US3857031A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic focus control for facsimile cameras
Assignee: National Aeronautics and Space Administration
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Filing: 1973-10-15
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Granted: 1974-12-24
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Expires: 1993-10-15
Abstract
Abstract A movable stage contains two photodetectors for focusing, as well as an imaging sensor. The imaging sensor produces the video data in the fashion standard to facsimile cameras. The two photodetectors are placed with one closer to the lens of the facsimile camera than the imaging sensor and with the other farther away. The movable stage is coupled to a linear motor which is driven from an error signal generated by the electronics. The electronics consists of balanced a.c. amplifiers, two square law function generators, and a differential amplifier and power drive. In order to insure that the electrical signals at the output of the two photodetectors and the imaging sensor are in phase, electrical delays are connected to the outputs of the two photodetectors. The invention also includes means for maintaining the imaging sensor at the expected location of the focal plane as the facsimile camera scans a scene or terrain. In a second embodiment of the invention, a 3-faced mirror is used to insure that all three of the detectors are detecting the same picture elements simultaneously thereby eliminating the need for the two electrical dalays at the outputs of the two photoconductors.
Inventors
- 👤 A Sinclair
- 👤 E Burcher
- 👤 S Katzberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 21:01
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/40
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
184 words
An automatic focus control for a facsimile camera that includes a scanning means, a lens, a focal plane and an imaging detector for producing electrical signals of the picture elements viewed by the imaging detector comprising: a movable stage with the imaging detector of said facsimile camera mounted thereon in the focal plane of said facsimile camera; means including a first photodetector mounted on said movable stage closer to said lens than said imaging detector for producing first electrical signals of the picture elements viewed by the imaging detector and in phase with the electrical signals produced by the imaging detector; means including a second photodetector mounted on said movable stage farther from said lens than said imaging detector for producing second electrical signals of the picture elements viewed by the imaging detector and in phase with the electrical signals produced by the imaging detector; and servo means receiving said first and second electrical signals for moving said movable means along a line in the direction of the lens of said facsimile camera so as to maintain said first and second electrical signals equal.
Claim 2
Dependent Claim
184 words
An automatic focus control for a facsimile camera that includes a scanning means, a lens, a focal plane and an imaging detector for producing electrical signals of the picture elements viewed by the imaging detector comprising: a movable stage with the imaging detector of said facsimile camera mounted thereon in the focal plane of said facsimile camera; means including a first photodetector mounted on said movable stage closer to said lens than said imaging detector for producing first electrical signals of the picture elements viewed by the imaging detector and in phase with the electrical signals produced by the imaging detector; means including a second photodetector mounted on said movable stage farther from said lens than said imaging detector for producing second electrical signals of the picture elements viewed by the imaging detector and in phase with the electrical signals produced by the imaging detector; and servo means receiving said first and second electrical signals for moving said movable means along a line in the direction of the lens of said facsimile camera so as to maintain said first and second electrical signals equal.
Claim 3
Dependent Claim
191 words
An automatic focus control for a facsimile camera according to claim 1 wherein said means for producing first electrical signals includes said first detector being mounted on said movable Means in line with said imaging detector such that the photodetector is in the line of scan of scanning means of the facsimile camera and first electrical delay means connected to the output of said first photodetector for delaying the electrical signals produced by said first photodetector a period of time equal to the period of time it takes the scanning means to scan from the first photodetector to said imaging detector and wherein said means for producing second electrical signals includes said second photodetector being mounted on said movable means in lines with the imaging detector such that the photodetector is on the line of scan of the scanning means of the facsimile camera and second electrical delay means connected to the output of said photodetector for delaying the electrical signals produced by said second photodetector a period of time equal to the period of time it takes said scanning means to scan from said second photodetector to said imaging detector.
Claim 4
Dependent Claim
77 words
An automatic focus control for a facsimile camera according to claim 1 wherein said means for producing said first and second electrical signals includes optical means for dividing the light from the scanning means into first, second and third parts and for directing them to said first photodetector, said second photodetector and said imaging detector, respectively, thereby assuring that said first and second electrical signals are in phase with the electrical signals produced by said imaging detector.
Claim 5
Dependent Claim
27 words
An automatic focus control for a facsimile camera acording to claim 3 wherein said means for dividing the light from said scanning means is a three-faced mirror.
Claim 6
Dependent Claim
77 words
An automatic focus control for a facsimile camera according to claim 1 including means for producing electrical signals indicative of predicted locations of said focal plane as said facsimile camera scans a flat terrain and a second movable stage means receiving said electrical signals indicative of predicted locations of said focal plane for moving said imaging detector so that it will remain in said predicted locations of said focal plane as said facsimile camera scans said terrain.
Claim 7
Dependent Claim
71 words
An automatic focus control for a facsimile camera according to claim 5 wherein said camera is located a distance L above said terrain and said means for moving said imaging detector includes means for moving said imaging detector proportional to f sin theta / L/f - sin theta where theta is the instantaneous angle that the scanning means makes with said terrain and f is the focal length of said lens.
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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) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |