JP3123415B2 - Single-chip color solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single-chip color solid-state imaging device with improved sensitivity.

[0002]

2. Description of the Related Art Conventionally, a solid-state image pickup device has a CCD (ch).
In a single-chip color imaging device using one arge coupled device, a color filter is arranged for each photosensitive portion of the CCD device as shown in FIG. 5 to synthesize a color video signal. That is, the signals are read out while adding up the signals of the vertically adjacent pixels.

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

A luminance signal (Y) and color difference signals (RY) and (BY) can be obtained by adding and subtracting the pixels adjacent to the signal to the extracted pixels. 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 BY = {(G + Ye) − (Mg + Cy)} = 2B−G

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

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

However, in the above-mentioned conventional example 1, it is impossible to use a method of adding signals of two pixels arranged in a horizontal direction in order to double the sensitivity. The reason is,
As described above, in the single-chip color CCD device, since four different color filters are arranged for each pixel, if the pixels in the horizontal direction are added, accurate color separation cannot be performed.

The following method has been proposed for obtaining independent signals between pixels using a single-chip color CCD device. In Japanese Patent Application Laid-Open No. 63-267068 "Solid-state imaging device", a plurality of readout registers are provided in a single-chip color camera, and signal charges of a plurality of horizontal lines are read out simultaneously by the plurality of readout registers. It is carried out.

Further, Japanese Patent Application Laid-Open No. 61-18978 of the prior art 3 is disclosed.
No. 7 “color solid-state imaging device” reads out a solid-state imaging 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 obtained without calculation. I have an independent signal.

[0011]

However, the prior arts 2 and 3 have a complicated circuit configuration. In particular, when the imaging time is lengthened, in the second conventional example, the capacity of the register increases in proportion to the lengthening of the imaging time. In the third conventional example, it is necessary to increase the time constant of the delay line.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a single-chip color solid-state imaging device in which the complexity of the circuit configuration is suppressed and the sensitivity is improved.

[0013]

In order to achieve the above object, a single-chip color solid-state imaging device according to the present invention includes a single-chip color solid-state imaging device in which color filters having different spectral sensitivity characteristics are arranged in each photosensitive portion; Image signals picked up by a single-chip color solid-state image sensor are converted into Y, RY, and BY image signals.
A color separation circuit that performs color separation, and an arithmetic circuit that horizontally adds and interpolates image signals of different pixels after color separation,
High sensitivity imaging is enabled by horizontally adding pixel signals of a plurality of pixels.

[0014]

Further, it is preferable that the single-chip color solid-state imaging device has a switch, and that the setting of the switch changes the addition condition so that the imaging sensitivity can be changed.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a single-chip color solid-state imaging device according to an embodiment of the present invention; 1 to 4 show an embodiment of a single-chip color solid-state imaging device according to the present invention. FIG. 1 is a block diagram of an embodiment, and FIGS. 2 to 4 are timing charts of an arithmetic circuit. FIG. 2 shows an input signal, and FIG.
FIG. 4 shows an output signal level when the FF is turned on, and FIG. 4 shows an output signal level when the sensitivity is increased.

Referring to FIG. 1, a single-chip color solid-state imaging device according to the present embodiment includes an imaging element 1, which is a photoelectric conversion element, a sample and hold circuit 2, a color separation circuit 3, an A / D conversion circuit 4,
It comprises 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 ON / OFF of sensitivity up.

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

Next, the signal is converted into a digital signal by the A / D conversion circuit 4 and further input to the arithmetic circuit 5. The arithmetic circuit 5 performs horizontal addition and interpolation, and outputs a processed signal. The 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 subjected to processes such as gamma correction, white clipping, and black clipping, and is output as a normal decoded video signal. The control circuit 8 controls horizontal addition and interpolation processing operations in the arithmetic circuit 5.

Next, the operation of the single-chip color solid-state imaging device according to the present embodiment will be described with reference to FIGS. FIG.
4 show the relationship between the input and output of the arithmetic circuit 5 of FIG. FIG. 2 shows the input signal levels of the luminance signal Y and the color difference signals RY and BY. When the normal mode is selected when the control circuit 8 sets the sensitivity up to “OFF”, the output of the arithmetic circuit 5 is the same as the input / output signal shown in FIG. 3, that is, FIG.

When the sensitivity increase "ON" is set and the double mode is selected, the output of the arithmetic circuit 5 is 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 becomes about twice and the horizontal resolution becomes 1/2 times. By performing such processing, the horizontal resolution is reduced, 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
Is converted. In the arithmetic circuit, two pixels arranged in the horizontal direction are added, and interpolation for two pixels is further performed. Further, the signal is returned to an analog signal by a D / A conversion circuit, and becomes a normal video signal in a subsequent circuit. Therefore, in a single-chip color solid-state imaging device, sensitivity can be improved by horizontal pixel addition.
This is because there is an arithmetic circuit that performs horizontal pixel addition and interpolation immediately after the color separation circuit. Further, the condition for increasing the sensitivity is not limited to twice. This condition can be easily changed.

[0024]

As is apparent from the above description, the single-chip color solid-state imaging device according to the present invention has a single-chip color solid-state imaging device in which color filters having different spectral sensitivity characteristics are arranged at respective photosensitive portions, and an image is picked up. Then, the image signals of the different pixels after the color separation are added and subjected to interpolation processing. Therefore, the sensitivity can be improved by adding a plurality of pixel signals in the single-plate color solid-state image device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a single-chip color solid-state imaging device according to 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]

 DESCRIPTION OF SYMBOLS 1 Image sensor 2 Sample hold circuit 3 Color separation circuit 4 A / D conversion circuit 5 Operation circuit 6 D / A conversion circuit 7 Process encoder circuit 8 Control circuit

Claims (2)

(57) [Claims] 1. A single-chip color solid-state imaging device in which color filters having different spectral sensitivity characteristics are arranged in respective photosensitive units, and an image signal captured by the single-chip color solid-state imaging device
A color separation circuit for performing color separation on Y, RY, and BY image signals; and an arithmetic circuit for horizontally adding and interpolating image signals of different pixels after the color separation, and A single-chip color solid-state imaging device characterized in that high-sensitivity imaging is enabled by horizontally adding pixel signals. Wherein said single-plate color solid-state imaging device includes a switch, changing the conditions of the horizontal addition the setting of the switch, according to claim 1 Symbol, characterized in that it possible to change the imaging sensitivity < single-chip color solid-state imaging device.