JP3055985B2 - White balance adjustment device - Google Patents

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 photometric method, which is designed to prevent the occurrence of color fear.

[0002]

2. Description of the Related Art Video cameras, video still cameras, etc.
In an image photographing apparatus , 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 photometric method, the color temperature is detected indirectly, so to speak, when the white balance is adjusted.
The control is based on the finding that averaging the entire screen results in an achromatic color (gray). That is, when the colors of the entire screen are averaged under the reference color temperature condition, the color difference signal R-
The integrated average value of Y, BY is set as a reference value, and the actual color difference signal R generated by the video camera at the time of shooting is set.
The gains for the R signal and the B signal are controlled so that the integrated average values of −Y and BY become substantially equal to the reference value.

[0005]

The above-mentioned condition that "the entire screen becomes an achromatic color (gray) by averaging" is satisfied when a general landscape in which various colors are randomly mixed is photographed. . 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 shooting a subject (person) with a solid background,
When performing white balance adjustment using the internal metering method,
Although the average color of the screen is not achromatic, it is regarded as an achromatic color, and the white balance is deemed to be achromatic. As a result, the reference white level shifts, the background fades, and the color of the main subject (person) is a complementary color (a complementary color to the background color). The correction is controlled in the direction of ()), and so-called color fear occurs.

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.

[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, determining the brightness of the subject, and controlling the entire screen under the reference color temperature condition. The integrated average value of each of the color difference signals RY and BY, which become an achromatic color when averaged, is set in advance as a reference value, and the integrated average value of the color difference signals RY and BY and the reference value are set. A white balance control signal for operating the white balance circuit so that the white balance control signal is equal to the white balance control signal. Thereafter, the difference between the integrated average value of the color difference signal and the reference value is equal to or greater than a predetermined value, the current luminance changes by a predetermined value or more from the luminance at the time of the previous convergence or the previous fixed time, and the white balance control signal And the processing unit changes the value of the white balance control signal by one step value on condition that the value of the white balance control signal falls within the movable region centered on the previous convergence value or the previous fixed value. When the value of the white balance control signal has reached the boundary value of the movable area, the value of the white balance control signal is fixed, and when the value of the white balance control signal is fixed or converges in the movable area, the movable area is changed. It is characterized by changing to a new movable area centered on the current fixed value or convergence value.

[0009]

The value of the white balance control signal changes by one step value when the difference between the integrated average value of the color difference signal and the reference value exceeds a predetermined value and the luminance changes by a predetermined value or more. Within.

[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 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, and the darker the iris 2 is opened, the more the iris 2 is opened and darker, the larger the gain of the AGC 4 becomes. When the electronic shutter is operated, the shutter speed becomes higher. 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 difference signals RY and BY output from the matrix circuit 8 are
And digitized by the A / D converters 15 and 16 before being sent to the microcomputer 10. The microcomputer 10 includes:
The value obtained by integrating and averaging the color difference signals RY and BY that become achromatic when the entire screen of the subject is averaged under the reference color temperature condition is
It is set as a reference value. Then, a white balance control signal R _cont for a red signal that makes the integrated average value of the color difference signal RY equal to the reference value for RY, and an integrated average value of the color difference signal BY and a reference value for BY. _Are output as serial data from the microcomputer 10 and the D / A
The data is converted into an analog signal by the converter 17 and sent to the white balance circuit 6. For this reason, the white balance circuit 6 adjusts the gain of the primary color red signal R and the primary color _blue signal B according to the values of the white balance control signals R _cont and B _cont , and performs white balance feedback control. In addition,
Techniques, such as limiting the amount of change in the white balance control signals R _cont and B _cont , that will be a point of the present invention will be described later.

Next, a first embodiment of the present invention
The operation will be mainly described. As shown in the flowchart of FIG. 2, when the power is turned on in Step 1, Step 2
, An initial operation of white balance adjustment is performed. That is, as shown in FIG.
White balance control signal R _CONT for red signal
And a _blue signal white balance control signal B _CONT having a value of b-0 is output first. The values r-0 and b-0 are preset. Next, the microcomputer 10 determines that the value is r-
0, b-0, the white balance control signal R
_CONT , B The integrated average value of the color difference signals RY, BY adjusted in white balance according to _CONT is input, and the integrated average value of the color difference signals RY, BY at this time and the reference value are calculated. Compare. As a result of the comparison, when the difference between the integrated average value of the color difference signal and the reference value is larger than a predetermined value, white balance control signals R _CONT and B _CONT shifted (increased or decreased) by one step value are output. . In this way,
Until the difference between the integrated average value of the color difference signals RY and BY and the reference value becomes equal to or less than a predetermined value, the white balance control signals R _CONT and B _CONT (sometimes only one of the control signals) are changed to one step value. Change and output each time. When the difference between the integrated average value of the color difference signals RY and BY and the reference value becomes smaller than a predetermined value (for example, 10 LSB (Least Significant Bit)), the values of R _CONT and B _CONT are made constant. _Making the values of R _CONT and B _CONT constant in this way is called “convergence”.

FIG. 4 shows a step value r−R _CONT and B _CONT when R _CONT and B _CONT (values are r−0 and b−0) shown in FIG. 1, b
-1 is indicated.

The white balance control signal R _CONT ,
Since B _CONT can be increased or decreased by one step value, the change pattern per time is as shown in FIG.
As shown in the figure, there are eight types.

Returning to FIG. 2, when the initial operation is completed, the process _proceeds to step 3, where the current values r- _CONT and B- _CONT are obtained.
1, b-1 (the example in FIG. 4) is stored, and the luminance at the time of convergence is obtained and stored. Further, a movable area α is set as shown in FIG. The movable area α in this example is a converged R
_CONT , B From the value of _CONT (r-1, b-1), increase in 4
The area is expanded by four step values in the step value and decreasing direction.

In step 4, the integrated average value of the color difference signals RY and BY is input. In step 5, 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. judge. If the difference exceeds a predetermined value, it indicates that the white balance adjustment is not good. Therefore, the process proceeds to step 6 where R _CONT and B are set to obtain a good white balance.
Calculate whether it is better to increase or decrease _CONT respectively.

In step 7, it is determined whether or not the current luminance has changed by a predetermined value (for example, 0.4BV: Brightness Value) from the luminance stored in the previous time (the luminance stored in step 3). If it has changed by more than the predetermined amount, it is determined that the subject has changed, and the process proceeds to step S8. It is one feature of the present invention to detect the change in the subject from the change in luminance.

In step 8, the current R _CONT , B
It is determined whether or not _CONT is within the movable area α set in step 3.
Move on to In step 9, R _CONT and B _CONT increased or decreased by one step value are output. Whether to increase or decrease is determined in step 6.

By repeating the control flow operation in which steps 4, 5, 6, 7, 8, and 9 are repeated, the white balance control signals R _CONT and B _CONT change. FIG. 6 shows that the control flow operation of steps 4 to 9 is repeated three times, so that R _CONT increases by three steps, B _CONT also increases by three steps, and R
The value of _CONT increases from r-1 to r-2, and the value of B _CONT increases to b-
The state increased from 1 to b-2 is shown.

On the other hand, for example, in FIG. 6, R _CONT, B
_When the values converge when the values of _CONT become r-2 and b-2, that is, when it is determined as YES in step 5 of the flow chart of FIG. 2, the process returns to step 3 and the values of R _CONT and B _CONT at the time of convergence are obtained. The value (r-2, b-2) is stored and the luminance at this time is stored. Further, the step value r
A new movable area α-1 is set that is expanded by ± 4 step values around −2 and b−2. That is, the movable area is changed from α to α
Update to -1.

