JPH06233197A - Driving method for solid state image pickup device - Google Patents

Abstract

PURPOSE:To provide a diriving method of a solid state image pickup device which can measure such characteristics as the smear, the transfer efficiency, etc., of a CCD in high accuracy. CONSTITUTION:The photoelectric converting parts 1, the vertical transfer parts 3, the switch parts 2, the horizontal transfer parts 5, the charge detecting parts, the reference potential setting parts, and the reset switch parts that secure the connection between the charge detecting parts and the reference potential setting parts at every cycle are arrayed in a two-dimensional shape. Then the operations of reset switch parts are discontinued for a certain period so that the potential setting operations are stopped at the charge detecting parts. In such a constitution, the residual charge is increased in addition in regard of the smear and the transfer efficiency of a CCD.

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 suitable for a method for measuring smear and vertical transfer efficiency of an image sensor applied to a solid-state image pickup device which can be used in an integrated video camera. .

[0002]

2. Description of the Related Art In recent years, solid-state image pickup devices have been widely put to practical use such as an image pickup section of an integrated video camera. Above all, CCD (Charge Coupled Device) with excellent noise characteristics
Is most practically used. Hereinafter, a conventional method for driving a solid-state imaging device will be described with reference to the drawings.

FIG. 2 is a diagram showing drive timing in a conventional method of driving a solid-state image pickup device. FIG. 3 is a diagram showing a schematic plan view of the solid-state imaging device. In Figure 2, φV
1, φV2, φV3 and φV4 are vertical transfer electrodes V1,
The pulse waveform applied to V2, V3 and V4, φH1,
φH2 is a pulse waveform applied to the horizontal transfer electrodes H1 and H2, φRG is a pulse waveform applied to the reset gate 7,
Sig indicates the signal output at the bottom of the screen when the J chart (white pattern) is imaged.

A pulse φV1 applied to the vertical transfer electrode V1
The pulse φV3 applied to the vertical transfer electrode V3 controls reading and transfer. When the level is high, reading is performed, and when the level is middle and low, the transfer is performed. The pulse φV2 applied to the vertical transfer electrode V2 and the pulse φV4 applied to the vertical transfer electrode V4 control the transfer, and the transfer is performed at the high level and the low level.

In FIG. 3, reference numeral 1 is a photodiode having a photoelectric conversion function, and 2 is an enhancement MOS that functions as a read gate (which constitutes a read switch section) for reading out signal charges accumulated in the photodiode.
(Metal Oxide Semiconductor) type transistor, 3 is a vertical transfer unit having an embedded channel structure for vertically transferring signal charges, 4 is a vertical transfer gate for controlling vertical transfer, and 5 is horizontal transfer for transferring signal charges in the horizontal direction. Part, 6
Is an output gate, and 7 is a reset gate that resets the output diffusion layer 9 to the voltage set by the output diode 8 before the charge transfer. Reference numeral 10 is a horizontal transfer gate.

The vertical transfer section 3 has a 4-gate 1-bit structure in which 1 bit is formed by including four vertical transfer gates 4 adjacent to each other in the vertical direction, and the vertical transfer section 3 reads data. Two gates 2 are provided per bit. Further, the vertical transfer gate 4 forming each bit is connected to the vertical transfer electrodes V1 to V1 for pulse application.
V4 is connected, and vertical transfer electrodes V1 and V3 are connected.
The operation of the driving method of the solid-state imaging device configured as described above, which is also connected to the read gate 2, will be described below.

First, at time t = t1 and t2, a pulse φV
1, φV3 becomes high level (hereinafter abbreviated as Hi),
The signal charges accumulated in the photodiode 1 are read out to the vertical transfer unit 3, and then two signal charges that are adjacent to each other in the vertical direction are mixed. Next, when t = t3, the pulses φV1, φV2, φV3, and φV4 enter the transfer period, and the signal charges are transferred step by step in one horizontal blanking period. At this time, the charges adjacent to the horizontal transfer section 5 are transferred to below the horizontal transfer gate corresponding to the horizontal transfer electrode H1 of the horizontal transfer section 5.

Next, when t = t4, the pulse φH1 becomes low level (hereinafter abbreviated as Lo), the pulse φH2 becomes Hi, and the charges are transferred under the horizontal transfer gate corresponding to the horizontal transfer electrode H2. Next, when t = t5, the pulse φH
2 becomes Lo and the pulse φH1 becomes Hi, and the charge is transferred by 1 bit.

Horizontal transfer is performed by repeating t = t4 to t = t5. At this time, the charges adjacent to the output gate 6 are transferred to the output diffusion layer 9 and output. Also,
When t = t4, the pulse φRG becomes Hi, the reset gate 7 is turned on, and the output diffusion layer 9 is reset to the voltage set by the output diode 8 before the charge transfer.

By repeating the above, signals are sequentially output.

[0011]

However, in the conventional method for driving a solid-state image pickup device, the signal output to the signal output Sig has a very small amplitude such as a smear signal (normal signal -8).
Those having 0 dB to 0.01 mV) have a problem that the measurement accuracy deteriorates.

[0012]

According to a method of driving a solid-state image pickup device of the present invention, a photoelectric conversion unit having a photoelectric conversion function and arranged two-dimensionally, and a signal photoelectrically converted by the photoelectric conversion unit are vertically arranged. In the horizontal direction, a read switch unit that controls the reading of the signal stored in the photoelectric conversion unit by coupling the photoelectric conversion unit and the vertical transfer unit to each other, and the charge transferred by the vertical transfer unit in the horizontal direction. To a horizontal transfer section, a charge detection section for detecting charges transferred from the horizontal transfer section, a reference potential setting section for setting the potential of the charge detection section, a charge detection section and a reference potential setting section. A method of driving a solid-state image pickup device, comprising: a reset switch unit for connecting each of the above-mentioned units every cycle, characterized in that the setting of the potential of the charge detection unit is stopped for a certain period.

[0013]

According to the driving method of the solid-state image pickup device of the present invention,
The amount of charges such as smear is added and increased by the charge detector, and a signal output proportional to the stop time (number of stages) is obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a drive timing of a method for driving a solid-state image pickup device according to an embodiment of the present invention. In FIG. 1, the difference from the conventional drive timing is that part of the pulse φRG is stopped. Others are the same as the conventional drive timing.

The operation of the driving method of the solid-state image pickup device configured as described above will be described below. First, at times t = t1 and t2, the pulses φV1 and φV3 become high level (hereinafter abbreviated as Hi), the signal charges accumulated in the photodiode 1 are read out to the vertical transfer unit 3, and then in the vertical direction. Mix two adjacent signal charges.

Next, when t = t3, the pulse φV1,
φV2, φV3, and φV4 become the transfer period, and the signal charges are transferred one stage at a time during one horizontal blanking period.
At this time, the charges adjacent to the horizontal transfer section 5 are transferred to the lower part of the horizontal transfer gate corresponding to the horizontal transfer electrode H1 of the horizontal transfer section 5. Next, when t = t4, the pulse φH1 becomes low level (hereinafter abbreviated as Lo), and the pulse φH2 becomes Hi,
The charges are transferred under the horizontal transfer gate of H2.

Next, when t = t5, the pulse φH2 changes to L
o, the pulse φH1 becomes Hi, and the charge is transferred by one bit. Horizontal transfer is performed by repeating t = t4 to t = t5. At this time, the charges adjacent to the output gate 6 are transferred to the output diffusion layer 9 and output. Also, t =
At t4, the pulse φRG becomes Hi and the reset gate 7
Is turned on, and the output diode 8
The output diffusion layer 9 is reset to the voltage set by.

By repeating the above, signals are sequentially output. When t = t6, the pulse φRG becomes Lo, the charges are transferred with the reset of the charges stopped, and the charges are added. In this case, the stop period is 5 bits, and the smear charge is expanded five times. As described above, in this embodiment, the smear charges and the like can be added and increased by temporarily stopping the reset of the charges.

Although the smear charges are added and increased in the embodiment, the same effect can be obtained in vertical transfer efficiency and the like. Here, the outline of the measurement of the vertical transfer efficiency will be described. The vertical transfer efficiency is obtained by measuring the signal (indicating transfer loss) at the stage subsequent to the final transfer stage and calculating the ratio with the signal. That is, the vertical transfer efficiency η is: vertical transfer efficiency η = {1- (transfer loss / signal)} × 100
It is represented by [%]. However, the level of the transfer loss at this time is about 0.1 mV, which is very small, and the measurement error becomes large. Therefore, like the above-described embodiment, the reset is stopped for a certain period and the transfer loss is added. By increasing the measurement accuracy, it is possible to improve the measurement accuracy as in the above-mentioned embodiment.

Further, in the embodiment, the driving example by the two-phase driving is shown, but the same effect can be obtained by the device by the one-phase, three-phase and four-phase driving.

[0021]

As described above, according to the present invention, by temporarily stopping the resetting of charges, smear charges and the like can be added and increased, and the measurement accuracy can be greatly improved. There is a great effect.

[Brief description of drawings]

FIG. 1 is a diagram showing drive timing in an embodiment of the present invention.

FIG. 2 is a diagram showing a drive timing of a conventional CCD.

FIG. 3 is a diagram showing a schematic plan view of a solid-state imaging device.

[Explanation of symbols]

 1 Photodiode (photoelectric conversion part) 2 MOS transistor (readout switch part) 3 Vertical transfer part 4 Vertical transfer gate 5 Horizontal transfer part 6 Output gate 7 Reset gate (reset switch part) 8 Output diode (reference potential setting part) 9 Output diffusion layer (charge detection unit) 10 Horizontal transfer gate V1, V2, V3, V4 Vertical transfer electrode H1, H2 Horizontal transfer electrode RG Reset gate electrode φV1, φV2, φV3, φV4 Vertical transfer pulse φH1, φH Horizontal transfer pulse φRG Reset Gate pulse S1, S2 signal output

Claims (2)

[Claims] 1. A photoelectric conversion unit having a photoelectric conversion function and arranged two-dimensionally, a vertical transfer unit for vertically transferring a signal photoelectrically converted by this photoelectric conversion unit, the photoelectric conversion unit and the photoelectric conversion unit. A read switch unit that couples with a vertical transfer unit to control the reading of the signal stored in the photoelectric conversion unit, a horizontal transfer unit that horizontally transfers the charges transferred by the vertical transfer unit, and the horizontal transfer Detection unit for detecting charges transferred from the charge detection unit, a reference potential setting unit for setting the potential of the charge detection unit, and a reset switch for connecting the charge detection unit and the reference potential setting unit for each cycle. The method for driving a solid-state imaging device, comprising: stopping the setting of the potential of the charge detection unit for a certain period of time. 2. The method of driving a solid-state imaging device according to claim 1, wherein the setting of the potential of the charge detection unit is stopped by stopping the pulse applied to the reset switch unit for a certain period.