Patent ID: 6825993
Filing Date: 2004-11-30
Classification: G02B

Abstract:
A wide-angle lens of fixed focal length consisting of four lens groups, in order from the object side, as follows:a first lens group of negative refractive power that includes a plastic negative lens element; a second lens group of positive refractive power that includes a plastic positive lens element; a diaphragm; a third lens group of positive refractive power that includes a positive lens component formed of a biconvex lens element joined on its image side to a negative lens element; and a fourth lens group; whereinthe wide-angle lens includes an optical axis and at least one lens element having at least one aspheric lens surface, and the following conditions are satisfied: 0.5<D2/f<1.0 Nave<1.65 &ngr;ave>44.0 whereD2 is the distance along the optical axis between the first lens group and the second lens group, f is the focal length of the wide-angle lens, Nave is the arithmetic average of the refractive indexes, at &lgr;=587.6 nm, of the materials from which all the lens elements of the wide-angle lens are made, and &ngr;ave is the arithmetic average of the Abbe numbers, at &lgr;=546.1 nm, of the materials from which all the lens elements of the wide-angle lens are made.