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US 2004/0164246 A1Published application
Scanning apparatus
AssigneeFarran Technology Limited
InventorAlan H. Lettington
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AssigneeFarran Technology Limited
InventorAlan H. Lettington
Estimating the term…
Scanning apparatus operable in the microwave, mm-wave and infrared ranges and comprises a hollow polygonal primary drum which is mounted for rotation about a central axis. The primary drum provides a plurality of internally presented sides or facets, which are capable of reflecting the microwave, mm-wave and infrared radiation concerned. A fixed Mangin mirror mounted within the primary drum directs such radiation emanating from a view of view of the apparatus, onto the internally presented sides or facets of the primary drum, such that in each of a succession of line scanning periods, radiation emanating from the field of view is directed onto a reflective side or facet of the primary drum to be reflected therefrom onto a further receiving assembly comprising a rotating faceted reflector, in the form of a secondary drum. The secondary drum is arranged to reflect the radiation striking it from the first drum to focus onto a radiation receiver or sensor. The secondary drum is arranged to be rotated, about an axis parallel with the rotary axis of the primary drum, in synchronism with the latter, in such a way that, over each line scanning period, radiation from substantially all of the respective facet of the primary drum can reach said receiver or sensor via said secondary drum. The invention provides a simply constructed robust and yet relatively inexpensive apparatus for forming images in the radiation concerned.
Scanning apparatus operable in the microwave, mm-wave and infrared ranges and comprising a support structure, a primary drum which is mounted in said support structure for rotation relative to the support structure about a central axis of the primary drum, said primary drum being hollow and internally polygonal to provide a plurality of internally presented sides or facets, which are capable of reflecting the radiation concerned, a radiation director disposed to direct radiation emanating from a view of view of the apparatus, being a field of view which is fixed with respect to said supporting structure, (as opposed to rotating with the primary drum), onto the internally presented sides or facets of the primary drum, such that in each of a succession of line scanning periods, as herein defined, radiation emanating from part of said field of view is directed onto a said reflective side or facet of the primary drum to be reflected therefrom onto a further receiving assembly comprising a rotating faceted reflector, herein referred to as a secondary drum, arranged to reflect the radiation striking it from the first drum onto a radiation receiver or sensor, the apparatus being so arranged that the radiation from said field of view is focussed onto said radiation receiver or sensor and wherein said secondary drum is arranged to be rotated, about an axis parallel with the rotary axis of the primary drum, in synchronism with the latter, in such a way that, over said scanning period, radiation from substantially all of a respective said facet of the primary drum, or from substantially all of a predetermined region of such facet, can reach said receiver or sensor via said secondary drum.
Apparatus according to any preceding claim wherein a diverging optical element is positioned to intercept the radiation reflected towards the secondary rotary drum from the reflective facets of the first drum such that, given a beam of radiation reflected from the first drum and intercepting the optical element and swinging through a given angle in a given time in correspondence with the scanning action of the apparatus, the corresponding beam leaving the optical element to strike the second drum swings through an angle which is a simple fraction of the first mentioned angle in said time, and the rate of rotation of the secondary drum is correspondingly slower, and the number of facets on the the secondary drum correspondingly greater so that, over a said scanning period, radiation from substantially all of a respective said facet of the primary drum, or from substantially all of a predetermined region of such facet, can reach said receiver or sensor via said secondary drum that, over said scanning period, radiation from substantially all of a respective said facet of the primary drum, or from substantially all of a predetermined region of such facet, can reach said receiver or sensor via said secondary drum.
Apparatus according to any preceding claim wherein different reflective facets of the primary drum are differently inclined to the rotary axis of the primary drum so that different said facets scan different bands or lines in the field of view, (such different lines being substantially parallel with each other but spaced apart perpendicularly with respect to the longitudinal direction of the lines), whereby the apparatus can generate a conventional, TV-type scanning raster as the primary drum rotates, the faces of the secondary polygon being correspondingly inclined with respect to the rotary axis of the secondary drum to remove any deviation of the beam arriving at the receiver or sensor, to ensure that, despite such variations in inclination of the facets of the primary drum, the beam of radiation arriving at arriving at the receiver or sensor does so with a fixed orientation.
Apparatus according to any preceding claim wherein the picture information for at least two different lines of the scanned image is provided by respective radiation receivers or sensors spaced apart in a direction perpendicular to the direction of line scan, and each receiving radiation from a respective elevation in the field of view relative to said support structure.
Apparatus according to any preceding claim wherein the picture information for each line of the scanned image may is provided by a respective radiation receiver or sensor in an array of such receivers or sensors, each receiving radiation from a respective elevation in the field of view relative to said support structure.
Dependencies are inferred from the claim text.