Optical apparatus for controlling the direction of a beam of optical radiation
AssigneeFerranti Limited
InventorsIan Drummond Crawford, Henry Bruce Marshall, Robert John Cormack
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Abstract
Apparatus for controlling the direction of a beam of optical radiation from, say, a laser, includes two prisms of small apex angle independently rotatable about a common axis. A control circuit is responsive to the actual angular positions of the prisms and to inputs indicating the desired beam position to cause the prisms to be moved to the appropriate positions.
Claims4
Optical apparatus for controlling the direction of a beam of optical radiation, which includes first and second prisms, each of small apex angle and mounted for rotation on a common axis in the planes bisecting their apex angles substantially parallel to one another and normal to said common axis, drive means operable to rotate each prism independently about said common axis, pick-off means operable to determine the angular position of each prism relative to a datum direction and to deliver outputs representing the sine and cosine of the angles between the datum direction and the orientation of each prism, and control means responsive to said outputs to derive the changes in said angles necessary to move the output beam to a position determined by azimuth and elevation demand inputs, the changes being defined by the expressions ##EQU4## where
- .alpha. is the angular displacement between the first prism and the datum,
- .beta. is the angular displacement between the second prism and the datum, d.alpha. and d.beta. are the respective changes in the angles .alpha. and .beta.,
- dA = A'/k - (sin .alpha. + sin .beta.),
- dE = E'/k - (cos .alpha. + cos .beta.),
- A' is the azimuth demand input and E' is the elevation demand input,
- and k is the deviation produced by each prism.
Dependencies are inferred from the claim text.