US4757336A
Expired / Lapsed
US
⏱️ 0.0 years remaining
View finder of variable magnification
Assignee: Canon Inc
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Filing: 1986-01-21
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Granted: 1988-07-12
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Expires: 2006-01-21
Abstract
Abstract A view finder having, from front to rear, a first lens unit of negative power, a second lens unit of positive power and a third lens unit of negative power, the second lens unit being moved axially forward as the magnification varies from the smallest to the largest value, while the first lens unit is moved to compensate for the diopter shift resulting from the variation of the magnification.
Inventors
- 👤 Hiroki Nakayama
- 👤 Yasuhisa Sato
- 👤 Kouji Oizumi
- 👤 Yasuyuki Yamada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 20:08
CPC Classifications
G; G02; G02B; G02B25/00; G02B25/001; G02B15/00; G02B15/14; G02B15/143; G02B15/1435; G02B15/143503; G02B15/16; G02B15/177; G02B23/00; G02B23/14; G02B23/145
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
63 words
A finder comprising, from front to rear, a first lens unit of negative power, a second lens unit of positive power and a third lens unit of negative power, so as to vary a magnification thereof while maintaining a constant diopter, said second lens unit is made to move axially forward, and, at the same time, another lens unit is made to move.
Claim 2
Dependent Claim
63 words
A finder comprising, from front to rear, a first lens unit of negative power, a second lens unit of positive power and a third lens unit of negative power, so as to vary a magnification thereof while maintaining a constant diopter, said second lens unit is made to move axially forward, and, at the same time, another lens unit is made to move.
Claim 3
Dependent Claim
16 words
A finder according to claim 1, wherein said another lens unit is said first lens unit.
Claim 4
Dependent Claim
55 words
A finder according to claim 2, satisfying the following conditions: 0.35<f.sub.1 /f.sub.3 <3.0 -4.0<β.sub.2 <-0.5 where f 1 and f 2 are focal lengths of said first and said third lens units, respectively, and β 2 is the paraxial lateral magnification of said second lens unit in the entire range of variation of the magnification.
Claim 5
Dependent Claim
45 words
A finder according to claim 1, wherein said first lens unit includes a negative lens whose rear lens surface has a stronger curvature than that of a front surface thereof and is concave toward the rear, and said second lens unit includes a bi-convex lens.
Claim 6
Dependent Claim
64 words
A finder comprising, from an object side, a first lens unit having a negative refractive power, an intermediate lens unit having a positive refractive power, and an ocular lens unit having a negative refractive power, wherein said first lens unit and said intermediate lens unit are simultaneously but independently moved so as to vary a magnification of the finder while maintaining a constant diopter.
Claim 7
Dependent Claim
64 words
A finder comprising, from an object side, a first lens unit having a negative refractive power, an intermediate lens unit having a positive refractive power, and an ocular lens unit having a negative refractive power, wherein said first lens unit and said intermediate lens unit are simultaneously but independently moved so as to vary a magnification of the finder while maintaining a constant diopter.
Claim 8
Dependent Claim
15 words
A finder according to claim 5, satisfying the following conditions: 0.35<f.sub.1 /f.sub.3 <3.0 -4.0<β.sub.2 <-0.5,
Claim 9
Dependent Claim
44 words
where f 1 and f 3 are focal lengths of said first lens unit and said ocular lens unit, respectively, and β 2 is the paraxial lateral magnification of said intermediate lens unit in a entire range of variation of magnification of the finder.
Claim 10
Dependent Claim
44 words
where f 1 and f 3 are focal lengths of said first lens unit and said ocular lens unit, respectively, and β 2 is the paraxial lateral magnification of said intermediate lens unit in a entire range of variation of magnification of the finder.
Claim 11
Dependent Claim
45 words
A finder according to claim 5, wherein said first lens unit includes a negative lens whose rear lens surface has a stronger curvature than that of a front surface thereof and is concave toward the rear, and said intermediate lens unit includes a bi-convex lens.
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) | 1991-07-12 | 1992-01-11 | 1992-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-07-12 | 1996-01-11 | 1996-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-07-12 | 2000-01-11 | 2000-07-12 | $7700.00 | Window Closed / Lapsed |