Bent Grating Assembly for X-ray Interferometry
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Solution Overview
Problem
The construction of a Dark-field X-Ray (DAX) system is challenged by the need for an analyzer grating that covers the entire detector area, is highly attenuating, and has a specific pitch, while existing manufacturing technologies like LIGA and foil stacking have limitations such as access to synchrotrons and grating size limitations, and difficulties in focusing gratings manufactured by different methods.
Innovation Solution
The solution involves an apparatus with three gratings (G0, G1, and G2) where two adjacent gratings are bent to maintain a constant distance as a function of fan angle, allowing for the use of LIGA technology for manufacturing gratings with varying pitches and foil stacking for planar gratings with constant pitches, thus simplifying manufacturing and ensuring correct interferometric operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LIGA technology is used to manufacture gratings, then gratings can be produced with precise pitch control, but the gratings are inherently flat and focused to infinity requiring complex bending procedures to achieve the desired focus distance
Solution Approach 1:
The patent changes the manufacturing parameter of grating pitch from constant to variable along the grating length. By incorporating a chirped pitch design where the pitch varies continuously, the grating can be manufactured flat by LIGA technology while inherently focusing X-rays to the desired distance without requiring post-manufacturing bending operations.
2Ease of manufacture
If foil stacking technology is used to manufacture gratings, then gratings can be produced with simple processes, but the gratings are flat and directly focused to a predefined distance making it impossible to change focus after manufacturing
Solution Approach 1:
The patent changes the focus distance parameter from fixed to variable by using a chirped pitch design. This allows the grating to be manufactured with simple foil stacking processes while enabling adjustment of the focus distance to match different X-ray source positions, thereby providing adaptability without compromising manufacturing simplicity.
3Adaptability or versatility
If gratings manufactured by different methods are combined, then various grating requirements can be met, but the focusing becomes problematic and interferometric operation is compromised
Solution Approach 1:
The patent applies chirped pitch design to gratings manufactured by LIGA technology, changing their focus parameter from infinity to the desired distance. This parameter change enables these gratings to work reliably with foil stacking gratings, ensuring proper interferometric operation while maintaining the flexibility to combine different manufacturing methods.
4Measurement precision
If the analyzer grating covers the entire detector area with high attenuation and small pitch, then imaging quality is improved, but the grating becomes extremely stiff and difficult to manufacture
Solution Approach 1:
The patent changes the pitch parameter from uniform to variable (chirped) along the grating length. This allows the grating to achieve the necessary small pitch for high imaging quality while distributing the manufacturing complexity across a gradual pitch variation rather than requiring uniform precision across the entire large-area grating.
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 arrangement simplifies the manufacturing of gratings, ensures proper alignment of fringe patterns, and allows for the production of high-quality X-ray imaging data with enhanced diagnostic capabilities for DAX and phase-contrast imaging.
Implementation Method 1
a quasi-periodic phase grating can be positioned between an object being imaged and a detector, and an analyzer grating can be disposed between the phase grating and the detector. Second-order approximation models for X-ray phase retrieval using paraxial Fresnel-Kirchhoff diffraction theory are also described.
Implementation Method 2
The basic concept for DAX imaging is to use a Talbot-Lau type interferometer, i.e., to add three gratings G0, G1, and G2 into the X-ray beam.
Implementation Method 3
The X-ray source is configured to produce X-rays. The first grating is positioned between the X-ray source and the second grating. The second grating is positioned between the first grating and the third grating. The third grating is positioned between the second grating and the X-ray detector.
Data Source
Figure 1~3e
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Figure 6~7
AI summary
The present invention relates to an apparatus (10) for generating X-ray imaging data. It is described to position (210) a first grating between an X-ray source and a second grating. The second grating is positioned (220) between the first grating and a third grating. A third grating is positioned (230) between the second grating and an X-ray detector. An object is positioned (240) between the first grating and the third grating. At least one of the three gratings has a pitch attribute of having a constant grating pitch. At least one of the three gratings has a pitch attribute of having a varying grating pitch. Both gratings of an adjacent pair of gratings are bent such that a distance between the two adjacent gratings is constant as a function of fan angle. Both gratings of the adjacent pair of gratings that are bent have the same pitch attribute. An X-ray detector detects (250) at least some of the X-rays transmitted by the three gratings and the object.