Adding electrostatic deflectors to a few choice locations in a transmission electron microscope (TEM) enables many operating modes for high-speed acquisition and dose control. For example, an electrostatic beam blanker early in the column lets you turn the beam on and off on the nanosecond scale without affecting focus or alignment. Synchronized with a scanning system, this lets you choose exactly where and when you apply dose to your sample. A fast deflection system placed before a camera allows framerate acceleration, including a compressive-sensing mode in which the total effective throughput of the camera can be enhanced by a factor of 5 or more. Having these tools, we need to think carefully about the best ways to use them, and the answers are not always obvious. Compressive sensing, for example, may speed up acquisition at the cost of substantially worsening the information return per electron. The best strategy depends on what you are trying to optimize: Information per electron, information per time, damage per electron, etc.
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