JPH0671329B2 - Video signal playback device - Google Patents

Description

The present invention relates to a video signal reproducing apparatus, and more particularly, to a video tape recorder using an azimuth recording method at a speed of 5 ×, 2 ×.
The present invention relates to a video signal reproducing apparatus most suitable for reproducing a multiple speed image such as 0 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. 5 is a schematic diagram showing the locus of the head of the magnetic tape in the conventional multiple speed reproduction, and FIG. 6 is a diagram showing the head arrangement and the reproduction signal in the conventional multiple speed reproduction.

The magnetic head in a conventional video tape recorder capable of reproducing at multiple speeds is arranged as shown in FIG. 6 (a). 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 3rd and 4th in each neighborhood
The magnetic heads 2b and 3b are arranged. Then, as shown in FIG. 6 (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, and The azimuth angle of the fourth magnetic head 3b arranged near the 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 the 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. . And
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 are used.
2a, 3a, 2b, 3b sequentially scan over the recording tracks on the magnetic tape 4 to obtain a reproduction 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 close to the first magnetic head 2a and having different azimuth angles are provided.
Scans the magnetic tape 4 from the lower right to the upper left in order over the recording tracks. At this time, the outputs of the first magnetic head 2a and the third magnetic head 2b are as shown by the solid and dotted lines in FIG. 6 (c). 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 first
The output of either one of the third magnetic heads 2a and 2b is always above a certain level.

Therefore, the outputs of the first and third magnetic heads 2a and 2b are changed to the first and the third by the head switching pulse described later.
By switching near the point where the outputs of the magnetic heads 2a and 2b become the same level, as shown in FIG. 6 (d), the output level slightly decreases near the head switching point, but there is no part that becomes 0, It is possible to obtain continuous reproduction output above a certain level. Even when the first and third magnetic heads 2a, 2b scan to the upper left of the magnetic tape 4 and then the second and fourth magnetic heads 3a, 3b start scanning, reproduction output is performed in the same manner as described above. By combining these reproduction outputs, it is possible to obtain a continuous reproduction video signal without interruption.

FIG. 7 is a block diagram showing a reproducing system circuit in a conventional video tape recorder, and FIG. 8 is a waveform diagram of each part of FIG.

Next, with reference to FIGS. 7 and 8, 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 are connected to changeover switches 6, 7, 8 and 9. One end of each of the changeover switches 6, 7, 8 and 9 is a preamplifier 10, 11, 1
2 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 changed over to one end side, and the first to fourth magnetic heads 2a, 3a,
2b and 3b are connected to preamplifiers 10 to 13, respectively. A switcher (not shown) is built in each of the preamplifiers 10 to 13 and is controlled by the Q output of the first and second head switching pulse generation circuits 14 and 15.

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. 8 (a), and this reproduction signal is detected by the first envelope detection. The envelope of the reproduction signal is supplied to the circuit 141 and is detected and supplied to the first waveform shaping circuit 142 as shown in FIG. The first waveform shaping circuit 142 changes the envelope waveform to a constant level, for example, 50 at the highest level.
The waveform is shaped into a pulse (see FIG. 8 (c)) such that the "H" level is reached when the percentage is above%, and the "L" level is reached when the percentage is below.
This pulse signal is applied to the first flip-flop 143, and the flip-flop 143 generates Q output and output as shown in FIGS. 8 (d) and 8 (e). These Q output and output are the first as a head switching pulse, respectively.
And controls the outputs of the third preamplifiers 10 and 12.

Similarly, the second head switching pulse generation circuit 15 is
Includes an envelope detection circuit 151, a second waveform shaping circuit 152, and a second flip-flop 153. Controlled.
Therefore, one of the outputs 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. 6D, that is, the output level of the first magnetic head 2a does not become zero, and continuous reproduction output of a certain level or more can be obtained.

[Problems to be Solved by the Invention] However, the switching points of the outputs of the first to fourth preamplifiers 10 to 13 and the first to fourth magnetic heads 2 described above.
When moving a, 3a, 2b, and 3b, noise is generated and the video contents of another track are changed, so that the video contents do not match and the split combined screen is displayed.

Therefore, a main object of the present invention is to provide a video signal reproducing apparatus in which noise is not generated on a reproduction screen and blurring due to lack of a sync signal does not occur.

[Means for Solving the Problems] The present invention relates to a video signal reproducing apparatus having a rotary cylinder for helically scanning a magnetic tape to record a video signal on an oblique track of the magnetic tape. On the other hand, a plurality of solid magnetic heads are provided at angular positions of 180 ° with respect to each other, and angular positions of 180 ° with respect to the center of rotation of the rotary cylinder, respectively, which are different from the fixed magnetic head. A plurality of movable magnetic heads which are provided at positions and whose position can be controlled in the width direction of the oblique track on the magnetic tape, and a first speed which is the same as when the magnetic tape is recorded, or an arbitrary second speed which is different from the first speed. A tape driving means for running the recording medium, and a switching means for switching and outputting a reproduction signal from the fixed magnetic head and a reproduction signal from the movable magnetic head. A position control means for controlling the position of the movable magnetic head in the track width direction when the magnetic tape travels at the second speed, and the fixed magnetic head or the movable magnetic head output from the switching means. When the speed of the magnetic tape and the demodulation means for demodulating a reproduction signal is the first speed, the switching means outputs the reproduction signal from the fixed magnetic head, and the speed of the magnetic tape is the second speed.
In the case of the above speed, when the amplitude level of the reproduction signal by the movable magnetic head is larger than a predetermined value and the vertical synchronization signal included in the reproduction signal is within a predetermined period near the switching point of the movable magnetic head. And a control means for causing the switching means to output a reproduction signal from the movable magnetic head, and otherwise causing the switching means to output a reproduction signal from the fixed magnetic head.

[Operation] In the video signal reproducing apparatus according to the present invention, when reproducing at a tape speed different from that at the time of recording, a movable magnetic head capable of position control is used to perform control so as to reproduce on a recording track. When the amplitude level of the reproduction signal is larger than a predetermined value and the vertical synchronizing signal included in the reproduction signal appears within a predetermined time near the head switching point, the reproduction signal by the movable magnetic head is demodulated.

[Embodiment of the Invention] FIG. 1 is a view showing the arrangement of a magnetic head used in an embodiment of the present invention. First, with reference to FIG. 1, an arrangement of magnetic heads in an embodiment of the present invention will be described. The cylinder 1 is provided with first and second magnetic heads 2a and 3a having different azimuth angles, and third and fourth magnetic heads 2b and 3b are provided near the magnetic heads 2a and 3a, respectively. 3b is arranged. The first to fourth magnetic heads 2a, 3a, 2b and 3b form a fixed magnetic head. 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, and the fourth magnetic head arranged near the second magnetic head 3a. The azimuth angle of 3b is selected to be the same as that of the first magnetic head 2a.

Further, the cylinder 1 is provided with actuators 18 and 19 for controlling the position in the width direction of the recording track,
Fifth and sixth magnetic heads 20 and 21 as movable heads are arranged at the tips of these actuators 18 and 19 at angular positions of 180 ° with respect to the center of rotation.

FIG. 2 is a schematic block diagram of a reproducing system according to an embodiment of the present invention. In FIG. 2, first to fourth magnetic heads
Reference numerals 2a, 3a, 2b and 3b are connected to changeover switches 6 to 9 via rotary transformers 24, 25, 26 and 27, respectively, and include a recording amplifier 5, preamplifiers 10 to 13 and 16, first and second amplifiers. The head switching pulse generating circuits 14 and 15 are constructed in the same manner as in FIG. Therefore, at the time of recording, the changeover switches 6 and 7 are switched to the recording amplifier 5 side, and the video signal is recorded on the magnetic tape 4 by the first and second magnetic heads 2a 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 will cause the preamplifier 10 to
The reproduction signal from the first magnetic head 2a and the second magnetic head 3a or the reproduction signal from the third magnetic head 2b and the fourth magnetic head 3b is switched to the 13 side and the preamplifier 10 is transmitted via the rotary transformers 24 to 27. , 11 or preamplifiers 12 and 13 to the preamplifier 16 in the next stage.
The output signal of the preamplifier 16 is given 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, the reproduction signals from the fifth and sixth magnetic heads 20 and 21 are passed through rotary transformers 22 and 23 to preamplifiers 30 and 31.
Given to. The output signals of the preamplifiers 30 and 31 are given to the end sides of the envelope detection circuit 33 and 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,
The output of the rotation detector 34 is shaped by the waveform shaping circuit 35, and the changeover switch 32 is switched by the output of the waveform shaping circuit 35.

The output signal of the envelope detection circuit 33 is given to the displacement voltage generation circuits 36 and 37. The output signals of the displacement voltage generating circuits 36 and 37 are given to the adding circuits 38 and 39, and the synchronizing signal generator 4
The output signals of 0 and 41 are added to drive the actuators 18 and 19 via the slip rings 42 and 43.

The displacement voltage generating circuits 36, 37 control the output signal generation by the displacement voltage generating signal d supplied from the sequence signal generating circuit 44 and the synchronization signal supplied from the sync separation circuit 45. Then, the displacement voltage generating circuits 36 and 37 control the voltage of each output signal so that the output signal of the envelope detection circuit 33 becomes maximum in accordance with the video head switching signal. The sync signal generators 40 and 41 are arranged at the same inclination as the tracks on the magnetic tape 4 according to the tape speed.
A signal for tracing 20, 21 is generated.

FIG. 3 is a timing chart of input / output and tape speed of the sequence signal generating circuit shown in FIG. 2, and FIG. 4 is a diagram for explaining the operation of one embodiment of the present invention.

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 speed-up signal b shown in FIG. 3B is output, the drive motor (not shown) is controlled, and the tape speed changes as shown in FIG. 3C. The displacement voltage generation signal (see FIG. 3D) is output from the sequence signal generation circuit 44 at the same time as the tape speedup signal b. When the displacement voltage generation signal d is output, the displacement voltage generation circuits 36 and 37 are activated, and the actuators 18 and 19 are controlled so that the fifth and sixth magnetic heads 20 and 21 trace the recording track. It When the tape speed stabilizes, the polarity of the changeover signal e changes to change over the switch changeover 28, the changeover switch 28 is changed over to the end side, and the output signals of the fifth and sixth magnetic heads 20, 21 are changed to the preamplifiers 30, 31. Is given to the demodulation circuit 29 via.

From the output of the tape speed-up signal f to the change of the polarity of the changeover signal e of the changeover switch 28, similarly to the conventional example, the first to fourth magnetic heads 2a, 3a, 2 are provided.
The outputs of b and 3b are given to the preamplifiers 10 to 13 via the rotary transformers 24 to 27. Preamp 10 to 13
One of the outputs is sequentially given to the preamplifier 16 and amplified. The demodulation circuit 29 converts the output of the preamplifier 16 into a video signal.

However, when the magnetic tape 4 travels at a high speed, the displacement amount of the actuators 18 and 19 increases, so that the linearity of the displacement deteriorates and the fifth and sixth magnetic heads 20 and 21 come off the recording track. This phenomenon is due to the changeover switch 32
Is generated near the point of change of the video head switching signal, and the signal output from the output of the demodulation circuit 29 (see FIG. 4 (c)) of the reproduced signal via the sync separation circuit 45 is the vertical sync signal 200. May be a missing signal.

As a solution to this problem, a method of ensuring synchronization of the television signal receiver by adding or replacing a pseudo vertical synchronizing signal (not shown) is generally performed. However, this method hinders the operation of the displacement voltage generating circuits 36 and 37 for controlling the actuators 18 and 19. The displacement voltage generating circuits 36, 37 operate so as to make the cycle of the vertical synchronizing signal of the reproduced synchronizing signals constant.

Then, the output signal of the envelope detection circuit 33 is given to the level determination circuit 46, and the level is larger than a predetermined value and the vertical synchronization signal in the signal output from the synchronization separation circuit 45 is the change point of the video head switching signal. When it does not appear within a predetermined time in the vicinity, the changeover switch 28 is switched to the side, and the output signal of the preamplifier 16 is output via the demodulation circuit 29.

As described above, according to the embodiment of the present invention, as the magnetic head, the fifth and sixth magnetic heads 20 and 21 are provided in addition to the first to fourth magnetic heads 2a, 3a, 2b and 3b. When reproducing at a tape speed different from that at the time of recording, position control is performed using the fifth and sixth magnetic heads 20 and 21 so as to trace the recording track, and position controllable fifth and sixth magnetic heads are used. head
When there is a reproduced signal in either or both of 20, 20 and the vertical synchronizing signal does not appear at a predetermined time, the first to fourth magnetic heads 2a, 3a, 2b, 3b, that is, the track width, is used as in the conventional example. Also select a wide head output signal.

Although the linearity of the actuator is mentioned as an example of the above condition, other than this, when the position of the vertical synchronizing signal around the recording track or on the recording track is significantly deviated from the predetermined format, or when the tape is transferred. Examples include vertical movement of the tape due to changes in the tape path. In these situations, noise is generated on the playback screen or blurring occurs due to the lack of the sync signal. The present invention can provide conditioning to avoid such problems.

As described above, according to the present invention, the position controllable movable magnetic head is provided in the rotary cylinder, and when the speed of the magnetic tape is the same as that at the time of recording, the signal reproduced by the fixed head is transmitted. When the speed of the magnetic tape is demodulated and the speed is different from that at the time of recording, the movable magnetic head is position-controlled in the width direction of the diagonal track of the magnetic tape, and the amplitude level of the reproduction signal by the movable magnetic head becomes larger than a predetermined value. In addition, when the vertical sync signal included in the playback signal appears within a predetermined time near the head switching point, the playback signal from the movable magnetic head is demodulated, so noise is suppressed and the video signal content is matched. The reproduced image can be obtained.

[Brief description of drawings]

FIG. 1 is a view showing the arrangement of magnetic heads used in an embodiment of the present invention. FIG. 2 is a schematic block diagram of a reproducing system included in one embodiment of the present invention. FIG. 3 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 timing chart for explaining the operation of the embodiment of the present invention. FIG. 5 is a schematic diagram showing the locus of the head during conventional multi-speed image reproduction. FIG. 6 is a diagram showing the arrangement of magnetic heads and reproduction signals in a conventional video tape recorder. FIG. 7 is a schematic block diagram of a reproducing system in a conventional video tape recorder. FIG. 8 is a waveform diagram of each part of FIG. In the figure, 1 is a cylinder, 2a is a first magnetic head, and 3a
Is the second magnetic head, 2b is the third magnetic head, and 3b is the fourth magnetic head.
Magnetic head, 4 magnetic tape, 6 to 9,28,32 changeover switches, 10 to 13,16,30,31 preamplifiers, 14,15
Is a head switching pulse generation circuit, 18, 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 is an envelope detection circuit, 34 is a rotation detector, 35, 142 and 152 are waveform shaping circuits, 36 and 37 are displacement voltage generation circuits, 38 and 39 are addition circuits, and 40 and 41 are synchronous. Signal generator, 44 is a sequence signal generation circuit, 4
Reference numeral 5 is a sync separation circuit, 46 is a level determination circuit, 141 and 151 are envelope detection circuits, and 143 and 153 are flip-flops.

Claims (4)

[Claims] 1. A video signal reproducing apparatus having a rotary cylinder for helically scanning a magnetic tape to record a video signal on an oblique track of the magnetic tape, wherein each of them is 180 ° with respect to a center of rotation of the rotary cylinder. A plurality of fixed magnetic heads provided at angular positions of
A plurality of movable magnetic heads which are provided at a position different from the fixed magnetic head at an angle position of 180 ° and are position-controllable in the width direction of an oblique track on the magnetic tape, the same as when recording the magnetic tape A tape drive means for traveling at a first speed or an arbitrary second speed different from the first speed, a switching means for switching and outputting a reproduction signal by the fixed magnetic head and a reproduction signal by the movable magnetic head, and the magnetic tape is the first one. Position control means for controlling the position of the movable magnetic head in the track width direction when traveling at a speed of 2, demodulation means for demodulating a reproduction signal from the fixed magnetic head or the movable magnetic head output from the switching means. , And when the speed of the magnetic tape is the first speed, the switching means outputs the reproduction signal from the fixed magnetic head. When the speed of the magnetic tape is the second speed, the amplitude level of the reproduction signal by the movable magnetic head is larger than a predetermined value, and the vertical synchronization signal included in the reproduction signal is movable. Control means for causing the switching means to output a reproduction signal by the movable magnetic head when within a predetermined period near the magnetic head switching point, and for causing the switching means to output a reproduction signal by the fixed magnetic head otherwise. A video signal reproducing device comprising: 2. The fixed magnetic head is selected so that its width is wider than the pitch of the tracks.
The video signal reproducing device according to the item. 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 disposed near the first magnetic head and the second magnetic head and having a different azimuth angle from the first magnetic head in the vicinity;
A fourth magnetic head having a different azimuth angle from the second magnetic head in the vicinity.
3. The video signal reproducing device according to claim 1 or 2, including the magnetic head. 4. Of the first to fourth magnetic heads,
4. The video signal reproducing apparatus according to claim 3, further comprising head selecting means for selecting a reproduction signal from the magnetic head having the largest output amplitude to be used as an output signal of the fixed magnetic head.