Patent ID: 7352508
Filing Date: 2008-04-01
Classification: G02B,G03B

Abstract:
1. A Fresnel lens sheet useful for condensing imaging light obliquely projected from a projector to let the light emerge toward a viewer's side as nearly parallel rays, comprising: a base in sheet form; and a plurality of prisms formed on an incident side of the base, each of the prisms having a plane of refraction that refracts the imaging light projected and a plane of total reflection that totally reflects, toward the viewer's side, at least a part of the light refracted at this plane of refraction, wherein at least some of the plurality of prisms are so made that the imaging light that has been incident at an angle of not more than 40° and has passed through the Fresnel lens sheet emerges in a direction inclined toward a projector side at a predetermined angle of not more than 13° with respect to a normal perpendicular to a sheet plane of the base.