Image reading apparatus

An image reading apparatus comprising:

• a signal output unit that periodically outputs a line start signal which defines a timing to start a reading operation;
• a reading unit that executes an operation, as the reading operation, of reading a document to be read in a main scanning direction, each time the line start signal is provided from the signal output unit, and generates line image data per line which indicates a read image of the line;
• a conveyance unit that has a motor, and conveys one of the reading unit and the document, as an object to be conveyed, in a sub-scanning direction with a driving force generated by the motor;
• a position detecting unit that detects a conveyance position of the object;
• a controller that controls the motor based on the conveyance position of the object detected by the position detecting unit and a predetermined first target position trajectory, thereby to accelerate the object to follow a position trajectory corresponding to the first target position trajectory from a conveyance start position up to a predetermined speed, and after the acceleration, convey the object at a constant speed;
• a target setting unit that sets to the controller a target position trajectory which starts from the conveyance start position, as the first target position trajectory;
• a mode switching unit that invalidates the reading operation by the reading unit when a predetermined interruption condition is satisfied;
• and
• a position specifying unit that specifies, as an interrupted position, the conveyance position of the object at a time Tf when the line start signal which defines the timing to start the first reading operation invalidated by the mode switching unit, among the line start signals outputted from the signal output unit, is outputted,
• wherein the controller interrupts the constant speed conveyance of the object when the interruption condition is satisfied, and controls the motor to stop the object, and, after the object is stopped, controls the motor based on the conveyance position of the object detected by the position detecting unit, thereby to dispose the object at a conveyance restart position moved back from the interrupted position,
• wherein the target setting unit is configured, when the interruption condition is satisfied, to set a target position trajectory which starts from the conveyance restart position to the controller as a second target position trajectory, and in that case adjusts a position trajectory of an acceleration section included in the second target position trajectory, thereby to set to the controller the second target position trajectory adjusted such that a conveyance time from the conveyance restart position to the interrupted position is an integral multiple of an output cycle of the line start signal,
• wherein the controller, when a predetermined restart condition is satisfied, starts control of the motor based on the second target position trajectory at a timing which coincides with a timing when the line start signal is outputted from the signal output unit, thereby to control the conveyance unit to accelerate the object from the conveyance restart position up to the predetermined speed to follow a position trajectory corresponding to the second target position trajectory, and after the acceleration to convey the object at the constant speed,
• wherein the mode switching unit, when the restart condition is satisfied, validates the reading operation executed by the reading unit based on and after the line start signal provided to the reading unit at a timing when the object reaches the interrupted position.