Fig. 2: Schematics of the QPM experimental setups investigated in this study.

a Bright-field microscopy. b Digital holographic microscopy (DHM), an off-axis QPM technique, involving a reference arm. c Cross-grating wavefront microscopy (CGM), a technique based on the use of a 2D diffraction grating placed at a millimeter distance from a camera (an association called quadriwave lateral shearing interferometry (QLSI)). d Diffraction phase microscopy (DPM), an off-axis QPM based on the use of a 1D-diffraction grating placed in the image plane of the microscope, and a mask placed in the Fourier plane. e Differential phase-contrast (DPC) microscopy, based on the use of a series of tilted illuminations. f Phase-shifting interferometry (PSI), the standard phase-shifting imaging technique. g Fourier Phase microscopy (FPM) and h spatial light interference microscopy (SLIM), which are phase-shifting techniques using a spatial light modulator (SLM). i Transport of intensity equation (TIE) microscopy, based on the acquisition of various images acquired at various focuses. All the setups are shown in transmission because it is more common, but reflection configurations also exist³³