Fig. 2.

(a) Raman spectroscopy system for transcutaneous and exposed-bone measurements. Light gray corresponds to the laser illumination path and dark gray corresponds to the Raman scattering collection path. Abbreviations: ST, shutter; L, lens; MMF, multimode fiber; BP, bandpass filter; BS, dichroic beam-splitter; MTS, motorized translation stage; NF, notch filter; FB, fiber bundle; SPEC, spectrograph; HG, holographic grating; CCD, charge-coupled device. (b) Image of the fiber bundle geometry. For the transcutaneous measurements submitted to SOLD, the data were binned together yielding three total spectra per acquisition (one from the center fiber and first annulus, one from the next annulus, and one from the last two annuli) as indicated by the semi-transparent green circle and rings. The circular array of collection fibers is rearranged into a line for delivery to the imaging spectrograph so that the Raman scattered light collected by each fiber can be separately recorded.