Patent ID: 6989929

Claim:
A Fresnel lens sheet for use in a rear projection screen that is used to display an image by allowing imaging light obliquely projected onto the sheet from a light-source side to emerge from the sheet toward a viewing side, the Fresnel lens sheet comprising: a sheet-shaped base; a plurality of first prisms having substantially triangular cross-sections formed on a light-source-side surface of the base on which the imaging light is projected, each of the first prisms having a first face from which the imaging light enters the first prism and which refracts the incident imaging light, and a second face that totally reflects toward the viewing side at least a part of the imaging light incident on and refracted at the first face; and a plurality of second prisms having substantially triangular cross-sections formed on a viewing-side surface of the base from which the imaging light emerges, each of the second prisms being so constructed that, of the imaging light incident on and refracted at the first face of each of the first prisms, those rays that travel to the viewing-side surface without being totally reflected at the second face of each of the first prisms to finally become stray light are controlled with respect to a reflection angle on the viewing-side surface to allow the rays becoming stray light to emerge toward an area outside of a visual field on the viewing side; wherein the plurality of first prisms are concentrically formed on the light-source-side surface around a center that is situated at a location off of the base.