Further, according to the present invention, as shown in FIG. 7, when the movable area is α, the values of the white balance control signals R _CONT and B _CONT are increased by four steps from r−1 and b−1 to r. −3, b−3 and reaches the boundary value of the movable area α, even if 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 a predetermined value, R _CONT , B _CONT
Is fixed without changing the value of. In the flowchart of FIG. 2, the determination at step 8 is NO, and the process does not proceed to step 9. When the values of R _CONT and B _CONT become the boundary values of the movable area, the values of R _CONT and B _CONT are fixed even if the difference between the color difference signal integrated average value and the reference value is equal to or _larger than a predetermined value. I do. Controlling such that the values of R _CONT and B _CONT become the boundary values of the movable region and do not change them is called “fixed”. In both “fixed” and “convergence”, R _CONT and B _CONT do not change.
In the case of, the difference between the color difference signal integrated average value and the reference value is equal to or larger than a predetermined value, but when the convergence is made, the difference is smaller than the predetermined value.

In step 8, it is determined NO and R _CONT ,
After the value of B _CONT is fixed, the process returns to step 3 to store the fixed values of R _CONT and B _CONT (r-3, b-3 in the example of FIG. 7), store the luminance at this time, and store the step value. r-
A new movable area α-2 is set by extending ± 4 step values around 3, b-3.

As described above, in this embodiment, R _CONT and B _CONT
Because the movable range of is limited within the movable area,
Even when a monochromatic subject is suddenly photographed, R _CONT , B
The value of _CONT does not change significantly. Therefore, the occurrence of color feria can be prevented. This is the most important point of the present invention. A specific shooting mode will be described later.

If it is determined in step 7 in FIG. 2 that the luminance has not changed by a predetermined value or more since the previous convergence or the previous fixation, the process returns to step 4.

Here, the application of the flow control shown in FIG. 2 will be described with reference to a specific photographing mode. As an example of this, a mode in which a beach is photographed at first, and then the bright blue sea is photographed will be described.

When the power is turned on at the beach, an initial operation of white balance adjustment is performed, the white balance control signals R _CONT and B _CONT converge (steps 1 and 2), the convergence value and the brightness of the beach are stored, and the movable area Is set.

Normally, the white balance on the beach does not greatly change, and the determination is YES even if the control proceeds to step 5, the control does not proceed to step 9, and the white balance control signals R _CONT and B _CONT change. I will not do it. In addition, even if a red swimsuit is photographed and the difference between the integrated average value of RY and BY and the reference value is large (NO in step 5), if the change in luminance is small, NO in step 7
Then, the process does not proceed to the step 9 side, and the color balance is not generated because the white balance control signals R _CONT and B _CONT do not change.

If it is assumed that the entire surface, which suddenly shines, is a blue sea, the difference between the integrated average value of RY and BY and the reference value becomes large (NO in step 5), and the brightness of the sea with respect to the brightness of the beach is increased. When the luminance increases (YES in step 7), R _CONT and B _CONT changed by one step value are output (step 9). While steps 4 to 9 continue several times, R _CONT , B
_{Since CONT} reaches the boundary of the movable area (Step 8 N
O), the process does not proceed to the step 9 side, and R _CONT and B _CONT are fixed.

As described above, R obtained by photographing the entire blue sea
Although the difference between the integrated average values of −Y and BY and the reference value is large, R _CONT and B _CONT are fixed when R _CONT and B _CONT reach the boundary of the movable region. Therefore, even if the blue sea is photographed, R _CONT and B _CONT do not change significantly, and color feria does not occur. If the movable area is not set, R _CONT and B _CONT greatly change, and even though the average color of the screen is blue, it is regarded as an achromatic color and a white balance is obtained. The sea turns gray and Caerfelia occurs.

By setting the movable area as described above, R _CONT , B
It is a feature of the present invention that the change of _CONT is limited.

When photographing the sea, the fixed R _CONT , B _CONT and the brightness of the sea are stored in memory, and a new movable area is set centering on this memory value (step 3). In step 7, since the brightness of the previous sea and the brightness of the current sea are the same, the determination is NO, and the process does not proceed to step 9 and R _CONT and B _CONT do not change.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, compared to the first embodiment (FIG. 2),
Step 2-1 has been added, and the other steps are the first.
This is the same as the embodiment.

In the eighth 2-1 step, zoom data P1 is input. When it is on the telephoto side, the range of the movable area set in step 3 is narrowed (for example, ± 2
(Step value), when it is on the wide side, the range of the movable region set in Step 3 is set to a normal width (for example, ± 4 step value).

The reason why the range of the movable area is narrowed at the tele side is as follows. In other words, when the image is taken on the telephoto side, most of the screen may be occupied by one subject. At this time, if the color of the subject is a single color, the color temperature changes even though the color temperature does not change. It is erroneously recognized that color has occurred, and color feria occurs. Therefore, when the telephoto side is set, the range of the movable area is narrowed, and the amount of change of the white balance control signals R _CONT and B _CONT is severely limited to suppress the occurrence of color fear.

[0037]

According to the present invention, the amount of change in the white balance control signal is limited to the movable range as described above in detail with the embodiment. Also, the occurrence of color feria can be prevented. Further, the movable region is updated when the white balance control signal converges or becomes fixed, so that a good white balance adjustment can be performed even when the color temperature actually changes. In addition, since the size of the movable area is reduced in the telephoto side in the zoom state, it is possible to prevent the occurrence of color fear that tends to occur when photographing in the telephoto side.

[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 an explanatory diagram showing values of a white balance control signal at the start of photographing.

FIG. 4 is an explanatory diagram showing a white balance control signal and a movable area.

FIG. 5 is an explanatory diagram showing a change mode of a white balance control signal.

FIG. 6 is an explanatory diagram showing a change state of a white balance control signal and an update state of a movable range.

FIG. 7 is an explanatory diagram showing a state in which a white balance control signal is fixed.

FIG. 8 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

Continued on the front page (31) Priority claim number Japanese Patent Application No. 3-224438 (32) Priority date September 4, 1991 (1991.9.4) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 3-224439 (32) Priority date September 4, 1991 (1991.9.4) (33) Priority claim country Japan (JP) (56) References JP-A-61- 199390 (JP, A) JP-A-60-186188 (JP, A) JP-A-63-262984 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/73

Claims (2)

(57) [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. two color difference signals R-Y, a matrix circuit for outputting the B-Y, together with obtaining the brightness of the subject, image at the reference color temperature conditions
Each color difference signal RY, B, which becomes an achromatic color when the entire surface is averaged
Each of the integrated average values of -Y is preset as a reference value, and a white balance control signal for operating a white balance circuit so that the integrated average value of the color difference signals RY and BY becomes equal to the reference value. To a white balance circuit, and the processing unit further includes: after the power is turned on, after the white balance control signal converges, when the difference between the integrated average value of the color difference signal and the reference value is equal to or greater than a predetermined value. The current luminance changes by a predetermined value or more from the luminance at the time of the previous convergence or the previous fixed value, and the value of the white balance control signal falls within the movable area centered on the previous convergence value or the previous fixed value. On the condition that the value of the white balance control signal is changed by one step value, the processing unit changes the value of the white balance control signal by one step value. When the value becomes the boundary value of the movable area,
When the value of the white balance control signal is fixed and the value of the white balance control signal is fixed or converges within the movable area, the movable area is changed to the current fixed value or a new movable area around the convergence value. A white balance adjustment device, characterized in that: 2. The processing unit according to claim 1, wherein the processing unit detects whether the photographing state is on the tele side or the wide side, and narrows the movable area when the photographing state is on the tele side, and reduces the movable area when the photographing state is on the wide side. A white balance adjustment device characterized by spreading.