Spatially encoded multibeam laser Doppler vibrometry using a single photodetector

Abstract

A laser Doppler vibrometer with single photodetector is introduced to measure the vibration on multiple

points of target simultaneously. A 2 5 beam array with various frequency shifts is generated by three

acousto-optic devices, illuminating different points on a vibrating object. The reflected beams interfere with

a reference beam on a high-speed photodetector, and the signal is amplified and digitized with a rate of

500 megasamples/s. To extract vibration information of different points, the carrier frequencies of each

beam are elaborately designed so that they can be separated from cross-talk regions in the spectrum. The

experimental results are compared with that from a commercial single-point vibrometer, and the comparison

shows that it is possible to do a precise measurement on multiple points simultaneously using a single

photodetector.