JPS622475B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking correction device for a rotary head type magnetic recording and reproducing device that uses a rotary head to sequentially record and reproduce signals as recording tracks inclined with respect to the longitudinal direction of a magnetic tape. be.

Specifically, in order to prevent the playback scanning locus from greatly deviating from the recording track and causing image quality deterioration when the running speed of the magnetic tape is faster or slower than the recording speed in a VTR, or when the tape is stopped and played back. Generally, during playback, an electro-mechanical converter is used to move the head perpendicular to the longitudinal direction of the recording track to correct the trajectory. , or unnecessary additions.

During playback on a VTR, the head's playback scanning locus does not necessarily match the recording track.

Causes of this include dimensional changes in the magnetic tape, dimensional changes in the recording/playback device, irregularities, and dimensional differences between different recording and playback devices, which usually results in a deterioration in the quality of the playback signal. appears.

For example, if the reproduction scanning locus for a recording track 2 recorded on a magnetic tape 1 is a locus 3 indicated by a dotted line as shown in FIG. 1, the reproduction output signal will have an amplitude as shown in FIG. The more the playback trajectory deviates from the recording track, the lower the output signal becomes, resulting in a deterioration in image quality. Conventionally, in order to eliminate this drawback, methods have been used to automatically track the relative positions of the magnetic head and the recording track of the magnetic tape so that they do not deviate.

For example, it is practical to use an electro-mechanical transducer as a support arm for the magnetic head to displace the position of the magnetic head and track the recording track.

As an electromechanical transducer, we use a material that has a very large piezoelectric effect or electric distortion effect, such as barium titanate porcelain, and when an electric field is applied in a certain direction, its shape expands in the direction of the electric field, and the shape extends in the direction perpendicular to it. To do this, the piezoelectric element plate is polarized by taking advantage of its shrinkage property, and the oppositely polarized surfaces are bonded together via electrodes, creating a so-called bimorph.

In FIG. 3A, the piezoelectric element plate 4 is polarized using electrodes 5 on both sides, the two plates are glued together to form a bimorph structure, one end is fixed with a fixture 6, and a magnetic head 7 is attached to the other tip. When attached, the bimorph is deformed as shown in FIG. 3B, and a potential of opposite polarity is applied to the terminals 10 and 11 with respect to the terminal 9 connected to the central electrode, which is placed in contact with the magnetic tape 8. The magnetic head 7 moves in position at right angles to the direction of rotation of the magnetic head. Therefore, the track misalignment in FIG. 1 can be corrected by moving the magnetic head in the directions of arrows A and B. FIG. 3C is a perspective view of a bimorph with a magnetic head 7 attached thereto.

FIG. 4 shows a specific example of a configuration for automatically tracking a recording track by a magnetic head.

In FIG. 4, an adder 1 uses an output signal of an oscillator 12 that oscillates at a specific frequency as a search signal.
3. In addition to the bimorph 15 having the configuration shown in FIG. 3 via the bimorph drive circuit 14, the magnetic head 1
6 to perform mechanical vibration. If the position of the magnetic head deviates in either direction from the recording track of the video signal on the magnetic tape, fluctuations in the same frequency as the frequency of the signal applied to the bimorph will occur in the envelope of the magnetic head output signal. If it shifts to either side, a fluctuation component with the same phase as the signal supplied to the bimorph is generated, but if it shifts to the opposite side, a fluctuation component whose phase is reversed by 180 degrees is generated.

Therefore, this fluctuating frequency component is detected by a detector 17, for example.
After detection, the error signal is separated by a bandpass filter 18, etc., detected by a synchronous detection circuit 19, and smoothed by a smoothing circuit 20. The error signal is sent together with the search signal from the adder 13 to the bimorph drive circuit 14 to the bimorph 15. The recording track is tracked by driving the magnetic head and displacing the position of the magnetic head. In addition, phase shifter 2
1 is for matching the phase with the fluctuating component of the synchronous detector input. FIG. 5 shows the waveform.

In FIG. 5A, if the output signal a of the oscillator 12 is supplied to the bimorph as a search signal and mechanical vibration is applied to the magnetic head, waveform b is obtained as the magnetic head output signal. Only the vibration component of this signal to obtain the c signal.

A d signal is obtained by synchronously detecting this with the a waveform, and an e signal is obtained by smoothing. The error signal e and the waveform a are added together to form an f signal, which is supplied to the bimorph to correct the trajectory of the magnetic head. If there is no trajectory deviation of the magnetic head with respect to the recording track, even if the search signal a is supplied to the bimorph as shown in Fig. 5 (b), the magnetic head output signal will be as shown in b, and the fluctuating component will be the same as the supplied frequency. Since only the doubled frequency component is obtained, the signal c obtained by separating only this signal is synchronously detected to obtain d. This signal is only a complete alternating current component, and even if it is smoothed, no error signal can be detected.

Therefore, the signal f supplied to the bimorph is only the search signal. In this way, the trajectory is corrected during playback, but for example, in so-called still playback in which the magnetic tape is stopped, as shown in Figure 6, in particular in the case of inclined azimuth high-density recording and playback, the head Since the amount of movement is large, it may take time for the reproduction locus to completely trace the recorded track using only the method described above, and a search signal with a large amplitude is required. 6A shows so-called H-sequence recording in which horizontal synchronizing signals of composite video signals recorded on adjacent recording tracks are recorded side by side, and FIG. 6B shows recording without H-sequence. A recording track 21 on which a video signal is recorded is arranged on the magnetic tape 1. If we now assume that the magnetic tape is in a still playback state where it has stopped running, the head will have a trajectory 2 that traverses the recording track.
It becomes 2.

Therefore, the head trajectory during still playback in a tilted azimuth recording/playback device, for example, requires a trajectory 24 shown by a dotted line in which the A head starts at the same position and is corrected in the direction of the arrow 23 as it progresses to the end, and the B The head is required to correct the starting point in the direction of the arrow 25 and then return to the original trajectory 26 as it progresses to the end. Therefore, the waveform shown in FIG. 7 can be added to the bimorph to move the head, or if automatic tracking correction is to be applied, a search signal can be added to this waveform to construct the block diagram shown in FIG. In FIG. 7, the vertical direction indicates the amount of movement of the head, and the unit is the pitch width of the recording track. Further, the horizontal direction indicates the field or humum of the video signal. The solid line represents the waveform required during reproduction, and the dotted line represents the retrace period.

When still reproduction is performed in this manner, the result will be as shown in FIG. 8 (b) and (c), for example.

In Figure 8, A normally plays the recording tape,
C. In the still playback of Figure 6, B, an unnecessary period Jifter occurs.

In addition, in the case of FIG. 8C, since the period X is not a multiple of the horizontal period, in a general television receiver equipped with a horizontal AFC circuit, the image is partially out of horizontal synchronization. To solve this problem, a delay element is generally used to correct the time axis and remove unnecessary periods, but this becomes expensive.

Slow playback also has similar drawbacks; for example, in triple speed playback, V shifter does not occur, but signal dropouts occur.

The present invention aims to solve this problem, and the basic idea of the present invention will be explained with reference to FIG. In FIG. 9, video signal recording track 2
7 are arranged with track width E and angle F. The method described above attempts to achieve the objective by moving the head by a width D, that is, the same amount as the track width E, and for this reason, an unnecessary period C is added. Therefore, in order to prevent this, the head should be moved in the direction G shown by the dotted line. One way to do this is to move the head by D perpendicular to the longitudinal direction of the recording track, and apply the same motion to the longitudinal direction of the track, moving it by C.

In the VHS system, which is one of the azimuth high-density recording systems, the track width is 58 μm and the angle is approximately 6 degrees, so C
The amount of movement is about 560 μm, which is about 9.7 times greater than the amount of movement in the vertical direction. When using a piezoelectric bimorph, the amount of movement is generally about 200 μm, although it depends on the length, so for example, It is preferable to use a structure that increases the amount of exercise as shown in FIG. 10. In FIG. 9A, there is a rotating body 31 rotatably engaged with a fixed shaft 30, and there is a piezoelectric bimorph 32 supported at one end and movable in the vertical direction, and a head 33 is provided at the tip of the rotating body 31. On the other hand, this rotating body 31
Mechanical pressure is applied from one side of the body with a spring 34 fixed at one end, and the other side is pressed by a piezoelectric element bimorph 35 whose one end is fixed. By applying a voltage to this bimorph 35, the head position is moved laterally. In order to increase the amount of movement, these contact points are provided closer to the fixed axis. FIG. 10B is a perspective view of FIG. Figure 3 shows a method in which a bimorph 36 is provided in place of the spring 34 to balance each other, and Figure 2 shows a method in which a bimorph 37 is mechanically connected to a bimorph 33 that provides vertical movement, and a bimorph 37 that provides horizontal movement is attached at one end. This is a method of fixing and installing. In addition, figure E is a perspective view of figure D.

Although these different bimorphs may be driven with different signals, the purpose can generally be achieved by applying similar waveforms.

Furthermore, since the ratio of the longitudinal momentum to the lateral momentum is determined by the recording track, the electric circuit can be simplified if the amplitude can be driven using the same signal waveform.

