US5198673A
Expired / Lapsed
US
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Radiation image detector with optical gain selenium photosensors
Assignee: General Electric Co
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Filing: 1992-01-23
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Granted: 1993-03-30
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Expires: 2012-01-23
Abstract
Abstract A large area radiation imager having a scintillator, an amorphous selenium photosensor, and a non-linear high voltage protective device employs a selected biasing voltage between about 100 volts and 1000 volts at the selenium photosensor to cause the photosensor to exhibit avalanche multiplication. The photosensor has an area not less than about 100 square centimeters. The amorphous selenium is doped slightly with arsenic or arsenic and tellurium. The device is advantageously coupled to a data read and reset circuit to selectively read charge generated in pixels of the photosensor. The read and data circuit is protected from an overvoltage condition by the non linear high voltage protective device, such as a protective thin film transistor or a two terminal protective device. The protective TFT is structured to have a relatively thick gate dielectric layer, which thickness is selected to cause the protective TFT to have a threshold voltage corresponding to a desired protective voltage.
Inventors
- 👤 Henri M. Rougeot
- 👤 George E. Possin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 22:43
CPC Classifications
H; H10; H10F; H10F39/00; H10F39/10; H10F39/12; H10F39/18; H10F39/189; H10F39/1898
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
115 words
A radiation imaging device comprising: a scintillator; a large area photosensor optically coupled to said scintillator and comprising an amorphous selenium photosensitive material exhibiting avalanche multiplication gain when a selected high biasing voltage is applied to said photosensor; a data read and reset circuit electrically coupled to said large area photosensor to selectively read the charge generated in said photosensor in response to incident light; and a protective thin film transistor (TFT) coupled to said data read and reset circuit to provide overvoltage protection from said selected high biasing voltage, said protective TFT comprising a gate dielectric layer having a thickness selected to cause said protective TFT to become conductive above a selected protective voltage.
Claim 2
Dependent Claim
115 words
A radiation imaging device comprising: a scintillator; a large area photosensor optically coupled to said scintillator and comprising an amorphous selenium photosensitive material exhibiting avalanche multiplication gain when a selected high biasing voltage is applied to said photosensor; a data read and reset circuit electrically coupled to said large area photosensor to selectively read the charge generated in said photosensor in response to incident light; and a protective thin film transistor (TFT) coupled to said data read and reset circuit to provide overvoltage protection from said selected high biasing voltage, said protective TFT comprising a gate dielectric layer having a thickness selected to cause said protective TFT to become conductive above a selected protective voltage.
Claim 3
Dependent Claim
19 words
The device of claim 1 wherein said selected high biasing voltage is between about 100 volts and 1000 volts.
Claim 4
Dependent Claim
21 words
The device of claim 1 wherein said large area photosensor has an area not smaller than about 100 cm 2 .
Claim 5
Dependent Claim
69 words
The device of claim 1 wherein said large area photosensor comprises: a substantially optically transparent electrically conductive electrode disposed adjacent to said scintillator; a layer of amorphous selenium disposed in electrical contact with the transparent electrode; a blocking barrier to substantially prevent the passage of holes therethrough disposed along the surface of the selenium layer opposite said transparent electrode; and a contact electrode electrically coupled to said blocking barrier.
Claim 6
Dependent Claim
16 words
The device of claim 4 wherein said optically transparent electrically conductive electrode comprises indium tin oxide.
Claim 7
Dependent Claim
18 words
The device of claim 4 wherein the amorphous selenium layer is doped with arsenic or arsenic and tellurium.
Claim 8
Dependent Claim
12 words
The device of claim 4 wherein said blocking barrier comprises cerium oxide.
Claim 9
Dependent Claim
21 words
The device of claim 7 wherein said cerium oxide blocking barrier has a thickness between about 50 Å and 200 Å.
Claim 10
Dependent Claim
20 words
The device of claim 4 wherein the amorphous selenium layer has a thickness between about 0.5 μm to 10 μm.
Claim 11
Dependent Claim
23 words
The device of claim 4 wherein said contact electrode comprises one of the group consisting of molybdenum, titanium, tungsten, chromium, nickel, and gold.
Claim 12
Dependent Claim
18 words
The device of claim 1 wherein the selected thickness of said gate dielectric layer is about 1 micron.
