JPH0349133B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a tracking control device,
The present invention relates to a tracking control device that controls tracking of a recorded track by a magnetic head using a mechanical transducer.

BACKGROUND TECHNOLOGY In recent years, magnetic playback devices (including magnetic recording and playback devices) that play back video signals recorded on tracks tilted in the longitudinal direction of a magnetic tape have been increasing their playback speed, such as still playback, high-speed playback, and reverse playback. Some devices are equipped with a tracking control device that allows the recorded track pattern to be accurately scanned even when the track pattern is changed. This tracking control device attaches a playback video head to a rotating cylinder using a bimorph element (an electromechanical transducer), and applies voltage to the bimorph element to displace the video head in a direction perpendicular to its rotating surface. This system enables accurate tracking of recorded track patterns during special playback such as still playback, high-speed playback, and reverse playback where the tape running speed is different from that during recording.

Problems to be Solved by the Invention The scanning locus during playback is obtained by vector composition of the tape velocity vector and the video head rotational velocity vector.

In a conventional tracking control device, a tape speed pattern signal as shown in FIG. 2B is generated in synchronization with a playback control signal as shown in FIG. 2A, which is tape velocity vector information. This tape speed pattern signal is for double speed playback, and the pattern tip voltage is - during normal playback.
V _T , pattern tip voltage during reverse 1x speed playback
This is V _T. Furthermore, the still pattern signal shown in FIG. 2D is generated in synchronization with the head switching pulse shown in FIG. 2C, which is the rotation speed vector information of the video head. By combining the tape speed pattern signal and still pattern signal described above, a drive pattern signal shown in FIG. 5E is generated. This drive pattern signal corresponds to the bimorph element of one video head, and a drive pattern signal with a waveform delayed by 1/2 cycle of the signal shown in FIG. 2E is generated for the bimorph element of the other video head. .

However, since the drive pattern signal shown in FIG. 2E has a negative average voltage, the piezoelectric sensitivity of the bimorph element deteriorates, and a hysteresis phenomenon occurs in which the displacement of the bimorph element does not return to the zero position even when the applied voltage is zero. This poses a problem of decreased stability and reliability, such as the occurrence of

For this reason, in the conventional device, during double speed playback, the signal shown in Figure 2B is delayed by 1/4 period and the second
By combining with the signal in Figure D, a drive pattern signal with an average voltage close to zero was generated. In this case, a delay circuit is required to generate a pseudo head switching pulse by delaying the head switching pulse shown in FIG. 2C by 1/4 period. Furthermore, since the tape speed pattern becomes a positive voltage during reverse playback, it is not possible to generate a drive pattern signal for reverse playback simply by delaying the tape speed drive pattern, and furthermore, the average voltage of this drive pattern signal is In order to make it zero, a complicated signal processing circuit is required. As described above, the conventional apparatus required a dedicated signal processing circuit for each different playback speed, resulting in problems such as increased costs and deterioration of the stability and reliability of the apparatus.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a tracking control device that solves the above problems by providing a drive pattern generating means and a tape position varying means.

Means for Solving the Problems The device of the present invention uses drive pattern generating means to
A triangular wave drive pattern signal whose height value corresponds to the reproduction speed and whose average level is zero is generated, and the tape running position is made to correspond to the reproduction speed by means of a tape position variable means.

Effect: In the device of the present invention, the driving pattern generating means generates a triangular wave driving pattern signal whose average value level is zero at a peak value corresponding to the reproduction speed,
A corresponding voltage is applied to the electro-mechanical transducer, and the magnetic head is displaced in a direction perpendicular to its rotating surface. Further, the tape position varying means adjusts the phase of the recorded track on the tape relative to the electromechanical transducer in accordance with the reproduction speed.

Embodiment FIG. 1 shows a block system diagram of an embodiment of the apparatus of the present invention. In the figure, each of 1 and 2 is a bimorph element as an electro-mechanical conversion element, one end of each is fixed to a rotating cylinder 3, and a free end of each bimorph element 1 and 2 has a video signal having the same -azimuth angle. Heads 4 and 5 are attached respectively. Furthermore, each of 34 and 35 is a conventional fixed video head with opposite azimuth angles. Further, reference numeral 6 denotes a magnet for detecting the rotational phase of the video heads 4 and 5, and the same magnet for detecting the position and phase is also fixed at a position at a rotational angle of 180 degrees of the rotary cylinder 3, and these magnets 6 are detected by a sensor 7. be done. The rotating cylinder 3 is rotated at high speed in the direction of arrow A by a DC motor 8. The DC motor 8 is provided with a frequency generator 9.
The frequency signal outputted by the drum servo circuit 10 and the rotational phase detection signal from the sensor 7 are respectively supplied to a drum servo circuit 10. The drum servo circuit 10 includes a reference oscillator 11.
A reference signal is supplied from The drum servo circuit 10 receives a frequency of 30Hz, for example, from the rotational phase detection signal.
A head switching pulse is generated, and the trapezoidal wave generated from this head switching pulse is sampled with a reference signal divided by a frequency of 30 Hz. The phase error signal obtained by this is mixed with the rotation speed signal obtained by F-V converting the rotation speed signal and supplied to the drive circuit 12, and the drive current generated here is supplied to the DC motor 8. As a result, the rotation speed and rotation phase of the rotary cylinder 3 are controlled.

The magnetic tape 13 wound around the rotating cylinder 3 is pressed against a rotating capstan 14 and a pinch roller (not shown) and is caused to travel in the direction of arrow B. The capstan 14 is rotationally driven by a DC motor 15, and a frequency signal from a frequency generator 16 provided in the DC motor 15 is supplied to a capstan servo circuit 17. Further, a control signal reproduced from the magnetic tape 13 by the control head 18 and a reference signal passed from the reference oscillator 11 through the drum servo circuit 10 are supplied to the capstan servo circuit 17. Further, a speed instruction signal generated by the reproduction speed instruction section 19 is supplied to the capstan servo circuit 17.

When the speed instruction signal instructs normal reproduction, the capstan servo circuit 117 samples a trapezoidal wave generated from a signal obtained by frequency-dividing the reference signal with a pulse obtained by shaping the control pulse to obtain a rotation phase signal. A rotational speed signal obtained by F-V converting the frequency signal is mixed and supplied to the drive circuit 20, and the drive current generated here is supplied to the DC motor 15 to control the rotational speed and rotational phase of the capstan 14. is controlled. The operation of the capstan servo circuit 17 during special reproduction will be described later.

The head switching pulse generated by the drum servo circuit 10 described above is supplied to a triangular wave oscillation circuit 22 in a drive pattern generation circuit 21. Further, the speed signal from the reproduction speed instructing section 19 is supplied to a triangular wave oscillation circuit 22 and a bias application circuit 23 that constitute the drive pattern generation circuit 21 . Triangular wave generation circuit 2
1 outputs a ground level signal at all times without generating a triangular wave when normal playback is instructed, and switches to fixed video heads 34 and 35. In addition, during double-speed playback, in synchronization with the head switching pulse shown in Figure 3A, the rising edge of the head switching pulse is 0V, and the falling edge is a voltage of -V _T (-V _T is the voltage that moves the video head vertically downward from its rotating surface). A triangular wave shown by the solid line in Figure 3B, which indicates the voltage to be applied to the bimorph element in order to displace the bimorph element by one track pitch (for example, 58 μm), and a triangular wave whose phase is delayed by 180 degrees from this triangular wave. generate. Further, during quadruple speed reproduction, as shown by the broken line in FIG. 3B, a triangular wave whose voltage is -3V _T at the fall of the head switching pulse and a triangular wave whose phase is delayed by 180 degrees are generated. Furthermore, during still playback, as shown by the dashed line, a triangular wave symmetrical to the solid triangular wave that becomes the voltage V _T at the fall of the head switching pulse, and a triangular wave whose phase is delayed by 180 degrees are generated. A triangular wave signal output from the triangular wave oscillation circuit 22 is supplied to a bias application circuit 23. The bias application circuit 23 sets the bias voltage to 0V during normal playback and always outputs a voltage of 0V, and switches to the fixed video heads 34 and 35 to perform normal playback. Voltage during double speed playback
Generate a bias voltage of 0.5V _T and superimpose it on the triangular wave shown by the solid line and the triangular wave whose phase is delayed by 180 degrees, to obtain the triangular wave drive pattern signals shown by the solid lines Ia and b in Figure 3 C and D, respectively. high voltage amplifier 2
4 and 25 respectively. In addition, during 4x speed playback, a bias voltage of 1.5V _T is generated and superimposed on the triangular wave shown by the broken line and the triangular wave whose phase is delayed by 180 degrees, thereby generating triangular wave drive pattern signals shown by the broken lines a and b, respectively. do. Furthermore, during still playback, a bias voltage of -0.5V _T is generated and superimposed on the triangular wave shown by the dashed-dotted line and the triangular wave whose phase is delayed by 180 degrees from this.
Triangular wave drive pattern signals indicated by b are generated. In this way, each drive pattern signal output from the bias application circuit 23 has a peak value that corresponds to the reproduction speed, and an average value of 0V.

