A study on spin-rate measurement using a uniquely marked moving ball

A method is proposed for measuring the spin rate of a ball moving through 3D space. The method uses only one high-speed camera and a uniquely marked ball. Five lines, each one a different color, are painted on the ball´s equator and on its perpendicular great circle, enabling measurement of both the rotational angular velocity (spin rate) and translational velocity. The proposed measurement algorithm consists of two steps. The first step is to measure the translational velocity, for which we developed a new semi-automatic translational speed measurement algorithm. The second step is to measure the ball spin rate employing a unique marker tracking method using a spin rate estimation algorithm based on a rotation matrix. Simulations and experiments were carried out to show the validity of the method, and reasonable results were obtained.