Fig. 1. A diagram of spectrometer used for reflectance measurements with polarized illumination/detection.

Fig. 2. Schematic presentation of polarized light scattering from diffusely scattering substrate alone (top) and from spherical scatterers placed atop the substrate (bottom). Five different types of scattering events (I–V) can take place and are described in the text.

Fig. 3. Reflectance spectra and forward and backward scattering spectra calculated from Mie theory for: 5 µm polystyrene beads in water (A); 5 µm polystyrene beads in glycerol (B); and 10 µm polystyrene beads in glycerol (C). Reflectance spectrum obtained using unpolarized detection is shown in purple; depolarization ratio spectra in black; fits to equation (12) in green; forward components of Mie scattering in red; backscattering Mie components in blue. The theoretical curves are multiplied by coefficients extracted from the least-square algorithm used to achieve the best fits for the experimental data. Arbitrary DC offsets are added to theoretical curves in order to facilitate comparison of all curves on one graph.

Fig. 4. Density dependence of scattering of 5 µm polystyrene beads in water: (A) a semi-regular monolayer of 5 µm polystyrene beads; (B) depolarization ratio spectra of a water suspension (blue) and of a monolayer of the beads (red).

Figure 5. Scattering spectra of SiHa cells: (A) phase-contrast photographs of cells in: a pure PBS buffer (left), BSA/PBS solution that matches the refractive index of the cytoplasm (middle), and acetic acid/PBS solution (right); (B) reflectance spectra of SiHa cells in the presence of acetic acid (red), in the PBS buffer (black), and in the presence of high concentration of BSA (blue). Experimentally measured depolarization ratio spectra and Mie theory calculations for scattering of: (C) cells in BSA/PBS (measured depolarization ratio spectrum - black, the best fit to equation (12) - green, forward Mie scattering component of the nucleus - red, backscattering of the nucleus - blue); (D) cells in PBS (measured depolarization ratio spectrum - black, the best fit to equation (12) - green, forward Mie scattering component of the cytoplasm - red, backscattering of the cytoplasm - blue, forward Mie scattering component of the nucleus - purple, backscattering of the nucleus - brown); (E) cells in acetic acid/PBS (measured depolarization ratio spectrum - black, the best fit to equation (12) - green, forward Mie scattering component of the nucleus - red, backscattering of the nucleus - blue). The theoretical curves are multiplied by coefficients extracted from the least-square algorithm used to achieve the best fits for the experimental data. Arbitrary DC offsets are added to theoretical curves in order to facilitate comparison within one plot.

Fig. 6. Measured reflectance spectra and Mie calculations for normal cervical biopsy: (A) reflectance spectra obtained using unpolarized (blue) and polarized (black) illumination/detection; (B) depolarization ratio spectrum (black), calculated fit to equation (12) (green), forward Mie component of nucleus (red), forward Mie component of cytoplasm (orange), and backward Mie component of cytoplasm (blue). The theoretical curves are multiplied by coefficients extracted from the least-square algorithm used to achieve the best fits for the experimental data. Arbitrary DC offsets are added to theoretical curves in order to facilitate comparison within one plot.

Fig. 7. Oral cavity reflectance spectra obtained in vivo and corresponding Mie theory calculations: (A) reflectance spectra obtained using unpolarized (blue) and polarized (black) illumination/detection. (B) Polarized reflectance spectrum (black), calculated fit to equation (12) (green), forward Mie component of scattering of nucleus (red), and backscattering Mie component of nucleus (blue). Arbitrary DC offsets are added to the theoretical curves in order to facilitate comparison within one plot.