WASP: weighted average of sequential projections for ptychographic phase retrieval.

We introduce the weighted average of sequential projections, or WASP, an algorithm for ptychography. Using both simulations and real-world experiments, we test this new approach and compare performance against several alternative algorithms. These tests indicate that WASP effectively combines the benefits of its competitors, with a rapid initial convergence rate, robustness to noise and poor initial conditions, a small memory footprint, easy tuning, and the ability to reach a global minimum when provided with noiseless data.

Efficient large field of view electron phase imaging using near-field electron ptychography with a diffuser.

Most implementations of ptychography on the electron microscope operate in scanning transmission (STEM) mode, where a small focussed probe beam is rapidly scanned across the sample. In this paper we introduce a different approach based on near-field ptychography, where the focussed beam is replaced by a wide-field, structured illumination, realised through a purpose-designed etched Silicon Nitride window. We show that fields of view as large as 100 μm can be imaged using the new approach, and that quantitative electron phase images can be reconstructed from as few as nine near-field diffraction pattern measurements.

Ten implementations of ptychography.

Ptychography is an increasingly popular phase retrieval imaging technique, able to routinely deliver quantitative phase images with extended field of view at diffraction limited resolution. Different variants of this technique, like Bragg ptychography and Fourier ptychography, have also been developed and applied to various fields. Here we experimentally demonstrate 10 ways to implement the conventional real space transmission ptychography, and compare their properties to provide a guide to choosing the optimal setup for a specific application.

Quantitative phase contrast optimised cancerous cell differentiation via ptychography.

This paper shows that visible-light ptychography can be used to distinguish quantitatively between healthy and tumorous unstained cells. Advantages of ptychography in comparison to conventional phase-sensitive imaging techniques are highlighted. A novel procedure to automatically refocus ptychographic reconstructions is also presented, which improves quantitative analysis.

Superresolution imaging via ptychography.

Coherent diffractive imaging of objects is made considerably more practicable by using ptychography, where a set of diffraction patterns replaces a single measurement and introduces a high degree of redundancy into the recorded data. Here we demonstrate that this redundancy allows diffraction patterns to be extrapolated beyond the aperture of the recording device, leading to superresolved images, improving the limit on the finest feature separation by more than a factor of 3.

Optical ptychography: a practical implementation with useful resolution.

Quantitative phase microscopy offers a range of benefits over conventional phase-contrast techniques. For example, changes in refractive index and specimen thickness can be extrapolated and images can be refocused subsequent to their recording. In this Letter, we detail a lensless, quantitative phase microscope with a wide field of view and a useful resolution.

An improved ptychographical phase retrieval algorithm for diffractive imaging.

The ptychographical iterative engine (or PIE) is a recently developed phase retrieval algorithm that employs a series of diffraction patterns recorded as a known illumination function is translated to a set of overlapping positions relative to a target sample. The technique has been demonstrated successfully at optical and X-ray wavelengths and has been shown to be robust to detector noise and to converge considerably faster than support-based phase retrieval methods. In this paper, the PIE is extended so that the requirement for an accurate model of the illumination function is removed.