Vibration monitoring by using a dynamic proximity sensor with interferometric encoding

An optical sensor for the dynamic measurement of proximity is presented. The sensor combines an extrinsic geometric transducer with interferometric encoding for high vibration sensitivity. Static calibration showed a unique variation in interference contrast over at least 60 fringes, leading to a measurement range of 20 mum and a resolution of at least 0.033mum. Dynamic excitation by using low-amplitude vibrations at 3.6 kHz showed a similar contrast variation, verifying fringe discrimination up to the sixth order. With verification of dynamic performance over all 60 fringes, the sensor should offer a low-cost approach to vibration monitoring in electrical switchgear.