JPH04367894A - Peripheral brightness correcting device of color crt - Google Patents

Abstract

PURPOSE:To provide a peripheral brightness correcting device of a color CRT so as not to generate differences in the correction amount of each of the R, G, B color signals. CONSTITUTION:-Y signals are amplitude modulated by the amplitude correcting wave form signals made by an amplitude correcting wave form signal generating circuit 2, an adder device 7 superimposes the amplitude correcting wave form signals on color gain control voltage signals and the superimposed signals simultaneously perform level adjustment of three color difference signals and amplitude correction at a color demodulating circuit 1 which is configured by ICs. Since the three color difference signals are simultaneously level adjusted and amplitude corrected by the same superimposed signals at amplifying systems which have the same characteristics, practically no difference exists in the amount of corrections among the three color difference signals and no degradation is realized in the white balance.uniformity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting peripheral brightness of a television receiver using a CRT.

0002

2 is a block circuit diagram of a conventional CRT peripheral brightness correction device, in which 1 is a color demodulation circuit, 2 is an amplitude correction waveform signal generation circuit, 3a to 3d are amplitude modulation circuits, and 4 is a CRT.
An RT drive circuit, 5 is a CRT, and 6 is a color gain control voltage generation circuit.

Next, the operation will be explained. The input composite video signal is converted into -Y signal and 3 by color demodulation circuit 1.
The color difference signals R-Y, B-Y, and G-Y are demodulated into three color difference signals R-Y, B-Y, and G-Y, and the color difference signals R-Y
, B-Y, and G-Y are adjusted and output.

The amplitude correction waveform signal generation circuit 2 generates an amplitude correction waveform signal, and the amplitude modulation circuits 3a to 3d each generate a -Y signal and three color difference signals R-Y, B-Y, Amplitude modulate G-Y.

[0005] Next, each signal is amplified by a CRT drive circuit 4 and input to a CRT 5, and an image with peripheral luminance corrected is displayed.

[0006]

A conventional color CRT peripheral brightness correction device requires four amplitude modulation circuits, resulting in high cost.

[0007] Furthermore, there is a problem in that when a difference occurs in the level of the color difference signal due to variations in the characteristics of each amplitude modulation circuit, it adversely affects white balance, uniformity, and the like.

The present invention has been made to solve the above-mentioned problems, and it is possible to simplify the circuit by reducing the number of amplitude modulation circuits required, and to create a color filter that has less negative impact on white balance and uniformity. The object of the present invention is to obtain an apparatus for correcting peripheral brightness of a CRT.

[0009]

[Means for solving the problem] Color C according to the present invention
The RT peripheral luminance correction device includes means for superimposing an amplitude correction waveform signal on the color gain control signal generated by the color gain control signal generation means, and uses this superimposed signal to convert each color difference signal in a color demodulation circuit composed of an IC. The feature is that the amplitude is corrected.

0010

[Operation] The peripheral brightness correction device for color CRT according to the present invention amplitude-modulates the -Y signal with an amplitude correction waveform signal, and the color difference signals R-Y, B-Y, and G-Y are superimposed signals and are composed of ICs. Amplitude correction is performed in the color demodulation circuit. Therefore, since there is almost no difference in the amplitude correction amount of each color difference signal, there is no adverse effect on white balance uniformity.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram of this embodiment. Components that are the same as those of the conventional example shown in FIG. 2 are given the same reference numerals and explanations will be omitted. In the figure, 7 is an adder that superimposes the amplitude correction waveform signal on the color gain control voltage signal.

This superimposed signal is input to the color demodulation circuit 1,
The amplitudes of the color difference signals R-Y, B-Y, and G-Y are corrected simultaneously with the level adjustment. On the other hand, the -Y signal is transmitted to the amplitude modulation circuit 3.
The amplitude is modulated by the amplitude correction waveform signal at a.

In the CRT peripheral brightness correction device configured as described above, the -Y signal and the three color difference signals R-Y, B-Y, G-Y are subjected to amplitude correction using the same amplitude correction waveform signal, and the three color difference signals R-Y, B-Y, G-Y are Since the amplitudes of the two color difference signals are corrected within the color demodulation circuit 1, which is composed of an IC and has well-matched amplitude characteristics for each system, the balance uniformity does not deteriorate.

In the above embodiment, the amplitude of the -Y signal is modulated by the amplitude correction waveform signal, but the amplitude correction waveform signal is superimposed on the video contrast control voltage signal, and this superimposed signal modulates the amplitude of the -Y signal. If correction is performed, the amplitude modulation circuit 3a can be omitted.

[0015]

Effects of the Invention As explained above, the present invention is capable of controlling the -Y signal and each color difference signal R-Y with one amplitude correction waveform signal.
, B-Y, and G-Y, and the amplitude of the three color difference signals is also corrected by an amplifier system with the same characteristics in the color demodulation circuit composed of an IC, which simplifies the configuration. In addition, since there is no difference in the amplitude correction amount of each color difference signal, it is possible to obtain a color CRT peripheral brightness correction device that does not deteriorate white balance uniformity.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention.

FIG. 2 is a block circuit diagram of an example of a conventional color CRT peripheral brightness correction device.

[Explanation of symbols]

1 Color demodulation circuit 2 Amplitude correction waveform signal generation circuit 3a Amplitude modulation circuit 5 Color CRT 6 Color gain control voltage generation circuit 7 Adder

Claims (1)

[Claims] [Claim 1] The brightness difference around the display surface of a color CRT is corrected by correcting the amplitudes of a brightness signal demodulated by a color demodulation circuit composed of an IC and three color difference signals using an amplitude correction waveform signal. Color CR configured to
The peripheral brightness correction device of T includes an adder that superimposes the amplitude correction waveform signal on a color gain control voltage signal that adjusts the levels of the three color difference signals, and the added signal is used to adjust the three color differences in the color demodulation circuit. 1. A peripheral luminance correction device for a color CRT, characterized in that it is configured to perform signal level adjustment and amplitude correction at the same time.