a focusing lens for focusing the incident laser beam at {HEAD ~ pinholes} to thereby produce {TAIL ~ a focused laser beam} 
a focusing lens for focusing the incident laser beam at { HEAD ~ pinholes } to thereby produce { TAIL ~ a focused laser beam }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL