| 摘要 |
PURPOSE: To prevent the size of a polygon mirror from becoming larger. CONSTITUTION: A light beam transmitted through an fθlens 1 is condensed at the detection part of a synchronism detection sensor 5 by a condenser lens 2. The gap G between the outermost angle of the lens 1 and the innermost angle of the lens 2 is made small and the angle range deflected by the polygon mirror 9 is made narrow. Thus, the size of the mirror 9 is made small. Besides, the starting time of a motor is shortened and the inclination error of the mirror 9 is made smaller.
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