1987-02-11
1989-08-08
Arnold, Bruce Y.
350253, G02B 702
Patent
active
048546712
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL BACKGROUND
The present invention relates to a mount for optical elements, such as lens elements.
Such mounts are required, for example, for lenses but also for optical instruments of all types, such as examining instruments, binoculars, etc.
STATE OF THE ART
The general problem with such mounts is that the rotational symmetry of mounted optical systems is impaired for the most part by the amount of play in the fitting between element and mount. By narrowing down the ISO (International Standard Organization) fitting tolerances it is possible to improve the rotational symmetry of the fully assembled system if increased production costs are also accepted. However, this method is subject to physical limits:
It will be normally so that the element materials have different thermal expansion coefficients to the mount materials. The amount of play in fitting at room temperature must be selected in such a way that sufficient contraction reserves are available for temperature variations. If this amount of play is not available in a sufficient amount, then high radial stress can occur in the elements which, under certain conditions, may lead to a dramatic decrease in the optical performance. Particular attenion in this respect must be paid to the fact that with the mount material aluminum, which is used in 99% of all cases, the difference between its expansion coefficient and representative expansion coefficients of optical glass materials can vary on the order of up to 16.times.10.sup.-6.
For this reason, it was suggested in U.S. Pat. No. 2,221,736, that a rubber-like coating be applied to the V-shaped rim of an ophthalmic lens. This coating of the V-shaped rim of an ophthalmic lens is not intended only to compensate for formal differences between a spectacle frame and spectacle lens but also to "absorb changes in thermal orders".
The formal differences addressed in the above U.S. Patent refer to the typical formal differences which occur on the edging of "uncut round" lenses into spectacle frames, that is they do not refer to fitting tolerances of high-precision optical systems. The use of the coating described in U.S. Pat. No. 2,221,736 for high-precision optical systems is not documented in the patent and is evidently not intended as the centration problem of high-precision optical systems are not encountered with spectacle frames.
A mount of a different type is known from the German Pat. No. DE-PS 1 113 101. With this mount, a rubber ring is used which is inserted into a groove in the mount body and which comes into contact with one surface of a lens element in such a way that the lens element is pressed elastically against a register.
The design described in this patent does permit the sealing of the mount body, but it is not able to provide any real reduction on the typical centration errors which occur due to fitting tolerances.
Further, lens element mounts where elastic elements are used are known from the DDR patent 207 047 and the German Pat. Nos. 1 122 738, 1 127 110, 1 547 276, 2 061 661 and 26 19 288. These mounts of a different type to that of the present invention, however, all have the disadvantage that they produce great efforts in their manufacture and, in addition, do not produce hardly any reduction in the centration errors of optical systems: For example, according to German Pat. No. 1 122 736, a divided mount into which the lens elements are inserted is used. Such a mount requires not only a great deal of manufacturing effort, but also has relatively large inherent errors which occur, for example, through the "dividing process" and which cannot be compensated for by the elastic material provided in the grooves which the lens elements are fitted into.
SUMMARY OF THE INVENTION
The object of the present invention is to describe a mount of simple construction for optical elements, such as lens elements or similar, where the centration of the optical elements is always ensured even when subject to thermal and dynamic strain.
This object is solved according to the present invention b
REFERENCES:
patent: 3904276 (1975-09-01), Whitaker et al.
Grimminger Rolf D.
Hanke Peter
Arnold Bruce Y.
Ben Loha
Optische Werke G. Rodenstock
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