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