An Improved Method or System by Means of which Pictures Pro- jected upon a Screen from an Optical or Magic Lantern Lanterns are seen in Relief or with Stereoscopic Effect.
Year: 1898

page_text: Date of Application, 24th Jan., 1898
Date of Application, 24th Jan., 1898
Complete Specification Left, 22nd Oct., 1898—Accepted, 20LN NOV., 1898
An Improved Method or System by Means of which Pictures Pro-
jected upon a Screen from an Optical or Magic Lantern
Lanterns are seen in Relief or with Stereoscopic Effect.
or
I, JOHN ANDERTON, of 142, Suffolk Street, Birmingham, in the County of War-
wick, Scientific Instrument Maker, do hereby declare the nature of this invention
to be as follows:-
This invention has for its object certain improvements upon the method or
system by means of which pictures projected upon a screen from an optical or
magic lantern or lanterns are seen in relief or with stereoscopic effect as described
in my former Specification of Patent bearing date the 7th day of July 1891 and
numbered 11,520.
In the above referred to specification it states that the images of the two stereo-
scopic slides each polarised in a plane at a right angle to the
other are projected and superposed on a screen of ground glass, metal
or any other substance or material that will not depolarise or elliptically or
circularly polarise the images it received. Preferably a calico screen covered with
dead silver paper is used. Now the dead silver paper referred to although serving
the purpose of reflecting the polarised light as received possesses certain defects
namely. The squares of silver leaf composing it are visible and greatly mar the
effect of the pictures projected upon it. Further the nature of its reflecting
surface causes a deficiency of lateral reflection and consequently the stereoscopic
pictures cannot be seen with proper effect, excepting when the observer or
observers are stationed within a certain limited space directly in front of the
screen. In other positions the pictures would appear darker than when seen from
a front position and also uneven in illumination, the side farthest from the
observer appearing darker than the side nearest to him.
In order to obviate these defects I cover the silver surface of the screen with
perpendicular lines or striations, the angle at which a bright and effective view
of the stereoscopic pictures may be seen being largely extended and the solidity and
general effect of the pictures is also improved by this means when seen from a
position directly in front of the screen.
An important point in my present improvements is the use of polarisers and
analysers in conjunction with a lined or striated metallic screen with the object
of obtaining stereoscopic effects from pictures projected upon such screen.
A further improvement upon my said prior patent consists in provision being
made for the protection of the thin glass plates of which the polarisers and
analysers may be composed from the action of the atmosphere and consequently
moisture becoming gradually condensed upon the inner surfaces thereby render-
ing them dim and practically useless. My present improvements in this respect
consist in covering the edges of the said thin plates with cement that will not
itself decompose, and will also sufficiently exclude the air, and again by cement-

page_text: lateral reflection and consequently the stereoscopic pictures projected upon it
cannot be seen with proper effect excepting when the observer or observers are
stationed within a certain limited space directly in front of the screen. In other
positions the pictures would appear darker than when seen from a front position
and also uneven in illumination, the side farthest from the observer appearing
darker than the side nearest to him.
It is to obviate these defects that my present improvements apply. I cover the
silver surface of the screen with perpendicular lines or striations the angle at
which a bright and effective view of the stereoscopic pictures may be seen being
largely extended, and the solidity and general effect of the pictures is also greatly
improved by this means when seen from a position directly in front of the screen.
An important point in my present improvements is the use of polarisers and
analysers in conjunction with a lined or striated metallic screen with the object of
obtaining stereoscopic effects from pictures projected upon such screen.
A further improvement upon my said prior patent of 1891 consists in pro-
vision being made for the protection of the thin glass plates of which the
polarisers and analysers may be composed from the action of the atmosphere and
consequently moisture becoming gradually condensed upon the inner surfaces,
thereby rendering them dim and practically useless. And my said improvements
in this respect consist in covering the edges of the said thin plates with cement
that will not itself decompose and will also sufficiently exclude the air, and again
by cementing the plates within a metallic frame mount or case as a further pro-
tection from deterioration, from condensation of moisture or from other cause or
causes.
Furthermore the thin glass plates were previously in my former specification
arranged at slightly varying angles to each other in order to distribute the
multiple reflection from the inner surfaces; this was effected by inserting thin
strips of metal or other material between the glass plates but at one end only.
An improvement upon this method consists in alternating the strips of metal or
other material for tilting the glass plates. I will here draw attention to the
diagram annexed in which "A represents the lens or objective of the tube "B"
of the lantern, "C," "C" is the mount or case into which the thin glass
plates "]" are cemented "E" represent strips of metal or other material placed
alternately at the top and bottom in order to give the thin glass plates "D"
different angles in the same plane for the purpose of producing the effect already
referred to.
"
As seen from "A." For example a strip "E" of metal or other material is
placed between the glass plates 1 and 2 "D on the right hand in the case
"C"
then a strip of metal "E" or other material is placed between the glass plates 2
and 3 "D" on the left hand in the case C" and again between plates 3
and 4 D" on the right hand and so on until the bundle of plates is completed.
By arranging the plates as described and shewn a well defined image is obtained.
I may sometimes deem it advisable to somewhat modify the details and arrange-
ment above set forth without however departing from the essential features of
my invention, but
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:-
Firstly. The scientific arrangement of the several parts forming an apparatus
for obtaining by polarisation or partial polarisation of the light a stereoscopic
effect from two pictures or such like projected upon a screen or elsewhere and
forming thereby a method or system by which such pictures or other objects
being so projected from an optical or magic lantern or lanterns or by analogous
means are seen in relief or with stereoscopic effect, substantially, as herein more
fully set forth and described.
Secondly. In connection with an apparatus for obtaining by polarisation or
partial polarisation of the light a stereoscopic effect from two pictures or the like