JPH11127449A - White balance adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the converging time of a white balance, and to accurately adjust the white balance. SOLUTION: A microcomputer 10 judges that a white balance is shifted when a difference is present between the integrated mean value and reference value of color difference signals R-Y and B-Y. Then, when the difference between the integrated mean value and reference value of the color difference signals R-Y and B-Y is more than a switching value, the value of a white balance control signal is changed by one step value, and an outputting time interval is shortened. When the difference is more than the switching value, the value of the white balance control signal is changed by one step value, and the outputting time interval is lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance adjusting device, which is designed so as to shorten the convergence time when performing white balance adjustment and to perform white balance adjustment with high accuracy.

[0002]

2. Description of the Related Art In an image photographing apparatus such as a video camera or a video still camera, a white balance is adjusted so that a white subject is reproduced white. The white balance is adjusted by controlling the gain of the red signal circuit and the gain of the blue signal circuit of the camera with reference to the green signal. To adjust the white balance, it is necessary to measure the color tone (color temperature) of the light in the shooting environment. As a method of white balance, there are an external photometric system and an internal photometric system which differ in color temperature measuring method.

In the external photometric method, a color temperature is directly detected by a color temperature sensor, and a white balance control signal for an R (red) signal and a white balance control signal for a B (blue) signal are generated based on the detected data, and the white light is output. I try to balance. The color temperature sensor is formed, for example, by integrally integrating a photosensor with a red filter, a photosensor with a green filter, and a photosensor with a blue filter, and calculates R, B from the output voltage of each photosensor. We are making white balance control signals for signals.

In the internal photometry system, the color temperature is detected indirectly, so to speak, if a predetermined range of the screen (for example, about 70% of the entire screen) is averaged when the white balance is matched, an achromatic color (gray color) is obtained. ) Is controlled based on the knowledge that In other words, the average value of the color difference signals RY and BY, which become achromatic when the colors in a predetermined range of the screen are averaged under the reference color temperature condition, is set as a reference value and generated by a video camera at the time of shooting. The white balance control signals for the R and B signals are output so that the gains for the R and B signals are controlled so that the integrated average values of the actual color difference signals RY and BY are substantially equal to the reference values. ing.

The values of the R and B white balance control signals are calculated by, for example, a microcomputer, and the microcomputer outputs a white balance control signal to a white balance circuit. The white balance circuit adjusts the gains of the red signal and the blue signal based on the value of the white balance control signal.

[0006]

In the conventional white balance adjusting device, a white balance control signal is output at regular time intervals. For this reason, if the output time interval is set short, hunting or the like may occur, and the white balance control signal may not converge accurately.
Conversely, if the output time interval is set long, the white balance control signal converges accurately, but it takes time to converge. For this reason, it is necessary to quickly converge, such as when the color temperature changes suddenly or when the power is turned on, but it takes a long time to reach a normal white balance state.

An object of the present invention is to provide a white balance adjusting apparatus capable of performing accurate white balance adjustment with a short white balance convergence time in view of the prior art.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a configuration of the present invention is a white-color adjusting device for controlling the amplification of the red and blue primary color signals among the red, green and blue primary color signals. A balance circuit, a matrix circuit for processing the white balance adjusted primary color signals to output two types of color difference signals RY and BY, and an achromatic color when a predetermined range of the screen is averaged under a reference color temperature condition. Each color difference signal RY,
Each of the integrated average values of BY is preset as a reference value, and white balance control for operating the white balance circuit so that the integrated average value of the color difference signals RY and BY becomes equal to the reference value. A processing unit that sends a signal to a white balance circuit, and the processing unit further includes:
After the difference between the integrated average value of the color difference signals RY and BY and the reference value becomes smaller than the switching value, or after the value of the white balance control signal has once converged, the value of the white balance control signal is changed. It is characterized in that the time interval for changing and outputting one step value is lengthened.

[0009]

By adjusting the time interval for outputting the white balance control signal, convergence can be achieved quickly and accurately. That is, the convergence time can be shortened by shortening the time interval, and accurate convergence can be achieved by increasing the time interval.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a video camera provided with a white balance adjusting device according to an embodiment of the present invention. As shown in FIG. 1, a subject image formed by a lens 1 is incident on an imaging surface of a charge-coupled device (CCD) 3 through an iris 2. A complementary color (cyan, magenta, yellow, green) filter is provided on the imaging surface of the CCD 3, and a charge signal E indicating a subject image passes through a sample hold (S / H) and an automatic gain control (AGC) circuit 4. The signal is input to the signal processing circuit 5. The signal processing circuit 5
The charge signal E is signal-processed to generate a luminance signal Y and a primary color signal R,
G and B are output. After the white balance is adjusted by the white balance circuit 6, the primary color signals R, G, B
The data is γ-corrected by the correction circuit 7 and then input to the matrix circuit 8. The matrix circuit 8 performs matrix processing on the primary color signals R, G, and B and outputs color difference signals RY, BY.
The encoder 9 adds a signal obtained by subjecting the color difference signals RY and BY to quadrature two-phase modulation and the luminance signal Y to output an NTSC video signal.

The output of the AGC circuit 4 is supplied to an A / D converter 18
, And are integrated by the integration circuit 19 before being input to the microcomputer 10. The microcomputer 10 outputs a signal through the D / A converter 11 based on the integrated value of the output of the AGC circuit 4.
An AGC control signal is sent to the GC circuit 4. The microcomputer 10
, Zoom information P1 is sent from the lens driving unit, and iris data P2 indicating the iris opening is sent from the Hall element 12 that detects the iris opening.

The microcomputer 10 calculates the opening of the iris 2
The brightness of the subject is calculated based on the gain of C4 and the electronic shutter speed. In other words, the higher the brightness of the subject, the narrower the iris 2 becomes, the darker the iris 2 is opened, and when the iris 2 is opened and becomes darker, the gain of the AGC 4 increases. Since the degree of opening of the iris 2 and the gain information of the AGC 4 become darker, the brightness of the subject can be detected by performing arithmetic processing on the information by the microcomputer 10.

On the other hand, the color output from the matrix circuit 8
The difference signals RY and BY are supplied to low-pass filters 13 and 14.
And digitized by A / D converters 15 and 16
After that, it is sent to the microcomputer 10. The microcomputer 10 includes:
Average a predetermined area of the subject screen under the reference color temperature condition
And the color difference signals RY and BY which become achromatic are integrated and averaged.
The value is set as a reference value. And the color difference signal R
Make the integrated average value of −Y equal to the RY reference value.
Red signal white balance control signal R_CONTAnd
The integrated average value of the color difference signal BY is equal to the reference value for BY.
White balance control signal B for green signal_CONT
Is output from the microcomputer 10 as serial data,
The analog signal is converted by the D / A converter 17 and the white balance
It is sent to Road 6. Therefore, the white balance circuit 6
Is the white balance control signal R _CONT, B_CONTDepending on the value of
Adjust the gain of the primary color red signal R and the primary color blue signal B,
The white balance feedback control is executed.
Note that the white balance control signal R_CONT, B_CONTOutput
Technology that is the key of the present invention, such as time intervals
Will be described later.

Next, a first embodiment of the present invention
The operation will be mainly described. In this embodiment, when the values of the white balance control signals R _CONT and B _CONT are far from the convergence value, the time interval for outputting R _CONT and B _CONT is shortened to perform quick convergence, and R _CONT and B _{CONT When} the value of _CONT approaches the convergence value, the time interval for outputting R _CONT and B _CONT is lengthened to perform accurate convergence. The difference between the values of R _CONT and B _CONT and the convergence value is determined by the color difference signal R
It is determined from the difference between the integrated average value of −Y and BY and the reference value. That is, when the difference between the color difference signal integrated average value and the reference value is large, R _{CO NT,} B _CONT value is determined to be far from the convergence value, when the difference between the color difference signal integrated average value and the reference value is small , R _CONT , and B _CONT are determined to be close to the convergence value.

Next, a control procedure according to the first embodiment will be described with reference to FIG.
Will be described. When the power is turned on in step 1, the
In step 2, the value is the initial value from the microcomputer 10.
White balance control signal R for red signal_CONTAnd the value is initial
White balance control signal B for green signal
_CONTIs output. The initial value is preset. Next
The microcomputer 10 sets the initial value in step 3.
White balance control signal R_CONT, B_CONTAccording to the
The product of the color difference signals RY and BY with the white balance adjusted
Enter the minute average. In step 4, the color difference signals RY,
The difference between the integrated average value of BY and the reference value is a predetermined value (for example, 1
0 LSB (Least Significant Bit))
Judge whether it is not converged if the judgment is NO
It moves to step 5. In Step 5,
To adjust the balance, R _CONT, B_CONTIncrease
Calculate whether to reduce or decrease.

In step 6, the color difference signals RY, BY
It is determined whether or not the difference between the integrated average value and the reference value is equal to or greater than the switching value. The switching value is larger than the predetermined value in step 4. And when the difference between the integrated average value and the reference value is equal to or larger than the switching value, R _CONT, since B _{CO NT} is far away from the convergence value, the process proceeds to step 7, one step value change (increase or decrease) the R Outputs _CONT and B _CONT .

When R _CONT and B _CONT are far from the convergence value and the difference between the color difference signal integrated average value and the reference value is equal to or greater than the switching value, the control of steps 3 to 7 is repeated, for example, for 0.5 seconds. R _CONT and B _CONT whose values are updated at intervals are output. Since R _CONT and B _CONT are updated and output at such a short time interval, convergence proceeds quickly.

If R _CONT and B _CONT approach the convergence value and the difference between the color difference signal integrated average value and the reference value becomes smaller than the switching value (NO in step 6), such a state is established in step 8. Count the number of times. If the number of times the difference has become smaller than the switching value does not reach the set count value (for example, four times), it is determined as NO in step 9 and the process returns to step 3, where R _CONT and B _CONT are not output. When the number of times the difference has become smaller than the switching value has reached the set value (YES in step 9), the process proceeds to step 7, and R _CONT and B _CONT changed by one step value are output, and the count value is reduced. Reset. After all,
When R _CONT and B _CONT approach the convergence value, R _CONT and B _CONT
CONT is output after being thinned out, and the output time interval becomes longer.
For this reason, convergence is accurately achieved without hunting or the like.

If the difference between the integrated average value of RY and BY and the reference value is smaller than a predetermined value in step 4 (YES),
Returning to step 3, R _CONT and B _CONT converge without being updated.

Next, a second embodiment of the present invention will be described. Second
In the embodiment, after convergence, R _CONT, B_CONTOutput
Convergence speed by increasing the time interval
Things.

The control procedure according to the second embodiment will be described with reference to FIG.
I will tell. When power is turned on in step 1, step
At 2, an initial operation of white balance adjustment is performed.
In other words, from the microcomputer 10, the initial value of the red
White balance control signal R for signal_CONTAnd values are initial values
White balance control signal B for green signal_{CO NT}
Is output first. The initial value is preset. Next
The microcomputer 10 uses the initial value of the white balun.
Control signal R_CONT, B_CONTWhite balance tone according to
Input the integrated average value of the adjusted color difference signals RY and BY
Then, the integrated average value of the color difference signals RY and BY at this time is
Compare with reference value. As a result of the comparison, the integration
When the difference between the average value and the reference value is larger than a predetermined value, 1
E of the value shifted (increased or decreased) by the step value
White balance control signal R_CONT, B _CONTIs output. This
And the integrated average value of the color difference signals RY and BY
White balance until the difference from the reference value is less than the specified value
Control signal R_CONT, B_CONT(Even if only one control signal is used
) Is changed and output one step value at a time. And
The difference between the integrated average value of the color difference signals RY and BY and the reference value is
A predetermined value (for example, 10 LSB (Least Significant Bit)
 )) If below, R_CONT, B_CONTKeep the value of
You. Thus, R_CONT, B_CONTThe value of
Are referred to as “convergence”.

In the above-mentioned initial operation, R _CONT , B
_The time interval for outputting the _CONT may be fixed to 0.5 seconds, or may be short when approaching the convergence value and away from the convergence value as in the first embodiment. Good.

After the convergence, the process proceeds to step 3 where the integrated average value of the color difference signals RY and BY during photographing is input. In step 4, it is determined whether the difference between the integrated average value of RY and BY and the reference value is equal to or smaller than a predetermined value. If the answer is YES, the white balance adjustment has been _{successfully performed} , and the process returns to step 3 to maintain the current R _CONT and B _CONT .
If NO, the process proceeds to step 5 because the white balance adjustment is inadequate. In step 5, the number of times that the difference between the integrated average value and the reference value has exceeded a predetermined value is counted.

In step 6, it is determined whether the count value has reached a set count value (for example, four times). NO
If it is, the process returns to step 3 and the current R _CONT , B _CONT
To maintain. If YES, at step 7
_The direction of change of _CONT and B _CONT is calculated, and R _CONT and B _CONT changed by one step value are output in step 8.

That is, the values of R _CONT and B _CONT are not updated unless the number of times the color temperature change state is detected reaches the count value. Therefore, even when the entire surface of a single-color subject is instantaneously photographed, R _CONT and B _CONT do not change, and a good white balance state can be maintained.

If the color temperature changes during shooting,
The values of R _CONT and B _CONT are updated gradually. In other words, once convergence occurs in the initial operation, the color temperature rarely changes abruptly, so it can be dealt with only by a gradual change. As long as you do not shoot for a long time, you can minimize it.

[0027]

According to the present invention, as specifically described above with the embodiment, when the difference between the integrated average value of the color difference signal and the reference value is larger than the switching value, that is, when the value of the white balance control signal is When it is far away from the convergence value,
Since the time interval for outputting the white balance control signal is shortened, the convergence time is shortened, and when the difference between the integrated average value of the color difference signal and the reference value is smaller than the switching value, that is, the white balance control signal When the value is close to the convergence value, the time interval for outputting the white balance control signal is long, so that the convergence is accurate without hunting or the like.

Further, according to the present invention, once the convergence is achieved,
Since the time interval for outputting the white balance control signal is extended, when the color of the subject changes instantaneously, the white balance adjustment state does not change, and good white balance adjustment can be continuously performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a video camera provided with a white balance adjustment device according to the present invention.

FIG. 2 is a flowchart showing the operation of the first embodiment.

FIG. 3 is a flowchart showing the operation of the second embodiment.

[Explanation of symbols]

Reference Signs List 1 lens 2 iris 3 CCD 4 S / H & AGC circuit 5 signal processing circuit 6 white balance circuit 7 gamma correction circuit 8 matrix circuit 9 encoder 10 microcomputer 11 D / A converter 12 Hall element 13, 14 low-pass filter 15, 16 A / D Converter 17 D / A converter 18 A / D converter 19 Integrator E Charge signal R, G, B Primary color signal RY, BY Color difference signal Y Luminance signal R _CONT White balance control signal for red signal B _CONT White balance control signal for green signal

Claims (2)

[Claims] 1. A white balance circuit for controlling the degree of amplification of the red and blue primary color signals of the red, green and blue primary color signals to perform white balance adjustment, and processing the white balance adjusted primary color signals. A matrix circuit that outputs two types of color difference signals RY and BY, and respective integrations of the color difference signals RY and BY that become achromatic when a predetermined range of the screen is averaged under a reference color temperature condition. An average value is preset as a reference value, and a white balance control signal for operating the white balance circuit so that the integrated average value of the color difference signals RY and BY becomes equal to the reference value is transmitted to the white balance circuit. A processing unit for transmitting the value of the white balance control signal by one step when the difference between the integrated average value of the color difference signals RY and BY and the reference value is larger than the switching value. When the difference between the integrated average value of the color difference signals RY and BY and the reference value is smaller than the switching value, the value of the white balance control signal is increased by one step. A white balance adjusting device, wherein a time interval for outputting a value by changing the value is lengthened. 2. A white balance circuit for controlling the amplification of the red and blue primary color signals of the red, green and blue primary color signals to perform white balance adjustment, and processing the white balance adjusted primary color signals. A matrix circuit that outputs two types of color difference signals RY and BY, and respective integrations of the color difference signals RY and BY that become achromatic when a predetermined range of the screen is averaged under a reference color temperature condition. An average value is preset as a reference value, and a white balance control signal for operating the white balance circuit so that the integrated average value of the color difference signals RY and BY becomes equal to the reference value is transmitted to the white balance circuit. And a processing unit that, after the white balance control signal has once converged, changes the value of the white balance control signal by one when changing the state of white balance adjustment. A white balance adjusting device characterized in that a time interval for changing and outputting a step value is longer than a time interval for outputting a white balance control signal when the white balance control signal once converges.