DIFFRACTING OPTICAL ELEMENT AND ITS MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a method of easily layering two diffracting optical elements with high precision. SOLUTION: This method of manufacturing a stack type diffracting optical element having two axially-symmetrical diffracting optical elements stacked has a ring part forming stage for forming ring-shaped recessed parts 3 and 4 having slightly different diameters coaxially with the optical axis in the vicinity of the optical axis 10 of the axially-symmetrical diffracting optical elements 1 and 2, a positioning stage for positioning the two axially-symmetrical diffracting optical elements so that the gap between the recessed parts 3 and 4 of the axially-symmetrical diffracting optical elements respectively having different diameters is nearly uniform in the circumferential direction, and a fixing stage for fixing the two axially-symmetrical diffracting optical elements having been positioned at the positioning stage.