KR940002610B1 - White balance controller for an image pick-up apparatus including an abnormality detector - Google Patents

Abstract

No content.

Description

White balance control

1 is a block diagram showing one embodiment of the present invention.

2 is a block diagram of the white detector of FIG.

3 and 4 are diagrams for explaining the operation of the white balance control device shown in FIG.

5 is a block diagram showing another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1 imaging device 2 color separator

11: WB matrix 71, 72: gate circuit

81,82: integrator 91,92: comparison amplifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance control device for an imaging device such as a video camera, and more particularly to a white balance control device that performs a stable white balance control function when the color temperature of a light source changes.

The conventional apparatus of the above-described type is fixed to the color difference signal (or the amplitude of the signal whose color difference signal is calculated) after the white balance adjustment, as described in Japanese Patent Laid-Open No. 63-219291 corresponding to US Patent No. 4,797,733. It was possible to run a white extraction process that uses the specified threshold.

In the above-mentioned prior art, attention is paid only to the saturation of the chromatic color portion in the state where the white balance is achieved, and no consideration has been given to the color temperature state of the illumination.

In addition, in the above-described prior art, the automatic exposure control characteristic for the white ratio of the screen or the sensitivity of the image pickup device is not considered very much, and from that point of view, there is a problem that the detection level is sometimes inappropriate depending on the subject or illuminance to be photographed. there was.

SUMMARY OF THE INVENTION An object of the present invention is to provide a white balance control apparatus capable of setting a stable range at the time of white extraction by combining information about the saturation of a subject with the color temperature of the illumination or the state of the adjusted white balance.

Another object of the present invention is to provide a white balance control apparatus capable of achieving accurate white extraction at all times corresponding to changes in photographing conditions of a subject.

According to a feature of the present invention, a range (color, saturation) regarded as white is adapted according to the color temperature of the illumination or the control state of the white balance.

According to another feature of the present invention, the range (light and dark) considered to be white is adapted according to the luminance distribution of the photographed image or the like.

When the white extraction range is determined for the initial state of the white balance achieved, the range of saturation considered to be white is always constant, but considering the change in color temperature such as white, the range changes according to the adjusted state or the white balance. Done. For example, when setting the color temperature up to 10000 ° K to be considered white as the initial state is set to 5000 ° K, if the white balance is achieved at 8000 ° K, it is also considered white at 20000 ° K and vice versa. The extraction range toward the color temperature is narrower. Here, the present invention can shift the white extraction range according to the adjusted state of the white balance. In particular, when white balance is achieved at a higher color temperature, for example, the white extraction range is expanded in the red direction (forward direction along the RB axis), and the white extraction range is controlled in the blue direction (negative direction along the RB axis). Is executed.

Conversely, when white balance is achieved at a lower color temperature, control is executed so that the white extraction range is narrowed in the red direction (forward direction along the RB axis) and the white extraction range is expanded in the blue direction (negative direction along the RB axis). do.

By the above-described configuration, it is possible to adapt the range of the color temperature as the object of white extraction to the color temperature of the illumination (adjustment state of the white balance) at the time of shooting or shooting. Therefore, more stable and more precise white extraction can be achieved.

In general, the white portion of the subject has a higher reflectance than the colored portion. Therefore, when the white portion and the colored portion are mixed, relatively high brightness portions can be regarded as white. Therefore, white is extracted with respect to the part which has brightness higher than a threshold value using the average brightness of the whole screen as a threshold value. Therefore, detection of "comparative" high doldol can be performed, so that stable detection can be achieved even when the luminance fluctuation of the entire screen or the prescribed luminance is not obtained due to insufficient illumination.

The above and other objects and novel features of the present invention will become apparent from the description and the accompanying drawings.

Hereinafter, one embodiment of the present invention will be described with reference to FIG. The color separator 2 generates a luminance signal and a color signal from the signal output from the image pickup device 1. The red (R) and blue (B) signals pass through the gain control circuits 3r and 3b and are then combined with the luminance Y in the matrix circuit 4 to generate the color difference signals R-Y and B-Y. The luminance Y signal and the color difference signals R-Y and B-Y generated in this way are partially output, and some are input to the white balance control system. The control system uses the luminance and color difference signals to detect white or achromatic portions of the photographed image, generates a signal for adjusting the white balance, and applies the gain control circuits 3r and 3b in the R and B signal paths. Supply the signal.

The color difference signals RY and BY extracted by the camera signal processing system are subtracted by the subtractor 5 and added by the adder 6 to detect the color temperature change and the saturation signal in the RB direction RB and Mg-G. Direction detection signal R + B-2Y is generated. In these two signals RB and R + B-2Y, only signals for the white portion are detected in the gate circuits 71 and 72, and the detected signals are integrators 81 and 82 so as to be averaged over the entire screen. The white balance control signal is integrated in accordance with the averaged white part signal RB (R + B-2Y) corresponding to the color tone (deviation in the white balance state) of the photographing screen. Is generated from. The reference voltage of the comparison input to the other inputs of the comparison amplifiers 91 and 92 is a signal corresponding to the white balance partial average signal R-B (R + B-2Y) in the white balance state. The control signal in the R-B axis direction output from the comparison amplifier 910 and the control signal in the R + B-2Y axis direction output from the comparison amplifier 92 are WB (white balance) matrix 11 in this embodiment. The white balance is adjusted by converting the gains of the red (R) and blue (B) signals of the circuits 3r and 3b into the signals respectively to control the WB matrix. ), An adder 112, and a load resistance 111.

A white or achromatic detection circuit (hereinafter referred to as a white detection circuit or a white detector) 10 is provided to drive the gate circuits 71 and 72 for extracting the white portion of the subtractor 5 and the adder 6. The two chroma detection signals (R-B, R + B-2Y) and the luminance signal (Y) detect low chroma and high luminance portions. The white detector 10 shown in FIG. 2 includes variable voltage sources 100a to 100d, amplifiers 101 to 105, and an AND gate 106. As shown in FIG. As shown, the output of the amplifier 91 naturalized with the white detector 10 is possible to control the variable voltage sources 100a and 100b used as comparison inputs of the amplifiers 101 and 102, It is possible to control the detection range in one direction. In the same way, the output of the amplifier 92 returns to the white detector 10 to control the variable voltage sources 100c and 100d to enable control of the detection range in the other direction. The variable voltage source generally has a relationship of (100b) <(100a) and (100d) <(100c). The trajectory of the color temperature change (color quality change of natural light) according to the black body radiation is displayed at the position on the chrominance plane as shown in FIG. 3, which is shown in the relation between the R-B axis and the R + B-2Y axis. In particular, the deviation from white due to the change in color temperature of the light source (the intersection of the R-Y and BY axes) is determined by R-B, and the deviation from white due to reasons other than the change in color temperature is determined by R + B-2Y. Is determined by Here, in order to set the range of white extraction (referred to as white), correction of at least a practical color temperature range (for example, from 2000 ° K to 10000 ° K) is possible, and according to the color temperature within the above range indicated in saturation. By having the coloring of white, the part enclosed by the dashed-dotted line in the figure is defined by the white extraction range (initial state).

When the color temperature of the light changes in the initial state, the saturation corresponding to the change up to 2000 ° K (or 1000 ° K) is regarded as white under the conditions set as above, and the condition of the white portion R-B = 0 ( The white balance control is executed to match R + B-2Y = 0). At this time, since the white balance control signal (for example, the output of the amplifier 91) changes in accordance with the color temperature change of the rough surface, the color temperature at this time can be estimated from the control signal generated after the white balance is achieved. In the case where the range of practical color temperatures is limited as described above, for example, if the camera is balanced against white at 2000 ° K, it can be assumed that the color temperature at that portion will not be lower. Under such conditions, any signal with amplitude in the red direction can be considered chromatic. That is, the boundary of the white extraction range on the red side at a low color temperature may be shifted toward the saturation lower than the above setting in the initial state according to the output of the amplifier 910. Conversely, the boundary on the blue side may be extended or shifted toward the higher saturation. good.

FIG. 4 shows the extraction range (dotted dashed line) in shooting or shooting under such a low color temperature. According to the white balance control signal (control state) as described above, there is an advantage that an appropriate white extraction range can be always set by changing the saturation level regarded as white at any time. In this embodiment, only the control of the direction in accordance with the change in color temperature is described, but it is better to perform the same control in the Mg-G direction (along the R + B-2Y axis) according to the output of the amplifier 92. Effect can be achieved.

5 shows another embodiment of the present invention using the luminance signal Y for white extraction. The configuration of the embodiment of FIG. 5 is similar to that of FIG. 1, except that the averaging circuit 12 and the comparator 13 are provided. In white extraction, its operation is the same as that of FIG. 1, which regards a portion of low saturation and high luminance as white and extracts a signal of this portion. However, if the luminance level regarded as white is fixed, the luminance level of the chromatic color portion is lowered by an operation such as automatic exposure control in accordance with the ratio between the white portion and the chromatic color portion, so that proper white extraction is sometimes impossible. In Fig. 5, the luminance Y signal extracted from the signal system is compared with the average value generated by the averaging circuit 12 in the comparator 13, and white extraction is performed according to the comparison result. Thereby, stable white extraction can be achieved under "comparative" high brightness conditions even when the photographing state fluctuates as described above. In this embodiment, the comparison reference value is generated by averaging instead of the averaging device, but as the reference value of the luminance to be detected by using a device that generates a value according to a luminance distribution such as a value at 80% of the peak luminance. You may have a part near the maximum value.

In order to accurately describe the above-described control operation, some subtle signal control is required. This can be easily accomplished, for example, using digital signal processing and some software.

According to the present invention, the saturation level adapted to the state of the white balance by the color temperature at the time of each shooting or shooting, the kind of illumination, etc., and the luminance level adapted to the state of the exposure by the illuminance, the ratio of the bright (white) color, etc. White extraction is performed. Therefore, the white balance control at the time of changing the shooting conditions can be stabilized, and the effect of reducing the malfunction can be achieved.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example, Of course, it can change variously in the range which does not deviate from the summary.

Claims (14)

Image pickup means for supplying an output for displaying an image, color separation means for generating a luminance signal and a plurality of color signals in accordance with the output of the image pickup means, and gains of at least two shifts of the plurality of shifts separated by the color separation means. A white balance control apparatus for an image pickup apparatus, comprising gain controlling means for controlling and means for generating a color difference signal from at least one of a color signal and a luminance signal, wherein at least one of white and achromatic portions in a photographed screen by the image pickup means in accordance with at least the color difference signal Detecting abnormality of the white / unchromatic detection means for detecting at least one of and the white balance in the photographing screen, and supplying its output to the input of the white / unchromatic detection means, the gain of the gain control means according to the detection result And white anomaly detection means for controlling white and enabling white adjustment. Ballguns Control. The white balance control according to claim 1, further comprising a comparison means for changing an operating range by said white / achromatic portion detecting means for detecting a white portion as white in accordance with the coarse color temperature used for photographing. Device. The white balance control apparatus according to claim 2, further comprising means for using a gain control amount of shift during white adjustment, and means for detecting a color temperature of illumination used for photographing. The method according to claim 2, wherein the color separation means supplies red (R), blue (B) and luminance (Y) signals, and the color difference signal generating means supplies white for supplying Y, RY and BY signals. Balance control. 5. The apparatus of claim 4, wherein the abnormality detecting means includes means for supplying an output representing the color difference signal R-B to an input of the white / chromatic color detecting means to enable control of the operating range in the first direction. White balance control. 5. The apparatus according to claim 4, wherein the abnormality detecting means supplies an output representing the color difference signal R + B-2Y to the input of the white / achromatic detecting means to enable control of the operating range in the second direction. White balance control device comprising a. 6. The apparatus according to claim 5, wherein the abnormality detecting means supplies an output representing the color difference signal R + B-2Y to the input of the white / achromatic detecting means to enable control of the operating range in the second direction. White balance control device having a. 8. The white balance control apparatus according to claim 7, wherein the gain control means includes first gain control means for controlling the gain of the red signal and second gain control means for controlling the gain of the blue signal. The method according to claim 7, further comprising generating a comparative threshold value in accordance with the luminance signal in response to the luminance signal and determining whether the portion has a high luminance and according to one of the average luminance level and the luminance distribution. Means for changing and supplying its output to the white / chromatic detection means. 8. The device according to claim 7, wherein the white / chromatic detection means receives a color difference signal R-B at each input on one side and a signal from the first and second variable voltage source means at each input on the other side. First and second amplifying comparison means, each receiving a color difference signal R + B-2Y at each input and receiving a signal from the third and fourth variable voltage source means at each input of the other, respectively. Receiving third and fourth amplification ratio means, fifth voltage comparing means receiving a luminance signal at one input and a fifth variable voltage source means at the other input and the first, second, And an AND gate for receiving an output from the third, fourth and fifth layer width comparing means, and supplying the output to the abnormality detecting means, wherein the first and second variable voltage source means are configured to receive the color difference signal R-B. When the signal thereof is changed in accordance with the output of the abnormality detecting means And the third and fourth variable voltage source means change the signal thereof in accordance with the output of the abnormality detecting means representing the color difference signal R + B-2Y. 12. The apparatus of claim 10, wherein the abnormality detecting means receives a color difference signal R-B and supplies an output to a sixth amplification comparison means to supply an output representing the color difference signal R-B. A first gate means for supplying an output to the integrating branch, a second for receiving a color difference signal R + B-2Y and supplying an output to a seventh amplifying comparison means for supplying an output representing the color difference signal R + B-2Y And second gate means for supplying an output to the integrator of the controller, wherein the output of the white / chromatic detection means is supplied to the first and second gate means. 12. The white balance control device according to claim 11, further comprising a white balance matrix means for receiving the outputs of the sixth and seventh amplification comparison means and controlling the gain of the gain control means accordingly. Image pickup means for supplying an output for displaying an image, color separation means for generating a luminance signal and a plurality of shifts in accordance with an output of the image pickup means, and gain of at least two shifts among a plurality of shifts separated by the color separation means A white balance control apparatus for an image pickup apparatus having a gain control means for controlling a control unit and a means for generating a color difference signal from at least one of a shift and a luminance signal, the white balance control apparatus for an imaging device using a luminance signal to detect a white portion in a photographing screen and to obtain a relatively high luminance. A detection means for considering a portion of the photographed screen as white and a comparison threshold for judging whether or not the portion has high luminance according to the luminance signal, and changing the value according to one of the average luminance level and the luminance distribution. And generating means for supplying its output to said detecting means. The apparatus according to claim 13, wherein said generating means includes an amplification control means for receiving a luminance signal at one input and receiving an average luminance level from an averaging circuit for averaging said luminance signal at the other input. Balance control.