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