Patent ID: 7529023
Filing Date: 2009-05-05
Classification: G02B,G03B

Abstract:
1. A projection type image display apparatus comprising an image forming source for forming an image, a screen and a projection optical device for magnifying the image formed by the image forming source and projecting it obliquely to have a predetermined angle with respect to a normal line of the screen, wherein the screen has at least a Fresnel lens sheet including a plurality of Fresnel lenses concentrically arranged on a light emitting side of the Fresnel lens sheet, prism angles of the Fresnel lenses increase in a direction radially outward from a center of the concentric Fresnel lenses, and the Fresnel lens sheet includes a plurality of incidence face prisms extending horizontally and juxtaposed vertically on a predetermined area of a light incidence surface of the Fresnel lens sheet, which area includes a position opposite to the center of the Fresnel lenses, wherein a vertical width of the predetermined area including the incidence face prisms is T/15-T/4, where T is a vertical width of the screen.