Analysis and design of a novel target coding method for a portable coordinate measurement system

The target coordinate measurement system features an extensive range of key applications. In many high- precision measurement systems wide scope, high precision and multiple cameras are used. However, the objective of this paper is to enhance the measurement accuracy and range of a monocular target owing to its portability and convenience. A systematic simulation of linear, planar and stereo target structures was carried out to investigate target structures. Based on our simulation results, the 3D target is more accurate and robust to tilt due to rich information available from 3D locations of the markers. To overcome the limitation in the measurement range for the monocular target, ideas of coded stereo target are presented in this paper. The measured coordinates can be calculated from only part of the markers, effectively enlarging the measurement range at short object distances. A stereo coded target system is designed based on this method and is compared to an ordinary monocular target. Stability experiments were conducted under different object distances and poses, which have shown that the Z direction accuracy of the stereo target is at least 23.8% or 10% higher than that of the 1D or 2D target, respectively. Additionally, the ranging experiment revealed that the measurement accuracy of the coded stereo target is 23.5% or 59.2% higher than that of the non-coded 1D or 2D target when measuring the Z direction and the distance of the far field.

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This work was support by the Key R&D Projects of the Shaanxi Province (No. 2023-ZDLGY-14), Science and Technology Project of the Shaanxi Province (No. 2023-YBGY-357).