Patent ID: 8300216

Claim:
A sheet identifying device for authenticating a plurality of types of sheets, comprising: a variable wavelength light-emitting section configured to irradiate a print area of a sheet with light beams having different wavelengths when the sheet is introduced into the sheet identifying device; a sensor configured to sense at least one of transmission light and reflection light obtained from the sheet with respect to light emitted from the variable wavelength light-emitting section when the sheet introduced into sheet identifying device; a storage section configured to store reference sheet wavelength data associated with at least one of the plurality of types of sheets, and sheet wavelength data obtained when the sheet introduced into sheet identifying device is irradiated by the variable wavelength light-emitting section with light of a wavelength; and an authentication judging section configured to compare the sheet wavelength data sensed by the sensor with the reference sheet wavelength data based upon the wavelength of the irradiated light, and thereafter, judge authentication of the sheet, wherein the variable wavelength light-emitting section comprises at least one light-emitting element capable of outputting at least one of a plurality of wavelengths of light based upon a wavelength control signal input into the light-emitting section, and wherein the wavelength control signal corresponds to at least one of a voltage or current value that is variable and selectable for outputting a predetermined wavelength of light from the light-emitting element optimal for the sheet introduced into the sheet identifying device.