JP2002057944A - Drive method for solid-state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive method for a solid-state imaging device by which smear can accurately be corrected to the utmost. SOLUTION: The method of this invention is characterized in that one drive pulse among 1st to n-th drive pulses is selected, signal charges are read from a pixel corresponding to a charge transfer electrode to which the selected drive pulse is applied and transferred in a way that charges under a charge transfer electrode different from the charge transfer electrode from which the signal charges are read are not mixed with the signal charges, and the difference between the signal charges and the charges is taken.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a solid-state image pickup device, and more particularly to a method for driving a still camera.

[0002]

2. Description of the Related Art In recent years, solid-state imaging devices have been used in movie cameras and still cameras. The solid-state imaging device for a still camera has a feature that it has more vertical charge transfer electrodes (hereinafter also referred to as VCCD electrodes) than a solid-state imaging device for a movie camera having a small number of pixels.

[0003] Normally, a solid-state image pickup device for movies uses VCC.
The D-electrode structure is four-phase and two-pixel four-electrode.

On the other hand, a solid-state image pickup device for a still camera uses a VC which has a narrow vertical charge transfer portion due to high resolution.
CD electrode capacity is small. To cope with this, the number of readouts is increased, and the VCCD electrode structure has eight phases and four phases.
There are eight pixel electrodes.

A still camera generally has a mechanical shutter and a monitoring mode function. Still camera mode (mode when used as a normal camera)
At the time, only at the moment when the shutter is released, the mechanical shutter opens, and there is light in the image sensor. Since the image signal is read in a state where the mechanical shutter is closed (a state where light does not hit the solid-state imaging device), no smear occurs and no problem occurs. Thus, when used as a primary function of a still camera, smear does not pose a problem due to the mechanical shutter. The monitoring mode is a function for determining an angle of view of a normal camera, and an image is read out in real time. For this reason, the mechanical shutter is in the released state, and the light always hits the solid-state imaging device, causing a large amount of smear, which is a problem. A general configuration of a solid-state imaging device used in a still camera will be described with reference to FIG.

In this solid-state imaging device, a plurality of sets each including a first pixel row _Pt1 and a second pixel row _Pt2 are arranged in parallel, and a vertical charge transfer section _CVT is provided for each pixel row. provided, the horizontal charge transfer portion C _HT has a configuration provided at the output ends of the vertical charge transfer section C _VT.

[0007] The first pixel column _Pt1 is a green pixel G1-i (i =
,... N) and red pixels R-i (i = 1,... N) are alternately arranged. The second pixel column _Pt2 includes a blue pixel Bi (i = 1,... N) and a green pixel G2-i (i =
1,... N) are alternately arranged. Therefore, the total number of lines of this solid-state imaging device is n × 2.

On the other hand, each vertical charge transfer section _CVT has two charge transfer electrodes for each pixel of the corresponding pixel column. The same drive pulse is applied to every eight charge transfer electrodes. In the first pixel row P _t1 as shown in FIG. 5, for example, charge transfer electrodes 7 and 8 are provided in the pixel G1-1, charge transfer electrodes 5 and 6 to the pixel R-1
The pixel G1-2 is provided with charge transfer electrodes 3 and 4, the pixel R-2 is provided with charge transfer electrodes 1 and 2, and the pixel G1-3 is provided with charge transfer electrodes 7 and 8. Configuration. In the second pixel column _Pt2 , the pixel B-1
Are provided with charge transfer electrodes 7 and 8, the pixel G2-1 is provided with charge transfer electrodes 5 and 6, the pixel B-2 is provided with charge transfer electrodes 3 and 4, and the pixel G2-2 is provided with the pixel G2-2. Charge transfer electrode 1,
2 and the pixel B-3 is provided with the charge transfer electrodes 7 and 8. Then, the charge transfer electrode i (i =
,..., 8) are applied with a drive pulse φVi.

Each of the pixels constituting the first and second pixel columns converts an optical signal into a signal charge, and sends out the signal charge to the corresponding vertical charge transfer section _CVT below the charge transfer electrode. The vertical charge transfer unit sequentially transfers the signal charges and sends out the signal charges to the horizontal charge transfer unit _CHT . The horizontal charge transfer unit C _HT sequentially transfers the signal charges sent from the vertical charge transfer unit, and sends the signal charges to the outside via the output unit Out.

Next, the charge readout timing of the vertical charge transfer section _{CVT in} the above-described still camera mode of the solid-state imaging device will be described with reference to FIGS. FIG. 6 is a diagram showing the read timing of the vertical charge transfer unit _{CVT in} the still camera mode, and FIG. 7 is a waveform diagram of the driving pulse at that time.

In the still camera mode, since a mechanical shutter is used, a read time may be required, and image data of all pixels is read in four fields per frame (one screen). In contrast, solid-state image sensors for movies
In order to read an image in real time, image data is usually read in two fields of one frame (one screen).

First, the first field includes a drive pulse φV
In response to the field shift pulse FS1, the pixel charges (R-2 G2-2, R-
4G2-4, R-6 G2-6,...) Are read out to a vertical charge transfer unit (hereinafter, also referred to as VCCD). Then, the data is transferred to a horizontal charge transfer unit (hereinafter also referred to as HCCD) by a line shift (see the line shift in FIGS. 6 and 7).

In the second field, charges (G1-2B-2, G1-4B-4, G1-4B-4) of the pixel corresponding to the drive pulse φV3 are generated by the shift pulse FS3 of the drive pulse φV3.
1-6 B-6,...) Are read out, and the third field is shifted by the shift pulse FS5 of the drive pulse φV5.
The charge (R-1 G2) of the pixel corresponding to the drive pulse φV5
-1, R-3 G2-3, R-5 G2-5,...) Are read out, and the electric charge (G1-G1) of the pixel corresponding to the drive pulse φV7 in the fourth field is shifted by the shift pulse FS7 of the drive pulse φV7. 1 B-1, G1-3 B-3, G1
−5 B-5,...) Are read out to the VCCD,
Transferred to HCCD.

The image data thus read out is as shown in FIGS. 8 (a), 8 (b), 8 (c) and 8 (d), and the image data of these four fields becomes one frame (screen). .

Next, a description will be given of charge addition and thinning-out read timing of the vertical charge transfer section in the monitoring mode of the solid-state imaging device.

In the monitoring mode, the image data is read out in real time, so that the image data is read out in one frame (one screen) and two fields in order to shorten the reading time. In the monitoring mode, since the resolution may be low, there is a method of adding and reading image data of two pixels in the vertical direction (addition reading) or a method of reading data by thinning out without reading data of all pixels (thinning reading). .

(A) The charge addition readout timing of the VCCD in the monitoring mode will be described.

FIG. 9 shows the charge addition readout timing of the VCCD in the monitoring mode, and FIG. 10 shows a waveform diagram of the driving pulse at that time.

The first field includes a shift pulse FS1 of the drive pulse φV1 and a shift pulse F of the drive pulse φV5.
By S5, the charges (R-2 G2-2, R-4 G2-4, R-6 G2) of the pixel corresponding to the drive pulse φV1
-6,...) And the charge (R-1 G2-1, R-3 G2-3, R-5G2) of the pixel corresponding to the drive pulse φV5.
-5,...) Are read out to the VCCD, added in the VCCD, and transferred to the HCCD.

The second field includes a shift pulse FS3 of the drive pulse φV3 and a shift pulse F of the drive pulse φV7.
By S7, the electric charge (G1-2 B-2, G1-4 B-4, G1-6 B-) of the pixel corresponding to the drive pulse φV3 is obtained.
,...) And the charge (G1-1B-1, G1-3B-3, G1-5B-) of the pixel corresponding to the drive pulse .phi.V7.
, 5) are read out to the VCCD, added in the VCCD, and transferred to the HCCD. The image data thus read out is as shown in FIG. 11, and the image data of these two fields constitutes one frame (screen).

Also, since two image data are added and read, the number of lines in the vertical direction is half that in the still camera mode, and the read time is also half that in the still camera mode.

(B) Monitoring Mode At this time, the charge thinning-out readout timing of the VCCD will be described.

VCCD in monitoring mode of FIG.
FIG. 13 shows a waveform diagram of the drive pulse at this time.

The first field is the F of the drive pulse φV1.
By S1, the charge (R-2 G2-2, R-4, G2-4, R-6, G2) of the pixel corresponding to the drive pulse φV1 is obtained.
−6,...) Are read out to the VCCD and transferred to the HCCD.

