JPH0660988B2 - Video camera device for finder of single-lens reflex camera - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a video camera device for a viewfinder of a single-lens reflex camera in which a video image pickup device is incorporated in the viewfinder.

(Background of the Invention) Conventionally, in a single-lens reflex camera employing a remote control system,
A radio control unit for remote control is installed on the camera, the shooting range is set to a predetermined range by looking through the viewfinder, and the situation is monitored away from the position where the camera is installed. I try to shoot.

However, in such remote-controlled still shooting, you cannot see the image in the viewfinder, so you cannot challenge the shooting timing or set the framing to capture the subject at an appropriate position on the shooting screen. In many cases, since it is not possible to get far from the shooting location, considerable patience was required for shooting, and it was difficult to effectively utilize a small number of shutter opportunities.

Therefore, a general video camera was attached to the eyepiece part behind the eyepiece of the viewfinder, the video image of the video camera was projected on the TV set away from the shooting location, and still photography was performed while watching the monitor image. A system is set up to do so.

However, when a video camera is attached to the eyepiece portion of the finder, the video camera is attached to the rear of the camera, which makes the camera larger and inconvenient to handle.

Therefore, there has been considered a video camera device for a finder in which a video image pickup device using a solid-state image pickup device such as CCD or an image pickup tube is integrally incorporated in a pentaprism type finder provided in a single-lens reflex camera.

By the way, in such a finder video camera device, light from the shooting lens in the open state is incident on the finder, and the incident light amount may exceed the dynamic range of the video camera. The video optical system is provided with an auto iris mechanism that suppresses the amount of incident light to a constant amount.

Also, since the single-lens reflex camera is used even in dark places such as when shooting with flash, it is necessary to increase the sensitivity by automatic sensitivity adjustment so that the video monitor can be used even in dark places where flash shooting is performed. An AGC amplifier having an automatic gain control function is used.

(Problems to be Solved by the Invention) However, in such a finder video camera apparatus, light is temporarily blocked from entering the finder during shutter operation by mirror up due to shutter release at the time of shooting. In this case, the auto iris of the video image pickup device provided in the finder operates on the open side to increase the incident light amount, and the sensitivity adjusting mechanism by the AGC amplifier operates on the side to increase the sensitivity.

Therefore, even if the shutter operation ends and light enters the viewfinder, there is a slight response delay in both the auto iris and the sensitivity adjustment mechanism. Cannot be followed, causing temporary overexposure or hunting on the monitor screen.

In order to avoid this, either the response delay of the auto iris and the automatic sensitivity adjustment mechanism should be made almost zero, or the response delay should be made extremely long so as not to be sensitive to the mirror up.

However, even if trying to eliminate the response delay, since the auto iris is a mechanical diaphragm operation, the mechanical operation delay cannot be avoided, and even if the response delay is lengthened,
Single-lens reflex cameras have a valve operation that keeps the shutter open for long-time exposure, and it is necessary to lengthen the operation delay indefinitely for mirror up by the valve operation, but this is actually impossible.

Furthermore, in the case of continuous shutter operation by the motor drive, light is intermittently incident on the viewfinder due to repeated mirror up, and the video signal level drops to the average level of the incident light, so the auto iris gradually opens. There is also a problem that the sensitivity adjustment mechanism operates to gradually increase the sensitivity, and overexposure occurs when the continuous shutter operation ends.

(Object of the Invention) The present invention has been made in view of such conventional problems, and is suitable when the shirt release is completed even if the light to the finder is cut off due to the mirror release by the shutter release. An object of the present invention is to provide a video camera device for a viewfinder of a single-lens reflex camera capable of obtaining a video exposure state.

(Summary of the Invention) In order to achieve this object, according to the present invention, in a video camera device for a viewfinder of a single-lens reflex camera in which a video image pickup device is incorporated in a pentaprism viewfinder, a mirror at the time of shutter release. The auto iris and the automatic sensitivity adjustment mechanism provided in the video imaging device are held in the operating state immediately before the mirror is raised for the up period, and the operating state is released after the mirror returns and light enters the finder. This is the technical point.

