Hexapole Aberration Corrector for Compact Electron Microscopes
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Solution Overview
Problem
Existing aberration correctors for electron microscopes, such as those described in JP-A-2019-179650, increase the apparatus size and height of the electron microscope by requiring multiple stages of multipole elements to correct higher-order geometrical aberrations.
Innovation Solution
An aberration corrector with a first and second multipole element producing hexapole fields, where the strength of these fields varies along the optical axis, and a transfer lens system between them, allowing for the correction of sixth-order three-lobe aberration while minimizing the size and height of the corrector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple stages of multipole elements are used to correct higher-order geometrical aberrations, then the aberration correction capability is improved, but the apparatus size and height of the electron microscope are increased
Solution Approach 1:
The patent changes the field strength parameter along the optical axis by introducing a transfer lens system between multipole elements. This allows the hexapole field strength to vary (e.g., stronger in the first region, weaker in the second region) rather than remaining uniform, enabling effective aberration correction with a more compact configuration that reduces overall apparatus height while maintaining correction capability for sixth-order three-lobe aberration and six-fold astigmatism
2Measurement precision
If the number of stages of multipole elements is increased to correct sixth-order three-lobe aberration, then the aberration correction performance is improved, but the device complexity and apparatus size are increased
Solution Approach 1:
The patent introduces dynamic variation in field strength along the optical axis using a transfer lens system. This creates a non-uniform hexapole field configuration where the field strength changes from a first region to a second region, enabling the system to correct sixth-order three-lobe aberration and six-fold astigmatism with a simpler two-stage multipole element configuration rather than requiring multiple uniform stages
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 aberration corrector effectively corrects sixth-order three-lobe aberration and six-fold astigmatism without increasing the apparatus size, enabling miniaturization and maintaining high resolution imaging capabilities.
Implementation Method 1
a first multipole element for producing a hexapole field, a second multipole element for producing a hexapole field
Implementation Method 2
At least one of the hexapole fields respectively produced by the first multipole element and the second multipole element varies in strength along the optical axis
Implementation Method 3
a transfer lens system disposed between the first and second multipole elements
Data Source
AI summary
An aberration corrector includes a first multipole element for producing a hexapole field, a second multipole element for producing a hexapole field, and a transfer lens system disposed between the first and second multipole elements. The first and second multipole elements are arranged along an optical axis. At least one of the hexapole fields respectively produced by the first multipole element and the second multipole element varies in strength along the optical axis.