A New or Improved Prismatic Telescope or Field Glass.
Year: 1898

page_text: Date of Application, 19th July, 1898-Accepted, 3rd Sept., 1898
A New or Improved Prismatic Telescope or Field Glass.
I, MORITZ HENSOLDT, of Wetzlar, (Germany), Optician, 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;-
This invention relates to an improved prismatic telescope, which can be formed
as a monocular or as a binocular telescope.
Fig. 1 shows a diagram of such a telescope, L is the objective, the eye lens
and A B are two prisms, which can be made separate or united as shown in Fig. V,
at their corresponding surfaces by means of a transparent cement. Fig. 2 is a
side view of the prism B. Fig. 3 is a plan view of the prism A. Fig. 4 is a plan
view of the prism B. Fig. 5 is a side view of the prisms A & B connected
together. Fig. 6 shows the total arrangement of the telescope in section for a
binocular telescope.
The instrument consists of a light collecting objective, a magnifying astro-
nomical eye lens in connection with a prismatic system for shortening the distance
between the eye piece and the objective and restoring or reinverting the inverted
image from the objective.
The prism system consists of two single prisms A, B (Fig. 1) either separated
from one another or connected with one another, of which the prism A is provided
with an even number of reflecting surfaces in the present case two surfaces d chi
and ea
afk. These two surfacus cause a deviation of the light axis from its
direction and this deviation is corrected by a second prism B, which is simul-
taneously a deviating and inverting prism, so that the axial ray passing through
the objective, on the first prism leaves parallel to this direction from the second
prism B and gives simultaneously an image which with an astronomical eye lens
gives a picture similar to the original, that is to say, standing upright and not
with reversed sides.
The prism A has two reflecting surfaces chid and afke, whilst the sur-
faces abgf and bchy are incident surfaces. These two incident surfaces are
inclined to one another at a right angle and are met and left by the axis ray in
the direction of the axis of incidence so that the ray passes unbroken from the
prism. The two reflecting surfaces chid and afke are inclined to one another
at an angle of 22½ degrees and symmetrically to the passage of the rays.
From the known property of an angular mirror, the reflecting surfaces of which
stand at right angles to one another, it results that one sees the picture of the
objective in the first mirror through the second one and the picture of the
objective in the second mirror through the first one the picture being inverted.
In order that the two pictures appear as a single uninterrupted picture, it is
necessary to keep a right angle with great precision.
The prism B is represented in Figs. 2 and 4 in a side view and in plan view
and is formed essentially by four planes consisting of two pairs, one member of which
is perpendicular to the other the meeting edge of one pair being turned through 90°
with regard to the meeting edge of the other pair. These planes are mnopq;

page_text: mrstq; nosr; and post. These two last planes no sr and post form surfaces
for totally reflecting the axis ray and the same is not broken by the incident
surfaces m n o p q and mrstq, as the axial ray enters and leaves the prism B again in
a perpendicular direction. The path of the ray is indicated by the direction of
the arrow. The ray enters through the objective L into the prism A, is reflected
by the mirror surface chid to the mirror surface afke and leaves through the
surface bg hc from the prism A, enters then into the prism B and leaves the
same through the surface mrstq without undergoing any refraction on the trans-
parent surfaces of this prism and passes to the eye lens parallel to the ray from
the objective. Fig. 6 gives a picture of a double telescope constructed in this
manner and its combination shown in the diagram.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is;-
An improved prism telescope having two prisms arranged separately or unitedly
in such a manner, that the one of these prisms A by means of two reflect-
ing surfaces chid and afke causes a deviation of the axis ray from its direction
and the other prism B by total reflection of two surfaces nors and post inclined
at right angles against one another and adjoining one another causes the ray to
leave in a line parallel to its entrance with simultaneous inversion of the picture.
Dated this 19th day of July 1898.
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Strand, London.