mutually outputted from the bias application circuit 23
Two triangular waves with 180 degrees different phase are high voltage amplifier 2
4 and 25, respectively, and the conductive brush 2
The voltage is applied to the bimorph elements 1 and 2 through the slip rings 6 and 27 and the slip rings 28 and 29, respectively. As a result, when a high voltage corresponding to the voltage V _T is applied, the bimorph elements 24 and 25 respectively displace the video heads 4 and 5 by one track pitch (=58 μm) perpendicularly above their rotational surfaces, and −
When a high voltage corresponding to V _T is applied, each of the video heads 4 and 5 is displaced one track pitch perpendicularly below its rotating surface, and the vertical position of each video head 4 and 5 relative to the rotating surface is changed according to the applied voltage. Displace.

During normal reproduction, the capstan servo circuit 17 samples a trapezoidal wave generated from a reference signal as shown in FIG. 4A using a reproduced control signal as shown in FIG. 4B. During double speed playback, the playback control signal is frequency-divided by 1/2 to obtain the same signal as shown in Figure B. This signal is delayed by a predetermined time by a monostable multivibrator whose time constant is varied by the speed instruction signal, and as shown in Figure C, the sampling pulse is delayed by a time corresponding to 1/2 track pitch with respect to the sampling pulse during normal playback. is obtained, and the phase of tape 13 is delayed by 1/2 track pitch. During 4x speed playback, the phase of tape 13 is 1/2
You can only advance by track pitch. Also, during still playback, the capstan servo circuit 17 advances the tape a predetermined distance from the control signal recording position.
Tape running is stopped at a position where the phase of the tape 13 has advanced by 1/2 track pitch. In this way, the phase of the recorded track on the tape 13 with respect to the bimorph element is set to a value corresponding to each reproduction speed.

During double speed playback, bimorph elements 1 and 2
Assuming that no voltage is applied to the tape 13, for example, the video head 4 scans the matte finish V surrounded by the dashed line on the tape 13 in FIG. 5A. The scanning start point of the video head 4, which is the lower end of the satin area V, is delayed by 1/2 track pitch from the recording start point of the previously recorded track due to the above-mentioned capstan servo, and the scanning end point is the position delayed by the recording start point of the previously recorded track. The position will be 1/2 track pitch ahead of the ending point.
However, in bimorph element 1, the solid line Ia in FIG.
As shown in FIG. 5, a voltage of 0.5 V at the scan start time _{T 1} and a voltage of -0.5 V at the scan end time _{T 2} is applied, so that the bimorph element 1 has a voltage of 0.5 V at the scan start time T 1 and a voltage of −0.5 V at the scan end time T ₂ . A is displaced by 1/2 track pitch in the direction of arrow C, and by 1/2 track pitch in the direction of arrow D at scanning end time _T2 , thereby causing the video head 4 attached to the bimorph element 1 to move the recorded track. Accurately scan and reproduce.
At time _T2 , the video head 4, which is displaced by 1/2 track pitch in the direction of arrow D, is at the next scanning start time.
By _T3 , the track pitch is displaced by 1/2 in the direction of arrow C. In this way, the voltage applied to the bimorph element 1 changes linearly between times T ₁ and T ₂ and between times T ₂ and _{T 3} , and the applied voltage does not change suddenly as in the conventional case. Vibrations are prevented from occurring. This also applies to the bimorph element 2. In addition, since the average voltage of the drive pattern signal is 0V, the bimorph element 1,
The deterioration of the piezoelectric sensitivity and the occurrence of hysteresis phenomenon in each of the two piezoelectric sensitivities are reduced.

Similarly, when playing at 4x speed, bimorph element 1
is not driven, video head 4 is
When scanning the matte area in FIG. 5B, a voltage obtained by amplifying the voltage waveform shown by the broken line a in FIG. 3C is applied to the bimorph element ₁ . A 3/2 track pitch is displaced in the direction of arrow E, and a 3/2 track pitch is displaced in the direction of arrow F at time _T2 , thereby accurately scanning and reproducing the recorded track.

Furthermore, when the bimorph element 1 is not driven during still playback, the video head 4 scans the satin area shown in FIG. Since the voltage is applied to the bimorph element 1, the video head 4
For example, at time _T1 , a _1/2 track pitch is displaced in the direction of arrow G in FIG.

In this way, once the playback speed is determined, a drive pattern signal is automatically generated based on the head switching pulse, so there is no need to provide a signal processing circuit for each different playback speed as in the past, and the device It is inexpensive, and stability and reliability are improved.

Note that the CPU is used as the drive pattern generation circuit 21.
It may be configured to use the rising and falling edges of the head switching pulse as a reference and generate the drive pattern signals shown in FIG. 3C and D in accordance with the speed instruction signal, but is not limited to the above embodiment .

Effects of the Invention As described above, the tracking control device according to the present invention generates a drive pattern signal according to the playback speed, so there is no need to provide many signal processing circuits that were conventionally required, and the circuit configuration is simple. Stability and reliability are improved at low cost, and since the drive pattern signal is a triangular wave with an average value of zero, it is possible to prevent deterioration of the piezoelectric sensitivity of the electro-mechanical transducer and the occurrence of hysteresis phenomenon, and it is possible to prevent the piezoelectric sensitivity of the electro-mechanical transducer from occurring. It has features such as being able to reduce unnecessary vibrations.

[Brief explanation of drawings]

FIG. 1 is a block system diagram of an embodiment of the device of the present invention, FIG. 2 is a waveform diagram for explaining the generation of drive pattern signals in a conventional device, and FIGS. 3 and 4 respectively show the device shown in FIG. 1. The signal waveform diagram of each part, FIG. 5, is a diagram for explaining the scanning state of the video head at each playback speed. DESCRIPTION OF SYMBOLS 11, 2... Bimorph element, 3... Rotating cylinder, 4, 5... Video head, 6... Magnet, 7
...Sensor, 8,15...DC motor, 9,16...Frequency generator, 10...Drum servo circuit, 11...Reference oscillator, 13...Tape, 14...Capstan,
17... Capstan servo circuit, 18... Control head, 19... Playback speed instruction section, 21... Drive pattern signal generation circuit, 22... Triangular wave oscillation circuit,
23...Bias application circuit, 24, 25...High voltage amplifier.

Claims (1)

[Claims] 1. A magnetic head is attached to the other end of an electro-mechanical transducer whose one end is fixed to a rotating cylinder, and a voltage according to a drive pattern signal is applied to the electro-mechanical transducer to cause the magnetic head to rotate on its rotating surface. A tracking control device for vertically displacing a recorded track on a tape, comprising a drive pattern generating means for generating a triangular wave drive pattern signal whose average level is zero at a peak value corresponding to a playback speed; A tracking control device comprising tape position varying means for varying the running position of the tape so that the phase of the recorded track on the tape with respect to the electromechanical transducer becomes a value corresponding to the reproduction speed.