Patent ID: 8599452

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 operate the first and second reading units in order to perform an ADF two-sided reading mode in which both sides of the document are read, the control unit determining a point in time when the main reading unit is changed, based on a frequency in use of the ADF two-sided reading mode, and changing the main reading unit to the second reading unit at the determined point in time, wherein the point in time when the main reading unit is changed becomes earlier at a higher frequency in use of the ADF two-sided reading mode, and wherein the control unit changes the main reading unit to the second reading unit if a number of times La of usage of the first reading unit satisfies La≧Lt[ 1−( Fd +α)], (α is 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.