| 摘要 |
PURPOSE:To reduce the form drag without narrowing a scanning range by performing the chamfering to a second corner part between an edge line and a chamfering part between plural reflecting mirror surfaces. CONSTITUTION:Chamfering is performed to the second corner part 19 in which corner parts 15, 17 to which chamfering is performed and an edge line between reflecting mirror surfaces of a polygon mirror intersect with each other, as well, and the generation of peeling is prevented. That is, in case of a state that chamfering is not performed to the corner part 19, this corner part 19 is pointed, and becomes a state that peeling is apt to be generated. As for each chamfering quantity, when width of the polygon mirror, the chamfering quantity in the first corner part and the chamfering quantity in the second corner part are denoted as h0, h1 and h2, respectively, it is desirable that h1, and h2 are set to 10%-40% of h0, and 10%-50% of h1, respectively. In such a way, by performing that chamfering to the corner part 19, the form drag is reduced. Also, since boundary parts 40, 41 between each reflecting mirror surface are left, the specular surface being effective for scanning can be secured. |
