Patent ID: 7483102

Claim:
A surface light source, comprising: a light source unit which has a light emitting surface, and selectively emits rays of linearly-polarized light having a polarization plane in a predetermined direction and rays of non-polarized light from the light emitting surface; and a retardation element disposed at a light emitting side of the light source unit and comprising a first retardation layer array in which a plurality of first retardation layers and second retardation layers having a predetermined shape are arranged alternately, and a second retardation layer array disposed so as to have a gap from the first retardation layer array and having third retardation layers formed into a shape corresponding to the first retardation layers and arranged correspondingly to the first retardation layers, and fourth retardation layers formed into a shape corresponding to the second retardation layers and arranged correspondingly to the second retardation layers, the retardation element being arranged such that it emits therefrom rays of linearly-polarized light, among the rays of linearly-polarized light emitted from the light source unit, that pass through the first and third retardation layers and the second and fourth retardation layers by transforming the rays into rays of linearly-polarized light having a polarization plane which is substantially orthogonal to the polarization plane of the rays of linearly-polarized light emitted from the light source unit, and it emits therefrom rays of linearly-polarized light that pass through the first and fourth retardation layers and the second and third retardation layers by transforming the rays into rays of linearly-polarized light having a polarization plane which is substantially parallel with the polarization plane of the rays of linearly-polarized light emitted from the light source unit.