KR900006469B1 - Automatic white level control circuit for video camera - Google Patents

Abstract

The method comprises (a) initializing colour signal output of a microprocessor and detecting the state of an automatic white level control switch, (b) returning to (a) or detecting the output of a second detector according to the state of said switch, (c) providing the colour signal and returning to (b) or comparing the absolute values of the output data of the first detector and the colour temperature value stored in memory with a predetermined value when the output of the second detector is not detected, (d) calculating the proper colour signal output when the absolute value is larger than the predetermined value, and (e) providing the colour signal according to the vertical synchronizing signal and returning to (b).

Description

Automatic White Level Control for Video Cameras

1 is a circuit diagram of an apparatus according to the method of the present invention.

2 is a flowchart for explaining the method of the present invention.

* Explanation of symbols for main parts of the drawings

1: color detectors 2,3: first and second detectors

4 sample and hold 5 converter

7: microcomputer 9,9 ': lowpass filter

The present invention relates to a method for automatically controlling a white level of a video camera, and more particularly, to a method for automatically controlling a white level for a video camera for installing a color detector to detect color temperature information and automatically controlling a white level.

Conventional video cameras are not equipped with a white level automatic control device, so when shooting a very bright place while shooting a very dark place there is a disadvantage that the shooting brightness is not matched and the screen is erased for a while.

Particularly, during the live broadcasting of soccer games, the shadow background part and the background part where the sunlight shines are taken alternately, and the screen becomes temporarily dark when shooting by moving the shadow background part rapidly from the background part where the sunlight shines. When the user cannot watch the screen and shoots by moving rapidly from the shadow background part to the background part where the sunlight shines on, the screen is temporarily very bright and there is a disadvantage that the screen cannot be viewed.

In order to solve the above disadvantages, the present invention detects the color temperature of the object and automatically controls the level of the white signal, thereby rapidly rotating the camera from the light background part to the dark background part or from the dark background part to the light background part. Another object of the present invention is to provide a method for automatically controlling a white level for a video camera, which can prevent viewing of a screen even when moving and photographing. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 and 2, the configuration of the apparatus related to the method of the present invention connects the signal from the imaging tube 10 in the video camera to the microcomputer 7 via the analog digital converter 11, and the vertical synchronization. The signal input VS and the oscillator 12 are connected to the microcomputer 7, and the color signal outputs R and B of the microcomputer 7 are respectively connected to the digital analog converters 6 and 6 'and the buffers 8 and 8. ') And low pass filters 9 and 9' to the control signal terminals RC and BC, and the output of the color detector l to the first and second detectors 2 and 3 respectively. The output of the first detector 2 is inputted as color temperature information to the microcomputer 7 through the sample and hold unit 4 and the analog digital converter 5, and the output of the second detector 3 is of low illuminance. It is connected to the microcomputer 7 by the detection output of.

The method of the present invention in connection with such a device comprises the first step of initializing the color signal outputs R and B of the microcomputer 7 and then detecting whether the automatic white level adjustment switch is turned on, and the automatic white level adjustment switch is turned on. If not, return to the first process and if it is on, the second process of detecting whether there is an output of the second detector 3, and if there is an output of the second detector 3, the color signal outputs R and B are output. Without returning to the process, the output of the first detector 2 is retrieved as data TC through the sample and hold section 4 and the analog digital converter 5 and stored in the memory inside the microcomputer 7. The absolute value Dif of the data TC and the color temperature value Dm is calculated in comparison with the value Dm so that the absolute value Dif is larger than the set value E stored in the memory inside the microcomputer 7. The third process of detecting whether the value is larger and the absolute value Dif is larger than the set value E Otherwise, the process returns to the second process and if the absolute value Dif is larger than the set value E, the color temperature value Dm of the memory is changed to the data TC, and the color signal outputs R and B suitable for the current color temperature TC are used. And a fourth process of detecting whether there is a vertical synchronization signal input VS, and if there is no vertical synchronization signal VS, wait until there is a vertical synchronization signal VS, and if there is a vertical synchronization signal VS, the color signal output R Outputs B, detects whether the automatic white level control switch is turned off, and returns to the second process if it is not turned off, and ends the fifth process if it is turned off.

Referring to the operation and effect of this method of the present invention. When the camera is powered up, the program starts running. That is, as shown in FIG. 2, the camera starts power-on and initializes data R, B, and E (where E represents an error value) required for processing.

The data R and B are data for output and are related to the control voltage of the wide area amplifier of the video camera.

Next, it is determined whether the automatic white level control switch is turned on or off. Determination is possible by searching for the automatic white level control switch on signal of FIG.

If it is determined that the automatic white level control switch is on, the process proceeds to the next step in order to perform automatic white control, and when the automatic white level control switch is off, it is in a standby state, and once the automatic white level control switch is turned on, data R and B are output.

At this time, the data R and B are initial values.

Next, it is determined whether the subject portion is in a low illumination state.

Even in low light conditions, automatic white level control (hereinafter referred to as AWC) has no meaning.

This is because the color distinction of the subject becomes unclear at low light. Therefore, at this time, the AWC is not necessary according to the color temperature of the light source, so a specific value (initial value) is output.

In FIG. 1, the second detector 3 detects low light, and the microcomputer 7 receives the output signal of the second detector 3 to determine whether the low light is low.

If the amount of light is sufficient, the color temperature information TC is received.

The received color temperature information TC is compared with the data Dm of the memory, and it is determined whether the difference Dif is greater than a specific value E. If the difference is large, the color temperature TC is stored instead of the memory data Dm. If it is small, it returns to the second process of detecting low light.

This process compares the currently accepted color temperature information (TC) with the previously received color temperature information (information stored in the Dm memory), and if the difference is small, it is possible to perform stable control by not changing the output data.

If the difference is large, the current color temperature information TC is stored in the memory for comparison with the next color temperature information to be received.

Next, output data (R, B) corresponding to the current color temperature information is calculated, output data (R, B) is output when a vertical synchronization signal is received, and waits when vertical synchronization is not entered.

Output data (R, B) is passed through the digital analog converter (6, 6 '), buffers (8, 8'), low pass filters (9, 9 '), control voltage output (RC, BC).

Outputting these values during the vertical synchronization period is to prevent the color from changing in the middle of the image (one screen).

If the automatic white level control switch is turned off, the AWC operation ends, otherwise the process returns to the second process and repeats the operation.

As described above, according to the method of the present invention, the optimum white level can be automatically controlled according to the color temperature of the subject to cope with a sudden change in the illumination of the subject of the video camera, thereby preventing the screen from being erased for a while. You can do it.

Claims (1)

Initializing the color signal output (R, B) of the microcomputer (7) and then detecting whether the automatic white level control switch is on, and if the automatic white level control switch is not on, the process returns to the first process. A second process of detecting whether there is an output of the second detector 3 if it is on, and a color signal output (R, B) if there is an output of the second detector 3, and a first detector if it is not returned to the second process. The output of (2) is taken as data TC through the sample and hold section 4 and the analog digital converter 5 and compared with the color temperature value Dm stored in the memory inside the microcomputer 7 to compare the data ( Calculating a absolute value Dif between the TC and the color temperature value Dm, and detecting whether the absolute value Dif is larger than the set value E stored in the memory inside the microcomputer 7, and If the absolute value (Dif) is not larger than the set value (E), the process returns to the second step and the setting is made. If the absolute value (Dif) is larger than the value (E), the color temperature value (Dm) of the memory is changed to the data (TC), and the color signal output (R, B) suitable for the current color temperature (TC) is calculated and the vertical synchronous signal input ( VS) detects the presence of VS, and if there is no vertical synchronous signal VS, waits for the vertical synchronous signal VS, and if there is a vertical synchronous signal VS, outputs the color signal outputs R and B and automatically And a fifth process of returning to the second process if the white level control switch is not turned off and ending if it is turned off.

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