JPS6126129B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is intended to solve the problems that arise when the rotary magnetic head of a VTR is made movable, for example.

In a helical scan type VTR, slow motion playback of 1/N can be performed by setting the tape speed during playback to 1/N (N≠0) during recording.

First, let's explain an example of such a VTR with reference to FIG.

In Fig. 1, during recording, the luminance signal is input terminal 11 → AGC amplifier 12 → clamp circuit 1
It is supplied to the FM modulation circuit 16 through the line 3 → pre-emphasis circuit 14 → dark and white clip circuit 15, and is converted into an FM signal.
The FM signal is supplied to the rotary magnetic heads 1A and 1B through the recording amplifier 17 and the recording side contact R of the recording/reproducing switch 31.

The heads 1A and 1B have an angular spacing of 180 degrees from each other, and are rotated by a motor 4 at a frame frequency, and the magnetic tape 2 is kept diagonally constant over an angular range of just over 180 degrees with respect to the rotational surface of the heads 1A and 1B. be driven at high speed.

Also, at this time, the rotation of heads 1A and 1B is as follows:
It is synchronized to the luminance signal by a servo circuit 40. That is, the luminance signal from the amplifier 12 is supplied to the synchronization separation circuit 41 to extract the vertical synchronization pulse, and this pulse is supplied to the frequency division circuit 42 and divided into pulses at the frame frequency, and this pulse is used for recording. The signal is supplied to the phase comparison circuit 43 through the recording side contact R of the reproduction changeover switch 32. Further, a pulse generating means 44A is provided on, for example, the rotating shaft 3 of the heads 1A and 1B.
One pulse is taken out for each rotation of A and 1B, and this pulse is supplied to the comparison circuit 43 through the shaping amplifier 45A.

Then, the comparison output of the comparison circuit 43 is
6 to the motor 4, and the heads 1A, 1
The rotation of B is synchronized with the luminance signal.

Therefore, as shown in FIG. 2, one field of the FM signal from the amplifier 17 is sequentially recorded diagonally on the tape 2 as one magnetic track 5.

In this case, by selecting the rotation radius of the heads 1A, 1B and the running speed of the tape 2, the position of the horizontal synchronizing pulse Ph on the track 5 is aligned on a line orthogonal to the track 5, so-called horizontal synchronizing alignment. will be held.

Further, the frequency-divided pulse from the frequency dividing circuit 42 is transmitted to the magnetic head 4 through the recording amplifier 47 and the recording side contact R of the recording/reproducing switch 33.
Control pulse Pc during playback
is recorded on the side edge of tape 2.

Recording of the luminance signal is performed as described above.

On the other hand, during normal playback, the tape 2 is run at the same speed as during recording, and the control pulse Pc is played back from the tape 2 by the head 48, and this pulse Pc is transmitted from the playback side contact P of the switch 33 to the playback amplifier. The signal is supplied to the comparison circuit 43 through the line 49→normal playback contact N of the normal playback/slow playback switch 61→playback contact P of the switch 32. Therefore, the tracking servo of the heads 1A and 1B with respect to the track 5 is performed, the heads 1A and 1B scan the track 5 in the same relationship as during recording, and the FM signal is reproduced from the track 5.

Then, the FM signal from the heads 1A and 1B is transferred from the playback side contact P of the switch 31 to the playback amplifier 2.
1→Demodulation circuit 23 through the limiter 22 line
is supplied to demodulate the luminance signal, and this signal is
Output terminal 25 through de-emphasis circuit 24
It is taken out.

Furthermore, for example, during 1/3 slow motion reproduction, the tape 2 is run at 1/3 the recording speed. At this time, the control pulse Pc from the head 48 has a frequency that is 1/3 that of recording, so the pulse Pc from the amplifier 49 is supplied to the multiplier circuit 51 and multiplied by 3, that is, the original frame frequency is This pulse Pc passes through the slow playback side contact S of the switch 61, and further passes through the contact P of the switch 32.
The signal is supplied to the comparison circuit 43 through.

Therefore, heads 1A and 1B have track 5 as 3
Since it repeatedly scans one time at a time, 1/3 is applied to terminal 25.
A luminance signal of slow motion reproduction is extracted.

In this way, slow motion playback is possible with this VTR, but in this case, the tape 2 is run continuously at 1/3 of the recording speed, so the scanning trajectories of heads 1A and 1B at this time are:
A trajectory 6 is shown by a broken line in FIG. 3, which is inclined with respect to the track 5 by 1/3 of the pitch Tp of the track 5, and the trajectory 6 shifts parallel by 1/3 Tp for each scan.

Therefore, when the position of the locus 6 is illustrated with the position of the track 5 as a reference (as the horizontal axis of the graph), it becomes as shown by a solid line in FIG. 4A.

However, when the heads 1A and 1B draw such a trajectory 6, the trajectory 6 spans two tracks 5 or deviates greatly from the track 5, so that the luminance signal reproduced in those parts guard band noise and a reduction in S/N.

Therefore, in the VTR shown in FIG. 1, this tracking deviation during slow motion reproduction is corrected.

That is, in FIG. 5, reference numeral 81 indicates a substantially band-shaped electrostrictive element, one end of which is attached to a substrate 83 with, for example, an adhesive 82, and the heads 1A and 1B are attached to the open end with, for example, an adhesive. In this case, the element 81 is attached by
When a voltage is supplied to this, it is made to bend in its thickness direction 85 in accordance with its polarity and level, and this thickness direction 85 is connected to the heads 1A and 1B.
head 1A, 1 so that it is in the direction of the track width.
B is supported.

The substrate 83 is arranged substantially parallel to the element 81 in a plane perpendicular to the thickness direction 85.
A, 1B, and an element 81 is provided at the free end.
A stopper 84 is attached, for example, with an adhesive, to the portion facing the . This stopper 84 is
It is made of a rigid body or an elastic body having some elasticity, such as a synthetic resin material, and as shown in FIG. 5B, a gap of a predetermined size is provided between the stopper 8 and the element 81.

On the other hand, the electrostrictive element 81 is configured as shown in FIG. 6, for example. That is, 81A and 81B indicate piezoelectric bending bimorph plates, which are formed into a substantially band shape, with the thickness direction 85 being the polarization direction, and the polarization directions being, for example, opposite to each other. In addition, a thin plate 81c of the same shape serving as an electrode and reinforcing member is sandwiched between these and bonded to each other using, for example, a cyanoacrylate monomer adhesive. And bimorph board 81
An electrode 81E is formed on each remaining surface of A and 81B by plating, for example, and a terminal 81F is taken out from the electrode 81E.

The heads 1A and 1B are attached to this element 81 as shown in FIG.
This is the track width direction of A and 1B, and the stopper 84 is positioned in this direction.

Then, these heads 1A and 1B are 180 degrees apart from each other.
The substrate 83 is mounted on a rotating drum (not shown) with an angular spacing of .degree. and rotated by the motor 4 at the frame frequency.

Additionally, a tracking correction circuit 50 is configured. That is, for example, as shown in FIG. 1, another pulse generating means 44B is provided for the rotary shaft 3, and from this, one pulse is generated every one rotation of the heads 1A, 1B.
and 1 for the pulse from means 44A.
A pulse shifted by a field period is extracted, and the pulse is passed through a shaping amplifier 45B to an OR circuit 52.
At the same time, the pulse from the amplifier 45A is supplied to the OR circuit 52, which outputs a pulse Pg every field period in synchronization with the rotation of the heads 1A and 1B as shown in FIG. 4B.
is taken out.

Then, this pulse Pg is supplied to the staircase wave signal forming circuit 53, and at the same time, as shown in FIG. A staircase wave signal (or a sawtooth wave signal may also be used) Sk whose level changes in three steps in synchronization with the pulses Pg and Pc is formed from the forming circuit 53 as shown in FIG. 4C, and this signal Sk is the adder circuit 5
5 → amplifier 56 → slow playback contact S of normal playback/slow playback switch 62 → playback contact P of recording/playback switch 34 through the electrostrictive element 8 that supports heads 1A and 1B.
1 and 81, respectively.

Therefore, the elements 81, 81 are deflected in the polarization direction 85 according to the polarity and level of the signal Sk, so that the heads 1A, 1B are displaced in the track width direction, and the heads 1A, 81 corresponding to the track 5 are displaced in the track width direction. The scanning locus 1B is a locus 6 shown by a broken line in FIG. 4A. That is, although the scanning trajectories 6 are inclined with respect to the track 5, they intersect each other at their centers and the trajectories 6 become parallel to each other.

Furthermore, the pulse Pg from the OR circuit 52 is supplied to the sawtooth wave signal forming circuit 54 to form a sawtooth wave signal Ss synchronized with the pulse Pg as shown in FIG. 4D. The signal is supplied to the elements 81 and 81 through the line 55→amplifier 56→switch 62→switch 34.

Therefore, since the elements 81 and 81 are further deflected by the signal Ss, the scanning locus 6 with respect to the track 5 is
(the slope shown by the dashed line in FIG. 4A) is corrected so that the trajectory 6 coincides with the track 5, that is, the heads 1A and 1B scan the track 5 correctly.

In this way, even during slow motion playback,
Correct tracking is performed and therefore the S/N is good. Also, a slow motion playback screen without guard band noise can be obtained.

However, with only the above configuration, as shown in FIG. 5, the element 81 is plate-shaped or strip-shaped, and the heads 1A and 1B are attached to the free ends of the element 81, so that the heads 1A and 1B are connected to the tape during recording. The element 81 vibrates or bends in the thickness direction 85 due to friction with the head 2, and as a result, the heads 1A, 1B vibrate or are displaced in the track width direction. It is distorted and formed.

Furthermore, during normal reproduction, the heads 1A and 1B may not scan the track 5 in a straight line for the same reason.

This invention attempts to solve such problems.

Therefore, in the present invention, the stopper 84 is provided as explained in FIG. 5, and during recording, voltage is supplied to the element 81 to forcibly press the open end of the element 81 against the stopper 84. Do it like this.

That is, in the VTR shown in FIG. 1, a DC power supply 71 is provided, and the DC voltage from the DC power supply is supplied to the normal reproduction side contact N of the switch 62 and also to the recording side contact R of the switch 34.

According to such a configuration, during recording, the power source 7
1 is supplied to the elements 81, 81 through the contact R of the switch 34, so that the elements 81, 81 are deflected and their open ends are pressed against the stops 84, 84. Therefore, due to the initial stress of the elements 81, 81 and the repulsive force of the stoppers 8, 8 opposing this, the elements 81, 81
The open end of will be held in a fixed position and will not vibrate or displace. Therefore, since the heads 1A and 1B are also held at fixed positions, the track 5 is formed in a straight line.

In addition, even during normal playback, the power source 71 connects the element 8.
Since voltage is supplied to heads 1 and 81, heads 1A and
1B scans the track 5 in a straight line.

Note that when recording is performed by displacing the heads 1A and 1B toward the stopper 84 in this way, the track 5 is formed shifted parallel to the track width direction from the original position shown in FIG. (that is, the positional relationship between the control pulse on the tape 2 and the track 5 is shifted), and when such a tape 2 is played back on a general VTR, a tracking shift occurs.

Therefore, in the VTR shown in Figure 1, head 1
The mounting positions of A and 1B with respect to the rotating drum are corrected in advance in the track width direction, and head 1
When a track 5 is formed with A and 1B displaced toward the stopper 84, the track 5 is brought to its original position.

The same applies to normal playback, but
During slow motion reproduction, the switch 63 is switched from the normal reproduction side contact N to the slow reproduction side contact S to change the delay time of the amplifier 49, so that the tracking correction by the signals Sk and Ss can be performed correctly as described above. be made into

Thus, according to the invention, the heads 1A, 1
Even if tracking correction is performed during slow-motion playback by using B as a movable type, when recording, head 1
Since the open end of the element 81 supporting A and 1B is pressed against the stopper 84, the track 5 can be formed correctly in a straight line.

In the above description, the present invention is applied to a tracking correction device during slow motion playback, but it can also be applied to a time axis error correction device during playback.

That is, in that case, heads 1A and 1B
is attached to the elements 81, 81 such that the track width direction thereof is the deflection direction 85 of the element 81.

Further, the time axis error correction circuit 90 may be
It is configured as shown in the figure. That is, the luminance signal from the de-emphasis circuit 24 is supplied to the sync separation circuit 91 to extract the horizontal sync pulse Ph, this pulse Ph is supplied to the PLL 92 to extract the error voltage based on the frequency fluctuation of the pulse Ph, and this The voltage is applied to the element 8 supporting the heads 1A and 1B through the amplifier 93 and the playback contact P of the recording/playback switch 34.
1,81.

Therefore, during reproduction, the heads 1A and 1B are displaced in the longitudinal direction of the track 5, and the time axis error of the reproduced luminance signal is corrected.

Also in this VTR, during recording, the DC voltage from the power supply 71 is supplied to the elements 81, 81 through the recording side contact R of the switch 34,
The open ends of 1 and 81 are pressed against stoppers 84 and 84. Therefore, at the time of this recording, heads 1A,
1B is held in a fixed position and does not vibrate or displace in the length direction of the track 5, so
No time axis error occurs during recording.

As described above, according to the present invention, even when the heads 1A and 1B are movable and various corrections are made during reproduction, the tracks 5 can be formed correctly during recording.

Note that during playback, when the scanning positions of the heads 1A and 1B in the width direction of the track 5 are detected, and the heads 1A and 1B are displaced in the width direction of the track 5 based on the detection signal, automatic tracking of the heads 1A and 1B is performed. This invention can also be applied to the following.
In addition, the positions of heads 1A and 1B are corrected during recording,
It can also be applied when holding a fixed position during playback. Furthermore, the element 81 may be an electromechanical transducer such as a magnetostrictive element.

Further, instead of the stopper 84, a Q damper material having appropriate elasticity may be provided between the open end of the element 81 and the substrate 83, and this may be used as a damper as well as a stopper.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of this invention, FIGS. 2 to 4 are diagrams for explaining its operation, FIGS. 5 and 6 are diagrams showing an example of essential parts of this invention, and FIG. The figure is a system diagram of another example of this invention. 1A and 1B are magnetic heads, 81 is an electrostrictive element, 8
4 is a stopper.

Claims (1)

[Claims] 1 comprising a magnetic head, an electromechanical transducer, a stopper, and a power source, the electromechanical transducer movably supporting the magnetic head;
A magnetic head device, wherein a voltage is supplied from the power source to the electromechanical transducer for a predetermined period of time to bring the electromechanical transducer into contact with the stopper, thereby displacing the magnetic head to a predetermined position.