IMPROVEMENTS IN STEREOSCOPIC APPARATUS
Year: 1862

page_text: LETTERS PATENT to Henry Swan, of Bishopsgate Street Without, for the
Invention of "IMPROVEMENTS IN STEREOSCOPIC APPARATUS."
Sealed the 12th May 1863, and dated the 4th December 1862.
PROVISIONAL SPECIFICATION left by the said Henry Swan at the
Office of the Commissioners of Patents, with his Petition; on the 4th
December 1862.
I, HENRY SWAN, of Bishopsgate Street Without, do hereby declare the
nature of thé. Invention for "IMPROVEMENTS IN STEREOSCOPIC APPARATUS," to be
as follows:-
According to my Invention I combine stereoscopic pictures with pieces of
glass or transparent crystal of suitable form in such manner that the pictures
which are in fact depicted on the exterior of the glass or crystal, or on surfaces
placed in contact therewith, shall produce an image apparently solid and
imbedded in the glass or crystal. For this purpose I take two prisms of
glass or crystal and place them with a side or surface of the one in contact
with a side or surface of the other. The prismis each have one of their angles
a right angle, or nearly so, and they are so placed together that they produce
a solid having parallel sides. The stereoscopic pictures are either produced
on or applied to the adjacent sides of this solid, one picture on one prism, and
the other on the other. On looking at one of the sides of the solid unoccupied
by a picture the image is seen, the light from one picture coming from it
through the two prisms and direct to one of the eyes of the observer; whilst

page_text: the light from the other picture is reflected at the surfaces of the prisms which
are in contact, and is thus directed to the other eye of the observer. The
picture which is reflected before coming to the eye will be reversed side for
side by the reflection; this is compensated for by a corresponding transposition
in the picture itself. The side of the prism through which the pictures are
viewed is conveniently made convex, the image is then seen magnified more or
less according to the degree of convexity.
The arrangement above described is suitable for pictures of. small size and
may be made sufficiently small to be worn as a locket or carried on a watch
chain.
The apparatus may also, if desired, be made of large size; it is then con-
venient to employ prisms of water contained in glass vessels, and (when a
certain size is exceeded) it becomes necessary to regulate the illumination of
the pictures so that the light coming from a direction directly or nearly directly
opposite to each picture is confined to such a space as to reach that particular
eye only for which it is intended.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry Swan in the Great Seal Patent Office on the 4th
June 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
SWAN, of Bishopsgate Street Without, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourth day of December, in the year of our
Lord One thousand eight hundred and sixty-two, in the twenty-sixth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Henry Swan, Her special licence that I, the said Henry
Swan, my executors, administrators, and assigns, or such others as I,
the said Henry Swan, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN STEREOSCOPIC APPARATUS," upon the condition (amongst
others) that I, the said Henry Swan, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,

page_text: and in what manner the same was to be performed, and cause the same to be
filed in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Henry Swan, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
According to my Invention I combine stereoscopic pictures with pieces of
glass or transparent crystal of suitable form in such manner that the pictures
which are in fact depicted on the exterior of the glass or crystal, or on surfaces
placed in contact with or at a small distance from them, shall produce an
image apparently solid and imbedded in a glass or crystal. For this purpose
a side or surface
The prisms each
I take two prisms of glass or crystal and place them with
of the one in contact with a side or surface of the other.
have one of their angles a right angle, or nearly so, and they are so placed
together that they produce a solid having parallel sides. The stereoscopic
pictures are either produced on, applied to, or placed near the adjacent sides
of this solid, one picture on one prism, and the other on the other. On
looking at one of the sides of the solid unoccupied by a picture the image is
seen, the light from one picture coming from it through the two prisms and
direct to one of the eyes of the observer, whilst the light from the other
picture is reflected at the surfaces of the prisms which are in contact, and is
thus directed to the other eye of the observer. The picture which is reflected
before coming to the eye will be reversed side for side by the reflection; this
is compensated for by a corresponding transposition in the picture itself.
The side of the prism through which the pictures are viewed is conveniently
made convex, the image is then seen magnified more or less according to the
degree of convexity.
Figure 1 is a plan, and Figure 2 is an end view, of a pair of prisms, such
as I employ, their longest sides are placed in contact the one with the other,
as the Drawings shew; one angle of each prism is a right angle, and the
other two angles 40° and 50° respectively, or thereabout. One picture of the
stereoscopic pair is either mounted or produced on one side of one of the
prisms, as is indicated by the red line at A, Figure 2, whilst the other picture
is mounted or produced on a side of the other prism, as is indicated by the red
line at B; if the observer then looks at the side C of the second prism he sees
the picture A by direct vision, and the picture B as reflected at the inclined
side of the prism at D, and these images occupying the same apparent
positions, and being stereoscopic, the effect of solidity is obtained as before

page_text: mentioned. The picture B. will be reversed side for side by the reflection, and
allowance for this effect should be made in arranging the pictures. Figure 3
is a transverse section of, the same prisms as they appear when mounted in a
manner which I have found convenient; the prisms are here mounted in a
frame a, conveniently covered with velvet, and they are retained in their
place by a shield or mat b. The back of the case c is made of white enamelled
glass, and there is a hollow in the case at d, which at the back d' is a reflector
conveniently of tin foil or white paper. In viewing the pictures the case
is held up to the light, and the light then passes in part through the white
glass, the picture A, and the prisms to the eye, and in part it passes through
the white glass and falls on the reflecting surface d¹, by this it is directed
through the picture B into the upper prism, and it is again reflected internally
on 'striking the inclined side of the prism; this last reflection directs this
portion of the light to the eye of the observer.. Figures 4 and 5 shew prisms
similar to those shewn at Figures 1 and 2, except that the side through which
the picture is viewed is made convex to magnify the pictures. In place of
mounting the prisms as above described, they are (more especially when-of
small size) conveniently mounted by surrounding the prisms on three sidės
with white enamelled glass or cornelian, leaving uncovered only. the side
through which the observer looks at the pictures. Pictures thus mounted
may be worn as lockets or carried on a watch chain.
The apparatus may also, if desired, be made of large size, it is then convenient
to employ. prisms of water contained in glass vessels, and (when a certain size
is exceeded) it becomes necessary to regulate the illumination of the pictures
so that the light coming from a direction directly or nearly directly opposite
to each picture is confined to such a space as to reach that particular eye only
for which it is intended.
In witness whereof, I, the said Henry Swan, have hereunto set my
hand and seal, this Third day of June, in the year of our Lord
One thousand eight hundred and sixty-three.
HENRY SWAN. (L.S.).