DIFFRACTION OPTICAL DEVICE AND ITS PRODUCTION METHOD

PROBLEM TO BE SOLVED: To provide a method by which two diffraction optical elements can be easily laminated and assembled with high accuracy. SOLUTION: By the method of producing a diffraction optical device, a laminated diffraction optical device consisting of two axially symmetric diffraction optical elements 10, 12 laminated is produced. The method includes a process of forming steps to form steps 1', 2' on the peripheral part of the axially symmetric diffraction optical elements 10, 11, respectively, in such a manner that the steps are concentric to the respective diffraction grating and have slightly different diameters from each other, a process of positioning to position the two axially symmetric diffraction optical elements in such a manner that the space between steps having different diameters from each other of the axially symmetric diffraction optical elements is made almost uniform as ( 1- 2)/2 in the circumference direction, and a process of fixing to fix the two axially symmetric diffraction optical elements in the positioned state in the positioning process.