Nonreflective Backup Cavity for Optical Sensors
Original Publication Date: 1978-Mar-01
Included in the Prior Art Database: 2005-Feb-20
Inexpensive, reflective optical sensors may be used to detect media, documents, surfaces of such materials, etc., independently of the surface finish, color, marks or reflectance level, provided that there is approximately zero reflectance from the background when the document or media to be detected is not present. Fig. 1A illustrates the typical situation where sensor 1, comprising a source of light 2 and an optical detector 3, is utilized to sense the presence of a document 4 moving in a fixed surface or a plane 5. The beam of light from source 2 strikes the document 4 and is detected at detector 3, where the difference in reflectance level from the background of the fixed surface 5 generates a signal.