Image processing for new optical pattern recognition encoders

An all new type of absolute, optical encoder with ultra-high sensitivity has been developed at NASA's Goddard Space Flight Center.(1) These position measuring encoders are unconventional in that they rely on computational pattern recognition of high speed, electronic images made of a moving, backlit scale which carries absolute position information of either linear or rotary format. The pattern recognition algorithms combine edge detection, threshold level sensing, spatial compression, and centroiding along with fault recovery through scale image defect detection. Details of the encoder scale patterns and their design rules and the image processing algorithm which gives these encoders their unique and unparalleled performance characteristics are discussed.