Electron Mirror Aberration Correction in Electron Microscopes
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Solution Overview
Problem
Electron microscopes suffer from positive spherical and chromatic aberrations, which limit resolution and require complex designs with high accuracy demands, particularly due to the focusing effects and dispersion caused by magnetic deflectors and energy-dependent deflection angles.
Innovation Solution
An aberration correcting device with two electron mirrors arranged opposite sides of an intermediate space, where the electron beam is reflected and deflected by magnetic and electrostatic deflectors to counteract optical aberrations, allowing for a more compact and accurate correction of spherical and chromatic aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If magnetic deflectors are used to deflect the electron beam in the known system, then the electron beam can be redirected towards the electron mirror and back, but the focusing effect and dispersion caused by the magnetic field deteriorate the resolution
Solution Approach 1:
The patent extracts and removes the magnetic deflector from the system, replacing it with an electrostatic deflector. This eliminates the harmful focusing effect and dispersion caused by magnetic fields while retaining the necessary beam deflection capability. The electrostatic deflector achieves the same functional purpose without the adverse side effects that limit resolution.
Solution Approach 2:
The patent substitutes the magnetic deflection system with an electrostatic deflection system. By replacing magnetic fields with electrostatic fields, the system achieves beam deflection without the focusing effect and energy-dependent dispersion that occur with magnetic deflectors, thereby improving resolution while maintaining operational capability.
2Ease of operation
If the actual deflection angle depends on electron energy, then dispersion occurs for electron beams with different energies, but this cannot be avoided with magnetic deflectors
Solution Approach 1:
The patent replaces the magnetic deflection mechanism with an electrostatic deflection mechanism. In electrostatic fields, the deflection angle is independent of electron energy, unlike magnetic fields where deflection angle varies with energy. This substitution eliminates the dispersion effect while preserving the deflection functionality, stabilizing the beam composition across different energy levels.
3Measurement precision
If complex designs with many magnetic coils are used, then aberration correction can be achieved, but manufacturing accuracy demands become very high
Solution Approach 1:
The patent removes the complex system of multiple magnetic coils and deflectors, retaining only the essential electron mirrors for aberration correction. By extracting the unnecessary magnetic deflection components, the design becomes simpler with fewer parts, reducing manufacturing complexity and accuracy demands while preserving the core aberration correction functionality.
Solution Approach 2:
The patent substitutes the complex magnetic coil system with a simpler electrostatic deflection system combined with electron mirrors. This replacement reduces the number of components and simplifies the overall design, making manufacturing more feasible with lower accuracy demands while maintaining effective aberration 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
This configuration enhances the resolution of electron microscopes by effectively correcting aberrations with a more straightforward design, reducing the need for complex magnetic coils and improving the accuracy of electron beam deflection and focusing.
Implementation Method 1
at least two electron mirrors, which are arranged such that the reflecting faces of these mirrors substantially face each other
Implementation Method 2
The first electron mirror is arranged at the exit side of an intermediate space, and the second electron mirror is arranged at an input side of the intermediate space
Implementation Method 3
which is arranged to receive the electron beam coming from the input side and to reflect said beam via the intermediate space towards the second mirror
Data Source
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AI summary
The invention relates to an aberration correcting device for correcting aberrations of focusing lenses in an electron microscope. The device comprises a first and a second electron mirror, each comprising an electron beam reflecting face. Between said mirrors an intermediate space is arranged. The intermediate space comprises an input side and an exit side. The first and second electron mirrors are arranged at opposite sides of the intermediate space, wherein the reflective face of the first and second mirror are arranged facing said intermediate space. The first mirror is arranged at the exit side and the second mirror is arranged at the input side of the intermediate space. In use, the first mirror receives the electron beam coming from the input side and reflects said beam via the intermediate space towards the second mirror. The second mirror receives the electron beam coming from the first mirror, and reflects the electron beam via the intermediate space towards the exit side. The incoming electron beam passes said second mirror at a position spaced apart from the reflection position on the second mirror. At least one of the electron mirrors is arranged to provide a correcting aberration to a reflected electron beam.