This chapter explains the working principle and the preparation techniques of a polymer dispersed liquid crystal (PDLC) film. It shows the numerical or approximate approaches usually followed in the description of electro-optical properties of PDLCs. An emulsion-type PDLC is obtained by preparing an emulsion of liquid crystals (LC) in an aqueous solution of a water-soluble polymer. Light scattering is due to refractive index mismatch, but requires droplets with size comparable with visible light wavelength. Light passing through a PDLC film is affected by the presence of LC droplets acting as ‘scattering objects’. PDLC-based devices are compact, low-weight and PDLC do not require use of polarizers, produce images bright enough to allow use in normally lighted rooms. Placing a PDLC film between a dielectric substrate and a conducting surface it is possible to measure two-dimensional charge distributions on dielectric surfaces in real time.