JP3932601B2 - Color imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image pickup apparatus using a solid-state image pickup device having a primary color filter as an image pickup device, and particularly detects an image pickup signal of a solid-state image pickup device such as a CCD (Charge Coupled Device) image sensor and the detection result thereof. The present invention relates to a color imaging apparatus having a function of automatically performing exposure control based on the above.
[0002]
[Prior art]
FIG. 6 shows a conventional example of a camera system which is this type of color imaging apparatus. In the figure, a CCD image sensor 101 is driven based on various timing signals such as a readout pulse, a vertical transfer pulse, a horizontal transfer pulse, and a shutter pulse generated by a timing generator (TG) 102. The output signal of the CCD image sensor 101 is sampled and gain-adjusted by a CDS (Correlated Double Sampling) & AGC (Automatic Gain Control) circuit 103 and then digitally output by an A / D converter 104. And supplied to the clamp circuit 105.
[0003]
The clamp circuit 105 clamps the black level in the imaging signal and outputs the signal level of each pixel with respect to the black level. The pixel signal output from the clamp circuit 105 passes through the white balance circuit 106 and the delay line 107, is then subjected to signal processing by the Y processing circuit 108 and output as a Y (luminance) signal, and is also output by the C processing circuit 109. Processed and output as a C (chroma) signal. The pixel signal from the clamp circuit 105 is further supplied to an AE (Automatic Exposure) detection circuit 110. The detection output of the AE detection circuit 110 is supplied to a system controller 111 composed of a microcomputer or the like.
[0004]
An AWB (Automatic White Balance) detection circuit 112 detects the output signal of the C processing circuit 109. The detection output of the AWB detection circuit 112 is supplied to the system controller 111. The system controller 111 automatically performs exposure control (iris control) by changing the timing of the shutter pulse output from the timing generator 102 and the gain of the AGC circuit 103 based on the detection output of the AE detection circuit 110. The white balance circuit 106 is controlled based on the detection output of the AE detection circuit 110 to automatically adjust the hue.
[0005]
In the configuration described above, an AE loop is formed by the path of the clamp circuit 105 → AE detection circuit 110 → system controller 111 → timing generator 102 / AGC circuit 103, C processing circuit 109 → AWB detection circuit 112 → system controller 111 → An AWB loop is formed by the path of the white balance circuit 106.
[0006]
In this AE loop, pixel signals are input to the AE detection circuit 110 in the same arrangement as the color coding of the color filter of the CCD image sensor 101. Then, the AE detection circuit 110 provides the system controller 111 with an output obtained by integrating all the pixel signals in one screen. Then, the system controller 111 changes the timing of the shutter pulse output from the timing generator 102 and the gain of the AGC circuit 103 based on the AE detection signal that is the output of the AE detection circuit 110. As a result, automatic exposure control (auto iris) is performed.
[0007]
[Problems to be solved by the invention]
In the conventional color imaging apparatus having the above-described configuration, it is assumed that a so-called histogram integration function for integrating and outputting only pixels corresponding to two brightness levels in one screen is mounted on the AE detection circuit 110. Then, if the color coding of the color filter of the CCD image sensor 101 is the “G checkered RB line sequential” method as shown in FIG. There are only two colors of information such as R or B and G, and not only the Y signal itself but also the pseudo Y signal based on (R + 2G + B) cannot be generated only from the information in one line. That is, since it is impossible to correctly compare the reference luminance for making a histogram and the detection signal to be integrated, accurate exposure control cannot be performed.
[0008]
The present invention has been made in view of the above problems, and the object of the present invention is to have all three colors of R, G, and B in one line when a CCD image sensor having a primary color filter is used. An object of the present invention is to provide a color imaging apparatus that realizes AE histogram detection without any need and enables accurate exposure control.
[0009]
[Means for Solving the Problems]
The color image pickup apparatus according to the present invention is a color image pickup apparatus using a solid-state image pickup element having primary color filters of color coding in which three primary colors do not exist simultaneously in one line, and only the G pixel component from the image pickup signal of the solid-state image pickup element. A G pixel extracting circuit for extracting the image signal, a comparison circuit for comparing the G pixel component extracted by the G pixel extracting circuit with a predetermined reference value, and integrating the imaging signal of the solid-state imaging device based on the comparison result of the comparison circuit And an controller for performing exposure control based on the integration output of the integration circuit, the controller based on the component ratio of the three primary colors in one screen obtained from the output of the color information integration circuit. the integrated output of the integrating circuit is corrected, or performs exposure control on the basis of the corrected integral output, the 1 in the screen obtained from the output of the color information integration circuit The reference value is corrected based on the component ratio of the primary colors, it has a configuration which gives the corrected reference value to the comparator circuit.
[0010]
In the color imaging device having the above configuration, when a pixel signal is input from the solid-state imaging device in the same arrangement as the color coding of the primary color filter, the G pixel extraction circuit extracts only the G pixel component from the pixel signal. The extracted G pixel component is compared with a predetermined reference value in the comparison circuit. The integration circuit integrates the imaging signal from the solid-state imaging device based on the comparison result of the comparison circuit. As a result, histogram integration for knowing the brightness distribution in one screen is realized using the pixel signal of the G pixel. Then, the controller corrects the integral output of the integration circuit based on the component ratio of the three primary colors in one screen, and performs exposure control based on the corrected integral output, or the component ratio of the three primary colors in one screen. Based on this, the reference value is corrected, and the corrected reference value is given to the comparison circuit .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the present embodiment, a case will be described in which the present invention is applied to a camera system that enables AE histogram detection using a CCD image sensor having primary color filters for sequential color coding of G checkered RB lines. FIG. 2 shows color coding of the G checkered RB line sequential.
[0012]
In FIG. 1, a CCD image sensor 11 is driven based on various timing signals such as a readout pulse, a vertical transfer pulse, a horizontal transfer pulse, and a shutter pulse generated by a timing generator 12. An output signal (imaging signal) of the CCD image sensor 11 is sampled and gain adjusted by the CDS & AGC circuit 13, digitized by the A / D converter 14, and supplied to the clamp circuit 15.
[0013]
The clamp circuit 15 clamps the black level in the imaging signal and outputs the signal level of each pixel with respect to the black level. The pixel signal output from the clamp circuit 15 passes through the white balance circuit 16 and the delay line 17 and is then processed by the Y processing circuit 18 and output as a Y signal, and is also processed by the C processing circuit 19. Output as C signal. The pixel signal from the clamp circuit 15 is further supplied to the AE detection circuit 20. The detection output of the AE detection circuit 20 is supplied to a system controller 21 composed of a microcomputer or the like.
[0014]
An AWB detection circuit 22 as a color information integration circuit obtains color information by detecting the output signal of the C processing circuit 19. The color information obtained by the AWB detection circuit 22 is supplied to the system controller 21. The system controller 21 automatically performs exposure control (iris control) by changing the timing of the shutter pulse output from the timing generator 12 and the gain of the AGC circuit 13 based on the detection output of the AE detection circuit 20. The white balance circuit 16 is controlled based on the detection output of the AWB detection circuit 22 to automatically adjust the hue.
[0015]
In the configuration described above, an AE loop is formed by the path of the clamp circuit 15 → AE detector circuit 20 → system controller 21 → timing generator 12 / AGC circuit 13, and C processing circuit 19 → AWB detector circuit 22 → system controller 21 → An AWB loop is formed by the path of the white balance circuit 16. In this AE loop, pixel signals are input to the AE detection circuit 20 in the same arrangement as the color coding of the primary color filter of the CCD image sensor 11.
[0016]
The AE detection circuit 20 extracts from the system controller 21 a G pixel extraction circuit 201 that extracts only the G pixel component from the pixel signal output from the clamp circuit 15, and the G pixel component extracted by the G pixel extraction circuit 201. A comparison circuit 202 that compares two kinds of brightness reference values REF1 and REF2 to be given, two integration circuits 203 and 204 that perform an integration operation based on the comparison result of the comparison circuit 202, and a pixel signal from the clamp circuit 15 Alternatively, a changeover switch 205 that selectively supplies the G pixel component from the G pixel extraction circuit 201 to the integration circuit 203 as an integration target signal, and a delay circuit that delays the selection output of the changeover switch 205 and supplies it to the integration circuit 204 ( D) 206.
[0017]
Here, the G pixel extraction circuit 201 has a circuit configuration in which only the G pixel component is extracted from the pixel signal by opening the gate at the timing of the G pixel using a gate circuit, or the G pixel at the pixel timing using the selector. A circuit configuration that extracts only the G pixel component by switching between the component and another pixel component can be used.
[0018]
Next, the circuit operation of the AE detection circuit 20 will be described with reference to the timing chart of FIG.
[0019]
Now, looking at a certain n-th line, the pixel signal (A) is input to the AE detection circuit 20 in the arrangement of pixels G1, R1, G2, R2,. Then, the G pixel extraction circuit 201 extracts only the G pixel component (B) from the pixel signal (A). The G pixel component (B) is compared with reference values REF 1 and REF 2 given from the system controller 21 in the comparison circuit 202. The comparison circuit 202 outputs a comparison result (C) of “H” level when the G pixel component (B), that is, the detection signal is larger than the reference values REF1 and REF2, and “L” level when the detection signal is smaller (C). Note that the final logic is possible even if the logic is reversed.)
[0020]
Here, since the comparison circuit 202 outputs a comparison result for each of the two types of reference values REF1 and REF2 for histogram integration, two systems are required as outputs. On the other hand, in this example, the output is set as one system, and as shown in FIG. 3C, a mode is adopted in which two comparison results are serially arranged and output on the time axis. The comparison result (C) of the comparison circuit 202 is supplied to the two integration circuits 203 and 204.
[0021]
In addition, the integration circuit 203, 204 selects the pixel signal (A) output from the clamp circuit 15 or the G pixel component (B) output from the G pixel extraction circuit 201 as an integration target signal by the changeover switch 205. Entered. The integration circuit 203 performs an integration operation only when the comparison result with the reference value REF1 in the comparison result (C) is at the “H” level. However, when the pixel signal (A) is selected as a detection target, integration is performed as a pair of G1 and R1.
[0022]
On the other hand, the integration circuit 204 performs an integration operation when the comparison result with the reference value REF2 in the comparison result (C) is at the “H” level. However, similarly to the integration circuit 203, when the pixel signal (A) is a detection target, both G1 and R1 are integrated. For this purpose, timing adjustment is performed by delaying the detection signal by the delay circuit 206. Note that when the two systems of comparison results are output for each of the reference values REF 1 and REF 2, it is not necessary to perform timing adjustment by the delay circuit 206.
[0023]
As described above, histogram integration is performed on the G pixel. It should be noted here that although the G pixel is sensitive to a relatively wide wavelength range, for example, under a light source that is very reddish, such as under a sunset sky, G The level of the pixel signal of the pixel itself is lowered. For this reason, as in the case of the present embodiment, when only the G pixel is selected as the integration target signal, the integration value itself becomes small. In addition, the level of the G pixel component shown in FIG. 3B for histogram determination is also a small value, and the reference values REF1 and REF2 that are appropriately set for the subject are usually too high.
[0024]
Therefore, in the present embodiment, the following method is used. In this camera system, a circuit for integrating color information, that is, an AWB detection circuit 22 is mounted. Therefore, the system controller 21 can know the ratio of the G, R, and B components in one screen from the detection output of the AWB detection circuit 22. For example, at sunset, the R component is considerably larger than the G and B components.
[0025]
At this time, the system controller 21 determines that the integration result supplied from the AE detection circuit 20 is smaller than the original one, and performs correction such as doubling the integration result to the AE algorithm. I will reflect it. Also, since the reference values REF1 and REF2 are too large as they are, for example, a value multiplied by 1/2 is given to the comparison circuit 202 in the detection circuit 20 for AE, as shown in FIG. In addition, correction is performed so that the reference values REF1 and REF2 come to substantially the same position as the normal subject in the luminance distribution in one screen.
[0026]
FIG. 5 shows the processing procedure of the AE control according to the present embodiment described above. This process is executed by the system controller 21. First, the system controller 21 takes in the detection output of the AWB detection circuit 22 (step S1), and obtains the ratio of G, R, and B components in one screen based on this detection output (step S2). Then, it is determined whether or not the R component is considerably larger than the G and B components (R component >> G, B component) (step S3). If the R component >> G, B component, shooting at sunset is performed. The integration result and the reference values REF1 and REF2 are corrected (step S4), and the shutter speed and the AGC gain are controlled based on the correction result (step S5).
[0027]
As described above, in the AE detection circuit 20, when performing the histogram integration for the G pixel, the component ratio of R, G, B is obtained based on the integration result of the color information obtained from the AWB detection circuit 22, By correcting the two types of brightness reference values REF1 and REF2 for performing the G pixel integration value and the histogram integration based on the component ratio, the G pixel can be used even in the case of shooting under sunset sky, for example. The exposure control can be performed accurately without being affected by the lowering of the level.
[0028]
In the above-described embodiment, the selector switch 205 is switched to selectively supply the pixel signal from the clamp circuit 15 or the G pixel component from the G pixel extraction circuit 201 to the integration circuit 203 as an integration target signal. However, the selector switch 205 may be omitted, and only the pixel signal from the clamp circuit 15 may be fixedly supplied to the integration circuit 203 as an integration target signal.
[0029]
Further, instead of the pixel signal from the clamp circuit 15, the G pixel component from the G pixel extraction circuit 201 may be fixedly supplied to the integration circuit 203 as an integration target signal. In this case, only G pixels are used as pixel information, which is half of all the pixels in one screen. Therefore, the word lengths of the integration circuits 203 and 204 can be shortened, so that the circuit configuration can be simplified. is there.
[0030]
【The invention's effect】
As described above, according to the present invention, in a color imaging apparatus using a solid-state imaging device having a primary color filter as an imaging device, only the G pixel component is extracted from the imaging signal of the solid-state imaging device, and this G pixel component is extracted. By comparing with a predetermined reference value, integrating the imaging signal of the solid-state imaging device based on the comparison result, performing histogram integration for the G pixel, and performing exposure control based on the integration result Since histogram integration using only G pixels can be realized, AE histogram detection can be performed even if all three colors of R, G, and B are not arranged in one line, and accurate exposure control can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a diagram illustrating color check of G checkered RB line sequential.
FIG. 3 is a timing chart for explaining the circuit operation of the AE detection circuit according to the embodiment;
FIG. 4 is a characteristic diagram showing a Y distribution with respect to reference values REF1, REF2 before correction (A) and after correction (B).
FIG. 5 is a flowchart showing a procedure of AE control.
FIG. 6 is a block diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... CCD image sensor, 12 ... Timing generator, 13 ... CDS & AGC circuit, 16 ... White balance circuit, 20 ... AE detection circuit, 21 ... System controller, 22 ... AWB detection circuit, 201 ... G pixel extraction circuit, 202 ... Comparison circuit 203, 204 ... Integral circuit, 205 ... Changeover switch

Claims (4)

A color imaging device using a solid-state imaging device having primary color filters of color coding in which three primary colors do not exist simultaneously in one line,
A G pixel extraction circuit that extracts only a G (green) pixel component from the imaging signal of the solid-state imaging device;
A comparison circuit for comparing the G pixel component extracted by the G pixel extraction circuit with a predetermined reference value;
An integration circuit that integrates the imaging signal of the solid-state imaging device based on the comparison result of the comparison circuit;
A controller that performs exposure control based on the integration output of the integration circuit;
A color information integration circuit that integrates color information based on an imaging signal of the solid-state imaging device;
The controller corrects the integration output of the integration circuit based on the component ratio of the three primary colors in one screen obtained from the output of the color information integration circuit, and performs exposure control based on the corrected integration output. A characteristic color imaging device. The color imaging apparatus according to claim 1, wherein the integration circuit uses the G pixel component extracted by the G pixel extraction circuit as an integration target. A color imaging device using a solid-state imaging device having primary color filters of color coding in which three primary colors do not exist simultaneously in one line,
A G pixel extraction circuit that extracts only a G (green) pixel component from the imaging signal of the solid-state imaging device;
A comparison circuit for comparing the G pixel component extracted by the G pixel extraction circuit with a predetermined reference value;
An integration circuit that integrates the imaging signal of the solid-state imaging device based on the comparison result of the comparison circuit;
A controller that performs exposure control based on the integration output of the integration circuit;
A color information integration circuit that integrates color information based on an imaging signal of the solid-state imaging device;
The controller corrects the reference value based on the component ratio of the three primary colors in one screen obtained from the output of the color information integration circuit, and supplies the corrected reference value to the comparison circuit. Imaging device. The color imaging apparatus according to claim 3, wherein the integration circuit uses the G pixel component extracted by the G pixel extraction circuit as an integration target.

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