Patent ID: 8432585

Claim:
An image reading device, comprising: a first carriage including optical elements for reading an image of a document; a second carriage including optical elements for reading the image of the document; a carriage driving unit including a pulse motor to move the first and second carriages; a home position sensor to detect a home position of the first carriage; a reference whiteboard to generate shading data and adjust a reference level to be read by the optical elements; a control unit to control the first and second carriages, the carriage driving unit, the home position sensor, and the reference whiteboard to read the image of the document placed on a contact glass through the optical elements; and a counter to count a pulse of a pulse signal driving the pulse motor, wherein, the control unit is configured to switch between a first homing process and a second homing process based on a state of the home position sensor when the image reading device is returned to an active mode from an energy-saving mode, a direction of motion of the first carriage in the first homing process being opposite a direction of motion of the first carriage in the second homing process, and the control unit is configured to detect a distance of movement of the first carriage based on the pulse counted by the counter.