{HEAD ~ A method} for manufacturing an infrared filter 11 wherein said coatings are composed of {TAIL ~ either PbF2} or ThF4 
{ HEAD ~ A method } for manufacturing an infrared filter 11 wherein said coatings are composed of { TAIL ~ either PbF2 } or ThF4
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH