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Proceedings Paper

Large-deviation achromatic Risley prisms pointing systems
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Paper Abstract

As part of the Infrared Eye project, this article describes the design of large-deviation, achromatic Risley prisms scanning systems operating in the 0.5 - 0.92 and 8 - 9.5 μm spectral regions. Designing these systems is challenging due to the large deviation required (zero - 25 degrees), the large spectral bandwidth and the mechanical constraints imposed by the need to rotate the prisms to any position in 1/30 second. A design approach making extensive use of the versatility of optical design softwares is described. Designs consisting of different pairs of optical materials are shown in order to illustrate the trade-off between chromatic aberration, mass and vignetting. Control of chromatic aberration and reasonable prism shape is obtained over 8 - 9.5 μm with zinc sulfide and germanium. The design is more difficult for the 0.5 - 0.92 μm band. Trade-offs consist in using sapphire with Cleartran® over a reduced bandwidth (0.75 - 0.9 μm ) or acrylic singlets with the Infrared Eye in active mode (0.85 - 0.86 μm). Non-sequential ray-tracing is used to study the effects of fresnelizing one element of the achromat to reduce its mass, and to evaluate detector narcissus in the 8 - 9.5 μm region.

Paper Details

Date Published: 4 June 2002
PDF: 9 pages
Proc. SPIE 4773, Optical Scanning 2002, (4 June 2002); doi: 10.1117/12.469192
Show Author Affiliations
Jean Lacoursiere, National Optics Institute (Canada)
Michel Doucet, National Optics Institute (Canada)
Eugene O. Curatu, National Optics Institute (United States)
Maxime Savard, National Optics Institute (Canada)
Sonia Verreault, National Optics Institute (Canada)
Simon Thibault, National Optics Institute (Canada)
Paul C. Chevrette, Defence Research and Development Canada (Canada)
Benoit Ricard, Defence Research and Development Canada (Canada)

Published in SPIE Proceedings Vol. 4773:
Optical Scanning 2002
Stephen F. Sagan; Gerald F. Marshall; Leo Beiser, Editor(s)

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