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