Share Email Print

Proceedings Paper

Fast-response variable-focusing micromirror array lens
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs® surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The rotation converges rays and the translation adjusts the optical path length difference of the rays to be integer multiples of the wavelength. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs® design rules. The fabricated lens is 1.8mm in diameter, and each micromirror is approximately 100mm x 100mm. The lens fill-factor is 83.7%, the numerical aperture is 0.018 for a wavelength of 632.8nm, and the resolution is approximately 22mm, whereas the resolution of a perfect aberration-free lens is 21.4μm for a NA of 0.018. The focal length ranges from 11.3mm to infinity. The simulated Strehl ratio, which is the ratio of the point spread function maximum intensity to the theoretical diffraction-limited PSF maximum intensity, is 31.2%. A mechanical analysis was performed using the finite element code IDEAS. The combined maximum rotation and translation produces a maximum stress of 301MPa, below the yield strength of polysilicon, 1.21 to 1.65GPa. Potential applications include adaptive microscope lenses for scanning particle imaging velocimetry and a visually aided micro-assembly.

Paper Details

Date Published: 22 July 2003
PDF: 9 pages
Proc. SPIE 5055, Smart Structures and Materials 2003: Smart Electronics, MEMS, BioMEMS, and Nanotechnology, (22 July 2003); doi: 10.1117/12.483577
Show Author Affiliations
James G. Boyd, Texas A&M Univ. (United States)
Gyoungil Cho, Texas A&M Univ. (United States)

Published in SPIE Proceedings Vol. 5055:
Smart Structures and Materials 2003: Smart Electronics, MEMS, BioMEMS, and Nanotechnology
Vijay K. Varadan; Laszlo B. Kish, Editor(s)

© SPIE. Terms of Use
Back to Top