Abstract: Scanning imaging systems are described in which an image of a viewed area is scanned across a detector by a line and frame scanning arrangement including a rotatable faceted mirror drum which is of smaller size than hitherto as radiation going to and from the drum passes through an optical system of two elements separated by their focal length. For radiation passing to the drum the optical system can be an objective lens and a collimating lens to produce a small exit pupil within the circumcircle of the drum facets. The drum and a plane oscillatable mirror may both scan the viewed area image of collimated radiation across the detector to permit the generation of a sequential radiation intensity signal and recreate an image, which may be viewable by eye through the optical system, by scanning a beam of parallel light of intensity corresponding to the radiation signal.

Abstract: A tracking and/or guidance system is disclosed for defining a route to be followed by a vehicle or projectile to a target. The system includes a tracking device which is arranged firstly to operate in an acquisition mode, applicable when the vehicle or projectile is close to the device, and subsequently to be progressively converted into a tracking mode as the distance between the vehicle or projectile and the device increases. In the acquisition mode, the device has a wide field of view but is relatively insensitive to deviations of said vehicle or projectile from said route. As the aforesaid distance increases, however, the field of view is progressively reduced and the sensitivity to said deviations is progressively increased. The invention thus provides a system which is suitable for the both initial acquisition and long range guidance of a vehicle or projectile aimed towards a distant target whilst using a conveniently small detector arrangement.