JPH0329230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a video tape recorder or a television receiver that can normally control the vertical synchronization signal even if a video signal with a vertical synchronization signal that is much smaller than the normal one is input. The present invention relates to a vertical synchronization signal sensitivity amplification device that allows the vertical synchronization signal to be applied.

Prior Art When recording a video signal with a VTR, as shown in Figures 1 and 2, a synchronization signal separation circuit extracts synchronization signal B from video signal A, and the synchronization signal B is filtered through a low-pass filter. remove the horizontal synchronization signal and extract only the vertical synchronization signal C,
This extracted vertical synchronization signal C is input to a switching circuit to obtain an output signal D.
A video signal A is input to a servo circuit and used as a reference signal for rotational phase control of a rotating video head, and a video signal A is recorded on a magnetic tape.

Problems to be Solved by the Invention In such a conventional configuration, if the synchronization signal B becomes small for some reason, the servo circuit becomes unable to operate.

Also, when displaying a VTR playback signal on a television receiver, it is necessary to
In the case of VTR playback signals, vertical synchronization on the television receiver side is difficult, and a normal screen cannot be obtained unless the vertical synchronization adjustment knob of the television receiver is operated.

Therefore, in the conventional configuration for controlling the rotational phase of a rotating video head, it was only possible to slightly increase the sensitivity of switching in a circuit after extracting the vertical synchronization signal C.

If the width of the vertical synchronization signal becomes narrow, even if the servo circuit operates normally, there is a problem in that it is difficult to achieve vertical synchronization of the television receiver when the signal is reproduced.

The present invention enables normal rotational phase control of a VTR even when the vertical synchronization signal of a video signal becomes small or has a narrow pulse width, and allows normal vertical synchronization of a television receiver. It is an object of the present invention to provide a vertical synchronization signal sensitivity amplification device that can be used as a vertical synchronization signal.

Means for Solving the Problems The vertical synchronization signal sensitivity amplification device of the present invention includes a vertical synchronization signal separation means 14 for extracting a vertical synchronization signal C from an input video signal A, and a vertical synchronization signal C whose magnitude is equal to V of the input sensitivity. The first step is to determine whether it has become _R or higher.
a second comparator 3 for determining that the magnitude of the vertical synchronizing signal C has become equal to or higher than the input sensitivity V _S which is lower than the _VR ;
a capacitor 12b connected to the output of the comparator 3 to expand the pulse width;
a waveform shaping means 15 for shaping the output of the second comparator 2b at a specific level into a rectangular wave wider than the output waveform of the second comparator 3; and a delay means 17 for delaying the rectangular wave output from the waveform shaping means 15. , a superimposing means 11 that superimposes the output signal of the delay means 17 on the input video signal A, and a vertical synchronizing signal C that has an input sensitivity V _R
The present invention is characterized in that a switch means 5 is provided which prohibits the superimposing operation by the superimposing means 11 when the first comparator 2 determines that the superimposing means 11 has reached the above.

Effect According to this configuration, the vertical synchronizing signal separating means 14
The level of the vertical synchronization signal C extracted from the input video signal A is determined by the first and second comparators, and the second comparator 3 whose input sensitivity is lower than the input sensitivity Vr of the first comparator 2
The pulse width of the output pulse is expanded by a capacitor 12 connected to the output of the second comparator 3. This signal is converted into a rectangular wave via waveform shaping means 15, and further delayed by delay means 17 to create a delayed signal.

When the vertical synchronization signal separation means 14 detects that the level of the vertical synchronization signal C extracted from the input video signal A has become smaller than the input sensitivity Vr of the first comparator 2, it separates the rectangular wave output from the delay means 17. The superimposing means 11 superimposes it on the input video signal A.

Therefore, the vertical synchronization signal of the output video signal becomes larger, and the pulse width also becomes wider than that of the input video signal A.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 3 to 5. Components having the same functions as in FIGS. 1 and 2 showing the conventional example will be described with the same reference numerals.

The vertical synchronization signal sensitivity amplification device of the present invention is constructed as shown in FIG. The input terminal 13 has
Vertical synchronization signal separation means 14 constituted by the synchronization signal separation circuit shown in FIG. 1 and a low-pass filter.
A vertical synchronization signal C generated at the output of is applied.
This vertical synchronization signal C is as shown in C in FIG.
This is the same waveform as C in FIG.

The vertical synchronizing signal C is applied to the inverting input terminals (-) of the first and second comparators 2 and 3 via the transistor 1 forming an emitter follower. In Figure 4, the output waveform of transistor 1 is
C”.

Here, the input sensitivities of the first and second comparators 2 and 3 are set as follows.

Non-inverting input terminal (+) of first comparator 2
A reference voltage Va is applied to the first comparator 2, and a bias voltage Vb is applied to the inverting input terminal (-) of the first comparator 2.
is applied, and the input sensitivity Vr of the first comparator 2 is set to (Va-Vb). Second
The reference voltage Vc is applied to the non-inverting input terminal (+) of the comparator 3, and the bias voltage Vd is applied to the inverting input terminal (-) of the second comparator 3. sensitivity
Vs is set to (Vc−Vd). Here, “Vr>Vs”.

The outputs of the first and second comparators 2 and 3 are
Capacitors 12a, 12 are used to widen the pulse width.
b is connected but this capacitor 12a is not connected, that is, the waveforms of the individual outputs of the first and second comparators 2 and 3 are as shown in 2c and 3c in FIG. Become. In Fig. 5, the level of the waveform C'' applied to the inverting input terminals (-) of the first and second comparators 2 and 3 is greater than the input sensitivity Vr, and when the level is smaller than the input sensitivity Vr, the input sensitivity is The case is shown where it is larger than Vs.

Note that the level difference between the "high level" and "low level" of the outputs of the first and second comparators 2 and 3 is larger than that of the vertical synchronizing signal C extracted by the vertical synchronizing signal separating means 14.

When the level of the waveform C'' is greater than the input sensitivity Vr, the output waveform 2c of the first comparator 2
is inverted to low level during the period when the input sensitivity is equal to or higher than Vr, and the output waveform 3c of the second comparator 3 is inverted to low level during the period when the input sensitivity is equal to or higher than Vs.

When the level of the waveform C'' is smaller than the input sensitivity Vr and larger than the input sensitivity Vs, the output waveform 2c of the first comparator 2 maintains a high level state, and the output waveform 3c of the second comparator 3
is inverted to low level during the period when the input sensitivity is higher than Vs.

Output waveforms E and G of the first and second comparators 2 and 3 with capacitors 12a and 12b connected
The pulse widths are widened as shown in waveforms E and G shown in FIG. 5, respectively.

The output waveform E of the first comparator 2 is converted via the transistor 4 into a rectangular waveform F shown in FIGS. 4 and 5. If the threshold value of the transistor 4 at this time is _V4 , the pulse width of the waveform F when the level of the waveform C'' is greater than the input sensitivity Vr is _W1 .

The output waveform G of the second comparator 3 is processed as follows by the waveform shaping means 15 made up of a transistor 6, and the delay means 17 made up of an integrating circuit 16, transistors 7, 8, etc.

Waveform G is converted via transistor 6 into a rectangular wave of waveform H shown in FIGS. 4 and 5. If the threshold value of transistor 6 at this time is V ₆ , then
The pulse width _W2 of waveform H when the level of waveform C'' is smaller than input sensitivity Vr and larger than input sensitivity Vs is wider than waveform 3c.

The pulse of the waveform H converted into a wider width is applied to the base of the transistor 7 through the integrating circuit ₁₆ as the waveform H16 shown in FIG. The waveform is converted into a rectangular wave shown in waveform J. Here, the threshold value of transistor 8 is _V8 . Therefore, when the timing of waveform H and the timing of waveform J are compared, waveform J is delayed from waveform H by the delay time of delay means 17, and when the level of waveform C'' is greater than input sensitivity Vr. The timing is matched to waveform F.

The signal of waveform J is converted into a signal of waveform K via transistor 9, and is used as a vertical synchronizing signal for controlling the rotational phase of the video head of the VTR.

Regarding the video signal to be output to the television receiver, if the level of the waveform C'' is smaller than the input sensitivity Vr and larger than the input sensitivity Vs, the waveform J is sent to the transistor 11 (superimposing means) via the transistor 10. The video signal waveform L is forcibly lowered to the reference level V ₀ (=zero volts) by the transistor 11, and the waveform J is superimposed on the video signal to obtain the video signal output of the waveform M.

When the level of waveform C'' is higher than input sensitivity Vr, there is no need to superimpose waveform J on the video signal with transistor 11, so in this case, transistor 5 forcibly turns off transistor 11, Waveform J is not superimposed on the video signal.

In this way, even if the vertical synchronization signal C becomes weak, as long as the input sensitivity is greater than or equal to Vs, head rotation control can be performed normally, and the vertical It is possible to send out a video signal containing a synchronization signal.

In the above embodiment, when the level and pulse width of the vertical synchronizing signal contained in the input video signal A applied to the input of the VTR are small, the level and pulse width are increased and the signal is sent to the television receiver. Although this was explained using an example, it is also possible to extract the vertical synchronization signal from the video signal on the television receiver side and superimpose it on the original video signal to achieve good vertical synchronization. .

Effects of the Invention As described above, according to the present invention, it is possible to detect that the level of the vertical synchronization signal C extracted from the input video signal A by the vertical synchronization signal separation means has become smaller than the input sensitivity Vr of the first comparator 2. When detected, the output pulse of the second comparator 3 whose input sensitivity is lower than _{the VR} is expanded in pulse width by the capacitor 12b connected to the output of the second comparator 3, and then shaped into a waveform. The original input video signal A obtained by conversion by means 15 and delay means 17
Since a signal having a wider signal size, a wider pulse width, and an appropriate timing than the vertical synchronizing signal C is superimposed on the input video signal A by the superimposing means 11, the vertical synchronizing signal of the output video signal becomes large.
The pulse width is also wider than that of the input video signal A. Therefore, vertical synchronization of the television receiver can be performed normally, and a video signal containing a vertical synchronization signal of a normal magnitude can be recorded on a magnetic tape.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a rotary head cylinder servo circuit of a conventional VTR, Fig. 2 is a waveform diagram of the main parts of Fig. 1, and Fig. 3 is a block diagram of an embodiment of the vertical synchronization signal sensitivity amplification device of the present invention. , FIG. 4 is a waveform diagram of essential parts of the same device, and FIG. 5 is a detailed waveform diagram of the same device. A...Input video signal, C...Vertical synchronization signal, 2
...First comparator, 3... Second comparator, 11... Transistor (superimposition means), 12
b... Capacitor, 14... Vertical synchronizing signal separation means, 15... Waveform shaping means, 17... Delay means.

Claims (1)

[Claims] 1. Vertical synchronization signal separation means 14 for extracting vertical synchronization signal C from input video signal A, and vertical synchronization signal C
A first comparator 2 that determines when the magnitude of V R has exceeded the input sensitivity V _R , and a vertical synchronization signal C
The input sensitivity V _S whose magnitude is lower than the above V _R
a second comparator 3 that determines whether the pulse width has reached the above level, a capacitor 12b that is connected to the output of the second comparator 3 and expands the pulse width, and a second comparator that shapes the waveform of the output of the capacitor 12b at a specific level to Waveform shaping means 15 that converts the output waveform of the comparator 3 into a wider rectangular wave; and delay means 1 that delays the rectangular wave output from the waveform shaping means 15.
7 and the output signal of the delay means 17 as the input video signal A.
A vertical synchronization system is provided with a superimposition means 11 for superimposing signals on the vertical synchronization signal C, _and a switch means 5 for prohibiting the superimposition operation by the superposition means 11 when the first comparator 2 determines that the vertical synchronization signal C has reached the input sensitivity VR. Signal sensitivity amplifier.