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