US4983837A
Expired / Lapsed
US
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Forward looking infrared imaging system
Assignee: Raytheon Co
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Filing: 1988-10-31
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Granted: 1991-01-08
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Expires: 2008-10-31
Abstract
Abstract Apparatus and methods for modifying existing forward looking infrared systems and for forming new forward looking infrared systems. Generally, the system comprises a Galilean afocal system in combination with a reimaging afocal system. A reimaging afocal lens system is formed with at least first and second lenses and a plane for forming an image therebetween. A thermal reference source is positioned in the imaging plane of the reimaging system. The method for modifying an existing forward looking infrared imaging system includes positioning the reimaging system along the optical path of the system between the Galilean lens combination and the scanning device. According to a method for forming a forward looking infrared system an imaging lens system is arranged along an optical path in combination with a detector array to focus collimated radiation upon the detector array. The detector array subtends the field of view along a first direction. A reimaging afocal system is incorporated along the optical path to provide collimated radiation to the imaging lens system and a scanning device is positioned between the reimaging afocal system and the imaging lens system to vary the field of view along a second direction in order to provide a two dimensional image. A Galilean afocal lens system is positioned to receive radiation from a scene and transmit the radiation to the reimaging afocal system.
Inventors
- 👤 Erwin E. Cooper
- 👤 Franklin L. Davis
- 👤 Stephen F. Sagan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:30
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/02; H04N3/08; H04N3/09
Claims Analysis
Total Claims: 44
Claim 1
Independent Claim
144 words
A method for modifying an existing forward looking infrared imaging system wherein the system is of the type which processes radiation received from a scene to form an image thereof, wherein the system includes a first Galilean afocal lens combination and wherein sensor components include a detector element array of the type which subtends the field of view along a first direction and a scanning device for varying the field of view along a second direction in order to provide a two dimensional image, the method comprising the steps of: forming a first reimaging afocal lens system comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in the reimaging system; and positioning the reimaging system along the optical path of the existing first system between the Galilean lens combination and the scanning device.
Claim 2
Independent Claim
144 words
A method for modifying an existing forward looking infrared imaging system wherein the system is of the type which processes radiation received from a scene to form an image thereof, wherein the system includes a first Galilean afocal lens combination and wherein sensor components include a detector element array of the type which subtends the field of view along a first direction and a scanning device for varying the field of view along a second direction in order to provide a two dimensional image, the method comprising the steps of: forming a first reimaging afocal lens system comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in the reimaging system; and positioning the reimaging system along the optical path of the existing first system between the Galilean lens combination and the scanning device.
Claim 3
Dependent Claim
23 words
The method of claim 1 further including the step of replacing the detector array of the existing system with a different detector array.
Claim 4
Dependent Claim
23 words
The method of claim 1 further including the step of incorporating into the existing system circuitry for performing detector electronic gain balance functions.
Claim 5
Dependent Claim
20 words
The method of claim 1 further including the step of incorporating into the existing system circuitry for performing DC restoration.
Claim 6
Dependent Claim
104 words
The method of claim 1 comprising additional steps to modify a second existing forward looking infrared imaging system wherein the second system includes a second Galilean afocal lens combination which is different in size or optical design from the first Galilean afocal lens combination, said additional steps including: forming a second reimaging afocal lens system comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in the second reimaging system; and positioning the reimaging system along the optical path of the existing second system between the second Galilean lens combination and the scanning device.
Claim 7
Dependent Claim
21 words
The method of claim 5 wherein the first and second reimaging afocal lens systems are identical in size and optical design.
Claim 8
Dependent Claim
35 words
The method of claim 5 wherein each reimaging afocal lens system is formed by combining at least one fold mirror with the first and second lenses to direct the optical path onto the scanning device.
Claim 9
Dependent Claim
99 words
The method of claim 1 wherein two thermal reference sources are positioned in the reimaging afocal lens system, so as to reduce thermal nonuniformities and provide more uniform temperature readings to each detector element said method further including the steps of: positioning a pair of mirrors in the image plane of the reimaging afocal system; cooperatively positioning a first focusing lens and one reference source to condense radiation from the reference source onto a first mirror; and cooperatively positioning a second focusing lens and the second reference source to condense radiation from the reference source onto a second mirror.
Claim 10
Independent Claim
219 words
A method for forming a forward looking infrared imaging system wherein the system is of the type which processes radiation received from a scene to form an image thereof, wherein sensor components of said desired design include a detector element array of the type which subtends the field of view along a first direction and a scanning device for varying the field of view along a second direction in order to provide a two dimensional image, the method comprising the steps of: forming a first reimaging afocal lens system comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in the reimaging system; arranging along an optical path an imaging lens system in combination with a detector array to focus collimated radiation upon the detector array, the detector array subtending the field of view along a first direction; incorporating the reimaging afocal system along the optical path to provide collimated radiation to the imaging lens system; positioning a scanning device between the reimaging afocal system and the imaging lens system to vary the field of view along a second direction in order to provide a two dimensional image; and positioning a Galilean afocal lens system to receive radiation from a scene and transmit radiation to the reimaging afocal system.
Claim 11
Independent Claim
219 words
A method for forming a forward looking infrared imaging system wherein the system is of the type which processes radiation received from a scene to form an image thereof, wherein sensor components of said desired design include a detector element array of the type which subtends the field of view along a first direction and a scanning device for varying the field of view along a second direction in order to provide a two dimensional image, the method comprising the steps of: forming a first reimaging afocal lens system comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in the reimaging system; arranging along an optical path an imaging lens system in combination with a detector array to focus collimated radiation upon the detector array, the detector array subtending the field of view along a first direction; incorporating the reimaging afocal system along the optical path to provide collimated radiation to the imaging lens system; positioning a scanning device between the reimaging afocal system and the imaging lens system to vary the field of view along a second direction in order to provide a two dimensional image; and positioning a Galilean afocal lens system to receive radiation from a scene and transmit radiation to the reimaging afocal system.
Claim 12
Dependent Claim
25 words
The method of claim 9 further including the step of incorporating into the forward looking infrared system circuitry for performing detector electronic gain balance functions.
Claim 13
Dependent Claim
22 words
The method of claim 9 further including the step of incorporating into the forward looking infrared system circuitry for performing DC restoration.
Claim 14
Dependent Claim
190 words
The method of claim 9 comprising additional steps to form a second forward looking infrared imaging system wherein the second system includes a second Galilean afocal lens system which is different in size or optical design from the first Galilean afocal lens system, said additional steps including: forming a second reimaging afocal lens system comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in the second reimaging system; arranging along a second optical path an imaging lens system in combination with a detector array to focus collimated radiation upon the detector array, the detector array subtending the field of view along a first direction; incorporating the second reimaging afocal system along the second optical path to provide collimated radiation to the imaging lens system; positioning a scanning device between the second reimaging afocal system and the imaging lens system to vary the field of view along a second direction in order to provide a two dimensional image; and positioning the second Galilean afocal lens system to receive radiation from a scene and transmit radiation to the reimaging afocal system.
Claim 15
Dependent Claim
21 words
The method of claim 12 wherein the first and second reimaging afocal lens systems are identical in size and optical design.
Claim 16
Dependent Claim
35 words
The method of claim 12 wherein each reimaging afocal lens system is formed by combining at least one fold mirror with the first and second lenses to direct the optical path onto the scanning device.
Claim 17
Dependent Claim
97 words
The method of claim 9 wherein two thermal reference sources are positioned in the reimaging afocal lens system to reduce thermal nonuniformities and provide more uniform temperature readings to each detector element said method further including the steps of: positioning a pair of mirrors in the image plane of the reimaging afocal system; cooperatively positioning a first focusing lens and one reference source to condense radiation from the reference source onto a first mirror; and cooperatively positioning a second focusing lens and the second reference source to condense radiation from the reference source onto a second mirror.
Claim 18
Independent Claim
264 words
A method for replacing a component in an existing first forward looking infrared system with a component which requires a thermal reference source and for forming a second forward looking infrared system with a component which requires a thermal reference source wherein the systems are of the type which process radiation received from a scene to form an image thereof, wherein the existing system comprises a Galilean afocal lens combination and sensor components including a detector array of the type which subtends the field of view along a first direction and a scanning device for varying the field of view along a second direction in order to provide a two dimensional image, the method comprising the steps of: forming at least first and second reimaging afocal lens systems each comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in each reimaging system; replacing an optical or electronic component in the existing first system with a component which requires a thermal reference source; positioning the first reimaging system along the optical path of the existing first system between the Galilean lens combination and the scanning device; forming the second forward looking infrared system in part by arranging along an optical path a Galilean afocal lens system followed by an imaging lens system in combination with an optical detector arranged to focus collimated radiation upon the detector; and incorporating the second reimaging system along the optical path of the second forward looking infrared system between the Galilean afocal lens system and the imaging lens system.
