JPH0789406B2 - Recording or playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a recording or reproducing apparatus, and more particularly to an apparatus for recording or reproducing by using a head attached to each of two electro-mechanical conversion elements having a residual displacement characteristic. .

<Description of Prior Art> In the field of magnetic recording in recent years, a magnetic head is attached to an electro-mechanical conversion element, and the position of the magnetic head is changed by driving the electro-mechanical conversion element to obtain a desired position on the recording medium. It has become possible to record or play back.

As the above-mentioned electro-mechanical conversion element, for example, a bimorph type piezoelectric ceramic element (hereinafter simply referred to as bimorph) is used. Such an element generally has a residual displacement characteristic. The residual displacement characteristic will be briefly described below. FIG. 1 is a diagram showing a characteristic of an applied voltage with respect to a bimorph and a displacement amount with respect to the applied voltage. As is clear from the characteristic diagram of FIG. 1, even if the same applied voltage is applied to the bimorph, the displacement amount of the bimorph varies depending on the characteristic due to the movement of the bimorph before that. Such residual displacement characteristics cause the following problems in a magnetic recording or reproducing apparatus using an electro-mechanical conversion element such as a bimorph.

The problems due to the above-mentioned residual displacement characteristics will be described below by taking a rotary two-head helical scan type magnetic recording / reproducing apparatus (VTR) as an example. FIGS. 2 (A) to 2 (C) are views for explaining the problems caused by the residual displacement characteristics of the electromechanical conversion element in the conventional VTR. Figure 2 (A)
FIG. 4 is a diagram showing the structure of a rotary head drum in a VTR. In FIG. 2 (A), 1 is a rotary drum, 2 and 3 are bimorphs, 4 and 5 are heads mounted on the bimorphs 2 and 3, and 6 and 7 are displacement directions of the heads 4 and 5, respectively. It is an arrow.
At this time, if the bimorphs 2 and 3 have the same displacement, the heads 4,5
Are configured to rotate on the same plane.
The heads 4 and 5 have the same magnetization direction.

In FIG. 2B, 13 is an arrow indicating the traveling direction of the magnetic tape 8. In normal recording, the tape is run at a predetermined speed in the direction of arrow 13 and the magnetic head 4 is moved in the direction shown by the solid line 9. Recording tracks are sequentially formed by tracing 5 and 5. The solid line 9 indicates the center line of the recording track.
Here, when the tape 8 is stopped, the loci traced by the heads 4 and 5 are in the directions shown by the alternate long and short dash line 10, and the heads 4 and 5 trace when the tape is run at a speed four times faster than during normal recording. The locus is in the direction shown by the chain double-dashed line 11.

In this way, when performing so-called high-speed search or still playback by making the tape running speed different from that during normal playback, by controlling the bimorph and displacing the head as shown by arrow 12, a playback screen without noise is obtained. It is what is done. FIG. 2 (C) is a timing chart showing the application timing of the applied voltage to the bimorphs 2 and 3 in the quadruple speed search in such a case. The waveform shown in (a) of FIG. 2 (C) is a signal related to the rotation of the drum 1, and when the level is low (the period shown by A in FIG. 2 (C)), the head 4 outputs high level. When (Fig. 2 (C)
It is assumed that the heads 5 are tracing on the magnetic tape during the period B). Further, (b) of FIG. 2 (C) is a voltage applied to the bimorph 2 to displace the head 4, and (c) of FIG. 2 (C) is a voltage applied to the bimorph 3 to displace the head 5. . However, when the heads 4 and 5 are actually tracing on the magnetic tape 8 in (b) and (c) of FIG. 2C, the part that controls the heads 4 and 5 is the right downward part. Is the waveform of.

Now, it is assumed that there is an instruction to return from the quadruple speed search to the normal reproduction at the moment indicated by t ₁ in FIG. 2 (C). At this time, the displacement amounts of the bimorphs 2 and 3 must be equal, and the positions of the heads 4 and 5 in the directions of arrows 6 and 7 (hereinafter simply referred to as head height) must be equal. However, as shown in FIG. 2 (C), if both applied voltages are set to zero from the next zero crossing point of both applied voltages, or both applied voltages are set to zero at the instant of t ₁ , the bimorph 2 is shown in FIG. Points A to A ', bimorph 3 is point B
Since the state changes from the point B ′ to the point B ′, the head heights cannot be adjusted and the deviation shown by 2 lb in FIG. 1 occurs. Therefore, even during normal reproduction, the head height always deviates, and it becomes impossible to trace the track satisfactorily.

In order to eliminate the influence of the residual displacement characteristic, it has been conventionally considered to apply a gradually decreasing AC applied voltage to the bimorph so that the state of the bimorph converges to the point O in FIG. However, according to this method, an applied voltage that gradually attenuates must be created, and the circuit configuration becomes complicated. Moreover, in this method, it takes too much time to remove the influence of the residual displacement characteristics. In other words, if it is attempted to converge the state of both bimorphs from the state shown by point A or B in FIG. 1 to point O, it will take some time, and the amount of displacement of the bimorph, that is, the displacement of the head in an instant. It was impossible to equalize the quantity. Considering the example of FIG. 2, this means that the head is completely useless for a while when switching from the high speed search reproduction to the normal reproduction, and a good reproduction screen cannot be obtained.

<Object of the Invention> In view of the above-mentioned drawbacks, the present invention provides a recording or reproducing apparatus capable of instantly making the displacement amounts of two electro-mechanical conversion elements having residual displacement characteristics equal at the time of mode switching. With the goal.

<Description of Embodiments> Hereinafter, the present application will be described in detail with reference to embodiments. Third
FIG. 4 is a diagram showing a circuit configuration of a bimorph control system of a VTR as one embodiment of the present invention, and FIG. 4 is FIG.
(I) It is a waveform diagram showing the waveform of each part. In Figure 3
Reference numerals 2 and 3 are bimorphs arranged as shown in FIG. 2 (A), and reference numerals 4 and 5 are magnetic heads similarly arranged as shown in FIG. 2 (A). Further, 20 is a mode selector including operation buttons, 21 and 22 are circuits for generating a triangular pattern of applied voltages to be supplied to the bimorphs 2 and 3, respectively according to the mode selector 20, and 23, 24, 25 and 26 are respectively in the figure. An analog switch that is turned on and off by the input to the control terminal shown by the arrow, 27 is the second
A terminal to which a 30 Hz rectangular wave signal (hereinafter referred to as 30PG) corresponding to the rotation of the drum 21 shown in FIG. 4A is input, and 28 is a 60 Hz rectangular wave as shown in FIG. Mono multivibrator that forms signals, 29 is an inverter, 3
0 and 31 are AND gates, 32 and 33 are D-type flip-flops (DFF), and 34 and 35 are low-pass filters (LP
F), 36 and 37 are amplifiers, respectively. The recording / reproducing system circuit is separately provided.

The operation of each part when performing a 4 × speed high-speed search during normal reproduction in this VTR and then returning to normal reproduction again will be described below. It is assumed that the periods indicated by An and Bn (n is an integer) in FIG. 4 are the periods in which the head 4 and the head 5 are tracing on the magnetic tape, respectively.

When the high speed search reproduction mode start is commanded from the mode selector 20 at the moment of τ ₁ shown in FIG.
The output (e) of 20 turns to high level. By the way, the AND gates 30 and 31 supply the output of the monomulti 28 to the clock input terminals of the DFFs 32 and 33 when 30PG is at low level and high level, respectively. The output of the AND gate 31 is shown in FIG. 4 (c), and the output of the AND gate 30 is shown in FIG. 4 (d). DFF32,
Reference numeral 33 sets the Q output to the high level at the first set timing (indicated by τ ₃ and τ ₂ in the figure) after the output (e) of the mode selector 20 turns to the high level. Therefore τ ₂
The switch 23 is turned on, and the switch 24 is turned on at τ ₃ . On the other hand, according to this, at τ ₂ switch 25
However, at τ ₃ , the switches 26 are turned off.

If τ ₁ is the timing as shown in FIG. 4, first, at τ ₂ , the potential at point (h) is changed from 0 [V] to the triangular pattern generation circuit.
There are 12 output voltages. At this time, since the head 4 is not tracing on the tape, the image distortion due to this switching does not occur. Further, at τ ₃ 1/60 seconds after that, that is, after the phase difference between the two triangular patterns is delayed, the potential at point (i) becomes 0.
The output voltage of the triangular pattern generation circuit 22 becomes from [V].
In this case as well, the head 5 does not trace on the tape.

Therefore, the changes in the applied voltage supplied to the bimorphs 2 and 3 are always in exactly the same pattern except that the phases are different.
In other words, considering the state of both bimorphs even during high-speed search playback, the state of one bimorph always follows that of the other bimorph in the characteristic diagram of FIG. 1, and the two bimorphs are 2 because they do exactly the same exercise
The displacement amounts of the two heads can always be made equal with a certain phase difference, and good high-speed search reproduction can be performed.

Next, when the high speed search reproduction mode is canceled by the mode selector 20 and the normal reproduction mode is instructed at the moment shown by τ ₄ , both D inputs of DFF32 and 33 shift to low level. DFF3
3 turned to the low level Q output in the first set the timing tau ₅ than tau _4, starts to a low level Q output in the first set the timing tau ₆ than even tau ₄ DFF circuit 32. Also at this time τ ₅ , τ ₆
Corresponds to the phase difference between the two triangular patterns. At τ ₅ , the output of DFF33 also turns to high level and switches 2
3 is off, switch 25 is on, and the potential at point (h) is 0
It is fixed at [V]. Also, at τ ₆ , the output of DFF32 changes to high level, so switch 24 is turned off and switch 24
26 is turned on and the potential at point (i) is fixed at 0 [V]. Even at the above-mentioned τ ₅ and τ ₆ , the heads 4 and 5 do not trace on the magnetic tape, so that the reproduced image is not adversely affected.

As described above, when switching from the high-speed search reproduction mode to the normal reproduction mode, the applied voltages supplied to the bimorphs 2 and 3 only have different phases and can always have the same pattern. Therefore, the relative head heights of the two heads in the high speed search reproduction and the normal reproduction after the mode switching can always be made equal to each other, and good high speed search reproduction and normal reproduction can be performed.

FIG. 5 is a diagram showing a VTR head structure as another embodiment of the present invention. In FIG. 5, reference numerals 41 and 42 denote magnetic heads, which have different azimuth angles as shown in the drawing, and are mounted on a rotating cylinder (not shown) with a phase difference of 180 °. In addition, 43 and 44 are bimorphs, which hold the heads 41 and 42, respectively.

Consider the variable speed reproduction in a VTR having such a configuration. FIG. 6 is a diagram showing how the head is traced on the tape when high speed search reproduction is performed in the VTR having the head structure shown in FIG. In FIG. 6, 45 is the center line of the track recorded by the head 41 or a head having the same azimuth angle as the head 41, and 46 is the head 42 or the head 42.
Is a center line of a track recorded by a head having the same azimuth angle. 47 is for 4x speed search playback,
Head when the applied voltage to the bimorph 43 is 0 [V]
The center line of the scanning locus of 41 and 48 are the center lines of the scanning locus of the head 42 when the applied voltage to the bimorph 44 is 0 [V].

Fig. 7 shows the bimorph 4 at the time of quadruple speed search in this VTR.
It is a figure which shows the voltage pattern signal applied to 3,44. 7th
In the figure, 51 indicates a voltage pattern signal applied to the bimorph 43, and 52 indicates a voltage pattern signal applied to the bimorph 44. Further, A indicates a period during which a reproduction signal is obtained from the head 41, and B indicates a period during which a reproduction signal is obtained from the head 42. That is, the actually required applied voltage pattern is the portion from point p to point q and from point r to point s. However, by applying the applied voltage pattern as shown in FIG. 7, the direct current component becomes 0, and the secular change of the bimorphs 43 and 44 can be prevented.
Further, the present invention can be applied as follows.

FIG. 8 is a diagram showing a circuit configuration of a bimorph control system of a VTR as another embodiment of the present invention corresponding to the head configuration shown in FIG. The same numbers are attached to the same components as in FIG. In FIG. 8, 53 and 54 are level comparison circuits, 55 and 56 are DFFs, and 57 is a 3-input OR gate.

The operation of each part when a normal speed reproduction is carried out in the VTR, a quadruple speed search is carried out, and then the normal reproduction is carried out again will be described. FIG. 9 is a timing chart showing the waveforms of the respective parts of FIGS.

When the start of the high speed search reproduction mode is instructed by the mode selector 20 at time t ₁ shown in FIG. 9, the mode selector 20
The output (b) of (1) shifts to the high level. At the instant of t _1, the triangular pattern generating circuits 21 and 22 start to generate outputs as shown in FIGS. The level comparison circuits 53 and 54 compare the output voltage of the triangular pattern generation circuits 21 and 22 with the 0 level, and the output voltage of the triangular pattern generation circuits 21 and 22 is 0 [V].
It is configured such that a higher level output is produced when the size becomes smaller. Therefore, the DFF55 and 56 are the triangular pattern generation circuits 21 and 22.
The D input will be sampled when the output voltage at the output changes from negative to positive.

Thus, the output of DFF55 (g) at the moment t ₂ in FIG.
Goes high and the output goes low. Therefore, at this moment, the switch 23 is turned on and the switch 25 is turned off, and the triangular pattern voltage starts to be supplied to the bimorph 43 via the LPF 34 and the amplifier 36. At this time, since the head 41 does not trace on the tape, the image distortion due to this switching does not occur. Then, the head 41 switches the tape running speed from the moment when the tape is next traced (shown in t ₃ in FIG. 9). By doing so, the timing of switching the tape running speed and the timing of switching to driving the bimorph according to the triangular pattern are completely matched.

Next, at the moment when the output of the triangular pattern generation circuit 22 exceeds 0 [V] (indicated by t ₄ in FIG. 9), the output of the DFF 56 is inverted, and from this moment, the output voltage of the triangular pattern is also applied to the bimorph 44. Begin to be. Of course, at this time as well, the head 44 is not tracing on the tape, and the image is not disturbed.

Thus, when switching from the normal reproduction mode to the high speed search reproduction mode, the displacement state of one head can be made equal to the displacement state of the other head with a certain phase difference even in the head configuration shown in FIG. Good high-speed search reproduction can be performed without causing relative head height deviation.

Next, when the mode selector 20 cancels the high-speed search mode at the moment t ₅ to give a command for the normal reproduction mode, the D inputs of the DFFs 55 and 56 both turn to the low level. The DFF at the next sampling DFF55 (shown in FIG. 9 t ₆₎
The Q output of 55 changes to low level, and the supply of the high speed search reproduction triangular pattern to the bimorph 43 is completed. At this moment, the head 42 traces on the tape, but when the tracing by the head 42 is completed, the running speed of the tape is returned to the normal speed by a servo circuit (not shown).
(Ninth moment shown in FIG. T ₇₎ immediately after t ₇ the trace of the normal reproduction is performed by the head 41, the triangular pattern voltage to bimorph 44 at the next sampling DFF56 (shown in FIG. 9 t ₈₎ Supply is also stopped. Also at the t ₈ the Q output of DFF55 (g), DFF56 of Q
Since the output (h) and the output (b) of the mode selector 20 are all at the low level, the output (i) of the OR gate 57 also changes to the low level and the generation of the triangular patterns from the triangular pattern generating circuits 21 and 22 is stopped.

As described above, also in the VTR having the head configuration as shown in FIG. 5, since the bimorph displacement pattern is the same, the head height is always the same during normal reproduction, and the high-speed search reproduction is also performed. The width of change in head height and the average height can be made equal, and good reproduction can be performed.

The present invention can be applied to VTRs other than the head configurations shown in the above two embodiments. For example, recording is performed while two adjacent heads having different azimuth angles are sequentially formed to form adjacent tracks, and for reproduction, one of the recording heads and the head having the same azimuth angle are used.
The present invention can also be applied to a VTR of a type in which these heads are provided on a bimorph and only one track formed by one of the recording heads is traced to perform special reproduction. Also in this case, the triangular patterns applied to the two bimorphs may be the same or similar, and the switching timing of the triangular patterns may be shifted according to the phase difference.

Further, in the above-mentioned embodiment, the switching between the high speed search reproduction mode and the normal mode is explained, but the switching between the high speed search reproduction mode and the slow motion reproduction mode or between the slow motion reproduction mode and the normal reproduction mode is performed. In this case, by applying the present invention to make the application state of the triangular pattern the same before and after the switching, the head height is made the same during normal reproduction, and the bimorph displacement pattern is made identical during variable speed reproduction. can do. However, in switching between the high speed search reproduction mode and the slow motion reproduction mode, the phase difference of the triangular patterns applied to the two heads in both modes is often different from each other. In this case, a predetermined voltage (for example, 0V) may be applied to any of the bimorphs for a predetermined time.

<Explanation of Effect> As described above, according to the present invention, a plurality of electro-mechanical conversion elements are provided in at least one mode,
Even after switching between the two modes of operating with a predetermined pattern signal each having a phase difference, it is possible to drive a plurality of electro-mechanical conversion elements in the same state, so that good recording or reproduction can be performed. Is what you can do.

[Brief description of drawings]

FIG. 1 is a diagram showing the applied voltage to the bimorph and the characteristic of the displacement amount against it, and FIGS. 2 (A) to (C) show the problems due to the residual displacement characteristic of the electro-mechanical conversion element in the conventional VTR. FIG. 3 is a diagram for explaining, FIG. 3 is a diagram showing a circuit configuration of a bimorph control system of a VTR as one embodiment of the present invention, FIG. 4 is a timing chart showing waveforms of respective parts in FIG. 3, and FIG. FIG. 6 is a diagram showing a head structure of a VTR as another embodiment of the invention, and FIG. 6 shows a state of head tracing on a tape when high speed search reproduction is performed in the VTR having the head structure shown in FIG. FIG. 7 is a diagram showing a voltage pattern applied to a bimorph at the time of quadruple speed search, and FIG. 8 is a VTR bimorph control system as another embodiment of the present invention corresponding to the head structure shown in FIG. FIG. 9 shows a circuit configuration of FIG. Is a timing chart showing a part of the waveform. 2 and 3 are bimorphs as electro-mechanical conversion elements, and 4,5
Is a head, 20 is a mode selector, 21 and 21 are triangular pattern generation circuits, 23, 24, 25 and 26 are analog switches, 28 is mono-multi, 29 is an inverter, 30 and 31 are AND gates, 32, and 33 are DFF, 41, 42 are heads, 43,
44 is a bimorph, 53 and 54 are level comparison circuits, 55 and 56 are DFFs, and 57 is an OR gate.

Claims (1)

[Claims] 1. An apparatus for recording or reproducing by displacing a plurality of electro-mechanical conversion elements having respective residual displacement characteristics, each head being mounted, wherein the device is applied to each of the plurality of electro-mechanical conversion elements. Control signal generating means for generating a plurality of control signals for controlling the voltage to be applied, and a predetermined difference having a phase difference with respect to each of the plurality of electro-mechanical conversion elements by the control signal generating means in at least one mode. Mode switching means for switching the device between two modes for generating a pattern signal, and the control signal generating means for controlling the mode switching means to switch the plurality of electric devices.
Means for shifting the switching timing of the control signal for each of the mechanical conversion elements for a period corresponding to the phase difference.