Patent ID: 6791764
Filing Date: 2004-09-14
Classification: G02B,Y10T

Abstract:
A metallic die for molding an optical element capable of transmitting light, wherein the optical element comprises an optical surface having an optical axis; diffractive grooves provided on at least a part of the optical surface and each of the diffractive grooves including a first surface capable of being approximated by a predetermined optical function and a second surface extending in a direction to cross the first surface;the metallic die comprising: a surface corresponding to the first surface of the optical element, wherein the predetermined optical function is represented by the following formulae: N=INT(Ah2+Bh4+C), X&af;(h,N)=h2/(rN&af;(1+&Sqrt;(1-(1+KN)&it;h2/rN2)))+A4N&it;h4+A6N&it;h6+A8N&it;h6+A10N&it;h6+Î”&it;â€ƒ&it;N,where N denotes the number of a ring-shaped zone of each of the diffractive grooves, h denotes a height from the optical axis, X denotes a distance from a tangent plane in the direction of the optical axis, rN denotes a radius of a curvature of N-th ring-shaped zone, KNA4N to A10N are coefficients of an aspherical surface of the N-th ring-shaped zone, and &Dgr;=âˆ’&lgr;0/(n<1) denotes an amount of a face shift corresponding to 1&lgr;0 on the optical axis.