| 摘要 |
PROBLEM TO BE SOLVED: To effectively reduce the influence of an asymmetric sag and to remove the influence of ghost light by using a scanning image forming optical system comparatively easy to machine and having the symmetry of a shape. SOLUTION: This optical scanning device is composed so that a light beam from a light source 1 is coupled by a coupling lens 2, deflected at a constant angular velocity by a polygon mirror 4, the deflected light beam is converged on a surface to be scanned 6 by means of a second optical system 5 including a scanning image forming element system and the surface to be scanned 6 is scanned at almost a constant speed. In this case, a number of deflection/ reflection surfaces of the polygon mirror: N, an inradius: R, an angle between the principal light ray A and the optical axis of a first optical system when the principal light ray of the deflected light beam is made to be in the direction orthogonal to the surface to be scanned:α, the width of a viewing angle corresponding to an effective writing width on the surface to be scanned 6:θand a distance between the rotating center of the polygon mirror and the optical axis B of the first optical system: (h) satisfy the conditions: (1)θ/2<α<(4π/N)-(θ/2), (2) R.sin(α/2)Ν1.03<h<R.sin(α/2).1.1. |
