Estimation of camera pose is an integral part and classical problem of augmented reality (AR) system and computer
vision. Accurate pose estimation is crucial in determining the rigid transformation relating 2D images to known 3D
geometry. Therefore, the algorithm should be not only fast and accuracy, but also robust in AR system. Orthogonal
iterative (OI) algorithm is a good method, but it requires a proper initialization and cannot deal with problems of pose
ambiguity. A new method based on OI we presented before, provides a good initialization and solves a problem of pose
ambiguity introduced by coplanar markers. However, two more potential problems usually make the algorithm calculate
some wrong results, and lead to the algorithm unsteady and not robust. In this paper, we develop the method by resolving
pose ambiguities, which originate from potential problems in algorithm. Two more constraints are employed in our
method. One is camera must be located in front of the marker, while the other is camera must be oriented to the marker.
It's proved that the improved method is steady in experiments, and can calculate the pose of camera fast and correctly.
Moreover, since the method can deal with pose ambiguity, it is rather robust in AR system.