JP2505271B2 - Video signal playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a helical scan type video tape recorder (hereinafter referred to as “VTR”), and more particularly to a VTR for improving reproduction image quality.

[Conventional technology]

FIG. 5 is a plan view of a rotary drum having a single video head having no opposing head, and FIG. 4 is a block circuit diagram of a conventional video signal reproducing system.

In FIG. 5, (20) is a rotary drum, (22) is a single video head, and (23) is a magnetic tape.

In FIG. 4, (3) is a rotary transformer, and (3
2) is an amplifier, (44) is a signal processing circuit, and the demodulation circuit (5
3), a clamp circuit (54) and a sync separation circuit (55). (45) is a clamp circuit, (46) is an A / D converter, (48) is a memory element, (49) is a recording element control circuit,
(51) is a D / A converter.

 Next, the operation will be described.

The heads (22) are alternately switched by a head switching signal (shown in FIG. 6 (b)) to detect a reproduced FM signal (shown in FIG. 6 (d)) from the magnetic tape (23).

The reproduced FM signal d reproduced by the head (22) is demodulated into a video signal by the demodulation circuit (53), and as shown in FIG. 6 (e), a field with a reproduced signal and a non-signal field are repeated. Video signal e. As pre-processing for performing sync separation, etc., the single chip level is input to the clamp circuit and fixed at a fixed level, but the time constant of the clamp circuit (54) is approximately 10 times the horizontal sync signal period. Since it is selected, a sag as shown in FIG. 6 (f) is generated in the video signal as shown in FIG. 6 (e). The video signal f is converted into a digital signal by the A / D converter (46), and the storage element (46) and the storage element control circuit (49) complement the video signal in the signal field period during the no-signal field period. As shown in Fig. 6 (g),
A video signal having a sag for each field period is converted into an analog video signal by the D / A converter (51).

[Problems to be Solved by the Invention]

Since the conventional device is configured as described above, a sag occurs in the reproduced video signal f. Therefore, the sync separation circuit of the TV cannot detect the vertical and horizontal sync signals during the period in which the sag occurs, which causes a problem that the screen is greatly disturbed.

The present invention has been made for the purpose of solving the above problems, and an object thereof is to obtain a video signal reproducing apparatus in which a reproduced video signal does not sag and the screen is not disturbed.

[Means for solving the problem]

The video signal reproducing apparatus according to the present invention reproduces an FM signal reproduced by a pair of heads arranged opposite to a rotary drum separately from a single head, in a no-signal field period of a reproduction FM signal of a single head. And a means for replacing the signal in the field in which the pair of head reproduction signals are inserted in the video signal demodulated from the reproduction FM signal with the signal in the field immediately before that. It is characterized by

[Action]

Since a continuous reproduced video signal having no signal field period is input to the clamp circuit, sag does not occur. Therefore, a period in which the horizontal and vertical sync signals are not detected by the sync separation circuit does not occur, so that the screen is not disturbed.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. (21a) and (21b) are a pair of heads arranged on the rotary drum (20) and facing each other.
The signals reproduced in (21b) and (22) are rotary transformers,
Through (1), (2) and (3), amplifiers (31a) and (3
The reproduced FM signal d (shown in FIG. 3 (d)), which has been input to 1b) and (32) and amplified by the amplifier (32), is input to the signal switch 2 (42).

On the other hand, the reproduced FM signal amplified by the amplifiers (31a) and (31b) is switched by the switching signal b (shown in FIG. 3 (a)), and the signal switch 1 (38) is reproduced FM signal c (first). Figure 3 (c)
Output). The reproduction FM signal c and the reproduction FM signal d are input to the signal switching device 2 (42), and the switching signal a (third
(B) shown in the figure), and a continuous reproduction FM signal is input to the signal processing circuit (44).

The reproduced FM signal is demodulated into a video signal by the demodulation circuit (53) and is connected to the reproduced video signal e (shown in FIG. 3 (e)) to be clamped to a certain level after passing through the clamp circuit 1 (54) and further clamped. After passing through the circuit 2 (45), the video signal f (shown in FIG. 3 (f)) matched with the input level of the A / D converter (46) is input to the A / D converter (46), It is converted into a digital signal and input to the storage element (48).

The recording element control circuit (49) sends a video signal reproduced in the head (22) during the field period and writes it in the storage element (48), and a pair of heads (21a), (21b).
The written signal is read out and replaced during the field period reproduced by. In this way, the video signal g (shown in FIG. 3 (g)), which is replaced only with the reproduction signal of the head (22), is converted into an analog value by the D / A converter (51), and is converted into a video signal. Is output.

Thus, according to this embodiment, the clamp circuit (5
Since the reproduced video signal e input to 4) is a continuous video signal, sag does not occur in the signal that has passed through the clamp circuit (54). Therefore, in the sync separation circuit (55) of the TV, a period in which the vertical and horizontal sync signals cannot be separated does not occur, and the screen is not disturbed.

In the above embodiment, the rotating drum (20) has a pair of heads (21a), (21b) facing the independent head (22).
However, a plurality of pairs of opposing heads may be provided. The independent head (22) is shown fixed to the rotating drum (20), but the head can be displaced in the width direction of the tape so that the head locus at the time of recording and at the time of reproduction can be achieved even at an arbitrary feed speed. The loci of may be movable heads to be matched.

〔The invention's effect〕

As described above, according to the present invention, when reproduction is performed using an independent rotary head, the reproduction FM signal reproduced by another pair of heads is inserted into the no-signal field of the reproduction signal. Therefore, the sag does not occur even when the signal passes through the clamp circuit in the signal processing circuit, and the TV can separate the sync signal without loss, so that there is an effect that a video signal reproducing device capable of reproducing a stable reproduced image can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a plan view of a rotary drum of this embodiment, FIG. 3 is a signal waveform diagram of each part of this embodiment, and FIG. 4 is a conventional image. FIG. 5 is a block circuit diagram of the signal reproducing device, FIG. 5 is a plan view of the rotary drum of this embodiment, and FIG. 6 is a signal waveform diagram of each part of this embodiment. (20) ... Rotary drum, (21a), (21b) ... A pair of heads, (22) ... Independent heads, (23) ... Magnetic tape, (38) ... Signal changer 1, ( 42) ... Signal switch 2, (44) ... Signal processing circuit, (45) ... Clamp circuit 2, (46) ... A / D converter, (48) ... Memory element, (4
9) …… Recording element control circuit, (51) …… D / A converter. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A video signal reproducing apparatus for reproducing a signal reproduced by the independent head into a video signal by providing one head independent from the rotary drum and at least one pair of heads different from the head. Means for inserting the FM reproduction signal reproduced by the pair of heads in the no-signal field period of the FM reproduction signal reproduced by the independent head, and demodulating from this inserted continuous FM reproduction signal and demodulating this Means for separating the sync signal from the reproduced video signal thus reproduced, and means for replacing the signal in the field period in which the reproduced signals of the pair of heads are inserted in the reproduced video signal with the signal in the immediately preceding field period. A video signal reproducing device characterized by being provided.