Making FEA results useful in optical analysis

Thermal and structural output from general purpose finite element and finite difference programs is not in a form useful for optical analysis software. Temperatures, displacements and stresses at arbitrarily located FE nodes can not be input directly into optical software. This paper discusses the post-processing steps required to present the FE data in a useable format. Specific issues include optical surface deformations, thermo-optic effects, adaptive optics, optimization, and dynamic response. Finite element computed optical surface deformations are fit to several polynomial types including Zernikes, aspheric, and XY polynomials. Higher frequency deformations are interpolated to a user-defined uniform grid size using linear, quadratic, or cubic finite element shape functions to create interferogram files. Three-dimensional shape function interpolation is used to create OPD maps due to thermo-optic effects (dn/dT), which are subsequently fit to polynomials and/or interferogram files. Similar techniques are also used for stress birefringence effects. Adaptive optics uses influence functions to minimize surface error before or after pointing and focus correction. A dynamic analysis interface allows optical surface perturbations (rigid-body motions, elastic surface deformations) to be calculated for transient, harmonic and random response.