| 摘要 |
PURPOSE:To prevent the degradation in the accuracy of the reflecting surfaces of a rotary polygon mirror by thermal expansion by fixing the polygon mirror to a seat provided to a revolving shaft by using screws having approximately the same coefft. of linear thermal expansion as the coefft. of linear thermal expansion of this polygon mirror. CONSTITUTION:M3 bind machine screws 3 are inserted into holes (b) provided on the polygon mirror 1 and the screws are screwed to M3 internal threads (c) cut to the seat 2a of the revolving shaft 2, by which the polygon mirror 1 is pinched and fixed to the revolving shaft 2. The polygon mirror 1 and the M3 bind machine screws 3 have approximately the same coefft. of linear thermal expansion. The mirror and the screws, therefore, expand by the same quantity even if the temp. of the optical deflector rises and the pressure in the part of screw heads 3a to be applied on the polygon mirror 1 does not change. The generation of the strain in the reflecting surface of the polygon mirror finished with the high accuracy is prevented in this way. |
