Multi-beam full-field laser Doppler vibrometer based on a high-speed area scan CMOS camera

Multi-beam laser Doppler vibrometers (MB-LDVs) are capable of measuring dynamic surface deformation and analyzing non-stationary and transient events by measuring vibration at multiple points simultaneously. However, the number of measurement channels in current MB-LDVs is limited due to the complexity of electronic hardware, which increases with the number of measurement points and includes pin photodiodes, multichannel amplifiers, A/D converters, and signal processors. We developed a full-field MB-LDV based on an array scan high-speed digital CMOS camera that simultaneously measures vibrations in a matrix array of 17×17 points. The MB-LDV provides a measurement of vibration in the frequency range from 0 to 25 kHz with velocity noise in the range from 2 to 8 nm/s. Simultaneous measurements over the whole area allow for shorter measurement time in comparison to scanning single-beam LDV and linear array MB-LDV and obtaining an instantaneous velocity image of the measured area at any moment in time due to saving the phase information between the measurement points. Using an array scan high-speed digital camera allows for a large number of measurement points and a compact design of the MB-LDV, since the complexity of the hardware does not depend on the number of beams, which is limited by the camera's number of pixels. The experimental setup and performance of the developed full-field MB-LDV are discussed in this paper.