JP2523617B2 - Driving method for solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a driving method of a solid-state imaging device.

2. Description of the Related Art Recently, in a video camera using a solid-state imaging device,
The photoelectric conversion time, which corresponds to the shutter speed of the film camera, is electrically controlled, and images with less blur can be obtained even for fast-moving subjects (hereinafter, the photoelectric conversion time of the solid-state imaging device is Electronically controlled is called electronic shutter).

A driving method of the solid-state imaging device for realizing the electronic shutter will be described below with reference to the drawings. The basic structure of the solid-state imaging device is, as shown in FIG. 3, a photoelectric conversion unit 1, a vertical transfer unit 2, a horizontal transfer unit 3, a signal charge detection unit 4,
The signal charge discharging unit 5 is included. The arrow indicates the normal signal transfer direction.

FIG. 4 is an example of a drive pulse for realizing an electronic shutter. a is a composite retrace line signal, b is a transfer pulse (hereinafter, abbreviated as a charge pulse) for transferring the signal charge accumulated in the photoelectric conversion unit to the vertical transfer unit, and c is a horizontal pulse of the signal charge existing in the vertical transfer unit. A transfer pulse for transferring to the transfer unit or the signal discharging unit (hereinafter, abbreviated as vertical transfer pulse), d is a transfer pulse for transferring the signal charge in the horizontal transfer unit to the signal charge discharging unit (hereinafter, abbreviated as horizontal transfer pulse) ).

When the first charge pulse 11 is applied during the vertical blanking period, unnecessary signal charges that are not used as a video signal photoelectrically converted during the period 14 are transferred from the photoelectric conversion unit 1 to the vertical transfer unit 2. And high-speed transfer pulse during period 13
By applying 15, unnecessary signal charges are transferred in the direction opposite to the direction of the arrow in FIG.

Next, the second charge pulse 12 is applied to the signal charge used as the video signal photoelectrically converted during the period 13,
Transfer from the photoelectric conversion unit 1 to the vertical transfer unit 2. After that, during the vertical scanning period, the signals are sequentially transferred from the vertical transfer unit 5 to the horizontal transfer unit 3 line by line, and the signal is output bit by bit through the signal detection unit 4 by the horizontal transfer pulse.

As a result, the signal output from the signal detector 4 is the fourth signal.
Only the signal photoelectrically converted in period 13 in the figure is used.
Equivalent to 1000 to 1/2000 seconds.

By driving the solid-state imaging device as described above, it is possible to obtain an image with little blur even for a high-speed subject.

Problems to be Solved by the Invention However, in the case of driving as described above, the period 13 is short, and in order to obtain sufficient sensitivity, the aperture of the video camera is set to several apertures as compared with the normal operation. I have to open it.

Therefore, the signal charges photoelectrically converted in the period 14 are likely to be in a supersaturated state. This supersaturated signal charge usually overflows to the substrate by devising the structure of the solid-state imaging device. FIG. 2 is a diagram showing the state of potential in the configuration. In the figure, 6 is a transfer gate for transferring the signal charges accumulated in the photoelectric conversion section to the vertical transfer section, 7 is a P well in the depth direction of the photoelectric conversion section, and 8 is a substrate. At the time of electronic shuttering, the saturation signal shown by hatching in FIG. 3 must be transferred to the vertical transfer unit and transferred by the high-speed reverse transfer pulse 15. This transfer pulse is so fast that it is not sufficiently transmitted to the vertical transfer gate of the vertical transfer unit. In particular, the transfer pulse is transmitted in a dull form as it moves away from the contact portion of the vertical transfer gate. For this reason, the saturated signal charges cannot be handled and all the unnecessary signal charges cannot be discharged to the discharging unit 5. For this reason, the signal charges to be discharged are output, and the image is disturbed.

In view of the above-mentioned drawbacks, the present invention provides a method for driving a solid-state imaging device capable of discharging all unnecessary signal charges to a discharging unit.

Means for Solving the Problems In order to solve the above problems, a method for driving a solid-state imaging device according to the present invention includes a photoelectric conversion unit in a semiconductor layer of an opposite conductivity type provided on a semiconductor substrate of one conductivity type, and a vertical converter. When driving the solid-state imaging device including the transfer unit, the horizontal transfer unit, the signal detection unit, and the signal discharge unit, the voltage applied to the semiconductor substrate during the first photoelectric conversion period in which unnecessary signal charge is accumulated is the signal charge. Is higher than the voltage applied to the semiconductor substrate during the second photoelectric conversion period in which is stored.

Action With this configuration, the amount of unnecessary signal charges is discharged to the discharge unit without being left behind even with the high-speed reverse transfer pulse.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a driving method of a solid-state imaging device according to an embodiment of the present invention.

In FIG. 1, a to d are the same as a to d in FIG. e is a pulse applied to the substrate voltage.

The operation of the driving method of the solid-state imaging device configured as described above will be described below. First, during the period 14 until the first charge pulse 11 is applied, the substrate voltage is set to a high level (voltage higher than the normal substrate voltage). At that time, the peak of the potential of the P well 7 in FIG. 3 has a shape shown by a broken line, and the saturation signal charge amount of the photoelectric conversion portion decreases. Next, this unnecessary signal charge is transferred to the vertical transfer unit 2 by the first charge pulse 11, and is discharged to the discharge unit 5 by the high-speed reverse transfer pulse 15. The amount of signal charges to be discharged is extremely smaller than that in the case of igniting a DC voltage on the substrate, so that even a high-speed reverse transfer pulse is not left behind.

The substrate voltage is set to a low level (normal substrate voltage) during the period 13 for accumulating the signal charges used for the image. At this time, the peak of the potential of the P-well 7 becomes as shown by the solid line in FIG. 3, and therefore the D range is not damaged.

EFFECTS OF THE INVENTION As described above, according to the present invention, the substrate voltage is set higher than the normal voltage and the saturation signal charge amount is electrically adjusted during the period of accumulating the signal charges that are not used for the video, so that high-speed sweep transfer Even a pulse can be discharged to the discharge part without leaving it, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a driving method of a solid-state imaging device according to an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining a driving method of the solid-state imaging device of FIG. 1, and FIG. FIG. 4 is a schematic diagram for explaining the configuration of the image pickup device, and FIG. 4 is an explanatory diagram of a driving method of a conventional solid-state image pickup device. 1 ... Photoelectric conversion part, 2 ... Vertical transfer part, 3 ... Horizontal transfer part, 4 ... Signal charge detection part, 5 ... Signal charge discharge part, 7
...... P well, 8 ...... Substrate, 11 ...... First charge pulse, 12 ...... Second charge pulse.

Claims (1)

(57) [Claims] 1. A solid-state imaging device comprising a photoelectric conversion part, a vertical transfer part, a horizontal transfer part, a signal detection part, and a signal discharge part in a semiconductor layer of opposite conductivity type provided on a semiconductor substrate of one conductivity type. In driving, the voltage applied to the semiconductor substrate in the first photoelectric conversion period in which unnecessary signal charges are accumulated is higher than the voltage applied to the semiconductor substrate in the second photoelectric conversion period in which signal charges are accumulated. A method of driving a characteristic solid-state imaging device.