Apparatus used in the tracking of objects

Claim 1

Apparatus for tracking an object within a plane area in space comprising a source of optical radiation, an optical system arranged to form the radiation from the source into a flat beam, movable reflector means including at least two multifaceted drums rotatable in synchronism with each other about their longitudinal axes, the axes being inclined at a finite angle to each other, a first of said drums being at least partly reflective of the radiation and so disposed in the path of the beam from the optical system that a part of the beam is reflected from the drum towards said plane area and scans over the area, as the drum rotates, in a direction transversely to the direction of greatest divergence of the beam at the plane, beam diverting means for diverting the part of the beam not reflected by the first drum towards the second drum, said second drum being so located as to reflect radiation incident thereon towards said plane area and to cause the beam to scan over the area transversely to the direction of greatest divergence of the beam at the plane, and a receiver system responsive to the irradiation of the object by the scanning beams and to the relationship between the time into the scan that the object is crossed by the beam reflected by the first drum and the time into the scan that the object is crossed by the beam reflected by the second drum to determine the position of the object in said plane.