{HEAD ~ a beam directing member} having an input surface and {TAIL ~ an output surface} which are spaced from and substantially parallel to each other 
{ HEAD ~ a beam directing member } having an input surface and { TAIL ~ an output surface } which are spaced from and substantially parallel to each other
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH