Fig. 1. Schematic diagram of the CP imaging method. (a) The colorless weaving tape placed on a 5 mm-thick cotton layer; (b) and (c) polarized light microscopy of a single cotton fiber and the tape, respectively. (d) Scheme of the experimental setup.

Fig. 2. (a) Experimental CP images of colorless weaving tape, (b) cotton layer and (c) their mixture where the tape is placed beneath the layer. In contrast to (c), a transmission image (d) was captured with the second linear polarizer removed.

Fig. 3. Schema of photon propagation in the fiber-contaminant mixture. (a) A realistic microscopic model, in which the above and beneath elements are two crossed polarizers, H and V, respectively. (b) Single scattering of oblique incident light by an anisotropic fiber in a cylindrical coordinate system pϕz. (c) Photon migration of birefringence and multiple bireflectances within the contaminant denoted in a local frame xyz.

Fig. 4. (a) The relative intensity of the transmission and reflection modes with only a contaminant. (b) and (c) show the simulated CP images of the contaminant uncovered and covered by the cotton layer, respectively.

Fig. 5. (a) The occurrences of the photons in the image vs. their scattering number n. (b) Corresponding calculated CP images for different values of n.

Fig. 6. (a) Simulated and (b) measured images and (c) their contaminants, which are the background color difference over the different layer thicknesses h.