Improvements in Optical Instruments.
Year: 1893

page_text: Date of Application, 22nd Sept., 1893—Accepted, 11th Nov., 1893
COMPLETE SPECIFICATION.
Improvements in Optical Instruments.
I ALFRED CONRAD BIESE of 32 Maassenstrasse, Berlin in the Empire of
Germany Gentleman do hereby declare the nature of my invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
This invention relates to a new system for the production of graduated enlarge-
ment and diminution of images and to optical instruments constructed to act upon.
this system which enable different degrees of magnifying power to be obtained
without the introduction of a separate lens not belonging normally to the system.
The said enlarging or diminishing of the image is obtained in the improved
instrument by displacing or moving a device acting as a dispersing lens which is
inserted between the objective or object glass projecting the image and the focus of
the object glass or practically between the object glass and the image of the
object the said image of the object produced by the instrument being gradually
enlarged or diminished according to the position of the said device relatively to the
object glass.
The accompanying drawing illustrates the invention applied to a a Galilean
telescope.
The new system is applicable to astronomical, terrestrial and Galilean telescopes,
microscopes photographic lenses and like optical instruments and it can be
constructed as follows and as will be clear by reference to the longitudinal section
Figure 1 and the diagrams Figures 2 and 3.
I have shewn the invention as applied to a telescope from which its other
applications will also be understood.
Between the object glass C and its focus D there is introduced a device B acting
as a concave or dispersing lens it and its setting or mounting being capable of being
moved in the tube of the instrument so as to be placed nearer to or farther from
the object glass C either by hand or by cther suitable means such for example as
a screw or rack and pinion or a worm wheel such as is commonly employed in
Galilean telescopes. This device B refracts the rays thrown upon it from the object
glass C in such a manner that when they emerge from the device B they converge more
slightly than before. The image D D₁ as produced by the object glass C is
consequently not really formed but appears more or less enlarged according to the focal
length of the device B in a new focal plane E E' situated nearer to the eye glass G.
This image E E' is then viewed through the eye glass G which may be composed
according to the nature of the telescope either of a combination of collecting lenses
or of a dispersing lens or of a system acting as a dispersing lens. As however, the
new image E E at different degrees of enlargement is not simultaneously produced
in the focus of the eye piece G provision must be made by means of a supplementary
arrangement for enabling the observer to see a sharply defined image through the
eye piece at all degrees of enlargement. The adjustment of the image E E¹ in
the focus of the eye piece is effected by a displacement of the object glass C
corresponding to that of the device B. This may be effected by means of a screw
rotated by hand, but as it is evident that the amount of displacement of the object
glass is in relation to that of the device B the displacement of both lenses may be
conveniently effected by means of one spindle with two screw threads of corre-
sponding pitch as shewn clearly in Figure 1.
The advantage of the new system that instrument: constructed in accordance
therewith are capable of producing any desired enlargement within two limits,
determined by the constants of the apparatus, without it being necessary to change
the eye glass, moreover by moving the device B and the object glass C a successive
D

page_text: or graduated enlarging or reducing is rendered possible which cannot be obtained
with any other optical instrument heretofore constructed. Moreover in place
of the eye glass any equivalent thereof may be employed such for example as the
screen in the solar microscope and the camera obscura or the sensitive plate in
photographic apparatus in which latter the new arrangement presents the advantage
of enabling a truly universal lens to be obtained by means of which not only different
degrees of enlargement can be obtained but also in consequence of the different
angular opening connected therewith the same lens can be used for either interiors
landscapes or portraits.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is-
1. In optical instruments the new system for producing gradual enlargement or
diminution of images the said system being characterised by the arrangement of
an adjustable optical device acting as a dispersing lens between the objective or
lens producing the image and the observing or receiving lens or its equivalent such
as an eye piece or a sensitised photographic plate for example.
2. An optical instrument in accordance with the system referred to in Claim 1
for enabling the image formed to be always presented in the same position and to
be consequently observed through the eye glass (or the like) in all positions of the
device B so as to be sharply defined the construction being such as to provide
means for moving the object glass or projecting lens forwards or backwards
correspondingly to the enlargement obtained by the position of the device B.
3. In optical systems or instruments such as are referred to in Claims 1 and 2
an arrangement for adjusting the object glass or projecting lens simultaneously with
the device B in order to obtain the requisite sharpness of definition the said
arrangement consisting of a transmitting device or gear such as a screw spindle
with threads adapted to effect the proper relative displacenients of the device B
and the object glass or projecting lens substantially as herein before described and
illustrated by the accompanying drawings.
Dated the 22nd day of September 1893.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, Agents.