JPS62132490A - White balance correcting circuit - Google Patents

Abstract

PURPOSE:To improve white balance correction, by performing RB-gain control by using the optimum chrominance components out of divided pictures. CONSTITUTION:One part of the output of an RB-gain controlling circuit 3 is inputted to a signal processing circuit 14 as chrominance components in video signals and the other part is inputted to a picture dividing circuit 4 as chrominance components components for white balance correction. The picture dividing circuit 4 fetches part of the chrominance components in the picture by using an analog switch, etc. Divided signals are inputted to a 1-V period peak holding circuit 5 and the output of the circuit 5 is inputted to an AD converter 6 as DC signals of each color which change at every 1-V period and converted into digital signals. The converted digital signals are inputted to a microcomputer 7. The RB-control signals outputted from the microcomputer 7 are converted into analog signals by a DA converter 12 and the analog signals are inputted to the RB-gain controlling circuit 3 and control chrominance components. Therefore, more accurate white balance correction can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a white balance correction circuit for a color camera used for home use, surveillance use, industrial use, etc.

Conventional technology Generally, video camera devices have a function to automatically correct white balance, which controls the signals of each color to be equal based on the color signals from the image pickup tube, image sensor, or color sensor. There is.

FIG. 5 shows the configuration of a white balance correction circuit in a conventional video camera device.

The output signal of the image sensor 51 is separated into RGB color signals by a signal processing circuit 52 and inputted to an RB gain control circuit 52 .

A part of the output of the RB gain control circuit 53 is input to the signal processing circuit 59 as a color signal in the video signal, and another part is input to the signal processing circuit 59 as a color signal for white balance correction in each vertical period (hereinafter abbreviated as 1v period). ) is input to a peak hold circuit 54 which performs peak hold. The peak hold circuit 54 may include an integrating circuit for each 1V period.

The output of the peak hold circuit 54 for the 1V period is sent to the comparator 55 as a DC signal of each color that changes every 1V period.
is input. This comparator 55 receives a green signal (
If the red signal (hereinafter abbreviated as R) and the blue signal (hereinafter abbreviated as B) are large, the output is output, and if they are small, the output is not output.

The output value of the comparator 55 is input to the microcomputer 56, and the output value calculation means 57 calculates the value of a signal (hereinafter abbreviated as RB control signal) that controls the magnitude of R and B. A control signal is output. As a result, the RB gain control circuit 53 is controlled so that R2G=B.

In this way, the conventional white balance correction circuit described above assumes that the color signal information (hereinafter referred to as color information) is always white, and uses the theory that the white balance can be corrected by setting R=G=B. It is built on top.

Problems to be Solved by the Invention However, in conventional white balance correction circuits, the photometric range of color signals is always constant, so if the color information is not white, for example, if there is a strong light source within the screen, However, there was a problem in that accurate white balance correction could not be performed.

The present invention solves these conventional problems,
It is an object of the present invention to provide an excellent white balance correction circuit that can minimize the influence even when color information is not white.

Means for Solving the Problems In order to achieve the above object, the present invention provides means for dividing a screen into a white balance correction circuit, and means for calculating an appropriate RB control signal output from the color signals of each divided screen. It is equipped with the following.

Therefore, according to the present invention, by averaging the color information of each screen, it is possible to perform white balance correction to determine whether the color information of one or more of the divided screens is close to white or not. It is possible to reduce the influence of color information that may be a hindrance.

Example FIG. 1 shows the structure of an embodiment of the present invention.

In FIG. 1, the signal extracted from the image sensor 1 is
The RGBO color signals are separated in the signal processing circuit 2, and the R
It is input to the B gain control circuit 3.

A part of the output of the RB gain control circuit 3 is input to the signal processing circuit 14 as a color signal in the video signal, and another part is input to the screen division circuit 4 as a color signal for white balance correction. The screen division circuit 4 is for switching color signals, using analog switches etc.
Extracts the color signal of a part of the screen. Figure 2 is an example showing the portion from which the color signal is extracted, and in this example, 21 to 2
It is divided into 4 M14 parts. For each IV, one of 21 to 24 is taken out in order or at random.

The divided signal is input to the peak hold circuit 5 for a period of 1v, but substantially any one of 1/4v from 21 to 24
The color signal of the period is held at its peak.

The output of the 4V period peak hold circuit 5 is that it is manually inputted to the A/D converter 6 as a DC signal of each color that changes every IV period, converted to a digital signal, and sent to the microcomputer 7.
is input. The operation example of the microcomputer 7 is shown in the fourth example.
As shown in the figure.

The RB control signal output from the microcomputer 7 is converted into an analog signal by the /A converter 12, and is manually input to the RB gain control circuit 3 to control the color signal as in the conventional case.

