JP4130885B2 - Solid-state imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state imaging device that performs contour enhancement processing on a readout signal from a solid-state imaging device such as a CMOS.
[0002]
[Prior art]
A conventional contour enhancement device is disclosed in, for example, “Solid-State Imaging Device” of Patent Document 1. A conventional contour emphasis device will be described below. FIG. 11 shows a configuration of a conventional contour emphasizing device, which includes a lens 20, a solid-state imaging device 21, a CDS circuit 22, an AGC circuit 23, a white balance circuit 24, a luminance signal synthesis circuit 25, an original signal aperture circuit 26, and a color signal. The circuit includes a ratio detection circuit 27, a color signal synthesis circuit 28, a luminance signal aperture control circuit 29, a delay circuit 30, variable gain amplification circuits 311 and 312, and addition circuits 321 and 322. An original signal aperture control circuit 26 that forms an edge enhancement signal from the signals of the R pixel, G pixel, and B pixel, and a luminance signal aperture control circuit that forms an edge enhancement signal from the luminance signal synthesized from the signals of the R pixel, G pixel, and B pixel. 29, and weights the output signal of the original signal aperture control circuit and the output signal of the luminance signal aperture control circuit in accordance with the detection output of the color signal ratio detection circuit 27, and then weights each of the weighted signals. An edge emphasis signal is obtained by addition.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-23437
[Problems to be solved by the invention]
However, in the conventional contour emphasizing apparatus as shown in the above publication, when color filters arranged in a checkered pattern used in a single-panel color camera are used, the luminance signal is weighted for the boundary of chromatic colors. Since the generated outline emphasis signal is generated, a jagged edge is generated at the boundary of the chromatic color, causing the image quality to deteriorate.
[0005]
An object of the present invention is to provide a fixed imaging device that can reduce the jaggedness that occurs at the boundary of chromatic colors and that can improve the resolution.
[0006]
[Means for Solving the Problems]
The solid-state imaging device according to the present invention includes a G signal contour enhancement signal generation circuit that generates a contour enhancement signal from a G pixel signal (G signal) among the color signals of the R pixel, G pixel, and B pixel of the solid-state imaging device. And a synthesis ratio of the output signal of the all-signal contour enhancement signal generation circuit and the output signal of the all-signal contour enhancement signal generation circuit, all the contour enhancement signal generation circuit that generates the contour enhancement signal from all the color signals, An edge emphasis signal synthesizing circuit that determines and synthesizes the output signal of the color signal, and adds a signal synthesized by the edge emphasis signal synthesizing circuit to the luminance signal from the solid-state imaging device as an edge emphasis signal. It has the composition to provide.
With this configuration, an edge emphasis signal can be generated in a solid-state imaging device provided with color filters arranged on a checkered pattern.
[0007]
In the solid-state imaging device according to the present invention, the G signal edge enhancement signal generation circuit is provided in a stage preceding the horizontal edge enhancement signal generation circuit that generates a horizontal edge enhancement signal from the G signal and the horizontal edge enhancement signal generation circuit. A configuration including a vertical low-pass filter, a vertical contour emphasis signal generation circuit that generates a vertical contour emphasis signal from the G signal, and a horizontal low-pass filter that is provided at a subsequent stage of the vertical contour emphasis signal generation circuit ing.
With this configuration, the contour emphasis signal can be smoothed only with respect to the oblique edge of the subject that is prominent, so that the jaggedness can be reduced while minimizing the decrease in resolution.
[0008]
Furthermore, the solid-state imaging device of the present invention has a configuration in which the vertical low-pass filter and the horizontal low-pass filter can independently determine whether to apply horizontal contour enhancement and vertical contour enhancement.
With this configuration, it is possible to easily select whether to give priority to reduction of the jaggedness generated at the oblique edge of the subject or to give priority to the resolution of the subject depending on the usage application of the solid-state imaging device including the contour enhancement device of the present invention. .
[0009]
Furthermore, in the solid-state imaging device of the present invention, the contour emphasis signal synthesizing circuit determines the synthesis ratio of the output signal of the G signal contour emphasis signal generation circuit and the output signal of the all signal contour emphasis signal generation circuit as the color signal ( It is determined by the level difference between the R signal and the G signal and the level difference between the B pixel signal (B signal) and the G signal.
With this configuration, since the level difference between the R signal and the G signal after color separation and the level difference between the B signal and the G signal are used for chromatic color and achromatic color determination, the determination of chromatic color and achromatic color is performed with high accuracy. be able to.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a solid-state imaging device including an edge emphasis device according to an embodiment of the present invention. The solid-state imaging device includes a solid-state imaging device 2 that captures an image through a lens 1, an OB correction circuit (OB) 3 that adjusts a black level with respect to an output signal from the solid-state imaging device 2, and an OB correction circuit 3. A shading correction circuit (shad) 4 that corrects the peripheral light loss of the lens with respect to the output signal, a white balance circuit (WB) 5 that adjusts white balance with respect to the output signal of the shading correction circuit 4, and a white balance circuit 5 An AGC circuit (AGC) 6 that performs automatic gain control on the output signal, a gamma correction circuit (γ) 7 that performs gamma correction on the output signal of the AGC circuit 6, and an output signal of the gamma correction circuit 7 The horizontal inversion circuit 8 that controls whether or not to perform reverse readout in the horizontal direction and the output signals of the left and right inversion circuit 8 are delayed from 1H to 3H. And H delay circuit (1HRAM) 91~93, and a defective pixel correction circuit 10 for correcting the defective pixel by using the output signal of the output signal and the 1H delay circuit 91 to 93 of the left and right inversion circuit 8. Assuming a solid-state imaging device having a color filter array as shown in FIG. 2, the a signal, b signal, c signal, and d signal in FIG. 1 are signals as shown in FIG.
[0011]
Furthermore, a luminance signal generation circuit 11 that generates a luminance signal using the output signal of the defective pixel correction circuit 10 and a delay adjustment circuit (delay) 12 that adjusts the delay of the output signal of the luminance signal generation circuit are provided. A G pixel sample and hold circuit (GS / H) 13 that samples only G pixels of the output signal of the pixel correction circuit 10 and an addition circuit 202 to add two upper and lower lines of the output signal of the G pixel sample and hold circuit 13 203 and a G signal contour emphasis signal generation circuit 14 for generating an edge emphasis signal from the output signals of the adder circuits 202 to 203, and three types of R pixel, G pixel, and B pixel of the output signal of the defective pixel correction circuit 10 An all-signal contour emphasis generating circuit 15 that generates an edge emphasizing signal using all the signals of the pixels, a G signal contour emphasizing signal generating circuit 14, and an all-signal contour emphasizing signal. An edge emphasis signal synthesis circuit 16 that synthesizes the respective edge emphasis signals output from the synthesis circuit 15, and an addition circuit 201 that adds the output signal of the delay adjustment circuit 12 and the output signal of the edge emphasis signal synthesis circuit 16. . Specifically, signals (b signal and c signal in FIG. 1) output from the defective pixel correction circuit 10 are input to the luminance signal generation circuit 11.
Luminance signal Y ′ = (R + 2G + B) / 4
Is output after being subjected to processing such as gain adjustment and offset adjustment. The luminance signal Y ′ is subjected to timing adjustment with the color difference signal by the delay adjustment circuit 12, added to the contour enhancement signal by the addition circuit 201, and output as the final luminance signal Y.
[0012]
The color separation circuit 17 that performs color separation using the output signal of the defective pixel correction circuit 10, the color difference signal generation circuit 18 that generates a color difference signal from the output signal of the color separation circuit 17, and the output signal of the color difference signal generation circuit 18 A color difference signal multiplexing circuit 19 for multiplexing is provided. Specifically, the a signal, b signal, c signal, and d signal in FIG. 1 that are the outputs of the defective pixel correction circuit 10 are input to the color separation circuit 17. In the color separation circuit 17, the level difference (R−) between the signal from the R pixel (R signal) and the signal from the G pixel (G signal) from the four signals of the a signal, b signal, c signal, and d signal. G), the level difference (B−G) between the signal from the B pixel (B signal) and the signal from the G pixel (G signal) is calculated and output.
