JPS60163591A - Solid-state color image pickup device - Google Patents

Abstract

PURPOSE:To eliminate the distortion of a luminance signal caused by a carrier of a chrominance signal and to obtain high horizontal resolution by arranging filters by four color iteration with respect to the horizontal scanning direction of a solid-state image pickup element, and setting a horizontal filter string to four color iteration with respect to the vertical scanning direction. CONSTITUTION:Picture elements 300 on an image pickup element of a solid-state color image pickup device are arranged in a zigzag in position by shifting a space phase in the horizontal direction at every horizontal picture elements string. A filter obtained by iteration of four colors such as an array of a magenta filter 301 and a yellow filter 302, a green filter 313 and a cyan filter 304 is arranged in the 1st line (nh) picture element 300. A combination of four color iteration of each (n+1)h, (n+2)h and (n+3)h is of the specific iteration array. The phase of carrier of a chrominance signal of each horizontal picture element 300 is shifted by 90 deg.. Then the distortion of a luminance signal caused by a carrier of a chrominance signal is eliminated, a horizontal resolution is made more satisfactory and a color picture with high quality is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to solid state color imaging devices used in video television cameras and the like.

Conventional configuration and problems A solid-state image sensor is a type of integrated circuit in which a two-dimensionally arranged photosensitive element such as a photodiode and a scanning circuit that scans this photosensitive element are integrated on a single silicon substrate. . Therefore, there is a limit to the number of photosensitive elements (pixels) that can be integrated, and this number also becomes a factor that determines the yield of solid-state image sensors. As a result, studies have been conducted on how to obtain high resolution with a small number of pixels for solid-state color cameras.

Among these methods, a staggered arrangement of pixels is a means for obtaining high resolution with the smallest number of pixels.

A solid-state image sensor with a staggered pixel arrangement and a coloring method using the same element are described in, for example, Japanese Patent Application Laid-Open No. 50-12891.
Publication No. 9 is raised.

FIG. 1 is a diagram illustrating a conventional color filter arrangement and scanning method.

In FIG. 1, the solid-state image sensor used is a solid-state image sensor (Japanese Unexamined Patent Publication No. 1481/1983) which has a scanning method of reading out two adjacent horizontal pixel columns in one horizontal scan. In addition, each pixel 1o1-to has magenta 10
2. Filters having spectral characteristics of yellow 103 and cyan 104 are arranged. Also, the arrangement of this filter is
The colors are arranged to be interleaved between two adjacent horizontal columns.

As a result, the spatially modulated color signal component contained in the element output signal obtained in each horizontal scan appears at a point of % of the horizontal clock frequency, as shown in FIG. As a result, the luminance signal band can be used up to % of the previous clock frequency.

Normally, the band of the luminance signal extends only up to half the horizontal clock frequency according to the sampling theorem.

From this point of view, it can be seen that this method is a method for obtaining high resolution. However, as can be seen from FIG. 2, the high resolution achieved by this method is based on the correlation of the object between the two horizontal pixel columns. Therefore, at points with no correlation, the carrier frequency of the previous color signal appears at a point that is % of the horizontal clock frequency. As a result, the previous carrier signal is mixed into the luminance signal and reproduced as an image signal. This method has such drawbacks.

OBJECTS OF THE INVENTION In view of these circumstances, the present invention aims to provide a solid-state color imaging device that substantially eliminates distortion of luminance signals due to color signal carriers occurring in portions of a subject image that have no vertical correlation. purpose.

Structure of the Invention The present invention uses a solid-state image sensor that simultaneously outputs two adjacent horizontal columns and has a staggered pixel arrangement, and four different spectral filters with a period of two pixels horizontally and four columns vertically. It is a solid-state color imaging device equipped with a mosaic-like color filter,
The low frequency component of the signal output from the color solid-state image sensor of the combination is used as the low frequency component of the total luminance signal, the element output signals for two horizontal scans are added, and this high frequency signal component is converted into the high frequency component of the luminance signal. By using it as a component, it is possible to obtain a broadband luminance signal.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows the configuration of an embodiment of the color filter of the present invention and the state of scanning by a solid-state image sensor.

In the figure, 30o indicates the positions of pixels on the solid-state image sensor, which are arranged in a staggered manner with the spatial phase in the horizontal direction shifted for each horizontal pixel column.

30174 is a magenta spectral filter that blocks only green light. Similarly, [302 is a yellow filter that blocks blue light, 3o3 is a green filter that transmits green light, and 3o4 is a cyan filter that blocks red light.

FIG. 4 shows the spectrum of the element output corresponding to each horizontal scan.

Here fc is the horizontal clock frequency.

As shown in FIG. 3, the color filter of this embodiment has two color filters with different spectral characteristics arranged on one pixel. As a result, the horizontal color repetition of each horizontal column is substantially every two pixels.

Therefore, the carrier frequency of the spatially modulated color signal appears at % of the horizontal clock frequency, ie, fc/2. FIG. 4 shows the carrier frequency of this color signal and its phase relationship using vectors. For example, the third
The color signals for n and h in the figure mean electrical signals obtained by photoelectrically converting light through (M+Y)-(G+C) at the pixels. Similarly, the signal for each horizontal pixel column is (n+1)h: (M+C)-(G+Y)(n+2)
h: (M+Y) −(G+C)(n+3)h:
(M+C)-(G+Y). Further, the phase of the carrier of the previous color signal in each horizontal pixel column is shifted by 900 as shown in FIG. For example, nh and (n+2)
The color signal components of h have the same value but a 180° phase difference.

A similar relationship also holds between (n+1)h and (n+s)h. By adding the signals n to (n+3)h, the carrier of the previous color signal included in the element output signal is removed. That is, the signal obtained by adding the four columns can extend the luminance band to the fc frequency. This means that in the conventional method, the carrier frequency was 2fC/3, but the band can be widened by fc/3.

When imaging a subject with no vertical correlation, as mentioned above, even if four columns are added, the carrier vectors of each horizontal pixel column will not have the same size, so the added signal will contain fc/2 components. become. In this case as well, the carrier frequency is fC/, whereas in the past it was fC/3, so it moves to a higher frequency and becomes less noticeable.

Furthermore, in actual applications, fc is usually 2fsc (fsc
: subcarrier frequency). In this case, the conventional carrier frequency is fC/3-2fSC/3 main 2.4, whereas in this embodiment, fC/2 = 'sc, which matches the subcarrier frequency. Normal color monitor televisions cannot reproduce subcarrier frequencies, so this signal cannot be confirmed on the reproduced image.

By the way, in the N-1-3C signal system, a phenomenon called cross color occurs when a luminance signal is mixed into a color signal. To avoid this phenomenon, help is used to attenuate the luminance signal system gain at the subcarrier frequency.

In this embodiment as well, the gain at the subcarrier frequency of the luminance system is attenuated.

FIG. 5 shows an embodiment of the signal processing circuit.

In the figure, reference numeral 501 is a solid-state image pickup device having a staggered pixel arrangement and capable of scanning two lines at the same time, in which the color filter of FIG. 3 is arranged.

The signals of two horizontal rows scanned simultaneously are output from two output terminals a,
It is output from the element via b.

The two output signals are delayed by one horizontal scan through wideband delay circuits 502 and 503. This signal is added together with the previous signals a and b in an adder circuit 505.

As a result, fC included in the element output signal as described above
The carrier component of the color signal at the /2 frequency is removed.

The added signal is passed through a bypass filter 508 and becomes a high-frequency component of a luminance signal.

On the other hand, the previous a and b signals (-i:, are added by the adder 604 and sent to the delay line (1) 506 and the bypass filter 50.
7 and is subtracted by a subtracter 509.

Here, the delay line (1) has 506 bypass filters 507 and the delay time. As a result, the subtraction circuit outputs a signal obtained by subtracting the high frequency band from the entire band, that is, a low frequency signal component. That is, the low frequency component of the previously added signal C is output.

The signal passed through the bypass filter 608 is added to this signal as a high-frequency luminance component in an adder circuit 510, and then limited to the luminance band via a low-pass filter 511. Here, the low-pass fi# 511 is 1 at the subcarrier frequency.
A device with attenuation of about 5 dB is used to reduce the cross color phenomenon. On the other hand, the previous element output signals a and b are transmitted via delay lines (2) 512 and 513, respectively.
Or directly connected to the switching circuit 516. Here, the delay time of delay line (2) 512, 513 is 1/2f
.

is set to .

6 and 7 show the state of the signal at each point of dleflq. As is clear from the figure,
Delay lines (2) 512 and 513 are used to match the phases of signal components included in the two element output signals a and b. As a result, signals with uniform phases are obtained at each point dq as shown in FIGS. 6 and 7. The same figure also shows the results of performing d - e or "J" for each horizontal scan. Looking at these results, we can see that Y-C or M-G with reversed polarity for each pixel. The traffic lights are lined up.

Further, the phase in which the polarity is reversed is reversed every horizontal scan. Furthermore, M-G and Y-C are exchanged for each field. Therefore, in the embodiment shown in FIG. 5, the signals applied to the subtracting circuits 518 and 519 are arranged through a switching circuit 514 for each field and a switching circuit 515 for each pixel and each horizontal scan. Further, the gain adjustment circuit 516.
517 is for the purpose of adjusting the signal value of one of the two signals applied to the subtraction circuits 518 and 519 to achieve white balance.

As a result, the signals at points h and i are represented by the primary color signal components included in each signal: Y-βC=R+G-β(G0B) (Here, α and β are 0 when capturing a white image. value), resulting in two color difference signals.

For example, if the R, G, and B components have the same signal value for white, α=2. It becomes β-1.

Adding the above two equations gives 2R-2G, subtracting it gives 2B-
It becomes 2G. This value is the two NTSC color difference signals R-Y.
, B-Y component.

Therefore, by performing this calculation in the matrix 520 and passing the luminance signal component from the low-pass filter 510 after the two obtained color difference signals through the encoder 521, a composite color signal can be obtained.

The above embodiments are based on magenta (Mq) 2. Green (G)
3. Four colors were used: yellow (Ye) and cyan (Cy), but for example, magenta (white) that transmits all color light)
(W) The same effect can be obtained by replacing it with a filter. However, in this case, the color signals are electrical signals obtained through each color filter as W and G.

In the case of Ye and Cy, (W+Ye) −(G+Cy)=(R〇+B+R×G
)-(G+G+B)=2R(W+Cy)-(G+Cy)-2B, a primary color signal is obtained. As a result, signal processing creates two color signals from these two primary color signals and the luminance signal.
Composite color signal.

Similarly, the green filter can also be a cyan filter. In this case as well, the color difference signals change to 2R-B and B, but the processing and effects are the same.

Effects of the Invention The solid-state color imaging device of the present invention not only achieves high horizontal resolution, but also eliminates the problem that carriers of color signals generated for objects with no vertical correlation are mixed into the luminance, which has been a problem with similar devices in the past. This phenomenon can be alleviated by increasing the carrier frequency, and in the case of NTSC signals, it can be substantially eliminated by placing the same frequency as a subcarrier frequency, and its practical value is high.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing a color filter configuration of a conventional example, FIG. 2 is a spectrum diagram of an element output signal of the conventional example, and FIG. 3 is a color diagram of a solid-state color imaging device according to an embodiment of the present invention. FIG. 4 is a plan view schematically showing the configuration of the filter, FIG. 4 is a spectrum diagram of the device output signal of the same example, and FIG. 5 is a circuit diagram showing the signal path circuit of the solid-state image sensor using the color filter of the same example. , FIGS. 6 and 7 are diagrams for explaining the signals on the signal processing circuit shown in FIG. 5. 30o...Pixel, 301...Magenta filter, 302...Yellow filter, 30
3...Clean filter, 3o4...
Cyan filter. Figure 2 (M)

Claims (5)

[Claims] (1) A color solid-state image sensor is provided in which a mosaic color filter corresponding to the solid-state image sensor is arranged on a solid-state image sensor having a staggered pixel arrangement, and the mosaic color filter is arranged on a solid-state image sensor that has a staggered pixel arrangement. A filter that transmits two different colored lights is disposed for each pixel, and the filter is configured to:
Solid-state color imaging characterized in that the solid-state imaging device is arranged with four colors repeated in the horizontal scanning direction, and the horizontal filter row has four scanning lines repeated in the vertical scanning direction. Device. (2) A filter that transmits the first and second color light is disposed on the first pixel of the first horizontal pixel column on the solid-state image sensor, and a filter that transmits the first and second color light is disposed on the second pixel of the first horizontal pixel column. A filter that transmits the third and fourth colored lights is arranged on the
A filter that transmits the first and 40th colored lights is arranged on the pixel, and a third and second filter is arranged on the second pixel on the second horizontal pixel column.
A color filter that transmits the 0th color light is disposed on the first pixel on the third horizontal pixel column, a color filter that transmits the 3rd and 40th color light is disposed on the first pixel on the third horizontal pixel column, and a color filter that transmits the 3rd and 40th color light is disposed on the first pixel on the third horizontal pixel column. A filter that transmits the first and twentieth colored lights is disposed on the pixel of the fourth horizontal pixel column, a filter that transmits the third and second colored light is disposed on the first pixel of the fourth horizontal pixel column, and a filter that transmits the third and second colored light is disposed on the first pixel of the fourth horizontal pixel column. 2. The solid-state color imaging device according to claim 1, further comprising a filter that transmits the first and fourth colored lights arranged on the second pixel on the horizontal pixel column. (3) The color filter that transmits the first color light is a filter that transmits gold light, the filter that transmits the 20th color light is a filter that transmits red and green light, and the filter that transmits the fourth color light is a filter that transmits blue and green light. 3. The solid-state color imaging device according to claim 2, wherein the filter that transmits green light and the filter that transmits 30th color light are filters that transmit green light. (4) The filter that transmits the first color light is a filter that transmits red and tonal light, the filter that transmits the 20th color light is a filter that transmits red and green light, and the filter that transmits the fourth color light is blue and green. 3. The solid-state color imaging device according to claim 2, wherein the filter that transmits light and the filter that transmits third color light are filters that transmit green light. (5) The filter that transmits the second color light is a filter that transmits red and blue light, the filter that transmits the fourth color light is a filter that transmits red and green light, and the filter that transmits the third color light is a filter that transmits blue and blue light. Solid-state color imaging device 0 according to claim 2, characterized in that the filter that transmits green light and the filter that transmits first color light are filters that transmit golden light.