Scanning grating based in-plane movement sensing

Abstract

A novel method for detecting the in-plane movement of MEMS devices has been presented, in which a scanning grating structure has been adopted. One end of the grating is directly connected to the movable platform under test, while the other end is fixed to a substrate, both by a suspending beam. Due to this structure design, any in-plane movement of the platform will be finally translated into grating rotation. When a laser beam is incident onto the grating, the direction of diffracted light as well as its spot position on a photosensitive device (PSD) will be changed accordingly due to the grating rotation. From the output of the PSD, the movement amplitude can be finally determined. With this novel sensing mechanism, not only static and dynamic movements, but also the transient structure response have been experimentally demonstrated. © 2010 IOP Publishing Ltd.