US4993814A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Zoom lens system
Assignee: Minolta Co Ltd
•
Filing: 1989-01-17
•
Granted: 1991-02-19
•
Expires: 2009-01-17
Abstract
Abstract A zoom lens system comprises from object side to image side, a front lens unit of a negative refractive power and a rear lens unit of a positive refractive power with a variable air space, which changes in the zooming operation, formed between the front and rear lens units. The rear lens unit consists of a first biconvex lens element, a second biconcave lens element and a third biconvex lens element. Futher, an aperture diaphragm, which is arranged between the front and rear lens units or at the image side next to the rear lens unit, is stationary on the optical axis of the lens system in the zooming operation. In a 2-components zoom lens system having a negative lens unit and a positive lens unit from object side according to the present invention, a zoom ratio of about 2 and a sufficiently long back focal length can be obtained in spite of a small number of lens elements. Moreover, cost reduction, compactness and a high performance in the whole lens system including the aperture diaphragm and a lens barrel are obtainable.
Inventors
- 👤 Kazuyoshi Hata
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 16:15
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/142; G02B15/1425
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
145 words
A compact two-unit zoom lens system providing a long back focal length, comprises from object side to image side: a front lens unit of a negative refractive power including at least two lens elements having relatively strong refractive powers facing each other to assist in correcting aberrations during zooming; and a rear lens unit of a positive refractive power with a variable air space formed between the front and rear lens units, said rear lens unit consisting of a first biconvex lens element, a second biconcave lens element and a third biconvex lens element, wherein the variable air space between the front and rear lens units changes during a zooming operation, the refractive powers of the front and rear lens units are chosen to permit correction of field curvature, and spherical, coma, and chromatic aberrations, with only three lens elements in the rear lens unit.
Claim 2
Dependent Claim
145 words
A compact two-unit zoom lens system providing a long back focal length, comprises from object side to image side: a front lens unit of a negative refractive power including at least two lens elements having relatively strong refractive powers facing each other to assist in correcting aberrations during zooming; and a rear lens unit of a positive refractive power with a variable air space formed between the front and rear lens units, said rear lens unit consisting of a first biconvex lens element, a second biconcave lens element and a third biconvex lens element, wherein the variable air space between the front and rear lens units changes during a zooming operation, the refractive powers of the front and rear lens units are chosen to permit correction of field curvature, and spherical, coma, and chromatic aberrations, with only three lens elements in the rear lens unit.
Claim 3
Dependent Claim
58 words
A zoom lens system as claimed in claim 1, wherein the front lens unit consists of, from the object side to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface and a positive meniscus lens element having an object side surface convex to the object side.
Claim 4
Dependent Claim
54 words
A zoom lens system as claimed in claim 2, wherein the lens system fulfills the following conditions: ##EQU4## wherein, φ I and φ II respectively represent the refractive powers of the front and rear lens units, f w and f r respectively represent the shortest and longest focal lengths of the whole lens system.
Claim 5
Dependent Claim
70 words
A zoom lens system as claimed in claim 3, wherein the zoom lens system fulfills the following conditions: 0.75<R.sub.1R /R.sub.2P <1.1 0.3<|R.sub.5R |/R.sub.5P <0.75|0(R.sub.5R <0) 0.75<R.sub.4R /|R.sub.4P |<1.35|0(R.sub.4P <0) wherein, R represents the radius of curvature, wherein the first subscript thereof represents the lens number counted from the object side, and the second subscript thereof, that is, P represents the object side surface and R represents the image side surface.
Claim 6
Dependent Claim
66 words
A zoom lens system as claimed in claim 4, wherein the zoom lens system fulfills the following conditions: Δν.sub.I >22 n.sub.I >1.70 n.sub.II >1.71 wherein, Δφ I represents the difference between the Abbe numbers of two lens elements of the front lens unit, n I and n II respectively represent the averages of the refractive indexes of lens elements composing the front and rear lens units.
Claim 7
Dependent Claim
50 words
A zoom lens system as claimed in claim 5, wherein the zoom lens system has an aperture diaphragm arranged at the object side of the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 8
Dependent Claim
46 words
A zoom lens system as claimed in claim 5, wherein the zoom lens system has an aperture diaphragm arranged between the first biconvex and second biconcave lens elements of the rear lens unit, said aperture diaphragm optical axis of the lens system in the zooming operation.
Claim 9
Dependent Claim
50 words
A zoom lens system as claimed in claim 5, wherein the zoom lens system has an aperture diaphragm arranged at the image side of the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 10
Dependent Claim
76 words
A zoom lens system as claimed in claim 1, wherein the front lens unit consists of, from the object side to the image side, a negative meniscus lens element having an object side surface convex to the object side, a negative lens element whose image side surface has a stronger refractive power than its object side surface and a positive lens element whose object side surface has a stronger refractive power than its image side surface.
Claim 11
Dependent Claim
29 words
A zoom lens system as claimed in claim 9, wherein the zone lens system fulfills the following conditions: ##EQU5## wherein, Z represents the zoom ratio of the lens system.
Claim 12
Dependent Claim
26 words
A zoom lens system as claimed in claim 10, wherein the zoom lens system fulfills the following conditions: 0.4<|R.sub.6R |/R.sub.6P <0.8|0(R.sub.6R <0) 0.7<R.sub.5R /|R.sub.5P |<1.4|0(R.sub.5P <0)
Claim 13
Dependent Claim
49 words
A zoom lens system as claimed in claim 11, wherein the zoom lens system fulfills the following conditions: 0.7<R.sub.3P /R.sub.2R <1.0 n.sub.6 >1.73 ν.sub.5 <32 wherein, n represents the refractive index, ν represents the Abbe number, wherein the subscript thereof represents the lens number counted from the object side.
Claim 14
Dependent Claim
50 words
A zoom lens system as claimed in claim 12, wherein the zoom lens system has an aperture diaphragm arranged at the object side if the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 15
Dependent Claim
55 words
A zoom lens system as claimed in claim 12, wherein the zoom lens system has an aperture diaphragm arranged between the first biconvex and second biconvex lens elements of the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 16
Dependent Claim
50 words
A zoom lens system as claimed in claim 12, wherein the zoom lens system has an aperture diaphragm arranged at the image side of the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 17
Dependent Claim
34 words
A zoom lens system as claimed in claim 1, wherein the front lens unit consists of a negative lens element whose image side surface has a stronger refractive power than its object side surface.
Claim 18
Dependent Claim
25 words
A zoom lens system as claimed in claim 16, wherein the zoom lens system fulfills the following conditions: 0.43<|φ.sub.I |·f.sub.w <0.60|0(φ.sub.I <0) 0.46<|φ.sub.I |/φ.sub.II <0.70
Claim 19
Dependent Claim
19 words
A zoom lens system as claimed in claim 17, wherein the zoom lens system fulfills the following conditions: ##EQU6##
Claim 20
Dependent Claim
50 words
A zoom lens system as claimed in claim 18, wherein the zoom lens system has an aperture diaphragm arranged at the object side of the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 21
Dependent Claim
50 words
A zoom lens system as claimed in claim 18, wherein the zoom lens system has an aperture diaphragm arranged at the image side of the rear lens unit, said aperture diaphragm being shiftable with the rear lens unit along the optical axis of the lens system in the zooming operation.
Claim 22
Dependent Claim
43 words
A zoom lens system as claimed in claim 1, wherein the zoom lens system has an aperture diaphragm arranged between the front and rear lens units, said aperture diaphragm being stationary on the optical axis of the lens system in the zooming operation.
Claim 23
Dependent Claim
22 words
A zoom lens system as claimed in claim 21, wherein the zoom lens system fulfills the following condition: 0.4<|φ.sub.I |/φ.sub.II <0.65|0(φ.sub.I <0)
Claim 24
Dependent Claim
34 words
A zoom lens system as claimed in claim 22, wherein the front lens unit consists of a negative lens element whose image side surface has a stronger refractive power than its object side surface.
Claim 25
Dependent Claim
58 words
A zoom lens system as claimed in claim 22, wherein the front lens unit consists of, from the object side to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface and a positive meniscus lens element having an object side surface convex to the object side.
Claim 26
Dependent Claim
46 words
A zoom lens system as claimed in claim 1, wherein the zoom lens system has an aperture diaphragm arranged at the image side next to the rear lens unit, said aperture diaphragm being stationary on the optical axis of the lens system in the zooming operation.
Claim 27
Dependent Claim
83 words
A zoom lens system as claimed in claim 25, wherein the zoom lens system fulfills the following conditions: 0<Δd.sub.I /Δd.sub.II <2.0 0.47<|φ.sub.I |/φ.sub.II <0.7|0 (φ.sub.I <0) wherein, Δd I and Δd II respectively represent the shifting amounts of the front and rear lens units from the longest focal length to the shortest focal length. (if the front lens unit moves toward the object side, Δd I is positive and if the rear lens unit moves toward the image side. Δd II is positive)
Claim 28
Dependent Claim
34 words
A zoom lens system as claimed in claim 26, wherein the front lens unit consists of a negative lens element whose image side surface has a stronger refractive power than its object side surface.
Claim 29
Dependent Claim
58 words
A zoom lens system as claimed in claim 26, wherein the front lens unit consists of, from the object side to the image side, a negative lens element whose image side surface has a stronger refractive power than its object side surface and a positive meniscus lens element having an object side surface convex to the object side.
Claim 30
Dependent Claim
158 words
A compact two-unit zoom lens system providing a long back focal length comprising, from object side to image side: a front lens unit of a negative refractive power, said front lens unit consisting of at most three lens elements and including at least two lens elements having relatively strong refractive powers forcing each other to assist in correcting aberrations during zooming; and a rear lens unit of a positive refractive power with a variable air space formed between the front and rear lens units, said rear lens unit consisting of a first biconvex lens element, a second biconcave lens element and a third biconvex lens element, wherein the variable air space between the front and rear lens units changes in the zooming operation, and the refractive powers of the front and rear lens units are chosen to permit correction of field curvature and spherical, coma, and chromatic aberrations, with only three lens elements in the rear lens unit.
Claim 31
Dependent Claim
158 words
A compact two-unit zoom lens system providing a long back focal length comprising, from object side to image side: a front lens unit of a negative refractive power, said front lens unit consisting of at most three lens elements and including at least two lens elements having relatively strong refractive powers forcing each other to assist in correcting aberrations during zooming; and a rear lens unit of a positive refractive power with a variable air space formed between the front and rear lens units, said rear lens unit consisting of a first biconvex lens element, a second biconcave lens element and a third biconvex lens element, wherein the variable air space between the front and rear lens units changes in the zooming operation, and the refractive powers of the front and rear lens units are chosen to permit correction of field curvature and spherical, coma, and chromatic aberrations, with only three lens elements in the rear lens unit.
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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) | 1994-02-18 | 1994-08-20 | 1995-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-18 | 1998-08-20 | 1999-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-18 | 2002-08-20 | 2003-02-19 | $7700.00 | Window Closed / Lapsed |