Optical: systems and elements – Prism – With reflecting surface
Reexamination Certificate
2000-05-01
2001-07-03
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Prism
With reflecting surface
C359S407000, C359S431000, C359S835000
Reexamination Certificate
active
06256156
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a convergence tube for stereomicroscopes, in which the two observation beam paths are inclined relative to one another at a convergence angle &agr; and image inversion elements are provided in both observation beam paths.
b) Description of the Related Art
Stereomicroscopes essentially comprise an objective, a tube system with image inversion elements, and oculars. Usually, there is a Galilean telescope system with a fixed or a variable (zoom) magnification arranged between the objective and the tube system. The distance between the two optical axes of the tube objectives is the stereo base.
Two characteristic types of tube have been developed: first, the parallel tube in which both optical axes emerge parallel to each other; second, the convergence tube in which the optical axes are presented to the observer at an inclination relative to each other of a convergence angle &agr;. The convergence angle &agr; corresponds to the viewing direction of the eyes accommodated to an object at a distance of about 250 mm, and usually has a value of between 14° and 16°.
While the ergonomic design of the convergence tube has proven itself based on its advantages for the observer, it is more complicated in terms of optics and also, therefore, in technical respects relating to manufacture compared to the parallel tubes, since the convergence of the observation beam paths demands that the image inversion elements be specially designed and positioned relative to one another in a special way.
The convergence of the observation beam paths is essentially achieved according to two basic principles. In the first one, the convergence tubes are outfitted with the conventional image-erecting Porro prisms which are preceded by optical wedges, e.g., achromatic wedges.
In the second principle, the convergence tubes are provided with modified Porro prisms. For example, a 90-degree or right-angle prism is arranged in each beam path, followed by at least one prism deviating from 90°. In this connection, as a rule, the 90-degree angle is deviated from by half the convergence angle &agr;.
These two basic principles form the basis for design variants in which some or all of the prisms are replaced by mirrors.
The insertion of optical wedges as well as the manufacturing of prisms or mirror subassemblies with a deflection angle deviating from 90° is uneconomical with regard to manufacturing techniques.
OBJECT AND SUMMARY OF THE INVENTION
On this premise, it is the primary object of the invention to develop further a convergence tube of the type mentioned in the beginning in such a way that manufacture is simplified while a high image quality is maintained.
According to the invention, four planar reflectors R
1
to R
4
are provided in each of the two beam paths of a convergence tube of the type mentioned above and, for purposes of image inversion as well as achieving the convergence angle &agr;, are arranged relative to one another in such a way that the axis beams incident on and emergent from the reflectors R
1
and R
2
are on a common plane E
1,2
, the axis beams incident on and emergent from reflector R
3
describe a plane E
3
that forms an angle &bgr;
1
=90°+&agr;/4 with the plane E
1,2
, wherein the axis beams emergent from R
2
and incident on R
3
lie on the lines of intersection of planes E
1,2
and E
3
, and the axis beams incident on and emergent from the reflector R
4
describe a plane E
4
that forms an angle &bgr;
2
=&agr;/2 with the plane E
3
, wherein the axis beams emergent from R
3
and incident on R
4
lie on the lines of intersection of planes E
3
and E
4
.
This results in a relatively simple construction which has only a few optical functional elements and by which image inversion as well as the intended convergence of both observation beam paths is achieved.
In a preferred arrangement of the invention, the reflectors R
1
and R
4
are formed at right-angle prisms. In an especially preferred arrangement of the invention, the reflectors R
1
and R
2
are formed by the two short faces of a first prism P
1
and reflectors R
3
and R
4
are formed by the hypotenuse faces of two further prisms P
2
and P
3
.
According to the invention, these three prisms are positioned in the beam path in such a way that the beam path coming from a tube objective first enters the first prism P
1
through the hypotenuse face and is then deflected by 90° at each of its short faces, exits through the hypotenuse face and enters the second prism P
2
through a first short face, and, after having been reflected at the hypotenuse face of the second prism P
2
, exits through the second short face and then, through a first short face, enters the third prism P
3
where it is reflected by the hypotenuse face and reaches the ocular by way of the second short face of the third prism P
3.
The essential advantage of this design consists in that six right-angle prisms of identical construction can be used; this reduces expenditure on this type of convergence tube insofar as, first of all, right-angle prisms are relatively easy to manufacture from a technological point of view on the one hand and, on the other hand, because of the plurality of constructionally identical prisms, automated or rationalized production methods can also be applied, especially for series production of convergence tubes.
The orientation in the beam path in accordance with given angles of inclination &bgr;
1
and &bgr;
2
can advisably be carried out in that the three prisms P
1
, P
2
, P
3
are fitted into a mounting which is fabricated to measure and has inclined stop faces for the prisms, and the prisms can be fixed at this inclination relative to one another in the mounting.
In further advisable arrangements of the invention, the prisms can also be cemented to one another between the entrance and exit faces of the beam path.
The insertion of diaphragms at the interfaces or transitions between the prisms for the purpose of limiting scattered radiation is also conceivable.
Further, the convergence tube according to the invention can be advantageously combined with a swiveling device for changing the distance between the oculars and/or with a swiveling device for changing the observation angle. The design of such swiveling devices is known per se from prior art and need not be discussed in more detail herein. However, it should be pointed out that the swiveling for changing the distance between the oculars should be carried out by rotation around the optical axes of the two tube objectives.
In this context, it is advisable to arrange the three prisms P
1
, P
2
, P
3
in the two beam paths relative to the tube objective in such a way that the optical axis of the tube objective already lies in plane E
1,2
and is directed directly to the hypotenuse face of the first prism P
1.
The sequence of numbers given in the reference numbers of the reflectors R
1
to R
4
can correspond to their positioning in the beam path proceeding from the tube objective. But, of course, it lies within the framework of the invention to arrange the reflectors R
1
to R
4
or the prisms P
1
to P
3
in reverse order, in which case the light coming from the tube objective first enters the third prism P
3
through a first short face, where it is reflected on the hypotenuse face, reaches the hypotenuse face of the second prism P
2
, where it is again reflected, and is then directed successively onto the two short faces of the first prism P
1
and then emerges from the latter to reach the ocular. However, the positioning of the three prisms P
1
, P
2
, P
3
relative to one another with respect to angles &bgr;
1
and &bgr;
2
must remain unchanged.
The invention will be described more fully in the following with reference to an embodiment example.
REFERENCES:
patent: 1637563 (1927-08-01), Gary
patent: 1795782 (1931-03-01), Konig
patent: 2087329 (1937-07-01), Ott
patent: 3051046 (1962-08-01), Thompson
patent: 4601550 (1986-07-01), Yoshino et al.
patent: 5072313 (1991-12-01), Schwei
Koschmieder Ingo
Luther Ergon
Mueller Lothar
Ruedel Reinhard
Carl Zeiss Jena GmbH
Nguyen Thong
Reed Smith LLP
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