Laser Doppler multi-beam differential vibrometry
Vyacheslav Aranchuk, Ina Aranchuk, Brian Carpenter, Craig J. Hickey · The Journal of the Acoustical Society of America · 2020
A Laser Multi-Beam Differential Interferometric Sensor (LAMBDIS) for measuring vibration fields has been developed that alleviates one of the major issues of traditional laser Doppler vibrometers: effect on measurements by motion of the vibrometer itself. The LAMBDIS simultaneously measures Doppler shifts of light reflected from different points on the object surface illuminated with a linear array of laser beams. As a result, the LAMBDIS measures relative velocities between points on an object surface, while the Doppler shift caused by the sensor motion is approximately the same for all beams and is automatically subtracted from the measurements. This allows measurements of vibration fields of objects with high sensitivity from a moving platform. Scanning the linear array of laser beams in the transverse direction provides a two-dimensional vibration image of the surface. Performance of the sensor for ground vibration sensing for acoustic detection of buried objects has been investigated in the laboratory and field experiments. The sensor proved effective at detecting buried objects from a moving vehicle. [Work supported by the Office of Naval Research.]