| 摘要 |
A magnetic objective lens for use in a scanning electron microscope comprises a lower magnetic pole piece (7) having a bore dimeter D1, an upper magnetic pole piece (6) having a bore diameter D2 which is larger than D1, an outer magnetic pole piece (20) having a bore diameter D3 which is larger than D1, a first excitation coil (12) for generating a magnetic field between the lower magnetic pole piece and the upper magnetic pole piece, and a second excitation coil (13) for generating a magnetic field between the lower magnetic pole piece and the outer magnetic pole piece.
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