US3636849A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic focus control for a camera
Assignee: AT&T Inc
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Filing: 1970-01-28
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Granted: 1972-01-25
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Expires: 1990-01-28
Abstract
Abstract A focus control for automatically maintaining the focus distance, i.e., lens-to-photoplate distance, of a camera within small tolerances utilizes gas-thrust bearings. The photoplate is mounted between two gas-thrust bearings called a lens bearing and a plate bearing. The lens bearing is very stiff and exerts a force which varies significantly with the float height; whereas, the plate bearing is very soft and exerts a force which is essentially independent of float height. Photoplate surface contours or irregularities are accommodated by a change in float height of the plate bearing while a substantially constant lensto-photoplate surface distance is maintained by the stiff lens bearing.
Inventors
- 👤 David Shepard Alles
- 👤 John William Elek
- 👤 Benjamin Edward Nevis
- 👤 Wallace Albert Schlegel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:16
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G03; G03B; G03B3/00; G03B3/04
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
170 words
Apparatus for maintaining a constant focus distance between a camera lens and a surface of a photographic plate by compensating for variations in said plate as said plate moves relative to said lens comprising, in combination, first and second gas-thrust bearings having opposed surfaces between which said plate is mounted, said first gas bearing applying a first force in a first direction to said plate, said first force being substantially proportional to the distance between said lens and said surface, said second gas bearing applying a second force to said plate in a second direction opposite to said first direction, said second force being substantially independent of said distance between said lens and said surface, said first and second forces causing said plate to move between said opposed surfaces until said first and second forces are in equilibrium, said first and second forces being in equilibrium when said distance between said lens and said surface equals said focus distance, whereby said focus distance is automatically maintained at a constant value.
Claim 2
Dependent Claim
170 words
Apparatus for maintaining a constant focus distance between a camera lens and a surface of a photographic plate by compensating for variations in said plate as said plate moves relative to said lens comprising, in combination, first and second gas-thrust bearings having opposed surfaces between which said plate is mounted, said first gas bearing applying a first force in a first direction to said plate, said first force being substantially proportional to the distance between said lens and said surface, said second gas bearing applying a second force to said plate in a second direction opposite to said first direction, said second force being substantially independent of said distance between said lens and said surface, said first and second forces causing said plate to move between said opposed surfaces until said first and second forces are in equilibrium, said first and second forces being in equilibrium when said distance between said lens and said surface equals said focus distance, whereby said focus distance is automatically maintained at a constant value.
Claim 3
Dependent Claim
104 words
Apparatus in accordance with claim 1 including holding means for mounting said plate between said opposed surfaces of said bearings in an initial equilibrium position corresponding to said focus distance for an initial portion of said plate, said holding means moving with said plate as said first and second forces cause said plate to move to subsequent equilibrium positions corresponding to said focus distance for subsequent portions of said plate, and means for supporting said holding means from a fixed base so that said plate remains parallel to said opposed surfaces during movement of said plate, said supporting means having a relatively small stiffness.
Claim 4
Dependent Claim
40 words
Apparatus in accordance with claim 2 wherein said first bearing has a stiffness at least 100 times greater than said stiffness of said supporting means so that said supporting means has a negligible effect on said movement of said plate.
Claim 5
Dependent Claim
18 words
Apparatus in accordance with claim 2 wherein said supporting means comprises parallel flexure springs and an inflatable diaphragm.
Claim 6
Dependent Claim
21 words
Apparatus in accordance with claim 1 wherein said second bearing is supported by a pneumatic support having a relatively low stiffness.
Claim 7
Dependent Claim
147 words
Apparatus for maintaining a constant focus distance between a camera lens and a surface of a photographic plate during relative motion of said lens with respect to said plate comprising, in combination, first means for applying a first force to said plate, said first force being proportional to the distance of said surface from said lens, and second means for applying a second force to said plate in a direction opposite of said first force, said second force being substantially independent of said distance of said surface from said lens said first and second forces causing said plate to move between said first and second means until said first and second forces are in equilibrium, said first and second forces being in equilibrium when said distance between said lens and said surface equals said focus distance, whereby said focus distance is automatically maintained at a constant value.
Claim 8
Dependent Claim
147 words
Apparatus for maintaining a constant focus distance between a camera lens and a surface of a photographic plate during relative motion of said lens with respect to said plate comprising, in combination, first means for applying a first force to said plate, said first force being proportional to the distance of said surface from said lens, and second means for applying a second force to said plate in a direction opposite of said first force, said second force being substantially independent of said distance of said surface from said lens said first and second forces causing said plate to move between said first and second means until said first and second forces are in equilibrium, said first and second forces being in equilibrium when said distance between said lens and said surface equals said focus distance, whereby said focus distance is automatically maintained at a constant value.
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) | 1975-01-24 | 1975-07-26 | 1976-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-24 | 1979-07-26 | 1980-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-24 | 1983-07-26 | 1984-01-25 | $7700.00 | Window Closed / Lapsed |