JPH0659095B2 - Video signal playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video signal reproducing apparatus, and more particularly to a video tape recorder using an azimuth recording method at 5 × speed.
The present invention relates to a video signal reproducing apparatus most suitable for reproducing a multiple speed image such as 20 times speed.

[Prior Art] Conventionally, as a method for reducing noise in multiple speed reproduction, there is a method disclosed in Japanese Patent Application Laid-Open No. 56-162578.

FIG. 4 is a schematic diagram showing the locus of the head of the magnetic tape in the conventional multiple speed reproduction, and FIG. 5 is a diagram showing the arrangement of the heads and the reproduction signal in the conventional multiple speed reproduction.

A magnetic head in a conventional video tape recorder capable of reproducing at multiple speeds is arranged as shown in FIG. That is, in addition to the first and second magnetic heads 2a and 3a having different azimuth angles, the cylinder 1 is in the same plane of rotation as these magnetic heads 2a and 3a, and the magnetic heads 2a and 3a have different azimuth angles. Third and fourth magnetic heads 2b and 3b are arranged in the vicinity of each. Then, as shown in FIG. 5 (b), the azimuth angle of the third magnetic head 2b arranged near the first magnetic head 2a is the same as that of the second magnetic head 3a,
The azimuth angle of the fourth magnetic head 3b arranged near the magnetic head 3a is selected to be the same as that of the first magnetic head 2a.

During recording, the magnetic tape 4 is run at a predetermined speed, and field signals are sequentially recorded as recording tracks on the magnetic tape 4 by the first and second magnetic heads 2a and 3a of the magnetic heads configured as described above. When the magnetic tape 4 is transported at the same speed as when it is rewound and high-speed reproduction in the reverse direction is performed, the first to fourth magnetic heads 2a, 3a, 2b, 3b are sequentially recorded on the recording tracks on the magnetic tape 4. Scan across and get playback output. In this case, the scanning locus of the magnetic head is as shown in FIG.

That is, first, the first magnetic head 2a and the third magnetic head 2b arranged near the first magnetic head 2a and having different azimuth angles sequentially scan the recording tape from the lower right to the upper left across the recording tracks. At this time, the first magnetic head 2
The outputs of a and the third magnetic head 2b are shown in FIG.
As shown by the solid and dotted lines. That is, when the first magnetic head 2a moves from the track a to the track b and the head output starts to decrease due to azimuth loss,
The head output of the third magnetic head 2b starts to increase. As a result, the output of either one of the first and third magnetic heads 2a and 2b is always above a certain level.

Therefore, by switching the outputs of the first and third magnetic heads 2a and 2b near the point where the outputs of the first and third magnetic heads 2a and 2b become the same level by the head switching pulse described later, As shown in Figure (d), the output level drops slightly near the head switching point,
There is no part that becomes 0, and continuous reproduction output above a certain level can be obtained. First and third magnetic heads 2
Even when a and 2b scan to the upper left of the magnetic tape 4 and then the second and fourth magnetic heads 3a and 3b start to scan, reproduction outputs are obtained in the same manner as described above, and reproduction outputs thereof are obtained. By synthesizing, it is possible to obtain a continuous playback video signal without interruption.

FIG. 6 is a block diagram showing a reproducing system circuit in a conventional video tape recorder, and FIG. 7 is a waveform diagram of each part of FIG.

Next, with reference to FIGS. 6 and 7, the structure and operation of the reproducing system of the conventional video tape recorder will be described. The first to fourth magnetic heads 2a, 3a, 2b,
3b is connected to the changeover switches 6, 7, 8 and 9, respectively. One end of each of the changeover switches 6, 7, 8 and 9 is connected to the preamplifiers 10, 11, 12 and 13, and the other ends of the changeover switches 6 and 7 are connected to the recording amplifier 5. Therefore, when the changeover switches 6 and 7 are switched to the other end side, the video signal output from the recording amplifier 5 is recorded on the magnetic tape 4 by the first and second heads 2a and 3a.

At the time of reproduction, the changeover switches 6, 7, 8 and 9 are respectively switched to one end side, and the first to fourth magnetic heads 2a and 3
a, 2b, 3b are preamplifiers 10, 11, 1 respectively
2 and 13 are connected. Each preamplifier 10, 11, 1
Although not shown, the switch heads 2 and 13 have a built-in switcher, and the first and second head switching pulse generation circuits 14 and
Controlled by 15 Q outputs and outputs.

Here, the first head switching pulse generation circuit 14 will be described with reference to the waveform diagram shown in FIG. The output of the third preamplifier 12, that is, the waveform of the reproduction signal obtained by scanning the track b by the third magnetic head 2b is as shown in FIG. 7 (a).
7 is supplied to the envelope detecting circuit 141, and the envelope of the reproduction signal is detected and supplied to the first waveform shaping circuit 142 as shown in FIG. 7 (b). The first waveform shaping circuit 142 sets the envelope waveform to a constant level, for example, "H" level at 50% or more of the maximum level,
The waveform is shaped into a pulse (see FIG. 7 (c)) such that the level becomes "L" below that. This pulse signal is given to the first flip-flop 143, and the Q output and the output as shown in FIGS. 7D and 7E are generated from the flip-flop 143. These Q outputs and outputs control the outputs of the first and third preamplifiers 10 and 12 as head switching pulses, respectively.

Similarly, the second head switching pulse generation circuit 15 includes a second envelope detection circuit 151, a second waveform shaping circuit 152, and a second flip-flop 153, and
The outputs of the second and fourth preamplifiers 11 and 13 are controlled by the Q output and the output obtained from the flip-flop 153. Therefore, the output of any one of the first to fourth preamplifiers 10 to 13 is given to the fifth preamplifier 16 and amplified. Then, it is converted into a video signal by the FM demodulation circuit 17.

By the above method, when reproducing a multiple speed image such as a high-speed reproduction, the reproduction output can be significantly increased by selecting the larger output of two adjacent magnetic heads having different azimuth angles and switching the head output. It never drops.

Although not shown, in another example, there is a method of making the width of the magnetic head wider than the width of the track. In this case,
The output level of A shown in FIG. 5C, that is, the output level of the first magnetic head 2a does not become 0, and continuous reproduction output above a certain level can be obtained.

[Problems to be Solved by the Invention] However, the above-described first to fourth preamplifiers 10 to 1 are used.
Switching points of the third output and the first to fourth magnetic heads 2a, 3
Since noise occurs when moving a, 2b, and 3b and the video contents of another track change, the video contents do not match, resulting in a split composite screen in which the video contents of a plurality of tracks are divided and composited.

Therefore, a main object of the present invention is to provide a video signal reproducing apparatus capable of obtaining a good reproduction screen without generating noise on the reproduction screen.

[Means for Solving Problems] An apparatus according to the present invention is a video signal reproducing apparatus for reproducing a video signal recorded on an oblique track of a magnetic tape by helically scanning the magnetic tape,
A rotary cylinder, a plurality of fixed magnetic heads, a plurality of movable magnetic heads, a tape drive means, a speed setting means, a switching means, a demodulation means, a position control means, and a switching control means. Each of the plurality of fixed magnetic heads is provided at an angular position of 180 ° with respect to the center of rotation of the rotary cylinder. Each of the plurality of movable magnetic heads is provided at an angle position of 180 ° with respect to the center of rotation of the rotary cylinder and different from the fixed magnetic head, and the position can be controlled in the width direction of the oblique track on the magnetic tape. It is something. The tape drive means runs a magnetic tape on a rotating cylinder at an arbitrary speed. The speed setting means sets the traveling speed of the magnetic tape to the same as that at the time of recording.
The tape driving means is instructed to set the second speed and the second speed different from the recording speed. The switching means is
The output signal from the fixed magnetic head or the output signal from the movable magnetic head is selected. The demodulation means demodulates the output signal selected by the switching means.

Further, the position control means controls the position of the movable magnetic head in the width direction of the oblique track so that the movable magnetic head traces on the oblique track of the magnetic tape when the speed setting means is set to the second speed. Is. The switching control means, when the speed setting means is set to the first speed,
When the switching means is in a state of selecting the output signal from the fixed magnetic head and the speed setting means is set to the second speed,
When the magnitude of the output signal from the movable magnetic head is smaller than a predetermined level, the switching means is brought into a state of selecting the output signal from the fixed magnetic head, and when the magnitude of the output signal from the movable magnetic head is larger than the predetermined level. The switching means is set in a state of selecting the output signal from the movable magnetic head.

[Operation] According to the video signal reproducing apparatus of the present invention, when reproducing at the second speed different from that at the time of recording, tracking control is performed so that the movable magnetic head traces on an oblique track of the magnetic tape. When the output signal from the movable magnetic head is higher than a predetermined level, the output signal from the movable magnetic head is demodulated. When the output signal from the movable magnetic head is lower than the predetermined level, the output from the fixed magnetic head is output. The signal is demodulated.

Therefore, it is prevented that the output signal from the movable magnetic head is so small that tracking control of the movable magnetic head becomes difficult and a lot of noise occurs in the demodulated video signal.

Further, when the output signal from the movable magnetic head is large, the output signal obtained by tracing the movable magnetic head on the diagonal track is demodulated, so that a divided combined screen in which the image contents of a plurality of tracks are divided and combined is displayed. In addition, a good screen with less noise can be obtained. further,
Even a magnetic tape in a poor recording state can be reproduced normally.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a reproducing system according to an embodiment of the present invention, and FIG. 2 is a diagram showing an arrangement of magnetic heads used in the embodiment of the present invention. First, with reference to FIG. 2, the arrangement of the magnetic head in one embodiment of the present invention will be described.

The cylinder 1 has a different first azimuth angle.
And the second magnetic heads 2a, 3a are provided at an angular position of 180 ° with respect to the center of rotation, and the third and fourth magnetic heads 2b, 3b are provided near the magnetic heads 2a, 3a, respectively. Are arranged. These first to fourth magnetic heads 2a, 3a, 2b and 3b form a fixed magnetic head. First magnetic head 2a
The azimuth angle of the third magnetic head 2b arranged in the vicinity of is equal to that of the second magnetic head 3a, and the azimuth angle of the fourth magnetic head 3b arranged in the vicinity of the second magnetic head 3a is No. 1 magnetic head 2a is selected.

In addition, the cylinder 1 has 18
Actuators 18 and 19 are provided at an angular position of 0 °, and the fifth and sixth magnetic heads 20 as movable heads are provided at the tips of these actuators 18 and 19.
21 is attached. The positions of the fifth and sixth magnetic heads 20 and 21 are controlled in the width direction of the recording track by actuators 18 and 19, respectively.

In FIG. 1, first to fourth magnetic heads 2a, 3a,
2b and 3b are rotary transformers 24, 25 and 2 respectively.
It is connected to the changeover switches 6, 7, 8, 9 via 6, 27. Recording amplifier 5, preamplifiers 10-13, 1
6, and first and second head switching pulse generation circuit 1
4, 15 are connected in the same manner as in FIG. 6 described above. Therefore, at the time of recording, the selector switches 6 and 7 are switched to the recording amplifier 5 side, and the first and second magnetic heads 2
A video signal is recorded on the magnetic tape 4 by a and 3a.

At the time of reproduction, if the traveling speed of the magnetic tape 4 is the same as that at the time of recording, the changeover switches 6 to 9 are switched to the preamplifiers 10 to 13 side, and the reproduction signals by the first magnetic head 2a and the second magnetic head 3a or Third magnetic head 2b
The reproduced signal from the fourth magnetic head 3b is applied to the preamplifier 16 of the next stage via the rotary transformers 24 to 27 and the preamplifiers 10 and 11 or the preamplifiers 12 and 13. The output signal of the preamplifier 16 is applied to the end of the changeover switch 28. At this time, the changeover switch 28
Is switched to the end side, and the output signal of the preamplifier 16 is given to the demodulation circuit 29 and converted into a video signal.

On the other hand, reproduced signals from the fifth and sixth magnetic heads 20 and 21 are given to preamplifiers 30 and 31 via rotary transformers 22 and 23. The output signals of the preamplifiers 30 and 31 are given to the envelope detection circuit 33 and the end side of the changeover switch 28 via the changeover switch 32 for changing over the video head. On the other hand, the rotation speed of the cylinder 1 is detected by the rotation detector 34, and the output from the rotation detector 34 is waveform-shaped by the waveform shaping circuit 35. The output from the waveform shaping circuit 35 is used as a video head switching signal, and the switching switch 32 is switched by the video head switching signal.

