| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffraction optical element capable of maintaining high diffraction efficiency in the whole service wave length area and an optical system using it. SOLUTION: In a diffraction optical element 1 formed so as to enhance diffraction efficiency of the specific degree (the design degree) in the whole service wave length area by laminating plural diffraction gratings, these plural diffraction gratings have (n) pieces [(n) is an integer not less than 2] of diffraction gratings opposed by mutually sandwiching an air layer, and in these (n) pieces of diffraction gratings, the plural diffraction degrees having high diffraction efficiency respectively exist in the service wave length area, and the shape of these (n) pieces of diffraction gratings is properly set.
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