Light scanning system

Claim 1

A light scanning system for scanning a light beam onto an image surface comprising: light means for generating a light beam; light deflecting means having a rotating mirror with a reflecting surface for deflecting an incoming light beam from said light means; focusing means disposed between said light means and said light deflecting means for focusing the light beam upon said reflecting surface of said rotating mirror of said light deflecting means to a line image; field curvature correcting means including a single spherical leans provided with a spherical surface and having positive power for focusing the light beam deflected by said light deflecting means onto said image surface, and said spherical lens enabling correction of the field curvature and partial correction of the scan-nonlinearity of an image formed on said image surface; a first reflecting mirror disposed in the scan plane with its optical axis inclined at an angle of θ 3 (θ 3 ≠0) with the scan plane for reflecting the light beam passing through said spherical lens; scan-nonlinearity correcting means including a second reflecting mirror with a toric-surface having a first circular arc with a larger radius of curvature in a first plane which is larger than a second radius curvature in a second plane perpendicular to the first plane, said second reflecting mirror of said scan-nonlinearity correcting means being disposed for reflecting the light beam reflected by said first reflecting mirror and for enabling correction of the scan-nonlinearity of the light beam which is not corrected by said spherical lens and having the toric-surface thereof with a concave shape optically facing said spherical lens, said toric-surface reflecting mirror of said scan-nonlinearity correcting means establishing an optically conjugated relationship between said reflecting surface of said rotating mirror of said light deflecting means and said image surface for preventing of the displacement of the light beam from the scan plane formed by the deflected light beam resulting from a tilt of said first reflecting surface of said rotating mirror of said light deflecting means, and said toric-surface reflecting mirror of said scan-nonlinearity correcting means being disposed with its optical axis inclined at an angle of θ 2 (θ 2 ≠0) with a scan plane formed by the light beam reflected on said first reflecting mirror, and said θ 2 being defined by the relation: ##EQU3## where R represents the larger radius of curvature of said toric-surfaced reflecting mirror and d represents the distance in the scanning direction of said toric-surfaced reflecting mirror.