Electron Microscope Objective Minilens Demagnification
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Solution Overview
Problem
Transmission electron microscopes equipped with energy filters face challenges in achieving low-magnification imaging while maintaining high resolution and image quality, especially when the objective lens is strongly excited, due to limitations in aberration correction and image demagnification.
Innovation Solution
The electron microscope incorporates a main objective lens, an objective minilens for demagnification, an intermediate lens system, and an energy filter, with a field-limiting aperture ahead of the intermediate lens system, allowing for low-magnification imaging while keeping the objective lens strongly excited, and includes a magnetic energy filter like the Omega filter for precise energy selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the objective lens is strongly excited to achieve high magnification and resolution, then the magnification and resolution are improved, but it becomes difficult to achieve low magnifications while maintaining image quality
Solution Approach 1:
The patent divides the objective lens system into two independent parts: the main objective lens and the objective minilens. This segmentation allows each lens to perform its specific function independently - the main objective lens maintains strong excitation for high resolution, while the minilens provides demagnification capability to achieve low overall magnification, thus resolving the contradiction between resolution and magnification range adaptability
Solution Approach 2:
The objective minilens acts as an intermediary element between the specimen and the intermediate lens system. It demagnifies the magnified image formed by the main objective lens, enabling low-magnification imaging while the main objective lens remains strongly excited. This intermediary component allows the system to achieve both high resolution and low magnification simultaneously
2Measurement precision
If the objective lens is strongly excited to maintain high resolution, then the resolution is improved, but the image quality of peripheral regions deteriorates at low magnifications
Solution Approach 1:
By segmenting the objective lens system into main objective lens and objective minilens, the patent enables the main objective lens to maintain strong excitation for high resolution while the minilens corrects peripheral image quality at low magnifications, resolving the contradiction between resolution and image quality reliability
3Speed
If the intermediate lens system is used to achieve low magnification, then the magnification is reduced, but aberrations increase and image quality deteriorates
Solution Approach 1:
The objective minilens performs preliminary demagnification of the image formed by the main objective lens before the electrons enter the intermediate lens system. This preliminary action reduces the magnification burden on the intermediate lens system, allowing it to achieve low overall magnification while maintaining image quality and minimizing aberrations
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 enables low-magnification imaging with high resolution and improved image quality of peripheral regions, enhancing the accuracy of energy selection and supporting applications like electron energy loss spectroscopy without sacrificing the performance of the objective lens.
Implementation Method 1
The objective lens 4 acts to magnify an image of a specimen first
Implementation Method 2
the lenses located ahead of the energy filter 6 focus a crossover image and a microscope image in the entrance window plane 24 and entrance image plane 25, respectively
Implementation Method 3
The energy filter 6 has a function of selecting only electrons having certain energies out of electrons transmitted through the specimen 3a
Implementation Method 4
The projector lens system 8 magnifies the microscope image created by the energy filter 6
Data Source
AI summary
There is disclosed an electron microscope that achieves low-magnification imaging while the objective lens is kept at high excitation in the same way as during high-magnification imaging. An objective minilens located immediately behind the objective lens demagnifies a specimen image magnified by the objective lens. Consequently, a sharply focused electron beam enters the first intermediate lens. This greatly reduces the effects of off-axis aberrations in the intermediate lenses. The first, second, and third intermediate lenses create a crossover image and a microscope image in the entrance window plane and entrance image plane, respectively, of an energy filter. The energy filter focuses the microscope image and crossover image onto the exit image plane and exit window plane, respectively. The output image from the filter is projected onto the final image plane by first and second projector lenses.