JPH0690375A - Means for improving focus characteristic - Google Patents

Abstract

PURPOSE:To improve the focus characteristic by superimposing a parabolic wave generated in a television receiver on a control voltage of a picture quality adjustment circuit so as to control the picture quality of a picture around a circumference of a cathode ray tube screen. CONSTITUTION:A video signal 1 is subject to various signal processing in a video signal processing circuit A and the result is outputted to a cathode ray tube 9 from a video output circuit 8. The circuit A has a picture quality control circuit 2 able to vary the picture quality of the video signal, and a parabolic wave whose amplitude is adjusted by a horizontal and vertical deflection parabolic waveform adjustment device 6 and whose level is shifted by a capacitor 7 is superimposed on a control voltage 4 and the resulting voltage is inputted to a control terminal of the circuit 2. The parabolic wave 5 via the waveform adjustment device 6 is superimposed on the control voltage 4 to the picture quality control circuit 2 to increase the sharpness at the circumferential part of the cathode ray tube thereby improving an apparent focus characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to means for improving the focus characteristic of a television receiver.

[0002]

2. Description of the Related Art As a conventional technique, as a means for improving focus characteristics, a parabolic wave is superposed on a focus voltage output from a flyback transformer as a focus correction voltage, as described in JP-A-58-4511. However, a method for improving the focus characteristic of the peripheral portion of the surface of the cathode ray tube and a method described in JP-A-62-279783,
There is a method of modulating the horizontal scanning speed of the electron beam emitted from the cathode ray tube to improve the sharpness of the reproduced image and give an impression that the focus is apparently improved.

[0003]

However, according to the above method, the circuit scale is large and a large number of high breakdown voltage parts are required, which causes a cost problem.

An object of the present invention is to solve the above-mentioned problems and to provide one means for improving the focus characteristic with an inexpensive circuit.

[0005]

The above object can be achieved by simultaneously superimposing a horizontal parabola wave, a vertical parabola wave, or both of them on a control voltage for controlling the image quality of a video signal.

[0006]

By superimposing the horizontal and vertical parabolic waves on the image quality control voltage of the image quality control circuit of the video signal, the image quality adapted to the deflected beam position can be obtained, and the focus characteristic around the cathode ray tube is apparently improved. Looks like.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the video signal 1 undergoes various signal processing in the video signal processing circuit A and is output from the video output circuit 8 to the cathode ray tube 9. The video signal processing circuit A has an image quality control circuit 2 capable of varying the image quality of the video signal, and the control control terminal 3 of this circuit has a horizontal and vertical deflection parabolic wave 5 whose amplitude is adjusted by a waveform adjuster 6. The parabolic wave level-shifted by the capacitor 7 is superimposed on the control voltage 4 and input.

FIG. 2 shows a control voltage waveform input to the control control terminal 3, where (a) is a vertical parabolic wave, (b) is a horizontal parabolic wave, and (c) is a horizontal and vertical parabolic wave superimposed on the control voltage 4. The waveform is shown.

The outline of the operation of the present invention is as follows. The parabolic wave 5 passing through the waveform adjuster 6 is superposed on the control voltage 4 to the image quality control circuit 3, and the image quality is increased as it goes to the peripheral part of the cathode ray tube. Sharpness is increased, and the effect that the focus characteristic is apparently improved is brought about. When the control voltage input to the control control terminal 3 superimposes the vertical parabolic wave shown in FIG. 2A, the sharpness in the vertical direction is increased, and when the horizontal parabolic wave shown in FIG. 2B is superposed. , The horizontal sharpness is increased, and FIG.
When both the horizontal and vertical parabolic waves shown in (c) are superimposed, both the horizontal and vertical sharpness are increased.

[0011]

As described above in detail, according to the present invention, it is possible to realize a circuit which has a small circuit scale, is inexpensive, and greatly improves the apparent focus characteristics.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating means in the present invention.

[Explanation of symbols]

 1 ... Video signal, 2 ... Image quality control circuit, 3 ... Control control terminal, 4 ... Control voltage, 5 ... Horizontal / vertical parabola wave, 6 ... Waveform adjuster, 7 ... Capacitor, 8 ... Video output circuit, 9 ... CRT, A ... Video signal processing circuit.

Claims (1)

[Claims] 1. A parabola wave generated in a television receiver is used, and by superimposing the parabola wave on an image quality control control section of an image quality control circuit of a video signal, the image quality of the peripheral portion of the surface of the cathode ray tube is controlled. A means for improving focus characteristics, which is characterized by improving focus characteristics.