Fig. 2.

Multislice ptychography [2] uses Fresnel propagation of the illumination probe to determine which of many axial slices an object is localized to. While propagating a single probe function between many axial planes (as well carrying out the standard ptychographic action of translating the probe to multiple transverse positions), at each axial plane the net wavefield is decomposed into contributions from the probe and from the optical modulation provided by any specimen features at that plane. This is accomplished through the fact that the probe is modified as it propagates plane-to-plane, so that prior experimental demonstrations [2, 17–20] have clearly shown the ability to separate even broad, low-spatial-frequency objects into their respective planes along the illumination direction. Multislice ptychography (as well as through-focus imaging methods that succeed to various degrees in separating objects into their respective planes along the illumination direction) therefore delivers axial slice images which can have objects of all transverse sizes (and therefore content at all transverse spatial frequencies) reconstructed at separate axial planes.