| 摘要 |
PURPOSE:To contrive the decrease, etc., of a rotating speed of a rotary polygon mirror by allowing a focusing light beam to be made incident on the rotary polygon mirror so that it is not shielded by a fixed plane mirror, reflecting repeatedly this focusing light beam between the rotary polygon mirror and the fixed plane mirror, and enlarging a deflection angle made by the rotary polygon mirror. CONSTITUTION:A fixed plane mirror 20 is placed so as to be opposed to a specular surface part 11 of a rotary polygon mirror 10, and a focusing light beam l1 is made incident on the rotary polygon mirror 10 at a prescribed elevation angle phi against a virtual plane being orthogonal to a rotation axis (m) of the rotary polygon mirror 10 so that it is not shielded by this fixed plane mirror 20. This focusing light beam l1 is reflected repeatedly between the rotary polygon mirror 10 and the fixed plane mirror 20 so as to enlarge a deflection angle made by the rotary polygon mirror 10. In such a way, by a simple constitution for only placing the fixed plane mirror in a prescribed position, the deflection angle can be enlarged satisfactorily, and the decrease, etc., of a rotating speed of the rotary polygon mirror can be contrived. |
