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