JPH02187066A - Solid-state image sensor with color filter - Google Patents

Abstract

PURPOSE:To obtain a corrected color signal from a unit photodetector by a method wherein a plurality of color filters are provided in a region corresponding to the unit photodetector with predetermined ratios. CONSTITUTION:Color filters 2 are formed on the part 3 of a semiconductor substrate containing unit photodetectors of a solid state image pickup device. The color filters 2 are so provided as to cover the aperture windows of the unit photodetectors and, for instance, in a region 31-3 corresponding to a green picture element, the part m22 of a corresponding 'G' filter 21-3, the part m21 of an adjacent 'R' filter 21-2 and the part m23 of an adjacent 'B' filter 21-4 are provided. The ratios of the respective parts m21, m22 and m23 are predetermined in accordance with spectral sensitivity characteristics. Therefore, for instance, the green picture element receives lights transmitted through the respective parts m21, m22 and m23 and, as a result, the green picture element not only has a large sensitivity to a green wavelength light but also has a certain sensitivity to the other red and blue wavelength lights and a G signal outputted by the green picture element is a signal obtained by correcting an original G signal with the other wavelength lights.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a solid-state image sensor having a color filter.

When obtaining a color image using a solid-state image sensor, an optical means called a nine-color filter is usually used.

For example, a method of obtaining three color (R, G, B) signals is adopted.

3. Detailed description of the invention (overview〕 Regarding a solid-state image sensor having a color filter.

Among the color filters that are color-corrected from the unit light-receiving elements of a solid-state image sensor (prior art), there is an "R1 filter (a red filter for obtaining a red color signal, that is, an R signal)."

For arrays such as “G” filters and mBs filters.

There are various methods.

For example, in a color image scanner, as shown in FIG. - It is made into a square shape with sides of 63.5#m.And,
Each of the filters "R", "IIQ" and "B" is made to correspond to a unit light-receiving (photoelectric converter fA) element or one pixel of the solid-state image sensor.Therefore, the unit light-receiving element is "R"
, "G" or "B", which receives only the light that has passed through the filter, and forms a color signal corresponding to it.
for example.

The unit light-receiving element (red pixel) corresponding to the ``R''R'' router mainly receives light with a red wavelength to form an R signal, and receives light with other shorter wavelengths (°G'' and ``G''). Almost no light (light that passes through the "B" filter) is received.

However, according to the spectral sensitivity characteristics determined from one-color reproducibility, even red pixels often need to have a certain degree of sensitivity to light with a wavelength shorter than that of the red filter. It is necessary to correct the R signal from the pixel under certain conditions, taking into account the amount of incident light with a shorter wavelength (see below).

This correction is called color correction).

Conventionally, color correction for this color signal has been performed by signal processing, like various other corrections.

Note that two-color correction is also performed on color signals from pixels of other colors. Further, color correction is also necessary for complementary color filters other than the three primary color filters described above.

[Problem to be solved by the invention]

According to the above-mentioned prior art, two-color correction is performed by subjecting color signals output as electrical signals from unit light-receiving elements to signal processing in a processing circuit.

Therefore, the signal processing circuit becomes complicated.

There is a problem in that the cost of the signal processing IC increases.

The present invention aims to provide a solid-state image sensor having a color filter capable of obtaining a color-corrected color signal from a unit light-receiving element of the solid-state image sensor.Means for solving Ct*a] FIG. 1 is a diagram showing the basic configuration of the present invention.

In FIG. 1, 1 is a solid-state image sensor, 2 is a color filter,
3 is a semiconductor base portion including a unit light-receiving element.

21 (21-1 to 2l-5) is one color filter.

31 (31-1 to 3l-5) is a region corresponding to a unit light receiving element.

The solid-state image sensor 1 is as shown in FIG. 1(C).

It has a semiconductor base portion 3 including a unit light receiving element such as a COD or a photodiode formed on a silicon semiconductor substrate or a-5i, and a color filter 2 formed thereon.

The unit light-receiving element has a known configuration such as COD, etc.9
For example, it is provided in a line shape. The unit light receiving element outputs an electric signal according to the amount of light received as a color signal. Of the unit light-receiving elements, the actually effective light-sensitive portion is the light-receiving portion within the aperture window.

The area 31 is determined corresponding to the unit light-receiving element, and the Sffl area 31, which is made to be equal to the planar shape of the unit light-receiving element (the aperture window thereof), is 1, for example, for a linear unit light-receiving element. , region 31-1.3 shown in FIG. 1(B)
1-2. It is determined as follows.

Now, when the functions of the unit light-receiving elements are determined in the order of red pixel, green pixel, and blue pixel, the area 31 also corresponds to the area 31-2, 31-3, 31-4, as shown in FIG. 1(B). It is done as follows.

Note that the II region 31 is actually determined by the aperture window of the unit light receiving element.

The color filter 2 is provided so as to cover at least the aperture window of the unit light-receiving element, and has filters 21-1, 21-2, .・・・
Filter 21-1.21-2. -...is...
Basically, it corresponds to the SN area 31-1, 31-2, ... (that is, the pixel arrangement), but its shape is made to be different from the shape of the corresponding area. When the shape of the area 31-3 corresponding to the green pixel is determined as shown in FIG. 1(B), the corresponding filter 21-3 has a green "G"
Although it is filtered, its shape is different from that of the region 31-3, and is a shape in which at least a part of the region 31-3 is missing. On the other hand, the filter 21-3 is shaped to extend into the adjacent regions 31-2 and 31-4, if necessary. Therefore, the filter 21-3 has a portion m within the corresponding region 31-3.

and the partial molecules fl, l, and mB in the other regions 31-2 and 31-4, and, conversely, the corresponding portions in the region 31-3 (corresponding to mo and mo) are missing. Ru. and,
This missing part is located in the adjacent areas 31-2 and 31-4.
R” filter 21-2 and “B1 filter 2 corresponding to
1-4 parts m□ and m. filled in by.

[Effect]

As is clear from the comparison of FIGS. 1(A) and (B), for example, in the area 31-3 corresponding to the green pixel,
Portion m of G'' filter 21-3.

, a portion m 1 of the adjacent 'R'' filter 21-2, and a portion mB of the "B" filter 21-4. That is, there are filters of at least two or more colors (m □
may be 0).

Each part "Il + m! Ratio of palm and rrg3 (area ratio)
teeth.

The ratio is set to 9 in consideration of the spectral sensitivity characteristics.

For example, in the IN area 31-3, m, >m.

mo, and the corresponding “portion m of the G0 filter 21-3
, is set to be at most 2 and sufficiently larger than the other portions m□ and m13.

Therefore, for example, the green pixel has each portion m□, mz.

As a result of receiving light that has passed through the wavelengths of 1 and 20 mB, in addition to being highly sensitive to green wavelength light, it also has a certain degree of sensitivity to other red and blue wavelength light. Therefore, the G signal output by the green pixel is the original G signal corrected (color corrected) using light of another wavelength.

As described above, a signal that has been color-corrected in consideration of the 9-spectral sensitivity characteristics can be obtained as a color signal from the unit light-receiving element.

〔Example〕

FIG. 2 is a configuration diagram of an embodiment.

In FIG. 2, 4 is a white level recording section, 5 is an A/D converter, 6 is a processing circuit, 7 is a document, and 8 is a light source.

9 is a lens.

The light from the light source 8 is transmitted to the document 7. The light enters the unit light receiving element of the semiconductor base portion 3 through the lens 91 and the color filter 2 .

Here, in order to obtain a color signal from a unit light-receiving element (pixel) as a color-corrected signal, the two-color filter 2 has a predetermined shape in advance.

When the relationship between each pixel and the color filter 2 is determined as shown in FIGS. 1(A) and 1(B), the input and output of each pixel is as follows.

That is.

Re ” m + IRI+ ffl lz G +G
o”m,IR,+m,,G.

Be = m3tR1+ms proverb G+ It can be expressed as. here.

+m, sB.

+m1181 +m2@13°R@, G@ and Be are the sum total of the amount of light received by the red pixel, green pixel and blue pixel (
That is, the level of the output color signal), R+, G+, and B1
are the incidence per unit area of light of red, green, and blue wavelengths on each pixel, respectively. m, H or m3= is the area of each part (
ratio).

Assume now that the parameters m11 to m33 have an area ratio of 9. In this case, 1 For example, in the area 31-1, the portion m□ of the 'R'' filter 21-2 does not exist, and the portion m of the 1G'' filter 21-3 and the
The portion m0 of the B7 filter 21-4 is made to occupy 0.9 and 0.1 of the area of the region 31-1. Therefore, the G signal (Go), which is a color signal from a green pixel, is determined by light of green and blue wavelengths.

m11 to m3. is obtained as follows. That is.

A comprehensive spectral sensitivity characteristic is determined from the color of the light B8, the color of the filter 21, etc. Next, if we directly calculate 9m, 1 to mH from the spectral sensitivity characteristic expressed by 5 relative sensitivity, we get 1, for example.

It can be found in a form that includes negative numbers, as in Further normalization etc. are performed on this and all are made positive values, m+t or m33
seek.

By performing such color correction, the color signal from the unit light-receiving element is corrected to a second order, for example, a ninth order.

Before correction AV 12.705 (NBS) MAX
23.1661 (NBS) AIN 4.94
077 (NBS) After correction AV 8.3399
2 (NBS) MAX 21.9489 (Na
S) MIN1, 17024 (NBS) The color-corrected color signals from the unit light receiving elements are transferred in order, and from the solid-state image sensor 1, as shown in FIG.
and B signals are repeated and output as an analog data string.

This analog data string is taken in by the white level recording section 4,
In order to perform normalization using the white level as a reference, the white level of each of the R, G, and B signals is recorded. And A/D
The converter 5 uses the white level from the white level recording section 4 as a reference (
A/D conversion is performed as maximum) to generate digital data of R, G, and B signals. Using this digital data, various signal processings except nine-color correction are performed in the processing circuit 6.

〔Effect of the invention〕

As explained above, according to one aspect of the present invention, in a solid-state image sensor having a two-color filter, at least two or more color filters are present in the area corresponding to the unit light-receiving element. You can get corrected color signal.

Since a signal processing circuit for correcting color signals can be made unnecessary, the cost for signal processing can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention. FIG. 2 is a configuration diagram of an embodiment. FIG. 3 is a diagram showing the output. FIG. 4 is an explanatory diagram of the prior art. 1 is a solid-state image sensor, 2 is a color filter, 3 is a semiconductor base portion, 21 is one color filter, and 31 is a region corresponding to a unit light receiving element. ml ff+3゜l'n3 Patent applicant Pfn Co., Ltd.

Claims (1)

[Scope of Claims] In a solid-state imaging device (1) having a color filter (2) for obtaining color signals, at least two or more colors are provided in an area corresponding to a unit light-receiving element of the solid-state imaging device (1). A solid-state imaging device having a color filter, characterized in that a filter (21) is present according to a predetermined ratio, and a color-corrected color signal is obtained from the unit light-receiving element.