Laser multi-beam differential interferometric sensor for acoustic detection of buried objects

Laser multibeam differential interferometric sensor for acoustic detection of buried objects

“…The relative velocity signals from LAMBDIS channels are used to form a relative vibration velocity image of the scanned area. The vibration velocity image in a selected frequency band is created by calculating a spectrogram for each channel, calculating the mean value of the signal magnitude over a selected frequency band and combining the mean values of the signal for all channels 4 , 12 …”

“…E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 7 ; 1 1 6 ; 4 4 4 The vibration velocity image in a selected frequency band is created by calculating a spectrogram for each channel, calculating the mean value of the signal magnitude over a selected frequency band and combining the mean values of the signal for all channels. 4,12 It should be noted that the Doppler shift of light reflected from each point on the object contributes to each of adjacent channels with an opposite sign. As a result, the demodulated vibration velocity phase flips by 180 deg for every other channel.…”

“…To overcome the limitations of LDVs for ground vibration measurement caused by its operation from a moving platform, we developed a novel laser multibeam differential interferometric sensor (LAMBDIS) that provides a measurement of vibration fields of objects with high sensitivity, while having low sensitivity to the whole-body motion of the object or sensor itself. 12,13 The principle of operation of the LAMBDIS is based on the interference of light reflected from different points on the object surface illuminated with an array of laser beams. The LAMBDIS measures relative vibration velocities between points on the object surface with interferometric sensitivity and has low sensitivity to the motion of the sensor itself.…”