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Laser Doppler vibrometer employing active frequency feedback



Akobuije D. Chijioke, John R. Lawall


We present a heterodyne Michelson interferometer for vibration measurement in which feedback is used to obviate the need to unwrap phase data. The Doppler shift of a vibrating target mirror is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the oscillator control voltage provides a direct measurement of the target velocity. Outside the servo bandwidth, phase-sensitive detection is used to evaluate high-frequency displacements. This approach is of great interest for the frequently-occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is important as well.
Applied Optics


interferometry, vibration


Chijioke, A. and Lawall, J. (2008), Laser Doppler vibrometer employing active frequency feedback, Applied Optics (Accessed April 17, 2024)
Created September 17, 2008, Updated February 17, 2017