a sensor for detecting a at least one of a secondary electron and reflected electron emanated from {TAIL ~ the object}, upon {HEAD ~ exposure} of the object to the electron beam 
a sensor for detecting a at least one of a secondary electron and reflected electron emanated from { TAIL ~ the object } , upon { HEAD ~ exposure } of the object to the electron beam
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH