CPnP: Consistent Pose Estimator for Perspective-n-Point Problem with Bias Elimination
This addresses camera pose estimation in computer vision, offering an incremental improvement for applications like 3D reconstruction and robotics.
The paper tackled the Perspective-n-Point (PnP) problem by proposing CPnP, a consistent estimator that eliminates bias to converge to the true camera pose as point count increases, achieving superior precision and computing time in experiments with dense visual features.
The Perspective-n-Point (PnP) problem has been widely studied in both computer vision and photogrammetry societies. With the development of feature extraction techniques, a large number of feature points might be available in a single shot. It is promising to devise a consistent estimator, i.e., the estimate can converge to the true camera pose as the number of points increases. To this end, we propose a consistent PnP solver, named \emph{CPnP}, with bias elimination. Specifically, linear equations are constructed from the original projection model via measurement model modification and variable elimination, based on which a closed-form least-squares solution is obtained. We then analyze and subtract the asymptotic bias of this solution, resulting in a consistent estimate. Additionally, Gauss-Newton (GN) iterations are executed to refine the consistent solution. Our proposed estimator is efficient in terms of computations -- it has $O(n)$ computational complexity. Experimental tests on both synthetic data and real images show that our proposed estimator is superior to some well-known ones for images with dense visual features, in terms of estimation precision and computing time.