Image display apparatus, and transmissive screen and reflecting mirror used for same
The present invention provides a technique suitable for making a set more compact by realizing reduction in height and reduction in depth. An image display apparatus of the present invention includes a reflecting mirror ( 4 ) for reflecting the image sent from a projection lens ( 2 ), and guiding the image to a transmissive screen ( 3 ). The reflecting-mirror ( 4 ) includes a planar mirror section ( 4 a ) for reflecting, of the entire image exiting the projection lens ( 2 ), only image portions projected onto the upper section of the transmissive screen ( 3 ), and a Fresnel mirror section ( 4 b ) with multiple reflective prisms for reflecting only image portions projected onto the lower section of the screen ( 3 ).
1. A screen onto which light from an image generation source is projected, said screen comprising:
a Fresnel lens sheet with concentric prisms each formed at the image-viewing side;
wherein centers of the concentric prisms are shifted from a center of said screen, and prism angles of the prisms change on the same circumference, and
wherein, when a substantially elliptic reference line is placed on said Fresnel lens sheet, the prisms at positions where they overlap the reference line have substantially the same required prism angle.
2. The screen according to claim 1 , wherein a center of the elliptic reference line is positioned in the centers of the prisms.
3. The screen according to claim 2 , wherein a prism angle of each prism positioned internally to the elliptic reference line, and a prism angle of each prism positioned externally to the elliptic reference line differ from each other.
4. The screen according to claim 2 , wherein the prism angle of each prism positioned internally to the elliptic reference line is smaller than the required prism angle, and the prism angle of each prism positioned externally to the elliptic reference line is greater than the required prism angle.