JP5154208B2 - Image signal processing device - Google Patents

Description

  The present invention relates to an image signal processing apparatus that processes a moving image signal that has undergone frame rate conversion, and in particular, by performing image processing by compensating image processing performed on a current frame image with the next frame image. The present invention relates to an image signal processing apparatus capable of improving the quality of moving images while suppressing side effects.

  Some display devices such as liquid crystal displays and CRTs are classified into a hold type and those classified into an impulse type. The liquid crystal display is classified as a hold type, and the CRT is classified as an impulse type. The difference between the two is whether or not each pixel of the display device always has substantially the same luminance for a period of one frame. In the case of CRT, the phosphor of each pixel is instantaneously scanned with an electron beam. The light is emitted in an impulse form only for a short period. On the other hand, each pixel of the liquid crystal display holds the charge obtained from the electrode during scanning in the capacitance of each pixel. Therefore, each pixel of the liquid crystal display maintains substantially the same luminance until the next scanning.

  The characteristics of the hold-type display such as the above-mentioned liquid crystal display provide advantages such as less flicker. On the other hand, when a moving image is displayed, a phenomenon called hold blur is caused by the human eye following the movement of the subject. This causes a problem that the moving image performance is deteriorated, that is, the quality of the displayed moving image is deteriorated.

  As one of the techniques for reducing the hold blur, a moving image signal input to the display device is analyzed, and an intermediate frame image is generated between two frame images continuously input to the display device. A method using frame rate conversion is known. In this method, processing such as block matching is performed on two consecutive frame images included in an input moving image signal whose normal frame rate is 60 frames per second or 50 frames per second, and the two consecutive images are processed. It detects how much the subject has moved between the frame images. Using the detected motion, a corresponding frame image is newly created and inserted between the two consecutive frame images.

  By such a method, the frame rate of the moving image signal is converted to 100 to 120 frames per second, and the moving image signal after the frame rate conversion is output to display the moving image. By increasing the frame rate of the moving image to be displayed, the hold blur is reduced because the time during which each pixel holds a constant luminance is shortened even in the hold-type display. Such a conversion device based on motion detection is disclosed in Patent Document 1, for example.

  Such a technique works effectively if a frame image inserted between two consecutively input frame images, that is, an interpolated frame image can be successfully created. It is difficult to detect the motion required for the image without any contradiction, and an interpolated frame image that is not consistent with the preceding and succeeding frame images may be generated. Further, when the motion to be detected is complicated, the display device becomes complicated.

  As another method for reducing hold blur, a method is known in which frame rate conversion is performed on an input moving image signal, the number of frame images is doubled, and different image processing is performed on each frame image. Although frame rate conversion using motion detection can be used for frame rate conversion in this method, simpler frame rate conversion by outputting two identical input frame images may be used. . Image processing using the target pixel and surrounding pixels, for example, processing for reducing the luminance value of the target pixel for one of the moving image signals whose frame image number has been doubled by frame rate conversion I do. In the image processing using the target pixel and surrounding pixels, if there are many pixels having lower brightness than the target pixel in the surrounding area, the target pixel is also output with lower brightness. Conversely, if there are many pixels with higher brightness than the target pixel in the vicinity, the brightness of the target pixel is also increased. As a result, the time during which each pixel of the display device holds a constant luminance is shortened, and the hold blur is reduced.

  However, since the luminance of the target pixel is influenced by surrounding pixels only by performing the image processing, the frame image subjected to the image processing is greatly different from the frame image included in the input moving image signal. It will be different. Therefore, for the other frame image in the moving image signal in which the number of frame images is doubled, compensation image processing having a function opposite to that of the image processing, for example, processing for increasing the luminance value of the target pixel is performed. I do. With respect to a moving image signal having a frame rate of about 100 to 120 frames per second by frame rate conversion, image processing having the opposite functions is performed and displayed. Accordingly, the human eyes perceive the luminance of the two frame images that have undergone the image processing and the compensation image processing as being integrated, and these two frame images are the frames included in the input moving image signal. It does not look like a frame image that is very different from the image.

  As described above, the frame rate of the input moving image signal is converted by outputting two identical input frame images, and image processing having the opposite functions is performed on each of the two identical input frame images. In this case, since the motion detection is not performed, the display device can be easily configured, and no mismatch occurs between the interpolated frame image and the preceding and following frame images.

