JPS60134566A - Picture quality adjusting circuit - Google Patents

Abstract

PURPOSE:To attain stabilization of a reproduced picture by inhibiting the supply of a video signal to a high frequency component emphasis circuit during the period of a synchronizing signal of an inputted video signal. CONSTITUTION:The video signal inputted from a terminal 1 is fed to an integration circuit 3 and also to a synchronizing signal separating circuit 8. The circuit 8 separates a synchronizing signal from the inputted video signal. The separated synchronizing signal is fed to one input of a gate circuit 9. The video input signal from the terminal 1 is fed to the other input of the circuit 9 and the output of the circuit 9 is fed to a double differentiation circuit 2. The part of the synchronizing signal in the video input signal is not differentiated double and neither pre-shoot nor overshoot is added thereto. Thus, the video output signal from a terminal 5 forms a stable reproducing pattern not affected by jittering or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image quality adjustment circuit, and particularly to an image quality adjustment circuit in, for example, a magnetic recording/reproducing device or a television receiver.

[Prior art] FIG. 1 is a block diagram showing a conventional image quality adjustment circuit.

In the figure, an input terminal 1 is supplied with a video signal.

This video signal is given to a double differentiating circuit 2 and also to an integrating circuit 3.

The output of the double differentiating circuit 2 and the output of the integrating circuit 3 are combined by a variable resistor 4 and outputted from an output terminal 5.

In the above configuration, the double differentiator circuit 2 emphasizes the high frequency components of the video signal, that is, applies preshoot and overshoot to the luminance signal to sharpen the image quality. On the other hand, the integrating circuit 3 emphasizes the low frequency components of the video signal,
This softens the image quality. The variable resistor 4 determines the degree to which the image quality is sharpened or softened by appropriately selecting the combination ratio of the output of the double differentiating circuit 2 and the output of the integrating circuit 3.

FIG. 2 is a waveform diagram of a video signal input to the input terminal 1 of FIG. 1 before image quality adjustment is performed.

FIG. 3 is a waveform diagram of a video signal of a bale whose image quality has been adjusted by the image quality adjustment circuit shown in FIG.

As understood from these Figures 2 and 3, the first
In the conventional image quality adjustment circuit shown in the figure, not only the luminance signal 7 but also the synchronization signal 6 are double differentiated and integrated, and overshoot and preshoot are added. Therefore, the image quality adjustment circuit as shown in FIG. 1 has the disadvantage that the reproduced screen becomes unstable due to jittering and the like.

[Summary of the Invention] This invention has been made to eliminate the drawbacks of the conventional ones as described above, and the video signal is not input to the high-frequency component emphasizing means during the period of the synchronization signal of the video signal. The purpose is to eliminate overshoot and preshoot in the synchronization signal portion.

Hereinafter, this invention will be described in more detail with reference to embodiments shown in the drawings.

[Embodiments of the invention] FIG. 4 is a block diagram showing one embodiment of the present invention.

This embodiment is similar to the circuit shown in FIG. 1 except for the following points, and corresponding parts are given the same reference numerals and their explanations will be omitted. In the figure, in this embodiment, a video signal input from an input terminal 1 is applied to an integrating circuit 3 and also to a synchronizing signal separation circuit 8. The synchronization signal separation circuit 8 extracts a synchronization signal (
(horizontal sync signal and vertical sync signal).

This separated synchronization signal is applied to one input of the gate circuit 9. Further, the video signal input from the input terminal 1 is given to the other input of the gate circuit 9. The output of this gate circuit 9 is a double differential circuit.

given to 2.

In the above-described configuration, the gate circuit 9 prohibits the input of the video signal to the double differentiation circuit 2 during the period of the synchronization signal provided from the synchronization signal separation circuit 8. During other periods, the gate circuit 9 supplies the video signal input from the input terminal 1 to the double differentiator circuit 2 as it is. Therefore, the synchronizing signal portion of the video signal input from the input terminal 1 is not double differentiated, and a video signal as shown in FIG. 5 is obtained from the output terminal 5. As shown in FIG. 5, no preshoot or overshoot is added to the synchronization signal portion, and the playback screen does not become unstable due to jittering or the like as in the conventional case.

[Effects of the Invention] As described above, according to the present invention, the video signal is not applied to the high-frequency component emphasizing means during the synchronization signal period of the input video signal, so that the synchronization signal portion is Preshoot and overshoot are not added, making the playback screen stable.

[Brief explanation of drawings]

The first diagram is a block diagram showing an example of a conventional image quality adjustment circuit. FIG. 2 is a waveform diagram showing a video signal input to the input terminal 1 of FIG. 1. FIG. 3 is a waveform diagram showing a video signal outputted from the output terminal 5 shown in FIG. 1, that is, a video signal after image quality adjustment. FIG. 4 is a block diagram showing one embodiment of the present invention. FIG. 5 is a waveform diagram showing the video signal output from the output terminal 5 shown in FIG. In the figure, 1 is an input terminal, 2 is a double differentiating circuit, 3 is an integrating circuit, 4 is a variable resistor, 5 is an output terminal, 8 is a synchronizing signal separation circuit, and 9 is a gate circuit. Agent Masuo Oiwa

Claims (3)

[Claims] (1) A circuit for adjusting the image quality of a video signal, comprising means for inputting the video signal, and a high-frequency circuit that emphasizes the high-frequency components of the video signal input from the input means in order to sharpen the image quality. component emphasizing means; low-frequency component emphasizing means for emphasizing the low-frequency components of the video signal input from the input means in order to soften the image quality thereof;
and means for prohibiting input of the video signal to the high-frequency component emphasizing means during a period of a synchronization signal included in the video signal input from the input means. (2) The image quality adjustment circuit according to claim 1, wherein the high frequency component emphasizing means is a double differentiation circuit. (3) The image quality adjustment circuit according to claim 1 or 2, wherein the low frequency component emphasizing means is an integrating circuit.