JPS6255204B2 - - Google Patents

Description

[Detailed Description of the Invention] Recent video recording and playback devices (VTRs) are capable of
In addition to normal playback where the tape is played back at the same tape speed, V _T , still playback is performed with the tape stopped, slow motion playback is performed at a tape speed slower than V _T , and quick motion playback is performed at a speed faster than V _T . It is now possible to play back at various tape speeds, such as

By the way, during normal playback, the tape speed is the same as during recording, so tape 1 in the playback head
The inclination angle θ _P of the scanning trajectory above is the arrow 2 in Figure 1.
As shown by , the inclination angle θ _T of the recording track T is equal to the angle of inclination, and the reproducing head correctly scans the recording track.

However, the playback speed is the recording tape speed V _T
If the moving direction of the tape 1 is the direction of arrow 5 in the figure, the scanning direction of the playback head on the tape 1 will be the direction of arrow 3 if the tape speed is faster than V _T . If it is slow, it becomes as shown by arrow 4, and its inclination angle is different from the inclination angle θ _T of the recording track T, as shown by θ _S and θ _f , respectively.

Therefore, in this case, the playback head will scan across multiple recording tracks,
There is a drawback that the reproduced image becomes unsightly due to the influence of guard band noise and the like.

Therefore, the reproducing rotary head is mounted on an electrically controllable movable element such as a bimorph plate.
A method has been devised to ensure that the reproducing rotary head always scans the recording track T correctly.

First, I will explain about the bimorph plate.As shown in FIG. 2, this plate has metal electrodes 6 on both sides.
A plate 6 made of a piezoelectric element on which a and 6b are attached by plating etc., and metal electrodes 7a and 7b on both sides similarly.
It is formed by bonding a plate 7 made of a voltage element to which a metal electrode 6b is adhered, and a surface to which a metal electrode 7a is adhered, for example.

Here, the polarization directions of the plates 6 and 7 made of piezoelectric elements are aligned in the thickness direction, but if an electric field is applied in the same direction as the polarization direction, the plates 6 and 7 will become polarized due to the piezoelectric effect. The plates 6 and 7 change to extend in the longitudinal direction, and when an electric field is applied in the opposite direction to the polarization direction, the plates 6 and 7 change to shrink in the longitudinal direction. Therefore, for example, the plates 6 and 7 are pasted together so that their polarization directions are the same as shown in the figure, and each electrode is connected to the power source B as shown in FIG. An electric field is applied to the plate 7 in the direction from the electrode 6a to the electrode 6b, and an electric field is applied to the plate 7 in the direction from the electrode 6a to the electrode 6b.
If an electric field is applied in the direction from b to electrode 7a, the bimorph plate will be distorted as shown, and the displacement will depend on the magnitude of the voltage. Furthermore, if the direction of the electric field is reversed, the direction of displacement of the bimorph plate will also be reversed.

Therefore, one end of such a bimorph plate should be connected to the third
As shown in Figures A and B, by fixing the bimorph plate to the substrate 8 with adhesive 9, attaching the magnetic head 10 to the other end of the bimorph plate, and applying a voltage to the electrodes of the bimorph plate as described above, the magnetic head 10 can be As shown by the arrow in FIG. 3A, it is displaced in a direction intersecting the scanning direction.

In a VTR, the bimorph plate to which the magnetic head is attached is fixed to a rotating body, such as an upper drum, with the head 10 facing outward, and the head 10 is displaced in the direction of its rotation axis.

Therefore, depending on the amount of deviation between the scanning direction shown by arrow 2 in Figure 1 during normal playback and the scanning direction shown by arrow 3 or 4 in the same figure when playing at other tape speeds, By supplying a voltage, in this case a sawtooth wave voltage, to the bimorph plate, the rotating magnetic head will correctly scan one recording track T, resulting in a noise-free reproduced image. .

By the way, this electromechanical conversion element such as a bimorph has a hysteresis characteristic in its conversion characteristics. Therefore, even when the above correction operation is completed and the correction voltage is no longer supplied to the bimorph plate, the bimorph plate does not completely return to its original state, but remains in its original state with residual distortion. It will stop in a more biased state. This residual distortion becomes large when the amount of deflection of the bimorph plate (the amount of deflection of the head) is large, so there is a risk of large residual distortion after slow motion playback, still playback, or quick motion playback. .

However, when recording is subsequently performed after playback is completed and the above-mentioned correction operation is completed, if there is acid distillation distortion as described above, the scanning position of the magnetic head on the tape may not match the intended recording track. Therefore, the intervals between the recording tracks become misaligned, resulting in the inconvenience that one recording track overlaps the previous recording track.

For this reason, conventionally, the head mounted on the bimorph board is used only for reproduction, and the rotary head for recording is provided separately. Therefore, the number of heads increased accordingly, making the VCR expensive.

In view of the above-mentioned points, the present invention provides a magnetic recording and reproducing device that can detect the height position of a magnetic head with respect to a reference plane and control the height position to bring it to a predetermined position. This is what I am trying to do.

Hereinafter, an example of the magnetic recording/reproducing apparatus according to the present invention will be explained using a VTR for video signals as an example with reference to FIG. 4 and subsequent figures.

FIG. 4 shows the structure of an example of a rotary drum device for a VTR, which is an example of the device of the present invention.

In the figure, 11 is a fixed lower drum, 12 is a rotating drum, and 13 is a rotating shaft.

A bimorph plate 14 is provided on the lower surface of the rotating upper drum 12.
is attached by attaching its one end side to this lower surface, and this bimorph plate 1
The other end of 4 is a free end, and a magnetic head 15 is attached to this free end. In addition, the rotating upper drum 1
A recess 16 is formed on the lower surface of the bimorph plate 14 at the other end where the head is attached to the bimorph plate 14.
The other end of the bimorph plate 14 is a free end.

In the present invention, a pair of detection means for detecting the height position of the head 15 from the reference plane is provided.

In this example, the reference surface is the chassis 17, and the pair of detection means is one of which is the head 15 itself and the other is a magnetic head 18 fixed to the chassis 17.

That is, the magnetic head 18 is mounted on a stand 19 mounted on the chassis 17.

In this case, the head 18 is arranged at a position facing the rotating peripheral surface of the head 15.

In this example, during recording, the height position of the head 15 from the reference plane is detected by this pair of detection means, so that the head 15 is always at a predetermined height position with respect to the reference plane 17. It is something that will be done.

That is, during recording, a recording current is supplied to the head 15, and the magnetic flux from the head 15 is transferred to the head 15.
8 and the head 15 is detected by the detection output.
The height position of is detected.

Here, let's examine the actual output of the head 18.

First, the width direction of the gap g _A of head 15 is head 1.
When examining the case where the gap _gB is approximately parallel to the width direction of the gap gB, that is, when the heads 15 and 18 are arranged in the relationship shown in FIG. 5, an example of the output characteristics is shown in FIGS. 6A to C. obtained as. Figure 6A
is the change in output amplitude when the head 15 is vertically displaced at a position where the heads 15 and 18 exactly face each other. In reality, the head 15 is placed on a rotating body, so if the rotational phase is plotted on the horizontal axis,
The output amplitude has an output characteristic as shown in FIG. 6B. In FIG. 6B, the solid line indicates the case where the heights are exactly the same, and the dotted line indicates the case where the height is displaced in either the upward or downward direction.

By the way, in the output waveform of FIG. 6B,
The phase of the carrier is reversed between the central part and the parts on both sides. Therefore, by phase-detecting the carrier provided to the head 18 using the carrier given to the head 15, a change in phase can be detected. Then, by integrating the output of the phase detector, an output waveform as shown in FIG. 6C is obtained. In this figure as well, the solid lines indicate when the heights are exactly the same, and the dotted lines indicate when the heights are displaced either upward or downward.

