CA1128200A - Video signal reproducing system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A video signal reproducing system having a normal signal reproducing mode and a still signal reproducing mode includes a control signal generating means for reproducing a still mode control signal. A support means for supporting a signal reproducing means irresponsive to the still mode control signal, whereby the signal reproducing means is maintained in substantial alignment with a recorded track of a recorded medium. Accordingly, the mis-tracking of the signal reproducing means relative to a predetermined recorded track is prevented, when the still signal reproducing mode is selected.

Description

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- BACRGROUND OF THE INVENTION
F~eld o~ the~Invention: .
15 ~- ~ :This ~nvention relates to a system for reproducing ~- ~ a video signal reGorded in parallel track sections on a ~; . records~ medium, and more paxticularly to a sys~em having à normal slqnal reproducing mode wherein the recorded medlum is transported at a predetermined normal speed relative : to a signal reproducing head,.and a ~till signal reproducing mode wherein the transportation of the recorded medium is :stopped.~
Generally, in a video slgnal reproducing system . in which the normal signal reproducing mode or `a normal ; '~`25 ~ play-back mode and the stiIl signal reproducing mode or ~: - a still play-bac~ mode can be selectively obtained, the .. ~ -scanniny direction of a slgnal reproducing head is inclinedto~ the~ transport~:ng-direction- of the recorded medium., ;i .: Accordingly, when the normal play-back mode and the stlll y ~ e ~r~ no~ diff rent from each o~her in the relative po~,itional relationship between the signal reproducing head and the recorded med~um, the predetermined recorded track on the recorded medium cannot be scanned tn at least one of the modes by the head without mistracki~g .
Descrlpt~on of the Prior Art:
A~cordingly, i~ a conventional ~ideo tape recorder (VTR), the level of at least one of tape guides arxanged axoun~ a head drum containing a magnetic head can be varied to control the inclination angle of the maqnetic tape to the head drum. Desirable inclination angles of the tape can be obtained with the variation o the level of the tape guide both in the normal play-back mode ~nd in the still play-back mode. However, a precise mechanism t S required to vary. the level of at least one of the tape guides so as to control the inclination angle of the magnetic tape to the head drum~ Accordingly, the conventional video signal reprodu~ing apparatus has the disadvantages that it ls large-sized and heavy and that it is expensive.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a video eignal reproducing system which overcomPs the above described disad~antages~.
~n accordance w~th the foregoing objec~, there is provided:
. . _ A ystem for xeproducing ~ video signal recorded in ~ucces~ive parallel tracks on a recording medium, said system comprisins: .
rotary support means, bi-morph leaf means~ mounting means securing one end portion of said bi morph leaf means to said rotary support means with ~aid bi~morph leaf mean~ being canti-.
:-~ 2-levered therefrom so as to be movable by flexing from a rest condition in either direction transYerse to the direction of said tracks, signal reproducing means for reproducing a video ~ignal in a re~pective one of said track~ and belny connec~-ed wikh the other end portion of said bi-morph leaf mean~ so as to be mo~able therewith, and damper means in addition to ~aid mounting means and being engageable with said other end portion of said ~i-morph leaf means at a distance along the latter spaced from said mounting means for damping free oscillations of said bi-morph leaf means due to bending forces applied to ~aid bi-morph leaf mean~.
The above and other objects, features and advantages of this invention, will he apparent in the following detailed description of illustrative embodiments which are to be read in connection with the accompany drawi~gs.

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BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a block diagram of a video signal reproducing system according to one embodiment o~ this invention;
S Fig. 2 is a view for explaining the embodiment and showing the relationship between the track on the magnetic tape and the scanning direction of the magnetic head;
, Fig. 3A to Fig. 3N are wave forms of signals generated in the system of Fig. l;
Fig. 4 is an enla~ged shematic bottom view of the magnetic head and a head-mounting means;
Fig. 5 is an enlarged schematic side view of the magnetic head and head-mountinq means o Fig. 4; and Fig. 6 is a connection diagram of an important part of a video signal reproducing system acc~rding to another embodiment of this invention;
DESCRIPTTON GF THE PREFERRED EMBODIMENTS
One e~bodiment of this invention will be described with reference ~o Fiy. 1 to Fig. 5.
Fig. 1 shows a block diagram of a video signal reproducing system which includes a rotary head drum assembly 2. A video signal is recorded on, and reproduced from a magnetic tape 1 as a magnetic medium by the rotary head drum assembly 2.
The drum assembly 2 includes a stationary lower head drum ~not shown). The magnetic tape 1 is obliquely guided in the shape of Q by the lower head dxum, and is transported at a predetermined normal speed. An upper head drum 3 is rotatably arranged above the lower head ' Oo drum, concentric with the latter. The upper head drum 3 rotates one revolution per period 2Tv of one frame of video signal, namely at the rate of 30 cycles per second.
A pair o magnetic heads 4A and 4B diametrically opposl~e to each other, or spaced ~rom each other at the angular intervals of 180 is arranged on the lower surface of the upper head drum 3. Air gaps are formed between the magnetic heads 4A and 4B, and the lower surface of the upper head drum 3,extending perpendicularly to the latter, as apparently shown on Fig. 5, respectively.
The heads 4A and 4B scan the magnetic tape 1 with the rotation of the upper head drum 30 When video signals to be recorded are supplied to the magnetic heads 4A and 4B, recorded tracks T are formed for every field of ~ideo signals on the m~gnetic tape 1, As sho~n on Fig. 2, the recorded tracks T are inclined to the lengthwise .
direction of the magnetic tape 1 by an angle ~N~ And in the reproducing operation, the magnetic heads 4A
and 4B scan the recorded tracks on the magnetic tape 1 to reproduce the video si~nals recorded on the recorded tracks T.
The aboye desc~ibed rotary head drum assembly 2 is the same as ~ rotary h~ad drum assembly in a so-called "helical two-head Q -type VTR". Accordin~lyr the construction~
of the rotary head drum assembly 2 will not be further described. Moreoyer~ since this in~ention is directed to the case that ~ideo signals are reproduced fxom the recoraed tracks on the magnetic tape~ a ~eco~d system by which video signals are recorded on the magnetic tape, will not be described in detail. The upper head drum J ~ 8~1~
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3 of the rotary head drum assembly 2 is connected to a-.
head motor 5 through a rotary shaft 30 which rotates at the rate of 30 cycles per second, namely at the period of 2Tv. Accordingly, the upper head drum 3 rotates ; 5 at the rate of 30 cycles per~second, namely at the period of 2Tv. _A drive circuit for the head motor 5 is not sho~n The magnetic tape 1 is pressed between a capstan 7 connected to a capstan motor 6, and a pinch roller 9 to be transported at a predetermined normal speed. The pinch'riller 9 is controlled by a plunger 8 so as to be separated from the capstan 7, and to be pressed to the capstan 7. The plunger 8 is actuated when a still-mode selecting button (not shown) is pushed to select the still signal reproducing mode.
Reproduced video signals obtained from the magnetic heads 4~ and 4B are denoted by reference letters a and a' respectively. When a reproduced video signal is obtained from the first field of video signals recorded on the magnetic tape 1, through the~magnetic head 4A, the reproduced video signal a consists of odd-numbered field (first field, third field, fifth field..... ) o video signals recorded on the magnetic tape 1, as shown on FigO 3A. And the reproduced video signal a' consists of even-numbered fields (second field, ~ourth field, sixth field, .... ~3 of video signals recorded on the magnetic tape 1, as shown on Fig. 3B.
The reproduced video signals a and alobtained from the magnetic heads 4A and 4B are supplied to a mixer 12~ through amplifiers llA and llB as occasion .
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demands, respectively, as shown on Fig. 1. In the mixer 12 t the reproduced video sig'nals a and a'are combined with each other. Thus, a continuous reproduced video signal b, recorded on the maynetic tape 1, ' as shown on ~ig. 3C is obtained.
The video signal recorded on the magnetic tape 1 may be a'frequency modulated signal as usual.
Accordingly, the.reproduced'video signals a, a'and b may be frequency modulated signals. After the reproduced video - 10 signal`b ~rom the mixer 12 passes thxough a limitter 13, it.is suppli.ed to a well.known freauency demodulator 14.
A demodulated reproduced video signal e is obtained from the frequency demodulator 14, and it is supplied to a monitor TV 15. A picture by the reproduced video signal ~ 15 ' e is obtained in the monitor TV 15.
In the video signal reproducing system of Fig. 1, when the plunger 8 is actuated to.separate the pinch roller 9 from the capstan 7, the transportation of thP
magnbtic tape 1 1~ stopped, while the magnetic tape 1 is guided by the lower head drum. The inclination àngle :of the scanning direction oE the magnetic heads 4A and 4B
. to the magnetLc tape 1 varies with the stop of the transport ation. Accordingly, the magnetic heads 4A a.nd 4B
scan the magnetic tape 1I deflected from the recorded .track T on the latter. The mis txacking occurs. The relationship between the scanning path S of the magnetic heads 4A and 4B and the recorded track T'is shown on Fig. 2. The inclination angle es of the.scanning path S is different from the inclination angle eN f the recorded track T, The difference t9N ~ ~S~ is a mistracking ~ ' 6 angle. In Fig. 2, both the rotational airection of the upper head drum 3 or the scan~ing direction of the magne~ic heads 4A and 4B to the magnetic tape 1, and the transporting direction of the magnetic tape 1 are Eo~ard~ ~
According to this embodiment, ~ith ~he stop of the 1~ransportation of the magnetic tape 1, the - relative positions of the magnetic heads 4A and 4B to the magnetic tape 1 are varied from the noraml positions so as to equalize the inclination angle eS of the scanning path S of the magnetic heads 4A and 4B with the inclination angle eN f the recorded track T.
As t~e resultj the magnetic heads 4A and 4B
move on a scanning path S', as shown on Fig. 2. And the terminal end of the scanning path S' coincides with that of the recorded track T. The ~ideo signal recorded on the track T is repeatedly reproduced. The reproduced - video signals c and c' as shown on Fig. 3D and Fig. 3E
are obtained from the magnetic heads 4A and 4B. It is apparent that the magnetic heads 4A and 4B track on the same portion o the magnetic tape 1, since the transport-ation o~ the magnetic tape 1 is stopped.
When the terminal end of the scanning path S' coincides with that of the track T on which the video signal of the N-th field is recorded, the video signal of the N-th ield is intermittently repeated in the reproduced video signals c, and ' as shown on Fig. 3D and Fig. 3E, respectively. The non-signal section of the reproduced video signal c'corresponds to the signal section of the reproduced video signal c. And the signal section of the reproduced video signal c' corresponds to the non-signal O

section of the reproduced video signal c. Accordingly, a continuously repeated video signal of the N~th field is obtained from the mixer 12, as shown on Fig. 3,F, and it-is similarly obtained from the frequency d~modulator 14. A still plcture by the reproduced video signal ~ from - the frequency~dem~d~lator 14 i5 obtained ~n the monltor TV lS.
As above described, in the video signal reproducing apparatus having the normal signal reproducing modej the transportation of the magnetic tape 1 is' stopped, and the,relative positions of the magne~ic heads 4A and 4B to the magnetic tape 1 are displaced from the normal positions to obtain the still video signal in the still play-back mode.
According to the one embodiment of this invention, the following construction is used for the displacement of the magnetic head~ 4A and 4B from the normal positions. ' ' In the~rotary head drum assembly 2, the magnetic . heads 4A and 4B are combined with the upper head drum 3 through piezo-ceramic leafs 20A and 20B so that the magnetic heads 4A and 4B can be displaced from the normal positions in the air gap between the lower surface of the upper head drum 3 and the magnetic heads 4A and 4B.
~~ In the still pl~y~back mode, a head position control signal, which will be hereafter descrl~ed, is supplied to the pie,Zo-ceramic leafs 20A and 20B.
Next, one example of the plezo-ceramic leafs 20A
and 20B will be described with reference to Fig. 4 and Fig. 5.
The piezo-ceramic leafs 20A and 20B lncludes pairs of plate-like piezo-ceramic materials 23 and 24, L2~ 0 respectively. Conductove layers 21 and 22 are ormed on bo~h sides of the piezo-ceramic materials 23 and 24. A
mono-morph leaf is formed by -the conductive layers 21 and 22 and the piezo-ceramic material 23 and 24. The one conductive layers 22 are combined with each other. Thus, a bi-morph leaf is obtained. According to this embodiment~
; the piezo-ceramic leafs ZOA and 20B are used as the bi-morph leaf.
- Lead wires 25 and 26 are connected to the other conductive layers 21 on the piezo-ceramic materials ; 23 and 24, respectively. And a lead wire 27 is connectedcommonly to the one conductive layers 22. In this embodiment, the piezo-ceramic leafs 20A and 20B connected to three lead wires are used as the bi-morph leaf. The piezo-ceramic materials 23 and 24 are controlled by separate control signals. Accordingly, the distortions of the materials 23 and 24, and the errors of the control signals are averaged, so that great error can be avoided.
- One ends of the piezo-ceramic leafs 20A and 20B
are fixed on the upper head drum 3. When voltages of ; opposite polarities are applied to the lead wires 25 and 26 with reference to the lead wire 27, respectively~ a bending force is generated in the piezo~ceramic materials 23 and 24, which function~ to bend the piezo-ceramic materials 23 and 24 in the same direction. Accordingly, ; the top ends of the leafs 20A and 20B are displaced fromthe normal positions in the direction perpendicular to the surfaces of the materials 23 and 24.
- As shown on Fig. 4 and Fig. S, mounting bases 28 are fixed to the lower surface bf the upper head drum 3 The base ends of the piezo-ceramic leafs 20A and 20B

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~re fixed to the mounting bases 28 by adhesive 29.
The leafs 20A and 20B are so arranged that the surfaces of the piezo-cramic materials 23 and 24 are - parallel with the lower sur~ace o~ the upper head dxum 3.
- The magnetic heads 4A and 4B are attached to the ~ree ends of the lea~s 20A and 20B. The lengthwise directions o the a1r ~aps of the heads 4A and 4B are perpendicular -to the surfaces o the materials 23 and 24. And the surfaces of the materials 23 and 24 are substantially .10 . perpendicular to the rotational shaft 30 of the upper head drum 3.
Damper members Sla and 51b may be provided for damping free oscillation due to the bending force applied to the piezo-cramic leafs 20A and 20B. The damper members 51a and 51b are attached to a pair of tabs 50a and 50b fixed to one end of à damper mounting plate 50 which is - fLxed to the lower surface of the upper head drum 3~
.The damper mounting plates SO extend toward the :
periphery of the upper head drum 3 from the outward side 20 - of the mounting base 28. The damper members Sla and Slb are pressed between the sides of the piezo-cramic leafs 20A and 20B and the tabs 50a and 50b, respectively. When no voltage ~
is supplied to the lead wires 25, 26 and 27 for the piezo- ~ .
ceramic leafs 20A and 20B r the piezo-ceramic }eafs 20A and . 20B are not displaced from the normal posltions, where the free ends of the leafs 20A and 20B ~in other words, the magnetic heads 4A and 4B) are located at the normal positions, respectively. Accordingly,: in the normal signal reproducing mode, the magnetic heads 4A and 4B
scan the tracks of the magnetic tape 1 without mistracking.

As above described, the reproduced video signals a and a' are obtained from the magnetic heads 4A and 4B, as shown on Fig. 3A and Fig. 3B. In ~he still play back mode, when no voltage is applied to the lead wires 25, 26 and 27 for the piezo-cramic leafs 20A and 20B, the magnetic heads 4A and 4B scan the magnetic tape 1 in the scannlng path S which is inclined by the angle ~s to the lengthwise : direction of the magnetic tape 1. When voltages of opposite polarities are applied to the lead wires 25 and 26 with reference to the lead wire 27, the free ends of the piezo-cramic leafs 20A and 20B (in other words the magnetic heads 4A and 4B)' are displaced from the normal positions, relative to the upper head drum 3.
~- When the volta~es supplied to the lead wires 25 and 26 .are alternating, the displacements of the magnetic heads 4A and 4B vary in accordance with the wave forms of the alternating voltages.
Next, one example of head position control signal as the alternating voltage and arrangements for generating the head position control signal will be described.
In the system of Fig. 1, well known pulse generators 31A and 31B are arranged in relation to the rotary shaft 30 of the upper head drum 3 in the rotary head drum assembly 20 In the reproduced video signal a obtained from the magnetic head dA, as shown on Fig~ 3A, initial times of the odd-numbered fields are denoted by tl t3, t5 ...... , while in the reproduced video signal a' obtaDined . 30 from the magnetic head 4B initial times of the even-numbered fields are denoted by ~, t4 r t6 ~
.

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Whether the system is in the still play-bac1x mode or not,'a row of pulses ~ shown'on Fig~ 3G is obtained from the pulse ~enerator 31A. And a row of pulses g' shown on Fig. 3H is obtained from the pulse generator 31~. The rcw of pulses ~ c~n,sists of a first pulse at tlme ~
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which is between time tl and time preceding the time t by one field period Tv'fox example, at time tl preceding the time tl by a half of one field period Tv, a sec~nd pulse at time t3' between time t2 and time t3, a third pulse at time t5' between time t4 and time t5, an~ so on. And the row of pulses ~'consists of a first pulse at time t2' between time tl and time t2, a second pulse at time t4' between time t3 and time t4, - and so on. Periods of the pulses g and g-' are 2Tv, respectively. A phase difference between the rows of pulses g'and g' is Ty.
- The pulses g and g' from the pulse generators 31A and 31B are supplied to controllers 32A and 32B which ' may be saw-wave generators. Saw-waves h and h'as shown on Fig. 3I and Fig. 3J are obtained from the controllers 32A and 32B. The saw wave h rises from the reference level at times tl', t3', t5' .... ~., reach the maximum level at times preceding times tl, t3, ..... , by a little timç and then gradually fall to the reference level at times between times t2, t4, .. , and times t3',,t5',.. ~., whlle the saw wave h' rises from the reference level at times t2', t4', t6' ...., reach the maximum level at times preceding times t2, t4, t6 - by a little time, and then, graduaIly fall to the reference level at times between times t3, t5, t7 .. ,.. and times t4', t6'~ t8' r~,h,,e~,saw,wa,ves,h.and;h'f,r~ , the controllers 32A and 32B are supplied to drive circuits 33A and 33B which may be , amplifiers. Saw wave i of the same polarity as the polarity of the saw wave h shown on Fig. 3K, is -, . obtained between ou~put terminals 34 and 36 o~ the drive circuit 33A, corresponding to the saw wave h. And saw wave j of the opposite polarity to the polarity of the saw wave h, shown on Fig. 3M,is obtained between output terminals 35 and 36 of the drive'circuit 33A, correspQnding to the saw wave h. Saw wave i' of the same polarity as the polarity of the saw wave h!, shown on Fig~
3L, is obtained between output terminals 34 and 36 of the drive circuits 33B, corresponding to the saw wave h'.
And saw wave ]' of the opposite polarity to the lS polarity of the saw wave h', shown on Fig. 3N, is obtained betwee,n output,terminals 35 and 36 of the drive circuit 33B, corxesponding to the saw wave h'.
The saw waves i and j are supplied as the head position control signals for the piezo-ceramic leaf 20A between the lead wires 25 and 27 of the piezo-ceramic lea~ 20A, and between,the lead wires 26 and 27 of the piezo-ceramic leaf 20A, in the rotary head drum assembly 2~
~ respectiYely. A na the saw waves i' and j' are supplied as the head position control'signals for the piezo-ceramic leaf 20B between the lead wires 25 and 27 of the , '. piezo-ceramic leaf 20B and between the lead wires 26 and 27 of the piezo-cramic leaf 20B, respectively.
The amplitudes of the saw waves i and j are so selected that the displacements of the magnet.ic~head 4A due to the level difference between the level'of the saw waves i at y~o times tl, t3, ...... when the magnetic head 4A
is positioned at the initiaI end of the track T, and the level oE the saw waves i at times t2, t4 . when the magnetic head 4A is positioned at ~he ~erminal S end of the track T, and due to the level diference between the level o~ the saw waves j at times tl, k3 - when the magnetic head-4A is positioned at the initial end of the track T, and the level of the saw waves j at times t2, t4, ..~.. when the magnetic head 4A is positioned - 10 at the terminal end of the track T, correspond to a half :. of the distance between the adjacent two tracks T. And similarly, the ampl-itrudes of the saw waves i' and j' are so selected that the displacements of the magnetic head 4B due to the level difference between the level of the saw wave i' at times t~, t4 ..... when the magnetic head 4B is positioned at the initial end of the track T, and . - the level of the saw waves i' at times t3, t5 .. when .he magnetic head 4B is positioned at the terminal end of .
the track T, and due to the level difference between the level of the saw wave j' at times t2, t4 ........ when the magnetic head 4B is positioned at the initial end of the track T, and the level of the saw waves j' at times t3, t5 ...... when the magnetic head 4B is positioned : at the terminal end of the track T, correspond to the half of the distance between the adjacent two tracks T.
- Only when electric power is supplied to the drive circuits 33A and 33B through power lines 37A and 37B~ the saw waves i, j/ i' and j' are obtained from the drive circuits 33A and 33B. When no electric power is supplied to the driYe circuits 33A and 33B, zero voltages are ~ 14 -~1~8~:1t0 obtained from the drive circuits 33~ and 33B. The power lines 37A and 37B are connected to the ground through a charging capacitor 38, and to a DC power source 41 ~hrough a switch 40 for the still play-back mode. The swl~ch 40 5 - consists of a movable contact 3gN, and a pair o st~tionar~
contacts 39S and 39M. The movable contact 39N is connected to the DC power source 41. The stationary contact 39S is conneted to the power lines 37A and 37B. The stationary contact 39M is a dead contact for the normal play-back mode.
; In the normal play~back mode, the magnetic tape l is pinched between the pinch roller 9 and the capstan 7, and so it is transported at the normal speed. Since the movable contact 39N of the switch 40 is connected to the stationary contact 39M, only zero~voltage is obtained from the drive circuits 33h and 33B. Accordingly, no voltage is applied to the piezo~ra~c: leafs 20A and 20B, and so the magnetic heads 4A and 4B are located at the normal positions to scan the tracks T of the magnetic tape l without mistracking.
The video signals recorded on the magnetic tape 1 are reproduced by the magnetic heads 4A and 4B. The reproduced video signals a and a'shown on Fi~. 3A and Fig. 3B are obtained from the magnetic heads 4A and 4B, and they are combined with each other by the mixer 12.
The continuous reproduced signal b is obtained from the mixer 12, as shown on Fig. 3C. The signal _ is demodulated by the fre~uency demodulator 14, and then the demodulated signal is supplied to the monitor TV 15 to obtain a normal picture therein.

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In the still play-back mode, the plunger 8 for controlling the pinch roller 9 is actuated with the pushing of the still-mode selecting button. The pinch roller 9 is separaked rom the capstan 7~ A ~ake~up reel (not shown) stops in relation to the still-mode selecting button. Accordingly, the magnetic tape 1 stops ,~2 -shapedly ! wound on the lower head drum.
The movable contact 39N of the switch 40 - interl~cked with the still-mode selecting button is connected to the stationary contact 39S for the still play-back mode.
Accordingly, the saw waves i, j, i',and j' are obtained from the drive circuits 33A and 33B, and they are supplied to the piezo-ceramic leafs 20A and 20B as the head position control signals. The free ends of the piezo-cramic leafs 20A and 20B, and in other words, the magnetic heads 4A and 4B are displaced relative to the upper head drum 3 from the normal positions in accordance with the wave forms of the control signals, in the lengthwise directions of the air gaps. Accordingly, when the wave forms and amplitudes of the control signals are suitably selected~
the magnetic head 4A and 4B scan the track T corresponding to the N-th field of video signals recorded on the magnetic tape 1, without mistracking, as shown by the dot-dash line S' on Fig. 2.
The N-th field of video signals is reproduced by the magnetic heads 4A and 4B. Th~ reproduced vldeo signals c and c'shown on Fig. 3D and Fig. 3E are obtained from the magnetic heads 4A and 4B, and they are combined with each other by the mixer 12~ The continuously repeated reproduced video signal d is obtained from the mixer 12 ~ ~o -) ~ :' as shown on Fig. 3F. The signal d is demodulated by the frequency demodulator 14. The demodulated video signal is supplied to the monitor TV 15 to obtain ~he still reproduced picture therein.
The still play~back mode is released with the operation of the still-mode selecting button. The movable contact 39N of the switch 40 is changed over to the stationary contact 39M for the normal'play-bac~ mode. Next, .. . .
operations of the circuit sho~n on Fig. 1, on the release of the still play-back mode will be described.
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When the mo~able contact 39N o the switch 40 is changed over to the stationary contact 39M, the capacitor 38 is disconnected ,fro~ the DC power source 41; The charging - ~oltage of the capacitor 38 gradually dxops. Accordinyly, ~' 15 the head position control signal constituted by the saw waVes i, i', j, and j' shown on Fig. 3K, Fig. 3L, Fig. 3M
and Fig. 3N graduall~ decays with time. 'The head position ' control signal com,es not to be supplied to the piezo-ceramic leafs 20A and 20B. Thus, the supply of the alternating voltage as the head position control signal to the leafs 20~ and 20B is not suddenly stopped, but ' the alternatiny voltage supplied to the leafs 20A and 20B '~
is gradually dropped to zero. Accordingly, no residual strain is imparted to the piezo-ceramic leafs 20A and 20B, but the free ends of the leafs 20A and 20B (in other words~ the magnetic heads 4A and 4B) are surely returned to the normal ~original) position.
In the above-described embodiment~ the three ' lead wires 25, 26 and 27 are connected to the pi'ezo-ceramic leafs 20A and 20B as the bi-morph leafs, respectively.

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The reference bias voltage is applied to the lead wire 27. The saw-wave control voltages, whose polarities are opposite to each other with reference to the bias voltage supplied to the lead wire 27, are supplied to the lead wires 25 and 26. However, withou~ using the lead wire 27, the reference bias voltage may be supplied to khe lead wire 25, and a saw-wave control voltage having a predétermined - amplitude may be supplied to the lead wire 26. Next, such an arrangement will be described with reference to Fig. 6.
In Fig. ~, the magnetic head 4A, the piezo-ceramic leaf 20A, the mounting structure for them, and a circuit extending from the controller 32A to the piezo-ceramic leaf 20A are shown. The magnetic head 4B, the piezo-ceramic leaf 20B and the mounting structure for them are omitted in Fig. 6, since they are the same as the above-described corresponding parts. Similarly, the controller 32B, and a drive circuit connected between the controller 32B and the piezo-ceramic leaf 20B are not shown in Fig. 6, since they are the same as the corresponding parts shown on Fig~ 6. The other parts which correspond to the parts in Fig. 1 are not shown in Fig. 6.
In Fig. 6. the output of the controller 32A
is supplied to a base electrode of an NPN-type transistor 55 in a drive circuit 33'A corresponding to the drive circuit 33A of Fig. 1. A collector electrode of the transistor 55 is connected to the lead wire 26 of the piezo-ceramic leaf 20A, and to the stationary contact 39S of the switch 40 through a load resistor 57. The structures and functions of the capacitor 38, switch 40 and DC power source 41 are the same as in Fig. 1.

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28;~00 .
. An emitter electrode of the transistor 55 is connected through a bias resistor 56 and a dividing , . resistor 59 to the lead wire 25. A connecting point o the resistors 5~ and 59 is connected ~,o the ground.
. 5 A connecting point of the load resistor 57 and stationary contact 39S is connected to one end of a dividing,resistor , '58. Another end of the dividing resistor 58 is connected . to a connecting point of the dividing resistor 59 and lead - wire 25. Accordingly, the reference bias voltage suppiied , to the lead wire 25 is decided by the dividing resistors . 58 and 59.
When the movable contact 39N of the switch 40 - is connected to the stationary contact 39S for still play-. back mode, the voltage from the DC power source 41 is : 15 supplied through the load resistor 57 to the collector . electrode of the transistor 55, and the reference bias voltage in accordance with the dividing ratio of the dividing resistors 58 and 59 is supplied to the lead wire 25. A saw-wave signal is obtainedifrom the collector electrode of the transistor 55~ coxresponding to the ` saw wave signal ~rom the controller 32A, and it is supplied to the'lead wire 26. Accordingly, the still reproduced plcture is obtained in the monitor TV, as . in Fig. 1.
25 . ~ .In Fig. 6, the bi-morph leaf is used as the piezo-ceramic leaf 20A. The two lead wires are used.
: It will be understood that a~mono morpX.:leaf,~may~,be.u~ed instead of the bi-morph.
Although there have bee~ described the preferred ernbodiments of this'invention~ this invention . . .
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is not limited to those embodiments, but various modifica~ons are possible on the basis of the spirit o this lnvention.
In the above embodiments, this lnvention is applied to the well-known helical two head Q -type VTR haYing the well known rotary head drum assembly. However, it may be - applied to the well-known helical one-head ~ -type VTR.
Moreover, this invention is applied to the VTR
- of the helical scanning type in which the magnetic head scans the magnetic tape so as to form recorded tracks thereon obliquely to the lengthwise direction of the magnetic tape. However, this invention may be applied to a VSR (video sheet recorder) in which a magnetic sheet is used instead of the magnetic tape, and a magnetic head scans the magnetic sheet so as to form recorded tracks thereon slightly obliquely to the direction perpendicular to the transportation direction of the magnetic sheet.
And in the above embodiments, this invention ~Is applled to the still reproduced picture. However, it may be applied to a slow-motion reproduced picture.
In that casej the magnetic tape is transported at a lower speed. The transportation speed is ~aried in accordance~- with the desired rate of the slow motion.
Accordingly,~the amplitude of the saw wave as a control signal is varied in accordance with the desired rate of the slow motlon.

' , ~ 20 -

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A system for reproducing a video signal recorded in successive parallel tracks on a recording medium, said system comprising:
rotary support means, bi-morph leaf means, mounting means securing one end portion of said bi-morph leaf means to said rotary support means with said bi-morph leaf means being canti-levered therefrom so as to be movable by flexing from a rest condition in either direction transverse to the direction of said tracks, signal reproducing means for reproducing a video signal in a respective one of said tracks and being connected with the other end portion of said bi-morph leaf means so as to be movable therewith, and damper means in addition to said mounting means and being engageable with said other end portion of said bi-morph leaf means at a distance along the latter spaced from said mounting means for damping free oscillations of said bi-morph leaf means due to bending forces applied to said bi-morph leaf means.

2. A system for reproducing a video signal according to claim 1, wherein said damper means generally presses said other end of the bi-morph leaf means.

3. A system for reproducing a video signal according to claim 2, wherein said damper means generally press the side of said bi-morph leaf means.

4. A system for reproducing a video signal according to claim 2, wherein said damper means consists of two damper members (51a, 51b) and said bi-morph leaf means being sandwiched by said two damper members.