JPS6019043B2 - magnetic playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a VTR (magnetic mirror image reproduction device), during recording, a rotating magnetic head is generally rotated in synchronization with a vertical synchronization pulse to record a video signal on a magnetic tape, and the vertical synchronization A pulse (or its frequency divided pulse) is recorded on the edge of the tape, and during playback, the servo is set so that the vertical synchronization pulse recorded on the tape edge causes the rotating magnetic head to rotate at the same rotational phase as during recording. The recording track of the video signal is tracked (scanned).

Therefore, during playback, the tracking errors of the rotating magnetic head, the tape path system, and the tape guide drum are caused by eccentricity, etc., and errors due to each are accumulated, and are determined by mechanical accuracy. .

Therefore, in such a VTR, in order to improve the recording density by narrowing the track width of the video track, extremely precise manufacturing techniques are required, and the mechanical accuracy of the VTR must be maintained, so the recording density must be increased. It is difficult to improve Therefore, it may be possible to automatically track the rotating head to the video track during playback.

Figures 1 to 4 show examples of this. In the example of Figure 1, the signal is reproduced by scanning the head song in the length direction of the track Ha, and wobbling in the width direction. , the direction and magnitude of the tracking deviation of the head ratio are determined from the direction of wobbling and changes in the playback level at that time, and the scanning position of the head Ha is corrected using this determination signal. However, in this method, Wobbling the head also has drawbacks such as lowering the playback level and lowering the S/N ratio of the video signal.

In the example shown in FIG. 2, a head Hb with a narrow gap width (track width) is provided integrally with the head side, and wobbling is performed while scanning a track Tb with this head Hb.

In this case, by making the azimuth angle different between the head ratio and Hb, track Ta is not reproduced by head Hb due to azimuth loss, so automatic tracking is performed using the output of head Hb as in the case of Fig. 1. be able to. At this time, even if the head ratio wobbles by the same amount as in the case of Fig. 1, the gap width of the head ratio is narrow, so the level change of the playback output becomes large, and therefore a small wobbling is sufficient. The reduction in the playback level of the head Ha is smaller, and the reduction in S/N of the video signal is smaller than in the case of FIG. However, even in this case, it is impossible to avoid a decrease in S/N due to wobbling, which is still disadvantageous in terms of reproduction.
Furthermore, in the example shown in FIG. 3, heads Hb and Hc with narrow gaps are provided before and after the head Ha, and if the tracking of the head HP is deviated, the head mark or H
Since the playback level changes, this is used to perform automatic tracking.

The same applies to the example shown in FIG. However, in these methods, while only the head Ha is used for video signal reproduction, it is necessary to add two heads Hh and Hc for tracking, and moreover, it is necessary to maintain high precision in the relative positional relationship between the head ratio and Hc. This makes it extremely difficult to manufacture, and even if it could be manufactured, it would be very expensive.In consideration of these points, the present invention is designed to: This is intended to improve recording density.

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

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

In FIGS. 5 and 6, 1 is a fixed lower drum, 2 is a rotating upper drum in this example, and the magnetic tape 3 is placed in a Q-shape over an angular range of 360 degrees with respect to the circumferential surfaces of these drums 1 and 2. A magnetic head device 10 is attached to the lower surface of the upper drum 2, which extends diagonally.

As shown in FIGS. 7 to 9, 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 bent 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, 218
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. This piezoelectric element 20 also serves as a head base, and the heads 11 and 12 are attached by adhesive, for example, to the electrode 23A at one end of the piezoelectric element 20 so that they are lined up in a direction perpendicular to the direction of arrow A. There is.

In this case, a spacer 13 made of a non-magnetic material is provided between the head 12 and the electrode 23A, and the heads 11 and 12 are attached to the piezoelectric element 20 with a predetermined step difference. , in FIG. 9, the head 11
The head 12 is attached so that the bottom surface of the head 12 is positioned below the top surface by 1/2w. Further, on the lower surface of the head 11, a notch 16 is formed at the tip of the core so that the working gap 11a of the head 11 has a required gap width w, for example, 40 mm.
A notch 17 is formed at the tip of the core on the upper surface of the head 2, and the gap width of the working gap 12a of the head 12 is set to 1.5w.

Furthermore, for example, the azimuth angle of the gap 1 1a is set to 00, the azimuth angle of the gap 12a is set to about 150 to 20 degrees, and the interval between the gap 11a and the gap 12a is set to, for example, one group (one day or one horizontal period). The length of the corresponding magnetic track. The length direction of the piezoelectric element 20 is the diameter direction of the drum 2, and the direction of the arrow A is the direction of the rotation axis of the drum 2, and the heads 11, .
Place the piezoelectric element 20 so that the tip of the piezoelectric element 12 slides against the tape 3.
The end of the pond is fixed to the lower surface of the drum 2 by a fixing piece 25.

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. If a DC voltage is connected to the terminal 24 in such a magnetic head device, the bimorph plate 21A is activated by this DC voltage.
, 21B are deflected in the polarization direction (direction of arrow A), so that the heads 11 and 12 are displaced in the direction of arrow A, that is, in the track width direction of the magnetic track, in accordance with the polarity and level of the DC voltage.

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

Therefore, in the present invention, automatic tracking during reproduction is performed in this manner, and in that case, a pilot signal is also recorded in advance on the track to be reproduced by the head 11, thereby performing automatic tracking. .

FIG. 10 shows the recording system, in which the video signal (luminance signal) is transmitted from the input terminal 31 through the preamplifier 32 to the FM
The FM signal S2 is supplied to the modulation circuit 33 and occupies a high frequency band in which recording and reproduction is possible. Ru.

Further, oscillation circuits 41A and 41B are provided to generate the FM signal S2.
Frequencies f that are lower and different from each other.

, fb are taken out, and these signals Pa and Pb are supplied to the switch circuit 42. Further, the video signal from the terminal 31 is supplied to a synchronization separation circuit 43 to extract a vertical synchronization pulse, and this pulse is supplied to a flip-flop circuit 44 to output a vertical synchronization pulse.
A rectangular wave signal that is inverted every field period is formed, and this rectangular wave signal is supplied to the switch circuit 42 as its control signal. Therefore, pilot signals Pa and Pb are alternately taken out from the switch circuit 42 every one field period. Then, the extracted pilot signals Pa and Pb are supplied to the adder circuit 34 and the FM signal S
2 and the addition signal S, (=S20 Pa or Pb
), and this signal S, is coupled to the head 11 through the recording amplifier 35.

At this time, the heads 11 and 12 are rotated by a servo circuit (not shown) in the direction of arrow B (direction in which head 12 precedes head 11) at the field frequency of the video signal, and during the vertical planking period, the heads 11 and 12 are rotated at the field frequency of the video signal. 11
The heads 11 and 12 are positioned at the edge of the tape 3.
The rotational phase of the tape 3 is controlled, and the tape 3 is transported at a constant speed in the direction of arrow C.

Note that no voltage is supplied to the piezoelectric element 20. Therefore, the first
As shown by the solid line in Figure 1A (this figure shows the tape 3 viewed from the base side), one field of the added signal S, is recorded as one magnetic track T, by the head 11. At the same time, an FM signal S2 of the same field as the video signal in the signal S is recorded by the head 12 as one magnetic track T2 adjacent to the track T.

However, in this case, by setting the running speed of the tape 3 in advance, the head 1 1 moves to the track T in the next field period, as shown by the broken line in FIG. 11A.
Recording is performed with an overlap of w on track L. At this time, the overlapping portion of track L is erased and the track width becomes 1/2W. Therefore, the first
1 As shown in FIG. 8, a track T with a track width w, and
Tracks T2 with a track width of 1'2w alternately, and
formed adjacent to each other.

For tracks T and T2, the video signals are as follows:
The same field is recorded, but in track T, both ends are vertical planking periods, whereas in track T2, head 12 is in the lead, so head 1 1 is in front of the top end of track L. The portion shifted in the direction of arrow B by one stroke, which is the interval between and 12, is the vertical planking period. Further, as shown in FIG. 12A, among the tracks T, the FM signal S2 and the pilot signal Pa are recorded as the signal S on every other track T, and the remaining every other track T. ,b, the FM signal S2 and the pilot signal Pb are recorded as the signal S. Note that in track T2, the FM signal S
2 are recorded. And the tracks T, . When the heads 11 and 12 perform reproduction scanning on the track T2, the head 11 scans the track T2 as shown in FIG. 12A.
, is a correct tracking state.If it is assumed that tracking is performed correctly in this way, the level from the head 11 decreases every vertical planking period, as shown in FIG. 13A. A sum signal S, is taken out.

In this case, since the azimuth angles are different between the head 11 and the track T2, even if the head 11 is displaced in the width direction of the track L, ie, in the A or A2 direction, the FM from the head 11 to the track L due to azimuth loss. The signal S2 is not obtained, that is, no inter-track crosstalk occurs in the added signal S from the head 11. The same applies to the reproduction output of the head 12, and the reproduction output from the head 12 is as shown in FIG.
As shown in FIG. 2, the level of the FM signal S2 decreases every time one cue precedes the vertical planking period, and the FM signal S2 is extracted at a level approximately 1/2 that of the signal S.

However, in this case, the head 12 simultaneously scans the tracks T2, a, T, and b on both sides, and the pilot signals Pa and Pb have low frequencies and small azimuth losses, so the head 12 scans the tracks T2 and T2. FM signal S
At the same time as 2, pilot signals Pa and Pb of tracks T, a, T, and b are also taken out. Therefore, in the present invention,
The reproduction system is configured as shown in FIG. 14, for example.

That is, the signal S from the head 11 and the signal S2 from the head 12 (including crosstalk signals Pa and Pb) are
The signal B9 is supplied to the reproducing amplifiers 51 and 52, and the signals are made to have the same level before being supplied to the input contacts of the switch circuit 53, respectively. Further, a pulse generating means 81 is provided on the drum 2 or its rotating shaft, and from this, the head 11,
One pulse is taken out for each rotation of the signal S, and this pulse is combined with the delay circuit 82 to produce a delay that occurs just before the level of the signal S starts to decrease, as shown in FIG. 13C. This pulse Pc is uniformly fed to the monostable multipipelator 83, and as shown in FIG. Pd is supplied to the switch circuit 53 as its control signal, and the switch circuit 53 is switched to the state shown in the figure when the pulse Pd is falling, and switched to the state opposite to that shown in the figure when the pulse Pd is rising. .

Therefore, during the falling period of the pulse Pd, the switch circuit 53 outputs the signal S. is taken out, and during the period when the pulse Pd is rising, the signal S2 is taken out, that is, the drop in the level of the signal S is corrected by the signal S2, and is taken out at a constant level.

Then, this level drop is corrected for the signal S. However, only the FM signal S2 supplied to the high-pass filter 54 is taken out, and this FM signal S2 is supplied to the demodulation circuit 56 through the limiter 55 to demodulate the original video signal, which is taken out to the terminal 57.

In the present invention, the head 11,
12 automatic tracking. That is, Figure 12A
As shown in , when the head 11 is correctly positioned on the track T, a, the levels of the pilot signals Pa, Pb from the head 12 are equal to each other, but the levels of the pilot signals Pa, Pb from the head 12 are equal to each other;
2 is displaced in the direction of arrow A or A2, the levels of the pilot signals Pa and Pb from the head 12 change as shown in FIG. 12B in accordance with the direction and amount of displacement. Further, when the heads 11, 12 are displaced in the direction of arrow A or A2 from the state in which the heads 11 are correctly positioned on the tracks T, b, the pilot signals Pa,
The level of Pb changes in an inverse relationship, as shown in FIG. 12C. Therefore, the track that the head 11 is scanning,
Pilots M No. Pa. Automatic tracking can be achieved by detecting the level relationship and level difference of Pb and supplying the detection signal to the piezoelectric element 201 to displace the heads 11 and 12 in opposite directions. Therefore, in the example of FIG. 14, the signals S2, Pa, and Pb from the amplifier 52 are
1A and 61B, pilot signals Pa and Pb are taken out respectively, and these signals Pa and P-range rectifier circuits 62A and 62B are supplied with DC signals Va and Vb ( Figure 12 B, C
), these signals Va and Vb are further supplied to a level comparison circuit 63 and compared in level with each other, and the signals Vc (=Va - Vb) and -Vc (=Vb - Va) are taken out as the comparison outputs. The signal Vc, -Vc is supplied to the input contact of the switch circuit 64.

Further, the addition signal S from the amplifier 51 is supplied to a bandpass filter 91.

This filter 91 has a passing frequency of f. Therefore, during the field period when the head 11 is scanning the track La, the pilot signal PaL is taken out, and during the field period when the head 11 is scanning the tracks T and b, nothing is output. No signal is extracted. The pilot signal Pa taken out from the filter 91 every one field period is connected to a rectifier circuit 92 and rectified, and the head 11 is connected to the track T, as the rectified output.
A rectangular wave signal that is rising during the field period in which track a is scanned and has a rising -F signal in the field period in which tracks T and b are scanned is extracted, that is,
A signal indicating whether the head 11 is scanning tracks T, a, T, or b is extracted, and this signal is supplied to the waveform shaping circuit 63 to form a sufficient rectangular wave signal, and then sent to the switch circuit. 64 as its control signal.
Therefore, the signals VC and -VC are output from the switch circuit 64.
The signals are taken out alternately every field period. For example, during the field period when the head 11 is scanning the tracks T and a, the signal Vc is taken out and the signal Vc is taken out from the track T.
, b is scanned, a signal peak Vc is extracted.

In this case, during the field period in which the head 11 scans the tracks T and a, the signals Va and Vb change as shown in FIG. 12B with respect to the displacement of the head 11, so the signals extracted during this field period Vc (=Va-V
In b), the polarity and level change as shown in FIG. 12B with respect to the displacement of the head 11. Also, during the field period when the head 11 is scanning tracks T and b,
The signals Va and Vb for the displacement of the head 11 are as shown in FIG.
Therefore, the signal -Vc (=Vb - Va) taken out during this field period is affected by changes in the head 11 &
As shown in FIG. 12C, the polarity and level change. That is, the signal Vc is extracted during the field period when the head 11 is scanning the tracks T, a,
The polarity and level of the signal -Vc taken out during the period when the head 11 is scanning the tracks T and b change in the same way as the head 11 is displaced. And these signals Vc
, -Vc indicates the direction of displacement of the head 11, and the level indicates the amount of displacement. And this extracted signal V
c, -Vc is supplied to a hold circuit 66 through a reset circuit 65, which will be described later.

This hold circuit 66 prevents the levels of the signals Va and Vb from being compared correctly when the levels of the pilot signals Pa and Pb decrease as the head 12 reaches the upper end of the next track T from the lower end of the track T. , this is to correct this error. That is, the pulse from the generating means 81 is supplied to the delay circuit 84, and as shown in FIG. This pulse Pe is supplied to the monostable multipipulator 85, and as shown in FIG. During the falling period of the pulse Pf, which is combined as a control signal, the signals Vc and -Vc supplied to the hold circuit 66 are taken out as they are to the output terminal, and the pulse Pf
During the period when f is rising, the signal Vc is held at the level of Vc immediately before it rises and is taken out. Therefore, from the hold circuit 66, the signal Vc, -Vc is taken out, in which the comparison error during the period when the level of the signal S2 is decreasing is corrected to the level at the time just before that. The corrected signals Vc and -Vc are then supplied to the piezoelectric element 20 of the head device 10 through an adder circuit (OR circuit) 67 and an amplifier 68.

Therefore, when the head 11 is correctly scanning the track T, since Va=Vb, Vc=0, -Vc=0, and the piezoelectric element 20 is in a state where it is not deflected, so the head 11, 12 is at the reference position. However, when the head 11 is displaced from the track T in the direction of arrow A or A2, the polarity and level of the signals Vc and Vc change in accordance with the direction and magnitude of the displacement.
Since the piezoelectric element 20 is deflected in the direction of the arrow A, and the head 11 is also displaced in the direction of the arrow A, the head 11 correctly scans the track T.

That is, automatic tracking of the head 11 is performed.
In this case, when the head 11 starts scanning from the upper end of the track T, if the head 11 is not returned to the reference position, the previous track T. The displacement of the head 11 when scanning is sequentially integrated.

Therefore, the above-mentioned reset circuit 65 is provided, and the pulse Pd from the monostable multipipulator 83 is supplied to the monostable multipipulator 86, and as shown in FIG. A pulse P that rises for a period of about 20 seconds is formed, and this pulse Pg is supplied to the reset circuit 65 as its control signal, and during the period that this pulse Pg falls, the signal Vc supplied to the reset circuit 65 ．． -Vc is taken out as it is to the output terminal, and is made zero during the period when the pulse Pg is rising.

Therefore, when the head 11 starts scanning from the rise of the track T, the pulse Pd rises and for a period of 1 to 2 days, V
Since c: 0, -Vc=0, the head 11 returns to the reference position.

When the camera returns to normal mode, if there is a tracking error, automatic tracking is performed again as described above. In addition, when the tape 3 stops running and the same track is repeatedly scanned for field stay playback, the tracks T, L, and the head 11,
Although it is originally different from the pattern of scanning trajectory of head 12,
Automatic tracking is performed during scanning 1 and 12.

Furthermore, the running of tape 3 is stopped, and tracks T and a are
When performing still playback (frame still) by alternately and repeatedly scanning tracks T and b, the switch 71 is turned on in conjunction with the still operation button. Then, the pulse Pg from the multipipulator 86 is supplied to the flip-flop circuit 72 to form a rectangular wave signal whose level changes between 0 and ΔVc every one field period, and this rectangular wave signal is added through the switch 71. It is supplied to circuit 67. Therefore, for example, during the field period when the head 11 scans the tracks T and a, the level of the rectangular wave signal from the flip-flop circuit 72 is 0, so the piezoelectric element 2 is supplied with the signal 1Vc as described above, and the track T , a is automatically tracked.

When the head 11 finishes scanning the tracks T and a and reaches the upper edge of the tape 3, the flip-flop circuit 7
The level of the rectangular wave signal from head 2 becomes ΔVc, and this signal is also supplied to piezoelectric element 20, so at this time, head 1
The reference positions of heads 1 and 12 change in the direction of arrow A2 by one pitch of tracks T, , T2, and head 1 moves to track T.
, b. Therefore, in the next field period, tracks T and b are scanned. Then, in the next field period, the level of the rectangular wave signal from the flip-flop circuit 72 becomes 0, so the first track T,
a is scanned. Then, since the same operation is repeated thereafter, still playback (frame stay) is performed. Thus, according to the present invention, the head 11 is connected to the track T.
Since the tape 3 is automatically tracked, mechanical errors in the running system of the tape 3 can be tolerated to a large extent, reducing costs and increasing compatibility.

Furthermore, since the track pitch can be reduced by 4 mm, high-density recording can be achieved and costs can be reduced from this point of view as well.
Furthermore, since the head 11 automatically tracks 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. Further, when the head 11 goes from the bottom end of the track T to the top end of the adjacent track T, "Head 1
Although the level of the FM signal S2 from the head 12 temporarily decreases, this level decrease is corrected by the FM signal S2 from the head 12, so that a regular video signal can be obtained. Moreover, in that case, since the head 12 is also used for automatic tracking, the configuration is simplified, and the step and gap between the heads 11 and 12 can be changed, which reduces costs.

Further, if the video signal is a color video signal, the pilot signals Pa, Pb or their harmonics may be set at a frequency such that their interference components are interleaved so as not to cause beat interference with the carrier color signal. Furthermore, the frequencies of the pilot signals Pa and Pb may be within the band of the FM signal S2.

Moreover, other electromechanical conversion elements such as electromagnetic type can also be used in place of the electromagnetic element 20. Further, by detecting dropout of the signal S, and switching the switch circuit 53 based on the detected signal, dropout can also be corrected.

[Brief Description of the Drawings] Figures 1 to 4 are schematic diagrams for explaining automatic tracking; - Figure 5 is a plan view showing an example of a rotating magnetic head device; Figure 6 is a front view thereof; FIG. 7 is a plan view of an example of a magnetic head mounting, FIG. 8 is a side view thereof, FIG. 9 is a front view thereof, FIG. 10 is a system diagram of an example of a recording system, and FIGS. 11 to 13.
The figure is a schematic diagram and a waveform diagram for explaining the present invention, No. 14.
The figure is a system diagram of an example of the present invention. 11, 12 are magnetic heads, 20 is a piezoelectric element, 61A, 6
1B is a filter, 62A and 628 are rectifier circuits, and 63 is a comparison circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 7 Figure 8 Figure 9 Figure 5 Figure 6 Figure 10 Figure 11 Figure 12 A Figure 12 Old Figure 13 Figure 14

Claims (1)

[Claims] 1. The first and second rotating magnetic heads 12, 11 having different operating gap directions are operated by a common electro-mechanical transducer 20 at different positions with respect to the track width direction and the track length direction. supported, these first
When the second rotating magnetic heads 12 and 11 rotate at any time, a video signal is recorded on the magnetic tape 3 by the first rotating magnetic head 12 as a first track T_2, and the video signal is recorded by the second rotating magnetic head 11 as a first track T_2. The above video signal and the first
the pilot signal, the video signal and the second pilot signal are adjacent to the first track T_2, and
Each track is alternately recorded as the second track T_1, and at the next rotation of the above rotation, the first track T_1 is recorded alternately.
A device for reproducing a recorded magnetic tape 3 on which a part of the first track T_2 recorded by the rotating magnetic head 12 of the magnetic tape is overlaid by the second rotating magnetic head 11, When reproducing a signal, the second rotating magnetic head 11 reproduces the video signal from the second track T_1, and the first rotating magnetic head 12 reproduces the video signal from the second track T_1 on both sides adjacent to the first track T_2. The video signal and the first and second pilot signals are reproduced from the second track T_1, and the levels of the reproduced first and second pilot signals are compared with each other at any time to obtain a tracking error signal. By supplying a tracking error signal to the electro-mechanical transducer 20, the first and second rotating magnetic heads 12, 11
A magnetic reproducing device in which automatic tracking of the second rotating magnetic head 11 is performed by displacing the position of the magnetic head in the width direction of the first and second tracks T_2 and T_1.