The output signal of the envelope detection circuit 33 is given to the displacement voltage generation circuits 36 and 37. Further, the displacement voltage generating circuits 36 and 37 are supplied with a video head switching signal from the waveform shaping circuit 35 and a displacement voltage generating signal d from a sequence signal generating circuit 44 described later. The displacement voltage generation circuits 36 and 37 generate output signals in response to the displacement voltage generation signal d, and the output signals are given to the adder circuits 38 and 39 to generate the synchronization signal generators 40 and 4.
The output signal of 1 is added to drive the actuators 18 and 19 via the slip rings 42 and 43. As a result, the positions of the fifth and sixth magnetic heads 20 and 21 attached to the actuators 18 and 19 are controlled so as to trace the recording tracks of the magnetic tape.

The voltage of the output signals of the displacement voltage generating circuits 36 and 37 is determined by the envelope detection circuit 33 according to the video head switching signal.
The output signal of is controlled so as to be maximum. The synchronizing signal generators 40 and 41 generate signals for tracing the magnetic heads 20 and 21 at the same inclination as the track on the magnetic tape 4 according to the tape speed.

If the level of the output signal of the envelope detection circuit 33 is smaller than a certain level, the displacement voltage generation circuits 36 and 37 will not accurately control the position of the fifth and sixth magnetic heads 20 and 21, and the fifth and sixth magnetic heads will not operate. The video signal obtained by demodulating the output signals of the magnetic heads 20 and 21 of No. 6 has a lot of noise. In order to prevent this, this embodiment is configured as follows.

That is, the output signal of the envelope detection circuit 33 is also given to the level determination circuit 45. Level determination circuit 45
Generates a level determination signal f when the level of the output signal of the envelope detection circuit 33 is higher than a certain level. The sequence signal generation circuit 44 is supplied with an ON / OFF signal of the switch 47, and the level determination circuit 45.
Is supplied with the level determination signal f. The sequence signal generation circuit 44 generates the tape speedup signal b and the displacement voltage generation signal d in response to the ON signal from the switch 47. The tape speed-up signal b is given to a drive motor (not shown) for running the magnetic tape. Further, the sequence signal generation circuit 44 gives a changeover signal e to the changeover switch 28 in response to the level decision signal f from the level decision circuit 45.

FIG. 3 is a timing chart of input / output and tape speed of the sequence signal generating circuit 44 shown in FIG. Next, the operation of the sequence signal generating circuit 44 will be described with reference to FIG.

As shown in FIG. 3A, when the switch 47 connected to the sequence signal generating circuit 44 is closed, the tape speedup signal b shown in FIG. 3B is output, and the drive motor (not shown). Is controlled, and the tape speed changes as shown in FIG. The displacement voltage generation signal d is output from the sequence signal generation circuit 44 at the same time as the tape speedup signal b. A displacement voltage generation circuit 36 in response to the displacement voltage generation signal d,
37 is actuated and the actuators 18, 18 are arranged so that the fifth and sixth magnetic heads 20, 21 trace the recording track.
19 is controlled. When the level determination signal f is output from the level determination circuit 45, the polarity of the switching signal e for switching the switching switch 28 changes, the switching switch 28 is switched to the end side, and the fifth and sixth traces for tracing a track are performed.
Output signals of the magnetic heads 20 and 21 of the preamplifier 30,
It is given to the demodulation circuit 29 via 31 and converted into a video signal. When the reproduction of one track is completed, a predetermined number of tracks are skipped and the reproduction of the next track is performed.

When the level of the output signal of the envelope detection circuit 33 is lower than a certain level, the outputs from the first to fourth magnetic heads 2a, 3a, 2b and 3b are the same as in the conventional example. It is given to the preamplifiers 10, 11, 12, and 13 via 26 and 27. One of the outputs of the preamplifiers 10 to 13 is sequentially given to the preamplifier 16 and amplified. The demodulation circuit 29 converts the output of the preamplifier 16 into a video signal.

A magnetic head having a width wider than the track pitch may be used as the fixed magnetic head.

As described above, according to the present invention, when reproducing at the second speed different from that at the time of recording, reproduction is performed by the movable magnetic head when the output signal from the movable magnetic head is higher than a predetermined level. However, when the output signal is smaller than a predetermined level, reproduction is performed by the fixed magnetic head, so that a good screen with less noise can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a reproducing system included in an embodiment of the present invention. FIG. 2 is a diagram showing the arrangement of magnetic heads used in an embodiment of the present invention. Fig. 3 (a) ~
(E) is a diagram showing the timing of input / output and tape speed of the sequence signal generating circuit shown in FIG. FIG. 4 is a schematic diagram showing the locus of the head during conventional multi-speed image reproduction. FIGS. 5A to 5D are diagrams showing the arrangement of magnetic heads and reproduction signals in a conventional video tape recorder. FIG. 6 is a schematic block diagram of a reproducing system in a conventional video tape recorder. FIGS. 7 (a) to 7 (e) are waveform diagrams of the respective portions in FIG. In the figure, 1 is a cylinder, 2a is a first magnetic head,
3a is a second magnetic head, 2b is a third magnetic head, 3
b is a fourth magnetic head, 4 is a magnetic tape, 6-9, 2
8 and 32 are changeover switches, 10 to 13, 16, 30, and 3
1 is a preamplifier, 14 and 15 are head switching pulse generation circuits, 18 and 19 are actuators, 20 is a fifth magnetic head, 21 is a sixth magnetic head, 22 to 27 are rotary transformers, 29 is a demodulation circuit, 33, 141 and 151 are envelope detection circuits, 34 is a rotation detector, and 35 and 14
2, 152 are waveform shaping circuits, 36, 37 are displacement voltage generation circuits, 38, 39 are addition circuits, 40, 41 are synchronization signal generators, 44 is a sequence signal generation circuit, 45 is a level determination circuit, and 143, 153 are Shows a flip-flop.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-83325 (JP, A) JP-A-56-114484 (JP, A) JP-A-60-40524 (JP, A) JP-A-57- 170680 (JP, A) JP 60-103514 (JP, A) JP 61-61167 (JP, B2)

Claims (4)

[Claims] 1. A video signal reproducing apparatus for reproducing a video signal recorded on an oblique track of a magnetic tape by helically scanning the magnetic tape, comprising: a rotating cylinder; A plurality of fixed magnetic heads, each of which is provided at an angular position of 180 ° with respect to the center of rotation of the rotary cylinder; A plurality of movable magnetic heads whose position can be controlled in the width direction of an oblique track on the magnetic tape, tape drive means for causing the magnetic tape to travel on the rotary cylinder at an arbitrary speed, and when the running speed of the magnetic tape is recorded A speed setting hand which gives a command to the tape driving means so as to make the same first speed and a second speed different from that during recording. Switching means for selecting one of the output signal from the fixed magnetic head and the output signal from the movable magnetic head, demodulation means for demodulating the output signal selected by the switching means, and the speed setting means for the second When set to the speed of
Position control means for controlling the position of the movable magnetic head in the width direction of the oblique track so that the movable magnetic head traces on the oblique track of the magnetic tape, and the speed setting means are set to the first speed. At this time, when the switching means is in a state of selecting the output signal from the fixed magnetic head, and the speed setting means is set to the second speed, the magnitude of the output signal from the movable magnetic head is predetermined. When it is smaller than the level, the switching means is brought into a state of selecting the output signal from the fixed magnetic head, and when the magnitude of the output signal from the movable magnetic head is larger than a predetermined level, the switching means is switched from the movable magnetic head. A video signal reproducing device comprising a switching control means for setting an output signal to a selected state. 2. The video signal reproducing apparatus according to claim 1, wherein the fixed magnetic head has a width selected to be wider than the pitch of the tracks. 3. The fixed magnetic head is provided in the same rotation plane as the first and second magnetic heads having different azimuth angles, and in the same rotation plane as the first and second magnetic heads, and each of the fixed magnetic heads has the first magnetic head. A third magnetic head arranged near the first magnetic head and the second magnetic head and having a different azimuth angle from the first magnetic head in the vicinity, and a second magnetic head in the vicinity and the azimuth angle The video signal reproducing device according to claim 1 or 2, further comprising a fourth magnetic head having a different magnetic field. 4. A head selecting means for selecting a reproduction signal from a magnetic head having the largest output amplitude among the first to fourth magnetic heads and setting it as an output signal of a fixed magnetic head. The video signal reproducing device according to the item.