JP3142603B2 - White balance device for imaging equipment - 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 apparatus for an image photographing apparatus, which is intended to reduce color fear when photographing indoors and outdoors.

[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, the color tone (color temperature) of the shooting environment
Need to be measured. 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 performed based on the finding that averaging a predetermined range of the screen (for example, about 70% of the entire screen ) results in an achromatic color (gray). 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 values of the R signal and the B signal are feedback-controlled so that the integrated average value of the actual color difference signals RY and BY becomes the reference value.

[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 a green lawn is captured on the entire screen and photographed, the above-mentioned condition is not satisfied, and the color becomes greenish on average. Therefore, when taking a picture of a green grass, automatically adjusting the white balance using the internal photometry method, that is, performing auto white balance, the screen is regarded as achromatic even though the average color is not achromatic. Since the white balance is automatically adjusted, the reference white level shifts, and the color of the reproduction object (grass) is corrected and controlled to have a magenta (complementary color to green) tint, resulting in a so-called color fear.

In order to solve the above-mentioned problems, it is considered at first sight that the white balance adjustment range should be limited to a narrow area when white balance is performed. For example, when expressed on a vector scope with the BY axis as the horizontal axis and the RY axis as the vertical axis, white balance adjustment is performed only in a narrow area near the I axis, and adjustment is not performed outside this area. It is. This idea is devised from the phenomenon that when the color temperature is changed on the vector scope as a parameter, the characteristic curve connecting the starting points of white is close to the I axis. In this way, even if, for example, the green grass is taken in over the entire surface and photographed, the amount of white balance adjustment is small in the green-magenta direction, so that the number of color failures is reduced.

However, limiting the range of the white balance adjustment to a narrow area during the automatic white balance adjustment is difficult from natural light (sun) to artificial light (fluorescent lamp, incandescent lamp).
It is not practical to apply it to a consumer video camera that shoots under the sun. In other words, when shooting with only natural light, white balance can be achieved by adjusting the white balance only in a narrow area near the I axis, but fluorescent light is placed on the color temperature change axis in artificial light. Therefore, when the adjustment area is limited to the vicinity of the I axis and the image is taken under the fluorescent light, the white balance cannot be obtained. Therefore, in the conventional method, even when illuminated with a fluorescent lamp, it is necessary to increase the width of the area in order to draw in the white balance, which is one of the causes of color feria.

SUMMARY OF THE INVENTION In view of the above prior art, the present invention provides an image capturing apparatus capable of adjusting color balance and suppressing white balance.
An object of the present invention is to provide a white balance device for a shadow device .

[0009]

According to a configuration of the present invention, which solves the above-mentioned problems, in a white balance apparatus using an internal photometry method, the brightness of a subject is detected, and when the brightness of the subject is higher than a set value, natural light (sunlight) is detected. ) Is determined as the outdoor mode where the camera is shooting outdoors, and when the subject brightness is lower than the set value, it is determined as the indoor mode where the camera is shooting indoors under artificial light (fluorescent light, incandescent light). In the outdoor mode, the white balance is adjusted only in the limited area selected in consideration of the color temperature of sunlight. In the indoor mode, the white balance is adjusted only in the limited area selected in consideration of the color temperature of each artificial light. It is characterized in that the balance is adjusted.

[0010]

According to the present invention, since the white balance adjustment area is determined separately for the outdoor mode and the indoor mode, the white balance can be adjusted in both modes. Also,
Since the adjustment area is limited, for example, when shooting green grass, white balance adjustment stops halfway, and there is no overcorrection that causes color fear, and at the same time, some white balance adjustment Can also.

