JPH11127450A - White balance adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize satisfactory photographing by preventing the occurrence of color failure. SOLUTION: A microcomputer 10 calculates a difference between the integrated mean value of color difference signals R-Y and B-Y and a reference value. Then, white balance control signals RCONT and BCONT are changed by each one step value so that the difference can be made less than a convergence judged value. The changing areas of the RCONT and BCONT are limited to an indoor mode area and an outdoor mode area. The switching of the both areas is operated by considering subject luminance and the value of a difference between a color difference signal integrated mean value and a reference value.

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 for performing white balance using an internal photometry system, which is devised so as to prevent the occurrence of color fear when taking pictures indoors and outdoors.

[0002]

2. Description of the Related Art In a video camera and 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 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.

[0005]

The above-mentioned condition of "averaging a predetermined area of the screen becomes an achromatic color (gray)" is a condition when shooting a general landscape in which various colors are randomly mixed. To establish. However, for example, when photographing a subject with a blue sky and a blue sea as a background or a subject with a red wall as a background, the above-described conditions are not satisfied, and the color becomes blue or red on average. Therefore, when a subject (person) with a single color background is photographed and white balance adjustment is performed using the internal photometry method, the screen is regarded as achromatic even though the average color of the screen is not achromatic. In order to balance, the reference white level is shifted, the background is faded, and the color of the main subject (person) is corrected and controlled in the direction of a complementary color (complementary to the background color), resulting in so-called color failure.

In the end, in a video camera that takes a white balance using the internal photometry method, the white balance can be correctly obtained when a general scene in which each color is mixed at random is taken, but a special scene with a large proportion of a specific color is taken. When photographing, color fear occurs.

An object of the present invention is to provide a white balance adjusting device which can prevent the occurrence of color feria even when a subject having a large proportion of a specific color is photographed in view of the above-mentioned prior art. And in the present invention,
Good white balance adjustment can be performed both indoors and outdoors.

[0008]

According to the present invention, there is provided an automatic white balance adjusting apparatus using an internal photometry system, which detects a subject brightness and outputs natural light when the subject brightness is higher than a mode switching value. (Sun light)
It is determined that the camera is in the outdoor mode in which the camera is shooting outdoors under the sunlight, and when the subject brightness is lower than the mode switching value, the indoor mode in which the camera is shooting indoors under artificial light (fluorescent light, incandescent light) is used. Judge and adjust the white balance only in the limited area selected in consideration of the color temperature of sunlight in outdoor mode, and only in the limited area selected in consideration of each color temperature of each artificial light in indoor mode. Adjust the white balance,
Further, after the white balance control signal converges to a value in the outdoor mode area, the subject luminance is smaller than the mode switching value, and the integrated average value and the reference value of the color difference signals RY and BY are set. When the difference is equal to or greater than the extended convergence determination value, the value of the white balance control signal is changed to a value in the indoor mode area, and after the white balance control signal becomes a value in the indoor mode area and converges, , The subject luminance is larger than the mode switching value, and the color difference signals RY, B-
When the difference between the integrated average value of Y and the reference value is equal to or greater than the extended convergence determination value, the value of the white balance control signal is changed to a value within the outdoor mode area.

[0009]

Since natural light and artificial light have considerably different spectral characteristics, if the white balance can be adjusted for both light sources, it is necessary to widen the adjustment area, and color fear is likely to occur. Conversely, if the white balance adjustment region is narrowed so as to prevent the occurrence of color fear, the white balance cannot be adjusted sufficiently. In contrast,
In the present invention, since the adjustment region is determined separately for the outdoor mode and the indoor mode, the white balance can be adjusted in both modes. In addition, since the adjustment region is limited, even when, for example, a green grass is photographed outdoors, it is possible to adjust the white balance without overcorrection to the extent that color fear occurs. Further, the switching between the outdoor mode area and the indoor mode area is performed in consideration of the difference between the subject luminance and the integrated average value of the color difference signal and the reference value, so that the mode area is accurately switched.

[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
Are integrated by the integrating circuit 19 and input to the microcomputer 10. The microcomputer 10 outputs a signal to the AG 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 C circuit 4. Further, the microcomputer 10 receives zoom information P1 from the lens driving unit, and iris data P2 indicating the iris opening 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.

The microcomputer 10 has an outdoor mode and an indoor mode as shown in FIG. When the indoor mode is set, the white balance control signals R _CONT , B
The value of _CONT can take only the value in the region X surrounded by the solid line in FIG. When a white paper illuminated with a light bulb, a white fluorescent lamp, a day white fluorescent lamp, or a daylight fluorescent lamp is photographed, the values of R _CONT and B _CONT take the values indicated by the _{circles in} the figure. That is, the area X in the indoor mode includes a value in which R _CONT and B _CONT converge when white paper illuminated by various artificial lights is taken and white balance is adjusted, and the area width is reduced. I have. On the other hand, when the outdoor mode is set, the values of the white balance control signals R _CONT and B _CONT can be surrounded by the alternate long and short dash line in FIG.

