| 摘要 |
PROBLEM TO BE SOLVED: To hold a diffraction optical element unit without causing the deformation of the diffraction optical element unit and upsizing thereof. SOLUTION: The optical device is provided with the diffraction optical element unit DU obtained by superposing 1st and 2nd diffraction optical elements D1 and D2 where diffraction gratings 1, 3 and 4 are formed on base members 12 and 13 so that the diffraction grating sides may face to each other, a holding member 15 having a 1st abutting part A1 on which the 1st diffraction optical element abuts in a 1st direction along an optical axis and holding the diffraction optical element unit, and a presser means 16 pressing the 2nd diffraction optical element in the 1st direction. The 1st and the 2nd diffraction optical elements respectively have a 2nd abutting part A2 where either of them abuts on the other in the optical axis direction out of the area where the diffraction element is formed. The 1st and the 2nd abutting parts and the pressing position A3 of the 2nd diffraction optical element by the presser means are arranged on the same axis A parallel with the optical axis. COPYRIGHT: (C)2005,JPO&NCIPI
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