JPS6276884A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the vertical color alias by providing the spectral characteristics in which the ratio of the signal quantity obtained by two pairs of two vertical picture elements adjoining in the horizontal direction out of the picture element column of two columns to constitute one horizontal scanning line and the ratio of the signal quantity obtained by two picture elements adjoining in the horizontal direction are equalized. CONSTITUTION:For the mosaic filter, corresponding to each picture element of a solid-state image pickup element 1, the column, in which respective color filters of Ye and Mg, respective color filters of Ye and Cy and respective color filters of Mg and Ye are respectively successively arranged in then horizontal direction, is repeatedly arranged and constituted in the sequence. Since the ratio (1:1) of the signal quantity to mix two vertical picture elements (Ye+Ye) of an N line and the signal quantity to mix two vertical picture elements (Cy+Mg) adjoining in the horizontal direction is equal to the ratio (1:1) of the signal quantity of one picture element (Ye) not to mix the two vertical picture elements and the signal quantity of one picture element (Cy or Mg) adjoining in the horizontal direction, in case of the achromatic color, the clear picture signal with a small quantity of the color alias can be obtained. Thus, the occurrence of the vertical edge color alias can be suppressed and the color picture signal with a good picture quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement of a solid-state R image device that uses a mosaic filter to obtain a color video signal with one solid-state image sensor.

[Technical background of the invention and its problems]

Solid-state image sensing devices such as CCD type and MOS type can be roughly classified according to the type of charge accumulation mode: frame accumulation mode, in which a signal is read out every frame period, and field accumulation mode, in which a signal is read out in every field period. It is divided into modes. In the frame accumulation mode, there is a time difference of one field period between two field signals due to interlaced readout, so there is an afterimage of one field. On the other hand, in field accumulation mode, when performing interlaced readout, the signals of two vertically adjacent pixels are read out simultaneously in each field, and the charges of all pixels are read out field by field, so there is no afterimage of one field. There are advantages. For this reason, in video cameras using solid-state image sensors, driving in field accumulation mode has come to be increasingly used.

A single-chip solid-state imaging device that obtains a color image using one solid-state imaging device in field storage mode is constructed by disposing a vertical stripe filter or a mosaic filter on the light-receiving surface of the solid-state imaging device.

In a colorization method that emphasizes resolution, it is desirable to use a mosaic filter that has excellent horizontal resolution.

However, this type of single-chip solid-state imaging device using a conventional mosaic filter has the problem of generating color artifacts when capturing an image that has no correlation in the vertical direction, such as a striped pattern extending in the horizontal direction. there were.

The mechanism by which this color false signal occurs will be explained below.

FIG. 5 is a diagram showing an example of color filter arrangement of a field accumulation mode mosaic filter used in a conventional color difference sequential type imaging device.

In this figure, if the output signal of the solid-state image sensor obtained by scanning N lines once is SN%, and the output signal obtained from N+1 lines is SN+1, then SN and SN+1 are respectively =R+ΣG+B+,
(2B-G) sin ωt...(1) + -(G+Cy -MCI -Ye) sin ω
tπ =R+HG+B+; (G-2R) sin cc+t
...(can be expressed as a.Here, Ye, Ma, C
y.

R, G, and B are yellow, magenta, and cyan, respectively.

Red, green, and blue color signal components are shown, and ω is the spatial modulation angular frequency.

The feature of this mosaic filter is that the modulation component of equation (1) and the modulation component of equation (21) are each in the form of color difference signals, so these signals are directly used as color signals to create a color television signal. The point is that you can.

That is, if the color signal obtained from N lines is CN%, and the color signal obtained from N+1 lines is CN+1, then these color signals are CN = (MO+CV) - (G+Ye), respectively.
=28-G...(3
)CN+1=(G+CV)−(Ma+
Ye)=G-2R (4).

When an achromatic object is imaged, both CN and CN+1 must be zero, so (Mill +CV
') and (G+Ye), and (G+Cy) and (M(]
+Ye) is such that the spectral characteristics of the color filters are set so that the respective signal amounts are equal when an achromatic object is imaged.

Consider a case where such a solid-state imaging device captures an image that changes from black to white in a vertical direction from above to below, as shown by L1 in FIG. First, when Ll is between the N-1 line and the N line, each color signal obtained from the N-1 line and the N line is 0N-1=O...(5) CN - (M!] +cy) -(G-1-Ye)
=・(6). (M(] +CV) and (G+
Since the spectral characteristics are selected so that the signal amounts of Ye ) are equal, the formula f6) becomes CN = O (7), and the color signal becomes O. Therefore, in this case, no vertical edge color false signals occur.

However, when Ll is located at the center of the N line, that is, between the N'-1 line and the N' line, the color signals obtained from the N-1 line and the N line are as follows: CN-1=O.・(8) CN = cy −Ye −
(9), (Mill 10V) and (G+Ye
Since the spectral characteristics are selected so that the signal amounts of ) are equal, the signal amounts of Cy and Ye are not necessarily equal, and a color signal component is generated. Therefore, in this case, a vertical edge color false signal occurs.

Similarly, when the boundary L2 is located at the center of the N-1 line, that is, between the N' line and the N'-1 line, the N-
The signals obtained from the 1st line and the Nth line are: ON-1=G-M! ;I...(1
0)CN=O... (11) Since the signal amounts of G and M(l are not equal, a color signal component is generated, and a vertical edge color false signal is also generated.

As described above, in the color filter arrangement of the mosaic filter for field accumulation mode such as the conventional color and difference sequential method, there is a problem in that color false signals occur due to extreme changes in brightness in the vertical direction.

[Purpose of the invention]

The present invention has been made based on such problems, and its purpose is to provide a field accumulation mode single-chip type that can prevent the occurrence of vertical color false signals and obtain color image signals of good image quality. An object of the present invention is to provide a solid-state imaging device.

[Summary of the invention]

The present invention is a field accumulation mode solid-state imaging device that simultaneously reads out mixed signals from two vertically adjacent pixels, in which a mosaic filter arranged on the light-receiving surface of the solid-state imaging device is configured as follows. It is characterized by

In other words, the mosaic filter calculates the ratio of signal amounts obtained by two sets of vertical pixels adjacent in the horizontal direction among the two pixel columns constituting one horizontal scanning line, and the ratio of the signal amounts obtained by two sets of vertical pixels of these two sets.
It is characterized by having spectral characteristics such that the ratio of signal amounts obtained by two horizontally adjacent pixels constituting each pixel is equal.

For example, the mosaic filter shown in FIG. 1 is an example of the present invention. According to this mosaic filter, R-=G=
B, the mixed signal of two sets of vertical 2 pixels obtained in any horizontal scanning line, for example, the ratio of (Ye +Ye) and (Cy +M(]), constitutes these 2 vertical pixels and is It is equal to the ratio of two adjacent pixels Ye and Cy.The present invention is characterized by using such a mosaic filter.

〔Effect of the invention〕

According to the present invention, even if one of the two pixel columns constituting one horizontal scanning line receives black light and the other pixel column receives white light, horizontally adjacent Since the ratio of two vertical pixels is equal to the ratio of two horizontally adjacent pixels, generation of color signals can be prevented. Therefore, according to the present invention, even in a field accumulation mode single-chip solid-state imaging device, the occurrence of vertical edge color false signals can be suppressed, and color image signals with good image quality can be obtained.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained based on illustrated embodiments.

FIG. 2 is a diagram showing a schematic configuration of a solid-state imaging device according to the same embodiment.

In FIG. 2, reference numeral 1 denotes a solid-state imaging device such as a CCD type, which is driven in a so-called field accumulation mode in which signal charges accumulated in a photoelectric conversion section are read out every field period. A mosaic filter is arranged on the light receiving surface of the solid-state image sensor 1.

As shown in the color arrangement pattern shown in FIG. 1, the mosaic filter has Ye
, Cy color filters are sequentially arranged in the horizontal direction -〇-, a column is formed with Ye, MQ color filters sequentially arranged in the horizontal direction, and Ye.

It is constructed by repeatedly arranging in this order a row in which Cy color filters are sequentially arranged in the horizontal direction, and a row in which MO and Ye color filters are sequentially arranged in the horizontal direction.

A signal output from the solid-state image sensor 1 is introduced into the color encoder 3 via a low-pass filter (LPF) 2, and is sampled and held by two sample-and-hold circuits 4.5. The output of the sample and hold circuit 4 is amplified by either the variable gain amplifier 7 or the variable gain amplifier 8 via the switching circuit 6. This signal is applied to one input of a subtracter 10 via a selection circuit 9. On the other hand, the output of the sample hold circuit 5 is
Via the switching circuit 11, the signal is amplified by either the variable gain amplifier 12 or the variable gain amplifier 13. This signal is applied to the other input of the subtracter 10 via the selection circuit 14.

The output of the subtracter 10 is passed through a low pass filter (LPF) 15.
is introduced into one input terminal of the matrix circuit 17 via the 1H delay line 16.
7 at the other input end. Two output ends of the matrix circuit 17 are provided to the color encoder 3.

In the solid-state imaging device configured as described above, an optical image incident through an imaging lens (not shown) is formed on the light-receiving surface of the solid-state imaging device 1 through the aforementioned mosaic filter. The solid-state image sensor 1 is driven by a drive pulse generation circuit (not shown), and outputs a signal from each pixel by, for example, charge-coupled transfer. Now, let SN be the output signal from the solid-state image sensor 1 obtained by scanning on N lines in FIG. 1,28+G) signals sequentially containing each color component, (b), (c), (
As shown in d), each color signal includes modulation frequency components for every other horizontal pixel. Therefore, SN is 2.

+ −G sinωt−±B sinωt ・(12
)π is denoted by π.

From this signal SN, first, 3
Only the high-frequency luminance signal YH is extracted by LPF2 of M H1. This luminance signal is introduced into the color encoder 3.

Further, SN is sampled and held by the sample and hold circuits 4 and 5, respectively, and is changed to 1 by the switching circuit 6°11.
The signal is alternately input to variable gain amplifiers 7 and 8 and variable gain amplifiers 12 and 13 during each horizontal scanning period. The variable gain amplifier 7.8.12.13 is used to maintain the white balance described above, and for example, when an achromatic subject is imaged with N lines, the signal amount of 2Ye and the signal amount of Cy +M(+ are These variable gain amplifiers 7 or 8 and variable gain amplifiers 12 or 1 are adjusted so that they are equal to each other.
The output of No. 3 is input to the subtracter 10 every horizontal scanning period by the switching circuits 9 and 14. Then, a color signal is generated in the subtracter 10.

This color signal is passed through an LPF with a passband of 0.5MHz.
After passing through 15, the signal is input to one input terminal of matrix circuit 17, delayed by one horizontal scanning period by 1H delay line 16, and introduced to the other input terminal of matrix circuit 17. For example, N lines of color signals CN are output from the LPF 15, and N-1 lines of color signals CN are output from the 1H delay line 16.
Assume that -1 is output. These color signals are CN-t = (Ye +M(1) - (Cy +Ye
) = (R + G + R 1 B) - (G + B 0 R + G) = RG ... (13) CN =
(Ye + Ye) - (CV + Ma) = (R
+G1R+G) - (G1B+R+B) =R+G-2B (14). The matrix circuit 17 performs the following calculations using the two input color signals to generate an R-Y signal and a B-Y signal.
I'm getting a signal.

RY = 0.7OR-0,59G -0,11B=
0.645 (R-G) 10.055 (R1G-2B)...(15)B
−Y = −0,3OR−0,59G + o,89[
3=0.145 (R-G) -0,445 (R+G-2B) ... (16
) Here, consider the case where an object is imaged with boundary portions L1 and L2 that change from white to black in the vertical direction as shown in FIG. 6 described above.

First, if Ll is between the N-1 line and the N line,
The color signal CN-1 obtained from the N-1 line and the N line,
From equations 13 and 14, ON is 0N-1= (Ye +
M(] ) −(Cy +Ye)−〇−〇=O...(17) CN = (Ye 10Ye) −(Cy 0MO>=
R+G-2B...(18)13~1
From formula 8, the R-Y signal and the B-Y signal are R-Y=0.055 (R1G-2B)...(
19) B −Y = −0,445(R+ G −2B
>...(20)' When RG=8, the R-Y signal and B-Y signal components are zero, so no vertical end color false signal occurs.

Furthermore, when L is located at the center of the line, that is, between the N'-1 line and the N' line, the color signals CN-1 and ON obtained from the N-1 line and the N line are as follows: 0N-1=( Ye 1MG > −(Cy +Ye)
=0-0 =○...(21)CN=
(Ye +Ye) -(CV +M(+
)=Ye −M(1 =G−B ...(22)(13
)~(16n, (21), (2:)) From formula, R-
The Y signal and B-Y signal are R-Y = 0.055 (G-B)
...(23) B −Y = −0,445(G −B
)...(24), and when R=G=8, the RY signal and BY signal components are zero, so no vertical end color false signal occurs in this case as well. Similarly, no vertical edge color false signal occurs at the boundary L2 in FIG. 6 as well.

The R-Y signal and B-Y signal thus obtained are combined with the high-band luminance signal YH in the color encoder 3 to form an NTSC color television signal, which is output.

As described above, according to this embodiment, the ratio (1: 1) is one pixel that does not mix two vertical pixels (
) and the signal amount of one horizontally adjacent pixel (Cy
or M(+) signal amount is equal to the ratio (1:1), so if the color is achromatic, vertical end color false signals will not occur even if the subject has low vertical correlation; It is possible to obtain a clear image signal with fewer color artifacts.

Note that the present invention is not limited to the embodiments described above.

For example, the color arrangement of the mosaic filter, the configuration of the device, etc., such as the mosaic filter array shown in FIG. 4, can be modified in various ways without departing from the gist of the present invention.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining a solid-state imaging device according to an embodiment of the present invention, in which FIG. 1 is a schematic diagram showing the color arrangement of a mosaic filter, and FIG. 2 is a schematic diagram of the device configuration. 3 is a schematic diagram showing color signal components contained in a signal obtained by horizontal scanning, and FIG. 4 shows a color arrangement of a mosaic filter of a solid-state imaging device according to another embodiment of the present invention. The schematic diagram, FIG. 5, and FIG. 6 are diagrams for explaining a conventional solid-state imaging device. DESCRIPTION OF SYMBOLS 1... Solid-state image sensor, 2, 15... Low pass filter, 3... Color encoder, 4.5... Sample hold circuit, 6, 11... Switching circuit, 7, 8, 12
゜13... Variable gain amplifier, 9.14... Selection circuit, 10... Subtractor, 16... 1H delay circuit, 17.
...Matrix circuit. Applicant's Representative Patent Attorney Takehiko Suzue 171 Figure 3 Figure 4 Figure 5 Black and White Figure 6

Claims (1)

[Claims] A solid-state image device comprising a solid-state image sensor and a mosaic filter disposed on a light-receiving surface of the solid-state image sensor, and using a mixed signal of two vertically adjacent pixels of the mosaic filter as a horizontal scanning signal. When imaging an achromatic subject, a mosaic filter calculates the ratio of signal amounts obtained from two sets of vertical pixels adjacent in the horizontal direction among the two rows of pixels constituting one horizontal scanning line, and
A solid-state imaging device characterized by having spectral characteristics such that the ratio of signal amounts obtained by two pixels adjacent to each other in the horizontal direction constituting each of a pair of two vertical pixels is equal.