Title :
A Varifocal Convex Micromirror Driven by a Bending Moment
Author :
Hokari, Ryohei ; Hane, Kazuhiro
Author_Institution :
Dept. of Nanomech., Tohoku Univ., Sendai, Japan
Abstract :
A varifocal micromirror is designed and fabricated using silicon micromachining technology. A spherical convex surface of mirror is generated by applying a bending moment to the circumference of micromirror. This method is different from the conventional technique in which a distributed force is exerted on the central area of mirror. On the basis of the theory of materials strength, the deformation of a plate is purely spherical if only a bending moment is applied to the circumference. Spherical surface is well approximated to be a parabola if deflection is small. In order to generate only a bending moment, a force is applied to the plate in the region outside the fulcrum, by which the plate is supported freely in rotation. The proposed mirror was fabricated from a silicon on insulator wafer and a glass plate, which were connected by anodic bonding. The deviation in surface profile of mirror from a parabola was measured with an optical interferometer to be less than 4.7 nm rms in the mirror region inside the 400-mum-diameter fulcrum at the voltage lower than 215 V. The focal length of the fabricated mirror was varied from approximate infinity to 24 mm.
Keywords :
adaptive optics; bending; bonding processes; light interferometry; micro-optomechanical devices; micromachining; micromirrors; optical design techniques; optical fabrication; silicon; surface topography measurement; adaptive optics; anodic bonding; bending moment; distributed force; materials strength; microelectromechanical devices; optical interferometer; plate deformation; silicon micromachining technology; size 400 mum; spherical convex surface; spherical surface; varifocal convex micromirror fabrication; Adaptive optics; microelectromechanical devices; mirrors;
Journal_Title :
Selected Topics in Quantum Electronics, IEEE Journal of
DOI :
10.1109/JSTQE.2009.2017034