  FIG. 7 is a block diagram of a conventional image signal processing apparatus 101 that performs frame rate conversion on an input moving image signal and performs different image processing on each frame image. The frame rate of the input moving image signal is doubled by the frame rate conversion processing unit 102. The moving image signal whose frame rate is doubled is subjected to image processing by the image processing unit 103 using the target pixel and surrounding pixels. The compensation image processing unit 104 uses the output of the image processing unit 103 and the output of the frame rate conversion processing unit 102 to perform image processing having the reverse function of the image processing unit 103. The signal selection unit 105 switches the output of the image processing unit 103 and the output of the compensation image processing unit 104 for each frame image and outputs a moving image signal.

  FIG. 8 is a graph showing the luminance at a certain pixel for displaying the frame image included in the input / output moving image signal processed by the conventional image signal processing apparatus 101, with time as the horizontal axis. In this graph, for simplicity of explanation, it is assumed that the frame rate conversion is performed by a method of outputting the same input image twice.

  R103 and R104 are the luminances of a certain pixel of the frame image constituting the input moving image signal, and the period T during which each of R103 and R104 continues is the period of one frame of the input moving image signal. .

  In this case, since the frame rate conversion is performed by outputting two identical input frame images, the luminance after the frame rate conversion is also R103 and R104, respectively. T / 2 and a frame image having the same luminance is input twice. R101, R102, R106, and R107 are the luminances of the frame images included in the output moving image signal.

  The signal selection unit 105 in FIG. 7 switches the output for each frame image, so that the frame image with the luminance R101 and the frame image with the luminance R106 are output from the image processing unit 103, and the frame image with the luminance R102 and the luminance R107. A frame image is output from the compensation image processing unit 104. By inserting a frame image with luminance R101 and a frame image with luminance R106, hold blur is reduced.

Also, a frame image with luminance R101 and a frame image with luminance R102, or a frame image with luminance R106 and a frame image with luminance R107 are integrated and perceived. Therefore, it is possible to make it appear that the frame images with the luminances R103 and R104 are displayed even though the frame images with the luminances R101, R102, R106, and R107 are actually displayed. .
JP-A-1-309597 (published on December 13, 1991)

  However, an actual display device has a maximum luminance and a minimum luminance that can be displayed, and can only display luminance within the range of both. Therefore, the output of the compensation image processing unit 104 in FIG. 7 may be saturated.

  In FIG. 8, when the luminance R107 of the frame image output from the compensation image processing unit 104 in FIG. 7 exceeds (saturates) the maximum displayable luminance, it is output from the compensation image processing unit 104 in FIG. When the luminance of the frame image is R108, it is as shown in FIG.

  In FIG. 9, as a result of performing image processing for creating a frame image of luminance R106 from a frame image of luminance R104 and reverse image processing for compensation, the luminance of the frame image becomes R107. However, since the luminance R107 exceeds the maximum luminance R108 that can be displayed by the display device, the luminance R107 is saturated at the maximum luminance R108. Therefore, originally, the luminance R106 and the luminance R107 are integrated and perceived as a frame image of the luminance R104, but a frame image of the luminance R105, which is an integration of the luminance R106 and the luminance R108, is perceived.

  In such a case, the display brightness is felt lower than the original at the location where the saturation of the luminance occurs, and if the image is a pure white image, the white is felt darker than the original (white sinking), causing image quality deterioration.

  Similarly, when the output of the compensation image processing unit 104 in FIG. 7 is lower than the minimum displayable luminance, the display luminance is felt higher than the original at the location where the luminance saturation occurs, and the image is a black image. , Black feels brighter than the original (black float), causing image quality degradation.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an image signal processing apparatus capable of preventing deterioration of image quality due to side effects of image processing.

  In order to solve the above problems, an image signal processing apparatus of the present invention is an image signal processing apparatus that converts a frame rate of a moving image to be displayed on a display device, and includes a plurality of frame images composed of a plurality of pixels. A frame rate conversion means for converting the frame rate of the moving image signal to twice, and a plurality of pixels constituting the current frame image in the plurality of frame images, Image processing means for performing image processing using luminance values of the target pixel and surrounding pixels, and image processing opposite to the image processing means for the frame image next to the current frame image A moving image signal by switching between the output of the image processing means for compensation and the output of the image processing means for compensation for each frame image. The image processing includes a first signal limiting unit in an image signal processing apparatus that increases or decreases a luminance value for each of a plurality of pixels constituting the current frame image. The first signal limiting unit compensates the luminance value of the frame image subjected to the image processing using the moving image signal output from the frame rate conversion unit, the image processing unit, and the compensation image processing unit. The luminance value is limited to a possible luminance value, and the average value of the luminance value when the frame image of the luminance value that can be compensated is displayed on the display device and the maximum luminance value that can be displayed by the display device, or the compensation is possible. The average value of the luminance value when the frame image of the luminance value is displayed on the display device and the minimum luminance value that can be displayed by the display device is the frame before the image processing is performed. Wherein the image is a luminance value when viewed in the display device.

  According to the invention, the luminance value of the frame image subjected to the image processing or the luminance value of the frame image subjected to the reverse image processing exceeds the maximum luminance or the minimum luminance that can be displayed by the display device. That is, when saturated, the first signal limiting means limits these luminance values to the compensable luminance values.

  Therefore, when the display device displays the frame image of the luminance value that can be compensated and the frame image of the maximum luminance value, the average value of these two luminances is the frame image before the image processing is performed. It becomes equal to the luminance value when displayed on the display device. Similarly, when the display device displays the frame image having the compensated luminance value and the frame image having the minimum luminance value, the average value of these two luminances is the frame image before the image processing is performed. It becomes equal to the luminance value when displayed on the display device.

  Therefore, the frame image limited to the compensationable luminance value is integrated and perceived, and in the moving image based on the moving image signal output from the signal selection means, white subsidence, which is a phenomenon in which white is felt darker than originally intended, Since black floating, which is a phenomenon in which black is perceived brighter, does not occur, it is possible to prevent deterioration of the image quality of the moving image due to the side effects of the image processing or the reverse side effects of the image processing.

  Further, the image signal processing apparatus includes a second signal limiting unit instead of the first signal limiting unit, and the second signal limiting unit is a moving image output from the frame rate converting unit and the image processing unit. The luminance value of the frame image subjected to the image processing may be limited to the compensable luminance value using a signal.

  Thereby, when the luminance value of the frame image output from the image processing means and input to the second signal limiting means is limited by the second signal limiting means, the output of the compensation image processing means is not necessary. . For this reason, the compensation image processing means can be temporarily stopped. Therefore, it is possible to reduce the power consumption of the image signal processing device and shorten the processing time of the image signal processing device.

  In the image signal processing apparatus, the first signal limiting unit includes a first lookup table, and the first lookup table is a frame in which the luminance of the current frame image and the reverse image processing are performed. Using the brightness of the image, the brightness value of the frame image subjected to the image processing may be limited to a brightness value that can be compensated.

  In the image signal processing apparatus, the second signal limiting unit includes a second look-up table, and the second look-up table is created using the result of the reverse image processing, and the current The luminance value of the frame image subjected to the image processing may be limited to a compensable luminance value by using the luminance of the frame image and the luminance of the frame image subjected to the image processing.

  By having these look-up tables, it is possible to prevent deterioration of the image quality of the moving image due to the side effects of the image processing or the reverse side effects of the image processing.

  As described above, the image signal processing apparatus of the present invention includes the first signal limiting unit, and the first signal limiting unit is output from the frame rate conversion unit, the image processing unit, and the compensation image processing unit. The luminance value of the frame image subjected to the image processing is limited to a compensable luminance value, and the average of the compensable luminance value and the maximum luminance value that can be displayed by the display device The value or the average value of the compensable luminance value and the minimum luminance value that can be displayed by the display device is the luminance value of the frame image before the image processing is performed.

  Therefore, there is an effect of providing an image signal processing device capable of preventing image quality deterioration due to side effects of image processing.

[Embodiment 1]
One embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a block diagram showing the configuration of the image signal processing apparatus 1 of the present embodiment. In FIG. 1, the image signal processing apparatus 1 includes a frame rate conversion processing unit 2, an image processing unit 3, a compensation image processing unit 4, a signal limiting unit 5, and a signal selection unit 6.

  The frame rate conversion processing unit 2 converts the frame rate of the input moving image signal to double. As a frame rate conversion method, a method of outputting two identical frame images, and a motion between two consecutive frame images included in the input moving image signal are detected, and the detected motion is detected. There is a method in which a corresponding image is newly created and inserted between the two consecutive frame images. The frame rate conversion processing unit 2 can apply both of these two methods.

  The image processing unit 3 receives the moving image signal output from the frame rate conversion processing unit 2, and performs image processing using luminance values of the target pixel and surrounding pixels, for example, reduces the luminance value of the target pixel. Process.

  The compensation image processing unit 4 receives the moving image signal output from the frame rate conversion processing unit 2 and the moving image signal output from the image processing unit 3, and converts it into the moving image signal output from the image processing unit 3. Based on this, image processing having the opposite effect to the processing performed by the image processing unit 3, for example, processing for increasing the luminance value of the target pixel is performed on the moving image signal output from the frame rate conversion processing unit 2.

  The signal limiting unit 5 first receives the moving image signal output from the frame rate conversion processing unit 2, the moving image signal output from the image processing unit 3, and the moving image signal output from the compensation image processing unit 4. . Next, the signal limiting unit 5 limits the luminance of the frame image included in the moving image signal output from the image processing unit 3 to a compensationable range based on the received moving image signal.

  Regarding the compensable luminance value described in the present embodiment, an average value of the compensable luminance value and a maximum luminance value that can be displayed by the display device 9 described later, or the compensable luminance value and the display device. The average value of 9 and the minimum luminance value that can be displayed is the luminance value of the frame image before the image processing is performed. As a result, the frame image limited to the compensationable luminance value is integrated and perceived, and in the moving image displayed by the display device 9, white subsidence, which is a phenomenon in which white is felt darker than originally, It does not cause black floating, which is a bright phenomenon, and does not cause image quality degradation.

  Hereinafter, the operation of the signal limiting unit 5 when the luminance of the frame image is saturated in the compensation image processing will be described.

  First, the signal limiting unit 5 does not have the maximum luminance of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 as the maximum luminance that can be displayed by the display device, and the compensation image processing unit 4. When the maximum luminance of the frame image included in the moving image signal output from the display device is the maximum luminance that can be displayed by the display device, the luminance of the frame image included in the moving image signal output from the compensation image processing unit 4 A flag signal (hereinafter simply referred to as a flag signal) indicating that is saturated is made valid. Similarly, the minimum luminance of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 is not the minimum luminance that can be displayed by the display device, and the moving image output from the compensation image processing unit 4 When the minimum luminance of the frame image included in the image signal is the minimum luminance that can be displayed by the display device, the flag signal is validated.

  If neither of the above two applies, the flag signal is invalidated. The flag signal is a signal generated inside the signal limiter 5.

  When the flag signal is invalid, the signal restriction unit 5 outputs the moving image signal output from the image processing unit 3 to the signal selection unit 6 as it is.

  In addition, the signal limiting unit 5 has a two-dimensional lookup table. When the flag signal is valid, the two-dimensional lookup table uses the moving image signal output from the frame rate conversion processing unit 2 and the moving image signal output from the compensation image processing unit 4 as inputs. Thus, a compensationable luminance value is obtained. The signal limiting unit 5 replaces the luminance value of the frame image included in the moving image signal output from the image processing unit 3 with the compensable luminance value and outputs the result.

  The signal limiting unit 5 calculates a value between the luminance value obtained from the two-dimensional lookup table and the luminance value of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 as a signal limiting unit. 5 may be used as the luminance value of the frame image included in the moving image signal output from the video signal 5. As a value between the two, a value intermediate between the luminance value of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 and the luminance value obtained by the two-dimensional lookup table, the frame rate If it is possible to set whether to use a value close to the output of the conversion processing unit 2 or a value close to the output of the two-dimensional lookup table, it can be used as gain control of the signal limiting unit 5.

  Note that the value close to the output of the frame rate conversion processing unit 2 here is a value between the above intermediate value and the luminance value of the frame image included in the moving image signal output from the frame rate conversion processing unit 2. Is the value of Similarly, the value close to the output of the two-dimensional lookup table is a value between the above intermediate value and the luminance value obtained by the two-dimensional lookup table.

  FIG. 2 is a diagram illustrating an example of the two-dimensional lookup table. The luminance of the frame image included in the moving image signal output from the compensation image processing unit 4 is arranged in the vertical direction (Y direction) in the first column from the left of the two-dimensional lookup table, and the frame rate conversion processing unit 2 The luminances of the frame images included in the output video signal are arranged in the horizontal direction (X direction) in the first line from the top. Also, the numerical value of the intersection of the luminance of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 and the luminance of the frame image included in the moving image signal output from the compensation image processing unit 4 is The luminance of the frame image included in the moving image signal output from the image processing unit 3 is shown. As the numerical value of the intersection point, a value calculated or measured in consideration of characteristics of a display or the like is input in advance.

  Only when the luminance value of the frame image included in the moving image signal output from the compensation image processing unit 4 is the minimum value that the display device can display or the maximum value that the display device can display, this two-dimensional Since the look-up table operates, the number of elements in the vertical direction is two. The number of elements in the horizontal direction depends on the bit width of the luminance value of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 when the signal limiting unit 5 is realized by a digital signal processing circuit. When the luminance value of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 is 8 bits / pixel, the number of elements in the horizontal direction is 256.

  It is possible to reduce the number of elements by thinning out the number of elements in the horizontal direction at a certain interval instead of having all the values of the pixels. The thinned value is obtained from the values of neighboring elements using an interpolation method such as linear interpolation. In the example of FIG. 2, in the horizontal direction, the luminance value is 8 bits / pixel, and thinned out every 32.

  The values used as the elements of the two-dimensional lookup table are the same image processing as the image processing unit 3 and the same compensation image processing as the compensation image processing unit 4 in advance for all the discretized pixel values, It can be created by determining whether the luminance value of the frame image included in the moving image signal output from the compensation image processing unit 4 is saturated. This processing may be performed using an actual image processing apparatus, or equivalent processing may be performed by a program on a computer. The values used as elements of the two-dimensional lookup table are newly determined based on the configuration of the image processing performed by the image processing unit 3 and the compensation image processing performed by the compensation image processing unit 4 and parameters, and the image signal processing device 1. You need to create it when you start using it. Examples of the parameter include a maximum value and a minimum value of luminance that can be displayed by the display device, and an interval between two consecutive elements.

  As described above, the operation of the signal limiting unit 5 when the luminance of the frame image is saturated in the compensation image processing has been described. However, the operation of the signal limiting unit 5 when the luminance of the frame image is saturated in the image processing. The same applies to. In this case, the signal restriction unit 5 restricts the luminance value of the frame image in the moving image signal output from the image processing unit 3, and the compensation image processing unit 4 performs the compensation image processing. Can be output as is. This process is performed simultaneously to determine whether or not the luminance of the frame image included in the moving image signal output from the image processing unit 3 is within a compensationable range and to limit the luminance. equal. When performing this processing, the luminance of the frame image included in the moving image signal output from the image processing unit 3 and the luminance of the frame image included in the moving image signal output from the frame rate conversion processing unit 2 A two-dimensional lookup table based on the above may be used.

  The signal selection unit 6 switches and outputs the moving image signal coming from the image processing unit 3 via the signal limiting unit 5 or the moving image signal coming from the compensation image processing unit 4 for each frame image. The moving image signal output from the signal selection unit 6 has a frame rate twice that of the moving image signal input to the frame rate conversion processing unit 2, and different image processing is alternately applied to each frame image. The obtained moving image signal.

  FIG. 3 is a graph showing the luminance at a certain pixel for displaying a frame image included in the input / output moving image signal processed by the image signal processing apparatus 1 with the horizontal axis as time. The luminance of the input moving image signal is R4. When frame rate conversion is performed by a method of outputting the same frame image two by two, the luminance of the frame image generated by the frame rate conversion processing unit 2 is also R4. is there.

  In FIG. 3, a period T in which R4 continues is a period of one frame of the input video signal. As described above, since the frame rate conversion is performed by outputting the same input frame image two by two, the luminance after the frame rate conversion is also R4. A frame image having T / 2 and the same luminance is input twice.

  The luminance of the frame image obtained by performing image processing in the image processing unit 3 on the frame image included in the moving image signal output from the frame rate conversion processing unit 2 is R6. In order to correspond to the luminance R6, the luminance of the frame image obtained by performing the compensation image processing on the frame image of the luminance R4 should be originally R7. However, since the luminance value of the frame image included in the moving image signal is limited to the range between the maximum luminance that can be displayed by the display device and the minimum luminance that can be displayed by the display device, the compensation image processing unit The luminance of the frame image subjected to the compensation image processing according to 4 is R8.

  Since the luminance R8 is saturated, a frame image having the luminance R6 and a frame image having the luminance R8 are output. When these are integrated and perceived, the luminance is close to the luminance R5 and should be perceived originally. A luminance different from the luminance R4 is perceived. Therefore, the luminance is limited by the signal limiting unit 5, and the luminance of the frame image output from the signal limiting unit 5 is R9.

  Therefore, as a moving image signal output from the signal selection unit 6, a frame image having the luminance R9 and a frame image having the luminance R8 are output, and these are integrated and perceived, so that the luminance close to the luminance R4 is perceived. Is done.

  In FIG. 3, the case where the luminance R7 is saturated at the maximum displayable luminance of the display device and becomes the luminance R8 has been described, but the same applies to the case where the luminance is saturated at the minimum luminance displayable by the display device. . That is, the luminance limited by the signal limiting unit 5 and the minimum luminance are integrated and perceived, so that the original luminance, that is, luminance close to the luminance before image processing and compensation image processing are performed is perceived. As described above, the signal limiting unit 5 may limit the luminance.

  Furthermore, when the average is taken at the output of the image signal processing apparatus 1 of the present embodiment, the original luminance is theoretically obtained, but actually, the original luminance is not obtained. This is because the average value of the luminance displayed on the display device 9 using the output of the image signal processing device 1 includes a calculation error, and the average value is not exactly the same as the original luminance value. The value is close to the original luminance.

〔Example〕
An example of the display device in this embodiment is shown in FIG. The display device 9 includes an image signal processing device 1, a display processing unit 10, and a display unit 11. A moving image signal is input to the image signal processing apparatus 1. A moving image signal that has been subjected to image processing by the image signal processing apparatus is input to the display processing unit 10. The display processing unit 10 outputs the input moving image signal and a control signal for controlling the display unit 11 to the display unit 11. Thereby, a moving image can be displayed on the display unit 11. In the present embodiment, the image signal processing device 1 is built in the display device 9. However, the present invention is not limited to this, and the image signal processing device 1 may be provided outside the display device 9.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. The configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  FIG. 5 is a block diagram showing the configuration of the image signal processing device 7 of the present embodiment. In FIG. 5, the image signal processing device 7 includes a frame rate conversion processing unit 2, an image processing unit 3, a compensation image processing unit 4, a signal limiting unit 8, and a signal selection unit 6.

  The signal limiting unit 8 receives the moving image signal output from the frame rate conversion processing unit 2 and the moving image signal output from the image processing unit 3, and outputs the moving image signal output from the image processing unit 3 to the next Limit to the range that can be compensated by the frame.

  The signal limiting unit 8 has a two-dimensional lookup table. This two-dimensional lookup table is created including the compensation image processing performed by the compensation image processing unit 4. The two-dimensional lookup table is output from the moving image signal output from the frame rate conversion processing unit 2 and the image processing unit 3. By using a moving image signal as an input, a compensable luminance value is obtained. The signal limiting unit 8 replaces the luminance value of the frame image included in the moving image signal output from the image processing unit 3 with the above compensable luminance value and outputs the result. This process is equivalent to simultaneously determining whether or not the luminance value of the frame image included in the moving image signal output from the image processing unit 3 can be compensated and limiting the luminance.

  As described above, unlike the two-dimensional lookup table described in the first embodiment, the two-dimensional lookup table described in the second embodiment uses the compensation image processing result performed by the compensation image processing unit 4. Has been created. Therefore, the signal limiting unit 8 can simultaneously determine whether the luminance value of the frame image included in the moving image signal output from the image processing unit 3 can be compensated and limit the luminance. It becomes possible.

  The signal limiting unit 8 determines a value between the luminance value obtained from the two-dimensional lookup table and the luminance value of the frame image included in the moving image signal output from the image processing unit 3 from the signal limiting unit 8. A configuration may be used in which the luminance value of the frame image included in the output moving image signal is used. As a value between them, the luminance value of the frame image included in the moving image signal output from the image processing unit 3 and the luminance value obtained by the two-dimensional lookup table are just intermediate values, the image processing unit 3 If it is possible to set whether to use a value close to the output or a value close to the output of the two-dimensional lookup table, it can be used as gain control of the signal limiting unit 8.

  The value close to the output of the image processing unit 3 here is a value between the above intermediate value and the luminance value of the frame image included in the moving image signal output from the image processing unit 3. . Similarly, the value close to the output of the two-dimensional lookup table is a value between the above intermediate value and the luminance value obtained by the two-dimensional lookup table.

  FIG. 6 is a diagram showing an example of the two-dimensional lookup table. The luminances of the frame images included in the moving image signal output from the image processing unit 3 are arranged in the vertical direction (Y direction) in the first column from the left of the two-dimensional lookup table, and output from the frame rate conversion processing unit 2 The luminances of the frame images included in the moving image signal are arranged in the horizontal direction (X direction) in the first line from the top.

  The number of elements in each of the vertical direction and the horizontal direction is the bit width of the luminance value of the frame image included in the moving image signal output from the image processing unit 3 and the frame when the signal limiting unit 8 is realized by a digital signal processing circuit. This depends on the bit width of the luminance value of the frame image included in the moving image signal output from the rate conversion processing unit 2. When these luminance values are both 8 bits / pixel, 256 elements are required in the vertical and horizontal directions. In each of the vertical direction and the horizontal direction, the number of elements can be reduced by thinning out at a certain interval instead of having all the values of the pixels. The thinned value is obtained from the values of neighboring elements using an interpolation method such as linear interpolation. In the example of FIG. 6, the luminance value is 8 bits / pixel in each of the vertical direction and the horizontal direction, and thinned out every 32.

  The values used as the elements of the two-dimensional lookup table are the same image processing as the image processing unit 3 and the same compensation image processing as the compensation image processing unit 4 in advance for all the discretized pixel values, It can be created by determining whether the luminance value of the frame image included in the moving image signal output from the compensation image processing unit 4 is saturated. This processing may be performed using an actual image processing apparatus, or equivalent processing may be performed by a program on a computer. The values used as the elements of the two-dimensional lookup table are newly determined based on the configuration of the image processing performed by the image processing unit 3 and the compensation image processing performed by the compensation image processing unit 4 and parameters, and the image signal processing device 7. You need to create it when you start using it. Examples of the parameters include a maximum value and a minimum value of brightness that can be displayed by a display device (not shown) that displays a moving image based on a moving image signal output from the signal selection unit 6, and an interval between two consecutive elements.

