Patent ID: 8585209

Claim:
A projection apparatus, comprising: an oblique projection optical system configured to project an image displayed at an image display surface in an obliquely enlarging way onto a transparent screen of a projection surface; wherein said transparent screen has an integral constitution, and has a form wherein a plurality of linear Fresnel lenses, with a cross-sectional shape configured to change depending on a position in a vertical direction of a screen, are installed continuously in the vertical direction of the screen on an incidence side of image light; wherein a diffusion layer containing a diffusion material having light diffusion action, and a substrate, are provided on the image viewing side of a linear Fresnel lens; wherein said oblique projection optical system is configured by a plurality of lenses and at least one mirror configured to fold a light path; wherein a region where light flux for forming an image on said screen passes, in a lens arranged at the nearest position to the projection surface, does not include an optical axis shared by a largest number of lenses among optical axes of said plurality of lenses; and wherein when L represents space between the lens arranged at the nearest position to said projection surface and said projection surface, and D represents diagonal dimension of the projection screen, a following relational expression is satisfied: 1.75 <D/L.