By {HEAD ~ changing conditions} of an electron optic system such as {TAIL ~ potential E0}, E1 and E2, the acceleration voltage and electric field on the object are controlled 
such as
By { HEAD ~ changing conditions } of an electron optic system such as { TAIL ~ potential E0 } , E1 and E2 , the acceleration voltage and electric field on the object are controlled
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH