Patent ID: 7471424

Claim:
An original size detecting apparatus comprising: an original platen; an original pressing member that presses an original placed on said original platen; a light source that irradiates light onto the original platen; a reading device that reads reflected light of the light irradiated from said light source onto the original platen; an open state-detecting device that detects that said original pressing member is in a first open state, in a second open state that is closed much more than the first open state, and in a third open state that is closed much more than the second open state, but not closed; and an original size-determining device that turns on said light source in dependence on said open state-detecting device detecting that said original pressing member is closed down to the second open state from the first open state, and causes said reading device to read the reflected light in dependence on said open state-detecting device detecting that said original pressing member is closed down to the third open state from the second open state, and determines a size of the original based on an output from said reading.