Ferranti Plc

John S St Clair

Nicolas L Brignall

A radiation path directing system, such as sighting means 10, (FIG. 1) has an imaging detector (not shown) below the apparatus has a field of view centered on a sightline deflected from the vertical axis 22 by mirror 12 rotatable in elevation about axis 13 in yoke 14 and directed in azimuth by rotation of the yoke about orthogonal azimuth axis 22. To enable rapid changes in sightline azimuth and/or if the yoke assembly has a limited extend of rotation the mirror 12 can be flipped about axis 13 to divert the sightline azimuth by 180.degree. insteads of moving the complete (and possibly heavy) yoke assembly. In one simple construction a yoke rotation of .+-.90.degree. and mirror flipping enables a 360.degree. sightline to be described. Preferably conditions are defined relating current yoke position and demanded sightline azimuth (FIG. 5) to determine whether the sightline is achieved by yoke rotation with or without mirror flipping.

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Dunfermline, United Kingdom

John S St Clair