Fourier ptychography is an imaging technique first developed for use in microscopes. The technique first collects a series of images of a microscopic sample of interest. Each image is acquired under a different angle of illumination from a coherent light source (typically from an array of LEDs). The acquired image set is then combined using an iterative phase retrieval algorithm into a final high-resolution image that can contain up to a billion pixels (a gigapixel). The technique also provides a non-interferometric phase image and near wavelength diffraction-limited resolution.
It is related to (conventional) ptychography in that it solves the phase problem by permuting the role of the real and the Fourier space, by swapping the focusing element and the object.
Among the advantages of Fourier ptychography is the ability to use imaging optics with a lower numerical aperture, hence improving the depth of focus, the working distance, and the size of the field of view. It also allows for the numerical correction of lens aberrations, leading to a very large effective space-bandwidth product (the resolution times exploitable size of an image).