| 摘要 |
In an electron microscope, focus correction is carried out automatically, an astigmatic difference amount is displayed and astigmatism correction is executed quantitatively. Enlarged specimen images obtained by irradiating an electron beam on a specimen while changing excitation currents of an objective lens and of a stigmator coil are picked up by a capturing unit comprised of an optical lens and a capturing device and image sharpness coefficients are calculated by means of an arithmetic logic unit. A suitable astigmatism correction direction is chosen on the basis of an angular component value of the obtained image sharpness coefficients and then, a correction excitation current is supplied to a stigmator coil to correct astigmatism and a correction excitation current is supplied to an objective lens coil to perform focus correction.
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