JPS6126148B2 - - Google Patents

Description

[Detailed Description of the Invention] In a so-called helical scan type VTR (magnetic recording and reproducing device), the magnetic tape is transferred at a standard speed (for example, 4.0 cm/sec) and at a slower speed (for example, 2.0 cm/sec). It can be used by switching between two speeds.

In such an apparatus, recording tracks Tr and control tracks Tc are formed on the tape in patterns as shown in FIGS. 1A and 1B, respectively. In the figure, at standard speed, the track width (=head width) of A is 38 μm, and the track pitch is 58.5.
A guard band of approximately 20 μm is provided between each track. On the other hand, at slow speed B, the trunk pitch is halved to 29.2 μm, so the head width is wider than the track pitch. is removed when recording the next track, the guard band between the tracks disappears, and the track width (=track pitch) becomes narrower.

Further, in each control track Tc, an alternating signal (control signal) having a predetermined phase is recorded with respect to the formation position of the track Tr at a rate of one period for every two tracks.

During playback in this device, each tape is transported at a predetermined speed, and an alternating signal from the track Tc is played back, and the rotational phase of the rotary head drum is controlled according to the phase of this signal to rotate the recording track Tr. So-called tracking is performed to match the reproduction scanning trajectories of the heads.

By the way, in such a device, the positional relationship between the control head that records and reproduces signals on the control track Tc and the rotary head device depends on the assembly accuracy during manufacturing, so there may be variations depending on the product. be. For this reason, there is no problem when recording and playing back with a single device, but tracking is required when playing back tapes recorded on other devices or when playing back commercially available recorded tapes. Sushi may not be completed completely.

Therefore, conventionally, a so-called tracking volume has been provided for manually correcting the tracking. Using this tracking volume, for example, the amount of delay of a variable delay circuit provided in the reproduction signal path of the control signal from the track Tc is controlled, and the phase of the reproduction control signal is controlled to correct tracking. ing.

However, as described above, in a device that is used by switching between two speeds, if a correction width of ±30 μm is provided for the standard speed, for example, the necessary delay amount is 16 m sec. On the other hand, if a correction is made for a slow speed with the same amount of delay, the transfer speed is halved, so the correction width decreases at the same rate to ±15 μm.

In this case, since the installation error between the control head and the rotating head device is an absolute length, if the above-mentioned method is used, there is a risk that the correction will be insufficient at low speeds.

On the other hand, if the delay amount is set to 32 m sec, for example, in order to obtain a sufficient correction width at slow speeds, the correction width at standard speeds will be ±60 μm.
Such a wide correction range is unnecessary, and the amount of change in tracking increases with the rotation angle of the tracking volume. This results in misalignment, making it difficult to correct tracking.

Furthermore, if the tape transport speed changes midway, for example from a standard speed to a slow speed, the tracking correction width at that point will be changed.
However, since the amount of tracking deviation on the tape is constant, the tracking must be corrected again at that point.

In view of these points, the present invention has a simple structure that allows a constant correction width to be obtained at all times regardless of the tape transport speed.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 2, signals recorded on a magnetic tape 1 are reproduced by a rotary head device 2 and outputted to an output terminal 4 through a reproduction circuit 3.

Further, 10 is a capstan mechanism for transporting the tape 1, and 11 is a capstan motor.The rotational speed of this motor 11 is controlled to carry out transport servo for the tape 1. That is, motor 1
1 is provided with a frequency generator connected to the generator 12, from which an alternating signal Sf as shown in FIG. 3A is provided.
is taken out. This signal Sf is, for example, 360Hz at standard speed and 180Hz at slow speed. This signal Sf is then supplied to the waveform shaping amplifier 13 and converted into a rectangular wave signal Sp as shown in FIG. 3B. This signal Sp is supplied to the monostable multivibrator 14 for delay to form a signal Sd as shown in FIG. A signal S _n1 as shown in D is formed. This signal S _n1 is then supplied to the trapezoidal wave signal generation circuit 16 to generate a trapezoidal wave signal St as shown in FIG. 3E, and this signal St is supplied to the sampling hold circuit 17.

On the other hand, the signal Sp from the amplifier ₁₃ is supplied to the monostable multivibrator 18 for gate pulse formation to form the gate signal S _g1 as shown in FIG. Ru.

Furthermore, the control signal recorded on the control track Tc is reproduced by the control head 21, and the reproduced signal from this head 21 is supplied to the waveform shaping amplifier 22 to be converted into a rectangular wave signal Sc.This signal Sc is composed of a frequency discrimination circuit. The signal is supplied to a circuit 31 that discriminates between standard speed and slow speed.
This discrimination signal is then supplied to the time constant control circuit 32 of the vibrator 15 and the gain switching circuit 33 of the trapezoidal wave signal generation circuit 16.

Therefore, in this circuit, when the speed is standard, a voltage at the level indicated by a is taken out from the sampling and hold circuit 17 as shown on the left side of FIG.
9 to the motor 11.

On the other hand, when the speed is slow, the discrimination circuit 3
1, the time constant of the multivibrator 15 is lengthened as shown on the right side of FIG. 3, and the level of the output signal St of the generating circuit 16 is lowered. From the sampling hold circuit 17 for this purpose, b
A voltage at a level shown by is taken out, and this voltage Vb
is supplied to the motor 11 through the amplifier 19.
Note that FIG. 3 shows a state in which the servo is engaged.

In this circuit, when the rotation of the motor 11 slows down, the period of the signal Sp from the amplifier 13 becomes longer, and the timing of generation of the gate signal S _g1 becomes slower. For this reason, sampling hold circuit 1
The level of the voltage taken out at step 7 is increased, the rotation of the motor 11 is accelerated, and the rotation of the motor 11 is servoed to a predetermined speed. Even when the rotation of the motor 11 becomes faster, the rotation of the motor 11 is similarly slowed down, and the rotation of the motor 11 is servoed to a predetermined value.

Then, at levels a and b, the motor 11 rotates at the standard speed and slow speed, respectively, and the multivibrator 15 is operated to stabilize the servo in this state.
, the gain of the generating circuit 16 and the amplifier 19
The gain of is set.

Further, the signal Sc from the amplifier 22 (see FIG. 4A) is supplied to the monostable multivibrator 23 for duty setting to form the signal Su shown in FIG. 4B, and this signal Su is sent to the integrating circuit 24. A signal Si as shown in FIG.
is supplied to

On the other hand, a 30 Hz reference oscillator 41 is provided, and a signal So as shown in FIG. The discrimination signal from the discrimination circuit 31 is supplied to the monostable multivibrator 42 for track shifting, and the discrimination signal from the discrimination circuit 31 is supplied to the multivibrator 42 for slow speed and reproduction only, as shown in FIG. 4E. A shift signal Ss is formed, and at other times a signal So from the oscillator 41 is generated.
is directly taken out to the output side of the multivibrator 42.

Then, this signal Ss or So is transmitted to the discrimination circuit 3.
The signal is supplied to the contact N on the standard speed side of the switch circuit 43 controlled by the discrimination signal from 1, and is also supplied to the monostable multivibrator 45 whose delay amount is controlled by the tracking volume 44. A signal S _n2 as shown in Figure F is formed,
This signal S _n2 is supplied to the contact S on the slow speed side of the switch circuit 43. And this switch circuit 4
The signal from 3 is linked to the volume 44, and the vibrator 4 is connected to the volume 46 having the same characteristics.
The signal S _n3 is supplied to the monostable multivibrator 47 whose delay amount is controlled in exactly the same way as the gate pulse forming signal S _n3 as shown in FIG. is supplied to the gate signal S as shown in FIG. 4H.
_g2 is formed, and this signal S _g2 is supplied to the sampling and holding circuit 25.

Therefore, in this circuit, a voltage at a level c corresponding to the phase difference between the signal Sc from the amplifier 22 and the signal So from the oscillator 41 is taken out from the sampling and hold circuit 25, and this voltage V _c is converted into a DC voltage with a predetermined gain. The signal is supplied to the time constant control circuit 32 through the amplifier 26. Note that FIG. 4 shows a state in which the servo is engaged.

In this circuit, when the phase of the signal Sc is early, the level of the voltage V _c becomes high, the time constant of the multivibrator 15 is lengthened, the rotation of the motor 11 is slowed down, and the phase difference between the signal Sc and the signal So becomes a predetermined value. The servo for transporting the tape 1 is performed so that the value is the same. Even when the phase of the signal Sc becomes late, the rotation of the motor 11 is accelerated in the same way, and the tape 1 is rotated so that the phase difference between the signal Sc and the signal So becomes a predetermined value.
The servo transfer is performed.

Then, at level c, the phase difference between the signal Sc and the signal So becomes a predetermined value, and the gain of the amplifier 26 and the like are set so that the servo becomes stable in this state.

Further, reference numeral 51 is a drum motor for rotating the rotary head device 2, and rotation phase servo of the rotary head device 2 is performed by controlling the rotation of this motor 51. That is, a pulse generator 52 is provided on the rotating shaft of the motor 51, and its output signal is supplied to the phase comparator circuit 54 through an amplifier 53, while the signal from the oscillator 41 is supplied to the phase comparator circuit 54 through a monostable multivibrator 55 for delay. supplied to,
This comparison output is supplied to the drum brake coil 57 through the amplifier 56.

Therefore, in this circuit, the signal Sc and the signal So have a predetermined phase difference, and the head drum is adjusted so that the rotary head device 2 scans almost along the recording track with the tape 1 transport speed servo applied. rotational phase servo is performed.

When the tracking is corrected using this circuit, the tracking volumes 44 and 46 are controlled to control the delay amount of the multivibrators 45 and 47.

That is, by controlling the amount of delay of the multivibrators 45 and 47, the phase of the signal So from the oscillator 41 is controlled. Here, the servo for transporting the tape 1 is performed so that the phase difference between the signal So and the signal Sc becomes a predetermined value, so by changing the phase of the signal So as described above,
The servo for transporting the tape 1 is also activated at a position shifted by an amount corresponding to the amount of delay. On the other hand, the rotational phase of the rotary head device 2 is always in a predetermined phase with the signal So from the oscillator 41. , tracking correction is performed.

In this case, when the speed is standard, the delay is performed only by the multivibrator 47, whereas when the speed is slow, the multivibrator 4
The delay is performed by both 5 and 47.

Therefore, in this circuit, the volumes 44, 4
When turning 6, the rate of change in the amount of delay is twice as much at slow speeds as at standard speeds,
Since the transport speed of tape 1 is halved, the amount of correction on tape 1 is equal. That is, for example, if the maximum delay amount at standard speed is 16 m sec, a maximum delay amount of 32 m sec can be obtained at slow speed, and in either case, a correction width of ±30 μm can be obtained.

In this way, tracking can be corrected, but according to the present invention, when the speed is slow, the amount of delay is twice as much as when the speed is standard, so the tracking can be corrected regardless of the tape transport speed. , a constant correction width can always be obtained, a sufficient correction width can be obtained even at slow speeds, and good correction can be performed at standard speeds.

In addition, in the above circuit, the multivibrator 42, 4
5 are both needed only at slow speeds, so
Multivibrator 42 to Multivibrator 4
5 may be included.

Furthermore, the present invention is not limited to reducing the tape transport speed to 1/2; for example, if the tape transport speed is reduced to 1/3, the amount of delay may be tripled, that is, the tape transport speed may be reduced to 1/3. When the transfer speed is set to 1/n, the same effect as described above can be obtained by increasing the delay amount by n times.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a tape pattern, FIG. 2 is a system diagram of an example of the present invention, and FIGS. 3 and 4 are waveform diagrams for explaining the same. 11 is a capstan motor, 21 is a control head, 31 is a tape speed determination circuit, 44,
46 is a tracking volume, 45 and 47 are monostable multivibrators, 51 is a drum motor,
52 is a pulse generator.

Claims (1)

[Claims] 1 In an apparatus for reproducing video signals from a recorded tape driven at a plurality of tape transport speeds, a first signal indicating the rotational phase of a rotary head device and a first signal obtained by reproducing a control signal recorded on the tape are used. Tracking servo is performed based on the phase difference between the first signal and the second signal.
a first tracking volume that arbitrarily controls a relative phase difference with the signal; and a first tracking volume that increases the relative phase difference by N times when the tape transport speed is reduced to 1/N. A video signal reproducing device characterized by being provided with a second interlocking tracking volume.