The system uses opposed pointers disposed on opposite sides of an irradiation center, each pointer including a light projecting portion for projecting {HEAD ~ a beam} aimed at {TAIL ~ the irradiation center}, a light receiving portion for generating a detection signal, and a control portion 
aimed at
The system uses opposed pointers disposed on opposite sides of an irradiation center , each pointer including a light projecting portion for projecting { HEAD ~ a beam } aimed at { TAIL ~ the irradiation center } , a light receiving portion for generating a detection signal , and a control portion
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH