Phase plate having fine periodic structure smaller than visible light wavelength and projection image display apparatus

摘要

A phase plate includes a transparent substrate and a periodic structure formed on a substrate surface of the transparent substrate. The phase plate is configured to provide light having a predetermined design wavelength that vertically enters the substrate surface with a phase difference from ¼ wavelength to ¾ wavelength. The periodic structure is configured to reduce a volume occupation rate with increasing distance from the transparent substrate, and the periodic structure has a height of at least 200 nm. An angle between a first direction in which a center of a width of a unit periodic structure at a position closest to the substrate surface is connected with a center of a width of a unit periodic structure at a position farthest from the substrate surface and a normal direction of the substrate surface is from 5 degrees to 30 degrees.