US3896311A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pyroelectric motion and temperature sensitive infrared detector with conductive fingers
Assignee: 3M Co
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Filing: 1974-01-02
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Granted: 1975-07-22
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Expires: 1994-01-02
Abstract
Abstract A passive motion and temperature sensitive infrared radiation detector includes a housing with a front wall having a plurality of laterally spaced apart apertures that are filled with a radiation transmissive material. The housing back wall is formed of a three layer construction with outer and inner conductive layers in surface-to-surface contact with and separated by a layer of poled, pyroelectric material. In a preferred embodiment, the outer conductive layer is electrically grounded and the inner conductive layer is etched to define two interdigitated, electrically unconnected sets of conductive fingers. The sets of conductive fingers are heated when exposed to infrared radiation and, in turn, heat portions of the pyroelectric layer. As a result, electrostatic charges are developed on the heated pyroelectric portions and appear as voltage potentials on the heated finger sets. Electronic circuitry is associated therewith for sensing the voltage potentials and for triggering an alarm when a certain pattern of voltage potentials are consecutively developed on both sets of fingers. In a modified embodiment, the housing back wall is arranged with an electrically grounded, conductive inner layer and an outer layer containing interdigitated finger sets.
Inventors
- 👤 Allen L Taylor
- 👤 Francis J Mcfadden
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:31
CPC Classifications
G; G01; G01J; G01J5/00; G01J5/10; G01J5/34; G08; G08B; G08B13/00; G08B13/18; G08B13/189; G08B13/19; G08B13/191
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
230 words
An infrared motion and temperature sensitive detector for detecting a moving source of infrared radiation and comprising: a front portion having a plurality of laterally spaced apart radiation transmissive apertures; a back portion spaced from said front portion and formed of a multi-layer construction that includes: inner and outer conductive layers, at least one of which is formed to provide one or more electrically connected sets of fingers that are substantially parallel to the apertures of said front portion, one of said conductive layers is electrically grounded, and said inner conductive layer has areas that are simultaneously exposed to and heated by radiation that emanates from said moving source and passes through the apertures of said front portion and has other areas that are shielded from such radiation; and a layer of poled, pyroelectric material interposed between and in surface-to-surface contact with such conductive layers and having areas that are heated by the heated areas of said inner conductive layer to result in the development of electrostatic charges on said heated pyroelectric areas and on at least one of said sets of conductive fingers in contact with said heated pyroelectric areas; and electronic circuitry for sensing the potential on said one of said sets of fingers and for triggering an alarm only when a certain pattern of voltage potentials are developed on said one set within one predetermined time period.
Claim 2
Dependent Claim
230 words
An infrared motion and temperature sensitive detector for detecting a moving source of infrared radiation and comprising: a front portion having a plurality of laterally spaced apart radiation transmissive apertures; a back portion spaced from said front portion and formed of a multi-layer construction that includes: inner and outer conductive layers, at least one of which is formed to provide one or more electrically connected sets of fingers that are substantially parallel to the apertures of said front portion, one of said conductive layers is electrically grounded, and said inner conductive layer has areas that are simultaneously exposed to and heated by radiation that emanates from said moving source and passes through the apertures of said front portion and has other areas that are shielded from such radiation; and a layer of poled, pyroelectric material interposed between and in surface-to-surface contact with such conductive layers and having areas that are heated by the heated areas of said inner conductive layer to result in the development of electrostatic charges on said heated pyroelectric areas and on at least one of said sets of conductive fingers in contact with said heated pyroelectric areas; and electronic circuitry for sensing the potential on said one of said sets of fingers and for triggering an alarm only when a certain pattern of voltage potentials are developed on said one set within one predetermined time period.
Claim 3
Dependent Claim
26 words
A detector as recited in claim 1 wherein said finger formed conductive layer is the inner layer and said grounded conductive layer is the outer layer.
Claim 4
Dependent Claim
26 words
A detector as recited in claim 1 wherein said finger formed conductive layer is the outer layer and said grounded conductive layer is the inner layer.
Claim 5
Dependent Claim
46 words
A detector as recited in claim 1 wherein the alarm of said electronic circuitry is triggered upon the development of several consecutive voltage potentials on said one of said sets of fingers, each such potential occurring within another predetermined time period following the immediately preCeding potential.
Claim 6
Dependent Claim
43 words
A detector as recited in claim 1 wherein said apertures are elongated and the spacing between the front and back portions is approximately four times as great as the width of the apertures and the individual fingers of said one of said sets.
Claim 7
Dependent Claim
21 words
A detector as recited in claim 1 wherein said finger formed conductive layer provides two electrically unconnected sets of interdigitated fingers.
Claim 8
Dependent Claim
40 words
A detector as recited in claim 6 wherein each of said sets of fingers is electrically connected to a differential amplifier to prevent actuation of the detector alarm when the voltage potentials of both sets of pyroelectric fingers are equal.
Claim 9
Dependent Claim
242 words
An infrared motion and temperature sensitive detector for detecting a moving source of infrared radiation and comprising: a housing formed from a non-radiation transmissive material, which housing includes: a front portion having a plurality of laterally spaced apart radiation transmissive apertures; a back portion spaced from said front portion and formed of a multi-layer construction that includes: inner and outer conductive layers, at least one of which is formed to provide one or more electrically connected sets of fingers that are substantially parallel to the apertures of said front portion, one of said conductive layers is electrically grounded, and said inner conductive layer has areas that are simultaneously exposed to and heated by radiation that emanates from said moving source and passes through the apertures of said front portion and has other areas that are shielded from such radiation; and a layer of poled, pyroelectric material interposed between and in surface-to-surface contact with said conductive layers and having areas that are heated by the heated areas of said inner conductive layer to result in the development of electrostatic charges on said heated pyroelectric areas and on at least one of said sets of conductive fingers in contact with said heated pyroelectric areas; and electronic circuitry for sensing the potential developed on said one of said sets of fingers and for triggering an alarm only when a certain pattern of voltage potentials are developed on said one set within a predetermined timer period.
Claim 10
Dependent Claim
242 words
An infrared motion and temperature sensitive detector for detecting a moving source of infrared radiation and comprising: a housing formed from a non-radiation transmissive material, which housing includes: a front portion having a plurality of laterally spaced apart radiation transmissive apertures; a back portion spaced from said front portion and formed of a multi-layer construction that includes: inner and outer conductive layers, at least one of which is formed to provide one or more electrically connected sets of fingers that are substantially parallel to the apertures of said front portion, one of said conductive layers is electrically grounded, and said inner conductive layer has areas that are simultaneously exposed to and heated by radiation that emanates from said moving source and passes through the apertures of said front portion and has other areas that are shielded from such radiation; and a layer of poled, pyroelectric material interposed between and in surface-to-surface contact with said conductive layers and having areas that are heated by the heated areas of said inner conductive layer to result in the development of electrostatic charges on said heated pyroelectric areas and on at least one of said sets of conductive fingers in contact with said heated pyroelectric areas; and electronic circuitry for sensing the potential developed on said one of said sets of fingers and for triggering an alarm only when a certain pattern of voltage potentials are developed on said one set within a predetermined timer period.
Claim 11
Dependent Claim
22 words
A detector as recited in claim 4 wherein at least three of said voltage potentials occur within said one predetermined time period.
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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) | 1978-07-21 | 1979-01-20 | 1979-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-21 | 1983-01-20 | 1983-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-21 | 1987-01-20 | 1987-07-22 | $7700.00 | Window Closed / Lapsed |