| 摘要 |
PROBLEM TO BE SOLVED: To suppress reduction in optical characteristic of a diffraction optical element by reducing harmful light. SOLUTION: In the diffraction optical element 20, diffraction gratings 21, 22, etc. and planes 23, 24, etc. substantially vertical to the optical axis of incident light are alternately formed on the incident surface, and diffraction gratings 31, 32, etc. and planes 34, 35, etc. substantially vertical to the optical axis of the incident light are alternately formed on the emitting surface, so that the diffraction gratings 21, 22, etc. on the incident surface and the planes 34, 35, etc. on the emitting surface are mutually opposed, and the planes 23, 24, etc. on the incident surface and the diffraction gratings 31, 32, etc. on the emitting surface are mutually opposed. COPYRIGHT: (C)2009,JPO&INPIT
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