Quantitative phase microscopy using quadriwave lateral shearing interferometry (QLSI): principle, terminology, algorithm and grating shadow description

Quadriwave lateral shearing interferometry (QLSI) is a quantitative phase imaging technique based on the use of diffraction grating placed in front camera. This creates wire-mesh-like image, called an interferogram, that postprocessed to retrieve both intensity and profiles incoming light beam. Invented 90s, QLSI has been used numerous applications, e.g., laser beam characterization, lens metrology, topography measurements, adaptive optics, or gas jet metrology. More recently, implemented optical microscopes characterize micro nano-objects for bioimaging nanophotonics applications. However, not much effort disseminating this powerful technology so far, while it yet particularly simple technique. In article, we intend popularize by describing all its facets framework microscopy, namely working principle, implementation microscope theory image formation, using pictures. Also, provide comment algorithm interferogram processing, written Matlab. Then, following new extension microscopy deviation from what was initially invented for, propose revisit description technique, particular discussing terminology, insisting more grating-shadow rather than quadriwave process, proposing alternative appellation, "grating shadow microscopy" "grating-assisted imaging".