JPH0898093A - Timing generation circuit, solid-state image pickup device using the circuit, video camera equipped with the device and driving method for solid-state image pickup element - Google Patents

Abstract

PURPOSE: To control accurately an exposure start timing and an exposure time by generating a shutter pulse in the same timing as an input timing of an external trigger so as to start exposure and terminating the exposure by a charge read pulse after a prescribed time. CONSTITUTION: A synchronizing signal generation circuit 71 generates a horizontal synchronizing pulse HD in the random trigger shutter mode in the solid-state image pickup element having an electronic shutter function, a pulse generation circuit 72 generates a shutter pulse XSUB for each 1H synchronously with the HD to throw away storage charge of a sensor section 1. Upon the receipt of a trigger TRIG externally, the synchronizing signal generatilkg circuit 71 resets the HD at its trailing and the pulse generation circuit 72 resets the XSUB simultaneously to throw away the charge of the sensor section 1 and to start exposure. After the set exposure time, an XSG is generated to allow a vertical transfer register 2 to read the charge of the sensor section 1 and transferred and the exposure is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a timing generation circuit for driving a solid-state image pickup device having an electronic shutter function and a method for driving the solid-state image pickup device, and more particularly, exposure is performed by randomly inputting a trigger from the outside. The present invention relates to a timing generation circuit for a solid-state image sensor that operates and a method for driving the solid-state image sensor.

[0002]

2. Description of the Related Art Some solid-state image pickup devices having an electronic shutter function have a so-called random trigger shutter function for performing an exposure operation by randomly inputting a trigger from the outside. Video cameras equipped with this type of solid-state image sensor are, for example, FA (Factory Automatio).
n) It is installed and used in a factory, for example, near a belt conveyor for use. That is, the sensor detects that the object to be photographed arrives in front of the video camera, and the detection output is given to the video camera as a trigger to photograph the object to be photographed on the belt conveyor, and the image is displayed on the monitor screen. It is projected on the screen.

FIG. 4 is a timing chart for explaining a random trigger shutter operation of a conventional example. In this conventional example, when the external trigger TRIG is input, the external trigger TRIG is fetched by the horizontal synchronizing pulse HD to start the exposure. That is, the shutter pulse XSUB is continuously generated in synchronization with the horizontal synchronizing pulse HD until the first horizontal synchronizing pulse HD after the input of the external trigger TRIG is generated, thereby sweeping out the signal charges accumulated in the sensor unit. Is repeatedly performed, and exposure (accumulation of signal charges) is started at the time when the final sweeping is completed. Then, signal charges are accumulated for an exposure time set corresponding to a desired shutter speed from the start of exposure, and when the exposure time elapses, a charge read pulse XSG is generated in synchronization with the horizontal sync pulse HD. The signal charge accumulated in the sensor section is read out to the vertical transfer register.

FIG. 5 is a timing chart for explaining another conventional random trigger shutter operation.
In this conventional example, when the external trigger TRIG is input,
The shutter pulse XSUB generated in synchronization with the horizontal synchronizing pulse HD is reset, and the exposure is started from that point. That is, until the external trigger TRIG is input, the shutter pulse XSUB is continuously generated in synchronization with the horizontal synchronizing pulse HD, so that the signal charge accumulated in the sensor unit is repeatedly swept out.
When the external trigger TRIG is input, the shutter pulse X
The SUB is reset to perform the final sweeping, and the exposure is started from that point. Then, the signal charge is accumulated for the exposure time set corresponding to the desired shutter speed from the start of the exposure, and when the exposure time elapses, the charge read pulse XSG is generated in synchronization with the horizontal synchronization pulse HD, and the sensor The signal charges accumulated in the unit are read out to the vertical transfer register.

[0005]

However, in the former conventional example, the exposure time is always constant because it is determined by the horizontal synchronizing pulse HD, but the external trigger TRI is used.
Horizontal sync pulse HD regardless of G input timing
Since the exposure is started at the timing of the trailing edge, there is a time difference between the input of the external trigger TRIG and the start of the exposure, and the exposure start timing varies. That is, in FIG. 4, the time difference from the fall of the external trigger TRIG to the fall of the shutter pulse XSUB is the time difference until the start of exposure. If the exposure start timing varies in this way, for example, the above-mentioned FA
In application to the intended use, the image of the object to be photographed is projected upward or downward in the monitor screen, which causes a problem that the display position is not fixed.

On the other hand, in the latter conventional example, the exposure start timing is determined by the input timing of the external trigger TRIG, but the exposure end timing is the horizontal synchronization pulse HD.
Therefore, the exposure time varies depending on the input timing of the external trigger TRIG, as shown in FIG. If the exposure time varies in this way, the image of the object to be photographed may become bright or dark, and the brightness may not be determined. This becomes more remarkable as the exposure time becomes shorter.

The present invention has been made in view of the above problems, and an object thereof is to accurately control the exposure start timing and the exposure time in a solid-state image pickup device having an electronic shutter function. Another object of the present invention is to provide a simple timing generation circuit, a solid-state imaging device using the same, and a method for driving a solid-state imaging device.

[0008]

A timing generation circuit according to the present invention is a timing generation circuit for generating various timing pulses including a shutter pulse and a charge read pulse for driving a solid-state image pickup device having an electronic shutter function. There is a sync signal generation circuit that generates the horizontal sync pulse and the vertical sync pulse based on the reference frequency signal, and resets the horizontal sync pulse at the timing when the external trigger is input, and the reference frequency signal, the horizontal sync pulse, and the vertical sync pulse. Various timing pulses are generated based on the synchronization pulse, a shutter pulse is generated at the reset timing of the horizontal synchronization signal in the synchronization signal generation circuit, and a charge read pulse is generated when a certain time has elapsed from the generation timing. It has a configuration with a pulse generation circuit

[0009]

In the timing generating circuit having the above structure, the synchronizing signal generating circuit resets the horizontal synchronizing pulse at the input timing when an external trigger is input. When the horizontal sync pulse is reset, the pulse generation circuit resets the shutter pulse generated in synchronization with the horizontal sync pulse at the same timing as the reset of the horizontal sync pulse.
As a result, the shutter pulse is generated at the same timing as the input timing of the external trigger. That is, the exposure is started from the time when the external trigger is input. Then, the pulse generation circuit generates a charge read pulse when a predetermined time (exposure time) has elapsed from the start of exposure. This completes the exposure.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention applied to, for example, an interline transfer type CCD solid-state image pickup device. In FIG. 1, a plurality of sensor units (photoelectric conversion units) 1 arranged in a matrix in a row direction (vertical direction) and a column direction (horizontal direction) and accumulating signal charges according to the amount of incident light, and these sensor units. An image pickup area 3 is configured by a plurality of vertical transfer registers 2 which are arranged for each vertical column and vertically transfer the signal charges read from each sensor unit 1.

In the image pickup area 3, the sensor section 1 is composed of, for example, a PN junction photodiode, and the vertical transfer register 2 is composed of a CCD. Sensor part 1
The signal charge stored in the vertical transfer register 3 is read by applying a charge read pulse XSG to a read gate (not shown). The vertical transfer register 3 is transfer-driven by, for example, three-phase vertical transfer clocks φV1 to φV3. The vertical transfer register 3 is driven by 3
It is needless to say that it is not limited to the phase drive and may be four phase drive or the like. The signal charge read out to the vertical transfer register 3 becomes 1 during a part of the horizontal blanking period.
The portions corresponding to the scanning lines are sequentially transferred in the vertical direction.

On the lower side of the image pickup area 3 in the drawing, a horizontal transfer register 4 composed of a CCD to which signal charges corresponding to one scanning line are sequentially transferred from a plurality of vertical transfer registers 3 is arranged. The horizontal transfer register 4 is transfer-driven by two-phase horizontal transfer clocks φH1 and φH2.
As a result, the signal charges for one scanning line are sequentially transferred in the horizontal direction in the horizontal scanning period after the horizontal blanking period. A charge detection unit 5 having, for example, a floating diffusion structure is arranged at an end of the horizontal transfer register 4, and the signal charges horizontally transferred are sequentially converted into a voltage signal by the charge detection unit 5. Then, this voltage signal is amplified by the output amplifier 6 and then derived as an imaging output OUT according to the incident amount of light from the subject.

In the CCD solid-state image pickup device 10 having the above-mentioned structure, a shutter pulse (charge sweeping-out pulse) XSUB is applied to the substrate, and the signal charge accumulated in each sensor unit 1 is swept out to the substrate so that the sensor unit 1 can operate. The electronic shutter operation is configured to control the accumulation time (exposure time) of the signal charges. That is, in normal operation, by biasing the substrate with a constant set voltage (substrate voltage), signal charges are accumulated in the sensor unit 1, whereas
During the electronic shutter operation, by adding the shutter pulse XSUB to the substrate voltage, the barrier on the substrate side is destroyed, and the signal charges accumulated in the sensor unit 1 are swept out to the substrate.

Three-phase vertical transfer clocks φV1 to φV3,
Charge read pulse XSG, two-phase horizontal transfer clock φH
1, φH2 and various kinds of timing pulses such as the shutter pulse XSUB are supplied from the original oscillation crystal oscillator 8 in the timing generation circuit 7, for example, 24.5454.
It is generated based on the original oscillation frequency signal (reference frequency signal) of MHz. The timing generation circuit 7 has a basic configuration of a synchronization signal generation circuit 71 that generates a horizontal synchronization pulse HD and a vertical synchronization pulse VD, and a pulse generation circuit 72 that generates various timing pulses, and is integrated into, for example, one chip. .

In this timing generation circuit 7, 2
The original oscillation frequency signal of 4.5454 MHz is divided by 1/2 by the 1/2 divider 73, supplied to the pulse generation circuit 72 as a master clock of 12.2727 MHz, and further divided by the 1/390 divider 74. The frequency is divided by 1/390 to double the horizontal scanning frequency of 15.75 KHz to 31.5.
The frequency signal of KHz is further divided by 1/525 frequency divider 7
The frequency is divided by 1/525 by 5 and supplied to the synchronization signal generation circuit 71 as a frequency signal of 60 Hz. An external trigger TRIG for a random trigger shutter operation is applied to the synchronizing signal generating circuit 71 and the pulse generating circuit 72.

The synchronizing signal generating circuit 71 is 31.5 KHz.
The horizontal synchronizing pulse HD is 60H based on the frequency signal of
The vertical synchronizing pulse VD is generated based on the z frequency signal, and when the external trigger TRIG is input, the horizontal synchronizing pulse HD is reset at the input timing. On the other hand, the pulse generation circuit 72 has 12.25 MH.
A three-phase vertical transfer clock φV1 based on the z master clock, horizontal sync pulse HD, and vertical sync pulse VD.
~ Various timing pulses such as φV3 and two-phase horizontal transfer clocks φH1 and φH2 are generated, and when an external trigger TRIG is input, the shutter pulse XSUB is reset at the input timing (reset timing of the horizontal synchronizing pulse HD). The final shutter pulse XS
Generate UB. Further, the charge read pulse XSG is generated when the exposure time determined by a certain shutter speed elapses after the reset of the horizontal synchronizing pulse HD.

Next, the operation of the CCD solid-state image pickup device using the timing generating circuit 7 having the above-mentioned configuration in the random trigger shutter mode will be described with reference to the timing chart of FIG. In FIG. 2, ID is a line identification signal for identifying an odd line / an even line. In the timing generation circuit 7, a mode changeover switch (not shown) switches the normal continuous operation mode to the random trigger shutter mode.

When the normal continuous operation mode is changed to the random trigger shutter mode, the synchronizing signal generating circuit 71 generates only the horizontal synchronizing pulse HD and the external trigger TRIG.
The generation of the vertical synchronizing pulse VD is stopped until is input. Along with this, the charge read pulse XSG is also stopped.
The pulse generation circuit 72 generates a shutter pulse XSUB which is a charge sweep-out pulse every 1H (H is a horizontal scanning period) in synchronization with the horizontal synchronization pulse HD. This allows
In the CCD solid-state image sensor 10, the signal charge accumulated in each sensor unit 1 is always swept to the substrate. Further, since the vertical transfer clocks φV1 to φV3 are also generated from the pulse generation circuit 72 and the vertical transfer register 2 is in the transfer state, the dark signal of the vertical transfer register 2 (dark current at the vertical transfer electrodes) is also eliminated. Will be.

In this state, an external trigger TRIG is externally supplied.
Is inputted, the synchronizing signal generating circuit 71 forcibly resets the horizontal synchronizing pulse HD at the fall of the external trigger TRIG. At the same time, the pulse generation circuit 72 resets the shutter pulse XSUB, generates the final shutter pulse XSUB at that timing, discards the signal charge accumulated in the sensor unit 1 on the substrate, and thereafter generates the shutter pulse XSUB. Stop. Further, the vertical transfer clocks φV1 to φV3 are also reset according to the horizontal synchronizing pulse HD. At this point, the exposure starts.

When the exposure time corresponding to the preset shutter speed elapses from the start of exposure, the pulse generation circuit 72 generates the charge read pulse XSG.
As a result, the signal charge accumulated in each sensor unit 1 is read out to the vertical transfer register 2 via the read gate (not shown), and the direct transfer is performed. This completes the exposure. The charge read pulse XSG at this time is generated at the time when the exposure time set by the normal electronic shutter based on the horizontal synchronizing pulse HD has elapsed, regardless of the vertical synchronizing pulse VD.

As described above, the shutter pulse XSUB has the same timing as the input timing of the external trigger TRIG.
Is generated and exposure is started, and when a predetermined time (exposure time) has elapsed from the start of exposure, the charge read pulse XSG
The exposure start timing is accurate because the exposure is always started at the input timing of the external trigger TRIG because the exposure is ended by generating. Also, the horizontal sync pulse H is generated in accordance with the falling edge of the external trigger TRIG.
Since D is reset, the exposure time controlled in units of H is also accurate.

FIG. 3 is a block diagram showing an example of a video camera equipped with the CCD solid-state image pickup device having the above structure. In FIG. 3, light from a subject is taken in by a lens 31, passes through an optical filter 32, and then enters the image pickup region 3 (see FIG. 1) of the CCD solid-state image pickup device 10 having the above configuration. The CCD solid-state image pickup device 10 is driven by various timing pulses generated from the timing generation circuit 7 described above. The image pickup output derived from the CCD solid-state image pickup device 10 is output as a video signal after being subjected to signal processing such as correlated double sampling (CDS) in the signal processing circuit 33.

The video camera equipped with the CCD solid-state image pickup device having the random trigger shutter function is most suitable for FA applications, for example. That is, when the detection output of the sensor arranged in the vicinity of, for example, the belt conveyor in the factory and detecting the arrival of the object to be photographed in front of the video camera is the external trigger TRIG, the object to be photographed is fixed on the belt conveyor. Even when the shooting object does not flow at intervals, that is, the shooting object does not move periodically, exposure is started when the shooting object passes in front of the video camera, and the exposure is always performed at a constant exposure time. Images can be captured. Therefore, the image of the object to be photographed can be always displayed with a constant brightness in the center of the monitor screen.

Further, the image data of the object to be photographed, which flows at a high speed asynchronously with the period of the television signal such as EIA, can be captured under stable exposure conditions. further,
Not only for FA applications but also for image processing applications, it is most suitable for capturing an image at an arbitrary time.

[0026]

As described above, according to the present invention,
In a solid-state image sensor having an electronic shutter function, a shutter pulse is generated at the same timing as the input timing of an external trigger to start exposure, and when a fixed time has elapsed from the start of exposure, a charge read pulse is generated to perform exposure. Since the processing is ended, it is possible to accurately control the exposure start timing and the exposure time.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention applied to an interline transfer type CCD solid-state imaging device.

FIG. 2 is a timing chart for explaining an operation in a random trigger shutter mode according to the present invention.

FIG. 3 is a configuration diagram showing an example of a video camera according to the present invention.

FIG. 4 is a timing chart for explaining a random trigger shutter operation of a conventional example.

FIG. 5 is a timing chart for explaining a random trigger shutter operation of another conventional example.

[Explanation of symbols]

 1 Sensor Section 2 Vertical Transfer Register 4 Horizontal Transfer Register 7 Timing Generation Circuit 8 Crystal Oscillator for Original Oscillation 10 CCD Solid-state Image Sensor 31 Lens 32 Optical Filter 33 Signal Processing Circuit 71 Synchronous Signal Generation Circuit 72 Pulse Generation Circuit

Claims (4)

[Claims] 1. A timing generation circuit for generating various timing pulses including a shutter pulse and a charge read pulse for driving a solid-state image pickup device having an electronic shutter function, the horizontal synchronization pulse being based on a reference frequency signal. And a synchronization signal generation circuit that generates a vertical synchronization pulse and resets the horizontal synchronization pulse at the timing when an external trigger is input, and the various types of the various types based on the reference frequency signal, the horizontal synchronization pulse, and the vertical synchronization pulse. A pulse generation circuit that generates a timing pulse, generates the shutter pulse at the reset timing of the horizontal synchronization signal in the synchronization signal generation circuit, and generates the charge read pulse when a certain time has elapsed from the generation timing. Timing is characterized by having Circuit. 2. A solid-state imaging device comprising: the timing generation circuit according to claim 1; and a solid-state imaging device having an electronic shutter function driven by various timing pulses generated by the timing generation circuit. apparatus. 3. A video camera comprising: the solid-state imaging device according to claim 2; and an optical system that guides incident light to an imaging region of a solid-state imaging device in the solid-state imaging device. 4. A driving method for performing exposure control by applying a shutter pulse and a charge reading pulse to an solid-state image pickup device having an electronic shutter function when an external trigger is input, the method comprising: A method for driving a solid-state image pickup device, comprising: generating the shutter pulse at the same timing to start the exposure, and generating the charge reading pulse at the time point when a predetermined time has elapsed from the start of the exposure and ending the exposure.