JPH0634509B2 - White balance correction circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. 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 and the like.

2. Description of the Related Art Generally, a video camera device has a function of automatically correcting white balance, and controls the signals of respective colors to be equal based on color signals from an image pickup tube, an image pickup element, or a 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 pickup device 51 is separated into RGB color signals in the signal processing circuit 52 and input to the RB gain control circuit 52.

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

The output of the peak hold circuit 54 during the 1V period is output as a comparator 55 as a DC signal of each color that changes every 1V period.
Entered in. This comparator 55 outputs a red signal (hereinafter abbreviated as R) from a green signal (hereinafter abbreviated as G),
If the blue signal (hereinafter abbreviated as "B") is large, an output is output, and if it is small, it is not output, which is a digital operation.

The output of the comparator 55 is input to the microcomputer 56, the output value calculating means 57 calculates the value of a signal for controlling the magnitude of R and B (hereinafter abbreviated as RB control signal), and the output control means 58 outputs RB. The control signal is output. As a result, the RB gain control circuit 53 is controlled so that R = G = B.

As described above, in the above-mentioned conventional white balance correction circuit, it is assumed that the color signal information (hereinafter referred to as color information) is always white, and the white balance can be corrected by setting R = G = B. It consists of the above.

Problems to be Solved by the Invention However, in the conventional white balance correction circuit, since the photometric range of the color signal is always constant, when the color information is not white, for example, when a strong light source is included in the screen, However, there was a problem that accurate white balance correction could not be performed.

The present invention solves such 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 the color information is not white.

Means for Solving the Problems In order to achieve the above object, the present invention provides a screen dividing means for dividing a screen, a means for holding a peak for each screen division, and a color adjustment based on the peak-held data. It is provided with a color signal determination means for determining whether or not it is possible and for determining the adjustment amplification amount.

Operation Therefore, according to the present invention, if one or a plurality of color information obtained by dividing the screen into a plurality of colors is close to white, the color information of each screen is averaged so that the white balance correction is not performed. It is possible to reduce the influence of the color information which becomes an obstacle.

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

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

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.
Extract the color signal of a part of the screen. FIG. 2 shows an example in which a color signal is extracted. In this example, 21 to 2 are used.
There are 4 vertical divisions. Any one of 21 to 24 is sequentially or randomly taken out for each 1V.

The divided signal is input to the 1V period peak hold circuit 5, but the color signal of any one of 21 to 24 in the 1 / 4V period is substantially peak-held.

The output of the 1V period peak hold circuit 5 is input to the A / D converter 6 as a DC signal of each color that changes for each 1V period, converted into a digital signal, and converted to a microcomputer 7
Entered in. The operation example of the microcomputer 7 is the fourth
Shown in the figure.

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

Next, regarding the operation of dividing the screen, FIG. 1, FIG.
A description will be given based on FIG.

In the case of vertical division into four as shown in FIG. 2, a signal such as 31 to 34 in FIG. 3 is required as a signal for operating the screen division circuit 4, and this is generated by a division signal generator. It is 13. The division signal generator 13 outputs any one of 31 to 34 according to the screen division control signal output from the screen division control means 11 in the microcomputer 7. The screen division control means 11 may send four kinds of screen division control signals to the division signal generator 13 in the case of four divisions, so that this signal is a 2-bit signal such as 35. In the case of this example, if the 2-bit signal 35 is 0.0, a signal 31 is output from the divided signal generator 13 and a portion 21 is selected. Similarly, if 0 · 1, 22 if 1.0, 23 if 1.1, and 24 if 1.1 are selected. The screen division control means 11 is currently 21-24 at the same time.
Information on which screen of the selected is selected is sent to the color signal calculation means 8.

Next, the operation of the microcomputer 7 will be described mainly based on FIG.

In step S1 when the apparatus is activated, the RB control signal of the predetermined magnitude is output in step S2, and the signal of the same magnitude continues to be output until it is changed thereafter. In step S3, the screen division control means 11 and the division signal generator 13 operate the screen division circuit 4, and while switching the division of the screen, the color signal of each screen is controlled by the peak hold circuit 5 for 1V period and the A / D converter 6. To the color signal calculating means 8, and in step S4 the color signal calculating 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, whether the color information of each screen can be used for white balance correction, that is, whether the color information is within the range of the amplification amount that can be corrected by the RG gain control 3 is valid or invalid. To determine.

In step S6, it is checked whether or not all the divided screens are invalid. If the entire screen is invalid, the process branches to 41, and the RB control output is not changed and the process returns to the color signal input of step S3. If even one screen is valid, the process branches to 42 and proceeds to step S7. This step S
4, S5 and S6 correspond to the color signal calculating means 8 in FIG.

In step S7, the output value calculating means 9 averages only valid screen color signals, and in step S8, the value of the RB gain control output is increased or decreased based on the averaged color signal, and R = G = B. Control so that. These steps S7 and S8 correspond to the output value calculating means 9 in FIG.

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

When step S9 ends, the process returns to the color signal input of step S3, and steps S3 to S9 are repeated to continue controlling the white balance.

As described above, according to the above-described embodiment, even if a subject that interferes with white balance correction enters a part of the screen, it is avoided and accurate white balance correction is performed by the color information of other parts. be able to.

Although the color information determining means is combined in the above embodiment, the color information determining means is not always necessary because some effects can be obtained by simply averaging all the screens. Also, as for the screen division method, horizontal division may be combined, and it is not necessary to divide the screen equally. Further, in the case where color information judging means is combined, the average value does not have to be taken as the “effective color signal”. For example, the color signal of the portion close to the center may be used, or the color signal of the portion having the largest signal amount may be used.

EFFECTS OF THE INVENTION As apparent from the above-described embodiment, the present invention divides a screen and performs white balance correction by a plurality of color signals, and reduces an influence of a subject that becomes an obstacle to white balance correction. This has the advantage that more accurate white balance correction can be performed.

Further, by additionally providing a color information determining means, it is possible to determine in advance the range in which white balance can be corrected, and thus it is possible to perform more accurate white balance correction.

[Brief description 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 view showing an example of screen division of the embodiment, and FIG. 3 is an example of a screen division signal of the embodiment. FIG. 4 is a signal waveform diagram shown in FIG. 4, FIG. 4 is a flow chart showing the operation of the main part of the embodiment, and FIG. 5 is a block diagram of a conventional white balance correction circuit. 1 ... Image sensor, 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, 1
0 ... Output value control means, 11 ... Screen division control means, 12D
/ A converter, 13 ... Screen division signal generator.

Claims (1)

[Claims] 1. A screen division control means for dividing an image, a peak hold means for detecting a peak of a video signal of the entire screen for each screen division, and a color signal adjustment from the data of each peak detection of the divided screen. A white balance correction circuit comprising: a color signal determination unit that calculates an amplification amount and determines whether or not an adjustable range is available; and a gain control unit that controls the color signal based on the adjustment amplification amount.