The optical encoder 1, wherein {TAIL ~ the set} of at least four light sources comprises {HEAD ~ eight light sources} 
The optical encoder 1 , wherein { TAIL ~ the set } of at least four light sources comprises { HEAD ~ eight light sources }
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD