High precision, non-destructive photoelastic verification of small thermal expansion differences within the 8.1 m gemini I UIe~(TM) primary astronomical mirror blank

摘要

Corning Incorporated's method of fabricating large solid astronomical mirror blanks by high temperature fusion of a nested array of hexagonal ULE~(TM) blocks demands not only near-zero, but also negligible differential coefficients of thermal expansion at every fusion joint for optimum performance at room temperature.