Thermal effects upon the performance of lens systems

Abstract

The effects of heterogeneous temperature-distribution and uniform temperature change upon optical performance are considered in their general relationships and the practical problems of eliminating heterogeneous disturbances in optical instruments are reviewed. The quantitative effects of uniform temperature-variation upon image position and image size are evaluated in general terms as thermal aberrations. The conditions (a) for arbitrary thermal correction and (b) for thermo-mechanical correction, by which variations of tube length and image position are mutually compensated, are considered. The results are applied generally to the generalized doublet having one air space and any number of components; and applications to photographic and astronomical objective lens design are given in the form of examples of thermo-mechanical correction, calculated for two-lens systems with and without an air space, and for a combination of two doublets.