US5087988A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Zoom lens
Assignee: Canon Inc
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Filing: 1991-07-30
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Granted: 1992-02-11
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Expires: 2011-07-30
Abstract
Abstract A zoom lens of simple structure is disclosed comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of positive refractive power and a third lens unit of negative refractive refractive power, wherein these three lens units each are constructed from a single block, and zooming from the wide-angle end to the telephoto end is performed by moving the first and third lens units axially toward the object side independent of each other.
Inventors
- 👤 Hiroki Nakayama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 20:53
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/143; G02B15/1431; G02B15/143103
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
78 words
A zoom lens comprising, from an object side, a first lens unit of positive refractive power, a second lens unit of positive refractive power and a third lens unit of negative refractive power, wherein each of said first, second and third lens units is constructed from a single block, and zooming from a wide-angle end to a telephoto end is performed by moving said first and third lens units axially toward the object side independent of each other.
Claim 2
Dependent Claim
78 words
A zoom lens comprising, from an object side, a first lens unit of positive refractive power, a second lens unit of positive refractive power and a third lens unit of negative refractive power, wherein each of said first, second and third lens units is constructed from a single block, and zooming from a wide-angle end to a telephoto end is performed by moving said first and third lens units axially toward the object side independent of each other.
Claim 3
Dependent Claim
55 words
A zoom lens according to claim 1, wherein said second lens unit is moved axially toward the object side in such a manner as to increase its air separation from said first lens unit and to decrease its air separation to said third lens unit when zooming from the wide-angle end to the telephoto end.
Claim 4
Dependent Claim
28 words
A zoom lens according to claim 2, wherein an object-side lens surface of the single block serving as said second lens unit is concave toward the object side.
Claim 5
Dependent Claim
21 words
A zoom lens according to claim 1, wherein each of said first, second and third lens units is a single lens.
Claim 6
Dependent Claim
23 words
A zoom lens according to claim 4, satisfying the following condition: N3<1.7 where N3 is the refractive index of said third lens unit.
Claim 7
Dependent Claim
23 words
A zoom lens according to claim 4, satisfying the following condition: 50<ν1 where ν1 is the Abbe number of said first lens unit.
Claim 8
Dependent Claim
45 words
A zoom lens according to claim 1, wherein said second lens unit is composed of a negative lens and a positive lens cemented together, satisfying the following conditions: N2N<7 1.6<N2P where N2N and N2P are the refractive indices of said negative and positive lenses respectively.
Claim 9
Dependent Claim
12 words
A zoom lens according to claim 7, satisfying the following condition: N2N<N2P
Claim 10
Dependent Claim
28 words
A zoom lens according to claim 8, satisfying the following conditions: ν2N<50 40<2P where ν2N and ν2P are the Abbe numbers of said negative and positive lenses respectively.
Claim 11
Dependent Claim
12 words
A zoom lens according to claim 9, satisfying the following condition: ν2N<ν2P
Claim 12
Dependent Claim
93 words
A zoom lens according to claim 1, wherein letting image magnifications of the i-th lens unit, when counted from the object side, in the wide-angle end and the telephoto end be denoted by βiW and βiT respectively, putting Zi=βit/βiW, and letting an amount of movement of the i-th lens unit as zooming from the wide-angle end to the telephoto end be denoted by Δi and a difference between focal lengths in the wide-angle and the telephoto end of the entire lens system of Δf, the following conditions are satisfied: Z2<Z3 0.4<{Δ2/Δf}<1.0 1.1<{Δ3/Δf}<1.7 1.1<Δ1/Δ2<1.8
References Cited (Backward Citations)
US4708444A
Cited
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1995-02-10 | 1995-08-12 | 1996-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-02-10 | 1999-08-12 | 2000-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-02-10 | 2003-08-12 | 2004-02-11 | $7700.00 | Window Closed / Lapsed |