Claim 19
Independent Claim
264 words
A method for replacing a component in an existing first forward looking infrared system with a component which requires a thermal reference source and for forming a second forward looking infrared system with a component which requires a thermal reference source wherein the systems are of the type which process radiation received from a scene to form an image thereof, wherein the existing system comprises a Galilean afocal lens combination and sensor components including a detector array of the type which subtends the field of view along a first direction and a scanning device for varying the field of view along a second direction in order to provide a two dimensional image, the method comprising the steps of: forming at least first and second reimaging afocal lens systems each comprising at least first and second lenses and a plane for forming an image therebetween; positioning a thermal reference source in each reimaging system; replacing an optical or electronic component in the existing first system with a component which requires a thermal reference source; positioning the first reimaging system along the optical path of the existing first system between the Galilean lens combination and the scanning device; forming the second forward looking infrared system in part by arranging along an optical path a Galilean afocal lens system followed by an imaging lens system in combination with an optical detector arranged to focus collimated radiation upon the detector; and incorporating the second reimaging system along the optical path of the second forward looking infrared system between the Galilean afocal lens system and the imaging lens system.
Claim 20
Dependent Claim
20 words
The method of claim 16 wherein the first and second reimaging afocal systems are of identical size and optical design.
Claim 21
Dependent Claim
23 words
The method of claim 17 further comprising the step of replacing the detector array of the existing system with a different detector array.
Claim 22
Dependent Claim
20 words
The method of claim 17 further comprising the step of incorporating into the existing system circuitry for performing DC restoration.
Claim 23
Dependent Claim
23 words
The method of claim 17 further comprising the step of incorporating into the existing system circuitry for performing detector electronic gain balance functions.
Claim 24
Dependent Claim
29 words
The method of claim 17 wherein the first and second reimaging afocal lens systems are formed by combining at least a third lens with the first and second lenses.
Claim 25
Dependent Claim
35 words
The method of claim 17 wherein each reimaging afocal lens system is formed by combining at least one fold mirror with the first and second lenses to direct the optical path onto the scanning device.
Claim 26
Dependent Claim
71 words
The method of claim 17 further comprising the step of replacing components in each of a plurality of additional existing forward looking infrared systems with components which require thermal reference sources, each additional system also including a Galilean afocal lens combination and a scanning device, said step including: positioning a reimaging system along the optical path of the each additional existing system between the Galilean lens combination and the scanning device.
Claim 27
Dependent Claim
73 words
The method of claim 17 further comprising the step of forming a plurality of additional forward looking infrared systems, each additional system formed by: arranging along an optical path a Galilean afocal lens system followed by an imaging lens system in combination with an optical detector arranged to focus collimated radiation upon the optical detector; and incorporating a reimaging system along the optical path to provide collimated radiation to the imaging lens system.
Claim 28
Dependent Claim
20 words
The method of claim 24 further including the step of positioning a thermal reference source in each additional reimaging system.
Claim 29
Dependent Claim
70 words
The method of claim 24 further comprising the step of replacing components in each of a plurality of additional existing forward looking infrared systems with components which require thermal reference sources, each additional system also including a Galilean afocal lens combination and a scanning device, said step including: positioning a reimaging system along the optical path of the each additional system between the Galilean lens combination and the scanning device.
Claim 30
Dependent Claim
20 words
The method of claim 26 further including the step of positioning a thermal reference source in each additional reimaging system.
Claim 31
Dependent Claim
125 words
A forward looking infrared system for processing radiation received from a scene to form an image thereof comprising: an infrared detector element array of the type which subtends the field of view along a first direction; an imaging lens system for focusing collimated radiation upon the detector; a scanning mirror for varying the field of view along a second direction in order to provide a two dimensional image of the scene; a Galilean afocal lens system positioned to receive radiation from the scene; and a reimaging afocal lens system positioned between the Galilean afocal lens system and the scanning mirror said reimaging system including at least first and second lenses for forming a reimaging plane therebetween and for providing collimated radiation to the scanning mirror.
