JPH05292533A - Automatic white balance device - Google Patents

Abstract

PURPOSE:To reduce an influence of chromatic colors with respect to the automatic white balance device used in a video camera or the like. CONSTITUTION:A block signal extracting part 4 which divides one picture into one or plural blocks to obtain a representative value of the video signal in each block, amplifiers 6 to 8 which adjust the amplification factors of color signals, and a computer 5 which calculates amplification factors of amplifiers are provided. Only representative values of blocks where the value obtained by dividing the red signal by a green signal is within a limited range and the value obtained by dividing the blue signal by the green signal is within a limited range and the product between these values is within a limited value are used, and only signals regarded as achromatic colors are used to calculate the amplification factors for the white balance. Thus, even chromatic colors having small luminance values are judged to be chromatic colors to extract the accurate color temperature.

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 auto white balance device used in a video camera or the like has improved in performance, and an internal photometric system that does not require an external sensor is becoming mainstream. The basic idea of the internal photometry method is that the subject is achromatic on average, that is, the average values of the red signal, the blue signal, and the green signal will be equal in the screen. However, if what is obviously chromatic color occupies most of the screen, it becomes a malfunction if the white balance is adjusted based on such a concept. Therefore, it is necessary to use other signals to achieve white balance without using signals that are obviously chromatic.

An example of a conventional automatic white balance device will be described below with reference to the drawings. FIG. 7 is a structural diagram showing the structure of a conventional auto white balance device. FIG. 8 is a vector scope diagram for explaining the operation of the conventional auto white balance device.

In FIG. 7, 1 is a G signal input terminal, 2 is an R signal input terminal, 3 is a B signal input terminal, 4 is a block signal extraction unit, 55 is a computer, 6 is a G signal amplifier, and 7 is an R signal amplifier. , 8 is a B signal amplifier, 9 is a G signal output terminal, 1
Reference numeral 0 is an R signal output terminal, and 11 is a B signal output terminal.

In FIG. 8, the horizontal axis is the BY axis and the vertical axis is the R axis.
On the -Y axis, the shaded area represents a range in which the R-B level obtained by subtracting the B signal from the R signal is below a certain level.

The color signals input to the G signal input terminal 1, the R signal input terminal 2 and the B signal input terminal 3 are input to the block signal extraction unit 4. The block signal extraction unit 4 divides the video signal of one field into 48 blocks of horizontal 8 × vertical 6 as shown in FIG. 2, and outputs the average value of the R signal, G signal, and B signal in each block. The 48 sets of R signal, G signal, and B signal output from the block signal extraction unit 4 are calculated by the computer 55.
Entered in. In the computer 55, an R-B differential signal obtained by subtracting each B signal level from each of the input 48 sets of each R signal level is calculated. The calculated difference signal is compared with a certain threshold level, and the R signal, G signal, and B signal of a block in which the difference signal falls within a certain range are integrated.

In this range, it is judged that the difference between the R signal and the B signal is not so large as in the shaded area in the vector scope shown in FIG. 8, that is, the video signal is not red or blue chromatic color. The range is Next, the amplification factor for white balance adjustment is calculated from the integrated values of the R signal, G signal, and B signal. The amplification factor for the R signal for white balance adjustment is obtained by dividing the integral value of the G signal by the integral value of the R signal, and the amplification factor for the B signal is the integral value of the G signal by the integral value of the B signal. Obtained by dividing. The gains of the R signal amplifier 7 and the B signal amplifier 8 are adjusted by the gains calculated in this way, and the white-balanced signals are output to the G signal output terminal 9, the R signal output terminal 10, and the B signal output terminal. Output from 11.

[0008]

However, in the conventional configuration as described above, since the signal amount of a signal having a low luminance value is small, the value of RB is small even if it is a chromatic color. Therefore, there is a problem in that the color temperature cannot be accurately extracted because it is treated as white balance data.

An object of the present invention is to provide an automatic white balance device capable of reducing the influence of chromatic color.

[0010]

In order to achieve the above object, the present invention divides a screen into one or a plurality of blocks and obtains a representative value of a video signal of each block, and a color signal amplifying unit. An amplifier that adjusts the ratio and a calculator that calculates the amplification factor of the amplifier are provided, and the representative value of the video signal of each block output from the block signal extraction unit is input to the calculator, and the red value obtained from the representative value is input. For the three green and blue signals, the red signal is divided by the green signal within the finite range, and the blue signal is divided by the green signal within the finite range. Calculate the white balance amplification factor using only the representative value of the block when the product of the value obtained by dividing the signal by the green signal and the value obtained by dividing the blue signal by the green signal is within a finite range. A configuration for adjusting the amplification factor of the amplifier You have me.

[0011]

According to the present invention, the red signal divided by the green signal falls within a finite range, and the blue signal divided by the green signal falls within a finite range. Even if the chromatic color has a low luminance value by using only the representative value of the block when the product of the value obtained by dividing the red signal by the green signal and the value obtained by dividing the blue signal by the green signal is within a finite range Since it can be determined that the color is chromatic, the color temperature can be extracted more accurately, and the white balance can be adjusted more accurately.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic white balance device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an automatic white balance device according to an embodiment of the present invention, FIG. 2 is a diagram showing image blocks of the automatic white balance device according to an embodiment of the present invention, and FIG.
Is a block diagram showing the internal configuration of the block signal extraction unit for the R signal, FIG. 4 is a flow chart for explaining the calculation flow of the computer of the auto white balance apparatus of this embodiment, and FIG. 5 is the auto white balance of this embodiment. FIG. 6 is a color distribution diagram for explaining the operation of the device.

In FIG. 1, 1 is a G signal input terminal, 2 is an R signal input terminal, 3 is a B signal input terminal, 4 is a block signal extraction unit, 5 is a computer, 6 is a G signal amplifier, 7 is an R signal amplifier, 8 is B signal amplifier, 9 is G signal output terminal, 10 is R
A signal output terminal 11 is a B signal output terminal. 1 in FIG.
2 is a horizontal counter, 13 is a switch, 14 is a first integrating circuit, 15 is a second integrating circuit, 16 is a third integrating circuit,
Reference numeral 17 is a fourth integration circuit, 18 is a fifth integration circuit, 19 is a sixth integration circuit, 20 is a seventh integration circuit, 21 is an eighth integration circuit, and 22 is a vertical counter. In Figure 5, the horizontal axis is B
The / G axis and the vertical axis are the R / G axes.

The operation of this embodiment having the above-mentioned structure will be described. First, the color signals input to the G signal input terminal 1, the R signal input terminal 2 and the B signal input terminal 3 are
Each is input to the block signal extraction unit 4. The block signal extraction unit 4 divides the video signal of one field into 48 blocks of horizontal 8 × vertical 6 as shown in FIG. 2 and outputs the integrated value of the R signal, G signal, and B signal in each block. The operation of the block signal extraction unit 4 will be described in detail, focusing on the R signal.

In FIG. 3, the switch 13 first selects the first integration circuit 14 at the beginning of the effective horizontal scanning period, and the R signal input to the switch 13 is input to the first integration circuit 14 and integrated. The horizontal counter 12 counts the clock signal, sends the control signal to the switch 13 after 1/8 of the effective horizontal scanning period, the switch 13 selects the second integrating circuit 15, and the switch 13 outputs the R signal. Is input to the second integrating circuit 15. The second integration circuit 15 integrates the R signal of the next 1/8 effective horizontal scanning period. In this way, the R signal is sequentially integrated with the third and fourth integrator circuits, and when the effective horizontal scanning period ends, the input of the R signal to the eighth integrator circuit 21 ends.

When the effective scanning period of the next scanning line starts, the switch 13 selects the first integrating circuit 14 again,
The R signal is integrated in the first integrating circuit 14. In this way, the R signal is integrated for each scanning line. During that time, the vertical counter 22 counts the number of scanning lines, and the control signals are supplied to the integrating circuits 14 to 21 after 1/6 of the effective vertical scanning period. send. Each integrator circuit that has received the control signal outputs the integrated value held by each integrator circuit as the output signal of the block signal extraction unit 4, and the contents of each integrator circuit are reset.

When the effective scanning period of the next scanning line starts, the integration is sequentially repeated from the first integrator circuit 14, and after the next 1/6 effective vertical scanning period, each integrator circuit again operates in the block signal extracting section 4. The integrated value is output as the output signal of. In this way, eight integrated values are output every 1/6 of the effective scanning period, and at the end of the effective vertical scanning period, the integrated values of all 48 blocks are output. This operation is also performed for the G signal and the B signal, and a signal of 48 blocks × 3 is output in one screen.

The 48 sets of R, G, and B signals output from the block signal extraction unit 4 as described above are input to the computer 5. Next, the flow of calculation in the computer 5 will be described with reference to FIG.

In the computer 5, the 48 sets of input R, G and B signals are first stored in the memory (2
3). Next, a value (R / G) obtained by dividing the R signal of the first block by the G signal of the same set and a value obtained by dividing the B signal by the G signal of the same set (B / G) are calculated (24). .. Then (R /
G) is in the range of 0.5 to 1.5 and (B /
It is calculated whether G) is in the range of 0.5 to 1.5.

If either (R / G) or (B / G) is not within the range, the next block is calculated (29). If both (R / G) and (B / G) are within the range, the product of (R / G) and (B / G) is calculated (26). Next, (R / G) and (B / G)
It is calculated whether the product of is in the range 0.8 to 1.2 (27). If the product of (R / G) and (B / G) is not within the range of 0.8 to 1.2, the next block is calculated (29). If (R / G) and (B /
If the product of G) falls within the range of 0.8 to 1.2, the R signal, G signal, and B signal of the block are integrated (28).

Next, the same calculation is performed on the second block. The range calculated in this way is shown in FIG.
It is represented by the hatched area in the figure. After this calculation is performed for all 48 blocks, the computer 5 calculates the amplification factor for white balance adjustment from the integrated values of the R signal, G signal, and B signal that satisfy the condition of achromatic color ( 30). The amplification factor for the R signal for white balance adjustment is obtained by dividing the integral value of the G signal by the integral value of the R signal, and the amplification factor for the B signal is obtained by dividing the integral value of the G signal by the integral value of the B signal. Can be obtained at.

The gains of the R signal amplifier 7 and the B signal amplifier 8 are adjusted by the gains calculated in this way, and a white-balanced signal is output to the G signal output terminal 9, the R signal output terminal 10, and the B signal. The signal is output from the signal output terminal 11.

Generally, the spectral characteristic of the light source is represented by the color temperature. When an achromatic color is picked up by a light source having a high color temperature, the B signal is larger and the R signal is smaller than the G signal. On the contrary, when an achromatic color is picked up by a light source having a low color temperature, the R signal is larger and the B signal is smaller than the G signal. When a signal obtained by normalizing the R signal with the G signal is X and a signal obtained by standardizing the B signal with the G signal is Y, when achromatic colors are picked up by light sources having various color temperatures, these X and Y are as shown in FIG. It is distributed in the vicinity of X × Y = 1 on the coordinates. If the color temperature of the light source is in the range of 3000K to 8000K, X, Y
Both fall within the range of 0.5 to 1.5. Using only the signals that fall within the range determined in this way means that the white balance amplification factor is calculated using only the signals that are considered to be achromatic, so a more accurate white balance adjustment can be made. The amplification factor for is obtained.

In this embodiment, the white balance is adjusted by using the signal before entering the amplifier for white balance, but as shown in FIG. 6, the white balance control after the amplifier for white balance is performed. The same effect can be obtained by using a signal with a black mark.

[0025]

As described above, according to the present invention, the value obtained by dividing the red signal by the green signal is within a certain finite range, and the value obtained by dividing the blue signal by the green signal is within the finite range. Achromatic color is obtained by using only the representative value of the block in the case where the product of the value obtained by dividing the red signal by the green signal and the value obtained by dividing the blue signal by the green signal is within a finite range. Since the white balance amplification factor is calculated using only possible signals, it is possible to determine even a chromatic color with a low luminance value as a chromatic color, and therefore a more accurate color temperature can be extracted,
The white balance can be adjusted more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an automatic white balance device according to an embodiment of the present invention.

FIG. 2 is a diagram showing image blocks of an automatic white balance device according to an embodiment of the present invention.

FIG. 3 is a block diagram showing an internal configuration of a block signal extraction unit for an R signal.

FIG. 4 is a flowchart showing a calculation flow in a computer of the automatic white balance device of the present embodiment.

FIG. 5 is a color distribution diagram for explaining the operation of the automatic white balance device of the present embodiment.

FIG. 6 is a block diagram showing the configuration of an automatic white balance device according to another embodiment of the present invention.

FIG. 7 is a block diagram showing the configuration of a conventional auto white balance device.

FIG. 8 is a vector scope diagram for explaining the operation of a conventional auto white balance device.

[Explanation of symbols]

 1 G signal input terminal 2 R signal input terminal 3 B signal input terminal 4 Block signal extraction section 5 Computer 6 G signal amplifier 7 R signal amplifier 8 B signal amplifier 9 G signal output terminal 10 R signal output terminal 11 B signal output terminal 12 Horizontal counter 13 Switch 14 First integration circuit 15 Second integration circuit 16 Third integration circuit 17 Fourth integration circuit 18 Fifth integration circuit 19 Sixth integration circuit 20 Seventh integration circuit 21 Eighth integration circuit Integration circuit 22 Vertical counter

Claims (1)

[Claims] 1. An automatic white balance device for obtaining white balance data using a video signal, wherein a screen is divided into one or a plurality of blocks and a representative value of the video signal of each block is obtained. A signal extraction unit,
An amplifier that adjusts the amplification factor of the color signal, and a calculator that calculates the amplification factor of the amplifier are provided, and the representative value of the video signal of each block output from the block signal extraction unit is input to the computer, The value obtained by dividing the red signal by the green signal is within a finite range for the three signals of red, green, and blue obtained from the representative value of the video signal of each block.
The value obtained by dividing the blue signal by the green signal is within a finite range, and the product of the value obtained by dividing the red signal by the green signal and the value obtained by dividing the blue signal by the green signal is within the finite range. An automatic white balance device characterized in that the amplification factor of white balance is calculated by using only the representative value of the block and the amplification factor of the amplifier is adjusted.