Optical tomograph with photon counting and projective reconstruction of the parameters of absorbing 'phantoms' in extended scattering media

A highly sensitive detection system with time-resolved photon counting was developed for modulation optical tomography (diode laser with a power of 15 — 30 mW, modulation frequency 100 MHz) of extended scattering objects. Experiments with model objects (linear dimensions up to 140 mm, absorption coefficients of 0.005 — 0.015, scattering coefficients of 1.4 mm^–1) showed that the propagation of optical radiation in such media is described by a relative path-lengthening coefficient which varied in the range 1.2—4.2, depending on the absorption coefficient and on the size of the object. A rapid projection algorithm for the solution of the inverse problem was used in the reconstruction of images of strongly absorbing inclusions known as 'phantoms' (cylinders 10 — 23 mm in diameter). An algorithm was developed for the solution of the direct problem, which made it possible to reduce the solution time to 5  —  10 min.