Claim 32
Dependent Claim
125 words
A forward looking infrared system for processing radiation received from a scene to form an image thereof comprising: an infrared detector element array of the type which subtends the field of view along a first direction; an imaging lens system for focusing collimated radiation upon the detector; a scanning mirror for varying the field of view along a second direction in order to provide a two dimensional image of the scene; a Galilean afocal lens system positioned to receive radiation from the scene; and a reimaging afocal lens system positioned between the Galilean afocal lens system and the scanning mirror said reimaging system including at least first and second lenses for forming a reimaging plane therebetween and for providing collimated radiation to the scanning mirror.
Claim 33
Dependent Claim
25 words
The forward looking infrared system of claim 28 further including a thermal reference source positioned in the reimaging plane of the reimaging afocal lens system.
Claim 34
Dependent Claim
15 words
The forward looking infrared system of claim 28 further including circuitry for performing DC restoration.
Claim 35
Dependent Claim
18 words
The forward looking infrared system of claim 28 further including circuitry for performing detector electronic gain balance functions.
Claim 36
Dependent Claim
33 words
The forward looking infrared system of claim 28 wherein the reimaging afocal lens system includes at least first and second lenses, a plane for forming an image therebetween and a thermal reference source.
Claim 37
Dependent Claim
35 words
The forward looking infrared system of claim 28 wherein the reimaging afocal lens system includes at least first and second lenses and wherein the relative positions of said lenses are adjustable to provide thermal focusing.
Claim 38
Dependent Claim
87 words
The forward looking infrared system of claim 28 wherein two thermal reference sources are positioned in the reimaging afocal lens system to reduce thermal nonuniformities and provide more uniform temperature readings to each detector element said system further comprising: a pair of mirrors in the image plane of the reimaging afocal system; a first focusing lens positioned to condense radiation from a first reference source onto a first mirror; and a second focusing lens positioned to condense radiation from the second reference source onto a second mirror.
Claim 39
Dependent Claim
24 words
The forward looking infrared system of claim 28 wherein the Galilean afocal lens system is adjustable to modify focal length and field of view.
Claim 40
Dependent Claim
130 words
A plurality of forward looking infrared systems each designed to process radiation received from a scene and form an image thereof, each system comprising: an infrared detector array of the type which subtends the field of view along a first direction; an imaging lens system for focusing collimated radiation upon the detector; a scanning mirror for varying the field of view along a second direction in order to provide a two dimensional image of the scene; a Galilean afocal lens system positioned to receive radiation from the scene; and a reimaging afocal lens system positioned between the Galilean afocal lens system and the scanning mirror said reimaging system including at least first and second lenses for forming a reimaging plane therebetween and for providing collimated radiation to the scanning mirror.
Claim 41
Dependent Claim
130 words
A plurality of forward looking infrared systems each designed to process radiation received from a scene and form an image thereof, each system comprising: an infrared detector array of the type which subtends the field of view along a first direction; an imaging lens system for focusing collimated radiation upon the detector; a scanning mirror for varying the field of view along a second direction in order to provide a two dimensional image of the scene; a Galilean afocal lens system positioned to receive radiation from the scene; and a reimaging afocal lens system positioned between the Galilean afocal lens system and the scanning mirror said reimaging system including at least first and second lenses for forming a reimaging plane therebetween and for providing collimated radiation to the scanning mirror.
Claim 42
Dependent Claim
46 words
The plurality of forward looking infrared systems of claim 36 wherein each system includes a reimaging afocal lens system of the same size and power and wherein first and second of the plurality of systems include Galilean afocal lens systems of different size or optical design.
Claim 43
Dependent Claim
30 words
The plurality of forward looking infrared systems of claim 37 wherein the Galilean afocal lens system of the first and second forward looking infrared systems provide different fields of view.
Claim 44
Dependent Claim
28 words
The plurality of forward looking infrared systems of claim 36 wherein the Galilean afocal lens systems are adjustable to modify focal length, system resolution and field of view.
References Cited (Backward Citations)
US4280050A
Cited
US4427259A
Cited
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