JPS5951047B2 - Jixisai Seisouchi - Google Patents

Description

[Detailed Description of the Invention] In a VTR (magnetic recording/reproducing device), generally during recording, a rotating magnetic head is rotated in synchronization with a vertical synchronizing pulse to record a video signal on a magnetic tape, and the vertical synchronizing pulse is (or its frequency divided pulse) is recorded on the edge of the tape, and during playback, the vertical synchronization pulse recorded on the tape edge causes the rotating magnetic head to rotate at the same rotational phase as during recording. It is servo controlled to track (scan) the recording track of the video signal.

Therefore, the tracking error of the rotating magnetic head during playback is
This error is caused by vibrations or eccentricity of the tape bus system, tape guide drum, etc., and is an accumulation of errors caused by each, that is, determined by mechanical accuracy.

Therefore, in such a VTR, very precise machining techniques are required to narrow the track width of the video track and improve the recording density, and the mechanical precision of the VTR must be maintained. It was difficult to improve the density.

In view of these points, the present invention attempts to improve the recording density without requiring extremely precise machining accuracy.

Therefore, in the present invention, a special magnetic head device is used as the rotating magnetic head, and the rotating magnetic head is automatically tracked with respect to the video track during reproduction.

First, let's explain the special magnetic head device.

In FIGS. 1 and 2, 1 is a fixed lower drum, 2 is a rotating upper drum in this example, and the magnetic tape 3 is attached to the circumferential surfaces of these drums 1 and 2 over an angular range of 360°. A magnetic head device 10 is attached to the lower surface of the upper drum 2, which is arranged diagonally in a character shape.

As shown in FIGS. 3 to 5, this magnetic head device 10 includes a magnetic head 11 for a main track, a magnetic head 12 for a sub-track, and a piezoelectric element 20 supporting them.
It is composed of.

That is, the piezoelectric element 20 is constituted by, for example, a PZT-based piezoelectric bending bimorph plate, and the piezoelectric elements 21A, 21
B indicates the bimorph plate, which is formed into a rectangular plate shape, and its thickness direction (direction of arrow A in FIG. 4) is the direction of polarization. And bimorph plates 21A, 21
B are laminated so that their polarization directions are in the same direction, and at this time, an electrode 22 made of a thin plate of the same shape that also serves as reinforcement is sandwiched between them, and a layer of, for example, cyanoacrylate is placed between them. They are bonded together using a monomer adhesive. Furthermore, bimorph plates 21A and 21B
Electrodes 23A, 23B are formed on each remaining surface by plating, for example, and terminals 24 are connected to the electrodes 22, 23A, 23B.
is connected. The piezoelectric element 20 also serves as a head base, and the heads 11 and 12 are attached to the electrode 23A at one end of the piezoelectric element 20 using adhesive, for example, so that they are lined up in the direction of arrow A.

In this case, a spacer 13 made of a non-magnetic material is provided between the head 12 and the electrode 23A, and the head 11 and the head 12 have a predetermined step difference with respect to the piezoelectric element 20. They are attached in a staggered manner, that is, the surface of the head 11 opposite to the electrode 23A is the reference surface 15, and the surface of the head 2 in contact with the spacer 13 is in the plane that includes this reference surface 15. Being located. Further, on the surface of the heads 11, 12 opposite to the reference surface 15, the heads 11, 12
A notch 16 is formed at the tip of the core of the head 11,1.
The gap width (track width) w of the two working gaps 11A and 12a is set to a required size, for example, 40 μm.

Furthermore, for example, the azimuth angle of the gap 11a is 0°, the azimuth angle of the gap 12a is about 15° to 20°, and the interval between the gap 11a and the gap 12a is, for example, 15H (H is one horizontal period). The length of the corresponding magnetic track. The length direction of the piezoelectric element 20 is the diametrical direction of the drum 2, and the direction perpendicular to the direction of arrow A is the rotational axis direction of the drum 2. The other end of the piezoelectric element 20 is fixed to the lower surface of the drum 2 by a fixing piece 25 so as to be in contact with the lower surface of the drum 2.

In the illustrated example, it is assumed that the head 12 is attached to the upper side and the head 11 is attached to the lower side. In such a magnetic head device 10, if a DC voltage is supplied to the terminal 24, the bimorph plates 21A, 2
1B bends in the polarization direction (direction of arrow A), the head 11 bends in accordance with the polarity and level of the DC voltage.
, 12 are displaced in the direction of arrow A, that is, in the track width direction of the magnetic track.

Therefore, when a VTR reproduces, if a voltage indicating a tracking error is supplied to the terminal 24 instead of the DC voltage, the heads 11 and 12 will correctly track the video track.

The present invention performs automatic tracking during playback in this manner, and an example thereof will be explained below.

FIG. 6 shows the recording system. A video signal (luminance signal) is supplied from an input terminal 31 through a preamplifier 32 to an FM modulation circuit 33 to be converted into an FM signal, and this FM signal is transmitted through a recording amplifier 34 to a 11 and 12.

In this case, the heads 11 and 12 are moved in the direction of arrow B (
The rotational phase of the heads 11 and 12 is controlled so that the head 12 is rotated in a direction preceding the head 11, and the head 11 is located at the edge of the tape 3 during the vertical blanking period. , and the tape 3 is transported in the direction of arrow C at a constant speed.

Note that no voltage is supplied to the piezoelectric element 20. Therefore, the seventh
As shown by the solid line in Figure A (this figure is a diagram when the tape 3 is viewed from the base side), one field of the video signal (FM signal) is transferred to one magnetic track T1 by the head 11. At the same time, the head 12 records the same field as one magnetic track T.

is recorded adjacent to track T1. However, in this case, by setting the running speed of the tape 3 in advance, the head 11 overlaps the track T2 by 1/2 W during the next field period, as shown by the broken line in FIG. is performed, so at this time,
The overlapping portion of track T2 is erased and the track width becomes 1/2W. Therefore, the final result is Figure 7B
As shown in FIG. 2, tracks T1 having a track width w and tracks T2 having a track width 1/2W are formed alternately and adjacently. The same field is recorded in tracks T1 and T2, but in track T1, both ends are vertical blanking periods, whereas in track T2, head 12 is in the lead, so the track The part shifted from the upper end of T2 by 15H, which is the distance between heads 11 and 12, in the direction of arrow B is a vertical blanking period. When performing reproduction scanning, the head 11 is moved to the track T1 as shown in FIG. 8A.
The correct tracking state is the state in which the tracking is consistent with The signal Sa is taken out from the head 12, and as shown in FIG. The FM signal Sb at the level of is extracted. In this case, as shown in FIG. The direction A is perpendicular to the direction B in which the leads 11 and 12 are the length directions of the tracks Tl and T2.
Even if the head 11 and the track T2 are displaced in the direction A2, the azimuth angle is different between the head 11 and the track T2, so the FM signal Sb of the track T2 cannot be obtained from the head 11 due to azimuth loss. That is, no inter-track crosstalk occurs in the FM signal Sa from the head 11.

Similarly, no inter-track crosstalk occurs in the FM signal Sb from the head 12. Therefore, the reproduction system
For example, it is configured as shown in FIG.

That is, the FM signals Sa and Sb from the heads 11 and 12 are supplied to reproducing amplifiers 41 and 42, made to the same level, and then supplied to the contacts of the switch circuit 43, respectively. Further, a pulse generating means 51 is provided for the drum 2 or its rotating shaft, from which one pulse is taken out for each rotation of the heads 11, 12, and this pulse is supplied to a delay circuit 52 as shown in FIG. As shown in FIG. 9D, the delayed pulse Pc is positioned before the level of the signal Sa starts to decrease, and this pulse Pc is supplied to the monostable multivibrator 53, and as shown in FIG. A pulse Pd that rises for a period of, for example, 15H from the rising time is formed, and this pulse Pd is supplied to the switch circuit 43 as its control signal, and the switch circuit 43 switches to the state shown in the figure when the pulse Pd is falling. When the pulse Pd is rising, the state is switched to the opposite state as shown in the figure.

Therefore, from the switch circuit 43, the signal Sa is taken out during the period when the pulse Pd is falling, and the signal Sb is taken out during the period when the pulse Pd is rising, that is, the level of the FM signal Sa is lowered. is corrected by the signal Sb and taken out at a constant level.

The signal Sa corrected for this level drop is supplied to a demodulation circuit 45 through a limiter 44 to demodulate the original video signal, which is taken out to a terminal 46.

In the present invention, the head 11,
12 automatic tracking is performed.

That is, when the heads 11 and 12 are correctly located on the tracks Tl and T2 as shown in FIG. 8A,
The levels of the FM signals Sa and Sb from the amplifiers 41 and 42 are equal to each other, but the heads 1 and 12 have the same level as the tracks Tl and T.
When the amplifiers 41 and 4 are displaced in the A1 or A2 direction, which is the width direction of 2, the amplifiers 41 and 4
The levels of the FM signals Sa and Sb from 2 change as shown in FIG. 8B. That is, when the heads 11 and 12 are displaced in the direction of the arrow A1, the signal Sb has a higher level than the signal Sa, corresponding to the amount of displacement, and when the heads 11 and 12 are displaced in the direction of the arrow A2, the level is higher than the signal Sa. As a result, the level of the signal Sa becomes higher than that of the signal Sb. Therefore, the signal Sa,
Automatic tracking can be achieved by detecting the level relationship and level difference of Sb and supplying the detection signal to the piezoelectric element 20 to displace the heads 11 and 12 in opposite directions. That is, in FIG. 10, the FM from amplifiers 41 and 42
The signals Sa and Sb are supplied to the rectifier circuits 61 and 62, and the DC signals Sc and Sc, respectively, have a level corresponding to the level of the signals Sa and Sb.
Sd, and these signals Sc and Sd are connected to resistors R,,R
.

and variable resistor R. ,R. through the emitter follower transistors Q,,Q. through transistor Q
. ,Q,. This transistor Q,
,Q. constitutes the differential amplifier 63. Therefore, the levels of the signals Sc and Sd are compared in the differential amplifier 63, and the difference signal Se=between the signals Sc and Sd is output from the collector of the transistor Q. Sc-Sd is taken out, and this difference signal Se is supplied to a hold circuit 64.
When the heads 11 and 12 reach the lower ends of the tracks T, , T, the hold circuit 64 holds the signals Sa and Sb.
When the level of the signals Sa and Sb decreases, the level comparison between the signals Sa and Sb is not performed correctly, resulting in an error, so the buffer transistor Q is used to correct this.

, a switching transistor Q6, a holding capacitor C, and a buffer FET (Q,). Then, the pulse from the generating means 51 is supplied to the delay circuit 54, and as shown in FIG. At the same time, the pulse Pd from the multipipulator 53 is supplied to the flip-flop circuit 55, and from this, as shown in FIG. 9F, a pulse Pf that falls when the pulse Pe rises and rises when the pulse Pd falls is taken out. It will be done. This pulse Pf is then supplied to the base of a transistor Q6, and the transistor Q6 is turned on when the pulse Pf is rising and turned off when it is falling. Therefore, when the signals Sa and Sb are obtained, the transistor Q6 is on, so the signal Se is the transistor Q.

~Q, and when the levels of the signals Sa and Sb decrease, the transistor Q. is turned off, so instead, the signal Se at the previous point in time is taken out from the capacitor C, and provided to the source of FETQ. In this way, in the hold circuit 64,
A comparison error due to a decrease in the levels of the signals Sa and Sb is corrected, and this corrected signal Se is applied to the transistor Q.

supplied to the base of This transistor Q8 constitutes a differential amplifier 65 together with the transistor Q9, and the base of the transistor Q is connected to the transistor Q.

through variable resistor R. to a predetermined level, i.e.
Heads 11 and 12 are tracks T,,T. A bias voltage of a level equal to the level VO of the signal Se when the signal Se is being scanned correctly is supplied. Also transistor Q.
, Q, are supplied to the piezoelectric element 20.
Therefore, heads 11 and 12 are tracks T,,T.

When scanning is performed correctly, the signal Se supplied to the base of the transistor Q and the base bias voltage of the transistor Q are both at the same level VO, so the piezoelectric element 20 does not deflect. It is in a state where there is no
Therefore, the heads 11 and 12 are also in the reference position. However, heads 11 and 12 are from tracks Tl and T2 to arrows A and A.

When the piezoelectric element 20 shifts in the direction indicated by the arrow A, the level of the signal Se changes around the level VO in accordance with the direction and magnitude of the shift. Or, since the heads 11 and 12 are also displaced in the direction of the arrow A2 or A, the heads 11 and 12 are deflected in the direction of the arrows Tl and T2.
scan correctly. That is, automatic tracking of heads 11 and 12 is performed. In this case, head 11,
12 is the truck T,,T.

When starting scanning from the upper end, if the positions of the heads 11 and 12 are not returned to their reference positions, the previous tracks T, , T
. The displacements of the heads 11 and 12 when they are scanned are sequentially integrated. Therefore, resistors R,,R.

transistors Q,,,Q, on the output side of, respectively. is connected, and the pulse Pc from the delay circuit 52 is supplied to the monostable multipipulator 56. As shown in FIG. A pulse Pg that falls after about 2H is formed, and this pulse Pg is applied to the transistors Q, , , Q,. supplied to the base of Therefore, when the heads 11 and 12 start scanning from the upper end of the tracks T, T, during the period 1 to 2H from the fall of the pulse Pd until the fall of the pulse Pg, Sa=Sb=0. Therefore, during this period, the signal Se supplied to the base of the transistor Q8 becomes VO, and the heads 11 and 12 return to their standard positions. When the system returns, if there is a tracking error, automatic tracking is performed again as described above. Furthermore, when the scanning of the tape 3 is stopped and the same track is repeatedly scanned to perform field stay playback, the inclinations of the tracks Tl and T2 and the inclinations of the scanning trajectories of the heads 11 and 12 are Although originally different, automatic tracking is performed when the heads 11 and 12 scan. Furthermore, while stopping the running of tape 3,
When performing stay playback (frame stay) by alternately and repeatedly scanning tracks in odd-numbered fields and tracks in even-numbered fields, switch 58 is turned on in conjunction with the stay operation button.

The pulse Pc from the delay circuit 52 is then supplied to the flip-flop circuit 57 to form a rectangular wave signal that is inverted every field period.
8 to the transistor Ql3, and the transistor Ql3 is turned on every other field period. Therefore, for example, when the heads 11 and 12 finish scanning the odd field track and then reach the upper edge of the tape 3, the transistor Ql3 is turned on, which causes the base potential of the transistor Q9 to change from 0 to ΔVO.
At this time, the reference positions of the heads 11 and 12 change by one pitch of the tracks 11 and 12. Therefore, in the next field period, the track in the even field, which is the track adjacent to the track in the odd field that has just been scanned, is scanned. Then, in the next field period, the transistor Ql3 is turned off and the base potential of the transistor Q9 becomes VO, so that the track of the first odd field is scanned again. And from then on,
Since similar operations are repeated, still playback (frame stay) is performed. Thus, according to the invention:
．． Since the heads 11 and 12 automatically track the tractors Tl and T2 over almost their entire lengths, correct playback can be performed even if the retractors Tl and T2 meander due to elongation of the tape 3 or the like. Furthermore, mechanical errors in the running system of the tape 3 can be largely tolerated, reducing costs.
Compatibility can be increased. Furthermore, since the track pitch can be reduced, high-density recording can be achieved and costs can be reduced from this point of view as well. Furthermore, since the heads 11 and 12 automatically track even when performing still playback and slow playback, noise bands due to track joints do not appear on the playback screen. Furthermore, there is no need to record control pulses for tracking servo on the tape 3 during reproduction, and high-density recording is possible. Furthermore, when the head 11 goes from the lower end of the track T1 to the upper end of the adjacent track T1, the level of the FM signal Sa from the head 11 temporarily decreases;
Since it is corrected by the FM signal Sb from 2, a regular video signal can be obtained.

Moreover, in that case, the head 12 is also used for automatic tracking, which simplifies the configuration and reduces costs. In the head device 10, after the head 11 and the spacer 13 are arranged side by side, their upper surfaces are wrapped.
The head 12 may be provided on the spacer 13 so that the upper surface of the head 11 and the lower surface of the head 12 are flush with each other.

Alternatively, as shown in FIG. 11, the heads 11 and 12 may be tilted so that the lower end of the gap of head 11 and the upper end of the gap of head 12 are located on the reference plane 15. Furthermore, it is also possible to record another signal on the track T2, for example, stereoscopic information in the case of a stereoscopic television, or answers in the case of a teaching machine. Furthermore, cliff electric element 2
0 may be replaced with other electromechanical conversion elements such as electromagnetic type.

Further, by detecting a dropout of the FM signal Sa and switching the switch circuit 43 based on the detection signal, the dropout can also be corrected.

[Brief explanation of drawings]

1 and 2 are a plan view and a front view showing an example of a rotating magnetic head device, FIG. 3 is a plan view of an example of a magnetic head device, FIG. 4 is a side view thereof, and FIG. 5 is a front view thereof. 6 is a system diagram of an example of a recording system, FIGS. 7 to 9 are route diagrams and waveform diagrams for explaining the present invention, FIG. 10 is a system diagram of an example of the present invention, and FIG. 11 is a system diagram of an example of a recording system. is a route map for explaining another example of the head device. 11 and 12 are magnetic heads, 20 is a piezoelectric element, 61 and 62
is a rectifier circuit.

Claims (1)

[Claims] 1. First and second rotary magnetic heads having different working gap directions are supported by a common electro-mechanical transducer at different positions relative to the axial and longitudinal directions of the track, and A predetermined information signal is recorded as an adjacent track on the magnetic tape during any rotation of the second rotating magnetic head, and is recorded by the second rotating magnetic head during the next rotation of the above rotation. A device for reproducing a recorded magnetic tape on which a part of the track is overwritten by the first rotary magnetic head, wherein during reproduction, the reproduction signals of the first and second rotary magnetic heads are adjusted to each other at any time. A tracking error signal is obtained over almost the entire length of the track by comparison, and by supplying this tracking error signal to the electro-mechanical conversion element, the scanning position of the first rotary magnetic head is adjusted to the width of the recording track. The magnetic reproducing device is configured to perform automatic tracking of the first rotary magnetic head over substantially the entire length of the track by the displacement.