title: Phase retrieval with a three-frame phase-shifting algorithm with an unknown phase shift.
abstract: A three-frame phase-shifting algorithm with a constant but unknown phase shift is proposed. The algorithm is based on background-intensity removal prior to phase retrieval to eliminate an undetermined factor in a fringe pattern. The proposed method is validated on three-dimensional profilometry by fringe projection and on deformation measurement by means of digital speckle shearing interferometry. For a fringe pattern with slow-varying background intensity, the background removal is achieved in the frequency domain. For a speckle pattern, a background removal technique is integrated with the three-frame algorithm. In this process, manual intervention is minimal, and high computational speed is achieved. In addition, high-frequency phase signals would not be removed in the noise-reduction process as is the case in the bandpass-filtering technique. Accuracy of the method is discussed.
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
authors.forename: Cho Jui
authors.initials: CJ
authors.lastname: Tay
authors.forename: Chenggen
authors.initials: C
authors.lastname: Quan
authors.forename: Lujie
authors.initials: L
authors.lastname: Chen