KR950002412B1 - Auto white-balance control method in camcoder - Google Patents

Abstract

calculating a color-difference signal of an object input from a camera tube processor, if two difference signals are not present, judging it as an achromatic color if they are present, judging it as a color ; comparing two difference signals and searching if the absolute value of the compared two difference signals is in a predetermined white region; outputting the inputted color-difference signal, if the absolute value is in a region other than the white region; and subtracting the difference signal from the inputted color-difference signal, if the absolute value is in the white region.

Description

How to control automatic white balance on your camcorder

1 is a block diagram of a white balance system of a conventional camcorder.

2 is a block diagram of an automatic white balance system of a camcorder of the present invention.

3 is an explanatory diagram for automatic white balance adjustment of FIG.

4 is a signal flow diagram for explaining the operation of FIG.

* Explanation of symbols for main parts of the drawings

1: imaging and processor 2: microcomputer

3: color processor

The present invention relates to automatic white balance adjustment of a camera-integrated V-Cal (hereinafter referred to as "camcorder"), and in particular, to reproduce a white color regardless of lighting conditions when a subject is photographed, and to capture the actual subject color and a subject photographed with a camcorder. The present invention relates to an automatic white balance control method of a camcorder which prevents discoloration and coloring due to a difference from color and improves color reproducibility of a camcorder.

In general, Auto White Balance is the effect of the lighting when shooting the subject with the camcorder, the color of the subject after the shooting is very different from the color of the real mortal, which is depending on the light source (luminance) R, G, It has different characteristics such as B, red (R) is large or blue (B) is large among the fundamental wavelengths, and these different characteristics are added to the object color, and red is stronger than the actual object color when shooting with a camcorder. There is a difference between the actual color of the object and the color of the object taken with the camcorder. In order to reduce this difference, it is only possible to balance the color by offsetting the amount of distortion caused by the influence of light in the actual object color. However, in the case of fluid colors, it is difficult to know how much the lighting is affected, so the camcorder is mainly made of white among achromatic colors. This is because white can be identified immediately if either red or blue is added.

Therefore, white balance is taken automatically under certain lighting, and the red or blue component added to it is detected and subtracted or added to it.

The white balance system of the conventional camcorder for this purpose is to sample the magenta, cyan, yellow, and green color signals that are captured and input from the imaging tube, as shown in FIG. And an image pickup tube processor 100 which combines the sample and holding the sample signal through the holding unit, and outputs the color difference signal of BY and the color difference signal of RY by combining the sampled and input color signals, and the color difference signal output from the image pickup tube processor 100 ( BY) and (RY), respectively, the first and second clamp portions 101 and 101a, and the respective color difference signals BY, which are clamped to the first and second clamp portions 101 and 101a, (RY) and the set reference voltage (V _Ref ) is compared with the first and second comparators (CP1) (CP2) and outputs the resulting signal and the comparison unit 102 is output from the comparison unit 102 First and second up / down count discrimination units (103) (103a) for determining up and down counts according to the signal; First and second counter units 104 and 104a for up and down counting the digital signals output from the two up / down count discrimination units 103 and 103a in 8-bit units, and the first and second counters. First and second digital / analog converters 105 and 105a for converting each of the digital signals up and down counted by the counters 104 and 104a into analog signals, and the first and second digital / A color processor 106 performs signal processing on the analog signal converted by the analog converters 105 and 105a to perform a white balance operation.

The white balance system of a conventional camcorder configured as described above is a magenta that is first picked up and output from an imaging tube. When cyan, yellow, and green signals are sampled and held in the sample and holding unit and input to the imaging tube processor 100, the imaging tube processor 100 combines the input color signals to output a color difference signal of BY and a color difference signal of RY. The color difference signal of BY and the color difference signal of RY output from the imaging tube processor 100 are clamped through each of the first and second clamping units 101 and 101a to be configured in the comparing unit 102. , The non-inverting terminal (+) of the second comparator (CP1) (CP2). Accordingly, the first and second comparators CP1 and CP2 of the comparator 102 have a color voltage signal BY, RY, which is input to the non-inverting terminal +, and an air voltage that is input, as an inverting terminal. When the color difference signal RY is higher than V _Ref and the color difference signal RY is lower than the reference voltage V _Ref , that is, when the color signal B is large due to the influence of the light source, the first comparator CP1 generates a high pulse. The second counter comparator CP2 outputs the low pulse to the second up / down count determination unit 103a, so that the first up / down count determination unit 103 The down count is determined according to the high pulse signal output from the first comparator CP1 and input to the first counter unit 104. The second up / down count discrimination unit 103a is sent to the second comparator CP2. The up count is determined according to the low pulse signal output from the second counter unit 104a. Therefore, when the first counter unit 104 counts down the pulse signal output from the first up / down count determination unit 103 to enter the reference voltage V _Ref and matches the reference voltage, It is input to the first digital / analog converter 105, and the second counter 104a outputs a pulse signal output from the second up / down count discriminator 103a to the reference voltage V _Ref . The UP and second counters 105 and 105a are executed by inputting the counted value to the second digital-to-analog converter 105a when the UP is counted to match the reference voltage. Converts the input digital color signal into an analog color signal and inputs it to the color processor 106.

On the contrary, the color difference signal BY inputted to the non-discharge terminal (+) of the first and second comparators CP1 is lower than the reference voltage V _Ref , and the color difference signal RY is lower than the reference voltage V _Ref . If high, that is, when the color signal R is large due to the influence of the light source, as described above, the first counter 104 performs an up count to match the reference voltage, and the second counter 104a matches the reference voltage. After performing the down count, the color processor 106 is inputted to the color processor 106 through the first and second digital / analog converters 105 and 105a. B is processed to perform a white balance operation.

However, when the automatic white balance operation is performed in the white balance system of such a conventional camcorder, the color difference signal BY of the object color itself is higher than the reference voltage, and the color difference signal RY is higher than the reference voltage, not the effect of illumination when the color is captured. When the color difference signal BY is lower than the reference voltage, or when the color difference signal RY is higher than the reference voltage, white balance operation is performed so that the object color may be discolored or slightly colored, thereby preventing the original color reproduction. There was this.

Accordingly, an object of the present invention is to use the color difference signal RY (BY) as a axis for the phenomenon of discoloration in the primary colors when white balance is performed using the color difference signal RY (BY) output from the imaging tube processor when photographing a subject. If the input color difference signal exists within the set area, the white balance is set. If the input color difference signal is not in the area, the white balance is stopped. The present invention provides an automatic white balance control method of a camcorder to improve color reproducibility.

The object of the present invention is to calculate the two color difference signals (RY), (BY) of the subject input from the imaging tube processor to determine achromatic color when there are no two difference signals, and to determine the fluid color when there is a difference. A second step of comparing the first difference with the two difference signals of the determined fluid color and searching whether the absolute value exists in the set white region by making the two difference signals compared as absolute values; A third step of outputting the input color difference signal as it is if the absolute value of is out of the setting area; and a fourth step of subtracting and outputting the difference signal from each of the input color difference signals if the absolute value of the two difference signals is within the set white area. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of the automatic white balance system of the camcorder according to the present invention. As shown in FIG. 2, magenta, cyan, yellow, and green color signals captured and input from an image capturing tube are sampled. An image pickup tube processor (1) for outputting a color difference signal of BY and a color difference signal of RY by combining and processing the sampled and held color signals inputted through the holding unit, and the color difference signal outputted from the image pickup tube processor (( RY) (BY), respectively, determine whether the calculated difference signal exists in the set white area, and if present, perform a white balance; otherwise, a microcomputer 2 for outputting an input color difference signal; And a color processor 3 which processes color difference signals output from 2) and outputs color signals.

The operation and effect of the present invention configured as described above will be described in detail with reference to FIG. 4 as a flowchart.

Magenta, cyan, yellow, and green signals captured by the imaging tube are sampled and held by the sample and holding unit and input to the imaging tube processor 1, and the imaging tube processor 1 processes the input color signals in combination to obtain a BY color difference signal. The color difference signals of and RY are outputted to the microcomputer 2. Therefore, the microcomputer 2 calculates the color difference signal RY and the color difference signal RY input from the imaging tube processor 1 in the first step 2a to obtain respective difference signals, and the result of the difference signal obtained. The achromatic and chromatic colors of the subject are determined. That is, the color difference signal RY and the color difference signal BY outputted from the imaging tube processor 1 are calculated to determine achromatic color when there is no difference signal, that is, when RY = O and BY = O. If RY = α, BY = β, it is determined by the chromatic color. After that, if it is determined that the chromatic color is obtained, the microcomputer 2 compares the two difference signals RY- (BY) = (α-β) of the determined fluid color in the second step (2b) (2c) and then compares them. It is searched whether one or two difference signals α-β exist in the set white area. That is, as an example, in the setting of the white area, as shown in FIG. 3, the color difference signal RY is taken as the vertical axis with the color difference signals RY and BY as the coordinate axis, and the color difference signal BY is set as the horizontal axis. When grasped, the area that can be considered white in the coordinate plane corresponds to a circle of radius r. At this time, if the radius r is set too small, the color is difficult to control when the color changes a lot, and if it is set too large, the white balance operation is performed even in the fluid color. Choose accordingly. The two difference signals α-β calculated in the second steps 2b and 2c do not exist in the set white area in this way, and the microcomputer 2 is transferred to the imaging tube processor 1 in the third step 2d. Outputs the color difference signal RY (BY) inputted from the color processor 3 as it is, and if the two difference signals α-β calculated in the second steps 2c and 2c exist in the white region, In the fourth steps 2e and 2f, a white balance operation is performed. That is, the difference signal α of the input color difference signal RY is subtracted by the difference signal α to be RY-α = 0, and the difference signal β of the input color difference signal BY Subtract the difference signal β so that (RY) -β = 0. At this time, the output of the microcomputer (2) is as follows.

(R-Y) '= (R-Y)-(R-Y) = 0, (B-Y)' = (B-Y)-(B-Y) = 0

In this way, the microcomputer 2 outputs the calculated color difference signals R-Y 'and (B-Y)' and performs a white balance operation, whereby R = B = Y is automatically set to white.

As described in detail above, the present invention generates a color signal that is actually white by erasing R or B added by the influence of lighting when the RY signal and BY signal, which are outputs of the imaging tube processor, are input from the microcomputer and are determined to be white. In the non-white area, the color difference signal output from the image tube processor is input to the color processor as it is, thereby preventing discoloration or coloring in the case of the primary color, as well as more accurate color reproduction, and from complicated hardware. By breaking away and using a simple microcomputer, the efficiency is increased.

Claims (1)

A first step of calculating color difference signals RY and BY of the subject input from the image tube processor to determine achromatic color when there are no two difference signals, and to determine chromatic color when there is a difference signal; Comparing the two difference signals, and searching whether the absolute value exists within the set white area by using the two difference signals as absolute values; and if the absolute value of the two difference signals is out of the setting area, A third step of outputting the color difference signal as it is; and a fourth step of subtracting the difference signal from each of the input color difference signals if the absolute value of the two difference signals is within the set white area and outputting the achromatic color. How to control the automatic white balance of your camcorder.