The first cusp includes a concave parabolic reflector 72 above a plane reflector 73, while the latter cusp includes {HEAD ~ a concave parabolic reflector} 74 below {TAIL ~ a plane reflector} 75 which is in fact the opposite surface of reflector 73 
below
The first cusp includes a concave parabolic reflector 72 above a plane reflector 73 , while the latter cusp includes { HEAD ~ a concave parabolic reflector } 74 below { TAIL ~ a plane reflector } 75 which is in fact the opposite surface of reflector 73
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH