Document detecting apparatus, image forming apparatus and document detecting method

摘要

According to one embodiment, a document detecting apparatus includes a light-emitting element, a photoelectric conversion element, a light-emission controller and a detection processor. The light-emitting element projects light onto a detection position of a document. The photoelectric conversion element outputs an electric signal obtained by converting the light from the detection position of the document. The light-emission controller changes the light quantity of the light emitted by the light-emitting element. The detection processor detects the presence or absence of the document at the detection position of the document based on the presence or absence of a change of an output value corresponding to the change of the light quantity caused by the light-emission controller in an output value from the photoelectric conversion element.