US3624286A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Noise cancellation in video signal-generating systems
Assignee: RCA Corp
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Filing: 1969-11-10
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Granted: 1971-11-30
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Expires: 1989-11-10
Abstract
Abstract A transparent optically recorded subject is scanned by light produced by electron beam excitation of a phosphor screen, the light transmitted through the subject being modulated in intensity proportionately (1) to the desired subject representative video signal and (2) to undesired noise effects inadvertently produced by the phosphor screen excitation. The light derived from the phosphor screen and the subject is divided by a semireflecting mirror, which may be a dichroic device, and the light transmitted through the mirror and modulated proportionately to both the desired video signal and the undesired noise effects is directed to a first detector to produce a first signal representative of such light, while the light reflected by the mirror and modulated substantially only by the undesired noise effects is directed to a second detector to produce a second signal representative of the noise effects. The first and second signals are applied to a third detector which functions to determine the ratio of the first and second signals and to produce an output signal including substantially only the desired subject representative video signal. In one embodiment, the subject is a photographic transparency and the semireflecting mirror is located between the subject and a flying spot cathoderay tube scanner. In another embodiment, the subject is a record made by a video signal modulated electron beam bombardment of a cathodochromic layer of a cathode-ray tube which also has, behind the cathodochromic layer, a light-producing phosphor layer which is scanned by an unmodulated electron beam, the first and second detector means comprising photomultipliers which, together with a dichroic semireflecting mirror and at least the screen of the cathode-ray tube, are enclosed in a light-tight structure which includes two hollow frustoconical internally reflecting lightconducting members located to direct light respectively transmitted and reflected by the dichroic mirror to the first and second photomultipliers respectively.
Inventors
- 👤 Douglas Robert Bosomworth
- 👤 Zoltan Joseph Kiss
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 20:48
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/222; H04N5/257
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
177 words
In a system for generating a video signal representative of an optically recorded subject by directing light through said subject from a source of illumination, apparatus for improving the signal-to-noise ratio of the generated video signal by effectively eliminating from said generated video signal undesired noise effects inadvertently produced by the light derived from said source of illumination, said apparatus comprising: first detector means responsive to light directed through said subject from said source of illumination to produce a first signal including said desired video signal representative of said subject and an undesired noise signal produced by the light derived from said source of illumination; second detector means responsive to light from said source of illumination substantially unaffected by said subject to produce a second signal representative of said noise signal to the substantial exclusion of said video signal; and third detector means responsive to substantially equivalent bandwidths of said first and second produced signals to detect the ratio of said first and second signals to produce an output signal including substantially only said desired video signal.
Claim 2
Dependent Claim
177 words
In a system for generating a video signal representative of an optically recorded subject by directing light through said subject from a source of illumination, apparatus for improving the signal-to-noise ratio of the generated video signal by effectively eliminating from said generated video signal undesired noise effects inadvertently produced by the light derived from said source of illumination, said apparatus comprising: first detector means responsive to light directed through said subject from said source of illumination to produce a first signal including said desired video signal representative of said subject and an undesired noise signal produced by the light derived from said source of illumination; second detector means responsive to light from said source of illumination substantially unaffected by said subject to produce a second signal representative of said noise signal to the substantial exclusion of said video signal; and third detector means responsive to substantially equivalent bandwidths of said first and second produced signals to detect the ratio of said first and second signals to produce an output signal including substantially only said desired video signal.
Claim 3
Dependent Claim
79 words
Apparatus as defined in claim 1, wherein: said source of illumination comprises a cathode ray tube having a faceplate and including; a target electrode having a layer of phosphor material located behind said faceplate and capable of emitting light through said faceplate having a given frequency spectrum when excited by an electron beam; and means for scanning said phosphor layer with an unmodulated reading electron beam to produce substantially uniform light emission from all scanned portions of said electrode.
Claim 4
Dependent Claim
55 words
Apparatus as defined in claim 2, and also having an optical system including: a semireflecting mirror to transmit a first portion of the light from said cathode-ray tube target electrode to said first detecting means and to reflect a second portion of the light from said cathode-ray tube target electrode to said second detecting means.
Claim 5
Dependent Claim
304 words
In a system for generating a video signal representative of an optically recorded subject from a source of illumination, said source of illumination comprising a cathode-ray tube having a faceplate and iNcluding a target electrode having a layer of phosphor material behind said faceplate and capable of emitting light through said faceplate having a given frequency spectrum when excited by an electron beam, and means for scanning said phosphor layer with an unmodulated reading electron beam to produce substantially uniform light emission from all scanned portions of said electrode; apparatus for improving the signal-to-noise ratio of the generated video signal by effectively eliminating from said generated video signal undesired noise effects inadvertently produced by the light derived from said source of illumination, said apparatus comprising: first detector means responsive to light directed through said subject from said source of illumination to produce a first signal including said desired video signal produced by the light derived from said source of illumination; second detector means responsive to light from said source of illumination substantially unaffected by said subject to produce a second signal representative of said noise signal to the substantial exclusion of said video signal; an optical system including a semireflecting mirror to transmit a first portion of the light from said cathode-ray tube target electrode to said first detecting means and to reflect a second portion of the light from said cathode-ray tube target electrode to said second detecting means; third detector means responsive to said first and second produced signals to detect the ratio of said first and second signals to produce an output signal including substantially only said desired video signal; said semireflecting mirror being a dichroic device which transmits a first portion of light having a first frequency spectrum and reflects said second portion of light having a second frequency spectrum.
Claim 6
Dependent Claim
304 words
In a system for generating a video signal representative of an optically recorded subject from a source of illumination, said source of illumination comprising a cathode-ray tube having a faceplate and iNcluding a target electrode having a layer of phosphor material behind said faceplate and capable of emitting light through said faceplate having a given frequency spectrum when excited by an electron beam, and means for scanning said phosphor layer with an unmodulated reading electron beam to produce substantially uniform light emission from all scanned portions of said electrode; apparatus for improving the signal-to-noise ratio of the generated video signal by effectively eliminating from said generated video signal undesired noise effects inadvertently produced by the light derived from said source of illumination, said apparatus comprising: first detector means responsive to light directed through said subject from said source of illumination to produce a first signal including said desired video signal produced by the light derived from said source of illumination; second detector means responsive to light from said source of illumination substantially unaffected by said subject to produce a second signal representative of said noise signal to the substantial exclusion of said video signal; an optical system including a semireflecting mirror to transmit a first portion of the light from said cathode-ray tube target electrode to said first detecting means and to reflect a second portion of the light from said cathode-ray tube target electrode to said second detecting means; third detector means responsive to said first and second produced signals to detect the ratio of said first and second signals to produce an output signal including substantially only said desired video signal; said semireflecting mirror being a dichroic device which transmits a first portion of light having a first frequency spectrum and reflects said second portion of light having a second frequency spectrum.
Claim 7
Dependent Claim
82 words
Apparatus as defined in claim 4, wherein: said optically recorded subject is a photographic transparency located between said dichroic device and said first detector means, whereby said first portion of light transmitted to said first detector means includes both the subject-representative light and the light representing the undesired noise effects derived from said cathode-ray tube target electrode, and said second portion of light reflected to said second detector means represents only the undesired noise effects derived from said cathode-ray tube target electrode.
Claim 8
Dependent Claim
57 words
Apparatus as defined in claim 4, wherein: said optically recorded subject includes a layer of cathodochromic material within said cathode-ray tube and located between said faceplate and said layer of phosphor material; and means for scanning said cathodochromic layer with a video signal-modulated writing electron beam to store in said cathodochromic layer an image desired for display.
Claim 9
Dependent Claim
105 words
Apparatus as defined in claim 6, wherein: said video signal-modulated writing electron beam is of a relatively high current intensity sufficient to penetrate said phosphor layer and to bombard said cathodochromic layer; and said cathodochromic material has the property of being normally white and of changing color under bombardment by said writing electron beam, the induced optical density of said color changes being proportional to said video signal modulation of said writing electron beam, and of persisting after cessation of said writing electron beam bombardment, whereby to store in said cathodochromic layer an image represented by said video signal modulation of said writing electron beam.
Claim 10
Dependent Claim
111 words
Apparatus as defined in claim 7, wherein: said cathodochromic material is of a character to have an induced absorption band peaking at a frequency which determines the color of the stored image; and the given frequency spectrum of said phosphor layer includes the peak induced absorption band frequency of said cathodochromic layer so that the uniform light radiation produced by said scansion of said phosphor layer by said unmodulated reading electron beam is absorbed in said cathodochromic layer in direct proportion to said induced optical density of respective points of said cathodochromic layer, whereby to produce light emission external of said cathode-ray tube which is inversely proportional to said stored image.
