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Proceedings Paper

Diffraction models of radiation entering an aperture for use in a Monte Carlo ray-trace environment
Author(s): Katherine L. Coffey; Kory J. Priestley; J. Robert Mahan; Maria Cristina Sanchez
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Paper Abstract

This manuscript presents multiple modeling efforts to describe diffraction of monochromatic radiant energy passing through an aperture for use in the Monte-Carlo ray-trace environment. Described is a deterministic model, based upon Heisenberg's uncertainty principle, which predicts the angle at which an approaching ray is diffracted. The result is a curve which approximates the analytical interference pattern, but does not model the side fringes (i.e. secondary maxima). This model is applicable to either Fraunhofer (far-field) or Fresnel (near- field) diffraction situations. In addition to this model, a diffraction model is presented that approximates the interference pattern including the secondary maxima, as produced by radiation passing through a slit or a circular aperture. This model, based on the Huygens-Fresnel principle with a correcting obliquity factor, is useful for predicting Fraunhofer (far-field) diffraction in the Monte-Carlo ray- trace environment. The motivation for this work is the need to properly model the diffraction of radiant energy as it approaches a detector intended for monitoring the Earth's radiation budget from a geo-stationary orbit. The proposed detector, a linear-array of thermopile elements, is housed in a wedge-shaped cavity with a 60-$micrometer slit through which radiant energy between wavelengths of 0.1 micrometer and 40 micrometer must pass. A radiative model of this cavity which does not account for diffraction effects has already been developed using the Monte Carlo ray-trace method. This detector was originally intended to fly on the Geo-Stationary Earth Radiation Budget (GERB) instrument.

Paper Details

Date Published: 29 October 1998
PDF: 7 pages
Proc. SPIE 3429, Current Developments in Optical Design and Engineering VII, (29 October 1998); doi: 10.1117/12.328547
Show Author Affiliations
Katherine L. Coffey, Virginia Polytechnic Institute and State Univ. (United States)
Kory J. Priestley, NASA Langley Research Ctr. (United States)
J. Robert Mahan, Virginia Polytechnic Institute and State Univ. (United States)
Maria Cristina Sanchez, Virginia Polytechnic Institute and State Univ. (United States)

Published in SPIE Proceedings Vol. 3429:
Current Developments in Optical Design and Engineering VII
Alson E. Hatheway; Robert E. Fischer; Malachy McConnell; Lawrence M. Germann; Lawrence M. Germann; Alson E. Hatheway; Malachy McConnell; Warren J. Smith, Editor(s)

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