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Proceedings Paper

Improvement of sensitivity of acousto-optical imaging using a powerful long pulse laser
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Paper Abstract

Acousto-optical imaging is based on the detection of strongly scattered light which is in part modulated by its interaction with an ultrasonic wave. This method benefits from the acoustic uniformity (low acoustic scattering and absorption) of an optically diffusive medium and the spectrally selective absorption of photons. In this work, we consider the use a pulsed single-frequency laser to increase the instantaneous optical power applied to the diffusive medium while maintaining the average power below the maximum permissible exposure. Such a laser source concentrates the illumination of the diffusive medium during the transit time of the ultrasonic toneburst. This allows collecting more ultrasound-modulated photons for a given ultrasonic wave amplitude. We found, however, that a pulsed laser of this kind generates additional noise which limits the sensitivity gain expected from its high peak power. Progress toward sensitive imaging was achieved by developing methods to reduce the impact of this additional noise. Results obtained with differential detection, laser beam spatio-temporal homogenization and variable delay synchronization are presented. With such measures, the use of a pulsed laser appears a promising solution for enhancing the sensitivity in acousto-optical imaging.

Paper Details

Date Published: 28 February 2008
PDF: 10 pages
Proc. SPIE 6856, Photons Plus Ultrasound: Imaging and Sensing 2008: The Ninth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 68561O (28 February 2008); doi: 10.1117/12.761667
Show Author Affiliations
Guy Rousseau, National Research Council Canada (Canada)
Alain Blouin, National Research Council Canada (Canada)
Jean-Pierre Monchalin, National Research Council Canada (Canada)


Published in SPIE Proceedings Vol. 6856:
Photons Plus Ultrasound: Imaging and Sensing 2008: The Ninth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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