{HEAD ~ An encoder} 10, wherein said {TAIL ~ light focus means} has a round head portion 
wherein
{ HEAD ~ An encoder } 10 , wherein said { TAIL ~ light focus means } has a round head portion
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH