US4779969A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Finding device of variable magnification
Assignee: Canon Inc
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Filing: 1986-07-03
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Granted: 1988-10-25
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Expires: 2006-07-03
Abstract
Abstract A variable magnification finder including from front to rear, a first lens unit of negative power, a second lens unit of positive power and a third lens unit of positive power, these three units constituting an objective lens of positive overall power, followed by an eyepiece lens of positive power, wherein a finder image formed by the first and second units near the third lens unit is observed by the eyepiece lens, and, with the other lens units being held stationary, the second lens unit is axially moved to vary the finder magnification.
Inventors
- 👤 Yasuhisa Sato
- 👤 Shinya Yomogizawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:42
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/143; G02B15/1435; G02B15/143507; G02B23/00; G02B23/14; G02B23/145
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
93 words
A device comprising: a fixed lens unit of negative refractive power; a movable lens unit of positive refractive power arranged in rear of said fixed lens unit to move along an optical axis to vary the magnification of an image of an object; a field lens disposed on or near a presumed image forming plane of a synthetic optical system composed of said fixed lens unit and said movable lens unit; and an eyepiece lens unit for observing the object image formed by said fixed lens unit and said movable lens unit, whereby
Claim 2
Independent Claim
93 words
A device comprising: a fixed lens unit of negative refractive power; a movable lens unit of positive refractive power arranged in rear of said fixed lens unit to move along an optical axis to vary the magnification of an image of an object; a field lens disposed on or near a presumed image forming plane of a synthetic optical system composed of said fixed lens unit and said movable lens unit; and an eyepiece lens unit for observing the object image formed by said fixed lens unit and said movable lens unit, whereby
Claim 3
Dependent Claim
26 words
1≦|f 1 /f 2 |≦2 is satisfied, where f 1 and f 2 are the focal lengths of said fixed and said movable lens units, respectively.
Claim 4
Dependent Claim
26 words
1≦|f 1 /f 2 |≦2 is satisfied, where f 1 and f 2 are the focal lengths of said fixed and said movable lens units, respectively.
Claim 5
Dependent Claim
28 words
A device according to claim 1, wherein said field lens is of positive refractive power and is arranged between said fixed lens unit and said eyepiece lens unit.
Claim 6
Dependent Claim
28 words
A device according to claim 1, further comprising prismatic optical means for inverting the object image vertically, horizontally between said fixed lens unit and said eyepiece lens unit.
References Cited (Backward Citations)
US696788A
Cited
FR85460E
Cited
US3227042A
Cited
GB1067428A
Cited
US3994572A
Cited
US4018510A
Cited
US4009928A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-10-25 | 1992-04-25 | 1992-10-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-25 | 1996-04-25 | 1996-10-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-25 | 2000-04-25 | 2000-10-25 | $7700.00 | Window Closed / Lapsed |