{HEAD ~ The returned beam} is focused to the optical disc via {TAIL ~ the optical member} and the beam splitter 
{ HEAD ~ The returned beam } is focused to the optical disc via { TAIL ~ the optical member } and the beam splitter
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH