US2410725A - Stereoscopic apparatus in relation to cinematograph reproduction and television - Google Patents

Description

Nav. 5, 1946. A

STEREOSCOPIC APP'ARAT REPRODUCTION AND TELEVISI Filed Aug. 25, 1944 2,410,725 OCINEMATQGRAPH P. FRANKLIN US IN RELATION T0 1l Sheets-Sheet l Nov. 5, 1946. A. P. FRANKLIN 2,410,725

STEREOSCOPIC APPARATUS IN RE LATION TO CNEMATOGRAPH REPRODUCTION AND TELEVISION Filed, Aug. 25. 1944 11 sheets-sheet s A. P. FRANKLlN 4l sTEREOscoPIc APPARAT RELATION To OINEMATOGE AND TELEVISION 11 Sheets-Sheet 4 Us IN REPRODUCTION Fil'ed Aug. 25, 1944 Abw firm/fwn'.

Nov. 5, 1946.

A. P YFRANKLlN 2,410,725 STEREOSCOPIC APPARATUS IN RELATION TO CINEMATOGRAPH REPRODUCTION AND TELEVISION Filed Aug. 25. 1944 11 Sheets-Sheet 5 NOV. 5, 1946. I A p FRANKUN 2 10,7254

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A. P. FRANKLlN 2,410,725 STEREOSCOPIC APPARATUS IN RELATION TO CINEMATOGRAPH v Nov. 5, 1946.

REPRODUCTION AND TELEVISION 4 l1 Sheets-Sheet 7 Filed Aug. 25. 1944 v.l ww M T T H Nov. 5, 1946. A P. FRANKLlN 2,410,725

sTEREoscoPIc APPARATUS 1N RELATION To GINEMATOGRAPH 1 REPRODUCTION AND TEI..\.':vIsIoNI Filed Aug. 25, 1944 11 Sheets-Sheet 8 yy, im

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Nov. 5, 1946. l11.1. FRANKLIN 2,410,725 STEREOSCOPIC APPARATUS IN RELATION TO CINEMATOGRAPH REPRODUCTION AND TELEVI S ION Filed Aug. 25, 1944 11 sheets-sheet 10 NW 5 .1946 A. P. FRANKLIN 2,410,725

STEREOSCOPIC APPARATUS IN RELATION TO CINEMATOGRPH REPRODUCTION AND TELEVISION Filed Aug. 2s. 1944 11 sheets-sheet 11 www@ v Patented Nov. 5, 119.4596

STEREOSCQPIC APPARATUS 1N RELATION TO `CINEMATGGIRAPH REPRODUCTIQN AND TELEVISION Alan Philip Franklin, Lower Kingswood; England Application August 25, 1944, Serial No. 551,128 In Great Britain August 31, 1943 This invention relates to stereoscopic apparatus for viewing stereoscopic pictures and in particular to moving pictures resulting from cine- /matograph or television reproduction where a number of people have to view the same picl torial reproduction.

One of the difficulties experienced with the design and construction of any apparatus suitable for use bythe public is that the average member of an audience will not use any device as an aid to vision which has .to .be held or manipulated continuously during a performance or which must be held close up to the eyes.

Another ditculty is that in stereoscopic reproduction any movement ci the viewer which moves' the eye-pieces of the viewing device out of the plane passing through thecentres of the two pictures destroys fusion and the stereoscopic eect is at once lost. If the device is held or worn by the viewer the necessary restraint would be most irksome, whereas when the device is mounted in the manner described hereinafter in relation to my own invention this diculty is overcome.

In the application of polarised light it has been suggested to provide special spectacles for viewlng, but the drawback to the provision of-glasses or other unattached device is that, apart from the expense, they are liable to become damaged or lost. If, however, they are made a xture and somewhat inexible control of focus and convergence they can produce currect' fusion of the two images without strain.` y

By use of a very complicated system oflmultll ple lenses and concave mirrors, individual aids to vision might possibly ybe dispensed with, but at a vprohibitive cost.

Persons using my apparatus in the'home, could move their viewing pieces, and fixtures erected on a suitably weighted stand to any position to suit the angle of the prism. Prisms could be changeable but would be chosen for a normai distance from the television set so that 3'or more people can view it at the same time.

A very few people can,

front of the viewer the two eye pieces will always be maintained with their axes in a plane passing through the centres of the two pictures.

The device may be made of metal, cardboard or one of the well-known plastics or-any other suitable material. The device can be moved to Conform to any movement of the Viewer.

In thesimplest form no, lenses or mirrors are needed for this invention. The probability is that only one prism will be necessary. y I

The device could also be used in the case of polarised light where the pictures to be viewed are superimposed. For this purpose a polarisng lter would be itted to each eye piece and the prism or prisms moved out of the line of vision. Y The drawings which will now be referred to show the `stages of development of the invention.

Fig. 1 is a perspective diagrammatic view of one form of apparatus made according tothe present invention. I

Fig. 2 is a part sectional plan view of another form of device made according to the present invention.

Fig. '3 is a cross-section on the line 2 2 of Fig. 2 looking inthe direction of the arrows.

Fig. 4 is a front view of the cap shown in Fig. 2.

Fig. 5 is a front .view of the device illustrated in Fig. 2 on a reduced scale to show part of the method of mounting.

Fig. 6 is a side view showing the complete device with mounting.

Fig. 7 is a sectional plan view of a modified form of the device shown in Figs. 4, 5 and 6.

Figs. 8 and 9 are end views of the device shown in Fig. 7.

Fig. 10 is a longitudinal sectional elevation of the device shown in Fig. 7.

Fig. 11 is a sectional plan view of one form of device made according to the present invention.

Fig. 12 is a cross section on the line 2'2 of Fig.-

11 looking in the direction of the arrows.-

Fig. 1'3 is a front view ofthe device illustrated in Fig. 11. a

Fig.' 14 is a side v iew on a reduced scale showing the complete device 'with mounting.

Fig. 15 is aplan of Fig. 14.

Fig. 1'6 is a sectionalp'lan view of a inodiiiedV l form of the device.

Figs. .17 and 18 are front and side elevations respectively of the device shown in Fig. 16.

Fig. 19 is a sectional plan view.

Fig. 20 is a transverse vertical section through i one of the prism holders, and

. As the device is xedly supported in position in /s Fig. 21 is aps Bil.vl l

an elevation sione' of the butterfly 'l is provided to assist manipulation, and the de- A vice is maintained in'position by tightening all pivotsor other adjustable parts. A pair of eye pieces tted with prisms 9 are arranged in relation to the bar I and are encased in a manner similar to the eye pieces of a stereoscope.

The bar I is made of such dimensions that 'if adjusted to its normal position it will block out the view of the right-hand picture from the left. eye and vice-versa so that the right eye of the viewer will only see the right-hand picture and the left eye the left-hand picture.

The operation of the device will be obvious from the drawings, therefore no further description will be given.` s

The arrangement will avoid discomfort of any attachment which has to be worn and, as will be seen, the eye pieces are of such a size as to enable them to be positioned at from three to six inches from the eyes of the viewer whilst permitting a full and correct view of the respective pictures to be obtained.

Referring to the construction shown in-Figs, 2 to 6, the device comprises an outer casing a similar in shape to the eye mask of a stereoscope. Pivots b provided with wing nuts c are secured to and extend laterally from the casing toengage supporting arms d. Mounted within the outer casing a are inner casings e and e' which are provided with pivots .f slidable in slots g in the outer casing and secured by thumb nuts h. The inner casings e and e' carry detachable ared tubes 7' and y" which are secured against unauthorized' removal by light chains shown in Fig. 6 ('25). Within the outer casing a is mounted an apertured partition lc adjacent the ends of the tubes j and 7". The tube e is provided with a prism m whilst the tube e' may be open-ended or provided with a piece of plane optical glass to keep out draughts. The end of the tubes i 7" are closed by a cap n having an eccentric aperture shown in detail in Fig. 4.

Referring tothe construction shown in Figs. '7 to- 10 inclusive, this form of the device comprises a box-like outer casing I of substantially .rec

tangularr cross-section two ends of the box being left open. One end is shaped to form an eye mask 2. Portions 3 of the side walls adjacent the other end are removed and replaced by shutters 4 hinged at 5 the said shutters having upper and lower flanges which t into the casing I and by friction therewith hold the shutters in the de-- -aperture thereof is a. detachable prism holder IllV provided with prism ll the holder being slidable laterally and pivoted in the same manner as in the form shown in Figs. 2 to 6. A similar holder may be provided in front of the other aperture and carry plane glass tov exclude draught.

The most convenient position for mounting the 4 device in the case of a cinema would be from the hack of the'front seat and slightly to one side to avoid the head of the front seat holder. They' can be on either his left or right or alternated according to circumstances, or the mounting can be accommodated in the recess between two seats and drawn out to the required position. A

The mounting as shown in Figs. 5, 6 and 8 mainly comprises a standard 28 pivoted to a slide 22, the slide being capable of adjustment in a lateral direction,- and the standard adjustable in. a vertical direction. The slide 22 enables the apparatus to be moved to conform to any lateral movement of the viewer. The apertures in the eye-pieces as seen in Fig. Bare elongated to allow for his movement up and down. After the device has been correctly positioned the various adjustable parts may be locked by a wing nut or a clamping device. The tting arrangement of the tubes as shown in Fig. 6, comprises a fork 23 which receives the transverse pivot 24.

In order to avoid loss of parts all parts are made so that nothing can be detached, although they can be loosened for purpose of adjustment.

.The arrangement as shown in Fig 6 enables the for each tube. In Fig. 7, however, ajustable shutters 4 and 'I are provided to serve the same purpose. Of course, foreach seat a different aperture can be xedly provided. Thi:J would obviate any adjustable apparatus.

In order to reduce the cost one prism only need be used and this can be located in one of the tubes, the other being left clear, preferably the right. The angle of the prism would naturally be selected according to the position of the seat from which the pictures are to be viewed, but it has been found in practice that a prism of about 20 willgive perfect fusion in the greater part of the auditorium so that special prisms would only 'l be required for a small number of seats.

Minor adjustments may be effected by moving the apparatus nearer or further from the eye, the major adjustment .being obtained by the prism.

In most cases the more important adjustments can `be effected permanently for each seat, leaving only a' few minor adjustments to be carried out by the members of the audience, which will only be of the simplest kind. y

No new equipment will be required for projection as the complementary pictures are arranged side by side on the film and projected through the same lens.

In order to make use of the same size frame as is now used in practice this area may be divided v v vent unauthorized withdrawal.

pictures together will be 30 and the height 10.

That means that the fused picture will be x 10'. On the other hand, if the two pictures are taken square on the normal lm, they could be projectedwithout the 90 prism, to make a fused picture of 10 x 10'. If the cinemas will not enlarge their screens, so as to make them v30 long, the latter arrangement can easily :be carried out.

Furthermore, if the square lms, which I contend, and, as I have proved by tests, with third dimensional vision would be quiteA appropriate, are objected to, the picture rwould have to be one quarter the size of the normal picture assuming also that is the maximum breadth available for the two pictures.

Referring to the form shown in Figs. 1l to 13, the device comprises a hollow body part or casing I having a mask portion 2 cut away to the approximate shape of the forehead and, therefore, somewhatsimilar in shape to the mask of the well-known stereoscope. The device according to the present invention however, diiers es- Forward of the guides s the sides of the body I are inclined outwarlly and terminate in pivoted shutters I4 of opaque material having actuating members through arcuate slots I6 in the bottom wall of I5 secured thereto which extendthe :body l a friction device or other means (not v shown) being provided to hold the pivoted shutters I 4 in position after being set. In a similar manner the central partition 6 terminates in two pivoted shutters I1 with actuating members I8 extending through arcuate slots I9. Secured to the bottom wall of the body.I near the point of.

balance isa bifurcated lug 20, the wings of which are drilled at 2l, to receive a rivet or bolt 22 shown dotted in Fig. 13.

In the drawings the prisms III are of relativelyy h v large angle and it is to be understood that such plane glass. The use of a singlet-prism will reduce cost of manufacture.

sentially from a stereoscope in that the viewer should not press his forehead against the device or vice versa and should on the contrary always arrange the device so that-it is clear of his forehead by a few inches. The mask portion 2 therefore only acts as a shield or shade to shut out unwanted light or views and so aid concentration. v

Slidably mounted in the body I adjacent the mask 2 are two shutters or movable blocking pieces 3, carried in guides 4, the shutters 3 extending through slots 5 in the body I, so as to be manually operable from outside the body I. Each slidable shutter 3 is formed from a sheet of opaque material of rectangular shape to slide in the guides @and is provided with .a rectangular aperture two inches square, the inner edge 'of which is spaced one inch from the edge of the shutter. I The two slidable shutters are arranged to be able to'overlap at their inner ends so that the opaque end portions of one inch width may overlie one another. l

Arranged longitudinally down the centre ofthe body I and extending forwardly from adjacent the guides 4 is a central partition yIi of opaque maf terial. Fixed to the central partition 6 adjacent the guides d is an opaquetransverse xedblocking piece 'I which is also of opaque material and one inch wide being bisected by the central partition 6.

Also mounted in the body I between guides 8 are prism mounts 9 holding the plane two inch V;

prisms Iii, the prism mounts 9 being provided -with an extension II which extending for the full depth of the prism and being made of opaque material serves the dual purpose of a handle and a lightexcluder. The side walls of the. body I are apertured at I2 to the full width of the prism mount 9 to enablel the mount 9 to be withdrawn for the purpose of changing or'cleaning the prism ID. Stops I3 which may be soldered or otherwise locked to the body I are provided to limit the outward movement of the prism mounts Sand precarryinga linked frame the Turning nowy to Figs. 14 and 15 of the drawings which show one formV of adjustable mounting which enables the device to be moved to the desired position whilst guarding against its being tilted sideways. l I

Mounted on the back of the seat 30 is a bracket 3| pivotally supporting a 'ertic'al member 32v embers 33 to 33 of which form two coupled parallelograms theouter vertical member 38 carrying avertical socket 39 in which is pivotally supported a pin Ml formed with a lug adapted to enter between the wings of the bifurcated lug 20 arid drilled to. receive the rivet or bolt 22.

Figs. 14 and 15.show clearly the movements which may be imparted to the device and its support. It will be obvious from Fig. '14 how the de- `vice can be raised or lowered, drawn towards the viewer' or pushed away while Fig. 15 shows by dotted lines how the whole support may be swung sideways to conform to the regulations of the London County Council or other local authority, by pivoting about the member 32 or directed angularly by turning the device about the pivot 39. Fig. 14 also .shows how the device may be tilted about the rivet or bolt 22. It should be noted that this varrangement entirely prevents any sideways tilting.

'I'he device above described is best suited for use where the viewer gets a relatively clear space between two members oi' the audience sitting in the seats immediately in front. In some cinemas the seats are not so well arranged. In such cases the seats should be rearrangd or the screen raised. If `this is not-possible then the alternative but more elaborate modified construction shown in Figs.1`6, 17 aid 18 may be employed. In these figures the same reference numerals have been used to denote the same partsy `\Ir\1- stead of direct vision,\"p'airs of mirrors 5I and 52 set in adjustable mountings so that their angularity may be adjusted about pivots 53 to suit Athe -seat from which the screen is to be viewed. Only very small angular adjustment would ever be required and the arrangement such that members of the public would not be able to alter the angularity once it had been set for the required accurate fine pensed with.

able shape.

with that shown in Figs. 11 to 13 except that a single prism I is shown on the right-hand side and a piece lof plane optical glass 53 on the left side. Two prisms may, of course, be used and in this construction as the' mirrors can be adjusted to produce fusion the use of a prism could `be dispensed with. However, the adjustment of the mirrors -being very delicate, a more rapid and adjustment can be secured empirically by changing the prism for one of a different angle.

Turningnow to Figs. 19 and 20 which show the latest and most simpliiied form of the device which was evolved from that illustrated in Figs., 11 to 13 of the drawings. Wherever possible the lsame'referencenumerals have been used to ndicate the same parts as in Figs. 11 to 13, and only the differences will be noted.

The following diierences will be noted;

1. The central front,laps l'l have been dis- 2, The shutters` |4 have been lengthened and the pivots made a good rm it so that the pins I5 and slots i6 are norlonger necessary.

3. Instead of the sliding shutters 3 a pair of hinged butteriiy shutters 6D are mounted on the partition 6 within the mask 2, the hinges being made stiff so that the buttery shutters 60 remain in the position in which they are set.

4. The blocking piece l has been omitted.

5. The prisms ID are nearer the eyes.

6. The top and bottom of the mask 2 are not cut away and so cover the butterfiy shutters 60.

7. Stops I3 to prevent removal of the prism holders are formed on the inner end of the prism holders instead of on the casing as shown in Figs. 1 to 6.

8. The prism mounts have been modified to ensure a smooth sliding action and a steady mount, as will be seen-from Fig. of the drawings led herewith. 9. The sides of the device Y have become straightened to reduce the number of corners and simplify construction.-v It may be found that without the blocking piece when the prism or glass holders 9 are drawn out slightly for adjustment light is admitted in the centre. It is probable that the butterfly shutters 60 when opened -out to the correct extent will exclude this Vunwanted light fromthe eyes. If not, it would be an easy matter to provide extensions at the inner ends of the prism holders 9 which will slide through slots in the central partition 6 and overlap each other when the prism holders are pushed in tothe full extent. These extensions should not need to be more than 1/2f' wide.

As will be seen fromFig. 21\,the top and bottom corners of the free edge of the butterfly ap B0 havebeen rounded off. This avoids sharp corners and is found in practice to be the most suit- Io enable the device tobe used in the home in conjunction with television sets, the support may comprise a weighted pedestal which can be stood on the ground in the desired position.

For use in a cinema the device will be equipped with all adjustments setaccording to the distance from the seat tothe screen and the angle subtended by the two pictures so that for normal j Y vision perfect fusion would be obtained. Whichever form of device is installed the viewer after taking his seat and making himself comfortable will draw the device down and 'towards him until it is only a few inches in front of his face and will vset it angularly to direct it onto the screen. He will then make such adjustments as may be necessary to ensure that with his left eye he can see only the left hand picture andwith the right eye only the right hand picture. It will be found that quite an appreciable movement of the head may be made without much ioss of vision. The shutters Aand prisms may be pre-set for normal y us'e and will only require adjustment so that the 10 pictures fuse in the most comfortable position. 1 It may also be necessary to make a slight adjustnient of the prism or prisms lll by sliding them in or out in order to look through the/icentre of the prismas some people are much 'wider between the eyes than others. Once set, however, no further adjustmentV is necessary. If anyone wishes to pass or if the viewer wishes to leave or, in the case of an emergency, the device can be swung instantly out of the way.

The iixture will be such that if the viewer wishes to lean over to one side or alter his position in any way, he can bring the device with him, by the very slightest movement of the instrument or the xture. He will in most cases be able to continue to view the pictures without any further adjustment, having drawn the device to the most comfortable position in front of the eye as before. With some kind of angie-poise" fixture this is an easy matter.

A further advantage is that as the device is supported at a reasonable distance from the eyes the viewer if obliged to wear spectacles may do so without inconvenience.

For the sake of convenience and when time permits the device when out of use should be (a) It can be employed with private televisionl sets being suitably mounted in a fixed relation.

(b) It may be used in a cinema for viewing stereoscopic pictures projected on the screen for a lm projector. (c) With suitable modifications and adjustments it can be adapted for use with complementary pictures arranged side by side in the normal manner of viewing stereoscopic pictures or it can be used for viewing superimposed pictures, separation of the two pictures being obtained by the bi-colour known process (which cannot-at present be used for viewing stereoscopic pictureslin colour). or the use of polarised light, the device being provided with red and green glasses or polarised lters in the already well-known manner for effecting separation of such pictures in place of the prisms. The prisms or plain glass eye-pieces could be removed and the necessary eye-pieces inserted. j

If a member of the audience does not wish to see stereoscopically but wishes to view one picture normally without any aid to vision, the prism or prisms would have to be drawn out of the line of Vision, and the line of vision from the two eyepieces confined to'one picture which, in the latest device, is secured by closing the front shutters so 'I0-that only one picture can .be seen either through plain glassor direct. In the case of the earlier tubular construction this, would be effected by pivoting both tubular extensions to direct them both onto the same picture. Some seats could be kept for this purpose.' preferably the outside A home for a television set. f

seats of the stalls, where practice has shown that the stereoscopic ee'ct is not quite as arresting.

It is intended that in the design finally adopted for production every reasonable measure will be adopted to render the device foolproof and to `guard against loss or damage or the removal by unauthorised persons of the device or any of the parts thereof.

For the purpose of photographing the pictures to be viewed an ordinary cinematographic camera can bevused, and one way of converting it to take stereoscopic pictures is to fix a simple at? tachment to the lens of the camera. This attachment will consist of a .box-like member the apertures of which (at each end) will be the size of .the lm to be taken but there will be a partition down the centre. From each side of this partirtion two tubular members diverge to eye distance apart. In the ends of ythese tubes prisms are placed and two parallel extensions connected to v the tubes are positioned to face the direction of the box-like structure above described. The angle between the end tubes and the divergent tubes can be as large as possible yand the degree of're fraction of the prisms lcorrespondingly small.

The prisms can be made of glass, plastics or other material such as perspexand this can equally apply to the pri-sms in the viewing or projecting device. This method of converting the oinematograph :camera into an apparatus capable of taking stereoscopic pictures will be both simple and inexpensive.

, Some or all of the following advantages are claimed for the various forms described:

1. It is the only form of stereoscope known for viwilg pictures at a distance or more than about a oo 2. No focussing is required when used in a cinema because the prism lused is not a lens. When a lens is used this is one which does not require focussing.

3. The prism angle is selected according to distance and size or picture to be viewed. 4. Only one prism is required in most cases.

.the viewing apparatus, the necessary magniflcation being fully provided by the projector` The prism used is .therefore plain glass and/no focussingis required. It has been possible thus to overcome the dimculty that has so often' presented itself in dealing with this problem, namely, how to combine focus and fusion in a stereoscope made for viewing at a distance. It has always been laid down that for perfect stereoscopy fusion and magnincation mus-t both be included in the.

viewing apparatus. A prism which did not embody a magnifying lens was therefore abandoned as useless many years ago in making inal stereoscopes.

What claim and desire .to secure by Letters Paten-tis:

l. Stereoscopic apparatus for viewing' adjacent pictures at a distance, comprising, a viewing dethe origvice having two sight openings and means for" effecting fusion in the eyes of the viewer, of the images seen by his two eyes therethrough, and anadjustable fixture supporting said device, a socket member adapted to be secured to a xed support, a vertical member pivotally mounted therein, a jointed frame pivoted thereto, for parn tial rotation-in a vertical plane and having an horizontal joint permitting adjustment -of the outer part of said frame in said plane towards and away from said socket member, a vertical pin rotatably mounted in the outer part of'said frame, and means for pivotally mounting said device upon said pin for angular adjustmentrela tive thereto about an axis parallel to aline joining the centres of said sight openings.

2. stereoscopic apparatus for viewing adjacent pictures at a distance, comprising, a viewing device having two sight openings and means for y eiecting fusion inthe. eyes of the viewer, of the 5. The only stereoscope in which blocking pieces and apertures are adjustable. Such adjustments may be xed for each seat and there need be n further adjustment.

6. The device i-s a fixture requiring no holding or wearing and need not bev positioned close to the eyes, but viewed at any distance up to that of about 6" from the prism. 'Ijhe fixture arrangement is novel for a cinema as well-as in the r1.v As a is a more the stereoscopic effect is not choose his vown distance, whereas the usual stereoscope has small eye-pieces and must be viewed closeup. 9. Anyone who has to wearspectacles can do to images seen by his two eyes therethrough, and an adjustable fixture supporting said device, a socket member adapted to be secured to a fixed. support, a vertical member pivotally mounted therein, avjointed frame pivoted thereto, for partial rotation in a vertical plane and having an horizontal joint permitting adjustment of the outer part of said frame in said plane towards and away from said socket member, a vertical f pin rotatably-'mounted in the outer part of said frame, and means for pivotally mounting said device upon said pin for angular adjustment relative thereto about an axis parallel to a line joining the centres of said sight lopenings whereby' l*said viewing device is .movable in any desired direction within the limits permitted and i" maintained with the eye pieces for the two :ies of vvice having two sight openings andmeans for effecting fusion in theeyes of the viewer, of the images seen by. his two eyestherethrough, and

\ 1l anadjustable xture supporting said device, a socket member adapted to be secured to a xed support, a lverticalmember pivotally 'mounted therein, a jointed frame pivoted thereto for partial rotation in a vertical plane and having an horizontal joint permitting adjustment of the outer part of said frame in said plane towards and away from said socket member, a vertical pin rotatably mounted in the outer part of said frame, and means for pivotally mounting said de-` vice upon said pin for angular adjustment relative thereto about an axis parallel'to a line joining the centres of said sight openings, prisms for said viewing device, means enabling said prisms to be interchangedA whereby the apparatus is usable from any part of an auditorium of a cinema.

one-half diopter and mounted in the line of vis- Y ion of one eye.

5. stereoscopic apparatus for viewing adjacent pictures at a distance, comprising, a viewing de- 4. Stereoscopic apparatus for viewing adjacent pictures at a distance, comprising, a viewing device having two sight openings and means for effecting fusion in the eyes of the viewer, of the images seen by his two eyes therethrough, and an .adjustable xture supporting said device, a socket member adapted to be secured to a fixed support, a vertical member pivotally mounted therein, a jointed frame pivoted: thereto, for partial rotation in a vertical plane and having an horizontal joint permitting adjustment of the outer part of said frame in said plane towards and away from said socket member, a vertical pinl rotatably mounted in the outer part of said frame, and means for pivotaily mounting said device upon said pintor angular adjustment-,relative vice having twosight openings and means for eiecting fusion in the eyes of the viewer, of the images seen by his two eyes therethrough, and an adjustable fixture supporting said device, a socketmember adapted to be secured to a xed support, a vertical member pivotally mounted thereirna jointed frame pivoted thereto for partial rotation in a vertical plane and having an horizontal joint permitting adjustment ofthe outer part of said frame in said plane towards and away from said socket member, a vertical pin rotatablymounted in the outer part of said screen is required and only half the area of the normal size of each individual frame, and' rhalf the area of the screen being used, provided y the usual proportion of length to breadth of the is retained.

individual picture ALAN PHILIP FRANKLIN.

Images