JPH0420091A - Color solid-state image pickup element - Google Patents

Abstract

PURPOSE:To improve vertical resolution without occurrence of a vertical color false signal, color shading and flicker by outputting a luminance signal and a red or blue color difference signal from a single picture element string in line sequence. CONSTITUTION:Color filters of each picture element are repetition of white cyan Wy and a pseudo cyan Cy' in n-th and n'-th lines and repetition of pseudo yellow Ye' and white cyan Wc in (n+1)-th and (n+1)'-th lines. Thus, the color filter array consists of repetitive patterns of 2X4 picture elements in longitudinal and lateral directions. A luminance signal Y and a color difference signal C are obtained from the sum and the difference of signals from picture elements adjacent in the horizontal direction in each single line by using each color filter. Thus, a picture with high resolution is obtained and occurrences of color false signal, color shading and flicker are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color solid-state image sensor, and particularly to a single-plate color solid-state image sensor in which color filters are arranged in a mosaic pattern.

[Prior Art] As a single-chip color solid-state image pickup device, a field readout type device with good dynamic resolution and suitable for the interlaced type, which is the current television scanning type, is mainly used.

In this method, as shown in Fig. 4, four color filters, cyan Cy, yellow Ye, magenta Mg, and green G, are arranged on each photoelectric conversion element (photodiode) (1:1), and the readout is , the signal charges are added and read out in the vertical direction for each field. That is, (2n-1
) line has Cy and Ye, 2n line has Mg and G, (2n+1) line has Ye and cy, (2n+2)
Mg and G are arranged alternately on the line, and cy and Ye are arranged on the (2n+3> line), and in the first field, the pixel signal of the (2n-1) line and the pixel signal of the 2n line are arranged alternately. In the second field, the pixel signals of the 2n line and the pixel signal of the (2n+1) line are added in the vertical direction [(2n+2) lines, etc.]. )
The same applies to lines, (2n+3) lines, etc.].

In this case, the luminance signal Y is obtained by the sum of the signal charges of horizontally adjacent pixels, and the color difference signal C is obtained by the difference between the signal charges of adjacent pixels.

That is, Y=G+Ye+Mg+Cy C= (G×Ye)−(Mg×Cy), or=
(G+Cy)-(Mg+Ye).

Here, Ye=G+R Mg=R0B Cy=G0B, and the spectral characteristics of the filter are adjusted so that the approximate expression G-28~Y-B G-2R~Y-R holds true. Therefore, the color difference signal C can be approximated as C~-(B-Y) or ~-(R-Y).

That is, this color solid-state imaging device can obtain color difference signals line-sequentially in each field. Further, the luminance signal is obtained from pixels of the same combination of filters in the signal of each horizontal line. Therefore, no level difference occurs between lines in the luminance signal.

However, in this type of field accumulation color system, signals of two vertical pixels are added and read out, so there is a drawback that the vertical resolution is reduced. Therefore, in order to obtain images with high vertical resolution, as in EDTV cameras and electronic still cameras, there is a movement to obtain signals for each horizontal line from a single pixel column. FIG. 5 is an arrangement diagram of color filters in a conventional image sensor of this kind. In this method, the same pixel is divided into two or three regions, and two types of color filters are arranged so as to occupy equal areas (see Fig. 5).
An example of dividing one pixel area into two is shown).

In this image sensor, in the lines n and n', Ye
+Mg color filter and cy+a color filter are repeated, and in the n+1, (n+1)' line, Cy0M
This is a repetition of color filtering of g and color filtering of Y e 10G. In this method, the luminance signal is determined from the sum of signals of horizontally adjacent pixels in each line, and the color difference signal is determined from the difference between signals of horizontally adjacent pixels. Therefore, according to this method, a luminance signal and a color difference signal are obtained for each line, and an image with high vertical resolution can be obtained.

"Problems to be Solved by the Invention" In the first conventional example described above, pixel signals were added in the vertical direction, so there was a drawback of a decrease in resolution.The second conventional example addresses this point. However, since two types of color filters are provided in the same pixel, misalignment in the manufacturing process of the color filters may cause filters to be misaligned, overlapped, missing, etc. This may result in the generation of color signals that are not present in the color filter, or color shading or flicker.

Furthermore, there were differences in signal amount between lines.

Therefore, an object of the present invention is to provide a color solid-state image sensor that can obtain high-resolution images and suppress the occurrence of brown shading, flicker, and color artifacts.

[Means for Solving the Problems] A color solid-state image sensor according to the present invention has pixels that have different spectral characteristics due to a combination of a photoelectric conversion element (photodiode) and a color filter, In the first horizontal line, pixels having the first spectral characteristic and pixels having the second spectral characteristic are arranged alternately, and in the second horizontal line, the pixels having the third spectral characteristic are arranged alternately.
Pixels having a spectral characteristic and pixels having a fourth spectral characteristic are arranged alternately, and the color filter corresponding to the pixel having the first spectral characteristic is a green color filter that covers the entire light receiving section. A yellow color filter having an area half of the light receiving area of the pixel is laminated on a magenta color filter having a certain transmittance, and the color filter corresponding to the pixel having the second spectral characteristic is layered on a magenta color filter having a certain transmittance. A yellow filter having an area half the light receiving area of the pixel is laminated on a cyan filter that covers the entire third pixel.
The color filter having the fourth spectral characteristic is obtained by laminating a cyan filter having an area half of the light receiving area of the pixel on a yellow filter that covers the entire light receiving section, and has the fourth spectral characteristic. A color filter corresponding to a pixel is a magenta color filter having a certain transmittance for green, which covers the entire light receiving section, and a cyan color filter having an area half the light receiving area of the pixel stacked thereon.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a color filter array showing one embodiment of the present invention.

The color filter in Figure 1 is designed to ensure vertical resolution.
It is configured so that the signal of each horizontal line can be obtained from a single line of pixels, and is driven by frame accumulation drive or pseudo field accumulation drive (Television Society Technical Report 198'
(February 2013).

As shown on the right side of FIG. 1, the color filter of each pixel is composed of repeating white cyan wy and pseudo cyan Cy' in the n and n' lines, and (n+
1), (n+1)' line, pseudo yellow Y
It is constructed by repeating e' and white cyan Wc. Therefore, this color filter array is
It is composed of a repeating pattern of 2×4 pixels vertically.

The spectral characteristics of these color filters are shown in Figures 2 (a) and (b).
), and white yellow W,y is a yellow having a transmittance of 50% in B (blue) and G (green) as shown by the broken line in FIG.
Furthermore, pseudo cyan Cy' has a transmittance lowered to 50% in B than normal cyan, as shown by the solid line in FIG. 2(a). Therefore, it can be written as Wy=B/20G/2+R (y'=B/2+G).

In addition, white cyan Wc is, as shown by the broken line in FIG. 2 (, b), in G and R (red).
Cyan has a transmittance of 50%, and pseudo yellow Ye' has a transmittance of 50% in R compared to normal yellow, as shown by the solid line in FIG. 2(b).
It was lowered to Therefore, W c = B + G / 2 + R / 2Ye' =
It can be called G+R/2.

By using a filter having such spectral characteristics, the luminance signal Y and color difference signal C can be obtained from the sum and difference of signals from horizontally adjacent pixels in the winter grass line. That is, at lines n and n', Y=W3/'+C3/ = (B/2+G/2±R)-1-(B/2+c)=B
+1.5G+R c=wy-cy = (B/2+G/2+'R)-(B/2+G)R-G
/2 is obtained, and on the line n+1, (n+1)', Y=Ye'+Wc = (G+R/2)+ (B+G/2+R/2)=B+
1.50+R C=Ye −Wc = (G+R/2)−(B×G/2+R/2)=−El
+G/2 is obtained. In other words, a luminance signal is obtained for each horizontal line, and a red difference signal is obtained from lines n and n', and a blue difference signal is obtained from lines n+1 and (n+1>') line-sequentially. As mentioned above, these color difference signals R-G/2 and -B+G/2 are each color difference signal R-
Y and Y-B can be approximated. Since a color difference signal and a luminance signal are thus obtained from each single vertical line, vertical resolution can be improved by using the color filter array of the embodiment.

Specifically, each of these color filters is configured as shown on the left side of FIG. In other words, for white yellow wy, the entire light receiving area of the pixel is 50% in G (green).
It is formed by covering it with magenta (WM), which has a transparency of

On the other hand, pseudo-cyan Cy' is one in which the entire light-receiving area of the pixel is covered with cyan Cy, and yellow is layered on this cyan filter so as to cover half of the light-receiving area (the layered portion is green). Pseudo-yellow Y e ' is obtained by laminating cyan color on a yellow filter layer that covers the entire light-receiving section so as to cover half the area (the laminated portion is green). And white cyan Wc is G
Magenta (W) with 50% transparency in (green)
M), and a cyan filter is layered on top of the magenta (Wm>Wm>filter) so as to occupy half the area.

