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