JPS5842676B2 - Video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video camera, and particularly to a video camera equipped with a shutter or a flash device that is effective for observing still images of moving objects.

Image pickup tubes, especially vidicon cameras, used in industrial television equipment and the like have a large afterimage, so when an industrial television camera photographs a moving object, the image is blurred and a clear image cannot be obtained.

As a method of taking still images or instantaneous images of such moving objects, there is a known method that uses an instantaneous flash of light such as a strobe, and devices that combine such a strobe with a video camera are also commercially available.

However, such flashes from strobes and the like are ineffective when photographing moving objects or moving light emitters that are outdoors during the day. It was not possible to obtain a still image.

In order to solve such problems, the present applicant & Chi. Patent Application No. 51-62525 ``Surface Inspection Method for Steel Slabs''
-26816 and Patent No. 1081208, a shutter mechanism is provided in front of the image pickup tube or in the lens system of a video camera, and by instantaneously opening the shutter, a still image of a luminescent moving object such as a red-hot piece of steel is projected onto the image pickup tube. proposed a method for obtaining still images of moving objects by projecting a complete image of one frame onto a receiver using the afterimage characteristics of an image pickup tube.

Although this method has extremely high practical value, since the photocathode scanning of the image pickup tube is performed completely unrelated to the cape ivy shooting, the level of the video signal is affected by the rise characteristics of the image pickup tube in response to pulsed light input and the afterimage. The characteristics change from moment to moment, making it impossible to obtain a high-quality homogeneous image.

That is, as shown in FIG. 1, it is clear from the relationship between the progressive scanning vertical synchronizing signal and the change in the magnitude of the video signal due to the influence of the rise characteristics and afterimage characteristics of the image pickup tube caused by the instantaneous opening of the shutter. When you look at one field from the vertical synchronization signal S1, the signal level corresponding to the upper half of the image is low, so the image becomes dark, and when you look at one field from the vertical synchronization signal S2, the lower half of the image becomes dark, indicating which field Even if you select (Frame), the image appears uneven.

This problem also occurs in video cameras equipped with a flash device such as a flash.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video camera for taking still images of moving objects, which solves these drawbacks and allows uniform still images to be obtained.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a first diagram showing the relationship between the vertical synchronization signal and the video signal level change that is to be achieved in the video camera of the present invention.
This is a waveform diagram similar to the one shown in the figure, starting with the vertical synchronization signal SA.
If one field is selected such that the peak of the video signal is located approximately at the center, the brightness of the screen will be approximately constant over the entire surface, and a homogeneous image will be obtained.

In order to perform such field scanning, it is necessary to synchronize the scanning period of the video camera and, for example, the opening timing of the shutter.There are two ways to do this: one is to synchronize the shutter operation with the synchronization signal of the video camera, and the other is to synchronize the shutter opening timing with the video camera's synchronization signal. One possible method is to synchronize the video camera with the operation, but the present invention adopts the former method.

In other words, even when the shutter is not operating (no light is coming in), the video camera scans and outputs a black level signal, and when it receives a shooting command signal, it synchronizes with the video camera and activates the shutter. Get the homogeneous video signal you need.

An embodiment of a video camera according to the invention that operates in this manner is shown in FIG.

In FIG. 3, reference numeral 1 is a main body of a video camera device housing an image pickup tube such as a vidicon, and a shutter such as an electric shutter 3 is provided between the main body and a lens system 2 of the video camera device.

The video signal from the video camera device 1 is sent to the recording device 4 and recorded, and read out from the recording device 4 as appropriate.
The image is displayed on the monitor receiver 5.

The invention further includes a synchronization signal generator 6 and a shutter control device 7.

The synchronization signal generator 6 outputs a vertical synchronization signal to the video camera device 1 to synchronize the vertical scanning lines of the video camera and to cause the video camera to scan.

The shutter control device 7 includes a shutter synchronization circuit 8, a delay circuit 9, and a shutter drive device 10 that supplies a drive current to a drive solenoid of the electric shutter 3, for example.

The shutter synchronization circuit 8 receives a vertical synchronization signal from the synchronization signal generator 6, and when it receives the photographing command signal S, the shutter drive command signal is sent to the delay circuit 9 in synchronization with the next vertical synchronization signal. Output to.

The drive command signal delayed by the delay circuit 9 is sent to the shutter drive device 10, causing the shutter drive device 10 to supply a drive current to the drive solenoid of the electric shutter 3.

Let T8 be the mechanical delay from when the electric shutter 3 receives the drive current until it opens, then the shutter shutter opens after a time Ts after the drive current is supplied, and the shutter opens for a preset opening time, for example, 1/100 second. Then close it again.

The apparatus described above is set and operates as follows.

First, the change in the brightness level of the video signal due to the rise characteristics and afterimage characteristics in response to the pulsed light input of the vidicon used in the video camera 1 is as shown in Fig. 2, and the vertical synchronization pulse SA is located after TI from the rise. If it is preferable, the time interval T of the vertical synchronizing pulse, the delay circuit 9
The delay time of the delay circuit 9 is set in advance so that the delay time TD of the delay circuit 9 holds: NT = TI + TS +'rD (where N: an integer).

Note that when using a flash device such as a strobe instead of a shutter, instead of the mechanical delay T8 in the above formula, the time Ts from when the drive current is supplied to the flash device until the flash device actually emits light is used. ’.

However, if Ts can be ignored compared to other T1 etc.
′−〇 may be used.

In a shooting preparation state in which there is no imaging command signal, the first electric shutter 3 is in a closed state, and the video camera 1 is outputting a black level signal including a synchronization signal.

Now, when the photographing command signal sI is sent in this state, the shutter synchronization circuit 8 outputs the shutter drive command signal Ss to the delay circuit 9 in synchronization with the subsequent vertical synchronization signal.

The shutter drive command signal S's delayed by a delay time TD in the delay circuit 9 is sent to the shutter drive device 10, and the shutter drive device 10 electrically controls the drive current in synchronization with the delayed shutter drive command signal S's. Supplied to the shutter 3 solenoid.

The motorized shutter 3 opens at time t, after a shutter-specific mechanical delay T8, and closes at t2 after a time defined by the shutter speed.

Due to the input of pulsed light due to the shutter opening at time t2-t1, the change in the video signal due to the rise characteristics and afterimage characteristics of the vidicon becomes as shown by curve C in FIG. 2, and the synchronization signal sA delayed by time T1 from time t1. The video signal level of the first field is approximately constant.

In this way, the vertical synchronizing signal and the output signal of the video camera are always maintained in a constant temporal relationship such that the level of the video signal in the field (1) is approximately constant.

By continuously outputting only one field starting with the vertical synchronization signal sA, that is, one field including the output peak, from the recording device 4, a uniform and uniform still image can be continuously displayed on the monitor receiver. .

FIG. 4 shows a modification of the embodiment shown in FIG. 3, and identical devices are given the same reference numerals.

In the embodiment shown in FIG. 4, a beam control device 11 comprising a delay circuit 12 and a beam synchronization circuit 13 is further provided.

In the photographing preparation state in which the photographing command signal sI is not issued, the shutter 3 is closed, but the electron beam deflection circuit of the image pickup tube of the television camera 1 operates in synchronization with the synchronizing signal from the synchronizing signal generator 6. ing.

However, by controlling the bridge voltage of the image pickup tube, a state is maintained in which the electron beam is not emitted.

When the photographing command signal sI is sent in this state, the shutter control device 7 operates as described above.

At this time, the shutter drive command signal S's output from the delay circuit 9 after being delayed by a delay time TD is sent to the delay circuit 12, and the mechanical delay Ts of the shutter 3 and the video signal peak value are the vertical synchronization signal. The sum (Ts + T
, ) is further delayed for a slightly shorter time and output to the beam synchronization circuit 13.

The beam synchronization circuit 13 outputs an output signal to the video camera 1 in synchronization with the synchronization signal from the synchronization signal generator 6 immediately after receiving the delayed input signal, changes the grid voltage of the image pickup tube, and changes the field Irradiation of the target with the electron beam is started from the first scanning line.

By doing so, it is possible to suppress the consumption of accumulated charges on the target surface when the image pickup tube is started up due to the input of the cursor light, and to make the field image more homogeneous immediately after the start of beam irradiation.

As is clear from the above, according to the present invention, a homogenized still image of a moving object without image unevenness can be obtained.

Further, the present invention is applicable to
It will be clear to those skilled in the art that it can be implemented and there are no restrictions on the subject.

Furthermore, in the case of a video camera equipped with a flash device, there is no delay from the supply of the energizing current to the generation of the flash, so looking at the circuit shown in FIG. 3, the delay time of the delay circuit 9 is TD+T.
If a flashing device, such as a flash, is activated by the drive device 10 at time t, as S, a flash is emitted at time t1, and a homogeneous still image is similarly obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the vertical synchronization signal and the output level change of the video signal in response to pulsed light input when photographing with a conventional shutter-type video camera, and FIG. A graph showing the relationship between the obtained vertical synchronizing signal and the output level change of the video signal with respect to the pulsed light input, FIG. 3 is a block diagram of one embodiment of the shutter type video camera according to the present invention, and FIG. 4 is a block diagram showing a modification of the embodiment shown in FIG. 3; FIG. 1... Video camera device, 2-... Lens system, 3...- Electric shutter, 4... Recording device,
5--Monitor receiver, 6--Synchronizing signal generator, 1--Shutter control device, 8--Shutter synchronizing circuit, 9-- Delay circuit, 10-・
...Shutter drive device, 11--Beam control device, 12--Delay circuit, 13--Beam synchronization circuit.

Claims (1)

[Claims] 1. A video camera provided with a shutter or a flash device and connected to a recording device; a synchronization signal generator for supplying a vertical synchronization signal to the video camera; A synchronization circuit receives the signal and outputs a drive command signal in synchronization with only the first vertical synchronization signal immediately after receiving the photographing command signal; a delay circuit delays the drive command signal by a predetermined delay time; and a delay circuit that delays the drive command signal by a predetermined delay time. and a drive device that drives the shutter or the flash device in response to a drive command signal, and the predetermined delay time TD by the delay circuit is delayed by the pulsed light incident on the image means of the video camera by driving the shutter or the flash device. NT=T1+TS+TD, which satisfies the following relationship so that the peak of the video signal output from the imager is located approximately at the center of two adjacent vertical synchronization signals, where N is an integer and T is the time of the vertical synchronization signal. The interval T is determined by the rise characteristics and afterimage characteristics of the imaging means at the time of the first pulse input, and is approximately at the center between the next vertical synchronizing signal and the image where the vertical synchronizing signal should be located, where the peak of the video signal is located. A video camera capable of taking still images, wherein the time Ts from the rise of a signal is the time from when a drive current is supplied until a shutter actually opens or a flash device actually emits light.