a beam splitting means for partially reflecting and partially transmitting {HEAD ~ a laser beam} irradiated from {TAIL ~ the laser source} 
irradiated from
a beam splitting means for partially reflecting and partially transmitting { HEAD ~ a laser beam } irradiated from { TAIL ~ the laser source }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL