| 摘要 |
In a diffractive optical element, first and second diffraction gratings of 10 mum or less in thickness made from materials of respective different Abbe numbers are laminated through an air layer. The grating thickness of the first diffraction grating is made to be 7.5 mum, and the grating thickness of the second diffraction grating is made to be 6.54 mum. Glass of the Abbe number of 63.8 is used for the material of the first diffraction grating, and an ultraviolet curable polymer of the Abbe number of 23.0 is used for the material of the second diffraction grating. Accordingly, the diffraction efficiency of the diffractive optical element is improved to 97% or higher throughout the entire visible spectrum.
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