METHOD FOR DESIGNING FRESNEL LENS TYPE DIFFRACTIVE OPTICAL ELEMENT

摘要

PROBLEM TO BE SOLVED: To reduce the amount of design data when a Fresnel lens type diffractive optical element manufactured through a semiconductor process is designed by CAD.;SOLUTION: A ring zone radius r_n and a phase distribution P1 are derived from a first design grid space a1 which is sufficiently smaller than the minimum processing size of the semiconductor process. A design grid a2 which is larger than the minimum processing size is set; a rounding process using a2 is performed for r_n, a ring zone radius rr_n and the focal length f2_n of each ring zone for the case are found; and further a second phase distribution P2 relating to rr_n is obtained. A plurality of concentric areas are set along the radius direction of a lens, a phase error (P1-P2) and weighted dispersions obtained by weighting it corresponding to each area size are found by the areas, and the sum of respective weighted dispersions is found. According to respective pieces of data obtained by a procedure of varying a2, design grids by the areas are selectively set on condition that the sum of the weighted dispersions is within a permissible range.;COPYRIGHT: (C)2004,JPO&NCIPI