  When the luminance value of the frame image output from the image processing unit 3 and input to the signal limiting unit 8 is limited by the signal limiting unit 8, the output of the compensation image processing unit 4 is not necessary. Therefore, the compensation image processing unit 4 can be temporarily stopped. As a result, the power consumption of the image signal processing device 7 can be reduced, and the processing time of the image signal processing device 7 can be shortened.

[Summary of Embodiment]
An image signal processing device 1 according to an embodiment of the present invention is an image signal processing device that converts a frame rate of a moving image to be displayed on a display device 9 and includes a plurality of frame images including a plurality of pixels. A frame rate conversion processing unit 2 that converts a frame rate of the moving image signal to twice, and a plurality of pixels constituting the current frame image in the plurality of frame images, Image processing unit 3 that performs image processing using luminance values of the target pixel and surrounding pixels, and image processing that is the reverse of image processing unit 3 for the frame image that follows the current frame image Image processing unit 4 for performing the compensation, and signal selection for outputting a moving image signal by switching the output of the image processing unit 3 and the output of the compensation image processing unit 4 for each frame image The image processing is a process for increasing or decreasing the luminance value for each of a plurality of pixels constituting the current frame image. The image signal processing apparatus includes a signal limiting unit 5 and a signal limiting unit 5. Uses the moving image signals output from the frame rate conversion processing unit 2, the image processing unit 3, and the compensation image processing unit 4 to limit the luminance value of the frame image subjected to the image processing to a luminance value that can be compensated. Then, the average value of the luminance value when the display device 9 displays the frame image having the compensable luminance value and the maximum luminance value that can be displayed by the display device 9, or the frame image having the compensable luminance value is obtained. The average value of the luminance value when displayed on the display device 9 and the minimum luminance value that can be displayed by the display device 9 is the luminance value when the frame image before the image processing is displayed on the display device 9. Image signal processing apparatus according to claim.

  According to the above configuration, the luminance value of the frame image subjected to the image processing or the luminance value of the frame image subjected to the reverse image processing exceeds the maximum luminance or the minimum luminance that can be displayed by the display device 9, That is, when saturated, the signal limiting unit 5 limits these luminance values to the above compensable luminance values.

  Therefore, when the display device 9 displays the frame image having the above-described compensationable luminance value and the frame image having the maximum luminance value, the average value of these two luminances is the frame image before the image processing is performed. It becomes equal to the luminance value when displayed on the display device. Similarly, when the display device 9 displays the frame image with the above-mentioned compensationable luminance value and the frame image with the minimum luminance value, the average value of these two luminances is the frame image before the image processing is performed. It becomes equal to the luminance value when displayed on the display device.

  Therefore, the frame image limited to the compensationable luminance value is integrated and perceived, and in the moving image based on the moving image signal output from the signal selection unit 6, white subsidence, which is a phenomenon in which white is felt darker than originally intended, Since black floating, which is a phenomenon in which black is perceived brighter, does not occur, it is possible to prevent deterioration of the image quality of the moving image due to the side effects of the image processing or the reverse side effects of the image processing.

  Further, the image signal processing apparatus 7 includes a signal limiting unit 8 instead of the signal limiting unit 5, and the signal limiting unit 8 uses the moving image signals output from the frame rate conversion processing unit 2 and the image processing unit 3. The luminance value of the frame image subjected to the image processing may be limited to the compensable luminance value.

  Thereby, when the signal limiting unit 8 limits the luminance value of the frame image output from the image processing unit 3 and input to the signal limiting unit 8, the output of the compensation image processing unit 4 is not necessary. Therefore, the compensation image processing unit 4 can be temporarily stopped. Therefore, the power consumption of the image signal processing device 7 can be reduced, and the processing time of the image signal processing device 7 can be shortened.

  In the image signal processing device 1, the signal limiting unit 5 has a first lookup table, and the first lookup table includes the luminance of the current frame image and the frame image subjected to the reverse image processing. The luminance value of the frame image subjected to the image processing may be limited to a luminance value that can be compensated using luminance.

  Further, in the image signal processing device 7, the signal limiting unit 8 has a second lookup table, and the second lookup table is created using the result of the reverse image processing, and the current frame image And the brightness of the frame image subjected to the image processing may be used to limit the brightness value of the frame image subjected to the image processing to a brightness value that can be compensated.

  By having these look-up tables, it is possible to prevent deterioration of the image quality of the moving image due to the side effects of the image processing or the reverse side effects of the image processing.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Such embodiments are also included in the technical scope of the present invention.

  Since the present invention can prevent deterioration of image quality due to side effects of image processing, it can be suitably used for display devices such as liquid crystal displays and CRTs.

1 is a block diagram of an image signal processing apparatus according to an embodiment of the present invention. It is a figure which shows an example of the two-dimensional lookup table which concerns on embodiment of this invention. It is a graph showing the brightness | luminance in a certain 1 pixel which displays the frame image contained in the input-output moving image signal processed by the image signal processing apparatus concerning embodiment of this invention. 1 is a block diagram of a display device according to an embodiment of the present invention. It is a block diagram of the image signal processing apparatus which concerns on other embodiment of this invention. It is a figure which shows an example of the two-dimensional lookup table which concerns on other embodiment of this invention. It is a block diagram of the conventional image signal processing apparatus. It is the graph showing the brightness | luminance in a certain 1 pixel which displays the frame image contained in the input-output moving image signal processed by the conventional image signal processing apparatus. It is a graph which shows that the brightness | luminance in a certain 1 pixel which displays the frame image contained in the input-output moving image signal processed by the conventional image signal processing apparatus was saturated.

Explanation of symbols

1, 7 Image signal processing device 2 Frame rate conversion processing unit (frame rate conversion means)
3 Image processing unit (image processing means)
4 Compensation image processing unit (compensation image processing means)
5 signal limiter (first signal limiter)
6 Signal selection part (signal selection means)
8 Signal limiter (second signal limiter)
9 Display Device 10 Display Processing Unit 11 Display Unit R4, R5, R6, R7, R8, R9 Luminance T Period

Claims (3)

An image signal processing device for converting a frame rate of a moving image to be displayed on a display device,
By converting the frame rate of a moving image signal composed of a plurality of frame images composed of a plurality of pixels to twice, the luminance value of each pixel from each frame image corresponds to each pixel corresponding to that frame image Frame rate conversion means for generating a first frame image and a second frame image following the first frame image, the same as the luminance value of
First luminance value changing means for increasing or decreasing the luminance value of each pixel of the first frame image;
The luminance value of each pixel of the second frame image is changed , and the average value of the luminance value of each pixel after the change and the luminance value of each pixel changed by the first luminance value changing means is a frame rate conversion. Second luminance value changing means for changing the luminance value of each pixel of the second frame image so as to be a display luminance value when the previous frame image is displayed on the display device;
Signal selection means for outputting a moving image signal by switching between the output of the first luminance value changing means and the output of the second luminance value changing means for each frame image ;
When the luminance value of each pixel of the second frame image changed by the second luminance value changing unit exceeds the maximum luminance value that can be displayed by the display device, the luminance value changed by the first luminance value changing unit is changed. The luminance value of each pixel of the first frame image is limited to a limited luminance value such that an average value of the luminance value and the maximum luminance value that can be displayed by the display device is the display luminance value , or the first When the luminance value of each pixel of the second frame image changed by the two luminance value changing means exceeds the minimum luminance value that can be displayed by the display device, the first luminance value changing means changes the first luminance value. Signal limiting means for limiting the luminance value of each pixel of the frame image to a limiting luminance value such that an average value of the luminance value and the minimum luminance value that can be displayed by the display device is the display luminance value ; are things Image signal processing apparatus according to claim. Upper relaxin No. limiting means stores the brightness value of each pixel of the first frame image output from the frame rate conversion means, the limit brightness value corresponding to the above maximum luminance value or the minimum luminance value And the luminance value of each pixel of the first frame image output from the frame rate conversion means and the luminance value of each pixel of the second frame image changed by the second luminance value changing means. A first look-up table for outputting the limited brightness value corresponding to the maximum brightness value or the minimum brightness value ;
2. The luminance value of each pixel of the first frame image changed by the first luminance value changing means is replaced with the limited luminance value output from the first look-up table and output. 2. An image signal processing apparatus according to 1. Upper relaxin No. limiting means, the luminance value of each pixel of the second frame image output from the frame rate conversion means, for each pixel of the modified the first frame image by the first luminance value change means The limited brightness value corresponding to the brightness value is stored, the brightness value of each pixel of the second frame image output from the frame rate conversion means, and the brightness value changed by the first brightness value changing means A second lookup table that outputs the limited brightness value corresponding to the brightness value of each pixel of the first frame image ;
Claim, characterized in that is replaced with the above limit luminance value of the luminance value of each pixel of the modified the first frame image output from the second look-up table by the first luminance value changing means 1 2. An image signal processing apparatus according to 1.

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