JPH0445336Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Background art [Figures 3 to 6] D. Problem that the invention attempts to solve E. Means for solving the problem F. Effect G. Example [Fig. 1, FIG. 2] H. Effects of the invention (A. Field of industrial application) The present invention relates to an electronic still camera, and particularly to an electronic still camera equipped with an electronic shutter function.

(B Overview of the invention) The present invention is an electronic still camera equipped with an electronic shutter function, in which the shutter speed can be precisely set and the shutter speed can be controlled with high precision according to the settings. Therefore, when generating a shutter-on pulse and a shutter-off pulse, a gate pulse having a width of approximately one horizontal scanning period is always created, that is, a shutter-on gate pulse and a shutter-off gate pulse, and the output of the original oscillator is used to generate a shutter-on pulse and a shutter-off pulse. One horizontal synchronizing pulse is extracted from a horizontal synchronizing pulse train created by frequency dividing a certain original oscillation pulse using the gate pulse, and this extracted horizontal synchronizing pulse is used as a shutter-on pulse and a shutter-off pulse. Therefore, by gating the horizontal synchronizing pulse train with a gate pulse having a width of approximately one horizontal scanning period, one horizontal synchronizing pulse serving as a shutter-on pulse and a shutter-off pulse can be reliably obtained, and light reception starts. In addition to being able to reliably control the termination, the light reception time can be set in units of one horizontal scanning period, so the shutter speed can be set finely, and the accuracy of the light reception time is also extremely high. be able to.

(C Background Art) [Figures 3 to 6] Solid-state imaging devices, which have recently come to be used as imaging means in video cameras, output video information by transferring photoelectric charges generated in the image sensor section. It is something to do. When such a solid-state imaging device is used in a video camera, each light receiving section is always irradiated with photographing light, and a video signal is output every one field period or one frame period. Due to the structure of transferring signal charges obtained in the sensor section, unnecessary charges leak from the sensor section to the transfer section or are thermally excited, which tends to cause so-called smear development or blooming phenomena. A readout gate is provided between the sensor and the transfer section to properly control the flow of charge from the sensor section to the transfer section, and an overflow drain is provided to absorb charges that exceed the allowable limit to prevent smear and blooming. It is normal to do so.

Incidentally, the use of such solid-state imaging devices not only in video cameras that take moving images but also in still cameras that take still images has been considered, and various proposals have been made. Electronic still cameras using such solid-state imaging devices are required to be able to control the shutter speed in the same way as general still cameras that take images on silver halide film. This point is a major difference from a video camera. Among the methods proposed for controlling the shutter speed in electronic still cameras, there is a method using a mechanical shutter as shown in FIGS. 3 and 4. The method of using this mechanical shutter is
As shown in FIG. 5, before photographing, the shutter is opened and the overflow drain is turned on (a state in which photoelectric charges generated by photoelectric conversion in the sensor section flow to the overflow drain). Then, substantial light reception is started by turning off the overflow drain (a state in which photocharges generated by photoelectric conversion in the sensor section cannot flow to the overflow drain and are accumulated in the sensor section), and Light reception is stopped by closing the mechanical shutter. That is, the period from when the overflow drain is switched from on to off until the mechanical shutter is closed is the charge accumulation time in the sensor section, that is, the substantial light reception time.

Such an electronic still camera has the disadvantage that it first requires a mechanical shutter, which complicates the mechanism and increases the number of assembly steps, leading to an increase in the size and price of the device. Furthermore, it is difficult to control the closing timing of a mechanical shutter with high precision; for example, even if the shutter speed is set to 1/1000th of a second, the light reception time may not be exactly 1/1000th of a second.

Therefore, a method has been proposed in which the shutter speed can be controlled by electrically controlling the solid-state imaging device without using a mechanical shutter, for example, in Japanese Patent Application Laid-Open No. 8966/1983. FIGS. 6A and 6B are diagrams explaining the principle of an electronic shutter that can control the light reception time in the same way as a mechanical shutter through such electrical control.
Figure A is a potential diagram of sensor a, vertical register b, read gate c, and overflow drain d, and figure B is a time chart.
This electronic shutter uses a 1/60th
The readout gate c is closed for 1 second (1 field period), but the overflow drain is turned on and off so that only the last 1/60th of a second during which the readout gate c is closed becomes the actual light reception time. let Specifically, the readout gate c is closed and the overflow drain d is left open, and the overflow drain d is closed only when the set light reception time is before the time when the readout gate c is closed. The overflow drain d is opened after the readout gate c is opened and charges are sent to the vertical register b. In such an electronic shutter, the shutter speed can be controlled by switching the timing at which the overflow drain d switches from on to off within 1/60th of a second when the readout gate c is closed, and the switching timing is slow. This means that the light reception time becomes shorter (shutter speed becomes faster).

(Problem that invention D aims to solve) By the way, even in the electronic shutter of an electronic still camera, no special consideration is required to make it possible to finely control the shutter speed or to control the shutter speed with high precision. Therefore, it is not possible to set the shutter speed in detail, and
The accuracy of the shutter speed was also not high.

Therefore, the purpose of the present invention is to make it possible to set the shutter speed in detail without using a special means for generating clock pulses for control, and to control the shutter speed with high precision according to the settings. be.

(E. Means for Solving Problems) In order to solve the above problems, the electronic still camera of the present invention controls the overflow drain of the solid-state image sensor or the opening/closing timing of the readout gate, so that the solid-state image sensor effectively receives light. In an electronic still camera equipped with an electronic shutter function that controls time, there is a release pulse generation circuit that generates a release pulse when the shutter button is operated, and a pulse width that is activated by the release pulse and that corresponds to the shutter speed setting. a first monostable multivibrator that generates a shutter speed pulse having a shutter speed pulse; and a second monostable multivibrator that is activated in connection with the shutter button operation and forms a first gate pulse having a time width of approximately one horizontal scanning period. and a third monostable multivibrator that is activated at the trailing edge of the shutter speed pulse and forms a second gate pulse having a time width of approximately one horizontal scanning period, A horizontal synchronization pulse train is created by frequency-dividing the original oscillation clock pulse generated from the original oscillator that serves as a reference for the synchronization system inside the camera, and the horizontal synchronization pulse obtained by gating the horizontal synchronization pulse train with the first gate pulse is generated. A shutter-on pulse is used as a shutter-on pulse, a horizontal synchronizing pulse obtained by gating the horizontal synchronizing pulse train with the second gate pulse is a shutter-off pulse, and the shutter-on pulse and the shutter-off pulse are used to perform the solid-state imaging. The device is characterized in that it determines the actual start and end of light reception for the element.

(Faction) According to the electronic still camera of the present invention, when generating a shutter-on pulse and a shutter-off pulse, a gate pulse having a horizontal period width of approximately 1, that is, a shutter-on gate pulse and a shutter-off gate is generated. One horizontal synchronizing pulse is extracted from the horizontal synchronizing pulse train created by dividing the original oscillation pulse, which is the output of the original oscillator, using the gate pulse, and this extracted horizontal synchronizing pulse is used as a shutter-on pulse. Since the shutter-off pulse is used as the shutter-off pulse, it is possible to gate the horizontal synchronizing pulse train with a gate pulse having a width of approximately one horizontal scanning period to reliably obtain one horizontal synchronizing pulse that becomes the shutter-on pulse and the shutter-off pulse. The start and end of light reception can be reliably controlled, and since the start and end of light reception is synchronized with pulses with extremely short cycles, the pulses can be divided into integer multiples of that short cycle. It may be possible to set the light reception time. Therefore, it becomes possible to set the shutter speed very precisely, and the accuracy of the light reception time can also be made very high.

(G Embodiment) [FIGS. 1 and 2] The electronic still camera of the present invention will be described in detail below according to the illustrated embodiment.

1 and 2 are for explaining one embodiment of the electronic still camera of the present invention, and FIG. 1 is a circuit block diagram showing the outline of the configuration of the electronic still camera.

In the drawing, 1 is a lens, 2 is an aperture, and 3 is a CCD, which is a solid-state image sensor, and this electronic still camera is not equipped with a mechanical shutter. 4 is an amplifier that amplifies the video signal read out from the CCD 3; 5 is a video processing circuit that performs various video processing processes on the video signal output from the amplifier 4; 6 is a magnetic head for recording; is magnetically recorded on a magnetic disk.

8 is the original oscillator, which generates a high frequency clock pulse of 14.318MHz. The original oscillation clock pulse A generated by the original oscillator 8 is appropriately counted down and used as a pulse for controlling various parts within the electronic still camera. A sync generator 9 generates a synchronizing signal for the video signal from the original oscillation clock pulse, and the synchronizing signal generated by the sync generator 9 is sent to the video processing circuit 5. 10 is a counter that counts down the original oscillation clock pulse A to generate the vertical synchronization signal V, 11 is a counter that also generates the horizontal synchronization signals H and B, and 12 is the same.
The outputs of the timing generator 12, the sync generator 9, and the counters 10 and 11 are input to a CCD drive circuit 13, which controls the CCD 3. The output of the counter 10 that generates the vertical synchronization signal is also transmitted to the servo circuit 14 that controls the rotation of the magnetic disk 7.
It is used to control the disk rotation motor 15.

16 is a shutter button, and when the shutter button 16 is released, a release pulse C is generated. 17 and 18 are monostable multivibrators that output one pulse using the release pulse C as a trigger, and the monostable multivibrator (second monostable multivibrator) 17 has one horizontal period (1/15750 second). Release gate pulses (first gate pulses) D having substantially equal pulse widths are generated.
This release gate pulse D is applied to the counter 11.
The horizontal synchronizing signals H and B outputted from the horizontal synchronizing signals H and B are input as control signals to a gate circuit 19 that gates them. The first monostable multivibrator 18 generates shutter speed pulses F having different pulse widths depending on the resistance value of the variable resistor 20. The resistance value of the variable resistor 20 is changed by operating the shutter speed setting section 21, and by changing the resistance value through the operation, the shutter speed can be set. Reference numeral 22 denotes a third monostable that generates a shutter off gate pulse (second gate pulse) G in synchronization with the falling edge (trailing edge) of the shutter speed pulse F output by the first monostable multivibrator 18. This is a table multivibrator, and the shutter-off gate pulse (second gate pulse) G has a pulse width approximately equal to one horizontal period. The gate circuit 19 generates a shutter-on pulse E in synchronization with horizontal synchronizing signals H and B when a release pulse (first gate pulse) D is generated from the monostable multivibrator 17. . On the other hand, the gate circuit 23 is a gate circuit that generates the shutter-off pulse H, and when the shutter-off gate pulse (second gate pulse) G is generated from the monostable multivibrator 22, the horizontal synchronizing signal H, When B occurs, a shutter-off pulse H is generated in synchronization with it. 24 is a monostable multivibrator that generates one readout gate pulse I in synchronization with the shutter-off pulse H, and the outputs of the monostable multivibrator 24 and gate circuit 19 are transmitted to an overflow drain controller 25 to prevent overflow. The drain controller 25 controls the overflow drain of the solid-state image sensor 3.

FIG. 2 is a time chart for explaining the operation of the electronic still camera, and the operation will be explained according to this time chart.

When the shutter speed is set by operating the shutter speed setting section 21, the resistance value of the variable resistor 20 changes to a value corresponding to the set shutter speed. Then, the pulse width of the shutter speed pulse F, which is output from the monostable multivibrator 18 using the release pulse C as a trigger, is set to a value corresponding to the shutter speed.

Then, when the shutter button 16 is released, a release pulse C is generated from the shutter button 16.
is generated, and the monostable multivibrators 17 and 18 are triggered by the release pulse C, which in turn triggers the release vibrators 17 and 18 to generate a release gate pulse D and a shutter speed pulse F. The release gate pulse D has approximately the same pulse width as the period of the horizontal synchronizing signal B, and one pulse of the horizontal synchronizing signal B is always generated while the release gate pulse D is "high". Then, when the horizontal synchronizing signal B is generated in this way, a shutter-on pulse E is generated from the gate circuit 19.
occurs. When the shutter-on pulse E is generated from the gate circuit 19, the overflow drain pulse J falls, and the overflow drain gate is closed. As a result, photocharge begins to accumulate in the light receiving section. That is, with the generation of the shutter-on pulse E, substantial light reception begins.

The shutter speed pulse F, which rises in synchronization with the generation of the release pulse C, falls when the time set by the shutter speed setting section 21 has elapsed after rising. Shutter speed pulse F
When the voltage falls, the monostable multivibrator 22 generates a shutter off gate pulse G using the falling as a trigger. The shutter-off gate pulse G has a pulse width approximately equal to the period of the horizontal synchronizing signal B, and while the shutter-off gate pulse G is being generated, the horizontal synchronizing signal B
One pulse is always generated, and when the horizontal synchronizing signal B is generated, a shutter-off pulse H is generated from the gate circuit 23. Then, using this pulse as a trigger, a read gate pulse I is generated from the monostable multivibrator 24. Then, the readout gate opens and the photocharge in the sensor section is read out to the vertical register. When the transmission is finished, the read gate pulse I falls, and in synchronization with the fall, the overflow drain pulse J
rises, and the charge in the sensor section flows to the overflow drain.

In this electronic still camera, the time from when the overflow drain J falls in synchronization with the rise of the shutter-on pulse E to when the readout gate pulse I rises in synchronization with the rise of the shutter-off pulse H is different from that of an ordinary still camera. The time the camera's mechanical shutter opens (exposure time)
corresponds to In this electronic still camera, the light reception time starts in synchronization with the horizontal synchronization signal generated during the generation of the release gate pulse D, and
The shutter-off gate pulse G is terminated in synchronization with the horizontal synchronization signal B generated during the generation of the shutter-off gate pulse G. In this way, since the start and end of light reception are performed in synchronization with the horizontal synchronization signal B generated by counting down the original oscillation clock pulse A of the original oscillator 8, even the pulse width of the monostable multivibrator 18 is small. In addition, if you can set it with high precision, you can set the light reception time, in other words, the shutter speed in horizontal period (1/15750th of a second) increments, and then control the shutter speed according to the setting. can. and,
Horizontal synchronization signal B is essential for driving the CCD as a pulse that determines the timing of the start and end of light reception.
, it is not necessary to provide a special oscillator to determine the timing of the start and end of light reception, and furthermore, it is not necessary to provide a circuit to frequency divide the output of the oscillator.

In the above embodiment, the horizontal synchronizing signals H and B are used as pulses obtained by counting down the original oscillation clock pulse A, which is the output of the original oscillator 8, but it is not necessary to do so, and the original oscillation clock pulse A is The start and end timing of the light reception time may be controlled by a pulse with a shorter period than the horizontal synchronizing signal during the countdown to the synchronizing signal B, or by a pulse obtained by further counting down the horizontal synchronizing signal. .

(H Effect of the invention) As described above, when the electronic still camera of the invention generates a shutter-on pulse and a shutter-off pulse, it always generates a gate pulse having a horizontal period width of approximately 1, that is, a shutter-on pulse. A gate pulse and a shutter-off gate pulse are created, and one horizontal synchronization pulse is extracted from the horizontal synchronization pulse train created by dividing the frequency of the original oscillation pulse that is the output of the original oscillator, and this extracted horizontal synchronization pulse is This is characterized in that the pulses are used as a shutter-on pulse and a shutter-off pulse.

Therefore, according to the electronic still camera of the present invention, when generating a shutter-on pulse and a shutter-off pulse, a gate pulse having a width of approximately one horizontal scanning period is always generated, that is, a shutter-on gate pulse and a shutter-off gate. One horizontal synchronizing pulse is extracted from the horizontal synchronizing pulse train created by dividing the original oscillation pulse, which is the output of the original oscillator, using the gate pulse, and this extracted horizontal synchronizing pulse is used as a shutter-on pulse. Since the shutter-off pulse is used as the shutter-off pulse, it is possible to gate the horizontal synchronizing pulse train with a gate pulse having a width of approximately one horizontal scanning period to reliably obtain one horizontal synchronizing pulse that becomes the shutter-on pulse and the shutter-off pulse. This makes it possible to reliably control the start and end of light reception, as well as to set the light reception time in very short period increments of pulses that are counted down from the original oscillation clock pulse. can be controlled with high precision.

Since the pulses obtained by counting down the original oscillation clock pulses are used to control the start and end of light reception, there is no need to provide a special oscillator as a pulse for controlling the timing of the start and end of light reception. Therefore, it is possible to finely set the light reception time and perform highly accurate control without unnecessarily complicating the circuit configuration. In particular, the start of receiving the horizontal synchronization signal,
If used to control the timing of termination,
There is no need to provide a special counter or frequency divider circuit for counting down the original oscillation clock pulse for controlling the light reception time.

[Brief explanation of the drawing]

Figures 1 and 2 are for explaining one embodiment of the electronic still camera of the present invention. Figure 1 is a circuit block diagram showing the circuit configuration of the electronic still camera, and Figure 2 is a timing diagram showing the operation. Charts 3 to 6 are for explaining the background technology.
Figure 3 is a front view of a lens shutter used in a conventional camera, Figure 4 is a side view of a focal plane shutter, and Figure 5 relates to light reception in a conventional electronic still camera using a mechanical shutter. Time chart, Figures 6A and 6B are explanatory diagrams of the electronic shutter, which is the background technology of the present invention.
is a potential diagram, and B is a time chart. Explanation of symbols, 3...Solid-state image sensor, 8...Original oscillator, 16...Shutter button, 17...Second
Monostable multivibrator, 18...
first monostable multivibrator, 22
...The third monostable multivibrator.

Claims (1)

[Claims for Utility Model Registration] An electronic still camera provided with an electronic shutter function that controls the actual light reception time of the solid-state image sensor by controlling the opening/closing timing of the overflow drain or readout gate of the solid-state image sensor. a release pulse generation circuit that generates a release pulse when the shutter button is operated; and a first monostable multivibrator that is activated by the release pulse and generates a shutter speed pulse having a pulse width according to the shutter speed setting. , a second monostable multivibrator that is activated in connection with the shutter button operation and forms a first gate pulse having a time width of approximately one horizontal scanning period; and activated at the trailing edge of the shutter speed pulse. and a third monostable multivibrator that forms a second gate pulse having a time width of approximately one horizontal scanning period; A horizontal synchronizing pulse train is created by dividing the frequency of the horizontal synchronizing pulse train, the horizontal synchronizing pulse obtained by gating the horizontal synchronizing pulse train with the first gate pulse is used as a shutter-on pulse, and the horizontal synchronizing pulse train is gated with the second gate pulse. The gated horizontal synchronizing pulse is used as a shutter-off pulse, and the shutter-on pulse and the shutter-off pulse determine the actual start and end of light reception for the solid-state image sensor. An electronic still camera featuring