Improvements relating to Double Objectives for Photographio Purposes.
Year: 1896

page_text: Date of Application, 24th Aug., 1896-Accepted, 26th Sept., 1896
COMPLETE SPECIFICATION.
Improvements relating to Double Objectives for Photographio
Purposes.
I, FRIEDRICH RITTER VON VOIGTLÄNDER, of 2 Monumentonstrasse, Brunswick,
Germany, 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 :-.
Since the invention of the unsymmetrical anastigmato-photographic objectives with
higher correction of the astigmatic error it has been the desire of the opticians
to construct symmetrical anastigmatical objectives of the same perfection. Such a
symmetrical anastigmat which has been called collinear and for which Letters Patent
wore granted in 1894 under No. 21458 consists of two equil systems of three bases
cemented together in that way, that one positive meniscus of least refractive power
lies between one biconvex lens of highest and one biconcave lens of least refraction.
This combination has met with a great success. But however useful it might be yet
the highest illuminating power of this construction i.e. the highest ratio of clear
aperture and length of focus could never bo brought above 1: 63, and so it has been
the case with all the other constructions of symmetrical anastigmats.
Recent mathematical researches and practical investigations made it likely that only
slight altorations of the optical properties of the medium lens in the so-called
"collinear" would afford the possibility of attaining a higher illuminating power.
Practical experiments and with the finest precision in the performance of the optical
surfaces assisted the mathematical researches, so that I finally succeeded in designing
and constructing a symmetrical anastigmatic collinear of the relative aperture 1: 4.5,
twice as luminous as the most luminous symmetrical anastigmat hitherto known.
Only a slight difference of the optical properties of the medium lens made this
success possible, whereas any greater alterations lead to impossible curvaturos and
impossible forms of lenses. This new construction is therefore a most sensitive one,
because it is not possible to neglect the least differences in the optical properties, the
curvatures and the thicknesses of the lenses. This sensitiveness undoubtedly is the
reason of all the ill successes of the constructing opticians in that direction.
In the accompanying drawing the new spherically chromatically and anastig-
matically corrected double-objective of the ratio of aportaro 1: 45, is shown in a
diagramimatic representation. The precise data of the construction are as follows:-

page_text: relative aperture 1: 4.5, consisting of equal systems of the same correction, of which
each is composed of a positive meniscus of least refractive power cemented between a
biconvex and a biconcave lens of higher refractive power substantially as set forth.
2. The employment of a single system of the kind referred to in the first claim as
an independent photographic objective.
August 1996.
10
JENSEN & SON,
77 Chancery Lane, London, W.C., Patent Agents.
Dated this 24th day of August 1890.
JENSEN & SON,
77 Chancery Lane, London, W.C., Patent Agents.