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