Effects of Shrinkage of Adhesive Resin on Dimensional Accuracy of Optical Elements

The effects of the shrinkage of adhesive resin on the dimensional accuracy of optical elements during curing were investigated analytically and experimentally. The optical elements of a lens and a holder bonded with epoxy resin were treated. The lenses were made of glass or polymethylmethacrylate (PMMA). The shrinkage and changes in the mechanical properties of the adhesive resin during curing at room temperature were measured. The strain distributions of the lens and its deformation were calculated using the finite element method, considering the viscoelasticity of the adhesive resin. The deformations of the lenses were measured using strain gauges and an interferometer. The measurement results of strain distribution qualitatively agreed with the analytical results. It was shown that the shrinkage of the epoxy resin caused the deformation of the lens, and the changes in the mechanical properties of the epoxy resin largely influenced the magnitude of the deformation.