JPS5944698B2 - The most important thing to do - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording in which information signals are sequentially recorded and reproduced by a rotating magnetic head in the running direction of a magnetic tape or as a recording locus inclined at a certain angle (not including 90°) with respect to the running direction. A reproducing apparatus is configured such that a magnetic head accurately scans a recording track during reproduction.

In recent years, in order to increase the recording density of magnetic tapes, there has been a trend to sufficiently narrow the width of recording tracks.

In particular, the width of the recording track in a rotary head type magnetic recording/reproducing device (hereinafter referred to as VTR) is narrow, and it is necessary to control the magnetic head so that it accurately scans over the recording track during reproduction. For this reason, the tracking servo system shown in FIG. 1 has been considered as a tracking servo system for controlling the rotary head to accurately scan the recording locus during reproduction in a VTR.

In FIG. 1, during recording, from the recorded video signal applied to terminal 6, only the vertical synchronization signal is removed by synchronization separation circuit T, and the frequency is divided into + by frequency divider 8, and the R contact of switch 9 is A control signal is recorded on the magnetic tape 1 by the control head 10.

Further, one end of the output of the frequency divider 8 is applied to the sample and hold circuit 12 through the R contact of the switch 11. On the other hand, the rotational phase of a rotary head disk 14 having rotating magnetic heads 13, 13' is detected by a detection head 15 using a magnet 14' provided on the head disk 14, and the detection signal is amplified by an amplifier 16, and then In addition to the monostable multicircuit IT with a stable period, it is converted into a pulse signal with a predetermined time width. The pulse signal is shaped into a trapezoidal wave by the trapezoidal wave shaping circuit 18 and input to the sample hold circuit 12, where the phase is compared with the signal obtained from the frequency divider 8 and a voltage corresponding to the phase difference is held. .
The output signal of the sample hold circuit 12 passes through a phase compensation filter 19, is current-amplified by a DC amplifier 20, and is applied to an electromagnetic brake 21 provided on the rotating shaft of the head disk 14.
added to. On the other hand, the motor 22 is one that rotates synchronously with a commercial power supply, and a capstan 25 is driven by a pulley 23 and a belt 24 to transport the magnetic tape 1. Further, the rotary head disk 14 is driven by the pulley 26 and the belt 21, and due to the diameter difference between the pulley 28 and the pulley 26, the rotation is set in advance to be higher than a predetermined rotation, and the magnitude of the phase difference is Accordingly, the electromagnetic brake 21 applies the brake, and the elasticity of the belt 27 reduces the rotation of the rotary head disk 14, thereby changing the rotation phase of the rotary head disk 14.
This is to perform phase synchronization control with the phase of the vertical synchronization signal of the recorded video signal. Next, explaining the reproduction system, the control signal reproduced from the control head 10 passes through the P contact of the switch 9, is amplified by the amplifier 29, is applied to the monostable circuit 30 having a metastable period, and is sent to a monostable circuit 30 having a predetermined time width. is converted into , passes through the P contact of switch 11,
It is added to the sample and hold circuit 12.

The sample and hold circuit 12 compares the rotational phase of the rotary head disk 14 and the phase of the reproduction control signal, and holds a voltage corresponding to the phase difference. The output of the sample hold circuit 12 passes through the phase compensation filter 19 in the same manner as described above, is amplified by the DC amplifier 20, and is applied to the electromagnetic brake 21, which controls the rotational phase of the rotary head disk 14 in phase synchronization with the phase of the reproduction control signal. do.
In this way, by reproducing the same conditions during reproduction as during recording, the rotating magnetic heads 13, 13' can scan the magnetization recording locus. However, if the magnetic tape 1 is slightly displaced in the direction perpendicular to the running direction, the rotating magnetic heads 13, 13' will scan the recording magnetization trajectory even though the control signal is reproduced at the conventional timing. Since it is not possible to do so, so-called track deviation occurs. The present invention provides a control system that can obtain good tracking even when the magnetic tape deviates in a direction perpendicular to its running direction, as described above.One embodiment of the present invention will be described below with reference to the drawings. Explain.

FIG. 2 shows an embodiment of the present invention, and FIG. 3 shows a waveform diagram of important points thereof. In FIG. 3, when a video signal to be recorded is input to the terminal 6 during recording, the synchronization separation circuit 7
extracts only the vertical synchronizing signal from the recorded video signal, passes it through the frequency divider 8, passes through the switch 31, 3Vf) R contact, and the extension lines of each head gap intersect with each other obliquely, and the magnetic tape The magnetic tape 1 is supplied to first and second magnetic heads 33 and 34, which are provided at fixed positions at predetermined angles in opposite directions with respect to the longitudinal direction of the magnetic tape 1.
recorded as a control signal. Further, a part of the output signal of the frequency divider 8 is shaped into a signal having a predetermined pulse width by a monostable multi-circuit 32 having a metastable period, and then applied to the sample-and-hold circuit 12. Rotating head disk 1 having rotating magnetic heads 13, 13' on the other hand
4 is detected by the detection head 15, the detected signal is amplified by the amplifier 16, added to the monostable multi-circuit 17 having a metastable period, converted to a pulse signal having a predetermined time width, and then converted to a pulse signal having a predetermined time width. The wave shaping circuit 18 shapes the signal into a trapezoidal wave. This shaped trapezoidal wave signal is input to the sample and hold circuit 12, where the phase is compared with the signal obtained from the frequency divider 8, and a voltage corresponding to the phase difference is held. The output signal of the sample hold circuit 12 passes through a phase compensation filter 19, is current-amplified by a DC amplifier 20, and is applied to an electromagnetic brake 2 provided on the drive shaft of the disk 14.
Added to 1. One drive shaft of the disk 14 is set to be rotatable at a higher rotation speed than a predetermined rotation speed via a pulley 26, a belt 27, and a pulley 28 by a motor 22 that is synchronously driven by a commercial power source. The rotational phase of the rotary head disk 14 is changed by applying a brake using the electromagnetic brake 21 in accordance with the phase difference between the two signals applied to the circuit 12, and reducing the rotation of the rotary head disk 14 by the elastic sliding of the belt 27. Phase synchronization control is performed to the phase of the vertical synchronization signal of the recorded video signal.

Further, the rotary head disk 14 can be moved up and down by an eccentric cam 36 connected to a motor 35, and during recording, a position detection voltage obtained from a potentiometer 37 linked to the eccentric cam 36 and a switch 40R contact are used. The applied reference voltage 38 is compared with a voltage comparison circuit 39, and the motor 35 is driven so that the two voltages are the same. Next, the time of reproduction will be explained.

In FIG. 2, the reproduction control signals (FIG. 3A, b) obtained from the first magnetic head 33 and the second magnetic head 34 are transmitted through the P contacts of the switches 31 and 31' to the amplifiers 41 and 34, respectively. 41'. A monostable multi-circuit 42 having a metastable period is triggered by the output signal of the amplifier 41, and a pulse signal (third
Fig. 3c) is obtained, and the monostable multi-circuit 43 having a metastable period for synchronous phase adjustment is triggered at the falling edge of the trailing edge of the output, and its output (Fig. 3g) is sampled through the P contact of the switch 11. The signal is supplied to the hold circuit 12. In the sample and hold circuit 12, the rotational phase of the rotary head disk 14 is detected by the detection head 15 (see Fig. 3h).
), the signal is amplified by the amplifier 16, shaped into a pulse signal of a predetermined time width (Fig. 3 1) by the monostable multi-circuit 17, and further shaped into a trapezoidal wave (Fig. 3 j) by the trapezoidal wave shaping circuit 18. The phases are compared and a voltage (k in Fig. 3) corresponding to the phase difference is held. The output signal of the sample and hold circuit 12 passes through a phase compensation filter 19, is amplified by a DC amplifier 20, and is applied to an electromagnetic brake 21, which brakes the rotation of the head disk 14 and changes the rotational phase of the rotary head disk 14 to a second phase. Phase synchronization control is performed with the phase of the reproduction control signal obtained from the magnetic head 34. Furthermore, in addition to the loop for performing the phase synchronization control, a monostable multicircuit 44 having a predetermined metastable period is triggered by the output signal of the amplifier 4V,
The output (FIG. 3e) is input to the sample and hold circuit 45.

On the other hand, a part of the output signal c of the monostable multi-circuit 42 is shaped into a trapezoidal wave (FIG. 3 d) by the trapezoidal wave shaping circuit 47, and the output signal c of the monostable multi-circuit 42 is shaped by the trapezoidal wave shaping circuit 47 into a trapezoidal wave (FIG.
The phase is compared with the phase of the trailing edge falling part of the output signal e of No. 4, and the voltage (third
Figure f) is retained. The output signal f of the sample and hold circuit 45 passes through the P contact of the switch 40 and is sent to the voltage comparison circuit 39.
The voltage is compared with the position detection voltage obtained from the potentiometer 37, and according to the error voltage, the motor 35 is driven, and the eccentric cam 36 moves the rotary head disk 14 up and down, and the sample and hold circuit The movement stops when the voltage is balanced with the voltage obtained from 45. Fourth
The figure shows a pattern diagram recorded on the magnetic tape 1 with the configuration shown in FIG.
, a magnetic tape 1 recorded by a rotating magnetic head
There is a magnetization locus 4 that obliquely intersects with the magnetic tape 1, and control signals 5 and 7 are recorded on the control track 5 by the first magnetic head 33 and the second magnetic head 34 at the bottom of the magnetic tape 1.

FIG. 5 shows a state in which the first magnetic head 33 and the second magnetic head 34 have a predetermined angle to each other and are arranged at fixed positions. The normal case is the same for both time and playback, and the opening shows a state in which the magnetic tape 1 is shifted downward during playback.

In other words, if the running position of the magnetic tape 1 is normal, the recorded control signal 5' is reproduced by the first magnetic head 33 and the second magnetic head 34 at the same timing, but as shown at the beginning of FIG. When the running position of the magnetic tape 1 shifts downward, the reproduction control signal is reproduced from the first magnetic head 33 with a time delay from the second magnetic head 34.

Conversely, when the magnetic tape 1 shifts upward (not shown), the reproduction control signal is reproduced by the second magnetic head 34 with a time delay from the first magnetic head 33. As described above, the first magnetic head 33 and the second magnetic head 3
4, a positional deviation in the vertical direction of the running of the magnetic tape 1 can be detected as a reproduction time deviation of the reproduction control signal. FIG. 3 is a timing diagram when the magnetic tape 1 runs at a normal position, while FIG. 6 shows waveforms at various parts when the running of the magnetic tape 1 deviates downward during reproduction.

As is clear from FIG. 5, when the magnetic tape 1 shifts downward, the control signal b' is reproduced by the first magnetic head 34, and the control signal a' is reproduced by the second magnetic head 33 with a time delay. Ru. Therefore, Fig. 6 a',
A signal as shown in b' is obtained from the first magnetic head 33 and the second magnetic head 34, and at the falling edge of the output signal e' of the monostable multi-circuit 44, the output signal d' of the trapezoidal wave shaping circuit 42 is Since the rising slope portion is sampled and the potential thereof is held, a voltage corresponding to the amount of movement in the direction perpendicular to the running direction of the tape, indicated by E2 in FIG. 6f', can be obtained. In response to E2, the voltage comparison circuit 39 compares the height position detection voltage of the rotary head disk 14 obtained from the potentiometer 37, and depending on the error, the motor 35
The eccentric cam 36 causes the disk 1 to rotate.
By adjusting the height of 4, the rotating heads 13, 13' are aligned with the magnetization locus 4.
I'm trying to scan the top.

Furthermore, in FIG. 2, the monostable multicircuit 44 is designed so that when the relative position of the control track 5 with respect to the video track 3 deviates when performing TR compatible playback, it can be manually adjusted to the best point. This is intended to absorb product variations due to precision errors.

In the embodiment, the rotating head disk is moved up and down as a means for controlling the relative position between the rotating magnetic head and the magnetic tape. The same effect can be obtained by doing the following.

As described above, according to the present invention, tracking defects caused by differences in tape running positions during recording and playback can be eliminated.

Furthermore, the present invention utilizes the control signals necessary for the VTR, and performs control by detecting the phase difference between the reproduction control signals from two magnetic heads having different azimuth angles. control can be expected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional tracking control system, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a waveform diagram of the same operation, and FIG. 4 is a block diagram showing an example of a conventional tracking control system. FIG. 5A is a diagram showing the relationship between the control head and the control signal as the tape position changes, and FIG. 6 is an operation waveform diagram for explaining the operation of the present invention. 1... Magnetic tape, 11... Vertical synchronizing signal separation circuit, 13, 13t... Rotating head (information reproducing head), 33, 34... Magnetic head (
first and second magnetic heads), 35...motor,
36... Eccentric cam, 37... Potentiometer, 39... Voltage comparison circuit, 41,4V
......Amplifier, 42,44...Monostable multi-circuit, 45...Sample and hold circuit, 4
6...Trapezoidal wave shaping circuit.

Claims (1)

[Claims] 1. During recording, information signals are sequentially recorded as recording trajectories inclined with respect to the longitudinal direction of the magnetic tape by a rotating magnetic head, and head gaps having head gaps inclined in mutually opposite directions with respect to the longitudinal direction of the magnetic tape are used. A control signal of a constant frequency is recorded in the longitudinal direction of the magnetic tape by the first and second magnetic heads, and during reproduction, the phases of the reproduction control signals from both the magnetic heads are compared, and the magnetic A tracking control device for a magnetic recording/reproducing device, characterized in that the relative positional relationship between a tape and the rotating magnetic head in a direction perpendicular to the longitudinal direction of the magnetic tape is controlled.