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