JPS631167A - Driving method for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To improve the picture quality by making the phase shift of a transfer pulse supplied to a vertical CCD different from each other as to plural horizontal periods so as to eliminate the generation of longitudinal stripes on a reproduced pattern. CONSTITUTION:A drive pulse (i) is fed to each vertical CCD during the i-th of row of horizontal period where, e.g, the i-th row of electric charge is transferred by a horizontal CCD, and a drive pulse (h) is fed each vertical CCD during the (i+1)th horizontal period when the electric charge of the (i+1)th row is transferred. Thus, noise appears on the i-th row of scanning line as a point of a line shown as the i-th row on a reproduced pattern (a), and a noise component appears on the scanning line of the (i+1)th row as a point of the line shown as the (i+1)th row. Since drive pulses as to the i-th-(i+6)th rows are different in phase, the noise component on the reproduced pattern appears not as longitudinal stripes but as points populated thinly. Thus, the noise component on the pattern is not made remarkably visually and the picture quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for driving a solid-state image device, particularly a method for driving a solid-state image device that performs charge transfer using a CCD (charge-coupled device). .

(Prior Art) Solid-state imaging devices using CCDs have become widespread in recent years. FIG. 2 shows the general configuration of this solid-state 11 image device.

One photoelectric conversion cell is composed of a light receiving and accumulating section 1 and a transfer gate 2 formed on a semiconductor substrate, and such photoelectric conversion cells S are arranged in a two-dimensional matrix.

In the figure, each photoelectric conversion cell is shown in the form S, . The transfer gate 2 is driven by a pulse given from the gate pulse &1160 circuit 3, and operates to take in the signal charges accumulated in the light receiving and accumulating section 1 by photoelectric conversion into the vertical CCD 4. I'? 1ccD4 are arranged in a row, and in the figure, each is shown in the shape of ■j. The vertical CCD 4 has m transfer electrodes per one photoelectric conversion cell. An n-phase glue is applied to each of these transfer electrodes, and the vertical CCD 4
The above signal charges are sequentially transferred between each transfer electrode toward the bottom of the figure. The signals at the bottom of each vertical CCD 4 are transferred to the horizontal CCD 5. And this horizontal C
The signal charges on CD5 are sequentially transferred to the right side of the figure.

This signal for 0001 horizontal lines is treated as a signal on the -horizontal scanning line, and an image is formed by sequentially performing horizontal scanning. In addition, in FIG. 2, a device in which the transfer gate 2 is also used as a vertical C0D40 transfer gate can perform almost the same operation.

FIG. 3 is a time chart showing the above-mentioned operation. FIG. 5A shows a synchronization pulse for each horizontal scan, and this cycle day corresponds to one horizontal period (between the horizontal scanning period and blanking 1llJ). That is, for each period day, the horizontal CC
I'll) Charges for 501 rows will be read out. FIG. 4B shows an example of a driving pulse for the vertical CCD 4. In FIG. While the horizontal CCD 5 is escaping while transferring the charge of the i-th row toward the side of FIG. 2, the vertical CCD 4 is
This means that the charges after the +1) row are transferred several steps downward in FIG.

(Problem to be solved by the invention) Now, Fig. 3 (phase of drive pulse of b>) - Fig. (a)
In relation to the synchronization pulse, the phase is the same for each horizontal period.

That is, the starting point t in the first horizontal period in the figure.

The time from tl to each displacement point of the drive pulse is tl.

1.1.14 and the same times ti' and t2' in the second and third horizontal periods.

t', t' and t", t", t3".

If t n, t = t'-t'', t2
-t'=t, t=t'-t'', t
4-t'=t''.

Since a plurality of vertical CCOs 4 are driven by the drive pulse shown in FIG. 3(b), charge is transferred between a large number of electrodes at each displacement point of the drive pulse. Therefore, at each displacement point, noise is mixed into the charge read out from the horizontal CCD 5, and this noise component appears on the reproduction screen. As mentioned above, since the phase of the drive pulse is the same for each horizontal period, this noise component will appear at the same position on each horizontal line to improve the playback image, and in the end, the playback screen will look like the one shown in Figure 3 (C). ) will result in vertical stripes as shown.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for driving a solid-state imaging device that can obtain good image quality without vertical stripes occurring on a reproduced screen.

(Structure of the Invention) (Means for Solving the Problems) The present invention includes a plurality of photoelectric conversion cells arranged in a two-dimensional matrix and vertically transferring signal charges converted by the photoelectric conversion cells. A plurality of vertical CCDs for horizontally transferring the signal charges transferred from the plurality of vertical CCDs, and a horizontal CCD for horizontally transferring the signal charges transferred from the plurality of vertical CCDs, and a signal charge converted by each photoelectric conversion cell through a predetermined gate. A method for driving a solid-state image device which horizontally scans a signal transferred from a horizontal CCD as a signal on one horizontal scanning line to form an image, comprising: a gate means for capturing a signal onto a vertical CCD; By varying the phase of the transfer pulses applied to the CCD, the generation of vertical stripes on the reproduced screen was eliminated and image quality was improved.

(Function) Since the phase of the transfer pulse applied to the vertical CCD is made to differ in multiple horizontal periods, the position where the noise component caused by the transfer pulse appears on the playback screen differs for each horizontal line, and the playback On the screen, this noise component appears not as vertical stripes but as sparse dots.

Therefore, noise components on the playback screen are visually less noticeable compared to conventional driving methods, and image quality can be improved.

(Example) The present invention will be described below based on an illustrated example. 1st
The figure is an explanatory diagram of a method for driving a solid-state imaging device according to an embodiment of the present invention. Figure (a) shows the playback screen when driven by this method, Figure (b) shows the synchronization pulse for each horizontal scan, and Figure (C) to (+).
These are diagrams illustrating an example of the driving Oj pulses of the vertical CCD 4 in each horizontal period for rows (i+6) to (i), respectively. For example, during the i-th horizontal period when the i-th row charges are transferred by the horizontal CCD 5, each vertical CCD 4 is given a drive pulse as shown in FIG. 1(i), and (i+
1) The charges in the row are transferred by the horizontal CCD 5 (i
During the horizontal period of the +1)th row, a driving pulse as shown in FIG. 1(h) is applied to each vertical C0D4. Therefore, on the playback screen, the image shown in FIG. 1(a) appears on the first scanning line.
A noise component appears as a point on the line indicated as (1) row, and a noise component appears as a point on the line indicated as (i+1> row) on the (i+1)th scanning line.

As shown in FIG. 1(C) to (i), rows (i) to (i)
Since the drive pulses for the +6) rows all have different phases, the noise components on the reproduced screen do not appear as vertical stripes as in the conventional case, but as sparse dots. Since points are visually less noticeable than lines, the playback screen shown in FIG. 1(a) has improved image quality compared to the conventional playback screen shown in FIG. 3(C).

Specifically, the noise component as a line has an S/N ratio of 1/100.
It has been confirmed that the noise component as a point is not recognized until the S/N ratio is about 5/1000, whereas it is visually recognized at an S/N ratio of about 0. In other words, according to the driving method according to the present invention, the image quality can be improved by about 5 degrees.

In the embodiment shown in FIG. 1, the drive pulses for each row have different duty ratios, but in the present invention, all that is required is to change the phase of each drive pulse, so drive pulses with the same duty ratio can be used. Of course, it does not matter if only the phase is changed. Further, it is not necessary that all the drive pulses for all the rows constituting one screen have different phases, and the effects of the present invention can be produced as long as the phases are different for at least some rows. For example, in the example of FIG. 1, the phases of the drive pulses for rows (i) to (i +6) are all different, but for row (1+7), a pulse with the same phase as row (i) is applied. For the (i+8)th row, pulses having the same phase as the (i+1)th row may be used.

In the above embodiment, the i-th horizontal period is always as shown in FIG.
) will be used.

That is, in the horizontal period of the first row belonging to a different vertical period (period for scanning one screen), the drive pulse shown in FIG. 1(i) is always used. To put it bluntly, the noise component as a point appears at exactly the same position on each screen. Therefore, in order to further improve the image quality, +i! horizontal Iy! for the same horizontal position (for example, the i-th row position). What is necessary is to make the phases different between the two. To be more specific, a certain lil
! Figure 1 (i
), if the same i of the next screen is used,
For the horizontal period of the row, a drive pulse having a phase different from that shown in FIG. 1(i) is used. If this is done, the noise component as a point will appear at a different position for each screen, and the point as noise will appear to flicker on the screen in terms of time.

When the position of a point changes over time in this way, the noise component of this point will not be recognized until the S/N ratio is around 10/1000, resulting in an image quality improvement of about 10 times compared to the conventional drive method. be able to.

〔Effect of the invention〕

As described above, according to the present invention, in the driving method of the solid-state RII & device, the phase of the transfer pulse applied to the vertical CCD is made different for a plurality of horizontal periods, so that vertical stripes occurring on the playback screen can be eliminated. Image quality can be improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a method for driving a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a general solid-state imaging device.
FIG. 3 is an explanatory diagram of a conventional method for driving a solid-state image device. DESCRIPTION OF SYMBOLS 1... Light reception accumulation part, 2... Transfer gate, 3... Gate pulse control circuit, 4... Vertical CCD, 5... Horizontal CCO. Applicant's agent Yumano Sato 1 Figure +-1

Claims (1)

[Scope of Claims] A plurality of photoelectric conversion cells arranged in a one- and two-dimensional matrix, a plurality of vertical CCDs for vertically transferring signal charges converted to the photoelectric conversion cells, and a plurality of vertical CCDs for vertically transferring signal charges converted to the photoelectric conversion cells; A horizontal CCD for horizontally transferring the signal charge transferred from the vertical CCD, and a horizontal CCD for transferring the signal charge transferred from each of the photoelectric conversion cells to the vertical CCD via a predetermined gate.
a gate means for capturing the signal transferred from the horizontal CCD into a signal on one horizontal scanning line to form an image by horizontally scanning the signal transferred from the horizontal CCD as a signal on one horizontal scanning line. 1. A method for driving a solid-state imaging device, characterized in that the phases of transfer pulses applied to the two devices are different from each other. 2. The method of driving a solid-state imaging device according to claim 1, wherein the phase of the transfer pulse is made different for horizontal periods for different horizontal positions belonging to the same vertical period. 3. The method for driving a solid-state imaging device according to claim 1 or 2, characterized in that the phase of the transfer pulse is made different for horizontal periods at the same horizontal position belonging to different vertical periods.