US4984877A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High zoom-ratio/zoom lens system for use in a compact camera
Assignee: Pentax Corp
•
Filing: 1990-06-08
•
Granted: 1991-01-15
•
Expires: 2010-06-08
Abstract
Abstract A high zoom ratio zoom lens system for use in a compact camera that has reduced variations in field curvature over the full zooming range. The lens system includes, in order from the object side, a first lens group having a positive focal length and a second lens group having a negative focal length, and which performs zooming by adjusting the distance between the two lens groups. In accordance with the invention, the first lens group is composed of a first lens subgroup having a small power and a second lens subgroup having a positive focal length. The distance between the two subgroups is increased during zooming from a wide-angle end to a middle-angle position and decreased during zooming from the middle-angle position to the narrow-angle end.
Inventors
- 👤 Takayuki Ito
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:42
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/16; G02B15/142; G02B15/1425
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
109 words
In a high zoom-ratio zoom lens system for use in a compact camera which comprises, in order from the object side, a first lens group having a positive focal length and a second lens group having a negative focal length, and which performs zooming by adjusting the distance between the two lens groups, the improvement wherein said first lens group comprises a first lens subgroup having a small power and a second lens subgroup having a positive focal length, the distance between said two subgroups being increased during zooming from a wide-angle end to a normal position and decreased during zooming from said normal position to a telephoto end.
Claim 2
Dependent Claim
109 words
In a high zoom-ratio zoom lens system for use in a compact camera which comprises, in order from the object side, a first lens group having a positive focal length and a second lens group having a negative focal length, and which performs zooming by adjusting the distance between the two lens groups, the improvement wherein said first lens group comprises a first lens subgroup having a small power and a second lens subgroup having a positive focal length, the distance between said two subgroups being increased during zooming from a wide-angle end to a normal position and decreased during zooming from said normal position to a telephoto end.
Claim 3
Dependent Claim
45 words
The zoom lens system according to claim 1, which satisfies the following condition: |f.sub.S /f.sub.1a |<0.5 where f S is the focal length of the overall zoom lens system at said wide-angle end, and f 1a is the focal length of said first lens subgroup.
Claim 4
Dependent Claim
34 words
The zoom lens system according to claim 1, which satisfies the following condition: |Δ|/f.sub.S <0.1 where Δ is a maximum value of the change in the distance between said first and second lens subgroups.
Claim 5
Dependent Claim
72 words
The zoom lens system according to any one of claims 1-3, wherein said first lens subgroup comprises, in order from the object side, a positive meniscus lens element having a convex surface of large curvature directed toward the object, a negative lens element having a concave surface of large curvature directed toward the object, and a positive meniscus lens element having a convex surface of large curvature directed toward the image plane.
Claim 6
Dependent Claim
53 words
The zoom lens system according to any one of claims 1-3, wherein said second lens subgroup comprises a cemented positive lens having a divergent surface of large power and which comprises a biconvex positive lens element and a negative meniscus lens element having a concave surface of large curvature directed toward the object.
Claim 7
Dependent Claim
56 words
The zoom lens system according to any one of claims 1-3, wherein said second lens group comprises, in order from the object side, a positive lens element having a convex surface of large curvature directed toward the image plane and two negative meniscus lens elements having a concave surface of large curvature directed toward the object.
References Cited (Backward Citations)
JPS56128911A
Cited
JPS57201213A
Cited
JPS58184916A
Cited
JPS6057814A
Cited
JPS6278522A
Cited
JPS6290611A
Cited
JPS62113120A
Cited
GB2184865A
Cited
JPS62264019A
Cited
US4720179A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-01-14 | 1994-07-16 | 1995-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-01-14 | 1998-07-16 | 1999-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-01-14 | 2002-07-16 | 2003-01-15 | $7700.00 | Window Closed / Lapsed |