Each trough shaped reflector has {TAIL ~ an associated flat reflecting mirror} for directing its beam of {HEAD ~ illuminating light} toward the document 
Each trough shaped reflector has { TAIL ~ an associated flat reflecting mirror } for directing its beam of { HEAD ~ illuminating light } toward the document
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH