Patent ID: 7173766

Claim:
A zoom lens used as a projection lens of a projector in which a prism is located between the projection lens and a spatial optical modulating element, wherein a lens closest to the spatial optical modulating element is a meniscus positive lens whose convex surface faces a screen, and a refractive index of the meniscus positive lens is 1.75 or more, and wherein the following conditional expressions (1) and (2) are satisfied: âˆ’0.3<( GLR 1 /GLndâˆ’Bfw )/ fw<âˆ’ 0.05â€ƒâ€ƒ(1) 2.5 <fGL/fw< 3.5â€ƒâ€ƒ(2) where GLR1 is a radius of curvature of a surface of the lens closest to the spatial optical modulating element, the surface facing the screen, GLnd is a refractive index at the d-line of the lens, Bfw is a air equivalent back focus of the zoom lens at a wide-angle end, and fw is a focal length of an entire zoom lens system at the wide-angle end, and fGL is a focal length of the lens closest to the spatial optical modulating element.