For each pixel, as shown on the left side of Figure 1, if a filter that occupies half the area is provided in the center of the light receiving area, there will be no misalignment in the vertical or horizontal direction during the manufacturing process. Even if the spectral characteristics of each pixel are changed, there will be no change in the spectral characteristics of each pixel, and even if the areas of the color filters to be stacked are slightly different, color mixing will not occur and the ratio of the two color filters will change. Only. In this way, in the present invention, each pixel is equivalent to having a single filter as shown on the right side of FIG. Unlike a filter in which a plurality of filters coexist within the filter, color shading, flicker, or color false signals do not occur due to misalignment.

In the above example, white yellow wy and white cyan Wc each have a transmittance of 50% in G, but this transmittance depends on the modulation of each color when white light of which color temperature is incident. It is changed depending on whether to minimize the difference in components. 0 Usually white yellow w
The transmittance of y in G is 5 that of pseudo-cyan Cy′
It is set to 0 to 60%, and the G of white cyan Wc
The transmittance is 30~ that of pseudo yellow Ye'.
Set to 50%. In that case, white yellow lol
It is desirable that the sum of transmittances in G of y and pseudo-cyan Cy' be equal to the sum of transmittances in G of white cyan Wc and pseudo-yellow Ye'.

Furthermore, in the above embodiment, the transmittance in B of white yellow Wy and pseudo cyan Cy' was set to 50%, but this means that the transmittance in B of white cyan Wc is 1.
00%, and it is assumed that the transmittance of pseudo yellow Ye' in B is 0%. If this assumption is not satisfied, white yellow wy and pseudo cyan C
The transmittance of y′ at B is white cyan W
1/ of the sum of transmittances in B of C and pseudo yellow Ye'
Set it to 2. Similarly, the transmittance in R of white cyan Wc and pseudo-yellow Ye' is 1 of the sum of the transmittance in R of white yellow wy and pseudo-cyan Cy', respectively.
/2.

FIG. 3 is a plan view of a color filter showing another embodiment of the present invention. The spectral characteristics of each filter are the same as in the previous embodiment and are as shown in FIG. This embodiment differs from the previous embodiments in that the phases of the filter arrays for lines n' and (n+1)' are inverted with respect to the filter arrays for lines n and n+1, respectively. In this way, by inverting the phase of the color filter for each horizontal line,
In a vertically correlated image, the color sampling points in the horizontal direction are equivalently doubled, thereby reducing the occurrence of horizontal color artifacts.

[Effects of the Invention] As explained above, the present invention provides a color filter for each pixel that includes a first color filter that covers the entire light-receiving surface of the pixel and a second color filter that covers half the area of the light-receiving surface of the pixel. Since the luminance signal and the red or blue color difference signal are obtained line-sequentially from a single pixel column, the present invention eliminates the generation of vertical color false signals for each color. Also,
It is possible to provide a color solid-state image sensor that does not cause color shading or flicker and has high vertical resolution.

[Brief explanation of drawings]

FIG. 1 is a plan view of a color filter array showing one embodiment of the present invention, FIGS. 2(a) and <b> are spectral characteristic diagrams of each color filter, and FIG. FIG. 4 is a plan view of a color filter array showing an embodiment. FIG. 4 is an example of a conventional field readout color filter array, and FIG. 5 is a conventional frame readout color filter array example.

Claims (1)

[Claims] a first horizontal line in which pixels having a first spectral characteristic and pixels having a second spectral characteristic are arranged alternately;
In a solid-state imaging device in which pixels having a spectral characteristic of and second horizontal lines in which pixels having a fourth spectral characteristic are alternately arranged, the pixels correspond to the pixels having the first spectral characteristic. The color filter is composed of a laminate of a magenta color filter having a certain transmittance to green that covers the entire light receiving area of the pixel, and a yellow color filter that covers half of the light receiving area, and has the second spectral characteristic. The color filter corresponding to the pixel having the third spectral characteristic is composed of a laminate of a cyan filter that covers the entire light-receiving area of the pixel and a yellow filter that covers half of the light-receiving area, and the color filter that corresponds to the pixel that has the third spectral characteristic The color filter corresponding to the fourth color filter is composed of a laminate of a yellow color filter that covers the entire light receiving area of the pixel and a cyan color filter that covers half of the light receiving area, and
A color filter corresponding to a pixel having spectral characteristics is composed of a laminate of a magenta color filter that has a certain transmittance to green that covers the entire light receiving area of the pixel, and a cyan color filter that covers half of the light receiving area. A color solid-state image sensor characterized by: