US4854679A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Photographic system having front conversion lens
Assignee: Canon Inc
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Filing: 1987-11-18
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Granted: 1989-08-08
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Expires: 2007-11-18
Abstract
Abstract To minimize the size of a front conversion lens, an aperture stop is arranged on the object side of a master lens, and the front conversion lens is made releasably attachable.
Inventors
- 👤 Sadahiko Tsuji
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:45
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/02; G02B15/04; G02B15/06
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
76 words
A photographic lens system comprising: a master lens unit comprising a plurality of lenses and having a positive refractive power and a predetermined image forming plane; an aperture stop positioned on the object side of said master lens unit to determine an F-number; a conversion lens unit attachable and detachable in front of said aperture stop for changing the focal length without changing the position of said predetermined image forming plane of said master lens unit.
Claim 2
Dependent Claim
76 words
A photographic lens system comprising: a master lens unit comprising a plurality of lenses and having a positive refractive power and a predetermined image forming plane; an aperture stop positioned on the object side of said master lens unit to determine an F-number; a conversion lens unit attachable and detachable in front of said aperture stop for changing the focal length without changing the position of said predetermined image forming plane of said master lens unit.
Claim 3
Dependent Claim
25 words
A photographic lens system according to claim 1, further comprising one meniscus lens of forward convexity positioned on the object side of said aperture stop.
Claim 4
Dependent Claim
37 words
A photographic lens system according to claim 2, satisfying the following condition: |f.sub.1 |>10f.sub.T where f 1 is the focal length of said meniscus lens, and f T is the focal length of the entire lens system.
Claim 5
Dependent Claim
24 words
A photographic lens system according to claim 2, wherein said meniscus lens is positioned in between said aperture stop and said conversion lens unit.
Claim 6
Dependent Claim
18 words
A photographic lens system according to claim 2, wherein said meniscus lens is positioned in a front-most position.
Claim 7
Dependent Claim
90 words
A camera comprising: a master lens unit comprising a plurality of lenses having a positive refractive power and a predetermined image forming plane; an aperture stop positioned on the object side of said master lens unit to determine an F-number; a conversion lens unit attachable and detachable in front of said aperture stop for changing the focal length without changing the position of said predetermined image forming plane of said master lens unit; and housing means for housing said master lens unit, said aperture stop and said conversion lens unit.
Claim 8
Dependent Claim
90 words
A camera comprising: a master lens unit comprising a plurality of lenses having a positive refractive power and a predetermined image forming plane; an aperture stop positioned on the object side of said master lens unit to determine an F-number; a conversion lens unit attachable and detachable in front of said aperture stop for changing the focal length without changing the position of said predetermined image forming plane of said master lens unit; and housing means for housing said master lens unit, said aperture stop and said conversion lens unit.
Claim 9
Dependent Claim
23 words
A camera according to claim 6, further comprising one meniscus lens of forward convexity positioned on the object side of said aperture stop.
Claim 10
Dependent Claim
35 words
A camera according to claim 7, satisfying the following condition: |f.sub.1 |>10F.sub.T where f 1 is the focal length of said meniscus lens, and f T is the focal length of the entire lens system.
Claim 11
Dependent Claim
22 words
A camera according to claim 7, wherein said meniscus lens is positioned in between said aperture stop and said conversion lens unit.
Claim 12
Dependent Claim
16 words
A camera according to claim 7, wherein said meniscus lens is positioned in a front-most position.
References Cited (Backward Citations)
US1169731A
Cited
US2829559A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-08-07 | 1993-02-06 | 1993-08-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-07 | 1997-02-06 | 1997-08-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-07 | 2001-02-06 | 2001-08-08 | $7700.00 | Window Closed / Lapsed |