JPS6032259B2 - recording/playback machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In general, the rotating magnetic head of a VTR (video tape recorder) fluctuates slightly in the direction of the rotation axis during rotation due to mechanical errors, etc., so it does not scan the tape in a straight line, but instead scans in a non-linear manner. Perform a specific scan.

The scanning non-linearity of this rotating magnetic head is unique to each machine, that is, VT
The tendency is determined for each R, and the fluctuations are not sudden, but a gentle sine wave of 1/2 skin length or 1 wavelength as the rotating head scans from one end of the tape in the width direction to the end of the tape. Met.

That is, for example, if the tape 1 is scanned from one end of the tape 1 in the width direction to the other end in one rotation of the rotary head,
This head performs a non-linear scan as shown by a broken line 3 in contrast to a linear scan as shown by a solid line 2 in FIG.

In this way, since the rotating head of each VTR has different scanning characteristics, when playing a recorded tape recorded on another VTR, the recording is performed along the length of the tape at one end in the width direction of the tape. control signal and a predetermined rotational angle &
Even if so-called tracking control is performed, in which the rotational speed of the rotary head or the tape speed is controlled using the pulses obtained at the As mentioned above, from one end of the width direction to the other end, non-linear scanning is performed depending on the machine, so there is a risk that the rotating head may scan in a state that is far off from each track in the middle of each track. , correct playback is not possible. Therefore, if the non-linear scanning characteristics of the rotary head are corrected for each VTR so that the scanning characteristics are always linear, the above-mentioned drawbacks can be avoided.

The present invention was invented from this point of view.

By the way, in a VTR, the tape is always wound at the same position on the droplet surface of the guide drum, so the scanning locus of the rotary head on the tape is always the same for the same VTR. Therefore, if the scanning characteristics of the rotary head on the tape are made linear, the above-mentioned drawbacks can be eliminated.

Therefore, in the present invention, the rotary head is made movable in a direction perpendicular to its rotation direction, and the rotation period of the rotary head with respect to the tape 1, that is, in the example of FIG. For each section, the rotary head is moved in the direction of the rotation axis so that it scans on the solid line 2 in FIG. 1, so that the rotary head always scans almost linearly over the tape 1. It is something to do.

Hereinafter, an example of a recording/reproducing apparatus according to the present invention will be described, in which the rotary head scans from one end of the tape in the width direction to the other end in one rotation, and the one rotation is divided into four sections. Let's take this as an example and explain it with reference to FIG.

In the present invention, an electromechanical transducer such as a bimorph plate is used to enable the rotating magnetic head to move in a direction perpendicular to its rotation direction.

To explain this bimorph plate, for example, as shown in FIG. 2A, it consists of a plate 4 made of a piezoelectric element on which metal electrodes 4a and 4b are attached by plating or the like on both sides, and a metal electrode 5a on both sides. , 5b are attached, and the surface on which the metal electrode 4b is attached and the surface on which the metal electrode 5a is attached are bonded together. In this case, the directions of polarization in the plates 4 and 5 are selected to be the same in the thickness direction as shown in the figure, and a voltage is applied as shown in FIG. When an electric field is applied in the direction of electrode 4b, plate 4 is displaced in the longitudinal direction as shown by the arrow due to the piezoelectric effect, and plate 5
When an electric field is applied in the direction from the electrode 5b to the electrode 5a, the plate 5 is displaced in the longitudinal direction as shown by the arrow due to the piezoelectric effect. Therefore, the bimorph plate bends as shown in FIG. 2B, and its displacement corresponds to the magnitude of the electric field, and if the direction of the electric field is reversed, the direction of displacement will also be reversed. In addition, as shown in FIG. 2C, plates 4 and 5 made of Shoelectric elements are pasted together so that their polarization directions are opposite to each other, and no voltage is applied to electrodes 4a and 5a, and electrode 5b is Applying the via column B, which changes from 0 to Vo to the electrode 4b, the drive voltage E is applied to the electrode 4b.In the cerebellum, as shown in Figure 2, the cerebellum /dimorph board' It will be displaced, and it will be displaced in the opposite direction from the entertainment to the large and small sea bream criticism.

Then, one end of such a bimorph board (for example, the configuration shown in FIG. 2C) is fixed to the substrate 6 with an adhesive 7 as shown in FIGS. 3A and 3B, and a magnetic head 8 is attached to the other end of the bimorph board.
Attach.

In addition, plate pieces 9a and 9b stand on the side surface of the bimorph plate near the other end of the bimorph plate, and damper members 10a and 10b are inserted between the plate pieces 9a and 9b and the side surface of the bimorph plate. The plate pieces 9a and gb stand upright from the slope 11, and the slope 11 is molded integrally with the substrate 6. Then, the wires derived from each electrode of the bimorph plate are shown in Figure 2C.
When a predetermined voltage is applied as shown in FIG. 3, the magnetic head 8 attached to the free end of the bimorph plate is displaced in the direction of its rotation axis, as shown by the arrow in FIG. 3B. Then, by appropriately adjusting the voltage supplied to the bimorph plate in each section, the scanning characteristics of the head are corrected.

FIG. 4 shows a voltage control circuit coupled to the bimorph board, 12 is a charging/discharging capacitor, 13 is a field effect transistor, the source of which is grounded through a resistor 14.
Its drain is connected to a power supply terminal 15 from which a positive direct current can be obtained, and the voltage charged in the capacitor 2 is supplied to the gate of the field effect transistor 13, and from the source side, the voltage charged in the capacitor 2 is 2C with the rotating head 8 installed.
The drive voltage ED is supplied to the bimorph plate 16 having the configuration shown in FIG.

Reference numerals 17, 18, 19, and 20 designate transistors constituting a constant current circuit, and these transistors also have reverse characteristics such that a constant current flows from the emitter side to the collector side.

The collectors of these transistors 17 to 20 are
The emitters of these transistors 17 to 20 are connected in common to the respective sliders of variable resistors 21, 22, 23, and 24, which are provided in parallel between the power supply terminal and the ground terminal. The connection point is connected to the connection point between the gate of the field effect transistor 3 and the capacitor 2.

Further, 25 is a pulse generator attached in relation to the head 8, which generates a pulse PG (
FIG. 5A) is obtained, which is integrated with the switching signal forming circuit 26, and from which the rotating head 8 is connected.
The signal S,, S2 becomes "1" for each 1/4 period of one rotation of the signal S, and the period in which it becomes "1" Z is sequentially shifted.
. Then, a standard tape on which a signal of a certain level is recorded and a reference track T with good linearity is formed as shown in Fig. 1 is prepared, and this standard tape is applied to the head 8 with so-called tracking servo applied. The variable resistors 21 to 24 are adjusted so that the level of the reproduced signal at the end point of each 1/4 rotation section 7, 72, 3, 74 becomes constant.

In this case, since the tracking servo is applied, if the head 8 is in the position to correctly reproduce the track T at the starting point Po of the track T, at this point the charging voltage of the capacitor 12 will be M reduction 1 A sword with an electric marking.

has been done.

If this continues, the rotating head will be P,,P2,P3
, P4, but by adjusting the variable resistors 21 to 24 as described above, in section 7,
The voltage obtained across the slider of variable resistor 21 is
2 becomes higher than the voltage charged in variable resistor 21.
A constant charging current determined by the resistance value on the power supply terminal side flows from the slider to the capacitor 12, and the gate voltage EG of the field effect transistor 13 rises at a constant slope according to the current value, as shown in FIG. 5F. However, in the section 72, the voltage obtained at the slider of the variable resistor 22 becomes even higher.
A constant charging current determined by the resistance value on the power supply terminal side flows from the slider of the variable resistor 22 to the capacitor 12, and the voltage of the field effect transistor 13 rises with a constant slope corresponding to this. In sections 73 and 4, the voltages obtained at the sliders of variable resistors 23 and 24 are selected to be lower than the charging voltage of the capacitors, so a constant discharge current flows in each section, and each has a constant slope depending on the current value. Then, the gate voltage of the field effect transistor 13 decreases.

Then, a voltage corresponding to the voltage EG changing in this way is taken out from the source side of the field effect transistor 13 and supplied to the bimorph plate 16.

Therefore, the rotary head 8 moves in the direction of its rotational axis in response to the voltage EG, and thus moves so as to scan substantially on the track T. That is, the rotating head scans the tape in a straight line. After adjusting the variable resistors 21 to 24 in this way, the transistors 17 to 20 are turned on every quarter rotation period of each rotation, and the gate voltage EG of the field effect transistor 13 is always as shown in FIG. Since something like F is obtained, the head always scans in a straight line.

In this way, according to the present invention, the non-linearity of the VTR's scanning is corrected and the VTR performs straight, straight scanning.
Even when playing back tapes recorded on other VTRs, if the tracking servo is applied using a control signal, the recorded tracks will always be scanned correctly and no track deviation will occur.

In addition, even when playing back a tape recorded with a VTR with non-linear scanning characteristics, linear scanning is performed, so
There is also the advantage that there is no risk of large track shifts and that playback can be performed at a playback level above a certain level.

Further, in the present invention, since the adjustment is made for each machine when manufacturing the VTR, there is no need for any subsequent adjustment.

In the above example, the transistors 17 to 20 are operated in the saturation region and the variable resistors 21 to 24 are adjusted, but it is possible to operate the transistors 17 to 20 in the active region without using the variable resistors. , the current value may be changed by changing the peak values of the signals S, -S4 supplied to the bases thereof, respectively.

In the above example, there are four adjustment points, but the linearity can be further improved by appropriately selecting this number depending on the non-linearity of the scanning of the rotary head.

Note that the above example is an example in which the tape is scanned from one end of the tape in the width direction to the other end in one rotation of the rotary head. Even when two rotating heads are configured to scan from one end of the tape in the width direction to the other end in half a rotation, each rotating head is attached to an electromechanical transducer and the direction of the rotation axis is The aircraft can be made into the same aircraft by dividing the two-way section into several sections, each of which is half a rotation.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, FIGS. 2 and 3 are diagrams for explaining an example of essential parts of the present invention, FIG. 4 is a circuit diagram of an example of the control system, and FIG. The figure is a waveform diagram for explaining the same. 1 is a tape, 8 is a rotating magnetic head, 16 is a bimorph plate, 17-20 are transistors for switching, 21-
24 is a variable resistor for current adjustment, and 26 is a switching signal forming circuit. Leopard 1 Illustration Key 2 Illustration Traditional 3 Illustration Key 4 Illustration 5

Claims (1)

[Claims] 1. A recording medium of the rotating head, which includes a rotating head that is attached to an electromechanical transducer and is movable in the direction of the rotational axis according to the voltage supplied to the electromechanical transducer, and a capacitor for charging and discharging. The connecting section to is divided into a plurality of sections, and the charging current or discharging current supplied to the capacitor is changed for each of the plurality of divided sections,
In the contact section of the rotary head with the recording medium, a voltage corresponding to the charging voltage obtained in the capacitor is supplied to the electromechanical transducer, so that the rotary head linearly scans the recording medium. A recording and reproducing machine designed to do this.