Optical Sectioning and Confocal Imaging and Analysis in the Transmission Electron Microscope

Aberration correction in the transmission electron microscope has led to a reduction in the depth of focus for imaging. The depth of focus in a state-of-the-art scanning transmission electron microscope system, which is currently just a few nanometers, creates an opportunity to explore the three-dimensional structure of a sample by focusing on specific layers, an approach known as optical sectioning. In this article, we review the performance of optical sectioning in the scanning transmission electron microscope. Limitations in the simple optical sectioning approach are used to motivate discussion of confocal electron microscopy. Three imaging modes in scanning confocal electron microscopy have been investigated both theoretically and experimentally, and are reviewed here. The method of implementing a confocal arrangement in a microscope is discussed, along with its comparative performance with other methods for three-dimensional imaging and analysis. Finally, current and future potential applications are discussed.