| 摘要 |
PROBLEM TO BE SOLVED: To shorten the startup time of a device by reducing the inertia of a rotary polygon mirror. SOLUTION: The rotary polygon mirror E1 has a prismatic main body 10 and is provided with reflecting surfaces 11 as its outer peripheral surface. Annular grooves 13 and 14 which are vertically symmetrical are cut in both the end surfaces of the main body 10 to reduce the inertia of the rotary polygon mirror E1. The inertia is effectively reduced without making the mechanical strength uneven vertically and circumferentially and the annular grooves 13 and 14 are usable as balance correcting grooves.
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