Improvements in Projection Lanterns and Polariscopes.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in Projection Lanterns and Polariscopes.
I WILLIAM ISAAC CHADWICK of 2 St. Mary's Street, Manchester, Scientific
Instrument Maker, do hereby declare the nature of this invention to be as
follows:-
My said invention relates to improvements in projection lanterns and polariscopes
to be used therewith.
The object of my said invention is to provide a projection lantern having a
polariscope for projection purposes so arranged that the same source of light and
the same condenser may be used for projecting either a direct picture through a
projection objective or through a polariscope without deranging or affecting the
adjustment of either the objective or the polariscope.
According to my said invention I mount on the front of the lantern a projection
objective and a projection polariscope. In front of the condenser I provide a
movable mirror or mirrors by which I am enabled to transmit the light either
through the projection objective or on to or through the polariser of the polariscope
according as the polarising effect is produced by reflection or refraction.
Means are provided for readily adjusting the polariser and for holding the
objects to be projected.
Dated Sirth don of Februar 1805
E. T. WHITELOW, A.M. Inst. C.E.,
70 Deansgate, Manchester, Agent for the Applicant.
I WILLIAM ISAAC CHADWICK of 2 St. Mary's Street, Manchester, Scientific
Instrument Maker, 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 and accompanying drawings to which reference
is hereinafter made :-
My said invention relates to improvements in projection lanterns and polariscopes
to be used therewith.
The object of my said invention is to provide a projection lantern having a
polariscope for projection purposes so arranged that the same source of light and
the same condenser may be used for projecting either a direct picture through a
projection objective or through a polariscope without deranging or affecting the
adjustment of either the objective or the polariscope.
According to my said invention I mount on the front c of the lantern a
projection objective a and a projection polariscope b. In front of the condenser
(indicated by dotted lines at d) I provide a movable mirror e. When the mirror
is removed as in Fig. 1 the light from the condenser passes directly to the
projection objective a. When the mirror is inserted as in Fig. 2 with the reflective

page_text: surface downwards the light is reflected downwards on to a reflecting polariser f
and thence through the polariscope b. The form of polariser I find most
convenient is a bundle of glass plates and by means of a projection from the
polariser engaging with an adjusting screw g I am able to readily adjust the
polariser to the most suitable angle. In case a refraction polariser such as a
Nicol prism is used at the rear of the polariscope a mirror or right angled prism is
substituted for the polariser f in order to receive the light from the mirror e and
transmit it through the polariser.
The usual means are provided for holding the objects to be shown.
For vertical projection which is desirable in some cases the mirror e is reversed
and placed in the position shown at el in Fig. 1 in order to throw up the rays
vertically to a right angled prism /.
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 1
claim is-
1. A combined direct projection and polarising lantern substantially as herein-
before set forth.
2. In an optical lantern a direct projection objective and a polariscope parallel
thereto in combination with a movable mirror and condenser substantially as and
for the purpose set forth and shown.
Dated this 4th day of November 1895.
E. T. WHITELOW, A.M. Inst. C.E.,
70 Deansgate, Manchester, Agent for the Applicant.