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We report the successful implementation of a fully automated tomographic data collection system in scanning transmission electron microscopy (STEM) mode. Autotracking is carried out by combining mechanical and electronic corrections for specimen movement. Autofocusing is based on contrast difference of a focus series of a small sample area. The focus gradient that exists in normal images due to specimen tilt is effectively removed by using dynamic focusing. An advantage of STEM tomography with dynamic focusing over TEM tomography is its ability to reconstruct large objects with a potentially higher resolution.

We present a simple theory for the evaluation of the axial resolution of a confocal scanning microscope with parallel-beam detection. The results demonstrate that, in certain cases, the collection efficiency is low compared with a conventional confocal microscope, but the axial resolution may be further improved.