DE2918259A1 - METHOD AND DEVICE FOR ELIMINATING THE REMANENT DEFLECTION IN A PIEZOCERAMIC HEAD HOLDER OF A VIDEO RECORDER - Google Patents

Description

Dipi.-Ing. H. MITSCHERLJCH D-8000 MÖNCHEN 2 2

Dipl.-Ing. K. GUNSCHMANN Steinso'urfstrasse 10

Dr. re r. η at. W. KÖRBER 8 _{QO (} . _Q ® (089) '29 66 84

Dipl. -Ing. J. SCHMIDT-EVERS 29ΐθ / 0 <3 Sch / jd
PATENT LAWYERS

May 7, 1979

SONY CORPORATION

7-35 Kitashinagawa 6-chome

Shinagawa-ku

Tokyo / Japan

Method and apparatus for eliminating remanent deflection in a piezoceramic head mount of a video recorder

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The invention relates to video signal recorders and more particularly to a method and a device for eliminating the remanent deflection that occurs in the piezoceramic Head mount of such a recorder is available.

Piezoceramic support assemblies, such as a monomorphic support sheet and a bimorphic support sheet, are designed to use the scan converter or head in a video signal recorder, for example a video tape recorder, to hold. The piezoceramic holder reacts to a control voltage applied to it by being in a direction and deflects by an amount determined by the Polarity and magnitude of the control voltage applied to them are determined. During playback operation of the video tape recorder, for example, if the head / then a scans a previously recorded recording track, deviates from this track, the piezoceramic holder is controlled in such a way that that it deflects itself by a certain amount, so that the head that is carried by it moves around the same Amount is shifted and thereby brought into the correct track alignment with the recording track scanned by it will. By appropriately controlling the piezoceramic holder, errors generated by incorrect scanning can both in normal playback mode, as well as in the various special playback modes, such as standstill mode, slow motion mode, time lapse mode or the like, can be minimized. As a result of minimizing such errors generated by mistracking, the finally reproduced image has a desirable quality. An example of a video tape recorder at which uses a piezoceramic mount is disclosed in U.S. Patent Application Serial Number 911 832 and on a filing date of June 2, 1978. Example of the material used to build the piezoceramic bracket

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can be used are described in the following references: Journal of Applied Physics, Volume 46 No. 1, January 1975, pages 222 to 229, and in the article "Effects of Aging and Compressive Stress on the Properties of BaTiO., Ceramics "by N. J. Poole, Journal of Physics (Great Britain) Volume 8, 1975.

If a pieζoceramic holder, for example a bimorph Blade arrangement made up of two piezoceramic blades with opposite polarization directions are supplied with a control voltage of a given polarity, the piezoceramic bends Bracket in a direction that is determined by this polarity. When the polarity of the control voltage is reversed the direction of deflection or deflection is similarly reversed. During playback it is assumed that a tracking control voltage of alternating magnitude and polarity is applied to the piezoceramic holder to correct tracking errors. The piezoceramic material was found to have a hysteresis having. That is, as the tracking control voltage increases, a first amount of deflection in response to a Tracking control voltage of a certain level is generated, but then as soon as the tracking control voltage is reduced, when this voltage level is reached again, a second, larger (or smaller) amount is obtained the deflection. Because of this hysteresis, there is residual deflection or remanent deflection, even if the tracking control voltage is reduced to zero. That means that when the tracking control voltage from the piezoceramic Holder is removed, the head carried by the holder does not return to its original position.

In view of the aforementioned phenomenon of the remanent foreign

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kung, which is referred to below as remanence, can
a tracking error during playback operation
arise because the piezoceramic bracket on the
it does not respond to the applied tracking control voltage in the manner for which the tracking control system was designed. If, for example, the video tape recorder is operated during an editing operation, previously recorded video signals are first reproduced and then new additional information is recorded. Due to the remanence of the piezoceramic holder, the distance between the last track played and the first track to be recorded can either be too large or too small. This discrepancy is attributed to the fact that there was no track control voltage of the piezoceramic during the recording part of the editing operation
Bracket is applied and therefore it is assumed that the attached head is returned to its original position for receiving. The discontinuity between the previously recorded and newly recorded tracks is caused by the fact that the head does not return to its original position. If, as a further example, the video tape recorder is a so-called two-head recorder and is operated in the editing mode, as above, the one piezoceramic holder can be deflected in one direction
Example upwards while the other piezoceramic
Bracket is deflected in the opposite direction,
to correct the tracking errors during the reproducing operation of the editing operation. If after the last track played back the video tape recorder is in its
Recording mode is switched over, in which no tracking control voltage is applied to the piezoceramic brackets, the remanence of these brackets leads to the fact that one head is displaced upwards from its starting position
the other head remains shifted downwards from its starting position. The pitch of the tracks recorded by such heads therefore becomes non-uniform, the pitch

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between adjacent tracks is larger than normal, followed by a smaller distance than normal, this in turn followed by a greater distance than normal, etc.

It is the object of the present invention to provide an improved method and an improved device for disposal the remanence in a piezoceramic holder such as is used in signal recording / playback devices, to accomplish.

Another object of the invention is to provide a method and a device that use the piezoceramic Control the holder of a video tape recorder in such a way that the transducer or head of the recorder is in its starting position returns when there is no tracking control voltage on the bracket.

Another object of the invention is to provide a dynamic tracking control system for use in a signal recording / reproducing apparatus, for example a video tape recorder, whereby the scanning heads are controlled in such a way that

she
that the tracks scan uniformly during both playback and recording, regardless of the inherent remanence of the piezoceramic head mount.

Another object of the invention is to provide a device that the above-mentioned disadvantages of the Prior art eliminated.

To solve this problem, the invention proposes a method and a device for eliminating the remanent deflection or remanence in a piezoceramic holder for a transducer that is used to make successive Tracks across a recording medium in the case of

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i 2318259

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play a video signal recording and / or playback device »The device is operated in selected operating modes, whereby in one of these operating modes a tracking control signal is applied to the piezoceramic holder in order to minimize incorrect tracking of the transducer. A source of an oscillating signal which is substantially larger than the tracking control signal is provided. When the recording and / or playback device is switched between selected operating modes, the oscillating signal of the piezoceramic holder is applied for a predetermined period. The magnitude of the oscillating signal, which is less than E_, where E _{p is} the largest magnitude of the tracking control signal to which the piezoceramic holder is responsive, is gradually reduced to a minimum during this predetermined period of time. In one embodiment, the oscillating signal is applied to the piezoceramic holder with decreasing magnitude when the recording and / or playback device is switched from playback mode to waiting mode. In another embodiment, the oscillating signal with gradually decreasing magnitude is applied to the piezoceramic holder when the device is switched to the recording mode. Preferably, the maximum size of the oscillating signal is in the range from about 0.25 E- to about 0.75 E_.

Further features, details and advantages of the invention emerge from the following description of preferred embodiments as well as based on the drawings. Here show:

Fig. 1 is a schematic side view of a piezoceramic holder that is used with the present invention can be used;

2Ά is a side view of one embodiment of a piezoceramic head mount that can be used with the present invention;

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FIG. 2B shows a plan view of the arrangement according to FIG. 2A; FIG.

Fig. 3 shows the relationship between the scan line of a head and the parallel recording tracks a recording medium;

Figure 4 illustrates the hysteresis of the piezoceramic mount used with the present invention;

Figure 5A is a block diagram of an embodiment of the invention;

Fig. 5B is a block diagram of a second embodiment of the invention;

Figures 6A and 6B show the correct dither tracks of a head along a recording track;

Fig. 6C shows a tracking error in one direction between the head and the recording track;

Fig. 6D shows a tracking error in the opposite direction between the head and the recording track;

Figure 7 is a waveform diagram of the oscillating signal used with the invention;

Fig. 8 is a graph showing the relationship between the remanence and the size of the piezoceramic Bracket applied, the remanence eliminating signal and

9 is a graph showing the relationship between the sensitivity of a piezoceramic holding

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tion and the magnitude of the tracking control voltage applied to them.

Figure 1 is a schematic side view of a piezoceramic holder used with the present invention can be. This piezoceramic holder is suitable for holding a transducer, such as a magnetic recording and / or playback head, and consists of piezoceramic material, which is applied to a Tension reacts in such a way that it bends or deflects. In the example shown in Fig. 1 is the piezoceramic holder a so-called bimorph leaf arrangement, which consists of a pair of sheet members 34 and 35, each member of piezoceramic material exists, the polarization directions of which are shown by the arrow. The opposing surfaces of the piezoceramic sheet member 34 are provided with electrodes 34a and 34b, which are opposite to each other Surfaces of the piezoceramic sheet element 35 are similarly provided with electrodes 35a and 35b. the Piezoceramic sheet members 34 and 35 are in an overlying, surface-to-surface relationship arranged so that the electrodes 34b and 35a are in contact with each other. If the bimorph arrangement in this Art is composed, it bends when a variable voltage is applied across the corresponding elements will. For example, if a voltage source 4o has a voltage opposite to that applied to electrode 35a A voltage of positive polarity is applied to the electrode 35b, and when the same voltage is applied to a positive polarity the electrode 34a is applied relative to the electrode 34b, then the bimorph sheet arrangement tends to deflect or bend in the direction indicated. That means the piezoceramic sheet element 34 tends to expand in the longitudinal direction, while the piezoceramic sheet element 35 tends to

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to contract. As a result of these forces acting in the opposite direction, the bimorph bends Sheet arrangement as shown, and by an amount that is a function of the strength of the contact with each element electric field is. This means the size and direction of the deflection of the bimorph leaf arrangement are a function of the magnitude and polarity of the voltage applied thereto by voltage source 4o. If the The polarity of the voltage applied across the bimorph blade assembly is reversed, d. H. if the polarity is that of the voltage applied to the voltage source 4o is opposite to that shown in the drawing, is accordingly the direction in which the bimorph blade assembly deflects is reversed.

In Fig. 1, a voltage is applied from the source 4o which is connected to the electrodes 34b and 35a. If the The polarization direction of the piezoceramic elements is made opposite to each other, d. i.e. when the electrode 34a of the piezoceramic element 34 is brought into contact with the electrode 35a of the piezoceramic element 35 is then the voltage generated by the source 4o across the external electrodes of the bimorph sheet assembly are applied, and the electrodes that are in contact with each other do not need to be connected to a common or Reference voltage to be supplied. Reference is made to the bimorph sheet arrangement disclosed in the application the serial number 832 638 with the filing date of September 12, 1977 is disclosed.

The piezoceramic mount of FIG. 1 is used as a head mount in accordance with that in FIG 2A and 2B, with FIGS. 2A and 2B being a side view and a plan view of such a head mount arrangement are. Although not shown, the head mount arrangement of FIGS. 2A and 2B is suitable for to be placed on the rotating guide drum, which is generally used in a video signal recorder

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for example a video tape recorder, the two-head system or the omega-shaped arrangement is provided. The headgear assembly comprises a mounting base 36 with an upwardly extending receiving portion 37, wherein the receiving portion 37 is suitable for receiving the bimorph arrangement, which is there with the help of a suitable Adhesive can be attached. The bimorph arrangement extends extending from the mounting base 36 in a generally parallel manner to a mounting plate 39 Direction which also extends outward from the base 36. Preferably, tabs 40A and 40B extend from the mounting plate 39 and cushioning members 4IA and 41B are attached to the corresponding tabs. The damping elements 41A and 41B are provided to the free or To dampen the resonance oscillation of the bimorph arrangement, the be caused by the forces exerted in response to the bending stresses applied to the respective electrodes can. For example, when a trembling, oscillating voltage is applied across the bimorph leaf assembly, the damping elements 41A and 41B attenuate the resonant Vibration that could otherwise occur. This damping effect is achieved in that the damping elements between the sides of the bimorph and the tabs 4oA and 4oB are pressed with an appropriate force to prevent swinging, but not so great as to deflect of the bimorph in response to the control voltage applied thereto. As in Fig. 2A and Fig. 2B is a head 38 which is the record and / or playback transducer of the video recorder to which piezoceramic sheet member 35 attached, for example by attaching the head to the electrode 35B with the aid a suitable adhesive. Corresponding leads are connected to the corresponding electrodes of the bimorph leaf arrangement connected so that this arrangement can respond to a voltage applied thereto in the manner shown in FIG.

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Fig. 3 shows recording tracks in parallel, oblique Relationship recorded on the magnetic tape T »The video signals are recorded along these tracks with the help of the Example of the head 38 added. As usual, each track can contain a single field interval, making two adjacent tracks form a complete frame. Control pulses CT are along a longitudinal edge of the tape T recorded, each control pulse representing the beginning of a frame, these control pulses adjacent to the The beginning of a track are arranged. These control pulses CT are in a servo control circuit during the playback operation used to synchronize the movement of the tape T with the rotation of the playback heads so that the Heads can scan successive tracks across the tape. Takes one for the purpose of the present discussion indicates that the video signal recorder is a video tape recorder which has two oppositely disposed heads for scanning alternately Lanes A and B across tape T contains. Or the video tape recorder can be of the type, the one has so-called omega-shaped configuration and a Includes head. It is also assumed that the video tape recorder are operated in various modes can. For example, the video tape recorder can be operated in a normal recording mode in which the illustrated Tracks and control pulses are formed on the tape T. The video tape recorder can also be in a playback mode operated, the information recorded on the displayed tracks from these tracks be reproduced. This reproduced information can be transmitted or used in conjunction with other transmission material and ultimately to form a an image corresponding to the reproduced information can be used. This playback operation can be a normal Playback operation or one of various special playback operations. Be an example of the latter

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Slow motion operation, standstill operation, time lapse operation, Reverse operation, etc. called. Another operating mode of the video tape recorder is the waiting mode, in which the Tape T is held stationary and the head (or heads) 38 continues to rotate at its synchronized speed, but in which information is neither recorded nor reproduced from the tape. As an example, can when the video tape recorder is switched on, the waiting position can be assumed, but neither recording nor playback mode will be chosen.

