Patent ID: 7172292
Filing Date: 2007-02-06
Classification: G02B

Abstract:
1. 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 a meniscus convex 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, the first, second, third and fourth lens groups being arranged in the mentioned order from the screen to the image source, wherein the power lens included in the second lens group has a refractive index in a range from about 1.63 to 1.70.