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Proceedings Paper

Computer-controlled fabrication of sapphire windows
Author(s): Joel Askinazi; Wasim Hasan; Daniel E. Dunn; L. David La Fleur
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Paper Abstract

Sapphire optical materials have limited index of refraction homogeneity. This homogeneity can limit the degree of transmitted wavefront error achievable with current, conventional optical finishing practices. Current practices can not typically compensate well for the localized inhomogeneities in the sapphire substrates resulting in limited transmitted wavefront values. Emerging transmitted wavefront requirements exceed those achievable with current practices. Hughes Danbury Optical Systems recently completed a successful demonstration program in which computer controlled polishing was applied to the fabrication of very low transmitted wavefront error sapphire window. This technique involves measuring the windows in transmission and then polishing them in localized areas to remove the wavefront errors arising from the material index inhomogeneity. The net effect of each localized correction is a high fidelity transmitted wavefront over each subaperture. In the demonstration completed, we stated with windows fabricated to the limit of current, conventional practices. Applying computer controlled polishing, the transmitted wavefront quality was rapidly improved by a factor of up to five over the starting value. These results not only satisfied emerging requirements, but the process also resulted in satisfying parallel requirements of extreme surface smoothness and scatter as defined by the bi- directional transmittance distribution function. This paper addresses the process developed, its results, benefits and applications.

Paper Details

Date Published: 1 November 1997
PDF: 6 pages
Proc. SPIE 3134, Optical Manufacturing and Testing II, (1 November 1997); doi: 10.1117/12.295135
Show Author Affiliations
Joel Askinazi, Hughes Danbury Optical Systems, Inc. (United States)
Wasim Hasan, Hughes Danbury Optical Systems, Inc. (United States)
Daniel E. Dunn, Hughes Danbury Optical Systems, Inc. (United States)
L. David La Fleur, Hughes Danbury Optical Systems, Inc. (United States)

Published in SPIE Proceedings Vol. 3134:
Optical Manufacturing and Testing II
H. Philip Stahl, Editor(s)

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