Corrective for Electron Microscope Aberration Correction
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Solution Overview
Problem
High-resolution electron-optical imaging systems are limited by third order spherical aberration and first order, first degree axial chromatic aberration, which existing corrective methods using multipoles fail to adequately correct, particularly in transmission electron microscopy where high resolution and large image fields are required.
Innovation Solution
A corrective system comprising two symmetrically constructed correction pieces with an uneven number of quadrupole fields and at least one octupole field each, where the quadrupole fields are anti-symmetric and the central quadrupole field is electromagnetic, combined with a transfer lens system that images central planes anamorphically, allowing independent adjustment of electrical and magnetic field intensities to correct both aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a double-symmetrical arrangement of quadrupole and octupole fields is used, then aperture aberration and chromatic aberration correction is achieved, but large coma-like fifth order image aberrations are generated and the number of image points is restricted
Solution Approach 1:
The patent applies asymmetry by using an odd number of quadrupole fields (at least five) arranged asymmetrically within each correction piece, rather than a symmetric arrangement. The quadrupole fields are positioned with specific spacing relationships that break symmetry, allowing the central quadrupole field to be centered on the optical axis while others are offset. This asymmetric configuration enables correction of both aperture and chromatic aberrations without generating large coma-like fifth order image aberrations, thus preserving a large number of image points for high-resolution transmission electron microscopy.
2Measurement precision
If octupole fields are arranged for aperture aberration correction, then third order spherical aberration is reduced, but large coma-like fifth order image aberrations are generated
Solution Approach 1:
The patent merges the functions of aperture aberration correction and chromatic aberration correction into a unified corrective system. By combining an odd number of quadrupole fields with at least one octupole field in each correction piece, and arranging them with specific spacing and symmetry relationships, the system simultaneously corrects both types of aberrations. The transfer lens system with anamorphic imaging further integrates these correction functions, allowing the system to reduce third order spherical aberration through the octupole field while avoiding the generation of large coma-like fifth order image aberrations that would otherwise result from separate correction approaches.
3Measurement precision
If a corrective system with multiple correction pieces is used, then aberration correction capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential correction functions into two distinct correction pieces, each containing a specific configuration of quadrupole and octupole fields. By separating the correction functionality into these two optimized units with antisymmetric quadrupole field arrangements, the system achieves comprehensive aberration correction (both aperture and chromatic) while managing complexity. The transfer lens system with anamorphic imaging further simplifies the overall structure by creating a compact arrangement where the central planes of the two correction pieces are imaged on one another, reducing the need for additional complex components.
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 effectively corrects third order spherical aberration and first order chromatic aberration, enabling the transmission of a larger image field with uniform optical quality, suitable for high-resolution electron microscopy by eliminating axial and extra-axial aberrations, thereby enhancing the resolution and capacity of electron microscopes.
Implementation Method 1
the central quadrupole field being arranged such that it is centered with respect to the central plane of the correction piece and is electromagnetic
Implementation Method 2
each correction piece having a plurality of quadrupole fields and at least one octupole field
Implementation Method 3
each correction piece having a plurality of quadrupole fields and at least one octupole field, the central quadrupole field being superimposed by an octupole field
Implementation Method 4
a transfer lens system being arranged such that it is symmetrical with respect to the central plane of the corrective, which comprises at least one circular lens
Data Source
AI summary
A corrective for eliminating the third-order aperture aberration and the first-order, first-degree axial chromatic aberration includes two correction pieces, which are arranged one behind the other in the direction of the optical axis, in which each correction piece has a plurality of quadrupole fields (QP) and at least one octupole field (OP.) Each correction piece is constructed such that it is symmetrical with respect to its central plane (S, S′) with each correction piece having an uneven number of at least five quadrupole fields (QP) and at least one octupole field (OP). Each correction piece is further constructed so that it is symmetrical with respect to its central plane. The central quadrupole field is arranged so that it is centered with respect to the central plane of the correction piece and is electromagnetic. The quadrupole fields of the two correction pieces are antisymmetrical and a transfer lens system is arranged such that it is symmetrical with respect to the central plane of the corrective between the correction pieces. The transfer lens system has two round lenses and the setting of the transfer lens system takes place so that the two round lenses image the central plane of the two correction pieces anamorphically onto one another, in which the enlargement in one main section is the reciprocal of the enlargement in the other main section and with an octupole field superimposed on the central quadrupole field.