EP0553578A1 - Bildverstärkerröhre mit Intensitätsverteilungkompensation - Google Patents

Bildverstärkerröhre mit Intensitätsverteilungkompensation Download PDF

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Publication number
EP0553578A1
EP0553578A1 EP92400258A EP92400258A EP0553578A1 EP 0553578 A1 EP0553578 A1 EP 0553578A1 EP 92400258 A EP92400258 A EP 92400258A EP 92400258 A EP92400258 A EP 92400258A EP 0553578 A1 EP0553578 A1 EP 0553578A1
Authority
EP
European Patent Office
Prior art keywords
photocathode
thickness
layer
image intensifier
scintillator
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
EP92400258A
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English (en)
French (fr)
Other versions
EP0553578B1 (de
Inventor
Yvan Raverdy
Gérard Vieux
François Chareyre
Alain Tranchant
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
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Filing date
Publication date
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Priority to DE1992610795 priority Critical patent/DE69210795T2/de
Publication of EP0553578A1 publication Critical patent/EP0553578A1/de
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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
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode
    • H01J29/385—Photocathodes comprising a layer which modified the wave length of impinging radiation

Definitions

  • the present invention relates to an image intensifier tube input screen, and very particularly, but not exclusively, to a radiological image intensifier tube screen (IIR tube).
  • IIR tube radiological image intensifier tube screen
  • Radiological Image intensifier tubes allow a radiological image to be transformed into a visible image, generally for medical observation.
  • These tubes are vacuum tubes comprising an input screen, an electronic optical system, and a screen for observing the visible image.
  • the input screen includes a scintillator which converts incident X photons into visible photons which then excite a photocathode, generally constituted by an alkaline antimonide, for example potassium antimonide doped with cesium.
  • a photocathode generally constituted by an alkaline antimonide, for example potassium antimonide doped with cesium.
  • the photocathode thus excited generates a flow of electrons.
  • the flow of electrons from the photocathode is then transmitted by the electronic optical system which focuses the electrons and directs them onto an observation screen made up of a phosphor which then emits visible light.
  • This light can then be processed, for example, by a television, cinema or photography system.
  • the input screen comprises an aluminum substrate covered by the scintillator, itself covered by an electrically conductive layer and transparent to the light coming from the scintillator, for example made of oxide of indium.
  • the photocathode is deposited on this transparent layer.
  • X-rays strike the entry screen on the side of the aluminum substrate and pass through this substrate to then reach the material constituting the scintillator.
  • the light photons produced by the scintillator are emitted a little in all directions.
  • a substance such as cesium iodide is generally chosen as scintillating material, which has the property of growing in the form of crystals perpendicular to the surface on which they are deposited.
  • the needle crystals thus deposited tend to guide the light perpendicular to the surface, which is favorable for good image resolution.
  • the surface of the input screen is not flat but curved; it can be parabolic or hyperbolic for large screens, or more generally in the form of a spherical cap for smaller screens.
  • the electronic density generated by the screen is not uniform.
  • the brightness curve represents the light intensity in each point of the diameter of the output screen.
  • this curve is not horizontal; it is generally in the form of an arc of a circle slightly flattened in the center; the brightness of the output screen is maximum towards the center but decreases markedly as one approaches the edges.
  • the reduction in gloss on the edges relative to the center is of the order of 25%.
  • the reduction reaches 35%.
  • the brightness curve of the intensifier tube can be improved much more easily without affecting the thickness of the scintillator and without adding an optically absorbent layer, and by using rather some very specific properties of the thin transparent layer placed under the photocathode.
  • the photocathode is made of a chemically fairly unstable material which will react with the under layer on which it is deposited; this reaction will modify the emissive properties of the photocathode, and this to an extent related to the thickness of the under layer in the case where this thickness is very thin, that is to say in the case where it does not exceed not a few hundred nanometers.
  • the invention therefore proposes to place under the photocathode a very thin intermediate layer of radially variable thickness.
  • This layer is preferably transparent; it is preferably conductive; its thickness is preferably less than a few hundred angstroms; it is preferably made of indium oxide.
  • photocathodes potassium antimonide doped with cesium. These photocathodes are very reactive, especially during their deposition because of the high temperature prevailing in the depository. They are highly reducing and react strongly with rather oxidizing substances.
  • the final brightness of the intensifier tube strongly depends on the thickness of the layer of indium oxide. The dependence is much stronger than that which results from the simple (negligible) optical absorption properties of this layer. This is why it is particularly advantageous to give a variable thickness radially to this layer in order to modify the gloss curve at will.
  • the order of magnitude of the thicknesses is preferably as follows: approximately 250 angstroms at the edges and 400 angstroms at the center.
  • FIG. 1 shows a conventional brightness curve of an image intensifier tube, taken along a diameter of the output screen: it represents the brightness of a line of dots of the image visible on the screen of output as a function of the distance of these points from the center of the screen, assuming uniform illumination of the input screen.
  • the illumination is a uniform beam of X-rays.
  • FIG. 2 The general structure of a conventional radiological image intensifier is shown in FIG. 2.
  • the vacuum tube enclosure contains an EE input screen at the front and an ES output screen at the rear. Electron beam focusing electrodes are provided in the enclosure.
  • the input screen is most often curved in parabolic or hyperbolic form, with a strong curvature, for reasons of electronic optics, that is to say to make possible a homogeneous focusing of the electrons on the screen of exit.
  • This curvature is one of the causes of the shape of the gloss profile of the tube.
  • the EE entry screen is most often formed by a curved aluminum sheet 10, on which a scintillating layer 12 has been deposited (cesium iodide, several hundred micrometers thick) itself covered with a transparent conductive electrode 14 (most often made of indium oxide In2O3) then a photocathode 16 (for example made of potassium and cesium antimonide).
  • a scintillating layer 12 cesium iodide, several hundred micrometers thick
  • a transparent conductive electrode 14 most often made of indium oxide In2O3
  • a photocathode 16 for example made of potassium and cesium antimonide
  • the transparent conductive electrode (14) is intended to uniformly fix the potential of the photocathode.
  • an intermediate layer between the scintillator layer and the photocathode (and this layer may be the transparent conductive electrode 14 itself) be deposited with a thickness that is radially variable from the center to the edges, this intermediate layer being chosen from a material which modifies the emissive properties of the photocathode as a function of the thickness deposited.
  • the intermediate layer is quite simply the layer of indium oxide 14 serving as transparent conductive electrode under the photocathode.
  • the thickness varies radially. It is greater (thickness e1) in the center of the screen than at the edges (thickness e2), because it turns out that an increase in thickness of layer 14 causes a reduction in gloss. We therefore compensate for the excessive curvature of the gloss profile of FIG. 1.
  • the thickness variation is in practice continuous from the center to the edges.
  • the deposit with variable thickness is carried out in a known manner by evaporation in the presence of a mask which rotates in front of the surface to be covered, the shape of the mask being defined as a function of the thickness profile to be obtained.
  • the thicknesses are a few hundred angstroms.
  • indium oxide In2O3 is possible.
  • Partially reduced indium oxide In x O y in thickness of the order of a few hundred angstroms may also be suitable.
  • the variation in thickness can be of the same order of magnitude as for stoichiometric indium oxide.

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
EP92400258A 1990-08-31 1992-01-31 Bildverstärkerröhre mit Intensitätsverteilungkompensation Expired - Lifetime EP0553578B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE1992610795 DE69210795T2 (de) 1992-01-31 1992-01-31 Bildverstärkerröhre mit Intensitätsverteilungkompensation

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR9010870A FR2666447B1 (fr) 1990-08-31 1990-08-31 Tube intensificateur d'image avec compensation de courbe de brillance.

Publications (2)

Publication Number Publication Date
EP0553578A1 true EP0553578A1 (de) 1993-08-04
EP0553578B1 EP0553578B1 (de) 1996-05-15

Family

ID=9399992

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92400258A Expired - Lifetime EP0553578B1 (de) 1990-08-31 1992-01-31 Bildverstärkerröhre mit Intensitätsverteilungkompensation

Country Status (3)

Country Link
US (1) US5256870A (de)
EP (1) EP0553578B1 (de)
FR (1) FR2666447B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0853813B1 (de) * 1995-10-03 2003-07-16 Gatan, Inc. Vorrichtung zur auflösungserhöhung eines optischgekoppelten bildsensors für einen elektronenmikroskop

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2758002B1 (fr) * 1996-12-27 2004-07-02 Thomson Tubes Electroniques Systeme de visualisation avec ecran d'observation luminescent
IL120774A0 (en) * 1997-05-04 1997-09-30 Yeda Res & Dev Protection of photocathodes with thin films
FR2782388B1 (fr) 1998-08-11 2000-11-03 Trixell Sas Detecteur de rayonnement a l'etat solide a duree de vie accrue
US6700123B2 (en) * 2002-01-29 2004-03-02 K. W. Muth Company Object detection apparatus
US20040036973A1 (en) * 2002-06-01 2004-02-26 Giuseppe Iori Multi-layer interference filter having colored reflectance and substantially uniform transmittance and methods of manufacturing the same
CN104749604B (zh) * 2013-12-30 2018-06-01 同方威视技术股份有限公司 多技术融合闪烁探测器装置
GB2524778A (en) * 2014-04-02 2015-10-07 Univ Warwick Ultraviolet light detection

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0399378A2 (de) * 1989-05-23 1990-11-28 Kabushiki Kaisha Toshiba Röntgenbildverstärker
WO1990015432A1 (fr) * 1989-05-30 1990-12-13 Thomson Tubes Electroniques Ecran d'entree de tube intensificateur d'image radiologique

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3716713A (en) * 1969-01-09 1973-02-13 Varian Associates Input screen for image devices having reduced sensitivity in the cental region
US3706885A (en) * 1971-01-29 1972-12-19 Gen Electric Photocathode-phosphor imaging system for x-ray camera tubes
US3838273A (en) * 1972-05-30 1974-09-24 Gen Electric X-ray image intensifier input
NL8602629A (nl) * 1986-10-21 1988-05-16 Philips Nv Roentgenbeeldversterkerbuis met een scheidingslaag tussen de luminescentielaag en de photocathode.
NL8900040A (nl) * 1989-01-09 1990-08-01 Philips Nv Roentgenbeeldversterkerbuis met selectief filter.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0399378A2 (de) * 1989-05-23 1990-11-28 Kabushiki Kaisha Toshiba Röntgenbildverstärker
WO1990015432A1 (fr) * 1989-05-30 1990-12-13 Thomson Tubes Electroniques Ecran d'entree de tube intensificateur d'image radiologique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 13, no. 207 (E-758)(3555) 15 Mai 1989 & JP-A-1 024 343 ( TOSHIBA CORP ) 26 Janvier 1989 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0853813B1 (de) * 1995-10-03 2003-07-16 Gatan, Inc. Vorrichtung zur auflösungserhöhung eines optischgekoppelten bildsensors für einen elektronenmikroskop

Also Published As

Publication number Publication date
FR2666447A1 (fr) 1992-03-06
EP0553578B1 (de) 1996-05-15
US5256870A (en) 1993-10-26
FR2666447B1 (fr) 1996-08-14

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