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.

© 1982 Optical Society of America

Carbon dioxide laser stabilization by optoacoustic tracking of an SF₆ Lamb dip

D. Souilhac and A. Gundjian
Appl. Opt. 21(8) 1478-1481 (1982)

Extended Helmholtz resonator in low-temperature photoacoustic spectroscopy

J. Pelzl, K. Klein, and O. Nordhaus
Appl. Opt. 21(1) 94-99 (1982)

Optoacoustic spectroscopy of C₂H₄ at the 9- and 10-μm C¹²O₂¹⁶ laser wavelengths

R. J. Brewer, C. W. Bruce, and J. L. Mater
Appl. Opt. 21(22) 4092-4100 (1982)

Pulsed laser optoacoustic detection of flame species

Gregory P. Smith, Mark J. Dyer, and David R. Crosley
Appl. Opt. 22(24) 3995-4003 (1983)

Optoacoustic measurement of HCl specific absorption coefficients at DF laser wavelengths

Gabriele Krüger
Appl. Opt. 21(15) 2841-2844 (1982)