Patent ID: 7661833

Claim:
A light guide device, comprising: a light guide substrate having a light input surface, a light output surface adjacent to the light input surface, a reflective surface opposite to the light output surface, and a plurality of microstructures formed on the reflective surface, the light guide substrate capable of generating phase retardation as a quarter wavelength retardation plate; and a sub-wavelength grating located on the light output surface; wherein two orthogonal stresses or strains in the light guide substrate form an angle in a range more than 0 and less than 90 degrees between one stress or strain and the light input surface of the light guide substrate; and further, a phase retardation due to the stress or strain difference is defined by the equation: δ=2 πCΔσL /λ=2 kπ+πk= 0,1,2,3,4 wherein δ represents the phase retardation value, L represents double a thickness of the light guide substrate, C represents a stress or strain optical coefficient, Δσ represents a stress or strain difference, and λ represents a wavelength of an incident light.