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