JPH089395A - Color image pickup device - Google Patents

Abstract

PURPOSE:To make luminance signals close to the signals of an NTSC system and to improve color reproducibility by providing a color filter for which the sum of the spectroscopic sensitivity of all the picture elements becomes approximately the ratio of R:G:B=2:3:1 and a signal processing circuit for which the component ratio of the luminance signal becomes approximately R:G:B=2:3:1. CONSTITUTION:While (n) is defined as a positive integer, the scanning signals of R+Cy, G+Ye, R+Cy and G-Ye are obtained at the time of the nH scanning of a first field. When a yellow light transmission filter Ye and a cyan light transmission filter Cy are respectively expressed by R+G and G+B, nH scanning signal components are defined as R+G+B, R+2G, R+G+B and R+2G and the luminance signals proportional to 2R+3G+B are obtained through a low-pass filter. Also, chrominance signals proportional to B-G are obtained through a band-pass filter. That is, the scanning signals of G+Cy, R+Ye, G+Cy and R+Ye are obtained at the time of the (n+1)H scanning of the first field and G+Cy, R+Ye, G+Cy and R+Ye are obtained at the time of the n'H scanning of a second field.

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 for converting a subject image into an electric signal having luminance information and color information, and more particularly to a color image pickup device having a color filter on a light receiving surface of an image pickup element.

[0002]

14 to 16 are views showing an example of the arrangement of color filters of a conventionally known color solid-state image pickup device.

In FIG. 14, a magenta light transmission filter Mg, a green light transmission filter G, a cyan light transmission filter Cy and a yellow (yellow) color light transmission filter Ye have two pixels in the horizontal direction and four pixels in the vertical direction. The color filters of 8 pixels are set as one unit and are arranged in the order shown in the figure. Figure 1
In FIG. 5, the white light transmission filter W, the green light transmission filter G, the cyan light transmission filter Cy, and the yellow light transmission filter Ye are two color filters in the horizontal direction and two pixels in the vertical direction. The units are arranged in the order shown in the figure. FIG. 16 shows a color filter array called a Bayer array, which is a green light transmission filter G.
Are arranged in a checkered pattern, and the red light transmission filters R and the blue light transmission filters B are arranged line-sequentially between the green light transmission filters G.

With respect to these color filter arrays, a normal luminance signal is obtained by adding two pixels in the horizontal direction and adding two pixels in the vertical direction as a unit, or through a low-pass filter circuit. That is, in the color filter array shown in FIG. 14, the luminance signal Y is obtained as Y = Mg + G + Cy + Ye. In the color filter array shown in FIG. 15, the luminance signal Y is obtained as Y = W + G + Cy + Ye. Similarly, in the color filter array shown in FIG. 16, the luminance signal Y is obtained as Y = R + 2G + B.

[0005]

However, in the color image pickup device having the conventional color filter array as described above, the luminance signal Y is W = R + G + B, Mg = R +.
If B, Cy = G + B, and Ye = R + G, then in the color filter array shown in FIG. 14, Y = Mg + G + Cy + Ye = 2R + 3G + 2B → 0.2
85R + 0.43G + 0.285B, and in the color filter array shown in FIG. 15, Y = W + G + Cy + Ye = 2R + 4G + 2B → 0.25
R + 0.5G + 0.25B, and in the color filter array shown in FIG. 16, Y = R + 2G + B → 0.25R + 0.5G + 0.25B, which are significantly different from the luminance signal Y = 0.30R + 0.59G + 0.11B in the NTSC system. However, there is a problem that the color reproducibility is deteriorated due to the output signal.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a color image pickup apparatus having good color reproducibility.

[0007]

A color image pickup device of the present invention converts a subject image into an electric signal having luminance information and color information, and is arranged in a two-dimensional grid pattern to form a subject image. The sum of the spectral sensitivities of the element and all the pixels arranged corresponding to the light receiving element and partitioned by the light receiving element is R.
The three primary colors of (red), G (green), and B (blue) are approximately R: G: B =
Signal processing in which the component ratio of the luminance signal or a part of the signal thereof is approximately R: G: B = 2: 3: 1 from the combination of the color filter having a ratio of 2: 3: 1 and the output signal of the light receiving element. A circuit, and is configured to generate a luminance signal and a color signal from the output signal of the light receiving element.

Further, the color filter is arranged so that the sum of the spectral sensitivities of all four pixels, that is, two pixels in the horizontal direction and two pixels in the vertical direction, is approximately R: G: B = 2: 3: 1. It was done.

The first color filter of the above color filters has a red light transmissive property, the second color filter has a green light transmissive property, and the third color filter has a cyan color light transmissive property. The fourth color filter has magenta color light transmittance.

Further, the first and second color filters of the above color filters have green light transmissivity, the third color filter has yellow color light transmissivity, and the fourth color filter has magenta color light transmissivity. To have.

Further, the first and second color filters of the above color filters have a green light transmissive property, the third color filter has a red light transmissive property, and the fourth color filter has a white light transmissive property. I had it.

Further, the first and second color filters of the above-mentioned color filters have yellow light transmissivity, the third color filter has green light transmissivity, and the fourth color filter has blue light transmissivity. To have.

[0013]

According to the color image pickup apparatus of the present invention, the ratio of the luminance signal or a part of the luminance signal is Y = 2R + 3G + B → 0.33R + 0.50G + 0.1
7B, it is possible to approach the luminance signal of the NTSC system, and the color reproducibility becomes good.

[0014]

The present invention will be described in more detail below with reference to the embodiments shown in the drawings. In each of the color image pickup devices of the following embodiments, a light receiving element arranged in a two-dimensional lattice and on which a subject image is formed, and all pixels arranged corresponding to the light receiving element and partitioned by the light receiving element are provided. The sum of spectral sensitivity is R (red), G
The three primary colors of (green) and B (blue) are approximately R: G: B = 2: 3: 1.
And a signal processing system circuit in which the component ratio of the luminance signal or a part of the signal thereof is approximately R: G: B = 2: 3: 1 from the combination of the output signals of the light receiving elements. And a luminance signal and a color signal are generated from the output signal of the light receiving element.

FIG. 1 is a view showing the arrangement of color filters in a color image pickup apparatus according to the first embodiment of the present invention.
In this color filter array, 2 pixels in the horizontal direction and 4 pixels in the vertical direction are the basic 8 pixels, and a red light transmission filter R and a green light transmission filter G are alternately arranged.
, Cyan light transmission filter Cy and yellow light transmission filter Y
e, a filter element row B in which e is alternately arranged, and a filter element row C in which a green light transmission filter G and a red light transmission filter R whose positions are inverted from the filter element row A are alternately arranged.
And a cyan light transmission filter Cy and a yellow light transmission filter Ye are alternately arranged at the same position as the filter element row B.

Next, the process of signal generation in the field storage type image pickup device for simultaneously reading out two lines in the horizontal direction of the interlace system will be described.

During nH (n is a positive integer) scan of the first field, as shown in FIG. 1, R + Cy, G + Ye, R
Scan signals of + Cy, G + Ye, ... Are obtained, and the yellow light transmission filter Ye and the cyan light transmission filter Cy are represented by R + G and G + B, respectively, as shown in FIG.
This nH scanning signal component is R + G + B, R + 2G, R + G
+ B, R + 2G, ..., A luminance signal proportional to (2R + 3G + B) is obtained through the low-pass filter, and a color signal proportional to (BG) is obtained through the band-pass filter.

During (n + 1) H scanning of the first field,
From FIG. 1, G + Cy, R + Ye, G + Cy, R + Ye,
.. are obtained respectively. From (b) of FIG.
(N + 1) H scanning signal components are 2G + B, 2R + G, 2G
+ B, 2R + G, ..., Through the low pass filter, a luminance signal similar to that at the time of nH scanning proportional to (2R + 3G + B) can be obtained, and through the band pass filter (-2R +
A color signal proportional to G + B) is obtained.

Further, in the n'H scanning of the second field, according to FIG. 1, G + Cy, R + Ye, G + Cy, R + Y.
Scan signals of e, ... Are obtained respectively, and the yellow light transmission filter Ye and the cyan light transmission filter Cy are respectively R +
Expressed as G and G + B, the n′H scanning signal components are 2G + B, 2R + G, 2G + B, 2R + G, ... From FIG.
... and becomes (2R + 3G +) through the low-pass filter.
A luminance signal proportional to B) is obtained, and a color signal proportional to (-2R + G + B) is obtained through the bandpass filter.

During (n + 1) 'H scanning of the second field, as shown in FIG. 1, R + Cy, G + Ye, R + Cy, G + Y.
The scanning signals of e, ... Are obtained, and from (d) of FIG. 2, this (n + 1) 'H scanning signal component is R + G + B, R + 2G,
R + G + B, R + 2G, ..., A luminance signal proportional to (2R + 3G + B) is obtained through the low-pass filter, and a color signal proportional to (BG) is obtained through the band-pass filter.

As described above, by using the color filter array shown in FIG. 1, the same scanning signal can be obtained in the first field and the second field. Further, a luminance signal proportional to (2R + 3G + B) is obtained from all of the scanning signals, and adjacent scanning signals are alternately (B−).
Since a color signal proportional to (G) and a color signal proportional to (-2R + G + B) are obtained, it is possible to perform color separation into R, G, and B by performing matrix processing.

FIG. 3 is a block diagram showing the arrangement of a signal processing system of a color image pickup apparatus using the image pickup device having the color filter array shown in FIG. In the figure, reference numeral 101 is a color filter array having the color filter array of FIG. For automatic gain control (AGC), 104 is a low-pass filter (LPF) for luminance signal generation, 105 is a gamma correction circuit (γ) for luminance signal, and 110 is a band limiting filter (for color difference signal generation). BPF), 111 is a delay circuit (1HDL) for one horizontal period (H), and 112 is R, G, B
Color separation matrix circuit for primary color separation of
Is a white balance amplifier (WB), 116 to 11
Reference numeral 8 is a gamma correction circuit (γ) for color signals, and 119 is a color difference matrix circuit for generating color difference signals.

Image pickup light from a subject is formed by a color filter array 1 of the color filter array shown in FIG. 1 by an image forming optical system (not shown).
It is incident on the image sensor (sensor) 102 in which 01 is arranged.
The scanning signal output from the image sensor 102 is supplied to an amplifier 103 for automatic gain control (AGC). Then, the signal that has passed through the low-pass filter (LPF) 104 is output as the luminance signal Y via the gamma correction circuit (γ) 105.

Further, the band limiting filter (BPF) 110
The signal that has passed through is passed through a delay circuit (1HDL) 111 and is divided into a signal delayed for one horizontal period and a signal not delayed,
The color separation matrix circuit 112 generates three primary color signals R, G, B from the respective signals. For this matrix processing,

[0025]

[Equation 1]

A matrix of the form is used.

The above three primary color signals are supplied to a color difference matrix circuit 119 via white balance amplifiers (WB) 113 to 115 and gamma correction circuits (γ) 116 to 118, respectively.

[0028]

[Equation 2]

The color difference signals R-Y,
BY is generated. Then, by using an NTSC encoder (not shown), the luminance signal Y and the color difference signal R
It is possible to generate an NTSC color video signal from -Y and BY.

The color filter array shown in FIG. 1 can be similarly applied to a non-interlace type image pickup device which reads all lines line by line. The signal processing system in this case can be realized by a configuration similar to that of FIG.
For the matrix processing in the B color separation matrix circuit 112,

[0031]

[Equation 3]

A matrix of the form is used.

Further, the signal processing system of the color image pickup apparatus using the image pickup element 102 having the color filter array shown in FIG.
The configuration shown in FIG. 4 may be used. Here, the same components as those in FIG. 3 are assigned the same reference numerals and explanations thereof are omitted, but in the figure, reference numeral 120 denotes a matrix circuit for generating a luminance signal and a color difference signal, and 130.
Is an adder.

In the signal processing system of FIG. 4, the luminance signal Y is formed of the high frequency component Y _H and the low frequency component Y _L. The output signal that has passed through the low-pass filter (LPF) 104 is output as a high-pass luminance signal Y _H through the gamma correction circuit (γ) 105, and the gamma-corrected R, G, and B signals are output.
From the primary color signal, from the matrix circuit 120,

[0035]

[Equation 4]

The low band luminance signal Y _L is output as a result of the matrix calculation, and the high band luminance signal Y _H and the low band luminance signal Y _L are added by the adder 130 to generate and output the luminance signal Y. It

Here, in the signal processing circuit shown in FIGS. 3 and 4, the sum of the spectral sensitivities of all pixels is R: G: B =, as described above.
For the color filter array 201 having a ratio of 2: 3: 1, the component ratio of the luminance signal or a part of the signal thereof is approximately R:
Since it is processed so that G: B = 2: 3: 1, Y = 2R
By setting + 3G + B → 0.33R + 0.50G + 0.17B, it is possible to approximate the luminance signal of the NTSC system, and the color reproducibility becomes good.

As a second embodiment of the present invention, in addition to the color filter array of FIG. 1 in which each filter R, G, Cy, Ye is combined, FIG. Even with the configuration shown, processing can be performed by the same processing system as in FIGS. 3 and 4 only by changing the coefficient of Expression 3.

Further, as a third embodiment, 8 pixels 1 in which the positions of the respective colors in the horizontal direction are inverted for every 2 pixels in the vertical direction
Even the color filter array shown in FIG. 6 of the set can be processed by the same processing system of FIGS. 3 and 4 as long as the coefficient of Expression 3 is changed.

By combining the color filters, R, G,
When Cy and Ye are used, the blue transmitted light filter B, which has a problem in sensitivity, is not used, so that the sensitivity is good, and
Since a pure color filter is partially used, the color S / N is good.

FIG. 7 shows the arrangement of color filters in the fourth embodiment of the present invention. In this color filter array, yellow light transmission filters Ye are arranged in a checkered pattern, and green light transmission filters G and magenta transmission filters Mg are arranged line-sequentially between the filters Ye.

FIG. 8 is a block diagram showing the arrangement of a signal processing system of a color image pickup apparatus using the image pickup device having the color filter array shown in FIG. In the figure, 201 is a color filter array having the color filter array of FIG. 7, 202 is an image sensor (sensor) in which the color filter array 201 is arranged, 203
Is an amplifier for automatic gain control (AGC), 204 is a low-pass filter (LPF) for luminance signal generation, 205 is a gamma correction circuit (γ) for luminance signal, 210 is an interpolation filter for synchronizing signals, Reference numeral 212 is a color separation matrix circuit for primary color separation, 213 to 215 are white balance amplifiers (WB), 216 to 218 are color signal gamma correction circuits (γ), and 219 is a color difference signal generation color difference matrix circuit. is there.

Similar to the circuits of FIGS. 3 and 4, the image pickup light from the subject is incident on the image pickup element (sensor) 202 in which the color filter array 201 of the color filter array of FIG. 7 is arranged by the image forming optical system (not shown). To do. The scanning signal output from the image sensor 202 is supplied to the amplifier 2 for automatic gain control (AGC).
03. And low pass filter (LPF)
The signal that has passed 204 is output as a luminance signal Y via a gamma correction circuit (γ) 205.

The luminance signal Y is obtained by an addition signal of 4 pixels, Y = Ye + G + G + Mg = (R + G) + G + G + (R + B) = 2R + 3G + B (Equation 5).

The signals that have passed through the interpolation filter 210 and are synchronized are the R, G, and B color separation matrix circuits 21.
2, and three primary color signals R, G, B are generated. The coefficient of the color separation matrix at this time is, for example,

[0046]

[Equation 5]

The coefficient is used. Where a, b
Are arbitrary constants.

The above-mentioned three primary color signals are supplied to the color difference matrix circuit 219 through the respective white balance amplifiers (WB) 213 to 215 and the gamma correction circuits (γ) 216 to 218, where the matrix calculation of equation 2 is performed. Color difference signals RY and BY are generated. Then, by using an NTSC encoder (not shown), an NTSC color image signal can be generated from the luminance signal Y and the color difference signals RY and BY.

Further, the signal processing system of the color image pickup apparatus using the image pickup device having the color filter array shown in FIG. 7 may have the configuration shown in FIG. 9 in addition to FIG. Here, the same components as those in FIG. 8 are assigned the same reference numerals and explanations thereof will be omitted, but in FIG.
0 is a matrix circuit for generating a luminance signal and a color difference signal, 2
30 is an adder.

In the signal processing system of FIG. 9, the luminance signal Y is formed by the high frequency component Y _H and the low frequency component Y _L. The output signal passed through the low pass filter (LPF) 204 is output as a high pass luminance signal Y _H through a gamma correction circuit (γ) 205, and the gamma-corrected R, G, and B signals are output.
From the primary color signals, the matrix circuit 220 outputs the low-frequency luminance signal Y _L as a result of the matrix calculation of Expression 4,
The high band luminance signal Y _H and the low band luminance signal Y _L are added by the adder 23.
The luminance signal Y is generated and output by adding 0.

In the signal processing circuits shown in FIGS. 8 and 9, the luminance signal component ratio is NT as in the circuits shown in FIGS.
SC system luminance signal Y = 0.30R + 0.59G + 0.
It is possible to approach 11B, and the color reproducibility becomes good.

As a fifth embodiment of the present invention, in addition to the color filter arrangement of FIG. 7 in which the filters Ye, Mg, and G are combined, the filters G may be arranged in a stripe shape as shown in FIG. Also, as the sixth embodiment, even the color filter array shown in FIG. 11 can be processed by substantially the same processing system as the signal processing system of FIGS. 8 and 9.

Further, with the arrangements of the color filters of the seventh and eighth embodiments shown in FIGS. 12 and 13, the same operational effects as the above-mentioned respective embodiments can be obtained. 12 shows an example in which a filter G is arranged between the checkered filters W and VR, and FIG. 13 shows a filter Y between the checkered filters G and B.
Examples of arranging e are shown.

In each of the above-mentioned embodiments, a combination of filters R, G, Cy, and Ye is used as a four-color filter, and filters G, Mg, and are used as a three-color filter.
The combination of Ye (the number of pixels of G is double), W, R, G (the number of pixels of G is double) and Ye, G, B (the number of pixels of Ye is double) is shown. Is almost R: G: B = 2:
It goes without saying that other colors or arrangements of combinations may be used as long as the combination of color filters is 3: 1.

[0055]

As described above, according to the present invention,
A color filter in which the sum of the spectral sensitivities of all pixels is approximately R: G: B = 2: 3: 1, and a component ratio of luminance signals is approximately R: G: B.
Since the signal processing circuit of = 2: 3: 1 is provided, the luminance signal can be brought close to the signal of the NTSC system, and the color reproducibility is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an arrangement configuration of color filters in a first embodiment.

FIG. 2 is an explanatory diagram showing a process of signal generation in an interlaced field accumulation type imaging device.

FIG. 3 is a block diagram showing the configuration of a signal processing system according to the first embodiment.

FIG. 4 is a block diagram showing another configuration of the signal processing system of the first embodiment.

FIG. 5 is an explanatory diagram showing an arrangement configuration of color filters in the second embodiment.

FIG. 6 is an explanatory diagram showing the arrangement of color filters in the third embodiment.

FIG. 7 is an explanatory diagram showing an arrangement configuration of color filters according to a fourth embodiment.

FIG. 8 is a block diagram showing the configuration of a signal processing system according to a fourth embodiment.

FIG. 9 is a block diagram showing another configuration of the signal processing system of the fourth embodiment.

FIG. 10 is an explanatory diagram showing an arrangement configuration of color filters in the fifth embodiment.

FIG. 11 is an explanatory diagram showing the arrangement of color filters in the sixth embodiment.

FIG. 12 is an explanatory diagram showing the arrangement of color filters in the seventh embodiment.

FIG. 13 is an explanatory diagram showing the arrangement of color filters according to the eighth embodiment.

FIG. 14 is an explanatory view showing an arrangement configuration example of color filters of a conventional color image sensor.

FIG. 15 is an explanatory view showing an arrangement configuration example of color filters of a conventional color image sensor.

FIG. 16 is an explanatory diagram showing an arrangement configuration example of color filters of a conventional color image sensor.

[Explanation of symbols]

 101 color filter array 102 image pickup element (light receiving element) 201 color filter array 202 image pickup element (light receiving element)

Claims (6)

[Claims] 1. A color image pickup device for converting an object image into an electric signal having luminance information and color information, and a light receiving element arranged in a two-dimensional grid pattern, on which an object image is formed, and a light receiving element corresponding to the light receiving element. The sum of the spectral sensitivities of all the pixels arranged and divided by the light receiving element is a ratio of approximately R: G: B = 2: 3: 1 for the three primary colors of R (red), G (green), and B (blue). From the combination of the color filter and the output signal of the light receiving element, the component ratio of the luminance signal or a part of the signal is approximately R: G: B = 2:
A color image pickup device comprising a 3: 1 signal processing circuit and generating a luminance signal and a color signal from an output signal of the light receiving element. 2. The color filter has a sum of the spectral sensitivities of all four pixels of two pixels in the horizontal direction and two pixels in the vertical direction, which is approximately R: G: B.
2. The color image pickup device according to claim 1, wherein the color image pickup device is arranged so as to have a ratio of = 2: 3: 1. 3. The first color filter of the color filters has a red light transmissive property, the second color filter has a green light transmissive property, and the third color filter has a cyan color light transmissive property. The color imaging device according to claim 2, wherein the fourth color filter has a magenta color light transmissive property. 4. The first and second color filters of the color filter have a green light transmissive property, the third color filter has a yellow light transmissive property, and the fourth color filter has a magenta light transmissive property. The color image pickup apparatus according to claim 2, further comprising: 5. The first and second color filters of the color filter have a green light transmissive property, the third color filter has a red light transmissive property, and the fourth color filter has a white light transmissive property. The color image pickup apparatus according to claim 2, further comprising: 6. The first and second color filters of the color filters have a yellow light transmissive property, the third color filter has a green light transmissive property, and the fourth color filter has a blue light transmissive property. The color image pickup apparatus according to claim 2, further comprising: