EP0851455A1 - Röntgenbildverstärkerröhre - Google Patents

Röntgenbildverstärkerröhre Download PDF

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Publication number
EP0851455A1
EP0851455A1 EP97403143A EP97403143A EP0851455A1 EP 0851455 A1 EP0851455 A1 EP 0851455A1 EP 97403143 A EP97403143 A EP 97403143A EP 97403143 A EP97403143 A EP 97403143A EP 0851455 A1 EP0851455 A1 EP 0851455A1
Authority
EP
European Patent Office
Prior art keywords
layer
electrons
screen
tube
phosphors
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.)
Granted
Application number
EP97403143A
Other languages
English (en)
French (fr)
Other versions
EP0851455B1 (de
Inventor
Yvan Raverdy
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.)
Thales Electron Devices SA
Original Assignee
Thomson Tubes Electroniques
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 Thomson Tubes Electroniques filed Critical Thomson Tubes Electroniques
Publication of EP0851455A1 publication Critical patent/EP0851455A1/de
Application granted granted Critical
Publication of EP0851455B1 publication Critical patent/EP0851455B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/28—Luminescent screens with protective, conductive or reflective layers
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • 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
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/185—Luminescent screens measures against halo-phenomena
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • G21K2004/04—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens with an intermediate layer

Definitions

  • the invention relates to image intensifier tubes.
  • the luminescent observation screen of the IIR tube has the role of generate a visible light image when the screen is excited by a electron beam hitting its photoluminescent surface.
  • the invention relates more particularly to the luminescent observation screen comprising means to improve the contrast of the image.
  • Image intensifier tubes are vacuum tubes including an entry screen, located at the front of the tube, an optical system electronic, and an image observation screen located at the rear of the tube, side of an exit window from the latter.
  • the screen input also has a scintillator screen that converts x photons visible photon incidents.
  • Visible photons excite a photocathode which in response generates a flow of electrons.
  • This flow of electrons is then transmitted by a electronic optics system that focuses electrons, and directs them on the observation screen.
  • the observation screen has one or more layers of luminophore grains deposited on a glass support transparent. The phosphors struck by the electrons then produce visible light from the outside of the tube through the transparent support.
  • Figure 1 schematically shows such an intensifier tube image of the radiological type.
  • the intensifier tube 1 comprises a glass envelope 2 one end of which, at the front of the tube, is closed by an inlet window 3, exposed to x-ray radiation.
  • the second end of the envelope forming the back of the tube is closed by the observation screen 4 transparent to light.
  • X-rays are converted into light rays by a screen scintillator 5.
  • the light rays excite a photocathode 6 which response produces electrons.
  • These electrons are extracted from the photocathode 6 and accelerated to the observation screen 4 using different electrodes 7, and an anode 8 arranged along an axis longitudinal 9 of the tube and which form the electronic optical system.
  • the observation screen 4 is formed by a transparent piece of glass attached tightly to the envelope 2. This piece of glass further constitutes in the example shown, a support which carries phosphors 10, for example.
  • establishing the acceleration potential of electrons from the photocathode of the tube is performed by a grid under voltage acceleration located near the observation screen. Electrons accelerated cross the grid reaching the phosphors 10, from the screen of observation, which produce visible light.
  • the acceleration potential is obtained by a voltage applied to a thin layer of conductive material, by example a metal deposited directly on the phosphor layer of the observation screen.
  • a metal deposited directly on the phosphor layer of the observation screen The small thickness of this metal layer allows the passage without significant loss of electrons to the phosphors.
  • the thickness of the metal layer for example in aluminum, is around 0.3 micrometer.
  • This thickness very small, is chosen so that the layer is transparent to electrons, so that they reach the photocathode without losses.
  • Aluminum is not naturally transparent to electrons except in very small thickness.
  • spoke tubes cathodic and not for radiological image intensifier tubes cover the aluminum layer with a carbon layer to limit the production of secondary electrons by the phosphor layer.
  • the carbon is indeed a material with a very low emission coefficient secondary, which therefore does not generate too many secondary electrons when it is struck by the electrons of the incident beam, and which is also relatively transparent for these incident electrons (high energy) but which is absorbing for the secondary electrons which would be emitted by the layer of phosphorous.
  • the backscatter electrons represent around 20% of the incident electron beam Ei, parasitizing strongly the image produced by the observation screen.
  • the electrons of backscatter are dispersed during their emission inside the tube and when they fall back on the observation screen, accelerated by the tensions polarization of the tube, these backscatter electrons, excite totally distributed, the phosphors of the observation screen.
  • This secondary phenomenon produces background noise, resulting in decrease in image contrast.
  • the invention proposes an IIR tube comprising a vacuum electronic tube and a luminescent observation screen (20), the screen having a support glass on which a layer of phosphors is deposited, the observation screen producing a bright image when the phosphors are excited by an electron beam, and the layer of phosphors being covered with a layer of aluminum, characterized in that the aluminum layer has a thickness of at least 1 micrometer in the aim of reducing on the one hand the quantity of electrons re-emitted from the screen observation towards the tube and on the other hand the proportion of these electrons which come back to strike the layer of phosphors.
  • the aluminum layer will act as an electron filter for backscatter, by first absorbing electrons from backscatter when at the time of their generation by the impact of the beam of incident electrons Ei on the phosphors, they cross the layer of aluminum in the opposite direction to that of the incident electron beam and by absorbing other backscatter electrons a second time, when they cross the same layer of aluminum again when they fall towards the observation screen, in the direction of the incident electrons.
  • the aluminum layer is in the form of a coating deposited, in principle directly on the phosphors of the screen of observation but which could possibly be on a support located in the path of incident electrons near the observation screen.
  • the coating also fulfills the function of establishing the potential for electron acceleration over the entire surface of the phosphors, what is necessary in the case of the tube observation screen image intensifiers.
  • the thickness of the aluminum layer is preferably included between 1 and 3 micrometers. A value of 1.5 to 2 micrometers is very suitable good.
  • the aluminum layer can also be separated, with a small distance, phosphors, by the vacuum of the tube, in this case the coating is supported by a thin grid.
  • An incident electron beam Ei crosses with a loss of electrons, the aluminum layer 30, in an area A1 of the screen of observation and excites the layers of phosphors 28 producing a light emission h1, visible through the support glass 22, and backscatter electrons Er1, Er2, Across Ern ,.
  • These backscatter electrons, generated by the phosphors, are returned to the inside of the tube and are found to be partially absorbed, a first time, by crossing the layer aluminum 30, in their displacement towards the inside of the tube, then find again partially absorbed a second time, falling back on the observation screen, attracted by the bias potential applied to the aluminum layer.
  • the reduction of the electrons backscatter absorbed by this aluminum layer leads to a noticeable improvement in image contrast.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
EP97403143A 1996-12-27 1997-12-23 Röntgenbildverstärkerröhre Expired - Lifetime EP0851455B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9616114 1996-12-27
FR9616114A FR2758002B1 (fr) 1996-12-27 1996-12-27 Systeme de visualisation avec ecran d'observation luminescent

Publications (2)

Publication Number Publication Date
EP0851455A1 true EP0851455A1 (de) 1998-07-01
EP0851455B1 EP0851455B1 (de) 2003-04-02

Family

ID=9499221

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97403143A Expired - Lifetime EP0851455B1 (de) 1996-12-27 1997-12-23 Röntgenbildverstärkerröhre

Country Status (5)

Country Link
US (1) US5981935A (de)
EP (1) EP0851455B1 (de)
JP (1) JPH10214573A (de)
DE (1) DE69720395T2 (de)
FR (1) FR2758002B1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7498557B2 (en) 2005-09-08 2009-03-03 Applied Materials Israel Ltd. Cascaded image intensifier
JP2007095631A (ja) * 2005-09-30 2007-04-12 Toshiba Corp Ｘ線イメージ管
US7728274B2 (en) * 2007-03-30 2010-06-01 Subrahmanyam Pilla Imaging system with negative electron affinity photocathode

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2152731A1 (de) * 1971-09-08 1973-04-27 Hitachi Ltd
FR2209213A1 (de) * 1972-12-04 1974-06-28 Hitachi Ltd
FR2217793A1 (de) * 1973-02-14 1974-09-06 Hitachi Ltd
DE2553507A1 (de) * 1975-11-28 1977-06-02 Licentia Gmbh Leuchtschirm, insbesondere fuer eine bildverstaerkerroehre
EP0067470A1 (de) * 1981-06-03 1982-12-22 Koninklijke Philips Electronics N.V. Bildröhre und Verfahren zur Herstellung eines Bildschirms für eine solche Bildröhre
DE4001516A1 (de) * 1990-01-19 1991-07-25 Siemens Ag Schichtanordnung mit wenigstens einer lichtdurchlaessgen schicht
EP0610872A2 (de) * 1993-02-08 1994-08-17 Matsushita Electric Industrial Co., Ltd. Elektronenstrahl-Bildwiedergabevorrichtung und Erzeugung derselben
JPH0822784A (ja) * 1994-05-02 1996-01-23 Matsushita Electric Ind Co Ltd 投写用陰極線管とその投写用陰極線管を用いた投写型表示装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2647955B1 (fr) * 1989-05-30 1991-08-16 Thomson Tubes Electroniques Ecran d'entree de tube intensificateur d'image radiologique
FR2666447B1 (fr) * 1990-08-31 1996-08-14 Thomson Tubes Electroniques Tube intensificateur d'image avec compensation de courbe de brillance.
FR2681727B1 (fr) * 1991-09-20 1993-11-05 Thomson Tubes Electroniques Tube intensificateur d'image a correction de brillance.
FR2683388A1 (fr) * 1991-10-31 1993-05-07 Thomson Tubes Electroniques Tube intensificateur d'image radiologique a resolution amelioree.

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2152731A1 (de) * 1971-09-08 1973-04-27 Hitachi Ltd
FR2209213A1 (de) * 1972-12-04 1974-06-28 Hitachi Ltd
FR2217793A1 (de) * 1973-02-14 1974-09-06 Hitachi Ltd
DE2553507A1 (de) * 1975-11-28 1977-06-02 Licentia Gmbh Leuchtschirm, insbesondere fuer eine bildverstaerkerroehre
EP0067470A1 (de) * 1981-06-03 1982-12-22 Koninklijke Philips Electronics N.V. Bildröhre und Verfahren zur Herstellung eines Bildschirms für eine solche Bildröhre
DE4001516A1 (de) * 1990-01-19 1991-07-25 Siemens Ag Schichtanordnung mit wenigstens einer lichtdurchlaessgen schicht
EP0610872A2 (de) * 1993-02-08 1994-08-17 Matsushita Electric Industrial Co., Ltd. Elektronenstrahl-Bildwiedergabevorrichtung und Erzeugung derselben
JPH0822784A (ja) * 1994-05-02 1996-01-23 Matsushita Electric Ind Co Ltd 投写用陰極線管とその投写用陰極線管を用いた投写型表示装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 096, no. 005 31 May 1996 (1996-05-31) *

Also Published As

Publication number Publication date
US5981935A (en) 1999-11-09
JPH10214573A (ja) 1998-08-11
DE69720395D1 (de) 2003-05-08
EP0851455B1 (de) 2003-04-02
DE69720395T2 (de) 2004-03-25
FR2758002A1 (fr) 1998-07-03
FR2758002B1 (fr) 2004-07-02

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