Original Publication Date: 1985-Oct-31
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
The sensor comprises an optical or infra-red emitter, e.g. a diode 1, and a detector, e.g. a phototransistor 2 mounted side by side in a block 3 of acrylic material which is shaped to provide lenses 4, 5 for them as well as a retro-prism 6 which returns the beam 7 emitted by the emitter 1 back to the detector 2. For example, the acrylic block may be L-shaped, with the emitter and detector mounted at the end of one limb, and with the prism at the end of the other limb of the L. This defines diagonal light paths 7 and the presence of, say, a paper sheet will be detected if it intersects either or both of the outward and return light paths.