| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffraction optical element being easy to manufacture and having a high diffraction efficiency, which has a diffraction grating which doesn't diffract one of two kinds of light having different wavelengths but diffracts the other. SOLUTION: In a diffraction optical element 1 which makes two lights having different wavelengths incident thereto, a diffraction grating 2 has many echelon gratings 4 provided with the prescribed number of stages of stepped parts 7 comprising rise surface parts 5 being along the incidence direction and diffraction surface parts 6 which are bulged from the rise surface parts 5 and are formed with narrow width, and such a height is given to the stepped parts 7 that an optical path difference being integer times as long as the wavelength of one light may be given to one of two lights passing adjacent diffraction surface parts 6. The diffraction grating 2 comprises a narrow part 8 where diffraction surface parts 6 are formed with narrower width and a wide part 9 where diffraction surface parts 6 are formed with wider width, and the number of stages of echelon gratings 4 in the narrow part 8 is made smaller than that in the wide part 9. COPYRIGHT: (C)2004,JPO
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