An image is worth a thousand words – how about hundreds or thousands of images? Recent developments in computational imaging and image detection have revolutionized the way we compile images and extract information from them. Ptychography and Fourier ptychography are special computational imaging techniques that use many diffraction data and images to retrieve both amplitude and phase information on objects. The knowledge of amplitude and phase enables the synthesis of high resolution images from pure diffraction data (lensless imaging) or from many low resolution images.The word ptychography was derived from the Greek words ptyché (πτυχή=fold) and gráphein (γράϕειν=to write). Ptychography computes the phase from multiple diffraction patterns, which are obtained from a transversal scan of the sample with a focused coherent beam while adjacent probe spots overlap significantly in the sample plane. In Fourier ptychography the sample is illuminated from different directions, corresponding to the transversal scan of the sample’s Fourier spectrum. Both techniques employ iterative algorithms to de-convolve (or unfold) the phase information from redundant datasets of overlapping spatial areas or spatial frequency areas, respectively.Originally invented by Walter Hoppe in 1969, ptychography has been developed to be a powerful technique for phase retrieval over the past 50 years.
Advanced Optical Technologies – de Gruyter
Published: Dec 20, 2017