Contact stresses and their optical effects in biconvex lenses.

Abstract

Stress analyses by the finite element and theory of elasticity methods are used to predict the stress fields and intensities in biconvex lenses subject to the contact forces of mounting. In particular, the effects of radial stress imposed by the cell and the contact stresses produced by retainer rings are investigated. Typical retainer ring geometries are utilized in the study. Stress distribution data are related to the stress birefringent characteristics of glass, and the effects of mounting forces on the performance of optical elements are predicted. Optical retardation due to stress birefringence as a function of lens radius is presented in graphical form. Results of the numerical analyses are verified by the photoelastic method. Effects on lenses using typical mounting methods are investigated and compared to the analytic predictions. Experimental results correlate well with the analytical predictions. Results of this research indicate that retainer ring mounts produce localized stress birefringence effects which occur only in the area of contact and that radial mounting produces a stress birefringence field which is evident throughout the entire clear aperture of the lens.