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.
Highlights
X-ray computed tomography (CT) allows for visualizing interior features of a sample in a non-destructive way
An important property of X-rays and their interaction with matter is that the real part of the refractive indices of many materials in the X-ray range is significantly higher than the imaginary part
Www.nature.com/scientificreports above 85 keV2,4, the fabrication of precision gratings or masks with the large aspect ratios that are required for high energy X-ray beams imposes a major technical challenge
Summary
The experiment was performed at Diamond Light Source’s I12 beamline. Monochromatic X-ray beam produced by a double Laue crystal monochromator at 53 keV (and 120 keV) was used for various samples. The wavefront modulator was moved to its position, and the trigger program was repeated so that images were again captured at zero degrees and at each selected increment In this way, the tomography rotation is performed in between modulator steps, saving all the time overhead of moving and stopping the rotation stage. The time overhead of motion will be only M steps of the modulator, and the corresponding operations of returning the tomography stage back to zero In this case, the proposed fly-scan method took 64 s to finish one tomography scan including the rewinding time of the rotation stage. Where v is the piezo scanning step size of the modulator, L1, L2 and L3 represent the distances between X-ray source, sample, modulator and detector, αx/y is the refraction angle in x or y direction, and Φ is the phase shift. The Ram-Lak filter was applied for both absorption and phase reconstruction if the phase shift projection images were used, while the Hilbert filter was chosen for the phase gradient case[35]
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