Patent ID: 8258474

Claim:
An apparatus for generating two spatially overlapping electron beams on a specimen, the apparatus comprising: a first electron beam source configured to generate a low-energy electron beam; a second electron beam source configured to generate a high-energy electron beam; a semitransparent electron mirror biased to reflect the low-energy electron beam and including an opening therein through which passes the high-energy electron beam; an energy-dispersive device configured to: bend the low-energy electron beam towards said electron mirror, bend both the low-energy electron beam reflected off of said electron mirror and the high-energy electron beam passing through said electron mirror towards a specimen, and bend the electron beam scattered by the specimen toward an electron detector; a deflection system positioned between said high-energy electron source and said electron mirror and configured to deflect the high-energy electron beam by an angle that compensates for the difference in bending angles between the low- and high-energy electron beam introduced by said energy-dispersive device.