Digital demodulation of an interferometer for the characterization of vibrating microstructures

摘要

The rapid expansion of the microelectromechanical systems (MEMS) industry and the increasing number of applications in communications, displays, and sensing has led to an increasing demand for robust characterization techniques capable of in situ characterization of MEMS structures. Interferometry is well suited to such characterization due to its wide measurement dynamic range, its fine resolution, and its non-invasive qualities. We have constructed a fiber optic interferometer for the in situ characterization of MEMS structures. We report the development and implementation of a real-time digital signal processing (DSP) algorithm to demodulate the interferometer. We have developed a computationally efficient algorithm for both stabilization of the interferometer at quadrature and determination of the target's vibration amplitude. We have verified our demodulation scheme using a piezoelectric transducer driven mirror as the target. Our current system will measure vibration amplitudes down to 10 nm. Both theoretical and experimental results are presented.