{HEAD ~ The focus information} of {TAIL ~ each solder ball} is used to determine the distance to the tips of each solder ball 
of
{ HEAD ~ The focus information } of { TAIL ~ each solder ball } is used to determine the distance to the tips of each solder ball
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH