Several embodiments of the invention are shown, including pairs of reflectors {HEAD ~ whose apposed surfaces} are convex and concave conic sections or {TAIL ~ convex} and concave spirals 
are
Several embodiments of the invention are shown , including pairs of reflectors { HEAD ~ whose apposed surfaces } are convex and concave conic sections or { TAIL ~ convex } and concave spirals
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH