Retroreflector

Details Retroreflector Retroreflector

1998-02-11

1999-08-31

Phan, James

Optical: systems and elements

Signal reflector

3-corner retroreflective

359834, G02B 5122

Patent

active

059461357

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a retroreflector or a retroreflector arrangement assembled from a plurality of retroreflectors and having structures for heating the faces of the retroreflector.
2. Description of Related Art
A retroreflector is an optical component comprised of a triple-mirror prism. A triple-mirror prism has three prism faces, which are at right angles to one another, that form a three-dimensional cube corner. Each of these prism faces constitutes a right-angled, isosceles triangle. The fourth limiting face of such a triple-mirror prism is an equilateral triangle. This face serves as the entrance and exit, simultaneously, for a light beam. Every beam entering the triple-mirror prism from outside is totally reflected at all three (isosceles) faces and exits the triple-mirror prism parallel to its direction of incidence and exits symmetrically to the central beam. When the triple-mirror prism is rotated about an arbitrary axis, the direction of the retroreflected beam is not changed.
Such retroreflectors are used in many fields of optics, for example, they are used frequently in optical surveying of open terrain. Difficulty arises, however, because, during operation of the retroreflector, weather conditions often have an adverse impact on the retroreflector's accuracy and performance.
The difficulties suggested in the preceding are not intended to be exhaustive, but are among many which tend to reduce the effectiveness of retroreflectors. Other noteworthy problems may exist; however, those presented above should be sufficient to demonstrate that such methods and apparatuses appearing in the past will admit to worthwhile improvement.


SUMMARY OF THE INVENTION

Accordingly, it is therefore a general object of the present invention to provide a retroreflector which will obviate or minimize difficulties of the type previously described.
It is a specific object of the invention to provide a retroreflector that remains fully functional under extreme weather conditions, particularly, in extremely cold weather.
A preferred embodiment of the invention that is intended to accomplish at least some of the foregoing objectives includes a retroreflector having a triple-mirror prism, which has three isosceles limiting faces and one equilateral limiting face; and at least one heating element in direct contact with the at least one heating element. Furthermore, each of the three isosceles limiting faces is heated equally and directly by the at least one heating element.
Additional objects and advantages of the invention will be set forth in the following description and, in part, will be clear from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by the instrumentalities and combinations particularly pointed out in the appended claims.


BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate a presently preferred embodiment of the invention, and, together with the general description of the preferred embodiment given below, serve to explain the principles of the invention.
FIG. 1a is a rear view of a retroreflector;
FIG. 1b is a side view of a retroreflector;
FIG. 1c is a front view of a retroreflector;
FIG. 2 is a first embodiment, according to the invention, of a retroreflector;
FIG. 3 is a second embodiment, according to the invention, of the retroreflector;
FIG. 4a is a side view in accordance with FIG. 1b, with a transparent substrate and an additional transparent, heatable layer;
FIG. 4b is a top view of the embodiment of FIG. 4a; and
FIG. 5 is a detailed portion of the embodiments represented in FIGS. 4a, 4b, with an additional adhesive/cement layer between the transparent substrate and the limiting face.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is explained in more detail with the aid of the drawings, in which, in purely diagrammatic representations, va

REFERENCES:
patent: 3836275 (1974-09-01), Finch

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