[0011]

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 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. The imaging surface of the CCD 3 is provided with a complementary color (cyan, magenta, yellow, green) filter. The charge signal E indicating the subject image is read through a readout circuit (CDS) 4 and an automatic gain control (AGC) circuit 5 , And is input to the signal separation circuit 6. The signal separation circuit 6 generates the charge signal E
, And outputs two types of image signals S1 and S2 and a luminance signal Y. The matrix circuit 7 processes the image signals S1 and S2 to output primary color signals R, G and B. The luminance signal Y is processed by the luminance signal processing unit 22. Primary color signals R, G, B
Is adjusted by the gamma correction circuit 9 after the white balance is adjusted by the white balance circuit 8, and then input to the matrix circuit 10. The matrix circuit 10 performs a matrix process on the primary color signals R, G, and B to generate color difference signals RY,
Outputs BY. In the encoder 11, the color difference signal R-
A signal obtained by quadrature two-phase modulation of Y and BY and a luminance signal Y are added to output an NTSC video signal.

The microcomputer 12 sends an AF (auto focus) control signal P1 to a lens driving unit for moving the lens 1, and sends an AE (auto iris) control signal P to the iris 2.
2 and sends an AGC control signal P3 to the AGC circuit 5.
Also, the microcomputer 12 sends the zoom information P from the lens drive unit.
4 is sent, iris data P5 indicating the iris opening is sent from the Hall element 13 that detects the iris opening, and C
Drive state information P6 indicating the CCD drive state is sent from the CD drive circuit 14. Note that the CCD drive circuit 14
When a movie mode or an electronic shutter mode is set by control means (not shown), the CCD 3 is driven according to each mode. Further, the gate array 15 obtains the iris state from the output signal of the CDS4, and obtains the iris state from the output of the AGC5.
The state of the GC is determined, and the determined state signal P7 is
Sent to

The microcomputer 12 has an iris opening, a CCD,
The brightness of the subject is calculated in consideration of the driving state of A and the gain of the AGC. In other words, the higher the luminance, the narrower the iris, and the darker the AGC gain, the greater the AGC gain.
Since the result of calculating the gain of the GC corresponds to the luminance of the subject, the microcomputer 12 can process these conditions to detect the luminance of the subject. Microcomputer 1
The subject brightness data P8 calculated in 2 is serially transmitted to the microcomputer 20.

On the other hand, the color difference signals RY and BY output from the matrix circuit 10 are applied to low-pass filters 16 and 17 respectively.
, And is digitized by the A / D converters 18 and 19 before being sent to the microcomputer 20. Microcomputer 2
A value obtained by integrating and averaging the color difference signals RY and BY that become achromatic when the predetermined range of the screen is averaged under the reference color temperature condition is set to 0. And the color difference signal R
A white balance control signal R _CONT for a red signal that makes the integrated average value of −Y equal to the reference value for RY, and
A white balance control signal B _CONT for a blue signal that makes the integrated average value of the color difference signal BY equal to the reference value for BY.
Is output from the microcomputer 20, converted into an analog signal by the D / A converter 21, and sent to the white balance circuit 8. For this reason, the white balance circuit 8 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, regarding the area which the white balance control signals R _CONT and B _CONT can take,
It will be described later.

Further, the microcomputer 20 outputs color difference gain control signals RY _GAIN , BY for controlling the gains of the color difference signals RY, BY output from the matrix circuit 10.
_GAIN and color difference signals R-Y, B-Y of for controlling the phase hue control signal R-Y _HUE, the B-Y _HUE is output. In the matrix circuit 10, the color difference gain control signal R-
Y _GAIN, B-Y _GAIN to adjust the saturation changed color difference signals R-Y, the gain of B-Y in accordance with the hue control signal R-Y
_The hue is adjusted by changing the phase of the color difference signals RY and BY according to _HUE and BY _HUE .

