Inverse Composite Alignment of a sphere under orthogonal projection for ball spin estimation

摘要

In this technical report, we propose a method for measuring the spin of a table tennis ball in the framework of Inverse Composite Alignment (ICA). We assume that the projection of the ball onto the image plane is orthographic, and the shape of the ball is a rigid sphere. Under these assumptions we derive an update rule for the motion parameters. Because of the precomputation of the Hessian matrix in ICA and the simplifying assumptions, the motion parameters estimation at each frame is very fast. We show experimental results obtained by our prototype system for measuring spins in real image sequences of table tennis rallies.