US3744894A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Servo amplifier for a self-positioning system
Assignee: Eastman Kodak Co
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Filing: 1971-05-04
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Granted: 1973-07-10
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Expires: 1991-05-04
Abstract
Abstract A servo amplifier for use with a DC motor and an AC power source. The motor is driven in a direction and by an amount determined by the polarity and amplitude, respectively, of an input half-wave rectified current which is controlled by a bridge at the input of the amplifier. The direction and degree of unbalance in the bridge determine the polarity and amplitude of the current. Such bridge unbalance can be used, for example, to indicate the amount and direction a projector is out of focus. By incorporating this circuit in a projector, correct focus can be automatically retained as slides or frames are sequenced. The ''''dead zone,'''' i.e., the amount of input signal variance allowed before current flows turning the motor is reduced in existing automatic focusing systems when the invention is incorporated therein.
Inventors
- 👤 H Hoadley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 13:30
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/14; G03B21/53
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
334 words
For use in a self-focusing projector wherein an imaged focus is adjusted by moving the image element and an objective lens relative to one another along the optical axis of the objective lens, the invention comprising: means for detecting displacement of said imaged element relative to a position of focus for said objective lens, said means comprising a first output for providing a first signal of a first polarity representative of displacement of said imaged element from its position of focus in a first direction, a second output for providing a second signal of a second polarity representative of displacement of said image element from its position of focus in a second direction opposite to said first direction, and a third output for providing a reference signal; means for moving said image element and said objective lens relative to one another along the optical axis of said objective lens; first circuit means responsive to said detecting means comprising a first control transistor of a first polarity the emitter of which is connected to said reference signal output, the base of which is connected to the first output so that said first control transistor is responsive to said first signal of said first polarity for energizing said moving means to move said lens and said element relatively closer together along said optical axis; second circuit means responsive to said detecting means comprising a second control transistor of opposite polarity to said first transistor the emitter of said second control transistor being connected to said reference signal output the base of said second control transistor being connected to the second output so that said second control transistor is responsive to said second signal of said second polarity for energizing said moving means to move said lens and said element relatively further apart along said optical axis; and a variable resistor means connected between the bases of the first and second control transistors, which resistor can be adjusted to produce substantially zero resistance between the two bases.
Claim 2
Dependent Claim
334 words
For use in a self-focusing projector wherein an imaged focus is adjusted by moving the image element and an objective lens relative to one another along the optical axis of the objective lens, the invention comprising: means for detecting displacement of said imaged element relative to a position of focus for said objective lens, said means comprising a first output for providing a first signal of a first polarity representative of displacement of said imaged element from its position of focus in a first direction, a second output for providing a second signal of a second polarity representative of displacement of said image element from its position of focus in a second direction opposite to said first direction, and a third output for providing a reference signal; means for moving said image element and said objective lens relative to one another along the optical axis of said objective lens; first circuit means responsive to said detecting means comprising a first control transistor of a first polarity the emitter of which is connected to said reference signal output, the base of which is connected to the first output so that said first control transistor is responsive to said first signal of said first polarity for energizing said moving means to move said lens and said element relatively closer together along said optical axis; second circuit means responsive to said detecting means comprising a second control transistor of opposite polarity to said first transistor the emitter of said second control transistor being connected to said reference signal output the base of said second control transistor being connected to the second output so that said second control transistor is responsive to said second signal of said second polarity for energizing said moving means to move said lens and said element relatively further apart along said optical axis; and a variable resistor means connected between the bases of the first and second control transistors, which resistor can be adjusted to produce substantially zero resistance between the two bases.
Claim 3
Dependent Claim
20 words
The invention of claim 1 wherein said moving means comprises means for repositioning said objective lens along said optical axis.
Claim 4
Dependent Claim
20 words
The invention of claim 1 wherein said moving means comprises means for repositioning said imaged element along said optical axis.
Claim 5
Dependent Claim
25 words
The invention of claim 1 and wherein said first circuit means further comprises a first current limiting means in series with said first control transistor.
Claim 6
Dependent Claim
45 words
The invention of claim 1 and wherein said first circuit means further comprises a first means for limiting current in series with said first control transistor and said second circuit means further comprises second means for limiting current in series with said second control trans-istor.
Claim 7
Dependent Claim
77 words
The invention of claim 1 and wherein said first circuit means further comprises first means for limiting current in series with said first control transistor and said second circuit means further comprises second means for limiting current in series with said second control trans-istor and wherein said first control transistor and first current limiting means pair and said second control trans-istor and said second current limiting means pair are both in parallel relative to said moving means.
Claim 8
Dependent Claim
54 words
The invention of claim 1 wherein said moving means has an electrical dead zone said adjustable resistance between the bases of said first and second transistors controlling said dead zone such that said dead zone decreases from its maximum to its minimum as said resistance is adjusted from effectively zero to a selected value.
Claim 9
Dependent Claim
32 words
The invention of claim 1 wherein said first circuit means comprises an additional transistor of the same polarity as said first control transistor connected in amplifying cascade with said first control transistor.
Claim 10
Dependent Claim
59 words
The invention of claim 1 wherein said first circuit means comprises an additional transistor of the same polarity as said first control transistor connected in amplifying cascade with said first control transistor and said second circuit means comprises an additional transistor of the same polarity as said second control transistor connected in amplifying cascade with said second control transistor.
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) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |