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Proceedings Paper

Advantages of using engineered chalcogenide glass for color corrected, passively athermalized LWIR imaging systems
Author(s): Katie Schwertz; Adam Bublitz; Scott Sparrold
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Paper Abstract

Long wave infrared (LWIR) optical systems are prone to defocus with changes in temperature. IR refractive materials are more thermally sensitive compared to conventional visible glass due to their larger therm-optic coefficients. LWIR systems can be designed to be passively athermal (little or no change to focus with varying temperatures). Chalcogenide glasses provide additional material choices for IR lens designers. In particular, AMTIR5 has been engineered so its therm-optic coefficient matches the coefficient of thermal expansion (CTE) of aluminum, allowing for an athermal singlet. This paper explores the benefits of using engineered chalcogenide glass for color corrected, passively athermal systems. Initially, we present color corrected and passively athermal doublets that are designed with different materials and / or diffractive surfaces. Their thermal and color performance are cataloged for axial beams only. These are intended to be starting components, which readers may then insert into common design forms, such as Petzval, Double Gauss, Telephoto, and Inverse Telephoto. A F/1.3, 20° full field of view, aspheric Petzval lens design form is explored and the MTF is evaluated for -50°C to 85°C in an aluminum housing. From this design, we explore the tradeoffs between using chalcogenide versus crystalline materials, diffractive versus pure refractive surfaces, and engineered chalcogenide (AMTIR5) versus "catalog" materials.

Paper Details

Date Published: 31 May 2012
PDF: 16 pages
Proc. SPIE 8353, Infrared Technology and Applications XXXVIII, 835326 (31 May 2012); doi: 10.1117/12.919430
Show Author Affiliations
Katie Schwertz, Edmund Optics Inc. (United States)
Adam Bublitz, Edmund Optics Inc. (United States)
Scott Sparrold, Edmund Optics Inc. (United States)

Published in SPIE Proceedings Vol. 8353:
Infrared Technology and Applications XXXVIII
Bjørn F. Andresen; Gabor F. Fulop; Paul R. Norton, Editor(s)

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