Papers by Author: Ming Wang

Abstract: The stress gradient of a deposited thin-film is a mechanical parameter that affects the performance of MEMS devices, so in-situ measuring stress gradient of a thin-film is great significant. A new in-situ measuring method based on a center-anchored circular plate is presented. The Mirau interferometer has been used to measure the out-of-plane height at the edge of circular plate, then the curvature radius of the plate and the stress gradient of the film can be calculated. The measuring method has been verified by CoventorWare. The accuracy of the presented measuring method is ideal. The advantages of the method also have been discussed.

Abstract: In order to improve the displacement measurement accuracy of the laser diode self-mixing interference (SMI), phase measurement method is introduced in the SMI signal analysis. In this paper, three modulation technique have been proposed: injection current modulation, external cavity length modulation and sinusoidal phase modulation. Measurement principle of the three modulation techinque are briefly explained. Design of the experimental system, measurement results of micro-displacement will be reported.

Abstract: A novel self-mixing interference signal analysis method is proposed based on the use of an electro-optic modulator (EOM). Self-mixing interference occurs in the laser cavity by reflecting the light from a mirror-like target in front of the laser. Sinusoidal phase modulation of the beam is obtained by an EOM in the external cavity. The phase of the interference signal is calculated by four-bucket integration technique. The interferometer is applied to measure the displacement of a high-precision commercial PZT with an accuracy of a few nanometers.