The microcomputer 20 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 area X surrounded by the solid line in FIG. In addition, light bulb, white normal type fluorescent lamp,
When shooting white paper illuminated by a white three-wavelength fluorescent lamp, a daylight white normal fluorescent lamp, a daylight three-wavelength fluorescent lamp, a daylight normal fluorescent lamp, or a daylight three-wavelength fluorescent lamp, R _CONT and B _CONT The value takes the value of the point indicated by the triangle in the figure. That is, the area X in the indoor mode
Is the value at which R _CONT and B _CONT converge when adjusting white balance by shooting white paper illuminated by various artificial lights, and white balance by shooting white paper under dim natural light outdoors. When adjusted, R _CONT , B
_CONT includes a value that converges and the area width is narrowed. On the other hand, when the outdoor mode is set, the values of the white balance control signals R _CONT and B _CONT can take only the values in the area Y surrounded by the dashed line in FIG. R _CONT , B
_{Assuming that} the value of _CONT is each value of the area Y, the color temperature characteristic at that time falls within a limited area close to the I axis when displayed on a vector scope.

The microcomputer 20 receives the subject brightness data P8 sent from the microcomputer 12, and determines that the subject mode is the outdoor mode if the subject brightness is higher than the reference value, and determines the indoor mode if the subject brightness is lower than the reference value. This is shown in FIG.
The fact that the level of color temperature and the level of illuminance correspond to each other is used.

The manner in which the microcomputer 20 adjusts the white balance is as follows. The microcomputer 20 sequentially changes the values of the white balance control signals R _CONT and B _CONT so that the integrated average value of the color difference signals RY and BY matches the reference value, and the color temperature at the time of this photographing. When the optimal white balance adjustment is performed, R _CONT and B
The value of _CONT becomes constant and converges. White balance control signal R _CONT, but B _CONT is gradually changed until it converges to a constant value, R _CONT if outdoor mode, B _CONT
Are limited to the values in the area Y. In the indoor mode, the possible values of R _CONT and B _CONT are limited to the values in the area X. When shooting a general scene in which each color is randomly mixed, good white balance adjustment can be performed if the values of R _CONT and B _CONT converge to a certain value in area X in indoor shooting, and R in outdoor shooting. _If the values of _CONT and B _CONT converge to a certain value in the area Y, good white balance adjustment can be performed.

[0019] If you've taken the green lawn to the shooting screen full of outdoor, R _CONT, the value of B _CONT is to let us toward changes to the outside of the value of gradually change to continue area Y but, R _CONT , B _CONT are fixed when the values of R _CONT and B _CONT become the boundary values of area Y. By doing so, the adjustment of the white balance is not largely shifted, and the color feria is greatly reduced.

Assuming that the red wall is photographed indoors to fill the photographing screen, the values of R _CONT and B _CONT gradually change, and try to change to values outside the area X.
_When the values of _CONT and B _CONT become the boundary values of area X, the values of R _CONT and B _CONT are fixed. By doing so, the adjustment of the white balance is not largely shifted, and the color failure is greatly reduced.

In addition, when the white balance is automatically adjusted and the color failure is reduced regardless of the sunlight mode or the artificial mode mode without dividing into the outdoor mode and the indoor mode, R _CONT , The control area of B _CONT is
It becomes wider like the area Z surrounded by the dotted line in FIG. Such a large control area means that the control is often performed using information other than the information relating to the color temperature. In the present invention, the mode is divided into an outdoor mode and an indoor mode, and the area used in each mode is narrowly limited. Therefore, color fear does not occur and white balance can be adjusted. FIG. 4 shows the correction status of the related art and the present invention on a vector scope. Arrows in the figure indicate the magnitude and direction of the correction amount. In this case, since a color that should not be corrected is originally considered, the larger the correction amount, the larger the amount of color feria. Conventionally, a color feria occurs as shown in FIG.
As shown in (c), it can be seen that the color change is small and the color feria is greatly reduced.

In the present invention, the outdoor mode and the indoor mode are switched in accordance with the luminance. The luminance value to be switched may be set to an optimum value according to the type of the video camera. The range can be arbitrarily selected according to the design concept. In addition, simply, the mode can be determined by looking at the aperture value instead of the luminance.

FIG. 5 is a flowchart showing the operation of the embodiment. As shown in the figure, immediately after the power is turned on (step 1), the preset values of the white balance control signals R _CONT and B _CONT are output (step 2). After the power is turned on, the color difference signals RY and BY are fetched (step 3), and the white balance control signal R _CONT which makes the difference between the integrated value of the color difference signals RY and BY and the reference value zero is set. , B _CONT (step 4). When the luminance is equal to or higher than the set value and the values of R _CONT and B _CONT are in the outdoor mode (steps 5 and 6), the new R calculated in step 4 is used.
_CONT, and outputs the B _CONT (step 7), R _CONT, B _CONT
Is not in outdoor mode (Step 6)
Output the previous R _CONT and B _CONT (step 8). On the other hand, when the luminance is less than the set value and the values of R _CONT and B _CONT are in the indoor mode (step 5,
9) Output the new R _CONT and B _CONT obtained in step 4 (step 10), and when the values of R _CONT and B _CONT are not in the indoor mode (step 9),
_CONT and B _CONT are output (step 8).

[0024]

According to the present invention, the white balance adjustment range 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, since the adjustment range of each white balance is limited to a narrow area, the color failure is greatly reduced.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a control area.

FIG. 3 is a characteristic diagram showing a relationship between luminance and color temperature.

FIG. 4 is a characteristic diagram showing a correction state on a vector scope.

FIG. 5 is a flowchart showing an operation state of the embodiment.

[Description of Signs] 1 lens 2 iris 3 CCD 4 readout circuit 5 AGC circuit 6 signal separation circuit 7 matrix circuit 8 white balance circuit 9 γ correction circuit 10 matrix circuit 11 encoder 12, 20 microcomputer 13 hall element 14 CCD drive circuit 15 gate array 16, 17 Low-pass filter 18, 19 A / D converter 21 D / A converter 22 Luminance signal processing unit E Charge signal S1, S2 Image 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 blue signal RY _GAIN , BY _GAIN color difference gain control signal RY _HUE , BY _HUE hue control signal

 ──────────────────────────────────────────────────の Continued on the front page (31) Priority claim number Japanese Patent Application No. 3-96551 (32) Priority date April 26, 1991 (1991. 4.26) (33) Priority claim country Japan (JP) (56) References JP-A-2-272892 (JP, A) JP-A-1-105686 (JP, A) JP-A-2-29191 (JP, A) JP-A-64-46393 (JP, A) JP-A-61-184079 (JP, A) JP-A-62-119911 (JP, A) JP-A-3-120988 (JP, A)

Claims (1)

(57) [Claims] An imaging unit for photoelectrically converting a subject image formed by an optical system; and a primary color signal of red and blue among red, green and blue primary color signals obtained by processing an output signal of the imaging unit. A white balance circuit that controls the amplification degree to perform white balance adjustment; a matrix circuit that processes the white balance adjusted primary color signals and outputs two types of color difference signals RY and BY; A luminance calculation processing unit for calculating the luminance of the subject based on the operation state of the member that operates according to the luminance of the subject, and each color difference signal that becomes an achromatic color when a predetermined range of the screen is averaged under the reference color temperature condition The integrated average values of RY and BY are preset as reference values, and the white balance is set so that the integrated average values of the color difference signals RY and BY at the time of shooting are equal to the reference values. Actuated circuit Has a function to continuously send the white balance control signal to the white balance circuit, and when the white balance is adjusted by shooting white paper illuminated with sunlight of the assumed color temperature outdoors. value but which the outdoor mode region narrowed and region includes values converge (Z) (Y), white balance control signals by photographing a white paper illuminated by various artificial light when the white balance adjustment is converged In addition, an indoor mode area (X) is set including a value in which the white balance control signal converges and narrowing the area (Z) when the white balance is adjusted by shooting white paper under dim natural light outdoors. When the brightness of the subject obtained by the brightness calculation processing unit is larger than a predetermined value, the value of the white balance control signal is set to a value within the outdoor mode area. And a white balance processing unit that sets the value of the white balance control signal to a value within the indoor mode area when the obtained brightness of the subject is smaller than a predetermined value. Balance device.