{HEAD ~ A system} employing the optical element may include {TAIL ~ a light source} and a detector 
include
{ HEAD ~ A system } employing the optical element may include { TAIL ~ a light source } and a detector
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH