Absolute Phase Unwrapping for Objects With Large Depth Range

Jian Yu, Feipeng Da

Abstract: This article presents a method for unwrapping the phase using only the geometric constraints and photometric information of the structured light system, which can cope with objects in a large depth range without the need for additional image acquisition or other cameras. Following the minimum phase method, this article also establishes an artificial plane and generates an initial unwrapped phase map from the absolute phase map of the plane. Starting from the reference plane, we divide the space into several <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\pi $ </tex-math></inline-formula> intervals pixel by pixel. The boundaries at phase discontinuities in the initial unwrapped phase map are then used to segment the object into independent regions. Regarding the projector as a point light source, synthetic images of each region corresponding to different spatial <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\pi $ </tex-math></inline-formula> intervals are generated sequentially according to Lambert’s cosine law. The interval in which the region corresponds is identified by comparing the similarity of these synthetic images with the modulation image, leading to the acquisition of an entire absolute phase map of the object. Experiments are conducted to evaluate the performance of the proposed method.