Fringe Scanning Interferometric Imaging of Small Vibration Using Pulsed Laser Diode.

概要

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We propose the interferometric method of imaging micro-vibration by using a semiconductor pulsed laser diode. The Michelson interferometer was used to obtain stroboscopic interference image of the vibrating surface. The stroboscopic interference fringes were obtained with a vidicon camera. A micro-cantilever for an atomic force microscopy was used as a sample to demonstrate usefulness of the proposed technique. The micro-cantilever was excited by pressure of sound at a resonant frequency of 18.4kHz. The measured interference fringes were analyzed by the phase-measurement method (fringe scanning method). By changing time delay for the laser pulse irradiation, vibrations of the micro-cantilever at different phases were obtained. The distribution of the vibration was visualized sequentially. The measurement error was calculated to be approximately 20nm. The measured distribution of the vibration agreed well with the theoretical results calculated by the finite-element method. The method investigated in this paper will be useful for measuring micro vibrations of ultrasonic devices and micro-mechanical systems.
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