The microcomputer 10 determines the subject brightness from the iris data P2 and the like. If the subject brightness is equal to or greater than the mode switching value, the microcomputer 10 determines that the mode is the outdoor mode. This utilizes the fact that, as shown in Table 1, outdoors are generally brighter than indoors.

[0016]

[Table 1]

The manner in which the microcomputer 10 adjusts the white balance is as follows. The microcomputer 10 determines that the difference between the integrated average value of the color difference signals RY and BY and the reference value is a convergence determination value (for example, 10 LSB: (Least Significant Bit)).
The white balance control signals R _CONT , B
The value of _CONT is sequentially changed by one step value, and the white balance adjustment optimal for the color temperature at the time of shooting is performed, and the difference between the integrated value of the color difference signal and the reference value becomes equal to or less than the convergence determination value. Then, the values of R _CONT and B _CONT are made constant. White balance control signal R _CONT, if B _CONT is outdoors mode R _CONT, the possible values of B _{CO NT} is limited to a value in the region Y, if the indoor mode R _CONT, the possible values of B _CONT is It is limited to the value in the area X. In indoor shooting, good white balance adjustment can be performed if the values of R _CONT and B _CONT converge to a certain value in the area X. In outdoor shooting, the values of R _CONT and B _CONT become constant values in the area Y. If the convergence is achieved, good white balance adjustment can be performed.

It should be noted that if the white balance is automatically adjusted and the color feria is reduced regardless of whether the light is natural light or artificial light without being divided into the outdoor mode and the indoor mode, R _CONT , B The control region of the _CONT is widened as shown by a region Z surrounded by a dotted line in FIG. The fact that the control area is wide as described above means that the control is often performed using information other than the information relating to the color temperature, so that the occurrence of color feria will inevitably increase. In the present invention, the outdoor mode is divided into the indoor mode and the indoor mode. In the outdoor mode, the white balance can be adjusted only in the color temperature change range under natural light. Because the white balance control area is narrow and limited to the extent possible, even if a subject that does not become achromatic even when averaging a predetermined area of the screen such as a green lawn or a red wall, the occurrence of color fear is greatly reduced And good white balance can be adjusted.

Further, according to the present invention, after the white balance control signals R _CONT and B _CONT converge to a value in the area Y of the outdoor mode, only when both of the following conditions are satisfied, R _CONT and B _{CONT are set} . B _CONT is changed to a value in the area X in the indoor mode. This is the point of the present invention. That is, (1) the subject brightness is smaller than the mode switching value. (2) When the difference between the integrated average value of the color difference signals RY and BY and the reference value is equal to or larger than the extended convergence determination value (for example, 30 LSB). The extended convergence judgment value (30 LSB) is the convergence judgment value (1
0LSB).

Therefore, even if a dark subject is photographed and the above condition (1) is satisfied when photographing outdoors,
Since the condition (2) is not satisfied, R _CONT and B _CONT are not changed to values in the area X in the indoor mode. Therefore, even when a dark subject is photographed outdoors, the white balance is adjusted by the values R _CONT and B _CONT of the values in the area Y in the outdoor mode, and good photographing is performed. It is assumed that (1)
In the case where the area is changed only under the condition (1), when a dark subject is photographed outdoors, R _CONT and B _CONT shift to values in the indoor area X, and the white balance is lost. On the other hand, when a person who has photographed outdoors enters the room while photographing with the camera, the above conditions (1) and (2) are satisfied, and R _CONT and B _CONT are values within the area X of the indoor mode. And good white balance adjustment can be performed indoors.

Further, according to the present invention, after the white balance control signals R _CONT and B _CONT have converged to a value within the indoor mode area X, only when both of the following two conditions are satisfied, R _CONT and B _{CONT are set} . B _CONT is changed to a value in the area Y of the outdoor mode. This is the point of the present invention. That is, (3) the subject luminance is larger than the mode switching value. (4) When the difference between the integrated average value of the color difference signals RY and BY and the reference value is equal to or larger than the extended convergence determination value (for example, 30 LSB). The extended convergence judgment value (30 LSB) is the convergence judgment value (1
0LSB).

Therefore, when shooting indoors,
By photographing the light source bulb, etc. directly, even if the condition (3) is satisfied, since no satisfied condition (4), R _CONT, B
_CONT is not changed to a value in the area Y in the outdoor mode. Therefore, even if a bright light source is photographed indoors, the white balance is adjusted by the values R _CONT and B _CONT of the values in the area X in the indoor mode, and good photographing is performed. Note If, when adapted to the only area change condition (3), when shooting a light source indoors, R _CONT, B _{CO NT} is will move to the value of the outdoor area Y, the white balance It will break. On the other hand, if a person who was shooting indoors goes outdoors while shooting with a camera, the above (3) and (4)
Is satisfied, and R _CONT and B _CONT are in the area Y in the outdoor mode.
, And good white balance can be adjusted outdoors.

In the present invention, the outdoor mode and the indoor mode are switched in accordance with the luminance. However, the value of the luminance to be switched, that is, the mode switching value may be an optimal value selected according to the type of the video camera. The ranges of the areas X and Y can be arbitrarily selected according to the design concept.

Next, the procedure of the control operation of the present invention will be described with reference to FIG. When the power is turned on in step 1, in step 2, the microcomputer 10 controls the white balance control signal R _CONT for the red signal whose value is the initial value and the white balance control for the _blue signal whose value is the initial value. Signal B
_CONT is output. The initial value is preset. Next, in step 3, the microcomputer 10 inputs the integrated average value of the color difference signals RY and BY that have been subjected to white balance adjustment in accordance with the white balance control signals R _CONT and B _CONT that are initial values. . In step 4, the color difference signals RY,
It is determined whether or not the difference between the integrated average value of BY and the reference value is equal to or less than a convergence determination value (for example, 10 LSB (Least Significant Bit)). Returning, if the determination is NO, it is determined that convergence has not occurred, and the routine proceeds to step 5.

In step 5, the brightness data is input to obtain the subject brightness. In step 6, if the subject brightness is equal to or more than the mode switching value, the outdoor mode area Y is selected. If the subject brightness is smaller than the mode switching value, the indoor mode is selected. Select region X. In step 7, it is determined whether the selected area is different from the previous area. If the previous area is the same as the selected area, the process proceeds to step 9.

[0026] In step 8, the region same west the previous region, R _CONT, the direction of change of the B _CONT calculated in step 9, R _CONT, if B _CONT is long enters the area (Step 10YES), 1 R _CONT and B _CONT whose step values have changed are output, and when R _CONT and B _CONT are out of the area (NO in step 10), new R _CONT and B _CONT are not output.

If it is determined in step 7 that the selected area is different from the previous area, it is determined whether the area has converged once (step 12). After the convergence (YES in step 12), when the difference between the integrated average value of RY and BY and the reference value is larger than the extended convergence value, the process proceeds to step 8, and the selected area is not used and the area is changed. Keep as before. This operation occurs when a light source is photographed indoors or when a dark subject is photographed outdoors.

It is determined that the answer is NO in step 12, or the convergence is once made (YES in step 12).
When the difference between the integrated average value of Y and the reference value is equal to or larger than the extended convergence value, the process proceeds to step S14. In step 14, the area is changed to the area selected in step 6, and R _CONT and B _CONT in the changed area are output. This operation occurs when the user goes outdoors from indoors while taking a picture, or enters the indoors from outdoors while taking a picture.

[0029]

According to the present invention, the white balance adjustment area is set separately for the outdoor mode and the indoor mode as described above in detail with the embodiments, so that the optimum white balance adjustment in each mode is performed. Can be secured. Further, in the present invention, after the white balance control signal has once converged, the change between the outdoor mode area and the indoor mode area is not limited to the magnitude of the subject luminance, but also the value of the difference between the color difference signal integrated average value and the reference value. Therefore, even if a light source is photographed indoors or a dark subject is photographed outdoors, the mode area does not change and correct white balance adjustment can be performed. The mode area is changed when the color temperature actually changes from the indoor state to the outdoor state or from the outdoor state to the indoor state.

[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 characteristic diagram illustrating a control area of the white balance control device.

FIG. 3 is a flowchart showing a procedure of a control operation.

[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 (1)

[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 for outputting two types of color difference signals RY and BY; calculating the brightness of the subject and averaging a predetermined range of the screen under a reference color temperature condition to obtain an achromatic color;
Each of the integrated average values of Y and BY is set in advance as a reference value, and the white balance is set so that the difference between the integrated average value of the color difference signals RY and BY and the reference value is equal to or less than the convergence determination value. A white balance control signal for operating the balance circuit is sent to the white balance circuit, and the value that the white balance control signal can take when adjusting the white balance under sunlight is determined to be a value within a predetermined range. An outdoor mode area and an indoor mode area in which a value that can take a white balance control signal when performing white balance adjustment under artificial light is determined to be a value within a predetermined range are set. When the brightness of the subject is larger than the mode switching value, the value of the white balance control signal is set to a value in the outdoor mode area, and the obtained brightness of the subject is smaller than the mode switching value. When the processing unit has a value of the white balance control signal in the indoor mode region, the processing unit further comprises, after the white balance control signal becomes a value in the outdoor mode region and converges, The subject luminance is smaller than the mode switching value, and the color difference signals RY, B-
When the difference between the integrated average value of Y and the reference value is equal to or greater than the extended convergence determination value, the value of the white balance control signal is changed to a value in the indoor mode area, and the white balance control signal is changed to the value in the indoor mode area. After the value has converged, the subject luminance is larger than the mode switching value and the color difference signal R−
White balance adjustment wherein the value of the white balance control signal is changed to a value within the outdoor mode area when the difference between the integrated average value of Y and BY and the reference value is equal to or greater than the extended convergence determination value. apparatus.