A SIMPLE CONCEPT FOR BETTER ALIGNMENT AND SIMPLIFIED OPERATION OF A TRANSMISSION ELECTRON-MICROSCOPE

The operation of transmission electron microscopes is still complicate d despite of the numerous improvements in the past. Many adjustment st eps are still necessary for the routine alignment and, above all, the microscope has to be readjusted frequently during operation. This prob lem is mainly caused by the dependence of the microscope alignment on the objective lens excitation. It will be shown that the focus range f or a good microscope alignment is limited to +/-50 mu m for CTEM and b s +/-4 mu m for HREM. Yet larger focus variations are frequently neces sary to compensate height variations of the specimen by tilting or by shifting if the specimen is buckled. As solution of this problem it is proposed to keep the objective lens current constant and to focus the image mechanically by adjusting the specimen height. The practicabili ty and consequences of this way of microscope operation are critically assessed.