| 摘要 |
PURPOSE:To obviate the need for field excitation re-adjusting when the same field excitation level is used again, by permitting the field excitation level of a convergent lens to be variable in plural steps and installing a deflection magnetic field generating means for adjusting an axis above an object lens, with its field excitation changeable in the number of plural steps. CONSTITUTION:A rotary switch 13 chanegable in 16 steps is a binary code switch with 4-bit output, which selects one of sixteen different voltages applied to sixteen input lines of an analog multiplexer 12 for driving a current amplifier 7 so as to excitate a convergent lens 2. The output of the rotary switch 13 is also used as switching inputs for multiplexers 14, 15 and demultiplexers 18, 19 respectively. This arrangement allows to obviate the need for axis re- adjusting when the previously used field excitation level is selected again, and makes operations of the electron microscope extremely easier.
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