{HEAD ~ The method} may further include filling {TAIL ~ a space} between the first optical window and the second optical window with a filler 
include filling
{ HEAD ~ The method } may further include filling { TAIL ~ a space } between the first optical window and the second optical window with a filler
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH