TEM Phase Plate Accessibility via Relay Lens Imaging
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Solution Overview
Problem
The back-focal plane of the objective lens in a Transmission Electron Microscope (TEM) is difficult to access due to its location inside the pole pieces, especially when biological samples are imaged in cryogenic conditions, making it challenging to install and center a phase plate, which affects the instrument's symmetry and resolution.
Innovation Solution
Placing at least part of the correction system between the sample position and the phase plate, allowing the back-focal plane of the objective lens to be imaged onto the phase plate using optical elements of the correction system, thus positioning the phase plate in a more accessible plane without adding additional optical elements or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the phase plate is placed in the back-focal plane of the objective lens, then the contrast transfer function is improved and large structures can be imaged, but the accessibility to the phase plate is poor and centering is difficult
Solution Approach 1:
The patent introduces a relay lens system as an intermediary between the objective lens and the phase plate. This relay lens creates an intermediate image plane that is accessible, allowing the phase plate to be positioned and centered easily while still functioning at the back-focal plane of the objective lens through optical coupling.
Solution Approach 2:
The patent extends the optical path by adding a relay lens system that creates an additional dimensional space (intermediate image plane) between the objective lens and phase plate. This allows the phase plate to be accessed from a different spatial location while maintaining its functional position in the back-focal plane.
2Ease of operation
If additional optical elements are added to improve phase plate accessibility, then the ease of operation is improved, but the device complexity and instrument height increase
Solution Approach 1:
The relay lens system is designed to serve multiple functions: it creates the intermediate accessible plane for phase plate positioning, maintains the optical conjugation to the back-focal plane, and corrects for aberrations. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The patent combines the relay lens system with the existing objective lens and phase plate assembly, integrating these components into a unified optical path rather than adding them as separate, independent systems. This merging reduces overall complexity.
3Measurement precision
If the phase plate is placed in the back-focal plane, then the contrast transfer function is improved, but mechanical interference with the objective lens symmetry occurs
Solution Approach 1:
The relay lens acts as an intermediary that optically couples the accessible intermediate plane to the back-focal plane of the objective lens. This allows the phase plate to be positioned in the intermediate plane without physically interfering with the objective lens symmetry, while still achieving the desired contrast transfer function.
Solution Approach 2:
By extending the optical path through the relay lens, the patent separates the physical location of the phase plate from the functional back-focal plane of the objective lens. The phase plate is positioned in an intermediate dimension that does not interfere with the objective lens symmetry while maintaining optical conjugation.
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 allows for improved accessibility and centering of the phase plate, reducing mechanical interference and maintaining the symmetry of the objective lens, while avoiding the added height and complexity of additional optical elements, thus enhancing the instrument's resolution and usability.
Implementation Method 1
at least part of the correction system is equipped to image the back-focal plane of the objective lens on the plane of the phase plate
Implementation Method 2
The phase plate causes a phase shift between scattered and unscattered electrons of e.g. π/2, thereby converting the sine-like behaviour of the CTF to a cosine-like behaviour
Implementation Method 3
an objective lens for forming a magnified image of the sample
Implementation Method 4
a condenser system for forming a parallel beam
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The invention relates to a TEM with a corrector (330) to improve the image quality and a phase plate (340) to improve contrast. The improved TEM comprises a correction system completely placed between the objective lens and the phase plate, and uses the lenses of the corrector to form a magnified image of the diffraction plane on the phase plate.