JPH09163236A - Drive method for solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive method for a solid-state image pickup element without reducing a read time of an optical black OB pixel even in the thinning read out mode. SOLUTION: In the drive method for the solid-state image pickup device provided with a pixel array 1 having an OB pixel 3 shielded around a light receiving pixel 2, in the thinning read out mode reading a signal of one pixel from two pixels, in the case of reading the OB pixel 3 conducted for a horizontal blanking period, the read frequency is reduced to 1/2 of a read frequency of the light receiving pixel 2. Thus, the read time of the OB pixel is made identical to the OB pixel read out time at usual scanning.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a light-shielded OB.
The present invention relates to a driving method of a solid-state imaging device including (Optical Black) pixels.

[0002]

2. Description of the Related Art Generally, in a solid-state image pickup device, an OB clamp is performed in order to perform a stable image pickup operation against changes in the surrounding environment such as temperature. In order to perform OB clamping, an OB pixel that blocks incident light is provided around the light-receiving pixel so that the signal of the OB pixel is read out during the horizontal or vertical blanking period, and a plurality of OB pixels are generally provided. Target.

[0003]

By the way, the conventional OB
The reading of OB pixels provided for clamping corresponds to a method of sequentially reading all the arranged pixels. For example, when reading out OB pixels provided in the horizontal scanning direction, when the horizontal driving frequency is 10 MHz, the O of 20 pixels is read out.
When B pixels are provided, the readout time of OB pixels per horizontal scanning is 20/10 MHz = 2 μs.

On the other hand, in the thinning-out scanning for reading out signals from the arrayed pixels at every arbitrary number of pixels, when the signals of OB pixels are read out by the above method, the OB pixel reading time is shortened. For example, under the above conditions, in the thinning-out scanning for reading out a signal from one of the four pixels, the readout time of the OB pixel per horizontal scanning is
20 ÷ 10 MHz ÷ 4 = 0.5 μs, which leads to a problem that the OB pixel read time is shortened and a stable OB clamp operation cannot be performed. Further, in the actual signal reading of the OB pixel, the OB near the boundary between the light receiving pixel and the OB pixel is
The pixel signal may not be sufficiently shielded, so
Some pixels at the boundary may not be used for the clamp operation, which further shortens the read time of the OB pixel.

The present invention has been made in order to solve the above-mentioned problems in a solid-state image pickup device having an OB pixel which performs a conventional thinning scanning, and does not shorten the OB pixel reading time even in the thinning reading mode. An object of the present invention is to provide a driving method of a solid-state imaging device. The purpose of each of the claims is to provide a driving method of a solid-state imaging device capable of outputting signals of OB pixels in a thinning-out reading mode. It is an object of the present invention to provide a method for driving a solid-state imaging device, which makes the OB pixel read time in the thinning-out read mode equivalent to that in the normal read mode. It is an object of the present invention to provide a driving method of a solid-state image pickup device capable of outputting a signal of an OB pixel in a normal read mode. It is an object of the invention of claim 6 to provide a method of driving a solid-state imaging device according to claim 4 or 5, wherein the OB pixel reading time in the thinning-out reading mode can be extended. To do. The invention described in claims 7 and 8 is the method for driving a solid-state imaging device according to claim 6,
An object of the present invention is to provide a method for driving a solid-state imaging device that shortens the OB pixel read time in the normal read mode. It is an object of the invention according to claim 9 to provide a method for driving a solid-state imaging device according to claim 3 or 6, which makes the amount of increase in the number of OB pixels appropriate.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 provides a solid-state image pickup device having light-shielded OB pixels in the periphery of light-receiving pixels, and receives a light-receiving pixel at an arbitrary number of pixels. In the driving method of the solid-state imaging device in which the thinning-out reading mode for reading out pixels and the normal reading-out mode for reading out all the pixels are performed, the OB pixels in the thinning-out reading mode are thinned out similarly to the light-receiving pixels. is there. By driving in this way, the signal reading of the OB pixel in the thinning-out reading mode can be easily performed.

According to a second aspect of the present invention, in the method for driving a solid-state image pickup device according to the first aspect, signal reading of OB pixels is performed at a lower speed than reading of light receiving pixels. By driving in this way, it becomes possible to extend the readout time of the OB pixel in the thinning readout mode.

According to a third aspect of the present invention, in the method for driving a solid-state image pickup device according to the first aspect, the number of OB pixels is set to be larger than the number required for the normal read mode. With this configuration, it is possible to extend the readout time of the OB pixel in the thinning readout mode.

According to a fourth aspect of the present invention, the solid-state image pickup device having light-shielded OB pixels around the light-receiving pixels is used in a thinning-out reading mode for reading light-receiving pixels at an arbitrary number of pixels and a normal reading mode for reading all pixels. In the driving method of the solid-state imaging device which is read by the method, the reading of the OB pixels in the thinning-out reading mode is performed in the normal reading mode without thinning out, unlike the reading of the light-receiving pixels. By driving in this way, O in the thinning-out read mode can be achieved without increasing the number of OB pixels.
It is possible to extend the read time of the B pixel.

According to a fifth aspect of the present invention, the solid-state image pickup device having light-shielded OB pixels around light-receiving pixels is used in a thinning-out reading mode for reading light-receiving pixels at every arbitrary number of pixels and a normal reading mode for reading all pixels. In the driving method of the solid-state imaging device which is read by the method, the reading of the OB pixel in the normal reading mode is performed in the normal reading mode similarly to the reading of the light receiving pixel. By driving in this way, it becomes possible to read out signals from OB pixels in the normal reading mode.

According to a sixth aspect of the present invention, in the method for driving a solid-state image pickup device according to the fourth or fifth aspect, the number of OB pixels is set larger than that required for the normal read mode. With this configuration, it is possible to extend the read time of the OB pixel when reading the OB pixel in the thinning-out reading mode.

According to a seventh aspect of the present invention, in the solid-state image pickup device driving method according to the sixth aspect, the reading of the OB pixel is performed at a higher speed than the reading of the light receiving pixel. By driving in this way, it becomes possible to shorten the read time of the OB pixel in the normal read mode.

According to an eighth aspect of the present invention, in the method for driving a solid-state image pickup device according to the sixth aspect, the reading of OB pixels is interrupted midway. By driving in this way, it becomes possible to shorten the read time of the OB pixel in the normal read mode.

According to a ninth aspect of the present invention, in the solid-state imaging device driving method according to the third or sixth aspect, the number of OB pixels is set in accordance with the thinning rate in the thinning readout mode. By setting in this way, it is possible to realize a driving method of a solid-state imaging device having an appropriate number of OB pixels.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] Next, an embodiment will be described. FIG. 1 shows a first method of driving a solid-state imaging device according to the present invention.
2 illustrates a pixel array 1 arranged two-dimensionally for explaining the embodiment of FIG. The pixel array 1 has 10 pixels in the horizontal direction and 6 pixels in the vertical direction. Each pixel (i, j) is i = 1, 2,
3, ..., 10, j = 1,2,3, ...
.., 6 Here, the hatched pixels in each column of i = 7, 8, 9, 10 are OB pixels 3 in which incident light is blocked, and the other pixels are light receiving pixels 2.

In the normal read mode in which signals are read out from all the pixels arranged as shown in FIG. 1, the signal output shown in the timing chart of FIG. 2 is obtained.
In FIG. 2, the horizontal axis represents time and the vertical axis represents pixel output. That is, j = 1 in the first horizontal scanning period (1H).
Pixels (1,1), (2,1), (3,1) in the first row of
Are sequentially read from i = 1, and when the horizontal blanking period (H-BL) is entered, O of i = 7, 8, 9, 10 is read.
B pixels (7,1), (8,1), (9,1), (10,
The signal 1) is obtained, and in the next horizontal scanning, the pixels in the second row with j = 2 are read out.

In the thinning-out reading mode in which the signal of one pixel out of two pixels is read out, for example, only the signals of odd pixels in both i and j are read out, a signal output as shown in the timing chart of FIG. 3A is obtained. . That is, in the first horizontal scanning period, after j = 1, the signals of the pixels (1, 1), (3, 1), (5, 1) of i = 1, 3, 5 are read out, and then the horizontal In the blanking period, the signals of the OB pixels (7, 1) and (9, 1) with i = 7, 9 are read. As described above, in the thinning-out reading mode, the signal of the OB pixel can be read out by continuing the reading in the thinning-out reading mode of the OB pixel portion as well.

By the way, in the thinning-out reading mode shown here, when reading is performed at the same reading frequency as in the normal scanning shown in the timing chart of FIG. 2, the OB pixel reading time is reduced to 1/2, and the normal reading mode is set. It is necessary to perform the OB clamp operation in a shorter time than the case. In addition, since the clamp operation must be performed in a shorter time than in the normal read mode, there is a possibility that sufficient OB clamp cannot be performed.

Therefore, O in the thinning-out reading mode
Another example of reading the B pixel will be described with reference to the timing chart shown in FIG. In the read method shown in the timing chart of FIG. 3B, when the OB pixel is read during the horizontal blanking period,
Compared with the reading frequency when reading the signal of the light receiving pixel,
It is reduced to 1/2.

By thus reducing the read frequency of the OB pixel to half the read frequency of the light receiving pixel, the OB pixel read time can be made the same as the OB pixel read time during normal scanning. Note that in the thinning-out reading mode in this embodiment, one of two pixels
Since the pixel signal is read out by ½ thinning, the reduction in the reading frequency of the OB pixel is set to ½ of the reading frequency of the light-receiving pixel, but the rate of the reduction in the reading frequency depends on the number of thinned pixels. Can be changed.

[Second Embodiment] In the first embodiment, in order to make the OB pixel read time the same in the normal read mode and the thinning read mode, the light receiving pixel and the OB
An example in which the signal read frequency of the pixel is changed has been shown. However, there is a problem that the driving frequency of the solid-state imaging device is changed in order to change the read frequency, and the control thereof becomes complicated.

In the second embodiment, the same OB pixel read time as in the normal read mode is obtained in the thinning read mode without changing the drive frequency of the solid-state image pickup device. FIG. 4 is a two-dimensionally arranged pixel array 11 for explaining the second embodiment.
Is shown. The pixel array 11 has 14 pixels in the horizontal direction and 6 pixels in the vertical direction. Each pixel (i, j) is i = 1, 2, 3, ...
., 14, vertically from the top, j = 1, 2, 3, ..., 6
Indicated by Where i = hatched
Pixels in each column of 7, ..., 14 are OB pixels 13, and other pixels are light receiving pixels 12. In this embodiment, the number of OB pixels is doubled in the horizontal direction as compared with the pixel array of the first embodiment.

FIG. 5 shows a timing chart of signals obtained when the thinning-out reading similar to that of the first embodiment is performed in the solid-state image pickup device having the pixel array 11 of the arrangement shown in FIG. For the first row, (7,1), (9,1), (11,1), (13,
The four OB pixels of 1) are read out. in this way,
By increasing the number of OB pixels, the same OB pixel read time as in the normal read mode shown in the timing chart of FIG. 2 can be obtained in the thinning read mode without changing the drive frequency of the solid-state imaging device. .

In the thinning-out reading mode in this embodiment, the signal of 1 pixel out of 2 pixels is read out 1
The number of OB pixels is twice as large as that of the solid-state image pickup device only in the normal read mode because the number of OB pixels is reduced. The rate of increase in the number of OB pixels can be changed according to the number of thinned pixels.

When a signal is read in the normal read mode in this state, the OB pixel read time in the normal read mode becomes longer as the number of OB pixels is increased. It is preferable that all the OB pixels can be read within the horizontal blanking period in the normal read mode, but when the number of OB pixels increases, the signals of all the OB pixels arranged in the horizontal blanking period must be read. May not be possible.

In such a case, as shown in the timing chart of FIG. 6A, the reading frequency may be increased when reading the OB pixel in the horizontal blanking period. Here, in the 1/2 thinning mode in which the signal of one pixel of the two pixels is read, and the number of OB pixels is twice as large as that in the solid-state imaging device in the normal read mode only, the read frequency of the OB pixel is The increase is said to double. The rate of increase in the read frequency can be changed according to the number of thinned pixels and the number of OB pixels.

By the way, in the driving example shown in the timing chart of FIG. 6A, it is necessary to change the driving frequency of the solid-state image pickup device at the time of reading the OB pixel in the normal reading mode, which makes the control complicated. In order to solve this problem, in the normal read mode, as shown in the timing chart of FIG. 6B, the reading of OB pixels is interrupted midway. In this driving example, if the OB pixels of (10, 1) are read out for the first row, the first row is read.
Row reading is suspended. The same applies to the second and subsequent rows.

As described above, in the normal read mode, as shown in the timing chart of FIG.
By interrupting the readout of OB pixels,
Even when the number of OB pixels is large and the signals of all the OB pixels arranged in the horizontal blanking period cannot be read, it is not necessary to change the drive frequency of the solid-state imaging device on the way.

[Third Embodiment] In the first and second embodiments, in both the normal read mode and the thinned-out read mode, sufficient read time of OB pixels for performing OB clamp is obtained. Therefore, a means for changing the read frequency at the time of reading the OB pixels or a means for preparing a large number of OB pixels in advance is adopted. However, with such means, there are problems that the control becomes complicated with a change in the driving frequency of the solid-state imaging device, the chip area increases due to the increase in the number of pixels, and the yield decreases. The third embodiment provides a driving method that enables sufficient reading of OB pixels in both modes without using the means in the first or second embodiment.

Next, a third embodiment will be described with reference to the above-mentioned drawings. First, as in the first embodiment, FIG.
By using the pixel array having the arrangement shown in (1), the signal output as shown in the timing chart of FIG. 2 can be obtained in the normal read mode. That is, in the first horizontal scanning period, the pixels in the first row with j = 1 are sequentially read from i = 1, and when entering the horizontal blanking period, i = 7,
8, 9, 10 OB pixels (7, 1), (8, 1), (9,
The signals 1) and (10, 1) are obtained.

In the thinning-out reading mode in which the signal of one pixel of the two pixels is read out, driving is performed so that a signal output as shown in the timing chart of FIG. 7 is obtained. That is, in the first horizontal scanning period, in the first row with j = 1,
After the signals of the pixels of i = 1, 3, 5 are read in the thinning-out reading mode, the same scanning as in the normal reading mode is performed during the horizontal blanking period, and the OBs of i = 7, 8, 9, 10 are read. Pixels (7,1), (8,1), (9,1), (10,
Read the signal of 1). In this way, in the thinning-out reading mode, the same reading as in the normal reading mode is performed on the OB pixels, thereby performing an operation of changing the reading frequency in the middle or an operation such as providing a large number of OB pixels in advance. In both normal read mode and thinned read mode, stable O
It becomes possible to read out signals of OB pixels sufficient for performing B clamp.

As described above in the first, second and third embodiments, according to the present invention, in the solid-state image pickup device for thinning-out reading, the signal of the OB pixel necessary for stable OB clamping. Can be read. In each of the above-described embodiments, the thinning-out scanning has been described in the 1/2 thinning-out reading mode in which the signal of one pixel of the two pixels is read out, but the thinning-out ratio is not limited. The number of pixels in the pixel array of the solid-state imaging device is not limited to that shown in FIG. 1 or 4. Further, in each of the embodiments, the example in which the OB pixel is provided at the trailing edge of the horizontal scanning is shown. However, when the OB pixel is provided at the leading edge of the horizontal scanning, after the signal of the light receiving pixel is read out. The operation to be performed during the horizontal blanking period may be performed during the horizontal blanking period before the signal of the light receiving pixel is read out. Further, when the OB pixel is provided at the leading edge or the trailing edge of the vertical scanning, it can be dealt with by replacing the horizontal scanning of each embodiment with the vertical scanning.

[0033]

As described above based on the embodiment, according to the invention described in claim 1, it is possible to easily read the signal of the OB pixel in the thinning-out reading mode. According to the inventions of claims 2 and 3, it is possible to extend the read time of the OB pixel in the thinning-out read mode. According to the invention described in claim 4,
It is possible to extend the readout time of the OB pixels in the thinning readout mode without increasing the number of OB pixels. According to the fifth aspect of the present invention, it is possible to read the signal of the OB pixel in the normal read mode. According to the invention described in claim 6, it becomes possible to extend the read time of the OB pixel when the OB pixel is read in the thinning-out reading mode. According to the invention described in claims 7 and 8, it is possible to shorten the read time of the OB pixel in the normal read mode. According to the invention described in claim 9, it is possible to realize a driving method of a solid-state imaging device having an appropriate number of OB pixels.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a pixel array for explaining a first embodiment of a method for driving a solid-state imaging device according to the present invention.

FIG. 2 is a timing chart showing a mode of reading the pixel array shown in FIG. 1 in a normal read mode.

FIG. 3 is a timing chart showing a mode of reading the pixel array shown in FIG. 1 in a thinning-out reading mode.

FIG. 4 is a diagram showing a configuration of a pixel array for explaining a second embodiment of the present invention.

5 is a timing chart showing a mode of reading the pixel array shown in FIG. 4 in a thinning-out reading mode.

FIG. 6 is a timing chart showing a mode of reading the pixel array shown in FIG. 4 in a normal read mode.

FIG. 7 is a timing chart showing a thinning-out reading mode according to the third embodiment of the present invention.

[Explanation of symbols]

 1 pixel array 2 light receiving pixel 3 OB pixel 11 pixel array

Claims (9)

[Claims] 1. A solid-state image pickup device having light-shielded OB pixels around light-receiving pixels is read in a thinning-out reading mode for reading light-receiving pixels at an arbitrary number of pixels and a normal reading mode for reading all pixels. In a driving method of a solid-state imaging device, OB in a thinning readout mode
A method of driving a solid-state image pickup device, wherein reading out of pixels is performed by thinning out similarly to reading out of light receiving pixels. 2. The reading of the OB pixel is performed at a lower speed than the reading of the light receiving pixel.
The driving method of the solid-state imaging device according to the above. 3. The method for driving a solid-state imaging device according to claim 1, wherein the number of OB pixels in the solid-state imaging device is set to be larger than the number required for the normal reading mode. 4. A solid-state image pickup device having light-shielded OB pixels around light-receiving pixels is read in a thinning-out reading mode for reading light-receiving pixels at an arbitrary number of pixels and a normal reading mode for reading all pixels. In a driving method of a solid-state imaging device, OB in a thinning readout mode
A method of driving a solid-state image pickup device, which is characterized in that reading of pixels is performed in a normal reading mode without thinning out, unlike reading of light receiving pixels. 5. A solid-state image pickup device having light-shielded OB pixels around light-receiving pixels is read in a thinning-out reading mode for reading light-receiving pixels at an arbitrary number of pixels and a normal reading mode for reading all pixels. In the driving method of the solid-state imaging device, the reading of the OB pixel in the normal reading mode is performed in the normal reading mode similarly to the reading of the light receiving pixel. 6. The method for driving a solid-state image pickup device according to claim 4, wherein the number of OB pixels in the solid-state image pickup device is larger than that required for the normal read mode. 7. The reading of the OB pixel is performed at a higher speed than the reading of the light receiving pixel.
The driving method of the solid-state imaging device according to the above. 8. The method for driving a solid-state imaging device according to claim 6, wherein the reading of the OB pixel is interrupted during the reading of the OB pixel. 9. The method for driving a solid-state imaging device according to claim 3, wherein the number of OB pixels in the solid-state imaging device is set according to a thinning rate in the thinning readout mode.