3D shape from phase errors by using binary fringe with multi-step phase-shift technique

Abstract

A three-dimensional shape measurement method is presented, which is a uniaxial measurement by measuring phase errors instead of the well-known phase, modulation or contrast. A sequence of exposures are captured by using a multi-step phase-shift technique with the binary fringes. Then the high-accuracy phases can be obtained by using all the exposures, meanwhile, a set of low-accuracy phases can be calculated by dividing those exposures into a set of four-step phase-shift measurements. For each pixel there will be a set of phase errors by subtracting low-accuracy phases from the high-accuracy ones. And the weighted phase error of every pixel can be calculated. Meanwhile the phase error caused by the improperly defocused binary fringes has a unique relationship with the depth z. Therefore, the 3D information of every pixel can be obtained by analyzing the phase errors. It will be promising for a uniaxial measurement, such as deep holes.