The bright and shadow images of an atom in the transmission electron microscope

Scherzer discussed in his paper of 1949 the phase contrast of an atom image which was given in the form i(psi-psi). The second order term psi psi, which gave the bright image of the atom, was neglected. Under the first Born approximation as adopted by him, the phase contrast disappears at the exact focus of the ideal electron microscope. Under the second Born approximation, the phase contrast does appear under the same condition. It can be interpreted as the shadow image because it compensates the bright image.