Proceedings Article | 31 July 2003
KEYWORDS: Microelectromechanical systems, Control systems, Manufacturing, Laser Doppler velocimetry, Patents, Fiber Bragg gratings, Silicon, Doppler effect, Velocity measurements, Optics manufacturing
The active silicon microstructures known as Micro-Electromechanical Systems (MEMS) are improving many existing technologies through simplification and cost reduction. Many industries have already capitalized on MEMS technology such as those in fields as diverse as telecommunications, computing, projection displays, automotive safety, defense and biotechnology. As they grow in sophistication and complexity, the familiar pressures to further reduce costs and
increase performance grow for those who design and manufacture MEMS devices and the engineers who specify them for their end applications.
One example is MEMS optical switches that have evolved from simple, bistable on/off elements to microscopic, freelypositionable beam steering optics. These can be actuated to discrete angular positions or to continuously-variable angular states through applied command signals. Unfortunately, elaborate closed-loop actuation schemes are often necessitated in order to stabilize the actuation. Furthermore, preventing one actuated micro-element from vibrationally
cross-coupling with its neighbors is another reason costly closed-loop approaches are thought to be necessary.
The Laser Doppler Vibrometer (LDV) is a valuable tool for MEMS characterization that provides non-contact, real-time measurements of velocity and/or displacement response. The LDV is a proven technology for production metrology to determine dynamical behaviors of MEMS elements, which can be a sensitive indicator of manufacturing variables such as film thickness, etch depth, feature tolerances, handling damage and particulate contamination. They are also
important for characterizing the actuation dynamics of MEMS elements for implementation of a patented controls technique called Input Shaping®, which we show here can virtually eliminate the vibratory resonant response of MEMS elements even when subjected to the most severe actuation profiles.
In this paper, we will demonstrate the use of the LDV to determine how the application of this compact, efficient algorithm can improve the performance of both open- and closed-loop MEMS devices, eliminating the need for costly closed-loop approaches. This can greatly reduce the complexity, cost and yield of MEMS design and manufacture.
