JPH0378388A - Color solid state image pickup element - Google Patents

Abstract

PURPOSE:To obtain a color solid state image pickup element suitable to an electronic still camera by constituting a color filter of the mosaic filter of a complementary color system. CONSTITUTION:The first line of the mosaic filter 30 of one unit to constitute the color filter 32 consists of an Mg filter element and a Ye' filter element, and the second line of it consists of a Cy filter element and the Ye' filter element, Thus, as for a color video signal to be outputted, the modulated component of the coloring matter of Mg-Ye' corresponding to the first line of the mosaic filter 30 of one unit of the color filter 32 is obtained, and the modulated component of the coloring matter of Cy-Ye' corresponding to the second line is obtained. Besides, since Ye' is arranged in all the lines of the mosaic filter 30 of the unit, the vertical resolution of an achromatic color subject up to a limit can be obtained by signal processing. Further, since the color filter element arrangement of the complementary color system is used, high sensitivity is obtained, and when it is applied to the electronic still camera, the balance of picture quality can be realized synthetically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a color solid-state image sensor, and more particularly to a color solid-state image sensor suitable for an electronic still camera.

(Prior Art) Generally, a color solid-state image sensor used in a color video camera or an electronic still camera has different color filter elements arranged in first and second directions perpendicular to each other, for example, in two directions, for example, a horizontal scanning direction and a vertical scanning direction. This color filter includes a plurality of unit mosaic filters arranged in rows and two columns, and a color filter configured by sequentially arranging the unit mosaic filters in the first and second directions. It consists of an imaging section made up of photoelectric conversion cells arranged at positions corresponding to each of the filter elements.

Broadly speaking, the arrangement of color filter elements can be classified into the following two types. In other words, as shown in Figure 5, pure red (
red, R), pure green (G)
A primary color mosaic filter uses the three primary colors of pure blue (bluθ, B) as color filter elements, and pure red-purple (magenta, Mg) as shown in FIG.

Pure blue-green (Schiff:/, cyan, Cy) and yellow (yel low).

There is a method of arranging complementary color mosaic filters using color filter elements.

The above-mentioned three primary colors R, G, and B and Cy, Mg, and Ye are complementary colors to each other as shown in FIGS. 7(a), 2, and (C).

(Company), (e) will be recognized. That is, if the spectrum in the visible light region is broadly divided into B (400 to 500n■)
G (500~600n++) and R (600~70Q
nm).

Then, by additively mixing two of each of these three groups of spectra, we get R0G-Yol, which is written as -B, G+B-Cy.
, This is written as -R, B+R...Mg,
This is written as -G, and Ye is the visible light region, that is, white (W
) minus B, so it is expressed as -B. Therefore, if Ye and B are additively mixed, white will be obtained, and Ye+B=-B+B-W, and the two are in a complementary color relationship.

Using this expression, if we overlap Ye and Cy.

Since Yθ+Cy--B-R, only G remains from white (W-R+G+B), resulting in green. Similarly, CF +Mg■-R-G■B Mg + --GBR.

The color filter element array of the primary color mosaic filter is color S
/N, color reproducibility is good, but sensitivity and resolution are poor. Further, although the color filter array of the complementary color mosaic filter has good sensitivity and resolution, it has poor color S/N and color reproducibility. but,
Among the color arrays of complementary color mosaic filters, as shown in FIG. Since the modulation degree is large and the color S/N ratio is not so bad, this arrangement is considered to have the best overall balance in color video cameras.

(Issue 1i to be solved by the invention) However, in order to obtain a luminance signal from the array of complementary color mosaic filters described above, it is necessary to use two-line correlation in the vertical scanning direction, which degrades the resolution in the vertical scanning direction. This is not desirable for still images such as those from electronic still cameras.

Furthermore, when the filter element arrangement method of the primary color mosaic filter is applied to an electronic still camera, there is a problem in that it is not suitable for increasing the number of pixels in terms of sensitivity.

Therefore, the present invention eliminates the above-mentioned disadvantages of conventional electronic still cameras, and provides a color solid-state image sensor that has excellent resolution in the vertical scanning direction, high sensitivity, can have a large number of pixels, and is suitable for electronic still cameras. This is what I am trying to do.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the color solid-state image sensor of the present invention basically has the structure shown in FIG. 1 (Claim (1)
). That is, as shown in FIG. 1, different color filter elements are arranged in two rows and two columns in the vertical scanning direction and in the horizontal scanning direction, respectively, so that a plurality of units of one unit of mosaic filter 30 are arranged in the horizontal scanning direction and the vertical scanning direction. A color filter 32 is formed by arranging unit mosaic filters adjacent to each other in the direction, and each color filter element (Mg, Y
θ', Mg, Ye', . . . ) and an imaging section composed of photoelectric conversion cells provided at corresponding positions.
The first row consists of a yellow filter element Yθ' whose green transmittance is larger than that of the red component, and the magenta filter element Mg, and the second row has the same transmittance of the green component as the first row. This filter is characterized by being composed of a yellow filter element Ye' whose transmittance is larger than that of the red component, and a cyan filter element Cy.

Further, the second (claim (claim)) of the color solid-state image sensor of the present invention
2)) The configuration was as shown in Figure 2. That is, in the color solid-state image sensor shown in FIG. 1, a plurality of mosaic filter units are arranged adjacent to each other in the horizontal scanning direction, and in a second row arrangement in the vertical scanning direction. The color filter elements (Ye', Mg, . . . ) constituting the mosaic filter 31 in units of are horizontally aligned with respect to the color filter elements (Yθ', Mg) constituting the mosaic filter 31 in units of the first row array. They are characterized in that they are arranged one pixel apart in the scanning direction.

(Function) As described above, a mosaic filter in which different color filter elements are arranged in two rows and two columns in the vertical scanning direction and horizontal scanning direction to form one unit is constructed such that the first row has transmittance of the green component. is larger than the transmittance of the red component (Ye'
) filter element and magenta (Mg) element,
The second row includes a yellow (Ye') filter element whose green component transmittance is larger than that of the red component, and a cyan (CY) filter element.
Since it is composed of filter elements, the color video signal output from the color solid-state image sensing device of the present invention is Mg corresponding to the first row of the mosaic filter of one unit of the color filter.
A color difference modulation component of -Ye' is obtained, and a color difference modulation component of CY-Ye' corresponding to the second row is obtained.

Further, since Yθ' is arranged in all lines of the mosaic filter, it is possible to obtain the maximum vertical resolution of an achromatic object through signal processing. Furthermore, since it uses a complementary color filter element array, it has good sensitivity, and when applied to an electronic still camera, the overall image quality can be balanced.

(Example) Next, an example of the color solid-state image sensor of the present invention will be described with reference to the drawings.

1 and 2 are plan views showing the arrangement of unit mosaic filters constituting the color filter of the color solid-state image sensor of the example, and FIG. 3 shows the spectral characteristics of each color filter element of the unit mosaic filter. It is a characteristic curve diagram of wavelength (rv) versus transmittance.

As shown in FIGS. 1 and 2, in one unit of the mosaic filter constituting the color filter according to this embodiment, the first row consists of an Mg filter element and a Yθ' filter element,
The second row consists of a cy filter element and a Yθ' filter element. In FIG. 1, one unit of mosaic filters is neatly arranged in the horizontal scanning direction and in the vertical direction perpendicular to the horizontal scanning direction. (In Fig. 2, the arrays are shifted by one pixel in the vertical direction.) Here, the spectral characteristics of each color filter element are determined by the third
As shown in the figure, Mg J=? They are selected as R1B Cy →G+B Ye' →G+R. That is, the magenta (Mg) filter element, the cyan (Cy) filter element uses a normal filter element, and the yellow (Ye') filter element has a transmittance in the red wavelength region compared to a normal yellow (Ye) filter element. It's getting smaller.

FIG. 4 shows a block diagram of a color imaging device including a color solid-state imaging device of the present invention using the above color filter. An imaging signal read out from a solid-state imaging device 1 having a color filter array shown in FIG. 1 or 2 is passed through a buffer 2,
The IH delay line 3 converts the signal into two lines of parallel signals. Thereafter, the Mg and Ye' lines and the Cy and Ye' lines are selected by the IH switches 4 and 5. IH switching 4
The Mg signal and Ye' signal of the selected Mg and Ye' lines are separated by a sample and hold circuit 6.7, and each is subjected to white balance 10.11 and gamma correction 14.15 separately.

On the other hand, the Cy and Ye' signals selected by the switching 5 are separated into the Cy signal and Ye' signal by the sample hold circuit 8.9, and the white balance 8.9 and Ye' signals are respectively separated.
13 and gamma correction 16.17.

The signal processed as described above is subjected to the following signal processing to obtain a luminance signal and two color difference signals.

Luminance signal high frequency component: Y)l -0,25(Mg +Na 1 +cy+Y
e2') (+) Luminance signal low frequency component (Mg Ye' line): yt-1-aI
(Mg-Yel)+β1(Cy-Ye2)
+Na + ' (2) Luminance signal low frequency component (Cy Y
e' line): YL2-al (Mg Yel
)+β1(C)' Ye 2 ) +Na 2
' (3) Color difference signal: R-Y-a ry (Mg-Ye H)+β "y(
Cy-Ye2) (4) B-Y-aby
(Mg-Ye+)+βby(Cy-Ye2)
(5) Here, Yol is the Ye' signal of the Mg Yθ' line, and Ye2 is the Ye signal of the Cy Ye' line. Also α, β, αry, β
ry, aby.

aby is a matrix coefficient, which is determined by the spectral characteristics of the color filter. As can be seen from (2) and (3) above, when an achromatic object changes in the vertical direction, the luminance signal is replaced by Ye' of that line, so the resolution can be maintained up to the pixel limit.

Furthermore, since the mosaic filters constituting the color filters are complementary color mosaic filters, the sensitivity is better than when primary color mosaic filters are arranged.

However, the present invention is not limited to the above embodiments, and it goes without saying that the color filter elements of the complementary color mosaic filter can be arranged in various ways without departing from the elements.

[Effects of the Invention] As is clear from the above description, the color solid-state image sensor according to the present invention not only has good sensitivity and resolution, but also has good vertical resolution because the color filter is composed of complementary color mosaic filters. Since the resolution can be broken down to the limit of the number of pixels when using achromatic colors, it is possible to provide a color solid-state image sensor suitable for electronic still cameras.

[Brief explanation of drawings]

1 and 2 are plan views showing the configuration of a mosaic filter constituting a color filter in the color solid-state image sensor of the present invention, FIG. 3 is a diagram showing the spectral characteristics of each color filter element in the same color filter, and FIG. 4 is a block diagram of a circuit configuration of a color solid-state imaging device according to an embodiment of the present invention; FIGS. 5 and 6 are diagrams showing configurations of a primary color mosaic arrangement and a complementary color mosaic arrangement of color filter elements in a conventional color filter;
Figure 7 (2) 2■, (C), (e) are the three primary colors R and G in the visible light region. FIG. 4 is a characteristic curve diagram showing the relationship between wavelength and transmittance, showing a spectral range having a complementary color relationship with B. FIG. 1: Solid-state image sensor 6-9: Sample hold circuit 10-13: White balance circuit 14-17: Gamma correction circuit 30.31. :Unit complementary color mosaic filter 32.3
37 color filter

Claims (2)

[Claims] (1) Multiple units of mosaic filters in which different color filter elements are arranged in two rows and two columns in the vertical scanning direction and in the horizontal scanning direction to form one unit, respectively in the horizontal scanning direction and the vertical scanning direction. A color filter formed by arranging mosaic filters adjacent to each other, and a photoelectric conversion cell provided at a position corresponding to each color filter element forming a plurality of mosaic filter units forming the color filter. In the color solid-state image sensor, the mosaic filter of the unit includes a yellow filter element whose first row has a green transmittance larger than a red component's transmittance;
A color solid comprising magenta filter elements, and a second row comprising yellow filter elements whose green component transmittance is equal to that of the first row and whose transmittance is higher than that of the red component, and a cyan filter element. Image sensor. (2) In claim (1), a plurality of units of mosaic filters are arranged adjacent to each other in the horizontal scanning direction, and a second row arrangement is arranged in the vertical scanning direction. Color solid-state imaging characterized in that the color filter elements constituting the unit mosaic filter are arranged one pixel apart in the horizontal scanning direction with respect to the color filter elements constituting the unit mosaic filter in the first row arrangement. element.