Abstract
In order to acquire an accurate three-dimensional (3D) measurement, the traditional fringe projection technique applies complex and laborious procedures to compensate for the errors that exist in the vision system. However, the error sources in the vision system are very complex, such as lens distortion, lens defocus, and fringe pattern nonsinusoidality. Some errors cannot even be explained or rendered with clear expressions and are difficult to compensate directly as a result. In this paper, an approach is proposed that avoids the complex and laborious compensation procedure for error sources but still promises accurate 3D measurement. It is realized by the mathematical model extension technique. The parameters of the extended mathematical model for the ’phase to 3D coordinates transformation’ are derived using the least-squares parameter estimation algorithm. In addition, a phase-coding method based on a frequency analysis is proposed for the absolute phase map retrieval to spatially isolated objects. The results demonstrate the validity and the accuracy of the proposed flexible fringe projection vision system on spatially continuous and discontinuous objects for 3D measurement.
Highlights
Industrial safety inspection has recently received considerable attention in the academic community and technology companies
In order to realize the accurate 3D measurement of multiple discontinuous objects with the abovementioned extended mathematical model, we propose a new phase-coding method to obtain the absolute phase map by only adding one additional fringe pattern
In order to verify the extended mathematical model for the phase to 3D coordinates transformation technique introduced in this paper, we measured the cylinder and hand plaster models shown in Firstly, we carried out the measurement for the cylinder plaster model in Figure 6a with the fringe projection vision system
Summary
Industrial safety inspection has recently received considerable attention in the academic community and technology companies. The accurate three-dimensional (3D) measurement provides important information on monitoring workplaces for industrial safety. In contrast to the polynomial fitting method [3,4] and least-squares method [5,6,7], the phase-to-depth transformation based on the geometrical modeling method [8,9,10,11,12,13] has been widely studied and used in the phase-shifting structured light technique owing to several advantages. There can be no restriction on the camera’s and projector’s relative alignment regarding parallelism and perpendicularity. It has a clear and explanatory mathematical expression for the phase to 3D coordinates transformation since it is derived from the triangulation relationship of the camera, projector, and detected object
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