Patent ID: 8977167
Filing Date: 2015-03-10
Classification: G03G

Abstract:
1. An image forming apparatus comprising: a rotatable image bearing member including a scale portion, provided through one full circumference along a rotational direction, formed of a plurality of marks continuously provided at a set interval; a driving member configured to rotationally drive said image bearing member; a first output portion comprising a first pair of sensors provided at a first interval with respect to a rotational direction of said image bearing member, said first output portion is configured to output a difference in time between when a sensor of said first pair of sensors detects a mark in the scale portion and when another sensor of said first pair of sensors detects the mark in the scale portion, wherein each sensor of said first pair of sensors is configured to detect the mark in the scale portion; a second output portion comprising a second pair of sensors, which is different from said first pair of sensors, and provided at a second interval, shorter than the first interval, with respect to a rotational direction of said image bearing member, said second output portion is configured to output a difference in time between when a sensor of said second pair of sensors detects the mark in the scale portion and when another sensor of said second pair of sensors detects the mark in the scale portion, wherein each sensor of said second pair of sensors is configured to detect the mark in the scale portion; a filter portion configured to suppress a high-frequency part of an output of said first output portion and a low-frequency part of an output of said second output portion; and a controller configured to control said driving member so that a speed of said image bearing member is a set speed based on an output of said filter portion.