Laser Doppler vibrometer with body vibration compensation

We report the development of a novel dual-beam laser Dop- pler vibrometer (LDV) that can eliminate the perturbation due to the vi- brometer body vibration without any external reference surface. A re- sidual laser beam from the beamsplitter is used to pick up the vibration of the damper, which is mounted in the vibrometer, and is combined with the reference beam at the photodetector. The output signal of this detec- tor and the main signal are processed to extract the object vibration, using a least-mean-squares adaptive algorithm. It is shown experimen- tally that the slowly varying statistics of the body vibration, which are valid in most practical cases, can be effectively removed from the mea- sured signal using digital signal processing (DSP) technology. © 2003