Imaging apparatus

Claim 1

Apparatus for producing a visible image of a scene by means of non-visible radiation from the scene, which apparatus, in this order, comprises: a mirror prism which is rotatable about an axis and whLch includes a plurality of planar mirrors which form an equiangular polygon in a cross section normal to said axis and which make a sequence of various tilt angles with said axis, an objective lens arranged to receive radiation from said scene via said planar mirrors, a linear array of radiation-sensitive detectors, a linear array of light sources coupled one each to a corresponding detector in said detector array, and viewing means arranged to receive the light beams refleo- ted by said planar mirrors and coming from the light sources, characterized in that the angular spacing between the scanning and reconstruction locations which are disposed around said prism is equal to an integral multiple of the angle between the normals to adjacent sides of said polygon, said multiple not being a submultiple of the number of planar mirrors on the prism, in that the difference in tilt angles of the planar mirrors is an integral multiple of half the angular length of said detector array and in that the sequence of tilt angles is such that, for all planar mirrors but one, the tilt angle of any mirror at the scanning location differs from that of the mirror simultaneously present at the reconstruction location by said half angle so that all but one of the planar mirrors take part in both the scanning and reconstruction of an image of the scene which comprises a number of bands one less than the number of planar mirrors.