Improvements in Objectives for Photographic Purposes.
Year: 1895

page_text: Date of Application, 8th July, 1895-Accepted, 17th Aug.,
1895
COMPLETE SPECIFICATION.
Improvements in Objectives for Photographic Purposes.
We, CARL PAUL GOERZ, of 140 Hauptstrasse, Schöneberg, Manufacturer and
EMIL VON HOEGH, of 20 Prinzregentenstrasse, Wilmersdorf, Optician, both near
Berlin, in the Empire of Germany, 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:-
Our invention relates to objectives for photographic purposes.
Objectives of high illuminating power which are used for photographic purposes
have nearly all of them astigmatic errors so that only the central part of the image
is sharply defined. Moreover the illuminating power of such objectives is reduced
when the astigmatic errors are corrected so that their use, in those cases where
considerable illumination is required, is limited.
Now the object of our invention is to provide an objective of high illuminating
power and free from astigmatic error.
To enable our invention to be fully understood we will describe the same by
reference to the accompanying drawing, in which:-
Figure 1 is a vertical section of our improved objective:
Figure 2 is a vertical section shewing the objective combined with a single
objective; and,
Figure 3 a similar view shewing the objective in use as a double objective.
According to our invention we form the objective of four single leuses cemented
together. The first lens L' is a double convex lens of high refractive index (1,62)
the second lens L2 is a concavo-convex lens of low refractive index (1,51); next
come two negative lenses L³, L, the first of which L³ is a concavo-convex lens of
high refractive index (1,61), the second being concave and having a low refractive
index (1,52).
With this arrangement the cement surfaces S₁ and S³ converge the light rays
and the surface Z acts divergently on the same; the astigmatic errors, occasioned
by the surface Z and which have a detrimental effect on the definition of the
margin of the image, are equalized by the surfaces S¹ and S which produce an
opposite effect whilst the spherical errors, occasioned by the surfaces S and S² and
which have a detrimental effect on the illumination and definition of the middle of
the image, are equalized by the opposite effect of the surface Z.
Our improved objective can be employed either as a single objective or it can be
combined with any other single system, as shewn in Figure 2, or it can be used as a
symmetrical double objective as shewn in Figure 3.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1
An objective for photographic purposes built up of four single lenses cemented
together, two adjacent lenses being positive and of different refractive indices,
the other two adjacent lenses being negative and of different refractive indices so
that a lens of low refractive index is always in contact with a lens of high
refractive index, substantially as described.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.