Objective Aperture Positioning in Transmission Electron Microscopes
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Solution Overview
Problem
Existing transmission electron microscopes face challenges in accurately and automatically positioning the objective aperture, which is crucial for obtaining high-quality images and diffraction patterns, as existing methods are not precise enough to ensure the aperture is correctly aligned with the optical axis.
Innovation Solution
A transmission electron microscope equipped with an objective lens, an objective aperture on its back focal plane, an aperture moving mechanism, and a control unit that acquires images of the aperture, binarizes them using a threshold, determines the aperture's position, adjusts for deviations, and changes the threshold as needed to ensure the aperture is accurately positioned within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an automatic alignment method using electron beam diffusion detection is employed, then the aperture positioning is automated, but the positioning precision is insufficient to ensure accurate alignment with the optical axis
Solution Approach 1:
The patent replaces the automatic alignment method based on electron beam diffusion detection with a method based on direct imaging of the aperture. By capturing an image of the aperture and processing it to determine its position, the system achieves more precise positioning while maintaining automation. The control unit acquires an image of the aperture, processes the image to obtain aperture position information, and compares this with the optical axis position to enable accurate automatic alignment.
2Measurement precision
If image processing with threshold binarization is used to determine aperture position, then the positioning accuracy is improved, but the processing complexity increases
Solution Approach 1:
The patent employs a self-adjusting threshold mechanism where the control unit automatically determines the threshold value based on the image data itself. The control unit acquires image data, determines a threshold value from this data, binarizes the image using this threshold, and then calculates the aperture position from the binarized image. This self-service approach eliminates the need for manual threshold setting or complex external processing systems, thereby improving positioning accuracy without proportionally increasing system complexity.
Data Source
AI summary
A transmission electron microscope includes a control unit for: acquiring an image of an objective aperture; obtaining a position of the objective aperture; obtaining an amount of deviation between an object position and the position of the objective aperture, based on the position of the objective aperture; and operating an aperture moving mechanism, based on the amount of deviation of the position of the objective aperture. The position of the objective aperture is obtained by: binarizing the image of the objective aperture by using a set threshold; obtaining an area of an aperture hole of the objective aperture from the binarized image; determining whether the area is within a predetermined range; changing the threshold when a determination is made that the area is outside the predetermined range; and obtaining a position of the objective aperture when a determination is made that the area is within the predetermined range.