{HEAD ~ A thickness} of {TAIL ~ the same substrate} may determine a numerical aperture of the optical element 
of
{ HEAD ~ A thickness } of { TAIL ~ the same substrate } may determine a numerical aperture of the optical element
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH