Note: Descriptions are shown in the official language in which they were submitted.
' ~ ~
- 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.
-2a- -
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! ~) ' 1
~o~
BRIEF DESCRIPTION OF THE DRAWINGS
~ . . _ . ~ .
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
-- 4 --
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
- 5 -
.
-
I"
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
-- 7 --
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
~ . r
. .
~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.
-- 10 --
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 ~
.
-- 11 ~
,æs~,"
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 ~
. . .
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
- 13 -
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.
..
- 15 -
8;2~
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
- 16 -
~ ~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.
~ . .
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.
- 17 -
.!~
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.
- 18 -
~ `~
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
. . .
-- 19 -- ,
_, . . . . . . . . . . . .
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 -
