Patent ID: 7075727
Filing Date: 2006-07-11
Classification: G02B,H04N

Abstract:
1. A projection lens system for an image projection apparatus, said projection lens system configured to magnify and to project on a screen images reflected from a panel and passed through a prism, said projection lens system comprising: a first lens group having first and second spherical lenses of positive refraction power, and movable along an optical axis; a second lens group having a third doublet lens formed with a lens of positive refraction power and a lens of negative refraction power in junction to correct chromatic aberration, and a fourth spherical lens being convex on both surfaces thereof to correct spherical aberration; a third lens group having fifth and sixth spherical lenses of positive refraction power; and a fourth lens group having a seventh spherical lens being concave on both surfaces thereof, an eighth spherical lens of negative refraction power having a concave surface on one side thereof which is opposite to the seventh spherical lens and a convex surface on the other side thereof, and a ninth aspheric lens of negative refraction power having an aspheric surface at least on one side thereof, and arranged for distortion correction, wherein the first to fourth lens groups are sequentially arranged on an optical path in a direction toward the screen from the prism.