| 摘要 |
PURPOSE:To simplify a current presetting system used for an electron microscope, and facilitate current presetting work by feeding optimum currents to lenses by controlling preset volumes in order, and storing the optimum current value in a memory every time when the current is fed to the lens. CONSTITUTION:In setting preset currents for various kinds of lens coils (C1- Cn) when acceleration voltage values, multiplying-factor values or the like are switched, currents are fed to the coils (C1-Cn) through switches (SW) by controlling the volumes (V1-Vn) special for the coils (C1-Cn), in order. Then, each preset current is compared, by means of each comparator (H), with signals given by sending through each DA converter, signals which are sent from a central processing unit and change at given time intervals. When each preset current becomes equal to the compared signal, the coincidental signal is read out in use so as to supply a current to each coil (C). As a result, setting of preset currents for an electron microscope can be simplified by reducing the number of change-over relays, and the presetting work can be facilitated. |