In the color difference signal generation circuit 18, from the input RG and BG,
U = (B−G) −α (R−G)
V = (R−G) −β (B−G)
And converted to U and V and output.
Further, the two signals U and V output from the color difference signal generation circuit 18 are multiplexed by the color difference signal multiplexing circuit 19 and output alternately as U, V, U, V.
[0013]
Next, the outline emphasis device in the present invention will be described.
The a signal, b signal, c signal, and d signal in FIG. 1 that are the outputs of the defective pixel correction circuit 10 are input to the G pixel sample and hold circuit 13. FIG. 4 shows the operation of the G pixel sample and hold circuit. FH2 shown in FIG. 4 is a signal that repeats “1” and “0” for each line, and CK2 is a signal that repeats “1” and “0” for each pixel. CK2 repeats normal rotation and inversion according to the polarity of FH2. That is, CK2 is a signal that is always “1” at the timing of the G pixel in the signals a, b, c, and d in FIG. According to CK2, the G pixel sample / hold circuit 13 samples the pixel when CK2 is “1”, and holds the pixel when it is “0” (FIG. 4A). As a result, the output of the G pixel sample and hold circuit 13 becomes the e signal, the f signal, the g signal, and the h signal in FIG. Here, the e signal, the f signal, the g signal, and the h signal are outputs corresponding to the a signal, the b signal, the c signal, and the d signal, respectively. In this way, it is possible to extract only G from the signals input alternately with G, B, G, B... (Or R, G, R, G...).
[0014]
The output e signal, f signal, g signal, and h signal of the G pixel sample and hold circuit 13 are added to the upper and lower lines by the second to fourth adders 202 to 204 as shown in FIG. The output signals i, j, and k of the second to fourth adders 202 to 204 are input to the G signal contour emphasis signal generation circuit 14. FIG. 5 shows details of the G signal outline emphasis signal generation circuit. A vertical low-pass filter (hereinafter, referred to as a vertical LPF) 141 is composed of three taps, and has an effect of reducing the jagged edges of a horizontal edge enhancement signal. Whether the vertical LPF 141 is applied or not can be selected by the selector 149, but the application of the vertical LPF 141 can further reduce the jagged edges. The horizontal outline emphasis signal generation circuit 142 is a filter that generates an outline emphasis signal in the horizontal direction, and is configured with three taps. The vertical outline emphasis signal generation circuit 143 is a filter that generates an outline emphasis signal in the vertical direction, and is configured with three taps.
[0015]
Each of the horizontal low-pass filter (hereinafter referred to as horizontal LPF) 144 and the horizontal LPF 145 is composed of three taps, and has an effect of reducing the jagged edges of the vertical edge enhancement signal. Whether or not to apply the horizontal LPF 144 and the horizontal LPF 145 to the contour emphasis signal can be selected by the selector 1410. However, when both the horizontal LPF 144 and the horizontal LPF 145 are applied, the jaggedness can be reduced most. The horizontal contour emphasis signal and the vertical contour emphasis signal generated by the filter are subjected to noise removal by the coring circuits 1411 and 1412, gain adjustment is performed by the multiplication circuits 1413 and 1414, and the horizontal contour emphasis signal and the vertical contour are added by the addition circuit 1415. It is output after the enhancement signal is added.
[0016]
FIG. 6 is an explanatory diagram showing how a contour emphasis signal is generated in each filter when an oblique edge is input as a subject. In FIG. 6, the filter coefficient FIL1 is a filter coefficient when all of the vertical LPF 143, the horizontal LPF 144, and the horizontal LPF 145 of FIG. 5 are not passed, and is derived by being calculated as shown in FIG. The filter coefficient FIL2 is a filter coefficient when passing through the vertical LPF 143 and the horizontal LPF 144, and is derived by calculation as shown in FIG. 7B. The filter coefficient FIL3 is a filter coefficient when all of the vertical LPF 143, the horizontal LPF 144, and the horizontal LPF 145 are passed through and is derived by being calculated as shown in FIG. Here, the addition of the two filter coefficients shown in FIG. 7 is performed by adding together the filter coefficients in the same row and the same column. For example, in FIG. 7A, the filter coefficient of 2 rows and 2 columns of the filter FIT1 is 2 + 2 = 4. Also, the multiplication of the two filter coefficients is obtained by multiplying and adding the rows and columns of the respective filter coefficients in the same manner as general matrix calculation.
[0017]
The contour emphasis signals AP1, AP2, and AP3 in FIG. 6 are diagrams showing the values of the contour emphasis signal when the filter coefficients FIL1, FIL2, and FIL3 are passed through the area A, respectively. Passing filter coefficients FIL1, FIL2, and FIL3 in area A in FIG. 6 means multiplying and adding the coefficients of each filter to each pixel in area A. For example, when the filter coefficient FIL1 is passed through the pixel in the upper right corner of the area A in FIG. 6, the calculation formula is the pixel value in the upper right corner of the contour enhancement signal AP1 = 4 × 1 + 0 × 0 + (− 1) × 1 + 0. X1 + (-1) x1 + (-1) x1 + 0x1 + (-1) x1 + 0x1 = 0. Similar calculations are performed for the other pixels in area A to calculate contour emphasis signals AP1, AP2, AP3. As shown in FIG. 6, in the contour emphasis signal AP1, the amplitude of the contour emphasis signal at the oblique edge portion of the subject is large and the degree of change is large, whereas the contour when passing through all of the vertical LPF 143, horizontal LPF 144, and horizontal LPF 145 is shown. It can be seen that the emphasis signal AP3 is smaller than the contour emphasis signal AP1 in both the amplitude and the degree of change of the contour emphasis signal, and as a result, it is possible to reduce the jaggedness generated at the oblique edge.
[0018]
FIG. 8 is an explanatory diagram showing how a contour emphasis signal is generated in each filter when a vertical edge is input as a subject. In FIG. 8, contour emphasis signals AP4, AP5, AP6 are diagrams showing values of the contour emphasis signal when the file coefficients FIL1, FIL2, and FIL3 are passed through area A, respectively. As shown in FIG. 8, it can be seen that the amplitude and the degree of change of the edge emphasis signal do not change with respect to the vertical edge when any of the file coefficients FIL1, FIL2, and FIL3 is passed. FIG. 9 is an explanatory diagram showing how a contour emphasis signal is generated in each filter when a horizontal edge is input as a subject. In FIG. 9, contour emphasis signals AP4, AP5, AP6 are diagrams showing the values of the contour emphasis signal when filter coefficients FIL1, FIL2, FIL3 are passed through area A, respectively. As shown in FIG. 9, the amplitude and the degree of change of the contour emphasis signal are not changed on the basis of the same principle as that of the vertical edge even when the filter coefficients FIL1, FIL2, and FIL3 are passed. Recognize. From the above, the vertical LPF 141, the horizontal LPF 144, and the horizontal LPF 145 in FIG. 4 have the effect of smoothing the contour enhancement signal only for the oblique edge of the subject that is easily noticeable, and these LPFs reduce the resolution. Giza can be reduced while minimizing.
[0019]
Further, the b signal and the c signal in FIG. 1 which are the outputs of the defective pixel correction circuit 10 are input to the all-signal outline enhancement signal generation circuit 15. FIG. 10 is a diagram showing details of the all-signal outline enhancement signal generation circuit. Horizontal high-pass filters (hereinafter referred to as horizontal HPFs) 151 and 152 are configured with two taps. The horizontal contour emphasizing signal is generated by passing the horizontal HPFs 151 and 152 to the b signal and the c signal, respectively, and then adding the two lines of signals by the adding circuit 154. The vertical high-pass filter (hereinafter referred to as vertical HPF) 153 is composed of 2 taps. The vertical contour emphasis signal is a signal obtained by delaying the signal after passing through the vertical HPF 153 and the signal after passing through the vertical HPF 153 by 1T delay circuit 1513 by the 1T delay circuit 1513 after receiving the signals b and c as inputs. It is generated by adding in the adding circuit 155. The horizontal contour emphasis signal and the vertical contour emphasis signal are respectively subjected to noise removal by coring circuits 158 and 159, gain adjustment is performed by multiplication circuits 1510 and 1511, and horizontal contour emphasis signal and vertical contour emphasis signal are added by an adder circuit 1512. Is output after addition.
[0020]
The output signal of the G signal contour enhancement generation circuit 14 (the l signal in FIG. 1) and the output signal of the entire signal contour enhancement generation circuit 15 (the m signal in FIG. 1) are input to the contour enhancement signal synthesis circuit 16. In the edge emphasis signal synthesis circuit 16, based on the level difference (R−G) between the R signal and the G signal, which is the output of the color separation circuit 17, and the level difference (B−G) between the B signal and the G signal, It is determined whether the subject is a chromatic color or an achromatic color, and based on the determination result, the synthesis ratio of the l signal output from the G signal edge enhancement generation circuit 14 and the m signal output from the all signal edge enhancement generation circuit 15 is determined. To decide. A synthesis formula of the l signal output from the G signal contour enhancement generation circuit 14 and the m signal output from the all signal contour enhancement generation circuit 15 can be expressed as follows, for example.
Edge enhancement signal = k × {l signal output from G signal edge enhancement generation circuit} + (1−k) × {m signal output from all signal edge enhancement generation circuit}
[0021]
Here, the k signal is a value calculated by a level difference (R−G) between the R signal and the G signal and a level difference (B−G) between the B signal and the G signal, and 0 <= k <= 1. The coefficient is such that k = 0 when the subject is determined to be a complete achromatic color, and k = 1 when the subject is determined to be a complete chromatic color. According to the above formula, for example, if the subject is determined to be completely achromatic,
Outline enhancement signal = m signal of the output of all signal outline enhancement generation circuit, and when the subject is determined to be a complete chromatic color,
Outline enhancement signal = G signal The l signal output from the outline enhancement generation circuit. In other words, the above expression combines the edge emphasis signal generated from the G signal and the edge emphasis signal generated from all signals by changing the weight according to the ratio of the color components of the subject. As a result, the contour enhancement generation from the G signal effective for reducing the chromatic edge jaggedness and the contour enhancement generation from all the signals effective for reducing the achromatic edge jaggedness are performed. It is possible to switch smoothly depending on the ratio. In addition, for achromatic subjects, weight is given to the generation of contour enhancement from the original signal, so that the resolution of achromatic subjects can be improved. Further, the level difference (R−G) between the R signal and the G signal, and the level difference (B−G) between the B signal and the G signal are signals generated by the color separation circuit 17, so that the chromatic color, no The determination of coloring can be performed with high accuracy.
[0022]
【The invention's effect】
As described above, according to the present invention, the pixel filter arranged in a checkered pattern is provided by including the contour emphasizing device that adds the signal synthesized by the contour emphasizing signal synthesizing circuit to the luminance signal from the solid-state imaging device as the contour emphasizing signal. Thus, it is possible to provide a solid-state imaging device that can reduce the jaggedness that occurs at the boundary of chromatic colors and can improve the resolution.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a solid-state imaging device provided with a contour emphasizing device in an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of a color filter array of a solid-state imaging device in an embodiment of the present invention. FIG. 3 is an explanatory diagram showing an output signal of a solid-state imaging device in an embodiment of the present invention. FIG. 4 is a timing diagram of a G pixel sample and hold circuit. FIG. 6 is an explanatory diagram showing a filter coefficient of a G pixel contour emphasizing signal generation circuit and how an edge emphasis signal is generated for a subject having an oblique edge. FIG. 7 is an explanatory diagram showing a filter coefficient calculation method. FIG. 9 is a diagram illustrating a state in which a contour enhancement signal is generated for a subject having a vertical edge with a filter coefficient of a pixel contour enhancement signal generation circuit. FIG. Configuration diagram of a solid-state imaging apparatus having a configuration diagram [11] Conventional edge enhancement device illustration Figure 10 total signal edge enhancement signal generation circuit showing a state of generation of the enhancement signal [Description of symbols]
DESCRIPTION OF SYMBOLS 1 Lens 2 Solid-state image sensor 3 OB correction circuit 4 Shading correction circuit 5 White balance circuit 6 AGC circuit 7 Gamma correction circuit 8 Signal horizontal inversion circuit 91, 92, 93 1H delay circuit 10 Defective pixel correction circuit 11 Luminance signal generation circuit 12 Delay Adjustment circuit 13 G pixel sample / hold circuit 14 G signal edge enhancement signal generation circuit 141, 144, 145 LPF
142 Horizontal edge enhancement signal generation circuit 143 Vertical edge enhancement signal generation circuits 146, 147, 148 Bit shift circuits 149, 1410 Selector circuits 1411, 1412 Coring circuits 1413, 1414 Multiplication circuit 1415 Addition circuit 15 All signal outline enhancement generation circuit 151, 152, 153 HPF
154, 155 Adder circuit 156, 157 Bit shift circuit 158, 159 Coring circuit 1510, 1511 Multiplier circuit 1512 Adder circuit 1513 1T delay circuit 16 Outline emphasis signal synthesis circuit 17 Color separation circuit 18 Color difference signal generation circuit 19 Color difference signal multiplexing circuit 201, 202, 203, 204 Adder circuit

Claims (4)

In a solid-state imaging device in which a lens for forming a subject and R (red), G (green), and B (blue) color filters for photoelectrically converting the formed image are arranged in a checkered pattern, Of the color signals of the R pixel, G pixel, and B pixel of the solid-state imaging device , smoothing is performed on the diagonal edge from the G pixel signal (G signal) that is effective in reducing chromatic edge jaggedness. A G signal contour enhancement signal generation circuit for generating a contour enhancement signal through a low-pass filter, an all signal contour enhancement signal generation circuit for generating a contour enhancement signal from all the color signals, and an output of the G signal contour enhancement signal generation circuit A contour emphasis signal synthesizing circuit that determines a synthesis ratio of a signal and an output signal of the all-signal contour emphasis signal generation circuit based on a determination result of whether all the color signals are chromatic or achromatic, and Have The solid-state imaging device characterized by comprising an edge enhancement device to be added to the luminance signal from the solid-state imaging device of the combined signal by the contour enhancement signal synthesizing circuit as contour enhancement signal.   The G signal contour emphasis signal generation circuit includes a horizontal contour emphasis signal generation circuit that generates a horizontal contour emphasis signal from the G signal, a vertical low-pass filter provided in a preceding stage of the horizontal contour emphasis signal generation circuit, 2. A vertical contour emphasis signal generation circuit that generates a vertical contour emphasis signal from the G signal, and a horizontal low-pass filter provided at a stage subsequent to the vertical contour emphasis signal generation circuit. Solid-state imaging device.   3. The solid-state imaging device according to claim 2, wherein the vertical low-pass filter and the horizontal low-pass filter can be independently determined as to whether or not to apply horizontal contour enhancement and vertical contour enhancement.   The contour emphasis signal synthesizing circuit determines a synthesis ratio between the output signal of the G signal contour emphasis signal generation circuit and the output signal of the all-signal contour emphasis signal generation circuit, and the color signal (R signal) of the R pixel and the G signal. 2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is determined by a level difference between the signal and a level difference between the B pixel signal (B signal) and the G signal.

Images