Electron Diffraction Gain Correction for Kikuchi Pattern Detection
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Solution Overview
Problem
Current methods for improving the sensitivity of electron diffraction pattern analysis in electron microscopes, such as Kikuchi pattern analysis, face challenges in effectively correcting for pixel gain variations in camera systems, which can corrupt the diffraction contrast and require multiple reference images or specific atomic number matches.
Innovation Solution
A method that involves obtaining a calibration image from an amorphous specimen to estimate pixel gain variations, allowing for the removal of these variations from target images without needing multiple reference images, thereby correcting for detector device gain without affecting the diffraction contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flat-fielding correction is applied using a reference image from an amorphous material, then pixel gain variations are corrected, but the correction becomes ineffective when analyzing particles with different local geometries and atomic numbers
Solution Approach 1:
The patent applies preliminary action by performing pixel gain correction during the image acquisition process itself rather than as a separate post-processing step. The system dynamically adjusts pixel gain values based on the actual diffraction pattern background, ensuring correction is tailored to each specific specimen and geometry combination. This resolves the contradiction by making the correction adaptive to different specimen types while maintaining precision.
Solution Approach 2:
The patent implements dynamics by transitioning from static flat-fielding correction (using a fixed reference image) to dynamic pixel gain correction (adjusting gains based on actual pattern characteristics). The system continuously adapts pixel gain values to match the specific diffraction pattern being analyzed, whether from particles, flat specimens, or materials with varying atomic numbers. This dynamic approach simultaneously improves measurement precision and adaptability to different specimen types.
2Measurement precision
If multiple reference images are used to correct pixel gain variations, then correction accuracy improves, but system complexity and processing requirements increase
Solution Approach 1:
The patent applies self-service by enabling the diffraction pattern image itself to serve as the reference for pixel gain correction. Instead of requiring external reference images from amorphous materials or multiple calibration samples, the system extracts the background signal directly from the acquired diffraction pattern and uses it to correct pixel gain variations. This self-referential approach achieves high correction accuracy while eliminating the complexity of managing multiple reference images.
Solution Approach 2:
The patent implements universality by creating a correction method that works across all specimen types and geometries using a single unified approach. The pixel gain correction algorithm universally applies to particles, flat specimens, crystalline and amorphous materials, regardless of atomic number or local geometry. This universal method replaces the need for multiple specialized reference images, reducing system complexity while maintaining or improving correction accuracy.
3Measurement precision
If beam scanning is performed to obtain background images from randomized crystallographic contrast areas, then background correction improves, but analysis time and productivity decrease
Solution Approach 1:
The patent applies taking out by extracting the background signal directly from the acquired diffraction pattern image without requiring separate scanning operations. The system isolates the background component from the total signal using signal processing techniques, then uses this extracted background for pixel gain correction. This eliminates the need for time-consuming beam scanning to locate and image randomized crystallographic contrast areas, thereby improving productivity while maintaining correction precision.
Solution Approach 2:
The patent applies preliminary action by performing background extraction and pixel gain correction as integrated preliminary steps within the standard image acquisition workflow. Rather than requiring a separate scanning phase to obtain background images, the system completes these corrections during the primary diffraction pattern acquisition. This preliminary integration maintains measurement precision while significantly improving analysis speed and productivity.
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 enables improved detection of Kikuchi diffraction patterns by isolating and correcting for pixel gain variations, enhancing the quality of electron diffraction pattern analysis without requiring specific reference samples or complex geometric controls.
Implementation Method 1
the angular modulation of intensity caused by diffraction effects on backscattered electrons rides upon the general angular intensity distribution of diffuse backscattering from a point on the sample
Implementation Method 2
systems have been commercially available for detecting the Kikuchi band patterns that are caused by diffraction of the emerging backscattered electrons
Implementation Method 3
a phosphor positioned close to the specimen, where it will be hit by a diverging beam of electrons backscattered from a point on the sloping specimen surface
Data Source
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AI summary
A method and system for processing a diffraction pattern image obtained in an electron microscope are disclosed. The method comprises, according to a first set of microscope conditions, causing an electron beam to impinge upon a calibration specimen so as to cause resulting electrons to be emitted therefrom and monitoring the resulting electrons using a detector device so as to obtain a calibration image comprising a plurality of pixels having values, the first set of microscope conditions being configured such that the calibration image includes substantially no electron diffraction pattern; obtaining, from the calibration image, a gain variation image comprising a plurality of pixels, each having a value representing relative detector device gain for a corresponding pixel of the calibration image; according to a second set of microscope conditions, causing an electron beam to impinge upon a target specimen so as to cause resulting electrons to be emitted therefrom and monitoring the resulting electrons using the detector device so as to obtain a target image comprising a plurality of pixels having values, the second set of microscope conditions being configured such that the target image includes an electron diffraction pattern; and for each pixel of the target image, removing from the pixel value, in accordance with the value of the corresponding pixel of the gain variation image, the contribution to the pixel value of the relative detector device gain, so as to obtain a gain variation-corrected image.