If the same video tape recorder to play back the information used by the tape that was used to record this information is stored in the generally any scan line of head 38 (or heads) coincide with the scan line of this head during recording during playback. Even if between there is a certain difference between the two, the scan line becomes generally parallel to during playback run along the recording track. Accurate alignment can be achieved by adjusting the speed at which the tape T can be achieved so that the scan line is brought into correspondence with the scanned track. However, when the tape T has been subjected to expansion or contraction after recording video information thereon, is it is possible that the scan line of the head or heads may not be parallel to the recording tracks during playback runs. As a result, if the scan line is not dynamically adjusted, a tracking error is generated. A tracking error can also be generated when a different VTR is used for playback of the video information is used when it was used to record the information.

In addition to the aforementioned tracking errors that can be generated during normal playback,

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are the scan lines of the playback head during various Special playback modes not in alignment with the recording tracks. For example, the head can be during a normal playback operation in which the tape T is transported at its normal forward speed, follow a scan line 13, see FIG Tape T is held stationary, the head of a scan line 12 follow across the tape. That is, as soon as the head hits the tape scans, the beginning of its scan line is in exact alignment with a track and then traverses that scan line the guard band between adjacent tracks and ends in alignment with the next adjacent track. Without compensating along scan line 12, the video image displayed during that scan line will contain distortion.

If the head or heads are from the bimorph blade assembly such as shown in Figs. 2A and 2B is, is held, a control voltage is applied to the bimorph as soon as the head of the tape T, for example during standstill, scans to scan line 12 in accordance with the desired Bring scan line 13. This control voltage can have a sawtooth waveform, the amplitude of which increases, as long as the head continues along its scan line. As a result of this control voltage, the bimorph is steered in a direction that is transverse to its scan line to move the head in the corresponding direction, and thereby brings the head into line with the recording track. Of course, the polarity determines the Control voltage applied to the bimorph, the direction in which the head moves laterally is relocated. In the example just described, the head is displaced in an upward direction relative to its scan line. As an alternative, the bimorph leaf arrangement in

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Downward direction deflected to the scan line 12 to be brought into agreement with, for example, track B. In this embodiment, it also has a sawtooth shape Control voltage has a gradually reduced amplitude as long as the head is along its scan line continues.

While FIG. 3 shows the relationship between scan line 12 and 13 for the idle operation and normal playback operation shows, other analog scan lines may be drawn to represent other special playback operations. In each of these special playback modes, the control voltage applied to the bimorph should be the Correct size and polarity to keep the scan line of the head in correct correspondence with the scanned one Keep track. In general, such a control voltage has a sawtooth waveform.

It was found that the piezoceramic bracket has a hysteresis, regardless of whether it is designed as a bimorph leaf arrangement or as a monomorphic leaf arrangement is. That is, if the control voltage, which is applied via the piezoceramic holder, is from, for example, one Size V1 grows to size V2 and passes through an intermediate value VO, is the deflection of the piezoceramic Holding in response to a voltage VO as soon as this control voltage increases from V1 to V2, not equal to that Deflection of this arrangement when the voltage VO is reached again when the control voltage is reduced from V2 to V1 will. An example of this hysteresis curve for a typical piezoceramic material from which the piezoceramic Bracket is built, is shown in FIG. The abscissa represents the control voltage V and the ordinate represents the deflection the piezoceramic holder. As soon as a control voltage is applied to the piezoceramic holder, it returns

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the device generally does not return to its starting position with zero deflection when this control voltage is taken away. If the head held by the piezoceramic holder during a recording operation, for example should have a zero deflection, the fact that the piezoceramic bracket means a Hysteresis has that in the absence of a tracking control voltage, which is normal during the recording operation, a retentive or residual deflection in the piezoceramic holder remains so that it gives the head some undesirable displacement. As mentioned above, this can be remanence the piezoceramic holder in a discontinuity between the reproduced and the immediately following ones, tracks recorded during an editing operation result. The remanence can also be non-uniform Spacing between the successive scan lines of each head in a two-head video tape recorder will result. All of this follows from the fact that the remanence of the piezoceramic holder prevents the head from getting into its Return to the starting position, even if the tracking control voltage is zero on the bracket.

The object of the present invention is to eliminate the remanence of the piezoceramic holder. The invention is based on the discovery that the remanence can be eliminated when the piezoceramic support is supplied with a voltage which follows the hysteresis curve shown in FIG. 4, but with a continuously decreasing size. That is, an oscillating voltage is applied to the piezoceramic holder, this oscillating Voltage begins with a relatively large amplitude, so the piezoceramic support during each half cycle this tension is deflected first in one direction and then in the other, and then the

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The size of this oscillating signal is gradually reduced, so that the amount of deflection of the piezoceramic bracket reduced. When the oscillating Signal is finally reduced to a minimum amplitude, for example zero, is the piezoceramic Hold in its neutral or starting position, and the remanence in it is eliminated.

An example of an easy way to carry out the above Principle of the circuit to be adapted is shown in Fig. 5A. To be complete, this includes those illustrated Circuit also includes the tracking control circuit, which is used to supply the control voltage to the piezoceramic bracket for dynamic adjustment of the scan line of the head carried by the holder. The one shown Circuit consists of a source of a dithering oscillating signal 16, an adder circuit 17, a Drive amplifier 18, a piezoceramic holder 19, an envelope detector 22, a phase detector 23 and a low-pass filter 24. The source 16, which is a suitable, for example a crystal oscillator with a suitable May contain oscillation frequency, produces a trembling oscillating signal SA, hereinafter referred to as the dither signal. The source 16 is with the adder circuit 17 connected, which is used to apply a DC voltage to the Add dither signal SA. This added DC voltage level is an error voltage that functions as a function of the tracking error of the head 2o, see FIG. 5A, is generated with respect to the track scanned by it. The output of the Adding circuit 17 is referred to as a tracking control signal and is applied to drive amplifier 18 via a changeover switch 14. This drive amplifier 18 is connected to the piezoceramic holder 19 and designed so that it applies the tracking control voltage to the bracket, causing the piezoceramic bracket to move in one direction and

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deflects by an amount determined by this tracking control voltage.

When the head 2o scans the recording medium, which can be, for example, a magnetic tape, the data on this medium recorded signals. It is now assumed that the video signals are frequency-modulated Signals have been recorded. Therefore, the head 2o reproduces these FM video signals. The output of the head 2o is applied to an envelope detector 22 via a video amplifier 21. The envelope detector is designed in such a way that that it determines whether the head 2o is in correct or incorrect correspondence with respect to that which it scanned Trace is. If the head is in proper alignment with the track being scanned, this will show from that head reproduced FM video signal has a maximum envelope. However, if the scan line of the head 2o from the recording track deviates, the envelope of the FM video signal is reduced. The output of the envelope detector 22 is connected to an input of the phase detector 23, while the other input of this phase detector is supplied with the dither signal SA from the source 16. Any phase difference between the detected envelope and the dither signal is caused by a tracking error and results in an output of the phase detector. This output goes through the low pass filter 24, which in turn generates a DC error voltage representing the tracking error of the head 2o. These Error voltage is applied to the modifying device 17, where it is added to the dither signal SA and used as Track control voltage applied to the piezoceramic bracket will.

The output of the video amplifier 21 is also a demodulator and a not shown video processing

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circuit supplied from which a video signal for use in transmission, monitoring or the like is derived will.

The operation of the tracking circuit described so far will now be described with reference to FIGS. 6A to 6D. Fig. 6A shows the relationship between the dashed line scan line of the head 2o and the track scanned by it. Note that this scan line in response to the dither signal Sj. represents an oscillating or trembling line. Further, in Fig. 6A, it is assumed that the scanning line is coincident with the track. When the head is displaced to one side of the track, such as when the head 2o is in the position shown as H, the envelope of the video signal reproduced by the head has a minimum height. This envelope is represented by the hatched area at the head end H. When the head is shifted to the other side of the track, as shown by the head position H _n , the envelope of the FM video signal reproduced by the head is again reduced to a minimum height, as shown by the hatched area within the head position H _ß . For proper tracking of the head with respect to the track, that is, when the scan line of the head is in alignment with the track scanned by it, the envelope of the reproduced FM video signal has the same minimum height at two positions during each cycle of the dither signal.

Assume that the head 20 is deviated from its correct track relationship so that it is displaced from track as shown in Fig. 6C. If the head 2o is in position H ₇ . occupied, the envelope of the head 2o represents

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the given FM video signal represents a minimum that is caused by the hatched area is shown in the head position EL. When the head reaches the position H_, the envelope is of the FM video signal is less than its maximum height but as shown by the hatched area this envelope is much larger than the envelope produced in the head position H. From Fig. 6 -; 'it can be seen that the envelope of the FM video signal reproduced by the head 2o reaches its minimum level only once during each cycle of the dither signal achieved. That is, the frequency of the enveloping waveform generated by the head 2o is then if the head has a tracking error, half the frequency of the enveloping waveform for the condition that none There is a tracking error.

When the tracking error between the head and the track is as shown in Fig. 6D, that is, when the head is displaced to the opposite side of the track, the waveform is the envelope of the FM video signal reproduced from the head 2o similar to the waveform of the envelope reproduced under the condition shown in Fig. 6, except that the waveform of the envelope has a phase shift. That is, in FIG. 6, the envelope assumes its minimum height in the head position H _ß . If this is compared with the envelope generated under the condition shown in FIG. 6C, in which the envelope assumes its minimum height in the head position H, then the envelope generated for the condition shown in FIG. 6B is 180 ° compared to that under the in 6, the generated envelope is shifted.

When the head 2o is in correct correspondence with the track it has scanned, the envelope of it lies reproduced FM video signal in phase with the dither signal S, .. For the tracking error shown in Fig. 6C

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condition is the envelope of the reproduced by the head 2o FM video signal out of phase with the dither signal. This out-of-phase condition can be less than 180 °, for example, and as a positive phase shift to be viewed as. The FM video signal generated by the head 2o under the condition shown in Fig. 6C is in the same way out of phase with respect to the dither signal, This out of phase condition can be greater than 180 and as a negative phase shift to be viewed as.

The envelope detector 22 generates the envelope of the FM video signal reproduced by the head 2o, examples of which are shown by the hatched areas for the head positions H and H ₁₃ in FIGS. 6B to 6D. The phase of this envelope with respect to the dither signal S ₂ . is detected by the phase detector 23 using the dither signal as the detection signal. The amplitude of the output of the phase detector 23 is an error signal representing the phase difference between the detected envelope of the FM video signal and the dither signal. The polarity of this error signal represents the direction (e.g. positive or negative) of this phase shift. Therefore, it can be seen that the magnitude of the error signal generated by phase detector 23 represents the magnitude of the tracking error, and the polarity of this error signal represents the direction in which the tracking error occurred. For example, if the head is misplaced above the track, see Figure 6C, the polarity of the error signal may be positive. Conversely, if the head is misplaced below the track, see Fig. 6D, the polarity of the error signal is assumed to be negative. This error signal is filtered to a direct current level with the aid of the low-pass filter 24 and then added to the dither signal S to be used as a correction signal or as

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Tracking signal applied to the piezoceramic holder 19 to become. Although the head 2o to its scanning path due to the dither signal S ,. oscillates, which is connected to the piezoceramic Bracket 19 is applied by the oscillator 16, the phase detector 23 delivers when this scanning path, for example is shifted upwards with respect to the scanned recording track, see Fig. 6C, a positive signal to the low-pass filter 24, which in turn adds a positive DC voltage to the dither signal in adder 17. the The magnitude of this DC voltage level represents the displacement of the actual scanning path of the head 2o from its desired one Scan path, d. H. from the track. As a result, that of the adder 17 of the piezoceramic Bracket 19 applied tracking control voltage as a positive DC voltage superimposed dither signal. The piezoceramic holder 19 deflects in response to this positive DC voltage level downwards and brings it thereby the scanning path of the head 2o in accordance with the track. Of course, the dither signal S leaves the head around swing its scan path as shown in Fig. 6A. On the contrary, when the head 2o has a tracking error in the downward direction opposite to the track scanned by it, as shown in FIG. 6B, the phase detector 23 generates a negative signal which is passed through the low pass filter 24 as a negative DC voltage for addition to the dither signal in the adder 17 is supplied. This negative DC voltage directs the piezoceramic bracket 19 in the upward direction, thereby leaving the scan path of the head 2o return in accordance with the track. Here, too, the dither signal S- leaves the head around its scanning path oscillate, see Fig. 6A.

The tracking control circuit so far described is generally effective to oppose the position of the head 2o the track scanned by it during a normal

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To adjust playback mode. That is, in the operation just described, the changeover switch 14 is brought into the position that its movable contact touches the reproducing contact C to thereby the output of the adder 17, that is, the dither signal S ₂ . superimposed DC voltage to connect with the piezoceramic holder 19. The tracking control circuit has an additional section which operates during special playback modes to remove tracking errors of the head 2o. This additional section therefore corrects tracking errors that may be present, for example, during slow-motion operation, standstill operation or time-lapse operation. If the scan line of the head 2o deviates from the scanned recording track during such special playback modes, this additional portion of the tracking control circuit corrects such deviations.

This is called an additional section of the tracking control circuit includes a sawtooth generator 26 and a special mode switch 25, on which hereinafter is referred to as a special switch. The sawtooth generator 26 generates a sawtooth waveform more constant Period and an amplitude which is a function of the expected maximum deviation of the scan line of the head 2o is from the track being scanned. Since this deviation is a function of the transport speed of the video tape, the amplitude of the sawtooth wave is therefore a function of the belt speed. For example, the Scan line 12, see Fig. 3, from the desired scan line 13 by a larger one during the still playback Amount from than during slow motion playback. Therefore, the amplitude generated by the sawtooth generator 26 must be sawtooth-shaped shaft during standstill

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be larger than during slow-motion operation. A tape speed detector circuit is connected to the input of the sawtooth generator 26 to generate an amplitude control signal to be supplied to the sawtooth generator 26 as a function of the detected belt speed.

In the illustrated embodiment, there is the tape speed detector circuit from a recording head 27, which is arranged such that it is along a longitudinal edge of the tape T reproduced control pulses CT, see FIG. 3, furthermore from a sensor 3o, the is designed in such a way that it always generates a pulse when the head 2o rotates into a predetermined position, as well as a phase detector 29 which is designed such that it the phase difference between the of the Head 27 reproduced control pulses CT and the position pulses generated by the sensor 3o detects. More accurate said the head 27 is connected to an input of the phase detector 29 via an amplifier 28, while the sensor is connected to the other input of the phase detector. The phase detector 29 supplies an amplitude control signal to the sawtooth generator 26, and this generator provides its sawtooth waveform to the output of the adder 17 via the special switch 25.

The special switch is on during normal playback 25 opened so that the sawtooth waveform generated by the sawtooth generator 26 does not correspond to the output of the adder 17 is superimposed. Continue to be during this normal reproducing operation transports the tape at its normal speed so that a predetermined Phase relationship between the control pulses CT reproduced by the head 27 and those from the sensor 3o generated position pulses exists.

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If the video tape recorder is to be operated in one of its special playback modes, the special switch 25 is closed. Furthermore, the transport speed of the video tape is changed from its normal speed. This means that the predetermined phase relationship between the control pulses CT reproduced by the head 27 and the position pulses generated by the sensor 3o no longer exists. This change in the phase relationship between the control pulses and the position pulses is detected by the phase detector 29 which in turn provides an amplitude control signal to the sawtooth generator 26 which is a puncture of the tape transport speed during this particular playback operation. As a result, the amplitude of the sawtooth waveform generated by the sawtooth generator 26 is set at a level which corrects the tracking error of the head 2o. That is, the properly set amplitude of the sawtooth waveform is superimposed on the tracking control voltage generated by the adder 17 to correct the scanning line of the head 2o and thereby bring it into agreement with the scanned track during this special playback mode. The switch 14 now supplies the piezoceramic holder 19 with a tracking control voltage which includes the dither signal component S _A , the direct voltage component derived from the phase detector 23 and the correctly selected sawtooth waveform S _n generated by the sawtooth generator 26. These components are combined to control the head 2o so that its scan line is brought into line with the track being scanned during this special playback operation (e.g. standstill operation, slow-motion operation or time-lapse operation) while the head 2o continues to oscillate its scan path, see FIG Figure 6A.

In addition to the tracking control just described

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The circuit, Fig. 5A shows an oscillator 32 which is selectively triggered when the video tape recorder is switched from its playback mode to the waiting mode, the oscillating signal generated by this oscillator 32 is then applied to the piezoceramic holder 19 to remove its remanence. The oscillator 32 may include a monostable multivibrator configured to apply an actuation voltage to the oscillator for a predetermined period of time depending on the time constant of the monostable multivibrator. In one embodiment, this monostable multivibrator may be of the type which generates a pulse signal having a substantially perpendicular leading edge and a gradually sloping trailing edge. When the oscillator 32 is supplied with an actuation voltage of this waveform, the oscillator 32 generates an oscillating signal whose envelope has the same shape. That is, during the predetermined period determined by the monostable multivibrator, the oscillating signal exhibits a substantially fixed constant amplitude during a first portion of that period, and then the amplitude of the oscillating signal gradually decreases during the following portion of the period. Such an oscillating signal with this envelope is shown in FIG. 7, the fixed amplitude of the signal being present during the section Ρ, and the gradually decreasing amplitude being present during the section Ρ _π .

In another exemplary embodiment of the oscillator 32, the actuation voltage applied thereto for the said predetermined period of time initially assume a maximum value, and then the amplitude of this actuation voltage gradually decrease from their maximum level over the entire period. That means with this one different embodiment, the waveform of the oscilloscope

0300A7 / 0041

lating signal be as shown in Fig. 7 during the section P _ß . One of ordinary skill in the art will be able to generate an actuation voltage that has a waveform similar to the envelope of the oscillating signal during the portion Ρ _π .

As can be seen in FIG. 5A, the oscillator 32 is connected to a voltage supply source 31 via a changeover switch 15, which is mechanically connected to the switch 14 for simultaneous actuation. When the movable contact of the Changeover switch 14 is in engagement with the playback contact P, is in particular the movable contact of the changeover switch 15 in similarly engages its playback contact P, which is isolated from the rest of the circuit. if the changeover switch 14 is operated so that its movable contact comes into engagement with the waiting position contact S, and thereby the oscillating generated by the oscillator 32 Signal S ^ connected to the piezoceramic holder 19 is, the movable contact of the switch 15 is in the same way with its waiting position contact S in connection and thereby provides the voltage from source 31 to oscillator 32. The sudden application of tension from the source 31 to the waiting position contact S of the changeover switch 15 is used to convert the contained in the oscillator 32 trigger monostable multivibrator, so that this oscillator at time t, that is to say at the time by switching the changeover switch 15 in this manner, the oscillating signal generated looks as shown in FIG. If, in the above-described alternative embodiment of the oscillator 32, the switch 15 is in its Waiting mode is switched, that is, if its movable contact is brought into engagement with its standby contact S, the result of the source 31 supplied voltage in a supplied to the oscillator 32-

030047/004

th actuation voltage, which has the gradually falling shape as indicated by the envelope of the oscillating Part during section P in FIG. 7 is shown.

In both embodiments of the oscillator 32, when the switches 14 and 15 are switched from their playback positions to their waiting operating positions, as before, the tracking control voltage applied to the piezoceramic holder 19 by the adder is replaced by the oscillating signal generated by the oscillator 32. That is, see FIG. 7, before the time t, the video tape recorder operates in its reproducing mode, such as, for example, its normal reproducing mode in which the dither signal S _{Ä is applied} as the tracking control signal of the piezoceramic holder 19. At time t, the video tape recorder is switched from its playback mode to waiting mode, the oscillating signal S ^ being applied to the piezoceramic holder 19 by the oscillator 32 via the switch 14. The. The size of the oscillating signal S ^, when this is initially applied to the piezoceramic holder at time t, is greater than the amplitude of the dither control signal S _A , which was previously applied to the piezoceramic holder. Even if the video tape recorder was operated in one of its special playback modes, the amplitude of the entire tracking control signal that was applied to the piezoceramic holder 19, namely the amplitude of the sawtooth waveform together with the superimposed, DC voltage-adjusted dither signal, is smaller than the magnitude of the oscillating signal S_ .

When the oscillating signal S "of the piezoceramic bracket 19 is applied, the holder is by its in Fig. 4 shown hysteresis loop driven. That means theirs

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maximum positive deflection depends on the size of the oscillating signal S during the positive half cycle, and its maximum negative deflection is dependent on the size of the oscillating signal during its negative half cycle. Since the size of the oscillating signal is gradually reduced, as during the section Ρ _Ώ ,

ti

the positive and negative deflections of the piezoceramic Bracket 19 reduced in the same way. This means that the hysteresis loop shown in FIG. 4 is smaller is made. Finally, when the magnitude of the oscillating signal has been reduced to zero, it becomes the same Way, the actual deflection of the piezoceramic holder 19 can be reduced to zero. Hence the remanence the piezoceramic bracket, which would otherwise prevent this device from returning to its starting position in the absence of a applied voltage is eliminated. As a result, it is at the end of the predetermined period of time after switching the switches 14 and 15 from their playback positions to their waiting operating positions, the head 2o to its starting position returned.

The relationship between the elimination of the remanence of the piezoceramic Bracket and the size of the oscillating signal to be applied to it is shown graphically in FIG. In this graphical representation, the abscissa represents the size of the oscillating signal and the ordinate represents the remanence For the purposes of the present discussion, it is assumed that the remanence is the amount of deflection of the piezoceramic bracket in response to an applied voltage of zero divided by the maximum deflection that the Device can learn is. For the special type of piezoceramic material used for the piezoceramic bracket is used, it is assumed that the piezoceramic material exhibits a remanence of 20% when the size of the oscillating signal is zero. As soon as the initial

030047 / 0CK1

tude of the oscillating signal becomes greater than zero, the remanence decreases. If the initial amplitude of the oscillating signal is, for example, 11o volts, is at the end of the aforementioned predetermined period of time, i.e. after the magnitude of this oscillating signal was reduced to zero, the remanence was reduced to 5%. When the initial amplitude of the oscillating signal is increased to 220 volts, is after the predetermined period of time during which the oscillating signal with after and after falling amplitude is applied, the remanence of the piezoceramic holder is reduced to about 2%. From Fig. 8 it can be seen that when the initial amplitude of the oscillating signal is further increased, a larger amount of remanence can thereby be eliminated.

The size of the to be applied to the piezoceramic bracket oscillating signal cannot be increased beyond a threshold voltage E, which is now referred to to the graph in FIG. 9. This graph shows the relationship between the insensitivity of the piezoceramic material to a control voltage applied to it when the control voltage is relatively high. When the polarity of the control voltage is opposite to the polarization of the piezoceramic Material, the material is subjected to expanding forces, similar to those in the piezoceramic There are element 34 discussed above with reference to FIG. 1. It is remembered that this Forces result in the deflection of the piezoceramic holder. In general, the amount of this deflection is that is, the sensitivity of the piezoceramic holder in relation to the size of the one resting against it Tension. However, the sensitivity of the piezoceramic material is reduced for higher voltages.

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Finally, at a threshold voltage E _r , the value of which is determined by the piezoceramic material, the piezokerainic holder becomes completely insensitive. 9 shows the insensitivity of the piezoceramic material to the magnitude of the voltage applied to it. In particular, the abscissa of this graphical representation represents the magnitude of the applied voltage and the ordinate the percentage of insensitivity. It can be seen that for the threshold voltage E " the piezokerainic holder has become completely (i.e. 100%) insensitive. The piezoceramic holder is completely sensitive (that is, 0% not sensitive) for a voltage whose magnitude is 0.5 E_ or less. In the range o, 5 E ^, to E ^, the insensitivity of the piezoceramic material increases from 0% to 100%.

When choosing the size of the oscillating signal that is initially applied to the piezoceramic holder 19, when the switch 15 is switched from its playback position to its waiting operating position, the graphic Representation in Fig. 8 and in Fig. 9 are taken into account. As can be seen from Fig. 8, the amount of remaining is Remanence very low if the size of the oscillating signal is selected to be very high. If, however, how out 9 shows that the amplitude of the oscillating signal is selected too high, the characteristics of the piezoceramic Bracket to be disturbed to a large extent, so that the bracket is no longer sufficiently sensitive to is a tracking control voltage applied thereto. That is, the insensitivity shown in Fig. 9 can be considered permanent can be viewed even if the oscillating signal has been removed. Therefore, if the size of the oscillating Signal is equal to E ^, the piezoceramic bracket constantly insensitive to subsequently applied

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Be control voltages, even with a very small size.

In view of the limitations illustrated by FIGS. 8 and 9, the preferred range of the magnitude of the oscillating signal S_ which is initially applied to the piezoceramic support 19 is in the range between 0.25 and 0.75 E_. If the characteristics of FIGS. 8 and 9 are drawn for the same piezoceramic material, then the following applies: 0.25 E = 11o volts, 0.75 E = volts, E = 44o volts. This range of the magnitude of the oscillating signal is much larger than the magnitude of the dither signal S _A which is applied to the piezoceramic holder 19 during the playback modes and is of the order of magnitude of approximately 0.05 E.

The relationship between the insensitivity of the piezoceramic Material as a function of the voltage applied thereto, as shown in Fig. 9, was obtained as a result of experiments found where each test voltage was applied to the piezoceramic sheet element for about 500 hours. After removing each test voltage, the piezoceramic sheet element was tested for its sensitivity to to determine a control voltage. The results of these experiments are shown in the graph of FIG shown.

By selecting the magnitude of the oscillating signal S within the range 0.25 E _c to 0.775 E ", where E ^ is the threshold voltage associated with the particular piezoceramic material being used, it can be seen that most of the remanence of the piezoceramic holder is eliminated, and the piezoceramic holder has only been made slightly insensitive to subsequent control voltages, due to the larger size of the oscillating signal. In choosing the desired size of the oscillating signal, it must be remembered that a

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larger amount of remanence only at the expense of the increase in the insensitivity of the piezoceramic holder subsequently applied tracking control voltages can be eliminated. Regardless of the specific size of the selected oscillating Signal, this size should of course be much larger than the level of the tracking control signal, as shown in Figs.

The embodiment of Fig. 5A illustrates the way in the oscillator 32 is used to eliminate the remanence of the piezoceramic holder 19 when the video tape recorder is switched from its playback mode to its waiting mode. The embodiment shown in Fig. 5B illustrates the manner in which the oscillator 32 is used to maintain the remanence of the piezoceramic support 19 to eliminate if the VCR either is switched from its playback mode or from its waiting mode to its recording mode. The in Fig. 5B Elements illustrated that are the same as elements described with reference to FIG. 5A are identified with the aid of FIG the same reference numerals identified. The only difference is that the switch 14 "(Fig. 5B) one includes additional contact, referred to as the receiving contact R, and that to the output of the oscillator 32 is connected. Furthermore, the waiting mode contact S is electrically isolated. This is different from the one above described embodiment of FIG. 5A, in which the switch 14 does not contain the receiving contact R and in which the waiting mode contact S is connected to the output of the oscillator 32. Furthermore, in Fig. 5B, the changeover switch has 15 'one connected to the input of the oscillator 32 Receiving contact R, and its movable contact is with the electrically isolated contact (S / P) either engaged during the waiting operation or during the reproducing operation. Otherwise, the one shown in Fig. 5B works.

Q3Q047 / 0041

apparatus provided in the same manner as discussed above with reference to Fig. 5A. When the video tape recorder of FIG. 5B is in its playback mode, the tracking control signal is applied to the piezoceramic holder 19, as discussed above. When the video tape recorder is switched to its recording mode, the oscillator 32 is triggered to generate the oscillating signal S ^ , see above, with a waveform of the type shown in the examples of FIG. During the recording operation, the output of the oscillator 32 is connected via the switch 14 'to a drive amplifier 18, whereby the oscillating signal S of the piezoceramic holder 19 is applied to eliminate its remanence during the initial part of the recording operation. At the end of the predetermined period of time, that is, when the oscillating signal Sp has decreased to zero, video signals can then be recorded on the recording medium with the aid of the head 2o at a uniform distance. The embodiment according to FIG. 5B is particularly advantageous when the video tape recorder is operated in an editing mode.

In the embodiment of FIG. 5B, the oscillating Signal S of the piezoceramic holder 19 is applied when the video tape recorder is in its playback mode Recording mode or is switched from its waiting mode to recording mode. That is, a predetermined period of time At the beginning of the recording operation, the removal of the remanence of the piezoceramic holder 19 is dedicated.

The apparatus to which the present invention can be applied need not only be a video recorder, for Example of a video tape recorder being limited, the present invention can be used with other recording and / or playback devices Find use in which a piezoceramic bracket is used to mount a transducer across a

030047/0041

take medium to move. The recording medium does not need any To be magnetic tape, nor does this medium need to be limited to a magnetic recording medium. Farther the tracking control circuit need not be limited to the type shown in Fig. 5A and one Dither signal source 16, an envelope detector 22, a phase detector 23 and a sawtooth generator 26 contains.

In summary it can be said:

The invention relates to a method and a device for controlling the piezoceramic head mount, used in the rotating head assembly of a video tape recorder, for example.

When attached to the piezoceramic bracket, which is a bimorph May be a sheet array or a monomorphic sheet array, a tracking control voltage is applied is, the holder is deflected in order to move the head carried by it accordingly. This technique is used to dynamically compensate for tracking errors that occur during various playback modes can occur when a head is scanning a prerecorded recording track. During a normal In playback mode, a dither signal is generally applied to the piezoceramic holder, so that the head vibrates about the recording track it is scanning, as seen in Figure 6A of the drawings of the application. One DC control voltage is generally superimposed on this dither signal to coincide with the scanning line of the head to bring with the recording track. During special playback modes, such as slow motion, standstill movement or time lapse, a tracking control voltage, generally sawtooth waveform

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the piezoceramic bracket is applied to ensure that the head scans the right track.

It was found that the piezoceramic holder shows a remanence or residual deflection, even if the Zero voltage is applied to the bracket. This remanence prevents the one held by the piezoceramic holder Head to return to its original position. The object of the present invention is this remanence from the piezoceramic bracket.

In accordance with the invention, an oscillating signal, which may have the waveform shown in Fig. 7, is applied to the piezoceramic holder for a predetermined period of time when the video recorder is switched from its playback mode to its standby mode or when the video tape recorder is from its playback mode - or waiting mode is switched to its recording mode. The magnitude of the oscillating signal is much greater than the magnitude of the tracking control voltage and, as can be seen in FIG. 7, this magnitude of the oscillating signal gradually decreases during at least a portion of the predetermined period of time. According to one embodiment, the oscillating signal has a fixed constant amplitude during a first section P-, and then the oscillating signal gradually decreases during the following section P _n . According to a second embodiment, the oscillating signal has the falling envelope during the entire period, as in the section P _n . When the oscillating signal drops to zero volts, essentially all of the remanence of the piezoceramic mount is removed.

ifaten ^ anwaLt

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Claims (20)

Claims ! .Device for recording and / or reproducing information on or from a recording medium in parallel, diagonal tracks and effective in selected operating modes, with at least one transducer for scanning successive tracks across the recording medium, with a piezoceramic Bracket for holding the transducer, which reacts to a signal applied to it by deflecting around the transducer to shift accordingly in a direction transverse to the scanning track, and a control circuit for applying a tracking control signal to the piezoceramic bracket while selected Operating modes, characterized by a source (32) of oscillating signals (S) with a size that is substantially is above the size of the tracking control signal (S ^), as well as by a switching circuit (14, 15; 14 ', 15') for switching between selected modes of operation of the device by applying the oscillating signal to the piezoceramic Bracket responds for a predetermined period during which the size of the oscillating signal slowly increases decreased from a maximum amplitude to a minimum amplitude. 030047/0041 2. Apparatus according to claim 1, characterized in that the circuit has a changeover switch (14, 15) with two Contains positions, the first position being used to set up a playback mode, meanwhile the tracking signal of the piezoceramic bracket is applied and the oscillating signal is not applied while the second position for setting up a waiting mode serves, during which information is neither recorded nor reproduced and the oscillating signal the piezoceramic holder is applied for the predetermined duration, while the tracking control signal is not on the holder is present. 3. Apparatus according to claim 1 or 2, characterized in that the control circuit is a source of a trembling, oscillating signal with a reference level around which the dither signal oscillates, a sensor circuit for sensing a tracking error between the track line of the transducer and a recording track scanned by it, and an adjustment circuit for adjusting the reference level of the dither signal as a function of the tracking error contains, whereby the dither signal of the piezoceramic holder is present when the switch (14, 15) is in its first position. 4. Apparatus according to claim 3, characterized in that the sensor circuit has a detector for detecting the Envelope of the signal reproduced by the transducer, a phase detector, its inputs to the envelope detector and the source of the dither signal for detection a phase difference therebetween, this phase difference being the tracking error represents, as well as a filter connected to the output of the phase detector for generating a direct current level which is determined by this phase difference. 030047/0041 - T - 5. Apparatus according to claim 3 or 4, characterized in that that the control circuit contains a sawtooth generator for generating a sawtooth waveform, the amplitudes of which is a function of the playback mode established, the dither signal being based on the sawtooth waveform is modulated before the The vibrating signal of the piezoceramic holder is applied. 6. The device according to claim 2, characterized in that the source of an oscillating signal to the second position of the switch (15) reacts in such a way that it generates the oscillating signal with a constant size for a first time interval (P) and then the size of the oscillating signal gradually reduced to zero during a subsequent second time interval (P _{7 ..).} 7. Apparatus according to claim 1, characterized in that the circuit includes a changeover switch (14 ', 15 ") with two positions, one by the first position Recording mode is established, during which normally neither the tracking control signal nor the oscillating Signal is applied to the piezoceramic holder, and wherein the second position is either a playback mode, during which only the tracking control signal is applied to the piezoceramic holder, or a Waiting position is determined during which neither the tracking control signal nor the oscillating signal to the piezoceramic Bracket is applied, the oscillating signal to the piezoceramic bracket for the predetermined Duration applied immediately after switching the switch (14 ', 15') into its first position will. 030047/0041 8. Apparatus according to claim 7, characterized in that the source of an oscillating signal reacts to the switching of the switch (15 ') in its first position in that it generates the oscillating signal of constant magnitude for a first time interval (P,) and then the size of the oscillating signal gradually reduced to essentially zero during a subsequent second time interval (P _ß ). 9. The device according to claim 1, wherein the piezoceramic holder responds to a voltage which is less than a maximum amplitude (E-,), beyond which the piezoceramic holder does not react further, characterized in that the maximum amplitude of the oscillating signal (S _c ) is smaller than E. 10. The device according to claim 9, characterized in that the maximum amplitude of the oscillating signal (S _c ) is in the range of about o.25 E_ to o.75 E _r . 11. Apparatus for use in a video tape recorder with a playback mode in which signals recorded in parallel inclined tracks on the magnetic tape are reproduced, with a waiting operating position and / or a recording operating position in which video signals are fed into the parallel, inclined tracks The video tape recorder has at least one transducer for scanning successive tracks across the tape, a piezoceramic holder for holding the transducer, which _{reacts to a signal applied to it which is smaller than a threshold value E c} by deflection so that it reacts accordingly displaced the transducer in a direction transverse to the scanning track, and a control circuit for applying a tracking control signal to the 030047/0041 piezoceramic holder during playback operation, characterized in that the piezoceramic holder normally shows a remanent deflection when the tracking control signal is switched off from it, the remanent deflection by a source of oscillating signals (32) with a size which is substantially larger than the size of the track control signal, but smaller than E_., is furthermore characterized by a circuit (14, 15; 14 ', 15') which reacts to a switch from the playback mode to the waiting mode /. or to a switch to the recording mode of the video tape recorder in such a way that it applies the oscillating signal (S _c ) to the piezoceramic holder for a predetermined period, the magnitude of the oscillating signal gradually increasing from its maximum amplitude to a minimum amplitude during at least part of the time this predetermined duration is reduced. 12. The device according to claim 11, characterized in that the circuit contains a changeover switch (14) with two positions, during the first position the tracking control signal (S _7th ) is applied to the piezoceramic holder during playback operation, and during the second position the oscillating signal (S ^) is applied to the piezoceramic holder while the tape recorder is waiting. 13. The apparatus according to claim 11, characterized in that the circuit includes a changeover switch (14 ') with a first position which is effective in the playback or waiting mode, and with a second position which is effective in the recording mode to the oscillating Signal (S _c ) to apply to the piezoceramic holder during the start of the recording mode. 030047/0041 14. Apparatus according to claim 12 or 13, characterized in that that the source of the oscillating signal contains an oscillator (32) and a switch (15, 15 "), which cooperates with the changeover switch (14, 14 ') to trigger the oscillator (32) for the predetermined duration, when the switch (14, 14 ') in its second Position is switched. 15. The device according to claim 14, characterized in that the source of the oscillating signal includes a monostable multivibrator for applying an actuation voltage to the oscillator (32) when the switch is actuated, this actuation voltage having a constant level during a first time interval (P- ) and has a gradually decreasing level during a second time interval (P _ß ) during which the size of the oscillating signal also decreases. 16. The device according to claim 15, characterized in that the maximum amplitude of the oscillating signal is in the range of about o.25 E _n to about o.75 E _n . 17. Method for eliminating retentive deflection in a Piezoceramic holder for a transducer, which is used to record successive tracks across a recording medium to be scanned in a video recording and / or playback device, this device having a recording mode, has a waiting mode and a playback mode, wherein a tracking control signal of the piezoceramic Bracket is applied during playback operation to minimize improper tracking of the transducer, characterized in that the piezoceramic holder is an oscillating for a predetermined duration Signal (Sp) is applied when the device is on hold is switched and / or when the device is switched to its recording mode, the 0300A7 / 0041 The size of the oscillating signal is less than Ε- ,,
where E is the largest magnitude of the tracking control signal,
to which the piezoceramic bracket responds, and
that the size of the oscillating signal during the
a predetermined duration reduced to a minimum level
will. 18. The method according to claim 17, characterized in that the oscillating signal has a fixed size during a first section (P,) of the predetermined period of time, and a gradually decreasing size during a subsequent section (Ρ _β ) of the predetermined period of time. 19. The method according to claim 17, characterized in that the oscillating signal has a gradually decreasing magnitude throughout the predetermined period of time. 20. The method according to claim 17, characterized in that the maximum size of the oscillating signal is in the range of about 0.25 E _c to about 0.75 E ". , 030047 / 004.1