POLYGON MIRROR FITTING STRUCTURE

摘要

PURPOSE:To enable highly accurate optical writing by setting the difference in coefficient of thermal expansion between a shaft fitting member on a rotary shaft side at a fitting place where a polygon mirror is fitted to the rotary shaft and an alignment member on the polygon mirror side to less than a specific value, and thus reducing variation in fitting gap which causes the axial deviation of the polygon mirror regardless of temperature variation and preventing deterioration in rotational balance and an increase of vibration. CONSTITUTION:In the polygon mirror fitting structure which fits the alignment part 33A of the polygon mirror to the fitting part 6a of the rotary shaft 6 supported by the noncontact bearing of a high-speed polygon scanner 32 rotating the polygon mirror 33, the difference in coefficient of thermal expansion between the shaft fitting member which forms the fitting part of the rotary shaft and the alignment part 33A of the polygon mirror 33 is set to <=0.7X10<-5>/ deg.C.