Tilted-Grating X-ray Interferometry for Scanning Imaging
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Solution Overview
Problem
Conventional grating interferometry is time-consuming and requires high system stability for phase-stepping, making it challenging to transition to commercial settings, especially when dealing with large field-of-view imaging, and the fabrication of large-area gratings is laborious and expensive.
Innovation Solution
A tilted-grating-based scanning method generates Moiré fringes perpendicular to the grating lines, allowing each line detector to record different phase steps during sample translation, eliminating the need for moving gratings and reducing the complexity of grating alignment, using a two- or three-grating setup with optional source grating, and applying Fourier-Component Analysis for signal reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase-stepping procedure is used, then different contrast signals can be retrieved, but the measurement time increases and system stability requirements become more stringent
Solution Approach 1:
The patent transforms the static phase-stepping procedure into a dynamic scanning measurement. By moving the sample continuously through the interferometer while maintaining a tilted grating configuration, the system captures phase-stepping information dynamically along the scan direction, converting a time-consuming multi-step static measurement into a continuous dynamic scan.
Solution Approach 2:
The patent introduces a spatial dimension (scan direction perpendicular to grating lines) to encode phase-stepping information. Instead of stepping the grating in one dimension, the sample is translated in a perpendicular dimension, and the tilted grating creates Moiré fringes that encode phase information across different spatial positions, effectively adding a dimensional transformation to the measurement process.
2Area of stationary object
If large-area gratings are fabricated to cover large field of view, then the field of view increases, but the fabrication complexity and cost increase
Solution Approach 1:
The patent segments the field of view coverage function between small-area gratings and sample translation. Instead of using one large grating to cover the entire field of view, the system uses small gratings that remain stationary while the sample is translated to bring different regions into the measurement area sequentially, dividing the coverage task into multiple scanned positions.
Solution Approach 2:
The patent introduces sample translation as an intermediary mechanism between the small grating and the large field of view requirement. By translating the sample through the fixed small grating, the system effectively extends the measurable field of view without requiring large-area gratings, using the sample motion as a mediator to achieve extended coverage.
3Productivity
If grating is tilted to generate Moiré fringes perpendicular to grating lines, then phase-stepping information is encoded spatially, but grating alignment precision requirements increase
Solution Approach 1:
The patent employs feedback through Moiré fringe detection to monitor and correct the tilted grating alignment. By detecting the Moiré fringe pattern generated by the tilted grating, the system can determine the actual tilt angle and make real-time adjustments to maintain optimal alignment, using the fringe pattern itself as a feedback signal for alignment verification and correction.
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 method enables efficient retrieval of absorption, DPC, and dark-field signals, reducing the need for large-area gratings and improving system stability, facilitating the integration of grating interferometry into commercial settings with enhanced imaging capabilities.
Implementation Method 1
generate a Moire fringe perpendicular to the grating lines by tilting one of the gratings
Implementation Method 2
generate a Moire fringe perpendicular to the grating lines by tilting one of the gratings
Implementation Method 3
a phase grating G1 and an absorption grating G2... retrieve absorption, DPC and dark field signals
Implementation Method 4
an absorption grating G2... retrieve absorption, DPC and dark field signals
Data Source
AI summary
Among the existent X-ray phase-contrast modalities, grating interferometry appears as a promising technique for commercial applications, since it is compatible with conventional X-ray tubes. However, since applications such as medical imaging and homeland security demand covering a considerable field of view, the fabrication of challenging and expensive large-area gratings would be needed. A scanning setup is a good solution, because it uses cheaper line detectors instead of large-area 2D detectors and would require smaller gratings. In this setup, the phase-retrieval using the conventional phase-stepping approach would be slow, so having a faster method to record the signals becomes fundamental. To tackle this problem, a scanning-mode grating interferometer configuration is used, in which a grating is tilted to form Moire fringes perpendicular to the grating lines. The sample is then translated along the fringes, so each line detector records a different phase step for each slice of the sample.