5-beam grating interferometry for extended phase gradient sensing

Wavefront Microscopy Using Quadriwave Lateral Shearing Interferometry: From Bioimaging to Nanophotonics

“…While the QLSI pattern of the cross-grating remains the most popular option, variations of this cross-grating have been used, with 3-fold or 4-fold symmetries, with different designs of the unit cell − or a binary random mask . A recent study even demonstrated the possibility of using a nonperiodic optical element, simply consisting of a thin diffuser, which creates a speckle-like pattern on the camera.…”

Cross-grating phase microscopy (CGM): In silico experiment (insilex) algorithm, noise and accuracy

“…In this article, we focus on the cross-grating used in QLSI, with a grexel characterized by a checkerboard pattern of 0 and 𝜋 phase shifts. The grexel pattern of QLSI remained mostly unchanged for 20 years, except in few articles [32][33][34][35]37].…”

“…In practice, to compensate for any imperfection of the incoming planar wavefront, a reference interferogram is recorded first, without the object of interest in the field of view, from which a reference OPD is calculated and subtracted from all subsequent images of interest. Different types of cross-gratings have been used in CGM, with 3fold or 4-fold symmetries [31], with different designs of the unit cell [32][33][34][35], or even with a thin (non-periodic) diffuser [36] or a binary random mask [37]. In the context of optical microscopy, the main instance of CGM that has been used so far is quadriwave lateral shearing interferometry (QLSI) [13,14,31].…”

Cross-grating phase microscopy (CGM): In-silico experiment (insilex) algorithm, noise and accuracy

“…where h is the thickness profile of the object, n the refractive index of the object and n 0 the refractive index of the environment. Different types of cross-gratings have been used in CGM, with 3-fold or 4-fold symmetries [30], with different designs of the unit cell [31][32][33][34], or even with a thin (non-periodic) diffuser [35] or a binary random mask. [36] In the context of optical microscopy, the main instance of CGM that has been used so far is quadriwave lateral shearing interferometry (QLSI) [13,14,30].…”

“…The grexel pattern of QLSI remained mostly unchanged for 20 years, except in a couple of articles. [31][32][33][34]36] • Λ and Z. Λ is the grexel lateral size, or equivalently the grating period. It is not a parameter that can be continuously modified experimentally, hence the interest of conducting in silico experiments.…”