JPH01151893A - Television camera - Google Patents

Abstract

PURPOSE:To avoid the deformed color balance by providing AGC detection circuit and an AGC amplifier circuit inputting an output of an AGC voltage sampling and holding circuit inputting an output of the AGC detection circuit to its control terminal so as to obtain a picture with proper lightness automatically even when the lightness of an object is changed. CONSTITUTION:An achromatic filter having an average transmittivity of each color filter 4 is placed in front of a lens 2 to pick up an object. With the AGC voltage sampling and holding circuit 11 kept to the hold release state in this case, the AGC circuit is operated and a video signal with a proper level is obtained. Then the AGC voltage sampling and holding circuit 11 is kept in the holding state, each color filter 4 is placed sequentially in front of the lens to fetch each color video signal into a picture memory 9. Since the AGC voltage is fixed, the gain of the AGC amplifier circuit is constant and the color balance is not unbalanced. Furthermore, an automatic dimmer circuit 15 is used to activate similarly the sampling and holding of the dimmer voltage, then a video image with a proper lightness is obtained even from an object with any luminous quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television camera, and in particular to an A of a television camera.
This invention relates to the configuration of a GC circuit and an automatic light control circuit.

[Conventional technology]

Conventionally, for example, a red filter, an edge filter, and a blue filter are sequentially installed in front of a lens, and the video signals for each filter are captured into an image memory and then reconstructed to obtain a color image. Television cameras can image objects of any brightness by adjusting the amount of light that enters the image sensor and the AGC circuit that keeps the size of the video signal constant even if the brightness of the object changes slightly. Time too,
There was no automatic light control circuit that could obtain images with appropriate brightness.

This is because each filter transmits a different amount of light, which causes the AGC circuit and automatic light adjustment circuit to work (and the color balance to shift).

In this case, a lens with a manual aperture was used as a means to adjust the amount of light depending on the brightness of the subject.

[Problem that the invention seeks to solve]

However, with the above-mentioned conventional technology, when the brightness of the subject changes, the large group of video signals changes, making it impossible to capture an image with appropriate brightness. Furthermore, there is a problem in that the iris of the manual aperture lens must be set each time depending on the brightness of the subject.

The present invention is intended to solve these problems, and its purpose is to automatically obtain images with appropriate brightness even if the brightness of the subject changes, and to eliminate the problem of color balance. There is also no TV camera provided.

[Means for solving problems]

The television camera of the present invention sequentially places color filters in front of a black and white television camera, captures video signals of each color into an image memory, and then reconstructs them to obtain a color image. circuit and A
AGCff! whose input is the GC detection circuit output. The present invention is characterized in that an AGC amplification circuit is provided which uses the output of the voltage sample and hold circuit as a control terminal input.

Furthermore, an automatic dimming detection circuit, a dimming voltage sample and hold circuit that receives the output of the automatic dimming detection circuit, and an automatic dimming output circuit that receives the output of the dimming voltage sample and hold circuit as input are further provided. Features.

〔（乍用〕）

According to the above configuration of the present invention, first, a colorless filter having an average transmittance of each color filter is placed in front of the lens, and an image of a subject is captured. At this time, the AGC voltage
Leave the pull-hold circuit in the hold release state. Then, the AGC circuit turns on and a video signal of an appropriate size is obtained. Next, after putting the AGC voltage sample and hold circuit into a hold state, each color filter is placed in front of the lens in order, and the video signal of each color is taken into the image memory. At this time,
Since the AGC voltage is fixed, the gain of the AGC amplifier circuit is constant, and the color balance will not be disturbed.

Furthermore, by similarly operating the sampling and holding of the dimming voltage using an automatic dimming circuit, an image with appropriate brightness can be obtained for any subject regardless of the amount of light.

〔Example〕

FIG. 1 is a block diagram of a television camera in an embodiment of the present invention. Reference numeral 1 denotes an image sensor, which converts a light image into an electrical signal according to the amount of light. Solid-state imaging devices such as CCDs are becoming mainstream. 2 is a lens, and 3 is a light control device such as an aperture. 4 is a color filter; for example, primary color filters of red, blue, and green are sequentially placed in front of the lens, and the light filtered by each color filter is sent to the image sensor 1 through the lens 2 and the light control device 3. lead 5 is a preamplifier that amplifies the electrical signal output from the image sensor l;
6 is an AGC amplifier circuit whose amplification degree changes depending on the voltage of the control terminal 16; 7 is a process amplifier that performs white level clipping, γ correction, blanking, etc.; 8 is an A/D converter that converts a video signal into a digital signal; 8 is an image memory.

Reference numeral 10 denotes an AGC detection circuit which receives the output signal of the process amplifier 7 and outputs the average value or peak value of the output signal as a DC voltage. 11 is a state in which the output of the AGC detection circuit 10 is output to the control terminal 16 of the AGC amplifier circuit 6 without any processing (hereinafter referred to as a hold release state), and a state in which the output voltage of the AGC amplifier circuit 10 is held for a certain period of time. Next, the control terminal 22 of the AGC amplifier circuit 6
The AGC flt pressure sample water sample hold circuit 3, which can set two states of output (hereinafter referred to as hold state) using the signal of the sample hold terminal 12, receives the output signal of the AGC amplifier circuit G as an input. This is an automatic dimming detection circuit that outputs the average value or peak value of the output signal as a DC voltage. 14C is a dimming voltage sample and hold circuit, which, like the AGC sample and hold circuit 11, can set the output voltage of the automatic dimming detection circuit 13 to two states: a hold release state and a hold state.

