ABSTRACT
This chapter focuses on the methods and physical properties of laser Doppler vibrometry that are important for the characterization of dynamics in Microelectromechanical Systems. An interferometer illuminates a specimen with a coherent light source having a frequency and measures the phase of the back-reflected or the back-scattered light. The theoretical limit of the noise of photodetectors is given by the quantum character of light and current. The impinging beam is frequency-shifted acousto-optically by 40 MHz in respect to the reference beams to realize a shot-noise-limited heterodyne interferometric detection. In addition, vibrometry in conjunction with optical profile measurement methods opens interesting measurement possibilities. The combination of interferometric profile determination techniques with 3-D motion data is important to combine oscillation data with geometry data. The scanning laser Doppler vibrometer technique was used to measure the resonance frequencies of the individual levers and for the presentation of the out-of-plane operational deflection shape.
