US3840298A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Mirror reflex viewfinder providing indications of photographing information
Assignee: Canon Inc
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Filing: 1973-02-02
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Granted: 1974-10-08
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Expires: 1993-02-02
Abstract
Abstract An auxiliary prism is mounted on a roof face of a pentagonal roof prism forming a mirror reflex viewfinder. The auxiliary prism has a light entry face or plane and a reflecting face or plane opposite to a front reflecting face or plane of the pentagonal prism. A light beam incident upon the light entry face of the auxiliary prism, from an indicator, is directed into the pentagonal prism by the reflecting face of the auxiliary prism and directed toward the front reflecting face of the pentagonal prism, which reflects the light beam to direct the light beam toward an eye piece. Thereby, the indicator can be observedn the visual field of the mirror reflex viewfinder.
Inventors
- 👤 Y Okuno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 20:09
CPC Classifications
G; G03; G03B; G03B19/00; G03B19/02; G03B19/12
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
167 words
In a single lens mirror reflex camera viewfinder providing therein a visual indication of photographing information, and of the type including a pentagonal roof prism having a bottom light entry face, a pair of angularly related roof reflecting faces, a first light exit face at a rear end, and a front end reflecting face oblique to the bottom light entry face and to the roof faces, the improvement comprising an auxiliary prism mounted on said roof prism and having a second light entry face directed toward a photographing information source, said auxiliary prism having two angularly related second light exit faces each in surface to surface engagement with a respective roof face of said roof prism to from respective interfaces therewith, and at least one internal reflecting face reflecting light, entering said auxiliary prism through said second light entry face, through said interface into said roof prism for reflection by said front end reflecting face through said first light exit face for projection through an ocular lens.
Claim 2
Dependent Claim
167 words
In a single lens mirror reflex camera viewfinder providing therein a visual indication of photographing information, and of the type including a pentagonal roof prism having a bottom light entry face, a pair of angularly related roof reflecting faces, a first light exit face at a rear end, and a front end reflecting face oblique to the bottom light entry face and to the roof faces, the improvement comprising an auxiliary prism mounted on said roof prism and having a second light entry face directed toward a photographing information source, said auxiliary prism having two angularly related second light exit faces each in surface to surface engagement with a respective roof face of said roof prism to from respective interfaces therewith, and at least one internal reflecting face reflecting light, entering said auxiliary prism through said second light entry face, through said interface into said roof prism for reflection by said front end reflecting face through said first light exit face for projection through an ocular lens.
Claim 3
Dependent Claim
193 words
In a single lens mirror reflex camera viewfinder providing therein a visual indication of photographing information, and of the type including a pentagonal roof prism having a bottom light entry face, a pair of angularly related roof reflecting faces, a first light exit face at a rear end, and a front end reflecting face oblique to the bottom light entry face and to the roof faces, the improvement comprising an auxiliary prism mounted on said roof prism and having a second light entry face directed toward a photographing information source, at least one second light exit face in surface to surface engagement with a roof face of said roof prism to form an interface therewith, and at least one internal reflecting face reflecting light, entering said auxiliary prism through said second light entry face, through said interface into said roof prism for reflection by said front end reflecting face through said first light exit face for projection through an ocular lens; said suxiliary prism having an internal reflecting face which is semi-transparent so that a photographing information source can be observed from the outer surface of said auxiliary prism at said semi-transparent face.
Claim 4
Dependent Claim
193 words
In a single lens mirror reflex camera viewfinder providing therein a visual indication of photographing information, and of the type including a pentagonal roof prism having a bottom light entry face, a pair of angularly related roof reflecting faces, a first light exit face at a rear end, and a front end reflecting face oblique to the bottom light entry face and to the roof faces, the improvement comprising an auxiliary prism mounted on said roof prism and having a second light entry face directed toward a photographing information source, at least one second light exit face in surface to surface engagement with a roof face of said roof prism to form an interface therewith, and at least one internal reflecting face reflecting light, entering said auxiliary prism through said second light entry face, through said interface into said roof prism for reflection by said front end reflecting face through said first light exit face for projection through an ocular lens; said suxiliary prism having an internal reflecting face which is semi-transparent so that a photographing information source can be observed from the outer surface of said auxiliary prism at said semi-transparent face.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-07 | 1978-04-08 | 1978-10-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-07 | 1982-04-08 | 1982-10-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-07 | 1986-04-08 | 1986-10-08 | $7700.00 | Window Closed / Lapsed |