| http://www.w3.org/ns/prov#value | - The third imaging element 27 of the reflecting optical system 16 is made up of an optical element such as a lens having a predetermined numeric aperture, and with the focal length on the diffraction grating 11T side as F1, and with the focal length on the reflector 26 side as F2, the diffraction grating 11T is disposed on around one of the focal positions of the third imaging element 27, and the r
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