JPH06351037A - Auto-white balance device - Google Patents

Abstract

PURPOSE:To obtain stable white balance even if a chromatic color object crosses within a screen in an auto-white balance device to be used for a video camera, etc. CONSTITUTION:This device has a color temperature information detection means 22 detecting the color temperature information on a light source from the video signal of a screen and an integration means 23 integrating the color temperature information obtained by the color temperature information detection means 22 corresponding to plural screens, and performs a white balance correction, using the output signal of the integration means 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic white balance device used for video cameras and the like.

[0002]

2. Description of the Related Art In recent years, an internal white metering system which is improved in performance and does not require an external sensor is becoming mainstream as an automatic white balance device used in a video camera or the like. The basic idea of the internal photometry method is that the subject is an achromatic color on average, that is, the average values of the red signal, the blue signal, and the green signal will be equal in the screen.

An example of a conventional automatic white balance device will be described below with reference to the drawings. FIG. 10 is a structural diagram showing the structure of a video camera for explaining the operation of a conventional auto white balance device.

In FIG. 10, 1 is a solid-state image sensor (CC
D), 2 is a low-pass filter, 3 is a γ correction circuit, 4 is a color separation circuit, 5 is a conventional auto white balance device, 6
Is an achromatic color extraction circuit, 7 is a first integration circuit, 8 is a microcomputer, 9 is a white balance correction circuit, and 10 is a matrix circuit.

In this conventional example, a single-chip camera that employs a color filter array called a color difference sequential system as the solid-state image sensor 1 will be described. The solid-state image sensor 1 of the color difference sequential system outputs a signal in a form in which the modulated color signal is superimposed on the luminance signal. The low-pass filter 2 removes the modulated color component from the output signal of the solid-state image sensor 1 to obtain a luminance signal Y, which is input to the γ correction circuit 3a. γ correction circuit 3a
In γ-correction, the luminance signal after γ-correction is obtained.

Next, the output signal of the solid-state image pickup device 1 input to the color separation circuit 4 is color-separated and R (red), G (green),
It is output as a B (blue) color signal. The R, G, B signals output from the color separation circuit 4 are input to the achromatic color extraction circuit 6, and only the color signals when the subject is close to achromatic color are input to the first integration circuit 7. The first integration circuit 7 integrates the output signal of the achromatic color extraction circuit 6 for one screen and outputs it. The one screen here corresponds to one field of the television system, for example. The output signal of the first integrating circuit 7 is input to the microcomputer 8 and the gain of white balance is calculated.

The white balance correction circuit 9 receives the R, G and B color signals output from the color separation circuit 4 and corrects the white balance according to the gain calculated by the microcomputer 8. The γ correction circuit 3b inputs the R, G, and B signals that have been white-balanced by the white balance correction circuit 9 and performs γ correction and outputs them. Matrix circuit 10
At a, the R, G, and B signals output from the γ correction circuit are input, matrix-converted into color difference signals RY and BY, and output.

[0008]

However, since the color information for only one screen is obtained in the above-described conventional configuration, the first method is used when a chromatic subject close to achromatic color crosses the screen. There is a problem that the integrated value of the integration circuit 7 changes and the gain of the white balance changes accordingly, causing malfunction. On the other hand, in Japanese Unexamined Patent Application Publication No. 4-989, an insensitive area is provided for a change in gain of white balance, and the white balance is not made to follow a change in gain below a certain level, so that malfunction is avoided. . However, even with this method, there is a problem that a malfunction occurs when the color of the object that crosses the screen is outside the dead region.

In view of the above points, it is an object of the present invention to obtain a stable white balance even if a chromatic subject crosses the screen.

[0010]

In order to achieve the above-mentioned object, the present invention achieves the above object, and a color temperature information detecting means for detecting color temperature information of a light source from a video signal of one screen, and a color temperature obtained by the color temperature information detecting means. Integrating means for integrating information for a plurality of screens, and white balance correction is performed using an output signal of the integrating means.

[0011]

According to the present invention, the integrated value of the color signal obtained from one screen is integrated in the time direction for several screens so that the gain of the white balance can be reduced even when a chromatic subject close to achromatic color crosses the screen. The amount of change is small and a stable white balance can be obtained.

Further, the response speed of white balance correction can be freely changed by changing the integration time according to the exposure amount and the detected color information.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic white balance device according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the first embodiment of the present invention.

In FIG. 1, 1 is a solid-state image sensor (CC
D) 2 is a low-pass filter, 3a and 3b are γ correction circuits, 4 is a color separation circuit, 5 is an auto white balance device, 8 is a microcomputer, 9 is a white balance correction circuit, 10 is a matrix circuit, and 22 is a color temperature. The information detecting means 23 is an integrating means.

In this embodiment, as the solid-state image pickup device 1, a single-chip camera adopting a color filter array called a color difference sequential system will be described. First, the color-difference-sequential solid-state imaging device 1 outputs a signal in a form in which a modulated color signal is superimposed on a luminance signal. The low-pass filter 2 removes the modulated color component from the output signal of the solid-state image sensor 1 to obtain a luminance signal Y, which is input to the γ correction circuit 3a. In the γ correction circuit 3a, γ correction is performed and a luminance signal after γ correction is obtained.

Next, the output signal of the solid-state image pickup device 1 input to the color separation circuit 4 is subjected to color separation, and R (red) and G are output.
It is output as color signals of (green) and B (blue). The R, G, B signals output from the color separation circuit 4 are input to the color temperature information detecting means 22. The color temperature information detecting means 22 integrates and outputs the R signal, G signal, and B signal for one screen. The one screen referred to here is, for example, one of the TV system.
Corresponds to the field.

Since it is generally said that the average of the colors on the entire screen will be an achromatic color, the color temperature information detecting means 22
The color temperature of the light source is estimated from the signal output from the. Next, the output signal of the color temperature information detecting means 22 is integrated by the integrating means 23 for an arbitrary period.

Here, the integrating means 23 will be described in detail. FIG. 2 is a block diagram showing the internal operation of the integrating means 23 of the automatic white balance device of this embodiment. In FIG. 2, 12 is a divider, 13 is an adder, 14 is a subtractor, 1
Reference numeral 5 is a delay circuit, and 16 is a multiplexer. The operation of the integrating means configured as above will be described.

First, R, G, and
The B signals are each multiplied by 1 / N by the divider 12a. However, this divider 12 can be realized by bit shift in the case of a digital circuit. The output signal of the divider 12a is input to the adder 13, and the output signal of the adder 13 is the delay circuit 15
Entered in. The delay circuit 15 delays the input signal for a certain period and outputs it. Output signal of delay circuit 15 and delay circuit 1
The signal obtained by dividing the output signal of No. 5 by the divider 12b is input to the subtractor 14, and the output signal of the subtractor 14 is added by the adder 13
Entered in.

As a result, the relationship between the nth input signal X (n) of the second integrating circuit 11 and the output signal Y (n) of the adder 13 is as follows: Y (n) = {X (n) + ( It is represented by N-1) Y (n-1)} / N. The output signal of the delay circuit 15 is selected by the multiplexer 16 and sequentially read by the microcomputer 8.

The microcomputer 8 calculates the white balance gain from the integrated R, G, B signals. The white balance gain is the integrated R,
R when G, B signals are SR, SG, SB respectively
Is given by SG / SR, and the gain of B is given by SG / SB.

The white balance correction circuit 9 receives the R, G, B color signals output from the color separation circuit 4 and performs white balance correction according to the gain calculated by the microcomputer 8.

The γ correction circuit 3b inputs the R, G, B signals which have been white-balanced by the white balance correction circuit 9, and γ-corrects them and outputs them. The matrix circuit 10 inputs the R, G, B signals output from the γ correction circuit 3b, performs matrix conversion to color difference signals RY, BY, and outputs the color difference signals RY, BY.

In this embodiment, for example, the R, G, B signals output from the color temperature information detecting means 22 are integrated by the integrating means 23.
If the integration is performed at 1 second intervals, the integrating means 23 can obtain an integrated value for N seconds. Therefore, even if a chromatic subject crosses the screen, the output of the integration unit 23 does not fluctuate and a stable white balance can be obtained.

In this embodiment, the color signals R, G,
Although the primary color signal processing method using the three primary colors B has been described, the same effect can be obtained also in the color difference signal processing method using Cr = 2R-G and Cb = 2B-G as color signals.

A second embodiment of the automatic white balance device of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the second embodiment of the present invention.

In FIG. 3, 1 is a solid-state image sensor (CC
D) 2 is a low-pass filter, 3a and 3b are γ correction circuits, 4 is a color separation circuit, 5 is an auto white balance device, 8 is a microcomputer, 9 is a white balance correction circuit, 10 is a matrix circuit, and 22 is a color temperature. Information detecting means, 23 is integrating means, 24 is signal amount detecting means, 25
Is a diaphragm, and 26 is a lens.

In this embodiment, the operations of the solid-state image pickup device 1, the low-pass filter 2, the γ correction circuits 3a and 3b, the color separation circuit 4, and the color temperature information detecting means 22 are the same as those in the first embodiment.

Next, the signal amount detecting means 24 is the solid-state image pickup device 1.
Input the output signal of, and detect the average signal amount of one screen,
Transfer to the microcomputer 8. The microcomputer 8 determines the aperture value of the aperture 25 according to the output signal of the signal amount detecting means 24 and controls the aperture 25. In this way, the microcomputer 8 can obtain information on the exposure amount. In particular, when the output signal of the signal amount detecting means 24 changes greatly, the microcomputer 8 reduces the number N of screens averaged by the integrating means 23.

Further, in the microcomputer 8, from the output signal of the integrating means 23, when there are many B signals, the high color temperature,
When there are many R signals, the color temperature of the light source of the subject currently being photographed can be estimated, such as low color temperature. The microcomputer 8 reduces the value of N from the information on the exposure amount and the information on the color temperature when the color temperature is low and the brightness is high.

The calculation of the white balance gain in the microcomputer 8 and the operations of the white balance correction circuit 9, the γ correction circuits 3a and 3b, and the matrix circuit 10 are in accordance with the first embodiment.

In the second embodiment, for example, when the video camera is directed from the indoor to the outdoor or from the outdoor to the indoor, the exposure amount greatly changes at the same time as the color of the light source. In such a case, the response speed of white balance correction can be increased by reducing the value of N.

In general, the illuminance is high outdoors, but when the color temperature information detected in the high illuminance indicates indoors, there is a high possibility of malfunction. Even in such a case, it is possible to quickly get out of the malfunction state by decreasing the value of N and increasing the response speed of the white balance correction.

An automatic white balance device according to a third embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the third embodiment of the present invention.

In FIG. 4, 1 is a solid-state image sensor (CC
D) 2 is a low pass filter, 3a and 3b are γ correction circuits, 4 is a color separation circuit, 5 is an auto white balance device, 6 is an achromatic color extraction circuit, 7 is a first integration circuit, 8 is a microcomputer, 9 Is the white balance correction circuit,
Reference numeral 10 is a matrix circuit, and 11 is a second integration circuit.

In this embodiment, the operations of the solid-state image sensor 1, the low-pass filter 2, the γ correction circuits 3a and 3b, and the color separation circuit 4 are the same as those in the first embodiment.

Next, the R, G, and
The B signal is input to the achromatic color extraction circuit 6, and only the color signal when the subject is close to achromatic color is input to the first integration circuit 7.

Now, the achromatic color extraction circuit 6 will be described in detail. FIG. 5 is a block diagram for explaining the internal operation of the achromatic color extraction circuit 6 of the automatic white balance device according to the third embodiment. In the figure, 12 is an achromatic color detection circuit, 1
3 is a gate circuit.

The operation of the achromatic color extraction circuit 6 of the present embodiment configured as described above will be described. First, the R, G, B signals input to the achromatic color extraction circuit 6 are input to the achromatic color detection circuit 12. To be done. In the achromatic color detection circuit 12, the relationship between the input signal levels of R, G, B is αG <R + B <β
The control pulse is output when the three relations of G, R> γG, and B> δG are simultaneously satisfied, and otherwise the control pulse is not output.

FIG. 6 shows a graph showing these three relationships. In FIG. 6, the horizontal axis represents B / G and the vertical axis represents R / G. An area that satisfies the three relationships at the same time is a portion indicated by diagonal lines on the graph. This area is a color distribution area when an achromatic color is picked up by various light sources. The gate circuit 13 inputs the R, G, B signals and the control signal of the achromatic color detection circuit 12, and when the achromatic color detection circuit 12 outputs a control pulse, the R, G, B signals are output.
The signal is output, and at other times, the R, G, B signals are not output. Therefore, the achromatic color extraction circuit 6 outputs only a signal close to an achromatic color.

The first integration circuit 7 integrates the output signal of the achromatic color extraction circuit 6 for one screen and outputs it. The one screen here corresponds to one field of the television system, for example.
The output signal of the first integrating circuit 7 is input to the second integrating circuit 11. The second integration circuit 11 integrates the R, G, B color signals for one screen integrated by the first integration circuit 7 for an arbitrary period. The operation of the second integrating circuit 11 conforms to the integrating means 23 in the first embodiment. The operations of the microcomputer 8, the white balance correction circuit 9, the γ correction circuits 3a and 3b, and the matrix circuit 10 are the same as those in the first embodiment.

In the present embodiment, the value of N in the second integrating circuit 11 may be a constant value, but the white balance is changed by changing the value of N according to the exposure amount at that time and the detected color temperature information. The response speed of correction can be changed.

Also, in the present embodiment, the achromatic color extraction circuit 6 is used.
May be omitted. However, in this case, the accuracy of white balance correction may be degraded.

In this embodiment, the color signals R, G,
Although the primary color signal processing method using the three primary colors B has been described, the same effect can be obtained also in the color difference signal processing method using Cr = 2R-G and Cb = 2B-G as color signals.

An automatic white balance device according to a fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the fourth embodiment of the present invention.

In FIG. 7, 1 is a solid-state image sensor (CC
D) 2 is a low pass filter, 3a and 3b are γ correction circuits, 4 is a color separation circuit, 5 is an auto white balance device, 8 is a microcomputer, 9 is a white balance correction circuit, 10 is a matrix circuit, and 17 is block integration. Circuit. The operations of the solid-state image sensor 1, the low-pass filter 2, the γ correction circuits 3a and 3b, and the color separation circuit 4 are the same as those in the first embodiment.

The operation of this embodiment having the above-described structure will be described. First, the R, G, B color signals output from the color separation circuit 4 are input to the block integration circuit 17. The block integration circuit 17 divides one screen into 48 blocks of 8 × 6 and integrates the input R, G, and B color signals for each block.

Here, the block integration circuit 17 will be described in detail. FIG. 8 is a block diagram for explaining the operation of the R signal integrating circuit in the block integrating circuit 17.
The integrating circuit for the G signal and the B signal performs the same operation.

First, the R signal input to the block integration circuit 17 is input to the multiplexer 16. In the multiplexer 16, the signal input at the beginning of one field is first input to the integrating circuit 19a. The horizontal counter 18 counts the clock pulse of the video signal,
A pulse is generated after the / 8 period, and the multiplexer 16 inputs the output signal to the integrating circuit 19b. The horizontal counter 18 counts the clock pulses of the video signal,
A pulse is generated after ⅛ of the effective horizontal period, and the multiplexer 16 inputs the output signal to the integrating circuit 19c. In this way, the multiplexer 16 switches the output every ⅛ period of the effective horizontal period, and after one horizontal period, the integrating circuit 19a is selected again.

During this period, the vertical counter 20 counts the number of scanning lines and generates a pulse after 1/6 period of one field. At this time, the integrated values of the integrating circuits 19a to 19h are sequentially output through the demultiplexer 21, and the integrating circuit 1
After the integrated value of 9h is output, each integrating circuit 19 is reset. In this way, the integrated value of the integrator circuit 19 is output every 1/6 period of one field, and after one field, 4
The integrated value of 8 blocks is output.

The integrated values of the 48 blocks output from the block integration circuit 17 in this manner are input to the microcomputer 8. The flow of processing in the microcomputer 8 is shown in FIG.

First, in the microcomputer 8, only the achromatic block data is extracted from the input 48 block data (process 22). For the extraction of achromatic color, αG <R + B <βG, R> γ as in the first embodiment.
The condition of G, B> δG is used.

Next, in the microcomputer 8, the R, G and B signals of the achromatic blocks in one screen are integrated (process 23).

Next, the integrated values of the R, G, B signals obtained from one screen are integrated for N screens (process 24).

The microcomputer 8 calculates a white balance gain from the integrated R, G, B signals (process 25). When the integrated R, G, B signals are SR, SG, SB, respectively, the gain of white balance is SG / SR, and the gain of B is SG / SR.
It is given by SB (process 26).

The operations of the white balance correction circuit 9, the γ correction circuit 3, and the matrix circuit 10 are the same as those in the first embodiment.

In the present embodiment, it can be considered that the operation of the automatic white balance device in the first embodiment is performed in the microcomputer 8. By using the block integration circuit 17 in this way, the circuit scale can be reduced.

Further, the number of screens N to be integrated in this embodiment is N
The response speed of white balance can be considered as in the first embodiment.

[0059]

As described above, according to the present invention, by integrating the integrated value of the color signal obtained from one screen in the time direction for several screens, a chromatic subject close to an achromatic color traverses the screen. Even in such a case, the amount of change in the gain of the white balance is small, and stable white balance can be obtained.

Further, by changing the integration time according to the exposure amount and the detected color temperature information, the response speed of white balance correction can be freely changed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a video camera for explaining the operation of an automatic white balance device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an integrating means of the automatic white balance device according to the first embodiment.

FIG. 3 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the second embodiment of the present invention.

FIG. 4 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the third embodiment of the present invention.

FIG. 5 is a block diagram of an achromatic color extraction circuit according to a third embodiment.

FIG. 6 is a color distribution diagram of an achromatic color detection circuit according to a third embodiment.

FIG. 7 is a block diagram showing the configuration of a video camera for explaining the operation of the automatic white balance device according to the fourth embodiment of the present invention.

FIG. 8 is a block diagram of an R signal integrating circuit in a block integrating circuit according to a fourth embodiment.

FIG. 9 is a flowchart showing the flow of processing in the microcomputer of the fourth embodiment.

FIG. 10 is a block diagram showing the configuration of a video camera for explaining the operation of a conventional auto white balance device.

[Explanation of symbols]

 1 Solid-state image sensor 2 Low-pass filter 3 γ correction circuit 4 Color separation circuit 5 Auto white balance device 6 Achromatic color extraction circuit 7 First integration circuit 8 Microcomputer 9 White balance correction circuit 10 Matrix circuit 11 Second integration circuit 17 block Integrating circuit 22 Color temperature information detecting means 23 Integrating means 24 Signal amount detecting means 25 Aperture 26 Lens

Claims (4)

[Claims] 1. A color temperature information detecting means for detecting color temperature information of a light source from a video signal of one screen, and an integrating means for integrating color temperature information obtained by the color temperature information detecting means for a plurality of screens. An automatic white balance device characterized in that white balance correction is performed by using an output signal of the integrating means. 2. The automatic white balance apparatus according to claim 1, wherein the number of screens integrated by the integrating means is changed based on the information on the exposure amount and the information on the color temperature. 3. An achromatic color extracting circuit for extracting an achromatic color signal, a first integrating circuit for integrating the achromatic color signal for one screen, and an integral for one screen by the first integrating circuit. A second integrating circuit for integrating the achromatic color signal for an arbitrary period, a microcomputer for obtaining a white balance correction coefficient based on the signal integrated by the second integrating circuit, and the white balance correction An automatic white balance device, comprising: a white balance correction circuit that corrects white balance based on a coefficient. 4. A block integrating circuit for dividing one screen into a plurality of blocks to obtain an integrated value of a color signal of each block, and integrating only a color signal of an achromatic block among the color signals of each block, and further integrating. And a white balance correction circuit that corrects the white balance based on the white balance correction coefficient. An auto white balance device characterized by being equipped.