Continuous scanning laser Doppler vibrometer for mode shape analysis

Abstract

The vibration mode shape measurement technique utilizing a continuous scanning laser Doppler vibrometer (SLDV) is addressed. Continuous scanning capability is added to the conventional discrete laser Doppler vibrometer by reflecting the laser beam on the surface of the object using two oscillating mirrors. Bow scanning resulting from the proposed scanning mechanism is compensated by controlling the two mirrors. If a continuous sinusoidal scanning method is used, it can be shown that the velocity output signal from the SLDV is modulated to give the spatial velocity distribution in terms of coefficients that are obtained from the Fourier transformation of the time-dependent velocity signal. Using the Chebyshev series form, the analysis of vibration mode shape techniques for 2-D scanning is presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate. (C) 2003 Society of Photo-Optical Instrumentation Engineers.