US5021657A
Expired / Lapsed
US
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Thermal imager
Assignee: BAE Systems Electronics Ltd
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Filing: 1989-05-15
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Granted: 1991-06-04
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Expires: 2009-05-15
Abstract
Abstract A thermal imager employs an intermediate field stop (8) which is preferably placed at an intermediate image plane (P) in front of a cryogenically cooled detector (1) mounted on a substrate (2). Radiation gathered by a telescope is directed onto the detector through an aperture (9) in the field stop. The field stop limits the rays which are emitted by the detector and substrate and which are subsequently retro-reflected back to the detector (called narcissus rays).
Inventors
- 👤 Jonathan P. Kettlewell
- 👤 Brian F. Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 00:33
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/20; H04N23/23
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
39 words
A thermal imager including a detector mounted on a cooled substrate, an optical system and a field stop which is positioned and is of a suitable size to limit narcissus rays to those which emanate from the detector only.
Claim 2
Dependent Claim
39 words
A thermal imager including a detector mounted on a cooled substrate, an optical system and a field stop which is positioned and is of a suitable size to limit narcissus rays to those which emanate from the detector only.
Claim 3
Dependent Claim
42 words
A thermal imager as claimed in claim 1 wherein the optical system provides an intermediate image plane and the field stop is located at the intermediate image plane and adapted to limit narcissus rays to those which emanate from the detector only.
Claim 4
Dependent Claim
24 words
A thermal imager as claimed in claim 2 wherein the optical system includes a lens system between the intermediate image plane and the detector.
Claim 5
Dependent Claim
77 words
A thermal imager, comprising: a detector mounted on a cooled substrate; means for forming an intermediate image plane in front of the detector; a field stop in the intermediate image plane, the field stop having an aperture; and at least one lens between the field stop and the detector and substrate, wherein the field stop limits narcissus rays to those which emanate from the detector only, the aperture being dimensioned to block radiation emanating from the substrate.
Claim 6
Dependent Claim
77 words
A thermal imager, comprising: a detector mounted on a cooled substrate; means for forming an intermediate image plane in front of the detector; a field stop in the intermediate image plane, the field stop having an aperture; and at least one lens between the field stop and the detector and substrate, wherein the field stop limits narcissus rays to those which emanate from the detector only, the aperture being dimensioned to block radiation emanating from the substrate.
Claim 7
Dependent Claim
23 words
A thermal imager as claimed in claim 4, wherein said aperture has an area that is smaller than the area of the detector.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-06-03 | 1994-12-03 | 1995-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-06-03 | 1998-12-03 | 1999-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-06-03 | 2002-12-03 | 2003-06-04 | $7700.00 | Window Closed / Lapsed |