Patent US4560239A successfully refreshed from Google Patents.
US4560239A
Expired / Lapsed
US
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Liquid crystal active light shield
Assignee: Individual
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Filing: 1984-02-29
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Granted: 1985-12-24
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Expires: 2004-02-29
Abstract
Abstract A device for protection against light of high and rapidly varying intensity which automatically and electronically maintains a constant intensity of transmitted light.
Inventors
- 👤 Amnon Katz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:54
CPC Classifications
A; A61; A61F; A61F9/00; A61F9/04; A61F9/06; A61F9/065; A61F9/067
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
121 words
In protective eyewear or transparent light shielding subject to varying intensity of incident light, apparatus comprising the combination of a layer of liquid crystal contained between two transparent electrodes and between two plane polarizers, a photocell which is placed behind said eyewear or shielding and measures only transmitted light, electronic circuitry to process the output of such photocell and produce a signal into said electrodes so as to reduce the transmission coefficient of lght through the combination of said polarziers and liquid crystal in proportion to the intensity of light incident thereon, and wherein the deviation of the signal produced by the photocell from a reference level is used as a negative feedback to maintain a constant intensity of transmitted light."
Claim 2
Dependent Claim
121 words
In protective eyewear or transparent light shielding subject to varying intensity of incident light, apparatus comprising the combination of a layer of liquid crystal contained between two transparent electrodes and between two plane polarizers, a photocell which is placed behind said eyewear or shielding and measures only transmitted light, electronic circuitry to process the output of such photocell and produce a signal into said electrodes so as to reduce the transmission coefficient of lght through the combination of said polarziers and liquid crystal in proportion to the intensity of light incident thereon, and wherein the deviation of the signal produced by the photocell from a reference level is used as a negative feedback to maintain a constant intensity of transmitted light."
Claim 3
Dependent Claim
15 words
Apparatus in accordance with claim 1 where the reference level is adjustable by the user.
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) | 1988-12-23 | 1989-06-24 | 1989-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-23 | 1993-06-24 | 1993-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-23 | 1997-06-24 | 1997-12-24 | $7700.00 | Window Closed / Lapsed |