Patent ID: 6801366
Filing Date: 2004-10-05
Classification: G02B,H04N

Abstract:
A projection lens system for enlarging and projecting an image from an image generating source onto a screen, said lens system having a plurality of lens elements therein which lens elements are arranged from a first end nearest said screen to a second end nearest said image generating source, as follows:a first lens for compensating an aberration, said first lens having an optical axis, and having a positive refraction power in a central portion thereof;; a second lens having a biconvex shape, and having strongest positive refraction power among the plurality of lens elements therein; and a third lens connected to a cooling liquid for cooling said image generating source, said third lens having a negative refraction power and being formed into a meniscus shape, with a concaved surface thereof directed toward said screen; wherein, a cross-section of said third lens is defined by a function Z(r); the absolute value of the second derivative values of said function Z(r) increase within a range of values of â€œrâ€  from zero up to a predetermined point, and monotonically decreases from said predetermined point to a maximum value of â€œrâ€ ; Z is the position of a point on a surface of said lens in a direction parallel to said optical axis thereof; and â€œrâ€  is a radial distance of said point from said optical axis.