Abstract
Inline holography is a common phase-contrast imaging method which uses free-space propagation to encode the phase signal into measured intensities. However, quantitative retrieval of the sample's image remains challenging, imposing constraints on the nature of the sample or on the propagation distance. Here, we present a way of simultaneously retrieving the sample's complex-valued transmission function and the incident illumination function from near-field diffraction patterns. The procedure relies on the measurement diversity created by lateral translations of the sample with respect to a structured illumination. The reconstruction approach, in essence identical to that employed in ptychography, is applied to hard X-ray synchrotron measurements and to simulations. Compared to other inline holography techniques, we expect near-field ptychography to reduce reconstruction artefacts by factoring out wavefront imperfections and relaxing constraints on the sample's scattering properties, thus ultimately improving the robustness of propagation-based X-ray phase tomography.
Highlights
Inline holography is a common phase-contrast imaging method which uses free-space propagation to encode the phase signal into measured intensities
The reconstruction approach, in essence identical to that employed in ptychography, is applied to hard X-ray synchrotron measurements and to simulations
A test pattern featuring a 30 mm diameter Siemens star, is placed in the beam expanding from the focus of a pair of Kirkpatrick-Baez mirrors
Summary
Inline holography is a common phase-contrast imaging method which uses free-space propagation to encode the phase signal into measured intensities. For short enough effective propagation distances, the technique reveals directly in the measured intensity the contours of samples that produce phase shifts in the incoming wave – an effect especially useful to make visible weakly absorbing objects While this so-called propagation-based phase contrast is sometimes sufficient for visualizing a sample’s features, many imaging applications require the phase shift to be recovered quantitatively from the measured hologram. Other paths to phase retrieval involve experimental devices where the incoming beam is prepared to produce well-controlled interference, either through crystal diffraction[12,13,14] or with gratings[15,16] These techniques do not necessarily scale to higher resolutions, they benefit greatly from the diversity provided by multiple measurements to decouple the patterned wavefront from the object transmission function. Speckle tracking techniques introduced recently[17,18] can be used to perform phase retrieval without prior knowledge of the disturbed wavefront, though at the price of a decreased spatial resolution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
