The use of circular optical grating for measuring angular rotation of mirrors

This paper explores the feasible use of circular optical grating for measur ing the rotation of mirrors that are commonly found in micro-systems. Both theoretical and experimental results show that distortion of the circular g rating that is projected onto the mirror surface is a simple function of th e angular rotation of the mirror. The circular grating may readily be gener ated using a standard Michelson interferometer or an LCD projector. Through manipulating the distance between the interferometer and the mirror surfac e, the diameter of the optical grating may be varied. Furthermore, the addi tional use of a converging lens enables a significant reduction in the size of the grating: with simple laboratory facility, small circular grating of about 400 mum is achieved for use on micro-systems. With the use of more s ophisticated optical elements, the angular rotation of even smaller micro-m irrors may be measured. (C) 2001 Published by Elsevier Science Ltd.