Abstract: Systems for determining motion characteristics of a sports object. In an embodiment, the system comprises a light grid structure and a processor. The light grid structure comprises a frame and light-source assemblies and photo-detector assemblies. Each of the light-source assemblies and photo-detector assemblies is mounted on the frame such that each light-source assembly is on an opposite side of the frame than a corresponding photo-detector assembly, and each light-source assembly emits a light beam which is detected by its corresponding photo-detector assembly. The processor receives data that is based on outputs of the photo-detector assemblies. The data indicates light beam(s) which have been interrupted. Based on the data, the processor determines motion characteristic(s) of an object which interrupted the light beam(s), including an angle of incidence.