Scanning arrangements

Claim 2

A scanning arrangement including reflector means having a planar reflecting surface arranged to direct received radiation toward detector means, means for rotating the surface in a first direction about an axis inclined to the normal to said surface, and means for causing said axis to precess about a second axis, inclined with respect to both said normal and said first mentioned axis, in a second direction, opposite to said first direction, the rotation and the precession being at substantially the same rate.

Claim 3

An arrangement according to claim 1 wherein said means for causing said first mentioned axis to precess includes a tubular shaft, drive means for rotating said shaft in said second direction and means for rotatably mounting a second tubular shaft within the first mentioned shaft, the axes of the two shafts being inclined to one another, and the axis of the second shaft being the said first mentioned axis.

Claim 4

An arrangement according to claim 2 wherein said planar reflecting surface is secured to one end of said second tubular shaft, the plane of the mirror being inclined with respect to a plane orthogonal to the axis of said second shaft.

Claim 5

An arrangement according to claim 3 wherein said drive means comprises a motor which is located so as to be stationary with respect to said first tubular shaft and is arranged to drive a gear wheel which is adapted to co-operate with gear teeth provided around the perihery of a region of said first tubular member.

Claim 6

An arrangement according to claim 4 wherein the first tubular member is formed with a flange having an aperture in which a further gear shaft is located so as to be freely rotatable therein, said further shaft being provided With respective gear wheels at either end thereof; wherein the said first tubular member is surrounded by a casing part which is stationary with respect thereto, and co-axial therewith, the said casing part being formed with gear teeth with which one of the gear wheels on said further shaft can co-operate to cause rotation of said further shaft when said first tubular member rotates; and wherein said second tubular shaft is provided with a flange which is formed with gear teeth around an annular part thereof, the last mentioned flange being positioned so as to co-operate with the other gear wheel on said further shaft so as to enable the second tubular shaft to be rotated.

Claim 7

An arrangement according to claim 2 wherein said first tubular shaft is formed with an encoding disc arranged to co-operate with a sensing device to enable the angular position of the said first tubular shaft to be monitored.