a light entering region on the beam directing member whereby {HEAD ~ the incoherent light beam} is directed between {TAIL ~ the two surfaces} 
a light entering region on the beam directing member whereby { HEAD ~ the incoherent light beam } is directed between { TAIL ~ the two surfaces }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL