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Proceedings Paper • Open Access

An optically athermalized lens covering a 200-degree temperature range
Author(s): John R. Rogers

Paper Abstract

There are several methods for athermalizing an optical system. Active athermalization requires that the focus of the system be actuated as a function of temperature. This adds complexity to the system and is often not desired for Space applications. Mechanical athermalization does not attempt to stabilize or otherwise influence the optical behavior over temperature, but relies on a mount structure that is engineered to keep the focal plane array (FPA) located at the position of best focus over temperature. Often such mounts involve dissimilar materials expanding in opposite directions to obtain the desired net expansion. Optical athermalization keeps the mount structure simple but uses a modified optical design to ensure that the position of best focus falls at the FPA location across the temperature range. To achieve this while still producing a sharp image, the lens materials must be chosen carefully.

In designing an athermalized lens, the mounting details of the elements must be taken into account carefully. A common approach for optimization is to assume that the elements are separated by spacers whose CTEs are known. Unfortunately, in most cases this is not how the optical system is actually assembled. More commonly, the individual lenses are either cemented to or otherwise preloaded against seats cut into the housing barrel. Furthermore, there are many ways in which the contact between the optical elements and the housing takes place, and this influences the location where each element is “pinned” to the housing, i.e., the position at which there is no relative motion between the element and the housing.

In this paper, we present the design of a lens optimized to be optically athermalized over a 200° C temperature range. The design includes the effects of the lens mounting details as well as the change in CTE of aluminum over temperature. We also explore the sensitivity of the design to the mounting details and the CTE.

Paper Details

Date Published: 12 July 2019
PDF: 19 pages
Proc. SPIE 11180, International Conference on Space Optics — ICSO 2018, 111808E (12 July 2019); doi: 10.1117/12.2536221
Show Author Affiliations
John R. Rogers, Synopsys, Inc. (United States)

Published in SPIE Proceedings Vol. 11180:
International Conference on Space Optics — ICSO 2018
Zoran Sodnik; Nikos Karafolas; Bruno Cugny, Editor(s)

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