{TAIL ~ Some part} of the incident laser beam is reflected by the optical member and then returned to {HEAD ~ the beam splitter} to be focused on an optical disc 
{ TAIL ~ Some part } of the incident laser beam is reflected by the optical member and then returned to { HEAD ~ the beam splitter } to be focused on an optical disc
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH