Patent CA873597A successfully refreshed from Google Patents.
Patent US3864033A successfully refreshed from Google Patents.
US3864033A
Expired / Lapsed
US
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Automatic focusing arrangement for a slide projector
Assignee: Agfa Gevaert AG
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Filing: 1973-05-25
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Granted: 1975-02-04
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Expires: 1993-05-25
Abstract
Abstract When the slide is in the projection position, a first beam is focussed thereon by a light source mounted in a fixed position relative to the projector lens, and the reflected beam is received by a differential photoresistor also mounted in a fixed position relative to the lens. A second beam is impinged upon the slide, the light from the beam falling on a different position in the slide than the light from the first beam. The second beam is furnished by a light source mounted in a fixed position relative to the slide and the corresponding reflected beam is received by a differential photoresistor also mounted in a fixed position relative to the slide. Each photoresistor forms part of a voltage divider. The center tap of each photoresistor is applied to one input of a differential amplifier whose output controls the direction of rotation of a motor which, through gearing, controls the relative position of the lens to the slide.
Inventors
- 👤 Alois Rieder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:53
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/14; G03B21/53
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
179 words
In a slide projector adapted to project a slide and having a projector lens and slide holding means for holding said slide, the relative positions of said projector lens and slide holding means being changeable with respect to each other, an automatic focusing arrangement, comprising, in combination, first optoelectrical means mounted in a fixed position relative to said projector lens for impinging a first light beam onto said slide holding means and creating a first test signal in dependence upon the position of the corresponding light beam reflected by said slide; second opto-electrical means mounted in a fixed position relative to said slide for impinging a second light beam onto said slide and creating a second test signal in dependence upon the position of the corresponding light beam reflected by said slide; regulator means connected to said first and second optoelectrical means, for furnishing a control signal in response to said first and second test signals; and moving means for changing the position of said projector lens relative to said slide holding means under control of said control signal.
Claim 2
Dependent Claim
179 words
In a slide projector adapted to project a slide and having a projector lens and slide holding means for holding said slide, the relative positions of said projector lens and slide holding means being changeable with respect to each other, an automatic focusing arrangement, comprising, in combination, first optoelectrical means mounted in a fixed position relative to said projector lens for impinging a first light beam onto said slide holding means and creating a first test signal in dependence upon the position of the corresponding light beam reflected by said slide; second opto-electrical means mounted in a fixed position relative to said slide for impinging a second light beam onto said slide and creating a second test signal in dependence upon the position of the corresponding light beam reflected by said slide; regulator means connected to said first and second optoelectrical means, for furnishing a control signal in response to said first and second test signals; and moving means for changing the position of said projector lens relative to said slide holding means under control of said control signal.
Claim 3
Dependent Claim
38 words
An automatic focusing arrangement as set forth in claim 1, wherein said first light beam impinges upon a first location on said slide and said second light beam impinges upon a second location different from said first location.
Claim 4
Dependent Claim
29 words
An automatic focusing arrangement as set forth in claim 2, wherein at least one of said first and second locations is a location near the edge of said slide.
Claim 5
Dependent Claim
61 words
An automatic focusing arrangement as set forth in claim 2, wherein said first and second opto-electrical means comprise a source of light, converging lens means operative on the light from said source of light and photoelectrical transducer means for furnishing said first and second test signals in dependence upon the said light beams corresponding to said first and second light beams.
Claim 6
Dependent Claim
27 words
An automatic focusing arrangement as set forth in claim 4, wherein said photoelectrical transducer means comprise a first and second differential photoresistor, each having a center tap.
Claim 7
Dependent Claim
92 words
An automatic focusing arrangement as set forth in claim 5, further comprising first and second fixed resistor means respectively connected in series with said first and second photoresistors, thereby forming, respectively, a first and second voltage divider; wherein said regulator means comprises comparator means having a first input connected to said center tap of said first photoresistor, a second input connected to said center tap of said second photoresistor, and a comparator output for furnishing said control signal as a function of the difference between signals at said first and second inputs.
Claim 8
Dependent Claim
16 words
An arrangement as set forth in claim 6, wherein said comparator means comprise a differential amplifier.
Claim 9
Dependent Claim
28 words
An automatic focusing arrangement as set forth in claim 6, further comprising a variable resistor connected in parallel with at least one of said first in second photoresistors.
Claim 10
Dependent Claim
92 words
An automatic focusing arrangement as set forth in claim 6, wherein said moving means comprise a motor connected to said regulator means for driving in a first or second direction in dependence upon the sign of the difference between the signals at said first and second input; and means for directly intercoupling said motor and said projector lens means for removing said projector lens means and said first opto-electrical means in a first or second direction relative to said slide holding means in dependence upon the direction of rotation of said motor.
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) | 1978-02-03 | 1978-08-05 | 1979-02-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-03 | 1982-08-05 | 1983-02-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-03 | 1986-08-05 | 1987-02-04 | $7700.00 | Window Closed / Lapsed |