Instrument for Measurement of Optical Parameters of Turbid Media by Using Diffuse Reflectance of Laser With Oblique Incidence Angle

摘要

An instrument for simultaneous measurement of absorption and reduced scattering coefficients of optically turbid materials is presented. Determination of the coefficient is based on scattering profile of a laser beam illuminating the sample at oblique incidence angle. The back reflected profile is recorded by imaging the scattered laser spot on material surface, and the coefficients calculated by determining the asymmetry and the slope of the reflectance profile. Several calibrated phantoms having different combinations of absorption and reduced scattering coefficients were measured. Measurement ranges were from 0.0047 to 0.118 ${rm mm}^{-1}$ for absorption and from 0.41 to 16.24 ${rm mm}^{-1}$ Results given by our instrument were compared together with manufacturer's values against calibrated reference results. Acquired absorption and scattering properties were in most of the cases smaller than reference values and variations of the relative errors were small. Instrument was not observed to be sensitive to small spatial deviations of sample from ideal measurement geometry. 95% of the determined parameters were within 10% of the average values in repeatability experiments.