DEPTH-FROM-DEFOCUS-BASED CONVENIENT COAXIAL PROJECTION PROFILOMETRY FOR LARGE MEASUREMENT RANGE

Xiaokai Song, Yating Ding, Zipeng Ran, Bolin Cai, and Xiangcheng Chen

Keywords

Coaxial system, three-dimensional (3D) shape measurement, depth-from-defocus (DFD) strategy

Abstract

Coaxial optical systems are typically used to measure objects with significant height changes. This paper proposes a new coaxial structured light three-dimensional (3D) shape measurement method to expand the effective measurement range of the coaxial system without reducing accuracy and adding additional mechanical moving parts and optical parts. The proposed method establishes a relationship between the lens blur radius and the physical size of the object through the depth-from-defocus (DFD) strategy, thereby obtaining the size of measured objects. In this way, the object can be measured without introducing mechanical moving parts. Experiments of the deep hole objects, step objects, and sculptures have been carried out. The results confirm that compared with the fringe projection profilometry, the proposed method can achieve a shadow-free measurement and obtain a larger surface reconstruction completeness within the measurement range of more than 95 mm. Meanwhile, the measurement of the standard gauge proved the accuracy of the method, with a reconstruction error of 0.5565 mm and a relative error of 1.11%.

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