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