Improvements in Photographic Objectives.
Year: 1897

page_text: Date of Application, 4th Aug., 1897-Accepted, 16th Oct.,
1897
COMPLETE SPECIFICATION.
Improvements in Photographic Objectives.
I, FRIEDRICH RITTER VON VOIGTLÄNDER of the Firm of Voigtländer & Son, 2 Monu-
mentstrasse 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:-
The need for the making of compound photographic lenses has grown in the
measure as practical optical science has found ways and means for improving each
of the component parts or halves of a double symmetrical photographic objective so
far that it can be advantageously applied for taking photographs without using too
small or narrow diaphragins and while avoiding the defects otherwise inherent in
single objectives. The quadruple lens combination of Zeiss in this respect is typical,
the component elements or halves of which consist each of four lenses with a light
power of f: 12.5 and which both give a sufficient central sharpness and flatness of
the field and are also by the limitation of the chromatic difference distinguished by
sufficient correction of the spherical error or aberration outside of the axis.
If the meniscus shaped collecting lens (the inner lens) of the single lens of the
so-called collinear be suitably divided by a section made symmetrically to both of
the two outer surfaces of this lens, and if the two parts are made of two kinds of
glass, in such manner that the part next to the biconcave lens is made of glass with
very low refractive and dispersive power, while the other part, (the one next to the
biconvex lens) is made of glass with medium refractive and dispersive power, then
the construction inay by suitable choice of glass and of curves be so materially
improved without bringing in other defects that not only the double objectives but
especially the single elements obtain superior optical effects.
The zones of the spherical aberration are of special importance for the oblique
pencils of rays. For it so happens that the slight spherical overcorrection of the
marginal zone, which is of no significance for the axis, shows itself more and more
towards the margin. The overcorrection of the marginal rays which are especially
active for the oblique rays will when the astigmatism is quite done away, cause the
oblique ray pencils to have no longer sharp points, and even with comparatively
large lens apertures, rays will be found inside of the useful zone which in extreme
cases do not intersect at all within the image.
The aforesaid division in two parts of the collecting meniscus when properly
effected allows both of the lessening of the spherical zones for the axis and also of
a better correction of the same defects for oblique rays, and that to so large an extent
that herein alone a considerable technical advance will be found. Moreover the
single halves of this double objective each half consisting of four lenses are as stated
materially better than the halves of a double objective each half consisting of three
lenses.
In order to show how such a four partite system may be constructed reference is

page_text: made as an example to the accompanying drawing and to the following particulars
of the component parts of same.
Kind of Glass.
n D)
L1
1-6079
L 1.5366
Lg 1.5063
L 1.5366
Exponents of refraction.
Radii.
Thickness of lens.
n¹ G
= 85.6 mm.
1.634
12
1.5701
88.0
21=120.0
d₁ = 10.0 mm.
d,= 5.8
1.5172
30= 70.0
d₁ = 12.0
1.5701
7.8 82.0
d₁ = 1.8
F 557.8 mm.
=
Aperture 47.0 mm.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is :-
1. A spherically chromatically and astigmatically corrected photographic single
objective consisting of four lenses cemented together viz. a biconcave lens of
medium refractive power and medium dispersion, in combination with a positive
meniscus made of glass of low refractive power and low dispersion both cemented
together and cemented to two other lenses consisting of a meniscus made of glass
of medium refractive power and medium dispersion, and a biconvex glass of higher
refractive power and higher dispersion, the biconvex lens having the highest
JENSEN & SON,"
77 Chancery Lane, London, W.C., Patent Agents.