Patent ID: 8159664

Claim:
A method of measuring sub-surface Raman scattering through a diffusely scattering sample, comprising: (a) supplying incident radiation at one or more entry regions on a surface of the sample; (b) collecting light scattered within the sample, from a collection region on the surface, wherein one or more of the one or more entry regions is located around the collection region and at least one of the one or more entry regions is spaced from the collection region; (c) detecting, in the collected light, one or more Raman features spectrally related to the incident radiation; and (d) deriving, from the one or more Raman features, one or more characteristics of a sub-surface region of the sample, wherein incident radiation is supplied to a plurality of said entry regions each located at a different distance from said collection region, and the step of collecting comprises collecting light, separately for each entry region, at said collection region on the surface of the sample.