JPH06189183A - Video camera and control method therefor - Google Patents

Abstract

PURPOSE:To make the level of video signals obtained by high-speed shutter speed photographing and normal shutter speed photographing almost equal at all times regardless of the fluctuation of the characteristics of an AGC. CONSTITUTION:The photographing at a high-speed shutter speed once in 18 fields and at a normal shutter speed at other times is cyclically repeated. For luminance signals for indicating adjacent pictures, the luminance signals for one field obtained by the photographing at the high-speed shutter speed are integrated at a first integration circuit 21 and the luminance signals for one field obtained by the photographing at the normal shutter speed are integrated at a second integration circuit 22. The difference data of integrated values are calculated by a difference detection circuit 23 and supplied to the AGC 6 as gain correction signals. At the AGC 6, gain control signals are corrected by the gain correction signals and the level of the video signals at the high-speed shutter speed and the level of the video signals at the normal shutter speed are made almost equal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera for performing still reproduction and movie reproduction from a video signal obtained by continuously photographing a subject, and a control method thereof.

[0002]

BACKGROUND ART In general, a video camera shoots at a shutter speed of 1/60 second. For this reason, when trying to perform still reproduction of one frame in the motion of the subject from this movie video signal, only the faint reproduction in which the image flows can be performed.

In order to obtain a clear image of a moving subject at the time of still reproduction, it is necessary to shoot at a high shutter speed. A movie video camera that continuously shoots at a high shutter speed has been proposed. However, when doing so, the sense of continuity of each frame of the image is lost when the movie is played back, and the movement of the subject in the played image is extremely high. It will be unnatural. It is difficult to combine movie playback and still playback.

Since photographing is performed only once in a plurality of times, the sense of continuity of images is not lost.

When shooting at a high shutter speed, the level of the video signal is lower than when shooting at a normal shutter speed, and the printed image may become dark when printed. If the subject is under fluorescent lighting, it may be affected by the flicker of the fluorescent lamp.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to make it possible to make the level of a video signal shot at a high shutter speed and the level of a video signal shot at a normal shutter speed always substantially equal. .

Another object of the present invention is to eliminate the influence of flicker from reproduced video.

The video camera of the present invention is a shutter realizing means for periodically repeating exposure of one of a plurality of consecutive predetermined frames taken at a high shutter speed, and otherwise exposing at a normal shutter speed. , A photographing means for outputting a first video signal when exposed at the normal shutter speed, and a second video signal when exposed at the high shutter speed, the first video signal An amplifier circuit for amplifying the first and second video signals output from the photographing means with two different amplification factors so that the level of the second video signal is substantially equal to the level of the second video signal, First integrating means for integrating a first video signal for one frame represented by the video signal and outputting a first integrated value; and second integrating means for one frame represented by the second video signal. Second integrating means for integrating the image signal and outputting a second integrated value, the first integrated value and the second integrated value obtained from video signals representing the adjacent first image and second image. And an adjusting means for adjusting two kinds of amplification factors of the amplifying circuits which are different from each other so as to eliminate the difference based on the difference calculated by the calculating means. It is characterized by

The control method of the video camera of the present invention is as follows:
Exposure is performed at a high shutter speed for one shot of a predetermined number of consecutive frames, and at other times, exposure is performed at a normal shutter speed, which is repeated cyclically. When the first video signal is exposed at the high shutter speed, the second video signal is obtained, and the level of the first video signal is
The first output from the photographing means with two different amplification factors so as to be substantially equal to the level of the second video signal.
And amplifying the second video signal, integrating the first video signal for one frame represented by the first video signal to obtain a first integrated value, and expressing the second integrated video signal by the second video signal. The second video signal for one frame is obtained to obtain a second integration value, and the first integration value and the above-mentioned first integration value obtained from video signals representing the adjacent first image and second image. It is characterized in that a difference from the second integral value is calculated, and based on the calculated difference, two different types of amplification factors in the amplification processing are adjusted so that this difference disappears.

In the above, the shutter realizing means may be a mechanical shutter or a so-called electronic shutter for controlling the readout time of the CCD.

According to the present invention, the first integral value of the video signal of the first image exposed at the normal shutter speed and the second image adjacent to the first image, which is the proper shutter The difference from the second integral value of the video signal of the second image exposed at speed is calculated. Based on this difference, the amplification factor of the amplification process for the first and second video signals is adjusted so that the calculated difference disappears.

When the difference between the first integrated value and the second integrated value disappears, the level of the first video signal becomes equal to the level of the second video signal. Regardless of characteristic changes such as a circuit for amplifying the level of the first video signal, the level of the first video signal becomes equal to the level of the second video signal, and an image printed based on the first video signal is also displayed. Get brighter.

The exposure at the above high shutter speed is
It is preferable to carry out once during the shooting of a plurality of consecutive frames in multiples of 6.

When the fluorescent lamp is turned on by an alternating current having a repetition frequency of 50 Hz, the peak period is every 1/100 second. When the fluorescent lamp is turned on with an alternating current having a repetition frequency of 60 Hz, the peak period becomes every 1/120 second. For this reason, if shooting is repeated at a shutter speed faster than 1/100 second, the amount of integration of the video signal at each shooting timing differs and flicker occurs.

On the other hand, since the photographing cycle is 1/60 second, 50
Even if the fluorescent lamp is turned on by an alternating current with a repetition frequency of 60 Hz or 60 Hz, even if the shutter speed is faster than 1/100 second, each shot is every three shots. The amount of integration of the video signal at the timing should be the same and flicker should be prevented from occurring. However, there is a photoelectric difference in the fluorescent lamp when discharged from right to left and vice versa. Therefore, in the case of shooting every six times, the integration amount of the video signal at each shooting timing becomes the same and the influence of flicker decreases.

Exposure is performed at a high shutter speed once in a plurality of multiples of 6. Therefore, the integration amount of the video signal becomes the same at each photographing timing, and the influence of flicker can be reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an embodiment of the present invention, and is a block diagram showing the electrical construction of a video camera.
FIG. 2 shows a time chart when shooting is performed using the video camera shown in FIG.

FIG. 3 shows the PI (Pr) included in the video camera.
FIG. 3 is a block diagram showing a specific configuration of an int Inhibit) signal (print inhibition signal) generation circuit.

4A and 4B show signals recorded by the video camera shown in FIG. 1. FIG. 4A shows a recording signal of a plurality of fields, and FIG. 4B shows a vertical blanking of the recording signals shown in FIG. The period is expanded and shown. FIG. 5 shows a PI signal for prohibiting printing.

The video camera has a shutter speed of 1
/ 60 seconds, the subject is continuously photographed over a predetermined number of fields (preferably 12 or 18 fields, which is a multiple of 6 fields), and one field (or one frame) between them is regularly used for high shutter speed. Take a picture (for example, 1/250 second).

Since a field having a multiple of 6 is photographed once at a high shutter speed, the reproduced image is prevented from being affected by flicker such as a fluorescent light. The reason for this will be described later.

A light image representing a subject image is formed on the CCD 4 by the imaging lens 2 through the diaphragm 3.

As described above, under the control of the shutter control circuit 14, continuous exposure is performed a predetermined number of times at a normal shutter speed of 1/60 second and once at a high shutter speed of 1/250 second. The electronic shutter operation in the CCD 4 is performed so that a series of the sequence of exposure and the exposure is repeated. This is shown in the uppermost row of FIG.
The hatched portion in the uppermost row of FIG. 2 indicates a field shot at a high shutter speed, and the other portion indicates a field shot at a normal shutter speed. Shooting is performed once in 18 fields at a high shutter speed. CCD
The video signal read from 4 is 1/60, like a normal video camera, regardless of the shutter speed value.
It goes without saying that it is performed every second.

As will be described later, a PI signal is superposed on a video signal obtained by photographing at a normal shutter speed among the video signals output from the CCD 4.

The video signal output from the CCD 4 is CDS
It is given to the automatic gain adjustment circuit 6 via (correlated double sampling circuit) 5.

The automatic gain adjustment circuit 6 switches the amplification factor based on the gain control signal given from the system controller 20, and amplifies the input video signal while one of two types of amplification factors is selected. It is a circuit that can. The automatic gain adjustment circuit 6 increases the amplification factor of the video signal obtained by shooting at a high shutter speed to be higher than the amplification factor of the video signal obtained by shooting at a normal shutter speed. The average level of the video signal is adjusted to be almost equal.

The video signal whose level has been adjusted by the automatic gain adjustment circuit 6 is supplied to the image pickup system signal processing circuit 7.
The video signal is subjected to signal processing such as color balance adjustment, gamma correction, and generation of color difference signals by the image pickup system signal processing circuit 7 and is given to the synthesis circuit 8.

The video camera includes a PI signal generation circuit 30. The PI signal generating circuit 30 receives the horizontal synchronizing signal HD, the vertical synchronizing signal VD and the clock signal CK as SS.
It is given from G15 respectively. Based on these input signals, the PI signal generation circuit 30 generates the PI signal and the interval timing pulse that determines the shooting cycle at the high shutter speed. System controller 20 for interval timing pulses
Then, the PI signal is given to the synthesis circuit 8.

The synthesis circuit 8 superimposes the PI signal output from the PI signal generation circuit 30 on the video signal output from the image pickup system signal processing circuit 7.

An example of the PI signal is shown in FIG.

The PI signal shown in FIG. 5 is inserted in the initial period IT of the vertical blanking period associated with the video signal obtained by shooting at a shutter speed of 1/60 second of normal. The PI signal is not inserted in the vertical blanking period associated with the video signal obtained by shooting at a high shutter speed.

The vertical blanking period associated with a video signal is preferably the vertical blanking period that appears immediately before the video signal.

As shown in FIG. 4B, the PI signal is the 17th horizontal synchronizing signal and the 18th horizontal synchronizing signal in the vertical blanking period.
The signal is output from the PI signal generation circuit 20 at the timing of being superimposed on the video signal between the second horizontal synchronizing signals.

The video signal output from the synthesizing circuit 8 is applied to the recording system processing circuit 9. The recording system processing circuit 9 performs recording processing such as pre-emphasis (high frequency emphasis) and FM modulation on the video signal, and the processed video signal is recorded on the video tape 40 by the recording / reproducing head 10.

The video camera shown in FIG. 1 is also capable of performing reproduction processing, and the reproduction system signal processing circuit is used for the reproduction processing.
Includes 50.

In playback mode, video tape 40
The video signal recorded in (1) is read by the recording / reproducing head 10 and given to the reproduction system signal processing circuit 17. In the reproduction system signal processing circuit 17, the input video signal is demodulated, de-emphasized, etc., and output as a reproduction signal to the outside.

The luminance signal generated in the image pickup system signal processing circuit 7 is also applied to the first integrating circuit 21 or the second integrating circuit 22 via the changeover switch 25. The first integrator circuit 21 and the second integrator circuit 22 are respectively provided with a reset signal RST1 provided from the system controller 20.
And a circuit which is reset based on RST2 and integrates an input luminance signal for one image. Since the video camera shown in FIG. 1 is a field camera, the luminance signal for one field is integrated, but in the case of a frame camera, the luminance signal for one frame is integrated.

When the luminance signal output from the image pickup system signal processing circuit 7 is obtained by high-speed shutter speed photography, the changeover switch 25 outputs the output signal from the image pickup system signal processing circuit 7 on the a terminal side. When the luminance signal to be generated is obtained by photographing at a normal shutter speed, the terminal b side becomes conductive. The brightness signal for one field obtained by high-speed shutter speed photography is integrated in the first integration circuit 21, and is represented by the brightness signal integrated in the first integration circuit 21 in the second integration circuit 22. The luminance signal of the image adjacent to the image, which is the luminance signal for one field obtained by photographing at a normal shutter speed, is integrated.

First integrated by the first integrating circuit 21
And the second integrated value integrated by the second integrating circuit 22 are applied to the difference calculating circuit 23. The difference calculation circuit 23 is a circuit for calculating difference data between the input first integrated value and the second integrated value. The difference data calculated by the difference calculation circuit 23 is given to the hold circuit 24 and temporarily held.

The difference data held in the hold circuit 24 is held by the switch circuit 26 being turned on.
Read from. The switch circuit 26 is turned on when a video signal shot at a high shutter speed is input to the AGC 6.

When the switch circuit 26 is turned on, the difference data is output from the hold circuit 24, and this difference data is used as a gain correction signal as the system controller 20.
It is given to the AGC 6 as a control signal together with the gain control signal output from.

The characteristics of the AGC 6 are slightly changed due to changes with time, temperature changes, etc., and the level of a video signal taken at a high shutter speed is amplified to always be the same as the level of a video signal taken at a normal shutter speed. It doesn't. In the video camera shown in FIG. 1, the integrated value of the video signals representing adjacent images, that is, the integrated value of the video signals taken at a high shutter speed and the integrated value of the video signals taken at a normal shutter speed. The gain control signal given to the AGC 6 is corrected so that the difference disappears, that is, the integrated values of the respective video signals become equal. Therefore, regardless of changes in the characteristics of the AGC 6, the level of the video signal obtained by high-speed shutter speed photography is always equal to the level of the video signal obtained by normal shutter speed photography.

A block diagram showing a partial configuration of the PI signal generating circuit 30 is shown in FIG.

The PI signal generating circuit 30 includes a counter 31 and an encoder 32. The clock signal CK output from the SSG 13 is given to the counter 31 and the encoder 32, and the horizontal synchronizing signal HD and the vertical synchronizing signal VD are given to the counter 31, respectively.

The counter 31 includes a first counter for counting the horizontal synchronizing signal HD and a second counter for counting the vertical synchronizing signal VD. A value of 17 is preset in the first counter. Further, the second counter counts a value indicating a cycle (for example, 16 fields) at which shooting should be performed at a high shutter speed, and repeats this counting operation every cycle. The second counter encodes the first signal when counting the above period.
Give to 32.

The first counter of the counter 31 counts the horizontal synchronizing signal HD input from the start of the vertical blanking period based on the input of the vertical synchronizing signal VD, and the 17th horizontal synchronizing signal of the vertical blanking period. The signal HD is detected, and this detection signal is given to the encoder 32. The encoder 32 is
When the horizontal synchronizing signal detection signal is input, the PI signal (FIG. 5) is generated if neither the first signal nor the second signal is input from the second counter. This PI signal is given to the synthesis circuit 8.

The encoder 32 further outputs an interval timing pulse in response to the first signal provided by the second counter. This interval timing pulse is provided to the system controller 20. The system controller 20 commands the shutter control circuit 14 to perform high speed shutter speed operation in response to the input of the interval timing pulse.

The principle that a reproduced image can be prevented from being affected by flicker such as a fluorescent lamp by taking a picture once at a high shutter speed once in a field that is a multiple of 6 will be described.

FIG. 6 shows the vertical synchronizing signal VD ₁ , the light emission cycle when the fluorescent lamp is lit by an alternating current having a repetition frequency of 50 Hz, and the fluorescent lamp is lit by an alternating current having a repetition frequency of 60 Hz. In case of light emission period and 1
It shows the integrated value of the amount of light emitted by the fluorescent lamp when shooting at shutter speeds of / 100 seconds and 1/500 seconds.

When a fluorescent lamp is turned on by an alternating current having a repetition frequency of 50 Hz, the peak period is every 1/100 second. When the fluorescent lamp is turned on with an alternating current having a repetition frequency of 60 Hz, the peak period becomes every 1/120 second. For this reason, if the photographing is repeated at a shutter speed of 1/500 second faster than 1/100 second, the integrated amounts A ₁ , A ₂ , A ₃ of the video signal at the respective photographing timings are repeated.
Alternatively, B ₁ , B ₂ , and B ₃ are different, resulting in flicker.

