US4831257A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gate coupled input circuit
Assignee: Lockheed Martin Tactical Systems Inc
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Filing: 1986-09-26
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Granted: 1989-05-16
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Expires: 2006-09-26
Abstract
Abstract What is disclosed is a preamplifier used with each pyroelectric detector in an infrared imaging array system. To bias the preamplifiers either a MOSFET transistor is utilized as a switch that is periodically operated to place charge on the gate of the MOSFET preamplifier transistor to maintain it at its bias level, or an NPN transistor is operated at a level to provide high impedance. When the bias switch is not operated, the associated detector detects and a reading is taken from each detector in the array. NPN transistor switches can be manufactured consistently and their conduction level can be adjusted to balance the gain of all preamplifiers in the detector array. The supply voltage to the preamplifiers in the array is monitored by a feedback circuit which compares a supply voltage to a reference voltage and adjusts the preamplifier bias voltage to compensate for changes in the supply voltage.
Inventors
- 👤 Jeff L. McClelland
- 👤 Shigesato Iwasa
- 👤 Neal R. Butler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:58
CPC Classifications
G; G01; G01J; G01J5/00; G01J5/10; G01J5/28; G01J5/30; G01J5/34; H; H04; H04N; H04N23/00; H04N23/20; H04N23/23
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
115 words
A circuit for use in a thermal imaging system comprising: an infrared detector for detecting an infrared signal impinging thereon, an amplifier having an input to which said detector is connected, and an output, said amplifier responding to said detector detecting an infrared signal to provide an amplified electrical signal representing said infrared signal at its output, and a bias transistor associated with and connected to the input of said amplifier, said bias transistor being operated to act as a high impedance variable resistor and being used to bias both said detector and said amplifier, said bias transistor normally operating as to have an impedance in the range of 10 12 to 10 15 ohms.
Claim 2
Dependent Claim
115 words
A circuit for use in a thermal imaging system comprising: an infrared detector for detecting an infrared signal impinging thereon, an amplifier having an input to which said detector is connected, and an output, said amplifier responding to said detector detecting an infrared signal to provide an amplified electrical signal representing said infrared signal at its output, and a bias transistor associated with and connected to the input of said amplifier, said bias transistor being operated to act as a high impedance variable resistor and being used to bias both said detector and said amplifier, said bias transistor normally operating as to have an impedance in the range of 10 12 to 10 15 ohms.
Claim 3
Dependent Claim
39 words
The invention in accordance with claim 1 further comprising a transfer switch connected to the output of said amplifier, said transfer switch being operated to read out the amplified electrical signal representing said infrared signal impinging on said detector.
Claim 4
Dependent Claim
15 words
The invention in accordance with claim 2 wherein said detector is a temperature sensitive capacitor.
Claim 5
Dependent Claim
20 words
The invention in accordance with with claim 3 wherein said detector is a pyroelectric utilizing lithium tantalate as the dielectric.
Claim 6
Dependent Claim
172 words
A thermal imaging system upon which an infrared image is focused to be detected and to generate an electrical signal representing said image, said system comprising: an array of a plurality of infrared detectors upon which said infrared image is focused for detecting said infrared image impinging thereon, said array being organized in rows and columns of closely spaced detectors, an amplifier associated with each of said detectors, each said amplifier having an input to which its associated detector is connected and each amplifier having an output, each said amplifier responding to its associated detector detecting a portion of said infrared image to provide an amplified image at its output, and a bias transistor associated with and connected to the input of each of said amplifiers, said bias transistors being operated to act as variable high impedance resistors and being used to apply a bias voltage to said detectors and said amplifiers, said bias transistors operating as to have an impedance normally in the range of 10 12 to 10 15 ohms.
Claim 7
Dependent Claim
172 words
A thermal imaging system upon which an infrared image is focused to be detected and to generate an electrical signal representing said image, said system comprising: an array of a plurality of infrared detectors upon which said infrared image is focused for detecting said infrared image impinging thereon, said array being organized in rows and columns of closely spaced detectors, an amplifier associated with each of said detectors, each said amplifier having an input to which its associated detector is connected and each amplifier having an output, each said amplifier responding to its associated detector detecting a portion of said infrared image to provide an amplified image at its output, and a bias transistor associated with and connected to the input of each of said amplifiers, said bias transistors being operated to act as variable high impedance resistors and being used to apply a bias voltage to said detectors and said amplifiers, said bias transistors operating as to have an impedance normally in the range of 10 12 to 10 15 ohms.
Claim 8
Dependent Claim
46 words
The invention in accordance with claim 5 further comprising a transfer switch connected to the output of each of said amplifiers, said transfer switches being operated to read out the amplified electrical signal representing the portion of said infrared image impinging on each of said detectors.
Claim 9
Dependent Claim
14 words
The invention in accordance with claim 6 wherein said detectors are temperature sensitive capacitors.
Claim 10
Dependent Claim
19 words
The invention in accordance with claim 7 wherein said detectors are pyroelectric detectors utilizing lithium tantalate as the dielectric.
Claim 11
Dependent Claim
34 words
The invention in accordance with claim 5 further comprising means for monitoring a supply voltage supplied to said thermal imaging system and changing said bias voltage to compensate for changes in said supply voltage.
Claim 12
Dependent Claim
36 words
The invention in accordance with claim 9 wherein said monitoring means comprises an integrator which compares said supply voltage to a reference voltage and changes said bias voltage to compensate for changes in said supply voltage.
Claim 13
Dependent Claim
204 words
A thermal imaging system upon which an infrared image is focused to be detected and to generate an electrical signal representing said image, said system comprising: an array of a plurality of infrared detectors upon which said infrared image is focused for detecting said infrared image impinging thereon, said array being organized in rows and columns of closely spaced detectors, an amplifier associated with each of said detectors, each said amplifier having an input to which its associated detector is connected and each amplifier having an output, each said amplifier responding to its associated detector detecting a portion of said infrared image to provide an amplified electrical signal representing said portion of said infrared image at its output, a bias switch associated with and connected to the input of each of said amplifiers, said bias switches being periodically operated and applying a voltage to bias their associated amplifier and detector connected thereto to a predetermined bias level, and said switches then being disable to permit said detectors to detect said infrared image impinging on the array of detectors, and means for monitoring a supply voltage supplied to said thermal imaging system and changing said bias voltage to compensate for changes in said supply voltage.
Claim 14
Dependent Claim
204 words
A thermal imaging system upon which an infrared image is focused to be detected and to generate an electrical signal representing said image, said system comprising: an array of a plurality of infrared detectors upon which said infrared image is focused for detecting said infrared image impinging thereon, said array being organized in rows and columns of closely spaced detectors, an amplifier associated with each of said detectors, each said amplifier having an input to which its associated detector is connected and each amplifier having an output, each said amplifier responding to its associated detector detecting a portion of said infrared image to provide an amplified electrical signal representing said portion of said infrared image at its output, a bias switch associated with and connected to the input of each of said amplifiers, said bias switches being periodically operated and applying a voltage to bias their associated amplifier and detector connected thereto to a predetermined bias level, and said switches then being disable to permit said detectors to detect said infrared image impinging on the array of detectors, and means for monitoring a supply voltage supplied to said thermal imaging system and changing said bias voltage to compensate for changes in said supply voltage.
Claim 15
Dependent Claim
36 words
The invention in accordance with claim 11 wherein said monitoring means comprises an integrator which compares said supply voltage to a reference voltage and changes said bias voltage to compensate for changes in said supply voltage.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-05-15 | 1992-11-14 | 1993-05-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-15 | 1996-11-14 | 1997-05-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-15 | 2000-11-14 | 2001-05-16 | $7700.00 | Window Closed / Lapsed |