POLYGON MIRROR, HOLDING DEVICE OF POLYGON MIRROR BLANK AND HOLDING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To secure the necessary accuracy of a mirror surface without machining a non-reference surface with high accuracy by providing a ring-like groove on at least one face and on the side of slightly inner periphery of the outer peripheral surface among plural flat end faces orthogonal to the reflection surface of a polygon mirror provided with plural reflection surfaces on the outer peripheral face. SOLUTION: Plural reflection surfaces 1a for reflecting a laser beam is provided on the outer peripheral surface and a ring-like groove 1f is provided on at least one face and on the side of slightly inner periphery of the outer peripheral surface among plural flat end faces (reference surface 1c and non-reference surface 1d) orthogonal to the reflection surface 1a. The positions of the grooves 1f are set to be the outer peripheral parts of a polygon mirror reference face holding part 2c with which a holding/indexing mechanism 2 of a polygon mirror blank is in contact and a non- reference face pressing/holding part 3d with which a pressing jig 3 is in contact. Consequently, almost all of deformation due to ununiform abutting on the holding part occurs on the inner peripheral side of the groove part 1f, deformation on the outer periphery of the groove 1f is reduced and thus the good planar accuracy and the good accuracy of plane tilt of the reflection surface are obtained.