US4081807A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reflex mirror for single lens reflex camera
Assignee: Pentax Corp
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Filing: 1977-01-13
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Granted: 1978-03-28
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Expires: 1997-01-13
Abstract
Abstract A reflex mirror 2, 2' for an SLR camera includes a fully reflective, elliptical area 2a, 2a' whose center coincides with the optical axis, and a surrounding, elliptical, semi-transparent area 2b, 2b'. The remaining area 2c, 2c' of the mirror is fully reflective. The semi-transparent area may be uniform in transmissivity, or it may be formed by a plurality of concentric elliptical slits in the reflective surface.
Inventors
- 👤 Fumio Urano
- 👤 Akihiro Arai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:02
CPC Classifications
G; G03; G03B; G03B19/00; G03B19/02; G03B19/12
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
141 words
In a reflex mirror for a single lens reflex camera including a semi-transparent area and a fully reflective area whereby some of the light entering the camera is reflected into a viewfinder/rangefinder optical system and some of the light also passes through the semi-transparent area onto a photodetector incorporated in the camera metering system, the improvements characterized by the reflex mirror comprising: a. a central, elliptical, fully reflective area whose center coincides with the optical axis of the camera, and b. a semi-transparent, elliptical area surrounding the central area, c. the remaining area of the mirror surrounding the semi-transparent area being fully reflective, whereby the projection of the mirror areas onto a focal plate of the camera forms a plurality of concentric circles, and a circular distance measuring and focusing area in the center of said focal plate is brightly illuminated.
Claim 2
Dependent Claim
141 words
In a reflex mirror for a single lens reflex camera including a semi-transparent area and a fully reflective area whereby some of the light entering the camera is reflected into a viewfinder/rangefinder optical system and some of the light also passes through the semi-transparent area onto a photodetector incorporated in the camera metering system, the improvements characterized by the reflex mirror comprising: a. a central, elliptical, fully reflective area whose center coincides with the optical axis of the camera, and b. a semi-transparent, elliptical area surrounding the central area, c. the remaining area of the mirror surrounding the semi-transparent area being fully reflective, whereby the projection of the mirror areas onto a focal plate of the camera forms a plurality of concentric circles, and a circular distance measuring and focusing area in the center of said focal plate is brightly illuminated.
Claim 3
Dependent Claim
15 words
A reflex mirror as defined in claim 1, wherein the semi-transparent area is uniformly semi-transparent.
Claim 4
Dependent Claim
27 words
A reflex mirror as defined in claim 1, wherein the semi-transparent area is formed by a plurality of concentric elliptical slits in the surface of the mirror.
References Cited (Backward Citations)
DE1208621B
Cited
US3093044A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-03-27 | 1981-09-26 | 1982-03-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-03-27 | 1985-09-26 | 1986-03-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-03-27 | 1989-09-26 | 1990-03-28 | $7700.00 | Window Closed / Lapsed |