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