▁the ▁spec imen ▁area ▁from ▁which ▁the ▁signal ▁will ▁be ▁displayed . ▁By ▁changing ▁the ▁strength ▁of ▁current ▁to ▁the ▁intermediate ▁l ens , ▁the ▁diff raction ▁pattern ▁is ▁project ed ▁on ▁a ▁screen . ▁D iff raction ▁is ▁a ▁very ▁powerful ▁tool ▁for ▁doing ▁a ▁cell ▁reconst ruction ▁and ▁cry stal ▁orientation ▁determ ination . ▁ ▁Con tr ast ▁formation ▁ ▁The ▁contrast ▁between ▁two ▁adjacent ▁areas ▁in ▁a ▁T EM ▁image ▁can ▁be ▁defined ▁as ▁the ▁difference ▁in ▁the ▁electron ▁dens ities ▁in ▁image ▁plane . ▁Due ▁to ▁the ▁scatter ing ▁of ▁the ▁incident ▁beam ▁by ▁the ▁sample , ▁the ▁amplitude ▁and ▁phase ▁of ▁the ▁electron ▁wave ▁change , ▁which ▁results ▁in ▁amplitude ▁contrast ▁and ▁phase ▁contrast , ▁corresponding ly . ▁Most ▁of ▁images ▁have ▁both ▁contrast ▁components . ▁ ▁Am plit ude – contr ast ▁is ▁obtained ▁due ▁to ▁removal ▁of ▁some ▁electrons ▁before ▁the ▁image ▁plane . ▁During ▁their ▁interaction ▁with ▁the ▁spec imen ▁some ▁of ▁electrons ▁will ▁be ▁lost ▁due ▁to ▁absor ption , ▁or ▁due ▁to ▁scatter ing ▁at ▁very ▁high ▁angles ▁beyond ▁the ▁physical ▁limitation ▁of ▁mic ros cope ▁or ▁are ▁blocked ▁by ▁the ▁objective ▁a pert ure . ▁While ▁the ▁first ▁two ▁losses ▁are ▁due ▁to ▁the ▁spec imen ▁and ▁mic ros cope ▁construction , ▁the ▁objective ▁a pert ure ▁can ▁be ▁used ▁by ▁operator ▁to ▁enh ance ▁the ▁contrast . ▁ ▁Figure ▁on ▁the ▁right ▁shows ▁a ▁T EM ▁image ▁( a ) ▁and ▁the ▁corresponding ▁diff raction ▁pattern ▁( b ) ▁of ▁P