JPH09182090A - Single solid state color image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the complication of a circuitry and to improve sensitivity. SOLUTION: This device has a single solid state color image pickup element 1 arranging the color filters having different spectroscopic sensitivity characteristics of each photosensitive part, a color separation circuit 3 performing the color separation of the image signal imaged by the single solid state color image pickup element 1 and an arithmetic circuit 5 additing the image signals of the different picture elements after the color separation and performing an interpolation processing. In this constitution, the image pickup of high sensitivity is performed by adding the picture element signals of plural picture elements. When a switch 9 is turned 'on' and a two times mode is selected, for instance, the signal in the horizontal direction is added to the output of the arithmetic circuit 5 and further, the signal is held for a two-picture element signal period. As a result, sensitivity becomes about two times and horizontal resolution becomes 1/2 times. By performing this processing, horizontal resolution is lowered and sensitivity can be increased about two times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-plate color solid-state image pickup device having improved sensitivity.

[0002]

2. Description of the Related Art In the past, solid-state image pickup devices have been especially used for CCD (ch
In a single-plate color imaging device using one arge coupled device), a color filter is arranged for each photosensitive portion of a CCD device as shown in FIG. 5 to synthesize a color video signal. That is, the signals of the vertically adjacent pixels are added and read out.

The procedure of Conventional Example 1 will be described below based on the color arrangement example of the color filter array shown in FIG. For example, in the A field, charges are mixed in pairs such as A1 and A2, and in the B field, pairs such as B are formed. Therefore, in the A1 line, (G + Cy), (Mg + Ye)
Are taken out in order, and on the A2 line, (Cy + M
g) and (G + Ye) are taken out in this order.

A luminance signal (Y) and color-difference signals (RY) and (BY) can be obtained by adding and subtracting pixels adjacent to each other to the extracted signals. The arithmetic expression is shown below.

Y = {(G + Cy) + (Mg + Ye)} × (1/2) = {(G + Ye) + (Cy + Mg)} × (1/2) = (1/2) (2B + 3G + 2R) R−Y = { (Mg + Ye)-(G + Cy)} = 2R-G B-Y = {(G + Ye)-(Mg + Cy)} = 2B-G

As can be seen from the above equation, the luminance signal Y
Are the same on the A1 and A2 lines. In addition, the color difference signal R
-Y and BY are obtained every other line. The same applies to the B field.

By the way, as a method of increasing the sensitivity of the image pickup apparatus, there is a method of adding signals of two pixels arranged in the horizontal direction. This is a method used particularly in an image pickup device using three channels of R, G, and B CCD elements, and doubles the sensitivity at the expense of horizontal resolution.

However, in the above-mentioned conventional example 1, it is not possible to use the method of adding the signals of the two pixels arranged in the horizontal direction in order to double the sensitivity. The reason is,
This is because, in the single-chip color CCD element, as described above, four different color filters are arranged for each pixel, and therefore accurate color separation cannot be performed if pixels in the horizontal direction are added together.

The following methods have been proposed for obtaining independent signals between pixels using a single-chip color CCD element. In Japanese Unexamined Patent Publication No. 63-267068 “Solid-state image pickup device” of Conventional Example 2, a plurality of readout registers are provided in a single-plate color camera, and the plurality of readout registers simultaneously read out signal charges of a plurality of horizontal lines. It is carried out.

Further, Japanese Patent Laid-Open No. 61-18978 of Conventional Example 3
No. 7 “color solid-state image pickup device” reads a solid-state image pickup device using a predetermined color filter array in a field accumulation mode, and further uses a delay line for one horizontal scanning period, so that three types of pixels between pixels can be calculated without calculation. You are getting an independent signal.

[0011]

However, the circuit configurations of the conventional examples 2 and 3 are complicated. In particular, when the imaging time is lengthened, in the second conventional example, the register capacity increases in proportion to the lengthened imaging time. Further, in Conventional Example 3, it is necessary to configure the time constant of the delay line to be large.

It is an object of the present invention to provide a single-plate color solid-state image pickup device which suppresses complication of a circuit structure and improves sensitivity.

[0013]

In order to achieve the above object, a single-plate color solid-state image pickup device of the present invention includes a single-plate color solid-state image pickup device in which color filters having different spectral sensitivity characteristics are arranged in respective photosensitive parts. It has a color separation circuit for performing color separation of image signals picked up by a single-plate color solid-state image pickup element, and an arithmetic circuit for adding and interpolating image signals of different pixels after color separation, and The feature is that high-sensitivity imaging can be performed by adding them.

Further, it is preferable that the above addition is horizontal addition, and the image signals after color separation are Y, RY and BY signals.

Further, it is preferable that the single-plate color solid-state image pickup device has a switch, and the addition condition is changed by setting the switch to change the image pickup sensitivity.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of a single-plate color solid-state image pickup device according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 4, there is shown one embodiment of a single-plate color solid-state image pickup device of the present invention. 1 is a block diagram of the embodiment, FIGS. 2 to 4 are timing charts of an arithmetic circuit, FIG. 2 is an input signal, and FIG.
The output signal level at the time of FF, and FIG. 4 is the output signal level at the time of sensitivity increase ON.

