Scanning optical system including an afocal system

摘要

An optical system for scanning is disclosed which comprises an afocal optical system and a first - and a second deflecting members so disposed respectively at an optically conjugate position relative to the afocal optical system as to substantially interpose the system therebetween. The plane formed by a beam deflected by the first deflecting member is substantially coincident with that formed by a beam deflected by the second one. In order to control the angle of deviation (deflection) of the beam finally scanned, there is provided, for the afocal optical system, means for differentiating the exit angle from the incident angle of a beam passing through the afocal optical system. Furthermore, the angle of deflection of a beam deflected by the first deflecting member in a unit time period is made different from that deflected by the second one.