SCANNING OPTICAL DEVICE, ORIGINAL READER AND IMAGE FORMING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide the scanning optical device that stably scans an original by avoiding resonance between a scanning optical system and its rotation drive means. SOLUTION: A drive belt 54 is tightened between and around an optical stepping motor (rotary drive means) 55 and a pulley 53 of a drive drum to deliver torque to a scanning optical system by way of the drive drum. A rocking pulley 21 provided to a support member 21-a with teeth 22 meshing with a worm gear 32 is pressed into contact with the drive belt 54. The driving of a stepping motor 24 is regulated in response to a copy magnification rate entered from an operation section 25 to rock the rocking pulley 21 thereby changing the tension of the drive belt.