Next, FIG. 1 shows the operation of dividing the screen.

This will be explained based on FIGS. 2 and 3.

In the case of vertical division into four as shown in Figure 2, signals such as 31 to 34 in Figure 3 are required as signals for operating the screen division circuit 4, and the division signal generator generates these signals. It is 13. This division signal generator 13 outputs any one of the signals 31 to 34 according to the screen division side signal outputted from the screen division control means 11 in the microcomputer 7. If the screen is divided into four, the screen division control means 11 sends four types of screen division control signals to the division signal generator 13.
For example, the signal for and should be sent to , such as 35.
It becomes a 2-bit signal. In this example, if the 2-pit signal 35 is 0.0, the 31 signal is sent to the divided signal generator 1.
3 and the part 21 is selected. Similarly 0・
If it is 1, it is 22.1.If it is 0, it is 23.1.If it is 1, the part 24 is selected. The screen division control means 11 simultaneously controls the current 21
-24 is sent to the color signal calculation means 8 as to which screen is selected.

Next, the operation of the micro computer tough will be explained mainly based on FIG.

At step S1 when starting up the present device, an RB control signal of a predetermined magnitude is output in step S2, and thereafter a signal of the same magnitude continues to be output until it is changed. In step S3, the screen division circuit 4 is operated by the screen division control means 11 and the division signal generator 13, and while switching the division of the screen, the color signal of each screen is controlled by the peak hold circuit 5 and the A/D converter 6 for a period of 1v. The color information is then input to the color signal calculation means 8, and in step S4, the color signal calculation means 8 calculates how close the color information of each screen is to white.

In step S5, based on the calculation result in step S4, it is determined whether the color information of each screen can be used for white balance correction, that is, whether it is valid or invalid.

In step S6, it is checked whether the entire divided screen is invalid, and if the entire screen is invalid, the process branches to 41, and the process returns to step S3 to input the color signal without changing the RB control output. If there is at least one valid screen, the process branches to 42 and proceeds to step S7. This step S
4. S5. S6 corresponds to the color signal calculation means 8 in FIG.

In step S7, the output value calculation means 9 averages only the valid screen color signals, and in step S8, the values of the RB gain control output are respectively increased or decreased based on the averaged color signals, and R=G=B Control so that This step S7.88 corresponds to the output value calculation means 9 in FIG.

In step S9, the output of the RB control signal is actually changed to control the RB gain control circuit 3 through the D/A converter 12. This step S9 corresponds to the output side (2) means 10 in FIG.

After completing step S9, the process returns to step S3 for color signal input, and steps S3 to 89 are repeated to continue controlling the white balance.

In this way, according to the above embodiment, even if a subject that interferes with white balance correction is included in a part of the screen, this can be avoided and accurate white balance correction can be performed using the color information of other parts. be able to.

In the above embodiment, a color information determining means is combined, but a certain degree of effect can be obtained by simply averaging the entire screen, so the color information determining means is not necessarily necessary. Further, the screen may be divided by a combination of horizontal divisions, and the screen does not have to be divided into equal parts. Furthermore, when color information determination means are combined, it is not necessary to take an average value as an "effective color signal". For example, a color signal from a portion near the center may be used, or a color signal from a portion with the largest signal amount may be used.

Effects of the Invention As is clear from the above embodiments, the present invention divides the screen and performs white balance correction using a plurality of color signals, and reduces the influence of a subject that may interfere with white balance correction. This has the advantage that more accurate white balance correction can be performed.

Further, by providing color information array means, the advantages of both can be utilized and the disadvantages can be compensated for, thereby making it possible to perform more accurate white balance correction.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a white balance correction circuit in an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of screen division in the embodiment, and FIG. 3 is an example of a screen division signal in the embodiment. FIG. 4 is a flowchart showing the operation of the main part of the same embodiment, and FIG. 5 is a block diagram of a conventional white balance correction circuit. 1... Imaging element, 2... Signal processing circuit, 3...
RB gain control circuit, 4... screen division circuit,
5...1v period peak hold circuit, 6...A/D
Converter, 7... Microcomputer, 8... Color signal calculation means, 9... Output value calculation means, 10... Output value control means, 11... Screen division side (goods) means, 12D
/A converter, 13... Screen division signal generator. Name of agent: Patent attorney Toshio Nakao and one other person (Fig. 1, Fig. 2, Fig. 3') 1 Fig. 4

Claims (1)

[Claims] It is equipped with screen division control means for performing screen division, color signal calculation means for calculating the degree of whiteness of each divided screen, and output control means for controlling the RB gain control circuit. A white balance correction circuit that performs RB gain control using color signals.