(Embodiment) FIG. 1 is an explanatory view of a single-lens reflex camera equipped with a video camera device for a finder of the present invention.

First, the structure will be described. Reference numeral 100 denotes a camera body of a single-lens reflex camera, and a detachable and replaceable photographing lens 200 is provided on a front portion.
The quick return mirror 1 reflects the light from the taking lens 200 upward to form a taken image on the focusing screen 3.

Further, a film surface 2 is located behind the quick return mirror 1, and when the shutter is released, the quick return mirror 1 rises so as to evacuate from the photographing optical path as indicated by 1a, and the light from the photographing lens 200 is made to pass through the film surface 2. Image.

At the top of the camera body 100, a single-lens reflex finder 3
00 is mounted, and the optical image formed on the focusing screen 3 in the camera body 100 is made incident on the pentaprism 5 of the single-lens reflex finder 300 by the condenser lens 4.
The light from the pentaprism 5 is reflected on the information by the roof prism 6, passes through a pair of master lenses 8 having an auto iris 7 therebetween, and is mounted on the printed circuit board 11 by the CC.
The still image-taking screen of the focusing screen 3 is imaged on the light-receiving surface of the solid-state image sensor 9 such as D.

On the printed circuit board 11 on which the solid-state image sensor 9 is mounted, the video camera circuit 12 which is shown in the circuit block diagram of FIG. 2 is incorporated.

FIG. 2 is a circuit block diagram showing an embodiment of the video camera circuit 12 incorporated in the printed circuit board 11 of the single-lens reflex finder 300 shown in FIG.

In FIG. 2, the viewfinder field image formed on the light receiving surface of the solid-state image sensor 9 through the master lens 8 having the auto iris 7 therebetween is read out as a light receiving signal by driving the CCD by the driving circuit 13. , Sample and hold circuit 1
0, and an automatic gain control circuit 2 as an automatic sensitivity adjustment mechanism
It is given to the video signal processing circuit 14 via 0, converted into a color television signal of, for example, an NTSC system, and output to the monitor television side.

On the other hand, the video camera circuit 12 shown in FIG. 2 is provided with an auto iris control circuit 30 which inputs the video signal obtained from the sample hold circuit 10 and controls the auto iris 7.

Therefore, first, the configuration of the automatic gain control circuit 20 will be described. The video signal output from the sample hold circuit 10 operates as a voltage gain control amplifier 2 that operates as an AGC amplifier.
2 and inputs the amplified output of the voltage gain control amplifier 22 to A
It is input to the GC detection circuit 24, and a DC voltage corresponding to the amplitude of the video amplification output is detected. The detected DC voltage of the AGC detection circuit 24 is input to one side of the AGC error amplifier 28 via the hold circuit 26, and the AGC error amplifier 28 inputs the constant voltage from the reference voltage source 25 to the other side. The deviation voltage between the constant voltage from 25 and the detected DC voltage of 24 of the AGC detection circuit is fed back to the voltage gain control amplifier 22 to form an AGC control loop, and a constant amplification gain determined by the reference voltage of the reference voltage source 25. Therefore, the amplification gain of the voltage gain control amplifier 22 is controlled based on the error voltage.

On the other hand, the auto iris control circuit 30 inputs the video signal output from the sample hold circuit 10 to the detection circuit 32 to detect the DC voltage according to the amplitude level,
The DC voltage detected by the detection circuit 32 is input to one of the iris error amplifiers 35 via the hold circuit 34.
The iris error amplifier 35 has a reference voltage source 36 at the other input.
Is input, and the amount of light incident on the solid-state image sensor 9 by the auto iris 7 is set by this reference voltage. The iris error amplifier 35 outputs to the iris drive circuit 38 an error voltage given by the difference between the DC detection voltage corresponding to the video signal obtained from the detection circuit 32 and the reference voltage, and a constant voltage given by the reference voltage source 36. The diaphragm opening of the auto iris 7 is mechanically adjusted so as to maintain the amount of incident light.

Further, in the video camera circuit of FIG. 2, in order to prevent unnecessary operation of the AGC control circuit 20 and the auto iris control circuit 30 when light does not enter the solid-state image sensor 9 due to mirror up during shutter release. , AG
The hold circuit 26 for the C control circuit 20 and the hold circuit 34 for the auto iris control circuit 30.
The hold circuits 26 and 34 are provided with an output of the timer circuit 40 to which the shutter release signal and the shutter speed signal are input, and prohibit the control operation over the mirror up period to keep the operating state immediately before the mirror up. ,
After the mirror returns, the holding of the operating state is released.

That is, when the timer circuit 40 receives the shutter release signal, it outputs the hold signal to the hold circuits 26 and 34 from the shutter speed signal given at that time for the mirror-up time corresponding to the shutter time. .

Next, the operation of the embodiment shown in FIG. 2 will be described.

First, in the state before performing shutter release,
As shown in FIG. 1, the captured image formed on the focusing screen 3 by the quick return mirror 1 is a single-lens reflex finder 300.
Since it is incident on the solid-state image sensor 9 by the video optical system inside, and the sample hold circuit 10 outputs a video signal having a signal level according to the incident light amount of the solid-state image sensor 9, the AGC detection circuit 24 and the auto iris side Each of the detection circuits 32 detects the DC voltage corresponding to the amount of incident light by detecting the video signal.

First, in the AGC control circuit 20, since the hold signal from the timer circuit 40 is not applied at times other than the shutter release, the detection voltage of the AGC detection circuit 24 is directly transmitted via the hold circuit 26 to the AGC error amplifier 28. The AGC error amplifier 28 feeds back the error voltage corresponding to the difference between the reference voltage of the reference voltage source 25 and the detected voltage to the voltage gain control amplifier 22, and if the error voltage is on the positive side, the voltage gain control amplifier 22 operates so as to reduce the amplification gain, and also operates so as to increase the amplification gain if the error voltage is on the negative side. As a result, the video signal processing circuit 14 is always constant regardless of the incident light amount. A video signal having a signal level between the white level and the black level of is output.

On the other hand, in the auto iris control circuit 30, similarly, since there is no hold signal from the timer circuit 40, the DC detection voltage of the detection circuit 32 is given to the iris error amplifier 35 as it is, and the iris error amplifier 35 receives the detection voltage and the reference voltage. An error voltage corresponding to the difference from the reference voltage from the voltage source 36 is output to the iris drive circuit 8, and if the error voltage is on the negative side, the auto iris 7 is opened and the error voltage is on the positive side. For example, the auto iris 7 is operated in the closing direction, and the amount of light incident on the solid-state image sensor 9 is controlled so that the video signal level becomes a constant video signal level determined by the reference voltage of the reference voltage source 36.

Next, when shutter release is performed for photographing, a shutter release signal is input to the timer circuit 40, and the timer circuit 40 outputs the hold signal for a predetermined shutter time determined by the shutter speed signal already obtained at this time. It outputs to the hold circuits 26 and 34. Therefore, the hold circuit 26 causes the AG when the shutter is released.
The detection voltage of the C detection circuit 24 is held, and the held constant DC detection voltage is continuously input to the error amplifier 28 regardless of the change in the detection voltage of the AGC detection circuit 24 thereafter. The amplification gain of is fixed to the amplification gain immediately before mirror up.

In addition, the hold circuit 34 of the auto iris control circuit 30.
Is the timer circuit 40 at the shutter release timing.
With the hold signal output from the detection circuit 32, the detected DC voltage of the detection circuit 32 at that time is held and continuously input to the iris error amplifier 35. Even if the light to the finder is cut off by the mirror up and the output of the detection circuit 32 disappears. ,
The detected DC voltage immediately before the mirror is raised is continuously input to the iris error amplifier 35, and the auto iris 7 is fixed to the operating state immediately before the mirror is raised. When the hold signal of the timer circuit 40 is cut off after the predetermined shutter time ends, the quick return mirror 1 returns and light is incident on the viewfinder. At this time, the hold circuit 2
The hold states of 6 and 34 are released. When the hold is released, the DC detection voltage of the detection circuits 24 and 34 corresponding to the signal level due to the light incident on the finder has already been obtained, so the AGC error amplifier 28
Also, the fluctuation of the detected DC voltage after the hold is released to the iris error amplifier 35 is very small, and even if the light is blocked by the mirror-up, there is no change in the opening or amplification gain of the auto iris during the blocking of the light, and the mirror The exposure of the solid-state image sensor 9 does not become excessive or the sensitivity of video amplification does not become excessive after the return of, and stable video operation can be performed.

In the above embodiments, a solid-state image pickup device such as a CCD is taken as an example, but the present invention is not limited to this, and can be applied as it is even when an image pickup tube is used. .

(Effect of the Invention) As described above, according to the present invention, in the video camera device for the viewfinder of the single-lens reflex camera in which the video image pickup device is incorporated in the pentaprism viewfinder, the mirror up at the time of shutter release. The auto iris and the automatic sensitivity adjustment mechanism, etc. provided in the video imaging device are held in the operating state immediately before the mirror is raised for a certain period, and the operating state is released after the mirror returns and light enters the finder. Therefore, without specially modifying the response characteristics of the auto iris and the automatic sensitivity adjustment mechanism, the operation of the auto iris to the open side and the high sensitivity side of the automatic sensitivity adjustment mechanism when the light to the viewfinder is cut off by the mirror up Of the auto iris when the mirror returns and the light enters the viewfinder. It is possible to reliably prevent hunting of a video signal due to excessive output or excessive amplification gain, and always obtain an image with proper exposure not only in normal shooting but also in flash shooting and continuous shutter shooting.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention together with a single-lens reflex camera, and FIG. 2 is a circuit block diagram showing an embodiment of a video camera circuit incorporated in the viewfinder of FIG. 100: camera body 200: shooting lens 300: single-lens reflex finder 1: quick return mirror 2: film surface 3: focusing plate 4: condenser lens 5: pentaprism 6: roof prism 7: auto iris 8: master lens 9: solid-state image sensor 10 : Sample hold circuit 11: circuit board 12: video camera circuit 13: drive circuit 20: AGC control circuit 22: voltage gain control amplifier 24: AGC detection circuit 25, 36: reference voltage source 26, 34: hold circuit 28: AGC error Amplifier 30: Auto iris control circuit 32: Detection circuit 35: Iris error amplifier 38: Iris drive circuit 40: Timer circuit

Claims (3)

[Claims] 1. A video camera device for a viewfinder of a single-lens reflex camera in which a video image pickup device is incorporated in a viewfinder, wherein the video image pickup device is kept in an operating state immediately before the mirror is raised for a mirror-up period at the time of shutter release. Then
A video camera device for a viewfinder of a single-lens reflex camera, which is provided with holding means for releasing the holding of the operating state after the mirror returns. 2. The holding means holds an auto iris, which operates so as to keep the amount of light incident on the video image pickup device constant over the mirror-up period, in the operating state immediately before the mirror-up. A video camera device for a viewfinder of a single-lens reflex camera according to claim 1. 3. The single-lens reflex camera according to claim 1, wherein the holding means holds the automatic sensitivity adjustment operation of the video image pickup apparatus in an operating state immediately before the mirror is raised for a mirror-up period. Video camera device for camera viewfinder.