Patent US4492440A successfully refreshed from Google Patents.
US4492440A
Expired / Lapsed
US
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Finder optical system
Assignee: Olympus Corp
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Filing: 1982-01-27
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Granted: 1985-01-08
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Expires: 2002-01-27
Abstract
Abstract A finder optical system wherein a field mask is arranged in a position near to an eyepiece from a field lens so that a distortionless image of the field mask may be observed. The field mask can be provided directly on the peripheral side of the field lens.
Inventors
- 👤 Kimihiko Nishioka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 22:52
CPC Classifications
G; G03; G03B; G03B19/00; G03B19/02; G03B19/12
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
50 words
A finder optical system comprising an objective, a field lens, a rectangular field mask placed at the image forming position by said objective, a pentagonal roof prism for bending the optical axis and an eyepiece, said objective, field lens, field mask, pentagonal roof prism and eyepiece being arranged in turn.
Claim 2
Dependent Claim
50 words
A finder optical system comprising an objective, a field lens, a rectangular field mask placed at the image forming position by said objective, a pentagonal roof prism for bending the optical axis and an eyepiece, said objective, field lens, field mask, pentagonal roof prism and eyepiece being arranged in turn.
Claim 3
Dependent Claim
22 words
A finder optical system according to claim 1 wherein said field mask is provided on the peripheral surface of said field lens.
Claim 4
Dependent Claim
25 words
A finder optical system according to claim 1 wherein said field mask is provided on the surface on said eyepiece side of said field lens.
Claim 5
Dependent Claim
222 words
A finder optical system according to claim 1 wherein said field lens is a positive lens; said eyepiece comprises a biconvex lens, a positive meniscus lens convex toward said biconvex lens and a negative lens concave toward said roof prism; and said field lens, pentagonal roof prism and eyepiece have the following numerical data, respectively: ______________________________________
r.sub.1 = ∞ (Exit pupil)
d.sub.1 = 24.297
r.sub.2 = 143.1785
d.sub.2 = 7.476
n.sub.1 = 1.6968
r.sub.3 = -143.1785
[d.sub.3 = 0.3738]
[r.sub.4 = 71.1005]
d.sub.3 = 0.3738
r.sub.4 = 71.1005
d.sub.4 = 4.6725
n.sub.2 = 1.6968
r.sub.5 = 985.6041
d.sub.5 = 10.8402
r.sub.6 = ∞
d.sub.6 = 3.738
n.sub.3 = 1.78472
r.sub.7 = 62.7479
d.sub.7 = 4.6725
r.sub.8 = ∞
d.sub.8 = 104.664
n.sub.4 = 1.79952
r.sub.9 = ∞
d.sub.9 = 0.0561
r.sub.10 = ∞
d.sub.10 = 5.981
n.sub.5 = 1.8061
r.sub.11 = -48.99865
______________________________________
Maximum image height = 13.08,
Exit pupil diameter = 15.2,
Diopter = 0.54 diopter wherein reference symbol r 1 represents an exit pupil of said finder optical system, reference symbols r 2 through r 11 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 10 respectively represent thicknesses of respective lenses and airspaces between respective lenses, and reference symbols n 1 through n 5 respectively represent refractive indices of respective lenses.
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) | 1988-01-08 | 1988-07-09 | 1989-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-01-08 | 1992-07-09 | 1993-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-01-08 | 1996-07-09 | 1997-01-08 | $7700.00 | Window Closed / Lapsed |