On the other hand, since the photographing cycle is 1/60 second, 50
Even if the fluorescent lamp is turned on by an alternating current with a repetition frequency of 60 Hz or 60 Hz, even if the shutter speed is faster than 1/100 second, each shot is every three shots. The amount of integration of the video signal at the timing should be the same and flicker should be prevented.
Therefore, the integrated values A ₁ and A ₄ or B ₁ and B ₄ obtained by taking the image every three times should be equal to each other. However, there is a photoelectric difference in the fluorescent lamp when discharged from right to left and vice versa. For this reason, in the case of shooting every six times, the integration amount of the video signal at each shooting timing becomes the same and flicker is prevented. That is, the integrated values A ₁ and A ₇ and the integrated values B ₁ and B ₇ are equal.

In the video camera shown in FIG. 1, shooting is performed at a high shutter speed once for each successive field (6 fields, 12 fields, 18 fields, etc.) which is a multiple of 6. For this reason, the integration amount of the video signal at each photographing timing becomes the same, and flicker is prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a video camera.

FIG. 2 is a time chart at the time of shooting with the video camera shown in FIG.

FIG. 3 shows a configuration example of a PI signal generation circuit.

4A and 4B show signals recorded by the video camera shown in FIG. 1, where FIG. 4A is a recording signal of a plurality of fields, and FIG. 4B is a vertical blanking period of the recording signal shown in FIG. Shows.

FIG. 5 shows an example of a PI signal superimposed on a video signal.

FIG. 6 is a time chart for explaining prevention of flicker.

[Explanation of symbols]

 4 CCD 7 Imaging system signal processing circuit 14 Shutter control circuit 20 System controller 21 First integration circuit 22 Second integration circuit 23 Difference calculation circuit

Claims (4)

[Claims] 1. A shutter realization means for periodically repeating exposure of one of a plurality of consecutive frames of a plurality of shots at a high shutter speed, and other exposures at a normal shutter speed. First when exposed at speed
A video signal for outputting the second video signal when exposed at the high shutter speed, and the level of the first video signal is substantially equal to the level of the second video signal. An amplifier circuit for amplifying the first and second video signals output from the photographing means with two different amplification factors, and a first video signal for one frame represented by the first video signal. A first integrating means for integrating and outputting a first integrated value; a second integrating means for integrating a second video signal for one frame represented by the second video signal to output a second integrated value. Integrating means, calculating means for calculating the difference between the first integrated value and the second integrated value obtained from video signals representing the adjacent first image and second image, and the calculating means Based on the calculated difference, this A video camera provided with an adjusting means for adjusting two kinds of amplification factors of the above-mentioned amplifier circuits so as to eliminate the difference. 2. The video camera according to claim 1, wherein the exposure at the high shutter speed is performed once in the shooting of a plurality of frames which are multiples of 6 in succession. 3. The exposure is performed at a high shutter speed in one of a plurality of consecutive predetermined frames, and the rest is exposed at a normal shutter speed, and the exposure is repeated at the normal shutter speed. First when done
Second video signal is obtained when the second video signal is exposed at the high shutter speed, and the level of the first video signal is different so as to be substantially equal to the level of the second video signal. Amplification processing is performed on the first and second video signals output from the photographing means with different amplification factors, and the first video signal for one frame represented by the first video signal is integrated to obtain the first video signal. Is obtained, the second video signal for one frame represented by the second video signal is integrated to obtain a second integrated value, and the adjacent first image and second image are The difference between the first integrated value and the second integrated value obtained from the video signal represented is calculated, and based on the calculated difference, two different amplification factors in the amplification processing are set so as to eliminate this difference. How to adjust, how to control the video camera . 4. The method of controlling a video camera according to claim 3, wherein the exposure at the high shutter speed is performed once during the shooting of a plurality of consecutive frames in multiples of 6.