US3866079A - Television camera tube in which the detrimental effect of the return beam is counteracted - Google Patents

Television camera tube in which the detrimental effect of the return beam is counteracted Download PDF

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Publication number
US3866079A
US3866079A US447563A US44756374A US3866079A US 3866079 A US3866079 A US 3866079A US 447563 A US447563 A US 447563A US 44756374 A US44756374 A US 44756374A US 3866079 A US3866079 A US 3866079A
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US
United States
Prior art keywords
photoconductive layer
layer
diaphragm
electron beam
television camera
Prior art date
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
Application number
US447563A
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English (en)
Inventor
Theodore G Schut
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Individual
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Individual
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to NL7109140A priority Critical patent/NL7109140A/xx
Priority to DE2230529A priority patent/DE2230529C2/de
Priority to CA145,875,A priority patent/CA950954A/en
Priority to AU44005/72A priority patent/AU463685B2/en
Priority to GB3042972A priority patent/GB1336970A/en
Priority to FR7224007A priority patent/FR2144742B1/fr
Application filed by Individual filed Critical Individual
Priority to US447563A priority patent/US3866079A/en
Application granted granted Critical
Publication of US3866079A publication Critical patent/US3866079A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/84—Traps for removing or diverting unwanted particles, e.g. negative ions, fringing electrons; Arrangements for velocity or mass selection
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/021—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof arrangements for eliminating interferences in the tube
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26—Image pick-up tubes having an input of visible light and electric output
    • H01J31/28—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen
    • H01J31/34—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen having regulation of screen potential at cathode potential, e.g. orthicon
    • H01J31/38—Tubes with photoconductive screen, e.g. vidicon

Definitions

  • the invention relates to a television camera tube comprising, centered along an axis, an electron gun and a photoconductive layer which is provided on a transparent, conductive-signal layer, on which photoconductive layer a potential distribution is formed on the surface which as not in contact with the signal layer by projecting an optical image on the photoconductive layer, which potential distribution is periodically reduced to the potential of the cathode by scanning the photoconductive layer with an electron beam produced by the electron gun, said tube furthermore comprising a hollow cylindrical electrode in which a diaphragm is provided having a final aperture, taken in the direction of the electron gun to the photoconductive layer, which restricts the cross-section of the electron beam.
  • Such a television camera tube is generally known and is termed vidicon.
  • the operation of a vidicon is as follows: Under the influence of the deflection fields an electron beam ofa sufficient current strength scans the free surface of the photoconductive layer according to a given frame and brings said surface pointwise at the potential of the cathode which is termed zero volts. Be-
  • each point of the free surface of the photoconductive layer increases under the influence of a positive potential which is applied to the signal layer and under the influence of photoconductivity which is produced in the photoconductive layer by the optical image projected thereon.
  • Each point, or more exactly each elementary surface element, of the photoconductive layer together with the signal layer constitutes a capacitor.
  • the charge of said capacitor is periodically replenished by the scanning electron beam, for which more charge is required according as more light impinges upon the relevant point.
  • the current which consequently flows through the connection of the signal layer comprises the information of the projected image as a function of time.
  • the current strength of the electron beam must be sufficiently large to provide elementary capacitors which are strongly discharged as a result of large current intensity, with sufficient charge.
  • the electrons of the electron beam can no longer reach said point. Their velocity becomes zero and then they are accelerated in the reverse direction and constitute the socalled return beam. Said return beam also experiences the influence of the deflection fields and scans the surface of the diaphragm facing the photoconductive layer.
  • a part of the secondary electrons produced on the diaphragm has substantially the same kinetic energy as the electrons of the return beam and constitutes a secondary beam which together with the original (primary) electron beam scans the photoconductive layer but in a place different from the primary electron beam because the secondary beam is formed by electrons which have traversed the deflection fields three times instead of once. As a result of this an interfering signal is formed which is visible in the picture to be displayed.
  • the surface of the diaphragm facing the photoconductive layer in so far as it is not present in the immediate proximity of the axis of the tube, encloses an acute angle with the direction of the said axis.
  • This is preferably realized by giving the diaphragm the shape of a truncated cone in the narrow side of which the aperture is provided.
  • the secondary beam has a major direction which is not directed towards the photosensitive layer because a very considerable part of the produced secondary electrons has a direction which coincides in the same manner with the direction a of the primary electrons and with the normal to the surface of the diaphragm as this is the case upon reflection oflight rays (the angle of incidence is equal to the angle of reflection).
  • the television camera tube shown has an evacuated glass envelope 1 with connection pins 2, an electron gun 3 with a cathode 4, a grid 5 and a anode 6, a focusing lens 7 consisting of the cylindrical electrodes 8, 9 and 10, a gauze-shaped electrode 11 and a photocon ductive layer 12 which is provided on a transparent, conductive signal layer 13, which signal layer 13 is provided on the window 14 of the tube.
  • the cylindrical electrode 8 comprises a diaphragm 15 having an aperture 6 which restricts the cross-section of the electron beam produced by the electron gun 3. As a result of this, aberrations of the electron beam as a result of the focusing lens 7 are reduced and the electron beam scans the photosensitive layer 12 with a very small spot.
  • the interfering signal as a result of the secondary beam is thus mainly produced at those instants at which the secondary beam passes the non-used parts of the photoconductive layer 12. Since the photoconductive layer 12 is circular and the frame is rectangular, said parts have the shape of four circle segments.
  • the secondary beam has traversed the deflection field three times and the primary beam only once.
  • the frame of the secondary beam is therefore approximately three times as large 4 as the frame of the primary beam. The result of this is that, in particular in the case of uniform and weakly exposed scenes, a dark rectangle is visible in the displayed television picture the size of a third of the picture surrounded by four brighter circle segments. Said disturbing effect is prevented with a television camera tube according to the invention.
  • the diaphragm 15 Since the return beam has traversed the deflection fields two times the diaphragm 15 is scanned by the return beam according to a raster which is twice as large as the frame of the primary beam on the photoconductive layer 12.
  • the part 17 of the diaphragm 15 still causes a secondary beam with a major direction to wards the photoconductive layer 12 and must be chosen to be so small that said secondary beam remains within the part of the photoconductive layer 12 scanned by the primary beam since said part has a potential in the proximaty of 0 volts so that the secondary beam can land there with difficulty.
  • the photoconductive layer 12 has a diameter of approximately 10 mm and the frame of the primary beam forms a rectangle of6 X 8 mm.
  • the diameter of the part 17 of the diaphragm must then be significantly smaller than of the smallest dimension of the frame scanned by the primary beam, so significantly smaller than 4 mm, and in the example shown it is 2 mm.

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US447563A 1971-07-02 1974-03-04 Television camera tube in which the detrimental effect of the return beam is counteracted Expired - Lifetime US3866079A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
NL7109140A NL7109140A (en, 2012) 1971-07-02 1971-07-02
DE2230529A DE2230529C2 (de) 1971-07-02 1972-06-22 Fernsehkameraröhre
CA145,875,A CA950954A (en) 1971-07-02 1972-06-28 Television camera tube (vidicon) in which the detrimental effect of the return beam is counteracted
AU44005/72A AU463685B2 (en) 1971-07-02 1972-06-28 Television camera tube
GB3042972A GB1336970A (en) 1971-07-02 1972-06-29 Television camera tube
FR7224007A FR2144742B1 (en, 2012) 1971-07-02 1972-07-03
US447563A US3866079A (en) 1971-07-02 1974-03-04 Television camera tube in which the detrimental effect of the return beam is counteracted

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL7109140A NL7109140A (en, 2012) 1971-07-02 1971-07-02
US26525972A 1972-06-22 1972-06-22
US447563A US3866079A (en) 1971-07-02 1974-03-04 Television camera tube in which the detrimental effect of the return beam is counteracted

Publications (1)

Publication Number Publication Date
US3866079A true US3866079A (en) 1975-02-11

Family

ID=27351688

Family Applications (1)

Application Number Title Priority Date Filing Date
US447563A Expired - Lifetime US3866079A (en) 1971-07-02 1974-03-04 Television camera tube in which the detrimental effect of the return beam is counteracted

Country Status (7)

Country Link
US (1) US3866079A (en, 2012)
AU (1) AU463685B2 (en, 2012)
CA (1) CA950954A (en, 2012)
DE (1) DE2230529C2 (en, 2012)
FR (1) FR2144742B1 (en, 2012)
GB (1) GB1336970A (en, 2012)
NL (1) NL7109140A (en, 2012)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4268777A (en) * 1978-09-14 1981-05-19 U.S. Philips Corporation Cathode-ray tube
EP0046610A1 (en) * 1980-08-22 1982-03-03 Koninklijke Philips Electronics N.V. Television camera tube
US4363996A (en) * 1979-12-19 1982-12-14 Hitachi, Ltd. Vidicon type camera tube
US4427917A (en) 1979-06-22 1984-01-24 Hitachi, Ltd. Television camera tube with electrostatic focusing
US4503354A (en) * 1980-11-27 1985-03-05 English Electric Valve Company Limited Camera tubes
US6356015B2 (en) 1999-01-21 2002-03-12 Imaging & Sensing Technology Corporation Getter flash shield
US6376850B1 (en) * 1997-05-16 2002-04-23 Leica Microsystems Lithography Limited Electron beam aperture element

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5996639A (ja) * 1982-11-26 1984-06-04 Hitachi Ltd 撮像管
FR2630586A1 (fr) * 1988-04-22 1989-10-27 Thomson Csf Tube de camera avec ecran de suppression d'image parasite

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2747133A (en) * 1950-07-05 1956-05-22 Rca Corp Television pickup tube
US2839601A (en) * 1950-09-27 1958-06-17 Julius Cato Vredenburg Inglesb Methods of and apparatus for rendering visible magnetic and electric field patterns
US3183400A (en) * 1962-05-31 1965-05-11 Westinghouse Electric Corp Pickup tube with dark current supply source
US3307061A (en) * 1963-09-16 1967-02-28 Gen Electric Electrostatic return beam camera tube

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL160428C (nl) * 1968-02-13 1979-10-15 Philips Nv Beeldopneeminrichting met een beeldopneembuis en beeldop- neembuis voor een dergelijke inrichting.

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2747133A (en) * 1950-07-05 1956-05-22 Rca Corp Television pickup tube
US2839601A (en) * 1950-09-27 1958-06-17 Julius Cato Vredenburg Inglesb Methods of and apparatus for rendering visible magnetic and electric field patterns
US3183400A (en) * 1962-05-31 1965-05-11 Westinghouse Electric Corp Pickup tube with dark current supply source
US3307061A (en) * 1963-09-16 1967-02-28 Gen Electric Electrostatic return beam camera tube

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4268777A (en) * 1978-09-14 1981-05-19 U.S. Philips Corporation Cathode-ray tube
US4427917A (en) 1979-06-22 1984-01-24 Hitachi, Ltd. Television camera tube with electrostatic focusing
US4363996A (en) * 1979-12-19 1982-12-14 Hitachi, Ltd. Vidicon type camera tube
EP0046610A1 (en) * 1980-08-22 1982-03-03 Koninklijke Philips Electronics N.V. Television camera tube
US4503354A (en) * 1980-11-27 1985-03-05 English Electric Valve Company Limited Camera tubes
US6376850B1 (en) * 1997-05-16 2002-04-23 Leica Microsystems Lithography Limited Electron beam aperture element
US6356015B2 (en) 1999-01-21 2002-03-12 Imaging & Sensing Technology Corporation Getter flash shield

Also Published As

Publication number Publication date
AU4400572A (en) 1974-01-03
CA950954A (en) 1974-07-09
FR2144742A1 (en, 2012) 1973-02-16
AU463685B2 (en) 1975-07-31
DE2230529C2 (de) 1982-12-02
GB1336970A (en) 1973-11-14
FR2144742B1 (en, 2012) 1977-07-22
NL7109140A (en, 2012) 1973-01-04
DE2230529A1 (de) 1973-01-11

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