Depth assessment of an absorber in a semi-infinite medium by continuous wave diffuse reflectance

Abstract

A method to locate an absorber embedded in a semi-in nite turbid medium by spatially-resolved continuous-wave di use re ectance measurements is introduced. The possible of use the method as a priori information in di use optical imaging is discussed. The depth of the absorber is assessed by single wavelength spatially-resolved continuous-wave di use re ectance measurements by two detectors in a radial row. The ratio of perturbations introduced by the defect at two detectors is used to be matched with Ratio-vs.-Depth curve which are generated by approximate formulae of continuous wave di use re ectance. The error due to approximation and the error in depth assessment are studied for di erent cases revealing favorable source-detector placements with respect to planar position of the defect. The e ect of lateral displacement of the source with respect to defect is studied. A strategy to overcome errors introduced by erroneous prediction of background medium optical properties is suggested. Theoretical results indicate that the depth of the absorber can be obtained with 0.1 mm precision independent of its absorption coe cient and its size for the values chosen in the study. The approach is tested experimentally, and it is observed that theoretical results t with experimental data.|Keywords : Spatially-resolved continuous wave di use re ectance, absorber localization, a priori information, di use optical imaging.