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