In addition, when automatically tracking by adding a unique signal waveform and search signal suitable for each playback such as still, slow, and double speed, search is performed when it is difficult to follow up with a high-frequency signal due to a large amount of lateral movement. As shown in FIG. 11, the signal drives only the bimorph that gives vertical motion, and the waveforms unique to each are applied to both. 1st
In FIG. 1, a magnetic tape 41 is fixed and attached to a rotating body 42 via a tape guide post 40, and the rotating body 42 has bimorphs 37, 37' that provide horizontal movement as shown in FIG. Bimorphs 32, 32' are provided which provide movement in the direction;
Magnetic heads 33, 33' are provided at the tips of the tapes, and the magnetic heads 33, 33' are placed in contact with the tape.
3 and 33' rotate. First, a signal from a signal generator 43 that generates a signal of a constant frequency, such as an oscillator, is applied to the bimorph 32 via a first adder 44 and a first bimorph drive circuit 45 to give longitudinal vibration to the magnetic head. The head output signal obtained as a result is detected by a detector 46, and only its vibration component is separated by a bandpass filter 47.
Add to 8. On the other hand, the oscillation output signal is passed through a phase shift circuit 49 for phase matching, and then added as a reference signal to the synchronous detection circuit 48, where polarity discrimination and width detection are performed, and after passing through a smoothing circuit 50, it is sent to a second adder 51. Switch the output signal of the unique waveform generator 52 necessary for head movement such as still, slow, double speed, etc.
It is added to the signal selected in S ₁₀₁ and applied to the transverse bimorph 37 via the second bimorph drive circuit 53, and also supplied to the first adder 44, and then sent to the longitudinal bimorph 3 via the bimorph drive circuit 45.
Drive 2. Since the search signal is a high frequency component, in addition to being common, it is also possible to remove it with a capacitor or the like before adding it to the transverse motion bimorph. By doing this, the head moves as indicated by the arrow 55 in FIG.
Since the B head is corrected to a trajectory of 57, a completely problem-free reproduction signal as shown in FIG. 8A can be obtained.

Similar effects can also be obtained in slow playback and double speed playback.

As far as still playback is concerned from a tape on which H-aligned recording has been performed, by moving the B head in advance by C in FIG. 9, a good image can be obtained with only vertical movement. Note that it is also possible to eliminate phenomena such as skew based on this idea.

As described above, according to the present invention, the magnetic head can be moved in the longitudinal direction of the recording track and in the direction perpendicular to it, so that it can be synchronized with the image during still, slow, double speed, and reverse playback. No negative effects such as disturbance appear.

Traditionally to remove this negative effect, generally
Analog delay lines such as CCDs and digital memories require a large amount of circuitry and are expensive, but according to the present invention, only slight fluctuations in the rotating body cause a small increase in costs.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the recording trajectory on the magnetic tape and the scanning trajectory of the reproducing head, FIG. 2 is a diagram showing the envelope of the output signal of the reproducing head, and FIG. Fig. 4 is a block diagram showing an example of an automatic tracking device using an electro-mechanical converter; Fig. 5 is a diagram showing an example of a mechanical converter;
6 is a diagram showing the relationship between the recording trajectory on the magnetic tape and the scanning trajectory of the reproducing head. FIG. 7 is a diagram showing the voltage waveform applied to the electro-mechanical converter. FIG. 8 is a diagram showing a reproduced video signal from the reproduction head, FIG. 9 is a diagram for explaining the basic operation of the present invention, FIG. 10 is a diagram showing the main part of an embodiment of the present invention, and FIG. 11 1 is a block diagram showing one embodiment of the present invention. FIG. 32, 32'...first electro-mechanical converter, 3
3, 33'...Rotating head, 37, 37'...Second
electro-mechanical converter, 41...magnetic tape, 43
... Signal generator, 44, 51 ... Adder, 45,
53... Bimorph drive circuit, 52... Unique waveform signal generator, _S101 ... Changeover switch.

Claims (1)

[Scope of Claims] 1. A rotary head type magnetic recording and reproducing device that sequentially records and reproduces signals on a magnetic tape as a recording locus inclined with respect to the longitudinal direction of the magnetic tape using a rotary head, the rotary head comprising: a first electro-mechanical transducer movable in a direction perpendicular to the recording trajectory; and a second electro-mechanical converter moves the first electro-mechanical transducer in a direction parallel to the recording trajectory. A rotary head type magnetic recording/reproducing device configured to be movable and applying control signals to each of the first and second electromechanical converters to correct tracking of the rotary head during reproduction. . 2. At the time of reproduction, a unique signal waveform corresponding to at least the traveling speed of the magnetic tape at the time of reproduction is applied to the first and second electro-mechanical conversion elements. Rotating head type magnetic recording and reproducing device.