Abstract: An omega energy filter capable of increasing energy dispersion while canceling out second-order aberrations. The energy filter is mirror-symmetric with respect to the center plane C. A beam enters a first nonuniform magnetic field produced by a first magnet, then enters a second nonuniform magnetic field region produced by a second magnet. The trajectory of the beam is curved by the field produced by the second magnet. Finally, the beam enters a third magnetic field region produced by the first magnet. The beam is deflected in this region and reaches an exit slit.

Abstract: There is disclosed an energy filter capable of reducing the Boersch effect. Also, an electron microscope using this energy filter is disclosed. This energy filter is composed of a first-stage energy filter and a second-stage energy filter arranged along the optical axis of an electron beam. The length L1 of the first-stage filter is selected to be greater than the length L2 of the second-stage filter. An energy-selecting slit is positioned in the electron beam path within the free space between the first- and second-stage filters. Each of these two stages of filters is a Wien filter having mutually perpendicular electric and magnetic fields.

Abstract: An omega energy filter capable of increasing energy dispersion while canceling out second-order aberrations. The energy filter is mirror-symmetric with respect to the center plane C. A beam enters a first nonuniform magnetic field produced by a first magnet, then enters a second nonuniform magnetic field region produced by a second magnet. The trajectory of the beam is curved by the field produced by the second magnet. Finally, the beam enters a third magnetic field region produced by the first magnet. The beam is deflected in this region and reaches an exit slit.

Abstract: There is disclosed an imaging energy filter equipped with a distortion corrector. The energy filter is incorporated in an electron microscope and includes a spectrometer having magnets for producing magnetic fields. In this spectrometer, coils for exciting the magnets and potentiometers having variable resistors are connected in parallel. The variable resistors of the potentiometers are shifted to control the ratio of currents flowing into coils of shunting circuits.