Effect of thermal deformations of an optical pick-up base on the optical properties of DVD optical system

An analytical method is presented to analyze the effect of thermal deformations of an optical pick-up base on the optical properties of DVD optical system. To measure the amount of thermal deformations of an optical pick-up base, finite element analysis and holographic interferometry were used. First, thermal deformations of an aluminum pick-up base was analyzed in thermal environments using finite element analysis; finite element analysis was carried out without the initial surface stress condition. The measurement of thermal deformations by holographic interferometry was carried out to verify finite element analysis results. However, since the finite element analysis results were deviated from those by experiment, the effect of the initial surface stress condition was considered; finite element analysis was carried out with the initial surface residual stress condition, which was obtained from X-ray diffraction measurement. The finite element analysis results with the initial surface stress condition agreed well with the experimental results by holographic interferometry. Finally, to analyze the effect of thermal deformations of the pick-up base on the optical properties of DVD optical system, the deformation of optical path was analyzed. However, the drastic changes of beam spot, beam intensity profile, modulation transfer function curve and wavefront aberration were not observed.