US3774038A - Imaging device comprising an image-intensifying tube - Google Patents

Imaging device comprising an image-intensifying tube Download PDF

Info

Publication number
US3774038A
US3774038A US00242693A US3774038DA US3774038A US 3774038 A US3774038 A US 3774038A US 00242693 A US00242693 A US 00242693A US 3774038D A US3774038D A US 3774038DA US 3774038 A US3774038 A US 3774038A
Authority
US
United States
Prior art keywords
layer
cover layer
image
tube
photocathode
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
US00242693A
Other languages
English (en)
Inventor
M Ligtenberg
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.)
US Philips Corp
Original Assignee
US Philips Corp
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 US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US3774038A publication Critical patent/US3774038A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING 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
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode

Definitions

  • the invention relates to an imaging device provided with an image-intensifying tube, comprising a photocathode and a luminescent layer for collecting electrons emitted by the photocathode, the side of the luminescent layer facing the photocathode being provided with a light-impervious, electrically conducting cover layer, said device comprising means for applying an adjustable acceleration voltage between the photocathode and the cover layer, and furthermore relates to an image-intensifying tube for use in a device of this kind.
  • the adjustability of the voltage to be applied to the tube is utilized for adjusting the intensity of the image produced by the luminescent screen.
  • This adjustability is utilized in particular when displaying X-ray images, and the imageintensifying tube is a tube for intensifying X-ray images and hence is provided with a luminescent entrance screen which converts the X-rays into light and which is optically coupled to the photocathode.
  • the control of the intensity of the image produced by the luminescent layer collecting the electrons is important if adaptation of the eye is involved, or when a television camera tube is coupled to the image-intensifying tube and control of the intensity of the image radiation collected by the image intensifier is not desirable or not very well possible, which is frequently the case when working with X-rays.
  • this operating voltage can practically not be decreased further than approximately half the value of the nominal operating voltage of the tube since the electron-optical system then ceases to produce a sufficiently defined image.
  • the nominal operating voltage of the tube is to be understood to mean the accelerating voltage between photocathode and cover layer which ensures correct imaging and to which the construction of the tube (configuration of the electrodes, including the photocathode and the luminescent layer with cover layer collecting the electrons) is adapted.
  • an intensity ratio of the luminescent image produced by the electrons of approximately 1 to one-third can be realized by controlling the voltage from the nominal operating voltage to approximately half the value thereof, which is often experienced to be too small.
  • the invention has for its object to provide a measure by which the control range of the said intensity can be substantially increased, said measure being based on the recognition of the fact that this can be achieved by constructing the cover layer such that with an everincreasing operating voltage of the tube, an everincreasing portion of the electrons impinging upon the cover layer lose their energy in this cover layer.
  • the imaging device is characterized in that the nature of the material and the thickness of the cover layer are chosen to be such that at an operating voltage of the tube which is less than one quarter of the value of the nominal operating voltage of the tube the cover layer allows substantially no further electrons to pass which cause the luminescent layer to luminesce.
  • the cover layer is constructed such that luminescence of the luminescent layer occurs only at an operating voltage which amounts to 50 to percent of the nominal operating voltage.
  • An image intensifying tube for use in the imaging device according to the invention said tube having an entrance screen with a photocathode and a luminescent screen collecting electrons originating from the photocathode, said luminescent screen comprising a luminescent layer which is covered on the side of the photocathode by an electrically conducting, lightimpervious cover layer, is characterized in that the na ture of the material and the thickness of the cover layer are chosen to be such that at an operating voltage of the tube which is less than a quarter of the nominal operating voltage of the tube, the cover layer allows substantially no electrons to pass which cause the luminescent layer to luminesce.
  • the cover layer is preferably constructed such that luminescence of the luminescent layer occurs only at an operating voltage which amounts to 50 to 80 percent of the nominal operating voltage of the
  • FIG. 1 is a schematic view of an imaging device having an X-rayimage intensifier and an adjustable operating voltage
  • FIG. 2 is a graph showing the relationship which is found between the operating voltage on the tube and the luminescence of the luminescent layer in the case of a commonly used X-ray image intensifier and in the case of different X-ray image intensifiers to be used in the imaging device according to the invention.
  • X-rays emitted by an X-ray tube 1 are col lected, after having passed an object 2 to be examined, by the entrance screen 4 of an X-ray image-intensifying tube 3.
  • This tube 3 has a glass envelope 5 and comprises a curved front face 6, the inner side of which ac commodates the entrance screen 4.
  • This entrance screen 4 is composed of a luminescent layer 7 which is provided directly on the glass of the front face 6, a thin transparent separating layer 8, and a photocathode layer 9 which is sensitive to the luminescent light of the layer 7.
  • the tube is provided with an exit window 10 on which is provided an exit screen 11 consisting of a luminescent layer 12 which is covered on the side facing the entrance screen 4 by an electrically conducting, light-impervious cover layer 13.
  • the exit screen is surrounded by and electrically connected to a funnel-like anode 14.
  • a rotating intermediate electrode 15 is provided on the inner wall of the envelope 5.
  • a voltage source 20 is provided, which is bridged by a resistor 21 which is constructed as a potentiometer.
  • the photocathode 9, the intermediate electrode 15, and the anode 14 together with the exit screen 11 are connected to this potentiometer, the photocathode being connected to an adjustable contact 22, the anode 14 and the exit screen 11 together being connected to an adjustable contact 23.
  • the intermediate electrode 15 is connected to a fixed point of the po tentiometer 21, so that this intermediate electrode 15 carries a positive potential of 200 to 250 volts with respect to the photocathode 9.
  • the positive voltage (tube voltage) V carried by the anode 14 together with the exit screen 11 with respect to the photocathode 9, is
  • the nominal operating voltage V of an image-intensifying tube is to be understood to mean the voltage to be applied between the photocathode and the luminescent layer collecting the photo-electrons for obtaining the most favourable electron-optical image of the photocathode on the luminescent layer at the given tube configuration.
  • the intensity of the image produced by the luminescent layer 12 can be varied by adjusting the tube voltage V by means of the contacts 22 and 23, the former contact serving to enable adaptation of the voltage difference between the photocathode 9 and the intermediate electrode to the changing tube voltage.
  • the cover layer 13 is formed on the luminescent layer 12 by a thin layer of vapourdeposited aluminum (the so-termed metal backing), having a thickness of 1,000 to a maximum of 3,000 A, the common value being approximately 1,250 A.
  • a first object of such a layer also commonly used in television display tubes and other cathode-ray tubes having a cathode luminescent layer is to reflect the light transmitted to the cover layer by the luminescent layer, a second object being the conducting away of the electrons impinging on the exit screen, while a layer of this kind can also serve to prevent interaction between the material of the photocathode, for example, cae sium, and that of the luminescent layer.
  • An aluminum layer having the above-mentioned thickness of 3,000 A is permeable to electrons having a velocity of 3 to 4 kV.
  • the penetration depth S of electrons into a material generally satisfies the formula S Cv lp, in which C is a constant, p is the specific gravity of the layer material, and V is the voltage by which the electrons have been accelerated when they reach the layer.
  • the cover layer 13 in the imageintensifying tube is considerably thicker than usual, and it may also consist of different sublayers of different material.
  • the decisive fact is that this cover layer is less permeable to electrons than the commonly used cover layer, so that electrons originating from the photocathode 9 can penetrate the cover layer and cause the luminescent layer 12 to luminesce only if the tube voltage is higher than the above-mentioned acceleration voltage of 3 to 4 kV.
  • the cover layer 13 is to be constructed such that photoelectrons cause luminescence only at a tube voltage V which amounts to one quarter of the value of the nominal operating voltage V this should preferably occur only at a tube voltage amounting from 50 to 80 percent of the nominal operating voltage V, of the image-intensifying tube 3.
  • FIG. 2 The effect of the measure according to the invention can be illustrated by means of FIG. 2, in which the variation in the luminance I of the exit screen is plotted as a function of the tube voltage V, for cover layers of different photoelectron-permeability, the luminance at the nominal operating voltage V being each time assumed to be equal to l.
  • a nominal operating voltage of 22 to 25 kV is commonly used for image-intensifying tubes;
  • FIG. 2 relates to an X-ray image intensifier where V, 25 kV.
  • Curve a in FIG. 2 relates to an X-ray image intensifier having the usual aluminum cover layer of a thickness of 1,000 to 2,000 A, curves 1;, c and d relating to X-ray image intensifiers in the device according to the invention.
  • Curve b applied to an X-ray image intensifier having a cover layer consisting of an aluminum layer of a thickness of approximately 10,000 A which is only permeable to electrons which have been accelerated beyond approximately 8 kV.
  • Curves c and d apply to image intensifiers whose cover layer is permeable only to electrons accelerated beyond 12.5 kV, i.e. half the nominal operating voltage V, or more than 16 kV, respectively.
  • the luminance of the luminescent layer 12 of the image intensifier can in practice be controlled by varying the adjustment of the tube voltage only in accordance with the portion of the curves a, b, c and d which is situated to the right of the dotted line V k V If the control range of the luminance is understood to mean the ratio between the luminance at the nominal operating voltage V,, and the minimum luminance achievable without decreasing the tube voltage to less than half the nominal operating voltage, FIG.
  • control range is approximately 3 in the known image intensifier (curve a), this range being approximately 10 in the image intensifier to be used in the device according to the invention and provided with an aluminum cover layer having a thickness of 10,000 AE, while for image intensifiers which are subject to the curves c and d the control range is substantially larger yet; in practice it can even be as high as 100.
  • the measure according to the invention consequently, provides a substantially larger control possibility for adaptation of the luminance of the exit screen to, for example, the eye or a television camera tube than is possible with the known devices.
  • the deposition, i.e., vapour-deposition, of an aluminum cover layer having a thickness exceeding approximtely 10,000 A is difficult, it is desirable to use a different method of forming cover layers which are only penetrated by electrons which have been accelerated beyond 8 kV.
  • cover layer is then composed of a number of sublayers.
  • An example thereof is a cover layer consisting of three sublayers, i.e.
  • a first layer of aluminum having a thickness of about 1,000 A which is provided directly on the luminescent layer, a gold or lead layer having a thickness of 3,000 to 6,000 A which is provided on this aluminum layer, and on this lead or gold layer a second aluminum layer having a thickness of, for example, approximately 600 A.
  • a titanium layer having a thickness of approximately 1,200 A which is provided directly on the luminescent layer, an aluminum layer of approximately 1,000 A being provided on the side thereof which faces the photocathode 9.
  • a guide for determining the required thickness of a layer or sublayer is the fact that thicknesses of different materials which are equivalent for' electron absorption relate inversely to the specific gravities of those materials.
  • a cover layer in accordance with the measure of the invention can be found in the application of metal oxides such as titanium monoxide (TiO), specific gravity 4.93 consequently, almost twice as high as that of aluminum and titanium dioxide, specific gravity 4.l7 or 3.84, depending on the modification.
  • metal oxides such as titanium monoxide (TiO)
  • specific gravity 4.93 consequently, almost twice as high as that of aluminum and titanium dioxide, specific gravity 4.l7 or 3.84, depending on the modification.
  • a suitable material for this purpose is zinc cadmium sulphide (Zn CdS) without activator, the specific gravity (approximately 4.5) of which is slightly more than one and a half times that of aluminum.
  • a cover layer 13 consisting of two sublayers: a first layer directly adjoining the luminescent layer 12 and composed of a sublayer of zinc cadmium sulphide and having a thickness of approximately 15,000 A which is obtained, for example, by settling, and vapour-deposited thereon an aluminum layer having a thickness of 500 to 1,000 A.
  • An image-intensifying tube comprising a photocathode, a luminescent screen spaced apart from said photocathode for collecting electrons originating from the photocathode, an electrically conducting, lightimpervious cover layer on the side of said luminescent layer facing the photocathode, the material and the thickness of the cover layer being such that the cover layer substantially prevents electrons from passing through that cause the luminescent screen to luminesce at voltages less than one quarter of the value of the nominal operating voltage of the tube.
  • cover layer comprises an aluminum layer adjoining the luminescent layer, said luminescent layer having a thickness of approximately 1,000A, said gold layer having a thickness of 3,000 to 6,000A, and said second aluminum layer having a thickness of 500 to 1,000A on the side facing the photocathode.
  • An imaging system for an image-intensifying tube comprising a photocathode, a luminescent layer positioned for collecting electrons emitted by said photocathode, an electrically conducting, light impervious cover layer on the side of said luminescent layer facing the photocathode, and means for applying an adjustable acceleration voltage between said photocathode and said cover layer, said tube having a nominal operating voltage V, and undergoing decelerates changes in the image produced thereby upon reduction of the operating voltage thereof to a value less than one-fourth of said nominal voltage value, the dimensions and characteristics of said cover layer beingchosen so as to substantially prevent electrons originating in said photocathode from causing said luminescent screen to luminesce at acceleration voltages between said photocathode and said cover layer less than one quarter of the nominal operating voltage of said tube.
  • cover layer is formed from a plurality of mutually adjoining sublayers, at least one of said sublayers being made of metal.
  • cover layer comprises two layers of aluminum and one layer of gold provided between said aluminum layers.

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)
  • Apparatus For Radiation Diagnosis (AREA)
US00242693A 1971-04-16 1972-04-10 Imaging device comprising an image-intensifying tube Expired - Lifetime US3774038A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NLAANVRAGE7105196,A NL168991C (nl) 1971-04-16 1971-04-16 Beeldversterkerbuis met een verminderd doorlaatbare afdeklaag van het elektronenopvangscherm.

Publications (1)

Publication Number Publication Date
US3774038A true US3774038A (en) 1973-11-20

Family

ID=19812939

Family Applications (1)

Application Number Title Priority Date Filing Date
US00242693A Expired - Lifetime US3774038A (en) 1971-04-16 1972-04-10 Imaging device comprising an image-intensifying tube

Country Status (9)

Country Link
US (1) US3774038A (it)
JP (1) JPS5525492Y2 (it)
BE (1) BE782165A (it)
CA (1) CA959907A (it)
DE (1) DE2214374C3 (it)
FR (1) FR2133694B1 (it)
GB (1) GB1392356A (it)
IT (1) IT954673B (it)
NL (1) NL168991C (it)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2904862A1 (de) * 1978-02-14 1979-08-16 Philips Nv Roentgenuntersuchungsanordnung
US6276980B1 (en) * 1998-08-05 2001-08-21 Lg Electronics Inc. Method for forming electrode for plasma display panel

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2436622C2 (de) * 1974-07-30 1983-12-01 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Bildwandler- oder Bildverstärkerröhre
DE3315011A1 (de) * 1983-04-26 1984-10-31 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Elektronenroehre mit leuchtschirm
NL9000267A (nl) * 1990-02-05 1991-09-02 Philips Nv Proximity roentgenbeeldversterkerbuis.
DE4213907A1 (de) * 1992-04-28 1993-11-04 Siemens Ag Roentgenbildverstaerker

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2523132A (en) * 1949-08-10 1950-09-19 Westinghouse Electric Corp Photosensitive apparatus
US2909703A (en) * 1955-09-12 1959-10-20 Gen Electric Radiant energy intensification system and method
US3232781A (en) * 1958-02-03 1966-02-01 Nat Res Dev Electron image intensifying devices
US3350594A (en) * 1963-08-02 1967-10-31 Emi Ltd Image intensifier having continuous conducting layer between porous metallic coating and luminescent layer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2523132A (en) * 1949-08-10 1950-09-19 Westinghouse Electric Corp Photosensitive apparatus
US2909703A (en) * 1955-09-12 1959-10-20 Gen Electric Radiant energy intensification system and method
US3232781A (en) * 1958-02-03 1966-02-01 Nat Res Dev Electron image intensifying devices
US3350594A (en) * 1963-08-02 1967-10-31 Emi Ltd Image intensifier having continuous conducting layer between porous metallic coating and luminescent layer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2904862A1 (de) * 1978-02-14 1979-08-16 Philips Nv Roentgenuntersuchungsanordnung
US6276980B1 (en) * 1998-08-05 2001-08-21 Lg Electronics Inc. Method for forming electrode for plasma display panel
USRE42855E1 (en) 1998-08-05 2011-10-18 Lg Electronics Inc. Method for forming electrode for plasma display panel

Also Published As

Publication number Publication date
FR2133694B1 (it) 1975-10-24
BE782165A (fr) 1972-10-16
CA959907A (en) 1974-12-24
NL168991C (nl) 1982-05-17
DE2214374C3 (de) 1983-11-03
JPS53166376U (it) 1978-12-26
DE2214374B2 (de) 1979-06-13
FR2133694A1 (it) 1972-12-01
IT954673B (it) 1973-09-15
GB1392356A (en) 1975-04-30
NL7105196A (it) 1972-10-18
DE2214374A1 (de) 1972-11-02
JPS5525492Y2 (it) 1980-06-19

Similar Documents

Publication Publication Date Title
US2523132A (en) Photosensitive apparatus
US2555423A (en) Image intensifying tube
US2555424A (en) Apparatus for fluoroscopy and radiography
US2555545A (en) Image intensifier
US3693018A (en) X-ray image intensifier tubes having the photo-cathode formed directly on the pick-up screen
US2739244A (en) Infrared sensitive tube
US2699511A (en) Storage tube for invisible radiation
US4255666A (en) Two stage, panel type x-ray image intensifier tube
US3940620A (en) Electrostatic recording of X-ray images
US3774038A (en) Imaging device comprising an image-intensifying tube
US2894160A (en) Electron microscopes
US3603828A (en) X-ray image intensifier tube with secondary emission multiplier tunnels constructed to confine the x-rays to individual tunnels
US2717971A (en) Device for storage of images of invisible radiation
US3749920A (en) System for x-ray image intensification
US2418779A (en) Alkali metal halide and luminescent screens of substantially coincident spectral absorption
US3304455A (en) Image-converter tube with output fluorescent screen assembly resiliently mounted
US2802963A (en) Tube for reproducing invisible images
US2100259A (en) Television
US2700116A (en) Device for intensification of X-ray images
US2817781A (en) Image storage device
US3370172A (en) Arrangement for producing two-dimensional images of an infra-red radiator
US2690516A (en) Method and device for producing neutron images
US2938141A (en) Photothermionic image converter with retarding fields
CN109686640A (zh) 一种平板倍增影像增强器及倍增方法
GB1417452A (en) Image tube employing high field electron emission suppression