US3781089A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Neutral density filter element with reduced surface reflection
Assignee: Eastman Kodak Co
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Filing: 1971-08-02
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Granted: 1973-12-25
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Expires: 1991-08-02
Abstract
Abstract A neutral density filter element for use with photographic apparatus is formed by depositing alternate layers of a metal or metal alloy and a dielectric on a transparent substrate, to a predetermined optical density or reflectivity respectively. The initial and final layers are of the metal or metal alloy. The dielectric layer has a lower index of refraction than the metal or metal alloy layer. In the preferred embodiment Inconel is used as the metal alloy layer and silicon monoxide as the dielectric layer.
Inventors
- 👤 R Fay
- 👤 J Cicotta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 05:42
CPC Classifications
C; C23; C23C; C23C14/00; C23C14/22; C23C14/54; C23C14/542; C23C14/545; C23C14/547; G; G02; G02B; G02B5/00; G02B5/20; G02B5/205
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
24 words
A neutral density filter element as in claim 1, wherein said metal alloy comprises 79.5 percent nickel, 13 percent chromium and 6.5 percent iron.
Claim 2
Dependent Claim
16 words
A neutral density filter element as in claim 1, wherein said dielectric material is silicon monoxide.
Claim 3
Dependent Claim
138 words
A neutral density filter element having a predetermined optical density; said filter element comprising a transparent substrate and a multilayer coating deposited thereon, said multilayer coating comprising alternate layers of a metal alloy and silicon monoxide, said metal alloy comprising 79.5 percent nickel, 13 percent chromium and 6.5 percent iron; said layer immediately adjacent to said substrate being a layer of said metal alloy; the total number of layers being at least five; there being one more layer of said metal alloy than of said silicon monoxide; the total thickness of said layers of metal alloy being selected to reduce the transmission of said filter element to said predetermined optical density and the thickness of each layer of said silicon monoxide being selected to reduce the reflectance of the preceding layers of said filter element to a minimum.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-24 | 1977-06-25 | 1977-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-24 | 1981-06-25 | 1981-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-24 | 1985-06-25 | 1985-12-25 | $7700.00 | Window Closed / Lapsed |