X-ray Phase Imaging via Spatial Frequency Spectrum Analysis
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Solution Overview
Problem
Existing X-ray imaging methods require multiple images to retrieve wavefront shape, increasing radiation dose and measurement time, and are prone to errors due to transmissivity distribution and uneven illumination.
Innovation Solution
An X-ray imaging apparatus that uses a diffraction grating and a calculator to obtain spatial frequency spectra from intensity distributions, allowing for phase information calculation and reducing the number of images needed while improving spatial resolution and eliminating noise from uneven illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the phase shift method using multiple images is used to retrieve wavefront shape, then the wavefront retrieval is achieved, but the X-ray radiation dose and measuring time are increased
Solution Approach 1:
The patent segments the wavefront measurement process into two independent one-dimensional measurements. By using separate gratings for horizontal and vertical directions, the system retrieves wavefront information in two stages rather than requiring multiple full 2D images, thereby reducing measurement time and radiation dose while maintaining accuracy.
Solution Approach 2:
The patent transforms the 2D wavefront measurement problem into two separate 1D measurement problems. By decomposing the measurement into horizontal and vertical components that can be independently measured and then combined, the system reduces the number of images required from multiple 2D images to just two 1D line profiles.
2Productivity
If the Fourier transform method is used to obtain phase distribution from self-image, then two-dimensional wavefront retrieval is achieved from one interference image, but components from transmissivity distribution and uneven illumination are included causing measurement errors
Solution Approach 1:
The patent extracts only the differential phase information from the interference pattern by using line profile analysis along specific directions. By focusing measurement on one-dimensional line profiles rather than analyzing the entire 2D self-image, the system isolates the phase information from confounding factors like transmissivity distribution and illumination不均匀ity.
Solution Approach 2:
The patent introduces a scanning mechanism that dynamically moves the detector or grating to capture line profiles at different positions. This dynamic approach allows sequential measurement of horizontal and vertical components, enabling accurate wavefront retrieval while eliminating static artifacts from the imaging process.
3Measurement precision
If at least six images are captured to obtain differential wavefronts in mutually perpendicular directions, then the wavefront shape is retrieved, but the X-ray radiation dose is increased
Solution Approach 1:
The patent segments the wavefront measurement into two independent one-dimensional measurements using separate gratings for horizontal and vertical directions. This segmentation reduces the required images from six 2D images to just two 1D line profiles, thereby reducing the X-ray radiation dose by more than half while maintaining measurement accuracy.
Solution Approach 2:
The patent applies partial action by measuring only the essential one-dimensional line profiles needed for wavefront retrieval rather than capturing complete two-dimensional images. By obtaining minimal sufficient data (two 1D profiles instead of six 2D images), the system reduces radiation exposure while achieving the measurement objective.
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
The apparatus achieves high-accurate X-ray phase image measurement with reduced radiation dose and measurement time, improved spatial resolution, and minimized errors from transmissivity and illumination issues.
Implementation Method 1
a diffraction grating configured to diffract an X-ray from the X-ray source
Data Source
AI summary
There is provided an X-ray imaging apparatus which images a specimen. The X-ray imaging apparatus comprises: an X-ray source; a diffraction grating configured to diffract an X-ray from the X-ray source; an X-ray detector configured to detect the X-ray diffracted by the diffraction grating; and a calculator configured to calculate phase information of the specimen on the basis of an intensity distribution of the X-ray detected by the X-ray detector, wherein the calculator obtains a spatial frequency spectrum from the plural intensity distributions, and calculates the phase information from the obtained spatial frequency spectrum.