Control is similarly performed using a signal at the sample hold control terminal 12.

Reference numeral 15 denotes an automatic dimming output circuit, which outputs a signal for driving the dimming device 3 from the output of the dimming voltage sample and hold circuit 14.

If the hold is now released, the AGC detection circuit 10 will send the AGC
ffi pressure is output. The AGC voltage passes through the AGC voltage sampling circuit 11 and is input to the control terminal of the AGC amplifier circuit 6. When the AGCffi pressure is large, the gain of the AGC amplifier circuit 6 becomes small, and the output of the process amplifier 7 is controlled to become small. As a result, even if the brightness of the subject changes to some extent, the magnitude of the output signal from the process amplifier 7 remains almost unchanged.

The control range of the AGC circuit has a limit (usually about 10 times the brightness range), so if the subject is brighter than that, use the light control device 3 to control the amount of light that reaches the image sensor 1. Set 3 to . That is, depending on the magnitude of the output signal of the AGC amplifier circuit 6, which has already reached the minimum gain, the self! I
! A dimming voltage is output from the l7Us photodetection circuit 13. The dimming voltage passes through the dimming voltage sample and hold circuit 14, is applied to the automatic dimming output circuit 15, and is applied to the dimming device 3.
to drive. As a result, even if the brightness of the subject exceeds the AGC range, the magnitudes of the output of the AGC amplifier circuit 6 and the output signal of the process amplifier 7 are controlled to remain approximately constant.

When the hold is released as described above, the magnitude of the video signal is automatically controlled to be approximately constant regardless of the brightness of the subject, and an image with appropriate brightness can be obtained.

Next, when the hold state is set, the output voltage of the AGC voltage sample and hold circuit 11 and the output voltage of the dimming voltage sample and hold circuit 12 are fixed, so the AGC amplifier circuit 6
The gain of is fixed, and the light transmission rate of the light control device 3 is also fixed. In this state, the color filters 4 are sequentially set in front of the lenses, and the output signal of the process amplifier 7 is
The image is taken into the image memory 9 through the D converter 8. The color filter 4 usually has three primary colors: red, blue, and green. Color filters have low light transmittance, so when the hold is released,
A colorless filter (ND) with an average transmittance of a color filter
If you set the filter), then put it in the hold state and capture the video signal when each color filter is set,
Images with appropriate brightness can be obtained.

FIG. 2 shows an explanatory diagram of a sample bold circuit.

In Figure 2, 18 is an input terminal, 19 is an output terminal, 2
0 is a control terminal, 21 is a switch, and 22 is a holding capacitor.

When the switch 21 is turned on by the control terminal 20, the input voltage is directly output as the output voltage. When the switch 21 is off, the voltage on the verge of off is held by the holding capacitor 22, and the output voltage is fixed at the voltage on the verge of off, regardless of the input voltage.

When the switch 21 is on, it is a hold release state, and when it is on, it is a hold state.

〔Effect of the invention〕

As described above, according to the invention, an AGC amplification circuit is provided, and even if the brightness of the subject changes within a certain range, an image with appropriate brightness can be obtained. Furthermore, since the AGC voltage sample and hold circuit is provided, the color balance is not disturbed.

Furthermore, by providing an automatic light control circuit, an image with appropriate brightness can be obtained even if the brightness of the subject varies over a wide range beyond the AGC range. Also, by providing a dimming voltage sample and hold circuit, the color balance will not be disrupted.

In this way, it was possible to provide a television camera that can obtain images with appropriate brightness and color balance over a wide illuminance range.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the television camera of the present invention. FIG. 2 is an explanatory diagram of the sample and hold circuit. 1...Image sensor 2...Lens 3...Dimmer 4...Color filter 5...Preamplifier 6...AGC amplifier circuit 7...Process amplifier 8...A/D Converter 9... Image memory 10... AGC detection circuit 11... AGC? ! Pressure sample hold circuit 12...
- Sample hold control terminal 13... Automatic dimming detection circuit 14... Dimming voltage sample hold circuit 15... Automatic dimming output circuit 16... Control terminal 18... Input terminal 19... Output Terminal 20...Control terminal 21...Switch 22...Holding capacity Applicant: Seiko Epson Corporation

Claims (2)

[Claims] (1) a) In a television camera of a camera system that sequentially places color filters in front of the lens of a black-and-white television camera and captures the video signals of each color into the image memory and then reconstructs them to obtain a color image, b) AGC A television camera comprising: a detection circuit; c) an AGC voltage sample and hold circuit that receives the output of the AGC detection circuit as an input; and d) an AGC amplifier circuit that uses the output of the AGC voltage sample and hold circuit as a control terminal input. (2) a) an automatic dimming detection circuit; b) a dimming voltage sample and hold circuit that receives the output of the automatic dimming detection circuit as an input; and c) an automatic dimming output circuit that receives the output of the dimming voltage sample and hold circuit as an input. A television camera according to claim 1, characterized in that the television camera is provided with: