| 摘要 |
PURPOSE:To reduce noises resulting from the fluctuation of the air by so providing wind protecting pipes as to allow optical axes between a polygon scanner and a first prism, between the polygon scanner and a beam splitter and between the polygon scanner and a first light source to pass therethrough, respectively. CONSTITUTION:In the title measuring apparatus, plastic or metallic wind protect ing pipes 2c-2a are provided in a manner to pass through each optical path between a polygon scanner 3 and a prism mirror 5, between the polygon scanner 3 and a beam splitter 4 and between the polygon scanner 3 and a light source 1a, respectively. Accordingly, the air outside the pipes 2a-2c is shut from the air where the light beams L1-L3 pass, whereby the noises due to the fluctuation of the air can be reduced, ensuring highly accurate measurement. If the pipes 2a-2c with undulatory inner shape in the longitudinal direction are used, the irregular reflection of the light beam scanned by the polygon scanner 3 within the pipes 2b, 2c can be prevented. |
