Effect of Multi-Mode Vibration on Signature Estimation Using a Laser Vibration Sensor

A Laser Vibrations Sensor (LVS) can be used to determine the vibrational spectrum of targets, such as vehicles, using heterodyne laser Doppler velocimetry. The vibrational spectra of vehicles are known to have characteristic resonances due to the motors, gears and other moving parts. Each particular class of vehicle has a unique vibrational spectrum. This research shows of how a body vibrating in higher order modes has the opportunity to eliminate spectral content of the target's vibrational spectrum while using an LVS to perform spectrum estimation. This is due to roughly equal amounts of laser photons with equal and opposite information about the target's velocity returning from the body under investigation.