The second field is the F of the drive pulse φV3.
By S3, the charge (G1-2, B-2, G1-4, B-4, G1-6 B-) of the pixel corresponding to the drive pulse φV3 is obtained.
6,...) Are read out to the VCCD and transferred to the HCCD.

The image data thus read out is as shown in FIGS. 14A and 14B, and the image data of these two fields is one frame (screen).

The charge of the pixel corresponding to the drive pulses φV5 and φV7 is not read.

The number of lines in the vertical direction is half that in the still camera mode, and the readout time is also half that in the still camera mode.

Smear is a phenomenon that cannot be avoided in a solid-state imaging device. In the related art, there is a technique for correcting the smear. Here, conventional smear correction and its problems will be described with reference to FIGS.

FIG. 15 shows a conventional smear correction in the monitoring mode. As shown in FIG. 15, when strong light is applied to the center of the screen, white line-shaped smear (false signal) is generated in the vertical direction. This smear is generated by the image data of the signal pixel for each line and the OB (Op
tical Black) The difference between the image data of the pixels is corrected.

The OB pixel has the same structure as the signal pixel, but does not respond to light because it is shielded from light, and is usually used as a black reference pixel for detecting dark output. Smear also occurs in this OB pixel, so that smear correction can be performed by taking the difference between the image data of the signal pixel line and the image data of the OB pixel line.

[0032]

However, when strong light is moving as shown in FIG. 16, it is impossible to accurately perform smear correction. At a certain point, VCC illuminated by strong light
Smear occurs only in D. Then, at the next point, strong light moves and smear occurs only in another VCCD. Thus, the smear does not become a vertical white line. For this reason, even if the difference between the image data of the signal pixel line and the image data of the OB pixel line is obtained, the smear component cannot be subtracted from the signal pixel having no smear, or the smear component cannot be subtracted from the signal pixel having the smear. Smear correction cannot be performed.

As described above, since the solid-state imaging device for a still camera requires high resolution, the width of the VCCD is narrowed, and the solid-state imaging device is often manufactured at the expense of smear prevention. When used as a still camera, which is an original function (still camera mode), no smear occurs because of the mechanical shutter. However, in the monitoring mode, which determines the angle of view of the camera, smears are liable to occur because the solid-state image sensor is always illuminated. Is disappearing. In the conventional smear correction method, smear correction cannot be performed accurately when light is moving.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a driving method of a solid-state imaging device capable of performing smear correction as accurately as possible.

[0035]

According to the present invention, there is provided a method for driving a solid-state imaging device, wherein a plurality of pixels are arranged in a matrix, each of which converts an optical signal into a signal charge, and is provided corresponding to each pixel column. To transfer the signal charges of the pixels forming the corresponding pixel column in the vertical direction.
A vertical charge transfer unit having a charge transfer electrode driven by the drive pulse of 2); and a horizontal charge transfer unit for transferring the charges transferred by the vertical charge transfer unit in a horizontal direction. In the solid-state imaging device to which a plurality of the charge transfer electrodes correspond, the first to n-th
, One of the drive pulses is selected, a signal charge is read out from a pixel corresponding to the charge transfer electrode to which the selected drive pulse is applied, and a charge different from the charge transfer electrode from which the signal charge is read out. The charge under the transfer electrode and the signal charge are transferred so as not to be mixed, and a difference between the signal charge and the charge is obtained.

According to the driving method of the present invention configured as described above, the signal charges and the charges indicating smear are transferred without being mixed, and the difference between them is taken, so that the smear correction can be performed. It can be done as accurately as possible.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for driving a solid-state imaging device according to the present invention will be described with reference to FIGS.

A solid to which the driving method of this embodiment is used
The imaging device has a configuration shown in FIG. That is,
Of the first pixel row P_t1And the second pixel
Row P _t2Are arranged in parallel, and each pixel row
Corresponding to the vertical charge transfer section C _VTAre provided, these hanging
Direct charge transfer section C_VTHorizontal charge transfer section C_HTProvided
Configuration.

The first pixel row _Pt1 is composed of green pixels G1-i (i =
,... N) and red pixels R-i (i = 1,... N) are alternately arranged. The second pixel column _Pt2 includes a blue pixel Bi (i = 1,... N) and a green pixel G2-i (i =
1,... N) are alternately arranged. Therefore, the total number of lines of this solid-state imaging device is n × 2.

