Abstract: A surface light source device is disclosed that provides greater light condensation in the frontal direction and higher luminance in comparison to a conventional surface light source device. Disclosed is a surface light source device providing a light source, a light guide having at least one of the side surfaces thereof as an incident surface and an outgoing surface substantially perpendicular to the incident surface, and at least two prism sheets, in which the surfaces formed by the prisms of the prism sheets are arranged so as to face upward, moreover the surfaces of the sides opposing the surfaces formed by the prisms of the prism sheets are arranged substantially parallel to the outgoing surface of the light guide.

Abstract: Provided are an easy-to-handle thin diffraction type light-condensing film exhibiting high light transmissivity and condensation ability, and a planar light source device using the film. A hologram optical element using diffraction/interference phenomena based on wave properties of light is used instead of a conventional prism sheet using refraction. As a result, the diffraction type light-condensing film and the planar light source device have high light transmissivity and are thin. In the diffraction type light-condensing film, dependence of bending angle on wave length is low and light entering from an oblique direction is bent in the vertical direction and emitted with spectral separation of white light suppressed. High light-condensation impossible in a conventional optical element is realized by suppressing angular variation in emission light for angular variation in incident light.

Abstract: Provided are an easy-to-handle thin diffraction type light-condensing film exhibiting high light transmissivity and condensation ability, and a planar light source device using the film. A hologram optical element using diffraction/interference phenomena based on wave properties of light is used instead of a conventional prism sheet using refraction. As a result, the diffraction type light-condensing film and the planar light source device have high light transmissivity and are thin. In the diffraction type light-condensing film, dependence of bending angle on wave length is low and light entering from an oblique direction is bent in the vertical direction and emitted with spectral separation of white light suppressed. High light-condensation impossible in a conventional optical element is realized by suppressing angular variation in emission light for angular variation in incident light.