| 摘要 |
PURPOSE:To provide a large polarizing angle even in a polygon mirror having a small mirror inscribed circle radius by constituting an optical system in such a manner that reflecting surfaces for reflecting light incident on the polygon mirror are optically conjugate with each other. CONSTITUTION:A beam of light incident on a first reflecting surface 11a is allowed to pass through optical systems 12-15 and enter a second reflecting surface 11b which is optically conjugate with the first reflecting surface 11a. The beam of light incident on the first reflecting surface 11a is polarized by rotation of a polygon mirror 10 and is further polarized by the second reflecting surface 11b. Thus the beam of light is emitted at twice as large a polarizing angle as when reflected only once. The first reflecting surface is rotated along with the polygon mirror 10 but the position of incidence of the beam of light entering the second reflecting surface 11b from the first reflecting surface 11a is not changed because of the optical systems. Therefore the length of each of mirror surfaces formed into the first and second reflecting surfaces can be reduced in the scanning direction and hence the inscribed circle radius of the polygon mirror 10 can be reduced. |
