Patent ID: 7468769

Claim:
A retardation compensator for compensating the phase retardation caused by birefringence of incident light to a liquid crystal layer of a liquid crystal device for a signal-plate type liquid crystal projector, the retardation compensator being located at a position to cover at least one of the incident surface and the emanation surface of the liquid crystal device, the retardation compensator comprising: a form birefringence in which the absolute value of the retardation, defined as the product of the birefringence and the thickness in the optical axis direction, is approximately the same as the absolute value of the retardation of the liquid crystal layer in operation at least at one wavelength in the visible band, wherein the form birefringence is a retardation compensation film comprising at least two kinds of thin film layers with different refractive indices that are alternately layered, and the optical thickness of each thin film layer is 1/100 to ⅕ of the standard wavelength of blue light.