JPH11205806A - White balance control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply accurate white balance control with respect to an achromatic object which is colored lightly. SOLUTION: A color space consisting of a chrominance signal, such as a color difference signal and a luminance signal, is divided into plural areas, and color signal detection circuits 61, 62,...6n detect the quantity of signals included in the respective areas. A white balance deviation discriminating circuit 7 detects a direction and a magnitude of white balance deviation, based on a color distribution of an object consisting of the signals and a white balance setting circuit 8 sets a white balance control signal accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera,
The present invention relates to a white balance control device in a TR-integrated camera, an electronic still camera, and the like, and more particularly to improving the performance of a white balance control device.

[0002]

2. Description of the Related Art A white balance control device used in a video camera or the like is a so-called external photometric type in which a color temperature sensor or the like directly detects and controls the color temperature of an illumination light source.
It can be roughly classified into two types, namely, so-called internal photometry type, which performs control by detecting a color shift of a subject from a video signal or the like.
The internal photometry type is mainly used in terms of easiness of configuration and cost.

As an internal photometric white balance control device, there is, for example, a device described in Japanese Patent Application Laid-Open No. Hei 5-344530. This white balance control device first obtains a primary color signal of red (R), green (G) and blue (B) obtained by color-separating an output signal of an image sensor.
It generates two color difference signals (RY), (BY) and a luminance signal Y, and further adds and subtracts the two color difference signals to convert a color difference signal into an axis (RB) signal and an (R + B) signal.
-2Y) Generate a signal. Next, a signal corresponding to only the achromatic portion (white portion) in the subject is extracted by providing a threshold corresponding to the level of the luminance signal Y to the (RB) signal and the (R + B-2Y) signal. (A white portion extraction range) is set, and the coloring (white balance deviation) of the achromatic subject is detected from a signal obtained by integrating the signal included in this region. afterwards,
By changing the gains of the primary color signals R and B according to the white balance shift, the white balance shift is corrected.

In the conventional apparatus described in Japanese Patent Application Laid-Open No. 5-344530, a white portion extraction range is set by a combination of a plurality of regions, thereby enabling more accurate detection of white balance deviation.

Such a conventional internal photometric white balance control device generally sets a white portion extraction range in a subsequent color signal such as a color difference signal, and integrates a signal included in this range to reduce a white balance deviation. The white balance is controlled by forming a feedback loop of detecting and controlling the gain of the preceding color signals such as the primary color signals R and B based on the detection result.

[0006]

In such a conventional white balance control device, a signal included in a white portion extraction range is regarded as a white balance deviation of an achromatic subject, and feedback control is performed so as to correct the white balance deviation. Therefore, if a signal of a chromatic object is included in the white portion extraction range, a malfunction occurs in that the object is regarded as achromatic and correction is performed. In order to reduce such a malfunction, in the conventional white balance control device, the white portion extraction range is finely set by a combination of a plurality of regions for each light source such as natural light and fluorescent light, and the photographing environment is estimated. The white portion extraction range is further limited for each shooting environment, and an attempt is made to avoid including a signal of a chromatic subject in the white portion extraction range. However, the actual imaging subject is a combination of subjects having various saturations, and the lighting conditions are variously different, so that the color of the achromatic subject that occurs due to the different color temperature of the light source ( It is very difficult to accurately separate white balance deviation) from lightly colored chromatic colors. For example, when photographing mountain trees on the whole screen, the shade of green and the state of the sun vary, and the light green part may be included in the white part extraction range assuming a fluorescent lamp. It is possible enough. In such a case, since the light green is regarded as an achromatic color and feedback control is performed so as to correct the color, the other green portions also sequentially enter the white portion extraction range. The coloration of green becomes lighter, and the other colors have a magenta hue.

Further, in the conventional white balance control device, since the white balance deviation is detected based on the integral value of the signal included in the white portion extraction range, the magnitude of the white balance deviation cannot be detected. .
That is, since the integral value is determined by the product of the magnitude of the white balance deviation of the achromatic portion and the area of the achromatic portion (the ratio in the screen), the ratio of the achromatic portion is large even if the white balance deviation is large. The smaller the value, the smaller the integral
Even if the white balance deviation is small, the integration value increases if the ratio of the achromatic portion is large. Therefore, only the direction of the white balance deviation of the signal included in the white extraction range can be reliably detected from the integral value, and in order to perform stable control, the feedback amount is always small regardless of the magnitude of the integral value. It is necessary to perform gradual correction control. For this,
When the white balance shift is large, it takes time to correct.

A first object of the present invention is to solve the above problem, to detect white balance deviation of an achromatic subject with high accuracy, and to control white balance which does not malfunction even for a chromatic subject with a light color. It is to provide a device.

A second object of the present invention is to provide a white balance control apparatus capable of detecting the magnitude of the white balance deviation of an achromatic subject and correcting the white balance deviation in a short time even when the white balance deviation is large. Is to provide.

[0010]

According to the present invention, there is provided a white balance shift detecting means for detecting a white balance shift of an achromatic subject from a primary color signal, a color difference signal, or another color signal generated from an output signal of an image sensor. White balance setting means for generating a gain control signal in accordance with the detection result of the white balance deviation detecting means, and controlling the gain of a variable gain amplifying means for amplifying the color signal by the gain control signal to perform white balance control. In the white balance control apparatus, the white balance shift detecting means includes a color signal detecting means for dividing a color space into a plurality of color areas and detecting the presence or absence of a color signal corresponding to each color area. White balance is determined based on the color distribution of the object obtained from the detection result of the means. By providing a Nsu deviation determination means, it is intended to improve detection accuracy.

The white balance shift determining means determines a white balance shift based on the position of the center of gravity of a plurality of continuous color regions where the presence of a color signal is detected, and a plurality of separated color regions where the presence of a color signal is detected. A method of determining the white balance deviation based on the position of the overall center of gravity, a method of determining the white balance deviation based on the position of the color region closest to the origin among the separated color regions where the presence of color signals is detected, and the like. Can be adopted.

Further, the white balance setting means includes:
By changing the control amount of the gain control signal according to the magnitude of the white balance shift amount obtained from the white balance shift detecting means, a large shift can be corrected in a short time.

The color signal detecting means comprises a plurality of detecting means for detecting in parallel the presence or absence of a color signal corresponding to the plurality of color areas, or a color signal corresponding to a plurality of color areas. Is detected by using one detecting means in a time-division manner.

[0014] The white balance shift detecting means is provided with a shooting environment estimating means for estimating the shooting environment of the image pickup device, and the white balance shift determining means is provided with a white balance according to the shooting environment estimated by the shooting environment estimating means. The deviation is determined.

The photographing environment estimating means estimates the photographing environment based on information such as illuminance, distance, date and time obtained from the automatic exposure function means, the automatic focusing function means, the clock function means and the like.

[0016]

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

FIG. 1 is a block diagram showing one embodiment of the white balance control device of the present invention. In the embodiment shown in FIG. 1, 1 is an image sensor, 2 is a color separation circuit, 31 and 32 are variable gain amplifier circuits, 4 is a color difference signal generation circuit, 5 is an arithmetic circuit, and 61, 62,. A signal detection circuit, 7 is a white balance deviation determination circuit, 8
Is a white balance setting circuit, 9 is a subtraction circuit, 10 is an addition circuit, 11 is a gate signal generation circuit, 12 and 13 are gate circuits, 14 is an integration circuit, and 15 is an integration circuit.

The color separation circuit 2 performs a color separation process on the output signal of the image sensor 1 to perform red (R), blue (B), and green (G).
The primary color signals R, B, and G for each color are generated. Of these primary color signals R, G, B, the primary color signals R, B are respectively amplified by the variable gain amplifying circuits 31, 32, and then supplied to the color difference signal generating circuit 4 together with the primary color signal G to provide two color difference signals (R −
Y), (B−Y) and a luminance signal Y are generated. These color difference signals (RY), (BY) and the luminance signal Y are supplied to a processing circuit (not shown) and also to a white balance control system described below.

The white balance control system includes an arithmetic circuit 5,
.. 6n, a white balance shift determining circuit 7 and a white balance setting circuit 8, and the white balance shift using the color difference signals (RY) and (BY) and the luminance signal Y. Is detected, and gain control signals S1 and S2 for correcting this are generated to control the gains of the variable gain amplifier circuits 31 and 32.

The arithmetic circuit 5 inputs the color difference signals (RY) and (BY) generated by the color difference signal generating circuit 4 to the arithmetic circuit 5, and a predetermined ratio (here, a (1: 1) is performed to convert the color signals into color signals represented by (RB) and (R + B-2Y). Here, these color signals (RB),
As shown in FIG. 2A, (R + B-2Y) is a signal that has been subjected to axis conversion on a color difference plane having the color difference signals (RY) and (BY) as orthogonal axes. (RB) is a saturation signal representing substantially red (R) ← → blue (B) direction, and (R + B-2Y) is a saturation signal representing substantially magenta (Mg) →→ green (G) direction. . These saturation signals (RB), (R + B-
2Y) are supplied in parallel to the respective color signal detection circuits 61, 62,... 6n.

The color signal detection circuit 61 includes a gate signal generation circuit 11 for generating gate signals G11, G12, G21, and G22 having different thresholds according to the level of the luminance signal Y supplied from the color difference signal generation circuit 4. A gate circuit 12 that transmits only the saturation signal (RB) included between the thresholds of the gate signals G11 and G12 generated by the gate signal generation circuit 11, and gate signals G21 and G22 also generated by the gate signal generation circuit 11 A gate circuit 13 that transmits only the saturation signal (R + B-2Y) included between the threshold values of:
An integrating circuit 14 for integrating the output signals from the gate circuits 12 and 13 and an integrating circuit 15 for integrating the output signal of the integrating circuit 14 for one screen, for example.

The color signal detecting circuit 61 constructed as described above
Is the gate signal G for the (RB) axis on the color difference plane.
11, within the area set by G12, and (R + B
For the (-2Y) axis, the amount of the color signal located in the area set by the gate signals G21 and G22 is detected and output.

The other color signal detection circuits 62,..., 6n are configured in the same manner as the color signal detection circuit 61, but the gate signals G11, G1 are different so that the respective color signals to be detected are different.
2 and the position of the region set by the gate signals G21 and G22. As a method of dividing each area, a method of equally dividing the color space coordinate axis or an unequal division method of finely dividing a portion to be separated may be used.

In this embodiment, these color signal detection circuits 61, 62,... 6n convert the color space represented by the color difference and the luminance into n as shown in FIGS. It is configured to detect and output the signal amount included in each area when divided equally into 8 (here, 8 × 16 = 128). That is, one color signal detection circuit 61 detects a color signal corresponding to one of these areas. Here, FIG. 2A is a diagram of the color space viewed on a color difference plane, and FIG. 2B is a diagram of FIG. 2A including a luminance axis.

The white balance deviation determination circuit 7 determines the color distribution of the entire subject from the signal amount of each color area output from the color signal detection circuits 61, 62,... 6n, and detects the direction and magnitude of the white balance deviation. I do. This detection (determination) method will be described with reference to FIGS.

FIGS. 3A, 3B, and 3C show examples of color distribution when different subjects are photographed.
A region A surrounded by a bold line in the figure is a white balance deviation with respect to an achromatic subject due to a light source represented by black body radiation such as sunlight or an incandescent lamp and a light source such as an artificial light source such as a fluorescent lamp. Indicates a white area in which a color (chromatic) signal may be detected when the image occurs.

FIG. 3A is an example of a color distribution of a color signal detected when a simple chromatic subject is photographed. In this example, the signal detection area B of the detected color signal is an area outside the white area A, and is not detected in the white area A. Is determined.

FIG. 3B shows a color distribution of a color signal detected when a white light source having a color temperature of 5000 ° K is changed from a state in which white balance is adjusted to a photographing environment using a fluorescent lamp as a light source. This is an example. All of the plurality of signal regions C where the corresponding color signal is detected are included in the white region A. The white balance shift determining circuit 7 obtains the center of gravity D of a plurality of signal regions in which color signals are detected, compares the relationship between the center of gravity D and the white region A, determines that there is a white balance shift, and determines on the color difference axis. Center of gravity D with respect to the origin (intersection) of
And the distance to the center of gravity D are determined as the direction and magnitude of the white balance deviation.

FIG. 3C shows an example of a color distribution when a mountain tree is photographed in a state where the white balance is adjusted for a light source having a color temperature of 5000 ° K. In the case of this example, the signal detection region E included in the white region A exists, but a part of the continuous signal region exists outside the color region A. The white balance deviation determination circuit 7 obtains the center of gravity F of the series of signal detection areas, and compares whether or not the center of gravity F is inside the white area A. Since the center of gravity F is outside the white area A, the white balance determination circuit 7 determines that there is no white balance deviation. By the way, in the case of (c), the conventional white balance control device determines that there is a white balance deviation and causes a malfunction.

The white balance shift determining circuit 7 determines the presence or absence of a white balance shift based on such a color distribution, and when it is determined that there is a white balance shift,
A detection signal indicating the direction and magnitude of the white balance deviation is output.

The color distribution in the actually generated color signal is various. For example, there is a color distribution in which a plurality of areas in which the presence of color signals is detected continuously form one signal detection area group, or a color distribution in which a plurality of separated signal detection area groups are formed. As a white balance deviation determination method based on such a color distribution, a method of determining white balance deviation based on the position of the center of gravity of a plurality of continuous signal detection region groups that have detected the presence of color signals, A method of determining the white balance deviation based on the position of the center of gravity of the detected plurality of separated signal detection regions, a region group closest to the origin among the separated signal detection regions detected presence of color signals There is a method of judging a white balance deviation based on the position of the center of gravity, and these methods can be implemented alone or in combination.

The white balance setting circuit 8 adjusts the variable gain amplifying circuits 31 and 32 so as to correct the white balance deviation detection signal output from the white balance deviation determination circuit 7 according to the detection signal indicating the direction and magnitude of the white balance deviation. It generates gain control signals S1 and S2 for setting the gain. At this time, by changing the variable amounts of the gain control signals S1 and S2 in accordance with the magnitude of the white balance deviation, the correction control can be completed within a fixed time regardless of the magnitude of the white balance deviation. It is possible.

According to the white balance control apparatus described above, the white balance deviation of an achromatic subject can be detected with high accuracy, and white balance control without malfunction can be performed. Further, since the magnitude of the white balance deviation can be detected at the same time, the correction control speed can be changed according to the magnitude of the white balance deviation.

In this embodiment, the white balance deviation is detected based on the (R−B) and (R + B−2Y) signals obtained by converting the color difference signals. BY) or other saturation signals may be used. In this embodiment, the white balance deviation determination circuit 7 is provided in the feedback control loop. However, the white balance deviation determination circuit 7 is provided in a state independent of the feedback control loop and is used only for determining the presence or absence of white balance deviation. The white balance correction control may be configured to be performed by a white balance control device or the like as described in JP-A-5-344530.

In this embodiment, one color signal detecting circuit is provided for each area to detect signals in each area at the same time.
It is preferable that one color signal detection circuit is configured to detect signals in a plurality of regions by using time division. Similarly, for simplification of the apparatus, it is also possible to detect a white balance shift by dividing an area only in a color difference plane while omitting information of a luminance signal.

The white balance deviation judging circuit 7 and the white balance setting circuit 8 may be constituted by a microcomputer and its program.

FIG. 4 is a block diagram showing another embodiment of the white balance control device of the present invention. In this embodiment, a photographing environment estimating unit 16 is added to the embodiment described above with reference to FIG. The same components are denoted by the same reference numerals, and redundant description will be omitted.

The photographing environment estimating unit 16 says indoor, outdoor, or unknown from information such as subject illuminance, subject distance, and date and time obtained from the automatic exposure function means, automatic focus function means, clock function means, and the like of the imaging apparatus. Estimate the current shooting environment.
The photographing environment estimating unit 16 is described in detail in
What is necessary is just to make it the structure as disclosed in -308563.

The photographing environment estimating section 16 supplies the estimation result to the white balance deviation judging circuit 7. The white balance shift determination circuit 7 determines a color signal when the white area A shown in FIG. 3 (the achromatic subject has a white balance shift due to a light source) according to the shooting environment. The white balance deviation is detected by changing the size of the white area. That is, when the shooting environment is unknown, it is the same as the white region A shown in FIG. 3, but when it is estimated that the shooting environment is outdoors,
In the white area A, a portion due to a light source such as a fluorescent lamp and a light source having a low color temperature (for example, 3000 ° K or less) such as an incandescent lamp is excluded, and when it is estimated that the shooting environment is indoors, From the white area A, a portion due to a light source having a high color temperature (for example, 5000 K or more) such as sunlight is excluded.

As described above, according to the present embodiment, it is possible to detect the deviation of the white balance with higher accuracy by performing the determination according to the photographing environment.

[0041]

According to the present invention, the white balance deviation can be detected with high accuracy by detecting the white balance deviation from the color distribution. White balance control can be realized.

Further, according to the present invention, since the magnitude of the white balance deviation can be detected, it is possible to realize a control that completes the white balance correction in a short time even when the white balance deviation is large. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a white balance control device of the present invention.

FIG. 2 is a diagram showing a color space for explaining the operation of the white balance control device of the present invention.

FIG. 3 is a diagram illustrating an example of a color distribution of a subject for explaining an operation of the white balance control device of the present invention.

FIG. 4 is a block diagram showing another embodiment of the white balance control device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image sensor, 2 ... Color separation circuit, 31 and 32 ... Variable gain amplifying circuit, 4 ... Color difference signal generation circuit, 5 ... Operation circuit, 6
1, 62,... 6n: color signal detection circuit, 7: white balance deviation determination circuit, 8: white balance setting circuit, 9
... Subtraction circuit, 10 addition circuit, 11 gate signal generation circuit, 12, 13 gate circuit, 14 integration circuit, 15
Integrating circuit, 16: photographing environment estimation circuit.

Claims (10)

[Claims] 1. A white balance shift detecting means for detecting a white balance shift of an achromatic subject from a primary color signal, a color difference signal or another color signal generated from an output signal of an image sensor, and a detection by the white balance shift detecting means. A white balance setting device that generates a gain control signal in accordance with a result, and controls a gain of a variable gain amplifying device that amplifies the color signal by the gain control signal to perform white balance control. The white balance deviation detecting means divides the color space into a plurality of color areas and detects the presence or absence of a color signal corresponding to each color area, and a subject obtained from the detection result of the color signal detecting means. White balance deviation judging means for judging white balance deviation based on the color distribution of A white balance control device. 2. The white balance shift determining device according to claim 1, wherein said white balance shift determining means determines the white balance shift based on the positions of the centers of gravity of a plurality of continuous color regions where the presence of a color signal is detected. Control device. 3. The apparatus according to claim 1, wherein said white balance shift determining means determines a white balance shift based on a position of a total center of gravity of a plurality of separated color regions where the presence of a color signal is detected. White balance deviation control device. 4. The white balance deviation determining means according to claim 1, wherein the white balance deviation determination means determines a white balance deviation based on a position of a color region closest to the origin among a plurality of separated color regions in which the presence of a color signal is detected. The white balance deviation control device characterized by the above. 5. The white balance setting means according to claim 1, wherein said white balance setting means changes a control amount of said gain control signal in accordance with a magnitude of a white balance deviation amount obtained from said white balance deviation detection means. A white balance control device. 6. A color signal detecting means according to claim 1, wherein said color signal detecting means is constituted by a plurality of detecting means, and detects the presence / absence of a color signal corresponding to said plurality of color regions in parallel. Characteristic white balance control device. 7. A color signal detecting device according to claim 1, wherein said color signal detecting means determines whether or not there is a color signal corresponding to a plurality of color regions.
A white balance control device, wherein the detection is performed by time-sharing using two detection means. 8. The white balance control device according to claim 1, wherein the plurality of color regions are divided by different boundaries according to luminance. 9. The apparatus according to claim 1, wherein said white balance deviation detecting means includes a photographing environment estimating means for estimating a photographing environment of said image sensor, and said white balance deviation judging means comprises: A white balance control device for determining a white balance deviation according to a shooting environment estimated by an estimation unit. 10. The photographing environment estimating means according to claim 9, wherein the photographing environment is estimated based on information such as illuminance, distance, date and time obtained from an automatic exposure function means, an automatic focus function means, a clock function means and the like. A white balance control device, characterized in that: