A passive homodyne fibre vibrometer using a three-phase detector array

Abstract
A non-contact, optical fibre-based vibrometer is described with output in the form of a set of spatial fringes. The fringe system is sampled at three different phases using a non-multiplexed linear detector array. No source frequency modulation is necessary, allowing convenient use of a wide variety of lasers, and surface motion is measured free from directional ambiguity. Fringe interpolation and multiple-fringe unwrapping are effected using a digital fringe processor. With a received power of 4 nW, a minimum noise-equivalent phase sensitivity of 150 mu Rad Hz-1/2 is demonstrated.

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