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Proceedings Paper

Multispectral angular domain optical tomography in scattering media with argon and diode laser sources
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Paper Abstract

Angular Domain Imaging (ADI) within highly scattering media employs micromachined angular filter tunnels to detect nonscattered photons which pass through the tunnels unattenuated while scattered photons collide with the tunnel walls. Each tunnel is micromachined approximately 51 &mgr;m wide by 10 mm long in silicon, giving a maximum acceptance angle of 0.29 degrees. The ADI technique is inherently independent of wavelength, and thus multispectral laser sources can be incorporated. Previous ADI experiments employed a 488-514 nm Argon ion laser source. This paper describes the construction of a new imaging system utilizing a high-power (up to 0.5 W) laser diode at the 670 nm wavelength, along with an aspheric and cylindrical lens system for shaping the beam into a collimated line of light. ADI results of biological samples (i.e. chicken breast tissue) are also presented. Image resolution is 204 &mgr;m or better in compressed chicken breast tissue approximately 3.8 mm in thickness. Digital image processing techniques are employed to improve image contrast, definition, and detectability of test structures. Because silicon is 40% reflective, scattered light at up to three times the acceptance angle is not sufficiently absorbed by the angular filter tunnels and contributes significant background noise, thus decreasing image contrast and detectability. Roughening of the tunnel surface using a NH4OH etchant solution scatters light hitting the walls, thus allowing it to be absorbed. Images after roughening show dramatic reductions in background scattered light levels between tunnels, suggesting that further experiments will make progress towards improved contrast and detectability of structures.

Paper Details

Date Published: 6 February 2007
PDF: 12 pages
Proc. SPIE 6435, Optical Interactions with Tissue and Cells XVIII, 64350M (6 February 2007); doi: 10.1117/12.701813
Show Author Affiliations
Paulman K. Y. Chan, Simon Fraser Univ. (Canada)
Fartash Vasefi, Simon Fraser Univ. (Canada)
Glenn H. Chapman, Simon Fraser Univ. (Canada)
Bozena Kaminska, Simon Fraser Univ. (Canada)
Nick Pfeiffer, Simon Fraser Univ. (Canada)

Published in SPIE Proceedings Vol. 6435:
Optical Interactions with Tissue and Cells XVIII
Steven L. Jacques; William P. Roach, Editor(s)

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