An optical compensator includes a C-plate adapted to be coupled to a liquid crystal cell and made from a polymer. The C-plate has a layer thickness ranging from 5 to 60 μm. The polymer is polyvinyl alcohol, has a polymerization degree greater than 2000 and less than 5000, and is cross-linked so that the C-plate has an optical axis substantially parallel to the direction of normally incident light, and so that the C-plate has a plate retardation, along the layer thickness of the C-plate, greater than 60 nm.