A system for in-situ monitoring of particles in a process fluid includes a flow channel having a window for flowing the process fluid therethrough. The window includes an inner surface having a coating thereon that reduces a buildup rate of the particles on the inner surface. A light source is for directing a polarized beam along a first beam path through the window into the process fluid such that an output beam emerges from the process fluid along a second beam path. A polarizing filter positioned in the second beam path is for filtering the output beam. A photodetector is for detecting the output beam after passing the polarizing filter that generates signals that represent images of the particles in the process fluid. A controller coupled to the photodetector is for analyzing the signals to determine at least one parameter related to the particles in the process fluid.