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Proceedings Paper

ULE - Zero expansion, low density, and dimensionally stable material for lightweight optical systems
Author(s): Suresh T. Gulati; Mary J. Edwards
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Paper Abstract

The zero expansion titania-silica binary glass ULE™ offers an optimum combination of thermal, mechanical, and optical properties which make it an ideal material for precision optical structures and lightweight telescope mirrors. Its near-zero thermal expansion over the ambient operating temperature range helps preserve optical figure; the absence of hysteresis in its thermal expansion curve ensures dimensional stability of the mirror in extreme environments; its low density affords high specific stiffness thereby reducing elastic deformation of lightweight structures; its high fatigue resistance permits higher long-term stress without compromising mechanical reliability; and its excellent optical and birefringence properties facilitate inspection and quality assurance in terms of thermal expansion homogeneity, defect level, and residual strain.

This paper reviews the key physical properties of ULE glass and the various fabrication techniques available for making lightweight mirrors. Special emphasis is given to ULE's mechanical behavior which controls the long-term reliability of mirror blanks during fabrication, shipping, installation, and operation. It describes the 8-meter class mirror blank manufacturing process and the stress/time histories to which such blanks are exposed. These parameters, together with strength and fatigue data, were used to optimize surface finish for adequate strength and to evaluate an 8-meter blank support system to ensure long-term reliability of the blank during transportation. The paper concludes with recent advances and development programs in support of the manufacture of precision optical mirror blanks.

Paper Details

Date Published: 28 July 1997
PDF: 30 pages
Proc. SPIE 10289, Advanced Materials for Optics and Precision Structures: A Critical Review, 1028909 (28 July 1997); doi: 10.1117/12.284710
Show Author Affiliations
Suresh T. Gulati, Corning, Inc. (United States)
Mary J. Edwards, Corning, Inc. (United States)

Published in SPIE Proceedings Vol. 10289:
Advanced Materials for Optics and Precision Structures: A Critical Review
Mark A. Ealey; Roger A. Paquin; Thomas B. Parsonage, Editor(s)

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