| 摘要 |
A measuring instrument of polygon mirror motors includes a first light source, a first photo detecting element for detecting first reflecting light beam, i.e. first measuring light beam emitted from the first light source and reflected on the polygon mirror, a second light source, a second photo detecting element for detecting second reflecting light beam, i.e. second measuring light beam emitted from the second light source and reflected on the polygon mirror; and a calculator for carrying out a calculation based on a time difference between an output from the first photo detecting element and an output from the second photo detecting element. The calculator outputs at least one of an eccentricity and a level difference between facets of the polygon mirror.
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