Magnetic recording/reproducing apparatus and method for controlling an inclination angle of a rotational drum in the magnetic recording/reproducing apparatus

An envelope is detected from each of a plurality of reproduced video FM signals successively read out from a magnetic tape, and a shape change of the envelope in one vertical scanning period is detected in a control microcomputer. In cases where the shape of the envelope is flattened, the flatness indicates that an inclination angle of a rotational drum is appropriately set and a scanning locus of a magnetic head attached on the rotational drum agrees with a track formed on the magnetic tape. In this case, a reproduced image having no noise is obtained. Therefore, the number of increase/decrease changes in the shape of the envelope is detected as a shape value. In cases where the shape value is high, the inclination angle of the rotational drum is largely and repeatedly changed until the shape value becomes low. In contrast, in cases where the shape value is low, the inclination angle of the rotational drum is slightly and repeatedly changed until the envelope shape is flattened. Accordingly, any noise does not occur in the reproduced image regardless of whether a magnetic recording and reproducing apparatus is used in interchangeable reproduction or self-recording/reproduction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a magnetic recording and reproducing 
apparatus for reproducing recorded data at a variable speed through a 
rotational head helically scanned and a method for controlling an 
inclination angle of a rotational drum on which the rotational head of the 
magnetic recording and reproducing apparatus is attached. 
2. Description of the Related Art 
In a helical scan type magnetic recording and reproducing apparatus 
represented by a household video tape recorder (VTR), recorded data is 
generally reproduced at a variable reproducing speed differing from a 
recording speed in a so-called variable speed reproducing mode. In this 
case, because the reproducing speed differs from the recording speed in a 
variable speed reproduction, a locus of a rotational magnetic head 
attached on a rotational drum on a magnetic tape does not accurately agree 
with a truck formed on the magnetic tape in a recording operation. 
Therefore, the track cannot be accurately traced by the magnetic head, and 
a quality of a reproduced signal is degraded. In particular, as the 
reproducing speed is heightened, the number of tracks crossed by the 
magnetic head is increased. As a result, a signal/noise (S/N) ratio is 
degraded, and noises formed in horizontal stripes occur in a reproduced 
image. 
Also, in a VTR for business use used in a broadcasting station or the like 
(For example, No. BR-S525 in a VTR for business use manufactured by Vitor 
Company of Japan, Ltd.), an actuator embodied by a movable coil is 
attached to a rotational head to displace the rotational head for the 
purpose of solving the above drawbacks. However, because it is required 
that the actuator is placed inside a rotated drum, the configuration of 
the VTR is complicated, and the manufacturing of the VTR is not easy. In 
addition, the connection of an electric source for the actuator is not 
easy, a control circuit for controlling the actuator is required. 
Therefore, the VTR becomes expensive, the VTR is not used for a household 
apparatus. 
2.1. Previously Proposed Art 
Also, a method for inclining the whole rotational drum to displace the 
rotational head attached on the rotational drum is disclosed. However, an 
apparatus operated according to the method is not manufactured. The reason 
is that the technique for inclining the rotational drum is not 
sufficiently advanced and a signal processing technique in a feed-back 
system is not sufficiently advanced to accurately trace a track on a 
magnetic tape. In the Victor company of Japan, Ltd. relevant to the 
present inventor, a technique for accurately controlling an inclination of 
a rotational drum at a desired angle at a high responsibility has been 
developed, and two Japanese patent applications have been filed (the name 
of invention common for the applications: magnetic recording and 
reproducing apparatus, the filing date: Feb. 22, 1995, and Feb. 28, 1995). 
The applications have not been laid open, and the technique is not an 
opened prior art. A rotational drum operated according to the technique is 
called a dynamic drum. In detail, the dynamic drum is inclined by a 
rotational power generated by an inclination angle changing motor, and a 
rotational angle provided by the motor is controlled by a microcomputer. 
An inclination angle of the dynamic drum is detected by a counter in which 
a FG pulse signal generated in synchronization with the change of the 
rotational angle is counted. In addition, a sensor for generating a reset 
signal is provided to reset the counter when the dynamic drum is inclined 
at a predetermined inclination angle. 
2.2. Problems to be Solved by the Invention 
In cases where a variable speed reproduction in a VTR is performed 
according to the method for inclining the whole rotational drum or in 
cases where a variable speed reproduction in a VTR is performed by using 
the dynamic drum, a drum inclination angle corresponding to each of the 
recording tape speeds and each of the reproducing tape speeds is 
predetermined, and one of the drum inclination angles is selected. In this 
case, when a so-called self-recording/reproduction in which the recording 
and reproduction are performed in the same VTR is performed, one drum 
inclination angle can be properly selected, and the reproduction can be 
favorably performed. However, when a so-called interchangeable 
reproduction in which data recorded in a first VTR are reproduced in a 
second VTR differing from the first VTR is performed, because mechanical 
characteristics of a tape running system in the first VTR differ from 
those in the second VTR, a track pattern formed on a magnetic tape in the 
recording operation does not perfectly agree with a trace pattern formed 
on the magnetic tape in the reproducing operation. Therefore, there is a 
drawback that noises occur in a reproduced image. 
Also, there is a case that an actual inclination angle of a rotational drum 
fluctuates from a predetermined inclination angle because of friction 
and/or abrasion occurring in a mechanical system for inclining the 
rotational drum. In cases where the actual inclination angle fluctuates, 
even though the self-recording/reproduction is performed, there is another 
drawback that the trace pattern does not agree with the track pattern 
unless the predetermined inclination angle is changed to compensate the 
fluctuation of the actual inclination angle. 
SUMMARY OF THE INVENTION 
A first object of the present invention is to provide, with due 
consideration to the drawbacks of such a conventional magnetic recording 
and reproducing apparatus and a conventional inclination angle control 
method, a magnetic recording and reproducing apparatus in which a track 
pattern formed on a magnetic tape in the recording operation perfectly 
agrees with a trace pattern formed on the magnetic tape by a magnetic head 
in the reproducing operation, and any noise does not occur in a reproduced 
image regardless of whether the apparatus is used in the interchangeable 
reproduction or the self-recording/reproduction, and to provide an 
inclination angle control method used in the magnetic recording and 
reproducing apparatus. 
A second object of the present invention is to provide a magnetic recording 
and reproducing apparatus in which the inclination angle of a rotational 
drum is accurately and easily set to an appropriate inclination angle even 
though a recording tape speed characteristic for a particular magnetic 
recording and reproducing apparatus differs from that for another 
apparatus or the recording tape speed characteristic in one magnetic 
recording and reproducing apparatus changes. 
The first object of the present invention is achieved by the provision of a 
magnetic recording and reproducing apparatus, comprising: 
a rotational head for helically scanning a magnetic tape and reading out a 
reproduced signal from the magnetic tape; 
a rotational drum on which the rotational head is mounted; 
inclination angle changing means for changing an inclination angle of the 
rotational drum with respect to the magnetic tape to change a scanning 
direction of the rotational head with respect to the magnetic tape; 
flatness detecting means for detecting a flatness degree of a variable 
level of the reproduced signal, in a predetermined period, read by the 
rotational head of which the scanning direction is changed by the 
inclination angle changing means; 
inclination angle control means for controlling the inclination angle 
changing means to maximize the flatness degree of the variable level of 
the reproduced signal detected by the flatness detecting means; and 
signal processing means for processing the reproduced signal in which the 
flatness degree of the variable level is maximized by the inclination 
angle changing means under control of the inclination angle control means. 
In the above configuration, when a reproduced signal is reproduced from the 
magnetic tape by the rotational head, a flatness degree of a variable 
level of the reproduced signal is detected by the flatness detecting 
means. Thereafter, the inclination angle changing means is controlled by 
the inclination angle control means to maximize the flatness degree. 
Therefore, an inclination angle of the rotational drum is changed under 
control of the inclination angle control means, and a scanning direction 
of the rotational head mounted on the rotational drum is changed to read 
out a following reproduced signal, in which a flatness degree of a 
variable level is maximized, from the magnetic tape through the rotational 
head. 
Accordingly, a track pattern formed on the magnetic tape in a recording 
operation can perfectly agree with a trace pattern formed on the magnetic 
tape by the rotational head in a reproducing operation and any noise does 
not occur in a reproduced image regardless of whether the apparatus is 
used in the interchangeable reproduction or the 
self-recording/reproduction. 
The first object of the present invention is also achieved by the provision 
of a method for controlling an inclination angle of a rotational drum on 
which a rotational head helically scanning a magnetic tape is mounted, 
comprising the steps of: 
producing an envelope in a predetermined period from each of a plurality of 
reproduced signals read from the magnetic tape one after another by the 
rotational head; 
detecting a changing degree of a shape of the envelope; 
judging whether the changing degree is high or low; 
largely changing the inclination angle of the rotational drum until the 
changing degree of the shape of the envelope becomes low in cases where it 
is judged that the changing degree is high; 
slightly changing the inclination angle of the rotational drum until the 
changing degree of the shape of the envelope is minimized in cases where 
it is judged that the changing degree is low; and 
processing the reproduced signal from which the envelope of which the shape 
changing degree is minimized are produced. 
In the above steps, a plurality of reproduced signals are read from the 
magnetic tape one after another by the rotational head, and an envelope is 
produced in a predetermined period from each of the reproduced signals. 
In cases where a changing degree of a shape of the envelope is high, a 
large number of tracks formed on the magnetic tape in a recording 
operation is crossed by a scanning locus of the rotational head in a 
reproducing operation. In this case, the inclination angle of the 
rotational drum is largely changed to largely change a scanning direction 
of the rotational head. Therefore, the number of tracks crossed by the 
scanning locus of the rotational head is rapidly reduced. 
In cases where a changing degree of a shape of the envelope is low, or in 
cases where a changing degree of a shape of the envelope is reduced to a 
low degree, the number of tracks crossed by the scanning locus of the 
rotational head is low. Therefore, the inclination angle of the rotational 
drum is slightly changed to slightly change a scanning direction of the 
rotational head, and the rotational head accurately scans a track when the 
changing degree is minimized. 
Accordingly, when a reproduced image is produced by processing the 
reproduced signal from which the envelope of which the shape changing 
degree is minimized is obtained, any noise does not occur in the 
reproduced image regardless of whether the apparatus is used in the 
interchangeable reproduction or the self-recording/reproduction. 
The first object of the present invention is also achieved by the provision 
of a method for controlling an inclination angle of a rotational drum on 
which a rotational head helically scanning a magnetic tape is mounted, 
comprising the steps of: 
judging whether or not a magnetic tape traveling speed is changed to a 
particular magnetic tape traveling speed; 
judging whether or not a particular inclination angle of the rotational 
drum appropriate to the particular magnetic tape traveling speed is known 
in cases where the magnetic tape traveling speed is changed to the 
particular magnetic tape traveling speed; 
changing the inclination angle of the rotational drum to the particular 
inclination angle in cases where the particular magnetic tape traveling 
speed is known; 
processing a plurality of reproduced signals read from the magnetic tape 
one after another by the rotational head mounted on the rotational drum of 
which the inclination angle is changed to the particular inclination 
angle; 
producing an envelope in a predetermined period from each of a plurality of 
reproduced signals read from the magnetic tape one after another by the 
rotational head in cases where the particular magnetic tape traveling 
speed is not known; 
detecting a changing degree of a shape of the envelope; 
judging whether the changing degree is high or low; 
largely changing the inclination angle of the rotational drum until the 
changing degree of the shape of the envelope becomes low in cases where it 
is judged that the changing degree is high; 
slightly changing the inclination angle of the rotational drum until the 
changing degree of the shape of the envelope is minimized in cases where 
it is judged that the changing degree is low; and 
processing the reproduced signal from which the envelope of which the shape 
changing degree is minimized is produced. 
In the above steps, in cases where the magnetic tape traveling speed is 
changed to a particular magnetic tape traveling speed in a reproducing 
operation, it is required to adjust the inclination angle of the 
rotational drum. In this case, complicated steps represented by the step 
of largely changing the inclination angle and the step of slightly 
changing the inclination angle are required to obtain a particular 
inclination angle of the rotational drum appropriate to the particular 
magnetic tape traveling speed. However, in cases where the particular 
inclination angle is known because the reproducing operation at the 
particular magnetic tape traveling speed has been already performed, the 
inclination angle of the rotational drum is easily changed to the 
particular inclination angle without performing the complicated steps. 
Accordingly, the inclination angle of the rotational drum can be easily 
changed at high speed even though the magnetic tape traveling speed is 
changed. 
