Abstract
While color-coding methods have improved the measuring efficiency of a structured light three-dimensional (3D) measurement system, they decreased the measuring accuracy significantly due to lateral chromatic aberration (LCA). In this study, the LCA in a structured light measurement system is analyzed, and a method is proposed to compensate the error caused by the LCA. Firstly, based on the projective transformation, a 3D error map of LCA is constructed in the projector images by using a flat board and comparing the image coordinates of red, green and blue circles with the coordinates of white circles at preselected sample points within the measurement volume. The 3D map consists of the errors, which are the equivalent errors caused by LCA of the camera and projector. Then in measurements, error values of LCA are calculated and compensated to correct the projector image coordinates through the 3D error map and a tri-linear interpolation method. Eventually, 3D coordinates with higher accuracy are re-calculated according to the compensated image coordinates. The effectiveness of the proposed method is verified in the following experiments.
Highlights
The structured light 3D measurement has been applied in many fields, such as industrial inspection, digital fashion, heritage conservation, reverse engineering, and aerospace [1,2,3].The measurement efficiency is improved by color-coding methods [4,5,6,7,8]
The longitudinal chromatic aberration causes image blur, while the lateral chromatic aberration (LCA) causes different positions for the object imaging with different colors the object is in the same space position
The error of radius is defined as the difference between the fitting radius and the real radius, which is obtained by a coordinates measuring machine (CMM)
Summary
The structured light 3D measurement has been applied in many fields, such as industrial inspection, digital fashion, heritage conservation, reverse engineering, and aerospace [1,2,3].The measurement efficiency is improved by color-coding methods [4,5,6,7,8]. The structured light 3D measurement has been applied in many fields, such as industrial inspection, digital fashion, heritage conservation, reverse engineering, and aerospace [1,2,3]. The chromatic aberration is divided into two forms, longitudinal chromatic aberration and lateral chromatic aberration (LCA). The longitudinal chromatic aberration causes image blur (the focus distance is different with different colors), while the LCA causes different positions for the object imaging with different colors the object is in the same space position. In the structured light system, the accuracy of the position of patterns in captured image is very important for the measurement accuracy. Compared with the LCA, the influence of longitudinal chromatic aberration can be neglected. Some methods have been developed to eliminate the influence of LCA, and those methods can be divided into two categories: Hardware-based and software-based
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