| 摘要 |
PURPOSE:To prevent a reflecting surface from tilting and to reduce the cost by forming a prism which have mirror surfaces (reflecting surfaces) as its flanks (polygonal surfaces) and then cutting it into plural rotary polygon mirrors. CONSTITUTION:A cylinder 1 made of aluminum alloy is cut to form the prism 2 almost in the same shape with the rotary polygon mirror, and the prism 2 is machined with high accuracy to form the reflecting surfaces 2a. Then one end surface 2b of the prism 2 is also machined with high accuracy to form the reflecting surfaces 2a and a reference surface 2c perpendicular to a hole 1a, and the prism is cut by thickness (t) corresponding to one rotary polygon mirror to form polygon plates (rotary polygon mirror) 3. Consequently, the parallelism of both end surfaces of each polygon plate 3 is irrelevantly to the formation of the reflecting surfaces, the reflecting surfaces 2a are prevented from tilting however many polygon plates 3 are formed, and the production cost is reduced. |
