| 摘要 |
PURPOSE:To make a lens system compact by constituting a reflecting face of a part of a spherical face. CONSTITUTION:Since the reflecting face is constituted of a part of a spherical face, the curvature of the reflecting face in a plane orthogonal to a revolving shaft of a rotary polygonal mirror 4 and that in a plane parallel with the revolving shaft of the rotary polygonal mirror are made equal to each other, and therefore, the reflecting face is concerned in image formation of light equally in both of the plane orthogonal to the revolving shaft of the rotary polygonal mirror and the plane parallel with it. Consequently, it is unnecessary to use a lens different in curvature in planes orthogonal to and parallel with the revolving shaft of the rotary polygonal mirror in a lens system arranged in the light incidence side of the rotary polygonal mirror. Thus, the lens system is made compact. |
