Integrated Vector Field Imaging Beam Tilt Correction
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Solution Overview
Problem
Integrated vector field imaging in scanning transmission charged particle microscopy is affected by geometric errors due to variations in the incident angle of the electron beam, which previous correction methods have not adequately addressed.
Innovation Solution
The technique involves pre-correcting the imaging vector field or the integrated vector field image by using reference measurements, assembling signals from segmented detectors to form gradient images, fitting quadratic intensity curves, and adjusting the deflector system to mitigate beam tilt errors, thereby reducing or eliminating pointwise errors associated with pivot point imperfections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional iVF imaging is performed without correction, then the imaging process is simple and fast, but geometric errors due to beam tilt variations significantly degrade image quality and measurement precision
Solution Approach 1:
The patent applies preliminary action by performing reference measurements and determining pointwise variations in beam incidence angle before acquiring the actual specimen image. The correction factors are calculated in advance and stored for application during image reconstruction, eliminating the need for complex real-time corrections and enabling straightforward application to subsequent images without requiring repeated calibration measurements.
Solution Approach 2:
The patent introduces an intermediary correction process that acts as a mediator between the raw imaging data and the final corrected image. By using reference measurements to determine beam tilt variations and applying these as correction factors to the imaging vector field, the system separates the error characterization from the image acquisition, allowing complex corrections to be applied systematically without complicating the primary imaging workflow.
2Measurement precision
If beam tilt correction is applied in real-time during imaging, then image quality improves, but the imaging speed and productivity decrease due to additional processing steps
Solution Approach 1:
The correction factors are determined in advance through reference measurements performed before actual specimen imaging. This preliminary determination of pointwise beam incidence angle variations allows the correction to be applied as a simple post-processing step rather than requiring complex real-time adjustments during image acquisition, thereby maintaining high imaging speed while achieving accurate correction.
Solution Approach 2:
The patent applies correction only to the imaging vector field data that requires it, rather than processing all imaging data uniformly. By identifying and correcting only the components affected by beam tilt variations through the reference measurement approach, the system achieves necessary correction accuracy without unnecessarily processing all data streams in real-time, thus preserving imaging productivity.
3Measurement precision
If complex correction algorithms are used to eliminate pivot point errors, then measurement precision improves, but the difficulty of detecting and measuring errors increases
Solution Approach 1:
The patent uses reference measurements as an intermediary to indirectly characterize beam tilt variations without requiring direct measurement of the complex pivot point errors. By measuring the imaging vector field in the absence of a specimen and comparing it to the expected uniform field, the system derives correction factors that account for all sources of geometric error, including pivot point imperfections, through a simplified measurement process.
Solution Approach 2:
The patent creates a copy of the imaging vector field under known conditions (without specimen) to establish a reference pattern. This reference copy captures the systematic errors introduced by the microscope optics and beam delivery system, which can then be subtracted from or used to correct subsequent measurements, simplifying the detection and correction of errors without requiring complex real-time analysis.
Data Source
AI summary
An example method of imaging a specimen in a Scanning Transmission Charged Particle Microscope may include scanning a beam of charged particles across a specimen, detecting, by a segmented detector, a flux of charged particles traversing through the specimen at each scan location, for each scan location, combining detection data from different segments of the detector to produce a respective vector output, forming, based on the respective vector output data for each scan location, an imaging vector field, forming, based on the imaging vector field, an integrated vector field image, and reducing error in either the imaging vector field prior to forming the integrated vector field image or correcting the integrated vector field image, wherein the error is due to pointwise variations in beam incidence angle on the specimen.