22 May 1997 Capillary-blood-flow monitoring using laser speckle contrast analysis (LASCA): improving the dynamic range
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We have developed a technique, called laser speckle contrast analysis (LASCA), to monitor capillary blood flow. Like the earlier method 'single-exposure speckle photography' it uses the phenomenon of time-varying speckle, drawing on models that relate the statistics of the speckle pattern, especially the contrast, to the velocity of the scatterers. Temporal variations in the pattern blur the captured image, whether photographic or digital, reducing the contrast. LASCA is a fully-digitized, full-field, non-invasive technique and operates in quasi-real-time: it grabs an image and then produces a 2-dimensional map of contrast variations representing differing velocities. Previously the data had been stretched, as a full range of contrasts could not be achieved. This problem has been addressed and we believe solved, thus giving us a full range of contrasts. In this paper we look at the effects of changing the exposure time. If it is varied it should be possible, according to the models used, to look at different ranges of velocity. Also we hope to show that by using different wavelengths together it is possible to distinguish between flow at different depths in the skin. We illustrate the validity of our technique with some of our results and then compare these to other methods of measuring capillary blood flow.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Glenn J. Richards, Glenn J. Richards, J. David Briers, J. David Briers, } "Capillary-blood-flow monitoring using laser speckle contrast analysis (LASCA): improving the dynamic range", Proc. SPIE 2981, Coherence Domain Optical Methods in Biomedical Science and Clinical Applications, (22 May 1997); doi: 10.1117/12.274304; https://doi.org/10.1117/12.274304

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