Scanning apparatus

Apparatus for scanning input radiation from a scene and for generating output radiation to form an image at a curved detector array comprising;

• a rotatable reflective plate, forming an entrance pupil to the apparatus, for receiving and reflecting input radiation, the reflective plate having an axis of rotation passing substantially through the centre of the plate, wherein the axis of rotation is inclined at a non-zero angle θa to a direction parallel with or orthogonal to the normal to the reflective plate at the centre of rotation,
• a rotor for rotating the reflective plate, and
• focussing element for producing an image at the detector array, wherein the converging effects of the focusing element and the rotatable reflective plate co-operate with the curvature of the detector array to focus the image onto the detector array, and wherein the focusing element comprises
• a lens arrangement, capable of selectively transmitting and focusing radiation having a particular direction of polarisation and arranged to receive both input radiation from the scene and input radiation reflected from the rotatable plate, the lens arrangement comprising a first polarising element, for selectively transmitting and selectively reflecting radiation having a particular direction of polarisation, the first polarising element having a first polarisation axis and having a substantially flat surface, a second element for rotating the direction of polarisation of radiation through substantially 45° and a third polarising element, for selectively transmitting and selectively reflecting radiation having a particular direction of polarisation, the third polarising element having a third polarisation axis and a substantially spherical surface having a centre of curvature, C, and a radius of curvature, R, the third polarisation axis making an angle of substantially 45° with the first polarisation axis, and
• wherein (i) the axis of rotation of the plate passes through the centre of curvature, C, and
• (ii) the separation of the first polarising element and the centre of curvature along the axis of rotation and the separation between the first polarising element and the disc along the axis of rotation are substantially equal,
• wherein optical aberrations in the image formed at the detector array are minimised.

Apparatus for scanning input radiation from a scene and for generating output radiation to form an image at a curved detector array comprising;

• a rotatable reflective plate, forming an entrance pupil to the apparatus, for receiving and reflecting input radiation, the reflective plate having an axis of rotation passing substantially through the centre of the plate, wherein the axis of rotation is inclined at a non-zero angle θa to a direction parallel with or orthogonal to the normal to the reflective plate at the centre of rotation,
• rotor for rotating the reflective plate and
• focussing element for producing an image at the detector array
• wherein the converging effects of the focusing element and the rotatable reflective plate co-operate with the curvature of the detector array to focus the image onto the detector array,
• wherein the rotatable reflective plate exhibits a concave profile for producing an image at the detector array, thereby incorporating the function of the focusing element into the rotatable reflective plate,
• and further comprising a dielectric layer located on the surface of the rotatable reflective plate to form a rotatable Mangin mirror configuration, for providing optical correction.

Apparatus for scanning input radiation from a scene and for generating output radiation to form an image at an image plane, said apparatus comprising;

• a rotatable reflective plate, forming an entrance pupil to the apparatus, for receiving and reflecting input radiation, the reflective plate having an axis of rotation passing substantially through the centre of the plate, wherein the axis of rotation is inclined at a non-zero angle θa to both the reflective plate and the normal to the reflective plate at the centre of rotation,
• means for rotating the reflective plate,
• a focussing element, and
• a detector situated in the image plane, wherein the image plane is curved and the converging effects of the focusing element and the rotatable reflective plate co-operate with the curvature of the image plane to focus the image onto the detector.