Patent ID: 7442929

Claim:
A scanning electron microscope comprising: a sample holder for holding a sample; an electron beam source; a plurality of convergence leases for converging the electron beam emitted from the electron beam source; an objective lens for radiating the converged electron beam as a micro spot on the sample; a scanning coil for scanning the electron beam on the sample; a detector for detecting the sample signal generated from the sample irradiated with the electron beam; an analog-to-digital (A/D) converter for converting the analog detection signal of the detector to a digital signal; a storage unit for storing the digital signal converted by the A/D converter as an image signal; and a display unit for displaying an image associated with the image signal stored in the storage unit; wherein the A/D converter can change the number of pixels per screen to change the resolution of the image by changing the sampling rate, the number of pixels being directly related to the sampling rate, and wherein the angle of aperture of the electron beam is changed in accordance with the pixel size (visual field area per pixel) determined in accordance with the number of pixels per screen.