Patent US 4,136,387

Electro-optical sensors measure the location of a plurality of spots on the surface of a golf club head or a golf ball at a minimum of two precisely spaced points in time. The two time points for the club head are just prior to impact with the golf ball. The two time points for the golf ball are just after impact by the club head. From the apparent displacements of the plurality of spots between measurements, the apparatus determines in substantially real time the velocity of the club head or ball and the spin about orthogonal axes.