removing the region R2AH on the high frequency side indicated by the oblique lines from the frequency spectrum of D21A.

  Therefore, the enlarged image D2A mainly has a frequency component corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din.

  Next, it will be described that the high frequency component image D3 mainly has a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din. If correction by the high frequency component image correction means 33A and 33B is not performed, the high frequency component image D3 is obtained by adding the intermediate image D32A and the intermediate image D32B. The intermediate image D32A is particularly Nyquist of the input image Din. The intermediate image D32B has a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din, and the high-frequency component image D3 has the frequencies of the intermediate images D32A and D32B. Since the components are added, the input image Din has a frequency component equal to or higher than the Nyquist frequency Fn.

First, the frequency spectrum of the intermediate image D32A will be described.
14 (a) to 14 (f) are diagrams schematically showing the action when the intermediate image D32A is generated, and FIG. 14 (a) shows the frequency response of the high-frequency component image generating means 1 as shown in FIG. b) shows the frequency spectrum of the high frequency component image D1 (or D1h or D1v), and FIG. 14C shows the zero insertion image D21B (or D21Bh or D21Bv) generated by the zero insertion means 21B in the image enlargement means 2B. 14D shows the frequency spectrum of the enlarged image D2B (or D2Bh or D2Bv), FIG. 14E shows the frequency response of the high-frequency component image generation means 32A (or 32Ah or 32Av), and FIG. (F) shows the frequency spectrum of the intermediate image D32A (or D32Ah or D32Av) output from the high frequency component image generating means 32A. It represents the torque.

  First, the frequency response of the high frequency component image generation means 1 and the frequency spectrum of the high frequency component image D1 will be described. Since the high-frequency component image generating means 1 generates the high-frequency component image D1 using a high-pass filter that mainly passes a component of the predetermined frequency Fb or higher in the input image Din, as shown in FIG. The frequency response of the high frequency component image generation means 1 increases as the frequency increases. The input image Din having the frequency spectrum shown in FIG. 13A passes through the high-pass filter having the frequency response shown in FIG. 14A, so that a high frequency component image D1 is obtained. In the illustrated example, the frequency spectrum of the high frequency component image D1 is small in a low frequency region (a region lower than the frequency Fb) as shown in FIG. 14B, and a high frequency region (a region higher than the frequency Fb). It will have a certain level of strength only.

  Next, the frequency spectrum of the zero insertion image D21B in the image enlarging means 2B will be described. Similar to the description of the zero insertion unit 21A of the image enlargement unit 2A, since the aliasing occurs by the zero insertion unit 21B, the frequency spectrum of the zero insertion image D21B in the image enlargement unit 2B is as shown in FIG. It becomes like this.

Next, the frequency spectrum of the enlarged image D2B will be described.
When generating the magnified image D2B, the frequency spectrum on the high frequency component side of the zero insertion image D21B (for example, a component in a region higher than the predetermined frequency Fc) is mainly removed by the low frequency component passing means 22B, so the magnified image The frequency spectrum of D2B is obtained by removing the high frequency side region (region higher than the frequency Fc) R32AH as shown in FIG.

  Finally, the frequency response of the high frequency component image generating means 32A and the frequency spectrum of the intermediate image D32A will be described. Since the high-frequency component image generating means 32A is a high-pass filter that mainly passes components of a predetermined frequency Fd or higher, the frequency response becomes higher as the frequency becomes higher as shown in FIG. The intermediate image D32A is generated by passing the enlarged image D2B having the frequency spectrum shown in FIG. 14D through the high-pass filter having the frequency response shown in FIG. Accordingly, the frequency response of the intermediate image D32A is, as shown in FIG. 14 (f), the lower frequency side region (region lower than the frequency Fd) R32AL is removed from the frequency spectrum of the enlarged image D2B shown in FIG. 14 (d). It will be.

  Accordingly, the intermediate image D32A mainly has a frequency component (frequency component from the frequency Fd to the frequency Fc) corresponding to the frequency close to the Nyquist frequency Fn of the input image Din.

Next, the frequency spectrum of the intermediate image D32B will be described.
FIGS. 15A to 15C are diagrams schematically showing the action when the intermediate image D32B is generated. FIG. 15A shows a high frequency component generated by the nonlinear processing means 31 (or 31h or 31v). FIG. 15 (b) shows the frequency response of the high-frequency component image generation means 32B, and FIG. 15 (c) shows the frequency spectrum of the intermediate image D32B.

  As will be described later, a high frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din is generated in the nonlinear processed image D31. FIG. 15A is a diagram schematically showing the state. In the illustrated example, a component having a frequency of Fe or higher is generated. The intermediate image D32B is generated when the nonlinear processed image D31 passes through the high frequency component image generating means 32B. The high-frequency component image generating means 32B is a high-pass filter that mainly passes components of the frequency Ff or higher, and the frequency response becomes higher as the frequency becomes higher as shown in FIG. Accordingly, as shown in FIG. 15C, the frequency spectrum of the intermediate image D32B is higher than the Nyquist frequency Fn of the input image Din because the low-frequency region R32BL is removed from the frequency spectrum of the nonlinear processed image D31. It corresponds to the frequency.

  The frequency spectrum of the intermediate image D32B will be described in more detail with reference to FIGS. 16 (a) to 16 (e) and FIGS. 17 (a) to 17 (f). In addition, in order to simplify description, each is described as a one-dimensional signal.

  16A to 16E show a step edge signal representing an image (step image) in which component values such as luminance and saturation change stepwise, and when the step edge signal is sampled at different sampling frequencies. The signal strength of the obtained signal and its high frequency component signal are shown. FIG. 16A shows a step edge signal.

FIG. 16B shows a signal obtained by sampling the step edge signal at the sampling interval S1, and FIG. 16C shows a high frequency component of the signal obtained by sampling the step edge signal at the interval S1, and FIG. d) shows a signal obtained by sampling the step edge signal at the sampling interval S2, and FIG. 16E shows a high frequency component of the signal obtained by sampling the step edge signal at the interval S1.
Note that the sampling interval S1 is shorter than the sampling interval S2, and shortening the sampling interval is the same as enlarging the image.

As shown in FIGS. 16B, 16C, 16D, and 16E, the center of the edge appears as a zero cross point Z in the high frequency component signal (FIGS. 16C and 16E). Further, as is apparent from a comparison between FIGS. 16B and 16C and FIGS. 16D and 16E, the slope of the high-frequency component signal before and after the zero-cross point Z decreases as the sampling interval decreases ( Alternatively, the position of the point giving the local maximum and minimum values of the high-frequency component near the zero-cross point Z also approaches the zero-cross point Z (according to the enlargement of the image).
The relationship between the sampling intervals S1 and S2 with respect to the step edge signal and the high-frequency component described with reference to FIG. 16 is not dependent on the combination of specific sampling intervals, but hereinafter, the sampling interval S2 is determined based on the input image Din. Assume that it is the same as the sampling interval.

  Therefore, when enlarging the image, the high frequency component of the input image Din is taken out, the change is made steep near the zero cross, and the point giving the local maximum and minimum values near the zero cross is brought close to the zero cross point. A high-frequency component that is not included in the resolution of Din (or higher than the Nyquist frequency of the input image Din) is generated, thereby making it possible to sharpen the edge.

  FIGS. 17A to 17F are diagrams schematically illustrating a procedure of high frequency component generation by the high frequency component image generation unit 1, the image enlargement unit 2B, the nonlinear processing unit 31, and the high frequency component image generation unit 32B. FIG. 17A shows an image (step image) in which component values such as luminance and saturation change stepwise, FIG. 17B shows an input image Din corresponding to the step image, and FIG. FIG. 17D shows an enlarged image D2B, FIG. 17E shows a nonlinear processed image D31, and FIG. 17F shows an intermediate image D32B.

  In FIGS. 17A to 17F, the coordinate P3 is a pixel corresponding to the boundary of the region where the signal intensity is low (on the low level side) near the edge, and the coordinate P4 is a region where the value is high (high). This is a pixel corresponding to the boundary on the level side.

  The input image Din and the high-frequency component image D1 corresponding to the step image are as described in FIGS. 16A to 16E, and the description thereof is omitted. First, the enlarged image D2B will be described.

  In the high frequency component image D1, the local maximum value in the vicinity of the zero cross point Z appears at the boundary on the high level side. Therefore, the local maximum value appears at the pixel represented by the coordinate P4, and conversely the local maximum value appears. Since the minimum value appears at the boundary on the low level side, a local minimum value appears at the pixel represented by the coordinate P3.

  The enlarged image D2B (or D2Bh or D2Bv) is passed through the low-frequency component after inserting one pixel per pixel (image D1) with a pixel value of 0 into the high-frequency component image D1 by the zero insertion means 21B. It is obtained by extracting the low frequency component by means 22B. Extracting the low frequency component is the same as obtaining the average pixel value in the local region for the high frequency component image D1 (FIG. 17C), and the enlarged image D2B (or D2Bh or D2Bv) is shown in FIG. As shown in d), the signal has the same shape as the high-frequency component image D1 and has an increased sampling number.

  Since the image is enlarged, a new pixel represented by the coordinate P1 between the zero-cross point Z and the pixel represented by the coordinate P3 is a new coordinate between the zero-cross point Z and the pixel represented by the coordinate P4. A pixel represented by P2 appears. Also in the enlarged image D2B, the local maximum value in the vicinity of the zero cross point Z appears in the pixel represented by the coordinate P4, and the local minimum value appears in the pixel represented by the coordinate P3.

  Next, the nonlinear processed image D31 will be described. The nonlinear processed image D31 is output as a result of the nonlinear processing means 31 detecting the zero cross point Z in the enlarged image D1 and amplifying the pixel values of the pixels before and after the zero cross point Z. Accordingly, in the nonlinear processed image D31 (or D31h or D31v), the pixel values of the pixels represented by the coordinates P1 and P2 are amplified, and the nonlinear processed image D31 has a signal as shown in FIG. Become.

  Finally, the intermediate image D32B will be described. The intermediate image D32B (FIG. 17 (f)) is obtained by extracting the high frequency component of the nonlinear processed image D31 (FIG. 17 (e)) by the high frequency component image generating means 32B. The high frequency component can be extracted by subtracting the low frequency component of the input signal (or a simple average value or a weighted average value of pixel values in the local region) from the input signal.

  In the nonlinear processed image D31 (FIG. 17 (e)), the pixel values of the pixels before and after the zero cross point Z (pixels represented by coordinates P1 and P2) are amplified by the signal amplification units 312h and 312v. The difference from the average pixel value in the local area becomes large. On the other hand, since the pixel values of other pixels near the zero cross point are not amplified, the difference from the average pixel value in the local region is a small value. Therefore, compared with the enlarged image D2B (FIG. 17D), in the intermediate image D32B (FIG. 17F), the points giving the local maximum value and the minimum value in the vicinity of the zero-cross point Z are coordinates P2 and P1, respectively. And approaches the zero cross point Z more. In addition, since the point that gives the local maximum and minimum values approaches the zero-cross point Z, the signal change near the zero-cross point also becomes abrupt.

  As described above, this means that the intermediate image D32B includes high frequency components that are not included in the resolution of the input image Din. In other words, the nonlinear processing means 31 amplifies pixel values around the zero cross point of the enlarged image D2B, thereby generating a high frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din.

  Further, since the intermediate image D32B is generated by extracting the high frequency component generated by the nonlinear processing means 31 by the high frequency component image generating means 32B, the high frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din is obtained. It becomes an image with.

  FIG. 21 shows frequency components of the enlarged image D2A, the intermediate image D32A, and the intermediate image D32B. The enlarged image D2A mainly includes a frequency component corresponding to a region RL corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din. On the other hand, the intermediate image D32A includes a frequency component corresponding to a region RM corresponding to a frequency close to the Nyquist frequency Fn of the input image Din, and the intermediate image D32B corresponds to a frequency higher than the Nyquist frequency Fn of the input image Din. The frequency component corresponding to the area | region RH to be included is contained.

  If the high frequency component image D3 is generated by adding the intermediate image D32A and the intermediate image D32B, the high frequency component image D3 includes both the frequency component of the intermediate image D32A and the frequency component of the intermediate image D32B. become. The intermediate image D32A includes a frequency component corresponding to a frequency close to the Nyquist frequency Fn of the input image Din, and the intermediate image D32B includes a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din. Therefore, the high frequency component image D3 includes frequency components equal to or higher than the Nyquist frequency Fn of the input image Din. Then, by adding the high frequency component image D3 to the enlarged image D2A to obtain the output image Dout, it becomes possible to give the output image Dout a frequency component equal to or higher than the Nyquist frequency Fn of the input image Din. The resolution can be increased.

  FIGS. 18A to 18D are diagrams for explaining the above effect from another viewpoint. FIG. 18A shows a step edge signal. In the edge shown in FIG. 18A, the luminance on the left side of the edge center is lower than that on the right side. That is, the left side from the center of the edge is the low level side, and the right side is the high level side. FIG. 18B shows an input image Din obtained by sampling the step edge signal at the sampling interval S2.

  FIG. 18C shows an enlarged image D2A obtained for the input image Din shown in FIG. Since the enlarged image D2A is obtained by performing an interpolation operation on the input image Din, the sampling interval is S1, which is twice as large as S2, but the change in the signal in the vicinity of the edge remains gentle, and the boundary on the low level side Is a pixel represented by the coordinate P3, and the boundary on the high level side remains the pixel represented by the coordinate P4.

FIG. 18D shows an image obtained by sampling the step edge signal at the sampling interval S1 (indicated by the symbol Din as in the image of FIG. 18B).
The boundary on the low level side is the pixel represented by the coordinate P1, and the boundary on the high level side is the pixel represented by the coordinate P2, and the change in the signal near the edge is abrupt compared to the enlarged image D2A. ing.

  By adding the intermediate image D32A and the intermediate image D32B, the inclination of the signal in the vicinity of the edge of the enlarged image D2 is corrected, and an image close to the image obtained by sampling the step edge signal shown in FIG. 18D at the sampling interval S1 is obtained. It can be obtained and the resolution of the image can be enhanced.

  As described above, by adding the intermediate images D32A and D32B (or high frequency components) to the enlarged image D2A, the sharpness of the image can be increased and the image quality can be improved. If it is excessively performed, image quality may be degraded. Therefore, in the image processing apparatus of the present invention, the high-frequency component image correction means 33A and 33B are used to prevent the deterioration of the image quality.

19 (a) and 19 (b) are diagrams for explaining image quality degradation due to addition of high frequency components.
FIG. 19A shows a case where the sharpness of the image is increased by appropriately adding the high frequency components, and FIG. 19B shows a case where the image quality is deteriorated as a result of excessive addition of the high frequency components. Indicates the invitation.

  In FIG. 19 (a), the intermediate image D32A shown in FIG. 17 (d) and the intermediate image D32B shown in FIG. 17 (f) are added to the enlarged image D2A shown in FIG. 18 (c). FIG. 18 is a diagram illustrating the result, and the boundary portion on the low luminance side of the step edge represented by the coordinate P3 in FIG. 18C is corrected to the position represented by the coordinate P1 in FIG. The boundary portion on the high luminance side of the step edge represented by the coordinate P4 in (c) is corrected to the position represented by the coordinate P2 in FIG. 19 (a), and as a result, FIG. 18 (c) and FIG. Comparing (a), it can be seen that FIG. 19 (a) is closer to the signal obtained by sampling the step edge shown in FIG. 16 (b) at the sampling interval S1. This represents that the sharpness of the image is increased by appropriately performing the addition of the high frequency component.

  On the other hand, FIG. 19B also shows an intermediate image D32A shown in FIG. 17D and an intermediate image D32B shown in FIG. 17F with respect to the enlarged image D2A shown in FIG. Although it is a figure which shows the result of adding, unlike the case of Fig.19 (a), the case where the addition of a high frequency component is performed excessively is represented. Compared to FIG. 19A, the luminance at the positions represented by the coordinates P1 and P3 is unnaturally lower than the surroundings (undershoot), or the luminance at the positions represented by the coordinates P2 and P4 is the surroundings. It can be seen that the image quality is degraded due to an unnatural increase (overshoot).

  When the magnitude of luminance (hereinafter referred to as a correction amount) added or subtracted by the intermediate image D32A or the intermediate image D32B becomes larger than necessary, undershoot and overshoot that cause a reduction in image quality are likely to occur. Therefore, it is considered that adjustment should be made so that the correction amount by the intermediate image D32A and the intermediate image D32B does not become larger than necessary.

As the method, for example, the local maximum value of the correction amount given by the intermediate image D32A or the intermediate image D32B is detected,
When the detected maximum value exceeds a predetermined value, a method is considered in which the correction amount is not increased more than necessary by appropriately applying a gain so that the correction amount by the intermediate image D32A or the intermediate image D32B is reduced. It is done.

  However, when such a method is adopted, data for several pixels must be referred to determine a local maximum value, resulting in an increase in circuit scale. Furthermore, if it is attempted to refer to data for several pixels in the vertical direction, line memory is added, which causes a cost increase.

  Therefore, the present invention changes the amplification factor applied to the intermediate image D32A and the intermediate image D32B based on the pixel value of the enlarged image D2A, so that the correction amount added by the intermediate image D32A and the intermediate image D32B is larger than necessary. In particular, the occurrence of overshoot is prevented. In the image processing apparatus according to the first embodiment, the high frequency component image correcting unit 33A and the high frequency component image correcting unit 33B appropriately amplify the intermediate image D32A and the intermediate image D32B depending on the pixel value of the enlarged image D2A. Adjust the correction amount by multiplying the rate.

In the high frequency component image correcting unit 33A, the intermediate image D32A is corrected by the amplification factor D3MA as shown in FIGS. 10A and 10B, and in the high frequency component image correcting unit 33B, the images shown in FIGS. The intermediate image D32B is corrected with the amplification factor D3HA as shown.
These amplification factors decrease as the pixel value of the enlarged image D2A increases. By correcting with such an amplification factor, the occurrence of overshoot can be suppressed. The reason is described below.

  The intermediate image D32A is generated by performing high-pass filter processing on the enlarged image D2B. Here, the high-pass filter processing corresponds to subtracting a local average value from each pixel value of the enlarged image D2B. Therefore, a pixel whose pixel value is a large positive value in the enlarged image D2B is highly likely to have a large positive value even after the high-pass filter processing given to that pixel, that is, the pixel value of the intermediate image D32A. .

On the other hand, the enlarged image D2B is generated by enlarging the high frequency component image D1. The enlargement process corresponds to weighted addition of pixel values near the pixel of interest.
Therefore, when calculating the pixel value of the enlarged image D2B, a large positive value may be obtained as the pixel value of the enlarged image D2B at a location where a pixel having a large positive value in the high-frequency component image D1 is used. Is expensive.

  The high frequency component image D1 is generated by performing high-pass filter processing on the input image Din. Here, the high-pass filter processing is equivalent to subtracting a local average value from each pixel value, so that a pixel having a large positive pixel value in the input image Din is a positive pixel having a large pixel value in the high-frequency component image D1. Is likely to be

  In other words, if there is a pixel having a large positive value in the input image Din, the pixel value of the pixel corresponding to the pixel in the high frequency component image D1 becomes a large positive value. Probability is high. In addition, in the high-frequency component image D1, when there is a pixel having a large positive value, the pixel value of the enlarged image D2B calculated using the same pixel value is likely to be a large positive value. Therefore, when there is a pixel having a large positive value in the input image Din, it is highly likely that a pixel at a position corresponding to the same pixel on the enlarged image D2B also has a large positive value. Further, in the enlarged image D2B, a pixel whose pixel value is a large positive value may have a large positive value for the output value after high-pass filter processing given to the pixel, that is, the pixel value of the intermediate image D32A. Therefore, if there is a pixel having a large positive value in the input image Din, there is a high possibility that a pixel at a position corresponding to the pixel on the intermediate image D32A also has a large positive value.

  On the other hand, the enlarged image D2A is generated by performing an enlargement process on the input image Din. The enlargement process corresponds to weighted addition of pixel values near the pixel of interest. Therefore, when calculating the pixel value of the enlarged image D2A, the pixel value of the enlarged image D2A is likely to be a large positive value at a location where a pixel having a large pixel value in the input image Din is used. . In addition, as described above, when there is a pixel having a large positive value in the input image Din, a pixel at a position corresponding to the pixel on the intermediate image D32A may also have a large positive value. Is expensive. Therefore, when there is a pixel having a large positive value in the input image Din, there is a possibility that a pixel at a position corresponding to the pixel in the intermediate image D32A or the enlarged image D2A has a large positive value. high.

  Therefore, when the pixel value of the enlarged image D2A is large, the pixel value of the intermediate image D32A is likely to be a large positive value. In other words, the correction amount is excessively added by the intermediate image D32A, and overshoot may occur. Increases nature.

  The intermediate image D32B is obtained by subjecting the enlarged image D2B to non-linear processing by the non-linear processing means 31 and then performing high-pass filter processing in the high-frequency component image generating means 32B. Since the non-linear processing means 31 amplifies the intermediate image D32A only in the vicinity of the zero cross point, basically, if the enlarged image D2B has a large positive value, the non-linear processing image D31 output from the non-linear processing means 31 also has a large positive value. It is considered to have. When the nonlinear processed image D31 has a large positive value, there is a high possibility that the intermediate image D32B, which is the high-pass filter processing result for the nonlinear processed image D31, also has a large positive value. Furthermore, when the pixel value of the enlarged image D2A is large, the pixel value of the enlarged image D2B is likely to be a large positive value.

  In summary, when the pixel value of the enlarged image D2A is large, the pixel value of the intermediate image D32A and the pixel value of the intermediate image D32B are likely to be large positive values. In other words, the correction amount is excessively added by the intermediate image D32A and the intermediate image D32B, and the possibility of occurrence of overshoot increases.

  Therefore, when the pixel value of the enlarged image D2A is large, it can be expected that the correction amount can be controlled so as not to become excessively large by reducing the amplification factor applied to at least one of the intermediate image D32A and the intermediate image D32B. In other words, it can be expected that control can be performed so that overshoot is less likely to occur.

  For example, as shown in FIGS. 10A and 10B, FIGS. 12A and 12B, or equations (2) to (5), the amplification factor decreases as the pixel value of the enlarged image D2A increases. By determining the amplification factor D3MA or the amplification factor D3HA based on such a monotonically decreasing function, such a process (which makes it difficult for overshoot to occur) can be performed.

  Note that the monotonically decreasing function as shown in FIGS. 10A and 10B, FIGS. 12A and 12B, or equations (2) to (5) is only an example, that is, the enlarged image D2A. If the pixel value is large, any method can be used as long as the amplification factor can be determined as a small value.

  As described above, the image processing apparatus according to the first embodiment has an effect that image enhancement processing can be performed while suppressing the occurrence of overshoot. If an excessive overshoot occurs in the image, only a part of the image flickers abnormally and feels unpleasant in terms of visual characteristics. Therefore, the image processing apparatus according to the first embodiment is very favorable in terms of visual characteristics.

  In summary, by adding the intermediate image D33A and the image D33B to the enlarged image D2A, it is possible to improve the resolution of the image while suppressing the occurrence of excessive overshoot.

  In this manner, the image processing apparatus according to Embodiment 1 obtains an output image Dout with a high resolution while suppressing the occurrence of excessive overshoot.

  As described above, the high-frequency component image processing unit 3 processes the image enlarging unit 2B obtained by enlarging the high-frequency component image D1 generated by the high-frequency component image generating unit 1 with the image enlarging unit 2B. A high frequency component image D3 including a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the image Din can be obtained. Then, in the adding means 4, an enlarged image D2A including a frequency component in a region corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din and a high frequency including a frequency component in a region corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din Since the enlarged image Dout is generated by adding the frequency component images D3, a high frequency component can be sufficiently given to the enlarged image Dout, and an enlarged image Dout with a sense of resolution can be obtained.

Further, the high frequency component image generation means 1 generates a horizontal high frequency component image D1h obtained by extracting the horizontal high frequency component and a vertical high frequency component image D1v obtained by extracting the vertical high frequency component. It is possible to generate a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din in any one of the horizontal direction and the vertical direction of the image. That is, by applying a horizontal high-pass filter to the enlarged image D2Bh obtained by enlarging the horizontal high-frequency component image D1h by the image enlarging means 2Bh by the horizontal high-frequency component image generating means 32Ah, the input image Din An intermediate image D32Ah having a frequency component corresponding to a frequency close to the Nyquist frequency Fn is generated, and a vertical high frequency component image generating unit is generated with respect to the enlarged image D2Bv obtained by enlarging the vertical high frequency component image D1v by the image enlarging unit 2Bv. By applying a high-pass filter in the vertical direction at 32 Av, an intermediate image D32Av having a frequency component corresponding to a frequency close to the Nyquist frequency Fn of the input image Din in the vertical direction is generated.
Further, by applying high-pass filters having different characteristics in the horizontal direction and the vertical direction, frequency components corresponding to frequencies close to the Nyquist frequency Fn are included in the horizontal direction and the vertical direction in different levels. You can also

Further, by applying a high-pass filter to the non-linearly processed image D31h generated by performing non-linear processing on the enlarged image D2Bh by the horizontal non-linear processing unit 31h, the horizontal direction high-frequency component image generating unit 32Bh applies an input in the horizontal direction. An intermediate image D32Bh having a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the image Din is generated, and the non-linearly processed image D31v generated by performing non-linear processing on the enlarged image D2Bv by the non-linear processing means 31v in the vertical direction. By applying a high-pass filter in the vertical high frequency component image generation means 32Bv, an intermediate image D32Bv having a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din in the vertical direction is generated.
Further, by performing nonlinear processing and high-pass filtering with different characteristics in the horizontal direction and the vertical direction, frequency components corresponding to frequencies higher than the Nyquist frequency Fn can be included in different levels in the horizontal direction and the vertical direction. .

  Then, the intermediate image D32A is corrected by the high frequency component correcting unit 33A, and the intermediate image D32B is corrected by the high frequency component correcting unit 33B with the amplification factor controlled so as to decrease when the pixel value of the enlarged image D2A is large. Thus, excessive overshoot can be prevented from occurring.

  Note that when the pixel value of the enlarged image D2A is large in order to prevent excessive overshoot as described above, the amplification factor is controlled so as to be small, and the enlarged image D2A and the amplification factor may be controlled according to the purpose. The relationship can be set as appropriate. For example, as in the image processing apparatus according to the first embodiment, when a high frequency component is extracted from an input image Din using a high pass filter, and components generated based on the high frequency component are added, the high frequency component passes through the pass band of the high pass filter. When such noise is included in the input image, the noise may be emphasized depending on the input image. Such a phenomenon is likely to occur particularly when the luminance of the image is low. Therefore, for example, as shown in FIG. 20, it is possible to set the amplification factor to be small when the pixel value of the enlarged image D2A is small to some extent and large to some extent. By doing so, it is possible to prevent excessive overshoot from occurring while preventing noise from being emphasized in the low-luminance portion of the image.

  Here, in FIG. 20, the symbol Gb is any one of GMhb, GMvb, GHhb, GHvb, the symbols k1 to k3 are any of kMh1 to kMh3, kMv1 to kMv3, kHh1 to kHh3, kHv1 to kHv3, and the symbols A1 and A2 are It corresponds to any of AMh1, AMh2, AMv1, AMv2, AHh1, AHh2, AHv1, and AHv2.

  In short, various artifacts that can occur in the output image Dout can be prevented by appropriately changing the amplification factors applied to the intermediate images D32A and D32B according to the pixel values of the enlarged image D2A.

  Further, the maximum effect can be obtained by correcting both the intermediate image D32A and the intermediate image D32B with the amplification factor as described above, but only one of the intermediate image D32A and the intermediate image D32B is as described above. The effect can be obtained simply by correcting with a large amplification factor.

  In the above embodiment, the high frequency component image processing means 3 includes both the high frequency component image correction means 33A and 33B, but only one of them may be provided. For example, the second correction component generation unit 3B does not include the high-frequency component image correction unit 33B, and the intermediate image D32B output from the nonlinear processed image generation unit 30 may be used as the output of the second correction component generation unit 3B. The first correction component generation unit 3A does not include the high frequency component image correction unit 33A, and the intermediate image D32A output from the high frequency component image generation unit 32A is used as the output of the first correction component generation unit 3A. Also good.

  Further, the high frequency component image D3 is obtained by adding the intermediate image D33A and the intermediate image D33B by the adding means 34, whereby a high frequency having a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din in any direction. A component image D3 can be obtained.

Note that the description has been made assuming that the enlargement ratio when generating the enlarged image Dout from the input image Din is double in both the horizontal and vertical directions, but the enlargement ratio is not limited to double. That is, the image enlargement unit 2A generates an enlarged image D2A obtained by enlarging the input image Din to a desired magnification both in the horizontal direction and the vertical direction. The high frequency component generation unit 1 generates the high frequency component image D1 based on the input image Din. The image enlarging means 2B generates an enlarged image D2B obtained by enlarging the high frequency component image D1 to a desired magnification (the same magnification as the magnification in the image enlarging means 2A) in both the horizontal direction and the vertical direction. The processing means 3 generates the high frequency component image D3 based on the enlarged image D2B, and the adding means 4 adds the enlarged image D2A and the high frequency component image D3 to obtain the final enlarged image Dout.
Furthermore, as described above, the horizontal enlargement factor and the vertical enlargement factor may not be the same, and enlargement may be performed only in one of the horizontal direction and the vertical direction.

  In the above description, the amplification factor is increased only for one pixel before and after the zero cross point in both the horizontal direction and the vertical direction. However, the example of the amplification factor control is not limited to this, and is appropriately changed according to, for example, the enlargement factor ( It can also be set to a value according to the enlargement ratio).

  Hereinafter, the case where the enlargement ratio is different from the above example will be described with reference to FIGS. 22 (a) to 22 (e) and FIGS. 23 (a) to 23 (f).

  FIG. 22A shows a step edge signal, FIG. 22B shows a signal obtained by sampling the step edge signal at the sampling interval S1, and FIG. 22C shows that obtained by sampling the step edge signal at the sampling interval S1. FIG. 22D shows a signal obtained by sampling a step edge signal at an interval S3 that is three times the interval S1, and FIG. 22E shows a step edge signal sampled at an interval S3. Represents the high frequency component of the resulting signal. In FIGS. 22D and 22E, pixel positions PL1 and PR1 represent step edge signal boundaries (points at which brightness brightness changes). Usually, in a signal representing a high-frequency component of an image obtained by sampling the step edge signal, the position of the pixel that gives the local maximum value and minimum value in the vicinity of the zero cross point Z substantially coincides with the position of the boundary of the step edge signal. .

  23A to 23F show high frequency component generation by the high frequency component image generation means 1, the image enlargement means 2B, the non-linear processing means 31, and the high frequency component image generation means 32B when the enlargement ratio is three times. FIG. 23A is an image (step image) in which component values such as luminance and saturation change stepwise, and FIG. 23B is an input corresponding to the step image. Image Din, FIG. 23C shows the high-frequency component image D1, FIG. 23D shows the enlarged image D2B, FIG. 23E shows the nonlinear processed image D31, and FIG. 23F shows the intermediate image D32B. In addition, in order to simplify description, each is described as a one-dimensional signal.

As shown in FIG. 23D, pixel positions PL1 and PR1 that give local maximum and minimum values near the zero-cross point Z in the enlarged image D2B are the positions of the boundary of the step edge signal in the enlarged image D2B. Almost matches. Normally, in the enlargement method used in the description of the present embodiment, the positions of PL1 and PR1 do not change, and the number of pixels existing between the positions represented by PL1 and PR1 and the zero-cross point Z increases. Further, the number of pixels existing between the positions represented by PL1 and PR1 and the zero-cross point Z increases as the enlargement ratio when generating the enlarged image D2B is increased (or the sampling interval is shortened).
On the other hand, in the signal representing the high frequency component of the image obtained by sampling the step edge signal at a short sampling interval, the position of the pixel giving the local maximum value and minimum value near the zero cross point Z is closer to the zero cross point Z, and the zero cross A pixel closer to the point than Z has a larger amplitude of a signal representing a high frequency component.

Accordingly, when generating the nonlinear processed image D31 by amplifying only the signals before and after the zero cross point Z, it is preferable to perform processing so that the amplitude becomes larger as the pixel is closer to the zero cross point Z than PL1 and PR1, for example, positions PL1, PR1 By amplifying the pixel value of the enlarged image D2B at a pixel closer to the zero cross point Z with a larger amplification factor as the pixel closer to the zero cross point Z and with a gain of 1 for pixels farther from the zero cross point Z than PL1 and PR1, FIG. As shown in (e), it is possible to generate a nonlinear processed image D31 having a larger amplitude as the pixel is closer to the zero cross point Z.
Then, by extracting only the high frequency component from the enlarged image D2B generated in this way by high-pass filter processing, an intermediate image D32B corresponding to the sampling interval S1 as shown in FIG. 23 (f) can be generated.

  In summary, since the number of pixels existing between the positions PL1 and PR1 and the zero cross point Z varies depending on the enlargement ratio at the time of generating the enlarged image D2B, the zero cross point Z is generated when generating the nonlinear processed image D31 from the enlarged image D2B. The number of pixels whose amplification factor is greater than 1 before and after may be changed in accordance with the enlargement factor of the image. Further, the amplification factors for these pixels may be changed according to the pixels, for example, according to the distance from the zero cross point Z. For example, the amplification factor may be increased as the pixel is closer to the zero cross point Z.

  Further, even by adding the intermediate image D33B to the enlarged image D2A, it is possible to give a high frequency component in a region higher than the Nyquist frequency Fn and increase the resolution of the image. Since the high frequency component in the region higher than the Nyquist frequency Fn is generated by nonlinear processing by the nonlinear processing image generation means 30, the high frequency component image processing means 3 only needs to include the nonlinear processing image generation means 30 therein. As such a modification, for example, the configuration shown in FIG. 35 is also conceivable. The operations of the components shown in FIG. 35 other than the adding means 35 are the same as those described in FIG. The adding means 35 adds the horizontal intermediate image D33Bh and the vertical intermediate image D33Bv. The addition result is output from the high frequency component image processing means 3 as a high frequency component image D3.

  35, the high frequency component in the region higher than the Nyquist frequency Fn generated by the nonlinear processed image generating means 30 is added to the enlarged image D2A via the high frequency component image D3, so that the output image The resolution of Dout can be enhanced.

Embodiment 2. FIG.
In the first embodiment, the present invention has been described as being realized by hardware. However, part or all of the configuration shown in FIG. 1 may be realized by software, that is, by a programmed computer. Processing in that case will be described with reference to FIG. 24 and FIGS.

FIG. 24 shows an image processing apparatus according to the second embodiment. The illustrated image processing apparatus includes a CPU 11, a program memory 12, a data memory 13, and a bus 14 for connecting them.
The CPU 11 operates according to a program stored in the program memory 12. Various data are stored in the data memory 13 in the course of operation. The enlarged image Dout generated as a result of the processing is supplied to the display unit 9 via the interface 15 and used for display by the display unit 9.
Hereinafter, processing performed by the CPU 11 will be described with reference to FIGS.

  25 is a diagram illustrating a flow of an image processing method performed by the image processing apparatus in FIG. 24. The image processing method illustrated in FIG. 16 includes an image enlargement step ST2A, a high-frequency component image generation step ST1, and an image enlargement. Step ST2B, high frequency component image processing step ST3, and addition step ST4 are included.

  In the image enlarging step ST2A, an enlarged image D2A is generated by enlarging the input image Din input in the image input step (not shown) by the same processing as the image enlarging means 2A in FIGS.

  As shown in FIG. 26, the high frequency component image generation step ST1 includes a horizontal direction high frequency component image generation step ST1h and a vertical direction high frequency component image generation step ST1v. In the horizontal direction high frequency component image generation step ST1h, the input image Din is processed in the same manner as the horizontal direction high frequency component image generation unit 1h in FIG. 3 to generate a horizontal direction high frequency component image D1h. On the other hand, in the vertical direction high frequency component image generation step ST1v, the input image Din is processed in the same manner as the vertical direction high frequency component image generation means 1v in FIG. 3 to generate the vertical direction high frequency component image D1v.

As shown in FIG. 27, the image enlargement step ST2B includes an image enlargement step ST2Bh and an image enlargement step ST2Bv.
In the image enlarging step ST2Bh, the horizontal direction high frequency component image D1h generated in the horizontal direction high frequency component image generating step ST1h is subjected to the same processing as the image enlarging means 2Bh in FIG. 3 to generate an enlarged image D2Bh.
In the image enlarging step ST2Bv, the vertical high frequency component image D1v generated in the vertical high frequency component image generating step ST1v is subjected to the same processing as the image enlarging means 2Bv in FIG. 3 to generate an enlarged image D2Bv.

Next, the operation of the high frequency component image processing step ST3 will be described.
As shown in FIG. 28, the high frequency component image processing step ST3 includes a high frequency component image generation step ST32A, a non-linear processing image generation step ST30, a high frequency component image correction step ST33A, a high frequency component image correction step ST33B, and an addition step. It has ST34.
The high frequency component passing step ST32A includes a horizontal high frequency component image generation step ST32Ah and a vertical high frequency component image generation step ST32Av.

The nonlinear processed image generation step ST30 has a nonlinear processing step ST31 and a high frequency component image generation step ST32B.
The nonlinear processing step ST31 includes a horizontal nonlinear processing step ST31h and a vertical nonlinear processing step ST31v.
The high frequency component image generation step ST32B includes a horizontal direction high frequency component image generation step ST32Bh and a vertical direction high frequency component image generation step ST32Bv.

In the horizontal high-frequency component passing step ST32Ah, the enlarged image D2Bh generated in the image enlargement step ST2Bh is subjected to the same processing as the horizontal high-frequency component image generating unit 32Ah in FIG. 3 to generate the horizontal intermediate image D32Ah. . In the vertical high-frequency component passing step ST32Av, the enlarged image D2Bv generated in the image enlargement step ST2Bv is subjected to the same processing as the vertical high-frequency component image generating means 32Av in FIG. 3 to generate the vertical intermediate image D32Av. .
In the high frequency component image generation step ST32A, an intermediate image D32A composed of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av is generated.
Thus, in the high frequency component passing step ST32A, the same operation as the high frequency component image generating means 32A of FIG. 3 is performed.

As shown in FIG. 29, the horizontal non-linear processing step ST31h includes a zero cross determination step ST311h and a signal amplification step ST312h.
The operation of the horizontal nonlinear processing step ST31h is as follows.
First, in the zero cross determination step ST311h, a change in the pixel value in the enlarged image D2Bh generated in the image enlargement step ST2Bh is confirmed along the horizontal direction. A location where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels located on the left and right sides of the zero cross point are specified. In the signal amplification step ST312h, the pixel values of the pixels located on the left and right of the zero cross point specified in the zero cross determination step ST311h in the enlarged image D2Bh are amplified, and an image obtained as a result is generated as the nonlinear processed image D31h.

As shown in FIG. 30, the vertical nonlinear processing step ST31v includes a zero cross determination step ST311v and a signal amplification step ST312v.
The operation of the vertical nonlinear processing step ST31v is as follows.
First, in the zero cross determination step ST311v, a change in pixel value in the enlarged image D2Bv generated in the image enlargement step ST2Bv is confirmed along the vertical direction. A portion where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels located above and below the zero cross point are specified. In the signal amplification step ST312v, the pixel values of the pixels located above and below the zero-cross point specified in the zero-cross determination step ST311v in the enlarged image D2Bv are amplified, and the resulting image is generated as the nonlinear processed image D31v.

In the high frequency component image generation step ST31, a nonlinear processed image D31 including a horizontal direction nonlinear processed image D31Ah and a vertical direction nonlinear processed image D32Av is generated.
Thus, in the non-linear processing step ST31, the same operation as that of the non-linear processing means 31 of FIG. 3 is performed.

In the horizontal high-frequency component passing step ST32Bh, a high-pass filter is applied to the nonlinear processed image D31h generated in the horizontal nonlinear processing step ST31h to generate a horizontal intermediate image D32Bh. In the vertical direction high frequency component passing step ST32Bv, a high-pass filter is applied to the nonlinear processed image D31v generated in the vertical nonlinear processing step ST31v to generate a vertical intermediate image D32Bv.
In the high frequency component image generation step ST32B, an intermediate image D32B composed of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv is generated.
Thus, in the high frequency component passing step ST32B, the same operation as that of the high frequency component image generating unit 32B in FIG. 3 is performed.

Next, the detailed operation of the high frequency component image correction step ST33A will be described.
As shown in FIG. 31, the high frequency component image correction step ST33A includes an amplification factor calculation step ST3MA and a pixel value amplification step ST3MB. The amplification factor obtained in accordance with the pixel value of the enlarged image D2A is used for the intermediate image D32A. Each pixel value is corrected. The correction mentioned here means that the amplification factor determined according to the pixel value of the enlarged image D2A is multiplied by each pixel value of the intermediate image D32A (or the pixel by the amplification factor determined according to the pixel value of the enlarged image D2A). Means to amplify the value).

  Here, since the intermediate image D32A is composed of a horizontal intermediate image D32Ah and a vertical intermediate image D32Av, the amplification factor is calculated for each of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av. That is, for the horizontal intermediate image D32Ah, the amplification factor for each pixel is determined in the horizontal direction amplification factor determination step ST3MAh, and for the vertical intermediate image D32Av, the amplification factor for each pixel is determined in the vertical direction amplification factor determination step ST3MAv. .

  Here, the operation of the horizontal direction gain determination step ST3MAh is the same as that of the horizontal direction gain determination unit 3MAh, and the operation of the vertical direction gain determination step ST3MAv is the same as that of the vertical direction gain determination unit 3MAv.

  Next, in the pixel value amplification step ST3MB, the pixel value of each pixel of the intermediate image D32A is amplified based on the amplification factor determined in the amplification factor determination step ST3MA. Here, since the intermediate image D32A is composed of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av, the pixel value is amplified for each of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av.

  That is, in the horizontal pixel value amplification step ST3MBh, an image D3MBh in which each pixel value of the horizontal intermediate image D32Ah is amplified based on the amplification factor determined in the horizontal amplification factor determination step ST3MAh is generated. Also, in the vertical direction pixel value amplification step ST3MBv, an image D3MBv in which each pixel value of the vertical direction intermediate image D32Av is amplified based on the amplification factor determined in the vertical direction amplification factor determination step ST3MAv is generated. This operation is the same as that of the pixel value changing means 3MB.

  Then, an intermediate image D33A composed of a horizontal intermediate image D33Ah corresponding to the image D3MBh and a vertical intermediate image D33Av corresponding to the image D3MBv is generated by the high frequency component image correction step ST33A.

  The above is the operation of the high frequency component image correction step ST33A, and the operation is equivalent to the operation of the high frequency component correction means 33A of FIG.

Next, the detailed operation of the high frequency component image correction step ST33B will be described.
As shown in FIG. 32, the high frequency component image correction step ST33B includes an amplification factor calculation step ST3HA and a pixel value amplification step ST3HB, and uses the amplification factor obtained in accordance with the pixel value of the enlarged image D2A. Each pixel value is corrected. The correction referred to here is the multiplication of the amplification factor determined according to the pixel value of the enlarged image D2A to each pixel value of the intermediate image D32B (or the pixel by the amplification factor determined according to the pixel value of the enlarged image D2A). Means to amplify the value).

  Here, since the intermediate image D32B is composed of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv, the amplification factor is calculated for each of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv. That is, for the horizontal intermediate image D32Bh, the amplification factor for each pixel is determined in the horizontal direction amplification factor determination step ST3HAh, and for the vertical direction intermediate image D32Bv, the amplification factor for each pixel is determined in the vertical direction amplification factor determination step ST3HAv. . Here, the operation of the horizontal direction gain determination step ST3HAh is the same as that of the horizontal direction gain determination unit 3HAh, and the operation of the vertical direction gain determination step ST3HAv is the same as that of the vertical direction gain determination unit 3HAv.

