Abstract: An object-space scanning system for radiation wherein the scanning device comprises sets of planar reflecting surfaces arranged in pairs, one from each set, such that the two surfaces in a pair are disposed substantially at right angles to each other and the line of intersection of the surfaces is at right angles to the axis of rotation of the scanning device which is so arranged that incident radiation is sequentially reflected from the two surfaces of a pair before entering a focussing arrangement which focusses the radiation into a detector, the secondary scan direction being achieved by the fact that the angle included between the planar reflective surfaces of respective pairs differs by a very small angle successively around said axis.

Abstract: A radiation scanning system having a radiation detector which receives radiation from a focussing system after reflection from first and second scanners which are rotatable about parallel axes, and in which the first scanner is annular having its reflective surfaces on its outer periphery, the rotational axis of the second scanner being displaced by a distance which is less than the radius of the second scanner from the plane containing the rotational axis of the first scanner and the axis of the radiation focussing system.

Abstract: In a radiation scanning system, scanning is achieved by rotation of two drums about parallel axes. The first drum is rotated at an angular speed s.sub.1 and has n.sub.1 reflective surfaces at a distance r.sub.1 from a first axis of rotation. The second drum is rotated at an angular speed s.sub.2 and has n.sub.2 reflective surfaces at a distance r.sub.2 from a second axis of rotation. The axes are separated by a distance d. A detector is located a distance a from the first axis. The following conditions hold:2 a(n.sub.1 /n.sub.2 -1).sup.2 + 2 d(n.sub.1 /n.sub.2).sup.2 +r.sub.2 (n.sub.1 /n.sub.2).sup.2 =r.sub.1 (2n.sub.1 /n.sub.2 -1).sup.2 , (i)n.sub.1 s.sub.1 =n.sub.2 s.sub.2.