Patent ID: 7580187
Filing Date: 2009-08-25
Classification: G02B

Abstract:
1. A diffractive optical element comprising a transparent substrate, wherein a surface of said transparent substrate is divided into fine rectangular areas of identical shape which line up in two orthogonal directions, wherein, with respect to light incident vertically on the surface of said transparent substrate, an l-th, and a (l+1)-th rectangular area in an l-th row, where l is an odd number, gives a phase 2pπ, and a phase {(4q+1)π/2+δπ/2}, respectively, and an l-th, and a (l+1)-th rectangular area in a (l+1)-th row gives a phase {(4r+3)π/2+3 δπ/2}, and a phase {(4s+2)π/2+δπ}, respectively, provided that −0.25≦δ≦0.25, and p, q, r, and s is an integer, characterized in that: wherein each rectangular area includes one or more intermediate areas adjacent to an adjacent rectangle such that the one or more intermediate areas have phase values that are substantially average of phase value of the rectangular area and the adjacent rectangle, wherein the phase values of the intermediate areas are computed after the phase values of the rectangular area and the adjacent rectangular areas are converted to a value of 0 to 2π wherein the intermediate areas are shaped like isosceles triangles with a base being equal to a side of the rectangular area and a height being equal to a/L where L is a repetitive pitch of a basic pattern in vertical and horizontal directions of the optical element and a is a variable.