Improvements relating to Doublet Lenses for Photographic Purposes.
Year: 1894

page_text: Date of Application, 7th Nov., 1894
Complete Specification Left, 7th Feb., 1895-Accepted, 9th Mar., 1895
PROVISIONAL SPECIFICATION.
Improvements relating to Doublet Lenses for Photographic
Purposes.
We, CARL PAUL GOERZ, Manufacturer, of 7^ Hauptstrasse, Schöneberg, and
EUIL VON HOEGH, Optician, of 60, Prinzregentenstrasse, Wilmersdorf, both near
Berlin, in the German Empire, do hereby declare the nature of this invention to be
as follows:-
Our invention relates to photographic doublet lenses or objectives which are
corrected for spherical, chromatic, and astigmatic errors.
In the Specification of former Letters Patent granted to us dated 19th December
1892 and numbered 23378 we described a double objective, the two separate
systems of which were spherically, chromatically, and astigmatically corrected,
each for itself, and were to this end made up each of three cemented lenses of
which one cemented surface converged the rays of light (to compensate the
astigmatic error) and the other cemented surface caused the rays of light to diverge
(for the purpose of compensating the spherical error) these two systems being
further composed either-
(a) Of a negative lens, enclosed between two positive lenses of which one had
a higher, and the other a lower refractive index than the negative lens so
enclosed, or
(b) Of a positive lens, enclosed between two negative lenses, one of which had
a higher and the other a lower refractive index than the positive lens so
enclosed.
With the object of obtaining as great and equable sharpness of field as possible,
this separate combination of the separate lenses was further varied by cementing
together in combination two identical lenses (either positive or negative) with a
third (negative or positive respectively). The only condition to be fulfilled was
that in each several case the characteristics of the combination should correspond
with those laid down in the first claiming clause of the Specification of our said
former Patent, viz. :-That of the two cemented surfaces, the one should act by
converging the rays of light, and the other by diverging them, and the two similar
lenses should possess, the one a higher, and the other a lower, refractive index than
the differently figured third lens.
According to our present improvements the two separate systems of the double
objective are made up of a negative lens of medium refractive index, cemented to
two positive lenses placed in juxtaposition with each other, one of these latter
having a higher and the other a lower refractive index than the negative lens
which lies outside, or of a positive lens of medium refractive index, cemented to
two negative lenses placed in juxtaposition with each other, of which one has a
higher and the other a lower refractive index than the positive lens which lies
outside.
Each separate system may, however, be used independently as a photographic
objective, since each is independently corrected for spherical, chromatic, and
astigmatic error.
Dated the 7th dow of Nuvamber 1901
G. F. REDFERN & Co.,
4, South Street, Finsbury, Loudon, Agents for the Applicants.

page_text: Improvements relating to Doublet Lenses for Photographio
Purposes.
We, CARL PAUL GOERZ, Manufacturer, of 7* Hauptstrasse, Schöneberg, and
EMIL VON HOEGH, Optician, of 60 Prinzregentenstrasse, Wilmersdorf, both near
Berlin, in the German Empire, 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 photographic doublet lenses or objectives which are
corrected for spherical, chromatic, and astigmatic errors.
In the Specification of former Letters Patent granted to us dated 19th December
1892 and numbered 23378 we described a double objective, the two separate
systems of which were spherically, chromatically, and astigmatically corrected,
each for itself, and were to this end made up each of three cemented lenses of
which one cemented surface converged the rays of light (to compensate the
astigmatic error) and the other cemented surface caused the rays of light to diverge
(for the purpose of compensating the spherical error) these two systems being
further composed either-
(a) Of a negative lens, enclosed between two positive lenses of which one had
a higher, and the other a lower refractive index than the negative lens so
enclosed, or
(b) Of a positive lens, enclosed between two negative leuses, one of which had
a higher and the other a lower refractive index than the positive lens so
enclosed.
With the object of obtaining as great and equable sharpness of field as possible,
this separate combination of the separate lenses was further varied by cementing
together in combination two like named lenses (either positive or negative) with a
third (negative or positive respectively). The only condition to be fulfilled was
that in each several case the characteristics of the combination should correspond
with those laid down in the first claiming clause of the Specification of our said
former Patent, viz. :-That of the two cemented surfaces, the one should act by
converging the rays of light, and the other by diverging them, and the two like
named lenses should possess, the one a higher, and the other a lower, refractive
index than the differently figured third lens.
In the accompanying drawing,
Figures 1 and 3 are reproductions of systems of lenses arranged according to our
said former Patent:
Figures 2 and 4 are sections of systems of lenses arranged according to our
present invention; and,
Figure 5 is a section of our improved doublet lens.
In Figure 1 of the drawing accompanying the said Specification there is shewn
a diagrammatic representation of a double objective, the separate systems of which
are built up in the manner shewn in Figure 1 of our present drawings.
In this case the surface of contact S between the lenses a and b acts by converging
the rays, since the convex side of the lens a is turned toward the lens b, the refractive
index of the latter being besides, less than that of the lens a. On the other hand,
the bounding surface Z of the lenses 6 and a' causes the rays to diverge, since the
convex side of the lens a¹ is turned toward the lens b, the refractive index of the
latter being, besides, higher than that of the lens a¹.
We now shift the lens a, which in Figure 1 is shewn upon the left side of the
system to the right side of the lens a', and the system will assume the form shewn

page_text: in Figure 2. The bounding surface Z between the lenses band a' continues to
act by diverging the rays, just as in the system shewn in Figure 1, since by
altering the position of the lenses an alteration of the surface Z has not been
produced; conversely, the bounding surface S' of the lenses a¹ and a acts by
converging the rays, for the same reason as was explained earlier with respect to
the surface S, Figure 1. The conditions for the simultaneous correction of the
spherical and astigmatic errors are thus present also in the new system. The
combination of the lenses is alone modified, in such a way that the negative lens is
no longer enclosed between two positive lenses, as in Figure 1, but one positive
lens lies between the negative lens and the other positive lens. The refractive
index of the separate lenses remains unaffected i.e. one positive lens has a higher,
and the other a lower refractive index than the negative lens, which now lies
outside.
Figure 3 shews the combination of a positive lens enclosed between two negative
lenses of which one has a higher and the other a lower refractive index than
that of the enclosed positive lens as described and claimed in our said former
Patent.
Here, according to exactly the same theoretical laws as those referred to in
connection with the previous example, the bounding surface Z between a and b
acts by diverging the rays, and the surface S between a and b' by converging
them.
We now shift the lens to the left side of the lens b whereby we obtain a
system shewn in Figure 4, in which two negative lenses are juxtaposed in front,
whilst the positive lens is cemented to the second negative lens which is then
located in the middle. In this case too, as is evident, the conditions for the
simultaneous correction of the spherical and astigmatic errors are present, since
the bounding surface Z still acts divergently and the new cemented surface S* acts
convergently.
In this case too the combination of the lenses is only so far modified as that the
positive lens no longer lies between two negative lenses, but one negative lens is
enclosed between the positive lens and the second negative lens. The refractive
index of the several lenses also remains unaltered, so that one negative lens still
possesses a higher and the other a lower refractive index than the positive lens which
now lies upon the outside.
The objective shewn in Figure 5 is made up of two separate systems of the kind
shewn in Figure 2.
Each separate system may however be used independently as a photographic
objective, since each is independently corrected for spherical, chromatic, and
astigmatic error.
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. A photographic double objective, the two separate systems of which are
independently corrected for spherical, chromatic, and astigmatic error, and to this
end consist each of three cemented lenses, one of the cemented surfaces of which
acts by converging, i.e., by collecting the rays of light (to correct the astigmatic
error) and the other cemented surface acts by diverging, i.e. by scattering the rays
of light (to correct the spherical error) the two systems being composed:
(a) Of a negative lens of medium refractive index, cemented to two positive
lenses placed in juxtaposition with each other, one of these latter having a
higher and the other a lower refractive index than the negative lens which
lies outside, or
(b) Of a positive lens of medium refractive index, cemented to two negative.
lenses placed in juxtaposition with each other, of which one has a higher
and the other a lower refractive index than the positive lens which lies outside.

page_text: 2. The employment of a single system, of the kind referred to in the first
claiming clause, as an independent photographic objective.
Dated the 7th day of February 1895.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.