Fig. 10. UMARS imaging of bilayer solid powders ammonium nitrate (AN) & trans-stilbene (TS) using 10 optical fibres (830 nm diode laser, laser power: 300 mW, acquisition time: 100 s). The imaging experiments have been carried out by keeping the excitation beam at the interface of the two layers while fibre numbers 1 through 5 were placed around the bottom layer while fibres 6 through were placed around the top layer. TS being a strong Raman scatterer showed intense spots (fibres 1–5, top) on the CCD as compared to AN. Identification of the spatial position is possible with UMARS imaging. Y axis: projection of 10 separate collection fibres on different pixel rows. Spectrum at the top of the figure corresponds to the sum of all y pixels (full vertical binning).