Large stable mirrors: a comparison of glass, beryllium, and silicon carbide

Stanley J. Kishner; George J. Gardopee; Matthew B. Magida; Roger A. Paquin

doi:10.1117/12.22882

1 November 1990 Large stable mirrors: a comparison of glass, beryllium, and silicon carbide

Stanley J. Kishner, George J. Gardopee, Matthew B. Magida, Roger A. Paquin

Proceedings Volume 1335, Dimensional Stability; (1990) https://doi.org/10.1117/12.22882
Event: 34th Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, 1990, San Diego, CA, United States

Abstract

The choice of a substrate material for large mirrors is a complex engineering task that must account for structural and thermal properties as well as mirror blank fabricability polishability and surface scatter. Nuclear hardness is also a consideration in some applications. Cost is almost always a concern. The standard material for mirror substrates has always been glass. Beryllium technology however is well developed and offers distinct advantages over glass in many applications. Reaction-bonded silicon carbide is a relatively new material that has matured to the point where it can now be considered as an alternative to either beryllium or glass in some large optics applications. The availability of these three different substrate materials offers the system designer a great deal of flexibility in optimizing the material for each particular application. In this paper we present a methodology for comparing the structural properties of mirror substrate materials and lightweighting designs. This methodology is used to compare glass beryllium and silicon carbide. 1. LIGHTWEIGHT MIRROR DESIGN PARAMETERS Basic lightweight mirror design parameters are illustrated in Figure 1. Sandwich mirrors comprise two faceplates with a structured core in between. Although the faceplates are shown as having equal thicknesses tf they can in general be unequal. Open-back mirrors have a single faceplate. For both sandwich and open-back mirrors the mirror core is characterized by its height hc the web thickness tw of the core elements

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Stanley J. Kishner, George J. Gardopee, Matthew B. Magida, and Roger A. Paquin "Large stable mirrors: a comparison of glass, beryllium, and silicon carbide", Proc. SPIE 1335, Dimensional Stability, (1 November 1990); https://doi.org/10.1117/12.22882

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