The first object of the present invention is also achieved by the provision 
of a method for controlling an inclination angle of a rotational drum on 
which a rotational head helically scanning a magnetic tape is mounted, 
comprising the steps of: 
judging whether or not a still reproduction is selected; 
producing an envelope in a predetermined period from each of a plurality of 
reproduced signals read from the magnetic tape one after another by the 
rotational head; 
detecting a changing degree of a shape of each of the envelopes; 
judging whether each of the changing degrees is high or low; 
largely changing the inclination angle of the rotational drum in a first 
direction each time it is judged that one of the changing degrees is high 
until one changing degree of one shape of one envelope becomes low; 
slightly changing the inclination angle of the rotational drum in the first 
direction each time it is judged that one of the changing degrees is low 
until one changing degree of one shape of one envelope is minimized; 
judging whether or not a level of each of the reproduced signals is 
decreased predetermined times in succession in cases where it is judged 
that the still reproduction is selected; 
resetting the inclination angle of the rotational drum to an original 
inclination angle, which corresponds to the inclination angle of the 
rotational drum not largely changed by the step of largely changing the 
inclination angle or slightly changed by the step of slightly changing the 
inclination angle, in cases where it is judged that the level of each of 
the reproduced signals is decreased the predetermined times in succession; 
producing a second envelope in the predetermined period from each of a 
plurality of reproduced signals read from the magnetic tape one after 
another by the rotational head after the inclination angle of the 
rotational drum is reset; 
detecting a second changing degree of a shape of each of the second 
envelopes; 
judging whether each of the second changing degrees is high or low; 
largely changing the inclination angle of the rotational drum in a second 
direction opposite to the first direction each time it is judged that one 
of the second changing degrees is high until one second changing degree 
becomes low; 
slightly changing the inclination angle of the rotational drum in the 
second direction each time it is judged that one of the second changing 
degrees is low until one second changing degree is minimized; and 
processing the reproduced signal from which the envelope of which the shape 
changing degree is minimized is produced. 
In the above steps, in cases where a still reproduction is selected, there 
is a probability that a scanning locus of the rotational head is shifted 
from a center of a track. To prevent this drawback, it is judged whether 
or not a level of each of the reproduced signals is decreased 
predetermined times in succession because the level is decreased when a 
scanning locus is shifted from a center of a track. In cases where the 
level of each of the reproduced signals is decreased the predetermined 
times in succession, it is judged that a scanning locus is shifted from a 
center of a track, the inclination angle of the rotational drum is reset 
to an original inclination angle, and the rotational drum is inclined in 
the opposite direction. 
Accordingly, because the rotational drum is inclined in both directions, a 
scanning locus of the rotational drum can reliably agree with a center of 
a track. 
The second object of the present invention is achieved by the provision of 
a magnetic recording and reproducing apparatus, comprising: 
a magnetic head for scanning a magnetic tape in a diagonal direction with 
respect to a width direction of the magnetic tape to record and reproduce 
a signal to/from a magnetic tape; 
a rotational drum on which the magnetic head is mounted, a scanning 
direction of the magnetic head changing with an inclination angle of the 
rotational drum, and an inclination angle of the rotational drum 
appropriate for the scanning of the magnetic head being proportional to a 
reproducing tape speed; 
rotational drum actuating means for actuating the rotational drum to 
incline the rotational drum, the rotational drum being not inclined in 
cases where an actuation degree of the rotational drum is within a 
non-sensitive zone, the rotational drum being inclined in cases where the 
actuation degree of the rotational drum exceeds an upper value of the 
non-sensitive zone, and an inclination angle of the rotational drum being 
proportional to an exceeding actuation degree defined as a difference 
between the actuation degree and the upper value of the non-sensitive 
zone; 
storing means for storing a referential actuation degree corresponding to a 
referential reproducing tape speed, the referential actuation degree 
exceeding the upper value of the non-sensitive zone; and 
control means for detecting a current reproducing tape speed, calculating a 
differential actuation degree between a target actuating degree 
corresponding to the current reproducing tape speed and the referential 
actuation degree stored in the storing means, calculating a required 
actuation degree by adding the referential actuation degree and the 
differential actuation degree together, and controlling the rotational 
drum actuating means to actuate the rotational drum by the required 
actuation degree. 
In the above configuration, the rotational drum actuated by the rotational 
drum actuating means is inclined in cases where the actuation degree of 
the rotational drum exceeds an upper value of the non-sensitive zone, and 
an inclination angle of the rotational drum is proportional to an 
exceeding actuation degree defined as a difference between the actuation 
degree and the upper value of the non-sensitive zone. Also, a scanning 
direction of the magnetic head change with the inclination angle of the 
rotational drum, and an inclination angle of the rotational drum 
appropriate for the scanning of the magnetic head changes in proportion to 
a reproducing tape speed. 
Therefore, a referential actuation degree corresponding to a referential 
reproducing tape speed is stored in the storing means in advance. 
Thereafter, because an exceeding actuation degree defined as a difference 
between the actuation degree and the upper value of the non-sensitive zone 
is proportional to the reproducing tape speed, a differential actuation 
degree between a target actuating degree corresponding to a current 
reproducing tape speed and the referential actuation degree stored in the 
storing means is calculated from the current reproducing tape speed and 
the referential actuation degree corresponding to the referential 
reproducing tape speed. Thereafter, a required actuation degree is 
calculated by adding the referential actuation degree and the differential 
actuation degree together, and the rotational drum actuating means is 
controlled to actuate the rotational drum by the required actuation 
degree. 
Therefore, the inclination angle of the rotational drum can be adjusted to 
an appropriate inclination angle appropriate for the scanning of the 
magnetic head. 
Accordingly, the inclination angle of the rotational drum can be accurately 
and easily set to the appropriate inclination angle even though a 
non-sensitive zone for a particular magnetic recording and reproducing 
apparatus differs from that for another apparatus or the non-sensitive 
zone in one magnetic recording and reproducing apparatus changes.

DETAIL DESCRIPTION OF THE EMBODIMENTS 
Preferred embodiments of a magnetic recording and reproducing apparatus and 
an inclination angle control method according to the present invention are 
described with reference to drawings. 
FIG. 1 is a block diagram of a dynamic drum inclination angle control 
system for controlling an inclination angle of a rotational drum, on which 
a rotational magnetic head helically scanned is attached, in a magnetic 
recording and reproducing apparatus according to an embodiment of the 
present invention. FIG. 2 is a diagonal view of a drum structure DS 
including a rotational drum arranged in the magnetic recording and 
reproducing apparatus. 
As shown in FIG. 1, a dynamic drum inclination angle control system 11 for 
controlling an inclination angle of a rotational drum comprises a video 
frequency-modulated (FM) integrating circuit 12 for integrating each of a 
plurality of reproduced video FM signals read out one by one from a 
magnetic tape MT according to FG reset pulses to detect a level (or 
amplitude) change of each reproduced video FM signal and outputting a 
level detecting output signal indicating the level change of each 
reproduced video FM signal. Also, a reproducing tape speed detecting unit 
13 for detecting a current reproducing tape speed, a control microcomputer 
10 for generating a motor speed control signal Scm, a motor front rotation 
control signal Scf and a motor reverse rotation control signal Scr from 
the level detecting output signal, a FG reset signal having the FG reset 
pulses, a motor FG pulse signal, a drum flip-flop output signal and the 
current reproducing tape speed to control the inclination angle of a 
rotational drum 20 shown in FIG. 2. Also, a motor driving amplifier 14 for 
generating a motor driving signal from the motor speed control signal Scm, 
the motor front rotation control signal Scf and the motor reverse rotation 
control signal Scr output from the control microcomputer 10, and an 
inclination angle changing motor 16 used as an actuating source for 
inclining the rotational drum according to the motor driving signal output 
from the motor driving amplifier 14 to change the inclination angle of the 
rotational drum 20. The control microcomputer 10 comprises a central 
processing unit 10a, a random access memory (RAM) 10b, an interface 10c, 
an analog/digital (A/D) converter 10d, a digital/analog converter 10e and 
a read only memory (ROM) 10f. 
As shown in FIG. 2, in a drum structure DS, a drum axis 24 is inserted into 
a center portion of a lower drum 22 under pressure, and an upper drum 21 
is coaxially supported by the drum axis 24 through a bearing put on the 
drum axis 24. A tape sliding surface 21a for leading a bound magnetic tape 
MT is formed at the periphery of the upper drum 21 at the same diameter 
with that of the upper drum 21, and a tape sliding surface 22a for leading 
the bound magnetic tape MT is formed at the periphery of the lower drum 22 
at the same diameter with that of the lower drum 22. In the lower drum 22, 
a small diameter portion 22b having a diameter smaller than that of the 
tape sliding surface 22a is helically formed on a lower side of the tape 
sliding surface 22a. A pair of magnetic heads 23a and 23b are attached on 
the upper drum 21 opposite to each other, and the upper drum 21 is rotated 
around the drum axis 24 by an actuating power provided by a drum motor 
(not shown). On a lower side of the periphery of the lower drum 22, a 
leading ring 27 formed of a helical lead 27a is separately provided. The 
leading ring 27 leads a reference edge of the magnetic tape MT. Also, a 
drum base 28 is provided to support the lower drum 22, and a pair of 
screws 24a and 24b are screwed into the drum base 28 to attach the lower 
drum 22 to the drum base 28 under pressure. The screw 24a is placed on a 0 
degree side, and the screw 24b is placed on a 180 degree side. A 
rotational drum 20 is composed of the upper and lower drum 21 and 22 and 
the leading ring 27. 
The screws 24a and 24b has a function for correcting an inclination of the 
whole rotational drum 20. In detail, in a fast feed (FF) reproducing mode 
operation, a location pin (not shown) for the 0 degree side is pressed up 
by a tip of the screw 24a, a 0 degree side bottom portion of the lower 
drum 22 is pressed up, the upper and lower drums 21 and 22 supported by 
the drum axis 24 are rotationally moved with the leading ring 27 by a 
whole drum inclination correcting angle .theta. in a clockwise direction 
with respect to the drum base 28, and the inclination of the rotational 
drum 20 in the FF reproducing mode operation is corrected. In contrast, in 
a fast back-feed (FB) reproducing mode operation, another location pin 
(not shown) for the 180 degree side is pressed up by a tip of the screw 
24b, a 180 degree side bottom portion of the lower drum 22 is pressed up, 
the upper and lower drums 21 and 22 supported by the drum axis 24 are 
rotationally moved with the leading ring 27 by a whole drum inclination 
correcting angle .theta. in a counterclockwise direction with respect to 
the drum base 28, and the inclination of the rotational drum 20 in the FB 
reproducing mode operation is corrected. 
The screws 25a and 25b are screwed into the leading ring 27 to attach the 
leading ring 27 to the lower drum 22 under pressure. The screw 25a is 
placed on the 0 degree side, and the screw 25b is placed on the 180 degree 
side. The screws 25a and 25b have a function for correcting an inclination 
of a track formed on the magnetic tape MT. In detail, in the FF 
reproducing mode operation, when a pin (not shown) for the 0 degree side 
is pressed up by a tip of the screw 25a, though a 0 degree side bottom 
portion of the leading ring 27 is pressed down by a track inclination 
correcting angle .theta.1 with respect to the lower drum 22, the 0 degree 
side bottom portion of the leading ring 27 are rotationally moved in the 
clockwise direction with respect to the drum base 28, and the inclination 
of the track in the FF reproducing mode operation is corrected. In 
contrast, in the FB reproducing mode operation, another pin (not shown) 
for the 180 degree side is pressed up by a tip of the screw 25b, a 180 
degree side bottom portion of the leading ring 27 is pressed down by a 
track inclination correcting angle .theta.1 with respect to the lower drum 
22, the 0 degree side bottom portion of the leading ring 27 are 
rotationally moved in the counterclockwise direction with respect to the 
drum base 28, and the inclination of the track in the FB reproducing mode 
operation is corrected. 
Therefore, the combination of the screws 24a and 24b functions as a whole 
drum correction actuating means for rotationally moving the upper and 
lower drums 21 and 22 supported by the drum axis 24 with the leading ring 
27 with respect to the drum base 28 in the FF reproducing mode operation 
and the FB reproducing mode operation. Also, the combination of the screws 
25a and 25b functions as a track inclination correction actuating means 
for successively inclining the drum axis 24 with respect to an imaginary 
central axis of the leading ring 27 according to a traveling speed of the 
magnetic tape MT to make a track pattern formed on the magnetic tape MT 
agree with rotational loci of the magnetic heads 23a and 23b formed on the 
magnetic tape MT in the FF reproducing mode operation and the FB 
reproducing mode operation. Also, the cooperative configuration of the 
combination of the screws 24a and 24b and the combination of the screws 
25a and 25b functions as a lead correction actuating means for 
successively inclining the imaginary central axis of the leading ring 27 
to make the helical lead 27a agree with a reference edge of the magnetic 
tape MT. 
Next, an actuating means in which the screws 24a and 24b rotationally 
moving the lower drum 22 and the screws 25a and 25b rotationally moving 
the leading ring 27 are rotationally and simultaneously actuated by the 
inclination angle changing motor 16 is described in brief with reference 
to FIG. 3. 
FIG. 3 is a plan view showing an internal configuration of the rotational 
drum 20 shown in FIG. 2. 
As shown in FIG. 3, a supporting base 41 to which an actuating means 40 is 
attached is provided on a back surface side of the drum base 28. The 
rotation of a first pulley 43 which is fixedly attached to an axis of the 
motor 16 placed on the supporting base 41 is transmitted though a belt 44 
to a worm 47 attached on an axis 46 to which a second pulley 45 is 
attached. Thereafter, the rotation of the worm 47 is transmitted to a 
first helical gear 48 engaged with the worm 47, and the rotation of the 
first helical gear 48 is transmitted to a second helical gear 49 engaged 
with the first helical gear 48. In this case, a rotational direction of 
the first helical gear 48 is opposite to that of the second helical gear 
49. 
The first helical gear 48 is connected to a two speed gear G.sub.1 composed 
of a larger diameter gear portion G.sub.11 and a smaller diameter gear 
portion G.sub.12 and functions to rotate the screw 24a engaged with the 
larger diameter gear portion G.sub.11 and the screw 25a engaged with the 
smaller diameter gear portion G.sub.12. Also, the second helical gear 49 
is connected to a two speed gear G.sub.2 composed of a larger diameter 
gear portion G.sub.21 and a smaller diameter gear portion G.sub.22 and 
functions to rotate the screw 24b engaged with the larger diameter gear 
portion G.sub.21 and the screw 25b engaged with the smaller diameter gear 
portion G.sub.22. Therefore, the rotation of the screws 24a and 25a is 
opposite to that of the screws 24b and 25b. In addition, the rotation of 
the two speed gear G.sub.2 connected to the second helical gear 49 is 
transmitted to a reset gear 50 through a series of gears. The rotation of 
the reset gear 50 is reduced to rotate the reset gear 50 in a range of 
about .+-.180 degrees. In this case, because the screws 24a and 24b are 
engaged with the larger diameter gear portions G.sub.11 and G.sub.21 of 
the two speed gears G.sub.1 and G.sub.2, the screws 24a and 24b for 
correcting the inclination of the whole rotational drum 20 are rotated by 
the motor 16 in a high degree according to a whole drum inclination angle 
correcting characteristic to rotate the upper and lower drums 21 and 22 by 
the whole drum inclination correcting angle .theta.. In contrast, because 
the screws 25a and 25b are engaged with the smaller diameter gear portions 
G.sub.12 and G.sub.22 of the two speed gears G.sub.1 and G.sub.2, the 
screws 25a and 25b for correcting the inclination of the track formed on 
the magnetic tape MT are rotated by the motor 16 at a low degree according 
to a lead inclination angle correcting characteristic to rotate the bottom 
portion of the leading ring 27 by a lead inclination correcting angle 
.theta.2 obtained by subtracting the track inclination correcting angle 
.theta.1 from the whole drum inclination correcting angle .theta.. 
A plurality of (for example, three) fan-shaped shielding plates (not shown) 
are attached to the second pulley 45. Therefore, when the motor 16 is 
driven, a beam of light is intermittently shielded by the shielding 
plates, the light intermittently shielded is detected by a photo-electro 
sensor 51, and the FG pulse signal is generated by the sensor 51. 
A fan-shaped shielding plate 50a spread about 180 degrees is attached to 
the reset gear 50. Therefore, when the rotational drum 20 is inclined at 
an inclination angle corresponding to a standard speed recording 
operation, an edge of the shielding plate 50a is detected by a 
photo-electro sensor 52, and the FG reset signal is generated by the 
photo-electro sensor 52. 
In the control microcomputer 10, a motor FG pulse signal occurring each 
time a rotor of the inclination angle changing motor 16 is rotated, is 
added to a current FG pulse counting value when the rotation caused by the 
inclination angle changing motor 16 is directed in a plus direction 
according to the motor front rotation control signal Scf, and the motor FG 
pulse signal is subtracted from the current FG pulse counting value when 
the rotation caused by the inclination angle changing motor 16 is directed 
in a minus direction according to the motor reverse rotation control 
signal Scr. Therefore, the current FG pulse counting value indicates a 
current inclination angle of the rotational drum 20 actuated according to 
the rotation of the rotor of the inclination angle changing motor 16. The 
current inclination angle is defined as a differential angle between a 
referential angle of the rotational drum 20 placed at a reference point 
and a current (or actual) angle of the rotational drum 20. The current FG 
pulse counting value is reset to zero by the FG reset signal. The drum 
flip-flop (FF) output signal indicates a magnetic tape MT scanning period 
of the scanning performed by the magnetic heads 23a and 23b which are 
attached to the rotational drum 20 in opposite to each other, and the 
magnetic tape MT scanning period agrees with a vertical scanning period 
(or a field) of a video signal. In the control microcomputer 10, a desired 
inclination angle of the rotational drum 20 is calculated according to a 
level detecting output signal which indicates a level of a reproduced 
video FM signal and is output from the video FM integrating circuit 12, 
the motor drive amplifier 14 is controlled, and the inclination angle 
changing motor 16 is driven. Also, in the control microcomputer 10, a 
differential angle between the referential angle and the current angle of 
the rotation al drum 20 is stored as a current inclination angle and i s 
indicated by the current FG pulse counting value, direction and angle of 
the rotation caused by the inclination angle changing motor 16 are 
determined to reduce a difference between a desired (or a target) FG pulse 
counting value corresponding to a desired (or a target) inclination angle 
and the current FG pulse counting value to zero, and the motor drive 
amplifier 14 is controlled to apply an appropriate voltage to the 
inclination angle changing motor 16. In other words, when the current FG 
pulse counting value indicating the actual inclination angle agrees with 
the target FG pulse counting value indicating the target inclination 
angle, the operation of the inclination angle changing motor 16 is 
stopped. 
In addition, in the control microcomputer 10, N division integrated values 
(N is an integral number higher than 1) indicated by the level detecting 
output signal output from the video FM integrating circuit 12 is received, 
each of vertical scanning periods of the reproduced video signal is 
divided into N scanning sub-periods, the shape change of FM envelope in 
the N scanning sub-periods is judged, a changing width (or a changing 
degree) of the FM envelope is detected, the inclination angle changing 
motor 16 is controlled to reduce the changing width according to the shape 
change, and the inclination angle of the rotational drum 20 is controlled. 
In this case, the judgement of the FM envelope shape change is performed 
by detecting a flat degree of the level of the reproduced video FM signal, 
and it is judged to what degree a trace pattern of the magnetic heads in 
the reproducing operation agrees with a track pattern formed on the 
magnetic tape MT in the recording operation. 
FIG. 4A is a block diagram of a magnetic recording and reproducing 
apparatus according to the present invention. 
As shown in FIG. 4A, a magnetic recording and reproducing apparatus 71 
comprises 
the rotational magnetic heads 23a and 23b for helically scanning the 
magnetic tape MT and reading out a plurality of reproduced signals one 
after another from the magnetic tape MT, 
the rotational drum 20 on which the rotational magnetic heads 23a and 23b 
are attached, 
the dynamic drum inclination angle control system 11 for controlling the 
inclination angle of the rotational drum 20, 
an auto-tracking control system 61 shown in FIG. 11 for performing an 
auto-tracking control to set a scanning locus of each of the rotational 
magnetic heads 23a and 23b at a center of a track formed on the magnetic 
tape MT, and 
a signal processing unit 72 for processing a plurality of reproduced 
signals read out by the rotational magnetic heads 23a and 23b which are 
controlled by the dynamic drum inclination angle control system 11 and the 
auto-tracking control system 61 and producing a produced image. 
The inclination angle changing motor 16 and the motor drive amplifier 14 of 
the dynamic drum inclination angle control system 11 and the actuating 
means 40 function as an inclination angle changing means for changing the 
inclination angle of the rotational drum 20 with respect to the magnetic 
tape MT to change a scanning direction of each of the rotational heads 23a 
and 23b. 
Next, a procedure of the control performed in the control microcomputer 10 
in a reproducing operation is described with reference to FIG. 4B. 
FIG. 4B is a flow chart showing an inclination angle control method 
according to a first embodiment of the present invention. 
As shown in FIG. 4B, the RAM 10b of the control microcomputer 10 is 
initialized in a step S1. In a step S2, a level detecting output signal 
output from the video FM integrating circuit 12 is stored in the RAM 10b, 
and a current pulse counting value calculated from the motor FG pulse 
signals which indicates the current inclination angle is stored in the RAM 
10b. Also, a plurality of target pulse counting values respectively 
corresponding to a reproducing tape speed are stored in the ROM 10f. In a 
step S3, a particular target pulse counting value corresponding to a 
current reproducing tape speed detected by the reproducing tape speed 
detecting unit 13 is selected from among the target pulse counting values 
stored in the ROM 10f and is transferred to the CPU 10a. In the CPU 10a, 
two control signals Scm and Scf or two control signals Scm and Scr are 
produced according to the particular target pulse counting value, the FG 
reset signal, the motor FG signal and the drum FF output signal and is 
transmitted to the motor drive amplifier 14 to set the current inclination 
angle of the rotational drum 20 to a target inclination angle 
corresponding to the current reproducing tape speed in an open loop. In a 
step S4, an auto-tracking operation is performed, and tracking data is 
stored in the RAM 10b. The auto-tracking operation is described later with 
reference to FIG. 11. In a step S5, a shape of an FM envelope obtained 
from one reproduced video FM signal is calculated by using the N division 
integrated values, and a shape value is obtained. The shape value denotes 
the number of increase/decrease changes of the FM envelope. The 
calculation of the FM envelope shape is described later in detail with 
reference to FIG. 6. 
In a step S6, it is judged whether or not the shape value is equal to or 
higher than 3. In cases where the shape value is equal to or higher than 
3, it is judged that the number of tracks crossed by one magnetic head 23a 
or 23b in one vertical scanning period is too high, and a control for 
largely changing the current inclination angle of the rotational drum 20 
is performed in a step S7. This control is called a macro-search. After 
the step S7, the step 6 is again performed, and the step S7 is repeated 
until the shape value is decreased to 1 or 2. In contrast, in cases where 
the shape value is not equal to or higher than 3, a control for slightly 
changing the current inclination angle of the rotational drum 20 is 
performed in a step S8. This control is called a micro-search. After the 
step S8, it is judged in a step S9 whether or not a changing degree of the 
FM envelope is minimized. That is, it is judged whether or not the shape 
value in one vertical scanning period is minimized to zero. In cases where 
the shape value in one vertical scanning period is not minimized, the step 
S8 is repeated until the change of the FM envelope value is minimized. In 
contrast, in cases where it is judged in the step S9 that the shape value 
in one vertical scanning period is minimized, the current FG pulse 
counting value obtained in the CPU 10a is stored in the RAM 10b in a step 
S10. In a step S11, the current inclination angle of the rotational drum 
20 is controlled according to the current FG pulse counting value. 
Thereafter, the auto-tracking is again performed in a step S12, and 
tracking data is stored in the RAM 10b. 
Next, the calculation of the FM envelope shape is described with reference 
to FIGS. 5 and 6. 
FIG. 5 shows an example of a tracing locus of one magnetic head scanning a 
recording pattern formed on the magnetic tape MT, a waveform of a 
reproduced video FM signal obtained by the scanning of the magnetic head, 
an FM envelope obtained by detecting a variable level of the reproduced 
video FM signal, one drum flip-flop output signal indicating one magnetic 
tape MT scanning period, an FG reset pulse signal and N division 
integrated values DATA(n) which are produced from the FM envelope, the 
drum flip-flop output signal and the FG reset pulse signal and are used 
for the calculation of the FM envelope shape. 
As shown in FIG. 5, each of the vertical scanning periods is divided into 
six sub-periods (N=6), and DATA(n) indicates a piece of n-th quantized 
data. 
The six division integrated values DATA(n) are obtained by converting a 
variable level of the reproduced video FM signal in one vertical scanning 
period into a direct current voltage (or an FM envelope) corresponding to 
the variable level, dividing the direct current voltage into six divided 
voltages respectively corresponding to 1/6 of one vertical scanning 
period, integrating each of the divided voltages for 1/6 of one vertical 
scanning period, holding each of six integrated voltages in a holding 
circuit and outputting the integrated voltages. Six divided integrating 
operations for the divided voltages are performed by resetting an 
integrating operation six times in synchronization with six reset pulses 
of the FG reset pulse signal. The reset pulses are obtained by counting 
one vertical scanning period ranging from a leading edge to a trailing 
edge in the drum flip-flop output signal by means of a free-run counter 
placed in the control microcomputer 10 and outputting six square waves in 
one vertical scanning period. The integrating operation is reset in 
synchronization with six leading edges of the reset pulses. Also, the 
integrated voltages are quantized by performing six A/D converting 
operations for the integrated voltages in synchronization with six 
trailing edges of the reset pulses, and six pieces of quantized voltage 
data are stored in the RAM 10b of the control microcomputer 10 as the 
division integrated values DATA(n). In this case, to prevent an erroneous 
detection of the variable level of the reproduced video FM signal caused 
by a sudden change of the variable level, each of integrating operations 
for a plurality of FM envelopes is performed on condition that each of 
drum flip-flop output signals is set to a high level. In other words, the 
integrating operations are repeatedly performed for a plurality of 
reproduced video FM signals transmitted through the same magnetic head 23a 
or 23b, and each of the six quantized voltage data is stored in an adder 
of the control microcomputer 10 for each of the reproduced video FM 
signals to perform a synchronization adding operation for each of the six 
quantized voltage data. 
