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Development of a continuous scanning laser Doppler vibrometer for vibration mode shape analysis

Addresses the vibration mode shape measurement technique utilizing a continuous scanning laser Doppler vibrometer (SLDV). The scanning capability is added to the conventional discrete LDV by reflecting the laser beams on the surface of the object using a harmonically oscillating mirror which is driven by an electromagnetic resonant scanning actuator. The precise and sufficient sweep angle is obtained without using a position controller. 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 which are obtained from the Fourier transformation of the time dependent velocity signal. Using the Chebyshev series form, the analysis of the vibration mode shape techniques for straight line scanning and 2D area scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a cantilever beam.