JP2760029B2 - Solid-state imaging device - Google Patents

Description

The present invention relates to a color solid-state imaging device using a CCD element or a MOS element.

[Prior Art] FIG. 5 is a block diagram showing the configuration of a conventional MOS type color image sensor and its output processing circuit. Reference numeral 10 denotes a photosensitive area, in which a large number of photoelectric conversion elements 10C are arranged in a two-dimensional plane. On the upper surface of the photoelectric conversion element 10C, micro-filters of four colors of W (clear), Cy (cyan), Ye (yellow), and G (green) are affixed on a set of 2 pixels × 2 pixels. ing. A known drive circuit (not shown) drives a vertical shift register 12 and a horizontal shift register 14 by a control clock from a clock circuit (not shown), and switches the switches in accordance with the scanning timing of the television signal.
16 and 18 are controlled, and the signal of the photoelectric conversion element 10C is output to the signal output line.
Read out at 20,22. The signals of the filters W and Ye are alternately output to the signal output line 20, and the filters G and
Cy signals are read alternately.

The signals on the signal output lines 20 and 22 are added by an adding circuit 24. That is, a high-band luminance signal is formed from signals of two pixels arranged in the vertical direction. On the other hand, the sampling circuit 26 has W, Cy, Ye
The signal is sampled, and the matrix circuit 28 calculates R = W−C
The R signal and the B signal are formed by subtraction processing of y, B = W−Ye. The process circuit 30 performs known video signal processing such as gamma correction and aperture correction on the luminance signal and the R and B signals formed as described above, and the encoder circuit 32 converts the signal into an NTSC television signal.

[Problems to be Solved by the Invention] However, in the above conventional example, since the saturation level with respect to the incident light amount is different for each color of the color filter, there is a problem that the dynamic range of the photoelectric conversion element is not effectively used. That is, assuming that the amount of light transmitted through W (transparent filter) and incident on the photoelectric conversion element is 1, approximately 2/3 of the light is incident on Cy and Ye, and approximately 1/3 of the light is incident on G. In other words, Cy and Ye saturate before G and W saturate before Cy and Ye.

If saturated, the linearity is lost and cannot be used as a video signal. Therefore, the amount of incident light is adjusted within a range where the W photoelectric conversion element is not saturated. In that case, Cy, Ye, G
However, there is a problem that the photoelectric conversion element does not reach the saturation level, cannot effectively use the dynamic range, and cannot obtain a good S / N ratio.

Therefore, an object of the present invention is to provide an imaging device that solves such a problem.

[Means for Solving the Problems] A solid-state imaging device according to the present invention is a solid-state imaging device using a micro color filter, and has two pixels vertically and two pixels horizontally.
A pixel is defined as one unit, and cyan and yellow color filters having a single-side ratio of 3/4 are arranged so that the overlapping area thereof is minimized.

[Operation] By the above means, the saturation of each pixel becomes substantially constant,
The dynamic range of the photoelectric conversion element can be fully utilized.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 shows the color filter arrangement. In the conventional example, one color is assigned to one photoelectric conversion element, but in the present embodiment, as shown in FIG. 2, the light receiving surface of one photoelectric conversion element (that is, pixel) is divided into two parts vertically and horizontally. (total,
4), and W, Cy, Ye, and G are assigned 1/4 each (P ₁₁ , P _{22 in} FIG. 2), and Cy or Ye is 3 /
4. Pixels (P ₁₂ and P _{21 in} FIG. 2) to which G is assigned to 1/4 are provided. The former pixel is used for generating a luminance signal, and the latter pixel is used for generating a color signal.

For example, when i the signal output of the pixel P _11, the signal output of the pixel P ₂₁ was j, the signal output of the pixel P ₁₂ and k, i, j, k is represented as follows.

i = W + Cy + Ye + G = (R + G + B) + (G + B) + (R + G) + G = 2 (R + 2G + B) (1) j = 3Cy + G = 3 (G + B) + G = 4G + 3B (2) k = 3Ye + G = 3 (R + G) + G = G = 3 3) From equations (1), (2) and (3), the R signal and the B signal are represented by the following equations.

