Ngoya Pepela

Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

Michael A. Marciniak, PhD


A laser vibration sensor (LVS) can be used to determine the vibrational spectrum of targets such as vehicles using heterodyne laser Doppler velocimetry. The vibrational spectra of exterior skin of vehicles are known to have characteristic resonances due to the physical structure driven by motor gears and other moving parts. Each particular class of vehicle has a unique vibrational spectrum. This research shows 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 vibrational velocity returning from the body under investigation. This is especially so when observing targets at large distances and the laser spot size has increased to encapsulate higher order modes vibrating at frequencies used for identification purposes. The research also contains preliminary investigations into the mitigation of these effects by use of laser scanning laser pattern intensity changing and advanced signal processing techniques.

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DTIC Accession Number