JPH0474912B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved imaging device capable of implementing both continuous imaging mode and one-shot imaging mode.

2. Description of the Related Art Conventional video cameras and the like are known to use, for example, an overflow drain gate to control the timing and accumulation time of photoelectric charge accumulation. However, in such a method, light is likely to be incident during the transfer of charges in the light-receiving part of the image sensor to the non-light-receiving part, resulting in smearing. In particular, when scanning an image sensor at a constant cycle, the transfer period is constant, so some noise component due to smear etc. is always present to some extent, whereas the signal component changes depending on the accumulation time. , the S/N changes drastically. This problem is particularly noticeable when the storage time is shortened. This is also noticeable in frame transfer type devices. Further, the provision of an overflow drain gate has the disadvantage that the yield of the image sensor is lowered and the resolution is lowered.

The purpose of the present invention is to solve the various drawbacks of the prior art, and it is aimed at solving the problems of the prior art.
The present invention is an imaging device with a good signal-to-noise ratio that allows easy control of the amount of image information, and can realize both continuous imaging mode and one-shot mode or still mode. Moreover, it is an object of the present invention to provide an imaging device whose switching is easy.

In order to achieve these various objects, the present invention is characterized in that the scanning synchronization of the image sensor is made constant even in the still mode. This has the effect of making it extremely easy to synchronize the entire system. Another feature of the present invention is that a shutter is used to take still images, and that the shutter is open during continuous mode and closed for a predetermined period of time during still mode. Another advantage is that, after the shutter is once closed, the shutter is not opened until the charge in the light-receiving section is transferred to the non-light-receiving section, thereby greatly reducing smear. or,
Still mode start switch (trigger switch)
Since the timing for shutter closing control is started after the first transfer signal is obtained after activating this switch, the synchronization for scanning the image pickup device is not disturbed. Further, according to the present invention, the scanning, etc. drive of the image pickup device is stopped from when the first transfer signal is obtained after the still mode start switch is activated until just before the first transfer signal is obtained after the shutter is closed. Since the stop means is provided, the scanning synchronization signal is not disturbed even during the still mode, and the continuous mode can be quickly returned to after the still mode ends.

The present invention will be described in detail below based on examples.

FIG. 1 is a block diagram of an embodiment of the imaging device of the present invention, FIG. 2 is a schematic diagram showing an example of an imaging device, and FIGS. 3a and 3b are timing charts of the circuit shown in the first diagram. Note that the shaded area in FIG. 3 represents a pulse group. In the figure, SW1 is a continuous mode switch,
SW2 is the still mode switch, switch SW
1 is turned on at the first stroke of a two-stroke button, and still mode SW2 is turned on at the second stroke. OS1 turns on the switch SW1
OS2 is a one-shot circuit that generates a pulse in synchronization with the rising edge when the switch SW2 is turned on. VSY is a synchronization signal generator, and the third
As shown in the figure, intermittent pulses with a period of V are generated.
OS3 is a one-shot circuit that generates a pulse in synchronization with the fall of this synchronization signal generator output.
AND1 to AND5 are AND gates, and CNT is a presettable counter whose preset input terminal is connected to the output of the side optical circuit LM, and this preset value Tp (shown in the third figure) corresponds to the exposure time.
In addition, R is the reset terminal, CL is the clock input terminal,
C is a carry output terminal which outputs a pulse when the clock is counted up to a preset value. This C
The terminal is connected to a one-shot circuit OS4 synchronized with the rise of the pulse width V. Also, the output of the one-shot circuit OS4 is the magnetic driver circuit DR2.
The shutter closing magnet Mg is controlled via.

In this embodiment, although not shown in the figure, the shutter is always biased by a spring in the opening direction, and when the magnet Mg is energized, the light receiving part of the image sensor (in the case of the second element shown in the figure) is activated only during that time. It is configured to close.

Note that this shutter may be physical in addition to mechanical. OR is an OR gate, FF is an R-S flip-flop, and its Q output controls AND gates AND3 to AND5.
SCTL is a sequence control circuit and controls the sequence of the entire imaging device.

DR1 is a driver circuit for the image sensor, and outputs drive pulses φ ₁ to _{φ 3} as shown in the third diagram based on the output of the oscillator OSC. ID is the image sensor.

The image sensor shown in the second figure is an example of a frame transfer type CCD, where I is a light receiving section, S is a storage section as a non-light receiving section, HR is a horizontal shift register, ABB is an anti-blooming barrier, OFD is an overflow drain, and AMP is an output. It's an amplifier. _φ1 is a pulse for transferring the charge in the light receiving section to the storage section, _φ2 is a pulse for shifting the charge in the storage section to the horizontal shift register HR, and _φ3 is a horizontal transfer clock pulse.

Figure 3a shows that the preset value of counter CNT is
A timing diagram in the case of Tp<V, and FIG. 1B is a timing diagram in the case of the preset value Tp'>V.

The operation of this embodiment will be explained below based on FIGS. 1 to 3.

When switch SW1 is turned on at time _t1 , power is supplied to each circuit and the one-shot circuit is turned on.
OS1 generates a pulse and flip-flop FF is set. Therefore, drive pulses φ ₁ to _{φ 3} outputted from the driver circuit DR1 by the output of the oscillator OSC are supplied to the image sensor ID to perform scanning.
In this state, the image sensor is scanned with synchronization V and continuous imaging is performed.

Next, the switch as a still mode switch.
When SW2 is turned on, a pulse with a pulse width of V is generated by the one-shot circuit OS2. On the other hand, the synchronization signal generation circuit VSY outputs a periodic pulse as shown in the third diagram, which outputs a high level only during the transfer period from the light receiving section of the image sensor to the storage section.
A pulse synchronized with the falling edge of this pulse is obtained from the one shot circuit. Therefore and gate AND1
The first shift pulse obtained after turning on the switch SW2 is output as is to the output terminal of the switch SW2.
This pulse resets the counter CNT (time t ₃ ), and when the clock counts by the exposure time Tp preset by the output of the side optical circuit LM (time t ₄ ), one pulse is output to the C terminal, and the one-shot circuit OS4 is activated. In synchronization with this rise, the period V
Activate the magnet Mg only during this time and close the shutter. In order to prevent smearing, this closing is preferably continued at least until immediately after the shutter is closed and the first shift pulse is supplied to the image sensor ID. In this embodiment, the closing period is set to V in consideration of the responsiveness of the shutter.

Incidentally, the flip-flop FF is set by turning on the continuous mode switch SW1, is reset with the reset of the counter (time _t3 ), and is reset again by the synchronization signal corresponding to the shift signal obtained after the shutter is closed. Therefore, the image sensor
The drive pulses φ ₁ to _{φ 3} to be supplied to ID are cut only while flip-flop FF is reset. That is, the driving of the image sensor is stopped until the timing of the first shift pulse after the shutter is closed. This is the exposure time as shown in Figure 3b.
The same holds true for Tp'>V. Therefore, the charge at the light receiving section whose exposure time is controlled by closing the shutter is read out in synchronization with the synchronization signal after closing the shutter, so the readout timing is always constant (V).
Alternatively, it is an integral multiple of V, making it easy to synchronize the entire device. Therefore, switching between continuous mode and continuous mode is smooth. Further, it has many effects such as being less likely to cause smear and producing a one-shot image with a high S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Fig. 2 is a diagram showing an example of an imaging means, Fig. 3 a, b
2A and 2B are diagrams showing timings at different exposure times. SW1...Continuous mode switch, SW2...Still mode switch, VSY...Synchronizing signal generation circuit, CNT...Counter, Mg...Shutter drive magnet, DR1...Image sensor driver circuit, ID...Image sensor.

Claims (1)

[Scope of Claims] 1. Imaging means having a light-receiving section that photoelectrically converts imaging light from a subject to obtain an image charge, and a storage section that temporarily accumulates the image charge from the light-receiving section; a signal generating means for outputting a periodic signal for reading out the video charge at a predetermined period from the image charge; an accumulation control means for setting the charge accumulation time in the light receiving section according to the brightness of the subject; and at least the charge accumulation. a shutter means for blocking light from the light receiving section to define the end of exposure after the expiration of the time; a trigger means for instructing photography; and a shutter means for instructing photography; control means for interlocking and controlling the drive of the trigger means, the control means removing unnecessary charges in the light receiving section in synchronization with the first periodic signal after the operation of the trigger means, and then accumulating new charges. starts, and after the accumulation time by the accumulation control means has elapsed regardless of the period of the periodic signal, the shutter means is closed to shield the light receiving section from light, and the shutter means is synchronized with the first periodic signal after the closing. An imaging device characterized in that the video signal is transferred from the light receiving section to the storage section.