| 摘要 |
PROBLEM TO BE SOLVED: To excellently correct the curvature of scanning line bend and the curvature of field, to reduce fluctuation in a light spot size and to realize excellent optical scanning by tilting a scan image forming lens, parallel-moving it and arranging it. SOLUTION: Reflected luminous flux by a polarized light reflecting plane 31 becomes polarization luminous flux polarizing in a constant angular velocity according to constant speed rotation of a rotary polygon mirror 30, and forms the light spot on a surface to be scanned 50 by the scan image forming lens 40 to optically scan the surface to be scanned 50. The luminous flux from a semiconductor laser 10 side is made incident on the polarized light reflecting plane 31 at an incident angleθfor the rotary shaft 30AZ of the polarized light reflecting plane 31 in an XZ surface. The scan image forming lens 40 whose optical axis is tilted by a tilt angle (α) in the X direction in an XY plane for reference arrangement, and is displaced by a displacement amountΔin the Z direction in the XY surface. Then, the lens surface shape, the tilt angle (α) and the displacement amountΔof the scan image forming lens 40 are decided so as to suppress respectively the scanning line bend, the image surface curve and the fluctuation in the light spot size within the allowable range. |