Claim 13
Dependent Claim
27 words
The device of claim 1 wherein said scintillator comprises one of the group consisting of cesium iodide, cadmium tungstate, zinc cadmium sulfide, yttrium oxisulfide, and gadolinium oxisulfide.
Claim 14
Dependent Claim
21 words
The device of claim 1 wherein said large area photosensor has an area not less than about 100 cm 2 .
Claim 15
Dependent Claim
150 words
An x-ray imaging device comprising: a scintillator; a large area photosensor comprising a plurality of photosensor pixel elements arranged in an array, each of said photosensor pixel elements coupled to said scintillator and comprising an amorphous selenium photosensitive material exhibiting avalanche multiplication gain when polarized at a selected high biasing voltage; a data read and reset circuit electrically coupled to each of said photosensor pixel elements to selectively read charge generated in respective pixel elements in response to light; and a plurality of protective thin film transistors (TFTs) electrically coupled to said data read and reset circuit to control said selected biasing voltage across each respective photosensor pixel element and to provide overvoltage protection to said data read and reset circuit, each of said protective TFTs comprising a gate dielectric layer having a thickness selected to cause each respective protective TFT to become conductive above a respective selected protective voltage.
Claim 16
Dependent Claim
150 words
An x-ray imaging device comprising: a scintillator; a large area photosensor comprising a plurality of photosensor pixel elements arranged in an array, each of said photosensor pixel elements coupled to said scintillator and comprising an amorphous selenium photosensitive material exhibiting avalanche multiplication gain when polarized at a selected high biasing voltage; a data read and reset circuit electrically coupled to each of said photosensor pixel elements to selectively read charge generated in respective pixel elements in response to light; and a plurality of protective thin film transistors (TFTs) electrically coupled to said data read and reset circuit to control said selected biasing voltage across each respective photosensor pixel element and to provide overvoltage protection to said data read and reset circuit, each of said protective TFTs comprising a gate dielectric layer having a thickness selected to cause each respective protective TFT to become conductive above a respective selected protective voltage.
Claim 17
Dependent Claim
19 words
The device of claim 14 wherein said selected high biasing voltage is between about 100 volts and 1000 volts.
Claim 18
Dependent Claim
21 words
The device of claim 14 wherein said large area photosensor has an area not smaller than about 100 cm 2 .
Claim 19
Dependent Claim
64 words
The device of claim 14 wherein each of said photosensor pixel elements further comprises a transparent electrode disposed adjacent to said scintillator, a layer of said amorphous selenium photosensitive material disposed adjacent to said transparent electrode, a blocking barrier layer to prevent passage of holes therethrough disposed adjacent to said photosensitive material layer, and a contact electrode disposed adjacent to said blocking barrier layer.
Claim 20
Dependent Claim
42 words
The device of claim 14 wherein said data read and reset circuit comprises a plurality of rows and columns of low voltage scan and data lines respectively, each of said pixel elements being coupled to one scan line and one data line.
Claim 21
Dependent Claim
43 words
The device of claim 18 wherein each of said protective thin film transistors is coupled to a respective one of said pixel elements and is conductive above a selected protective voltage to prevent an overvoltage condition on said data read and reset circuit.
Claim 22
Dependent Claim
14 words
The device of claim 19 wherein said selected protective voltage is about 10 volts.
Claim 23
Dependent Claim
17 words
The device of claim 20 wherein the thickness of said gate dielectric layer is about 1 micron.
Claim 24
Dependent Claim
24 words
The device of claim 21 wherein each of said pixels has a cross-sectional area between about 0.2 mm 2 and 5 mm 2 .
Claim 25
Dependent Claim
28 words
The device of claim 14 wherein said scintillator comprises a plurality of scintillator elements arranged in an array corresponding to the pattern of said photosensor pixel element array.
Claim 26
Dependent Claim
29 words
The device of claim 23 wherein each of said scintillator elements has substantially the same cross-sectional area as that of the respective pixel elements to which it is coupled.
Claim 27
Dependent Claim
21 words
The device of claim 14 wherein said large area photosensor has an area not less than about 100 cm 2 .
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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) | 1996-03-29 | 1996-09-28 | 1997-03-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-03-29 | 2000-09-28 | 2001-03-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-03-29 | 2004-09-28 | 2005-03-30 | $7700.00 | Window Closed / Lapsed |