A Finder or Camera Obscura for Photographic or other Purposes.
Year: 1896

page_text: Date of Application, 21st May, 1896
22nd Man 4907 Accented
21ot May 1897
PROVISIONAL SPECIFICATION.
A Finder or Camera Obscura for Photographic or other Purposes.
JOHN AIRS Scientific Instrument Maker 84 Hatton Garden London do hereby
declare the nature of this invention to be as follows:-
An improved finder or camera obscura in which the reflecting surfaces are
adjustable & which can be rotated in conjunction with or without the rotation of
the lens and so arranged as to give a true or distorted image or reflection on the
screen or screens at any angle of its rotation.
It is the usual practice in hand cameras to use two view finders or camera
obscuras with fixed mirrors & lenses in each one for obtaining the vertical, and
the other the horizontal view.
By using a revolving mirror or reflecting surface I obtain both views with one
finder or any number of views according to the screens employed, the mirror being
directed to whichever screen the image is required on.
For instance a lens and mirror placed at a given angle so as to revolve inside a
drum consisting of a ground glass surface, a view could be obtained on any part
of the aforesaid drum.
The above finder may also be used on or as a range finder, levels and such like
instruments.
1, JOHN AIRS of 84 Hatton Garden, London, Scientific Instrument Maker, do
hereby declare the nature of my said invention 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 my invention is to manufacture an improved finder or camera
obscura, in which the reflecting surfaces are adjustable, and which can be rotated
in conjunction with or without the rotation of the lens; and so arranged as to give
a true or distorted image or reflection on the screen or screens at any angle of its
rotation.
It is the usual practice, in hand cameras, to use two view finders or camera
obscuras, with fixed mirrors and lenses in each, one for obtaining the vertical, and
the other the horizontal view.
By using a revolving mirror or reflecting surface, I obtain both views with one
finder, or any number of views, according to the screens employed, the mirror
being directed to whichever screen the image is required upon. For instance a
lens and mirror placed at a given angle so as to revolve inside a cylinder consisting
of a ground glass surface, a view or reflection can be obtained on any part of the
aforesaid cylinder.

page_text: And in order that my said invention may be particularly described and
ascertained, reference is hereby made to the accompanying drawings, in which
similar letters of reference indicate corresponding parts.
Fig. 1 is an elevation of a rectangular finder, and Fig. 2 is a top view of the
same.
Fig. 3 is an elevation of the lens and reflector detached from the case, and Fig. 4
is a vertical section of the same.
The case a may be rectangular, (as shown) polygonal, or cylindrical, according
to the number and direction or angles of views required. 6 is the cover of the
finder. The lens c is fitted, as shown in Fig. 4, and is held in position in the
cylinder d by a ring e. fis an annular disce, which is screw-threaded to fit the screw
formed at the lower end of the cylinder d, acting as a nut to secure the cylinder d
to the cover b. g is a plate soldered to the annular disc f, which sustains the
reflector in position.
The cylinder d is capable of being rotated by hand in any required direction,
independently of the cover b; and, when so rotated, it carries therewith the
annular disc f, plate g, and reflector h. These movements enable the operator to
obtain any number of views, according to the screens employed; a ground glass
cyliuder being sometimes used, as before mentioned.
When applying my invention to a rectangular finder as shown in the drawings,
a pin k is fitted to the cylinder to limit its motion to an angle of 90 degrees, by
contact with stops m n.
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 :-
1. The improved finder camera obscura for photographic or other purposes,
substantially as descreu
2. In a finder or camera obscura for the purposes aforesaid, the combination of
a cylinder d, lens c, annular disc f, plate g, and reflector f, all capable of being
rotated independently of the case a; or the case being rotated independently of
the lens mount and its attachments, substantially as herein before described and
illustrated by the drawings.
Dated 22nd March 1897.
GEORGE DOWNING & SONS,
8 Quality Court, London, W.C., Agents.