Patent ID: 8320048
Filing Date: 2012-11-27
Classification: G02B

Abstract:
1. A projection lens comprising: a first lens having at least an aspheric surface; a second lens having a concave surface facing the reduction side of the projection lens, and having negative refractive power; a third lens; a fourth lens having a convex surface facing the reduction side, and having positive refractive power; a fifth lens having a concave surface facing the reduction side, and having negative refractive power; and a sixth lens having a convex surface facing the reduction side, and having positive refractive power, which are sequentially arranged from the magnification side of the projection lens, wherein the following formulas (1) and (2) are satisfied: f: focal length of the entire system of the projection lens, Bf: back focus in air of the entire system, and fa: combined focal length of lenses from the second lens to a most-reduction-side lens.