Note: Descriptions are shown in the official language in which they were submitted.
~06389~;~
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This invention relates generally to viewers for -~
stereoscopic transparencies and the like.
A typical example of a conventional stereoscopic
- viewer is that sold under the trade mark "Viewmaster". ;~
Transparencies to be viewed are mounted in a disc-shaped -
holder which is inserted into a slot in the viewer. The ~
holder is turned by hand to bring successive pairs of ~ ;
frames into positions for viewing. The transparencies
are illuminated by naturally available light entering
- 10 through the back of the viewer. Accordingly, the viewer
must be directed towards a source of light for proper
illumination of the transparencies.
~, A problem with this type of viewer is that it
cannot conveniently be used in association with reading
material. For example, where the transpàrencies carry
educational material or promotional material related
to a commercial product, it may be convenient to provide
written notes or other information to be read in con-
junction with the filmstrips. Since this type of viewer
is normally used in an upwardly directed position in -
order to obtain adequate illumination, it is inconvenient
for the user to continually have to look down at written
material.
,
Also, the transparency holders are awkward and
expensive to manufacture because the transparency frames
^ must be individually mounted in the holder~ Accuracy
; - ::
- of mounting is of paramount importance in order to
achieve proper registration of corresponding stereoscopic ~,
frames. ;~
- 30 An object of the present invention is to provide
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~L063~347
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an improved stereoscopic viewer.
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According to one aspect of the invention there is pro- -
vided a viewer which employs a s-tereoscopic filmstrip having
a plurality of spaced perforations along one longitudinal
margin and including a series of pairs of left and right
hand stereoscopic frames. The viewer includes a casing
for receiving the filmstrip and the casing includes a
front wall, a rear wall, and a top wall. A pair of lenses ~
are mounted in positions spaced transversely of the front -
- 10 wall for use in viewing the filmstrip. Film masking means
are disposed inside the casing at a position spaced
from and generally parallel to said front wall. The masking
means defines a pair of apertures positioned to permit
viewing of the respective left and right hand frames of
successive frame pairs as the filrnstrip is advanced through
the viewer in use. Means are provided for guiding the
filmstrip in a path which extends transversely of the
casing rearwardly of the masking means. The viewer also
` includes a film transport mechanism disposed inside the
- 20 casing and positioned laterally of said apertures in the
masking means. The transport mechanism includes a film-
engaging disc which is turnable about an axis normal to
the direction of filmstrip movement and which has a
peripheral series of teeth for engagement in said perfor-
ations in the filmstrip so that turning of the disc advances
the filmstrip past said apertures. A drive member is pro-
vided for turning the disc and is itself turnable about
an axis parallel to the turning axis of the disc. The
drive membex includes an operating lever which projects
~L~)63891~
to the exterior of the casing for turning the member
and which is movable from a rest position to a fully
advanced position. The arive member is biassed to
normally maintain the operating lever in said rest
position. Ratchet means couple the drive member and
disc so that movement of the operating lever from
said rest position to said fully advanced position
causes the disc to turn and advance the filmstrip uni- ~
directionally by an amount equal to the spacing between -
successive pairs of films on said filmstrip. Detent
means cooperate with said disc for preventing return
movement of the disc in a direction counter to the
film advance direction upon release of the operating
lever. The viewer also includes means for illuminating
the filmstrip. The illuminating means are defined by
at least one light admitting aperture in the top wall
of the casing, the aperture being positioned rearwardly
of said masking means. Reflector means are arranged
in an angular position at the rear of the film path
for reflecting incoming light through the apertures in
the masking means to illuminate the filmstrip.
According to another aspect of the i,nvention there '
is,pro~ided a method of manufacturing a stereoscopic filmstrip.
The method comprises the steps of:
a) simultaneously exposing to a series of subjects
intended to appear on the filmstrip, successive portions
of two conventional still-camera films,each two simul- ','
taneous exposures being taken from positions which are
spaced laterally to an extent appropriate to pro~uce '
respective left and right stereoscopic frames; -
b) processing the films:
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1()638~7
c) separating individual frames from the two
films;
d) mounting the individual frames in a carrier
with the frames arranged in first and second parallel
rows in each of which the frames are equally spaced:
from one another, the respective left and right hand
frames for each subject being spaced from one another
longitudinally of the relevant row by four intervening
frames and from the corresponding frames of adjacent
subjects each by one intervening frame, the frames in
said first row being arranged in a viewing sequence
from a first end of the carrier to a second end thereof
with the upper ends of the frames disposed adjacent
the frames in the second row, and the frames in said
second row being arranged in a viewing sequence from
said second end of the carrier to said first end with
the upper ends of the frames disposed adjacent the
frames in said first row;
e) photorgraphing said rows of frames using a
conventional colour film having a row of perforations along
each longitudinal margin;
f) processing said colour ~llm to produce a film
element carrying said two rows of frames in the form of
positive transparencies; and .
g) separating said film element longitudinally
between said two rows of frames to produce two filmstrips.
A still further aspect of the invention provides a
filmstrip per se.
~063~347
The invention will be better understood by
reference to the accompanying drawings, in which:-
Fig. 1 is a perspective view of a stereo-
scopic viewer according to the invention;
Fig. ~ is an exploded perspective view of the
viewer of Fig. l;
Fig. 2a is an enlarged detail of part of Fig.
2;
Fig. 3 is a horizontal sectional view on line
III-III of Fig. 2;
Fig. 4 is a transverse sectional view on line -
;- IV-IV of Fig. 3; -
Fig. 5 is a perspective view of part of the
film transport mechanism of the viewer;
Figs. 6 to 9 are sequential views corresponding
to part of Fig. 3 and illustrate the operation of the
film transport mechanism;
. , . , ~ .
Fig. 10 is a perspective view of the continuous
filmstrip employed in the viewer shown in the previous
figures; and,
Figs. 11 to 14 illustrate steps in the manufacture
;;~ of the filmstrip of Fig. 10.
` Reference will first be made to Fig. 1 which
- illustrates the external appearance o~ the viewer. As
; can be seen, the viewer includes a generally box-form
casing generally denoted 20. The height of the casing
- as seen in Fig. 1 is relatively small and is designed
so that the viewer will fit relatively and easily into
a pocket orpU~e of a user, or into a small package for
mailing purposes. For the same reason, the casing is
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~063~4t7 : ::
smoothly contoured.
Casing 20 includes an initially separate top 22
and a bottom section 24 to which the top is permanently
sealed during manufacture. A continuous stereoscopic
filmstrip (to be described) is housed in casing 20 and
is viewed through a pair of lenses 26 in the front of the
casing. The film is illuminated using naturally available
light which enters the casing through a translucent panel
,8 in top 22. The viewer includes a film transport
mechanism (also to be described) operated by a lever
30 which projects through a slot in the side of casing
20. As can be seen, the casing is recessed at 32 in
the region of the lever 30 so that the lever is disposed
within the general external contour of the casing,-main-
taining the smooth external appearance thereof.
Fig. 2 shows the viewer of Fig. 1 in exploded
form. As can be seen, the bottom section 24 of the
casing 20 includes a rectangular base 34 having upstanding
walls 36, 38 and 40 on three sides. Walls 36 and 38
are plain, while wall 40 is specially shaped to define
the recess 32 for the operating lever of the film trans-
port mechanism. Wall 40 also defines a slot 42 which
extends parallel to base 34 and along which lever 30
moves. Wall 38 forms the rear wall of the casing and
walls 36 and 40 the side walls.
Base 34 is formed with a generally semi-circular
recess 44 which opens into the front edge of the base
and which is surrounded by a bulbous formation 46 designed
- to accommodate the nose of a person using the viewer.
A generally rectangular projection 48 extends upwardly
10~38~ I
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from formation 46 and forms a support for an initially- t
separate front panel 50 of the viewer. The ends of panel
50 are fitted in inwardly directed vertical slots
52, 54 formed in the respective side walls 36 and 40 ~ ,
of the bottom section 24 of the viewer casing. Panel
50 fits in front of projection 48 and has depending
tabs 56, 58 in its lower edge which fit into compli- -~
mentary recesses 60, 62 in the base 34. Two similar
tabs 64 and 68 on the upper edge of panel 50 fit into -
other, similar recesses 70 and 72 in the top 22 of
the casing. A generally semi-circular recess 74 in
panel 50 cooperates with the bulbous formation 46 ,
on the base 34.
Panel 50 is formed with two circular apertures
76, 78 which receive plastic lenses 80 and 82 respectively ''
fitted to panel 50 from the rear side and secured in , ,,
place by sonic welding. ,
Casing top 22 is shaped to fit snugly onto the '
upper edyes of the wall 36, 38 and 40 of the bottom
section 24 and is secured to those walls so as to hold ~'~
in place the front panel S0 and the other components '
of the viewer (to be described). Angled ribs 84, 86, '
88 and 90 on the underside of top 22 fit inside the '~
walls 36, 38 and 40 and the"front panel 50 to laterally ' ,'
locate the top 22. The bottom section 24 and the top '~ ',
22 of the viewer (as well as substantially all of the
other components of the viewer)'are injection molded
in plastic. Top 22 is accordingly secured to the bottom
section 24 by sonic welding. Miniature ribs, one of '~'
which is denoted 92 in Figs. 2 and 2a are provided on
the underside of top 22 positions corresponding to the ,
upper edges of the walls 36, 38 and 40 of the bottom
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~(~6384~
section 24. These ribs are designed to fuse with
the walls during the sonic welding operation and are
designed so as other areas of the parts to be welded
-~ are not damaged during the actual welding operation.
A similar technique is employed to prevent damage to -
the lenses80,82 when they are attached to the front
panel 50 although, for ease of illustration, the
miniature ribs have not been shown on lense 82.
~ masking panel somewhat similar to panel 50 is located
in the casing in a position parallel to and spaced from
panel 50 and is formed with t-wo film viewing apertures. This
panel is shown at 94 in Fig. 2. The two apertures are
denoted 96 and 98. These apertures are of standard
35 mm film size and are spaced to correspond with the
spacing of the frames in each pair on the film contained
in the viewer (to be described). The spacing corresponds
to the spacing of the lenses 18 and 82 in panel 50
which in turn conforms generally with the spacing between ;~
an average person's eyes. Panel 94 is fitted into
vertical slots 100 and 102 in the walls 36 and 40 re- `
spectively of the bottom casing section 24 and is
- located against a rib 104 molded into the base 34.
It will be convenient at this stage to refer
to Fig. 3 which is, in effec* a plan view of the assembled
viewer with the top 22 removed. In this view, the filmstrip
is represented by a chain dotted line denoted F and the
film transport mechanism is generally denoted 106.
The film is in the form of a continuous loop and is
arranged to follow a path defined by the transport
mechanism 106 and a series of guide pinsdenoted 108
~063847
110, 112 and 114. As can be seen from Fig. 2, the
; pins 112 and 114 are in fact of tubular form while
pins 108 and 110 are of solid cylindrical shape and
are of somewhat smaller diameter. All of the pins
are integrally molded with the base 34 of the casing.
. . .
' The direction of film advance is indicated by
i arrows in Fig. 3 and it will be seen that pin 112
guides the film leaving the transport mechanism
106 adjacent the rear wall 38 of the casing and
then directs the film inwardly into a bight or loop
~; L in which the film passes around the central spindle
assembly 116 (to be described) of the film transport
mechanism 106. Portions of the film F respectively
approaching and receeding from assembly 116 are sepa-
- rated by pin 108. Film leaving loop L passes around
- pin 114 and travels transversly of the casing closely
adjacent the rear surface of panel 94 before it is again
engaged by the transport mechanism 106. Pin 110 main-
tains the film closely adjacent pànel 94 during its
travel from pin 114 to the transport mechanism. -~
As indicated above, film being viewed is illumin- -
ated by naturally available light entering casing
through the translucent panel 28 in its top 22. Fig. 4
illustrates the path of this light in travelling into
and through the viewer. The light path is denoted LP ;
~ in Fig. 4. As can be seen from that view, panel 28 is
- positioned ~ehind an opening 118 in the top 22 of the
viewer casing and is located just rearwardly of the
viewing panel 94 and accordingly also just rearwardly
of frames on the film F to be viewed. A reflector 120
is providedinside the casing to direct incoming light
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~ ... . ' . ~ '' . . .
~063847
through the film F. Since the light can be considered
entering the casing generally normal to the top 22,
reflector 120 is positioned generally at a 45 angle
and extends from the innermost margin of panel 28 to
a position just rearwardly of the film F.
Referring again to Fig. 2, the reflector 120
is formed by a piece of cardboard having a white finish
on lts reflective surface. The reflector is secured
in position by a flap 122 which is folded inwardly with
respect to the main portion of the reflector so as to
lie in contact with the under surface of the trans-
lucent panel 28. Panel 28 is attached to the top 22
by a series of small cylindrical "pips" or studs 124
arranged in a recess 126 around the opening 119 in
top 22. The studs 24 pass through corresponding holes
128 in panel 28 and melt during the sonic welding oper-
ation performed to attach the top 22 to the bottom section
; 24 of the casing, the fused studs serving to hold the
panel 28 in position. Reflector 120 is located along
one longitudinal margin of panel 28 and its flap 122 is
- formed with openings 130 corresponding to the openings
128 along the relevant margin of panel 28. Accordingly,
flap 122 can be positioned over the relevant studs 124
so that the reflector is also secured in place during
the sonic welding operation. The cutout 133 in the
bottom longitudinal margin of the main portion of the
; reflector 120 fits around the film guide pin 110, thereby
further assisting in the location of the reflector.
; Referring back to Fig. 2, the film transport
~ 30 mechanism includes a film-engaging disc 132 and a drive'' ',' ,
- 11 - '
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~063847
- member 134 which is positioned below disc 122 and is
adapted to drive the disc to advance the film as will
be described. Disc 122 and member 134 are rotatably
mounted in superposed positions on a pin 136 which ~ `
projects upwardly from the base 34 of the bottom casing
section 24. Member 134 includes a main disc-shaped
portion 138 having at its centre an aperture 140 which
receives the pin 136. The operating lever 30 for the
film transport mechanism (referred to above) i9 formed ;~
integrally at the periphery of the disc-shaped portion '`
138 of member 134 and projects through the slot 42 in
the side wall 40 of the viewer casing as described l~
above. It will be seen from Fig. 2 that lever 30 has ~;
a serrated outer surface 142 which is contoured to ~
receive the thumbof a person using the viewer so as ~ `
to facilitate operation of the transport mechanism.
The direction of movement of lever 30 to advance the
.
; film is indicated by the arrow denoted A in Fig. 2. ,~
It will be appreciated that movement of lever 30 in
; 20 the direction of arrow A will ~ause the drive member
~` 134 to turn about pin 136 to an extent determined by
; the extent of movement of lever 30.
~` Drive member 134 is spring biassed to a position
in which the operating lever 30 is disposed at the
end of slot 42 nearest the front of the viewer as shown
for example in Figs. 3 and 6. Member 138 is biassed by
a spring 144, one end of which engages the outer end
- of a radial arm 146 on the disc-shaped portion 138 of
member 134. Arm 146 extends below the internal panel
94 of the viewer and is held by spring 144 against an
- 12 _
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~L~63~34~
angled end portion 148 of the rib 104 molded into the
basin 34 of the bottom viewer casing section. Accora-
ingly, this end portion 148 defines the rest position
of arm 146 and hence the rest positon of the drive
member 134. The opposite end of 144 is engaged with a
hook member 150 molded onto base 34.
It will be appreciated from the foregoing that
the drive member 134 is turnable about the pin 136 from
the normal rest position in which it is shown in Fig.
6 progressively through the position of Fig. 7 to the
Fig. 8 position in which spring 144 is fully extended.
If lever 30 is released at this time, the drive member
134 will return to its rest position under ~he action of
spring 144. Member 134 is coupled with the film-engaging
- disc 132 by what is in effect a pawl and ratchet arrange-
- ment designed so that disc 132 advances unidirectionally
in incrementseach time lever 30 is moved from its rest '
position to its fully advanced position while return
movement of the drive member under the action of spring
144 does not affect disc 132. The pawl and ratchet
arrangement includes an integral spring-like arm 152
which projects from the disc-shaped portion 138 of drive
member 134 at a position generally opposed to the position
of lever 30 and which cur~-es around the periphery of
portion 138 to a position adjacent arm 146. A projection
154 at the outer end of arm 152 extends above the
general plane containing the remainder of the member 134 ,~
for engagement with the unaerside of disc 132. Disc 132
is integrally connected to the lower end of a tubular
member 156 which is turnably mounted on the pin 136 which
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~)63~347 ~ `
also carries drive member 134. Around the periphery
of disc 134 are a series of equally spaced sprocket
teeth 158 for engagement in the sprocket holes 160
of the film F.
Referring now more particularly to Fig. 5,
it will be seen that the under side of disc 132 is
formed with a series of ratchet tee-th 162 which are
disposed inwardly of the sprocket teeth 158 of disc
132. Each tooth 162 has a profile which progressively
curves upwardly from the root of the teeth. Each
tooth defines a shoulder 164 for engagement by the
projection 154 on the drive member 134 (see Fig. 2).
Figs. 6 to 9 illustrate the operation of this pawl
and ratchet arrangement. In Fig. 6, the film trans-
port mechanism is shown at rest with the projection
154 of the drive member engaged on one of the
shoulders 164 of the ratchet teeth 162. Accordingly,
` movement of the operating lever 30 in the direction
of arrow A in Fig. 6 (from its rest position towards
its advancedposition) causes projection 154 to rotate
the disc 132 in the CQunter clockwise direction
as shown in Figs. 6 to 9. Fig. 7 shows the components
at an intermediate position before lever 30 has
reached the end of its trave~. This fully advanced
position of the operating lever 30 is shown in Fig.
~' 8. The transport mechanism is designed so that - ;
the peripheral movement of disc 132 which occurs when
lever 30 moves from its rest position to its fully
advanced position is equal to the length of two frames
of film F. The purpose of this will become apparent later.
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1063t347
In any event, assuming that lever 30 is now in its
fully advanced position (Fig. 8), if the lever is
released, the drive member 134 is returned to the
rest position by spring 144. Disc 132 is restrained
against return movement with drive member 13~ by a
spring biassed ball 166 (see Fig. 2) which engages in
one of a series of angularly spaced depressions
168 in the upper surface of disc 132. Ball 166 is
urged downwardly against the upper sur~ace of disc
132 by a coil spring 170 housed in a tubular member
172 which depends from the underside of the casing
top 22. The arrangement is in fact such that, when
the viewer is fully assmebled, ball 66 just projects
..
from the lower end of tubular member 172. The
depressions 168 are spaced so that the angular movement
of disc 132 which occurs between a position in which
ball 166 is engaged in one depressions and a position
in which the ball is engaged in the next depression,
~; corresponds to movement of the operating lever 30
;-~ 20 from the rest position to the fully advanced position.
In Figs. 6, 8 and 9 the position of ball 166 is indi-
,.~ . :-: -
cated by a black circle denoted 166. In each of these ,
views, the ball 166 is engaged in one of the depressions
168. ,'~
It will be appreciated that each time lever
30 is moved from the rest position to the fully
advanced position, the film F will be advanced (in the ;
,, .
direction of the arrows in Fig. 3) by an amount
corresponding to the length of two frames of film F. ~
Because of the arrangement of the frames on the film -
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1063~47
(to be described) this will result in successive
pairs of stereoscopic frames being positioned behind
the apertures 96, 98 in panel 94 of the viewer so
that the frames can be observed through the lenses
; 80 and 82. The frames displayed will be illuminated ~-
by incoming light reflected through the film by re-
flector 120. The provision of translucent panel 28
in the top 22 of the viewer, together with reflector
120 allows naturally available overhead light to be ;~
used for illuminating the film. This avoids the need
for the viewer to be angled towards a source of light
as in conventional viewers. An advantage of this
arrangement is that the user can readily use the
viewer inconjunction with other material, e.g. written
notes. The viewer can be used in an orientation
in which it is angled generally downwardly towards the
notes so that the user can readily shift his eyes from
the lenses 80, 82 onto the notes adjacent the viewer.
Fig. 10 shows a loop of film F used in the
viewer described in conjunction with the previous
` figures. The film is made from conventional 35 mm
'' ' ,
colour transparency film as will be described. ~A
number of successlve frames of the film are visible
~ in Fig. 10 as are some of the sprocket holes 160, which are
,~ located along the bottom margin of the film considered in the
position in which it is used in the viewer.
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Reference will now be made to Figs. 11
to 14 in more specifically describing the film and its
method of manufacture.
By way of example, Fig. 11 shows two conventional
- 16 ~
1063847
; 35 mm cameras 174, 176 mounted side by side on a support
178. A subject to be photographed is generally indicated
at 180. The cameras are spaced by an amount correspond-
~ ing generally to 1/30 of the distance between the cameras
- and the subject 180. This spacing formula has been found
to result in realistic stereoscopic pictures even for large
,
camera-to-subject distances. Both cameras are loaded with
conventional 35 mm colour transparency film. Both films
are simultaneously exposed to the subject 180, producing ~-
respective stereoscopic left and right ha~d frames showing
the subject 180. Other subjects to appear on the film-
strip are similarly photographed using subsequent frames
of the films in came~ras 174 and 176. After exposure of
all of the frames on both films, the films are processed
and the indicidual frames are identified and separated ~ -
from adjacent frames in the film.
The frames are then photographed in a pre-
determined arrangement (to be described). This is done
by mounting the frames in groups of six on a series of -
carriers, one of which is shown in Fig. 12. In that view,
; the individual frames are denoted by the reference numeral
182. The carrier is in the form of a cardboard sheet 184, ~,
formed with six rectangular apertures 186, each of a size
corresponding to the size of the portion of each frame to
: .
be viewed. The frames are attached to the lower side of
the carrier using pressure-sensitive tape (not shown). If ;
forty-eight pairs of frames are used, sixteen cardboard
carriers will be prepared in this way. The carriers are
then photographed (from above) in a predetermined sequence
using a standard 35 mm colour film having a series of
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1~)631347
perforations on each longitudinal margin. The film is ~`~
then processed to produce a film element carrying the
frames in two rows in the form of positive transparencies '~
and the film element is divided longitudinally to form -
two relatively narrow elongate filmstrips. In Fig. 13,
a typical film element is indicatea at 194. The frames
which appear on the film element are denoted 196 and the
sprocket holes along each longitudinal margin are denoted
- 198 and 200 respectiveIy. The film element is divided
by cutting as indicated at 202 and the resulting film-
strips are denoted 204 and 206. Each strip is formed
into a continuous loop by splicing to produce a con'tinuous
loop filmstrip such as that shown in Fig. 10. The carriers
may be photographed using a colour transparency film
which is simply developed to produce the film element.
This technique will normally be employed where relatively ~
few copies of a particular series of frames is required. ~ ;
Where a large number of copies are required, the carriers
may be photographed using a colour negative film from which
copies can readily be made by contact printing. In this
~- event, the developed négative film may be formed into an t-`
endIess loop and copied in a motion picture contact printer.
Whichever method is used, the arrangement of the ``
frames on the resulting film element 194 of Fig. 13 is as
,
shown in Fig. 14. It will of course be appreciated that this
;~ layout corresponds to the layout of the frames or the carriers
184 and to the sequence in which the carriers are photographed. i;
It will be seen that the frames are arranyed in two parallel
rows Rl and R2. Each row contains 24 pairs of stereoscopic
frames, the frames in each pair including a left hand view
- 18 -
iO63847
and a right hand view of the subject in question. For
identification purposes, corresponding frames are denoted
by the same number and the letters L and R are used to
denote respectively the left and right hand frames of a
pair.
In the embodiment being described, different
frames are used in rows Rl and R2. Accordingly, film 194
as a whole carries 48 pairs of different frames. The two
filmstrips which result from longitudinal division of film
194 will therefore be different. It will of course be -
~ appreciated that, in an alternative embodiment, it will J: '. '
; be possible to make both filmstrips 202 and 204 the same
by using 24 pairs of frames in duplicate. In this event,
the frames in rows Rl and R2 would be the same.
It will be noted from Fig. 14 that the respective
left and right hand frames for each subject are spaced
from one another longitudinally of the relevant row Rl
and R2 by four intervening frames and are spaced from
corresponding frames of adjacent subjects each by one
intervening frame. For example, in row Rl, the frames
dentoed 1L and 1R are spaced from one another by the
frames 23R~ 2L~ 24R and 3L and the frames 1L and 1R are
spaced from the frames 2L and 2R each by one frame (23R
and 4L). It will also be noted that, in row Rl, the frames
23R and 24R are positioned adjacent frames lL and 2L
respectively. This is done so that the frames appear ~
in the correct sequence when film 194 is divided longi- -
tudinally and each half of the film is formed into a con-
tinuous loop.
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1063~7
It will be noted from Fig, 10 and from the
preceding description of the viewer that the perforations
in the filmstrip (denoted 160 in Fig. 10) are disposed
at the lower margin of the filmstrip as used in the
viewer. In other words, when the filmstrip is in the
position shown in Fig. 10, the perforations 160 are at
the bottom and the lower ends of the frames are adjacent
the perforations. For this reason, the frames as positioned 5.
in the carrier (Fig. 12) are disposed with their lower
ends adjacent the relevant row of perforations in the ¦
filmstrip. Considering the frames as shown in Fig. 14, L:
./ '.
therefore, the frames in row Rl would appear upside down
although to avoid confusion, the numbers used to denote
the frames have not been inverted in the drawing. It should
also be noted that, for proper positioning of the frames ~-
with respect to the perforations, the frame sequence runs
from lift to right in row R]. and from right to left in
row R2.
It will be appreciated that the arrangement of
frames shown in Fig. 14 is advantageous in that it is ~ot
necessary to include blank or "jump" frames in order
to achieve proper registration of the respective left and
right hand frames in each pair with the viewing lenses 80
and 82 of the viewer. Also, the arrangement avoids the
need for prisms, mirrors or other expedients in the light ~
path between the viewer lenses and the filmstrip as is ~ -
commonly found in the prior art.
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1~6384'7
It will of course be appreciated that the pre-
ceding description applies to specific embodiments of the
invention only and that many modifications are possible
within the broad scope of the claims. For example, refer-
ring to the viewer, although the description refers to the
use of a filmstrip in the form of a continuous loop, it
will be understood that the viewer could be adapted to ~,- I
accept a discontinuous length of filmstrip. Film exit and ,~;
entry slots could be provided in the casing of the viewer ~ -~
to permit passage of the filmstrip therethrough.
A further possible modification of the viewer
would be to allow the casing to be opened by the user for
replacement of the filmstrip. For example, the rear por-
tion of the casing top could be hingable to provide access
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to the filmstrip.
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