Use of scanned detection in optical position encoders

The use of scanning detection in optical noncontact position sensing is proposed, and a prototype is implemented, using optical scanning of pseudorandom binary sequences printed in bar-code format. Light from a vibrating fiber tip is imaged onto the printed code using a GRIN (graded index) lens, and the reflected light detected via the same lens, resulting in a single scanner module. Improved flexibility and signal processing possibilities are obtained compared to conventional diode array optical code readers. Performance limitations of scanning position encoders are analyzed and discussed. Suggestions for implementation using microoptoelectromechanical systems are presented.