Hexapole Corrector for Electron Microscopy Aberrations
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Solution Overview
Problem
High-resolution electron microscopy is limited by third-order spherical aberrations and extra-axial coma, which restrict the image field and resolution, with existing correctives only able to eliminate the radial component of coma, leaving anisotropic coma unaddressed.
Innovation Solution
A corrective system comprising at least three coaxially arranged hexapole fields with circular lenses in between, where the hexapole fields are imaged on each other and rotated relative to the optical axis, allowing for the elimination of both third-order spherical aberration and anisotropic extra-axial coma, and optionally including additional components to correct higher-order aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the image region is enlarged beyond the coma-free limit, then larger field of view is achieved, but image quality deteriorates due to uncorrected anisotropic coma
Solution Approach 1:
The corrector applies preliminary correction for anisotropic coma before the image formation process, using hexapole fields that generate electric or magnetic fields to deflect electron trajectories. This preliminary anti-action counteracts the coma aberration that would otherwise limit the usable image field size, allowing enlargement of the image region while maintaining image quality.
2Measurement precision
If additional hexapole fields and lenses are added to correct anisotropic coma, then correction capability is improved, but device complexity increases
Solution Approach 1:
The corrector components are arranged in a nested configuration where hexapole fields and round-lens doublets are interleaved along the electron beam path. The hexapole fields are positioned between the round-lens doublets, creating a compact nested structure that minimizes the overall length and complexity of the corrector while maintaining full correction capability.
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 system achieves complete or partial correction of all second-order and fourth-order aberrations, enabling a larger image field and improved resolution by eliminating both isotropic and anisotropic components of extra-axial coma, potentially approaching aplanat properties.
Implementation Method 1
The corrector comprises at least three hexapole fields, between which round-lens doublets are interposed, which generate electric or magnetic hexapole fields
Implementation Method 2
The corrector comprises at least three hexapole fields, between which round-lens doublets are interposed, which generate electric or magnetic hexapole fields
Implementation Method 3
round-lens doublets are interposed, which generate electric or magnetic hexapole fields, the like being imaged on one another in pairs by the round-lens doublets
Implementation Method 4
The invention relates to an electron-optical corrector for eliminating both the third-order spherical aberration and the anisotropic (azimuthal) component of the third-order extra-axial coma
Data Source
AI summary
An electron-optical corrector for rendering superfluous both the third-order opening error and the anisotropic part of the extra-axial third-order coma, using round lenses and hexapole fields, the corrector includes at least three coaxially arranged hexapole fields with at least one round lens field is arranged between adjacent hexapole fields, so that the hexapole fields are imaged onto each other in pairs. The intensities of the hexapole fields are selected so that the image error coefficient of the three-fold astigmatism is equal to 0, and at least three hexapole fields in the Larmor reference system are rotated in relation to each other at an angle about the optical axis.