Control signals can be created by using the properties of these waveforms, but in the case of the arrangement shown in Figure 5, the amplitude only changes regardless of the displacement in either the up or down direction, so it is not possible to directly measure the displacement. Information about the direction, ie, whether it is shifted upward or downward, cannot be obtained.

Next, as shown in FIG.
When the gaps g _A and g _B are arranged so that their width directions intersect with each other, the following characteristics are obtained.

That is, when arranged in this way, the head 18 when the head 15 is displaced in the height direction
The output changes as shown in FIGS. 8A to 8C. FIG. 8A shows a case where the heights are exactly matched, FIG. 8B shows a case where the heights are shifted downward, and FIG. 8C shows a case where the heights shift upward. In each figure, the horizontal axis indicates the rotational phase of the head 15.

As is clear from these Figures 8A to 8C, when the height position of the head shifts, the phase of the carrier is reversed depending on whether it is shifted upward or downward. The change in the amplitude of the portion differs between the left and right sides, and the phase of the waveform also changes.

In this case, the integrated output of the phase detector will change depending on the displacement direction as shown in Figure 9. Therefore, for example, if the sample pulse indicating the rotational phase is set at an appropriate position, , the control signal can be obtained directly.

FIG. 10 shows an example of a height position control circuit that uses the above-mentioned arrangement in which the heads 15 and 18 are arranged as shown in FIG. 7.

In FIG. 10, numeral 20 is a recording amplifier, from which a recording current is supplied to the head 15 during recording. When the head 15 rotates and faces the head 18, the magnetic flux from the head 15 is detected by the head 18, and the detection output is supplied to the reproduction amplifier 21. The output of this regenerative amplifier 21 is transmitted to the phase detector 22.
and phase detection is performed based on the recording signal from the recording amplifier 20. The phase detection output thus obtained is integrated by the integrating circuit 23 to obtain the waveform shown in FIG. 9.

On the other hand, a pulse generator 24 is provided to detect the rotational phase of the head 15. This pulse generator 24 is designed to obtain pulses by detecting magnetic flux from a magnetic piece attached to a rotating part to which the head 15 is attached. This pulse generator 2
The output of 4 is electrically adjusted by a monostable multivibrator 25 to match the rotational phase of the head 15, and then supplied to a sample pulse generation circuit 26 where it is converted into a sampling pulse. This sampling pulse is then supplied to the sample hold circuit 27, which causes the integration circuit 23 to
The output waveform of is sampled. In this case, the sample voltage changes according to the direction of displacement in the height direction, as shown in FIG. Therefore, this sample and hold voltage is supplied to the control signal generation circuit 28, from which a control signal is obtained, which is supplied to the bimorph 14 via the drive circuit 29.
Its displacement is controlled.

It should be noted that FIG. 10 shows only a diagram of the principle, and it goes without saying that a separate control circuit is required during reproduction.

FIG. 11 shows another example of the device of the present invention. In this example, the reference surface is the chassis 17, and one of the pair of detection means is the rotary head 15 itself. 2 magnetic heads 18
A and 18B are arranged at equal distances from the normal height position H _O of the rotary head 15 in a direction perpendicular to the scanning direction of the head 15.

In this case as well, the width direction of the gap _gA of the head 15 and the width direction of each gap of the heads 18A and 18B are arranged so as to intersect with each other.

In this way, for the head 15, the head 18A,
18B, the amplitude characteristics of the detection outputs of the heads 18A and 18B are symmetrical about the position Ho with respect to the deviation, so if the detection output levels of the heads 18A and 18B are equal, the head 15 It is at the correct height position Ho.

The example shown in FIG. 11 takes advantage of the above, and the output of the head 18A is supplied to one input terminal of the differential amplifier 32 through the regenerative amplifier 30.
The output of the head 18B is supplied to the other input terminal of the differential amplifier 32 through a reproducing amplifier 31 and an inverter 33. Therefore, the output of the differential amplifier 32 is zero when the head 15 is at the height of the position Ho, and when the height deviates from the position Ho, the output has a polarity according to the direction of the deviation.
A signal with a level corresponding to the amount of deviation is obtained. Then, the output of this differential amplifier 32 is supplied to the control circuit 28, and in the same way as the example shown in FIG. It is controlled so that the position is Ho.

In addition, in the case of this example, the gap g of the head 15
Almost the same effect can be obtained even if the width direction of head _A is arranged parallel to the width direction of the gap between heads 18A and 18B.

By the way, in the example shown in FIG. 4, there is only one recording/reproducing head, and since the tape is wound around the frequency of the drum, the pair of detection means is provided via the tape. 2 recording/playback heads
In the case of an apparatus in which more than one head is used, for example, two recording/reproducing heads 15a and 15 as shown in FIG.
If b is used, tape 1 is placed on the drum.
This tape 1 is not wrapped because it is wrapped around an angular range of 180 degrees.
The detection head 18 can be provided at any position within the 180 degree range. In this case, the magnetic flux from the heads 15a and 15b can be directly detected by the head 18 without using the tape 1.

FIG. 13 shows an example of a rotating magnetic head device according to still another example of the present invention, in which the reference surface is the lower surface 12a of the upper rotating drum 12, and the pair of detection means is a rotating magnetic head 15 for recording and reproducing. Two other heads 34 and 35 are used.

That is, as shown in FIG. 13, one head 34 is mounted on the bimorph plate 14, and the other head 35 is mounted on the lower surface 12a of the rotating upper drum 12.
The gap surfaces of both heads face each other, and the directions of the respective gaps intersect with each other.

For example, when controlling the height position during recording, the recording signal current is supplied not only to the head 15 but also to the head 34, the magnetic flux from this head 34 is detected by the head 35, and the detected output is Therefore, the bimorph plate 1 is created almost in the same way as in the previous case.
4 is controlled so that the head 15 is brought to a predetermined height position.

In this example, a pair of heads 34 and 35
Therefore, a detection output is always obtained, and the height position of the head 15 is continuously controlled regardless of the rotation of the head 15. Further, even when the rotating drum is stopped, the height position of the head 15 can be detected and controlled.

As described above, according to the present invention, the height position of the movable element, for example, the magnetic head provided on the bimorph plate, from the reference plane is detected, and the detected output is used to move the rotating magnetic head to a desired height. Since the head mounted on the bimorph board can be used not only for reproduction but also for recording, even if the bimorph board has hysteresis, recording can be performed without any problem.

Therefore, the magnetic head mounted on the movable element can be used for both recording and reproduction.

Although the above example is a case of a rotating magnetic head for recording and reproducing, it goes without saying that the device of the present invention can also be applied to a fixed magnetic head.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the relationship between the tape speed and the scanning locus of the rotating head on the tape, Figures 2 and 3 are diagrams for explaining the bimorph plate, and Figure 4 is a diagram for explaining the magnetic field according to the present invention. 5 to 9 are diagrams showing an example of a pair of detection means and their output characteristics,
FIG. 10 is a system diagram of one example of the height position control circuit of this invention device, FIG. 11 is a system diagram of another example of the height position control circuit of this invention device, and FIGS.
The figure shows another example of the rotating magnetic head device of the apparatus of the present invention. 11 is a fixed lower drum, 12 is a rotating upper drum,
14 is a bimorph plate, 15 is a magnetic head for video signals, 17 is a chassis, 18 is a magnetic head constituting one of a pair of detection means, and 34 and 35 are magnetic heads constituting a pair of detection means.

Claims (1)

[Scope of Claims] 1. A magnetic head attached to an electrically controllable movable element, and a magnetic head provided opposite to the magnetic head, to which a recording signal is supplied to the magnetic head during recording. and a control signal generator that controls the movable element according to the detection output from the detector. A magnetic recording/reproducing device configured such that the height position of the head is maintained at a predetermined height position.