EP0255742A2 - Vorrichtung mit einer Fernsehkameraröhre und eine Fernsehkameraröhre für eine solche Vorrichtung - Google Patents

Vorrichtung mit einer Fernsehkameraröhre und eine Fernsehkameraröhre für eine solche Vorrichtung Download PDF

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Publication number
EP0255742A2
EP0255742A2 EP87201388A EP87201388A EP0255742A2 EP 0255742 A2 EP0255742 A2 EP 0255742A2 EP 87201388 A EP87201388 A EP 87201388A EP 87201388 A EP87201388 A EP 87201388A EP 0255742 A2 EP0255742 A2 EP 0255742A2
Authority
EP
European Patent Office
Prior art keywords
control grid
cathode
target
television camera
outer apertures
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.)
Withdrawn
Application number
EP87201388A
Other languages
English (en)
French (fr)
Other versions
EP0255742A3 (de
Inventor
Johannes Hendrikus Theodorus Van Roosmalen
Aart Adrianus Van Gorkum
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0255742A2 publication Critical patent/EP0255742A2/de
Publication of EP0255742A3 publication Critical patent/EP0255742A3/de
Withdrawn legal-status Critical Current

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Classifications

    • 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 present invention relates to an apparatus having a television camera tube and a television camera tube for use in such an apparatus.
  • the present invention is concerned with eliminating what is known as the "comet tail effect" which occurs when the electron beam is not sufficiently intense during the line sweep period to recharge or stabilise an anode target of the tube after a large discharge of the anode target has taken place due to a large intensity light source having been focused onto the camera picture tube.
  • the cathode voltage is increased to 5V and the voltage applied to the lens element is made negative with the result that the cross-over is refocused at the opening in the diaphragm and a large current is available for stabilization of the photo-conductive layer to 5 volts.
  • an apparatus having a television camera tube comprising an envelope within which are provided a target for producing a potential image corresponding to a scene and an electron gun for producing an electron beam directed to the target, the electron gun comprising a cathode, a control grid having an inner aperture surrounded by a plurality of outer apertures, and an anode having an inner aperture of smaller cross-sectional area than that in the control grid surrounded by the same number of outer apertures as are provided in the control grid, means for focusing the electron beam onto the target and deflection means with the aid of which a periodic scanning of the target by the electron beam is obtained for stabilization of the potential of the target to cathode potential for supplying output signals which correspond to the potential image, the deflection means comprising a deflection member for line sweeps and line fly-backs and a deflection member for frame sweeps and frame fly-backs, means for applying during line sweeps a first voltage to the cathode and a second voltage to the control grid
  • the cross sectional shape of the outer apertures in the control grid is different from that of the inner aperture.
  • the inner apertures of the control grid and the anode may be disposed substantially co-axially of the longitudinal axis of the envelope.
  • the outer apertures in the anode may be of a different size to those in the control grid and/or the outer apertures in the anode may be offset radially with respect to the outer apertures in the control grid.
  • the focusing means may be electrostatic or electromagnetic.
  • a television camera tube comprising an envelope within which are provided a target and an electron gun for producing an electron beam directed to the target, the electron gun comprising a cathode, a control grid having an inner aperture surrounded by a plurality of outer apertures and an anode having an inner aperture of smaller cross-sectional area than that in the control grid surrounded by a corresponding plurality of outer apertures as are provided in the control grid.
  • the camera tube shown in Figure 1 comprises an evacuated cylindrical envelope 10 of glass.
  • the tube comprises a target plate 11 which consists of a layer of substantially lead monoxide which is vapour deposited on a signal plate 12 which consists of a very thin layer of a readily conducting tin oxide provided on the inside of a window 13 formed by one end of the envelope 10.
  • a rotationally-symmetric electron gun 14 Near the other end of the interior of the envelope 10 is situated a rotationally-symmetric electron gun 14 which is coaxial with the envelope 10 and consists of a cathode 15, a multi-apertured control grid 16 and a multi-apertured acceleration anode 17.
  • a second cylindrical anode 18 and an electrically conductive mesh 20 provided on a cylindrical electrode 19.
  • a focusing electrode 23 which, in cooperation with the second cylindrical anode 18, forms a focusing lens is situated within the second cylindrical anode 18.
  • the tube is partly surrounded by line deflection coils and frame deflection coils, collectively denoted by the reference numeral 25.
  • the signal plate 12 is connected through a supply conductor 27 passed through the envelope 10 and a signal resistor 28 to one terminal of a voltage source 29, the other terminal of which is connected to earth.
  • Pulse generators 30, 32, and 36 are connected by respective conductors 31, 33, and 37 to the cathode 15, the control grid 16 and the focusing electrode 23.
  • a d.c. source 34 is connected by a conductor 35 to the accelerating anode 17.
  • the control grid 16 comprises a central (or inner) aperture 40 disposed coaxially of the envelope 10 and a plurality of outer apertures 42 surrounding the inner one.
  • a central (or inner) aperture 40 disposed coaxially of the envelope 10 and a plurality of outer apertures 42 surrounding the inner one.
