| 摘要 |
A diffractive optical element (1) composed of a ceramic, in which the optical characteristics are enhanced by enhancing the machining precision, is composed of an infrared-transmissive ceramic, and prominent portions (11) and groove portions (12) are repeatedly formed on a surface of the diffractive optical element (1). The average value of the surface roughness Ra within an optical effective area (10) of the surface of the diffractive optical element is 0.05 μm or less, and the difference in the surface roughness Ra within the optical effective area (10) of the surface is 0.02 μm or less.
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