JPH0746609A - Color image sensor - Google Patents

Abstract

(57) [Summary] [Purpose] The objective is to increase the light utilization rate and improve the absolute sensitivity. A color imaging device having a complementary color checkered array color filter has a spectral sensitivity characteristic in a black and white state having a peak at a wavelength of 500 to 570 nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image pickup device suitable for application to a complementary color checkered array CCD image pickup device applied to, for example, a video camera.

[0002]

2. Description of the Related Art Conventionally, a complementary color checkerboard array C as shown in FIG.
A video camera using a CD image sensor has been proposed. In FIG. 13, reference numeral 1 denotes a complementary color checkered array CCD image pickup device, and an image pickup signal from the complementary color checkered CCD image pickup device 1 is supplied to a correlated double sampling circuit (CDS circuit) 3 via a preamplifier circuit 2. A sample and hold circuit 5 for extracting the specific color signals S ₁ and S ₂ from the output signal of the CDS circuit 3 through the auto gain controller 4.
a and 5b.

Reference numerals 6, 7 and 8 in FIG. 13 add or subtract the output signals S ₁ and S ₂ of the sample and hold circuits 5a and 5b to form color signals Cr and Cb and a luminance signal Y. It is a subtraction circuit. In addition, in FIG.
Reference numerals 11, 12 and 13 denote delay circuits for one horizontal period, respectively.

The complementary color checkered array CCD image sensor 1 is a CC
The surface of the D image pickup device is provided with a color filter of a complementary color checkerboard arrangement as shown in FIG. 14, for example. The output signals of the complementary color checkerboard arrangement CCD image pickup device 1 are the primary color signals R, G and B of red, green and blue. In order to take out, it is necessary to add or subtract a certain color signal and another color signal.

For example, in the case of a color filter having a complementary checkered pattern as shown in FIG. 14, that is, yellow Ye and cyan C in which the color filters of even scan lines 2n are laterally arranged.
A color filter of an odd number of scanning lines 2n + 1 is formed in a horizontal direction by a repeating pattern of 4 pixels including a y portion, a magenta Mg portion and a green G portion which are arranged in parallel to the yellow Ye portion and the cyan Cy portion and are arranged therebelow. The yellow Ye and cyan Cy parts, and the green G arranged in parallel to the yellow Ye and cyan Cy parts below the yellow Ye and cyan Cy parts.
When it is composed of a repeating pattern of 4 pixels including a magenta Mg portion, signals Y and C are calculated by the following equation.
Obtain r, Cb.

Y = Ye + Cy + Mg + G = 2R + 3G + 2B Cr = (Ye + Mg)-(Cy + G) = 2R-G-Cb = (Ye + G)-(Cy + Mg) =-(2B-G)

Then, each of the signals Y, Cr, Cb is supplied to the primary color separation circuit 14, and in the primary color separation circuit 14, for example, the arithmetic processing of the following equation is performed to perform the red, green and blue signals R, which are the primary color signals. G and B are obtained.

2.5R = Cr + 1/4 (Y-Cb) = 1.5Ye + Mg-Cy-0.5G 5G = (Y-Cr-Cb) = Ye + Cy + 3G-Mg 2.5B = Cb + 1/4 (Y-Cr) = 1.5Cy + Mg-Ye-0.5G

By the way, when the addition / subtraction operation for forming the signals Cr, Cb, Y to be input to the primary color separation circuit 14 is performed, the addend, the augend, or the subtraction, and the addend are simultaneously signals as a complementary color checkered array CCD image pickup device. Not supplied from 1. Therefore, it is necessary to make use of the line correlation and to simultaneously add and subtract the signal one horizontal period before and the current signal, and this 1 plays the role of forming the signal one horizontal period before. Horizontal period delay circuits 11 to 13
Is.

Red, green and blue signals R, G and B which are primary color signals from the primary color separation circuit 14 are supplied to a white balance circuit 15, respectively. This white balance circuit 1
In 5, the color temperature detecting means 16 determines the color temperature of the subject based on the input red, green and blue signals, and controls the gain of the signal system of the red signal R and the blue signal B based on the determination result. And try to get a white balance.

The red signal R, the green signal G and the blue signal B obtained at the output side of the white balance circuit 15 are respectively passed through the gamma correction circuit 17a to the color difference matrix circuit 1.
Supply to 7. This color difference matrix circuit 17
In the above, the color difference signals RY and BY are obtained from the red color signal R, the green color signal G and the blue color signal B which are the primary color signals.

Color difference signals RY and BY from the color difference matrix circuit 17 are supplied to the modulation circuit 18. In the modulation circuit 18, the color difference signals R-Y and B-
This conversion circuit 1 modulates Y and then superimposes them.
The output signals of 8 are supplied to the color signal suppressing circuit 19.

The color signal suppression circuit 19 is composed of an amplifier circuit capable of gain control, and is adapted to suppress the color signal by the vertical edge detection signal.
This vertical edge detection signal is formed by adding the output signal of the CDS circuit 3 to the output signal of the vertical contour correction circuit 10 by the addition circuit 9.

That is, the vertical contour correction circuit 10 emphasizes the contour in the vertical direction, and detects the vertical edge by using these output signals to suppress the color signal.

In FIG. 13, 20 is a horizontal period delay circuit for obtaining a signal delayed by 1 horizontal period, 21 is a low pass filter, 22 is an adder circuit, 23 is a band pass filter, 24 is a color signal and a luminance signal and synchronization It is an adder circuit that adds the signal and.

In FIG. 13, 25 is a gamma correction circuit for performing gamma correction in the luminance signal system, 26 is a 1 horizontal period delay circuit for obtaining a signal delayed by 1 horizontal period,
Reference numeral 27 is a low-pass filter, 28 is an adder circuit, 29 is a horizontal contour correction circuit, and 30 is an adder circuit that forms a luminance signal, and a circuit 31 performs white clipping, synchronization signal addition, etc., and an output signal of this circuit 31. Is supplied to the adder circuit 24, and an NTSC color video signal is obtained at the output side of the adder circuit 24.

[0017]

By the way, the transmission spectral sensitivity characteristic as a general example of this color filter is as shown in FIG. 2, and the color filter which sees which wavelength range of this color filter transmits most light is shown. The total transmission spectral sensitivity characteristic of is as shown in FIG.

In FIG. 3, the amount of light transmitted through each color filter of yellow Ye, cyan Cy, green G and magenta Mg is added for each wavelength.
It can be seen that it has the maximum light transmission amount in nm.

In the complementary color checkered array CCD image pickup device, various spectral sensitivity characteristics have been hitherto examined in terms of luminance and color reproduction characteristics, but have not yet been examined in terms of light utilization rate.

In view of the above point, the present invention aims to increase the utilization rate of this light and improve the absolute sensitivity.

[0021]

The color image pickup device of the present invention, for example, in a color image pickup device having a complementary color checkered array color filter as shown in FIG. 1, has a peak in the wavelength range of 500 to 570 nm as a spectral sensitivity characteristic in a monochrome state. It is the one.

[0022]

According to the present invention, since the spectral sensitivity characteristic in the black and white state has a peak at a wavelength of 500 to 570 nm, there is a peak of the black and white spectral sensitivity characteristic at the wavelength where the transmission spectral sensitivity characteristic of the color filter is the highest. , The light utilization rate is increased, and the absolute sensitivity can be improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the color image pickup device of the present invention will be described below with reference to the drawings. The color image pickup device according to this example is also a complementary color checkered array CCD image pickup device 1 used in a video camera as shown in FIG.
The arrangement of the color filters of the image pickup device is as shown in FIG. 14, and the luminance signal Y of the video camera using such a complementary color checkered CCD image pickup device is Y = Ye + Cy + G + Mg as described above.

The signal levels of the yellow Ye, cyan Cy, green G and magenta Mg are determined from the spectral sensitivity characteristics of the complementary color checkered array CCD image pickup device as shown in FIG. 5, for example. The characteristics are determined by the black-and-white spectral sensitivity characteristic of this image sensor and the transmission spectral sensitivity characteristic of the color filter as shown in FIG. The luminance signal Y of this video camera can also be expressed by the spectral sensitivity characteristic as follows.

Y = (monochrome spectral sensitivity characteristic) × (Ye, C
y, G, Mg color filter transmission spectral sensitivity characteristics sum)

This means that even if the transmission spectral sensitivity characteristics of the color filters are the same, if there is a difference in the black and white spectral sensitivity characteristics, there will be a difference in the luminance signal level. In other words, the luminance signal level can be increased if the peaks of the black and white spectral sensitivity characteristics of the wavelength at which the color filter has the maximum transmission can be matched.

By the way, the transmission spectral sensitivity characteristics of the color filter of the complementary color checkered pattern are as shown in FIG. 2 as described above, and the color filter of the complementary color checkered pattern in which the wavelength range of the color filter is the most transparent is seen. The total transmission spectral sensitivity characteristic of is as shown in FIG.

In FIG. 3, the light transmission amount of each color filter of yellow Ye, cyan Cy, green G and magenta Mg is added for each wavelength, and the color filter of the complementary color checkered array has 500 wavelengths. It has the maximum light transmission amount at 10 nm.

Therefore, the black-and-white spectral sensitivity characteristic of this complementary color checkered array CCD image pickup device has a peak at wavelengths of 510 to 540 nm as shown in FIG. 1 (hereinafter referred to as image pickup device A). As shown in FIG. One having a shorter wavelength of 460 to 470 nm (hereinafter referred to as image pickup element B), and one having its peak at a wavelength of 610 to 620 nm having a longer wavelength than this (hereinafter referred to as image pickup element C).
Say. ) Will be considered.

