A general recursive linear method and unique solution pattern design for the perspective-n-point problem

In this paper, a new method for solving the perspective-n-point (PnP) problem is developed. With an auxiliary point, the linear method for the special case of four coplanar points is extended to find the coarse solutions for the general P3P problem. A recursive least square algorithm with a forgetting factor is introduced to find all the accurate solutions for the P3P problem. Then the algorithm is extended to the general PnP problem. The solution stability issues are investigated for the P3P, P4P and P5P problem, respectively. Furthermore, a pattern is designed to ensure unique solution for the PnP problem. Experiments are performed to verify the effectiveness of the proposed method.