JP2540826B2 - Color imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image pickup device, and more particularly to an achromat (chroma suppressor).

[Outline of Invention]

According to the present invention, the image pickup output signal from the solid-state image pickup device having the color filter is supplied to the first matrix circuit to form the luminance signal and the color difference signal. The second matrix circuit for performing the processing is provided, the image pickup output signal is restored from the second matrix circuit, and the sum of the color signals is detected based on the restored image pickup output signal.

[Conventional technology]

As one of CCD color image pickup devices, one using a single plate imager to which a color filter of a complementary color checkered system shown in FIG. 3A is attached is known. The line of the field with the broken line in FIG. 3 is shown, and G, Mg, Cy, Ye are
Green, magenta, cyan, and yellow are shown respectively, and (4 ×
2) A pixel is one unit. 2 pixels (Mg, Cy or G, Y
e) are read and mixed simultaneously.

The read output of each line is sampled by each of the sampling pulses SP1 and SP2 shown in FIG. 3B, and the imaging output signals C1 and C2 are obtained. For example, in line LN, (M
g + Ye) sequential signal is obtained as the imaging output signal C1,
A (G + Cy) sequential signal is obtained as the image pickup output signal C2.

In the CCD color imaging device described above, the signal level is saturated if there is a high-luminance portion such as a spotlight reflected in the subject. For example, when only the green signal of the three primary color signals is saturated, the high-intensity part that should be white is colored magenta. In order to solve this problem, the CCD color image pickup device is provided with a saturation detection circuit, and an achromatic (chroma suppressor) circuit for controlling the gain of the carrier color signal by the output signal of the saturation detection circuit.

FIG. 4 is an example of a saturation detection circuit previously proposed by the applicant of the present application. In FIG. 4, 1 is a CCD imager having the above color filter, 2 is an AGC circuit, and 3 and 4 are sample and hold circuits. Sample and hold circuits 3 and 4
Are supplied with sampling pulses SP1 and SP2 shown in FIG. 3B, and image pickup output signals C1 and C2 are obtained from the sample hold circuits 3 and 4, respectively. The imaging output signal C1 is supplied to the cascade connection of the 1H (1 horizontal period) delay lines 12 and 14, and the imaging output signal C2 is supplied to the cascade connection of the 1H delay lines 13 and 15.
The development output signals of the (n + 1) th, nth, and (n-1) th lines obtained by these 1H delay lines 12 to 15 are RG.
It is supplied to the B matrix circuit 11. PGB matrix circuit 11
Is for performing vertical correlation calculation and primary color separation calculation, and three primary color signals Rn, Gn, Bn are obtained from the RG matrix circuit 11.

The imaging output signals Cln and C2n output from the 1H delay lines 12 and 13 for saturation detection are supplied to the maximum value selection circuit 16. The image pickup output signals Cln and C2n are signals synchronized with the three primary color signals Rn, Gn, Bn obtained from the RGB matrix circuit 11. The maximum value selection circuit 16 uses the imaging output signals Cln and C2n
It is a circuit that selects and outputs the signal with the higher level between the two. The output signal of the maximum value selection circuit 16 is the slice circuit 17
Is supplied to. In the slice circuit 17, the maximum value selection circuit 16
The signals above the predetermined slice level in the output signal of are separated. When the level of the image pickup output signal exceeds this slice level, the process of achromatization is required. The output signal of the slice circuit 17 is supplied to the low-pass filter 18, and the gain control signal CSn is obtained from the low-pass filter 18.

Although not shown, the carrier color signal formed from the three primary color signals from the RGB matrix circuit 11 is supplied to the gain control circuit. Chroma suppression is performed by controlling the gain of the carrier color signal by the gain control signal CSn described above by this gain control circuit.

By the way, as a color imaging device, the video output signal C1
In addition to the method of performing vertical correlation calculation and primary color separation calculation from C2 and C2, there is a method of performing the above calculation after converting the image pickup output signal into a luminance signal and a color difference signal. When the saturation detection shown in FIG. 4 is applied to this latter method, the configuration shown in FIG. 5 is obtained.

In FIG. 5, the image pickup output signals C1 and C2 are supplied to the matrix circuit indicated by 5. In the matrix circuit 5, the luminance signals Yn + 1 are formed by adding the image pickup output signals C1 and C2, and the color difference signals (2R-G) and (2B-G) are obtained by subtracting the image pickup output signals C1 and C2. A line-sequential line-sequential color difference signal DEn + 1 is obtained. These luminance signals and color difference signals are 1H delay lines 12 to 15 and RGB.
The signals are supplied to the matrix circuit 11 and the three primary color signals Rn, Gn, Bn are obtained.

In the color image pickup device that performs processing in the form of the luminance signal and the color difference signal, the luminance signal is supplied to the slice circuit 17 for saturation detection. The output signal of the slice circuit 17 is supplied to the low-pass filter 18, and the gain control signal CSn is obtained. FIG. 6 shows an example of the image pickup output signals C1 (shown by diagonal lines) and C2. The luminance signal Yn is formed by the operation of [Yn = 1/2 (C1n + C2n)] in the matrix circuit 5, and becomes a signal shown by a broken line in FIG.

[Problems to be solved by the invention]

In the luminance / color difference processing method, saturation detection cannot help being performed using a luminance signal. However, since the luminance signal Yn is the average value of the imaging output signals C1n and C2n, as is clear from FIG. 6, when the level of C1n or C2n is high, that is, when the modulation degree of the carrier color difference signal is high, The luminance signal Yn has an averaged level. Therefore, when the saturation detection is performed by supplying the luminance signal Yn to the slice circuit 17, it is very difficult to set the slice level, and the saturation detection cannot be performed correctly.

An object of the present invention is to provide a luminance and color difference processing type color image pickup device capable of correctly performing saturation detection.

[Means for solving problems]

According to the present invention, the image pickup output signals C1 and C2 from the solid-state image pickup device 1 having a color filter are supplied to the first matrix circuit 5 to form the luminance signal Y and the color difference signal. A second matrix circuit 19 for performing inverse matrix processing is provided for the circuit 5, the image pickup output signals C1 and C2 are restored from the second matrix circuit 19, and saturation is performed based on the restored image pickup output signals C1 and C2. Detection is done.

[Action]

The second matrix circuit 19 causes the imaging output signals C1 and C2
Is restored. Saturation is detected from the image pickup output signals C1 and C2. Unlike the case of using the luminance signal Y, the level of the image pickup output signal can be accurately detected, and the saturation detection operation is correctly performed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 1 indicates a CCD imager. This CCD imager 1 is a single plate imager to which color filters of the complementary color checkered system shown in FIG. 3A are attached. The image pickup signal read from the CCD imager 1 is supplied to the AGC circuit 2, and the output signal of the AGC circuit 2 is supplied to the sample hold circuits 3 and 4. The sampling pulses SP1 and SP2 shown in FIG. 3B are supplied to the sample and hold circuits 3 and 4, respectively, and the imaging output signals C1n + 1 and
C2n + 1 is obtained from the sample and hold circuits 3 and 4.

The image pickup output signals C1n + 1 and C2n + 1 are supplied to the matrix circuit 5. The matrix circuit 5 is for forming the luminance signal Y and the color difference signal DE as described below. The matrix circuit 5 is provided in the stage before the vertical correlation processing, and a luminance signal is formed from the signal before passing through the 1H delay line.

Y = 1/2 (C1 + C2) DE = α (C1-C2) The luminance signal Yn + 1 from the matrix circuit 5 is supplied to the RGB matrix circuit 11 and the 1H delay line 12, and the color difference signal DEn +
1 is supplied to the RGB matrix circuit 11 and the 1H delay line 13. The 1H delay lines 12 and 13 are connected in series with the 1H delay lines 14 and 15, respectively, and output signals Yn, DEn and 1 of the 1H delay lines 12 and 13, respectively.
The output signals Yn−1 and DEn−1 of the H delay lines 14 and 15 are supplied to the RGB matrix circuit 11. The RGB matrix circuit 11
This is for performing vertical correlation calculation and primary color separation calculation.
Three primary color signals Rn, Gn, Bn are obtained from the B matrix circuit 11.

The imaging output signal C1 is (Mg + C) on the line L (N-1).
y), on line LN (Mg + Ye), on line L (N + 1) (Mg + Ye)
g + Cy). The image pickup output signal C2 has a line L (N-
1) (G + Ye), line LN (G + Cy), line L
It becomes (G + Ye) at (N-1). RGB matrix circuit 11
Then, from the image pickup output signals C1 and C2 of the line LN to the three primary color signals R,
Another complementary color signal that is insufficient for calculating G and B is formed by vertical correlation calculation using the signals of the upper and lower lines L (N-1) and L (N + 1).

The output of the AGC circuit 2 is supplied to the brightness signal processing circuit 6 as a brightness signal Y _H (n + 1) which is surrounded by a broken line through the low pass filter 27. The luminance signal processing circuit 6 includes a gamma correction circuit 7, a 1H delay line 8 for phase matching, and an amplifier 9. Luminance signal Yn from the luminance signal processing circuit 6
Are supplied to the Y / C mixing circuit 10.

The three primary color signals Rn, Gn, Bn from the RGB matrix circuit 11 are supplied to the white balance circuit 21 and white balance adjustment is performed. The output signal of the white balance circuit 21 is supplied to the gamma correction circuit 22, and the output signal of the gamma correction circuit 22 is supplied to the matrix circuit 23. Matrix circuit 23
Thus, the color difference signals R-Y and B-Y are formed. These color difference signals RY and BY are quadrature two-phase modulation circuit 24.
And a carrier color signal is obtained from the quadrature two-phase modulation circuit 24. The carrier color signal is supplied to the gain control circuit 25, the output signal of the gay control circuit 25 is supplied to the Y / C mixing circuit 10, and the composite color video signal is obtained at the output terminal 26 of the Y / C mixing circuit 10. Gain control circuit
The gain control signal CSn is supplied to 25.

The luminance signal Yn from the 1H delay line 12 and the color difference signal DEn from the 1H delay line 13 are supplied to the matrix circuit 19. The matrix circuit 19 performs an inverse matrix operation of the matrix operation of the matrix circuit 5. That is, Imaging output signal C1n obtained by the matrix circuit 19,
C2n is supplied to the maximum value selection circuit 16.

The maximum value selection circuit 16 selects a signal having a higher level between the imaging output signals C1n and C2n. Maximum value selection circuit
The output signal of 16 is supplied to the slice circuit 17. The slice circuit 17 outputs a level equal to or higher than a predetermined slice level Vt. The output signal of the slice circuit 17 is the low-pass filter 18
The gain control signal CSn is obtained from the low pass filter 18.

The formation of the gain control signal CSn will be described with reference to FIG. FIG. 2A shows an example of the image pickup output signal C1n from the matrix circuit 19, and FIG. 2B shows an example of the image pickup output signal C2n from the matrix circuit 19. These imaging output signals Cln and C2n have a time lag corresponding to the sampling phase. As shown in FIG. 2C, the maximum value selection circuit 16 selects a signal having a higher level between the image pickup output signals C1n and C2n. In FIG. 2C, the signal shown in FIG. 2D which is equal to or higher than the slice level Vt is obtained from the slice circuit 17. This slice level Vt
The above levels mean saturation of the color signal, and the gain control signal CSn is formed by passing the output signal of the slice circuit 17 shown in FIG. 2D through the low pass filter 18. The higher the level of the gay control signal CSn, the smaller the gain of the gain control circuit 25, the saturation of the color signal is prevented, and the coloring of the image which should be achromatic can be prevented.

〔The invention's effect〕

According to the present invention, it is possible to prevent the saturation detection accuracy from being lowered or the saturation detection to be erroneous as in the case of detecting saturation from a luminance signal in a color image pickup apparatus of a luminance / color difference processing method. Therefore, it is possible to correctly control the chroma suppress operation and the Y _L / Y _H switching operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram used for explaining a gain control signal forming operation in an embodiment of the present invention, and FIG. An example of a color filter pattern of a CCD imager to which the invention can be applied and schematic diagrams used for explaining sampling pulses, FIGS. 4 and 5 are block diagrams of an example of a saturation detection circuit and another example, and FIG. The drawing is a waveform diagram used for explaining the problems of another example of the saturation detection circuit shown in FIG. Description of main symbols in the drawing 1: CCD imager, 3, 4: Sample and hold circuit, 5, 19: Matrix circuit, 11: RGB matrix circuit, 12, 13, 14, 15: 1H
Delay line, 16: Maximum value selection circuit, 17: Slice circuit, 25: Gain control circuit.

Claims (1)

(57) [Claims] 1. A color image pickup device in which an image pickup output signal from a solid-state image pickup device having a color filter is supplied to a first matrix circuit, and a luminance signal and a color difference signal are formed, with respect to the first matrix circuit. A second matrix circuit for performing inverse matrix processing is provided, the image pickup output signal is restored from the second matrix circuit, and saturation of the color signal is detected based on the restored image pickup output signal. A color image pickup device.