JP3075018B2 - Auto white balance device - Google Patents

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 a video camera or the like.

[0002]

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

An example of a conventional auto 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 automatic white balance device.

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

In this conventional example, a single-chip camera employing a color filter array referred to as a color difference sequential system as the solid-state imaging device 1 will be described. The solid-state imaging device 1 of the color difference sequential system outputs a signal in which a modulated color signal is superimposed on a luminance signal. The output signal of the solid-state imaging device 1 is obtained by removing a modulated color component from the low-pass filter 2 to obtain a luminance signal Y, which is input to the γ correction circuit 3a. γ correction circuit 3a
Is performed, and a luminance signal after the γ correction is obtained.

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

The white balance correction circuit 9 receives the R, G, and 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 receives the R, G, B signals white-balanced by the white balance correction circuit 9, inputs γ correction, and outputs. Matrix circuit 10
In a, the R, G, and B signals output from the gamma correction circuit are input, matrix-converted into color difference signals RY, BY, and output.

[0008]

However, in the above-described conventional configuration, only color information for one screen is obtained. Therefore, when a chromatic object close to an achromatic color crosses the screen, the first method is used. However, there is a problem that the integrated value of the integrating circuit 7 changes, and the gain of the white balance changes accordingly, causing a malfunction. On the other hand, Japanese Patent Application Laid-Open No. Hei 4-989 discloses a method of providing a dead zone for a change in gain of white balance and preventing a white balance from following a change in gain below a certain level to avoid malfunction. . However, even in this method, there is a problem that a malfunction occurs when the color of a subject crossing the screen is outside the dead area.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to obtain a stable white balance even when a chromatic object crosses a screen.

[0010]

In order to achieve the above object, the present invention provides 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 information obtained by the color temperature information detecting means. Integrating means for integrating the temperature information for a plurality of screens , and information on the exposure amount representing the brightness of the subject from the video signal;
And a signal detecting means for detecting, have rows white balance correction using the output signal of the integrating means, the integrating
The exposure means changes the exposure amount according to the information on the detected exposure amount.
Changes to reduce the number of screens to be integrated
With an automatic white balance device
is there. In addition, the present invention provides a method of calculating the color of a light source
Color temperature information detecting means for detecting temperature information; and the color temperature
Integrates the color temperature information obtained by the information detection means for multiple screens
Integration means and exposure representing the brightness of the subject from the video signal
Signal amount detecting means for detecting the amount information,
White balance correction using the output signal of the
The integrating means is configured to determine whether the information on the detected exposure amount is
When the exposure amount is large and the color temperature is low,
In this case, change the number of screens to integrate
An automatic white balance device characterized by the following.

[0011]

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

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

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an automatic white balance device according to a first embodiment of the present invention will be described 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, reference numeral 1 denotes a solid-state image sensor (CC
D), 2 is a low-pass filter, 3a and 3b are gamma 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, 22 is a color temperature. The information detecting means 23 is an integrating means.

In this embodiment, a single-chip camera employing a color filter array called a color difference sequential system as the solid-state imaging device 1 will be described. First, a signal in which a modulated color signal is superimposed on a luminance signal is output from the color difference sequential type solid-state imaging device 1. The output signal of the solid-state imaging device 1 is obtained by removing a modulated color component from the low-pass filter 2 to obtain a luminance signal Y, which is input to the γ correction circuit 3a. The γ correction circuit 3a performs γ correction and obtains a luminance signal after γ correction.

Next, the output signal of the solid-state imaging device 1 input to the color separation circuit 4 is subjected to color separation, and R (red), G
(Green) and B (blue) are output as color signals. 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 detection means 22 integrates and outputs the R signal, G signal, and B signal for one screen. Here, one screen means, for example, a TV system 1 screen.
Equivalent to a field.

It is generally said that the average of the colors of the entire screen will be an achromatic color.
The color temperature of the light source is estimated from the signal output from. 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 integration 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 the present embodiment. In FIG. 2, 12 is a divider, 13 is an adder, 14 is a subtractor, 1
5 is a delay circuit, and 16 is a multiplexer. The operation of the integrating means configured as described above will be described.

First, the R, G,
Each of the B signals is multiplied by 1 / N in the divider 12a. However, this divider 12 can be realized by a 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
Is input to 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
5 and a signal obtained by dividing the output signal of the subtractor 12 by the divider 12b are input to the subtractor 14, and the output signal of the subtractor 14 is
Is input to

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

The microcomputer 8 calculates a white balance gain from the integrated R, G, B signals. The gain of the white balance is the integrated R,
When the G and B signals are SR, SG and SB, respectively, R
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, and 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 gamma correction circuit 3b receives the R, G, and B signals white-balanced by the white balance correction circuit 9, performs gamma correction, and outputs the result. The matrix circuit 10 receives the R, G, and B signals output from the gamma correction circuit 3b, converts the signals into a matrix of color difference signals RY, BY, and outputs the signals.

In this embodiment, for example, the R, G, B signals output from the color temperature information detecting means 22 are integrated with the integrating means 23.
If the integration is performed at 1-second intervals, the integration means 23 obtains an integrated value for N seconds. Therefore, even if a chromatic subject crosses the screen, the output of the integration means 23 can obtain a stable white balance with little fluctuation.

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

Hereinafter, an automatic white balance device according to a second embodiment of the present invention will be described 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, reference numeral 1 denotes a solid-state image pickup device (CC
D), 2 is a low-pass filter, 3a and 3b are gamma 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, 22 is a color temperature. Information detecting means; 23, integrating means; 24, signal amount detecting means;
Is an aperture, and 26 is a lens.

In this embodiment, the operations of the solid-state imaging device 1, the low-pass filter 2, the gamma 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 signal is detected, and the average signal amount of one screen is detected.
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 detection means 24 and controls the aperture 25. Thus, 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 of screens N averaged by the integrating means 23.

The microcomputer 8 determines from the output signal of the integrating means 23 that if the B signal is large, the color temperature is high.
When the number of R signals is large, the color temperature of the light source of the subject that is currently being photographed can be estimated as a low color temperature. The microcomputer 8 reduces the value of N in the case of low color temperature and high luminance from the information on the exposure amount and the information on the color temperature.

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

In the second embodiment, for example, when a video camera is pointed from indoors to outdoors or from outdoors to indoors, the exposure amount greatly changes simultaneously with the color of the light source. In such a case, the response speed of the 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 state indicates indoors, there is a high possibility of malfunction. In such a case as well, the response speed of the white balance correction is increased by reducing the value of N, whereby the malfunction can be quickly escaped.

Hereinafter, an automatic white balance device according to a third embodiment of the present invention will be described 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, reference numeral 1 denotes a solid-state image pickup device (CC
D), 2 is a low-pass filter, 3a and 3b are gamma 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 a white balance correction circuit,
10 is a matrix circuit, and 11 is a second integration circuit.

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

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

Here, 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 FIG.
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. Is done. In the achromatic color detection circuit 12, the relationship between the input R, G, and B signal levels is represented by αG <R + B <β.
A control pulse is output when the three relations of G, R> γG and B> δG are simultaneously satisfied, and otherwise, no control pulse is output.

FIG. 6 is a graph showing these three relationships. In FIG. 6, the horizontal axis represents B / G, and the vertical axis represents R / G. A region that satisfies the three relationships at the same time is a portion indicated by oblique lines on the graph. This area is a color distribution area when an achromatic color is imaged by various light sources. The gate circuit 13 receives the R, G, B signals and the control signal of the achromatic color detection circuit 12, and outputs R, G, B when the control pulse is output from the achromatic color detection circuit 12.
Signal, and does not output the R, G, B signals at other times. Therefore, the achromatic color extraction circuit 6 outputs only signals close to achromatic colors.

The first integration circuit 7 integrates the output signal of the achromatic color extraction circuit 6 for one screen and outputs it. Here, one screen corresponds to, for example, one field of a television system.
The output signal of the first integration circuit 7 is input to the second integration circuit 11. The second integration circuit 11 integrates the R, G, and 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 that of the integrating means 23 in the first embodiment. The operations of the microcomputer 8, the white balance correction circuit 9, the gamma correction circuits 3a and 3b, and the matrix circuit 10 are in accordance with the first embodiment.

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

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

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

Hereinafter, an automatic white balance device according to a fourth embodiment of the present invention will be described 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, reference numeral 1 denotes a solid-state image pickup device (CC
D), 2 is a low-pass filter, 3a and 3b are gamma 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, 17 is block integration. Circuit. The operations of the solid-state imaging device 1, the low-pass filter 2, the gamma correction circuits 3a and 3b, and the color separation circuit 4 are the same as those in the first embodiment.

The operation of the present embodiment configured as described above 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, 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 integration circuit in the block integration circuit 17.
The G signal and B signal integration circuits perform 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 integration circuit 19a. The horizontal counter 18 counts the clock pulse of the video signal, and counts 1 in the effective horizontal period.
A pulse is generated after the / 8 period, and the multiplexer 16 inputs the output signal to the integration circuit 19b. The horizontal counter 18 counts clock pulses of the video signal,
A pulse is generated after 1/8 of the effective horizontal period, and the multiplexer 16 inputs an output signal to the integration circuit 19c. As described above, the multiplexer 16 switches the output every 1/8 period of the effective horizontal period, and the integration circuit 19a is selected again after one horizontal period.

During this time, 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 integration values of the integration circuits 19a to 19h are sequentially output through the demultiplexer 21, and
After the integrated value of 9h is output, each integrating circuit 19 is reset. In this way, the integrated value of the integration circuit 19 is output every 1/6 period of one field, and 4 hours after one field,
The integrated values of eight blocks are output.

The integration values of the 48 blocks output from the block integration circuit 17 in this manner are input to the microcomputer 8. FIG. 9 shows a flow of processing in the microcomputer 8.

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

Next, the microcomputer 8 integrates the R, G, and B signals of the achromatic blocks in one screen, respectively (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 the white balance gain from the integrated R, G, B signals (process 25). When the integrated R, G, and B signals are SR, SG, and SB, respectively, the gain of R is SG / SR, and the gain of B is SG /
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 in accordance with 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 manner, the circuit scale can be reduced.

In this embodiment, the number of screens N to be integrated is N
And the response speed of the white balance can be considered in the same manner as in the first embodiment.

[0059]

As described above, according to the present invention, by integrating the integral values of the color signals obtained from one screen in the time direction for several screens, a chromatic object close to achromatic crosses the screen. Even in such a case, the amount of change in the gain of the white balance is small, and a stable white balance can be obtained.

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

[Brief description of the drawings]

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

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

FIG. 8 is a block diagram of an R signal integration circuit in a block integration 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 automatic white balance device.

[Explanation of symbols]

 DESCRIPTION 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 Integrator 22 Color temperature information detector 23 Integrator 24 Signal amount detector 25 Aperture 26 Lens

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-203085 (JP, A) JP-A-3-1791 (JP, A) JP-A-64-5286 (JP, A) JP-A-2- 288579 (JP, A) JP-A-64-60088 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/04-9/11 H04N 9/44-9/78

Claims (2)

(57) [Claims] 1. A color temperature information detecting means for detecting color temperature information of a light source from a video signal of one screen, an integrating means for integrating color temperature information obtained by the color temperature information detecting means for a plurality of screens, and a video signal Exposure information indicating the brightness of the subject from
And a signal detecting means for detecting a, have rows white balance correction using the output signal of the integrating means, the product
The dividing means determines the exposure amount based on the information on the detected exposure amount.
If it changes, change so that the number of screens to be integrated becomes small.
Auto white balance and wherein the to of. 2. Color temperature information of a light source from a video signal of one screen.
Color temperature information detecting means for detecting color temperature information,
Means for integrating the color temperature information obtained by means for multiple screens
Step and exposure information that indicates the brightness of the subject from the video signal
Signal amount detecting means for detecting the output of the integrating means.
The white balance is corrected using the force signal and the product
The dividing means is configured to detect the information of the detected exposure amount and the color temperature information.
According to the report, when the exposure amount is large and the color temperature is low, integration is performed.
The feature is to change so that the number of screens
Automatic white balance device.