US4595270A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Finder system
Assignee: Canon Inc
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Filing: 1984-04-23
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Granted: 1986-06-17
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Expires: 2004-04-23
Abstract
Abstract The disclosed finder system includes, from front to rear, a first objective lens of negative power, an optical member having a half-mirror, an eyepiece of positive power and a viewfinder frame arranged near the eyepiece to be observed by the eyepiece with the aid of a reflection from the half-mirror. The finder system satisfies the condition 0.2<d/D<0.6 where D is the air separation between the first objective lens and the eyepiece lens and d is the air separation between the optical member and the eyepiece lens. Thus the first objective lens is exchangeable for a second objective lens of different power from that of the first objective lens to change the magnification of the finder system.
Inventors
- 👤 Yasuyuki Yamada
- 👤 Kazuo Fujibayashi
- 👤 Yasuhisa Sato
- 👤 Hideo Yokota
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:59
CPC Classifications
G; G02; G02B; G02B13/00; G02B13/18; G02B13/22; G02B25/00; G02B25/001
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
122 words
A finder system comprising: (a) an eyepiece having a positive refractive power and defining an optical axis; (b) a first objective lens having a negative refractive power and arranged on the object side of said eyepiece with an optical axis in coincidence with the optical axis of said eyepiece; (c) a viewfinder frame representing a viewfield; (d) an optical member having a reflection surface for providing a reflected image of said viewfinder frame to said eyepiece and positioned in a space between said first objective lens and said eyepiece; and (e) a second objective lens interchangeable with said first objective lens, having a refractive power different from that of said first objective lens, and including a positive lens and a negative lens.
Claim 2
Dependent Claim
122 words
A finder system comprising: (a) an eyepiece having a positive refractive power and defining an optical axis; (b) a first objective lens having a negative refractive power and arranged on the object side of said eyepiece with an optical axis in coincidence with the optical axis of said eyepiece; (c) a viewfinder frame representing a viewfield; (d) an optical member having a reflection surface for providing a reflected image of said viewfinder frame to said eyepiece and positioned in a space between said first objective lens and said eyepiece; and (e) a second objective lens interchangeable with said first objective lens, having a refractive power different from that of said first objective lens, and including a positive lens and a negative lens.
Claim 3
Dependent Claim
26 words
A finder system according to claim 1, wherein when said second objective lens replaces said first objective lens, the entire system changes to a telephoto mode.
Claim 4
Dependent Claim
28 words
A finder system according to claim 2, wherein said second objective lens takes a position closer to said optical member than the position of said first objective lens.
Claim 5
Dependent Claim
29 words
A finder system according to claim 1, wherein the ratio m of the magnification with said first objective lens to the magnification with said second objective lens satisfies 1<m≦2.5
Claim 6
Dependent Claim
161 words
A finder system comprising: (a) an eyepiece having a positive refractive power and defining an optical axis; (b) a first objective lens comprising a negative lens of strong concave curvature toward said eyepiece and arranged on the object side of said eyepiece with an optical axis in coincidence with said optical axis; (c) a viewfinder frame representing a view field; (d) an optical member having a reflection surface for providing a reflected image of said viewfinder frame to said eyepiece and positioned in a space between said first objective lens and said eyepiece; and (e) a second objective lens arranged to be interchangeable with said first objective lens, having a refractive power different from that of said first objective lens, and comprising, from front to rear, a bi-convex lens and a negative lens of strong concave curvature toward said eyepiece, so that said first objective lens is interchanged by said second objective lens, the entire system changes to a telephoto mode.
Claim 7
Dependent Claim
161 words
A finder system comprising: (a) an eyepiece having a positive refractive power and defining an optical axis; (b) a first objective lens comprising a negative lens of strong concave curvature toward said eyepiece and arranged on the object side of said eyepiece with an optical axis in coincidence with said optical axis; (c) a viewfinder frame representing a view field; (d) an optical member having a reflection surface for providing a reflected image of said viewfinder frame to said eyepiece and positioned in a space between said first objective lens and said eyepiece; and (e) a second objective lens arranged to be interchangeable with said first objective lens, having a refractive power different from that of said first objective lens, and comprising, from front to rear, a bi-convex lens and a negative lens of strong concave curvature toward said eyepiece, so that said first objective lens is interchanged by said second objective lens, the entire system changes to a telephoto mode.
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) | 1989-06-16 | 1989-12-16 | 1990-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-16 | 1993-12-16 | 1994-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-16 | 1997-12-16 | 1998-06-17 | $7700.00 | Window Closed / Lapsed |