JPH07284118A - White balance device for video camera - Google Patents

Abstract

PURPOSE:To attain excellent video image pickup by effectively suppressing occurrence of a color failure. CONSTITUTION:An image pickup signal S corresponding to an optical image is outputted from a CCD 3. A luminance signal processing circuit 11 of a signal processing circuit section 9 processes a luminance signal component of the image pickup signal S, a color separation circuit 13 obtains primary color signals R, G, B from the image pickup signal S, and a white balance circuit 19 implement white balance control based on white balance control signals Rcont, Bcont. An integration device 25 obtains a luminance integral value IY and color synthesis integral values ICr, ICb, and a matrix arithmetic section 29 of a microcomputer 27 obtains IR/IG, IB/IG of color signal integral values IR,IG,IB. A control value arithmetic section 33 obtains the white balance control signals Rcont, Bcont based on the IR/IG, IB/IG when an almost-white level discrimination section 31 discriminates an object to be a nearly white level. A lighting light discrimination section 35 discriminates the type of a lighting light source based on the control signal Rcont. The almost-white level discrimination section 31 discriminates a nearly white level depending whether or not the IR/IG, IB/IG are within the nearly white level detection range set for each lighting light source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance device for a video camera, which is devised so that a good-quality image can be taken without a color failure even when a single-colored object having a low density is taken.

[0002]

2. Description of the Related Art In a video camera, white balance control is performed so that a white reproduced image can be obtained when a white subject is photographed. The white balance control adjusts the gains of the red signal circuit and the blue signal circuit of the camera with reference to the green signal.

An image integration type auto white balance circuit in the auto white balance (AWB) circuit is controlled based on the knowledge that when the color signal components of the entire image pickup screen are integrated, an achromatic color is obtained.

Specifically, the red signal R, the green signal G, and the blue signal B are integrated for each field to obtain a red integrated value IR, a green integrated value IG, and a blue integrated value IB, and further, an integrated value for the integrated value IG. The IR ratio IR / IG and the ratio IB / IG of the integrated value IB to the integrated value IG are obtained. Then, the white balance control signals R _cont and B _cont such that (IR / IG) = (IB / IG) = 1
Ask for. Then, according to the value of the control signal R _cont , the red signal R
And the gain of the _blue signal are adjusted according to the value of the control signal B _cont to perform white balance control.

The above-mentioned condition "when the entire screen is averaged, it becomes an achromatic color (gray)" is satisfied when a general landscape in which various colors are randomly mixed is photographed.
However, for example, a subject against the blue sky and blue sea,
When a subject or the like against a red wall is photographed, the above-mentioned conditions are not satisfied, and on the average, the color turns into blue or red. Therefore, when a subject (person) whose background is monochromatic is photographed, if image integration type white balance control is performed, white balance control is performed assuming that the averaged screen color is achromatic, even if the average color is not achromatic. As a result, the reference white level is deviated, the background is discolored, and the color of the main subject (person) is corrected and controlled in the direction of complementary color (complementary color to the background color), so-called color flare occurs.

Conventionally, the following measures have been taken in order to solve the above-mentioned problems. That is, the black body radiation approximate curve CBL and the substantially white detection range A1 as shown in FIG. 8 are set in the automatic white balance device. Blackbody radiation approximate curve C
BL captures a "white" subject under light sources having different color temperatures, and correlates the ratio IR / IG, IB / IG of the integrated values of the signal levels of the primary color signals R, G, B in the captured signal. Obtained by asking for a relationship. Above and below the black body radiation approximation curve CBL, a substantially white detection range A1 for performing an appropriate white balance is provided, and the ratio IR / IG,
When IB / IG falls within the substantially white detection range A1, white balance control is performed by the white balance control signals R _cont and B _cont obtained based on the ratios IR / IG and IB / IG at this time. When a subject with a large proportion of a certain specific color is photographed, the ratios IR / IG and IB / IG fall outside the substantially white detection range A1, and at this time, the previous white balance control signals R _cont and B _cont are used. The white balance is controlled.

[0007]

By the way, in FIG. 8, since the substantially white detection range A1 is wide, when a monochrome object is photographed, when the density of the monochrome is considerably high, the ratio IR /
IG and IB / IG go out of the substantially white detection range A1, but when the density of a single color is relatively low, the ratio IR / IG, IB / I
G may fall within the substantially white detection range A1. Therefore, when a single-color subject having a low density is photographed, this specific single color may be erroneously determined to be white, and white balance control may be performed, resulting in a color failure.

In view of the above-mentioned conventional technique, it is an object of the present invention to provide a white balance device for a video camera in which the occurrence of color ferria is further reduced.

[0009]

The structure of the present invention which solves the above-mentioned problems is to integrate a red signal R, a green signal G and a blue signal B obtained by processing an image pickup signal outputted from an image pickup section to obtain a red signal. While obtaining the integrated value IR, the green integrated value IG, and the blue integrated value IB,
A calculation unit for obtaining ratios IR / IG and IB / IG of the red integrated value IR and the blue integrated value IB with respect to the green integrated value IG, and the ratio IR /
Based on IG, IB / IG, a substantially white determination unit for determining whether or not the image pickup screen becomes substantially white when integrated, and a ratio IR / IG,
White balance control signal can optimum white balance control based on IB / IG R _cont, while calculating the B _cont, white balance control the substantially white determination unit is calculated to date when it is determined that substantially white signal R _cont, When B _cont is output and the substantially white determination unit determines that it is not substantially white, the control value calculation unit that outputs the white balance control signals R _cont and B _cont when the determination is made to be substantially white before is output. White balance control signals R _cont , B
_In a white balance device for a video camera having a white balance circuit for controlling white balance by adjusting the amplification degree of the red signal R and the blue signal B based on _cont , when the subject brightness is obtained and the subject brightness is equal to or more than a set value, illumination is performed. The light is determined to be sunlight, the illumination light is determined to be artificial light when the subject brightness is less than the set value, and the type of artificial light is determined from the convergence value of one of the white balance control signals. An illumination light determination unit is provided, and the substantially white determination unit is provided in a determination area using the ratios IR / IG and IB / IG as parameters, and the substantially white determination range for sunlight and the substantially white determination range for sunlight are provided. A plurality of narrow substantially white determination ranges for artificial light are set, and a substantially white determination range corresponding to the illumination light determined by the illumination light determination unit is selected to obtain a ratio IR / IG, I.
It is characterized in that it has a function of determining that it is substantially white when B / IG falls within the selected substantially white determination range and determines that it is not substantially white when it is not likely to occur.

[0010]

In the present invention, it is determined whether the illumination light is sunlight or artificial light, and when it is artificial light, the type of artificial light is determined, and the determination is made in the substantially white determination range having different area widths. It is determined whether the subject is substantially white by using the substantially white determination range corresponding to the illumination light. Therefore, under artificial light illumination with a narrow determination range, even if a single subject having a low density is photographed, the occurrence of color ferria is reduced.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<Circuit Configuration of Video Camera of Embodiment> FIG. 1
FIG. 3 is a circuit diagram showing an image pickup type of a video camera incorporating the present invention. As shown in the figure, an optical image formed by the lens 1 is formed on the light receiving surface of the CCD 3, and the image pickup signal S is output from the CCD 3. The image pickup signal S is subjected to sample hold processing and gain adjustment in the sample and hold and AGC circuit 5, and further converted into a digital signal by the A / D converter 7, and then the luminance signal processing circuit 11 and the color separation of the signal processing circuit unit 9. It is input to the circuit 13 and another color separation circuit 15.

The luminance signal processing circuit 11 uses signal processing to
This digital brightness signal DY is created and output.
DY is an analog luminance signal by the D / A converter 17.
Converted to Y and output. The color separation circuit 13 is a signal processing unit.
The three types of primary color signals R, G, and B are created and output according to the logic.
The primary color signals R, G, B are white balance control signals R
_cont, B_contDepending on the white balance circuit 19
Balance control (gain adjustment), white balun
The primary color signals R, G and B, which have been subjected to the step control, are processed by the color signal processing circuit 21.
Signal processing is carried out to obtain a digital color signal DC. This
The color signal DC of is converted into an analog signal by the D / A converter 23.
Is converted into the color signal C and output.

The color separation circuit 15 performs signal processing to perform digital processing.
Brightness signal Y and color synthesis signal C of Tal _r, C_bOutput
It In the subsequent stage of the color separation circuit 15, an integrator 25 and a macro
The micro computer 27 is connected. Microco
The computer 27 includes a matrix calculation unit 29 and a substantially white determination unit.
31, a control value calculator 33, and an illumination light determiner 35
There is.

The integrator 25 performs integration processing to obtain a luminance signal Y
And a color synthesis integrated value IC _r and IC _b obtained by respectively integrating the color synthesis signals C _r and C _b .

The matrix calculation unit 29 of the microcomputer 27 performs matrix processing to obtain integrated values IY, IC.
_r, green integrated value IG from IC _b, red integrated value IR, asked the blue integrated value IB, and further the ratio I of the integrated value IR for the integral value IG
R / IG and the ratio IB / of the integrated value IB to the integrated value IG
Ask for IG.

The substantially white determination unit 31 is provided with a ratio IR / IG and a ratio IB.
Based on the value of / IG, it is determined whether the subject images are achromatic when averaged (this is referred to as "substantially white determination"). This substantially white determination method is the point of the present invention, and its details will be described later together with the operation of the illumination light determination unit 35.

The control value calculation unit 33 calculates the ratio IR / IG, IB
Based on / IG, white balance control signals R _cont and B _cont capable of optimal white balance control are calculated. That is, the white balance control signals R _cont and B _cont such that (IR / IG) = (IB / IG) = 1
Is calculated.

Further, the control value calculation unit 33 includes a substantially white determination unit 31.
When it is determined that the average of the subject images is substantially white, the white balance control signal R calculated at that time is calculated.
_cont and B _cont are output and sent to the white balance circuit 19. However, when it is determined that the white balance is not substantially white, the white balance control signals R _cont and B _cont that were previously determined to be substantially white are output and sent to the white balance circuit 19.

The white balance circuit 19 performs white balance control based on the sent white balance control signals R _cont and B _cont .

<Operation of Selecting Near White Detection Range for Near White Judgment to Determine Near White> The illumination light judging unit 35 considers the iris opening, the electronic shutter speed, and the AGC gain. To determine the brightness of. When the brightness is equal to or higher than a preset value, it is determined that the sunlight is illuminating, and when the brightness is lower than the preset value, artificial light (fluorescent lamp, incandescent lamp, etc.) is illuminating. judge.

Further, when it is determined that the artificial light is used for illumination, the illumination light determination section 35 determines the type of artificial light as follows. That is, as shown in FIG. 2, in the illumination light determination unit 35, sections are set for the value of the white balance control signal R _cont , and when the control signal R _cont is the value of the section, an incandescent bulb or white. If the control signal R _cont is a value within the section, it is determined to be a daylight white fluorescent lamp, and if the control signal R _cont is a value within the section, it is a daylight color fluorescent lamp. .

The above-mentioned judgment can be made by the white rose.
Control signal R_cont, B_contIs an incandescent light source
Sometimes P₁The value of P when a white fluorescent lamp is used
₂To the value of P₃Value of the day
P when the color fluorescent light _FourBecause it converges to the value of
It

As shown in FIGS. 3 to 6, the substantially white determination section 31 includes a substantially white detection range a0 for sunlight, a substantially white detection range a1 for incandescent light bulbs / white fluorescent lamps, and a substantially white for daylight white fluorescent lamps. Detection range a
2. A substantially white detection range a3 for daylight fluorescent lamps is set. Then, as shown in Table 1 below, the substantially white determination unit 31 selects a substantially white detection range corresponding to the light source determined by the illumination light determination unit 35. Then, when the ratios IR / IG and IB / IG fall within the selected substantially white detection range, it is determined to be substantially white,
When the ratios IR / IG and IB / IG are out of the selected substantially white detection range, it is determined that they are not substantially white.

[0025]

[Table 1]

As described above, when the illumination light source is the artificial light source, the substantially white detection range is narrowed to a1, a2, and a3. Therefore, it is determined that the light is not substantially white even when a light single color subject is photographed. In this case, the white balance control is performed by the white balance control signals R _cont and B _cont when the white balance control signals R _cont and B _cont were finally determined to be substantially white. Therefore, a light single color is not erroneously determined to be white, and color ferria is less likely to occur.

Therefore, for example, if a red paper is photographed under illumination of an incandescent light bulb, since the following range a1 is in an area that does not include dark red (an area on the left side in FIG. 4), a color feria is unlikely to occur with respect to red. Further, for example, when a green paper is photographed under a daylight fluorescent lamp, the tracking range a3 is in an area that does not include dark green (an area on the right side in FIG. 6), and thus a color feria is unlikely to occur with respect to green.

<Modification> In the above embodiment, as shown in FIG. 2, the section along the white balance control signal R _cont is set to discriminate the type of the artificial illumination light source, but as shown in FIG. It is also possible to set the sections (1), (2), and (3) along the control signal B _cont to determine the type of the artificial illumination light source. That is, when the control signal B _cont has a value within the section (1), it is determined to be an incandescent bulb or a white fluorescent lamp, and when the control signal B _cont has a value within the section (2), it is a daytime white fluorescent lamp. Judge and control signal B
_{When cont} has a value within the section (3), it is determined to be a daylight fluorescent lamp.

Further, the control signal R _cont or the control signal B _cont
Each tracking range for artificial light may be set more finely according to the value of.

[0030]

According to the present invention as specifically described above with reference to the embodiments, when illuminating with artificial illumination light,
The white detection range of a narrow area according to the type of each illumination light is used to determine the white color, so even if a single subject with a low density is photographed under artificial illumination light, it is good without color faria. You can shoot.

[Brief description of drawings]

FIG. 1 is a block diagram showing a signal system of a video camera equipped with a white balance control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an illumination light source determination characteristic.

FIG. 3 is a characteristic diagram showing a substantially white detection range for sunlight.

FIG. 4 is a characteristic diagram showing a substantially white detection range for an incandescent light bulb / white fluorescent lamp.

FIG. 5 is a characteristic diagram showing a substantially white detection range for a neutral white fluorescent lamp.

FIG. 6 is a characteristic diagram showing a substantially white detection range for a daylight fluorescent lamp.

FIG. 7 is a characteristic diagram showing another example of an illumination light source determination characteristic.

FIG. 8 is a characteristic diagram showing a substantially white detection range in the related art.

[Explanation of symbols]

1 Lens 3 CCD 5 Sample and Hold and AGC Circuit 7 A / D Converter 9 Signal Processing Section 11 Luminance Signal Processing Circuit 13 Color Separation Circuit 15 Color Separation Circuit 17 D / A Converter 19 White Balance Circuit 21 Color Signal Processing Circuit 23 D / A Converter 25 Integrator 27 Microcomputer 29 Matrix calculation unit 31 Substantial white determination unit 33 Control value calculation unit 35 Illumination light determination unit S Imaging signals R, G, B color signals IR, IG, IB Integration values IR / IG, IB / IG Ratio R _cont , B _cont White balance control signal C Color signal Y Luminance signal

Claims (1)

[Claims] 1. A red signal R, a green signal G, and a blue signal B obtained by processing an image pickup signal output from an image pickup section are integrated to obtain a red integrated value IR, a green integrated value IG, and a blue integrated value IB. Together with the red integrated value IR and the blue integrated value I with respect to the green integrated value IG
A calculation unit for obtaining the ratios IR / IG and IB / IG of B, and a substantially white determination unit for determining whether or not the image pickup screen becomes substantially white based on the ratios IR / IG and IB / IG, and a ratio IR / IG, IB / IG White balance control signals R _cont , B capable of optimal white balance control based on
_{In addition} to calculating _cont , the white balance control signal R calculated most recently when the substantially white determination unit determines that the white balance is substantially white.
_cont , B _cont, and a control value calculation unit for outputting the white balance control signals R _cont , B _cont at the time when the white-white determination unit determines that the white-white determination unit is not substantially white, and outputs the white balance control signals R _cont and B _cont . In a white balance device for a video camera, which has a white balance circuit that adjusts the amplification of the red signal R and the blue signal B based on the output white balance control signals R _cont and B _cont to control the white balance, When the obtained subject brightness is equal to or higher than the set value, it is determined that the illumination light is sunlight. When the subject brightness is less than the set value, it is determined that the illumination light is artificial light. Of the artificial light from the convergent value of the artificial light, and the substantially white determination unit determines the ratio IR / IG and IB / IG as parameters. In the rear, a substantially white determination range for sunlight and a plurality of substantially white determination ranges for each artificial light narrower than the substantially white determination range for sunlight are set, and the illumination determined by the illumination light determination unit Select a substantially white judgment range according to the light and set the ratio IR
/ IG, IB / IG is a white balance device for a video camera having a function of determining that it is substantially white when it is within a selected substantially white determination range and determining that it is not substantially white when it is not likely to be.