JPH035706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging device that photoelectrically converts a subject image, a storage device that stores still image signals obtained by the imaging device, and a single-lens reflex electronic camera equipped with an optical viewfinder. .

A device that uses an imaging device such as a solid-state imaging device to obtain an electrical signal according to the brightness of the subject image and stores the electrical signal on a magnetic disk or semiconductor memory.
It is known as a so-called electronic camera. This electronic camera has the advantages of not requiring film that requires chemical processing, and can be quickly played back using a television receiver, so it can replace conventional film-based cameras. Many proposals have been made so far for cameras.

The finder device used in this electronic camera can use all the finder systems used in conventional film cameras, and by using the image pickup device, it can use electronic A viewfinder is also available. Among these viewfinder systems, the so-called single-lens reflex viewfinder has the most excellent functions in that the viewfinder field of view and imaging range are equal, and interchangeable lenses can be used.

In single-lens reflex camera viewfinders, a semi-transparent mirror is placed in the imaging light beam to branch the light to the viewfinder optical system, and a so-called quick return mirror is used to switch the imaging light beam between the viewfinder optical system and the photographic optical system. There is something to guide you. Although the quick-return mirror method has a movable part, we believe that it has many advantages over the method using a semi-transparent mirror due to the brightness of the viewfinder image and the absence of attenuation of the light star to the imaging device. It will be done.

In order to equip an electronic camera with a quick return mirror in this single-lens reflex viewfinder, the drive device for the quick return mirror must be electrically connected to the imaging device, which is different from conventional film-based cameras. A new mechanism is required.

However, since conventional electronic cameras use a single-lens reflex viewfinder with a semi-transparent mirror, the viewfinder image becomes dark and the amount of light to the imaging device is inevitably attenuated, making it difficult to capture high-quality still images of dark subjects. was not obtained. In particular, the sensitivity of current solid-state image sensors is lower than that of film, so attenuation of the amount of light is a major drawback.

There is also the problem of when to issue the charge removal signal and readout signal to the imaging device. For example, in a conventional video camera, a subject image is photoelectrically converted using an imaging device like an electronic camera, but the vertical synchronization signal that drives the imaging device is a periodic pulse every 1 field period (1/60 second). It's summery.
The method uses these pulses to discharge unnecessary accumulated charge before shooting still images and to read out the charges that become the still image signal. It takes time to read out the charges after completion, and the image quality deteriorates due to an unnecessary increase in dark current. Furthermore, it is not advisable to apply the technique for video cameras to electronic cameras because the problem of delays in photographing operations cannot be avoided.

Furthermore, in order to electrically charge the mirror and shutter, it is possible to use a motor drive device in a conventional film camera, but the known motor drive mechanism requires a large winding force to wind the film. The mechanism is complicated because it has a mechanism and the winding time is set relatively long, and the electric circuit is also complicated because it requires a switch mechanism etc. to indicate when winding is complete. It cannot be used.

The first objective of the present invention is to obtain a bright viewfinder image by using a quick return mirror, and to obtain a high-quality still image even of a dark subject by maximizing the amount of light to the imaging device. The purpose is

In addition, regarding the time to remove and read out the charge from the imaging device, the unnecessary charge before shooting is removed as soon as the release switch is turned on, and the charge that becomes the still image signal is read out at the same time as the exposure ends, allowing for quick shooting operation. The purpose is to extract only necessary image signals and obtain still images with the best image quality.

Furthermore, the charging mechanism for the shutter and mirror has a simple configuration without a winding mechanism, and its drive motor is driven at the same time as the shutter finishes traveling, and stops at the same time as charging is completed, allowing for continuous shooting. Aim to get the camera.

In order to achieve the above object, the present invention basically provides a viewfinder that photoelectrically converts a subject image formed by a photographing lens using an imaging device, and stores an image signal obtained from the imaging device in a storage device. In an electronic camera with a built-in optical system, a shutter that controls the imaging light flux incident on the imaging device, an exposure control device that controls exposure via this shutter according to the brightness of the subject image, and a shutter that is normally located within the imaging light flux path. a quick return mirror that guides the imaging light flux to the viewfinder optical system, retreats from the imaging light flux path during photography, and supplies the imaging light flux to the imaging device; a release switch that issues a photography start signal; A vertical synchronization signal generation circuit that generates a vertical synchronization signal aperiodically is provided,
The vertical synchronization signal of this vertical synchronization signal generation circuit generates a signal to remove the charges accumulated in the image pickup device after the release switch is turned on and before the quick return mirror starts to retract. After the exposure is completed, the charges accumulated while the shutter is in the open state are read out.

