JPH01160271A - Video signal noise reduction device - Google Patents

Abstract

PURPOSE:To obtain an optimum noise reduction effect automatically by passing an output video signal only during a period when a horizontal synchronizing signal exists, extracting only an AC component and controlling the effect or reducing the noise component. CONSTITUTION:A gate circuit 2 is opened for the existing period only of a horizontal synchronizing signal extracted from a horizontal synchronizing signal separation circuit 1, only the noise component included in an input video signal is extracted, a DC voltage proportional to the noise component is obtained by an amplifier 4, a rectifier circuit 5 and an integration circuit 6, and the noise reduction effect of the noise reduction circuit 7 is adjusted optimizingly in response to the quantity of the DC voltage. Thus, the optimum noise reduction effect is obtained automatically in response to difference from the quantity of noise on a disk.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal noise reduction device that reduces noise contained in a video signal and improves the signal-to-noise ratio.

As an example of a conventional technique, a noise reduction device for a video disc reproducing apparatus that reproduces an original video signal from a video disc on which the video signal is recorded using the FM system will be described.

FIG. 3 is a very simple block diagram of a video disc playback device. In FIG. 3, 8 is a playback signal amplification circuit that amplifies the disc playback signal taken out from the video disc by a reading device such as an optical pickup to an appropriate size, and 9 is a playback signal amplification circuit that amplifies the video signal from the FM-modulated disc playback signal. 1o is a time base collector that absorbs fluctuations on the time axis of the video signal caused by disk eccentricity, rotational fluctuations, etc., and 11 is a noise reduction circuit.

Conventionally, various circuit systems have been proposed for noise reduction circuits, which reduce easily noticeable noise components such as white noise contained in the reproduced video signal or beat noise with the audio signal that is FM multiplexed at the same time as the video signal. The aim was to reduce the noise and improve the signal-to-noise ratio. Furthermore, the reduction effect of the noise reduction circuit may be adjustable by the user from the outside using a variable volume or a changeover switch, but in most cases it is generally fixed.

Problems to be Solved by the Invention However, if the reduction effect of the noise reduction circuit is fixed, the amount of noise will vary depending on the disk, so the reduction effect may not be optimal. For example, in the case of optical video discs, there are two types: CLV (Constant Linear Velocity) discs and CAV (Constant Angular Velocity) discs.Generally, the entire circumference of a CLV disc and the inner circumference of a CAV disc have a higher noise component than the outer circumference of a CAV disc. There are many. Even for the same CLV disc or CAV disc, the amount of noise varies depending on the quality of the original source, the cutting conditions, and the state of storage of the disc. Therefore, in this case, if the effect of the noise reduction circuit is fixed (generally optimized for disks with a medium amount of noise), the effect will be insufficient for disks with a lot of noise, and the effect will be insufficient for disks with a lot of noise. However, there are problems in that the amount of reduction is too large, resulting in a loss of resolution, and the user still has to adjust the noise reduction circuit for each disc, which is cumbersome. was.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a noise reduction device that can automatically obtain an optimal noise reduction effect in response to differences in the amount of noise depending on the disc.

Means for Solving the Problems In order to solve the above problems, the noise reduction device of the present invention passes the input video signal only during the presence of a horizontal synchronization signal separated from the input video signal of the device. means for extracting only the alternating current component of the passing signal;
The present invention is constructed by means for obtaining a DC voltage proportional to the magnitude of the AC component, and means for controlling the effect of reducing the noise component contained in the input video signal by the magnitude of the DC voltage.

Function The present invention is configured to automatically obtain the optimum noise reduction effect in response to the difference in noise amount depending on the disc, using the above-described configuration.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention. 1st
In the figure, 1 is a horizontal sync signal separation circuit that extracts the horizontal sync signal included in the input video signal, 2 is a gate circuit that opens only when the horizontal sync signal extracted by the horizontal sync signal separation circuit 1 exists, and 3 is a gate. A capacitor that passes only the alternating current component in the signal passing through the circuit, 4 is the capacitor 3
An amplifier that amplifies the alternating current component that has passed through the
6゜6 is a rectifier circuit and an integrator circuit for obtaining a DC voltage proportional to the magnitude of the output signal of the amplifier 4, and 7 is an integrator circuit e.
This is a noise reduction circuit that allows the noise reduction effect to be controlled by the output voltage.

Normally, the horizontal synchronization section of a video signal as shown in FIG. 2(a) should originally consist of only DC components, but in reality, noise components are superimposed thereon as shown in FIG. 2(b). Therefore, only this noise component is extracted by the gate circuit 2 and capacitor 3, and a DC voltage proportional to the magnitude of the noise component is obtained by the amplifier 4, rectifier circuit 6, and integration circuit 6. Correspondingly, the noise reduction effect of the noise reduction circuit 7 can be set optimally.

Effects of the Invention As described above, according to the present invention, the noise reduction device includes means for passing the input video signal only during the existence period of the horizontal synchronization signal separated from the input video signal of the device, and an alternating current component of the passing signal. means for extracting only the noise component contained in the input video signal, means for obtaining a DC voltage proportional to the magnitude of the AC component, and means for controlling the effect of reducing the noise component contained in the input video signal by the magnitude of the DC voltage. With this configuration, it is possible to automatically obtain the optimum noise reduction effect in response to differences in the amount of noise depending on the disc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
) is a waveform diagram showing an example of a video signal, (b) is an enlarged waveform diagram of the horizontal synchronization signal portion of the video signal in (a),
FIG. 3 is a very simple block diagram showing the signal flow of the video disc playback device. 1...Horizontal synchronization signal separation circuit, 2...
Gate circuit, 3... Capacitor, 4...
・Amplifier, 6... Rectifier circuit, e... Integrating circuit, 7... Noise reduction circuit, 8...
・Reproduction signal amplification circuit, 9...FM detection circuit, 1
0... Time base collector, 11...
・Noise reduction circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person3-
Co/Tensa 4-Five prefectures 1 map

Claims (1)

[Claims] means for passing the input video signal only during the existence period of a horizontal synchronization signal separated from the input video signal; means for extracting only the alternating current component of the passing signal; and obtaining a direct current voltage proportional to the magnitude of the alternating current component. and means for controlling the effect of reducing noise components contained in the input video signal by the magnitude of the DC voltage.