Abstract
The application of transfer theory to image formation in the electron microscope is discussed. The equivalence of the transfer theory and the diffraction integral formulation of image formation is established for a coherent monochromatic incident electron beam, and for elastic electron scattering. The transfer theory is extended to include partially coherent and nonmonochromatic radiation. The use of the results of the transfer theory leads to the diffraction integral formulation, which includes the effects of chromatic aberration (thermal energy effect) and the coherence of the incident electron beam. The modification to a criterion for optimum contrast in the final image when chromatic aberration is taken into account is discussed.