Polygon mirror and optical scanning device having the same

摘要

A polygon mirror including a plurality of reflection surfaces. Each reflection surface has a writing region and two non-writing regions. The writing region includes a first reflecting section and a second reflecting section positioned downstream of the first reflecting section in a rotating direction of the polygon mirror. One non-writing section is positioned at an upstream end of each reflecting surface, and the other non-writing region is positioned at a downstream end of each reflecting surface. The first reflecting section has a reflection factor higher than a second reflection factor of the second reflecting section. A foggy region appears in the first reflecting section.