Improvements in Lenses for Photographic Purposes.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in Lenses for Photographic Purposes.
I, RUDOLF STEINHEIL of 7, Theresienhöhe, München, Bavaria, Manufacturer
do hereby declare the nature of this invention to be as follows:-
:-
The discovery of new sorts of glass has rendered it possible to produce two kinds
of lenses which consist of two positive, equal or similar parts, each of which is in
itself chromatically, spherically, and astigmatically corrected, consequently the
finished lens contains these three corrections, whereas formerly lenses of two
positive, equal or similar parts, could only be corrected chromatically and
spherically, as in attempting to effect the astigmatic correction an unsymmetrical
construction resulted. Astigmatic corrections can only be made on a divisional
surface of two mediums which presents the concave side to the more highly
refractive medium, whilst the spherical correction can only be made on a divisional
surface which presents the concave side to the not so highly refractive medium.
Having this principle as a basis lenses can be constructed out of symmetrical or
similar halves which on the first divisional surface of the separate halves are
corrected astigmatically and on the second surface are corrected spherically.
Lenses so constructed have this characteristic, that a positive lens is enclosed by
a double convex one, and by a double concave one, both of which have a higher
refractive power than the enclosed positive lens.
The lens shown on the accompanying sheet of drawings consists of symmetrical
or similar halves, differing only in proportion, each of which is composed of three
cemented lenses. The middle lens is a positive one and is enclosed by a double
convex lens and by a double concave lens, both of the two latter possessing
stronger refraction than the enclosed positive lens.
Taking a focal distance of 493 mm., a lens constructed on the principle of this
invention with a degree of exposure of 1:6, would have the following elements :

page_text: whilst with a focal distance of 476 mm. with an exposure proportion 1:4 the
elements of a lens constructed from the foregoing point of view are the following:
I, RUDOLF STEINHEIL of 7 Theresienhöhe, Munich in the Kingdom of
Bavaria, Manufacturer, 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 :-
The discovery of new sorts of glass has rendered it possible to produce two kinds
of lenses which consist of two positive, equal or similar parts, each of which is in
itself chromatically, spherically and astigmatically corrected, consequently the
finished lens contains these three corrections, whereas formerly lenses of two
positive, equal or similar parts, could only be corrected chromatically and
spherically, as in attempting to effect the astigmatic correction an unsymmetrical
construction resulted. Astigmatic corrections can only be made on a divisional
surface of two mediums which presents the concave side to the greater refractive
medium, whilst the spherical correction can only be made on a divisional surface
which presents the concave side to the lesser refractive medium.
With this principle as a basis, lenses can be constructed out of symmetrical or
similar halves which on the first divisional surface of the separate halves are
corrected astigmatically and on the second surface are corrected spherically.
Lenses so constructed have this characteristic, that a positive lens is enclosed by a
double convex one, and by a double concave one, both of which have a higher
refractive power than the enclosed positive lens.
The lens shown on the accompanying sheet of drawings consists of symmetrical
or similar halves differing only in proportion, each of which is composed of three
cemented lenses. The middle lens is a positive one and is enclosed by a double
convex lens and by a double concave lens, each of the two latter possessing
stronger refractive power than the enclosed positive lens.

page_text: x0 =
Radius of lens aperture
whilst with a focal distance of 476 mm. with an exposure proportion of 1:4, the
elements of a lens constructed from the foregoing point of view are the following:-
-
x 0 =
59,5
-
RO R14= + 229
Sn
n D = 1,62356
R 2 = R 12562,95
In F
= 1,63498
Sn D
=
1,50786
R4 = R 10
= ± 142,03
n F
'n D
====
1,51351
1,60301
=
R6 R8
- -
490,196
In F
==
1,61428
=
D1 D 13:
-
20; D3 D 11 = 25; D 5-D9-4; Difference D 7 = 50.
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 :-
A lens consisting of symmetrical or similar halves differing only in proportion,
each of which is composed of three cemented lenses, namely, a positive lens, a
double convex lens and a double concave lens, the two latter enclosing the former
and both of said double convex and double concave lenses possessing stronger
refractive powers than the enclosed positive lens, substantially as herein before
described.
Dated this 31st day of March 1896.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.