| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffractive optical element capable of obtaining an excellent image by reducing flare generated from the grating wall surface of a diffraction grating, when the diffractive optical element is used to reduce the chromatic aberration of an imaging optical system and to provide the imaging optical system having the diffractive optical element. SOLUTION: The diffractive optical element is provided in the optical path of the imaging optical system. The diffractive optical element has a diffraction surface including a grating surface and the grating wall surface arranged at a predetermined grating pitch in at least a part of the boundary between a first material and a second material different from each other in dispersion and refractive index. When the side of the first material is set as a light incident side, the refractive index of the first material is smaller than the refractive index of the second material; and when a position where the grating wall surface is in parallel with the center axis of the diffractive optical element is set as the reference position of the grating wall surface, the grating wall surface is inclined in a direction where a vertex angle of grating formed by the grating wall surface and the grating surface is smaller than that in the reference position in at least a part of the range of the diffraction surface. COPYRIGHT: (C)2011,JPO&INPIT
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