Image reading device, image forming apparatus provided therewith, and method for controlling image reading device

摘要

An image reading device has a motor, an optical sensor (a light emitting portion, a light receiving portion), a carriage, a motor, a moving portion for rotating a belt, a pulse generating gear provided with a plurality of light shielding teeth along its circumference, and a control portion. The light shielding teeth of the pulse generating gear pass through a gap between the light emitting portion and the light receiving portion. First and second widths are set such that the movement amount of the pulse generating gear resulting from the motor rotating one step is equal to or larger than both the width of each of the light shielding teeth (first width) and the width of the interval between adjacent light shielding teeth (second width). The control portion recognizes when, during standby of the carriage, the level of an output signal changes.