Tilted Grating Structures for Phase-Contrast Imaging
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Solution Overview
Problem
Phase-contrast imaging systems, particularly in cone-beam geometry, suffer from strong distortions outside the center of the field of view due to non-focused grating structures, which limit the effectiveness of X-ray differential phase-contrast imaging.
Innovation Solution
The development of a grating structure with tilted trenches, where each trench is angled slightly more than the previous one, and a combination of laser writing and etching processes to create focused, smooth trench walls, allowing for precise alignment and reduced phase-contrast distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-focused grating structures are used, then the imaging system can be simpler to manufacture, but strong phase-contrast distortions occur outside the center of the field of view
Solution Approach 1:
The patent applies local quality by varying the trench tilt angles across different regions of the grating structure. Each trench is tilted by a specific angle relative to the primary axis, with the tilt angle varying systematically to create a focused geometry that compensates for cone-beam distortions at different field of view positions. This local variation in geometric properties (tilt angles) enables distortion correction while maintaining manufacturing feasibility through systematic patterning.
Solution Approach 2:
The patent employs asymmetry by introducing non-uniform tilt angles for different trenches rather than using a symmetric, uniform grating structure. The asymmetric tilt configuration creates a focused geometry that redirects X-rays from different angles to converge at appropriate detector positions, thereby correcting phase-contrast distortions. This asymmetric design is achieved through controlled variations in trench orientation while maintaining overall structural regularity for manufacturability.
2Manufacturing precision
If tilted trenches with varying angles are implemented, then phase-contrast distortions are reduced and focused geometry is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-defining the specific tilt angles for each trench before fabrication. The tilt angle for each trench is determined in advance based on its position and the desired focusing geometry, allowing the complex angled structure to be manufactured systematically. This preliminary design stage enables the subsequent fabrication process to follow a predetermined pattern, reducing actual manufacturing complexity despite the sophisticated final structure.
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the tilt angle parameter across different trenches. Instead of maintaining a constant trench orientation, the tilt angle is changed as a function of trench position to achieve the desired focused geometry. This controlled parameter variation allows the grating to correct distortions at multiple field of view positions while maintaining a regular, manufacturable structure through predictable parameter progression.
3Manufacturing precision
If smooth trench walls are achieved through laser writing and etching, then image quality improves, but the manufacturing process time increases
Solution Approach 1:
The patent applies mechanics substitution by replacing traditional mechanical drilling or simple etching methods with a combination of laser writing and chemical etching processes. The laser writing step creates precise trench paths with controlled profiles, followed by etching that smooths the trench walls through chemical action rather than mechanical removal. This substitution of mechanical processes with optical and chemical processes achieves superior surface smoothness and dimensional precision while maintaining reasonable production rates through non-contact and chemically-efficient methods.
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 enables improved image quality by reducing phase-contrast distortions and allowing operation in focused geometry, enhancing the effectiveness of phase-contrast imaging systems, especially in cone-beam geometries, and enabling higher energy applications without increasing physical aspect ratios.
Implementation Method 1
writing, with a laser beam, a first trench or trench structure into a wafer material
Implementation Method 2
optimizing of the geometry / finishing by smoothing surfaces of the written first trench by etching
Data Source
Figure 1a~1b
Figure 1c~2
Figure 3
AI summary
The present invention relates to phase-contrast imaging which visualizes the phase information of coherent radiation passing a scanned object. Focused gratings are used which reduce the creation of trapezoid profile in a projection with a particular angle to the optical axis. A laser supported method is used in combination with a dedicating etching process for creating such focused grating structures.