System Model for MEMS based Laser Ultrasonic Receiver
W. C. Wilson
NASA Langley Research Center, US
Keywords: MEMS, Laser Ultrasonic, MOEMS,
This paper investigates the system modeling of a MOEMS based Laser Ultrasonic receiver system. See Figure 1 for a block diagram of the system. The LUT receiver is comprised of a laser, and an optical system that detects the ultrasonic waves. The laser beam is reflected off a material in which ultrasonic waves have been created. The laser beam interacts with induced ultrasonic waves creating an ultrasonically modulated reflected beam. This reflected beam is directed by the micro-optical components to a photo-emf detector  where the beam is combined with a reference beam to demodulate the ultrasonic signal. The photo-emf detector outputs a signal that is proportional to the velocity of the ultrasonic waves. Materials integrity is established by analysis of the received signals.
The system model is constructed using MATLAB?s dynamical simulator, Simulink. The model employs the top down design approach which hierarchically breaks down the LUT receiver into manageable components. See Figure 2 for the top level block diagram. Each component is modeled using matrix geometrical optic methods and includes some image processing. The optical models employ geometrical system matrices for calculations involving the focus, and magnification factor.
NSTI Nanotech 2003 Conference Technical Program Abstract