JPH08265792A - Correction circuit - Google Patents

Abstract

PURPOSE: To maintain fixed white balance in any luminance states by detecting the change of brightness and contrast by a CPU and controlling the cathode current ratio of RGB to be fixed. CONSTITUTION: The CPU 10 detects brightness and contrast input signals 11 and 12 varied by the adjustment of a user. Then, RGB gain control signals and RGB offset control signals to which a correction value calculated by the varying amount is added are outputted to a voltage control circuit and the fixed cathode current ratio is maintained at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance correction circuit for an image receiving device having a cathode ray tube.

[0002]

2. Description of the Related Art An image receiving device using a cathode ray tube connected to a computer or the like, commonly called a display monitor, is required to be able to adjust a white balance color temperature desired by a user.

The color temperature in an image receiving device having a cathode ray tube is determined by the R, G, B cathode current ratio determined by the cathode ray tube, and this is converted into a cathode amplitude voltage according to the gamma characteristic of the cathode ray tube and applied to the cathode to thereby obtain a predetermined value. It becomes the color temperature. When the contrast and brightness are changed on the conventional display monitor, the white balance that is initially set, that is, regardless of the R / G / B cathode current ratio, Voltage amplitude,
When the brightness is variable, the cathode cutoff voltage is set to RG
Since B is controlled with the same voltage value, the cathode current ratio is different from the cathode current ratio in the initial setting state, and the color temperature changes.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a white balance correction circuit for keeping the R, G, B cathode current ratio constant even when the contrast and brightness are variable.

[0005]

In order to solve the above-mentioned problems, the white balance correction circuit of the present invention detects a change when the contrast and brightness are changed, and outputs the change to a correction signal with which the white balance becomes constant. The calculation part for conversion and the voltage control circuit for giving the calculation result to the cathode ray tube as the change of the cathode voltage correct the white balance even if the contrast and brightness are changed.

[0006]

The bright / contrast change detecting unit detects the control signal input by the user and corrects the current R, G, B cathode voltages in accordance with the change ratio. This correction calculation is performed before the cathode voltage control.

In order to keep the color temperature constant when the brightness / contrast is changed, the cathode current of each of R, G, and B is calculated by the cathode current ratio of the color temperature, which is the total of the cathode currents that change due to the increase / decrease of the brightness / contrast. The color temperature is maintained constant by determining the cathode voltage, which is the cathode current value, from the gamma characteristics of the cathode ray tube, and applying the corrected value added to the cathode voltage before correction to the cathode.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a white balance correction circuit diagram in the embodiment of the present invention.

In FIG. 1, the contrast input 11 arbitrarily changed by the user is detected inside the CPU. Based on the detected contrast input, the CPU 10 calculates a correction value for the R, G, B data 14 stored as adjustment data so that the R, G, B cathode current ratio is always constant due to the gamma characteristic of the cathode ray tube. Then, the arithmetic unit 13 in the CPU performs the correction and outputs the corrected R, G, B gain control signal ABC.

When the bright input is changed by the user, the correction is similarly performed and the corrected data is output. In this case, the offset voltage control signals DEF of R, G, B are output.
Is output.

By performing such correction using the CPU, the white balance correction can be performed by making the cathode current ratio of R, G, B supplied to the cathode ray tube constant at any brightness.

[0012]

According to the present invention, it is possible to perform correction for maintaining the initial state of white balance under any contrast / bright control of the user.

[Brief description of drawings]

FIG. 1 is a white balance correction circuit diagram according to an embodiment of the present invention.

FIG. 2 is a block diagram of a CPU in the white balance correction circuit according to the embodiment of the present invention.

[Explanation of symbols]

1 ... input terminal, 2 ... input terminal, 3 ... input terminal, 4 ... output terminal, 5 ... output terminal, 6 ... output terminal, 7 ... voltage control circuit, 8 ... voltage control circuit, 9 ... voltage control circuit, 10 ... CP
U, 11 ... Contrast signal input terminal, 12 ... Bright signal input terminal.

Claims (2)

[Claims] 1. A correction circuit for an image receiving apparatus using a cathode ray tube having a cathode amplitude varying circuit, wherein white balance is kept constant when contrast is varied. 2. A correction circuit, characterized in that in an image receiving device using a cathode ray tube having a cathode cutoff voltage varying circuit, white balance is kept constant when the brightness is varied.