Patent US3748021A successfully refreshed from Google Patents.
US3748021A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reverse telephoto lens for near-distance photography
Assignee: Canon Inc
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Filing: 1971-04-05
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Granted: 1973-07-24
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Expires: 1991-04-05
Abstract
Abstract In the disclosed telephoto lens a front divergent lens group passes light to a rear convergent lens group. The front divergent lens group forms a variable air space in which light from a point on an object on the optical axis travels almost parallel to the optical axis. The air space is varied so that when the lens is focused at a nearby object, the air space is reduced almost proportional to the advanced length of the whole lens. This avoids deterioration of close-up images.
Inventors
- 👤 A Tajima
- 👤 K Momiyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:14
CPC Classifications
G; G02; G02B; G02B13/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
97 words
A lens system, comprising reverse telephoto lens means having a front divergent lens group and a rear convergent lens group, said lens means being focusable by movement of the lens means as a whole, aberration correcting means in said lens means for correcting for aberration over a wide range of focusing positions of said lens means, said aberration correcting means including a plurality of movable elements in the front lens group forming a variable air space and directing light flux from an object along an optical axis of said lens means substantially parallel to the optical axis.
Claim 2
Dependent Claim
97 words
A lens system, comprising reverse telephoto lens means having a front divergent lens group and a rear convergent lens group, said lens means being focusable by movement of the lens means as a whole, aberration correcting means in said lens means for correcting for aberration over a wide range of focusing positions of said lens means, said aberration correcting means including a plurality of movable elements in the front lens group forming a variable air space and directing light flux from an object along an optical axis of said lens means substantially parallel to the optical axis.
Claim 3
Dependent Claim
27 words
A system as in claim 1, said aberration correction means in said lens means correcting for aberration when the lens means is focused on a nearby object.
Claim 4
Dependent Claim
43 words
A lens system as in claim 1, wherein when said lens means is focused at a nearby object said movable elements in said aberration correction reduce the air space substantially proportional to the degree to which said lens means is shifted for focusing.
Claim 5
Dependent Claim
27 words
A sysTem as in claim 3, said aberration correction means in said lens means correcting for aberration when the lens means is focused on a nearby object.
Claim 6
Dependent Claim
65 words
A system as in claim 1, wherein said front divergent lens group includes first negative lens means and positive lens means and second negative lens means arranged in sequence, said positive lens means and said second negative lens means each including one of said movable elements so as to form the variable air space between said positive lens means and said second negative lens means.
Claim 7
Dependent Claim
27 words
A system as in claim 5, said aberration correction means in said lens means correcting for aberration when the lens means is focused on a nearby object.
Claim 8
Dependent Claim
42 words
A system as in claim 5, wherein when said lens means is focused at the nearby object said movable elements in said aberration correction reduce the air space substantially proportional to the degree to which said lens means is shifted for focusing.
Claim 9
Dependent Claim
27 words
A system as in claim 7, said aberration correction means in said lens means correcting for aberration when the lens means is focused on a nearby object.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-23 | 1977-01-22 | 1977-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-23 | 1981-01-22 | 1981-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-23 | 1985-01-22 | 1985-07-24 | $7700.00 | Window Closed / Lapsed |