Patent ID: 8169674

Claim:
An image reading apparatus comprising: an automatic document feeder; a first reading unit to read a first side of a document fed by the automatic document feeder and to function as a main reading unit; a second reading unit to read a second side of the document fed by the automatic document feeder; and a control unit to change the main reading unit from operating as the first reading unit to operating as the second reading unit if a number of times L a , of usage of the first reading unit reaches a reference value and to determine whether the main reading unit is to be changed based on frequencies in use of the first reading unit and the second reading unit, the control unit including an ADF two-sided reading mode to read the first side and the second side of the document fed by the automatic document feeder using the first reading unit and the second reading unit, wherein the control unit changes the main reading unit to the second reading unit if the number of times L a of usage of the first reading unit satisfies La≧Lt[ 1=( Fd +α)], (α a constant and <0 F d +α<1) in a relationship between a predicted lifetime usage L t of the first reading unit and a frequency F d in use of the ADF two-sided reading mode.