Electron Diffraction Imaging With Adaptive Coincidence Areas
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Solution Overview
Problem
Traditional scintillator-based cameras struggle to detect weak diffraction peaks in electron diffraction patterns due to limited dynamic range, while direct detection cameras face challenges with coincidence losses at high dose rates, reducing detective quantum efficiency (DQE).
Innovation Solution
The method involves using different sets of counting parameter values for high and low dose rate regions in a diffraction image generated by counting electron detection events. Pixels belonging to diffraction peaks use a first set of parameters corresponding to a smaller coincidence area, while background pixels use a second set corresponding to a larger coincidence area, thereby extending the dynamic range of the direct detection camera.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a direct detection camera operates in electron counting mode to detect weak diffraction peaks, then detection sensitivity for weak peaks is improved, but detective quantum efficiency decreases at high dose rates due to coincidence loss
Solution Approach 1:
The patent applies local quality by implementing different coincidence area thresholds for different spatial regions within the detector. Pixels are categorized into peak regions (requiring smaller coincidence areas to maintain high DQE at high dose rates) and background regions (allowing larger coincidence areas to suppress noise). This spatially-dependent parameter adjustment resolves the contradiction by optimizing detection performance locally for each region's specific dose rate characteristics.
Solution Approach 2:
The patent implements dynamics by making the coincidence area parameter adaptive rather than fixed. The system dynamically selects appropriate coincidence area values based on the local dose rate conditions and pixel location. This dynamic adjustment allows the detector to maintain optimal detective quantum efficiency across varying dose rates while preserving sensitivity to weak diffraction peaks.
2Adaptability or versatility
If a scintillator-based camera is used to capture electron diffraction patterns, then the camera can handle high dynamic range, but weak diffraction peaks cannot be detected accurately
Solution Approach 1:
The patent applies parameter changes by transitioning from scintillator-based photon detection to direct electron detection with adjustable coincidence area parameters. By modifying the detection mechanism and its associated parameters (coincidence area thresholds), the system achieves both high dynamic range capability and improved sensitivity to weak diffraction peaks that were previously undetectable with scintillator-based cameras.
3Ease of operation
If a fixed coincidence area is used for all pixels in electron counting mode, then the system is simple to operate, but the dynamic range is limited due to coincidence loss at high dose rates
Solution Approach 1:
The patent applies segmentation by dividing the detector into distinct pixel categories (peak pixels and background pixels) with different coincidence area assignments. This segmentation enables the system to handle a broader dynamic range by treating high-dose-rate peak regions and low-dose-rate background regions differently, while maintaining operational simplicity through automated classification and parameter assignment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the detective quantum efficiency (DQE) at high dose rates by reducing coincidence losses and allows for the accurate capture of diffraction peaks with large dynamic ranges, resulting in high-quality electron diffraction images.
Implementation Method 1
electron diffraction patterns of crystals of these molecules
Implementation Method 2
irradiating a sample with an electron beam
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Method and system for generating a diffraction image comprises acquiring multiple frames from a direct-detection detector responsive to irradiating a sample with an electron beam. Multiple diffraction peaks in the multiple frames are identified. A first dose rate of at least one diffraction peak in the identified diffraction peaks is estimated in the counting mode. If the first dose rate is not greater than a threshold dose rate, a diffraction image including the diffraction peak is generated by counting electron detection events. Values of pixels belonging to the diffraction peak are determined with a first set of counting parameter values corresponding to a first coincidence area. Values of pixels not belonging to any of the multiple diffraction peaks are determined using a second, set of counting parameter values corresponding to a second, different, coincidence area.