JPH0575896A - Video signal gain control device for video camera - Google Patents

Abstract

(57) [Abstract] [Purpose] To reproduce the gradation of the main subject beautifully regardless of backlight or forward lighting. [Constitution] The reflected light from the subject is imaged on the CCD image sensor by the lens and converted into an electric signal, the black level is adjusted by the black level adjusting means, and the gamma processing is performed by the gamma circuit, and then by the AGC circuit. The gain signal is adjusted, the luminance signal is output, the luminance signal is detected by the detection circuit and fed back to the control input of the AGC circuit, and the luminance distribution detection circuit detects the luminance distribution from the luminance signal. The constant is switched to optimize the detection characteristics of the AGC circuit. [Effect] The brightness of the main subject can be always kept appropriate for shooting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal gain of a video camera capable of obtaining an optimum gradation characteristic without blackout or overexposure regardless of conditions such as backlight and over-forward light. The present invention relates to a control device.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram of a video signal gain control device for a conventional video camera. In FIG. 10, 1 is a lens, 2 is a CCD image pickup device, 3 is an optical black clamp circuit, and 4 is a pedestal set circuit. Reference numeral 5 is a gamma circuit, and 6 is an automatic gain control circuit (hereinafter referred to as AGC circuit).

The luminance signal output from the AGC circuit 6 is detected by the luminance distribution detection circuit 7, passed through the amplifier circuit 8 and fed back to the AGC circuit 6. The internal structure of the brightness distribution detection circuit 7 is configured as shown in FIG.

That is, the start signal output from the AGC circuit 6 is applied to the base of the detection transistor Q1 as shown in FIG. The detection transistor Q1 has a collector connected to the power supply and an emitter connected to a resistor R
1 is connected to the input end of the amplifier circuit 8 and the connection point between the input end of the amplifier circuit 8 and the resistor R1 is the resistor R1.
2 and the capacitor C1 are grounded via a parallel circuit.

Next, the operation will be described. The light from the subject is imaged on the CCD image pickup element by the lens. This C
The electric signal photoelectrically converted by the CD image pickup device 2 is an optical black clamp circuit 3 and a pedestal set circuit 4.
The black level is adjusted by, the gamma processing is performed by the gamma circuit 5, and then the black level is input to the AGC circuit 6.

The luminance signal output from the AGC circuit 6 is detected by the detection circuit 7 and is fed back to the control input of the AGC circuit 6 through the amplifier 8.

Now, the operation of the AGC circuit 6 will be described in more detail. For example, the output of the AGC circuit 6 increases as the illuminance of the subject increases. As a result, the output of the brightness distribution detection circuit 7 also becomes high, and a high voltage is fed back to the control input of the AGC circuit 6.

The control input-output characteristics of this AGC circuit are
The output of the AGC circuit 6 becomes low because it works to reduce the gain for a high control input voltage. Even when the illuminance of the subject becomes low, the output voltage of the AGC circuit becomes high by the operation which is completely opposite to the above description.

As described above, the operation of the AGC circuit 6 always provides a constant luminance signal output regardless of the illuminance of the subject.

Next, the operation of the conventional luminance distribution detection circuit 7 shown in FIG. 11 will be described. The luminance signal output from the AGC circuit 6 is charged from the detection transistor Q1 through the resistor R1 into the capacitor C1 and simultaneously discharged through the resistor R2.

Due to the balance between the resistors R1 and R2, if the charging current is larger, the peak detection is closer to the peak, and a slight high-brightness spot is likely to be reflected in the detection output voltage. However, if the charging current and the discharging current are equal, The average value is detected, and the average value of the luminance signal is the detection output voltage. In any case, the AGC circuit 6 operates so that the detected output voltage is always constant.

Now, consider the case where a part of the subject includes a high-luminance spot. When complete peak detection is performed, the high-brightness spot is reflected in the detection output, so there is no blowout of the high-brightness spot, but the other parts are blackened.

On the other hand, when the average value detection is used, blackening of the entire screen disappears, but high-luminance spots are blown out. Depending on the subject, the high-intensity part may or may not be the main subject, and it is difficult to set a detection time constant that satisfies all subject.

Next, an actual subject will be described as an example with reference to FIGS. First, FIG. 16 shows a normal illuminating subject. The outer frame in the figure shows the imaging screen 101, and the inner frame shows the photometric area 102. In the consumer video camera, a photometric area 102 is provided in the center of the screen where many main subjects are present in order to realize center-weighted photometry. In the case of normal light, the luminance distribution is uniform. Therefore, if the average output level (APL) is 50%, the luminance signal rises and falls around approximately 50% as shown in FIG. Absent.

Next, FIG. 12 shows a backlit subject. In this case, since direct sunlight is shining on the person 103 other than the main subject, only the person 103 is dark and the others are bright. In this situation, if APL is set to 50%,
As can be seen from the luminance signal waveform shown in, the person is crushed in black.

Next, FIG. 14 shows an object with excessive forward light. This is the case with spotlights on a pitch-black stage. If APL is set to 50% by the average value detection in this situation, as can be seen from the luminance signal waveform in FIG.
The person 103, which is the main subject, is completely overexposed. This case can be solved by performing complete peak detection, but in any case, with the fixed detection time constant as in the conventional case, it is difficult to set all of FIG. 12, FIG. 14, and FIG.

[0017]

Since the conventional video signal gain control device for a video camera is constructed as described above, a main subject is crushed by black and underexposure occurs under conditions such as backlight and over-forward light. There was a problem that it was easy. In addition,
As approximation techniques, for example, JP-A-61-96876, JP-A-63-67874, and JP-A-2-17 are available.
9174, etc.

The first aspect of the present invention has been made to solve the above problems, and a video signal gain of a video camera which beautifully reproduces the gradation of a main subject under conditions such as backlight and over-forward light. The purpose is to obtain a control device.

It is an object of the present invention to provide a video signal gain control device for a video camera, which can more finely deal with backlight, forward light and over-forward light and can beautifully reproduce the gradation of a main subject.

It is an object of the present invention to provide a video signal gain control device for a video camera, which can switch the detection time constant and can always hold the brightness of the main subject in an optimum condition for shooting. ..

[0021]

According to a first aspect of the present invention, there is provided a video signal gain control device for a video camera, wherein a plurality of detection time constants can be switched and a detection circuit for detecting a luminance signal and a luminance distribution of an object are measured. A luminance distribution detection circuit for determining whether the main subject is normal light or backlight and selecting the detection time constant of the detection circuit based on the determination result.

A video signal gain control device for a video camera according to a second aspect of the present invention is provided with a brightness distribution detecting circuit for judging back light, forward light, and over-back light from the respective brightness distributions of a plurality of divided image pickup screens. Is.

A video signal gain control device for a video camera according to a third aspect of the present invention is provided with a luminance distribution detection circuit for switching the detection time constant of the detection circuit according to the luminance distribution of the image pickup screen.

[0024]

According to the first aspect of the present invention, the luminance signal is detected by the detection circuit, the luminance distribution of the subject is measured by the luminance distribution detection circuit, and it is determined from the measurement result whether the main subject is normal light or backlight. Then, the detection time constant of the detection circuit is selected according to the result of the judgment.

According to the second aspect of the present invention, the brightness distribution detecting circuit determines the backlight, the forward light, and the over backlight by detecting the brightness distribution of each of the plurality of divided image pickup screens.

According to the third aspect of the present invention, the luminance distribution detection circuit detects the luminance distribution of the image pickup screen, and the detection time constant is switched according to the detection result.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a video signal gain control device for a video camera of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the structure of an embodiment of the present invention. In FIG. 1, the same parts as those in FIG.

In FIG. 1, 1 is a level, 2 is a CCD image pickup device, 3 is an optical black clamp circuit, 4 is a pedestal set circuit, 5 is a gamma circuit, 6 is an AGC circuit, 9 is a detection circuit, and 8 is detection. An amplification circuit for amplifying the output and feeding it back to the AGC circuit 6 is a luminance distribution detection circuit.

In FIG. 1, a detection circuit 9 is newly added to the configuration of FIG. 10, and this detection circuit 9 detects the luminance signal output from the AGC circuit 6 and outputs the detection output to the amplification circuit 8. It is possible to switch a plurality of detection time constants.

The switching of the detection time constant is performed by the luminance distribution detection circuit 7. The brightness distribution detection circuit 7 detects the brightness signal output from the AGC circuit 6,
Detects whether the subject is normal light, backlight, or excessive backlight,
The detection time constant is switched according to the detection result.

The connection between the internal structure of the detection circuit 9 and the luminance distribution detection circuit 7 is shown in FIG. In FIG. 2, the bases of the detection transistors Q2 to Q3 are
It is connected to the output terminal of the AGC circuit 6, and the luminance signal is input to each. The collectors of these detection transistors Q2 to Q4 are respectively connected to the power supply.

The collector of the transistor Q2 is a switch S.
It is connected to one movable terminal S1a. This switch S
The fixed terminal S1b of No. 1 is connected to the input terminal of the amplifier circuit 8. Further, the emitter of the detection transistor Q2 is a resistor R
3 and the capacitor C2 are grounded via a parallel circuit. Thus, the detection transistor Q2, the resistor R3, the capacitor C2, and the switch S1 form a first detection circuit.

The emitter of the detection transistor Q3 is connected to the movable terminal S2a of the switch S2 through the resistor R4, and is also grounded through the parallel circuit of the resistor R5 and the capacitor C3. The fixed terminal S2b of the switch S2 is connected to the input terminal of the amplifier 8. Thus, the detection transistor Q3, the resistors R4 and R5, the capacitor C2, and the switch S2 form a second detection circuit.

Similarly, the emitter of the detection transistor Q4 passes through the resistor R6 and the movable terminal S3a of the switch S3.
Connected to a resistor R7 and a capacitor C4
It is grounded through a parallel circuit with. Switch S3
The fixed terminal of is connected to the input end of the amplifier circuit 8. Detection transistor Q4, resistors R6 and R7, capacitor C
4, the switch S3 constitutes a third detection circuit. The first to third detection circuits have different time constants. Movable terminals S1a to S of the switches S1 to S3
3a is selectively switched by the output of the luminance distribution detection circuit 7.

Next, the operation will be described. The light from the subject is imaged on the CCD image pickup device 2 by the lens 1. Then, the black level is adjusted by the black level adjusting means by the optical black clamp circuit 3 and the pedestal set circuit 4, and the gamma circuit 5 receives the gamma processing and then inputs it to the AGC circuit 6.

The luminance signal output from the AGC circuit 6 is detected by the detection circuit 9, passed through the amplifier 8 and fed back to the control input of the AGC circuit 6.

At the same time, the luminance signal is input to the luminance distribution detection circuit 7, and the information such as the backlight, the forward light and the over-forward light determined here is input to the detection circuit 9.

FIG. 2 shows an embodiment around the luminance distribution detecting circuit 7 and the AGC circuit 6 according to the present invention.
The luminance signal output from the circuit 6 is the detection transistors Q2, Q3,
It is input in parallel to Q4 and has different time constants
It is input to the third detection circuit.

In the figure, the detection transistor Q2, the resistor R3,
The first detection circuit composed of the capacitor C2 is an almost perfect peak detection circuit, and the third detection circuit composed of the detection transistor Q4, resistors R6 and R7, and the capacitor C4 is an average value detection circuit. Although three types of detection circuits are shown in the figure, the greater the number, the finer the control is possible.

On the other hand, the brightness signal output from the AGC circuit 6 is input to the brightness distribution detection circuit 7. Here, the backlight, the over-forward light, and the forward light are detected by the pattern of the brightness distribution. 3 to 5
Shows this detection method. The central 9-division lattice in the diagrams of FIGS. 3 to 5 indicates the luminance detection range. White areas in the grid indicate high brightness areas, shaded areas indicate normal brightness areas, and fine hatched areas indicate low brightness areas.

In FIG. 3, since the central portion of the screen, which is the main subject, is dark and the peripheral portion is bright, it is judged that the backlight is present and the detection time constant near the average value is selected to make it less susceptible to the white peak in the peripheral portion. It works to improve the blackout of the main subject.

Further, in FIG. 4, since the central portion of the screen, which is the main subject, is very bright and the peripheral portion is dark, it is determined that the light is over-forward and peak detection is selected to improve the whiteout of the main subject. work.

In FIG. 5, since the entire screen has normal brightness, it is determined that the light is normal light, and the intermediate detection characteristic of the above two examples is selected.

Next, the effect of the present invention will be described by taking an actual subject as an example. FIG. 6 shows an example of over-forward light. When a person is in the spotlight on a dark stage, the person who is the main subject will fly completely white with the normal detection characteristics shown in FIG. 7A. Therefore, by detecting over-forward light and setting peak detection according to the present invention,
As shown by the luminance signal waveform in FIG. 7B, the person who is the main subject can be reproduced with appropriate luminance.

FIG. 8 shows an example of backlight. When a person is photographed against the sun, the person is crushed in black with the normal detection characteristics as shown in FIG. 9A. Therefore, by detecting the backlight according to the present invention and setting the average value detection as shown in FIG. 9B, the influence of the sun is less likely to occur and the blackout of the person can be improved.

[0046]

As described above, according to the invention of claim 1, the brightness distribution of the object is detected by the brightness distribution detection circuit,
Since the detection characteristic of the AGC circuit is optimally controlled based on the result, it is possible to shoot while maintaining the brightness of the main subject always proper even in the case of backlight, over-forward light and the like.

According to the second aspect of the present invention, the image pickup screen is divided into a plurality of parts, and the brightness distribution of each image pickup screen
Since the backlight distribution, the forward light, the excessive backlight, and the like are determined by the brightness distribution detection circuit, the brightness of the main subject can be more appropriately kept and the image can be captured.

Further, according to the third aspect of the present invention, the luminance distribution of the image pickup screen is detected by the luminance distribution detection circuit, and the detection time constant is switched according to the detected luminance distribution. It is possible to shoot while keeping the brightness of the subject optimal.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal gain control device for a video camera according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of a detection circuit and a configuration of a peripheral portion thereof in the embodiment.

FIG. 3 is an explanatory diagram when the luminance distribution detection circuit in the above-described embodiment detects the luminance of the main subject at the time of backlighting.

FIG. 4 is an explanatory diagram when the luminance distribution detection circuit in the above-described embodiment detects the luminance of the main subject during over-forward light.

FIG. 5 is an explanatory diagram when the luminance distribution detection circuit in the above-described embodiment detects the luminance of the main subject during normal lighting.

FIG. 6 is an explanatory diagram of a main subject at the time of forward light applied to the embodiment.

FIG. 7 is a waveform diagram for explaining detection characteristics of the main subject of FIG. 6 when photographing.

FIG. 8 is an explanatory diagram of a main subject at the time of backlighting applied to the embodiment.

9 is a waveform diagram for explaining the detection characteristics of the main subject in FIG. 8 during shooting.

FIG. 10 is a block diagram of a video signal gain control device for a conventional video camera.

11 is a block diagram of an internal configuration of a luminance distribution circuit and its peripheral portion in the video signal gain control device of the video camera of FIG.

12 is an explanatory diagram of a main subject at the time of backlighting applied to the video signal gain control device of the video camera of FIG.

13 is a waveform diagram of a luminance signal at the time of photographing the main subject of FIG.

14 is an explanatory diagram of a main subject at the time of over-lighting, which is applied to the video signal gain control device of the video camera of FIG.

15 is a waveform diagram of a luminance signal at the time of photographing the main subject of FIG.

16 is an explanatory diagram of a main subject at the time of forward light applied to the video signal gain control device of the video camera of FIG.

17 is a waveform diagram of a luminance signal when the main subject of FIG. 16 is photographed.

[Explanation of symbols]

 1 lens 2 CCD image sensor 3 optical black clamp circuit 4 pedestal set circuit 5 gamma circuit 6 AGC circuit 7 brightness distribution detection circuit 8 amplification circuit 9 detection circuit Q2 detection transistor Q3 detection transistor Q4 detection transistor C2 capacitor C3 capacitor C4 capacitor S1 switch S2 Switch S3 switch

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[Procedure amendment]

[Submission date] July 9, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

The luminance signal output from the AGC circuit 6 is detected by the detection circuit 7, passes through the amplification circuit 8, and then the AGC.
It returns to the circuit 6. The internal configuration of the detection circuit 7 is configured as shown in FIG.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

That is, the brightness output from the AGC circuit 6
The frequency signal is applied to the base of the detection transistor Q1 as shown in FIG. The detection transistor Q1 has a collector connected to the power supply and an emitter connected to a resistor R
1 is connected to the input end of the amplifier circuit 8 and the connection point between the input end of the amplifier circuit 8 and the resistor R1 is the resistor R1.
2 and the capacitor C1 are grounded via a parallel circuit.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

Now, the operation of the AGC circuit 6 will be described in more detail. For example, the output of the AGC circuit 6 increases as the illuminance of the subject increases. As a result, the detection times
The output of path 7 is also high and a high voltage is fed back to the control input of AGC circuit 6.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

Next, the operation of the conventional detection circuit 7 shown in FIG. 11 will be described. The luminance signal output from the AGC circuit 6 passes from the detection transistor Q1 through the resistor R1 to the capacitor C1.
And is discharged at the same time through the resistor R2.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

In FIG. 1, 1 is a lens , 2 is a CCD image pickup device, 3 is an optical black clamp circuit, 4 is a pedestal set circuit, 5 is a gamma circuit, 6 is an AGC circuit, 7 is a detection circuit, and 8 is detection. An amplification circuit that amplifies the output and returns it to the AGC circuit 6, and 9 is a brightness distribution detection circuit.

[Procedure Amendment 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

In FIG. 1, a luminance is newly added to the configuration of FIG.
A distribution detection circuit 9 is added to detect the brightness distribution.
The path 9 depends on the distribution of the luminance signal output from the AGC circuit 6 .
In addition, backlight, forward light, and over-light are detected.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

Backlight detected by the brightness distribution detection circuit 9, forward
The information of light and over-forward light is sent to the detection circuit 7, and this information is
Originally, multiple detection time constants can be switched.
It

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

The connection between the internal structure of the detection circuit 7 and the luminance distribution detection circuit 9 is shown in FIG. In FIG. 2, the bases of the detection transistors Q2 to Q4 are
It is connected to the output terminal of the AGC circuit 6, and the luminance signal is input to each. The collectors of these detection transistors Q2 to Q4 are respectively connected to the power supply.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

Similarly, the emitter of the detection transistor Q4 passes through the resistor R6 and the movable terminal S3a of the switch S3.
Connected to a resistor R7 and a capacitor C4
It is grounded through a parallel circuit with. Switch S3
The fixed terminal of is connected to the input end of the amplifier circuit 8. Detection transistor Q4, resistors R6 and R7, capacitor C
4, the switch S3 constitutes a third detection circuit. The first to third detection circuits have different time constants. Movable terminals S1a to S of the switches S1 to S3
3a is selectively switched by the output of the luminance distribution detection circuit 9 .

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

The luminance signal output from the AGC circuit 6 is detected by the detection circuit 7 , passed through the amplifier 8 and fed back to the control input of the AGC circuit 6.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

At the same time, the brightness signal is input to the brightness distribution detection circuit 9 , and the information such as the back light, the forward light, and the over-forward light determined here is input to the detection circuit 7 .

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

FIG. 2 shows a luminance distribution detecting circuit according to the present invention.
9 and an example around the AGC circuit 6 are shown.
The luminance signal output from the circuit 6 is the detection transistors Q2, Q3,
It is input in parallel to Q4 and has different time constants
It is input to the third detection circuit.

[Procedure Amendment 13]

[Document name to be amended] Statement

[Item name to be corrected] 0040

[Correction method] Change

[Correction content]

On the other hand, the brightness signal output from the AGC circuit 6 is input to the brightness distribution detection circuit 9 . Here, the backlight, the over-forward light, and the forward light are detected by the pattern of the brightness distribution. 3 to 5
Shows this detection method. The central 9-division lattice in the diagrams of FIGS. 3 to 5 indicates the luminance detection range. White areas in the grid indicate high brightness areas, shaded areas indicate normal brightness areas, and fine hatched areas indicate low brightness areas.

[Procedure Amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

Next, the effect of the present invention will be described by taking an actual subject as an example. FIG. 6 shows an example of over-forward light. When a person is in the spotlight on a dark stage, as shown in FIG. 7A , with a normal detection characteristic, the person who is the main subject flies completely white. Therefore, by detecting the over-forward light and setting the peak detection according to the present invention, it is possible to reproduce the person who is the main subject to an appropriate brightness as shown by the brightness signal waveform in FIG. 7B.

[Procedure Amendment 15]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

FIG. 6 is an explanatory diagram of a main subject at the time of over- lighting applied to the embodiment.

[Procedure 16]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 11

[Correction method] Change

[Correction content]

11 is a block diagram of an internal configuration of a detection circuit and its peripheral portion in the video signal gain control device of the video camera of FIG.

[Procedure Amendment 17]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Description of symbols] 1 lens 2 CCD image sensor 3 optical black clamp circuit 4 pedestal set circuit 5 gamma circuit 6 AGC circuit 7 detection circuit 8 amplification circuit 9 luminance distribution detection circuit Q2 detection transistor Q3 detection transistor Q4 detection transistor C2 capacitor C3 capacitor C4 capacitor S1 switch S2 switch S3 switch

[Procedure Amendment 19]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure amendment 20]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure correction 21]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

[Procedure correction 22]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

[Procedure amendment 23]

[Document name to be corrected] Drawing

[Correction target item name] Figure 12

[Correction method] Change

[Correction content]

[Fig. 12]

Claims (3)

[Claims] 1. An image pickup device for forming a subject image and converting it into an electric signal, a black level adjusting means for adjusting a black level of the electric signal, and a gamma circuit for gamma processing an output of the black level adjusting means. An automatic gain control circuit for performing gain control of the output of the gamma circuit to output a luminance signal, a detection circuit for detecting the luminance signal and feeding back the detection output to the control input of the gain control circuit, and the luminance signal A video signal gain control device for a video camera, comprising: a luminance distribution detection circuit for detecting and switching the time constant of the detection circuit. 2. The video signal of the video camera according to claim 1, wherein the brightness distribution detection circuit determines backlight, forward light, and over-light based on the respective brightness distributions of the video screen divided into a plurality of parts. Gain control device. 3. The video signal gain control device for a video camera according to claim 1, wherein the luminance distribution detection circuit switches the detection time constant of the detection circuit in accordance with the luminance distribution of the image pickup screen.