In this case, in order to control the peak wavelength of the black and white spectral sensitivity characteristic, a protective film (for example, a nitride film) 40 of this complementary color checkered array CCD image pickup device as shown in FIG.
The thickness was controlled and the effect of multiple interference was utilized.

FIG. 4 is a sectional view of a unit pixel of a complementary color checkered array CCD image pickup device, wherein 41 is a sensor section, 42 is a transfer section, 43 is a flattening film, 44 is a complementary color checkered array color filter, and 45 is a microlens. Is.

The spectral sensitivity characteristic of the image pickup device A is as shown in FIG. 5, and the spectral sensitivity characteristic of the luminance signal is as shown in FIG. The spectral sensitivity characteristic of the image sensor B is as shown in FIG. 9, and the spectral sensitivity characteristic of the luminance signal is as shown in FIG. The spectral sensitivity characteristic of the image sensor C is shown in FIG.
12 and the spectral sensitivity characteristic of the luminance signal is as shown in FIG.

FIG. 8, which shows the spectral sensitivity characteristic of the luminance signal,
As can be seen by comparing FIGS. 10 and 12, as shown in FIG. 1, the peak wavelength of the black and white spectral sensitivity characteristic is 510 to 540n.
The area of the complementary color checkered array CCD image pickup device A having m is the largest (sensitivity is high). Although FIG. 12 seems to have a high sensitivity for long wavelengths, the long wavelengths are regions that are dropped by the IR cut filter, and actually do not contribute much to raising the luminance signal level.

Color temperature of 3200K based on the spectral data
And the luminance signal level of the white subject at 9000K are compared (normalized by the image sensor A), the results are shown in the following table.

[0035]

[Table 1]

As described above, the peak wavelength of the black and white spectral sensitivity characteristic of the complementary color checkered array CCD image pickup device is 500 to 570.
Those having a peak wavelength of the black-and-white spectral sensitivity characteristic in the vicinity of the wavelength having the highest transmittance of the color filter have high sensitivity regardless of the color temperature.

Therefore, in this example, this complementary color checkered array C
The black-and-white spectral sensitivity characteristics of the CD image sensor are set to wavelengths of 500 to 570
have a peak at nm.

According to this example, since the black and white spectral sensitivity characteristic has a peak at a wavelength of 500 to 570 nm, the black and white spectral sensitivity characteristic is close to the wavelength where the transmission spectral sensitivity characteristic of the color filter of the complementary checkered pattern is the highest. There is a peak, the utilization rate of light is high, and there is a benefit that the absolute sensitivity can be improved.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0040]

As described above, according to the present invention, since the spectral sensitivity characteristic in the black and white state has a peak at a wavelength of 500 to 570 nm, the transmission spectral sensitivity characteristic of the complementary color checkered color filter is the highest. Since there is a peak of the black and white spectral sensitivity characteristic in the vicinity of the wavelength, the utilization factor of light becomes high, and there is an advantage that the absolute sensitivity can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of black and white spectral sensitivity characteristics according to the present invention.

FIG. 2 is a diagram showing an example of transmission spectral sensitivity characteristics of a color filter having a complementary checkered pattern.

FIG. 3 is a diagram showing an example of a total transmission spectral sensitivity characteristic of a color filter having a complementary color checkered pattern.

FIG. 4 is a cross-sectional view showing an example of a unit pixel of a complementary color checkered array CCD image sensor.

FIG. 5 is a diagram showing an example of spectral sensitivity characteristics of a complementary color checkered array CCD image sensor.

FIG. 6 is a diagram showing an example of black and white spectral sensitivity characteristics.

FIG. 7 is a diagram showing an example of black and white spectral sensitivity characteristics.

FIG. 8 is a diagram showing an example of luminance signal spectral sensitivity characteristics.

FIG. 9 is a diagram showing an example of spectral sensitivity characteristics of a complementary color checkered array CCD image sensor.

FIG. 10 is a diagram showing an example of luminance signal spectral sensitivity characteristics.

FIG. 11 is a diagram showing an example of spectral sensitivity characteristics of a complementary color checkered array CCD image sensor.

FIG. 12 is a diagram showing an example of luminance signal spectral sensitivity characteristics.

FIG. 13 is a configuration diagram showing an example of a video camera.

FIG. 14 is a diagram showing an example of a complementary color checkered array color filter.

[Explanation of symbols]

 1 Complementary color checkered array CCD image sensor 40 Protective film

Claims (1)

[Claims] 1. A color image pickup device having a complementary color checkered array color filter, wherein spectral sensitivity characteristics in a black and white state are wavelengths of 500 to 570 n.
A color image pickup device having a peak at m.