Patent ID: 8859964

Claim:
A method of adjusting an electron microscope having an electron beam source for producing an electron beam, an electron beam detecting portion for detecting a part of the electron beam, an image detecting portion for detecting a signal produced in response to impingement of the electron beam on a sample, a shutter between the electron beam source and the image detecting portion and a noise canceling portion for subtracting an offset signal from an output signal from the image detecting portion and dividing the resulting difference by an output signal from the electron beam detecting portion, said method comprising the steps of: (1) measuring the output signal from the image detecting portion while with the shutter temporarily blocking the signal produced in response to the impingement of the electron beam on the sample from entering the image detecting portion; (2) calculating said offset signal based on the measured output signal from the image detecting portion in step (1); and (3) setting the calculated offset signal into the noise canceling portion.