Fig. 1. Schematic comparing different SORS approaches with conventional Raman. (A) Conventional backscattering Raman: laser excitation and Raman photon collection take place at the same point. (B) Conventional SORS: the point of collection is offset from the point of excitation by a spatial offset of Δs. (C) Ring collection SORS. The Raman photons are collected in a circular array around the point of excitation. (D) Ring illumination SORS: the laser illumination zone is in the shape of a ring and Raman photons are collected at the centre of the ring. (E) Transmission Raman: the laser excitation and the Raman collection zone are separated to the extreme. Raman collection takes place on the opposite side to laser illumination.