JPH0583727A - White balance controller - Google Patents

Abstract

PURPOSE:To improve the accuracy of white balance control by eliminating object information not on a color temperature curve in advance and to decrease an error in the color temperature decision when the color temperature of an object is decided. CONSTITUTION:A color temperature deciding means 17 decides whether or not chroma signal data average for each block by a block averaging circuit 10 are valid, and only the valid data are inputted to a full pattern average detection means 18 and a color temperature deciding means 13 obtains finally color temperature information of an object. A white level detection means 14 extracts a block having same color temperature information as a color temperature obtained by the color temperature deciding means 13 and a white balance gain control means 15 realizes an optimum white balance based on the block data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance control device used in a color camera.

[0002]

2. Description of the Related Art FIG. 3 shows the configuration of a white balance control device in a conventional single-chip color camera. In FIG. 3, reference numeral 1 is a solid-state image sensor (hereinafter referred to as CCD),
It photoelectrically converts a photographed subject into a video signal.
2 is correlated double sampling (hereinafter referred to as CDS),
The video signal is sampled to remove noise. A Y / C separation circuit 3 separates a luminance signal (hereinafter referred to as Y signal) and a chroma signal (hereinafter referred to as C signal). Reference numeral 4 is a Y signal processing circuit that processes only the Y signal. Reference numeral 6 is a C signal processing circuit for processing only the C signal, which converts the C signal into color difference signals which are RY and BY signals. Reference numeral 7 is a gain control circuit for R-Y signals (hereinafter, R.G.C.), and 8 is a gain control circuit for B-Y signals (hereinafter, B.G.C).
Then, the signal level of each color difference signal is adjusted to achieve white balance. Reference numeral 9 denotes a modulation circuit for modulating the RY signal and the BY signal at the subcarrier frequency.
It produces a signal. An adder 5 mixes the Y signal and the modulated C signal. 10 is
It is a block averaging circuit that divides the C signal obtained from the Y / C separation circuit 3 into a plurality of blocks, and averages the chroma signals corresponding to the color filters of the CCD for each block independently for each color filter. Reference numeral 12 denotes an entire screen average color difference detection means for averaging the C signals averaged for each block by the block averaging circuit 10 for the entire screen, and further separating them into RY signals and BY signals which are color difference signals. is there. Reference numeral 13 is a color temperature determination means for making a determination by comparison with preset color temperature determination color difference data. Reference numeral 14 is for detecting a white signal from the data of the block averaging circuit 10, and the result of the color temperature judging means 13 is used for this detection. A white balance gain control unit 15 sets a white balance gain based on the data obtained from the white detection unit 14. In the above, the full-screen average color difference detection means 12 and the color temperature determination means 1
3, the white detection means 14 and the white balance gain control means 15 are processed in the microcomputer 16.

The white balance operation of the white balance control device having the above configuration will be described below. The C signal is taken out by the Y / C separation circuit 3, and further separated by the C signal processing circuit 6 into RY signals and BY signals which are color difference signals. Then, these color difference signals are R. G. C7, B.I. G. At C8, the gain is set by the output signal from the white balance gain control means 15, and the white balance is taken.

Next, the white balance gain control means 15
A method of generating the signal output of will be described. The C signal averaged for each block by the block averaging circuit 10 is input to the full-screen average color difference detection means 12 in the microcomputer 16, and after averaging the C signals of all the blocks, the RY signal and the B-signal. The color difference signal of the -Y signal is obtained. Next, the color temperature determination unit 13 compares the color difference signal obtained by the average full-screen color difference detection unit 12 with preset color temperature determination color difference data to determine whether the subject is within a preset color temperature range. To do. Then, if valid, the color temperature of the subject is obtained. Next, the white detection unit 14 obtains a color difference signal for each block from the output of the block averaging circuit 10 and determines whether the color difference signal is within the range of the color difference corresponding to the color temperature of the subject obtained by the color temperature determination unit 13. In other words, if the color temperature of each block matches the color temperature of the entire screen after the color temperature of the entire screen is obtained, the block is achromatic (white).
Can be judged. Then, if the color difference for each block is within the range, it can be determined as an achromatic (white) block.
Next, the white balance gain control means 15 adds all the C signals of the blocks determined to be achromatic (white) blocks by the white detection means 14 to obtain the gain set values corresponding to the respective color difference signals.

[0005]

However, in the above-mentioned conventional white balance device, when determining the color temperature of the entire screen, even a subject that does not follow the color temperature curve is averaged, and the white value is calculated based on such data. When the detection is performed, the error of the color temperature determination becomes large, and as a result, the accuracy of the white balance control deteriorates.

The present invention solves such a conventional problem. When determining the color temperature of the entire screen, it is determined in advance whether or not the data for each block is along the color temperature curve. Since only the data on the color temperature curve is used, it is an object of the present invention to provide an excellent white balance control device capable of reducing the error of color temperature determination and improving the accuracy of white balance control. is there.

[0007]

In order to achieve the above object, the present invention provides block averaging means for averaging a chroma signal into a plurality of blocks, and data obtained by this block averaging means for each block. A color temperature curve judging means for judging whether or not the color temperature curve is in accordance with a preset color temperature curve, a full screen average detecting means for averaging the results obtained by the color temperature curve judging means for all screens, and this full screen average detection Color temperature determining means for obtaining a color temperature from the data obtained by the means, and white detecting means for obtaining a block along the color temperature obtained by the color temperature determining means from among the blocks obtained by the block averaging means. And a white balance gain control means for determining an amplification amount for taking a white balance of the color camera from the result obtained by the white detection means. By providing, in which the white balance control.

[0008]

According to the present invention, by disposing the color temperature curve determination means for eliminating unreliable information deviating from the preset color temperature curve before obtaining the average color difference of all screens, the color temperature It is possible to prevent misjudgment and realize highly accurate white balance control.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. However, circuit blocks that perform the same operations and functions as those of the conventional example are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

FIG. 1 is a block diagram of a white balance control apparatus showing an embodiment of the present invention, and FIG. 2 is a color temperature curve diagram showing a region which is a reference for determination in color temperature determination according to the present invention.

In FIG. 1, as compared with the conventional example, reference numeral 17 denotes a color temperature curve determination means, which separates the data obtained by the block averaging circuit 10 into color difference signals, and then compares and determines with a preset color temperature curve. That is, reference numeral 18 denotes an all-screen average detection circuit, in which means for averaging the results of comparison and judgment for each block by the color temperature curve judgment means 17 with respect to the entire screen is added.

Next, the specific operation of the above embodiment will be described. In FIG. 1, the chroma signal averaged for each block by the block averaging circuit 10 is input to the color temperature curve determination means 17. Then, the color temperature curve determination means 17 first divides the C signals averaged for each block into color difference signals. Then, the color difference signal for each block is compared with a preset color difference data table for allowable color temperature range comparison, and if the color difference signal of the block is within the allowable range, it is judged as highly reliable data close to achromatic color (white). Then, the data is sent to the full screen average detection means 18, and if the data is out of the allowable range, the data is excluded.

A concrete method of the above comparison and judgment is shown in FIG.
Use to explain. In FIG. 2, a is a generally well-known color temperature curve for the RY signal and the BY signal which are color difference signals. Further, in the generally-used automatic tracking white balance control, the control range is 3000K to 6000K, and the color temperature is 3000K.
It is well known that color difference signal data below or above 6000K has low reliability. 3000K to 6000
The allowable color difference range of K is shown by b in FIG. Further, a straight line (RB) max and (RB) min that sandwich the color temperature curve between the upper and lower sides.
If you set, color difference data that does not fall between the upper and lower straight lines can be judged to be unreliable data that is far from achromatic color (white),
(RB) max and (RB) min are shown in FIG.
Denote by d.

Therefore, in the color temperature curve judging means 11, when the data averaged for each block is separated into color difference signals and plotted on the color temperature curve diagram shown in FIG. 2, the color temperature range from 3000K to 6000K. Within,
And the preset straight line (R-B) max, straight line (R-B)
B) Only the data contained in the range surrounded by min (area A in FIG. 2) is sent to the full screen average detection means 18.

As described above, since the data deviated from the area A is excluded by the color temperature curve judging means 11, the full-screen average color difference signal obtained by the full-screen average detecting means 18 uses all the data as it is, and the whole screen is used. It is more reliable data that is closer to achromatic color (white) than when calculating the average color difference.
The color temperature determined by the color temperature determination means 13 is also highly reliable.

In this embodiment, because of the processing time of the microcomputer 19, (R−B) max and the straight line (R
-B) min corresponds to a straight line such as c and d in FIG. 2, but a curve along the color temperature curve may be used for c and d, in which case the detection accuracy can be further improved. it can.

[0017]

As is apparent from the above embodiment, the present invention averages the entire conventional screen to obtain color difference signal information,
While the color temperature of the subject was judged, by preliminarily excluding unreliable information deviating from the color temperature curve before obtaining the color difference of the entire screen, erroneous judgment of color temperature is prevented and accuracy of An effect that high white balance control can be realized is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a white balance control device that is an embodiment of the present invention.

FIG. 2 is a color temperature curve diagram showing a region serving as a judgment reference in the color temperature judgment of the present invention.

FIG. 3 is a block diagram of a conventional white balance control device.

[Explanation of symbols]

 1 CCD 2 CDS 3 Y / C separation circuit 4 Y signal processing circuit 5 adder 6 C signal processing circuit 7 R. G. C 8 B. G. C 9 Modulation circuit 10 Block averaging circuit 13 Color temperature determination means 14 White detection means 15 White balance gain control means 17 Color temperature curve determination means 18 Full screen average detection means 19 Microcomputer

Claims (1)

[Claims] 1. A block averaging means for dividing a screen of a video signal into a plurality of blocks and averaging a chroma signal, and a color temperature preset for each of the data obtained by the block averaging means. Color temperature curve determining means for determining whether or not a curve is met, full screen average detecting means for averaging the results obtained by this color temperature curve determining means for all screens, and data obtained by this full screen average detecting means A color temperature determining means for obtaining a color temperature from the white color detecting means, a white detecting means for obtaining a block along the color temperature obtained by the color temperature determining means from among the blocks obtained by the block averaging means, and the white detecting means. And a white balance gain control means for determining the amount of amplification for obtaining the white balance of the color camera from the result obtained by Nsu control device.