On the other hand, each vertical charge transfer section _CVT has two charge transfer electrodes for each pixel of the corresponding pixel column. The same drive pulse is applied to every eight charge transfer electrodes. In the first pixel row P _t1 as shown in FIG. 5, for example, charge transfer electrodes 7 and 8 are provided in the pixel G1-1, charge transfer electrodes 5 and 6 to the pixel R-1
The pixel G1-2 is provided with charge transfer electrodes 3 and 4, the pixel R-2 is provided with charge transfer electrodes 1 and 2, and the pixel G1-3 is provided with charge transfer electrodes 7 and 8. Configuration. In the second pixel column _Pt2 , the pixel B-1
Are provided with charge transfer electrodes 7 and 8, the pixel G2-1 is provided with charge transfer electrodes 5 and 6, the pixel B-2 is provided with charge transfer electrodes 3 and 4, and the pixel G2-2 is provided with the pixel G2-2. Charge transfer electrode 1,
2 and the pixel B-3 is provided with the charge transfer electrodes 7 and 8. Then, the charge transfer electrode i (i =
,..., 8) are applied with a drive pulse φVi.

Each of the pixels constituting the first and second pixel columns converts an optical signal into a signal charge, and sends out the signal charge under the charge transfer electrode of the corresponding vertical charge transfer section _CVT . The vertical charge transfer unit sequentially transfers the signal charges and sends out the signal charges to the horizontal charge transfer unit _CHT . The horizontal charge transfer unit C _HT sequentially transfers the signal charges sent from the vertical charge transfer unit, and sends the signal charges to the outside via the output unit Out.

Next, a driving method according to the present embodiment will be described. FIG. 1 shows the read timing of the vertical charge transfer section _{CVT in} the monitoring mode according to this driving method, and FIG. 2 shows the waveform of the driving pulse at this time. At the addition readout timing in the conventional monitoring mode, the first field includes the pixel charges (R-2, G2-2, R-4, G2-4, R-6, G2) corresponding to the drive pulse φV1.
-6,...) And the charge (R-1, G2-1, R-3, G2-3, R-5, G) of the pixel corresponding to the drive pulse φV5.
2-5,...) Are read out to the VCCD and added in the VCCD.

On the other hand, in the present embodiment, the FS of the drive pulse φV1 (see FS1 in FIGS. 1 and 2) causes the charge (R−R) of the pixel corresponding to the drive pulse φV1.
2, G2-2, R-4, G2-4, R-6, G2-6,
..) Is read out, and further, the charge of the pixel corresponding to the drive pulse φV5 is not added in the VCCD.

In this case, the electric charge of the pixel corresponding to the drive pulse φV5 does not have the shift pulse FS, so that the electric charge of the pixel is equal to VCC.
D is not read out, and the first line: the charge of the first line corresponding to φV1 (R-2 G2-2) The second line: empty The third line: the charge of the third line corresponding to φV1 (R-4 G2) -4) Fourth line: The image data is read as follows: empty.

Here, when smear occurs, the empty second line, fourth line,... Become charges of only the smear for each line, and become image data such as the first field shown in FIG. . The reading time is twice as long as that of the conventional addition or thinning-out reading, which is twice as many lines. In order to make this the same reading time as in the prior art, reading is performed twice as fast (see FIGS. 1 and 2).

Similarly, in the second field, signal charges and charges of smear only are alternately read (see FIG. 3B).

If a difference of signal charge line−smear line (first line−second line, third line−fourth line...) Is performed on the image data read as described above, smear correction is performed for each line. This makes it possible to perform smear correction even when strong light is moving, which has not been possible with the prior art.

Next, FIG. 4 shows a configuration of a solid-state imaging device for realizing the driving method of the above embodiment. The solid-state imaging device includes a synchronization signal generator 20, an image sensor drive timing generator 25, an image sensor 30, a multiplexer 35,
A line image memory 40 and a differentiator 45 are provided.

The synchronization signal processing circuit 20 generates a reference synchronization signal processing pulse.

Based on the synchronizing signal, the image pickup device driving timing is generated from the image pickup device driving timing from the circuit 25 and from the solid-state image pickup device 30 to the image data such as signal charge lines, smear lines, signal charge lines, smear lines,. Output.

In the output image data, the signal charge line sends a synchronizing signal to the line image memory 40 via the multiplexer 35 and temporarily stores the signal.

The next output smear line is sent to a differentiator 45 via a multiplexer 35, and at the same time, a signal pixel from the line image memory 40 is converted to a differentiator 45.
Send to Then, the difference between the signal pixel and the smear pixel is calculated one pixel at a time by the differentiator 45 to obtain a smear-corrected image.

The DS mounted on the still camera
A frame correction (filtering or the like) may be performed using P or a buffer memory to obtain a smear-corrected image.

In the present embodiment, the driving method in the still camera mode is the same as that shown in FIGS.

In the above-described embodiment, the solid-state imaging device has a four-pixel eight-electrode structure in which the driving pulse has eight phases as shown in FIG. 5, but the driving pulse has six or more phases. Then, it goes without saying that the driving method of the present invention can be applied. For example, when the driving pulse is six phases,
The present invention can be applied to a three-pixel six-electrode structure or a two-pixel six-electrode structure. Also, when the driving pulse is 12 phases and 6
The present invention can be applied to the case of the pixel 12 electrode.

[0056]

As described above, according to the present invention, smear correction can be performed as accurately as possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining read timing of a vertical charge transfer unit according to one embodiment of a driving method according to the present invention.

FIG. 2 is a waveform diagram of a driving pulse at a read timing shown in FIG. 1;

FIG. 3 is a schematic diagram showing an array of image data read by an embodiment of the driving method according to the present invention.

FIG. 4 is a block diagram illustrating a configuration of a solid-state imaging device that implements the driving method of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a solid-state imaging device.

FIG. 6 is a diagram illustrating read timing of a vertical charge transfer unit in a still camera mode.

FIG. 7 is a waveform diagram of a driving pulse at the time of reading shown in FIG. 6;

FIG. 8 is a schematic diagram showing an array of image data read in the still camera mode.

FIG. 9 is a diagram illustrating timing of conventional charge addition reading in the monitoring mode.

FIG. 10 is a waveform diagram of a driving pulse at the time of reading shown in FIG. 9;

FIG. 11 is a diagram showing an array of image data read by conventional charge addition reading.

FIG. 12 is a view for explaining conventional charge thinning-out read timing in the monitoring mode.

FIG. 13 is a waveform diagram of a drive pulse at the read timing shown in FIG.

FIG. 14 is a diagram showing an array of image data read by conventional charge thinning-out reading.

FIG. 15 is a view for explaining conventional smear correction in a monitoring mode.

FIG. 16 is a view for explaining a problem of the conventional smear correction.

[Explanation of symbols]

1-8 Charge transfer electrode 20 Synchronous signal generation circuit 25 Image sensor drive timing generation circuit 30 Image sensor 35 Multiplexer 40 Line image memory 45 Differentiator C _VT Vertical charge transfer unit C _HT Horizontal charge transfer unit _Pt1 pixel column _Pt2 pixel column

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H054 AA01 4M118 AA05 AB01 BA10 DB01 DB05 FA06 GC08 GC14 5C024 AX01 BX01 CX13 DX04 GY01 GZ03 HX15 HX29 HX55 JX27

Claims (3)

[Claims] A plurality of pixels arranged in a matrix, each of which converts an optical signal into a signal charge, and a plurality of pixels which are provided corresponding to each pixel column and which form a corresponding pixel column. First to n-th (n ≧ 2) for vertical transfer
A vertical charge transfer unit having a charge transfer electrode driven by a drive pulse, a horizontal charge transfer unit that transfers the charges transferred by the vertical charge transfer unit in a horizontal direction,
Wherein a plurality of the charge transfer electrodes correspond to each pixel, wherein one of the first to n-th drive pulses is selected, and the selected drive pulse is A signal charge is read from a pixel corresponding to the applied charge transfer electrode, and the signal charge is transferred so that the signal charge is not mixed with a charge under a charge transfer electrode different from the read charge transfer electrode, and the signal charge is transferred. A method for driving a solid-state imaging device, wherein a difference between an electric charge and the electric charge is obtained. 2. The method according to claim 1, wherein n is 6 or more. 3. The driving method for a solid-state imaging device according to claim 1, wherein said solid-state imaging device is used in a still camera.