JPH033591A - White balance controller - Google Patents

Abstract

PURPOSE:To reduce malfunction of white balance correction by providing a detection means detecting zoom position of a camera lens and controlling the output of a color signal gain control signal in response to the signal level. CONSTITUTION:A microprocessor 21 controls a zoom position discrimination function, an output function of a color signal control signal and an output of a control signal with a signal from a zoom position sensor 22. That is, when a zoom position is at the WIDE side considered to include lots of lighting color temperature information to generate and output a color signal gain control signal to approach a color difference signal to a white level. Further, it is consider that the most part of screen is chromatic information when the zoom position is at a TELE side. Even when there is a difference with a white level in a color difference output, a color signal gain control signal outputs a data outputted at present to try to prevent decoloring of an object. Thus, malfunction of white balance correction is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic white balance control device for a color video camera.

2. Description of the Related Art Conventionally, an auto white balance device for a color video camera is constructed as shown in FIG. Here, 1 is a color signal gain control signal generating section, and 2 is a color signal gain circuit. Optical information passing through the lens unit 3 of the color video camera is incident on a CCD 4 as a solid-state image sensor. The CCD 4 photoelectrically converts the optical information into an electrical signal and sends it to the color separation circuit 5. The color separation circuit 5 separates only the color components from the CCD output signal and outputs R and B signals. The two color signals are subjected to white balance correction in the color signal gain circuit 2 upon receiving the control signal generated by the control signal generator 1, and then sent to the matrix circuit 6. The matrix circuit 6 performs matrixing of the color signals to create color difference signals of R-Y signal and B-Y signal. The color difference signal passes through the encoder 7, and the Y
It is mixed with the signal and output as a composite video signal.

Next, we will introduce the fourth method of controlling the conventional auto white balance.
This will be explained using figures. Matrixed R-Y, B-Y
The color difference signals are smoothed by an integrating circuit 8.9, and the signal level is compared with each reference voltage and a comparison amplifier circuit 10.11.
are compared. When there is a difference between the color difference signal and the white level, the gain of the color signal is changed in the R color signal gain circuit and the B color signal gain circuit 13 to approach the white level. When the color temperature changes, the level of the color difference output changes, so by controlling the gain of the color signal so that it always approaches the white level, an appropriate white balance can be obtained.

Problems to be Solved by the Invention However, in the conventional technology, changes in the smoothed output of color difference signals, which are detection signals, are not caused by changes in the color temperature of lighting (but are caused by input of chromatic color information). Even in this case, the control operation of the color signal gain circuit is performed in the same way as in the prior art, and as a result, there is a problem that chromatic color information is lost and a malfunction occurs in white balance correction.

Means for Solving the Problems In order to solve the above-mentioned problems, the white balance control device of the present invention includes a detection means for detecting the zoom position of the camera lens, and controls the output of the color signal gain control signal according to the signal level of the detection means. The present invention is characterized in that malfunctions in white balance correction are reduced.

Function: The white balance control device of the present invention has a zoom position determination function using a signal from a sensor for knowing the zoom position of a camera lens, a color signal gain control signal output function, and a control for controlling the output of the control signal. When the zoom position is on the WIDE side, which is thought to include a lot of illumination color temperature information, a color signal gain control signal is generated to bring the color difference signal closer to the white level. output, and perform white balance correction according to the color temperature.

On the other hand, when the zoom position is on the E side, most of the screen is considered to contain chromatic color information, so even if there is a difference between the color difference output and the white level, no control operation is performed to bring it closer to the white level, and the color signal is The gain control signal outputs the currently output data to prevent fading of the subject. These operations can reduce white balance correction malfunctions.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings. 1st
The figure shows one embodiment of the present invention, and the same reference numerals in FIG. 3 indicate the same components. In FIG. 1, 21 is a microprocessor for detecting the zoom position and generating a color signal gain control signal, 22 is a position sensor for knowing the zoom position, and 23 is inputting the signal from the position sensor 22 as data to the microprocessor 21. A/D converter for, 24.25
The detection signal, that is, the color difference signal, is sent to the microprocessor 21.
The A/D converters 26 and 27 are D/A converters for converting the color signal gain control signal into an analog signal.

Next, the operation of the present invention will be explained. A/D converter 24°25
The R-Y and B-Y color difference signal levels are continuously input to the microprocessor 21.

Further, zoom position information is also continuously input to the microprocessor by the A/D converter 23. The color signal gain control signal is then output according to the flowchart shown in FIG.

First, A/D converted zoom position data and color difference data are taken into the microprocessor. Next, the zoom position is determined from the captured zoom position data, and it is determined whether the zoom position is within a predetermined range. When the zoom position is outside the predetermined range, the currently output control signal is output as is, and the process ends. Next, if the zoom position is within a predetermined range, the color difference output value is determined and compared with the white level value input as initial data. If there is no difference between the white level value and the color difference data, the currently output control signal is output and processing ends. If there is a difference between the color difference signal and the white level value, the calculation is performed so that the color difference output matches the white level. The process ends after calculating and outputting the color signal gain control signal. Thereafter, white balance correction is performed by repeating this loop.

Effects of the Invention As described above, according to the present invention, it is possible to obtain the effect of preventing color fading due to zooming up of the video camera, and to obtain an appropriate white balance even if the zooming during shooting with the video camera changes. It is something.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a white balance control device of the present invention, FIG. 2 is a flowchart of internal processing of a microcomputer in the present invention, and FIG. 3 is a block diagram showing a conventional white balance control device. FIG. 4 is a block diagram of main parts for explaining the operation of the device. 21...Microprocessor, 22...
・Zoom position sensor, 23, 24.25...A
/D converter, 26.27...D/A converter.

Claims (1)

[Claims] a first detection means for detecting a change in color temperature of illumination using a video signal taken out from the signal processing system; a color signal gain control circuit controlled by the signal detected from the first detection means; and a color signal gain control circuit for controlling a camera lens. 2nd to detect the zoom position
a detection means for determining whether or not the second detection signal is within a predetermined range, and a control means for outputting a control signal according to the determination result; A white balance control device comprising: operation determining means for operating a color signal gain control circuit based on a detection signal from the first detection means only when conditions are met.