JPS6318779A - Separating device for horizontal synchronizing signal - Google Patents

Abstract

PURPOSE:To stably remove noise with a high accuracy in a simple circuit constitution by providing the second monostable multivibrator triggered by the output of the first monostable multivibrator and generating the output of the pulse duration of a horizontal synchronizing signal. CONSTITUTION:A signal obtained by delaying a composite synchronizing signal by a time shorter than the pulse duration of an equalizing pulse with a delay circuit 4 and an original composite synchronizing signal are integrated in an AND arithmetic circuit 6. The first monostable multivibrator 8 generating the output shorter than the cycle TH of the horizontal synchronizing signal and having a longer period than TH/2 is triggered. Then, according to the output of the first monostable multivibrator 8, the second monostable multivibrator 10 generating the output of the pulse duration of the horizontal synchronizing signal is triggered to obtain the horizontal synchronizing signal. Thereby, the device can be constituted with a compact size, a light weight and a low cost and a noise eliminating capacity thereof is extremely stable and high accurate and the horizontal synchronizing signal can be effectively separated.

Description

[Detailed Description of the Invention] Purpose of the Invention [Industrial Field of Application] The present invention provides a method for decoding a composite synchronization signal multiplexed onto a video signal.
The present invention relates to a horizontal synchronization signal separation device that separates and extracts horizontal synchronization signals.

[Prior art] Conventionally, in the NTSC system, the horizontal synchronization signal is separated from the composite synchronization signal in the vertical synchronization period, horizontal synchronization is maintained even during the vertical synchronization period, and bearing phenomena are suppressed by ensuring increment. ing.

A conventional PLL (ptla
Horizontal synchronization signal separation devices using a se I 0Cked l 00p circuit or two monostable multivibrators are well known. In the PIL circuit, even if the horizontal synchronization signal is disturbed by noise, if the fluctuation range is within a certain range, the phase difference is corrected and horizontal synchronization is maintained.

In addition, in a device using two monostable multivibrators, one monostable multivibrator operates with retriggering disabled by the equalization pulse, and uses its output to trigger the other monostable multivibrator. This avoids generating a horizontal doubling signal, and the equalization pulse and 214t? '
(removal of i).

[Problems to be Solved by the Invention] However, the horizontal synchronizing signal separation device as described above is still not sufficient and has the following problems.

A horizontal synchronization signal separation device that uses a PLL circuit is a PLL circuit.
The circuit itself has a complicated configuration, which hinders the reduction in size and weight of the device, and also increases costs.

On the other hand, a horizontal synchronization signal separation device that uses two monostable multivibrators does not require the above-mentioned complicated circuit configuration and is small, lightweight, and inexpensive. Since the noise varies depending on the surrounding humidity, etc., sufficient noise removal becomes impossible. In other words, one monostable multivibrator is outputting a signal, and the noise superimposed during the period in which re-registration is not possible does not affect the re-registration of the monostable multivibrator in the next stage. Since this period varies depending on the temperature, temperature compensation becomes difficult.

The present invention has been made to solve the above problems, and provides a horizontal synchronization signal separation device that has a simple circuit configuration, is small, lightweight, and inexpensive, and that achieves stable and highly accurate noise removal. Its purpose is to.

Structure of the Invention [Means for Solving the Problems] In order to solve the above-mentioned problems, the horizontal synchronization signal separation arrangement of the present invention removes the noise contained in the composite synchronization signal and separates the horizontal synchronization signal. a horizontal dome signal separation device for mtr, which receives the composite dome signal and delays the composite synchronization signal by a time shorter than the pulse width of the equalization pulse included in the composite synchronization signal; an AND operation circuit that calculates an AND between the output of the delay circuit and the composite same signal; and an AND operation circuit that is triggered by the output of the AND operation circuit, and which is shorter than the period of the horizontal synchronization signal and longer than 1/2 period. A first monostable multivibrator that generates an output; and a second monostable multivibrator that is triggered by the output of the first monostable multivibrator and generates an output with a pulse width of a horizontal synchronization signal. .

[Operation] The horizontal synchronizing signal separation device of the present invention integrates the composite synchronizing signal delayed by a delay circuit by a time shorter than the pulse width of the equalization pulse and the original composite synchronizing signal using an AND operation circuit, and thus The obtained signal triggers a first monostable multivibrator that generates an output for a period shorter than the period TH of the horizontal synchronization signal and longer than TH/2. A second monostable multivibrator generates an output with the pulse width of the horizontal synchronization signal by the output of the first monostable multivibrator.
ti Stable Mardiver triggers the ibrator to generate 1q horizontal synchronization signal.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, examples will be given and explained.

[Example] Fig. 1 is an electric circuit block diagram of a horizontal synchronizing signal separation device according to an embodiment, and Fig. 2 is a timing chart in which the voltage waveform appearing on the signal line in Fig. 1 is plotted against time on the horizontal axis. It is.

As shown in the figure, a video signal multiplexed with synchronization signals is applied to a synchronization separation circuit 2, and only the synchronization signal assigned to the black level is extracted (FIG. 2(A)).

At this time, as shown in FIG. 2<A), there is a possibility that the video signal contains noise d having the same level as the synchronization signal.

However, noise that is too large for the video signal is usually completely removed by a well-known dropout compensation circuit (not shown) provided at the previous stage, so that only extremely sharp pulse-like noise d is left as shown in the figure. This signal @(A) is directly inputted to the AND circuit 6 via the delay circuit 4, and a logical product is taken. The delay time TD of the delay circuit 4 is shorter than the pulse width of the equalization pulse (typically 2.5 μs) (see Fig. 2).
B)), therefore, the multiplication result in the AND circuit 6 is shown in Figure 2 (C
), it is a signal that has the same phase as the composite synchronizing signal (B) and simply has all pulse widths TD (G-J) shorter. In other words, the noise d, which is the sharp pulse described above, does not exist at any time during the time TD, and can be reliably removed by the logical product operation. The signal (C) that has been reduced by 1η in this way
The first stage monostable multivibrator 8 is triggered at the rising point of , and the activation for time 1-w is not repeated (Fig. 2 (D)).
). The time Tw is the output period of the horizontal synchronization signal T I-
1, it has the relationship 1/2TI-1<Tw<TH, and the equalization pulse P and vertical synchronization pulse Q in the composite synchronization signal inserted every 1/2 of the period TH re-1 to It makes Riga impossible. Therefore, the signal (D>
is a pulse train generated at exactly the same period as the horizontal synchronizing signal, and it is clear that only the pulse width Tw is different from the horizontal synchronizing signal. Therefore, the output (D) of the first stage monostable multivibrator 8 triggers the second stage monostable multivibrator 10 whose output is the same as the pulse width of the horizontal synchronizing signal (approximately 5 μs) to 1, and the final The horizontal synchronization signal E is set to 1.

According to the horizontal dome signal separation device of the above embodiment, the noise d mixed in the dome signal is reliably removed by the simple AND circuit 6 that performs logical product, and is equalized by the two monostable multivibrators in the subsequent stage. The oxidation pulse is removed.

In other words, since the two monostable multivibrators simply remove the equalization pulse, there is no need for strict temperature compensation during their emission period. Therefore, although the horizontal synchronization signal separation device of this embodiment has a simple, compact, lightweight, and inexpensive circuit configuration, its noise removal and horizontal synchronization signal separation are performed with high precision regardless of humidity. Therefore, if a video signal is reproduced using this horizontal synchronization signal separation device, an extremely stable and clear image can be obtained.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment in any way, and it goes without saying that the present invention can be implemented in various forms without departing from the spirit thereof.

As described in detail with reference to the embodiments, the horizontal dosing signal separation device of the present invention is small, lightweight, and inexpensive by using simple electric elements such as AND operation means and a monostable multivibrator. configured. Moreover, its noise removal ability is extremely stable.
High accuracy and reliable separation of horizontal synchronization signals.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a horizontal synchronizing signal separation device according to an embodiment, and FIGS. 2(A) to 2(E) show timing charts without representing the voltage waveforms of each line of the same embodiment. 2...Synchronization separation circuit 4...Delay circuit 6...AND circuit

Claims (1)

[Scope of Claims] A horizontal synchronization signal separation device that separates a horizontal synchronization signal while removing noise contained in the composite synchronization signal, the said composite synchronization signal being input, and the equalization pulse contained in the composite synchronization signal being input. a delay circuit that delays the composite synchronization signal by a time shorter than the pulse width of the composite synchronization signal; an AND operation circuit that performs an AND operation between the output of the delay circuit and the composite synchronization signal; a first monostable multivibrator that is triggered and generates an output with a period shorter than the period of the horizontal synchronization signal and longer than 1/2 period; A horizontal synchronization signal separation device comprising: a second monostable multivibrator that generates an output;