| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system in which the broadening of a luminous flux having a predetermined wavelength band is suppressed while keeping the function to divide or combine a plurality of wavelength bands having different dispersions by using a diffraction grating, and to provide an optical apparatus using the optical system. SOLUTION: The optical system 2 divides or combines a plurality of wavelength bands having different dispersions and has the reflection type diffraction grating 4 which performs a diffractive reflection by a periodic ruggedness on the surface. The surface of the diffraction grating 4 is composed of a material for increasing the reflectivity and the cross section of the diffraction grating in the plane parallel to the incident face is rectangular or substantially rectangular. For the wavelength of an arbitrary light beam in the plurality of wavelength bands, the conditions 0.6<λS/Λ<0.85, 0.85<λL/Λ<1.1 and 0.55<h/Λ<0.75 are satisfied so that a light beam S1 in a short wavelength band is specularly reflected and light beams L1 to L8 in a long wavelength band are diffracted and reflected on the diffraction grating 4, whereλS represents the longest wavelength in the short wavelength band,λL represents the shortest wavelength in the long wavelength band (λS<λL), h represents the height of the diffraction grating andΛrepresents the period of the surface ruggedness of the diffraction grating. COPYRIGHT: (C)2008,JPO&INPIT |