  Next, in the pixel value amplification step ST3HB, the pixel value of each pixel of the intermediate image D32B is amplified based on the amplification factor determined in the amplification factor determination step ST3HA. Here, since the intermediate image D32B is composed of the horizontal direction intermediate image D32Bh and the vertical direction intermediate image D32Bv, the amplification of the pixel value is performed for each of the horizontal direction intermediate image D32Bh and the vertical direction intermediate image D32Bv.

  That is, in the horizontal pixel value amplification step ST3HBh, an image D3HBh is generated by amplifying each pixel value of the horizontal intermediate image D32Bh based on the amplification factor determined in the horizontal amplification factor determination step ST3HAh. Also, in the vertical direction pixel value amplification step ST3HBv, an image D3HBv in which each pixel value of the vertical direction intermediate image D32Av is amplified based on the amplification factor determined in the vertical direction amplification factor determination step ST3MAv is generated. This operation is the same as that of the pixel value changing means 3HB.

  Then, an intermediate image D33B composed of a horizontal intermediate image D33Bh corresponding to the image D3HBh and a vertical intermediate image D33Bv corresponding to the image D3HBv is generated by the high frequency component image correction step ST33B.

  The above is the operation of the high frequency component image correction step ST33B, and the operation is equivalent to the operation of the high frequency component correction means 33B of FIG.

The combination of the high frequency component image generation step ST32A and the high frequency component image correction step ST33A corresponds to the operation of the first correction component generation means 3A.
The combination of the nonlinear processed image generation step ST30 and the high frequency component image correction step ST33B corresponds to the operation of the second correction component generation means 3B.

  In the addition step ST34, the intermediate image D33A generated in the high frequency component image correction step ST33A and the intermediate image D33B generated in the high frequency component image correction step ST33B are added to obtain a high frequency component image D3. Thus, in step ST34, the same operation as that of the adding means 34 in FIG. 3 is performed.

  The above is the operation of the high frequency component image processing step ST3, and this operation is the same as that of the high frequency component image processing means 3 of FIGS.

The adding step ST4 generates an image Dout obtained by adding the enlarged image D2A generated in the image enlarging step ST2A and the high frequency component image D3 generated in the high frequency component image processing step ST3. Then, the generated image Dout is output as a final enlarged image through a step (not shown).
This operation is the same as that of the adding means 4 in FIGS.

  The above is the operation of the image processing method according to the second embodiment. As is clear from the above description, the image processing method according to the second embodiment can also enlarge an image by the same processing as that of the image processing device according to the first embodiment, so that the same effect as the image processing device according to the first embodiment can be obtained. It is done. Also, the image processing method according to the second embodiment can be modified in the same manner as the image processing apparatus according to the first embodiment, and the effect obtained in that case is the same as that of the image processing apparatus according to the first embodiment. .

  For example, an example in which the high frequency component image processing step ST3 is modified to the configuration shown in FIG. 36 other than the addition step ST35 in the operation of each step in FIG. 36 is the same as that described in FIG. In the addition step ST35, the horizontal intermediate image D33Bh and the vertical intermediate image D33Bv are added. The obtained addition result is output as a high frequency component image D3 from the high frequency component image processing step ST3. Even by simply adding the high frequency component image D3 obtained in this way to the enlarged image D2A, a high frequency component in a region higher than the Nyquist frequency Fn can be given, so that an effect of increasing the resolution of the image can be obtained. In short, since the high frequency component in the region higher than the Nyquist frequency Fn is generated by the nonlinear processing in the nonlinear processing image generation step ST30, the high frequency component image processing step ST3 can execute the nonlinear processing in the nonlinear processing image generation step ST30 therein. Good.

  Note that the modifications are not limited to those described above, and all modifications applied to the image processing apparatus according to the first embodiment can be applied to the image processing method according to the second embodiment. For example, it is possible to appropriately change (set) the operation of the nonlinear processing image generation step ST30 according to the enlargement ratio. At this time, it is clear from the comparison with the first embodiment how each component of the image processing method according to the second embodiment should be modified.

  In addition, since the image processing apparatus according to the second embodiment can be used as a part of the image display apparatus similar to the image processing apparatus described in the first embodiment, the image Dout generated by the image processing apparatus according to the second embodiment. The image display apparatus that displays the same effect as the image processing apparatus described in the first embodiment can also be obtained. Further, the image processing method implemented using the image processing apparatuses of the first and second embodiments and the image display method using the same can obtain the same effects.

Embodiment 3 FIG.
FIG. 33 is a diagram illustrating a configuration of an image processing apparatus according to the third embodiment of the present invention. The image processing apparatus according to Embodiment 3 includes an image enlarging unit 2A, a high frequency component image generating unit 1, an image enlarging unit 2B, a high frequency component image processing unit 3, a high frequency component image correcting unit 33C, and an addition. Means 4. The high frequency component image processing means 3 includes a high frequency component image generation means 32A, a nonlinear processed image generation means 30, and an addition means 34. Similar to the image processing apparatus according to the first embodiment, the image processing apparatus according to the third embodiment can be used as a part of the image display apparatus shown in FIG.

  Here, the operations of the image enlarging means 2A, the high frequency component image generating means 1, the image enlarging means 2B, the high frequency component image generating means 32A, and the nonlinear processed image generating means 30 are the same as those of the image processing apparatus according to the first embodiment. is there.

  The adding means 34 adds the intermediate image D32A and the intermediate image D32B. The obtained image is output as a high frequency component image D3.

  The high frequency component image correcting unit 33C amplifies each pixel value of the high frequency component image D3 with an amplification factor determined according to the pixel value of the enlarged image D2A, and outputs a high frequency component image D33C.

  The detailed operation of the high frequency component image correcting unit 33C is the same as that performed by the high frequency component image correcting unit 33A on the intermediate image D32A or the high frequency component image correcting unit 33B in the image processing apparatus according to the first embodiment. Similar to the operation performed on the intermediate image D32B, the pixel value of each pixel of the correction target image (D3) is amplified at an amplification factor determined according to (the pixel value of the same pixel) of the enlarged image D2A. Therefore, the description thereof is omitted. The same applies to the detailed configuration of the high-frequency component image correcting unit 33C.

  The adding means 4 adds the enlarged image D2A and the high frequency component image D33C, and outputs a final output image Dout.

  Similarly to the image processing apparatus according to the first embodiment, the image processing apparatus according to the third embodiment resolves the output image Dout by giving a high frequency component equal to or higher than the Nyquist frequency of the input image Din in the high frequency component image processing means 3. It is possible to increase the feeling.

  The operation performed by the high frequency component image correcting unit 33C on the high frequency component image D3 is the operation performed by the high frequency component image correcting unit 33A on the intermediate image D32A in the image processing apparatus according to the first embodiment. The operation is the same as that performed by the high frequency component image correcting unit 33B on the intermediate image D32B. Accordingly, it is possible to prevent the problem that the correction by the high frequency component (high frequency component image D3) is excessively performed, the overshoot or the like occurs, and the image quality is deteriorated.

  Further, when compared with the image processing apparatus according to the first embodiment, since the number of high frequency component image correction means is small, it can be configured with a circuit scale smaller than that of the first embodiment.

  Since the high frequency component in the region higher than the Nyquist frequency Fn is generated by nonlinear processing by the nonlinear processed image generating means 30, the high frequency component image processing means 3 may include the nonlinear processed image generating means 30 therein. For example, a configuration shown in FIG. 37 is also conceivable as such a modification. The operations of the components shown in FIG. 37 other than the adding means 35 are the same as those described in the first embodiment or FIG. The adding means 35 adds the horizontal direction intermediate image D32Bh and the vertical direction intermediate image D32Bv included in the intermediate image D32B. The addition result is output from the high frequency component image processing means 3 as a correction target image (D3).

  37, the high frequency components in the region higher than the Nyquist frequency Fn generated by the nonlinear processed image generation means 30 are added to the enlarged image D2A via the high frequency component image D33C, so that the output image The resolution of Dout can be enhanced.

  The modifications are not limited to those described above, and modifications applied to the image processing apparatus according to the first embodiment can be applied to the image processing apparatus according to the third embodiment as necessary. For example, it is possible to appropriately change (set) the operation of the nonlinear processed image generating means 30 according to the enlargement ratio. At this time, it is clear from the comparison with the first embodiment how each component of the image processing apparatus according to the third embodiment should be modified.

Embodiment 4 FIG.
FIG. 34 is a diagram showing a configuration of an image processing method according to the fourth embodiment of the present invention. The image processing method according to the fourth embodiment includes an image enlargement step ST2A, a high frequency component image generation step ST1, an image enlargement step ST2B, a high frequency component image processing step ST3, and a high frequency component image correction step ST33C. Step ST4. The high frequency component image processing step ST3 includes a high frequency component image generation step ST32A, a non-linear processing image generation step ST30, and an addition step ST34. Similarly to the image processing method according to the second embodiment, the image processing method according to the fourth embodiment can be used as a part of the image display apparatus shown in FIG.

  Here, the operations of the image enlargement step ST2A, the high frequency component image generation step ST1, the image enlargement step ST2B, the high frequency component image generation step ST32A, and the non-linear processing image generation step ST30 are the same as those of the image processing method according to the second embodiment. is there.

  The adding step ST34 adds the intermediate image D32A and the intermediate image D32B. The obtained image is output as a high frequency component image D3.

  The high frequency component image correction step ST33C amplifies each pixel value of the high frequency component image D3 with an amplification factor determined according to the pixel value of the enlarged image D2A, and outputs a high frequency component image D33C.

  The detailed operation of the high frequency component image correction step ST33C is the same as that performed by the high frequency component image correction step ST33A on the intermediate image D32A in the image processing method according to the second embodiment or the high frequency component image correction step. Since the operation can be the same as that performed by ST33B on intermediate image D32B, a description thereof will be omitted. The same applies to the detailed configuration of the high-frequency component image correction step ST33C.

  In the addition step ST4, the enlarged image D2A and the high frequency component image D33C are added, and a final output image Dout is output.

  Since the operation of the image processing method according to the fourth embodiment is the same as that of the image processing apparatus according to the third embodiment, the same effect as that of the image processing apparatus according to the third embodiment can be obtained.

  Since the high frequency components in the region higher than the Nyquist frequency Fn are generated by the nonlinear processing by the nonlinear processing image generation step ST30, the high frequency component image processing step ST3 includes the nonlinear processing image generation step ST30 therein. For example, the configuration shown in FIG. 38 is also conceivable as such a modification. Of the components in the configuration shown in FIG. 38, the operations other than the addition step ST35 are the same as those described in the second embodiment or FIG. The adding step ST35 adds the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv included in the intermediate image D32B. The addition result is output from the high frequency component image processing step ST3 as the high frequency component processed image D3.

  Since the high frequency components in the region higher than the Nyquist frequency Fn generated by the non-linear processing image generation step ST30 are also added to the enlarged image D2A via the high frequency component image D33C by the image processing method shown in FIG. The resolution of Dout can be enhanced.

  Note that the modifications are not limited to those described above, and modifications applied to the image processing apparatus according to the first embodiment can be applied to the image processing method according to the fourth embodiment as necessary. For example, it is possible to appropriately change (set) the operation of the nonlinear processing image generation step ST30 according to the enlargement ratio. At this time, it is clear from the comparison with the first embodiment how each component of the image processing method according to the fourth embodiment should be modified.

  DESCRIPTION OF SYMBOLS 1 High frequency component image generation means, 2A Image expansion means, 2B Image expansion means, 3 High frequency component image processing means, 3A Correction component generation means, 3B Correction component generation means, 4 Addition means, 30 Nonlinear image generation means, 31 Nonlinear Processing means, 32A high frequency component image generation means, 32B high frequency component image processing means, 33A high frequency component image correction means, 33B high frequency component image correction means, 33C high frequency component image correction means, 34 addition means, Din input image D1 high frequency component image, D2A enlarged image, D2B enlarged image, D3 high frequency component image, D32A intermediate image, D32B intermediate image, D33A intermediate image, D33B intermediate image, D33C high frequency component image, Dout output image.

Claims (25)

