US4245901A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interchangeable-lens type TTL automatic exposure camera
Assignee: Pentax Corp
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Filing: 1978-06-14
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Granted: 1981-01-20
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Expires: 1998-06-14
Abstract
Abstract Automatic exposure control is enhanced by providing a fixed diaphragm equivalent to the maximum aperture of the adjustable camera diaphragm so that the fixed diaphragm limits the maximum aperture to a consistent value. Consistent light measurements are possible as long as the lens being used does not interfere with the quantity of light entering the diaphragm.
Inventors
- 👤 Tohru Karikawa
- 👤 Kunio Mita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:34
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/20
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
123 words
In an interchangeable lens type automatic exposure camera of the type having an objective lens, an adjustable diaphragm having a maximum aperture position, a light receiving element for receiving light which actually passes through said objective lens for measuring the quantity of light passing through said lens and said adjustable diaphragm when said adjustable diaphragm is in its maximum aperture position and an exposure controlling circuit for automatically controlling an exposure time and diaphragm aperture according to the quantity of light detected by said light receiving element, the improvement comprising: a fixed diaphragm member adjacent said adjustable diaphragm and having an aperture which limits to a constant value the quantity of light passing through said adjustable diaphragm when in its maximum aperture position.
Claim 2
Dependent Claim
123 words
In an interchangeable lens type automatic exposure camera of the type having an objective lens, an adjustable diaphragm having a maximum aperture position, a light receiving element for receiving light which actually passes through said objective lens for measuring the quantity of light passing through said lens and said adjustable diaphragm when said adjustable diaphragm is in its maximum aperture position and an exposure controlling circuit for automatically controlling an exposure time and diaphragm aperture according to the quantity of light detected by said light receiving element, the improvement comprising: a fixed diaphragm member adjacent said adjustable diaphragm and having an aperture which limits to a constant value the quantity of light passing through said adjustable diaphragm when in its maximum aperture position.
Claim 3
Dependent Claim
25 words
A camera according to claim 1, wherein the effective aperture of said objective lens does not limit the quantity of light entering said fixed diaphragm.
References Cited (Backward Citations)
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US2616342A
Cited
US3552289A
Cited
US3968504A
Cited
US3858224A
Cited
US3977012A
Cited
US3962711A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-20 | 1984-07-21 | 1985-01-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-20 | 1988-07-21 | 1989-01-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-20 | 1992-07-21 | 1993-01-20 | $7700.00 | Window Closed / Lapsed |