US3797915A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Binocular rangefinder-viewfinder with fresnel optics
Assignee: Polaroid Corp
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Filing: 1972-09-25
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Granted: 1974-03-19
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Expires: 1992-09-25
Abstract
Abstract This disclosure depicts a number of novel Fresnel imaging structures incorporated in photographic rangefinding and viewfinding means. Each Fresnel imaging structure is both focal and afocal for simultaneously providing a view of a selected field and for projecting into the field a virtual image of a rangefinding or framing reticle.
Inventors
- 👤 E Land
- 👤 P Norris
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:38
CPC Classifications
G; G03; G03B; G03B13/00; G03B13/02
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
50 words
A partially reflective catoptric Fresnel lens comprising a transparent plate having confocal positive and negative Fresnel image-forming front and rear surfaces with opposite and equal imaging effect such that in transmission said plate has substantially zero dioptric power, said rear surface of said plate having thereon a partially reflective coating.
Claim 2
Dependent Claim
50 words
A partially reflective catoptric Fresnel lens comprising a transparent plate having confocal positive and negative Fresnel image-forming front and rear surfaces with opposite and equal imaging effect such that in transmission said plate has substantially zero dioptric power, said rear surface of said plate having thereon a partially reflective coating.
Claim 3
Dependent Claim
41 words
A Fresnel lens comprising: a dioptric first pattern of Fresnel image-forming elements having a predetermined power; and a catoptric second pattern of Fresnel image-forming elements, of different power than said first pattern of elements, intercalated with said first pattern of elements.
Claim 4
Dependent Claim
41 words
A Fresnel lens comprising: a dioptric first pattern of Fresnel image-forming elements having a predetermined power; and a catoptric second pattern of Fresnel image-forming elements, of different power than said first pattern of elements, intercalated with said first pattern of elements.
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) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |