JPS63318870A - Separating circuit for synchronizing pulse of picture signal - Google Patents

Abstract

PURPOSE:To obtain a horizontal synchronizing pulse free from a noise component by separating a synchronizing pulse of a picture signal and then extracting the repetitive frequency component of the horizontal synchronizing pulse of said separated synchronizing pulse through a band-pass filter (BPF). CONSTITUTION:A diode clamper consisting of a capacitor 2 and a diode 3 fixes the tip of the synchronizing pulse of an inputted picture signal at a ground level when a picture signal is supplied to a picture signal input terminal 1. The synchronizing pulse is separated from the picture signal by a voltage comparator 4 having the reference voltage Vref. Then a basic wave equal to the repetitive frequency of the horizontal synchronizing pulse of the picture signal is extracted out of said separated signal by a BPF 6 having a center frequency equal to the repetitive frequency of the horizontal synchronizing pulse of the picture signal. Furthermore the extracted signal is transformed into a pulse by a limiter 7 and the width of this pulse is controlled by a monostable multivibrator 8. Thus it is possible to delete the noise component and to separate an accurate horizontal synchronizing pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image signal synchronous pulse separation circuit used in an image signal clamper or the like.

[Conventional technology]

Conventionally, this type of image signal synchronization pulse separation circuit has a third
As shown in the figure, it consists of a diode clamper made up of a capacitor 2 and a diode 3, and a voltage comparator 4. In this circuit, when the signal shown in FIG. 4 (4) is input to the input terminal 1, the ends of the synchronization pulses are clamped by the diode crank. This flange voltage is input to the voltage comparator 4, and the reference voltage Vreft- shown in FIG. 4 is applied to the comparison voltage input terminal 5 of the voltage comparator 4, thereby separating the synchronization pulses as shown in FIG. There is.

[Problem that the invention seeks to solve]

The conventional image signal synchronization pulse separation circuit described above has a fifth
As shown in FIG.
If there is, there is a drawback that noise SN is generated even in the separated synchronous/4' pulse as shown in FIG. 5).

[Means for solving problems]

The image signal synchronization iE pulse separation circuit according to the present invention is as follows.

As shown in FIG. 1, a diode clamper consisting of a capacitor 2 and a diode 3, a voltage comparator 4, a bandpass filter 6 whose center frequency is the repetition frequency of the synchronization A' pulse of the two image signals, and a limiter 7. This limiter has a monostable multivibrator for adjusting the Nockle width of the output.

〔Example〕

FIG. 1 shows an embodiment of the present invention. When the image signal shown in FIG. 2 (,) is input to the image signal input terminal 1, the diode clamper consisting of a capacitor 2 and a diode 3 in FIG. Fixed at ground level. From the image signal with the tip of this synchronization pulse fixed at the ground level,
) with the voltage comparator 4 having a reference voltage vref of
The synchronization pulses as shown in b) are separated. This separated signal is next.

A fundamental wave that is the same as the horizontal synchronization/-f' pulse repetition frequency is extracted by the bandpass filter 6 which uses the repetition frequency of the horizontal synchronization pulse of the image signal as the entire center frequency. Furthermore, this extracted signal is converted into a nockle signal by a limiter 7 as shown in FIG.
As shown in Figure 2(d), /J? The loop width is adjusted.

〔Effect of the invention〕

As explained above, in the present invention, after separating the synchronization pulses of two image signals, the horizontal synchronization and pulse repetition frequency components of the synchronization pulses are extracted using a band-pass filter, and the horizontal synchronization Noculus is extracted from the extracted signal. It is being produced.

Therefore, even if there is noise in the two image signals, the noise component is removed by the bandpass filter, and accurate horizontal synchronizing pulses can be separated.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention. FIG. 2 shows signal waveforms at major points in FIG. 1. FIG. 3 is a block diagram of a conventional image signal synchronization pulse separation circuit, FIG. 4 shows input/output waveforms of the circuit of FIG. 3, and FIG. 5 shows input/output waveforms of the circuit of FIG. 3. 4: Voltage comparator, 6: Bandpass filter, 7: Limiter, 8: Monostable multivibrator. Figure 1 Figure 2 1 Tatami :: (b) -m-Jl"-m-"1--(rim-"-shi"- (d)-"shi-几-

Claims (1)

[Claims] 1. Image signal synchronization pulse separation circuit consisting of a clamper that fixes the tip of the synchronization pulse of the image signal to a constant DC voltage level, and a voltage comparator that separates the synchronization pulse fixed to the constant DC voltage level by the clamper. In,
A bandpass filter that extracts the repetitive frequency component of the synchronization pulse separated by the voltage comparator, a limiter that converts the extracted repetitive frequency component into a pulse, and a monostable multivibrator that adjusts the output pulse width of the limiter. An image signal synchronization pulse separation circuit characterized by being provided.