| 摘要 |
PROBLEM TO BE SOLVED: To attain a large operating distance and satisfactory lens characteristics in low voltage area by constituting a magnetic lens as a single pole lens in a field magnetic lens device. SOLUTION: A field magnetic lens device 6 basically has a magnetic lens constituted as a single pole lens 61 and an electric field lens 62 arranged within the magnetic lens to generate a rotation symmetric electric field. This electric field lens has two electrodes held in mutually different potentials, so that different potentials can be applied to these electrodes. Thus, a charged particle, for example, an electron is reduced in speed from a first energy to a second energy lower than it. In this case, the first energy is 1.2-10 times the second energy, and a maximum operable distance can be attained with satisfactory resolution and image characteristics.
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