| 摘要 |
PROBLEM TO BE SOLVED: To obtain a diffraction optical device in which undesired light generated on a grating side face hardly degrades imaging performance, even when incident light reaches the grating side face, and to provide an optical system having the grating optical device. SOLUTION: The diffracting optical device has a diffraction grating section, in which the concentric circular periodic structure is given, such that blazed diffraction gratings have a lens action, each blazed diffraction grating including a grating face and a grating side face and diffracting light in specific order (designed order) in the entire area of a wavelength being used. The grating side face is inclined so as to be obtuse-angled greater than the angle between a face normal and a grating face at each grating leading end of an enveloping face in which the grating leading ends of the diffraction grating are connected. The inclination of the grating side-face is set such that the inclination angle formed between the enveloping face and the face normal changes from the central area of the diffraction grating section to peripheral area thereof and so as to have at least one area, where the amount of change in the inclination angle between the adjacent diffraction gratings is not zero in succession. COPYRIGHT: (C)2006,JPO&NCIPI
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