  • Two embodiments of the control grid 16 showing different outer aperture shapes are shown in Figures 6 and 7. Irrespective of the aperture shapes the total cross sectional area of the outer apertures 42 exceeds the cross sectional area of the inner aperture 40.
  • the accelerating anode 17 has a generally similar arrangement of inner and outer apertures 44, 46, respectively, as are provided in the control grid 16.
  • the inner aperture 44 is of smaller cross-sectional area than that of the aperture 40.
  • the aperture 44 has a tubular extension 48 pointing towards the control grid 16 in order to provide more effetgriff.
  • the central portion of the accelerating anode including the extension 48 functions as a diaphragm to limit the cross sectional area of the electron beam passing through the aperture 44.
  • the number of outer apertures 42 in the control grid 16 corresponds to the number of outer apertures 46 in the accelerating anode 17.
  • the apertures 46 may be at the same radial distance as the apertures 42 - see aperture 46A ( Figure 7).
  • the apertures 46 may be bigger than the apertures 42 - see the aperture 46B ( Figure 7).
  • the apertures 46 may be at a different radial distance compared to those in the control grid 16 - see the aperture 46C ( Figure 7).
  • the outer apertures 42, 46 in both the electrodes 16, 17 may be arranged in two or more concentric rings.
  • the electron gun 14 when operating as an anti-comet-tail gun has different operating voltages on the cathode 15, control grid 16 and focusing electrode 23 during the line scanning mode than when during the line flyback mode.
  • the cathode 15 In the line scanning mode the cathode 15 is at zero volts (0 V), the control grid 16 has a mean voltage of -15 V and the accelerating anode 17 is at a voltage of 500 V.
  • the scene to be recorded is projected, by means of an optical system diagrammatically denoted by a lens 50, onto the target plate 11 of the tube through the window 13 and the signal plate 12.
  • a lens 50 An optical system diagrammatically denoted by a lens 50, onto the target plate 11 of the tube through the window 13 and the signal plate 12.
  • the free surface of the target plate 11 is scanned according to a rectangular frame by the electron beam produced by the electron gun 14.
  • an electron beam Under the influence of the mentioned voltages an electron beam is formed by electrons emitted only from the central portion of the cathode, as shown in Figure 3, due to the enlarged field strength. This means that the electron beam has a small cross-sectional area.
  • the electron beam cross-over is in the inner aperture of the accelerating anode so that little or no cathode current flows into the accelerating anode 17.
  • the electron beam leaving the accelerating anode is focused at the target by the electrostatic focusing lens formed by the electrodes 18 and 23.
  • the surface of the target plate is stabilised substantially at the potential (0 V) of the cathode, electric signals being formed which are derived from the signal resistor via a capacitor 52.
  • the pulse generator 30 supplies a positive pulse of 5 volts to the cathode 15. Simultaneously the pulse generator 32 supplies a negative pulse of 1 volt (that is -1 V) to the control grid 16.
  • the accelerating anode 17 remains at 500 V.
  • electrons emerge through the outer apertures 42 of the control grid 16 as well as from the central aperture 40 to form a plurality of electron beams as shown in Figure 4.
  • a central electron beam is present this is not essential and in any event its beam current is smaller say by an order of magnitude compared to the total beam current of the outer electron beams each one of which has a low beam current.
  • the focusing voltage is adjusted by the pulse generator 36 so that at the target plate 11, the electron beams are merged to form a large diameter spot which stabilises the target plate at the cathode voltage of 5V.
  • the desired stabilisation of the target plate can be achieved without the risk of damage by ions or x-rays to the photo-conductive layer of the target plate.
  • the large spot may follow a path such that it covers the line which has just been scanned.
  • Figure 5 are graphs of field strength (ordinate) against radius R (abscissa) of the conditions prevailing during line scanning, curve A, and during flyback, curve B.
  • R abcissa
  • the computer trajectory plots of Figures 3 and 4 have assumed that the radius of the inner aperture 40 is 185 ⁇ m and that the internal radius of the tubular extension 48 is 50 ⁇ m.
  • the diameter of the outer apertures 42, 46 is 150 ⁇ m.
  • the diameter of the cathode 15 is at least as large as the distance between diametrically located outer (or outermost holes.
  • the distance between the cathode 15 and the control grid is 1.0 mm
  • between the cathode 15 and the nearer edge of the tubular extension 48 is 3.5 mm
  • between the cathode 15 and the accelerating anode 17 is 5.5 mm
  • between the control grid 16 and the accelerating anode 17 is 4.0 mm.
  • the length of the tubular extension 48 is approximately equal to its diameter.
  • the operating voltages are as specified previously.
  • Figure 2 illustrates an embodiment of a television camera tube having electromagnetic focusing coils shown collectively by the reference numeral 60. Although it is a characteristic of electromagnetic focusing means that the electron beam remains focused during flyback, the fact that during flyback the electron beam comprises a multiplicity of low current beams avoids damage to the photo-conductive layer of the target plate 11.
  • Figure 2 also shows the electrical connections to the cathode heater 62, the cathode 15, the control grid 16 and the accelerating anode 17 to be by way of pins 64 extending through the envelope 10.
  • the operation of the television camera tube is substantially the same as for the tube shown in Figure 1, it will not be described.

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Electron Sources, Ion Sources (AREA)
EP87201388A 1986-08-01 1987-07-21 Vorrichtung mit einer Fernsehkameraröhre und eine Fernsehkameraröhre für eine solche Vorrichtung Withdrawn EP0255742A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8618854 1986-08-01
GB868618854A GB8618854D0 (en) 1986-08-01 1986-08-01 Television camera tube

Publications (2)

Publication Number Publication Date
EP0255742A2 true EP0255742A2 (de) 1988-02-10
EP0255742A3 EP0255742A3 (de) 1989-04-26

Family

ID=10602103

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87201388A Withdrawn EP0255742A3 (de) 1986-08-01 1987-07-21 Vorrichtung mit einer Fernsehkameraröhre und eine Fernsehkameraröhre für eine solche Vorrichtung

Country Status (3)

Country Link
EP (1) EP0255742A3 (de)
JP (1) JPS6343244A (de)
GB (1) GB8618854D0 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003054907A1 (en) * 2001-12-20 2003-07-03 Koninklijke Philips Electronics N.V. Cathode ray tube and electron gun

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1059415A (fr) * 1952-07-02 1954-03-24 Cfcmug Perfectionnement aux tubes cathodiques
FR1309662A (fr) * 1961-01-04 1962-11-16 Thomson Houston Comp Francaise Perfectionnements apportés aux canons à électrons
US3426235A (en) * 1966-12-20 1969-02-04 Rca Corp Pickup device
US3548250A (en) * 1968-02-13 1970-12-15 Philips Corp Apparatus having a television camera tube and television camera tube for use in such an apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1059415A (fr) * 1952-07-02 1954-03-24 Cfcmug Perfectionnement aux tubes cathodiques
FR1309662A (fr) * 1961-01-04 1962-11-16 Thomson Houston Comp Francaise Perfectionnements apportés aux canons à électrons
US3426235A (en) * 1966-12-20 1969-02-04 Rca Corp Pickup device
US3548250A (en) * 1968-02-13 1970-12-15 Philips Corp Apparatus having a television camera tube and television camera tube for use in such an apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ELECTRONIC APPLICATIONS, vol. 30, no. 1, March 1971, pages 18-32, Centrex Publishing Co., Eindhoven, NL; "Advances in plumbicon camera tube design" *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003054907A1 (en) * 2001-12-20 2003-07-03 Koninklijke Philips Electronics N.V. Cathode ray tube and electron gun

Also Published As

Publication number Publication date
JPS6343244A (ja) 1988-02-24
GB8618854D0 (en) 1986-09-10
EP0255742A3 (de) 1989-04-26

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Inventor name: VAN ROOSMALEN, JOHANNES HENDRIKUS THEODORUS