Practical Electron Microscopy and Database

The current direct electron detectors are mainly produced by three companies: Gatan, FEI, and Direct Electron. These detectors, often referred to as Direct Detection Devices (DDD), yield significantly better images compared to film. All three types utilize similar sensor technology, where electrons strike a lightly doped silicon epilayer supported by a more heavily doped silicon substrate. Each frame of the exposure is continuously read out in a rolling-shutter mode, creating a “movie” of the capture process. In rolling-shutter mode, the sensor reads out each frame line by line rather than capturing the entire frame at once. In other words, each row or set of rows is exposed and read out sequentially, creating a slight time delay across the frame. Rolling-shutter mode is common in video and imaging sensors because it allows for continuous capture with lower power consumption and is typically faster for reading out large sensors, especially those with high resolutions. However, it can introduce minor distortions if the subject or detector moves during capture, as different parts of the frame are recorded at slightly different times. In the direct electron detectors, rolling-shutter mode enables continuous capture of high-speed electron images as a series of frames (or a "movie") without missing data, which is essential for studying dynamic processes at high resolution.