Retractable SEM Projector for High-Resolution Diffraction Imaging
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Solution Overview
Problem
Existing scanning electron microscopes (SEMs) are limited by the resolution of on-axis diffraction imaging techniques due to the lack of space for projectors with multiple magnetic lenses, which are too large and heavy for typical SEM systems.
Innovation Solution
Incorporating a retractable projector with a single electromagnetic lens that can be positioned along the optical axis for improved resolution in thin samples and moved away to accommodate thicker samples, combined with a pixelated detector for enhanced imaging capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a projector with multiple magnetic lenses is used to improve resolution, then imaging resolution is improved, but the device size and weight increase making it incompatible with typical SEM systems
Solution Approach 1:
The patent divides the projector into two functional parts: a fixed condenser lens that remains in the SEM chamber, and a movable projector lens assembly that can be positioned close to the detector. This segmentation allows the heavy multi-lens projector to be split, with only the essential projection function requiring high precision near the detector while the condensing function is handled by a simpler fixed lens.
Solution Approach 2:
The patent introduces a movable projector lens assembly that can dynamically adjust its position between the sample and detector. This dynamic positioning allows the system to optimize the projection geometry for different sample thicknesses and imaging conditions, achieving high resolution without requiring a permanently large and heavy projector structure fixed in the SEM chamber.
2Measurement precision
If a projector is positioned along the optical axis to improve diffraction imaging, then resolution is improved, but thicker samples cannot be accommodated due to space constraints
Solution Approach 1:
The movable projector lens assembly can be dynamically repositioned along the optical axis. For thin samples requiring high-resolution diffraction imaging, the projector is positioned close to the detector along the optical axis. For thicker samples, the projector can be moved away from the optical axis or repositioned to accommodate the increased sample thickness, thus achieving versatility across different sample types.
Solution Approach 2:
The patent utilizes the third dimension (depth along the optical axis) by making the projector movable. Instead of being fixed in a position that compromises either resolution or sample thickness accommodation, the projector can be moved along the optical axis to optimize performance for the specific sample being imaged, effectively using dimensional flexibility to resolve the contradiction.
3Weight of stationary object
If a single electromagnetic lens is used instead of multiple magnetic lenses, then device size and weight are reduced, but projection capability may be compromised
Solution Approach 1:
The projection system is segmented into a fixed condenser lens and a movable projector lens. The condenser lens handles the initial beam conditioning and focusing, while the single electromagnetic projector lens handles the final projection onto the detector. This segmentation allows each lens to be optimized for its specific function, with the projector lens being a simpler single-element design that is lighter and easier to manufacture while still achieving effective projection when positioned correctly.
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 higher resolution on-axis transmission diffraction imaging for thin samples while allowing normal SEM imaging of thicker samples without compromising on size, weight, or cooling capabilities.
Implementation Method 1
Incorporating a retractable projector with a single electromagnetic lens that can be positioned along the optical axis for improved resolution
Implementation Method 2
Enables higher resolution on-axis transmission diffraction imaging for thin samples
Data Source
AI summary
In accordance with the present invention, there is provided a scanning electron microscope comprising: an electron source; a sample holder for holding a sample to be analysed; a projector; and a first detector. Each of the electron source and the sample holder are arranged upon an optical axis of the scanning electron microscope. The projector is moveable between a first, operational position in which the projector is located along the optical axis downstream of the sample holder and between the sample holder and the first detector, and a second, retracted position in which the projector is located away from the optical axis. There is also provided a method of imaging a sample with the scanning electron microscope.