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Proceedings Paper

Spectral design and verification of HIRDLS filters and antireflection coatings using an integrated system performance approach
Author(s): Gary John Hawkins; Roger Hunneman; John J. Barnett; John G. Whitney
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Paper Abstract

The HIRDLS instrument contains 21 spectral channels spanning a wavelength range from 6 to 18 micrometer. For each of these channels the spectral bandwidth and position are isolated by an interference bandpass filter at 301 K placed at an intermediate focal plane of the instrument. A second filter cooled to 65 K positioned at the same wavelength but designed with a wider bandwidth is placed directly in front of each cooled detector element to reduce stray radiation from internally reflected in-band signals, and to improve the out- of band blocking. This paper describes the process of determining the spectral requirements for the two bandpass filters and the antireflection coatings used on the lenses and dewar window of the instrument. This process uses a system throughput performance approach taking the instrument spectral specification as a target. It takes into account the spectral characteristics of the transmissive optical materials, the relative spectral response of the detectors, thermal emission from the instrument, and the predicted atmospheric signal to determine the radiance profile for each channel. Using this design approach an optimal design for the filters can be achieved, minimizing the number of layers to improve the in- and transmission and to aid manufacture. The use of this design method also permits the instrument spectral performance to be verified using the measured response from manufactured components. The spectral calculations for an example channel are discussed, together with the spreadsheet calculation method. All the contributions made by the spectrally active components to the resulting instrument channel throughput are identified and presented.

Paper Details

Date Published: 18 November 1998
PDF: 11 pages
Proc. SPIE 3437, Infrared Spaceborne Remote Sensing VI, (18 November 1998); doi: 10.1117/12.331311
Show Author Affiliations
Gary John Hawkins, Univ. of Reading (United Kingdom)
Roger Hunneman, Univ. of Reading (United Kingdom)
John J. Barnett, Univ. of Oxford (United Kingdom)
John G. Whitney, Univ. of Oxford (United Kingdom)

Published in SPIE Proceedings Vol. 3437:
Infrared Spaceborne Remote Sensing VI
Marija Strojnik; Bjorn F. Andresen, Editor(s)

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