In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
First correction component generation means including second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Second correction component generation means including non-linear processing image generation means for outputting a second intermediate image obtained by performing processing including non-linear processing on the second enlarged image;
A second addition means for adding the output of the first correction component generation means and the output of the second correction component generation means;
The result of the addition in the second addition means is used as the output of the high frequency component image processing means,
The first correction component generation means outputs a third intermediate image obtained by amplifying each pixel value of the first intermediate image with a first amplification factor obtained according to the pixel value of the first enlarged image. Further comprising first high frequency component image correcting means
The image processing apparatus, wherein the third intermediate image is used as an output of the first correction component generation unit. In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
First correction component generation means including second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Second correction component generation means including nonlinear processing image generation means for outputting a second intermediate image obtained by performing processing including nonlinear processing on the second enlarged image;
A second addition means for adding the output of the first correction component generation means and the output of the second correction component generation means;
The result of the addition in the second addition means is used as the output of the high frequency component image processing means,
The second correction component generation means outputs a fourth intermediate image obtained by amplifying each pixel value of the second intermediate image with a second amplification factor obtained according to the pixel value of the first enlarged image. A second high frequency component image correcting means for
The image processing apparatus, wherein the fourth intermediate image is used as an output of the second correction component generation unit. The second correction component generation means outputs a fourth intermediate image obtained by amplifying each pixel value of the second intermediate image with a second amplification factor obtained according to the pixel value of the first enlarged image. A second high frequency component image correcting means for
The image processing apparatus according to claim 1, wherein the fourth intermediate image is used as an output of the second correction component generation unit. The nonlinear processed image generation means includes:
Nonlinear processing means for generating a first nonlinear processed image obtained by performing nonlinear processing on the second enlarged image;
The image according to any one of claims 1 to 3, further comprising third high-frequency component image generation means that extracts a high-frequency component from the first nonlinear processed image and sets the second intermediate image as the second intermediate image. Processing equipment. The first high frequency component image correction means includes:
First amplification factor calculating means for determining the first amplification factor;
4. The image processing apparatus according to claim 1, further comprising first pixel value amplifying means for amplifying each pixel value of the first intermediate image at the first amplification factor. The second high frequency component image correcting means includes:
Second amplification factor calculating means for determining the second amplification factor;
4. The image processing apparatus according to claim 2, further comprising a second pixel value amplifying unit that amplifies each pixel value of the second intermediate image at the second amplification factor. 5. The first high frequency component image correction means includes:
First amplification factor calculating means for determining the first amplification factor;
First pixel value amplifying means for amplifying each pixel value of the first intermediate image at the first amplification factor;
The second high frequency component image correcting means includes:
Second amplification factor calculating means for determining the second amplification factor;
The image processing apparatus according to claim 3, further comprising a second pixel value amplifying unit that amplifies each pixel value of the second intermediate image at the second amplification factor. The first high frequency component image generation means includes:
A first horizontal high-frequency component image generating unit that generates a horizontal high-frequency component image using a pixel value of a pixel existing in the vicinity of the horizontal direction for each pixel of the input image;
The second image enlargement means includes:
A third image enlarging means for enlarging the first horizontal high-frequency component image and outputting a third enlarged image;
The second enlarged image includes the third enlarged image,
The second high frequency component image generating means includes:
A second horizontal high frequency component image generating means for extracting only the high frequency component of the third enlarged image and outputting the first horizontal intermediate image;
The nonlinear processing means includes:
A horizontal nonlinear processing means for outputting a second nonlinear processed image obtained by performing nonlinear processing on the third enlarged image;
The third high frequency component image generation means includes:
A third horizontal high frequency component image generating means for extracting a high frequency component from the second nonlinear processed image and outputting a second horizontal intermediate image;
The first intermediate image includes the first horizontal intermediate image;
The second intermediate image includes the second horizontal intermediate image;
The first amplification factor calculation means includes first horizontal amplification factor calculation means for calculating a first horizontal amplification factor according to a pixel value of the first enlarged image,
The first pixel value amplifying means outputs a first horizontal pixel that outputs a third horizontal intermediate image obtained by amplifying each pixel value of the first horizontal intermediate image at the first horizontal gain. Having value amplification means,
The second amplification factor calculation means includes second horizontal amplification factor calculation means for calculating a second horizontal amplification factor,
The second pixel value amplifying means outputs a second horizontal pixel that outputs a fourth horizontal intermediate image obtained by amplifying each pixel value of the second horizontal intermediate image with the second horizontal gain. Having value amplification means,
The third intermediate image includes the third horizontal intermediate image;
The image processing apparatus according to claim 7, wherein the fourth intermediate image includes the fourth horizontal intermediate image. The horizontal nonlinear processing means includes:
A horizontal direction zero cross determining means for determining a point where the pixel value of the third enlarged image changes from positive to negative or from negative to positive as a zero cross point;
Horizontal signal amplification means for amplifying the pixel value of the third enlarged image at an amplification factor determined according to the determination result of the horizontal direction zero-cross determination means,
The third horizontal high-frequency component image generating means is
The image processing apparatus according to claim 8, wherein a high-frequency component is extracted from an image output from the horizontal signal amplification unit. The horizontal direction signal amplification means includes
The amplification factor for the pixel value of the pixel existing in the first region including the zero-cross point determined by the horizontal zero-cross determination unit is set to a value larger than 1, and the amplification factor for the pixel values of the other pixels is set to 1. The image processing apparatus according to claim 9. The image processing apparatus according to claim 10, wherein the first area is determined according to an enlargement ratio in the second image enlargement unit. The image processing apparatus according to claim 10 or 11, wherein an amplification factor for a pixel existing in the first region is determined according to the pixel. The first high frequency component image generation means includes:
First vertical high-frequency component image generation means for generating a vertical high-frequency component image using pixel values of pixels existing in the vicinity of the vertical direction for each pixel of the input image;
The second image enlargement means includes:
A fourth image enlarging means for enlarging the first vertical high-frequency component image and outputting a fourth enlarged image;
The second enlarged image includes the fourth enlarged image,
The second high frequency component image generating means includes:
A second vertical high frequency component image generating means for extracting only the high frequency component of the fourth enlarged image and outputting the first vertical intermediate image;
The nonlinear processing means includes:
Vertical nonlinear processing means for outputting a third nonlinear processed image obtained by performing nonlinear processing on the fourth enlarged image;
The third high frequency component image generation means includes:
A third vertical high frequency component image generating means for extracting a high frequency component from the third nonlinear processed image and outputting a second vertical intermediate image;
The first intermediate image includes the first vertical intermediate image;
The second intermediate image includes the second vertical intermediate image;
The first amplification factor calculation means has first vertical amplification factor calculation means for calculating a first vertical amplification factor according to a pixel value of the first enlarged image,
The first pixel value amplifying means outputs a first vertical pixel that outputs a third vertical intermediate image obtained by amplifying each pixel value of the first vertical intermediate image with the first vertical gain. Having value amplification means,
The second amplification factor calculation means has second vertical amplification factor calculation means for calculating a second vertical amplification factor,
The second pixel value amplifying means outputs a second vertical pixel that outputs a fourth vertical intermediate image obtained by amplifying each pixel value of the second vertical intermediate image at the second vertical gain. Having value amplification means,
The third intermediate image includes the third vertical intermediate image;
The image processing apparatus according to claim 7, wherein the fourth intermediate image includes the fourth vertical intermediate image. The vertical nonlinear processing means includes:
Vertical zero-cross determination means for determining a point where the pixel value of the fourth enlarged image changes from positive to negative or from negative to positive as a zero-cross point;
Vertical direction signal amplification means for amplifying the pixel value of the fourth enlarged image at an amplification factor determined according to the determination result of the vertical direction zero cross determination means,
The image processing apparatus according to claim 13, wherein the third vertical high-frequency component image generation unit extracts a high-frequency component from an image output from the vertical signal amplification unit. The vertical signal amplification means includes
The amplification factor for the pixel value of the pixel existing in the second region including the zero-cross point determined by the vertical zero-cross determination unit is set to a value larger than 1, and the amplification factor for the pixel values of other pixels is set to 1. The image processing apparatus according to claim 14. 16. The image processing apparatus according to claim 15, wherein the second area is determined according to an enlargement ratio in the second image enlargement unit. The image processing apparatus according to claim 15 or 16, wherein an amplification factor for a pixel existing in the second region varies depending on the pixel. The first high frequency component image generation means includes:
First horizontal high-frequency component image generating means for generating a horizontal high-frequency component image using pixel values of pixels existing in the horizontal direction for each pixel of the input image, and a vertical direction for each pixel of the input image First vertical high frequency component image generation means for generating a vertical high frequency component image using pixel values of pixels present in the vicinity;
The second image enlargement means includes:
Third image enlarging means for enlarging the first horizontal high-frequency component image and outputting a third enlarged image;
A fourth image enlarging means for enlarging the first vertical high-frequency component image and outputting a fourth enlarged image;
The second enlarged image includes the third enlarged image and the fourth enlarged image,
The second high frequency component image generating means includes:
A second horizontal high frequency component image generating means for extracting only the high frequency component of the third enlarged image and outputting a first horizontal intermediate image;
A second vertical high frequency component image generating means for extracting only the high frequency component of the fourth enlarged image and outputting the first vertical intermediate image;
The nonlinear processing means includes:
A horizontal nonlinear processing means for outputting a second nonlinear processed image obtained by performing nonlinear processing on the third enlarged image;
Vertical nonlinear processing means for outputting a third nonlinear processed image obtained by performing nonlinear processing on the fourth enlarged image;
The third high frequency component image generation means includes:
Third horizontal high frequency component image generation means for extracting a high frequency component from the second non-linearly processed image and outputting a second horizontal intermediate image;
A third vertical high frequency component image generating means for extracting a high frequency component from the third nonlinear processed image and outputting a second vertical intermediate image;
The first intermediate image includes the first horizontal intermediate image and the first vertical intermediate image;
The second intermediate image includes the second horizontal intermediate image and the second vertical intermediate image;
The first amplification factor calculation means calculates a first horizontal amplification factor according to a pixel value of the first enlarged image, and a pixel of the first enlarged image. First vertical gain calculating means for calculating the first vertical gain according to the value;
The first pixel value amplifying means outputs a first horizontal pixel that outputs a third horizontal intermediate image obtained by amplifying each pixel value of the first horizontal intermediate image at the first horizontal gain. Value amplification means and first vertical pixel value amplification means for outputting a third vertical intermediate image obtained by amplifying each pixel value of the first vertical intermediate image with the first vertical gain. ,
The second gain calculating means includes second horizontal gain calculating means for calculating a second horizontal gain and second vertical gain calculating means for calculating a second vertical gain. Have
The second pixel value amplifying means outputs a second horizontal pixel that outputs a fourth horizontal intermediate image obtained by amplifying each pixel value of the second horizontal intermediate image with the second horizontal gain. Value amplification means and second vertical pixel value amplification means for outputting a fourth vertical intermediate image obtained by amplifying each pixel value of the second vertical intermediate image with the second vertical gain. ,
The third intermediate image includes the third horizontal intermediate image and the third vertical intermediate image;
The image processing apparatus according to claim 7, wherein the fourth intermediate image includes the fourth horizontal intermediate image and the fourth vertical intermediate image. In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
A third high frequency for outputting a third high frequency component image obtained by amplifying each pixel value of the second high frequency component image with a third amplification factor obtained according to the pixel value of the first enlarged image Component image correction means;
In the image processing apparatus having the first enlarged image and the first addition means for adding the third high-frequency component image,
The high frequency component image processing means includes
Second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Nonlinear processed image generation means for outputting a second intermediate image obtained by performing processing including nonlinear processing on the second enlarged image;
Second addition means for adding the first intermediate image and the second intermediate image;
The result of the addition by the second addition means is output from the high frequency component image processing means as the second high frequency component image.   An image display device comprising the image processing device according to claim 1. In an image processing method for enlarging an input image,
A first image enlargement step of enlarging the input image and outputting a first enlarged image;
A first high-frequency component image generation step of extracting a high-frequency component of the input image and generating a first high-frequency component image;
A second image enlargement step of enlarging the first high frequency component image and outputting a second enlarged image;
A high frequency component image processing step of applying processing to the high frequency component image of the second enlarged image;
In the image processing method comprising: the first enlarged image; and a first addition step of adding an image obtained as a result of the processing by the high-frequency component image processing step.
The high frequency component image processing step includes:
A second high-frequency component image generating step for extracting a high-frequency component of the second enlarged image;
A non-linearly processed image generating step for performing processing including non-linear processing on the second enlarged image;
A second addition step of adding the image obtained by the second high-frequency component image generation step and the image obtained by the nonlinear processing image generation step,
The at least one of the image obtained by the second high-frequency component image generation step, the image obtained by the nonlinear processing image generation step, and the image obtained as a result of the second addition step, the first enlargement A high frequency component image correction step for correcting the high frequency component image based on the image;
The high frequency component image correction step includes:
An image processing method, wherein the pixel value of each pixel of the image to be corrected is amplified by an amplification factor obtained according to the first enlarged image.   An image display apparatus that displays an image processed by the image processing method according to claim 21. In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
Non-linear processing image generation means for performing processing including non-linear processing on the second enlarged image;
A high-frequency component image correcting unit that amplifies the pixel value of the image nonlinearly processed by the non-linearly processed image generating unit by an amplification factor determined according to the pixel value of the first enlarged image; and the high-frequency component image correcting unit An image processing apparatus comprising addition means for adding the processed image and the first enlarged image. In an image processing method for enlarging an input image,
A first image enlargement step of enlarging the input image and outputting a first enlarged image;
A first high-frequency component image generation step of extracting a high-frequency component of the input image and generating a first high-frequency component image;
A second image enlargement step of enlarging the first high frequency component image and outputting a second enlarged image;
A non-linearly processed image generating step for performing processing including non-linear processing on the second enlarged image;
A high frequency component image correction step for amplifying the pixel value of the image nonlinearly processed by the nonlinear processing image generation step by an amplification factor determined according to the pixel value of the first enlarged image; and the high frequency component image correction step. An image processing method comprising: an adding step of adding the processed image and the first enlarged image.   An image display device that displays an image processed by the image processing device according to claim 23 or the image processing method according to claim 24.

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