JPS62150234A - Video camera device for finder of single-lens reflex camera - Google Patents

Abstract

PURPOSE:To prevent hunting, etc., of video signals so as to always obtain a properly exposed image, by holding a video image pickup device at the operating state just before a mirror is lifted up over the mirror-up period at the time of shutter releasing and releasing the image pickup device from the operating state when the mirror is returned to the original state and light is made incident to a finder. CONSTITUTION:The holding circuit 34 of an auto-iris controlling circuit 30 continues the input to an iris error amplifier 35 by holding the detecting DC voltage of a detecting circuit 32 by means of hold signals outputted from a timer circuit 40 at the timing of shutter releasing. The detecting DC voltage just before mirror-up is performed is continuously inputted to the iris error amplifier 35 even after the light to a finder is intercepted and the detecting circuit 32 does not make any output. Accordingly, an auto-iris 7 is fixed to the operating state just before the mirror-up. When the hold signal of the timer circuit 40 is interrupted after a prescribed shutter time has passed, a quick return mirror 1 is returned and light is made incident to the finder, and then, the holding circuits 26 and 34 are released from their held states.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a video camera device for a finder of a single-lens reflex camera that incorporates a video rotation device in the finder.

(Background of the Invention) Conventionally, in single-lens reflex cameras that use a remote control method,
A radio-controlled unit for remote control is installed in the camera, and after looking through the viewfinder and setting the copying range to a predetermined range, the user can monitor the situation from a distance from the camera installation position, capture the shutter timing, and remotely control the camera. This allows for still copying.

However, when performing still copying using remote control, it is not possible to see the image in the viewfinder, so it is possible to miss the copying timing or to set the framing to capture the subject at the appropriate position within the photographic screen. In many cases, this is not possible, and since it is not possible to move too far from the shooting location, a considerable amount of patience is required to take decoy shots, making it difficult to make effective use of the few photo opportunities available.

Therefore, we attached a general video camera to the eyepiece part behind the viewfinder's eyepiece, projected the video camera's monitor image onto a TV set far away from the shooting location, and remotely shot still decoys while looking at the monitor image. Attempts have been made to create a system that does this.

However, when the video camera is attached to the eyepiece portion of the finder, the video camera is attached to the rear of the camera, which increases the size and makes handling inconvenient.

Therefore, a finder video camera device has been considered in which a video image device using a solid-state image carrier such as a COD or a video image tube is integrated into a pentaprism type finder installed in an eye reflex camera. There is.

By the way, in such a finder video camera device, light from the decoy lens that must be in the open state enters the finder, and the amount of incident light may exceed the Quinamin range of the video camera. Since this is necessary, an auto iris 3HM is provided in the video optical system to suppress the incident light m into a constant beam.

In addition, since eye reflex cameras are used in dark places such as when using a strobe at 1 o'clock, it is necessary to increase the sensitivity by automatic sensitivity adjustment so that video can be monitored even in dark places where strobe shadows are used. An AGC amplifier with an automatic gain control function is used.

(Problem to be Solved by the Invention) However, in such a viewfinder video camera device, light entering the viewfinder is temporarily blocked while the shutter is operating when the mirror is raised by the shutter release in dark shadows. In this case, the auto iris of the video imager provided in the finder operates to the open side to increase the amount of incident light, and the sensitivity adjustment mechanism using the AGC amplifier operates to the side to increase the sensitivity.

For this reason, even after the shutter operation is completed and light enters the viewfinder, there is a slight response delay in both the auto iris and sensitivity adjustment mechanism, so the auto iris and sensitivity adjustment mechanism operate in response to sudden changes in the amount of incident light. cannot be tracked, resulting in temporary overexposure and hunting on the monitor screen.

In order to avoid this, it is possible to either make the response delay of the auto iris and automatic sensitivity adjustment mechanism almost negligible, or to make the response delay extremely long so as not to be sensitive to mirror-up.

However, even if we try to eliminate the response delay, since the auto iris is a mechanical aperture operation, mechanical operation delay cannot be avoided.On the other hand, even if the response delay is lengthened,
- Eye-reflex cameras have a bulb operation that keeps the shutter open and performs long exposures, and in order to raise the mirror by bulb operation, the delay in operation would have to be infinitely long, which is practically impossible.

Furthermore, in the case of continuous shutter operation using a motor drive, light enters the viewfinder intermittently as the mirror is repeatedly raised, and the video signal level drops to the average level of the incident light, so the auto iris gradually shifts to the open side. Furthermore, the sensitivity adjustment mechanism also operates to gradually increase the sensitivity, resulting in overexposure when the continuous shutter operation is completed.

(Purpose of the Invention) The present invention was made in view of such conventional problems. Even if the light to the viewfinder is cut off when the mirror is raised by the shutter release, an appropriate light source is provided when the shutter release ends. An object of the present invention is to provide a video camera device for a finder of a single-lens reflex camera, which allows a video exposure state to be obtained.

(Summary of the Invention) In order to achieve this object, the present invention provides a video camera device for the finder of a single-lens reflex camera in which a video camera device is incorporated in the pentaprism finder. During the mirror-up period, the auto iris and automatic sensitivity adjustment mechanism installed in the video imager are maintained in the operating state immediately before the mirror is raised, and then the operating state is maintained after the mirror returns and light enters the viewfinder. The technical point is that it can be released.

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

First, to explain the configuration, 100 is the camera body of a single-lens reflex camera, and a removable and replaceable copying lens 200 is attached to the front part.
The light from the dynamic lens 200 is reflected upward by the quick return mirror 1 to form a patterned image on the focus plate 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 evacuates from the copying optical path as shown in 1a.
The light from the shooting lens 200 is directed to the film surface 2.
to form an image.

At the top of the camera body 100, - an eye reflex finder 3;
00 is attached, and the optical image formed on the focus plate 3 in the camera body 100 is made incident on the pentaprism 5 of the single-lens reflex finder 300 through the condenser lens 4.
The light from the pentaprism 5 is reflected by a roof prism 6, passes through a pair of mask lenses 8 with an auto iris 7 between them, and passes through a CO mounted on a printed circuit board 11.
The still imitation screen of the focusing plate 3 is imaged on the light receiving surface of the solid-state image carrier 9 such as D.

solid! On the printed circuit board 11 on which the a-image element 9 is mounted,
A video camera circuit 12, 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 carrier 9 through the master lens 8 with the auto iris 7 in between is read out as a light reception signal by driving the CCD by the drive circuit 13. sample hold circuit 1
0, and automatic gain control circuit 2 as a sensitivity automatic adjustment wave groove
0 to the video signal processing circuit 14, where it is converted into, for example, an NTSC color television signal and output to the monitor television.

On the other hand, the video camera circuit 12 shown in FIG. 2 is provided with an auto-iris control circuit 30 that controls the auto-iris 7 by inputting the video signal 1q from the sample-and-hold circuit 10.

First, the configuration of the automatic gain control circuit 20 will be explained. The video signal output from the sample and hold circuit 10 is passed through the voltage gain control amplifier 22 which operates as an AGC amplifier.
and the amplified output of the voltage gain control amplifier 22 is input to AG
The signal is input to the C 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 other side of the AGC error amplifier 28 inputs a constant voltage from the reference voltage source 25, and the reference voltage source The deviation voltage between the constant voltage from the reference voltage source 25 and the detected DC voltage of the AGC detection circuit 24 is fed back to the voltage gain control amplifier 22 to form an AGC control loop.
The amplification gain of the voltage gain control amplifier 22 is controlled based on the error voltage so as to have a constant amplification gain determined by the reference 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 and detects a DC voltage according to the amplitude level.
The DC voltage detected by the detection circuit 32 is input to one side of the iris error amplifier 35 via the hold circuit 34.

The iris error amplifier 35 has a reference voltage source 36 at its other input.
A constant voltage is input from the Ml voltage, and the amount of light incident on the solid-state image element 9 by the auto iris 7 is set by this Ml voltage. The iris error amplifier 35 outputs an error voltage given by the difference between the DC detection voltage according to the video signal obtained from the detection circuit 32 and the reference voltage to the iris drive circuit 38, The aperture opening degree of the auto iris 7 is mechanically adjusted so as to maintain the amount of incident light.

Furthermore, in the video camera circuit shown in FIG. 2, unnecessary operations of the AGC control circuit 20 and the auto-iris control circuit 30 are avoided when light is no longer incident on the solid-state imaging element 9 due to mirror up during shutter release. In order to prevent this, AG
A hold circuit 26 is used for the C control circuit 20, and a hold circuit 34 is used for the auto iris control circuit 30.
These hold circuits 26 and 34 inhibit the control operation during the mirror-up period using the output of the timer circuit 40 that receives the shutter release signal and the shutter speed signal, and maintain the operating state immediately before the mirror-up. ,
After the mirror returns, the state of operation is released.

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

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

First of all, in the state before shutter release,
As shown in FIG. 1, the imitation image formed on the focus plate 3 by the quick return mirror 1 is shown in a single-lens reflex finder 300.
Since the sample and hold circuit 10 outputs a video signal having a signal level corresponding to the amount of light incident on the solid-state dark image element 9, the AGC detection circuit 24 and Each of the detection circuits 32 on the auto-iris side detects a DC voltage according 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 detected voltage of the AGC detection circuit 24 is directly passed through the hold circuit 26 to the AGC error amplifier 28. The AGC error amplifier 28 feeds back an error voltage corresponding to the difference between the reference voltage of the reference voltage source 25 and the detected voltage to the voltage sum 1q control amplifier 22, and if the error voltage is necessarily on the positive side, the voltage sum 1q! l11iI'II amplifier 22
operates to lower the amplification gain, and if the error voltage is on the negative side, it operates to increase the amplification gain.As a result, the video signal processing circuit 14 always receives a constant signal regardless of the amount of incident light. A video signal having a signal level between the white level and the black level will be output.

On the other hand, in the auto iris control circuit 30, since there is no hold signal from the timer circuit 40, the DC detection voltage of the detection circuit 32 is directly applied to the iris error amplifier 35, and the iris error amplifier 35 uses 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 operated in the direction of opening, and vice versa. The auto iris 7 is operated in the direction of closing, and the amount of light incident on the solid state image carrier 9 is controlled so as to maintain a constant video signal level determined by the reference voltage of the reference voltage source 36.

Next, when the shutter is released for copying, a shutter release signal is input to the timer circuit 40, and the timer circuit 40 holds the shutter for a predetermined one hour determined by the shutter speed signal already obtained. The signal is output to hold circuits 26 and 34. For this reason, the hold circuit 26 is
The detection voltage of the C detection circuit 24 is held, and regardless of subsequent changes in the detection voltage of the AGC detection circuit 24, the held constant DC detection voltage continues to be input to the error amplifier 28, and the voltage gain I11 control is performed. The amplification gain of the amplifier 22 is fixed to the amplification gain immediately before mirror up.

Further, the hold circuit 34 of the auto iris control circuit 30 uses the hold signal output from the timer circuit 40 at the timing of the shutter release to hold the DC voltage detected by the detection circuit 32 at that time and continues to input it to the iris error amplifier 35. Even if the light to the finder is cut off by mirror up and the output of the detection circuit 32 disappears, the detected DC voltage immediately before mirror up continues to be 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 predetermined shutter time ends and the hold signal of the timer circuit 40 is cut off, the quick return mirror 1 returns to allow light to enter the finder, and at this time the hold circuit 26
The hold state of 34 is released. When the hold is released, the DC detection voltage of the detection circuit 24, 34 corresponding to the signal level of the light incident on the finder has already been obtained, so that after the hold is released for the AGC error amplifier 28 and the iris error amplifier 35. The fluctuation of the detected DC voltage is extremely small, and even if the light is blocked by the mirror up, there is no change in the opening degree of the auto iris or the amplification gain while the light is blocked, and after the mirror returns, the solid state imager 9 It is possible to perform stable video operation without overexposure or oversensitivity of video amplification.

Incidentally, in the above embodiments, a solid image carrier such as a CCD was rarely used as an example, but the present invention is not limited to this, and may be applied as is to a case where a history image tube is used. can.

(Effects of the Invention) As explained above, according to the present invention, the video lfa 'A Vfj
In a video camera device for the viewfinder of a single-lens reflex camera incorporating By holding the camera in its previous operating state and releasing it after the mirror returns and light enters the viewfinder, there is no need to modify the response characteristics of the auto iris or auto sensitivity adjustment mechanism. This prevents the auto iris from operating to the open side and the automatic sensitivity adjustment mechanism from operating to the high sensitivity side when the light to the finder is cut off by mirror up, and prevents the auto iris from operating to the high sensitivity side when the mirror returns and light enters the finder. It reliably prevents video signal hunting caused by overexposure and excessive amplification gain, and ensures that images with proper exposure are always obtained not only in normal copying, but also in strobe shadowing, continuous shutter copying, etc. can.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram 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 fine camera shown in FIG. . 100: Camera body 200: E-shadow lens 300 Knee-eye reflex finder 1: Quick return mirror 2: Film plane 3: Focus plate 4: Condenser lens 5: Pentaprism 6: Roof prism 7: Auto iris 8: Master lens 9: Solid dark Image element 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 Ni-iris control circuit 32: Detection circuit 35 Ni-iris error amplifier 38 Ni-iris drive circuit 40: Timer circuit

Claims (3)

[Claims] (1) In a video camera device for the finder of a single-lens reflex camera that incorporates a video imaging device in the viewfinder, the video imaging device is maintained in an operating state immediately before mirror up during the mirror up period at the time of shutter release;
A video camera device for a finder of a single-lens reflex camera, characterized in that a holding means is provided for releasing the holding of the operating state after the mirror returns. (2) A patent claim characterized in that the holding means maintains an auto iris that operates to maintain a constant amount of light incident on the video imaging device over a mirror-up period in an operating state immediately before mirror-up. A video camera device for a finder of a single-lens reflex camera according to item 1. (3) The single-lens reflex camera according to claim 1, wherein the holding means maintains the automatic sensitivity adjustment operation of the video imaging device in the operating state immediately before mirror-up over a mirror-up period. Video camera device for finder.