| 摘要 |
PROBLEM TO BE SOLVED: To obtain a diffraction optical element which has high diffraction efficiency for diffracted light of specific order (design order) in a wide wavelength range and can sufficiently suppress unnecessary diffracted light, is easely manufactured and to improve internal transmittance of the diffraction optical element at this time. SOLUTION: The diffraction optical element has a structure in which a first diffraction grating made of a first material and a second diffraction grating made of a second material are stacked so that diffraction surfaces of diffraction parts of respective diffraction gratings are in contact with each other. The second material is made of a material obtained by mixing a particulate material with a resin material. Then a refractive index of the first material to a (d) line, an Abbe number, partial dispersion ratios to a (g) line and an F line, and partial dispersion ratios to the (g) line and (d) line are denoted as nd1,νd1,θg and F1, andθg and d1 and set to suitable values. Similarly, values of the second material are also denoted as nd2,νd2,θg and F2, andθg and d2 and refractive index, Abbe number to a (d) line are denoted as ndb2,νdb2 and set to suitable values. COPYRIGHT: (C)2009,JPO&INPIT
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