means for directing substantially collimated source supplied {HEAD ~ radiation} toward {TAIL ~ the second focusing reflector} in the reflectance mode; and 
toward
means for directing substantially collimated source supplied { HEAD ~ radiation } toward { TAIL ~ the second focusing reflector } in the reflectance mode ; and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH