In an optical scanning module, for reading indicia with portions of differing light reflectivity, having a light emitter assembly for emitting a light beam towards the indicia, and a detector for receiving light reflected back from the indicia and producing an electrical signal corresponding...http://www.google.de/patents/US5698835?utm_source=gb-gplus-sharePatent US5698835 - Slim scan module with interchangeable X-Y scan element
