Silver-coated Crossed Surface Relief Gratings (CSRGs) are fabricated and used for imaging and detecting localized refractive index variations in inhomogeneous water-based solutions via polarization-contrast Surface Plasmon Resonance (SPR). When placed in between crossed polarizers, incident light was transmitted at intensity levels directly and precisely related to the local refractive index value. This occurred due to the in-plane polarization conversion of the SPR light in between the orthogonal grating vectors. When viewed with a camera, SPR light from a monochromatic source enabled the acquisition of polarization-contrast microscopy images of a water and silicon oil mixture placed over the CSRG’s surface.