R = (1/3) (3i−2j−k) (4) B = (1/3) (3i−j−2k) (5) The color filter arrangement of the portion not shown in FIG. , Based on the color filter arrangement of four pixels in FIG.
It is shifted horizontally and vertically, respectively.

FIG. 1 will be described. 40 is a photosensitive area, and 40C is a photoelectric conversion element. The light receiving surface of the photoelectric conversion element 40C has a second
A color filter having an arrangement as shown in the figure is attached. 42 is a vertical shift register, 44 is a horizontal shift register, and the signal of each photoelectric conversion element 40C is read out to signal output lines 46, 48 as in the conventional example. The switch 50 serializes the signal from the signal output lines 46 and 48 and converts the signal into an A / D converter.
Numeral 52 digitizes each pixel. The digital data is written to the memory 56 via the memory control circuit 54. The memory control circuit 54 controls the image data in the memory 56
An interpolation operation and a known matrix operation, which will be described later, are performed, and the result is output in the form of a luminance signal Y and color difference signals RY and BY. These are converted into analog signals by the D / A converter 58, and are converted into NTSC signals by the encoder 60.

Referring to FIG. 3 showing the pixel arrangement, a memory control circuit 54
Will be described. In Figure 3, the pixels indicated by hatching (such as _{P 11, P 31, P 51} ) is a pixel of a filter arrangement for a luminance signal generation described above. Here, paying attention to the pixel P _32, forming the interpolated data by _{P 32 = (1/4) (P} 31 + P 33 + P 22 + P 42). Similarly, for _P52 , _P72, etc., interpolation calculation is performed from the surrounding four pixels. Thereby, a luminance signal of each horizontal line is formed. On the other hand, for the color signal, an R signal and a B signal can be formed from the equations (4) and (5), and a color difference signal is formed by subtracting the above-described luminance signal.

Next, a method for realizing the filter arrangement shown in FIG. 2 will be described. As shown in FIG. 4, a square Ye filter having a length ratio of 3/4 on one side is arranged on the lower left side, and the length of one side is on the upper right side. The ratio is 3 /
Place a 4 square Cy filter. The Ye filter and the Cy filter overlap at the center, and become the portion G in FIG.
The portion without both the Ye filter and the Cy filter is the portion of W (clear) in FIG. With this configuration, the size of the filter for each color does not become too small, which is advantageous in the manufacturing process.

In the above description, a MOS device is taken as an example, but the present invention uses a C device.
It can also be applied to other image sensors such as a CD type. Needless to say, the signal processing circuit can be realized not only by a digital system but also by an analog system combining 1H delay lines.

[Effects of the Invention] As can be easily understood from the above description, according to the present invention, the saturation light amounts of the respective pixels become equal, and the dynamic range can be effectively used. In addition, there is an effect that it can be manufactured simply and inexpensively without becoming complicated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of an embodiment of the present invention, FIG.
FIG. 3 is a diagram illustrating a color filter array according to an embodiment of the present invention, FIG. 3 is a diagram illustrating an interpolation operation, FIG. 4 is a diagram illustrating a method for realizing the color filter array of FIG. 2, and FIG. FIG. 3 is a configuration block diagram. 40: photosensitive area, 40C: photoelectric conversion element, 42: vertical shift register, 44: horizontal shift register, 46, 48: signal readout line, 50: switch, 54: memory control circuit, 56: memory, 60:
Encoder

Claims (1)

(57) [Claims] 1. A solid-state imaging device using a micro color filter, wherein two pixels vertically and two pixels horizontally are defined as one unit.
A solid-state imaging device comprising a cyan color filter and a yellow color filter each having a single-side ratio of 3/4, arranged such that an overlapping area thereof is minimized.