| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffraction optical element which can be easily manufactured, can reduce the wavelength dependence of diffraction efficiency, and can effectively prevent the occurrence of flare or ghost or the like. SOLUTION: In the diffraction optical element having a first relief pattern 201 formed at a boundary between a first domain 101 and a second domain 102 and a second relief pattern 202 formed at a boundary between the second domain 102 and a third domain 103, the first domain, the second domain, and the third domain are substantially transparent to a used wavelength and have different refractive indexes. Further, the first relief pattern and the second relief pattern have serrated cross sections passing a common symmetry axis of rotation and have a plurality of first ramps and a plurality of second ramps which are alternately and successively formed in a concentric circular shape around the symmetry axis of rotation. The first ramp has a slope more gentle than that of the second ramp and length of the ramp becomes gradually shorter from the symmetry axis of rotation toward an outer peripheral part and one end of the longest ramp among the first ramps is in agreement with the symmetry axis of rotation. COPYRIGHT: (C)2005,JPO&NCIPI
|
