Abstract: A sheet thickness measuring device includes: an illumination unit that outputs a light that is illuminated into a stack of sheets from a first area defined on one of faces including a top face, a bottom face, and side faces of the stack of sheets; a detection unit that detects a light amount distribution of light entered into the stack of sheets and propagated to a second area through the stack of sheets, the second area defined on one of the side faces of the stack of sheets; and a calculation unit that calculates a thickness of a sheet in the stack of sheets based on the light amount distribution detected by the detection unit.

Abstract: A laser beam is irradiated on a record medium, a speckle generated by surface scattering is measured by an image sensor, speckle information obtained is subjected to FFT transform, and a paper quality of the record medium is discriminated from a peculiar pattern due to roughness of the surface of the record medium.

Abstract: A record medium determining device 1, which determines a kind of a record medium 16 by irradiating a laser light 17 to a surface of the record medium 16, detecting a received light position and a received light intensity of a reflected light 18 by a line sensor 14, and comparing a distribution state of the received light position and the received light intensity with a previously determined distribution state, is disposed on the upstream side of a record medium conveyance path 653 with respect to a fixing unit.

Abstract: A laser beam is irradiated on a record medium, a speckle generated by surface scattering is measured by an image sensor, speckle information obtained is subjected to FFT transform, and a paper quality of the record medium is discriminated from a peculiar pattern due to roughness of the surface of the record medium.

Abstract: In a discriminating apparatus, a substrate portion of printed matter is irradiated with a light beam emitted from a light source, and the intensity of the light beam reflected from the substrate is detected by a photodetector. The discrimination as to whether the printed matter is the original or a reproduction is performed by a discriminating unit based on the contrast value in the intensity of the reflected light detected by the photodetector. Thus, the discriminating apparatus discriminates whether the printed matter is the original or a reproduction at high speed and also permits lowering the possibility of an erroneous discrimination.