JPS6188683A - Color solid-state image pickup device - Google Patents

Abstract

PURPOSE:To attain an object to be colored hardly in green by using a color filter decreasing the transmitted luminous amount of a transparent element to 70% for a picture element group arranged in the order of transparent, cyan and yellow element even when a high-brightness white object is picked up for its image. CONSTITUTION:The picture element group 51 of a color solid-image pickup device is arranged alternately in a way that a row element shifted by 3/2 picture element's share in the row direction is arranged in the column direction alternately with the same constitution as the row element arranged in the order of transparent element W', cyan element Cy and yellow element Ye. Further, the color filter 52 decreasing the transmitted luminous amount of the transparent element W' to 70% is provided. Thus, in picking up the image of the object of white high brightness, the color difference signal amount is a value close to zero and the green coloring hardly takes place.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a so-called single-chip type device that obtains color signals by arranging a color separation filter (hereinafter referred to as a color filter) in front of one solid-state image sensor. The present invention relates to a color solid-state imaging device.

(Structure of conventional example and its problems) In recent years, solid-state cameras that have entered the practical stage have been improved in characteristics, image quality, etc. In particular, recently, in order to improve the horizontal resolution of solid-state cameras, each pixel 1 of the light sensing section is shifted in the row direction by half a pixel between adjacent rows, as shown in Figure 1. Solid-state imaging devices with similar configurations have been attracting attention.

In order to configure a single-chip color camera using one solid-state image sensor, as shown in Figure 2, on the front of the solid-state image sensor,
It is necessary to arrange a color filter 22 having a color arrangement corresponding to the pixel group 21 of the solid-state image sensor. However, in FIG. 2, the pixel group of the image sensor is represented by Alj to AGS, and each element of the color filter is represented by C11 to C65.

Conventionally, a filter configuration with good luminance sensitivity using transparent, cyan, and yellow as shown in FIG. 1,982)).

Here, processing of an element output signal when this color filter is arranged in an image sensor will be explained. Light - 2 = The signal charges accumulated in each pixel of the sensing section are 2
Each row is read out simultaneously and converted into a composite video signal through a signal processing circuit. Moreover, since the composite video signal is interlaced scanned to reproduce the image, the signal charge is read out as follows. That is, in the first field, the first and second rows, the third and fourth rows, the fifth and sixth rows of the pixel group of the image sensor (continued below), For 2 fields, 2nd and 3rd rows, 4th and 5th rows, 6th and 7th rows
The signal charges in the rows (continued below) are read out and reproduced at the same time.

A composite video signal consisting of a luminance signal and a color signal is created as follows. Signal charges are simultaneously read out in two rows one after another from the photo-sensing section of the image sensor, which consists of 398 pixels horizontally and 496 pixels vertically. Consider the case where signal charges in rows n and n+1 are read out. These signals pass through a sampling circuit 42 and are divided into W, Cy, and Ye signals. Furthermore, these signals pass through a low-pass filter 43 and a process circuit 44, and are added to the luminance signal Y.
becomes. On the other hand, after the Y process circuit 44, W-Cy, W
-Ye calculation, R and B signals are generated, and then subtracted by a and b times luminance signals, and after passing through a 0.5 MHz low-pass filter 45, color difference signals R-aY and B-bY are obtained.

Here, a and b are parameters determined so that the color difference signal becomes zero for white light (white balance adjustment). Luminance signal Y and color difference signal R-a Y .

B-bY is further encoded in 46 ways and becomes a composite video signal. However, with this method, the following problem occurs when white light with such brightness as to saturate the accumulated charge in the photodiode is imaged. The color difference signal C,,C2 is C1=R-aY= (W-Cy)-a (W+Cy+
Ye)-...(1)C2=B-bY= (W-Ye)-
a (W+Cy+Ye)−・(2), but
When the accumulated charge of each photodiode is completely saturated, W-Cy=O (3) W-Ye=O・
......(4) and the color difference signal C□
, C2 is C1=-aY (5)
c2=-by (6). As a result, the high-brightness white color becomes green (highlight green), and since the brightness signal Y is large, the degree of this change is remarkable, and the image quality is greatly degraded.

(Objective of the Invention) In view of the above-mentioned drawbacks, the present invention provides a color solid-state imaging device that can significantly reduce coloring of a high-luminance white object when the object is imaged.

(Structure of the Invention) In order to achieve this object, the color solid-state imaging device of the present invention has row elements arranged in the order of transparent, cyan, and yellow, and 3/2 pixels in the row direction with the same configuration as the row elements. The separated row elements are arranged alternately in the horizontal direction, and have color separation filters that reduce the amount of light transmitted through the transparent elements.

With this configuration, when a high-brightness white subject is imaged, coloring of the subject can be significantly reduced.

(Description of Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows the configuration of a color filter 52 in one embodiment of the present invention, and the color filter elements correspond to pixels 51 of the image sensor as shown. Here, the transmittance of the transparent element (W') is set to 70% (wavelength 400 to 700).
(W' = 0.7W) (with fluctuations of ±5% around 70% in nm).

With this configuration, the luminance signal Y and color difference signals C1°C2 are as follows.

Y=0.7W+Cy+Ye -----(7)C□=0.
7W-Cy-aY・・・・・・・・・・・・(8)C,
=0.7W-Ye-bY --(9) Here, the color difference signals C□ and C2 will be explained.

Crystal filters used in cameras, infrared cut filters,
3200 and the spectral characteristics of the light source are Cr(λ), respectively.

■(λ), L(λ) and that of W, Cy, Ye is W(
λ).

Cy(λ), Ye(λ). In formulas (8) and (9), 0.7W-Cy and 0.7W-Ye are 3200
When the K light source is imaged with a camera, 0.7W-Cy= (0.7W(λ)-Cy(1))C
r(L)I(λ) ・L(λ)d l # 00.7W
−Ye= (0,7W(λ)−Ye(λ))Cr(λ)
I (λ)·L(λ)dλ#O, and when the white balance is adjusted, a and b become almost zero.

Therefore, even if a white, high-brightness subject is imaged, the color difference signal amount will be close to zero, and green coloring will hardly occur.

C□=-aYYO 22=-by 吋○ On the other hand, since the amount of transparent transmitted light decreases to 70%, the amount of luminance signal decreases, but in actual reproduced images, this is hardly a problem. Furthermore, no green coloring occurred even when an image was taken of a white object with such high brightness that the accumulated charge in the photodiode was saturated.

(Effects of the Invention) As described in ``2'' below, the present invention has row elements arranged in the order of transparent, cyan, and yellow, and 372 row elements in the row direction with the same configuration as the row elements.
fic, in which row elements shifted by a pixel are arranged alternately in the column direction,
By using a color filter that reduces the amount of light transmitted through the transparent element to 7 parts, there is an advantage that when capturing an image of a high-brightness white subject where the accumulated charge in the photodiode is from unsaturated to saturated, the subject will hardly be colored green. Yes, it has great practical effects.

[Brief explanation of drawings]

Fig. 1 is a pixel configuration diagram of a solid-state image sensor, Fig. 2 is a diagram for explaining the arrangement relationship between the pixel group of the solid-state image sensor and each element of a color filter, and Fig. 3 is a color arrangement of a conventional color filter. figure,
FIG. 4 is a diagram for explaining signal processing of a solid-state imaging device,
FIG. 5 is a diagram showing the arrangement of color filters and a correspondence diagram with pixel groups of an image sensor in an embodiment of the present invention. 21.51... Pixel group of solid-state image sensor, 52... Color filter element section of the present invention. Figure 3

Claims (2)

[Claims] (1) Row elements arranged in the order of transparent, cyan, and yellow in the row direction and row elements that have the same configuration as the previous row element but are shifted by 3/2 pixels in the row direction are arranged alternately in the column direction. Also, a color solid-state imaging device having a color separation filter that reduces the amount of transmitted light of the transparent material. (2) The color solid-state imaging device according to claim (1), wherein the transparent element has a transmittance of 65 to 75%.