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Diffraction Effects in a Grating SpectrometerThis paper describes a numerical study of diffraction effects in the AIRES optical system using GLAD by Applied Optics Research. AIRES (or Airborne Infrared Echelle Spectrometer) employs two gratings in series. The small, first-order (i.e., predisperser) grating sorts orders for the large, high-order echelle grating, thus providing moderately high spectral resolution over 3.6 octaves in wavelength. The AIRES' optical design includes three field stops (i.e., a circular aperture and two long, narrow slits) and four pupil stops. A detailed diffraction analysis is required to evaluate critical trade-offs between spectral resolution, optical throughput, detector background, scattered light, and system size and weight. Such an analysis must consider diffraction effects at the pupil stops (edge diffraction), at the field stops (spatial filtering), and at intermediate positions where other optical elements are located. The effects of slit width, slit length, oversizing of the second slit relative to the first, baffling at the Lyot stop and subsequent pupil stops, and the necessity for oversizing other optical elements are presented and discussed. It is found that for narrow slits, the downstream energy distribution is significantly broadened relative to that for large slits, where telescope diffraction dominates, leading to significantly more light loss than anticipated, unless other key optical elements are oversized. The importance of performing a proper diffraction analysis is emphasized and the suitability of GLAD for this task is discussed.
Document ID
20020054234
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Haas, Michael R.
(NASA Ames Research Center Moffett Field, CA United States)
DeVincenzi, D.
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Optics
Meeting Information
Meeting: SPIE Conference on Astronomical Telescopes and Instrumentaiton
Location: HI
Country: United States
Start Date: August 22, 2002
End Date: August 28, 2002
Sponsors: International Society for Optical Engineering
Funding Number(s)
PROJECT: RTOP 263-10-30
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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