<title>In-plane deformation measurement by digital phase-shifting speckle interferometry</title>

A high accuracy measurement method based on vortex polar axis rotation phase-shifting interferometry (VPAR-PSI)

“…In the 1980s, phase shift interferometry (PSI) was introduced by Bruning et al [ 1 ] and then applied to the area of optical interferometry. The basic theory of the PSI method is to recover the wavefront phase information by phase-demodulation of the image sequence (at least three frames), thus achieving a 3D reconstruction of the target's surface form [ [2] , [3] , [4] ]. A series of advantages including simple in construction, full-field sensing, contactless, precision, high sensitivity, non-damage and a high speed of measurement are offered by PSI.…”