Patent ID: 7162139
Filing Date: 2007-01-09
Classification: G02B,Y10S

Abstract:
1. A surface light source device equipped with a light source and a transparent plate emitting light from a light emitting surface which is situated at the reverse side against an observation side surface by conducting light from the light source, wherein a plural number of minute concave portions or convex portions for prevention of reflection are periodically arranged on at least one of the observation side surface and the light emitting surface, the lower limit value of the period of the concave portions or convex portions is defined to be the period at which incident light to the surface where the concave portions or convex portions are arranged generates diffraction light, with respect to a determined value of the wavelength in vacuum of visible light having the shortest wavelength which emits from the light source and a determined value of the refractive index of the transparent plate, and the concave portions or convex portions are formed at a smaller period than the lower limit value.