Image detecting unit having emitting means and light receiving means and method for arranging the light emitting means and the light receiving means

摘要

An image detecting unit includes a light emitting system for emitting a light beam which is projected onto a surface of a document and a light receiving system for receiving a light obtained by a reflection of the light emitted from the light emitting system on the surface of the medium. The light receiving system includes optical waveguides and photoelectric conversion devices coupled to the optical waveguides. The light emitted from the light emitting system is projected on an area on the surface of the document, to which an end surface of the optical waveguide is opposed, and an incident angle phi of the light incident on the surface of the document is determined by the following formula; phi 0-25 DEG < phi < phi 0+ DIFFERENCE DEG where phi 0 represents an optimum incident angle.