Tomographic Projection Correction via Capacitive Sensor Displacement Measurement
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Solution Overview
Problem
Conventional rotating stages for 3D x-ray and transmission electron microscope imaging struggle with achieving high positional precision due to random errors from bearings, spindle wobble, and thermal expansion, leading to misregistered projections and artifacts in tomographic reconstructions.
Innovation Solution
A passive correction method using precision-machined, low-coefficient-of-thermal-expansion gold-coated cylinders with capacitive distance sensors to measure and correct for sample displacements during tomography, applying shifts in image processing without active spindle correction, allowing for accurate reconstruction without altering the acquisition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional rotating stages are used for tomography, then the system is simpler and easier to manufacture, but positional precision deteriorates due to bearing errors, spindle wobble, and thermal expansion
Solution Approach 1:
The patent replaces active mechanical correction systems with a passive software-based correction approach. Instead of using complex active correction mechanisms to physically adjust the sample position, the invention measures the actual position using capacitive sensors and corrects the projections through computational shifting, thereby achieving high precision without complex mechanical correction hardware
Solution Approach 2:
The patent creates a digital model of the rotation stage errors by measuring the actual sample position at each angle using capacitive sensors. This digital representation of position errors is then used to correct the projections computationally, replacing the need for physical correction mechanisms
2Manufacturing precision
If active correction systems are implemented, then positional accuracy is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent substitutes mechanical active correction systems with a software-based correction method. Instead of using actuators and sensors to physically adjust the sample holder position during acquisition, the invention measures position errors with capacitive sensors and applies computational corrections to the projections, eliminating complex mechanical correction hardware
Solution Approach 2:
The system performs self-measurement and self-correction by using capacitive sensors to measure the actual sample position and then applying appropriate shifts to the projections during reconstruction, without requiring external active correction mechanisms
3Measurement precision
If X/Y/Z stages are placed on top of theta stage for active correction, then sample positioning is improved, but tip/tilt and runout errors increase
Solution Approach 1:
The patent replaces mechanical X/Y/Z correction stages with a software-based correction approach. Instead of adding another mechanical stage that introduces tip/tilt errors, the invention uses capacitive sensors to measure position and applies computational shifts to projections, achieving high positioning precision without additional mechanical error sources
4Device complexity
If passive software correction is used, then device complexity is reduced and cost is lowered, but measurement precision must be maintained through accurate position sensing
Solution Approach 1:
The patent uses capacitive sensors to measure the actual sample position with high precision and replaces complex mechanical correction systems with software-based projection shifting. This substitution achieves both reduced device complexity and maintained measurement precision by relying on accurate electrical field-based position sensing rather than mechanical measurement systems
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 approach effectively corrects for sample position errors in x-ray and electron microscope imaging, reducing artifacts and maintaining high precision in tomographic reconstructions by accurately shifting projections based on measured displacements, thus enhancing image quality and accuracy.
Implementation Method 1
three or more capacitive distance sensors
Data Source
AI summary
The position of the sample is measured and used to correct for any off-axis motion during tomography using x-ray projection microscope system with a rotation stage system. The position is sensed using a precision-machined, low-CTE gold-coated cylinder or disc and three to five capacitive distance sensors. The correction can then be performed purely as image processing in software, by applying an appropriate shift in X and Y of the captured x-ray projections. A calibration is often necessary for each system (gold disc plus sensors plus sample stage) to account for any machining errors of the gold disc or positioning errors of the capacitive sensors. This calibration should also be repeated whenever any maintenance is performed on the metrology setup.