Camera pose estimation from less than eight points in visual servoing

The problem of estimating the camera pose in eye-in-hand visual servoing is considered for the case in which the available point correspondences are less than eight. Two strategies based on the properties of the essential matrix are hence described, which mainly consist of the computation of the roots of a one-variable polynomial in the seven points case and the minimization of a two-variables polynomial through a gradient algorithm in the six points case.