In FIG. 1, the single-plate color solid-state image pickup device of the present embodiment has an image pickup device 1 which is a photoelectric conversion device, a sample hold circuit 2, a color separation circuit 3, an A / D conversion circuit 4,
An arithmetic circuit 5, a D / A conversion circuit 6, a process encoder circuit 7, a control circuit 8 and a switch 9 for switching the sensitivity increase ON / OFF.

In each component of the single-plate color solid-state image pickup device constructed as described above, the image pickup signal output from the image pickup device 1 is a sample hold circuit 2 and a color separation circuit 3.
Are converted into a luminance signal Y and color difference signals RY and BY.

Next, it is converted into a digital signal by the A / D conversion circuit 4 and is further input to the arithmetic circuit 5. The arithmetic circuit 5 performs horizontal addition and interpolation, and outputs a processed signal. Output signals Y ', RY', B of this arithmetic circuit 5
-Y 'is converted back to an analog signal by the D / A conversion circuit 6 and output.

The output signal of the arithmetic circuit 5 is input to the process encoder circuit 7. In the process encoder circuit 7, the analog signal is processed for gamma correction, white clip, black clip, etc., and output as a normal decoded video signal. The control circuit 8 controls the horizontal addition and interpolation processing operations in the arithmetic circuit 5.

Next, the operation of the single-plate color solid-state image pickup device of this embodiment will be described with reference to FIGS. FIG.
4 shows the input / output relationship of the arithmetic circuit 5 of FIG. Of these, FIG. 2 shows the input signal levels of the luminance signal Y and the color difference signals RY and BY. When the sensitivity increase “OFF” is set by the control circuit 8, when the normal mode is selected, the output of the arithmetic circuit 5 is the same input / output signal as that of FIG. 3, that is, FIG.

When the double mode is selected when the sensitivity is set to "ON", the output of the arithmetic circuit 5 is as shown in FIG.
Becomes That is, in the double mode, signals in the horizontal direction are added and the signals are held for two pixel signal periods.
Therefore, the sensitivity is about double and the horizontal resolution is 1/2. By performing such processing, the horizontal resolution is lowered, but the sensitivity can be approximately doubled.

According to the above embodiment, the signals Y, RY and BY output from the color separation circuit are respectively A / D.
To be converted. In the arithmetic circuit, two pixels arranged in the horizontal direction are added, and interpolation for two pixels is further performed. Further, the D / A conversion circuit returns the analog signal, and the circuit in the subsequent stage becomes a normal video signal. Therefore, in the single-plate color solid-state imaging device, the sensitivity can be improved by adding horizontal pixels.
This is because it has an arithmetic circuit for performing horizontal pixel addition and interpolation immediately after the color separation circuit. Also, the condition for increasing the sensitivity does not need to be doubled. This condition change can be easily performed.

[0024]

As is apparent from the above description, in the single-plate color solid-state image pickup device of the present invention, a color filter having different spectral sensitivity characteristics is arranged in each light-sensitive portion of the single-plate color solid-state image pickup device to pick up an image. The separated image signals are color-separated, and the image signals of different pixels after color separation are added to perform interpolation processing. Therefore, in a single-plate color solid-state image device, the sensitivity can be improved by adding a plurality of pixel signals.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a single-plate color solid-state imaging device of the present invention.

FIG. 2 is a timing chart 1 of the arithmetic circuit.

FIG. 3 is a timing chart 2 of the arithmetic circuit.

FIG. 4 is a timing chart 3 of the arithmetic circuit.

FIG. 5 is a diagram showing a color arrangement example of a conventional color filter array.

[Explanation of symbols]

 1 Image sensor 2 Sample and hold circuit 3 Color separation circuit 4 A / D conversion circuit 5 Arithmetic circuit 6 D / A conversion circuit 7 Process encoder circuit 8 Control circuit

Claims (4)

[Claims] 1. A single-plate color solid-state imaging device in which color filters having different spectral sensitivity characteristics are arranged in each photosensitive section, and a color separation circuit for performing color separation of image signals picked up by the single-plate color solid-state imaging device. A single-panel color characterized by having an arithmetic circuit for adding and interpolating image signals of different pixels after the color separation, and enabling high-sensitivity imaging by adding pixel signals of a plurality of pixels Solid-state imaging device. 2. The single-chip color solid-state imaging device according to claim 1, wherein the addition is horizontal addition. 3. The image signal after the color separation is Y, R-
3. A single-plate color solid-state image pickup device according to claim 1, wherein the single-chip color solid-state image pickup device is a Y, B-Y signal. 4. The single-chip color solid-state image pickup device further has a switch, and the addition condition can be changed by setting the switch to change the image pickup sensitivity. 4. The single-plate color solid-state imaging device according to any one of 3 above.