 |
Description  |
|
|
CROSS-REFERENCE TO A RELATED APPLICATION
Reference is made to commonly assigned copending application Ser. No.
242,658, entitled Camera Apparatus for Magnetically Encoding a Film
Leader, and filed Sept. 12, 1988 in the name of Donald M. Harvey.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to photography, and particularly to a film
cassette with a magnetic film leader.
2. Description of the Prior Art
Generally speaking, commercially available 35 mm film cassettes such as
manufactured by Eastman Kodak Co. and Fuji Photo Co., Ltd. comprise a
hollow cylindrical shell having an integral throat or lipped portion which
extends tangentially from the shell. A film spool on which the filmstrip
is wound is freely rotatable within the cassette shell. The filmstrip has
a leading section, commonly referred to as a "film leader", which
protrudes from a light-trapped slit in the throat portion to the outside
of the cassette shell. Typically, the protruding leader extends 2-3 inches
in length.
In conventional 35 mm film cassettes, one end of the film spool on which
the filmstrip is wound has a short axial extension which projects from the
cassette shell, enabling the spool to be turned by hand. If the spool is
manually rotated initially in an unwinding direction, the film
convolutions inside the cassette shell will tend to expand radially since
the inner end of the filmstrip is attached to the spool, and the film
leader protruding from the slit will remain stationary. The film
convolutions can expand radially until a non-slipping relation is
established between the outermost convolution and the inner curved wall of
the cassette shell. Once this non-slipping relation exists, there is a
binding effect between the outermost convolution and the shell which
prevents further rotation of the spool in the unwinding direction.
Consequently, rotation of the spool in the unwinding direction cannot
serve to advance the filmstrip out of the shell, and it is necessary in
the typical 35 mm camera to engage the protruding leader to pull the
filmstrip out of the shell. If the spool is manually rotated initially in
a winding direction, it will draw the protruding leader into the shell.
Thus, the film leader will not be able to be engaged to pull the filmstrip
out of the shell.
A 35 mm film cassette has been proposed which, unlike conventional film
cassettes, includes a film leader that does not extend outside the
cassette shell. The film leader, instead, is located entirely within the
cassette shell. Specifically, in U.S. Pat. No. 4,423,943, granted Jan. 3,
1984, there is disclosed a film cassette wherein the outermost convolution
of the film roll wound on the film spool is radially constrained by
respective circumferential lips of two axially spaced flanges of the spool
to prevent the outermost convolution from contacting an inner wall of the
cassette shell. The trailing end of the filmstrip is secured to the film
spool, and the leading end of the filmstrip is reduced in width to allow
it to protrude from between the circumferential lips and rest against the
shell wall. During unwinding rotation of the film spool, the leading end
of the filmstrip is advanced to and through a film passageway opening in
order to exit the cassette shell. Thus, all that is needed to advance the
film leader to the outside of the cassette shell is to rotate the film
spool in an unwinding direction
While the film cassette disclosed in U.S. Pat. No. 4,423,943 includes a
non-protruding film leader which is automatically advanced to the outside
of the cassette shell when the film spool is rotated in the undwinding
direction, the film cassette is intended to be loaded in a camera only
after the film leader is advanced to protrude from the cassette shell. In
the patent, it is suggested that one manually rotate the film spool
relative to the cassette shell until the leader can be manually grasped
and attached to a film advancing device in the camera.
THE CROSS-REFERENCED APPLICATION
Like the type of film cassette disclosed in U.S. Pat. No. 4,423,923, the
cross-referenced application discloses a film cassette that contains a
non-protruding film leader which can be advanced automatically to the
outside of the cassette shell in response to rotation of the film spool in
a unwinding direction. In addition, the film leader can be returned to the
inside of the cassette shell in response to rotation of the film spool in
a winding direction. However, unlike the patent, the cross-referenced
application discloses a motor-driven film transport apparatus (rather than
manual means) for rotating the film spool to propel the non-protruding
leader out of the cassette shell, when the film cassette is loaded in a
camera. Also, the cross-referenced application discloses encoding
apparatus for magnetically encoding the film leader, when it is located
outside the cassette shell, with various information that controls
subsequent film movement in the camera. Specifically, when the filmstrip
is completely exposed in the camera, double-exposure prevention (DEP) data
is magnetically applied to the film leader substantially immediately
before the leader is rewound with the filmstrip into the cassette shell.
The DEP data indicates there are no unexposed imaging areas remaining on
the filmstrip. If the filmstrip is rewound into the cassette shell
prematurely, i.e. without it being completely exposed, midroll interrupt
(MRI) data is magnetically applied to the film leader instead of the DEP
data to indicate the next-available unexposed imaging area of the
filmstrip. When the film cassette is re-loaded into the camera, the film
leader is advanced from the cassette shell initially to determine whether
is is encoded with DEP or MRI data. If the DEP data is detected, the
leader is rewound into the cassette shell since all of the imaging areas
of the filmstrip are exposed. If the MRI data is detected, the filmstrip
is advanced from the cassette shell to locate the next-available unexposed
imaging area in an exposure position.
SUMMARY OF THE INVENTION
The invention parallels the cross-referenced application in that it relates
to a film cassette containing a film spool which is rotatable in an
unwinding direction to propel a filmstrip including an integral film
leader out of the cassette and is rotatable in a winding direction to wind
the filmstrip including its film leader back into the cassette. The film
leader has a magnetic area on which alterable data can be magnetically
written and read to indicate whether the filmstrip is completely exposed
or is only partially exposed. Thus, when the film leader is wound into the
cassette the data will be protected and when the film leader is propelled
from the cassette the data will be made accessible to read and alter it.
More specifically, the filmstrip has successive perforations along one
longitudinal film edge which are separated by respective imperforate film
sections, each having an identical length slightly greater than the width
of a single film frame. The magnetic area of the film leader is positioned
opposite one of the perforations along another longitudinal film edge to
make the magnetic area immediately accessible when the filmstrip is
propelled initially from the cassette a predetermined multiple (one or
more times) of the imperforate film sections.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of a film cassette having a
non-protruding magnetic film leader, according to a preferred embodiment
of the invention;
FIG. 2 is an elevation view in cross-section of the film cassette;
FIG. 3 is an end view in cross-section of the film cassette;
FIG. 4 is an elevation view in cross-section of a film spool and an annular
constraining flange depicted inside the cassette shell shown in FIGS. 1
and 2;
FIG. 5 is a schematic view of camera apparatus for magnetically encoding
the film leader and for controlling film movement as disclosed in the
cross-referenced application;
FIG. 6 is a plan view of the film leader;
FIG. 7a, 7b are a flow chart illustrating a load/double exposure prevention
(DEP) routine of the camera apparatus;
FIG. 8 is a flow chart illustrating an expose routine of the camera
apparatus; and
FIGS. 9a, 9b are a flow chart illustrating a midroll interrupt (MRI)
routine of the camera apparatus
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention is disclosed as being embodied preferably in a 35 mm still
camera. Because the features of this type of camera are generally well
known, the description which follows is directed in particular to elements
forming part of or cooperating directly with the disclosed embodiment. It
is to be understood, however, that other elements not specifically shown
or described may take various forms known to persons of ordinary skill in
the art.
The Film Cassette
Referring now to the drawings, FIGS. 1-3 depict a 35 mm film cassette 1
generally as disclosed in the cross-referenced application. Specifically,
the film cassette 1 comprises a light-tight cassette shell 3 and a film
spool 5 which is rotatable about an axis X within the cassette shell. The
cassette shell 3 consists of two shell halves 7 and 9 which are mated
along respective groove and stepped edge portions 11 and 13. The mated
halves 7 and 9 define upper and lower aligned openings 1 and 17 for
relatively longer and shorter opposite end extensions 19 and 21 of a spool
core or hub 23. Also, they define a light-trapped film passage slit or
mouth 25. The light-trapping means for preventing ambient light from
entering the film passage slit 25, although not shown, may be a known
velvet or plush material which lines the interior of the slit.
The spool core 23 as shown in FIGS. 1-3 includes relatively longer and
shorter coaxial holes 27 and 29 opening at the respective longer and
shorter opposite end extensions 19 and 21 of the spool core. A pair of
spaced keying ribs 31 and 33 integrally formed with the spool core 23 are
located within the longer coaxial hole 27, and a single keying rib 35
similarly formed with the spool core is located within the shorter coaxial
hole 29. The several keying ribs 31, 33, and 35 according to custom may be
engaged to rotate the film spool in an unwinding direction indicated by
the arrow U in FIG. 1, or to rotate the spool in a rewinding direction
indicated by the arrow W in the same FIG.
A roll 37 of convoluted 35 mm film F having a uniform width is wound about
the spool core 23. As indicated in FIG. 3, the film roll 37 has an inner
or trailing end 39 attached to the spool core 23 by a suitable piece of
adhesive tape 41 and a film leader 43. The film leader 43 has leading or
forward and 45 and comprises 2-3 convolutions of the film roll 37. One of
these leader convolutions is the outermost convolution 47 and another of
them is the next inward succeeding convolution 49.
A pair of identical flanges 51 and 53 are coaxially spaced along the spool
core 23 as shown in FIGS. 1 and 2. The two flanges 51 and 53 comprise
respective integral disks 55 and 57 and respective integral annular lips
or skirts 59 and 61 which circumferentially extend from the disks. The two
disks 55 and 57 cover opposite sides, i.e. ends, 63 and 65 of the film
roll 37 and they have respective central holes 67 and 69 through which the
spool core 23 longitudinally extends to permit rotation of the spool core
relative to the flanges 51 and 53. Each of the lips 59 and 61 as depicted
in FIG. 4 includes the following:
(1) an annular constraining section 71 positioned relatively remote from
one of the disks 55 and 57 a predetermined radial distance R.sub.1 from
the spool core 23 to enable each of the lips 59 and 61 to contact the
outermost convolution 47 of the film roll 37, to radially confine the
outermost convolution and thereby prevent the film roll from radially
expanding or clock-springing against an inner wall 73 of the cassette
shell 3;
(2) an annular relief section 75 extending from one of the disks 55 and 57
to the annular constraining section 71 of one of the lips 59 and 61 and
positioned a predetermined radial distance R.sub.2 from the spool core 23,
greater than the radial distance R.sub.1, to enable each of the lips to
avoid contacting the outermost convolution 47 substantially between one of
the disks and the annular constraining section; and
(3) an annular free end section 77 inclined radially outwardly from the
annular constraining section 71 of one of the lips 59 and 61 and away from
the outermost convolution 47. The annular relief section 75 of each of the
lips 59 and 61 is inclined radially inwardly from one of the disks 55 and
57 toward the outermost convolution 47 to form an acute relief angle
A.sub.1 with the outer most convolution. See FIG. 4. The relief angle
A.sub.1 may be 11.degree.45', for example. The annular constraining
section 71 of each of the lips 59 and 61 is curved radially inwardly with
respect to the film roll 37 to enable both of the lips to contact the
outermost convolution 47 in a substantially tangential manner (in the
vertical sense in FIG. 4) and thereby limit the area of contact between
the lips and the outermost convolution. The annular free end section 77 of
each of the lips 59 and 61 is tilted slightly upwardly as shown in FIG. 4
to form an acute relief angle A.sub.2. The relief angle A.sub.2 may be
10.degree., for example. Thus, as shown in FIG. 2 the lips 59 and 61 are
either shaped in the form of a "Z" or an "S".
A pair of rigid identical spreader surfaces 79 and 81 are fixed to the
cassette half 9 at separate locations inwardly of the film passage slit 25
as shown in FIG. 2. The respective spreader surfaces 79 and 81 deflect
opposite limited portions 59' and 61' of the annular lips 59 and 61
axially away from each other to an axial dimension slightly exceeding the
film width. See FIG. 2. In essence, the deflected portions 59' and 61' of
the annular lips 59 and 61 are axially spaced sufficiently to prevent
those portions of the lips from radially confining corresponding portions
of the outermost convolution 47 of the film roll 37. As indicated in FIG.
2, the remaining portions of the two lips 59 and 61 are maintained in
place by inner semicircular flat surfaces 83 and 85 of the cassette shell
3. The flat surfaces 83 and 85 abut the respective disks 55 and 56, except
in the vicinity of the spreader surfaces 79 and 81. Thus, the remaining
portions of the two lips 59 and 61 continue to radially confine the
outermost convolution 47.
As shown in FIG. 2, the annular free end section 77 of each of the annular
lips 59 and 61, at the deflected portions 59' and 61' of the two lips,
bears against the respective spreader surfaces 79 and 81. Since the
annular free end section 77 of each of the lips has a gentle curve to it
as best seen in FIG. 4, very little wear occurs between the free end
section and either of the spreader surfaces 79 and 81. The relief angle
A.sub.2 of the annular free end section 77 of each of the lips is useful
during assembly of the film cassette 1 to position either of the spreader
surfaces 79 and 81 relative to an annular free end section.
When the spool core 23 is initially rotated in the unwinding direction U,
the two flanges 51 and 53 may remain substantially stationary and the film
roll 37, since its inner end 39 is attached to the spool core, tends to
expand radially or clock-spring to ensure a non-slipping relation between
the outermost convolution 47 of the film roll and the annular lips 59 and
61 of the flanges. Then, rotation of the spool core 23 in the same
direction will similarly rotate the two flanges 51 and 53. As a result,
the two spreader surfaces 79 and 81 will deflect successive portions 59'
and 61' of the annular lips 59 and 61 axially away from each other as the
respective portions are rotated past the spreader surfaces. The deflected
portions 59' and 61' of the two lips 59 and 61 are returned to their
original non-flexed condition by the semicircular flat surfaces 83 and 85
of the cassette shell 3. As can be appreciated from FIG. 3, the leading
end 45 of the film roll 37 will be freed from the radial confinement of
the two lips 59 and 61 in the vicinity of the two spreader surfaces 79 and
81, and it will be advanced against a pair of rigid identical
stripper-guide surfaces 87 and 89 integrally formed with the respective
spreader surfaces. The two stripper-guide surfaces 87 and 89 operate to
direct the leading end 45 into the film passage slit 25, thereby allowing
succeeding portions of the outermost convolution 47 to be freed from
corresponding portions of the two lips 59 and 61 as those portions of the
lips are deflected by the two spreader surfaces 79 and 81. Consequently,
continued rotation of the spool core 23 will thrust the film leader 43
from the inside to the outside of the cassette shell 3.
When the spool core 23 is rotated in the rewinding direction W, the
filmstrip F will be wound back onto the spool core since the trailing end
39 of the filmstrip is attached to the spool core. Other aspects of this
portion of operation of the film cassette 1 are substantially similar to
the portion of operation when the spool core 23 is rotated in the
unwinding direction U.
The Camera Apparatus
Referring now to FIG. 5, camera apparatus 101 is depicted for use with the
type of film cassette 1 having a normally non-protruding film leader 43.
Briefly, the camera apparatus 101 is intended to magnetically apply
alterable data to the film leader 43, only when the leader is located
outside the cassette shell 3.
As shown in FIG. 5, the camera apparatus 101 includes a conventional rear
or bottom door 103 pivotally mounted on the camera body 105 for opening to
permit insertion of the film cassette 1 laterally or axially (endwise)
into a loading chamber 107. Motorized film transport means 109 comprising
a conventional bi-directional circuit 111 for reversing a drive motor 113,
a suitable drive transmission 115 similar to the one disclosed in the
Harvey patent application cross-referenced above, and respective drive
hubs 117 and 119 which engage the spool core 23 of the film cassette 1 and
a take-up spool or drum 121 rotatably supported within a take-up chamber
123, is provided for rotating the spool core and the take-up drum either
in the unwinding direction U or in the winding direction W. When fresh
unused (unexposed) film is loaded in the camera apparatus 101, the film
transport means 109 is operated initially to rotate the spool core 23 in
the unwinding direction U to propel the non-protruding film leader 43 out
of the cassette shell 3, across a back frame opening 125 situated at the
focal plane of a taking lens 127, and onto the take-up drum 121. At the
same time, the drum 121 is rotated in the unwinding direction U to permit
a tooth, not shown, located on its periphery, to engage the film leader 43
at a hole 129 cut in the leading end 45 of the leader. See FIG. 6. Then, a
predetermined length of the filmstrip F slightly greater than three frame
widths X is wound onto the take-up drum 121 to locate a first-available
film frame #1 in FIG. 6, i.e. a first-available imaging area of the
filmstrip F, in a proper exposure position at the back frame opening 125.
After the first picture is taken, the film transport means 109 is operated
to wind the first exposed frame onto the take-up drum 121 and to advance
the next-available unexposed frame #2 in FIG. 6 into the exposure
position. When the filmstrip F is completely exposed, that is there are no
remaining unexposed frames, the motor 13 is reversed to rotate the spool
core 23 in the winding direction W, and the drive hub 119 is uncoupled
from the motor. This is done to rewind the filmstrip F, including the film
leader 43, back into the cassette shell 3.
Other elements of the camera apparatus 101 include a conventional array of
DX sensors 131, a conventional metering switch 133, a conventional
magnetic read/write head 135, a conventional digital film frame counter
137, a normally open door switch 139, a normally open cartridge switch
141, a normally open shutter release switch 143, a normally open midroll
interrupt (MRI) switch 145, and respective conventional midroll interrupt
(MRI), partial film use (PU), and double exposure prevention (DEP) warning
circuits 147, and 149, and 151. Each of the elements 131, 133, 135, 137,
139, 141, 143, 145, 147, 149, and 151, as well as the film transport means
109, is connected individually to a conventional digital microcomputer 153
such as used in many recent cameras. As shown in FIG. 5, the DX sensors
131 are connected to the microcomputer 153 via a conventional DX decoder
155, and the read/write head 135 is connected to the microcomputer via a
conventional read/write circuit 157. The microcomputer 153 as is customary
includes a central processing unit (CPU) 159, a random access memory (RAM)
161, a read-only memory (ROM) 163, and a timer 165.
The DX sensors 131 are positioned in the loading chamber 107 to read a
known DX encodement on the outside of the cassette shell 3 which indicates
the maximum number (m) of exposures that can be taken, i.e. the total
number of available film frames, using the filmstrip F. Typically, the
maximum number M is 20, 24, or 36. The metering switch 133 is closed each
time a perforation sensor 167 of the switch drops into any one of a series
of evenly spaced film perforations 169 in the filmstrip F. As shown in
FIG. 6, the perforations 169 are located along one longitudinal edge 171
of the filmstrip F and are separated by respective imperforate film
sections 173, each having an identical length slightly greater than the
width X of a single film frame. When the metering switch 133 is closed, it
indicates that the filmstrip F has been moved slightly more than a single
frame width X, and a pulse is generated in the microcomputer 153 which may
be counted by a conventional up/down counter, not shown, or by the frame
counter 137. The frame counter 137 as is customary has thirty-six numbered
settings or frame number indications represented by the numbers "1, 2, . .
. 36" which correspond to the respective available film frames #1, #2,
etc., in FIG. 6. That is, each numbered setting of the frame counter 137
indicates the next-available unexposed film frame. An original or initial
setting of the frame counter 137 is represented by the letter "S". This
setting usually indicates that the loading chamber 107 is empty, and it is
separated from the first available frame setting "1" by three discrete
settings each represented by a dot ".". When the film leader 43 is
propelled from the film cassette 1 and onto the take-up drum 121, and the
first-available frame #1 in FIG. 6 is located in the exposure position,
the metering switch 133 will have closed four times, due to its
perforation sensor 167 successively dropping into four perforations 169,
since the filmstrip F will have advanced slightly more than four frame
widths X. Thus, the frame counter 137 will be incremented from its "S"
setting, successively to its three dot "." settings, and then to its first
frame setting "1". Thereafter, each time the filmstrip F is advanced
slightly more than one frame width X to locate a fresh film frame in the
exposure position, the frame counter 137 will be incremented to its next
numbered setting (until it reaches the maximum number M).
The read/write head 135 is intended to magnetically write certain data on
the film leader 43 at a relatively small magnetic area 175 of the leader
containing uniformly dispersed magnetic particles, and to magnetically
read the same data. As shown in FIG. 6, the magnetic area 175 is arranged
along a longitudinal edge 177 of the filmstrip F at a location opposite
one of the perforations 169.
The door switch 139 is closed when the rear door 103 is closed and is
opened when the rear door is opened. The cartridge switch 141 is closed
whenever the film cassette 1 is present in the loading chamber 107 and is
open whenever the chamber is empty. The shutter release switch 143 is
closed each time a conventional shutter, not shown, is opened and is open
whenever the shutter is closed. The midroll interrupt (MRI) switch 145 is
closed when an MRI button, not shown, on the camera body 105 is manually
depressed to initiate rewind of the filmstrip F into the film cassette 1
prematurely, i.e. before all of the available film frames have been
exposed.
Flow Charts FIGS. 7-9
FIGS. 7a, 7b, 8, and 9a, 9b are respective flow charts which depict three
explicit routines or modes of the microcomputer 153 which are effected in
cooperation with the switches 133, 139, 141, 143 and 145, with the film
transport means 109, with the DX sensors 131, with the read/write head
135, with the frame counter 137, and with the midroll interrupt (MRI),
partial use (PU), and double-exposure prevention (DEP) warning circuits
147, 149, and 151.
(1) Load/Double Exposure Prevention (DEP) Routine--FIGS. 7a, 7b
If in this routine the door switch 139 is closed because the rear door 103
is closed, the cartridge switch 141 is closed because the film cassette 1
is present in the loading chamber 107, and the maximum number M of
exposures, i.e. the total number of available film frames, using the
filmstrip F, is determined by the DX sensors 131 reading a known DX
encodement on the outside of the cassette shell 3, the maximum number M
will be stored in the RAM 163 and the motor 113 will be energized to
rotate the spool core 23 of the film cassette in the unwinding direction
U, thereby propelling the film leader 43 to the outside of the cassette
shell. When the metering switch 133 is closed three times to indicate that
the immediate frame area preceeding the first-available frame #1 in FIG. 6
is in the exposure position at the back frame opening 125, the relatively
small magnetic area 169 of the film leader 43 will be positioned in
contact with the read/write head 135 and the read/write circuit 157 will
be changed by the CPU 159 to a read mode.
If the read/write head 135 does not detect any frame number data (C) at the
magnetic area 169 of the film leader 43, this indicates that the filmstrip
F is completely unexposed, i.e. the maximum number M of film frames is
available for picture-taking. Then, when the metering switch 133 is closed
one more time, the frame counter 137 will be incremented by the CPU 159 to
"1" and the motor 113 will be de-energized. At this time, the
first-available frame #1 in FIG. 6 will be in the exposure position.
If the read/write head 135 instead does detect frame data C at the magnetic
area 169 of the film leader 43, and the data represents the particular
number "0", this indicates that the filmstrip F was completely exposed
before the film cassette 1 was inserted into the loading chamber 107, i.e.
there are no unexposed frames available for picture-taking. As a result,
the DEP warning circuit 151 will be activated to alert the user of such
condition. Then, the motor 113 will be reversed to rotate the spool core
23 in the winding direction W to rewind the film leader 43 back into the
cassette shell 3. At the same time, the timer 165 will be activated. When
the timer 165 determines that a sufficient time, e.g. one-half second, has
elapsed to rewind the film leader 43 into the cassette shell 3, the motor
113 will be de-energized. Since the DEP warning circuit 151 remains
activated, the user is reminded to remove the film cassette 1 from the
loading chamber 107, whereupon the circuit will be de-activated.
If the read/write head 135 detects frame number data C at the magnetic area
169 of the film leader 43, and the data represents a particular number
greater than "0" but less than the maximum number M, this indicates that
the filmstrip F was partially exposed before the film cassette 1 was
inserted into the loading chamber 107, i.e. there is at least one
unexposed frame available for picture-taking. As a result, the PU warning
circuit 151 will be activated to alert the user of such condition. Then,
when the metering switch 113 is closed a sufficient number of times to
increment the frame counter 137 to a numbered setting equal to the
particular number indicated by the frame number data C, the motor 113 will
be de-energized and the PU warning circuit 151 will be de-activated. At
this time, the next-available unexposed frame will be in the exposure
position.
(2) Expose Routine--FIG. 8
If in this routine the shutter release switch 143 is closed because the
camera shutter is opened, and the setting of the frame counter 137 is a
numbered one less than the maximum number M, the motor 113 will be
energized to rotate the spool core 23 in the unwinding direction U to
advance the filmstrip F from the cassette shell 3. When the metering
switch 133 is closed one time to indicate that the next-available
unexposed frame is in the exposure position, the frame counter 137 will be
incremented by "1" to a numbered setting which represents that frame.
Then, the motor 113 will be de-energized.
If the setting of the frame counter 137 is a numbered one equal to the
maximum number M, and the shutter release switch 143 is closed, indicating
that the last-available frame was exposed, the motor 113 will be energized
to rotate the spool core 23 in the winding direction W to return the
filmstrip F to the cassette shell 3. When the metering switch 133 is
closed a sufficient number of times to decrement the frame counter 137 to
its dot "." setting immediately following its "1" setting, i.e. to a "-1"
setting in the flow chart, the film leader 43 will be positioned with its
magnetic area 169 in contact with the read/write head 135. Then, the
read/write circuit 157 will be changed to its write mode and the
read/write head 135 will write frame number data C on the leader area 169
which represents a "0", indicating that the filmstrip F is completely
exposed. At the same time, the timer 165 will be activated. When the timer
165 determines that a sufficient time has elapsed to rewind the film
leader 43 into the cassette shell 3, the motor 113 will be de-energized.
(3) Midroll Interrupt (MRI) Routine -- FIGS. 9a, 9b
If in this routine the MRI switch 145 is closed because the user has
manually depressed the MRI button, the MRI warning circuit 147 will be
activated to alert the user of such condition. When the particular setting
of the frame counter 137 is either "1" or a dot ".", this means that the
first-available frame #1 in FIG. 6 has not been exposed, i.e. the
filmstrip F is completely fresh. Thus, no frames count will be stored in
the RAM 163 and the motor 113 will be reversed to rotate the spool core 23
in the winding direction W to rewind the film leader 43 into the cassette
shell 3. At the same time, the timer 165 will be activated. When the timer
165 indicates that a sufficient time has elapsed to rewind the film leader
43 into the cassette shell 3, the motor 113 will be de-energized and the
MRI warning circuit 143 will be de-activated.
When the particular setting of the frame counter 137 is between "2" and the
maximum number M, to indicate that unexposed frame #2 or greater in FIG. 6
is in the exposure position, and the MRI switch 145 is closed, the frame
| | |
