| 摘要 |
PURPOSE: To reduce a number of parts by unnecessitating a leaf spring and to attain reduction in cost. CONSTITUTION: A diffraction grating holder 1 to which a diffraction grating 2 is fixed at a side end part 1b is force-fitted into a hole 3 bored in a frame, plural protrusions 1a in the direction of an optical axis X provided on the outer peripheral cylindrical surface 1c of the diffraction grating holder 1 are in press-contact with the hole 3 and the whole outer peripheral surface is made not to be in press-contact with the hole 3. The diffraction grating holder 1 is made rotatable about the optical axis X after being force-fitted and a leaf spring, pressing against the diffraction grating holder 1 so as to be rotatable, is unnecessitated. |
