▁the ▁missing ▁w edge ▁is ▁possible . ▁In ▁addition , ▁numerical ▁techniques ▁exist ▁which ▁can ▁improve ▁the ▁collected ▁data . ▁ ▁All ▁the ▁above - ment ioned ▁methods ▁involve ▁recording ▁t ilt ▁series ▁of ▁a ▁given ▁spec imen ▁field . ▁This ▁in ev it ably ▁results ▁in ▁the ▁summ ation ▁of ▁a ▁high ▁do se ▁of ▁re active ▁electrons ▁through ▁the ▁sample ▁and ▁the ▁accomp any ing ▁destruction ▁of ▁fine ▁detail ▁during ▁recording . ▁The ▁technique ▁of ▁low - d ose ▁( min imal - d ose ) ▁imag ing ▁is ▁therefore ▁regularly ▁applied ▁to ▁mit ig ate ▁this ▁effect . ▁Low - d ose ▁imag ing ▁is ▁performed ▁by ▁def lect ing ▁ill um ination ▁and ▁imag ing ▁regions ▁simultaneously ▁away ▁from ▁the ▁optical ▁axis ▁to ▁image ▁an ▁adjacent ▁region ▁to ▁the ▁area ▁to ▁be ▁recorded ▁( the ▁high - d ose ▁region ). ▁This ▁area ▁is ▁maintained ▁centered ▁during ▁til ting ▁and ▁ref oc used ▁before ▁recording . ▁During ▁recording ▁the ▁def lections ▁are ▁removed ▁so ▁that ▁the ▁area ▁of ▁interest ▁is ▁exposed ▁to ▁the ▁electron ▁beam ▁only ▁for ▁the ▁duration ▁required ▁for ▁imag ing . ▁An ▁improvement ▁of ▁this ▁technique ▁( for ▁objects ▁rest ing ▁on ▁a ▁s lop ing ▁substr ate ▁film ) ▁is ▁to ▁have ▁two ▁symmet rical ▁off - axis ▁regions ▁for ▁foc using ▁followed ▁by ▁setting ▁focus ▁to ▁the ▁average ▁of ▁the ▁two ▁high - d ose ▁focus ▁values ▁before ▁recording ▁the ▁low - d ose ▁area ▁of ▁interest . ▁ ▁Non - tom ographic ▁variants