Abstract

It is well-known that pairs of glasses (or other optical materials) for the design of thermally compensated achromatic objectives can be selected from a "γV-vs-V" plot: V is the Abbe number and γ is the thermal glass constant. Each point on the plot represents a particular glass. If the slope of a line defined by a pair of points is equal to the coefficient of thermal expansion (CTE) of the metal structure that supports the focal surface, then the image of a distant point remains sharply in focus through a homogeneous change in temperature.

© 1990 Optical Society of America