High sensitivity pulsed laser vibrometer and its application as a laser microphone

We experimentally demonstrate a high sensitivity pulsed laser vibrometer that is capable of detecting optically rough surfaces vibrating with the displacement value of 75 pm as well as its application as a laser microphone. By directing the probe light beam repeatedly onto the vibrating diaphragm and/or pressure sensing interface, the sensitivity of the pulsed laser vibrometer in detecting the displacement of the vibrating diaphragm is significantly improved down to an estimated value of less than 4 pm In this paper, we present the principles of operation of this new kind of laser microphone together with experimental validations.