Patent ID: 7347566

Claim:
A projection lens unit having a plurality of lens elements for magnifying and projecting an original image displayed on an image source, onto a screen, comprising: a first lens group including a meniscus lens which has a positive refractive power and which has a center part configured so as to be convex on the screen side thereof; a second lens group including a power lens having a highest positive refractive power among the plurality of lens elements; a third lens group composed of a single lens element having opposite side surfaces which are convex near an optical axis thereof, having a positive refractive power, and having a peripheral part which has meniscus concave configuration on the image source side thereof, and a fourth lens group having a lens surface which is concave on the screen side thereof and having a negative refractive power, wherein the power lens has a following relationship: 49<(1 /P 2 )<57 where P 2 =((1/R 3 )−(1/R 4 )) R 4 : a radius of curvature of an incident surface of the power lens, and R 3 : a radius of curvature of an emergent surface of the power lens.