Patent ID: 6771435
Filing Date: 2004-08-03
Classification: G02B,Y10T

Abstract:
An optical element capable of transmitting light, comprising: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; a second surface extending in a direction to cross the first surface and being parallel to the optical axis with an angular error not greater than 1Â°; and a third surface not approximated by the predetermined optical function and to connect the first surface and the second surface; wherein a width of the third surface in the direction perpendicular to the optical axis is 0.5% to 15% of the sum of a width of the first surface in the direction perpendicular to the optical axis and the width of the third surface in the direction perpendicular to the optical axis, and wherein the predetermined optical function is represented by the following formula: N=INT(Ah2+Bh4+C), X(h,N)=h2/(rN(1+(1âˆ’(1+KN)h2/rN2)))+A4Nh4+A6Nh6+A8Nh8+A10Nh10+&Dgr;N, wherein 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/(nâˆ’1) denotes an amount of a face shift corresponding to 1&lgr;0 on the optical axis.