| 摘要 |
PURPOSE:To obtain a rotating polygon mirror made of synthetic resin which has highly durable surface accuracy by varying the thickness of a plate-like part, which connects a boss part forming a hole in the center of the rotating polygon mirror to faces of the polyhedron, in the center and edge part of the surface. CONSTITUTION:The plate-like part 14 tangent to the mirror face part 11 is provided with a curved slope 30A, so that the molding pressure of resin can be uniformly applied to the center (a), an intermediate part (b) and an erect face part (c). Namely, as cross sections I-I-III-III show the center (a), the intermediate part (b) and the edge (c), respectively, slope lengths lambdaa, lambdab and lambdac are set so as to become gradually lower, although the thickness (t) of the bottom of the slope 30A is the same. The titled mirror is constituted so that the molding pressure of resin injected to each face of the mirror face part 11 can be kept uniform. Thus such troubles as the warp and deformation of the mirror face part, which have been difficult to circumvent at the time of molding resin, can be eliminated. Besides, weight of said mirror can be lightened to mass- produce the mirrors without imposing a burden on a drive system and a control system. |
