Improvements in Means or Apparatus for Viewing Stereoscopic and other Pictures.
Year: 1897

page_text: Date of Application, 25th May, 1897
Complete Specification Left, 28th June, 1897-Accented 31st July 1807
PROVISIONAL SPECIFICATION.
Improvements in Means or Apparatus for Viewing Stereoscopic and
other Pictures.
I, THOMAS CUNNINGHAM PORTER, of Eton College, in the County of Bucks, Master
of Arts, do hereby declare the nature of this invention to be as follows:-
The object of the present invention is to enable a number of persons assembled
in one room to view pictures, in stereoscopic relief, and otherwise, projected by
optical lanterns or similar apparatus.
My invention consists first in projecting onto a screen two stereoscopic pictures,
or a succession of such pictures, alternately, and in providing means whereby one
eye sees one picture or set of pictures only and the other eye sees the other picture
or set of pictures only.
One method of carrying my invention into effect is as follows:-In front of the
two lenses of the lantern or lanterns I mount a revolving disc which has portious
removed forming apertures so that as the disc revolves first one picture and then
the other is projected upon the screen, one picture only being projected at a time.
This disc has a second set of apertures arranged circumferentially in two concentric
rings and at such a distance apart that each eye looks through one ring of apertures;
or the apertures which serve for the lanterns may also serve for the eyes. These
apertures are so arranged in relation to each other that when one picture is on the
screen it is seen by one eye only the other eye having in front of it a solid portion
of the disc. It will be understood that when the disc is rotated rapidly the images
or pictures are changed so quickly that apparently the eyes are looking at a
stationary picture having the usual stereoscopic relief. In the method above
described one person only can view the pictures, but if a number of discs are used
for each spectator, having apertures arranged to allow each eye to view the picture
alternately, any number of persons may view the pictures at a time.
The discs for the spectators may simply have one set or ring of apertures suitably
spaced or they may have two or more sets or rings of apertures arranged con-
centrically in which latter case two or more persons could look through one disc.
These discs would be driven in correct relationship with the disc in front of the
lanterns.
It will be understood that I may employ hands, shutters or other means of inter-
rupting the rays from the lanterns and the vision so long as each eye sees its own
icture alternately and in rapid succession.
By means of my invention I am able to produce moving pictures having stereo-
scopic relief. The two sets of pictures are produced on two separate films or on
ue film which is afterwards divided lingitudinally and the first picture on each
lm is viewed by each eye respectively in succession, then the second two pictures
y each eye in succession and so on. In some cases I prefer to produce the pictures
the film with interspaces between the successive pictures.
My invention may be employed to produce stereoscopically coloured pictures by
ny of the well known processes.

page_text: Another method of carrying my invention into effect is to project onto the screen
two entirely different pictures which when viewed direct or through the disc with
both eyes appear mixed or blended so that neither picture can be seen. If, however,
when looking through the disc, one eye be closed, one picture will be seen distinctly
by the other eye, and upon closing this eye and opening that previously shut the
other pictures will be clearly visible.
Improvements in Means or Apparatus for Viewing Stereoscopic and
other Pictures.
I, THOMAS CUNNINGHAM PORTER, of Eton College, in the County of Bucks, Master
of Arts, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:―
The object of the present invention is to enable a number of persons assembled
in one room to view pictures, in stereoscopic relief, and otherwise, projected by
optical lanterns or similar apparatus.
My invention consists first in projecting onto a screen two stereoscopic pictures,
or a series of such pictures, alternately and in rapid succession, and in providing
means whereby of the two pictures or sets of pictures projected one eye sees one
picture or set of pictures only and the other eye sees the other picture or set of
pictures only.
One method of carrying my invention into effect is as follows:-In front of the
two objectives of the lantern or lanterns I mount a revolving disc having portions.
removed forming slots or apertures so that as the disc revolves first one picture and
then the other is projected upon the screen, one picture only being projected at a
time. This disc has a second set of slots or apertures arranged circumferentially
in two concentric circles at such a distance apart that each eye of an observer may
view the projected image through one of the two circles of apertures forming the
said second set; or, the slots or apertures which serve for the lantern objective may
also serve for the eyes of the spectator. These slots or apertures are all so arranged
in relation to each other that when one picture is on the screen it is seen by one
eye only the other eye having in front of it a solid portion of the disc. It will
lie understood that when the disc is rotated rapidly the images or pictures are
changed so quickly that apparently the eyes are looking at a stationary picture
having the usual stereoscopic relief. In the method above described one person
only can view the pictures but if a number of discs are used, one for each spectator
or group of spectators, having slots or apertures arranged to allow each eye of an
observer to view the projected picture alternately, any number of persons may view
the pictures at a time.
The discs for the spectators may simply have one circle of slots or apertures
suitably spaced or they may have one or more sets of slots or apertures arranged
concentrically, each set comprising two circles of slots or apertures, in which latter
case two or more persons could look through one disc. These discs would be driven
in correct relationship with the disc in front of the lanterns.
It will be understood that I may employ perforated brands, vibrating or oscillating
shutters, or other means of intercepting the rays from the lanterns and the vision,
so long as each eye sees its corresponding icture alternately and in ravid succession.

page_text: By means of my invention I am also able to produce moving pictures having
stereoscopic relief. The two series of stereoscopic pictures are produced on two
separate films, or on one film which is afterwards divided longitudinally, and the
first picture on each film is viewed by each eye respectively in succession, then the
second stereoscopic pair by each eye in succession and so on. In some cases I
prefer to produce the pictures on the film with interspaces between the successive
pictures, so that as the pair of films are moved across the two objectives a blank
space will be opposite one objective whilst a picture is being projected through the
other. The movement of the pair of films across the objectives at the correct speed
may be effected by any of the usual devices employed in Cinematographs.
Another method of carrying my invention into effect is to project onto the screen
alternately and in rapid succession two entirely different pictures which when
viewed direct or through the perforated revolving disc with both eyes appear mixed
or blended. If, however, when looking through the disc one eye be closed, one
picture will be seen distinctly by the other eye, and upon closing this eye and
opening that previously shut the other picture will be clearly visible. The picture
seen will of course in this case not be in stereoscopic relief.
"
three
My invention may also be employed for viewing in stereoscopic relief and other-
wise pictures projected in natural or other colours, as by the well known
colour process" for example as will be hereinafter made clear.
I will now fully describe by way of example a convenient method of carrying my
invention into effect, having reference to the accompanying drawings in which
similar letters refer to like parts in all the figures, and wherein :-
Figures 1 and 2 are diagrams illustrating a method of applying my invention to
a bi-unial optical lantern. Figure 3 is a diagram illustrating a method of applying
my invention to two optical lanterns placed side by side, and,
Figures 4 and 5 are diagrams representing suitable separate discs for use by
spectators.
Referring to Figure 1, the objectives a, a¹ of the lantern A are alternately covered
and uncovered in rapid succession, so that only one picture is projected at a time,
by means of the set of slots or apertures b, in the disc B which revolves about the
centre c. Near the periphery of this dis is a second set of slots or apertures d d
arranged in two concentric circles at such a distance apart that one eye r of a
spectator looks through one circle of apertures d. and the other eye 1,
through the other circle of apertures d¹, said apertures d, d being further
so spaced and arranged relatively to the apertures b, as shewn, that the visual rays
of each eye are alternately intercepted by solid portions of the revolving disc
synchronously with the alteration or change of the picture projected on the
screen by the lantern, the effect being that each eye views one picture only of the
two projected. To make this more clear we will assume that r 1 respectively indi-
cate the right and left eyes of the spectator and that the right eve's stereoscopic
slide is placed in the top lantern and the left eye's slide in the bottom lantern. The
dise B being in the position illustrated, the right eye will then view through the
slot, its corresponding picture projected on the screen by the objective a, and as
the disc B revolves the visual rays of this eye will be intercepted by a solid portion
of the disc and the left eye uncovered by a slot d¹, at the same time the top
obiective a, will be covered and the lower objective a¹ uncovered so that the left eve
will in turn view its corresponding picture projected on the screen, and, the disc B
being revolved at a sufficient speed, the effect to the observer will be that of viewing
a stationary picture in stereoscopic relief. The best position for the disc B in every
case is that either in front of the lenses or between the combinations, wherein the
whole of the pencils of light rays from each lantern come to a focus in the plane of
the disc, this disposition permitting the length of the slots or apertures in the disc
to be increased relatively to the opaque spaces between them so as to avoid loss of
light. The dimensions of the apertures in figures 2, 3, 4 and 5 have been calcu-
lated upon this supposition.
The diagram Figure 2 clearly shews how one and the same set of slots or aper-

page_text: tures d, arranged in two concentric circles' in 'the disc B may be utilised for
alternately covering and uncovering the lantern objectives and the eyes of the
observer.
The diagram Figure 3 shews 'a disc B similar to that represented in Figure 1
(ie., having separate sets of slots or apertures for the lantern objective and the
observer's eyes), arranged for use with two separate lanterns A A' disposed side by
side. This arrangement is especially adapted to the ordinary lanterns in which
the electric are light is used. "The arrangement represented in this last mentioned
figure would necessitate the picture corresponding with the right eye being placed
in the left lantern. There is no need for the lanterns being placed symmetrically
with respect to the centre of the disc, as shewn in Figure 3, as it is obviously casy
to modify the circles of slots or apertures for many other arrangements.
The diagrams Figures 4 and 5 represent suitable separate revolving discs for use
by spectators.
In Figure 4 the alternate interception of the vision of each eye is effected by
one circle of slots or apertures only, the screen being viewed through the top
or bottom of the dise B so that each aperture & travels across both eyes as the
disc revolves.
Figure 5 represents a disc adapted for simultaneous use by several observers, in this
particular arrangement four. 1 r, 111, 12 2 and 3 indicate respectively the
positions of the four, pairs of eyes which view the screen through the various circles
of slots or apertures d, arranged, as in Figures 1, 2 and 3, to intercept the vision
of each eye of a pair alternately as the disc revolves. In this figure, and also in
Figure 4, the spectator is imagined to be on the near side of the disc.
The speed of rotation of the observers' dise B' must in all cases bear such relation-
ship to that of the lantern disc B that the interceptions of the visual rays of either
eye will be synchronous with the covering of the objective with which that eye
corresponds, or, in other words the interceptions of vision must be coincident with
the change of picture on the screen, each eye will thus only view its own picture.
Fixity of relation between the speeds of the lantern and spectators discs may easily
be secured in many ways, for example by driving all the discs by suitable gearing
or.connections from the same shaft, or, if independent motors be employed, by
mounting the discs similarly with relation to the dividing line of a two part com-
mutator and adjusting the rate of rotation by a resistance. In practice I find
it very easy to arrange that the discs shall rotate either at the same rate, or one at
a simple multiple of the other's rate, for a practically indefinite period, especially
if the small motors employed be similar and the discs of the same dimensions and
weight. A glance through the lantern disc at any of the spectators discs will shew
at once if the disc viewed is revolving at the correct speed, for if one revolving disc
be viewed through another, black bands, which I call interference banas. will 4
appear to radiate from the centre of the disc viewed like the spokes of a wheel, and
if the discs are not perfectly adjusted as to relative speed these bands will appear to
rotate, whilst if the speed adjustment is perfect they will apparently be quite
stationary. The discs or other shutter devices employed may be enclosed within
transparent casings or may be viewed through suitable eyeholes.
It will be noted on referring to Figure 5 that one circle of slots or apertures is not
being used by any of the observers, this circle of slots is not, however, entirely useless
as besides reducing the weight of the disc it might be used in the event of the
transposition of the slides in the lantern, the observers in this. case, moving their
eyes one circle of slots to the right or left as most convenient..
A powerful illuminant such as lime light or the electric arc light being used
in the lantern, flickering of the image entirely vanishes when the discs are rotated
at a very moderate speci.
4
5
In adapting my invention for viewing in stereoscopic relief pictures projected in
their natural or other colours by the well known "three colour process
" wherein. 5
the complete picture is built up from three precisely similar superposed pictures
each of a different monochrome, such as red, yellowish green and bluish violet,

page_text: each stereoscopic pair would require to be projected through two sets of three
objectives each in lieu of through two objectives, one set of objectives projecting the
three different monochromes of one slide and the other set projecting those of the
other slide. This may obviously be readily done--for example, imagine three pre-
cisely similar devices such as represented in Figure 1 or in Figure 2 to be placed
side by side, let the three different monochromes of one stereoscopic slide be placed
in the three top lanterns respectively and let those of the other slide be placed in
the three botton lanterns respectively, then if the three discs B be revolved at
precisely the same speed, first the coloured picture produced by the blending of one
set of monochromes and then that produced by the blending of the other set will
be alternately projected on the screen in rapid succession and the observer will view
a coloured picture in stereoscopic relief. Or in lieu of stereoscopic slides, two
entirely different pictures cach built up from superposed monochromes' may
obviously be projected on the screen in colours natural or otherwise and viewed
as hereinbefore described.
Although I have represented perforated discs as a convenient method of carrying
out my invention I do not confine or limit myself to their use it being obvious that
perforated moving bands, or vibrating or oscillating shutter devices might be
substituted for alternately covering and uncovering the two lantern objectives and
the two eyes of a spectator synchronously for the purposes of the invention as set
forth.
In Figure 6, B is a rectangular box of convenient size, h h holes in the side of b,
opposite to ele the position in which the spectator's eyes are to be placed. SS are
shutters capable of covering or uncovering the holes h¹². The picture when being
viewed will occupy the position 1. If each of the complementary pair of
stereoscopic pictures is made to take the position P alternately and in quick succes-
sion, it is evident that if the eye of the observer at el only sees one picture of the
complementary pair of stereoscopic pictures and the eye of the observer at c² sees
only the other picture of the pair the stereoscopic effect will be produced. This
result can easily be obtained by arranging mechanically that when one picture is
in position at P, the shutter S obscures the eye at c' and when the other picture is
in position the shutter $2 obscures the eye at e². Lenses may be used in the
holes h¹ h2.
It is obvious that many variations may be made in applying my invention and I
do not confine myself to the particular methods described, for example it is clear
that my invention could be used with only one lantern instead of two, for the
complementary slides could easily be arranged to pass alternately or in any desired
manner and at any desired time into position in the lantern.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:-
1. The process of displaying stereoscopic pictures consisting in bringing into the.
field of vision of an observer alternately and in quick succession each of two com-
plementary stereoscopic pictures the eyes of the observer being so screened that one
eye sees only one of the pair of pictures and the other eye sees only the other of
the pair of pictures.
2. The process of displaying stereoscopic pictures in a cinematograph consisting
in so arranging the series of pictures that one of each pair of complementary
pictures in the series shall appear in the field of vision of an observer immediately
and in quick succession after the other complementary picture of the pair the eyes
of the observer being so screened that one eye can see only one of each pair of
complementary pictures and the other eye can see only the other of each pair of
complementary pictures.
3. The process of displaying pictures consisting in bringing into the field of
vision of an observer alternately and in quick succession two entirely different
pictures the eyes of the observer being so screened that either one or other of the

page_text: pictures alone or a blend or mixture of the two pictures can be seen by the observer
substantially as hereinbefore described.
Apparatus for the purpose set forth consisting of one or two optical lanterns,
devices arranged to throw upon a screen alternately and in quick succession each
picture of the complementary pair and a device adapted to alternately and syn-
chronously cover and uncover the two eyes of an observer so that each eye only views
its corresponding picture substantially as described.
5. Apparatus for the purpose set forth substantially as described and illustrated
in Figures 1, 2 and 3, of the Specification.
6. Apparatus for the purpose set forth substantially as described and illustrated
in Figure 4 of the Specification.
Dated this 28th day of Tuns 1897
-
E. P. ALEXANDER & SON,
Chartered Patent Agents,
19, Southampton Buildings, Chancery Lane, London, W.C., Agents.