Diffraction Imaging with Pinhole and Soller Slit
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Solution Overview
Problem
Existing methods for imaging phase distributions in polycrystalline samples using X-rays, such as X-ray fluorescence and diffraction, are limited in their ability to distinguish specific crystal phases and require highly collimated beams or pinhole arrangements, which are not suitable for all materials and can result in distorted images.
Innovation Solution
The method involves imaging in a Bragg condition with a two-dimensional detector oriented parallel to the sample surface, using a pinhole arrangement at the focussing distance of reflected X-rays to maintain a single diffraction condition across an extended sample area, allowing for imaging of specific component phases by adjusting the diffraction angles and using monochromatic X-rays with a Soller slit to control beam divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a highly collimated incident beam or pinhole on the incident beam side is used to visualise defects in crystals, then measurement precision is improved, but device complexity increases and the method is limited to almost perfect single crystals
Solution Approach 1:
Instead of placing the pinhole on the incident beam side to achieve collimation, the patent places the pinhole on the diffracted beam side. This inversion allows the use of a less collimated incident beam while still achieving sharp defect images, simplifying the overall beam path and reducing device complexity.
Solution Approach 2:
The pinhole acts as an intermediary element placed in the diffracted beam path rather than the incident beam path. This intermediary position allows the pinhole to selectively transmit diffracted beams from specific crystal regions, achieving high measurement precision without requiring complex incident beam collimation systems.
2Measurement precision
If a pinhole arrangement is used to maintain a single diffraction condition across an extended sample area, then measurement precision is improved, but the method becomes more complex compared to fluorescence imaging
Solution Approach 1:
The patent transitions from the conventional configuration where the detector is perpendicular to the diffracted X-rays to orienting the detector parallel to the sample surface. This dimensional change in detector orientation, combined with the pinhole placement, enables two-dimensional phase distribution imaging while maintaining Bragg conditions, achieving high measurement precision without excessive complexity.
3Area of stationary object
If low incident beam angles are used to get a sufficiently large illuminated area on the sample, then area of stationary object is improved, but measurement precision deteriorates due to inability to maintain single diffraction condition
Solution Approach 1:
The patent segments the imaging process by using a pinhole to select specific diffracted beams from different regions of the extended illuminated area. This segmentation allows each detected signal to correspond to a specific Bragg condition from a particular crystal region, maintaining measurement precision even when the total illuminated area is large.
Solution Approach 2:
The patent replaces the mechanical approach of limiting the illuminated area through tight collimation with an optical selection method using a pinhole in the diffracted beam path. This substitution allows a large illuminated area to be maintained while still achieving precise phase distribution measurements through selective detection of diffracted beams.
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 sharp imaging of multiple component phases without the need for high-quality equipment, minimizing distortions and improving particle statistics, while allowing for flexible adjustment of beam angles and pinhole sizes to achieve accurate Bragg conditions across the sample.
Implementation Method 1
imaging in a Bragg condition with a two-dimensional detector oriented parallel to the sample surface, using a pinhole arrangement at the focussing distance of reflected X-rays to maintain a single diffraction condition across an extended sample area
Implementation Method 2
the pinhole arrangement is located at the focussing distance of the reflected X-rays
Implementation Method 3
using monochromatic X-rays with a Soller slit to control beam divergence
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method of imaging phases in an inhomogeneous polycrystalline sample having a plurality of crystallites of at least a first crystalline component includes illuminating an illuminated area extending across a surface of a sample with substantially monochromatic X-rays incident at a Bragg-Brentano parafocussing geometry at first angle θ1 to the surface of the sample. X-rays diffracted by the sample at a second angle θ2 pass through a pinhole. The diffraction angle θ1 + θ2 fulfils a Bragg condition for the first crystalline component which is imaged by a detector to provide a two-dimensional image of the first crystalline component at the surface of the sample.