Aberration Computing Device Diffractogram Line Profile Fitting
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Solution Overview
Problem
Current methods for quantitatively measuring defocus and two-fold astigmatism in transmission electron microscopy are computationally slow, especially when dealing with large images, due to higher-dimensional computations involved in existing techniques.
Innovation Solution
An aberration computing device and method that fits line profiles of a diffractogram to a fitting function in radial directions to find fitting parameters, reducing computational complexity and accelerating the process by filtering in a circumferential direction and using anisotropic filters, thereby improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two-dimensional pattern fitting or three-dimensional transformation is applied to diffractogram to measure defocus and two-fold astigmatism, then measurement precision is improved, but computational speed deteriorates
Solution Approach 1:
The patent segments the diffractogram analysis into two independent one-dimensional line profile measurements along orthogonal directions (x and y axes), rather than performing comprehensive two-dimensional pattern fitting. Each line profile is fitted separately to a one-dimensional CTF function, reducing the computational complexity from 2D to 1D while still extracting the necessary defocus and two-fold astigmatism parameters from the combined results.
Solution Approach 2:
The patent extracts only the essential information needed for aberration measurement by fitting line profiles along specific orthogonal directions, rather than analyzing the entire two-dimensional diffractogram structure. This extraction approach isolates the critical parameters (defocus and two-fold astigmatism) from redundant data, significantly reducing computation time while maintaining measurement accuracy.
2Measurement precision
If two-dimensional pattern fitting is applied to diffractogram, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the complex 2D pattern fitting task into simpler 1D line profile fitting operations along orthogonal directions. By segmenting the analysis into separate x and y direction measurements, the system reduces algorithmic complexity and makes the measurement process more computationally tractable while still achieving accurate aberration parameter extraction.
3Measurement precision
If three-dimensional parameter space transformation is performed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent extracts defocus and two-fold astigmatism parameters directly from one-dimensional line profile fits along orthogonal directions, avoiding the time-consuming transformation to three-dimensional parameter space. This extraction method obtains the necessary aberration information from simplified 1D measurements rather than comprehensive 3D analysis, dramatically reducing computational time.
Solution Approach 2:
Instead of transforming the diffractogram into 3D parameter space and then extracting parameters, the patent inverts the approach by directly fitting 1D line profiles in the original 2D diffractogram space and deriving aberration parameters from these simpler fits. This inversion eliminates unnecessary dimensional transformations and reduces computational overhead.
Data Source
AI summary
An aberration computing device (100) includes a fitting section (48) for fitting line profiles of a diffractogram taken in radial directions to a fitting function and finding fitting parameters of the fitting function and a computing section (49) for finding at least one of an amount of defocus and two-fold astigmatism, based on the fitting parameters.