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Proceedings Paper

Optical design of an achromatic re-imaging lens system for a cryogenic near-infrared astronomical camera
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Paper Abstract

This paper describes an infrared imaging system developed to match the physical pixel sizes of the near infrared arrays used in the UCLA IR camera to the typical seeing disk at the f/15 focus of the W. M. Keck telescope. A field of view of 64 arcseconds (') at 0.25' per pixel is required, no internal focussing mechanism is possible and the system must perform under vacuum at 77 K. In our design, an achromatic triplet lens of calcium and barium fluoride provides an image of the entrance pupil and collimates the beam before it passes through a dichroic beam-splitter which divides the system into two independent channels; the wavelength split occurs at approximately 2.5 micrometers . Each beam is re-imaged onto IR arrays with 30 and 40 micrometers pixels to yield 0.25'/pixel and each imager is independently optimized to be achromatic and aberration free. Spot diagrams and aberration plots will be given. We also describe the steps required to compensate for environmental changes, since these lenses are used at LN2 temperature, and we discuss AR coatings and throughput.

Paper Details

Date Published: 20 October 1993
PDF: 12 pages
Proc. SPIE 1946, Infrared Detectors and Instrumentation, (20 October 1993); doi: 10.1117/12.158708
Show Author Affiliations
Suzanne Casement, Univ. of California/Los Angeles (United States)
Ian S. McLean, Univ. of California/Los Angeles (United States)
Robert E. Fischer, OPTICS 1, Inc. (United States)

Published in SPIE Proceedings Vol. 1946:
Infrared Detectors and Instrumentation
Albert M. Fowler, Editor(s)

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