JP2965372B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device using a solid-state imaging device adopting a two-row mixed readout system, a two-row simultaneous readout system, or the like.

[0002]

2. Description of the Related Art FIG. 11 shows a configuration of a main part of a solid-state imaging device. In FIG. 1, an image light L from a subject (not shown) passes through an imaging lens 1 and is a single-chip CCD color solid-state imaging device 2 having a complementary color checkerboard color filter.
Supplied to

FIG. 12 is a schematic diagram of the color coding of the image pickup device 2. As shown in the figure, field reading is performed. In the A field, charges are mixed in pairs such as A1 and A2, and in the B field, B is mixed.
The charge is mixed in pairs such as 1, B2. .. In the A field, and B1, B2 in the B field.
Charges are output in the order of 2,.

Here, the order of the charges a, b,... Is (Cy +
G), (Ye + Mg),..., And (Cy + Mg), (Ye + G),.
In the line, (G + Cy), (Mg + Ye),
..., and in the B2 line, (Mg + Cy),
(G + Ye),...

The electric charge output from the image sensor 2 as described above is supplied to a CDS circuit (correlated double sampling circuit) 3 and is extracted from the CDS circuit 3 as an image signal. By using the CDS circuit 3, reset noise can be reduced as is well known. Note that timing pulses necessary for the above-described image sensor 2 and CDS circuit 3 are supplied from a timing generator 4.

Here, a process for obtaining a luminance signal Y and a chroma signal (color difference signal) from an image pickup signal output from the CDS circuit 3 will be described. The luminance signal Y is obtained by adding signals of adjacent competitors. In FIG. 13, addition signals of a + b, b + c, c + d, d + e,... Are sequentially formed.

For example, the A1 line is approximated by the following equation. Here, Cy = B + G, Ye = R + G, Mg
= B + R. In addition, the A2 line is approximated by the following equation.

[0008] Other lines in the A field and lines in the B field are similarly approximated. As for the chroma signal,
It is obtained by subtracting signals of neighboring competitors.

For example, the A1 line is approximated by the following equation. In addition, the A2 line is approximated by the following equation. Similarly for the other lines in the A field and the lines in the B field, the red difference signal RY and the blue difference signal-(BY) are obtained alternately in a line-sequential manner.

[0010]

It is assumed that the solid-state imaging device shown in FIG. 1 captures a monochrome image as shown in FIG. This black-and-white image is an image having a white stripe having a width of two pixel pitches in the vertical direction with a slope of 1/2 (the horizontal direction H is a rate of one pixel pitch in the vertical direction V with respect to the two pixel pitches). It is. In FIG. 3, the numbers assigned to the respective pixels in the horizontal and vertical directions indicate addresses in the respective directions. The same applies to the following drawings.

Here, reading in the vertical direction V will be considered. For example, the relationship between the image and each pixel in the vertical direction (pixel addresses N-1, N, N + 1,...) Is shown in FIG.
A description will be given of a vertical pixel column (the pixel address in the horizontal direction is m) as shown in FIG. The number assigned to each pixel in FIG. 6B indicates a quantized level of a signal obtained from each pixel. The same applies to FIG.

In this case, as described above, since the image pickup signal is a signal obtained by synthesizing signals of two horizontal pixel columns, the level of the image pickup signal of each line An, An + 1,... In the A field is shown in FIG. , And the levels of the imaging signals of the respective lines Bn-1, Bn, Bn + 1,... Of the B field are as shown in FIG. Accordingly, the level of the image pickup signals in the A and B fields in the vertical pixel column having the pixel address m in the horizontal direction is as shown in FIG.

For example, the relationship between an image and each pixel in the vertical direction (pixel addresses N-1, N, N + 1,...)
A vertical pixel row (pixel address in the horizontal direction is m + 1) as shown in FIGS. 16A and 16B will be described. In this case, the levels of the imaging signals of the lines An, An + 1,... In the A field are as shown in FIG. C, and the levels of the imaging signals of the lines Bn, Bn + 1,. D. Accordingly, the level of the image pickup signals in the A and B fields in the vertical pixel column having the horizontal pixel address of m + 1 is as shown in FIG.

FIG. 17 shows the level of the imaging signal of each line obtained as described above, corresponding to each pixel. FIG. 18 shows only the imaging signal of each line. FIG. 19 shows the level of the imaging signal of each line in a three-dimensional space. FIG. 15E
In this case, the difference between the white and black signal levels is (2.0-0.
0) = 2.0, whereas in the case shown in FIG. 16E, the signal level difference between white and black is (1.5−0.0) = 1.
It becomes 5. That is, when the pattern is shifted by a half pixel pitch in the vertical direction, the difference between the signal levels of white and black greatly changes. Therefore, when capturing an image in which black and white inclined stripe patterns are alternately arranged, a false signal (moire) due to the periodic change of the level difference is generated, and the oblique line becomes unclear.

Therefore, in the present invention, it is possible to suppress the generation of a false signal at the time of imaging the inclined stripe pattern, and to make the oblique lines clear.

[0016]

According to a first aspect of the present invention, in a first field period, a first signal composed of a line signal obtained by combining signals of 2n-1 and 2n (n is a natural number) two horizontal pixel columns is provided. A solid-state imaging device that outputs an imaging signal of a second field composed of line signals obtained by combining signals of two horizontal pixel columns of 2n and 2n + 1 during a second field period; A pixel shifting means for shifting a position of an image picked up by the solid-state image sensor in the vertical direction; and a first shifting means for shifting the position of the image by the pixel shifting means.
And a first memory for storing the imaging signals of the first and second fields output from the solid-state imaging device as imaging signals for one screen, and a position of the image by the pixel shifting means. Is a second position shifted from the first position by a half pixel pitch in one direction perpendicular to the first position, the imaging signals of the first and second fields output from the solid-state imaging device are set to 1 A second memory for storing an image pickup signal for a screen, and a third position in which the position of the image is shifted from the second position by the pixel shifting means in the vertical direction by a half pixel pitch. The first and second signals output from the solid-state imaging device
And a third memory for storing the image pickup signal of the field as an image pickup signal for one screen, and averaging the image pickup signals for one screen respectively stored in the first to third memories. Combining means for obtaining an image signal.

According to a second aspect of the present invention, in the first field period, the imaging signal of the first field composed of the line signal obtained by combining the signals of the 2n-1 and 2n (n is a natural number) two horizontal pixel columns is used. Output, and in the second field period,
A solid-state imaging device that outputs an imaging signal of a second field composed of a line signal obtained by combining signals of two horizontal pixel columns of 2n and 2n + 1, and a position of an image captured by the solid-state imaging device is vertically shifted. A pixel shifting means, a first position, a second position shifted from the first position by a half pixel pitch in one direction perpendicular to the first position, and a second position in each field period. And control means for controlling the operation of the pixel shifting means so as to be positioned at equal time intervals at a third position shifted by a half pixel pitch in the vertical direction.

[0018]

According to the first aspect of the invention, the image position is set to １ ／ in the vertical direction.
An image pickup signal for one screen is obtained by synthesizing image pickup signals for three screens obtained by shifting by a pixel pitch. As a result, when the black and white pattern is shifted by a half pixel pitch in the vertical direction, the level difference between white and black is reduced. For example, the generation of a false signal at the time of imaging of an alternately black and white inclined stripe pattern is suppressed. You.

In the second invention, in each field period, the position of an image picked up by the solid-state image sensor is controlled so as to be sequentially shifted by a half pixel pitch in the vertical direction at equal time intervals. . Thereby, the imaging signals of the first and second fields output from the solid-state imaging device are the same as the combined imaging signals in the first invention, and the same operation and effects as those of the first invention can be obtained. Becomes possible. Further, according to the second aspect of the present invention, it is possible to capture a moving image, and it is not necessary to use a frame memory for combining images.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In this example, the image light L that has passed through the imaging lens 1 is supplied to the imaging element 2 through a glass plate 11 for changing the optical path. The glass plate 11 is provided so as to be rotatable around a rotation axis (not shown) extending in the horizontal direction. The rotation of the glass plate 11 is controlled by a rotation driver 12 so as to be at a first frame position (shown by a solid line), a second frame position (shown by a broken line), and a third frame position (shown by a dashed line). The timing pulse used in the rotation driver 12 is supplied from the timing generator 4.

Here, by setting the glass plate 11 at the second frame position from the first frame position, the optical path of the image light L is changed so that the image position (captured image position) picked up by the image pickup device 2 is changed. The rotation angle is set so as to be shifted in the vertical direction by Pv / 2 (Pv is the pixel pitch in the vertical direction). Further, by setting the glass plate 11 at the third frame position from the second frame position, the rotation angle is set so that the optical path of the image light L is changed and the captured image position is shifted by Pv / 2 in the vertical direction. You.

As described above, shifting the position of the captured image is as follows.
This is equivalent to shifting the image sensor 2 in the vertical direction by Pv / 2 pitch as shown in FIG. Therefore, the image sensor 2 may be shifted in the vertical direction without changing the optical path of the image light L. The imaging signal output from the CDS circuit 3 is A /
After being converted into a digital signal by the D converter 13, it is supplied to the frame memories 14a, 14b and 14c. Writing and reading of these frame memories 14a to 14c are controlled by a memory controller 15, and the glass plate 1
It is controlled in synchronization with one rotation drive. Horizontal and vertical synchronizing signals are supplied from the timing generator 4 to the memory controller 15 to synchronize the rotation of the glass plate 11, the operation of the image sensor 2, and the like.

The frame memories 14a to 14c store one frame of imaging signals (first to third frame signals) output from the imaging device 2 with the glass plate 11 at the first to third frame positions, respectively. ) Is written. Also,
The first to third frame signals written in the frame memories 14a to 14c are repeatedly read out in parallel, converted into analog signals by the D / A converters 16a to 16c, respectively, and then added and averaged by the adder 17. You. And
The output signal of the adder 17 is output as an imaging signal.

In the above configuration, a monochrome image as shown in FIG. 3 is taken. This monochrome image is the same as the monochrome image in FIG. FIG. 3 shows a glass plate 11.
Is a state where the rotation is controlled to the first frame position, and in a state where the glass plate 11 is rotationally controlled to the second and third frame positions, the broken line and the dashed line in FIG. Images are sequentially shifted by Pv / 2 in the vertical direction.

Here, reading in the vertical direction V will be considered. For example, the relationship between the image and each pixel in the vertical direction (pixel addresses N-1, N, N + 1,...) Is shown in FIGS.
The vertical pixel column (the pixel address in the horizontal direction is m) will be described. The numbers assigned to the respective pixels in FIG. 6B represent the quantized levels of the signals obtained from the respective pixels, and correspond to the first to third frame signals in order from the top. The same applies to FIG.

In this case, as described above, since the image pickup signal is a signal obtained by synthesizing the signals of two horizontal pixel columns, the levels of the image pickup signals of the lines An, An + 1,... In the A field are shown in FIG. , And the levels of the imaging signals of the respective lines Bn-1, Bn, Bn + 1,... Of the B field are as shown in FIG. However, first to first from the top
It corresponds to the third frame signal.

Therefore, the levels of the image pickup signals in the A and B fields of the first to third frames in the vertical pixel row having the pixel address m in the horizontal direction are as shown in FIG.
Accordingly, the level of the image pickup signal in the vertical pixel column whose pixel address is m output from the adder 17 is as shown in FIG. Further, for example, a vertical pixel column (the pixel address in the horizontal direction is m + 1) in which the relationship between the image and each pixel in the vertical direction (pixel address N-1, N, N + 1,...) Is as shown in FIGS. Will be described.

In this case, each line An of the A field,
The levels of the imaging signals An + 1,... Are as shown in FIG. C, and the lines Bn, Bn + 1,.
The level of the image pickup signal is as shown in FIG. However, they correspond to the first to third frame signals in order from the top. Therefore, the levels of the imaging signals in the A and B fields of the first to third frames in the vertical pixel column having the horizontal pixel address of m + 1 are as shown in FIG. Therefore, the pixel address output from the adder 17 is m +
The level of the imaging signal in one vertical pixel column is as shown in FIG.

FIGS. 6 to 8 show the levels of the imaging signals of the respective lines of the first to third frames obtained as described above, corresponding to the respective pixels. FIG. 9 shows the first
3 shows the level of the image pickup signal (output of the adder 17) of each line obtained by averaging the lines of the third frame. FIG. 10 shows, in a three-dimensional space, the level of the imaging signal of each line obtained by averaging.

In the present example, as shown in FIG. 4F, the difference between the signal levels of white and black is (1.67-0.0) = 1.67.
In contrast, in the case shown in FIG. 5F, the difference between the signal levels of white and black is (1.5−0.0) = 1.5. That is, when the pattern is shifted by a half pixel pitch in the vertical direction, the change in the difference between the white and black signal levels is smaller than in the conventional example shown in FIG. Therefore, when capturing an image in which inclined stripe patterns that are alternately black and white are arranged, generation of a false signal (moiré) caused by a periodic change in the level difference is suppressed, and oblique lines Becomes clear.

Also, since the image pickup signals of each line of the first to third frames are added and averaged and output, random noise is reduced to 1/3 and S / N can be improved.
Although the above-described embodiment is an example in which a still image is captured, a moving image may be captured. That is, the glass plate 11 is moved to the accumulation period of the image sensor 2,
For example, control may be performed so as to be positioned at equal time intervals in the first to third frame positions during one field period. In this case, the same image pickup signal as that obtained by averaging each line of the above-described first to third frames in each field can be obtained from the CDS circuit 3, so that a moving image having a large motion can be imaged. In this case, the A / D converter 13, the frame memories 14a to 14c, and the D / A converters 16a to 16 in FIG.
There is also an advantage that the configuration such as c is unnecessary.

[0032]

[0033]

According to the present invention, the change in the difference between the white and black signal levels when the black and white pattern is shifted by 1/2 pixel pitch in the vertical direction can be reduced. , The generation of a false signal (moiré) at the time of imaging can be effectively suppressed, and oblique lines can be made clear. Furthermore, since an image pickup signal obtained by shifting the picked-up image by 1/2 pixel pitch in the vertical direction is averaged and output, random noise can be reduced, and S / N can be reduced.
Can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment.

FIG. 2 is a diagram illustrating a pixel shift amount.

FIG. 3 is a diagram illustrating an example of a captured image.

FIG. 4 is a diagram illustrating an image pickup signal level of a vertical pixel column (horizontal pixel address m).

FIG. 5 is a diagram illustrating an image pickup signal level of a vertical pixel column (horizontal pixel address m + 1).

FIG. 6 is a diagram illustrating a level (first frame) of an imaging signal.

FIG. 7 is a diagram illustrating a level (second frame) of an imaging signal.

FIG. 8 is a diagram illustrating a level (third frame) of an imaging signal.

FIG. 9 is a diagram illustrating a level of an image pickup signal (addition average signal).

FIG. 10 is a diagram illustrating levels (three-dimensional spatial display) of image pickup signals.

FIG. 11 is a block diagram illustrating a main configuration of a solid-state imaging device.

FIG. 12 is a schematic diagram of color coding.

FIG. 13 is a diagram illustrating an output of a horizontal output register.

FIG. 14 is a diagram illustrating an example of a captured image.

FIG. 15 is a diagram illustrating an image pickup signal level of a vertical pixel column (horizontal address m).

FIG. 16 is a diagram illustrating an image pickup signal level of a vertical pixel column (horizontal address m + 1).

FIG. 17 is a diagram illustrating levels of image pickup signals.

FIG. 18 is a diagram illustrating a level of an imaging signal.

FIG. 19 is a diagram showing levels (three-dimensional space display) of imaging signals.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 imaging lens 2 CCD solid-state imaging device 3 CDS circuit 4 timing generator 11 glass plate for changing optical path 12 rotation driver 13 A / D converter 14 a to 14 c frame memory 15 memory controller 16 a to 16 c D / A converter 17 adder

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein in the first field period, 2n-1
And an image signal of a first field composed of a line signal obtained by combining signals of two horizontal pixel columns of 2n (n is a natural number). In a second field period, two horizontal pixel columns of 2n and 2n + 1 are output. A solid-state imaging device that outputs an imaging signal of a second field composed of a line signal obtained by combining the above signals; a pixel shifting unit that shifts a position of an image captured by the solid-state imaging device in a vertical direction; and a pixel shifting unit. A first memory that stores the image pickup signals of the first and second fields output from the solid-state image pickup device in a state where the position of the image is the first position, as an image pickup signal for one screen; The image output from the solid-state imaging device in a state where the position of the image is shifted to a second position by a half pixel pitch in one direction perpendicular to the first position by the shifting means. A second memory for storing the image pickup signals of the first and second fields as an image pickup signal for one screen, and the pixel shifting means for shifting the position of the image from the second position in the vertical direction by 1 / A third memory configured to store the imaging signals of the first and second fields output from the solid-state imaging device in a state where the third position is shifted by two pixel pitches as an imaging signal for one screen; A solid-state imaging device comprising: synthesis means for averaging the imaging signals for one screen stored in the first to third memories to obtain an imaging signal for one screen. 2. In a first field period, 2n-1
And an image signal of a first field composed of a line signal obtained by combining signals of two horizontal pixel columns of 2n (n is a natural number). In a second field period, two horizontal pixel columns of 2n and 2n + 1 are output. A solid-state imaging device that outputs an imaging signal of a second field composed of a line signal obtained by synthesizing the signals of the above, a pixel shifting unit that shifts the position of an image captured by the solid-state imaging device in a vertical direction, Each of the images has a first position, a second position shifted from the first position by one-half pixel pitch in one direction perpendicular to the first position, and 1 / two in the vertical direction from the second position. A solid-state imaging device comprising: control means for controlling the operation of the pixel shifting means so as to be positioned at equal time intervals at a third position shifted by two pixel pitches.