US4842386A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable focal length objective
Assignee: Canon Inc
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Filing: 1986-06-23
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Granted: 1989-06-27
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Expires: 2006-06-23
Abstract
Abstract A variable focal length objective having a plurality of lens units with at least one unit separation being varied to vary the focal length of the entire system, in which at least one of the plurality of lens units has at least gradient-index lens having a refractive index distribution of the form: N(h)=N 0 +N 1 h 2 +N 2 h 4 +N 3 h 6 + . . . where h is the height from the optical axis, N 0 is the refractive index on the optical axis, and N 1 , N 2 , N 3 , . . . are constants, satisfying the following conditions: φ.sub.G ·N.sub.1 <0 K·φ.sub.G ·N.sub.2 <0 where φ G is the refractive power of that lens unit which has that gradient-index lens, and K is +1 or -1 when the stronger of the curvatures of both surfaces of that gradient-index lens is convex or concave to the air respectively.
Inventors
- 👤 Nozomu Kitagishi
- 👤 Hiroki Nakayama
- 👤 Shigeyuki Suda
- 👤 Jun Hattori
- 👤 Akihisa Horiuchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 23:32
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/144; G02B15/1441; G02B15/144113
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
187 words
A variable focal length objective comprising a plurality of lens units of which the first from the object side is a positive lens unit, the second from the object side is a negative lens unit, and in which when varying the image magnification, the separation between said first and said second lens units varies, wherein at least one of the plurality of lens units has at least one gradient-index lens having a gradient of refractive index defined by the following equation: N (h)=N.sub.0 +N.sub.1 h.sup.2 +N.sub.2 h.sup.4 +. . . wherein h is the height from the optical axis; N 0 is the refractive index on the optical axis, and N 1 , N 2 , . . . are constants, and wherein when the refractive power of said at least one lens unit is denoted by φ G , and when the sign of the strongest curvature surface of said gradient-index lens is denoted by K such that K=+1 when said strongest curvature surface is convex, and K=-1 when said strongest curvature surface is concave, the following conditions are satisfied: φ.sub.G ·N.sub.1 <0 K·φ.sub.G ·N.sub.2 <0
Claim 2
Dependent Claim
187 words
A variable focal length objective comprising a plurality of lens units of which the first from the object side is a positive lens unit, the second from the object side is a negative lens unit, and in which when varying the image magnification, the separation between said first and said second lens units varies, wherein at least one of the plurality of lens units has at least one gradient-index lens having a gradient of refractive index defined by the following equation: N (h)=N.sub.0 +N.sub.1 h.sup.2 +N.sub.2 h.sup.4 +. . . wherein h is the height from the optical axis; N 0 is the refractive index on the optical axis, and N 1 , N 2 , . . . are constants, and wherein when the refractive power of said at least one lens unit is denoted by φ G , and when the sign of the strongest curvature surface of said gradient-index lens is denoted by K such that K=+1 when said strongest curvature surface is convex, and K=-1 when said strongest curvature surface is concave, the following conditions are satisfied: φ.sub.G ·N.sub.1 <0 K·φ.sub.G ·N.sub.2 <0
Claim 3
Dependent Claim
20 words
A variable focal length objective according to claim 1, wherein said gradient-index lens is provided in said first lens unit.
Claim 4
Dependent Claim
30 words
A variable focal length objective according to claim 1, wherein said gradient-index lens is arranged in at least a lens unit which moves to effect variation of the image magnification.
Claim 5
Dependent Claim
98 words
A variable focal length objective according to claim 1, wherein of said plurality of lens units, there is a last lens unit that is furthest from the object side and comprises a front part and a rear part that are separated from each other by a distance that is larger than the distance separating a front and a rear part of any other of the plurality of lens units, and wherein at least one of said front and said rear parts of said last lens unit has at least one gradient-index lens that satisfies said equation and conditions.
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) | 1992-06-26 | 1992-12-26 | 1993-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-06-26 | 1996-12-26 | 1997-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-06-26 | 2000-12-26 | 2001-06-27 | $7700.00 | Window Closed / Lapsed |