JP3459538B2 - Color signal processing circuit for single-chip color camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing circuit of a single-chip color camera, and more particularly, to a color filter arranged in an array by a color difference sequential method. The present invention relates to a color signal processing circuit of a single-chip color camera having a color separation circuit for processing a signal from a solid-state imaging device including photoelectric conversion elements arranged in an array. 2. Description of the Related Art In a color camera, a CCD (Charge Coupled D) widely used as an imaging device at present is used.
evice) merely changes the amplitude of the output signal according to the brightness of the received light, and the output signal does not include color information. Therefore, in order to obtain color information, it is necessary to use optical means to apply a filter to light incident on the CCD. [0003] In a home color camera, a so-called single-panel system for extracting three primary color signals from a single CCD is adopted, and a so-called simultaneous color imaging system using a color filter array on the light receiving surface side of the CCD. Has been adopted. FIG. 2 is a configuration diagram of a CCD in which color filter arrays are arranged in a color difference sequential system. As shown in FIG. 2, in the color filter of the color difference sequential system, magenta (hereinafter, represented by Mg), green (hereinafter, represented by G), cyan (hereinafter, represented by Cy), and yellow (hereinafter, represented by Cy). Ye) are arranged in a mosaic pattern. Here, when separating the three primary color signals R, G, B from the CCD output signal, the three primary colors red (R),
Mg, Ye, C, which are complementary colors to green and blue (B)
The fact that the following approximation holds between y and y is used. Mg = R + B (1) Ye = R + G (2) Cy = B + G (3) FIG. 3 is a block diagram showing a color signal processing circuit of a conventional single-panel color camera. As shown in FIG. 2, the color filter array
When n is a natural number, including a first row including a magenta color filter and a green filter that are alternately arranged, and a plurality of second rows including a yellow filter and a cyan filter that are alternately arranged. , The second row contains y = 4n−3 and y
= 4n-1 and x includes a yellow filter in an even column, the first row is y = 4n-4 and y = 4n-
X has a green filter in an odd-numbered column if it belongs to row 2 and y = 4n-4, and x has a green filter in an even-numbered column if it belongs to y = 4n-2. In this case, the color signal generating means is as follows. In the above-described color filter array, an arbitrary 2 × 2
The matrix contains Mg, G, Ye, and Cy. Next, FIG.
, The generation of a color signal at the center position of the 2 × 2 matrix will be considered. The light passing through the optical system 1 in FIG.
An image is formed on the light receiving surface of D2. The CCD 2 converts the formed light into electric signals corresponding to the color filters Mg, Ye, Cy, and G. These electric signals Mg, Ye, Cy, and G are converted into CC signals by a CCD driving pulse output from the driving circuit 7.
The data is sequentially read from D2. The signal read from the CCD 2 is input to a synchronization circuit 3, and the synchronization circuit 3 uses a memory to store Mg,
The four signals of Ye, Cy, and G are synchronized. Synchronization circuit 3
The four signals of Mg, Ye, Cy, and G output from
It is input to the L, CR, CB generation circuit 5. YL, CR,
In the CB generation circuit 5, the following equations (4), (5),
The calculation of the expression (6) is performed, and Mg, Ye, Cy, and G
A luminance signal YL, a first color signal CR, and a second color signal CB are created from the signals. CR = (Mg + Ye) − (G + Cy) = {(R + B) + (R + G)} − {G + (B + G)} = 2R−G (4) CB = (Mg + Cy) − (Ye + G) = ｛(R + B) ) + (B + G)｝-｛(R + G) + G｝ = 2B-G (5) YL = Mg + G + Ye + Cy = (R + B) + G + (R + G) + (B + G) = 2R + 3G + 2B ... (6) YL, CR, CB generation circuit 5 YL and C output from
The R and CB signals are input to the matrix circuit 6. In the matrix circuit 6, the following equations (7), (8),
The matrix calculation of Expression (9) is performed to create R, G, and B signals. G = (2YL-2CR-2CB) / 10 (7) R = (YL + 4CR-CB) / 10 (8) B = (YL-CR + 4CB) / 10 (9) FIG. 3 is a diagram showing the spectral sensitivity characteristics of a color filter of a CCD. As shown in FIG. 3, in an actual CCD color filter, the Mg signal includes a G component. That is, the signal of Mg is not approximated by the expression (1) but is approximated by the following expression (10). Mg = (R + B) + ΔG (10) Accordingly, CR, CB, and CR of the above-mentioned equations (4), (5) and (6) using the approximation of equation (1)
YL is actually CR, C as shown in the following equation.
The signal becomes larger by ΔG than B and YL. CR = (2R−G) + ΔG (11) CB = (2B−G) + ΔG (12) YL = (2R + 3G + 2B) + ΔG (13) Equations (7) and (8) , R in equation (9),
G and B are newly set as R ', G' and B ', and the original R and
Assuming that B and B are R, G and B, G ′ = G− (2ΔG / 10) (14) R ′ = R + (4ΔG / 10) (15) B ′ = B + (4ΔG / 10) (15) 16), which deviates from the original RGB signal level, and has a disadvantage in that the saturation and the hue are adversely affected. Therefore, the main object of the present invention is to provide a C
An object of the present invention is to provide a color signal processing circuit of a single-chip color camera capable of performing spectral sensitivity correction of a Mg signal before R, CB, and YL generation signal processing. Means for Solving the Problems The invention according to claim 1 is:
A solid-state image sensor in which photoelectric conversion elements corresponding to each of the pixels are arranged in an array, and four pixels in an arbitrary two rows and two columns in a color filter array are provided corresponding to the light receiving surface side of the solid-state image sensor. In a single-panel color camera having a color filter array having correspondingly green and three types of complementary color filters, a color signal corresponding to every four pixels is received by receiving an output signal read out from a solid-state image sensor independently for all pixels. A color separation unit configured to generate the color separation filter; and a correction unit configured to correct a spectral sensitivity characteristic of the magenta color filter using an output signal corresponding to the green color filter in response to the output signal to the magenta color filter. Is done. FIG. 1 is a block diagram showing an embodiment of the present invention. In this embodiment, the optical system 1, the CCD 2, the synchronization circuit 3, the YL,
CR / CB generation circuit 5, matrix circuit 6, and drive circuit 7
And An Mg signal generation block 4 which is a feature of the present invention is provided between the synchronization circuit 3 and the YL, CR, CB generation circuit 5. The Mg signal generation block 4 subtracts a signal obtained by multiplying the G signal by the coefficient α from the Mg signal to create a signal Mg ′ having been subjected to spectral sensitivity correction.
This signal Mg 'is input to the YL, CR, CB generation circuit 5. The present invention provides an interlace method, a progressive scan method, or any other method as a method for reading from the CCD 2 as long as it can output four signals of Mg, Ye, Cy, and G independently. But it is applicable. Next, the operation will be described. The light passing through the optical system 1 forms an image on the light receiving surface of the CCD 2. The CCD 2 converts the formed light into electric signals corresponding to the color filters Mg, Ye, Cy, and G. These electric signals Mg, Ye,
Cy and G are sequentially read from the CCD 2 by the CCD drive pulse output from the drive circuit 7. The signal read from the CCD 2 is input to a synchronization circuit 3, and the synchronization circuit 3 uses a memory to store Mg,
The four signals of Ye, Cy, and G are synchronized. Of the synchronized four signals of Mg, Ye, Cy, and G, the Mg and G signals are input to the Mg signal generation block 4. And M
The signal obtained by multiplying the G signal by the coefficient α is subtracted from the Mg signal by the g signal generation block 4, a signal Mg ′ having been subjected to spectral sensitivity correction is created, and supplied to the YL, CR, CB generation circuit 5. Ye, Cy, output from the synchronization circuit 3
The three G signals are also supplied to the YL, CR, CB generation circuit 5. In the YL, CR, CB generation circuit 5, the (4)
Expressions (5) and (6) are calculated, and M
YL, CR, and CB signals are created from the four signals g ', Ye, Cy, and G. The YL, CR, CB signals output from the YL, CR, CB generation circuit 5 are input to a matrix circuit 6. The matrix circuit 6 performs the matrix calculations of the above-described equations (7), (8) and (9), and calculates R, G,
Create a B signal. As described above, according to this embodiment, M
In the g signal generation block 4, Mg ′ corrects ΔG in equation (10), so that approximation in equation (1) holds. Therefore, the signal processing after the Mg signal generation block 4, that is, the YL, CR, CB generation circuit 5 and the matrix circuit 6 can perform signal processing with better color reproducibility even if they are the same as the conventional method. When the color signal that needs to be subjected to spectral sensitivity correction extends not only to Mg but also to Ye and Cy due to the spectral sensitivity characteristic of the color filter of the CCD 2, it is the same as the processing performed in the Mg signal generation block 4 described above. Signal processing of Ye,
What is necessary is just to carry out also about Cy. As the luminance signal, the above YL, C
The luminance signal YL created by using the signal subjected to the spectral sensitivity correction by the R and CB generation circuit 5 may be used, but the spectral sensitivity of G is close to the spectral sensitivity of the luminance signal and has a large specific gravity with respect to the luminance signal. Therefore, it may be created using a correction signal that has not been subjected to spectral sensitivity correction. As described above, according to the present invention, the spectral sensitivity characteristic of the magenta color filter is obtained by using the output signal corresponding to the green color filter corresponding to the output signal to the magenta color filter. , The original RGB signal level can be met, and the saturation and hue are not adversely affected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a CCD when a conventional color filter array is arranged in a color difference sequential system. FIG. 3 is a diagram showing spectral sensitivity characteristics of a conventional CCD color filter. FIG. 4 is a schematic block diagram of a conventional single-chip color camera. [Description of Signs] 1 Optical system 2 CCD 3 Synchronization circuit 4 Mg signal generation block 5 YL, CR, CB generation circuit 6 Matrix circuit 7 Drive circuit

Claims (1)

(57) Claims 1. A solid-state imaging device in which photoelectric conversion elements corresponding to pixels are arranged in an array, and a solid-state imaging device is provided corresponding to a light-receiving surface side of the solid-state imaging device. A single-panel color camera including a color filter array having green and three types of complementary filters corresponding to four pixels in an arbitrary two rows and two columns in a color filter array, wherein all pixels are independently read from the solid-state imaging device Color separation means for receiving the output signal generated and generating a color signal corresponding to each of the four pixels, and for an output signal corresponding to a magenta color filter, using an output signal corresponding to a green color filter. A color signal processing circuit for a single-chip color camera, comprising a correction unit for correcting the spectral sensitivity characteristic of a magenta color filter.