| 摘要 |
PROBLEM TO BE SOLVED: To provide a laser scanner that a scanning optical system id constituted of one mirror and which has more excellent image-formation performance by constituting a scanning mirror of a free curved surface and appropriately setting a parameter showing the angle of the free curved surface. SOLUTION: An optical axis X (reflected light from a polygon mirror 5 when a deflection angle is 0) is taken on an x-axis, a main scanning direction is taken on a y-axis and a subscanning direction is taken on a z-axis. A laser beam 2 is made incident on the reflection surface 5a of the mirror 5. Such a direction is set so that the beam 2 advances on a plane perpendicular to the rotary shaft 5b of the mirror 5. Then, a point where the surface 5a is crossed with the optical axis X is set as an origin. The shape of the scanning mirror 6 is expressed by an expression. In the expression, aij means that (y) is the coefficient of i-degree and (z) is the coefficeint of j-degree. Furthermore, the mirror 6 satisfies conditional expressions 0<f1(0)/f1(ymax)<1 and 0<f1(0)/ f1(ymin)<1. Provided that ymax and ymin are the values of respective (y) coordinates corresponding to the incident position of the beam 2 on the mirror 6. |
