Patent ID: 7843610

Claim:
A document reading apparatus, comprising: a storage unit configured to store digital conversion parameters and time data associated therewith, said time data representing a time when digital conversion parameters are updated; a scanner including an image sensor for converting image light reflected from a document into an image signal, an image signal processing unit for converting the image signal into digital image data based on set digital conversion parameters, and a control unit configured to perform a digital conversion parameter setting control for reading the digital conversion parameters in the image signal processing unit; a power supply unit, operatively connected to the scanner, for providing operating voltages to the scanner in a waiting mode, and for suspending the operating voltages in a pause mode; an input unit, connected to the scanner, for inputting operation directions to the scanner; a state change detection unit operatively connected to the scanner and the input unit for detecting a signal change in input signals and for generating a change detection signal representing the signal change; a clock unit, connected to the storage unit and the input unit, for continuously counting time and for generating the time data; and an energy-saving control unit operatively connected to the state change control unit, the energy-saving control unit being configured to perform an energy-saving control for switching the power supply unit to the pause mode when there is no operation direction being issued and the waiting mode lasts a predetermined period, and for switching the power supply unit to the waiting mode when the change detection signal is input from the state change detection unit during the pause mode; wherein in response to outputs of operating voltage by the power supply unit, the control unit of the scanner is configured to determine whether an elapsed time from the last updating time is equal to or greater than a predetermined value based on the time data obtained from the storage unit and an updating time of the digital conversion parameters, and performs a digital conversion parameter correction control when the control unit determines that an elapsed time from the last updating time is equal to or greater than the predetermined value, and when performing said digital conversion parameter correction control, the control unit of the scanner is further configured to perform correction of the digital conversion parameters and store the digital conversion parameters and the current time associated therewith in the storage unit.