Electron Ptychography for Automatic Zone Axis Mistilt Correction
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Solution Overview
Problem
Conventional electron microscopy imaging methods are affected by sample tilt, leading to artificial contrast and errors in atomic resolution images, making it difficult to quantify structural information due to zone axis mis-tilt.
Innovation Solution
An electron ptychography method and apparatus that automatically corrects zone axis mis-tilt by acquiring diffraction patterns, initializing object and electron beam functions, constructing a forward propagation model, calculating a loss function, and iteratively optimizing tilt angles using gradients to obtain high-resolution images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electron microscopy imaging methods are used, then imaging is simple and fast, but image quality deteriorates due to zone axis mis-tilt causing artificial contrast and measurement errors
Solution Approach 1:
The patent changes the parameter of tilt angle by treating it as a variable to be optimized rather than a fixed value. The tilt angle is included as a variable parameter in the propagation function between sample slices, allowing the system to automatically determine the correct tilt angle that minimizes the loss function and eliminates artificial contrast caused by mis-tilt.
Solution Approach 2:
The patent implements feedback by using the loss function to compare calculated diffraction patterns with acquired ones, then using gradient descent to iteratively adjust the tilt angle and other parameters. This closed-loop feedback mechanism continuously refines the tilt angle until the difference between calculated and measured patterns is minimized, thereby correcting zone axis mis-tilt.
2Measurement precision
If ptychography with iterative optimization is used, then measurement precision and resolution are improved, but calculation time and computational complexity increase
Solution Approach 1:
The patent segments the optimization process by dividing the sample into multiple slices along the beam direction and treating each slice's potential distribution as a separate object function. This segmentation allows parallel computation of gradients for each slice and enables the use of efficient gradient descent algorithms, reducing the overall computational burden while maintaining high precision.
Solution Approach 2:
The patent replaces traditional mechanical tilt adjustment methods with a computational approach. Instead of physically tilting the sample to achieve zone axis alignment, the system uses mathematical optimization to calculate and correct the tilt angle effects through the propagation function, substituting mechanical adjustment with computational correction.
3Reliability
If manual tilt adjustment is performed, then zone axis alignment can be improved, but operation complexity and time consumption increase
Solution Approach 1:
The patent enables the system to self-correct zone axis mis-tilt automatically without requiring manual intervention. The optimization algorithm autonomously adjusts the tilt angle parameter by minimizing the loss function through gradient descent, allowing the system to self-service the alignment task that would otherwise require skilled manual operation.
Solution Approach 2:
The patent performs preliminary action by including the tilt angle as a variable parameter in the propagation function before the actual image reconstruction process. This preliminary inclusion of tilt correction in the mathematical model allows the system to automatically compensate for mis-tilt during the standard ptychography reconstruction process, eliminating the need for separate manual tilt adjustment steps.
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
The method and apparatus enable high space-resolution and precision structure measurement by correcting zone axis mis-tilt, allowing for sub-angstrom resolution and picometer-level precision even when the zone axis deviates from the electron beam.
Implementation Method 1
A diffraction pattern of each scan point of the sample is acquired by scanning the sample through using an electron beam
Data Source
AI summary
An electron ptychography method and an electron ptychography apparatus for automatically correcting a mistilt of a zone axis of a sample. The method includes: acquiring a diffraction pattern of each scan point of the sample by scanning the sample through using an electron beam; initializing an object function and an electron beam function, constructing a forward propagation model according to a propagation function between sample slices, and calculating a loss function to be a difference between a calculated diffraction pattern and the acquired diffraction pattern, where the calculated diffraction pattern is obtained from the forward propagation model and parameters to be optimized; calculating gradients of the loss function with respect to parameters to be optimized respectively, and optimizing the parameters to be optimized according to the gradients; executing the calculating the loss function of the forward propagation model, the calculating the gradients of the loss function with respect to the parameters to be optimized respectively, and the optimizing the parameters to be optimized according to the gradients, iteratively, till a termination condition for iterations is satisfied; and outputting the optimized parameters.