Abstract: At least one temporary visible reference line is projected onto a target surface, as for example, an athletic field, by several laser sources. A first laser source emits optical energy—at a wavelength of between 380 nm and 750 nm—along at least a first selectable path upon the target surface so as to form a temporary line thereon. A second laser source disposed at a second elevated, stationary location relative to the target surface different from the first stationary location emits optical energy along at least a second selectable path upon the target surface so as to form a temporary line thereon. In some instances, each laser light source may be capable of traversing the entire width of the target surface, in which case each laser source covers a discrete region.

Abstract: An apparatus for providing at least one temporary visible line on a surface within the view of at least one video camera. The system comprises a first laser source disposed at a first elevated, stationary location relative to the surface, and a second laser source disposed at second elevated, stationary location relative to the surface. The output of each laser source is synchronously deflected so as to repetitively sweep each output beam across the same region of the surface and thereby project a visible composite line that is, for example, transverse to the lateral sidelines of an athletic field. A controller comprising a synchronization module synchronizes the sweep frequency rate, at which the beams sweep the surface, to a scan rate of at least one camera arranged to receive an image of the composite temporary line.

Abstract: The surface of an athletic field is divided into multiple regions or zones. A first of these zones is served by a first group of laser sources. A second of the zones is served by a second group of laser sources. Each group includes at least two lasers arranged to project visible light onto the field from opposite lateral sides of the field. The output from each group is focused onto the field so as to form a composite line across the field—anywhere within the associated zone. A controller is operative, in response to receipt of a command from either a keyboard terminal or a wireless, hand held user interface device, to select one of the first group of laser sources and the second group of laser sources to project a composite temporary visible line. The zones may be contiguous or may be separated by one or more intermediate zones, with each intermediate zone having its own associated group of laser sources.