{HEAD ~ The interference filter} has {TAIL ~ two metal reflective films}, at least one of which is semi transparent 
has
{ HEAD ~ The interference filter } has { TAIL ~ two metal reflective films } , at least one of which is semi transparent
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