US3717399A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical interference filter for shifting color temperature
Assignee: Pilkington Group Ltd
•
Filing: 1971-03-18
•
Granted: 1973-02-20
•
Expires: 1991-03-18
Abstract
Abstract AN OPTICAL FILTER COMPRISES A GLASS CARRIER AND FOUR LAYERS DEPOSITED IN SUPERIMPOSED RELATIONSHIP ON THE CARRIER, THE LAYERS HAVING LOW AND HIGH REFRACTIVE INDICES IN ALTERNA- TION, AND THE FILTER BEING PARTICULARLY DESIGNED TO PRODUCE A DESIRED SHIFT IN COLOR TEMPERATURE.
Inventors
- 👤 H Taylor
- 👤 M Tuck
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 04:52
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/20; G02B5/28; G02B5/285; G02B5/286
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
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) | 1976-02-20 | 1976-08-21 | 1977-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-20 | 1980-08-21 | 1981-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-20 | 1984-08-21 | 1985-02-20 | $7700.00 | Window Closed / Lapsed |