Claim 11
Dependent Claim
61 words
Apparatus as defined in claim 8, wherein: said unmodulated reading electron beam is of a relatively low current intensity sufficient only to excite said phosphor layer to produce said uniform light emission without penetrating it to bombard said cathodochromic layer; and the given frequency spectrum of said phosphor material extends outside of the induced absorption frequency band of said cathodochromic material.
Claim 12
Dependent Claim
73 words
Apparatus as defined in claim 9, wherein: said dichroic device is of a character to transmit light having the peak induced absorption band frequency of said cathodochromic layer and to prevent the transmission of light having frequencies outside of the induced absorption frequency band of said cathodochromic layer, and said dichroic device also being of a character to reflect light having frequencies outside of the induced absorption frequency band of said cathodochromic layer.
Claim 13
Dependent Claim
19 words
Apparatus as defined in claim 10, wherein: said first and second detector means respectively comprise first and second photomultipliers.
Claim 14
Dependent Claim
289 words
Apparatus comprising the combination of: a cathode-ray tube having a faceplate; a layer of cathodochromic material on the inside of said faceplate for storing an image; a phosphor layer overlying said cathodochromic layer, said phosphor layer being subject to the production of light over a frequency spectrum encompassing at least a portion of the effective induced absorption frequency band of said cathodochromic layer and additionally encompassing frequencies lying outside said effective absorption band; and electron beam source; and beam deflection means for tracing a scanning raster on the inside of said faceplate with an electron beam from said source; means for selectably altering the mode of operation of said cathode-ray tube between a write mode in which said beam is of a relatively high current intensity and modulated in accordance with video input signals representative of an image to be stored, and a read mode in which said beam is of a relatively low current intensity and substantially unmodulated; frequency-selective optical means disposed to receive light transmitted through said faceplate during operation of said cathode-ray tube in said read mode for directing components of said transmitted light having frequencies falling within said absorption band to a first light path and for directing components of said transmitted light having frequencies falling within said frequency spectrum of light production by said phosphor layer but lying outside said effective absorption band to a second light path; first light-detecting means disposed in said first light path for generating a first signal; second light-detecting means disposed in said second light path for generating a second signal; and means coupled to said first and second light detecting means for modifying said first signal in response to said second signal to provide a corrected output signal.
Claim 15
Dependent Claim
289 words
Apparatus comprising the combination of: a cathode-ray tube having a faceplate; a layer of cathodochromic material on the inside of said faceplate for storing an image; a phosphor layer overlying said cathodochromic layer, said phosphor layer being subject to the production of light over a frequency spectrum encompassing at least a portion of the effective induced absorption frequency band of said cathodochromic layer and additionally encompassing frequencies lying outside said effective absorption band; and electron beam source; and beam deflection means for tracing a scanning raster on the inside of said faceplate with an electron beam from said source; means for selectably altering the mode of operation of said cathode-ray tube between a write mode in which said beam is of a relatively high current intensity and modulated in accordance with video input signals representative of an image to be stored, and a read mode in which said beam is of a relatively low current intensity and substantially unmodulated; frequency-selective optical means disposed to receive light transmitted through said faceplate during operation of said cathode-ray tube in said read mode for directing components of said transmitted light having frequencies falling within said absorption band to a first light path and for directing components of said transmitted light having frequencies falling within said frequency spectrum of light production by said phosphor layer but lying outside said effective absorption band to a second light path; first light-detecting means disposed in said first light path for generating a first signal; second light-detecting means disposed in said second light path for generating a second signal; and means coupled to said first and second light detecting means for modifying said first signal in response to said second signal to provide a corrected output signal.
Claim 16
Dependent Claim
16 words
Apparatus in accordance with claim 12 wherein said frequency-selective optical means comprises a dichroic semireflecting mirror.
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) | 1974-11-29 | 1975-05-31 | 1975-11-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-29 | 1979-05-31 | 1979-11-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-29 | 1983-05-31 | 1983-11-30 | $7700.00 | Window Closed / Lapsed |