Alignment tolerances and optimal design of MEMS-driven Alvarez lenses

Abstract

The Alvarez lens offers variable focal lengths through lateral shifting of two lens elements. Imaging characteristics and alignment tolerances of the Alvarez lens are studied, and one analytic method for optimal coefficient selection is proposed. Results show that the performance of the Alvarez lens decays with increasing element displacements, and dominant optical aberrations are spherical aberrations, defocus and coma. The lens performance is most sensitive to misalignments in the y direction. If the tolerance is defined as a 10% rise of normalized RMS spot radius, the misalignment should be smaller than 0.01 mm and the tilt angle about any axis can never exceed 1°. By adopting the new coefficient-selection method, lens performance is improved evidently and the degrading trend with increasing displacements is mitigated markedly. In addition, alignment tolerance is increased as well. © 2013 IOP Publishing Ltd.