US4146305A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable lens which can have its focal distance range easily changed
Assignee: Canon Inc
•
Filing: 1977-04-05
•
Granted: 1979-03-27
•
Expires: 1997-04-05
Abstract
Abstract A variable magnification lens which can have its focal distance range easily changed and has a focusing lens group, a variable lens group and an imaging lens group positioned in said order from an object side, wherein said imaging lens group has a fixed front lens group, a movable middle lens group, a fixed rear lens group in said order from an object side, further an attachment lens is provided in a freely dismountable manner on an optical axis between said front lens group and the rear lens group, and when said attachment lens is mounted said middle lens group is shifted to a prescribed position, thus the focal distance range of the variable magnification lens will be different between a time when the attachment lens is mounted and a time when the same is not mounted.
Inventors
- 👤 Kazuo Tanaka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 02:59
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/02; G02B15/14; G02B15/143; G02B15/145; G02B15/146
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
156 words
A variable magnification lens group which can have a focal distance range easily shifted comprising, in the order given from an object end: a focusing lens group, a magnification variation lens, which varies the magnification of the luminous flux from said focusing lens group, an imaging lens group, which consists of a fixed front lens group, a movable middle lens group, a fixed rear lens group, and images the luminous flux from said magnification variation lens group, and an attachment lens, which is provided in a freely insertable and withdrawable manner within an optical path between said front lens group and said rear lens group, wherein a focal distance range of the total lens system is different between a case when said attachment lens is mounted and a case when the same is dismounted; in which said middle lens group is shifted along an optical axis of the lens system when the attachment lens is mounted.
Claim 2
Dependent Claim
156 words
A variable magnification lens group which can have a focal distance range easily shifted comprising, in the order given from an object end: a focusing lens group, a magnification variation lens, which varies the magnification of the luminous flux from said focusing lens group, an imaging lens group, which consists of a fixed front lens group, a movable middle lens group, a fixed rear lens group, and images the luminous flux from said magnification variation lens group, and an attachment lens, which is provided in a freely insertable and withdrawable manner within an optical path between said front lens group and said rear lens group, wherein a focal distance range of the total lens system is different between a case when said attachment lens is mounted and a case when the same is dismounted; in which said middle lens group is shifted along an optical axis of the lens system when the attachment lens is mounted.
Claim 3
Dependent Claim
39 words
A variable magnification lens according to claim 1, in which the above mentioned middle lens group is shifted toward the front lens group, and the attachment lens is provided between the middle lens group and the rear lens group.
Claim 4
Dependent Claim
19 words
A variable magnification lens according to claim 2, in which the middle lens group has a positive refractive power.
Claim 5
Dependent Claim
37 words
A variable magnification lens according to claim 1, in which the middle lens group is shifted toward the rear lens group and the attachment lens is provided between the middle lens group and the front lens group.
Claim 6
Dependent Claim
19 words
A variable magnification lens according to claim 4, in which said middle lens group has a positive refractive power.
References Cited (Backward Citations)
US2906172A
Cited
US4015895A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-03-26 | 1982-09-25 | 1983-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-26 | 1986-09-25 | 1987-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-26 | 1990-09-25 | 1991-03-27 | $7700.00 | Window Closed / Lapsed |