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