JPH04111696A - White balance controller - Google Patents

Abstract

PURPOSE:To reduce a control time of white balance even with respect to a light source in which an object control variable in existence by using a border of a white balance control range closest to an object control variable as a white balance control variable so as to terminate the control operation. CONSTITUTION:A microprocessor 8 discriminates whether or not color difference signals R-Y, B-Y inputted from a signal processing circuit 5 are 0 and when the signals are 0, the control operation is stopped. When they are not 0, the microprocessor calculates R and B control variables to variable gain amplifiers 4a, 4c. When an object control variable exists in a table, an R control signal and a B control signal based on the control variable are outputted to amplifiers 4a, 4b. The operation is repeated within a setting time of a timer and the control operation is terminated when the time exceeds the setting time of the timer. When an object control variable exists at the outside of white balance control range, the control variable is replaced to a border representing the white balance control range and the R control signal and the B control signal are outputted to the amplifiers 4a, 4c to terminate the control operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a white balance control device for a television camera that limits the control range of white balance.

[Conventional technology]

FIG. 2 is a block diagram showing a schematic configuration of this type of white balance control device for a television camera. In the figure, reference numeral 1 indicates imaging light from the subject, and this imaging light 1 enters the light receiving section of the imaging device 3 through a lens 2, where it is photoelectrically converted into R' (red), G' (green), and B. ' (blue) color signal (electrical signal). Among the color signals output from this imaging device 3, the R' and B' color signals are amplified by voltage-controlled variable gain amplifiers 4a and 4c for white balance control, and the G' color signal is normally amplified by voltage-controlled variable gain amplifiers 4a and 4c. The R and G signals are amplified by the amplifier 4b and each color balance corrected.

This becomes a B color signal and is manually input to the signal processing circuit 5. In this No. 3 processing circuit 5, necessary signal processing is performed, and from there, a luminance signal Y and a color difference signal RY are generated.

B-Y is output to the encoder circuit 6. The encoder circuit 6 then outputs the synthesized video signal to the outside.

On the other hand, the color difference signal R- outputted from the signal processing circuit 5 is
Y, B-Y are A/D (analog/digital) converters 7
It is also input to the microprocessor 8 via a and 7b,
Color difference signal R input by this microprocessor 8
White balance control is performed based on -Y and BY. That is, a white balance control signal is sent to the variable gain amplifiers 4a and 4c or the D/A (digital/analog) converter 9a so that these R-Y and B-Y signals become "0".

9b. The white balance is controlled by controlling the gains of the variable gain amplifiers 4a and 4b.

Further, a switch circuit 10 is connected to the microprocessor 8, and a switch 10a of the circuit 10 is turned on (O
N), the microprocessor 8 operates, closes the white balance control system circuit, and performs white balance control.

FIG. 3 is a flowchart showing the conventional white balance control operation in the white balance control device configured as described above.

When the switch 10a is closed to start the white balance control operation, first, in step S1, the microprocessor 8 shown in FIG. 2 is initialized, and then in step S2
The timer in the microprocessor 8 is set (initialized). This timer may be set to a relatively long time to prevent the white balance control operation from continuing for a long time if the white balance is not adjusted forever. Next, in step S3, the above-mentioned color difference signal RY,
It is determined whether B-Y is "0" or not.

At this time, if the color difference signals R-Y, B-Y are "0", it is determined that the white balance is correct and the white balance control operation is stopped, or if it is not "0", step S4 variable gain amplifiers 4a and 4c for R signal and B signal
Calculate each R control amount and B control amount for. Then, in step S5, these controls i! (target control value) is within a preset white balance control range, that is, whether it is within the control table stored in the microprocessor 8. In step S7, an R control signal and a B control signal corresponding to the calculated control amount are output to each of the variable gain amplifiers 4a and 4c. However, in step S5, if the target control value is not in the control table, that is, if it is outside the control table, in step S6, the R and B control values are replaced with the table boundary values closest to the target control value, In step S7, the RIIJ control signal and B control signal are similarly output in accordance with the replaced control values. Then, in step S8, it is determined whether or not the time is within the set time of the timer. If it is within the set time, the process returns to step S3 and the subsequent routine operations are repeated; if the set time has been exceeded, the current time The R control signal and the B control signal at are output, and the white balance control operation is completed.

FIG. 4 shows an example of the white balance control range. The area surrounded by the solid line (a) in the figure is the table mentioned above. Also, the dashed line (b) in the table (a) is the locus when white balance is adjusted under a black body radiation light source.
Its position changes depending on the color temperature of the light source. The reason why this table (a) has a width with respect to the locus of black body radiation (b) is to adjust the white balance for artificial light sources such as fluorescent lights. Also, if the width of this table (A) is made too wide, the color will disappear when white balance is taken for a monochromatic subject, so the width of the table (A) should be set to a level that does not pose a practical problem. be.

[J problem to be invented or solved]

However, with conventional white balance control devices such as those described above, when attempting to adjust white balance under a light source outside the black body radiation tracking color temperature setting range or under a special artificial light source, the control will fail. Since both color difference signals do not become "0" due to interference with the table boundary, the white balance control operation continues until the timer set time elapses, and the white balance control time is shorter than the normal white balance convergence time. The problem was that it was long.

That is, as shown in FIG. 5, if the control position at the start of white balance control is point A in the table (A) and the target control position is at point B outside the table (A), the control or target control When it reaches the 6th point of the boundary of the table (A) closest to the position, it gets stuck on the table (A), and after that, the control amount does not change until the time limit set by the timer is reached, but the white balance control operation is not correct. It will be continued.

The present invention has been made with attention to such problems, and the present invention does not increase the white balance control time even under a light source where the target control value is outside the white balance control range.
The object is to obtain a white balance control device with improved usability.

[Means to solve the problem]

In the white balance control device of the present invention, in a white balance control device that limits a white balance control range, when a target control value exists outside the white balance control range, the boundary of the white balance control range closest to the target control value is provided. The present invention is provided with a control means that uses the value as a white balance control value and ends the white balance control operation.

[Effect]

In the white balance control device of the present invention, when a target control value exists outside the white balance control range, it is output as the boundary value or control value of the white balance control range that is closest to the target control value. Balance control operation ends.

[Embodiment] FIG. 1 is a flowchart showing a white balance control operation according to an embodiment of the present invention, and the same step numbers as in FIG. 3 indicate the same operations. The hardware configuration of this embodiment is the same as that shown in FIG. 2, so the explanation will be omitted, or the table (a) in FIG.
is stored, and the control range of white balance is limited. Furthermore, when the white balance target control value is outside the white balance control range, the microprocessor 8 performs a white balance control operation by setting the white balance control value to the boundary value of the white balance control range that is closest to the target control value. A control means is configured to terminate the process.

When the white balance control operation shown in FIG. 1 starts, first, in step S1, the microprocessor 8 is initialized, and in step S2, the above-mentioned timer is set.

Next, in step S3, the microprocessor 8 determines whether the color difference signal R-YB-Y input from the signal processing circuit 5 is "0" or not, and if it is rQJ, it means that the white balance is correct. to stop this control operation. If there is no rQJ in step s3, move to step S4,
Here, the aforementioned R control amount and B control amount for the variable gain amplifiers 4a and 4c are calculated. Next, in step S5, it is determined whether or not the target control value is in the control table, and if the target control value is in the table, in step S7, the R control signal and the B control signal are varied based on the control value. It outputs to gain amplifiers 4a and 4b. Then, in step S8, if the time is within the set time of the timer, the above operation is repeated;
If the timer setting time has been exceeded, this control operation ends.

When the target control value is not in the table in step S5,
That is, when the target control value exists outside the white balance control range, the process moves to step S6, where the control value is replaced with the boundary value of the table, that is, the boundary value of the white balance control range closest to the target control value. Then, in step S9, an R control signal and a B control signal based on the replaced control value are output to the variable gain amplifiers 4a and 4c, and this white balance control operation is completed.

In this way, when the white balance target control value is outside the control range, the white balance operation is terminated using the boundary value of the white balance control range closest to the target control value as the control value. Even under a light source, the control time is not longer than necessary, and usability is improved.

〔Effect of the invention〕

As described above, according to the present invention, when a target control value exists outside the white balance control range, the control operation is ended using the white balance control value as the boundary value of the white balance control range that is closest to the target control value. As a result, even under a light source where the target control value exists outside the white balance control range, the white balance control time does not become long, and usability is improved.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a white balance control operation according to an embodiment of the present invention, FIG. 2 is a block diagram showing a schematic configuration of a white balance control device for a television camera, and FIG. 3 is a flowchart showing a white balance control operation according to an embodiment of the present invention. FIG. 4 is an explanatory diagram showing an example of the white balance control range; FIG. 5 is an explanatory diagram showing the control operation when the target control value is outside the white balance control range. . 1... Imaging light 3... Imaging device 4a, 4cm... Variable gain amplifier 5...
Signal processing circuit 6...Encoder circuit

Claims (1)

[Claims] In a white balance control device in which a white balance control range is limited, when a target control value exists outside the white balance control range, a boundary value of the white balance control range closest to the target control value is set as a white balance control value for white. A white balance control device comprising a control means for terminating a balance control operation.