High-energy, high-resolution, fly-scan X-ray phase tomography

Abstract

High energy X-ray phase contrast tomography is tremendously beneficial to the study of thick and dense materials with poor attenuation contrast. Recently, the X-ray speckle-based imaging technique has attracted widespread interest because multimodal contrast images can now be retrieved simultaneously using an inexpensive wavefront modulator and a less stringent experimental setup. However, it is time-consuming to perform high resolution phase tomography with the conventional step-scan mode because the accumulated time overhead severely limits the speed of data acquisition for each projection. Although phase information can be extracted from a single speckle image, the spatial resolution is deteriorated due to the use of a large correlation window to track the speckle displacement. Here we report a fast data acquisition strategy utilising a fly-scan mode for near field X-ray speckle-based phase tomography. Compared to the existing step-scan scheme, the data acquisition time can be significantly reduced by more than one order of magnitude without compromising spatial resolution. Furthermore, we have extended the proposed speckle-based fly-scan phase tomography into the previously challenging high X-ray energy region (120 keV). This development opens up opportunities for a wide range of applications where exposure time and radiation dose are critical.

Hard X-ray omnidirectional differential phase and dark-field imaging

“…In addition to the low cost, robustness, and availability in large sizes, sandpaper with different grain sizes can be chosen to suit the spatial resolution requirement of the detector. In addition, the modulator can be replaced with a strongly absorbing mask for the study of thick, dense materials with high-energy X-rays ( 32 , 33 ). The spatial correlation length can be adjusted to study variable feature sizes by choosing a suitable window size.…”

Nano-precision metrology of X-ray mirrors with laser speckle angular measurement

“…For instance, the present measurement speed is limited due to the significant time taken in using the linear motor in step-scan mode. The measurement speed can be significantly enhanced by applying the advanced fly scan technique 51 . This novel technique of speckle angular measurement can then expand the capabilities of current metrology instruments to new X-ray optics that now cannot be made because they cannot be measured.…”

Progress on In Situ and Operando X-ray Imaging of Solidification Processes

“…The darker regions of the images (fewer X-rays reaching the detector) represent a more attenuating phase, i.e., a region of higher electron density, which increases with increasing atomic number (Z) and physical density; while the lighter regions represent less dense, lower Z regions. In order to obtain three-dimensional tomographic reconstructions, a series of radiographs are collected and then reconstructed in 3D using filtered back projection or iterative reconstruction techniques [ 43 , 44 , 45 , 46 ], which normally assumes the features to be static during acquisition. In cases where distinct phases in the materials have similar attenuation characteristics, phase contrast imaging techniques can be used which are up to 1000× more sensitive, and are based on the shift in phase that occurs as the X-rays travel at slightly different speeds, and can be captured as constructive or destructive interference on a detector placed at different distances from the specimen [ 11 , 43 , 47 ].…”