FIG. 6 is a flow chart showing a procedure of the calculation of the FM 
envelope shape performed in the CPU 10a of the control microcomputer 10 in 
the step S5 shown in FIG. 4B. 
As shown in FIG. 6, in a step S21, an average value AVERAGE of six 
quantized data DATA(n) is calculated. In a step S22, a number n is 
initially set to 1, a shape value SHAPE indicating a degree of the change 
of the FM envelope shape is initially set to 0, a positive flag POSITIVE 
is initially set to 0, and a negative flag NEGATIVE is initially set to 0. 
In cases where one magnetic head correctly traces a track of a recording 
track pattern formed on the magnetic tape MT, the shape value SHAPE is 
maintained to 0. As the number of tracks crossed by one magnetic head in 
one vertical scanning period is increased, the shape value SHAPE is 
increased. The positive flag POSITIVE is set to 1 in cases where one 
quantized data DATA(n) is equal to or higher than a compared reference 
value. The negative flag NEGATIVE is set to 1 in cases where one quantized 
data DATA(n) is lower than the compared reference value. 
In the calculation of the FM envelope shape, in cases where a differential 
value DATA(n)-DATA(n-i) (i&lt;n) (or a differential value DATA(n-i)-DATA(n)) 
is higher than 1/3*AVERAGE on condition that the latest increment of the 
shape value SHAPE is not caused by the increase (or decrease) of the FM 
envelope, it is judged that the shape of the FM envelope is changed and 
the increment of the shape value SHAPE is required. 
In a step S23, a piece of quantized data DATA(n) is set as a compared value 
COME. That is, the compared value COME agreeing with the quantized 
data DATA(1) is initially set. In a step S24, the number n is incremented. 
In a step S25, it is judged whether or not the number n is equal to 7 
higher than the number N. In cases where the number n is lower than 7, it 
is judged in a step S26 whether or not another piece of quantized data 
DATA(n) is equal to or higher than the compared value COME. 
In cases where the quantized data DATA(n) is equal to or higher than the 
compared value COME, it is judged that the FM envelope is changed in a 
increasing direction. Thereafter, it is judged in a step S27 whether or 
not the positive flag POSITIVE is equal to 1. In cases where the positive 
flag POSITIVE is equal to 1, it is judged that the increment of the shape 
value SHAPE caused by the decrease of the FM envelope has not been 
performed since the shape value SHAPE is incremented because of the 
increase of the FM envelope. In this case, even though the FM envelope is 
greatly increased and a differential value DATA(n)-COME is higher than 
1/3*AVERAGE, it is not required to increment the shape value SHAPE. 
Therefore, the procedure returns to the step S23, and the compared value 
COME is renewed. In contrast, in cases where the positive flag POSITIVE 
is not equal to 1 in the step S27, it is judged that the latest increment 
of the shape value SHAPE is not caused by the increase of the FM envelope. 
Thereafter, the procedure proceeds to a step S28. In the step S28, it is 
judged whether or not a differential value DATA(n)-COME is higher than 
a value 1/3*AVERAGE. In cases where the differential value DATA(n)-COME 
is not higher than the value 1/3*AVERAGE, it is judged that the increment 
of the shape value SHAPE is not required even though the FM envelope is 
increasing on condition that the latest increment of the shape value SHAPE 
is not caused by the increase of the FM envelope. Thereafter, the 
procedure returns to the step S24, and the number n is incremented. In 
contrast, in cases where the differential value DATA(n)-COME is higher 
than the value 1/3*AVERAGE in the step S28, it is judged that the 
increment of the shape value SHAPE is required, and the procedure proceeds 
to a step S29. In the step S29, the positive flag POSITIVE is set to 1, 
and the negative flag NEGATIVE is set to 0. Thereafter, the shape value 
SHAPE is incremented in a step S30, and the procedure returns to the step 
S23 to renew the compared value COME. 
In contrast, in cases where the quantized data DATA(n) is lower than the 
compared value COME in the step S26, it is judged that the FM envelope 
is changed in a decreasing direction. Thereafter, it is judged in a step 
S31 whether or not the negative flag NEGATIVE is equal to 1. In cases 
where the negative flag NEGATIVE is equal to 1, it is judged that the 
increment of the shape value SHAPE caused by the increase of the FM 
envelope has not been performed since the shape value SHAPE is incremented 
because of the decrease of the FM envelope. In this case, even though the 
FM envelope is greatly decreased and a differential value COME-DATA(n) 
is higher than 1/3*AVERAGE, it is not required to increment the shape 
value SHAPE. Therefore, the procedure returns to the step S23, and the 
compared value COME is renewed. In contrast, in cases where the 
negative flag NEGATIVE is not equal to 1 in the step S31, it is judged 
that the latest increment of the shape value SHAPE is not caused by the 
decrease of the FM envelope. Thereafter, it is judged in a step S32 
whether or not the differential value COME-DATA(n) is higher than the 
value 1/3*AVERAGE. In cases where the differential value COME-DATA(n) 
is not higher than the value 1/3*AVERAGE, it is judged that the increment 
of the shape value SHAPE is not required even though the FM envelope is 
decreasing on condition that the latest increment of the shape value SHAPE 
is not caused by the decrease of the FM envelope. Thereafter, the 
procedure returns to the step S24, and the number n is incremented. In 
contrast, in cases where the differential value COME-DATA(n) is higher 
than the value 1/3*AVERAGE, it is judged that the increment of the shape 
value SHAPE is required, and the procedure proceeds to a step S33. In the 
step S33, the positive flag POSITIVE is set to 0, and the negative flag 
NEGATIVE is set to 1. Thereafter, the procedure proceeds to the step S30, 
and the shape value SHAPE is incremented. 
Accordingly, even though the FM envelope is increased (or decreased) after 
the shape change of the FM envelope caused by the increase (decrease) of 
the FM envelope is judged, the shape change of the FM envelope is not 
judged. 
Also, any fixed value is not used to judge whether or not the FM envelope 
is considerably increased (or decreased), but the value 1/3*AVERAGE is 
used. Therefore, the judgement of the FM envelope change corresponding to 
the level of the FM envelope in one vertical scanning period can be 
performed, and an erroneous judgement caused by a low level change of the 
FM envelope can be prevented. 
An example of N division integrated values DATA(n) from which the shape 
value SHAPE=0 is obtained as a judging result in the flow chart shown in 
FIG. 6 is shown in FIG. 7A, an example of N division integrated values 
DATA(n) from which the shape value SHAPE=1 is obtained as a judging result 
in the flow chart shown in FIG. 6 is shown in FIG. 7B, an example of N 
division integrated values DATA(n) from which the shape value SHAPE=2 is 
obtained as a judging result in the flow chart shown in FIG. 6 is shown in 
FIG. 7C, an example of N division integrated values DATA(n) from which the 
shape value SHAPE=3 is obtained as a judging result in the flow chart 
shown in FIG. 6 is shown in FIG. 7D, and an example of N division 
integrated values DATA(n) from which the shape value SHAPE=4 is obtained 
as a judging result in the flow chart shown in FIG. 6 is shown in FIG. 7E. 
The shape value SHAPE=1 is obtained in cases where one magnetic head 
crosses two tracks in one vertical scanning period, the shape value 
SHAPE=2 is obtained in cases where one magnetic head crosses three tracks 
in one vertical scanning period, the shape value SHAPE=3 is obtained in 
cases where one magnetic head crosses four tracks in one vertical scanning 
period, and the shape value SHAPE=4 is obtained in cases where one 
magnetic head crosses five tracks in one vertical scanning period. 
In the judgement for the changing degree of an FM envelope in one vertical 
scanning period performed in the step S9 shown in FIG. 4B, as shown in 
FIG. 7C, a maximum value and a minimum value are selected from among the 
division integrated values DATA(n), a difference between the maximum and 
minimum values is calculated as the changing value of the FM envelope, and 
it is judged whether or not the difference is minimized. Examples of 
differences for the same shape value SHAPE=2 are shown in FIGS. 8A to 8C. 
As shown in FIGS. 8A to 8C, even though the number of tracks crossed by 
one magnetic head in one vertical scanning period is the same, the 
difference is greatly changed according to an angle between a tracing 
direction of one magnetic head and a track direction. 
Next, the macro-search and the micro-search performed in the steps 7 and 8 
shown in FIG. 4B are described. 
In the macro-search in the step S7, in cases where the shape value SHAPE 
equal to or higher than 3 is obtained five times in succession on 
condition that the inclination of the rotational drum 20 is changed in the 
same direction, an inclination angle of the rotational drum 20 repeatedly 
changed in the step S7 is reset to an original inclination angle set in 
the step S3. Thereafter, a motor reverse rotation control signal Scr is 
transmitted from the control microcomputer 10 to the motor driving 
amplifier 14, and the rotational drum 20 is inclined in the opposite 
direction. Thereafter, in cases where the shape value SHAPE does not 
become lower than 3 even though the inclination of the rotational drum 20 
is changed in the opposite direction five times in succession, the step 
S12 is performed. 
In case of the micro-search in the step S8, a first condition that the 
changing degree of the FM envelope is gradually decreased three times in 
succession on condition that the shape value SHAPE is within a range from 
0 to 2 is defined. In cases where the changing degree of the FM envelope 
is increased after the first condition is satisfied, in cases where the 
changing degree of the FM envelope is increased five times in succession 
while ranging the shape value SHAPE from 0 to 2 without satisfying the 
first condition, or in cases where the shape value SHAPE is increased to a 
value equal to or higher than 3 after the first condition is satisfied, an 
inclination angle of the rotational drum 20 repeatedly changed in the step 
S8 is reset to an original inclination angle set in the step S3. 
Thereafter, a motor reverse rotation control signal is transmitted from 
the control microcomputer 10 to the motor driving amplifier 14. 
Thereafter, the steps S6 to S9 are repeated in the same manner to 
gradually incline the rotational drum 20 in the opposite direction. After 
the detection of the changing degree of the FM envelope for the 
inclination change of the rotational drum 20 in the both directions is 
finished, the step Sil is performed. 
In the above detection, the number of successive times of the judgement for 
the shape value SHAPE is expressed by a positive integral number relating 
to a range of the changed inclination angle of the rotational drum 20. 
That is, in cases where the number of successive times is increased, the 
inclination angle of the rotational drum 20 is changed in a wider range. 
In an actual operation, the range of the changed inclination angle of the 
rotational drum 20 is determined by considering a changing degree of the 
inclination angle of the rotational drum 20 changed for each changing 
operation and the current inclination angle of the rotational drum 20 on 
condition that any excessive noise occurs in a reproduced image. 
Therefore, the control microcomputer 10 of the system 11 functions as a 
flatness detecting means for detecting a flatness degree of a variable 
level of the reproduced video FM signal, in one vertical scanning period, 
read by each of the rotational heads 23a and 23b of which the scanning 
direction is changed by the motor 16 and the motor driving amplifier 14. 
Also, the control microcomputer 10 of the system 11 functions as an 
inclination angle control means for controlling the motor 16 and the motor 
driving amplifier 14 to maximize the flatness degree of the variable level 
of the reproduced signal. 
FIG. 9A shows a scanning direction of one magnetic head moved according to 
the auto-tracking control performed in the steps S4 and S12, and FIG. 9B 
shows a scanning direction of one magnetic head controlled in the 
macro-search and the micro-search performed in the steps S7 and S8. 
As shown in FIG. 9A, because one magnetic head is controlled in an 
auto-tracking control direction indicated by dotted lines, a head trace 
locus of one magnetic head in the reproducing operation agrees with a 
track formed on the magnetic tape MT. The head trace locus is indicated by 
a real line. Also, as shown in FIG. 9B, because the inclination angle of 
the rotational drum 20 is controlled in an inclination angle control 
range, a head trace locus of one magnetic head in the reproducing 
operation agrees with a track formed on the magnetic tape MT. 
Next, an example that the inclination angle control method performed in the 
steps S1 to S12 is applied for a magnetic recording and reproducing 
apparatus is described with reference to FIG. 10. 
FIG. 10 is a flow chart showing a processing procedure performed in the CPU 
10a in which the control for a magnetic recording and reproducing 
apparatus is performed. 
As shown in FIG. 10, it is judged in a step S41 whether or not a magnetic 
recording and reproducing apparatus is set in a reproducing operation 
condition. In cases where the magnetic recording and reproducing apparatus 
is not set in the reproducing operation condition, a current inclination 
angle of the rotational drum 20 is set to a predetermined inclination 
angle (or a recording position) to set the rotational drum 20 in a 
recording condition (step 42). This setting of the rotational drum 20 is 
performed by inclining the rotational drum 20 according to an open loop 
control and stopping the operation of the motor 16 when one FG reset 
signal is received by the CPU 10a. In contrast, in cases where the 
magnetic recording and reproducing apparatus is set in the reproducing 
operation condition in the step S41, it is judged in a step S43 whether or 
not a tape speed in the reproducing operation is changed. 
In cases where the tape speed in the reproducing operation is not changed, 
it is judged in a step S47 whether or not the control of the inclination 
angle of the rotational drum 20 is again required. For example, in cases 
where the shape of an FM envelope is considerably changed during the 
reproducing operation, in cases where the auto-tracking control set to an 
off condition is changed to an on condition, in cases where a video 
cassette tape is exchanged for another one, or in cases where an 
alternating current (AC) electric source set to an off condition is 
changed to an on condition, a retrial condition for the inclination angle 
control is satisfied, and the control of the inclination angle of the 
rotational drum 20 is again required. In this case, the control of the 
inclination angle of the rotational drum 20 is performed in a step S48. 
That is, the steps S1 to S12 shown in FIG. 4B are performed. Thereafter, 
the procedure returns to the step S43. In contrast, in cases where the 
control of the inclination angle of the rotational drum 20 is not again 
required in the step S47, the procedure returns to the step S43. 
In contrast, it is judged in the step S43 that the tape speed in the 
reproducing operation is changed, it is judged in a step S44 whether or 
not an appropriate (target) inclination angle of the rotational drum 20 
corresponding to a current tape speed has been already calculated. In 
other words, it is judged whether or not a target FG pulse counting value 
corresponding to the target inclination angle has been already calculated 
and stored. In cases where the target inclination angle of the rotational 
drum 20 has been already calculated, the target inclination angle (or the 
target FG pulse counting value) is read out from the RAM 10b in a step 
S45, and the current inclination angle of the rotational drum 20 is 
controlled to make the current inclination angle agree with the target 
inclination angle by operating the motor 16. In this case, a complicated 
procedure composed of the judgement of the envelope shape change (the step 
S5), the macro-search (the step S7) and the micro-search (the step S8) is 
not required. Thereafter, in a step S46, pieces of auto-tracking data are 
read out from the RAM 10b, and an auto-tracking control is performed 
according to the auto-tracking data. Thereafter, the procedure returns to 
the step S43. In contrast, it is judged in the step S44 that the target 
inclination angle of the rotational drum 20 has not been yet calculated, 
it is required to calculate the target inclination angle and control the 
inclination angle of the rotational drum 20. Therefore, the step S48 is 
performed. 
Accordingly, the inclination angle of the rotational drum 20 is adjusted in 
the reproducing operation each time the tape speed in the reproducing 
operation is changed or set, and the inclination angle of the rotational 
drum 20 is merely set to the predetermined inclination angle in the 
recording operation. 
Also, in cases where a target inclination angle (or a target FG pulse 
counting value) for a particular tape speed is not stored in the RAM 10b, 
the target inclination angle is calculated in the step S48 and is stored 
in the RAM 10b. Therefore, even though the apparatus is again operated at 
the particular tape speed in another reproducing operation, because the 
target inclination angle is stored in the RAM 10b, the inclination angle 
control can be easily performed in the step S45. In other words, the 
apparatus has a learning function. 
The step S47 is performed for any tape speed in the reproducing operation. 
In cases where the retrial condition is satisfied, the control of the 
inclination angle of the rotational drum 20 is again required regardless 
of whether the tape speed in the reproducing operation is changed. 
Next, the auto-tracking operation performed in the steps S4 and S12 is 
described with reference to FIG. 11. 
FIG. 11 is a block diagram of an auto-tracking control system arranged in 
the magnetic recording and reproducing apparatus. 
As shown in FIG. 11, in an auto-tracking control system 61, each of a 
plurality of reproduced video FM signals obtained from the magnetic heads 
23a and 23b attached on the rotational drum 20 is transmitted to a level 
detecting circuit 64 through a video signal amplifier 62. Also, each of a 
plurality of reproduced audio signals obtained from the magnetic heads 23a 
and 23b is transmitted to the level detecting circuit 64 through an audio 
signal amplifier 63. Thereafter, levels of the reproduced video FM signals 
and/or levels of the reproduced audio signals are detected one after 
another in the level detecting circuit 64 and are transmitted to a system 
controller 65. In the system controller 65, an appropriate tracking 
position is calculated according to each of the levels, and a plurality of 
tracking addresses indicating the appropriate tracking positions are 
transmitted one after another to a servo circuit 66. In the servo circuit 
66, a first actuating signal for actuating the rotational drum 20 is 
generated for each of the tracking addresses and is transmitted to the 
rotational drum 20. Also, a second actuating signal for actuating a 
capstan 67 is generated for each of the tracking addresses and is 
transmitted to the capstan 67. Therefore, a relative position between each 
of the rotational heads and the magnetic tape MT is adjusted. 
Accordingly, because the auto-tracking operation is performed in the 
auto-tracking control system 61, a head locus of each of the rotational 
heads can agree with a track of a track pattern formed on the magnetic 
tape MT with a high accuracy in cooperation with the inclination angle 
control performed for the rotational drum 20. 
In the first embodiment, the inclination angle control method is applied 
for a variable speed reproducing operation differing from a normal speed 
reproducing operation. However, in cases where the inclination angle 
control method according to the first embodiment is applied for the normal 
reproducing operation in which the magnetic tape MT is traveled at a 
standard speed, a trace locus of each magnetic head can agree with a track 
of a track pattern formed on the magnetic tape MT with a very high 
accuracy, and a reproduced image having a very high quality can be 
obtained. 
Next, an inclination angle control method appropriate for a still 
reproduction is described according to a second embodiment of the present 
invention with reference to FIGS. 12 and 13. 
In the still reproduction, a capstan motor for actuating the capstan 67 
according to the second actuating signal is not operated. Therefore, an 
inclination angle of the rotational drum 20 is controlled without 
performing any auto-tracking operation. In this case, as shown in FIG. 
12A, when a head locus direction of one rotational head is inclined with 
respect to an extending direction of a track formed on the magnetic tape 
MT (for example, the shape value SHAPE=1), the inclination angle of the 
rotational drum 20 is adjusted to direct the head locus of one rotational 
head in parallel to the extending direction of the track. As a result, as 
shown in FIG. 12B, even though the head locus of one rotational head is 
directed in parallel to the extending direction of the track, the head 
locus is often shifted from a center of the track. In other words, the 
head locus is undesirably shifted in a width direction of the track. In 
this case, even though the shape value SHAPE=0 is obtained and the level 
of the reproduced video FM signal is flattened, the level value of the 
reproduced video FM signal is considerably lowered. 
To prevent the above drawback, an inclination angle controlling method 
shown in FIG. 13 is performed according to a second embodiment of the 
present invention. 
FIG. 13 is a flow chart showing an inclination angle control method 
appropriate for a still reproduction according to a second embodiment of 
the present invention. 
As shown in FIG. 13, after the steps S1 to S8 are performed, a sum of the 
division integrated values DATA(n) is calculated in a step S13, and it is 
judged in a step S14 whether or not the sum is decreased three times in 
succession. Because the procedure between the step S8 and the step S9 is 
repeated to minimize the changing degree of the FM envelope in one 
vertical scanning period, the sum is repeatedly calculated in the step 
S13. 
In cases where it is judged in the step S14 that the sum is not decreased 
three times in succession, the step S9 is performed. In contrast, in cases 
where the sum is decreased three times in succession, it is judged that 
the micro-search and the macro-search performed in the steps S7 and S8 are 
not appropriate. Therefore, in a step S15, the inclination angle of the 
rotational drum 20 repeatedly changed in the steps S7 and S8 is reset to 
an original inclination angle set in the step S3, and a motor reverse 
rotation control signal Scr is transmitted from the control microcomputer 
10 to the motor driving amplifier 14. Thereafter, the steps S5 to S8 are 
performed in the same manner to gradually incline the rotational drum 20 
in the opposite direction. 
Though the first embodiment is described with reference to FIG. 4B and the 
second embodiment is described with reference to FIG. 13, it is applicable 
that a step for judging whether or not a still mode is selected be added 
to unify the flow chart of the first embodiment and that of the second 
embodiment. 
Next, a third embodiment of the present invention, in which the inclination 
angle of the rotational drum 20 is accurately and easily set to an 
appropriate inclination angle even though a recording tape speed 
characteristic for a particular magnetic recording and reproducing 
apparatus differs from that for another apparatus or the recording tape 
speed characteristic in one magnetic recording and reproducing apparatus 
changes, is described. In the third embodiment, in cases where the 
magnetic tape MT is traveled at an N-times reproducing tape speed which is 
N-times as high as a normal reproducing tape speed, N tracks recorded on 
the magnetic tape MT is scanned by each of the magnetic heads 23a and 23b 
in one vertical scanning period. 
The drum structure DS shown in FIG. 2 is described in more detail. 
FIG. 14 is a longitudinal sectional view of the drum structure DS shown in 
FIG. 2. FIG. 15 is a top view of the drum structure DS shown in FIG. 2. 
FIG. 16 is a sectional view taken generally along a line G--G of FIG. 15. 
FIG. 17 is a sectional view taken generally along a line X-O-Y-Z of FIG. 
15. FIG. 18 is a sectional view taken generally along a line E--E of FIG. 
15. FIG. 19 is a bottom view of the drum structure DS shown in FIG. 2. 
FIG. 20 shows a whole drum inclination angle correcting characteristic, a 
lead inclination angle correcting characteristic and a track inclination 
correcting angle. 
As shown in FIGS. 2 and 14, the drum axis 24 is inserted into a center 
portion of the lower drum 22 under pressure, and the upper drum 21 is 
coaxially supported by the drum axis 24 through a pair of bearings 19a and 
19b put on the drum axis 24. The tape sliding surface 21a for leading a 
bound magnetic tape MT is formed at the periphery of the upper drum 21 at 
the same diameter with that of the upper drum 21, and the tape sliding 
surface 22a for leading the bound magnetic tape MT is formed at the 
periphery of the lower drum 22 at the same diameter with that of the lower 
drum 22. In the lower drum 22, the small diameter portion 22b having a 
diameter smaller than that of the tape sliding surface 22a is helically 
arranged on a lower side of the tape sliding surface 22a, and a lower 
small diameter portion 22d having a diameter smaller than that of the 
small diameter portion 22b, is arranged on a lower portion of a center of 
a bottom surface portion 22c of the lower drum 22 and extends toward the 
drum portion 28. 
The upper drum 21 on which the magnetic heads 23a and 23b are attached is 
rotated around the drum axis 24 by an actuating power provided by a drum 
motor 26. In this case, the drum motor 16 is composed of a stator 26a 
fixed on an upper end side of the drum axis 24 and a rotor 26b rotated 
with the upper drum 21. Also, signals transmitted from the magnetic heads 
23a and 23b are received by a rotational transformer 36a attached to the 
upper drum 21 and a rotational transformer 36b attached to the lower drum 
22, and signals transmitted from the rotational transformers 36a and 36b 
are received by the magnetic heads 23a and 23b. 
On a lower side of the periphery of the lower drum 22, the leading ring 27 
formed of the helical lead 27a is separately provided. The leading ring 27 
is movably placed close to an outer periphery of the small diameter 
portion 22b which is formed in a helical shape at a lower portion of the 
lower drum 22. The leading ring 27 is composed of an annular portion 27b 
having the helical lead 27a at its upper end and a bottom surface portion 
27c. Also, a penetrating hole is formed at a center portion of the bottom 
portion 27c of the leading ring 27, and a knife edge portion 27d is formed 
at an inner circular portion of the penetrating hole. The knife edge 
portion 27d is inserted into the lower small diameter portion 22d. 
As shown in FIGS. 15 and 16, a pair of location pins 37a and 37b having a 
superior wear and abrasion resistance are fixedly attached to an outer 
periphery of the bottom surface portion 22c of the lower drum 22 on a 
0(degree)-180(degree) L2 line symmetrical to each other with respect to a 
90 (degree)-270(degree) L1 line, and a pair of lower ends of the location 
pins 37a and 37b are projected into an elliptic hole 27c1 and a circular 
hole 27c2 arranged in the bottom surface portion 27c of the leading ring 
27. In this case, the location pin 37a placed on a 0 degree side is 
movably inserted into the elliptic hole 27c1 in a 0(degree)-180(degree) 
direction, and the location pin 37a is fixedly placed in another direction 
perpendicular to the 0(degree)-180(degree) direction. Also, the location 
pin 37b placed on a 100 degree side is movably inserted into the circular 
hole 27c2. 
Also, top ends of the screws 24a and 24b screwed into the drum base 28 are 
detachably touched to the lower ends of the location pins 37a and 37b, and 
the lower drum 22 is pressed by the screws 24a and 24b screwed into the 
drum base 28. Therefore, the screws 24a and 24b have a function for 
correcting an inclination of the whole rotational drum 20. That is, in an 
FF reproducing mode operation, the location pin 37a placed on the 0 degree 
side is pressed up by a tip of the screw 24a, a 0 degree side bottom 
surface portion 22c of the lower drum 22 is pressed up, the upper and 
lower drums 21 and 22 supported by the drum axis 24 are rotationally moved 
with the leading ring 27 by a whole drum inclination correcting angle 
.theta. in a clockwise direction with respect to the drum base 28, and the 
inclination of the rotational drum 20 in the FF reproducing mode operation 
is corrected. In contrast, in an FB reproducing mode operation, the 
location pin 37b on the 180 degree side is pressed up by a tip of the 
screw 24b, a 180 degree side bottom surface portion 22c of the lower drum 
22 is pressed up, the upper and lower drums 21 and 22 supported by the 
drum axis 24 are rotationally moved with the leading ring 27 by a whole 
drum inclination correcting angle .theta. in a counterclockwise direction 
with respect to the drum base 28, and the inclination of the rotational 
drum 20 in the FB reproducing mode operation is corrected. 
In this case, even though the lower drum 22 is rotationally moved by the 
screws 24a and 24b screwed into the drum base 28 in the FF reproducing 
mode operation and the FB reproducing mode operation, the screws 24a and 
24b are not inclined. Therefore, gear portions of the screws 24a and 24b 
are directly engaged with the two speed gears G.sub.1 and G.sub.2 of the 
actuating means 40. 
As shown in FIGS. 15 and 17, the location pin 37a (or 37b) having a 
superior wear and abrasion resistance is fixedly attached to an outer 
periphery of the bottom surface portion 22c of the lower drum 22 on the 
0(degree)-180(degree) L2 line symmetrical to each other with respect to 
the 90 (degree)-270(degree) L1 line, and lower ends of the location pin 
37a (or 37b) is projected into a relief hole 27c3 (or 27c4) arranged in 
the bottom surface portion 27c of the leading ring 27. In addition, a top 
end of the screw 25a (or 25b) screwed into the bottom surface portion 27c 
of the leading ring 27 is penetrating through a relief hole 28a (or 28b) 
of the drum base 28 and is detachably touched to a lower end of a pin 38a 
(or 38b). 
In this case, the screws 25a and 25b screwed into the leading ring 27 press 
the lower drum 22, and the screw 25a is placed on the 0 degree side, and 
the screws 25a and 25b have a function for correcting an inclination of a 
track formed on the magnetic tape MT. That is, in the FF reproducing mode 
operation, when the pin 38a placed on the 0 degree side is pressed up by a 
tip of the screw 25a placed on the 0 degree side, though the 0 degree side 
bottom surface portion 27c of the leading ring 27 is pressed down by a 
track inclination correcting angle .theta.1 (shown in FIG. 20) with 
respect to the lower drum 22, the 0 degree side bottom surface portion 27c 
of the leading ring 27 is rotationally moved in the clockwise direction 
with respect to the drum base 28, and the inclination of the track in the 
FF reproducing mode operation is corrected. In contrast, in the FB 
reproducing mode operation, the pin 38b placed on the 180 degree side is 
pressed up by a tip of the screw 25b placed on the 180 degree side, the 
180 degree side bottom surface portion 27c of the leading ring 27 is 
pressed down by a track inclination correcting angle .theta.1 with respect 
to the lower drum 22, the 0 degree side bottom surface portion 27c of the 
leading ring 27 is rotationally moved in the counterclockwise direction 
with respect to the drum base 28, and the inclination of the track in the 
FB reproducing mode operation is corrected. 
Therefore, in the FF reproducing mode operation, a leading correction 
inclination angle .theta.2 is obtained by subtracting the track 
inclination correcting angle .theta.1 caused by the screws 25a and 25b 
screwed into the leading ring 27 from the whole drum inclination 
correcting angle .theta. caused by the screws 25a and 25b screwed into the 
drum base 28, and a leading correction is performed by the leading 
correction inclination angle .theta.2 in the FF reproducing mode operation 
in which the leading ring 27 is rotationally moved in the clockwise 
direction with respect to the drum base 28. In the same manner, another 
leading correction is performed by the leading correction inclination 
angle .theta.2 in the FB reproducing mode operation in which the leading 
ring 27 is rotationally moved in the counterclockwise direction with 
respect to the drum base 28. 
The object of the leading correction is described. Because of the rotation 
of the drum structure DS caused by the track correction, the magnetic tape 
MT is pulled in a direction of the rotation. As a result, the reference 
edge Te of the magnetic tape MT intends to depart from the helical lead 
27a of the leading ring 27 on an inlet side of the magnetic tape MT with 
respect to the drum structure DS, and the reference edge Te of the 
magnetic tape MT intends to push to the helical lead 27a on an outlet side 
of the magnetic tape MT with respect to the drum structure DS. Therefore, 
the leading ring 27 is rotationally moved to make the helical lead 27a 
match with the reference edge Te of the magnetic tape MT. In brief, to 
compensate the displacement of the reference edge Te of the magnetic tape 
MT caused by the track correction, the leading ring 27 is rotationally 
moved in the leading correction to make the helical lead 27a match with 
the reference edge Te of the magnetic tape MT. 
Therefore, the combination of the screws 24a and 24b functions as a whole 
drum correction actuating means for rotationally moving the upper and 
lower drums 21 and 22 supported by the drum axis 24 with the leading ring 
27 with respect to the drum base 28 in the FF reproducing mode operation 
and the FB reproducing mode operation. Also, the combination of the screws 
25a and 25b functions as a track inclination correction actuating means 
for successively inclining the drum axis 24 with respect to an imaginary 
central axis of the leading ring 27 according to a traveling speed of the 
magnetic tape MT to make a track pattern formed on the magnetic tape MT 
agree with rotational loci of the magnetic heads 23a and 23b formed on the 
magnetic tape MT in the FF reproducing mode operation and the FB 
reproducing mode operation. Also, the cooperative configuration of the 
combination of the screws 24a and 24b and the combination of the screws 
25a and 25b functions as a lead correction actuating means for 
successively inclining the imaginary central axis of the leading ring 27 
to make the helical lead 27a agree with a reference edge of the magnetic 
tape MT. 
In this case, because the screws 25a and 25b are inclined with respect to 
the drum base 28 in the FF reproducing mode operation and the FB 
reproducing mode operation when the leading ring 27 is rotationally moved 
by the screws 25a and 25b screwed into the leading ring 27, gear portions 
arranged in lower ends of the screws 24a and 24b are movably inserted into 
ends of coupling gears KG to connect the screws 24a and 24b to the 
coupling gears KG, and gear portions arranged at lower ends of the 
coupling gears KG are engaged with the two speed gears G.sub.1 and G.sub.2 
arranged in a series of gears of an actuating means 59 (FIG. 19). 
Also, in the neighborhood of the screws 25a and 25b screwed into the bottom 
surface portion 27c of the leading ring 27, a pair of compression springs 
39a and 39b are arranged at a narrow region between a reverse surface of 
the bottom surface portion 27c of the leading ring 27 and the drum base 
28, and the leading ring 27 is pressed by a weal force of the compression 
springs 39a and 39b toward the lower drum 22 
Also, a pair of location pins 80a and 80b are arranged among an outer 
peripheral portion of the bottom surface portion 22c of the lower drum 22, 
an outer peripheral portion of the bottom surface portion 27c of the 
leading ring 27 and the drum base 28 and are placed on the 
90(degree)-270(degree) L1 line symmetrical to each other with respect to 
the 0(degree)-180(degree) L2 line. The location pins 80a and 80b position 
the lower drum 22 and the drum base 28. 
Also, as shown in FIGS. 15, 17 and 18, a pair of stepped holes 28c and 28d 
are opened on a rear surface side of the drum base 28 and are placed on 
the 90(degree)-270(degree) L1 line symmetrical to each other with respect 
to the 0 (degree)-180(degree) L2 line. A flanged screw 82a (or 82b) 
inserted into a compression spring 81a (or 81b) is inserted into the 
stepped hole 28c (or 28d) from a lower side, and a top of the flanged 
screw 82a (or 82b) is screwed into the lower drum 22 through a penetrating 
hole of the leading ring 27. 
In this case, a spring force of the compression spring 81a (or 81b) is 
stronger than that of the compression spring 39a (or 39b), and the lower 
drum 22 is pushed toward the drum base 28 by a strong force of the 
compression spring 81a (or 81b) narrow-placed between the flange of the 
flanged screw 82a (or 82b) and the stepped hole 28c (or 28d). 
Next, a rotational movement supporting point of the lower drum 22 for 
rotating the upper and lower drums 21 and 22 and the leading ring 27 in a 
clockwise or counterclockwise direction with respect to the drum base 28 
is described with reference to FIGS. 15 and 18. 
As shown in FIGS. 15 and 18, a pair of first rotational movement supporting 
points 28e1 and 28e2 are placed in the neighborhood of an outer periphery 
of an upper surface of the drum base 28 symmetrical to each other with 
respect to the 0(degree)-180(degree) L2 line, and a pair of second 
rotational movement supporting points 28f1 and 28f2 are placed in the 
neighborhood of the outer periphery of the upper surface of the drum base 
28 symmetrical to each other with respect to the 0(degree)-180(degree) L2 
line. A group of the first rotational movement supporting points 28e1 and 
28e2 is symmetrical to a group of the second rotational movement 
supporting points 28f1 and 28f2 with respect to the 90(degree)-270(degree) 
L1 line, and the first and second rotational movement supporting points 
28e1, 28e2, 28f1 and 28f2 are projected toward the lower drum 22 while 
maintaining the height accuracy. In other words, the first rotational 
movement supporting points 28e1 and 28e2 are placed on the left side (or 
the 0 degree side) with respect to the drum axis 24, and the second 
rotational movement supporting points 28f1 and 28f2 are placed on the 
right side (or the 180 degree side). 
In this embodiment, the first rotational movement supporting points 28e1 
and 28e2 (or the second rotational movement supporting points 28f1 and 
28f2) are placed on the drum base 28 in parallel to the 
90(degree)-270(degree) L1 line. However, it is applicable that the first 
rotational movement supporting points 28e1 and 28e2 (or the second 
rotational movement supporting points 28f1 and 28f2) be placed on a line 
almost parallel to the 90(degree)-270(degree) L1 line. 
In addition, the first rotational movement supporting points 28e1 and 28e2 
and the second rotational movement supporting points 28f1 and 28f2 placed 
on the drum base 28 penetrate though a plurality of relief holes 27c5 to 
27c8 opened in the bottom surface portion 27c of the leading ring 27 and 
are detachably touched to a reverse surface of the bottom surface portion 
22c of the lower drum 22. As described in detail later, in a normal 
reproducing mode, the first rotational movement supporting points 28e1 and 
28e2 and the second rotational movement supporting points 28f1 and 28f2 
are touched to the bottom surface portion 22c of the lower drum 22. In the 
FF reproducing mode, the second rotational movement supporting points 28f1 
and 28f2 are touched to the 180 degree side bottom surface portion 22c of 
the lower drum 22. In the FB reproducing mode, the first rotational 
movement supporting points 28e1 and 28e2 are touched to the 0 degree side 
bottom surface portion 22c of the lower drum 22. 
Also, a pair of first rotational movement supporting points 27e1 and 27e2 
are placed in the neighborhood of an outer periphery of an upper surface 
of the bottom surface portion 27c placed in the inner circular portion of 
the leading ring 27 symmetrical to each other with respect to the 
0(degree)-180(degree) L2 line, and a pair of second rotational movement 
supporting points 27f1 and 27f2 are placed in the neighborhood of the 
outer periphery of the upper surface of the bottom surface portion 27c 
placed in the inner circular portion of the leading ring 27 symmetrical to 
each other with respect to the 0(degree)-180(degree) L2 line. A group of 
the first rotational movement supporting points 27e1 and 27e2 is 
symmetrical to a group of the second rotational movement supporting points 
27f1 and 27f2 with respect to the 90(degree)-270(degree) L1 line, and the 
first and second rotational movement supporting points 27e1, 27e2, 27f1 
and 27f2 are projected toward the lower drum 22 while maintaining the 
height accuracy. In other words, the first rotational movement supporting 
points 27e1 and 27e2 on the leading ring 27 are placed on the left side 
(or the 0 degree side) with respect to the drum axis 24, and the second 
rotational movement supporting points 27f1 and 27f2 on the leading ring 27 
are placed on the right side (or the 180 degree side). Also, the first 
rotational movement supporting points 27e1 and 27e2 (or the second 
rotational movement supporting points 27f1 and 27f2) are placed outside 
the first rotational movement supporting points 28e1 and 28e2 (or the 
second rotational movement supporting points 28f1 and 28f2) placed on the 
drum base 28. 
In this embodiment, the first rotational movement supporting points 27e1 
and 27e2 (or the second rotational movement supporting points 27f1 and 
27f2) are placed on the leading ring 27 in parallel to the 
90(degree)-270(degree) L1 line. However, it is applicable that the first 
rotational movement supporting points 27e1 and 27e2 (or the second 
rotational movement supporting points 27f1 and 27f2) be placed on a line 
almost parallel to the 90(degree)-270(degree) L1 line. 
In addition, the first rotational movement supporting points 27e1 and 27e2 
and the second rotational movement supporting points 27f1 and 27f2 placed 
on the leading ring 27 are detachably touched to the reverse surface of 
the bottom surface portion 22c of the lower drum 22. As described in 
detail later, in the normal reproducing mode, the first rotational 
movement supporting points 27e1 and 27e2 and the second rotational 
movement supporting points 27f1 and 27f2 are touched to the bottom surface 
portion 22c of the lower drum 22. In the FF reproducing mode, the second 
rotational movement supporting points 27f1 and 27f2 are touched to the 180 
degree side bottom surface portion 22c of the lower drum 22. In the FB 
reproducing mode, the first rotational movement supporting points 27e1 and 
27e2 are touched to the 0 degree side bottom surface portion 22c of the 
lower drum 22. 
In this case, it is not required to produce the reverse surface of the 
leading ring 27 with a high size precision, and it is required to produce 
the inner circular portion of the upper surface of the leading ring 27 
with a high size precision. 
In this embodiment, the first rotational movement supporting points 27e1 
and 27e2 and the second rotational movement supporting points 27f1 and 
27f2 are placed on the inner circular portion of the upper surface of the 
leading ring 27. However, it is applicable that the first rotational 
movement supporting points 27e1 and 27e2 and the second rotational 
movement supporting points 27f1 and 27f2 be placed on the reverse surface 
of the bottom surface portion 22c of the lower drum 22. In other words, it 
is applicable that the first rotational movement supporting points 27e1 
and 27e2 and the second rotational movement supporting points 27f1 and 
27f2 be placed between the leading ring 27 and the lower drum 22 through 
the drum axis 24. 
Next, an actuating means 59 in which the screws 24a and 24b rotationally 
moving the lower drum 22 and the screws 25a and 25b rotationally moving 
the leading ring 27 are rotationally and simultaneously actuated by a 
rotational drum actuating motor 42 is described in brief with reference to 
FIG. 19. 
As shown in FIG. 19, constitutional elements of the actuating means 59 
except for the motor 42 are operated in the same manner as those of the 
actuating means 40 shown in FIG. 3. Therefore, because the screws 24a and 
24b are engaged with the larger diameter gear portions G.sub.11 and 
G.sub.21 of the two speed gears G.sub.1 and G.sub.2, the screws 24a and 
24b for correcting the inclination of the whole rotational drum 20 are 
rotated by the motor 42 at a high degree according to a whole drum 
inclination angle correcting characteristic (FIG. 20) to rotate the upper 
and lower drums 21 and 22 by the whole drum inclination correcting angle 
.theta.. In contrast, because the screws 25a and 25b are engaged with the 
smaller diameter gear portions G.sub.12 and G.sub.22 of the two speed 
gears G.sub.1 and G.sub.2, the screws 25a and 25b for correcting the 
inclination of the track formed on the magnetic tape MT are rotated by the 
motor 42 at a low degree according to a lead inclination angle correcting 
characteristic (FIG. 20) to rotate the bottom portion of the leading ring 
27 by a lead inclination correcting angle .theta.2 obtained by subtracting 
the track inclination correcting angle .theta.1 from the whole drum 
inclination correcting angle .theta.. 
Also, as shown in FIG. 20, the whole drum inclination angle correcting 
characteristic and the lead inclination angle correcting characteristic 
have a non-sensitive zone in which the correcting angle .theta. (or 
.theta.1) is not changed even though the screws 24a and 24b (or 25a and 
25b) are rotated by the motor 42. The non-sensitive zone corresponds to 
the normal reproducing mode operation in which the screws 24a and 24b 
screwed into the drum base 28 are detached from the lower drum 22, the 
screws 25a and 25b screwed into the leading ring 27 are detached from the 
lower drum 22 and the first rotational movement supporting points 28e1 and 
28e2 and the second rotational movement supporting points 28f1 and 28f2 
placed on the drum base 28 and the first rotational movement supporting 
points 27e1 and 27e2 and the second rotational movement supporting points 
27f1 and 27f2 placed on the leading ring 27 are touched to the reverse 
surface of the bottom surface portion 22c of the lower drum 22. 
Also, because the fan-shaped shielding plates (not shown) are attached to 
the second pulley 45, the number of pulses (or the current pulse counting 
value) indicating the number of rotations of a rotor of the motor 42 is 
detected by a pulse counter through the photo-electro sensor 51, so that 
it is detected whether or not the inclination angle of the rotational drum 
20 reaches a target inclination angle. Also, when the rotational drum 20 
is inclined at an inclination angle corresponding to a standard speed 
recording operation, an edge of the fan-shaped shielding plate 50a 
attached to the reset gear 50 is detected by the photo-electro sensor 52, 
and the number of pulses detected by the pulse counter is reset by a 
detecting signal of the photo-electro sensor 52. 
Next, the movement of the drum structure DS according to the third 
embodiment is described with reference to FIGS. 20, and 21A to 21C. 
FIG. 21A shows the movement of the rotational drum, composed of the leading 
ring 27 and the upper and lower drums 21 and 22 supported by the drum axis 
24, in the normal reproducing mode operation, FIG. 21B shows the movement 
of the rotational drum in the FF reproducing mode operation, and FIG. 21C 
shows the movement of the rotational drum in the FB reproducing mode 
operation. 
In FIGS. 21A to 21C, the 0 degree side indicates a magnetic tape inlet side 
(the left side with respect to the drum axis 24) in the normal reproducing 
mode operation, and the 180 degree side indicates a magnetic tape outlet 
side (the right side with respect to the drum axis 24) in the normal 
reproducing mode operation. 
As shown in FIG. 21A, in cases where the reproducing operation is performed 
for the magnetic tape MT traveled at a standard speed, the leading ring 27 
and the upper and lower drums 21 and 22 supported by the drum axis 24 are 
not inclined with respect to the drum base 28 but are in parallel to the 
drum base 28. That is, the first rotational movement supporting points 
28e1 and 28e2 and the second rotational movement supporting points 28f1 
and 28f2 placed on the drum base 28 and the first rotational movement 
supporting points 27e1 and 27e2 and the second rotational movement 
supporting points 27f1 and 27f2 placed on the leading ring 27 are touched 
to the reverse surface of the bottom surface portion 22c of the lower drum 
22. In this case, the screws 24a and 24b screwed into the drum base 28 are 
relieved in the lower direction without touching the location pins 37a and 
37b (FIG. 16) fixedly attached to the bottom surface portion 22c of the 
lower drum 22, and the screws 25a and 25b screwed into the leading ring 27 
are relieved in the lower direction without touching the location pins 38a 
and 38b (FIG. 17) fixedly attached to the bottom surface portion 22c of 
the lower drum 22. 
Also, the lower drum 22 is pushed toward the drum base 28 by a strong force 
of the compression springs 81a and 81b narrow-placed between the lower 
drum 22 and the drum base 28, and the leading ring 27 is pushed toward the 
lower drum 22 by a weak force of the compression springs 39a and 39b 
narrow-placed between the leading ring 27 and the drum base 28. Therefore, 
the lower drum 22 is reliably supported on the supporting points 27e1, 
27e2, 27f1, 27f2, 28e1, 28e2, 28f1 and 28f2 while maintaining the height 
size, and the leading ring 27 is also reliably supported while maintaining 
the height size. 
Accordingly, an imaginary central axis of the leading ring 27 agrees with 
the drum axis 24 with a high precision, and a condition that these axes 
are perpendicular to the drum base 28 is obtained. In this condition, when 
the magnetic tape MT on which data are recorded at the standard mode is 
traveled at a prescribed speed (for example, 33.35 mm/sec in case of the 
VHS type VTR) corresponding to the normal reproducing mode operation while 
the reference edge Te of the magnetic tape MT is lead by the helical lead 
27a of the leading ring 27, rotational loci of the magnetic heads 23a and 
23b agree with a track pattern recorded on the magnetic tape MT. This 
condition corresponds to the non-sensitive zone (FIG. 20) in which the 
inclination angles of the lower drum 22 and the leading ring 27 are not 
changed, and a reproduced signal indicating an envelope set in a superior 
condition. 
Also, in cases where data are recorded on the magnetic tape MT traveled at 
the standard speed, the adjustment of the inclination angles of the drum 
axis 24 and the imaginary central axis of the leading ring 27 is performed 
in the same manner as in the reproducing operation. 
As shown in FIG. 21B, in cases where the recording or reproducing operation 
is performed for the magnetic tape MT traveled at a fast feeding speed 
differing from the standard speed in a plus direction (for example, in 
cases where the normal reproducing mode is changed to the FF reproducing 
mode), the motor 42 (FIG. 19) is operated to push out the screws 24a and 
25a placed on the 0 degree side in the upper direction according to the 
fast feeding speed. In this case, the screws 24b and 25b placed on the 180 
degree side are pushed out in a relief direction apart from the lower drum 
22 because the rotation of the screws 24b and 25b is opposite to that of 
the screws 24a and 25a. That is, when the screw 24a screwed into the drum 
base 28 is pushed out in the upper direction, the location pin 37a (FIG. 
16) fixedly attached to the 0 degree side bottom surface portion 22c of 
the lower drum 22 is pushed up by a top of the screw 24a. Therefore, the 
180 degree side bottom surface portion 22c of the lower drum 22 is touched 
to the second rotational movement supporting points 28f1 and 28f2 placed 
on the 180 degree side of the drum base 28, and the first rotational 
movement supporting points 28e1 and 28e2 placed on the 0 degree side of 
the drum base 28 become apart from the 0 degree side bottom surface 
portion 22c of the lower drum 22. As a result, the leading ring 27 and the 
upper and lower drums 21 and 22 supported by the drum axis 24 are 
rotationally moved in the clockwise direction around the second rotational 
movement supporting points 28f1 and 28f2 while resisting the spring power 
of the compression springs 81a and 81b (FIGS. 16 and 18). 
Therefore, the leading ring 27 and the upper and lower rums 21 and 22 
supported by the drum axis 24 are rotationally moved in the clockwise 
direction by the whole drum inclination correcting angle .theta. (FIG. 20) 
with respect to the drum base 28, and the rotational drum 20 is inclined 
in the FF reproducing mode according to the whole drum inclination angle 
correcting characteristic (FIG. 20) and the tape traveling speed. Also, 
because the screw 25a screwed into the leading ring 27 on the 0 degree 
side is pushed out while pushing out the screw 24a, when a top of the 
screw 25a is touched to the pin 38a (FIG. 17) fixedly attached to the 0 
degree side bottom surface portion 22c of the lower drum 22, the 180 
degree side bottom surface portion 22c of the lower drum 22 is touched to 
the second rotational movement supporting points 27f1 and 27f2 placed on 
the 180 degree side of the leading ring 27 by a reaction force generated 
by the contact of the screw 25a and the pin 38a, and the first rotational 
movement supporting points 27e1 and 27e2 placed on the 0 degree side of 
the leading ring 27 becomes apart from the 0 degree side bottom surface 
portion 22c of the lower drum 22. 
Therefore, though the 0 degree side bottom surface portion 27c of the 
leading ring 27 is rotationally moved by the track inclination correcting 
angle .theta.1 in the lower direction (or the counterclockwise direction) 
with respect to the lower drum 22 around the second rotational movement 
supporting points 27f1 and 27f2 positioned on the 180 degree side leading 
ring 27 while resisting the spring power of the compression spring 39a 
(FIG. 17), because the 0 degree side bottom surface portion 27c of the 
leading ring 27 is rotationally moved in the clockwise direction with 
respect to the drum base 28, a track correction is performed. In this 
track correction, the inclination angle of the drum axis 24 is 
successively changed according to the traveling speed of the magnetic tape 
MT with respect to the imaginary central axis of the leading ring 27 in 
the FF and FB reproducing mode operations to make a recorded track formed 
on the magnetic tape MT agree with a scanning locus of each of the 
magnetic heads 23a and 23b. 
And, the leading correction is performed by the lead inclination correcting 
angle .theta.2 obtained by subtracting the track inclination correcting 
angle .theta.1 caused by the screw 25a screwed into the leading ring 27 
from the whole drum inclination correcting angle .theta. caused by the 
screw 24a screwed into the drum base 28, and the inclination of the 
leading ring 27 is corrected along the lead inclination angle correcting 
characteristic (FIG. 20) according to the tape traveling speed. 
Because the magnetic tape MT is pulled in a direction of the rotation of 
the drum structure DS caused by the track correction, the reference edge 
Te of the magnetic tape MT intends to be apart from the lead 27a on the 
inlet side of the magnetic tape MT, and the reference edge Te of the 
magnetic tape MT intends to be pushed to the lead 27a on the outlet side 
of the magnetic tape MT. Therefore, in the leading correction in the FF 
reproducing mode operation, the leading ring 27 is rotationally moved to 
make the lead 27a match with the reference edge Te of the magnetic tape 
MT. In this case, a relative angle between the lead 27a adjusted for a 
fast feeding tape traveling speed in the FF reproduction and a scanning 
locus of each of the magnetic heads 23a and 23b is maintained. 
Therefore, even though the reference edge Te of the magnetic tape MT is 
induced by the track correction to be apart from the lead 27a, because the 
leading correction is performed, the reference edge Te of the magnetic 
tape MT is stably lead by the lead 27a over the entire binding range of 
the magnetic tape MT bound to the drum structure DS. Accordingly, when the 
magnetic tape MT is traveled at a prescribed fast feeding tape speed, a 
scanning locus of each of the magnetic heads 23a and 23b agrees with a 
track pattern recorded on the magnetic tape MT, and a reproduced signal 
indicating an envelope set to a superior condition can be obtained. 
Next, as shown in FIG. 21C, in cases where the recording or reproducing 
operation is performed for the magnetic tape MT traveled at a fast 
back-feeding speed differing from the standard speed in a minus direction 
(for example, in cases where the normal reproducing mode is changed to the 
FB reproducing mode), the motor 42 (FIG. 19) is operated to push out the 
screws 24b and 25b placed on the 180 degree side in the upper direction 
according to the fast back-feeding speed. In this case, the screws 24a and 
25a placed on the 0 degree side are pushed out in a relief direction apart 
from the lower drum 22. That is, when the screw 24b screwed into the drum 
base 28 is pushed out in the upper direction, the location pin 37b (FIG. 
16) fixedly attached to the 180 degree side bottom surface portion 22c of 
the lower drum 22 is pushed up by a top of the screw 24b. Therefore, the 0 
degree side bottom surface portion 22c of the lower drum 22 is touched to 
the first rotational movement supporting points 28e1 and 28e2 placed on 
the 0 degree side of the drum base 28, and the second rotational movement 
supporting points 28f1 and 28f2 placed on the 180 degree side of the drum 
base 28 become apart from the 180 degree side bottom surface portion 22c 
of the lower drum 22. As a result, the leading ring 27 and the upper and 
lower drums 21 and 22 supported by the drum axis 24 are rotationally moved 
in the counterclockwise direction around the first rotational movement 
supporting points 28e1 and 28e2 while resisting the spring power of the 
compression springs 81a and 81b (FIGS. 16 and 18). 
Therefore, the leading ring 27 and the upper and lower drums 21 and 22 
supported by the drum axis 24 are rotationally moved in the whole drum 
correction along the whole drum inclination angle correcting 
characteristic (FIG. 20). 
Also, because the screw 25b screwed into the leading ring 27 on the 180 
degree side is pushed out while pushing out the screw 24b, when a top of 
the screw 25b is touched to the pin 38b (FIG. 17) fixedly attached to the 
180 degree side bottom surface portion 22c of the lower drum 22, the 0 
degree side bottom surface portion 22c of the lower drum 22 is touched to 
the first rotational movement supporting points 27e1 and 27e2 placed on 
the 0 degree side of the leading ring 27 by a reaction force generated by 
the contact of the screw 25b and the pin 38b, and the second rotational 
movement supporting points 27f1 and 27f2 placed on the 180 degree side of 
the leading ring 27 becomes apart from the 180 degree side bottom surface 
portion 22c of the lower drum 22. 
Therefore, though the 180 degree side bottom surface portion 27c of the 
leading ring 27 is rotationally moved in the lower direction (or the 
clockwise direction) with respect to the lower drum 22 around the first 
rotational movement supporting points 27e1 and 27e2 positioned on the 0 
degree side leading ring 27 while resisting the spring power of the 
compression spring 39b (FIG. 17), because the 180 degree side bottom 
surface portion 27c of the leading ring 27 is rotationally moved in the 
counterclockwise direction with respect to the drum base 28, a track 
correction is performed, the leading correction obtained by subtracting 
the track correction caused by the screw 25b screwed into the leading ring 
27 from the whole drum correction caused by the screw 24b screwed into the 
drum base 28 is performed, and the inclination of the leading ring 27 is 
corrected along the lead inclination angle correcting characteristic (FIG. 
20) for the FB reproducing mode operation. 
Because the magnetic tape MT is pulled in a direction of the rotation of 
the drum structure DS caused by the track correction, the reference edge 
Te of the magnetic tape MT intends to be apart from the lead 27a on the 
inlet side of the magnetic tape MT, and the reference edge Te of the 
magnetic tape MT intends to be pushed to the lead 27a on the outlet side 
of the magnetic tape MT. Therefore, in the leading correction in the FB 
reproducing mode operation, the leading ring 27 is rotationally moved to 
make the lead 27a match with the reference edge Te of the magnetic tape 
MT. 
Therefore, even though the reference edge Te of the magnetic tape MT is 
induced by the track correction to be apart from the lead 27a, because the 
leading correction is performed, the reference edge Te of the magnetic 
tape MT is stably lead by the lead 27a over the entire binding range of 
the magnetic tape MT bound to the drum structure DS. Accordingly, when the 
magnetic tape MT is traveled at a prescribed fast back-feeding tape speed, 
a scanning locus of each of the magnetic heads 23a and 23b agrees with a 
track pattern recorded on the magnetic tape MT, and a reproduced signal 
indicating an envelope set to a superior condition can be obtained. 
As shown in FIG. 22, the inclination angle of the rotational drum 20 
composed of the leading ring 27 and the upper and lower drums 21 and 22 
can be adjusted in advance to a target angle by using a pair of whole drum 
correction adjusting screws SC1 and SC2 and a pair of track correction 
adjusting screws SC3 and SC4. However, as shown in FIG. 23, in cases where 
a width of the non-sensitive zone is shifted from an ideal width because 
of non-uniformity of constructional parts, a phase difference between the 
photo-electro sensor 52 and the series of gears and friction and abrasion 
of the adjusting screws SC1 to SC4, even though the inclination of the 
rotational drum 20 is adjusted according to the number of pulses (or the 
current pulse counting value) corresponding to the target angle, the 
inclination of the rotational drum 20 cannot be adjusted to the target 
angle, and the magnetic heads 23a and 23b cannot accurately trace a track 
pattern. 
Next, an adjusting method for adjusting the non-sensitive zone (FIG. 20) of 
the rotational drum 20 is described with reference to FIGS. 24 and 25. In 
this case, as shown in FIG. 23, regardless of the width of the 
non-sensitive zone, the inclination angle of the rotational drum 20 
corresponding to a reproducing tape speed changes in proportion to the 
pulse counting value, indicating the number of rotations of a rotor of the 
motor 42, counted by the pulse counter through the photo-electro sensor 
51. This proportional relationship is obtained for the forward tape 
traveling direction and the reverse tape traveling direction. The tape 
traveling directions for a slow reproduction and a still reproduction are 
classified into the reverse tape traveling direction. Therefore, even 
though the width of the non-sensitive zone changes, the difference in the 
pulse counting value between a first tape traveling speed and a second 
tape traveling speed is constant. 
FIG. 24 is a block diagram of a rotational drum actuating system of a 
magnetic recording and reproducing apparatus corresponding to the third 
embodiment of the present invention. 
As shown in FIG. 24, in this adjusting method, a reference pulse counting 
value corresponding to a referential reproducing tape speed directed in 
the forward or reverse direction is stored in a non-volatile memory 101 in 
advance, and a target counting value corresponding to a target reproducing 
tape speed is obtained as a sum of the reference pulse counting value and 
a differential counting value between the referential reproducing tape 
speed and the target reproducing tape speed. In this case, the referential 
reproducing tape speed is an arbitrary speed except for a normal 
reproducing tape speed and a recording tape speed. Therefore, in cases 
where a width of the non-sensitive zone for a particular magnetic 
recording and reproducing apparatus differs from that for another 
apparatus or the width of the non-sensitive zone changes, the reference 
pulse counting value stored in the non-volatile memory 101 is only 
adjusted. 
An 8-bit rotational speed signal indicating a rotational speed of a rotor 
of the rotational drum actuating motor 42 and a rotational direction 
signal indicating a rotational direction of the rotor of the motor 42 are 
transmitted from a control microcomputer 100 to a motor actuating circuit 
102 having a D/A converter, and the rotational drum actuating motor 42 is 
actuated by the motor actuating circuit 102 according to the 8-bit 
rotational speed signal and the rotational direction signal. Also, a 
counting pulse obtained from the motor 42 for each rotation of a rotor of 
the motor 42 and a reset signal are fetched into the control microcomputer 
100. Each of the counting pulses fetched is added to a pulse counting 
value in cases where the rotor of the motor 42 is rotated in a plus 
direction, and each of the counting pulses fetched is subtracted from a 
pulse counting value in cases where the rotor of the motor 42 is rotated 
in a plus direction. Pulse counting values corresponding to the normal 
reproducing tape speed and the recording tape speed are reset to zero by 
the reset signal. Also, a differential counting value between the 
referential reproducing tape speed and the target reproducing tape speed 
is stored in a ROM of the control microcomputer 100. Because the 
differential counting value is constant, it is not required to change the 
differential counting value. Therefore, a current inclination angle of the 
rotational drum 20 is detected. 
FIG. 25 shows the relationship between a reproducing tape speed and a pulse 
counting value in the magnetic recording and reproducing apparatus. 
As shown in FIG. 25, a first case that a triple reproducing tape speed 
three times as high as the normal reproducing tape speed is set as the 
referential reproducing tape speed directed in the forward direction and a 
second case that a still/slow reproducing tape speed is set as the 
referential reproducing tape speed directed in the reverse direction are 
selected, and a first reference pulse counting value corresponding to the 
triple reproducing tape speed and a second reference pulse counting value 
corresponding to the still/slow reproducing tape speed are set. Also, four 
target reproducing tape speeds for the first reference pulse counting 
value and three target reproducing tape speeds for the second reference 
pulse counting value are shown. 
The adjustment of the first (or second) reference pulse counting value is 
as follows. After the rotational drum 20 is attached to the magnetic 
recording and reproducing apparatus, a reproduced video FM signal is 
reproduced from a magnetic tape MT on which the straightness of a 
recording track pattern is guaranteed at the referential reproducing tape 
speed, a rotor of the motor 42 is rotated while observing the reproduced 
video FM signal, the inclination angle of the rotational drum 20 is 
adjusted to flatten an envelope of the reproduced video FM signal, a 
reference pulse counting value corresponding to the adjusted inclination 
angle is stored in the non-volatile memory 101 as a renewed reference 
pulse counting value. 
Accordingly, in cases where a width of the non-sensitive zone for a 
particular magnetic recording and reproducing apparatus differs from that 
for another apparatus or the width of the non-sensitive zone changes, an 
appropriate reference pulse counting value is stored in the non-volatile 
memory 101 of each apparatus, even though the magnetic tape MT is traveled 
at a target reproducing tape speed representing a fast feeding or 
back-feeding speed, a target pulse counting value corresponding to the 
target reproducing tape speed can be obtained as a sum of the reference 
pulse counting value stored in the non-volatile memory 101 and a 
differential counting value between the referential reproducing tape speed 
and the target reproducing tape speed stored in the ROM of the control 
microcomputer 100. Therefore, the inclination angle of the rotational drum 
20 can be set to a target angle corresponding to the target pulse counting 
value. 
As a result, a plurality of effects can be obtained as follows. 
First, because the reference pulse counting value can be easily and 
accurately adjusted and stored in the non-volatile memory 101, even though 
a large number of apparatuses are manufactured, the inclination angle of 
the rotational drum 20 in each of the apparatuses can be easily and 
accurately set. 
Secondly, even though a width of the non-sensitive zone for a particular 
magnetic recording and reproducing apparatus differs from that for another 
apparatus or the width of the non-sensitive zone changes, because the 
inclination angle of the rotational drum 20 appropriate for each of target 
reproducing tape speeds can be obtained by adjusting the reference pulse 
counting value, the adjustment of the target reproducing tape speed can be 
easily performed, and the reproductivity of the apparatus can be 
heightened. 
Thirdly, because the reference pulse counting value is stored in the 
non-volatile memory 101 in which data are writable and readable, the 
inclination angle of the rotational drum 20 shifted from a target angle 
because of the friction and abrasion of constitutional parts can be easily 
corrected. 
In the third embodiment, one reference pulse counting value is determined 
for the reproducing tape speed directed in the forward direction, and 
another reference pulse counting value is determined for the reproducing 
tape speed directed in the reverse direction. However, because the 
magnetic tape MT is traveled at one of N-times reproducing tape speeds 
which respectively is N times as high as the normal reproducing tape 
speed, it is applicable that one reference pulse counting value be 
determined for each of the N-times reproducing tape speeds and a plurality 
of reference pulse counting values corresponding to the N-times 
reproducing tape speeds be stored in the non-volatile memory 101. In this 
case, any differential counting value between one referential reproducing 
tape speed and one target reproducing tape speed is not required. 
Therefore, the inclination angle of the rotational drum 20 can be 
accurately set according to one of the reference pulse counting values 
stored in the non-volatile memory 101. 
Having illustrated and described the principles of the present invention in 
a preferred embodiment thereof, it should be readily apparent to those 
skilled in the art that the invention can be modified in arrangement and 
detail without departing from such principles. We claim all modifications 
coming within the spirit and scope of the accompanying claims.