Patent ID: 8345254

Claim:
A method of analyzing an optically thin sample comprising: a) providing an optically thin sample and an optical system, said optical system comprising at least one optical probe arranged to emit a collimated ray, at least one detector and a detector plane and said sample being within the optical system, thereby defining a sample plane; b) constructing an n×m C matrix based on said sample, wherein (n) rows represent logical detector regions and (m) columns represent sample regions by dividing the detector plane into n logical regions with a coordinate system commensurate with the optical system, and diving the sample plane into m regions; c) propagating a collimated ray through the optical system from each vertex on the sample plane such that said ray is directed through the sample and then reflected back through the sample one or more times, and noting the coordinates each time the sample surface is intersected, wherein angle of incidence for the ray is the same for each sample pass; d) for each set of sample plane intersections from (c), execute steps (e) and (f); e) for each row representing a detector region, execute step (f); f) for each sample region, calculating the fraction of the sample region that lies within the detector region; g) adding each value obtained in step (f) for each sample region to the value in the column of the C matrix for that sample region; h) calculating the inverse of the C matrix; and i) calculating the distribution of absorbency in the optically thin sample using the inverse of the C matrix and a column vector of absorption measured by each detector.