Laser schlieren microphone for optoacoustic spectroscopy

J. G. Choi, G. J. Diebold

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

This paper describes a laser schlieren microphone, where a low-power He-Ne laser beam is deflected by a reflecting diaphragm mounted on an optoacoustic Helmholtz resonator. The sinusoidal pressure variations in the resonator distort the surface of the diaphragm so that the reflected laser beam is alternately focused and defocused. The deflection is converted into an amplitude modulation of the beam by an iris located at a distance from the resonator and detected with a photodiode. The light beam can be modulated at a high frequency and the signal from the photodiode processed with a lock-in amplifier so that noise with a power spectral density proportional to the inverse of the frequency is significantly reduced in the final optoacoustic signal. A mathematical description of the laser schlieren microphone is given that shows the system to respond linearly to small signals. An experiment was done to determine the range of linear response of the microphone to large amplitude optoacoustic signals.

Original languageEnglish
Pages (from-to)4087-4091
Number of pages5
JournalApplied Optics
Volume21
Issue number22
DOIs
Publication statusPublished - 1982 Nov 15

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering

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