US5321552A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rear-focus-type zoom lens equipped with index-distribution-type lens
Assignee: Canon Inc
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Filing: 1992-06-16
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Granted: 1994-06-14
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Expires: 2012-06-16
Abstract
Abstract A zoom lens having four groups and wherein at least one of the four groups is equipped with an index distribution type lens. A first lens group has a positive refracting power; a second group has a negative refracting power; a third lens group has a positive refracting power; and a fourth lens group has a positive refracting power. The first through fourth lens groups are arranged in this order from the object side, and the second group is moved to perform zooming while the fourth lens group is moved to compensate for image plane fluctuation which is incident to the zooming and also to perform focusing.
Inventors
- 👤 Akihisa Horiuchi
- 👤 Hiroyuki Hamano
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 20:09
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/16; G02B15/163; G02B15/167; G02B15/173; G02B15/144; G02B15/1441; G02B15/144113; G02B3/00; G02B3/0087
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
105 words
A zoom lens comprising: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power, said first through fourth lens groups being arranged in this order from the object side, wherein said second lens group is moved to effect zooming, said fourth lens group is moved so as to compensate for image plane fluctuations which are incident to zooming and also to perform focusing, and at least one of the four lens groups is equipped with an index-distribution-type lens.
Claim 2
Dependent Claim
105 words
A zoom lens comprising: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power, said first through fourth lens groups being arranged in this order from the object side, wherein said second lens group is moved to effect zooming, said fourth lens group is moved so as to compensate for image plane fluctuations which are incident to zooming and also to perform focusing, and at least one of the four lens groups is equipped with an index-distribution-type lens.
Claim 3
Dependent Claim
27 words
A zoom lens according to claim 1, wherein said index-distribution-type lens has a refractive index which varies gradually with an increase in distance from an optical axis.
Claim 4
Dependent Claim
50 words
A zoom lens according to claim 1, wherein said zoom lens satisfies the following conditional expressions: 0.7<|f2/fw|<0.9 0.58<f3/f4<1 where i varies between 1 and 4 and fi represents the focal length of the i-th lens group and fw represents the focal length of the entire system at a wide-angle end.
Claim 5
Dependent Claim
85 words
A zoom lens according to claim 1, wherein said first lens group has an index-distribution-type lens and satisfies the following conditional expressions: 0.53<fT/(N.sub.od.sup.2 ·f1)<0.65 ##EQU4## where N.sub.od and N.sub.og represent d-line and g-line refractive indexes on an optical axis, respectively; N.sub.1d and N.sub.1g represent d-line and g-line refractive indexes at positions corresponding to 75% of an effective lens diameter, respectively; and f1 and fT represent the focal length at a telephoto end of said first lens group and that of the zoom lens system, respectively.
Claim 6
Dependent Claim
93 words
A zoom lens according to claim 1, wherein said third lens group includes an index-distribution-type lens and satisfies the following conditional expressions: 0.65<γ.sub.3,1 /f3<0.98 0.002<ΔN.sub.7d /f3<0.006 where γ 3 ,1 represents the radius of curvature of the first lens surface of said third lens group; f3 represents the focal length of said third lens group; and ΔN 7d represents the difference in d-line refractive index between the section of the index-distribution-type lens of said third lens group where the refractive index is maximum and the section thereof where the refractive index is minimum.
Claim 7
Dependent Claim
86 words
A zoom lens according to claim 1, wherein said fourth lens group includes an index-distribution-type lens and satisfies the following conditional expressions: 0.04<fw/(N.sub.od.sup.2 ·f4)<0.31 ##EQU5## where f4 represents the focal length of said fourth lens group; fw represents the focal length at the wide-angle end of the zoom lens system; N.sub.od and N.sub.og represent d-line and g-line refractive indexes on an optical axis, respectively; and N.sub.1d and N.sub.1g represent the d-line and g-line refractive indexes at positions corresponding to 75% of the effective lens diameter, respectively.
Claim 8
Dependent Claim
125 words
A zoom lens comprising: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; a fourth lens group having a positive refracting power; and a stop located between said second lens group and said third lens group, and wherein said first through fourth lens groups are arranged along the optical axis in this order from the object side, and wherein said second lens group is moved to effect zooming, said fourth lens group is moved so as the compensate for image plane fluctuations, which are incident to zooming, and to perform focusing, and wherein at least one of the four lens groups is equipped with an index-distribution-type lens.
Claim 9
Dependent Claim
125 words
A zoom lens comprising: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; a fourth lens group having a positive refracting power; and a stop located between said second lens group and said third lens group, and wherein said first through fourth lens groups are arranged along the optical axis in this order from the object side, and wherein said second lens group is moved to effect zooming, said fourth lens group is moved so as the compensate for image plane fluctuations, which are incident to zooming, and to perform focusing, and wherein at least one of the four lens groups is equipped with an index-distribution-type lens.
References Cited (Backward Citations)
US5011272A
Cited
JPS61172110A
Cited
US4907866A
Cited
US4776679A
Cited
US4842386A
Cited
US4810070A
Cited
JPS62247316A
Cited
US4854684A
Cited
US4802747A
Cited
US4832471A
Cited
US4892397A
Cited
US4988174A
Cited
JPH0239011A
Cited
US5009492A
Cited
US4934796A
Cited
US5050972A
Cited
US4998809A
Cited
US5134524A
Cited
US5095387A
Cited
US5056900A
Cited
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