STEM Aberration Correction via Real-Time Feedback Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current aberration correction methods in scanning transmission electron microscopes (STEM) are inadequate for high-resolution imaging, particularly when defocus and two-fold astigmatism vary during long data acquisition sessions, leading to deteriorated spatial resolution in applications like EDS and EELS imaging.
Innovation Solution
A system and method that calculates autocorrelation functions from STEM images obtained at different foci or incident angles, fits aberration functions to iso-intensity lines, and uses feedback control to adjust the electron optical components, such as the objective lens and aberration corrector, to correct defocus and astigmatism in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior-art aberration correction method is used, then aberration correction can be performed, but observation must be interrupted and spatial resolution deteriorates during long data acquisition
Solution Approach 1:
The patent enables continuous aberration correction during ongoing data acquisition by using a Ronchigram obtained during the imaging process itself, rather than requiring separate correction measurements. This allows the useful action of data acquisition to continue uninterrupted while aberration parameters are continuously monitored and corrected.
Solution Approach 2:
The system implements feedback control by calculating aberration parameters from the Ronchigram and automatically adjusting the electron optical components based on these calculations. This closed-loop feedback mechanism maintains optimal focus and aberration correction throughout the data acquisition process without requiring manual intervention or interruption.
2Quantity of substance
If long data acquisition is performed for high-resolution imaging, then more comprehensive data is obtained, but defocus and astigmatism vary causing resolution deterioration
Solution Approach 1:
The patent transforms the static aberration correction approach into a dynamic system that continuously adapts to changing conditions during data acquisition. By calculating aberration parameters from the Ronchigram obtained during imaging and automatically adjusting correction parameters in real-time, the system maintains optimal spatial resolution throughout the entire data acquisition process regardless of duration.
3Adaptability or versatility
If Ronchigram-based aberration correction is used, then correction can be performed during imaging, but requires specific imaging conditions
Solution Approach 1:
The patent makes the Ronchigram serve multiple functions: it is used both for obtaining imaging data and for calculating aberration parameters. This multi-functional approach allows aberration correction to be performed during various imaging modes without requiring separate correction procedures, enhancing the system's adaptability while utilizing existing imaging data.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Scanning transmission electron microscope (STEM) and method of aberration correction are offered which can correct defocus and astigmatism during imaging and which can provide atomic resolution. The STEM (2) has plural electron optical means. Furthermore, the STEM has autocorrelation function calculation means, aberration coefficient calculation means, and feedback control means. At least two images are obtained by varying a value at which one of the electron optical means is set. The autocorrelation function calculation means calculates autocorrelation functions of the at least two images. The aberration coefficientcalculation meansfitsaberrationfunctions to iso-intensity lines of the autocorrelation functions and calculates aberration coefficients based on the obtained aberration functions. The feedback control means provides feedback control of the electron optical means (23,25) based on the aberration coefficients.