Improvements in Apparatus for Taking Stereoscopic Photographs and for Exhibiting the same.
Year: 1899

page_text: Date of Application, 29th Mar., 1899-Accepted, 20th May, 1899
COMPLETE SPECIFICATION.
Improvements in Apparatus for Taking Stereoscopic Photographs
and for Exhibiting the same.
1, WILLIAM KENNEDY-LAURIE DICKSON, of 18 and 19, Great Windmill Street,
near Piccadilly Circus, London, Gentleman, 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:-
My invention relates to improvements in apparatus for taking stereoscopic photo-
graphs and for exhibiting the same, and consists in the provision of means for
varying the angle of divergence between the axes of the pencils of light by which
the twin stereoscopic pictures are produced, or transmitted to the eye, without
varying the distance between the twin images on the photographic plate, or on the
stereoscopic picture card, and for bringing the centers of the images on the photo-
graphic plate much closer together than the distance between the axes of the
pencils of light by which said images are produced, and for obviating the neces
sity of cutting apart, transposing, and reconnecting the twin pictures of photo-
graphic prints made from a stereoscopic negative, in order to prepare the same for
exhibition; in the provision of means for varying the distance between the twin
lenses and generally in the novel combination, construction, and arrangement of
the parts.
In the taking of stereoscopic photographs it is sometimes desirable to vary the
angle of divergence between the axes of the pencils of light by which the twin
images are produced, so as to exaggerate or diminish the effect of perspective pro-
duced. In the taking of consecutive series of stereoscopic pictures of moving objects,
such as are to be employed in the reproduction to the eye of the movements of
such objects in what are known as consecutive view or moving picture apparatus.
it is very desirable to bring the twin images much closer together upon the photo-
graphic plate or film then the distance between the axes of the pencils of light
by which those images are produced. The photographs usually employed in con-
secutive view apparatus are comparatively small, and if the distance between the
centers of the twin images produced by a stereoscopic consecutive view camera be
the same as the distance between the centers of the lenses of an ordinary stereo-
scopic camera, there is a great waste of film, and the inertia of the excessively
wide strip of film seriously interferes with the taking of pictures in such rapid
succession as is desirable for the production of the desired effects. Furthermore,
in the making of stereoscopic pictures from ordinary stereoscopic negatives it is
necessary to ut apart the twin pictures of the photographic print, transpose
them, and reconnect them or mount them side by side on a common support. It
is impracticable to do this with the large number of prints required for a single
set of pictures of a consecutive view exhibiting apparatus.
The objects of my invention are, first, to provide means for varying, in stereo-
scopic cameras, or exhibiting apparatus, the degree of perspective effect produced,
and for bringing the images much closer together than is ordinarily the case in
stereoscopic negatives or pictures, such images, however, being in fact substan-
tially the same as though observed from points more widely separated than the

page_text: actual distance between their centers; second, to provide means for obviating the
necessity of transposing the twin pictures of stereoscopic photographic prints;
and third, to make the apparatus simple, durable, efficient, and as inexpensive as
possible.
These objects are attained in the invention herein described and illustrated in
the drawings, which accompany and form a part of this specification, in which
the same reference numerals indicate the same or corresponding parts, and in
which:
-
Fig. 1 is a plan view of the lens mountings, prisms, and connected parts of a
stereoscopic photographic apparatus embodying my invention, detached from the
camera, a portion of the front board only of which is shown in section; Figure 2
is a side view of the parts shown in Figure 1, taken from the right of Figure 1:
Figure 3 is a front view of the parts shown in Figure 1, said parts having been
inverted and Figure 4 is a diagram illustrating the action of the apparatus.
In the drawings, 1 and are the lens tubes of two twin photographic lenses.
They are telescopic, and racks 2 and 24, a pinion shaft having a thumb serew 3',
and pinions and are provided, for the purpose of focussing the lenses. In
front of the lens tubes are mounted refleeting prisms 5 and 5'. The prism 5' may
be secured directly to its lens tube, while the prism 5 may be mounted upon guide
rods 6 in such manner that it may be moved toward or from its lens tube upon said
rods. The length of the guide rods is such that the distance between the reflected
extensions of the optical axes of the lenses may be at least as great as the distance
between the axes of the lenses of an ordinary stereoscopie camera.
In Figure 1, and also in Figure 1, the lines and 7 represent the axes of the
lenses, the distance being the distance between them. The lines 8 and 8 repre-
sent reflected extensions of these axes, and proceed from the central point of the
reflecting surfaces of the prisms 5 and 5. The lines 8 and 81 may be termed
reflected optical axes. The distance is the distance between the lines 8 and S¹.
It is apparent that the distance y may be varied by moving the prism 5 in or cut
on its guides 6, without altering the distance. The images projected upon the
sensitive plate within the camera are substantially the same as the images which
would be observed from points on rearward extensions of the lines S and 81, and
differ from each other to the same extent that the images which might be seen
from rearward extensions of the lines 8 and 8', if the prisms were removed. would
differ. By moving the prism 5 in or out, therefore, the angle of divergence
between the pencils of light by which the different images reflected on to the
sensitive plate within the camera are produced, may be varied; and by varying
this angle of divergence the degree of the perspective effect produced is varied.
The distance y, when measured close to the prism, is the measure of this angle
of divergence, and also serves, by comparison with the distance r. to show the
degree of concentration of the images upon the negative plate which results from
the use of the prisms. From Figure 4 it is evident that the images on the
negative are very much closer together than would be the case if an ordinary
stereoscopic camera, the axes of the lenses of which are as far apart as the lines
and 81, were used, while the effect of perspective obtained is the same as would be
obtained by the use of an ordinary stereoscopic camera with the axes of its lenses
as far separated as are the lines 8 and 81. The reflection of the pencils of light
by which the twin images are produced necessarily results in a crossing of the rays
of each of said pencils, and, therefore, results in the reversal, in the negative, of
the relations of right and left of the image from those relations which would exist
in a negative made by an ordinary camera. This, however, is an advantage; for
prints made from stereoscopic negatives produced in an ordinary stereoscopic
camera must be cut apart, do that the twin pictures may be transposed and then
reunited by mounting upon a common backing. This is well known. The nega-
tive made in a stereoscopic camera constructed in accordance with my invention
are printed from with the emulsion side of the negative turned away from the
sensitive side of the positive. Were an ordinary stereoscopic negative printed

page_text: trom in this manner, the right and left of each image would be transposed with
respect to the right and left of the object photographed; but by reason of the
reversal which takes place in the reflecting prisms, prints made in the manner
described from negatives produced in my camera have the correct relation of right
and left in each image as well as the correct relation of the two images. Projec-
tion printing is however, preferable.
It is sometimes desirable to adjust the distance between the lenses, as the size
off image produced sometimes varies, and for this reason the lens tubes are
mounted in separate slides 9 and 91, mounted in grooves in a plate 10 itself arranged
to slide in a direction at right angles to the direction of motion of the slides 9
and 9', in grooves in a base plate 11, adapted to be secured to the front board of
the camera.
While this invention has been shown as applied to a photographic camera, it
may equally be applied to a stereoscopic exhibiting apparatus. if desired: though
ordinarily this will not be necessary. Instead of employing reflecting prisms, as
shown. mirrors may be used, the mirrors being equivalents of prisms.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The combination, with a stereoscopic apparatus, of reflectors located in the
paths of the pencils of light by which the twin images are produced or observed.
one of said reflectors being adjustably mounted. substantially as described.
2. The combination, with a stereoscopic apparatus, of reflecting prisms located
in the paths of the pencils of light by which the twin images are produced or
observed, one of said reflecting prisms being adjustably mounted, substantially as
described.
3. In a stereoscopic camera, the combination, with the lenses, of reflectors
located in the path of rays of light passing through said lenses, one of said
reflectors being adjustably mounted, substantially as described.
4. In a stereoscopic camera, the combination, with the lenses, of reflecting
prisms intercepting the axes of said lenses and adapted to reflect rays of light
passing through the lenses, one of said prisms being adjustably mounted, substan-
tially as described.
5. In a stereoscopic camera, the combination, with the lenses and lens mount-
ings, of reflecting prisms intercepting the axes of said lenses and adapted to reflect
rays of light passing through the lenses. one of said prisms being adjustably
mounted upon guides carried by the corresponding lens mounting, and adapted
to permit adjustment of said prism in the direction of the axis of its corresponding
lens, whereby the angle of divergence of the pencils of light by which the twin
images are produced may be varied. substantially as described.
6. In a stereoscopic camera, the combination, with the lenses movably mounted
and adapted to be adjusted laterally, of reflectors located in the path of rays of
light passing through said lenses, one of said reflectors being movable so as to
permit adjustment of the distance between the reflected optical axes of the lenses,
substantially as described.