{HEAD ~ The composite light beam} passes through {TAIL ~ the quarter wave plate} 828 and the beam expander 829 and enters the light deflector unit 804 
passes through
{ HEAD ~ The composite light beam } passes through { TAIL ~ the quarter wave plate } 828 and the beam expander 829 and enters the light deflector unit 804
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH