Improved Lenses and Reflectors for Radiant Energy.
Year: 1893

page_text: Date of Application, 3rd Jan., 1893—Accepted. 18th Mar., 1893
COMPLETE SPECIFICATION.
Improved Lenses and Reflectors for Radiant Energy.
I ALBERT EDGAR ALEXANDER, of 19 Southampton Buildings, in the County
of Middlesex, Fellow of the Chartered Institute of Patent Agents, do hereby
declare the nature of this invention (communicated to me from abroad by Charles
Frederic Crowell, Cashier, Francis Doane, Stationer and Melvin Linwood Severy,
Stenographer, all of 31 Milk Street, Boston, in the County of Suffolk and Common-
wealth of Massachusetts) 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 this invention is the production, in devices for reflecting or
refracting radiant energy, of curved surfaces by means which enables such surfaces
to be formed more cheaply and of larger size than heretofore and also increases the
efficiency of the reflecting or refracting device.
To this end the invention consists :-
:-
First In a chamber having a curved reflecting surface which surface is given
the desired curvature by establishing a difference of pressure between the contents
of the chamber and the external medium as will be hereinafter more fully set
forth.
Second-In a chamber having a curved surface or curved surfaces forming the
boundary or boundaries to a refracting medium within the chamber, which surface
is given the desired curvature by establishing a difference of pressure between
the contents of the chamber and the external medium as will be hereinafter more
fully set forth.
Third: In the combination with the chamber having a curved or reflecting
surface or a curved surface or curved surfaces forming the boundary or boundaries
to a gaseous or liquid refracting medium within the chamber, of a compensating
device connected therewith whereby the contents of the chamber can be maintained
at a uniform density notwithstanding the changes in temperature or the barometric
changes to which the contents of the chamber are exposed.
Fourth-In the combination with the above described chamber of a compensating
chamber, connected therewith and means for varying at will the pressure in the said
chamber whereby the contents of the larger chamber can be maintained at a uniform
density, notwithstanding the changes in temperature, or the barometric changes to
which the contents of this chamber are exposed.
In the accompanying drawing are shown several devices which embody the
principle of this invention.
In this drawing
Fig. 1, is a sectional view of a chamber transparent to radiant energy and having
curved surfaces which are convex to one another.
Fig. 2, is a sectional view of a chamber transparent to radiant energy and having
curved surfaces which are concave to one another.
Fig. 3, is a sectional view of a chamber having one curved surface transparent to
radiant energy.
Fig. 4, is a sectional view of a chamber having a curved reflecting surface.
Fig. 5, is a view of the compensating chamber.
Fig. 6, is a view of another form of compensating chamber.
Fig. 7, is a sectional view of the packing rings.
In these several figures the same letter refers to the same parts.
The chambers which are transparent to radiant energy are formed of two elastic

page_text: parallel plates, or membranes, of any suitable substance transparent to the form of
radiant energy which is to be refracted, each having its sides parallel, said plates
or membranes being supported at any desired distance from one another in a ring and
hermetically sealed therein.
If the form of radiant energy which is to be refracted is light, the plates will be
made of glass or of some other substance which is transparent to light; if heat,
they may be made of ebonite or of some resinous substance; .if actinic energy, of
some substance which is transparent to actinic energy, as glass; and if sound, of
membranes, or other suitable substance.
If it is desired that these plates should be concave to one another the space
between the plates is filled under pressure, with any gas or liquid denser or rarer
than the surrounding medium according as it is intended to produce convergence or
divergence, and this pressure causes the surfaces to become curved. If it is intended
to produce surfaces convex to one another the chamber is wholly or partially
exhausted of its previous contents until the pressure of the external medium upon
the elastic and yielding plates causes the required concavity. In this case the
chamber may be filled with any suitable gas or liquid, or a vacuum may be formed
in any manner, within the chamber.
The same principle can be carried into effect in the production of curved reflecting
surfaces, either convex or concave, and this result when it is desired to reflect light
may be accomplished by the use, for one of the walls of the chamber, of an elastic
and yielding plate suitably silvered, and then producing the desired curvature in
this plate by causing a difference of pressure between the contents of the chamber
and the surrounding medium.
The walls of the chamber may be made of glass and the chamber be filled with
mercury or any other reflecting substance, for the form of radiant energy which is
reflected as this invention is applicable to devices for reflecting any form of radiant
energy, or the curved wall may be itself the reflecting surface, or be silvered.
The accompanying drawing shows a device by means of which my invention is
carried into effect,-
A, A, are two plates of any elastic material transparent to the form of radiant
energy which is to be refracted as for example, for light we use plates of glass.
The surfaces of these plates are parallel, and the plates are parallel to one another.
B, B, are two external rings of metal or of other suitable material which project
beyond the edges of the plates, and C, is the central ring between the plates and
the external rings. This ring C, is of less width horizontally than the rings B, B,
and it may be of any desired vertical width, as for example, of the width shown in
Fig. 3, where the ring is shown as conical. Between the rings and the edges of
the plates are placed rings D, D, of some suitable packing material which forms a
packing hermetically tight to the contents of the chambers, and also permits the
edges of the plates to yield when the plates are curved, by the pressure from within
or without. Inserted in the ring C, and communicating with the chamber is a
tube E, by means of which the chamber can be exhausted. This tube is capable of
being hermetically sealed. F, is a ring which is placed around the chamber between
the rings B, B, and G, is a suitable screw by means of which the rings can be
clamped together. The tube E passes through the ring F.
It is preferable that the faces of these rings D, D, should be concave, and that
the face of C, should be convex as shown in Fig. 7, thus. permitting the edges of
the plates when the plates are pressed upon, either outwardly or inwardly, to
conform to the surface of the ring. It is desirable that .the inner surface of the
rings B, B, should be convex, for the same reasons.
Any other device may be used for clamping the plates together...
The liquid or gas used as the refracting medium is supplied under pressure by.
means of any suitable air compressor or by a pump, and the plates are thus caused
to bulge ontwards, as shown in dotted lines in Fig. 1. When the desired convexity
is obtained the tube is closed, or sealed.

page_text: When the contents of the chamber are exhausted the plates become concave as
shown in dotted lines in Fig. 2.
For the reason that the plates have parallel surfaces, radiant energy will pass
through the plates without convergence or divergence, and they serve merely as
boundary surfaces to the refracting medium contained in the chamber. By means
of this device, media not generally used for the purpose can be availed of as
refracting media.
For example, a chamber filled with hydrogen, and having its
glass surfaces rendered concave, will be convergent to rays of light passing from
the air or from a medium denser than hydrogen.
: :
This concave converging and convex diverging lens is believed to be new.
For the reason that variation in temperature and barometric changes will produce
variations in the density, or pressure of the contents of the chamber, we provide a
device by means of which the contents of the chamber may be maintained at a
uniform pressure.
This device consists of a small chamber H, which is in communication with the
larger chamber and has one of its walls formed by an elastic diaphragm I, which
can be depressed at will by means of a set screw J. Or the device may be any
other suitable compensating chamber, as for example the device shown in Fig. 6,
which consists of a bulb of any suitable material communicating with chamber so
that when the contents of the chamber expand, the bulb in communication there-
with will expand and receive a portion of the contents of the larger chamber.
Such a compensating device can be applied to any lenses containing liquids or
gases.
In the chamber shown in Fig. 3, only one of the plates is curved, for the reason
that the focus is formed within the refracting medium contained in the chamber.
A refracting chamber of this character is, we believe new.
In this chamber the surface upon which the rays are incident will be convex or
concave according as the pressure in the chamber is greater or less than that of the
surrounding medium.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:
First In a device for reflecting and refracting radiant energy, a chamber
enclosing a fluid, and having a lenticular surface or surfaces, the convexity or con-
cavity of the surface or surfaces being maintained by a difference of pressure
between the enclosed and external media, substantially as shown and described.
Second-The combination substantially as and for the purpose set forth, of two
opposite flexible or elastic plates, separated from one another; a suitable wall or
ring embracing the edges of said plates, and means for establishing a difference of
pressure between the medium enclosed by these plates and the medium in juxta-
position to their outer surfaces.
Third The combination, substantially as and for the purpose set forth, of the
opposed flexible or elastic plates A, A, having surfaces parallel to one another;
the rings, B, B, the ring C; the packing rings D, D; the tube E; the ring F; and
screws G.
Fourth-The combination, substantially as and for the purpose set forth, of the
parallel flexible or elastic plates A, A, having surfaces parallel to one another; the
rings B, B; convex on their inner sides; the ring C, convex on its face, and
the packing rings, D, D, concave on their faces.
Fifth The combination, substantially as and for the purpose set forth, of a
chamber having a lenticular surface or surfaces; a secondary chamber connected
with the first mentioned chamber; a movable wall to the secondary chamber and
a device for moving said wall.
Sixth The combination, substantially as and for the purpose set forth, with the
chamber formed of opposed flexible or elastic plates having their edges clamped by

page_text: a suitable wall or ring, of the secondary chamber connected with the first mentioned
chamber; the movable diaphragm I, forming one of the walls of the secondary
chamber, and a screw for moving the diaphragm.
Dated this 3rd day of January 1893.
A. E. ALEXANDER, Fel. Chartered Inst. P.A.,.
19, Southampton Buildings, London, W.C.