JPH0619262Y2 - White balance adjustment circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a white balance adjusting circuit for a color video camera, and more particularly to a white balance adjusting circuit capable of performing manual adjustment and automatic adjustment under a single system of control.

(Prior Art) A conventional general video camera is provided with an automatic mode and a manual mode change switch for white balance adjustment, and a control volume for manual adjustment separately.

That is, as shown in FIG. 3, the red (R) signal and the blue (B) signal supplied via the input terminals 1 and 2 are supplied to the matrix circuits 5 and 6 via the amplifiers 3 and 4, respectively. It

In addition, a luminance signal (YL) supplied via the input terminal 7
Is supplied to each of the above matrix circuits 5 and 6, and these matrix circuits 5 and 6 are supplied with these signals R, B and Y.
Based on L, R-YL and B-YL color difference signals are generated and output.

Then, these color difference signals are combined with a synchronizing signal or the like by the encoder 8 and output as a general composite video signal.

On the other hand, the color difference signal is supplied to each input terminal of the differential amplifier 9, and the differential output of this differential amplifier 9 is supplied to one terminal of the mode changeover switch 10.

The other terminal of the mode changeover switch 10 is connected to the manual adjustment potentiometer 11.

Here, the mode change switch 10 is used to set whether the white balance is automatically adjusted or manually. In the case of automatic adjustment, the differential output is used for controlling the gain of the amplifiers 3 and 4 as well. To the differential amplifiers 12 and 13 of. The differential amplifiers 12 and 13 are provided with white balance adjusting potentiometers 14 and 15, respectively.

Further, in the case of manual adjustment, the differential amplifiers 12 and 13 are adjusted by appropriately adjusting the midpoint voltage of the volume 11.
It is possible to control the gains of the amplifiers 3 and 4 by varying the output level of.

(Problems to be solved by the invention) By the way, in the conventional video camera as described above,
After operating the mode changeover switch 10 for changing over between the manual mode and the automatic mode, this switch 10
It is necessary to operate another volume 11 provided separately from the above to manually adjust the white balance, and the operation is complicated.

In addition, there is a system for transmitting and receiving power and other signals with a single coaxial cable for video cameras for surveillance, but in such a system, a control signal for white balance adjustment is not provided to other systems. It is superposed on the signal and sent to the video camera having the above-mentioned configuration.

Therefore, a special circuit for superimposing is required, and especially in a video camera capable of both manual and automatic adjustment as described above, the number of types of control signals increases, which makes the superimposing circuit complicated and causes a cost increase. There was a problem that it would end up.

(Means for Solving Problems) The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a white balance adjustment circuit capable of performing the setting of the manual mode and the automatic mode in the white balance adjustment and the adjustment in the manual mode by a single-system control, that is, a single switch operation. .

In order to achieve this object, the present invention, as shown in FIG. 1, is a mode for switching between automatic mode and manual mode in a white balance adjusting circuit that can selectively perform white balance adjustment manually or automatically. Changeover switch 20 and volume 21 for white balance adjustment in manual mode
When the midpoint voltage E _{1 of the} volume control 21 is higher than the predetermined reference voltage level Vref, the mode changeover switch 20 is set to the manual mode, and the midpoint voltage E ₁ is lower than the reference voltage level Vref. In this case, the changeover control circuit 22 for setting the mode changeover switch 20 to the automatic mode
It is an object of the present invention to provide a white balance adjustment circuit characterized by including:

(Operation) According to the white balance adjusting circuit having the above-described configuration, the automatic mode and the manual mode can be selectively set by operating the volume 21 to change the midpoint voltage E ₁ of the volume 21. In addition, the white balance can be adjusted in one operation in the manual mode, and these modes can be set and adjusted in one system.

(Embodiment) A preferred embodiment of the white balance adjusting circuit according to the present invention will be described in detail below with reference to FIGS. 1 and 2.

For convenience of explanation, the same parts as those of the white balance adjusting circuit shown as the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

The white balance adjusting circuit according to the present embodiment is mounted on a general video camera, and as shown in FIG. 1, a mode changeover switch 20, a white balance adjusting volume 21 and a changeover control according to the present embodiment. It is provided with a comparator 22 which is a circuit.

One input terminal 20A of the mode changeover switch 20
As described above, the differential output of the differential amplifier 9 for white balance adjustment in the automatic mode is supplied to the other input terminal 20B, and the other middle terminal voltage E ₁ of the volume 21 for white balance adjustment in the manual mode. Are being supplied.

The midpoint voltage E ₁ is supplied to one terminal of the comparator 22, and the other terminal of the comparator 22 is supplied with a reference signal of a predetermined reference voltage level Vref.

The output E _{2 of the} comparator 22 becomes high level when the voltage level of the midpoint voltage E ₁ is higher than the reference voltage level Vref, and at this time, the switch terminal 20C of the mode changeover switch 20 is set to the other side. This mode selector switch 20 is connected to the input terminal 20B of
To the manual mode.

Then, in this state, the white balance can be manually adjusted by operating the volume control 21.

Further, when the output of the comparator 22 is low level, that is, when the voltage level of the midpoint voltage E ₁ is lower than the reference voltage level Vref, the switch terminal 20.
C is connected to one terminal 20A, whereby the mode changeover switch 20 is set to the automatic mode.

Then, in this state, the gains of the amplifiers 3 and 4 are variably controlled according to the operation output of the differential amplifier 9, that is, the difference between the color difference signals R-YL and B-YL to adjust the white balance. It's done automatically.

As described above, the white balance adjusting circuit according to the present embodiment can select the automatic mode and the manual mode and adjust the white balance in the manual mode only by operating the volume control 21.

Next, another embodiment of the white balance adjusting circuit according to the present invention will be described.

In this embodiment, a white balance adjusting circuit according to the present invention is applied to a video camera for surveillance, and white balance adjustment in a manual mode is provided in a control unit 26 connected to the camera by a coaxial cable 25. This is performed by operating the knob 27.

The same members as those in the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the video camera according to the present embodiment, the three primary color signals of red (R), green (G), and blue (B) supplied from the image pickup unit (not shown) via the input terminals 30, 31, 32 are amplified by the amplifier 3,
The color difference signals R-Y, B-Y and the luminance signal Y are supplied from the matrix circuit 34 via the reference numerals 4, 33, respectively.

The color difference signal and the luminance signal are sent to the encoder 35.
Is supplied to the control unit 26 via the coaxial cable 25. The composite video signal is supplied to the control unit 26.

After that, the composite video signal is sent to a monitor (not shown) or the like via the control signal removing circuit 36, the amplifier 37, and the like.

On the other hand, the color difference signals RY and BY output from the matrix circuit 34 are supplied to the respective input terminals of the differential amplifier 9 as described above, and the differential amplifier 9 corresponds to the level difference of each color difference signal. The differential output is supplied to one input terminal 20A of the mode changeover switch 20.

Further, the control unit 26 is provided with a volume 21 for white balance adjustment in the manual mode, and this volume 21 is operated by rotation of an adjustment knob 27.

Then, the midpoint voltage E ₁ of the volume control 21 is applied to the white balance control signal generation circuit 38, and the control signal generation circuit 38 outputs the control signal of the frequency corresponding to the voltage level via the coaxial cable 25 to the video camera. Of the FV (frequency-voltage) converter 39.

Therefore, the FV converter 39 supplies the comparator 22 with a voltage of the same level as the midpoint voltage E ₁ which is changed by the operation of the volume control 21.

The comparator 22 controls the setting of the mode changeover switch 20 according to the comparison result E _{2 of the} midpoint voltage E ₁ and the reference level Vref.

The frequency signal output from the white balance control signal generation circuit 38 is removed from the composite video signal by the control signal removal circuit 36 together with other control signals so that the reproduced image is not adversely affected. .

Further, the control unit 26 is provided with other control signal generation circuits 40, and other control signals output from these circuits are also sent to the video camera through the coaxial cable 25. ing.

Also in the embodiment having the above-mentioned configuration, similarly to the previous embodiment, by adjusting the volume 21, the selection between the automatic mode and the manual mode and the white balance adjustment in the manual mode can be performed.

Also, in this way, the mode setting related to white balance adjustment,
Since the adjustment can be performed by one system, the control signal generation circuit 38 in the case where the control unit 26 is connected to the video camera by the coaxial cable 25 as in the present embodiment has one white balance adjustment. Therefore, the cost can be reduced and the structure of the control unit can be simplified.

(Effect of the Invention) As is apparent from the above description, according to the white balance adjusting circuit of the present invention, the automatic balance and the manual mode for the white balance adjustment are selected, and the white balance adjustment in the manual mode operates one volume. You can do it simply by doing.

Therefore, the operation of white balance adjustment becomes easy, and in the case where the control unit is connected to the video camera by the coaxial cable like the surveillance camera, the white balance adjustment can be performed by one system. Can be simplified.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a white balance adjusting circuit according to the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the same.
FIG. 3 is a circuit diagram showing a conventional example. 20: Mode switch, 21: Volume,
22 ... Switching control circuit (comparator).

Claims (1)

[Scope of utility model registration request] 1. A white balance adjusting circuit capable of selectively performing white balance adjustment manually and automatically, comprising a mode changeover switch for switching between an automatic mode and a manual mode, and a volume for white balance adjustment in the manual mode. , If the midpoint voltage of this volume is higher than a predetermined reference voltage level, set the mode changeover switch to manual mode, and if the midpoint voltage is lower than the reference voltage level, set the mode changeover switch to automatic mode. A white balance adjusting circuit comprising a switching control circuit for setting a mode.