Phase measuring profilometry based on binary grating projection for fringe order self-extraction

Abstract

A phase measuring profilometry (PMP) based on binary grating projection for fringe order self-extraction is proposed. In traditional PMP based on sinusoidal grating projection, the phase is wrapped between (−π, π] due to the arctangent operation. And wrapped phase needs to be unwrapped using relative phase unwrapping algorithms such as diamond-type phase unwrapping algorithm in which the accumulation of phase errors is easy to occur or even lead to wrong phase unwrapping; or with the assistance of some additional structured light patterns such as Gray code, the fringe order may be determined to achieve phase unwrapping without the phase error accumulation. In the proposed method, three-dimensional measurement is achieved by just projecting a set of phase-shifted binary gratings, which can not only avoid the gamma non-linearity influence of the projector, but also increase the refresh frequency of the projector by more than ten times. At the same time, by using the image characteristics of the binary grating itself, the fringe order can be extracted without increasing any additional structured light pattern. So that the phase unwrapping can be achieved by combining the phase of extracted fringe order with the wrapped phase without the phase error accumulation. The experimental results verify the feasibility and effectiveness of the proposed method, and the solution result is in good agreement with the solution result of the diamond algorithm without cumulative errors.