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US2188679A - Television and like system - Google Patents

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Publication number
US2188679A
US2188679A US276160A US27616039A US2188679A US 2188679 A US2188679 A US 2188679A US 276160 A US276160 A US 276160A US 27616039 A US27616039 A US 27616039A US 2188679 A US2188679 A US 2188679A
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United States
Prior art keywords
light
screen
sensitive device
light sensitive
spot
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US276160A
Inventor
Dovaston George
Graham George Edward Gordon
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Baird Television Ltd
Original Assignee
Baird Television Ltd
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Filing date
Publication date
Application filed by Baird Television Ltd filed Critical Baird Television Ltd
Application granted granted Critical
Publication of US2188679A publication Critical patent/US2188679A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/222—Studio circuitry; Studio devices; Studio equipment
    • H04N5/257—Picture signal generators using flying-spot scanners

Definitions

  • This invention relates to improvements in television and like system and is especially concerned with systems of the type in Which at a transmitter the luminescent screen of a cathode ray tube is scanned to produce a moving light spot which is projected upon the object to be scanned so that light passing through, in the case of a transparent object, or diffusely reflected from, in the case of an opaque object, becomes incident upon a light sensitive device to give rise to an image signal. It is found that in systems of this type uneven thickness of the fluorescent-material, relatively insensitive portions of material forming the screen of the cathode ray tube and uneven thickness of the glass end Wall of the tube cause an uneven background in the received image.
  • the present invention seeks to overcome this dimculty either wholly or in part by the provision of means whereby the brightness of the scanning spot is maintained substantially constant irrespective of local variations in the activity of the fluorescent screen or of the value of ray current e. g. due to hum, interference splashes and so on.
  • an auxiliary light sensitive device which is aected only by light incident directly thereon from the uorescent screen of a cathode ray tube, the output from the said light sensitive device being employed to oontrol the intensity of the electron beam incident upon the said screen.
  • the output from the said auxiliary light sensitive device is employed to control the gain of an amplier through which the signal derived from the signal-producing light sensitive device is passed.
  • Fig. 1 of the drawing the luminescent screen l of a cathode ray tube 2 is scanned and an image of the screen l is projected upon the transparency 3 by means of an optical system 4. Light passing through the transparency 3 is received upon a light sensitive cell 5 Which feeds a vision amplifier 6.
  • An auxiliary light sensitive cell is arranged to receive light from any part of the luminescent screen l and the output from this light sensitive cell is amplified by an aux- "5 iliary amplifier S and is used to control the amplification ⁇ of the amplifier in such a way that when the brightness of the luminous spot on the screen l increases, the amplification of the amplier 6 decreases and vice versa, the system 10 being adjusted so that the image signal output from the amplier 6 remains substantially constant independently of the brightness variation, Within a certain range, of the scanning spot on the screen l. 1
  • part of the output from the amplifier 8 may be used to control the intensity of the electron beam scanning the screen l so as to bring the brightness of the luminescent spot on the screen l to some predetermined level.
  • the auxiliary cell 'l should be placed at some distance from the screen l so that it is affected equally by light spots at different positions on the screen I but if this condition cannot be fulfilled the ampliiication of the auxiliary amplifier 8 may be caused to vary with the position of the scanning spot on the screen I. This may be effected by means of a variable-mu valve in the amplifier 8 which is arranged to be biassed by a signal derived from the scanning generators controlling the electron beam in the tube 2.
  • a television system comprising a cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means connected to said light sensitive device for providing an image vsignal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, and means connected to said auxiliary light sensitive device to compensate for local variations in the brightness of the spot of light on the screen.
  • a television system comprising a cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means connected M to said light sensitive device for providing an image signal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, and means connected to said auxiliary light sensitive device for controlling the intensity of said electron beam.
  • a television system comprisingl a cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means comprising an image signal amplier connected to said light sensitive device for providing an image signal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, and means connected to said auxiliary light sensitive device for controlling kthe gain of said irnage signal amplifier.
  • a television system comprising a ⁇ cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means connected to said light sensitive device for providing an image signal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, means connected to said auxiliary light sensitive device to compensate for local variations in the brightness of the spot of light on the screen, and means for controlling said last mentioned means so that for a given brightness of scanning spot on said screen it is substantially independent of the position of the said spot of light on said screen.
  • a television system according to claim 1 wherein the light spot is projected upon a transparent object so that light passing therethrough is incident upon the light sensitive device.
  • a television system according to claim 1 wherein the light spot is projected upon an opaque object so that light diiiusely reflected therefrom is incident upon the light sensitive device.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Transforming Electric Information Into Light Information (AREA)
  • Closed-Circuit Television Systems (AREA)

Description

Jan. 30, 1940. G. DovAsToN ET AL 2,188,679
TELEVISION AND LIKE SYSTEM Filed May 27, 1939 l//oEa AMPLIFIER.
PART 0F /wx/L/ARY MPL/HER carpar- ATTO RN EY Patented Jan. 30, 1940 v TELEvisIoN ANnLiKE SYSTEM George Dovaston and George Edward Gordon Graham, London, England, assignors to Baird Television Limited, London, England, a British Company Application May 27, 1939, Serial No. 276,160 In Great Britain November 5, 1937 6 Claims.
This invention relates to improvements in television and like system and is especially concerned with systems of the type in Which at a transmitter the luminescent screen of a cathode ray tube is scanned to produce a moving light spot which is projected upon the object to be scanned so that light passing through, in the case of a transparent object, or diffusely reflected from, in the case of an opaque object, becomes incident upon a light sensitive device to give rise to an image signal. It is found that in systems of this type uneven thickness of the fluorescent-material, relatively insensitive portions of material forming the screen of the cathode ray tube and uneven thickness of the glass end Wall of the tube cause an uneven background in the received image.
The present invention seeks to overcome this dimculty either wholly or in part by the provision of means whereby the brightness of the scanning spot is maintained substantially constant irrespective of local variations in the activity of the fluorescent screen or of the value of ray current e. g. due to hum, interference splashes and so on.
According to the present invention in a television or like system of the type described there is provided means for compensating for local variations in the brightness of the scanning spot on the screen of the cathode ray tube.
According to a feature of the present invention in television or like system of the type referred to there is provided an auxiliary light sensitive device which is aected only by light incident directly thereon from the uorescent screen of a cathode ray tube, the output from the said light sensitive device being employed to oontrol the intensity of the electron beam incident upon the said screen.
According to an alternative feature of the present invention the output from the said auxiliary light sensitive device is employed to control the gain of an amplier through which the signal derived from the signal-producing light sensitive device is passed.
In order that the present invention may be more particularly described reference is now made to the accompanying diagrammatic drawing which illustrates in Figs. l and 2 by Way of example two embodiments of the invention.
In Fig. 1 of the drawing the luminescent screen l of a cathode ray tube 2 is scanned and an image of the screen l is projected upon the transparency 3 by means of an optical system 4. Light passing through the transparency 3 is received upon a light sensitive cell 5 Which feeds a vision amplifier 6. An auxiliary light sensitive cell is arranged to receive light from any part of the luminescent screen l and the output from this light sensitive cell is amplified by an aux- "5 iliary amplifier S and is used to control the amplification `of the amplifier in such a way that when the brightness of the luminous spot on the screen l increases, the amplification of the amplier 6 decreases and vice versa, the system 10 being adjusted so that the image signal output from the amplier 6 remains substantially constant independently of the brightness variation, Within a certain range, of the scanning spot on the screen l. 1
Alternatively, or in addition, as shown in Fig. 2 part of the output from the amplifier 8 may be used to control the intensity of the electron beam scanning the screen l so as to bring the brightness of the luminescent spot on the screen l to some predetermined level. The auxiliary cell 'l should be placed at some distance from the screen l so that it is affected equally by light spots at different positions on the screen I but if this condition cannot be fulfilled the ampliiication of the auxiliary amplifier 8 may be caused to vary with the position of the scanning spot on the screen I. This may be effected by means of a variable-mu valve in the amplifier 8 which is arranged to be biassed by a signal derived from the scanning generators controlling the electron beam in the tube 2.
We claim:
1. A television system comprising a cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means connected to said light sensitive device for providing an image vsignal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, and means connected to said auxiliary light sensitive device to compensate for local variations in the brightness of the spot of light on the screen.
2. A television system comprising a cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means connected M to said light sensitive device for providing an image signal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, and means connected to said auxiliary light sensitive device for controlling the intensity of said electron beam.
3. A television system comprisingl a cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means comprising an image signal amplier connected to said light sensitive device for providing an image signal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, and means connected to said auxiliary light sensitive device for controlling kthe gain of said irnage signal amplifier.
4. A television system comprising a` cathode ray tube having a luminescent screen exposed to an electron beam, means for projecting the scanning spot of light formed by said beam on said screen upon an object to be scanned, a light sensitive device for receiving the light after it has been incident upon said object, means connected to said light sensitive device for providing an image signal corresponding to the light and shade of the object, an auxiliary light sensitive device arranged to receive light directly from said screen, means connected to said auxiliary light sensitive device to compensate for local variations in the brightness of the spot of light on the screen, and means for controlling said last mentioned means so that for a given brightness of scanning spot on said screen it is substantially independent of the position of the said spot of light on said screen.
5. A television system according to claim 1 wherein the light spot is projected upon a transparent object so that light passing therethrough is incident upon the light sensitive device.
6. A television system according to claim 1 wherein the light spot is projected upon an opaque object so that light diiiusely reflected therefrom is incident upon the light sensitive device.
GEORGE] DOVASTON. GEORGE EDWARD GORDON GRAHAM.
US276160A 1937-11-05 1939-05-27 Television and like system Expired - Lifetime US2188679A (en)

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GB30445/37A GB505197A (en) 1937-11-05 1937-11-05 Improvements in or relating to television and like systems

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US2188679A true US2188679A (en) 1940-01-30

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Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2523328A (en) * 1948-06-30 1950-09-26 Gen Electric Cathode-ray mapping system
US2530275A (en) * 1946-03-16 1950-11-14 Weingarten Joseph Cathode-ray tube image control
US2604534A (en) * 1946-08-02 1952-07-22 Cinema Television Ltd Apparatus for controlling scanning accuracy of cathode-ray tubes
US2625265A (en) * 1947-04-01 1953-01-13 Electric Sorting Machine Compa Photoelectric sorting apparatus
US2701850A (en) * 1951-02-02 1955-02-08 Philco Corp Automatic focus control for cathoderay tubes
US2705901A (en) * 1946-01-15 1955-04-12 Chalmers W Sherwin Oscillographic integrator
US2719247A (en) * 1951-03-29 1955-09-27 Marconi Wireless Telegraph Co Cathode ray tube flying spot scanners
DE1009231B (en) * 1955-01-15 1957-05-29 Fernseh Gmbh Television film scanners
US2794361A (en) * 1952-11-14 1957-06-04 Jr Philip A Shaffer Electric photometer
US2804498A (en) * 1950-10-17 1957-08-27 Pye Ltd Gamma control for flying spot scanner
US2804550A (en) * 1952-08-14 1957-08-27 Artzt Maurice Automatic light control
US2817702A (en) * 1951-10-12 1957-12-24 Bell Telephone Labor Inc Feedback intensity control for continuous film scanner
DE1023077B (en) * 1955-04-27 1958-01-23 Emi Ltd Circuit for cathode ray display tubes
US2844706A (en) * 1953-04-15 1958-07-22 Engelhard Ind Inc Method of producing minute perforations in solid bodies by thermal impact exerted byconcentrated corpuscular rays
US2862051A (en) * 1952-03-05 1958-11-25 Times Facsimile Corp Method and apparatus for facsimile telegnosis
US2890278A (en) * 1952-11-28 1959-06-09 Philips Corp Circuit-arrangement for use in television transmitting devices for scanning films
US2901539A (en) * 1956-04-20 1959-08-25 Russell H Morgan System for the automatic adaptation of television camera apparatus to varying light intensity levels
US2905757A (en) * 1954-02-03 1959-09-22 Emi Ltd Light correcting apparatus for electron pick-up tubes
US2915582A (en) * 1956-03-27 1959-12-01 Rca Corp Dynamic control circuit for cathode ray tubes
US2934653A (en) * 1957-03-07 1960-04-26 Itt Readout system
US3004467A (en) * 1953-06-09 1961-10-17 Fernseh G M B H Fa Film for use in televising pictures
US3030546A (en) * 1957-12-23 1962-04-17 Robert C Ohlmann Thermal image converter system
US3054999A (en) * 1955-07-20 1962-09-18 Frank P Forbath Correlation evaluator
US3065457A (en) * 1956-03-29 1962-11-20 Solartron Electronic Group Electronic apparatus for reading symbols
DE1193091B (en) * 1957-08-14 1965-05-20 Hazeltine Corp Image scanner of improved stability
DE1262644B (en) * 1963-02-08 1968-03-07 Ncr Co Character reading device
US5150957A (en) * 1989-10-20 1992-09-29 Walker David L Real time registration weave correction system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2476698A (en) * 1946-11-05 1949-07-19 Philco Corp Beam-velocity control system for cathode-ray tubes

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2705901A (en) * 1946-01-15 1955-04-12 Chalmers W Sherwin Oscillographic integrator
US2530275A (en) * 1946-03-16 1950-11-14 Weingarten Joseph Cathode-ray tube image control
US2604534A (en) * 1946-08-02 1952-07-22 Cinema Television Ltd Apparatus for controlling scanning accuracy of cathode-ray tubes
US2625265A (en) * 1947-04-01 1953-01-13 Electric Sorting Machine Compa Photoelectric sorting apparatus
US2523328A (en) * 1948-06-30 1950-09-26 Gen Electric Cathode-ray mapping system
US2804498A (en) * 1950-10-17 1957-08-27 Pye Ltd Gamma control for flying spot scanner
US2701850A (en) * 1951-02-02 1955-02-08 Philco Corp Automatic focus control for cathoderay tubes
US2719247A (en) * 1951-03-29 1955-09-27 Marconi Wireless Telegraph Co Cathode ray tube flying spot scanners
US2817702A (en) * 1951-10-12 1957-12-24 Bell Telephone Labor Inc Feedback intensity control for continuous film scanner
US2862051A (en) * 1952-03-05 1958-11-25 Times Facsimile Corp Method and apparatus for facsimile telegnosis
US2804550A (en) * 1952-08-14 1957-08-27 Artzt Maurice Automatic light control
US2794361A (en) * 1952-11-14 1957-06-04 Jr Philip A Shaffer Electric photometer
US2890278A (en) * 1952-11-28 1959-06-09 Philips Corp Circuit-arrangement for use in television transmitting devices for scanning films
US2844706A (en) * 1953-04-15 1958-07-22 Engelhard Ind Inc Method of producing minute perforations in solid bodies by thermal impact exerted byconcentrated corpuscular rays
US3004467A (en) * 1953-06-09 1961-10-17 Fernseh G M B H Fa Film for use in televising pictures
US2905757A (en) * 1954-02-03 1959-09-22 Emi Ltd Light correcting apparatus for electron pick-up tubes
DE1009231B (en) * 1955-01-15 1957-05-29 Fernseh Gmbh Television film scanners
DE1023077B (en) * 1955-04-27 1958-01-23 Emi Ltd Circuit for cathode ray display tubes
US3054999A (en) * 1955-07-20 1962-09-18 Frank P Forbath Correlation evaluator
US2915582A (en) * 1956-03-27 1959-12-01 Rca Corp Dynamic control circuit for cathode ray tubes
US3065457A (en) * 1956-03-29 1962-11-20 Solartron Electronic Group Electronic apparatus for reading symbols
US2901539A (en) * 1956-04-20 1959-08-25 Russell H Morgan System for the automatic adaptation of television camera apparatus to varying light intensity levels
US2934653A (en) * 1957-03-07 1960-04-26 Itt Readout system
DE1193091B (en) * 1957-08-14 1965-05-20 Hazeltine Corp Image scanner of improved stability
US3030546A (en) * 1957-12-23 1962-04-17 Robert C Ohlmann Thermal image converter system
DE1262644B (en) * 1963-02-08 1968-03-07 Ncr Co Character reading device
US5150957A (en) * 1989-10-20 1992-09-29 Walker David L Real time registration weave correction system

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Publication number Publication date
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