Optical sensing of microsystem motion and performance $ @ a

Microsystems involve several fabrication technologies, but share the common trait of dimensions and motions measured in microns. Small feature sizes and deflections make the detection of microdevice motion particularly diftlcult. The rapid operating frequencies of many microactuators compound the detection problem. Effective feedback, control, and performance measurement of microactuators thus become problematic. These measurements are particularly important, however, due to the developmental nature of many rnicrosystem technologies. Wear, lifetime issues, and optimized drive signals, for example, are poorly understood for many actuation devices. As microactuators move out of the development stage, and begin to perform work on external assemblies and environments, the various load conditions will also come into account. Since rnicroactuators involve small masses and inertias, effective driving of external loads may require feedbackbased control of the rnicrodevice. Optical sensing technologies offer solutions to these problems of sensor motion, microactuator analysis during the development process, and integrated feedback for microactuators driving extemai loads. Optical methods also lend themselves to the effectively one-dimensional nature of many microsystem motions, limiting the required signal analysis to practical levels that support real-time measurement and control. This paper describes several optical techniques for sensing motion, performance, and feedback data. some of which can integrated with the Microsystems themselves. For microactuators, experimental results indicate that real-time performance measurements are particularly revealing for understanding device motion and response. For microsensors, experimental results are also presented for interpreting motion using external and integrated optical techniques.