US4291945A
Expired / Lapsed
US
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Pentagonal roof prism for viewfinder
Assignee: Olympus Corp
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Filing: 1980-03-26
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Granted: 1981-09-29
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Expires: 2000-03-26
Abstract
Abstract A pentagonal roof prism for a viewfinder has a portion adjacent to its surface of incidence which has a non-homogeneous distribution of refractive indices, whereby said portion serves as a convex lens.
Inventors
- 👤 Yoshisada Hayamizu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:46
CPC Classifications
G; G03; G03B; G03B19/00; G03B19/02; G03B19/12; G02; G02B; G02B5/00; G02B5/04
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
89 words
A pentagonal roof prism for a viewfinder, comprising a pentagonal prism having an apex and a planar surface located opposite said apex, said prism having a region formed therein adjacent said planar surface, said region having a non-uniform index of refraction, said region having a shape which cooperates with said non-uniform index of refraction to cause light passing into said prism through said planar surface to be refracted in the same manner as if said prism had a uniform index of refraction and said surface had a predetermined curvature.
Claim 2
Dependent Claim
89 words
A pentagonal roof prism for a viewfinder, comprising a pentagonal prism having an apex and a planar surface located opposite said apex, said prism having a region formed therein adjacent said planar surface, said region having a non-uniform index of refraction, said region having a shape which cooperates with said non-uniform index of refraction to cause light passing into said prism through said planar surface to be refracted in the same manner as if said prism had a uniform index of refraction and said surface had a predetermined curvature.
Claim 3
Dependent Claim
19 words
A pentagonal roof prism according to claim 1, in which said planar surface is centrally formed with a microprism.
Claim 4
Dependent Claim
21 words
A pentagonal roof prism according to claim 1, in which said predetermined curvature is convex toward the exterior of said prism.
Claim 5
Dependent Claim
57 words
A pentagonal roof prism according to claim 1, in which said region has an inner boundary separating it from the rest of said prism, said inner boundary being concave toward said rest of said prism, and said non-uniform index of refraction of said region increasing continuously from said planar surface to said inner boundary of said region.
Claim 6
Dependent Claim
57 words
A pentagonal roof prism according to claim 1, in which said region has an inner boundary separating it from the rest of said prism, said inner boundary being convex toward said rest of said prism, and said non-uniform index of refraction of said region decreasing continuously from said planar surface to said inner boundary of said region.
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) | 1984-09-28 | 1985-03-30 | 1985-09-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-28 | 1989-03-30 | 1989-09-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-28 | 1993-03-30 | 1993-09-29 | $7700.00 | Window Closed / Lapsed |