US Patent 7449708 Paper detection apparatus and printing method

Provided is a paper detection apparatus for detecting the size of a sheet of paper transferred along a paper transfer path, which includes a light source and an optical sensor. A plurality of light emitting optical fibers are located at a first side of the paper transfer path and receive light radiated by the light source and emit the received light to a plurality of positions in a widthwise direction of the paper. A plurality of light receiving optical fibers are located at a second side of the paper transfer path and guide the light emitted by the light emitting optical fibers toward the optical sensor. A determination unit detects the size of the paper based on the amount of light detected by the optical sensor.