Ptychography with broad-bandwidth radiation

Abstract

Ptychography, a scanning Coherent Diffractive Imaging (CDI) technique, has quickly gained momentum as a robust method to deliver quantitative images of extended specimens. A current conundrum for the development of X-ray CDI is the conflict between a need for higher flux to reach higher resolutions and the requirement to strongly filter the incident beam to satisfy the tight coherence prerequisite of the technique. Latest developments in algorithmic treatment of ptychographic data indicate that the technique is more robust than initially assumed, so that some experimental limitations can be substantially relaxed. Here, we demonstrate that ptychography can be conducted in conditions that were up to now considered insufficient, using a broad-bandwidth X-ray beam and an integrating scintillator-based detector. Our work shows the wide applicability of ptychography and paves the way to high-throughput, high-flux diffractive imaging.

Strategies for high-throughput focused-beam ptychography

“…This requires coherent superposition between waves with a path length difference from the top and bottom edges of the illumination spot to a distant detector of d sin , or a number m of wavelengths of longitudinal coherence (Spence et al, 2004;van der Veen & Pfeiffer, 2004;Enders et al, 2014) of…”

Coherent X-ray diffractive imaging on the single-cell-level of microbial samples

“…Moreover, the ptychographic method has also been used for elemental speciation [21,135,285] and for sequential imaging of chemical reactions [142]. More recent ptychographic studies investigate the maximum derivable information from ptychographic data under non-simple experimental conditions for the illuminating wave-eld or the object such as position uncertainties [20,110,182], partial coherence and multiple wavelenghts [15,44,78,299], multiple object planes [181,284] and undersampling of the recorded di racted intensities [71]. In the rst place, however, the probably most important result has been the understanding that the ptychographic method not only is able to solve for the encoded object information but also for the illuminating wave-eld [183,294,296] making ptychography a valuable tool for analysing the wave-elds of X-rays [134,144,159,160,265,268].…”

“…If the experimental conditions are su ciently good ptychography has even proven to yield quantitative phase maps with a resolution of the object information below 10 nm in two dimensions [266,287] and around 16 nm in three dimensions [133]. Recently, ptychography could also be shown to yield information under non-ideal experimental conditions such as a low degree of spatial and temporal coherence of the illuminating wave-eld [78,299] but also vibrational modes of the object could be extracted [42]. In case of unstained biological samples, quantitative two-dimensional images of frozen-hydrated yeast cells [172], freeze-dried cells of the bacterium Deinococcus radiodurans [97] and a three-dimensional representation of a mouse femur [61] were obtained before or during the time of this thesis (more ptychographic applications are listed in section 1.3.6, p. 40).…”

High-flux ptychographic imaging using the new 55 µm-pixel detector `Lambda' based on the Medipix3 readout chip

“…Importantly, this overlap constraint is powerful enough to estimate not only the object but also the illumination function (probe) even in non-ideal experimental conditions, e.g. partial coherence, broad bandpass illumination or a thick object (Maiden & Rodenburg, 2009;Thibault et al, 2009;Thibault & Menzel, 2013;Claus et al, 2013;Edo et al, 2013;Suzuki et al, 2014;Batey et al, 2014;Clark et al, 2014;Enders et al, 2014). Hence, ptychography is also an ideal tool for analysing X-ray wavefields (Schropp et al, 2010;Kewish, Guizar-Sicairos et al, 2010;Kewish, Thibault et al, 2010;Hö nig et al, 2011;Vila-Comamala et al, 2011;Wilke et al, 2012;Schropp et al, 2013;Huang et al, 2013).…”