Electron Microscope Monochromator Automatic Alignment
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Solution Overview
Problem
Adjusting the focal plane to coincide with the achromatic plane in a two-stage filter type monochromator of an electron microscope is complex and requires skilled user intervention, making it difficult to achieve optimal imaging conditions.
Innovation Solution
An electron microscope with a monochromator equipped with an image acquiring portion, line profile acquiring portion, energy dispersion direction identifying portion, and optics controller that automatically controls the optical system based on line profiles to bring the focal plane into coincidence with the achromatic plane, eliminating the need for user skill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a two-stage filter type monochromator is used to achieve a virtual source of monochromatized and achromatic electron beam, then the resolution and coherence of electron microscope images are improved, but the device complexity and difficulty of adjustment increase significantly
Solution Approach 1:
The patent implements an automatic adjustment mechanism that uses interference fringe patterns as feedback to control the optical system. The controller acquires images of interference fringes, analyzes their orientation, and automatically adjusts the first and second electrostatic lenses to achieve isotropic (circular) fringe patterns, thereby bringing the focal plane and achromatic plane into coincidence without requiring manual skill
Solution Approach 2:
The system performs self-adjustment by automatically acquiring interference fringe images, analyzing their characteristics, and controlling the optical components to achieve optimal alignment. This eliminates the need for skilled operators to manually adjust the complex optical system, making the sophisticated monochromator easier to use while maintaining its high resolution capabilities
2Measurement precision
If manual adjustment by skilled users is required to bring focal plane and achromatic plane into coincidence, then optimal imaging conditions can be achieved, but the ease of operation decreases and user expertise is required
Solution Approach 1:
The automatic adjustment system uses interference fringe patterns as real-time feedback to control the optical alignment. The controller continuously monitors the fringe patterns and adjusts the electrostatic lenses accordingly, replacing manual skill-based adjustment with automated feedback control that achieves the same optimal imaging conditions
Solution Approach 2:
The patent replaces manual mechanical adjustment with an automated electronic control system. The controller uses image processing and electronic feedback to adjust the electrostatic lenses, substituting the mechanical skill-based adjustment process with an automated electronic system that achieves optimal alignment without requiring user expertise
3Device complexity
If the focal plane and achromatic plane are not brought into coincidence, then the adjustment process is simplified, but anisotropy appears in resolution and coherence of electron beam
Solution Approach 1:
The system uses interference fringe patterns as feedback indicators to detect whether the focal plane and achromatic plane are aligned. When the planes are not coincident, the fringes show anisotropic (directional) patterns; when aligned, they become isotropic (circular), providing automatic feedback on alignment status without complex measurement procedures
Solution Approach 2:
The patent uses changes in the visual characteristics of interference fringe patterns (from anisotropic to isotropic) as an indicator of proper alignment. The transition of fringe patterns from directional to circular provides a clear visual signal that the focal and achromatic planes have been brought into coincidence, eliminating the need for complex measurement procedures
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
Enables easy and automatic adjustment of the focal plane to the achromatic plane, ensuring isotropic interference fringes and optimal imaging conditions without relying on user expertise, thus improving the resolution and coherence of electron microscope images.
Implementation Method 1
a first energy filter for dispersing an electron beam according to kinetic energy
Implementation Method 2
a second energy filter for canceling energy dispersion of the electron beam passed through the energy-selecting slit
Implementation Method 3
an image acquiring portion for obtaining an electron microscope (EM) image containing interference fringes of the electron beam formed by an aperture located behind the monochromator
Implementation Method 4
the optics controller controls an electrostatic lens mounted ahead of the monochromator to bring the focal plane into coincidence with the achromatic plane
Data Source
Figure 1
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Figure 3~4
AI summary
There is provided an electron microscope in which an adjustment for bringing a focal plane for an electron beam exiting from a two-stage filter type monochromator into coincidence with an achromatic plane can be performed easily. The electron microscope (100) is equipped with the monochromator (20), and further includes an image acquiring portion (52) for obtaining an electron microscope (EM) image containing interference fringes of the electron beam formed by an aperture (12) located behind the monochromator (20), a line profile acquiring portion (54) for obtaining a plurality of line profiles passing through the center of the aperture on the EM image, an energy dispersion direction identifying portion (56) for identifying the direction of energy dispersion of the monochromator (20) on the basis of the line profiles obtained by the line profile acquiring portion (54), and an optics controller (58) for controlling an optical system on the basis of a line profile in the direction of energy dispersion to bring the focal plane for the electron beam exiting from the monochromator (20) into coincidence with the achromatic plane.