US4691107A
Expired / Lapsed
US
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Infra red photo detector systems
Assignee: UK Secretary of State for Defence
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Filing: 1985-10-04
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Granted: 1987-09-01
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Expires: 2005-10-04
Abstract
Abstract An infra red photo detector system comprises a piece of detector material, such as Cd x Hg 1-x Te, InSb, InAs, etc, carrying at least a pair of spaced electrodes. An optical arrangement directs a small spot of radiation onto the detector. The position of the small spot on the much larger detector is found by applying an electrical bias between the electrodes causing a drift of photo carriers. The bias may be of alternating polarity and the detector output measured at each polarity. Alteratively a high frequency bias may be applied and the A.C. offset from the detector used to indicate spot position. Alternatively the spot position may be modulated or swept along the detector by a mirror moving in a sawtooth scanning action.
Inventors
- 👤 Charles T. Elliott
- 👤 Anthony M. White
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:10
CPC Classifications
H; H10; H10F; H10F30/00; H10F30/10; G; G01; G01B; G01B11/00
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
111 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region; applying a DC electrical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the element output signal by reversing the bias polarity; detecting the controlled element output signal; and extracting the light source image position from a difference/sum ratio of element resistance for the two bias polarities.
Claim 2
Independent Claim
111 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region; applying a DC electrical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the element output signal by reversing the bias polarity; detecting the controlled element output signal; and extracting the light source image position from a difference/sum ratio of element resistance for the two bias polarities.
Claim 3
Dependent Claim
15 words
A method according to claim 1 further comprising the step of cooling the photoconductive element.
Claim 4
Dependent Claim
30 words
A method according to claim 1 further comprising the step of forming the photoconductive element from material selected from the group comprising Cd x Hg 1-x Te, InSb and InAs.
Claim 5
Independent Claim
117 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region; applying an electrical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the bias signal polarity by reversal at a high frequency; detecting the controlled element output signal; and extracting the light source image position by detecting the light source image position from asymmetry in the element output signal arising from resistance directionality.
Claim 6
Independent Claim
117 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region; applying an electrical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the bias signal polarity by reversal at a high frequency; detecting the controlled element output signal; and extracting the light source image position by detecting the light source image position from asymmetry in the element output signal arising from resistance directionality.
Claim 7
Dependent Claim
31 words
A method according to claim 4 wherein the light source image position is detected from an offset asymmetry in the element output signal, the offset being detected in magnitude and direction.
Claim 8
Dependent Claim
31 words
A method according to claim 5 wherein the offset is processed to provide an offset counteracting DC bias feedback signal, the feedback signal being detected to indicate light source image position.
Claim 9
Dependent Claim
15 words
A method according to claim 4 further comprising the step of cooling the photoconductive element.
Claim 10
Dependent Claim
30 words
A method according to claim 4 further comprising the step of forming the photoconductive element from material selected from the group comprising Cd x Hg 1-x Te, InSb and InAs.
Claim 11
Independent Claim
118 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region; applying a DC electrical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the element output signal by scanning the light source image in a direction opposite to carrier flow; detecting the controlled element output signal; and extracting the light source image position by timing the element output signal relative to the image scan.
Claim 12
Independent Claim
118 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region; applying a DC electrical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the element output signal by scanning the light source image in a direction opposite to carrier flow; detecting the controlled element output signal; and extracting the light source image position by timing the element output signal relative to the image scan.
Claim 13
Dependent Claim
16 words
A method according to claim 9 wherein the image is scanned in a saw tooth manner.
Claim 14
Dependent Claim
15 words
A method according to claim 9 further comprising the step of cooling the photoconductive element.
Claim 15
Dependent Claim
30 words
A method according to claim 9 further comprising the step of forming the photoconductive element from material selected from the group comprising Cd x Hg 1-x Te, InSb and InAs.
Claim 16
Independent Claim
139 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region and the element being arranged as one arm of a bridge circuit having a variable resistor as a second arm, the bridge being balanced by adjusting the variable resistor; applying an electical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the element output signal by reversing the bias polarity; detecting the controlled element output signal; and extracting the light source image position from a difference/sum ratio of element resistance for the two bias polarities.
Claim 17
Independent Claim
139 words
A method of detecting the position of an infrared light source in a scene, the method including the steps of: imaging the scene on to a photosensitive surface region of an infrared sensitive photoconductive element, the element having bias electrodes arranged to define at least one bias current path substantially parallel to the said photosensitive surface region and the element being arranged as one arm of a bridge circuit having a variable resistor as a second arm, the bridge being balanced by adjusting the variable resistor; applying an electical bias signal to the bias electrodes to generate an output signal from the photoconductive element; controlling the element output signal by reversing the bias polarity; detecting the controlled element output signal; and extracting the light source image position from a difference/sum ratio of element resistance for the two bias polarities.
Claim 18
Dependent Claim
15 words
A method according to claim 13 further comprising the step of cooling the photoconductive element.
Claim 19
Dependent Claim
30 words
A method according to claim 13 further comprising the step of forming the photoconductive element from material selected from the group comprising Cd x Hg 1-x Te, InSb and InAs.
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) | 1990-08-31 | 1991-03-02 | 1991-09-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-08-31 | 1995-03-02 | 1995-09-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-08-31 | 1999-03-02 | 1999-09-01 | $7700.00 | Window Closed / Lapsed |