| 摘要 |
PURPOSE:To hold a reflecting surface with high accuracy by gripping a polygon mirror with a receiving seat surface and a ring-shaped member provided on a rotary shaft and clamping the ring-shaped member threadably to a male screw provided on the rotary shaft. CONSTITUTION:After the polygon mirror 1 which has eight reflecting surfaces 2 at its periphery and is provided with a through hole 3 in the center is fitted to the fitting part 7 of the rotary shaft, the ring-shaped member 10 is clamped threadably to the male screw part 8 of the rotary shaft 4. Then the polygon mirror 1 is fixed while pressed against the receiving seat surface 5 which is finished into a highly accurate plane at right angles to the axial direction of the rotary shaft 4. At this time, the rotating direction wherein the screw is fastened is set to the opposite direction from the rotating direction of the polygon mirror 1 at the time of a rotary scan. Therefore, the screw is never loosened at the time of the rotary scan of the polygon mirror 1, which can stably be held. |
