We report on time-resolved reflectance imaging experiments on a scattering medium containing a spatially limited absorber. The medium is illuminated at two positions with pulses from a mode-locked and cavity dumped picosecond dye laser. Time-resolved imaging of the back-scattered light is realized by means of a RF-phase-sensitive camera, synchronized to the laser pulses. The camera consists of a sinusoidally modulated proximity-focused image intensifier, a thermo-electrically cooled CCD camera, and a digital image processor unit. In operation, at least two images are taken under different image intensifier modulation conditions, such as modulation phase or modulation degree. By processing the stored images, a final image can be created the contrast of which is based only on time differences of the back-scattered photons. We found that this image reveals the presence and, to a certain extent, the position of a spatially limited absorber within the scattering medium. These experiments have been performed to evaluate possible ways towards an eventual optical tomography in living tissue.

Date Published: 1 May 1991
PDF: 12 pages
Proc. SPIE 1431, Time-Resolved Spectroscopy and Imaging of Tissues, (1 May 1991); doi: 10.1117/12.44186

Published in SPIE Proceedings Vol. 1431:
Time-Resolved Spectroscopy and Imaging of Tissues
Britton Chance, Editor(s)