The invention will now be described with reference to the illustrated embodiments. 1 and 2 show the basic configuration of the electronic camera of the present invention, in which a lens barrel L having a photographing lens 11 is shown.
and a body B, and elements for processing the image of the subject 10 formed by the photographing lens 11 are built into the body B. That is, an imaging device (image sensor) 12 is disposed on the optical axis (on the imaging light beam), and a shutter 25 and a quick return mirror 13 are disposed in front of the image sensor 12. The quick return mirror 13 normally forms an angle of 45 degrees with respect to the optical axis, and directs the imaging light flux to the focus plate 15, mirror 16, relay lens 17, and eyepiece lens 19.
However, at the time of photographing, it retreats from the imaging light flux and provides the light flux to the image sensor 12 side. The finder optical system 14 may use a conventional pentaprism. Therefore, according to the optical system of this electronic camera, the image of the subject is always guided to the viewfinder optical system 14 and re-imaged on the re-imaging surface 18, and this can be observed with the eyepiece lens 19. The quick return mirror 13 can be flipped up to guide the imaging light flux to the image sensor 12 side.

The charge stored in the image sensor 12 is discharged and read out by an image sensor drive circuit 20, an exposure control circuit 21, a photometric element 22, a mirror drive system 23, a shutter drive system 24, and a shutter 2.
5. The signal processing circuit 26 and the storage device 27 perform the processing roughly as follows. The image sensor drive circuit 20 performs scanning for one field or one frame period by pressing down the release switch during photographing, and discharges unnecessary charges accumulated in the image sensor 12. On the other hand, the exposure control circuit 21 outputs an exposure control signal in accordance with the output of the photometric element 22 that photoelectrically converts the brightness of the subject image.
The photometric element 22 is suitably installed in the finder optical system 14. The mirror drive system 23 moves the quick return mirror 1 after the above-mentioned exposure scanning is completed.
3 out of the imaging light flux, and then the exposure control circuit 2
The shutter drive system 24 receives an output of 1 to open the shutter 25, and after proper exposure, the shutter 25 closes. When the exposure is completed, the quick return mirror 13 returns to the state before retraction, and at the same time the image sensor drive circuit 20 scans one field or one frame.
When the shutter 25 is open, the image sensor 1
The charges accumulated in the signal processing circuit 26 are read out by the signal processing circuit 26. The image signal obtained by the signal processing circuit 26 is subjected to appropriate processing and stored in the storage device 27. On the other hand, when the shutter 25 is in the closed state, motors (described later) included in the shutter drive system 24 and the mirror drive system 23 are driven to restore the driving force of the shutter 25 and the quick return mirror 13 in preparation for the next photograph.

FIG. 3 shows specific examples of drive mechanisms for the quick return mirror 13 and shutter 25, and various timing switches. The shutter 25 is a focal plane shutter consisting of a front curtain 32 and a rear curtain 34, and the front curtain 32 and the rear curtain 34 are pulled to the right in the figure by a front curtain spring 40 and a rear curtain spring 42, respectively. The leading curtain locking pawl 39 and the trailing curtain locking pawl 41 hold the leading curtain 32 and the trailing curtain 34 in the charge position against the forces of the leading curtain spring 40 and the trailing curtain spring 42. The stop pawl 39 is operated by the leading curtain lock release lever 29c.
The trailing curtain locking pawl 41 is disengaged from the leading curtain 32 and the trailing curtain 34, respectively, by the trailing curtain magnet 31. A motor 35 charges the shutter 25, that is, charges the leading curtain 32 and the trailing curtain 34. That is, when the motor 35 rotates once, the shutter charge lever 50 reciprocates once by the crank lever 49, and the shutter charge lever 50 pushes the front curtain 32a and moves the front curtain 32 against the force of the front curtain spring 40. At the same time, the rear curtain 34a is pushed by the front curtain 32, and the rear curtain 34 also becomes one with the front curtain 32, and the rear curtain spring 42
is charged against the force of The shutter switch 33 is turned on when the front curtain 32 is in a charged state, and turned off when the front curtain 32 starts running.

The quick return mirror 13 rotates (swings) around a mirror rotation shaft 29b that is integrally provided at its rear end, and the leading curtain lock release lever 29c is fixed to this mirror rotation shaft 29b. ing.
29d is a torsion spring that urges the quick return mirror 13 in a downward direction. A mirror up lever 37 and a mirror down lever 44 are slidably supported on the sides of the mirror box.The mirror up lever 37 is moved forward in the figure by a spring 38, and the mirror down lever 44 is moved backward in the figure by a spring 45. are drawn to each. The mirror up locking pawl 36 restricts the movement of the mirror up lever 37, and is engaged with and disengaged from the mirror up lever 37 by the mirror magnet 28. Behind the mirror up lever 37 is a quick return mirror 13.
A mirror up lever 37a that is engaged with a pin 29a projecting from the side surface of the mirror is provided, and when the mirror up lever 37 is slid forward by a spring 38, the quick return mirror 13 is flipped up. second act 3
The pin 34a protruding from the mirror 4 hits the mirror down lever locking pawl 43 at the end of travel to free the mirror down lever 44, and the mirror down lever 44 lowers the quick return mirror 13. This quick return mirror 13 is provided with a mirror switch 30 which is turned on when the mirror 13 begins to rise and turned off when it descends again. Further, the mirror down lever 44 and the mirror up lever 37 are charged by a mirror charge lever 48 which is oscillated by a certain angle by a gear 47 that meshes with a gear 46 of the motor 35.

The operation of the apparatus having the above structure and the processing of signals generated with the operation are performed as shown in the timing chart shown in FIG. When the release button on the camera body is pressed, the release switch turns on, and at the same time the image sensor drive circuit 2
A vertical synchronizing signal is generated from 0 to the image sensor, scanning corresponding to one screen (one field or one frame) is performed, and unnecessary charges accumulated up to that point are discharged. When this exposure scan is completed, a release signal (ON) is sent to the mirror magnet 28. Then, the mirror up locking pawl 36 and the mirror up lever 37 are disengaged, and the lever 37 is pulled by the spring 38 and slides forward, pushing the pin 29a, that is, the quick return mirror 13, upward on the inclined surface 37a. . At the beginning of the rise of the mirror 13, the mirror switch 30 is turned on, and at the same time the rear curtain magnet 31 is also turned on, locking the rear curtain 34 (at this time, the rear curtain 34 is integrated with the front curtain 32 and is in the charge position. be).

When the quick return mirror 13 flips up,
At the final stage, the leading curtain lock release lever 29c hits the leading curtain locking pawl 39 to disengage the leading curtain 32. Then, the front curtain 32 moves while being pulled by the front curtain spring 40, and the image sensor 12 is exposed to light. In addition, the shutter switch 33 is turned off at the beginning of the movement of the leading curtain 32, and after the exposure time calculated by the exposure control circuit 21 has elapsed, the trailing curtain locking claw 4
1, a release signal (off) is sent, and the locking claw 41 is removed from the rear curtain 34. Therefore, the trailing curtain 34 is pulled by the trailing curtain spring 42 and runs, and the exposure is completed. When the trailing curtain 34 finishes traveling, the pin 34a releases the mirror down lever locking pawl 43, and the mirror down lever 44 is pulled by the spring 45 and slides. At this time, the mirror up lever 37 also slides together. The quick return mirror 13 is lowered by its own weight and the force of the torsion spring 29d. When the mirror 13 returns, the mirror switch 30 turns off, and this return signal generates a vertical synchronization signal in the image sensor drive circuit 20. This signal is applied to the image sensor 12, which corresponds to one screen (one field or one frame). The charges accumulated when the shutter 25 is in the open state are read out by the signal processing circuit 26 and stored in the storage device 27.

On the other hand, when the mirror switch 30 is turned off, the motor 35 starts to be driven at the same time, and the quick return mirror 13 and shutter 25 are charged.
That is, the rotation of the motor 35 is caused by the gears 46 and 47.
, the mirror charge lever 48 swings, the mirror down lever 44 slides forward, the spring 38 and the spring 45 are charged, and the mirror down lever 44 is engaged with the mirror down lever locking pawl 43 and stopped. , mirror charge is completed. Shutter charge is performed by reciprocating the shutter charge lever 50 via the crank lever 49 by rotation of the gear 46. In other words, the pin 32a of the leading curtain 32 is connected to the shutter charge lever 50.
When pressed, the pin 34a is pushed by the front curtain 32 and the front curtain 32
The rear curtain 34 slides as one. At this time, the leading curtain spring 40 and the trailing curtain spring 42 are charged, and the leading curtain 32 is hooked on the leading curtain locking pawl 39.
The rear curtain 34 is stopped by being hooked to the rear curtain locking pawl 41,
Shutter charge is complete. At this final stage, the shutter switch 33 is turned on again by the front curtain 32, and this signal outputs a drive stop signal for the motor 35. After receiving the stop signal, the motor 35 moves for a while due to inertia and stops at the original position before charging.

FIG. 5 shows a specific example of an electric circuit for operating the electronic camera. In the figure, a mirror switch 30, a shutter switch 33, a photometric element 2
2. Mirror magnet 28, rear curtain magnet 31
and motor 35 are the same elements as those in the above explanation, and in addition to these, the switches include a release switch 51 that is turned on when the release button is pressed, a memory switch 54 for recording image signals, and a self-timer. A self-switch 66 that is turned on at times is provided. In the figure, before photographing, the mirror switch 30, release switch 51, memory switch 54, and self-switch 66 are off, and the shutter switch 33 is on. Since the release switch 51 is off, the transistor 55 is not conductive, and no power is supplied to the circuit, so the circuit does not operate. When the release switch 51 is turned on (the shutter button is pressed), the transistor 55 becomes conductive and power is supplied to the circuit. A power supply timer 56 is configured to operate the transistor 5 for a certain period of time after power is supplied to the circuit.
generates an output that causes 7 to conduct. Therefore, even if the release switch 51 is turned off, power supply to the circuit is maintained for a certain period of time.

The photometric circuit operates when power is supplied to the circuit. The photocurrent flowing through the photometric element 22 is logarithmically compressed by the transistor 59, and a voltage corresponding to Bv is generated at the base. On the other hand, a constant current flows through the variable resistor 60, which is set according to the film sensitivity and aperture, and a voltage corresponding to Sv-Av is generated across the variable resistor 60. Therefore, the emitter of transistor 61 has
A voltage corresponding to Bv+Sv-Av, that is, Tv, is generated. By the way, when power is supplied to the circuit, since the mirror switch 30 is off, the control signal of the memory switch 54 becomes "L" and the memory switch 54 is turned on. The voltage corresponding to Tv is transmitted to the memory capacitor 63 via the level shift resistor and memory switch 54.

Now, when power is supplied to the circuit, the delay circuit 64 receives the vertical synchronization signal and after a certain period of time,
Send an “H” signal to the S terminal of the RS flip-flop 65. When using the self-timer, the self-switch 66 is turned on. At this time, the delay circuit 64 sends an "H" signal to the S terminal of the RS flip-flop 65 after the time set by the self-timer has elapsed since receiving the vertical synchronizing signal.
On the other hand, since the mirror switch 30 is off, the R terminal via the inverter 67 is at "L". Therefore, when an "H" signal is applied to the S terminal, the RS flip-flop 65 makes the transistor 68 conductive and the mirror magnet 28 is energized.

When the mirror magnet 28 is energized, the mechanical mechanism described above operates, the mirror switch 30 is turned on, and the transistor 70 becomes conductive. On the other hand, since the shutter switch 33 is on, the transistor 7
1 is conductive, so the output of the comparator 72 is "L". Therefore, the transistor 73 is not conductive, but the transistor 74 is conductive, and the trailing magnet 31 is energized. Further, since the mirror switch 30 is turned on, the control signal of the memory switch 54 becomes "L", and the memory switch 54 is turned off.

Next, when the front curtain 32 is turned off by the aforementioned mechanical mechanism and the shutter switch 33 is turned off, the transistor 71 is also turned off. The voltage of the transistor 73 is applied to the base of the transistor 77 via a buffer 76 formed of a voltage follower operational amplifier. An expansion current flows through the collector of the transistor 77, thereby charging the capacitor 78. When the (-) input terminal of the comparator 72 becomes lower than the reference voltage Vref of the (+) input terminal, the output of the comparator 72 becomes "H" and the transistor 73 is turned on. Then, the transistor 74 is turned off, cutting off the power to the trailing curtain magnet 31, and as a result, the trailing curtain 34 runs.

The movement of the rear curtain 34 activates a mechanical mechanism to turn off the mirror switch 30 again. Since the shutter switch 33 is also off at this time, both inputs of the AND gate 79 become "H" for the first time, and the output also becomes "H". As a result, the transistor 80 is turned on, and the motor 35 is energized and rotates.

As the motor 35 rotates, the shutter switch 3
3 turns on again, the output of the AND gate 79 becomes "L", the transistor 80 turns off, and the motor 35 stops.

Further, after a certain period of time has elapsed, the output of the power supply timer 56 becomes "L" and the transistor 57 is turned off. If the release switch 51 is not turned on at this time, the transistor 55 is turned off, the power supply to the circuit is cut off, and the original state is restored.

Next, FIG. 6 shows the image sensor drive circuit 20.
FIG. The image sensor drive circuit 20 includes an oscillation circuit 83, a horizontal drive pulse generation circuit 84, a horizontal synchronization signal generation circuit 85, a vertical drive pulse generation circuit 86, a vertical synchronization signal generation circuit 87, and a one-screen scanning circuit 88. When the signal from the release switch 51 is input to the one-screen scanning circuit 88 and the camera enters the release state, the one-screen scanning circuit 88 sends a reset signal to the oscillation circuit 83. When the oscillation circuit 83 is reset, it returns to the initial state, and the horizontal drive pulse generation circuit 84, the horizontal synchronization signal generation circuit 85, and the vertical drive pulse generation circuit 8
6. Send pulses to the vertical drive pulse generation circuit 86 and vertical synchronization signal generation circuit 87. Each circuit receiving this pulse receives a horizontal drive pulse ΦH1,
ΦH2, horizontal synchronization signal ΦHin, vertical drive pulses ΦV1, ΦV2 and vertical synchronization signal ΦVin are generated. When these signals are sent to the image sensor 12, the image sensor operates and outputs a video signal. The vertical synchronizing signal ΦVin is also input to the one-screen scanning circuit 88, and when the scanning of one field or one frame is completed, the oscillation circuit 83 is kept in a reset state. Next, the signal from the mirror switch 30 is input to the one-screen scanning circuit 88, and when the readout scan starts, the oscillation circuit 83 is reset again and one screen (one field or one frame) is scanned in the same way. . The video signal output from the image sensor 12 at this time becomes a still image signal.

FIG. 7 is a detailed circuit diagram of the one-screen scanning circuit 88. When the signal from the release switch 51, which goes to the "L" level when the release button is pressed, is input to the one-screen scanning circuit 88, a differentiating circuit composed of an inverter 90, a capacitor 91, and a resistor 92 causes a falling edge to be detected. is detected and the resulting pulse is input to the OR gate 93 and resets the counter 94. At the same time RS
The flip-flop 95 is reset, and the Q terminal, which had been set to the "H" level by the capacitor 96 and the resistor 97, is brought to the "L" level. The output from the Q terminal changes the reset signal from the "H" level to the "L" level through the OR gate 98, thereby releasing the reset of the oscillation circuit 83. From then on, a pulse for driving the image sensor 12 is generated and a vertical synchronizing signal ΦVin is input to the C terminal of the counter 94. When this vertical synchronizing signal ΦVin is counted 3, the output of the AND gate 99 becomes "H" level, the reset signal output from the OR gate 98 becomes "H" level, the oscillation circuit 83 is reset again, and the image sensor 12 is reset. drive is stopped.
Next, when the signal from the mirror switch 30 becomes "L" level after the exposure is completed, a falling edge of this "L" level signal is detected by a differentiating circuit constituted by a capacitor 100, a resistor 101, and an inverter 102. , the resulting pulse is input to OR gate 93 and resets counter 94. At this time, the reset signal becomes "L" level again and the reset of the oscillation circuit 83 is released.
Then, when the vertical synchronizing signal is counted 3 again, the reset signal becomes "H" level and the driving of the image sensor 12 is stopped. In this way, a print scan and a read scan corresponding to one frame are performed. When scanning one field, the vertical synchronizing signal ΦV1 may be configured to be counted by two by the counter 94.

FIG. 8a shows the above-mentioned image sensor driving circuit which non-periodically generates the vertical synchronizing signal ΦV1 as described above based on the signals from the release switch 51 and the mirror switch 30, and performs unnecessary charge discharge scanning and image signal readout scanning. 20 shows a timing chart. Further, FIG. 8b shows an example of a timing chart of horizontal drive pulses ΦH1, ΦH2, horizontal synchronization signal ΦHin, vertical drive pulses ΦV1, ΦV2, and vertical synchronization signal ΦVin for driving the image sensor drive circuit 20.

As described above, according to the electronic camera of the present invention, since a quick return mirror is used,
The bright viewfinder allows the subject to be observed, and even for a dark subject, the entire amount of light is given to the image sensor, making it possible to obtain still images of high quality. In addition, the synchronization signal generation circuit that emits the vertical synchronization signal to the imaging device emits it aperiodically, discharges the accumulated charge just before the shutter release, and reads it immediately after exposure.
A good image signal that is not affected by dark current can be obtained, and continuous shooting is possible.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of essential parts showing an embodiment of the electronic camera of the present invention, Fig. 2 is a systematic connection diagram including the same optical system, and Fig. 3 is a perspective view showing the vicinity of the quick return mirror and shutter. , FIG. 4 is a time chart of the above embodiment, FIG. 5 is a specific circuit diagram of the above embodiment, FIG. 6 is a block diagram showing an image sensor driving circuit, and FIG. 7 is a specific example of a single screen scanning circuit. The circuit diagrams, FIGS. 8a and 8b, are time charts of FIG. 6. 10...Subject, 11...Photographing lens, 12...
...Imaging device (image sensor), 13...Quick return mirror, 14...Finder optical system, 20...Image sensor drive circuit, 21...
Exposure control circuit, 22...Photometric element, 25...Shutter, 26...Signal processing circuit, 27...Storage device, 28...Mirror magnet, 30...Mirror switch, 31...Rear curtain magnet, 33... ...Shutter switch, 35...Motor, 86...Vertical drive pulse generation circuit, 87...Vertical synchronization signal generation circuit.

Claims (1)

[Scope of Claims] 1. An electronic camera with a built-in viewfinder optical system, which includes an imaging device that photoelectrically converts a subject image formed by a photographic lens, and a storage device that stores image signals obtained from the imaging device. a shutter that controls the imaging light flux incident on the device; an exposure control device that controls exposure via the shutter according to the brightness of the subject image; guidance,
a quick return mirror that retreats from the imaging light flux path during photography and supplies the imaging light flux to the imaging device; a release switch that issues a photography start signal;
a vertical synchronization signal generation circuit that aperiodically generates a vertical synchronization signal for the imaging device, and the vertical synchronization signal generation circuit generates the quick return signal for the imaging device after the release switch is turned on. It is characterized in that before the mirror starts retracting, a signal to remove charges accumulated in the imaging device is emitted, and after exposure by the shutter is completed, a readout signal for the accumulated charges is issued when the shutter is in an open state. electronic camera. 2. An electronic camera according to claim 1, wherein the charge readout signal for the imaging device is emitted in synchronization with a signal for detecting return of the quick return mirror to the state before retraction. 3. In claim 1 or 2, a motor for charging the quick-return mirror and the shutter is further provided, and this motor is driven by a shutter end-of-travel signal, and the motor is driven before the quick-return mirror is retracted. An electronic camera whose drive is stopped in response to a detection signal returning to the state.