| 摘要 |
PURPOSE:To form the polygonal mirror with which surface inclination hardly arises and which has high accuracy by providing an outer peripheral layer consisting of plastic to the outer peripheral surface of an aluminum alloy body having a high Young's modulus and forming a specular surface by vapor deposition of metals on the surface thereof. CONSTITUTION:The Al alloy material having the Young's modulus as high as >=8,000kg/mm<2>, for example, an AC9A material and AC9B material (8,500 to 9,000kg/mm<2> Young's modulus) are used for a bar-shaped member 1 as the body material. A plastic material is joined by injection molding, etc., to the outer peripheral surface of this bar-shaped member to form the outer peripheral layer 2. This member is properly cut. The specular surface is formed by the vapor deposited film of the metal (for example, Al, Cu, Mg) having the excellent reflecting characteristic to laser light on this composite stock. Since the specular surface is supported from the inner side by the body having the high Young's modulus, the high-accuracy mirror which is not deformed at the time of working and obviates the generation of the surface inclination is obtd. |
