JPH0469848A - Tracking circuit - Google Patents

Abstract

PURPOSE:To keep the normal tracking operation by controlling a capstan motor by the error signal of the time difference detected from the synchronizing signals read by two heads. CONSTITUTION:A timing pulse 60 is outputted when the envelope of a reproduced RF signal is maximum, and this pulse is outputted to gates 39 and 40 when a signal holding permission signal 83 rises. Signal holding circuits 41 and 42 hold a time error signal 57 when pulses are outputted from gates 39 and 40. Outputs 61 and 62 of signal holding circuits 41 and 42 are the errors for the best tracking states of head assemblies 23 and 24; and when the head assembly 23 is selected, the output 62 of the signal holding circuit 41 is selected and outputted and has the polarity inverted by an inverting amplifier 44 and is inputted to an adder 16 of a capstan control circuit 22 to cancel the error signal due to assembling errors or the like of head assemblies 23 and 24. Thus, an influence of assembling errors or the like upon tracking control is excluded to keep the normal tracking state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking circuit for a magnetic recording/reproducing device.

[Conventional technology]

FIG. 2 shows a schematic diagram of a head assembly used in a magnetic tape recording and reproducing apparatus that simultaneously records and reproduces information on two adjacent tracks. The two heads A and B have azimuth angles θ in opposite directions to reduce crosstalk from adjacent tracks.

Now, if we consider that the head is shifted downward by h with respect to the track on the tape during playback, then head A and
The phase difference d of the reproduction signal of head B is d==2・h −t
It is expressed as anθ. If the diameter of the drum to which this head is attached is D and the rotation speed is fd, then the time difference ΔT between the reproduced signals from head A and head B is ΔT=d/π
-fclD=2□1l-tanθ/yr -f d
-D, and it can be seen that it is proportional to h. therefore,
By controlling the magnetic tape feed speed so that this time difference is minimized, a normal tracking state can be maintained at all times.

FIG. 3 is a block diagram of an example of a conventional tracking circuit. 8 The magnetic heads 1 to 4 are arranged such that ], 3.2, and 4 respectively look at gaps of the same azimuth angle θ, and 1, 2, .
Head assemblies 23 and 24 are constructed by stacking the heads 3 and 4 perpendicularly to the running direction. The outputs of the magnetic heads 1 to 4 are amplified to appropriate levels by preamplifiers 5 to 6, respectively, and sent to changeover switches 9 and 10.

The head assemblies 23, 24 are mounted one to another on the outer circumference of the rotating drum.
They are attached at an included angle of 80 degrees, and during playback, a playback RF signal is output alternately every half rotation of the drum. The changeover switch 9.10 appropriately selects these reproduced RF signals with a head switching pulse 81 and outputs two consecutive reproduced RF signals 5] and 52 to the demodulators 11. ．． 12
Output to. The reproduced RF signal 51.52 is sent to the demodulator 11.1.
．． 2, and are sent to the signal processing section as reproduced signals 53.54, and are also input to the synchronization separation circuit 13.14, where the synchronization signals 55.56 of several tens of microseconds included in each reproduction signal are It is output to the time difference detector 15. The time difference detector 15 detects the time difference between synchronizations 55 and 56 and outputs an error signal 57. The capstan control circuit 22 to which the error signal 57 is inputted includes a capstan motor 18 that feeds the magnetic tape in the longitudinal direction, a frequency generator 19 that outputs a frequency that is proportional to the number of revolutions of the capstan motor 18, and a frequency generator that outputs a frequency that is proportional to the number of rotations of the capstan motor 18. an amplifier 20 that appropriately amplifies the output of the amplifier 19; a comparator 21 that receives the output of the amplifier 20 and the reference signal 82 and outputs a signal 58 proportional to the frequency difference; Adder 16
The capstan motor 18 is controlled so that the signal 58 from the comparator 21 is minimized; By controlling the rotational speed of the capstan motor 18 so that the error signal 57 caused by the error signal 57 is minimized, a normal tracking state can be maintained at all times.

[Problem to be solved by the invention]

In the conventional tracking circuit described above, due to head assembly errors etc., two overlapping heads 1 and 2 and 3 and 4 are
If the reproducing RF
Since the signal is reproduced with a deviation of ΔT'=d'/π・fd-D, it is as if h'=d'/'2-tanθ -F
Since the error signal 57 is output as if the tracking has deviated, there is a problem that a normal tracking state cannot be maintained even if it is held in a state where the tracking is shifted downward by h'.

[Means to solve the problem]

In the trunking circuit of the present invention, a plurality of head assemblies each having two heads having different azimuth angles and arranged perpendicularly to the running direction of the magnetic tape are mounted on the same outer periphery of a rotating drum at equal intervals from each other. The magnetic tape is wrapped around the outer periphery of the rotating drum so that the outer periphery of the rotating drum is in contact with a winding angle corresponding to the intervals at which the plurality of head assemblies are attached to the rotating drum from one end of the magnetic tape to the other end. The magnetic tape is wound diagonally, and the magnetic tape is wound in such a way that the trajectory of the head assembly on the magnetic tape moves by the head width of the head assembly in a direction substantially perpendicular to the trajectory every time the rotating drum makes a half rotation. Magnetic tape recording and reproducing that simultaneously records and reproduces two adjacent trackings by selecting the signal of one of the plurality of head assemblies that is in contact with the magnetic tape and using it for recording and reproducing while moving the tape in the longitudinal direction. detecting a time difference between two reproduced RF signals from the plurality of head assemblies of the apparatus;
Perform tracking control so that the time difference is minimized,
an envelope detector that outputs an envelope waveform of two reproduced RF signals from the plurality of head assemblies; a peak detector that outputs a pulse when the envelope waveform shows a maximum value; a time difference detector that inputs two reproduced RF signals and outputs a signal proportional to their relative time difference; an output pulse of the peak detector and an output signal of the time difference detector are input; a signal holding circuit that holds the output signal when a pulse is output;
The output pulse of the peak detector is configured to be applied to the signal holding circuit when one of the two head assemblies is in the best tracking state.6 [Embodiment] Next, the present invention will be described with reference to the drawings. explain. FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, when the magnetic tape recording/reproducing apparatus is in a reproduction state, reproduction RF signals output from magnetic heads 1 to 4 are appropriately amplified by preamplifiers 5 to 8, respectively.
At the same time, one of the signals (51 in FIG. 1) is selected by the changeover switch 9.10 and sent to the demodulator 11.12 as a reproduced RF signal 51.52 to the envelope detector 3.
Added to 5. Five envelope signals from envelope detector 35 are applied to peak detector 36, which outputs a timing pulse 60 when the envelope of the regenerated RF signal is at its maximum. This timing pulse 6
0 is input to the gate 37 and output to the gate 39.40 when the signal holding enable signal 83 rises. This signal holdable signal 83 is a signal that rises when it is guaranteed that the tape feed speed during playback is made faster or slower than during normal playback, and the tracking state is reached at least once during half a rotation of the rotating drum. For example, immediately after loading a magnetic tape or when using CUE/RE.
It is a confrontation with V, 5TILL, etc.

The other ends of the gates 39 and 40 receive a head switching pulse 81 and a signal of opposite polarity to the head switching pulse 81 from the inverter 38, respectively, and the gates 39 and 4
Timing pulses 60 are alternately output from one side of 0,
Each signal is sent to the signal holding circuit 4]1.42. Also,
Signal holding circuit 41, . 42 inputs the error signal 57, and holds the error signal 57 when a pulse is output from the three gates 40. At this time, there is a time when the best tracking state is reached at least once depending on the output conditions of the signal that can hold the signal, so if this is regarded as the time when the envelope of the reproduced RF signal reaches the maximum, the error signal 57 at that time will be transmitted to the head assembly 23. This is caused by an assembly error of .24. Therefore, the outputs 61 and 62 held by the signal holding circuits 41 and 42 are respectively
．． Since 24 is the value of the error signal 57 that occurs when the best tracking state is achieved, when the head assembly 23 is selected by the changeover switch 9.10, the output 62 held by the signal holding circuit 41 is selected by the switch 43. The signal is outputted, has its polarity inverted by the inverting amplifier 44, and is input to the adder 16 of the capstan control circuit 22, thereby canceling out error signals caused by assembly errors of the head assemblies 23, 24, etc.

In this way, it is possible to eliminate the influence of assembly errors of the head assemblies 23 and 24 on tracking control, and to maintain a normal tracking state at all times.

In this embodiment, the peak of the envelope of one of the reproduced RF signals is detected, but the timing pulse 60 is output when the envelopes of both reproduced RF signals are detected and both simultaneously indicate a good tracking state. You may also do so.

Further, in this embodiment, tracking control is performed by a gear bus stan motor, but it can be similarly performed by controlling the mounting height of the head assembly to the rotating drum using a piezoelectric actuator or the like.

〔Effect of the invention〕

As explained above, the present invention detects the time difference between two reproduction signals of a magnetic head read from adjacent tracks of a magnetic tape, performs tracking control so that the time difference is minimized, and eliminates mounting errors of the magnetic head. The resulting error signal is stored in advance, and the opposite polarity signal is applied to the gear bus control circuit during playback so that it can be canceled out. Even if the deviation in the running direction of the two magnetic heads is different between the recording head and the reproducing head or different from that of other devices, the present invention has the effect that a normal tracking state can always be maintained.

road, ], 5... time difference detector, ] 6 adder, 17...
Motor drive circuit, ]-8... Capstan motor, 1
9... Frequency generator, 20... Amplifier, 21... Comparator, 22... Capstan control [11'' path, 23. 4 head assembly, 35/envelope detector, 36...
Peak detector, 37, 39.40・Gate, 3844
...Inverter, 41.42...Signal holding circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
A schematic diagram of a head assembly used in a recording/reproducing device that records two adjacent docks simultaneously; Figure 3 is a block diagram of an example of a conventional dragging circuit; and Figure 4 shows tracking by head assembly with assembly errors. FIG. 2 is a schematic diagram showing a state in which a misalignment occurs.

Claims (1)

[Claims] A plurality of head assemblies in which two heads with different azimuth angles are arranged at track pitch intervals are mounted on the outer periphery of a rotating drum at equal intervals, and the two heads simultaneously record on two adjacent tracks of a magnetic tape. In a helical scan type magnetic recording and reproducing device that performs reproduction, the above-mentioned 2.
means for outputting first and second synchronization signals detected from the first and second reproduction signals read by the first and second heads;
and means for outputting an error signal of the time difference detected from the first or second synchronization signal, means for outputting a pulse signal when the first or second reproduction signal is at a maximum value, and storing the error signal using the pulse signal. A tracking circuit comprising means for holding the magnetic tape, and means for controlling a capstan motor for driving the magnetic tape using the error signal stored by the means and the error signal.