17 July 1996 Holographic microscope for measuring displacements of vibrating microbeams using time-average holography
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An optical microscope, utilizing the principles oftime-average hologram interferometry, is described for MicroElectroMechanical Systems (MEMS) applications. MEMS are devices fabricated via techniques such as micro photolithography to create miniature actuators and sensors. Many ofthese sensors fmd their way into applications which rely on, or depend upon, the dynamic behavior ofthe sensor. Typical dimensions of current MEMS devices are measured in microns, and the current trend is to further decrease the size of MEMS devices to submicron dimensions. However, the smaller MEMS become, the more challenging it is to measure with accuracy the dynamic characteristics of these devices. In this paper, the theory and construction of an electro-optic holographic microscope (EOHM) for the purpose ofstudying the dynamic behavior ofMEMS devices are described. Additionally, by performing measurements within an EOHM image, object displacements are determined as illustrated by representative examples. With the EOHM, MEMS devices with surface sizes ranging from approximately 35 x400 microns down to 5 x 18 microns have been studied while undergoing resonant vibrations at frequencies as high as 2 MHz.
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Gordon C. Brown, Gordon C. Brown, Ryszard J. Pryputniewicz, Ryszard J. Pryputniewicz, "Holographic microscope for measuring displacements of vibrating microbeams using time-average holography", Proc. SPIE 2860, Laser Interferometry VIII: Techniques and Analysis, (17 July 1996); doi: 10.1117/12.276296; https://doi.org/10.1117/12.276296

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