Ferranti Plc

Nicolas L Brignall

William Blain

John S St Clair

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.

Radiation path axis directing system

In known sightline stabilizing apparatus 10 (FIG. 1) a gyro-stabilized reflector 25 maintained in orientation in space about two axes 18 and 26 by gyro means in the mechanism 22. The reflector mechanism is contained in housing 17 and is pivotable about elevation axis 18 in relation thereto. The housing also carries a sensor, e.g. a tv camera providing signals to a remote (non-stabilized) image display device, and is itself rotatable in elevation relative to a platform 16 rotatable in azimuth. The apparatus is normally carried by a vehicle and movements thereof cause servo responses of the mechanism 22 to stabilize the mirror and follow-up movements of the housing and pedestal 16 restore the mirror to the center of its limited motion in the housing. However, changes in elevation angle of the reflector cause rotation of the remote image about the center of its field of view and motion induced changes can rapidly lead to motion sickness in an observer of the image. The improvement of the invention consists of introducing an elevation offset between the mirror and the housing so that the sensor is offset about axis 18 and has essentially the same field of view from the mirror but the image formed is rotated about its receptive axis 20. The image rotation is equal to the elevation offset of the housing/sensor and is applied as a demand signal into the housing elevation-restoring feedback loop.

Sightline stablisation apparatus

Reaction force compensation means 70 (FIG. 1) for countering the reaction torque of a heavy body, such as rotatable yoke assembly 20, when accelerated relative to flimsily supported body 21 about axis 22, comprises a reaction member 71 rotatable about the, or a parallel, axis 22 and a reaction drive motor 74 coupled to rotate the reaction member by way of velocity step-down gearing 75. In response to acceleration of the body 21 the reaction drive motor 74 accelerates member 71 in the opposite direction producing an equal and opposite reaction torque on the structure. The reaction member is made with a higher moment of inertia about axis 22 than the body and is accelerated at a correspondingly lower rate to give the balancing reaction torque while requiring a smaller mechanical power input than might be expected. The power required of the drive motor is minimized by optimizing the gearing ratio having regard to the moments of inertia of the reaction member and drive motor.

Reaction force compensator

An optical scanning system includes scanning means arranged to scan an object field and comprising, in one form, a rotatable drum (10) carrying a plurality of pairs of mirrors (12, 13). A detector (21) is provided which is sensitive to optical radiation directed on to it by the scanning means. Means, such as telescopes (17, 22) collect radiation from at least two fields of view for presentation to the object field of the scanning means. Optical switching means are provided so that radiation reaches the detector (21) from each field of view in turn. The switching means may be an optical shutter (14) having reflective regions (15) and transparent regions (16).

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Edinburgh, United Kingdom

Nicolas L Brignall