US3801740A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Light pen circuit and remote noise-immune pulse detector for raster scan crt display system
Assignee: AT&T Inc
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Filing: 1971-12-15
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Granted: 1974-04-02
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Expires: 1991-12-15
Abstract
Abstract Video telephone stations, which include raster scan cathode-ray tubes, may be connected to each other or to a computing machine by way of a telephone switching system. Each station includes a light pen for providing sensings of the electron beam when video signals are received from the computing machine. The beam sensings are converted to pen pulses, combined with the synchronizing signals of the incoming video signals and the combined signals are transmitted to the computer. In order to distinguish between pen pulses and interference on the signaling link, the light pen aperture is arranged to be sufficient in size to enable the pen to sense an area covering elements of two successive scan lines on the screen, whereby two pen pulses are produced during a field. The computer recognizes a true light probe signal when successive ones of the received pen pulses are separated by an interval of time corresponding to the interval between beam traversals.
Inventors
- 👤 C Buzzard
- 👤 L Drew
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:51
CPC Classifications
G; G06; G06F; G06F3/00; G06F3/01; G06F3/03; G06F3/033; G06F3/038; G06F3/0383; H; H04; H04N; H04N7/00; H04N7/14; H04N7/141; H04N7/142
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
91 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen, a light pen for sensing the electron beam, the light pen having an aperture sufficient in size to enable the pen to sense an area covering elements of two successive scan lines on the screen, means responsive to each electron beam sensing for providing an output pulse, and means for producing a light probe signal when successive output pulses are separated by an interval of time corresponding to the interval between successive beam traversals.
Claim 2
Dependent Claim
91 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen, a light pen for sensing the electron beam, the light pen having an aperture sufficient in size to enable the pen to sense an area covering elements of two successive scan lines on the screen, means responsive to each electron beam sensing for providing an output pulse, and means for producing a light probe signal when successive output pulses are separated by an interval of time corresponding to the interval between successive beam traversals.
Claim 3
Dependent Claim
75 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen in accordance with claim 1, wherein the light pen includes a bundle of light sensitive fibers displaced in the aperture of the light pen and extending to the providing means and wherein the providing means includes a light sensitive device for sensing a light pulse passed through the fibers and for producing an electron pulse in response thereto.
Claim 4
Dependent Claim
61 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen in accordance with claim 1, wherein the traversing of the electron beam is controlled by synchronizing signals and wherein the system further includes means responsive to the producing means and the synchronizing signals for identifying the screen area being sensed by the light pen.
Claim 5
Dependent Claim
65 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen in accordance with claim 3, wherein the providing means includes means for combining the synchronizing signals and the output pulses, the means for producing detects the output pulses in the combined signals and pulses and the identifying means detects the synchronizing signals in the combining signals and pulses.
Claim 6
Dependent Claim
117 words
A video telephone system comprising at least one video telephone station and a remote data station, the video telephone station including a cathode-ray tube responsive to synchronizing signals for controlling an electron beam to traverse successive scan lines on a display screen, a light pen for sensing the electron beam and arranged to sense an area covering elements of two successive scan lines on the screen, and means responsive to each beam sensing for transmitting a pen pulse to the remote data station, the remote data station including means for producing a light probe signal in response to the reception of successive pulses separated by an interval of time corresponding to the interval between successive beam traversals.
Claim 7
Dependent Claim
117 words
A video telephone system comprising at least one video telephone station and a remote data station, the video telephone station including a cathode-ray tube responsive to synchronizing signals for controlling an electron beam to traverse successive scan lines on a display screen, a light pen for sensing the electron beam and arranged to sense an area covering elements of two successive scan lines on the screen, and means responsive to each beam sensing for transmitting a pen pulse to the remote data station, the remote data station including means for producing a light probe signal in response to the reception of successive pulses separated by an interval of time corresponding to the interval between successive beam traversals.
Claim 8
Dependent Claim
74 words
A video telephone system in accordance with claim 5 wherein the transmitting means further includes means for combining the synchronizing signals with the pen pulses and transmitting the synchronizing signals together with the pen pulses to the remote data station and wherein the remote station further includes means responsive to the reception of the synchronizing signals and to the produced light probe signal for identifying the screen area being sensed by the light pen.
Claim 9
Dependent Claim
55 words
A video telephone system in accordance with claim 6 wherein the remote data station further includes video signal producing and transmitting means for transmitting the synchronizing signals and video signals to the video telephone station and the video telephone station further includes receiving means for applying received video and synchronizing signals to the cathode-ray tube.
Claim 10
Dependent Claim
77 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen, a method of determining a true light probe signal in the presence of interference comprising the steps of: sensing an area on the screen sufficient in size to cover elements of two successive scan lines and producing a light probe signal when successive beam sensings are separated by an interval of time corresponding to the interval between successive beam traversals.
Claim 11
Dependent Claim
77 words
In a system for sensing an electron beam which traverses successive scan lines on a display screen, a method of determining a true light probe signal in the presence of interference comprising the steps of: sensing an area on the screen sufficient in size to cover elements of two successive scan lines and producing a light probe signal when successive beam sensings are separated by an interval of time corresponding to the interval between successive beam traversals.
Claim 12
Dependent Claim
56 words
A method of determining a true light probe signal in accordance with claim 8, wherein the sensing of an area on the screen includes the step of positioning an aperture of a light pen over the screen area to be sensed, the light pen aperture being dimensioned to correspond to the screen area to be sensed.
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) | 1977-04-01 | 1977-10-01 | 1978-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-01 | 1981-10-01 | 1982-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-01 | 1985-10-01 | 1986-04-02 | $7700.00 | Window Closed / Lapsed |