Cryogenic Scintillator Sample Holder for Correlated Optical Inspection
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Solution Overview
Problem
Integrated systems of light optical microscopes and electron microscopes face challenges in obtaining high-resolution images of biological samples at cryogenic temperatures due to low contrast and limited penetration depth, especially when using Transmission Electron Microscopes (TEM) and Scanning Electron Microscopes (SEM), and require objective lenses with large working distances and small Numerical Aperture (NA), which limits light collection and image quality.
Innovation Solution
Incorporating a sheet of scintillator material in the sample holder, positioned between the sample and the charged particle optical column, which converts charged particles into photons, allowing the light optical microscope to collect and image these photons, thereby enhancing image quality with a cooling system to maintain cryogenic temperatures and prevent sample heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an objective lens with large working distance is used in the light optical microscope, then the Numerical Aperture (NA) is relatively small, but this results in less light collection and difficulty in obtaining high resolution light optical images
Solution Approach 1:
A scintillator screen is introduced as an intermediary component between the charged particle beam and the light optical microscope. The scintillator converts charged particles into photons, which can then be collected by the light optical microscope's objective lens, effectively bridging the gap between the electron microscopy system and optical detection
Solution Approach 2:
The system changes the detection parameter from direct electron detection to photon detection via scintillation. By converting the signal type from charged particles to photons, the system can utilize the light optical microscope's detection capabilities even with a small NA objective lens
2Temperature
If a cooling system is used to maintain cryogenic temperatures, then sample heating is prevented, but the complexity of the apparatus increases
Solution Approach 1:
The cooling system is integrated into the sample holder assembly, combining the sample mounting function with the temperature control function in a single unit. This reduces the number of separate components and simplifies the overall apparatus structure
Solution Approach 2:
The sample holder is designed to be self-cooling through its inherent thermal conductivity and direct contact with the cold stage, eliminating the need for additional active cooling mechanisms for the sample itself
3Measurement precision
If a Transmission Electron Microscope (TEM) is used for biological samples, then imaging capability is provided, but the contrast between various constituents is very low making it difficult to obtain useful images
Solution Approach 1:
The scintillator material is selected to emit photons with specific wavelengths that can be optimized for the biological sample's properties. By tuning the emission characteristics of the scintillator, contrast enhancement is achieved similar to staining techniques in traditional electron microscopy
4Length of stationary object
If a Scanning Electron Microscope (SEM) is used for biological samples, then surface imaging is provided, but the penetration depth of the electron beam is very limited imaging only the outer surface
Solution Approach 1:
The scintillator screen acts as an intermediary that converts the limited-penetration charged particle beam into photons that can penetrate deeper into the sample, effectively extending the imaging depth beyond what direct electron beam can achieve
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 improves image quality by increasing photon emission and signal-to-noise ratio, even with objective lenses of relatively small NA, and allows for high-quality imaging of samples at cryogenic temperatures without heating the sample, enabling detailed observation of biological samples.
Implementation Method 1
the sample holder comprises a sheet of a scintillator material, wherein the sample holder is configured to position the sample in between the charged particle optical column and the sheet of the scintillator material
Implementation Method 2
at least the sample holder comprises a cooling system which is configured for cooling at least the sample
Data Source
AI summary
The invention relates to an apparatus and a method for inspecting a sample. The apparatus includes a sample holder for holding the sample, at least the sample holder comprises a cooling system which is configured for cooling at least the sample, preferably to cryogenic temperatures; a charged particle exposure system includes an assembly for projecting a focused beam of primary charged particles onto the sample held by the sample holder; and a light optical microscope. The sample holder includes a sheet of a scintillator material, and the sample holder is configured to position the sample in between the charged particle optical column and the sheet of the scintillator material. The light optical microscope includes a detection system configured for acquiring an optical image of at least a part of the sheet of the scintillator material.