Electron gun and electron microscope

An electron microscope comprising:

• a vacuum chamber in which a differential exhaust diaphragm is provided;
• an electron optical system disposed in the vacuum chamber and configured to irradiate a sample with an electron beam that is emitted from an electron gun and passes through the differential exhaust diaphragm;
• a detector configured to detect charged particles generated by irradiating the sample with the electron beam;
• a signal processing unit configured to process a signal detected by the detector;
• and
• a control unit, wherein
• the electron gun includes a photocathode that has a substrate and a photoelectric film formed on the substrate, a condenser lens configured to condense, onto the photoelectric film, excitation light emitted to the photoelectric film of the photocathode, and a first anode electrode and a second anode electrode that are arranged in an order away from the photoelectric film of the photocathode in a direction opposite to the substrate, and
• the control unit controls a position at which the excitation light is condensed on the photoelectric film, and controls a voltage applied to the first anode electrode and a voltage applied to the second anode electrode such that an electron beam emitted from the position of the photoelectric film at which the excitation light is condensed passes through the differential exhaust diaphragm.