Scanning apparatus
First Claim
1. Scanning apparatus operable in the microwave, mm-wave and infrared ranges and comprising a support structure, a first reflective disc or mirror which is mounted in said support structure for rotation relative to the support structure about a first axis, a second reflective disc or mirror which is mounted in said support structure for rotation relative to the support structure about a second axis, the arrangement being such that radiation from a scene being scanned can reach a reflective surface of the first disc or mirror to be reflected thereby onto a reflective surface of the second disc or mirror, to be reflected by the latter, in turn, onto said reflective surface of the first disc or mirror again, to be reflected from the first disc or mirror into or onto a further part of the apparatus incorporating a receiver or receivers for such radiation, and wherein said reflective surface of the first disc or mirror has an axis of rotational symmetry tilted at a first small angle relative to said first axis and wherein said reflective surface of the second disc or mirror has an axis of rotational symmetry tilted at a second angle relative to said second axis, and driving means for said discs or mirrors arranged to drive these in respective opposite senses, the arrangement being such as to effect a substantially linear scan, the size of said second angle relative to said first angle being selected so as to reduce or eliminate pupil wander in the direction orthogonal to the direction of line scan.
2 Assignments
0 Petitions
Accused Products
Abstract
Scanning apparatus operable in the microwave, mm-wave and infrared ranges and comprises a support structure, a first reflective disc or mirror (10) which is mounted in said support structure for rotation relative to the support structure about a first axis (14), and a second reflective disc or mirror (12) which is mounted in said support structure for rotation relative to the support structure about a second axis (16) and driving means for said discs or mirrors arranged to drive these in respective opposite senses. In operation of the apparatus, radiation from a scene being scanned reaching a reflective surface of the first disc or mirror is reflected thereby onto a reflective surface of the second disc or mirror, to be reflected by the latter, in turn, onto the reflective surface of the first disc or mirror again, to be reflected from the first disc or mirror into or onto a further part of the apparatus incorporating a receiver or receivers for such radiation. The reflective surface of the first disc or mirror has an axis of rotational symmetry, tilted at a first small angle relative to said first axis and the reflective surface of the second disc or mirror has an axis of rotational symmetry tilted at a second angle relative to said second axis. The driving means for the discs or mirrors is arranged to drive these in such a way as to effect a substantially linear scan. the size of said second angle relative to said first angle being selected so as to reduce or eliminate pupil wander in the direction orthogonal to the direction of line scan.
-
Citations
9 Claims
- 1. Scanning apparatus operable in the microwave, mm-wave and infrared ranges and comprising a support structure, a first reflective disc or mirror which is mounted in said support structure for rotation relative to the support structure about a first axis, a second reflective disc or mirror which is mounted in said support structure for rotation relative to the support structure about a second axis, the arrangement being such that radiation from a scene being scanned can reach a reflective surface of the first disc or mirror to be reflected thereby onto a reflective surface of the second disc or mirror, to be reflected by the latter, in turn, onto said reflective surface of the first disc or mirror again, to be reflected from the first disc or mirror into or onto a further part of the apparatus incorporating a receiver or receivers for such radiation, and wherein said reflective surface of the first disc or mirror has an axis of rotational symmetry tilted at a first small angle relative to said first axis and wherein said reflective surface of the second disc or mirror has an axis of rotational symmetry tilted at a second angle relative to said second axis, and driving means for said discs or mirrors arranged to drive these in respective opposite senses, the arrangement being such as to effect a substantially linear scan, the size of said second angle relative to said first angle being selected so as to reduce or eliminate pupil wander in the direction orthogonal to the direction of line scan.
-
9. Scanning apparatus operable in the microwave, mm-wave and infrared ranges and comprising a support structure, a first reflective disc or mirror which is mounted in said support structure for rotation relative to the support structure about a first axis, a second reflective disc or mirror which is mounted in said support structure for rotation relative to the support structure about a second axis, the arrangement being such that radiation from a scene being scanned can reach a reflective surface of the first disc or mirror to be reflected thereby onto a reflective surface of the second disc or mirror, to be reflected by the latter, in turn, onto a further part of the apparatus incorporating a receiver or receivers for such radiation, and wherein said reflective surface of the first disc or mirror has an axis of rotational symmetry, tilted at a small angle relative to said first axis and wherein said reflective surface of the second disc or mirror has an axis of rotational symmetry tilted at a small angle relative to said second axis, and driving means for said discs or mirrors arranged to drive these in respective opposite senses, and wherein said first and second reflective discs or mirrors are both concave mirrors, arranged with their concave sides facing one another and wherein a wire grid polariser is located between the mirrors inclined at an angle with respect to the two mirrors so as to receive radiation, from a scene being scanned, arriving transversely with respect to said first and second axes and to reflect a plane polarised component of such radiation towards said first mirror, and wherein a quarter wave plate or Faraday rotator is located between said first mirror and said wire grid polariser, whereby the radiation passing to said first mirror and reflected thereby towards said second mirror has its polarisation direction shifted through 90 degrees in passing twice through said quarter wave plate or Faraday rotator and can thus pass through said wire grid polariser to said second mirror to be focussed by said second mirror onto a radiation detector or receiver located between said first mirror and said second mirror.
Specification