Thus, {HEAD ~ a touch point C} in the detecting area 219 can generate {TAIL ~ a mirror point C1} 
Thus , { HEAD ~ a touch point C } in the detecting area 219 can generate { TAIL ~ a mirror point C1 }
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL