EP0091170B1 - Elektronenvervielfacher vom Kanalplattentyp und mit einem derartigen Elektronenvervielfacher versehene Bildröhre - Google Patents

Elektronenvervielfacher vom Kanalplattentyp und mit einem derartigen Elektronenvervielfacher versehene Bildröhre Download PDF

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Publication number
EP0091170B1
EP0091170B1 EP19830200464 EP83200464A EP0091170B1 EP 0091170 B1 EP0091170 B1 EP 0091170B1 EP 19830200464 EP19830200464 EP 19830200464 EP 83200464 A EP83200464 A EP 83200464A EP 0091170 B1 EP0091170 B1 EP 0091170B1
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EP
European Patent Office
Prior art keywords
channel
input
input face
plate
face
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
Application number
EP19830200464
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English (en)
French (fr)
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EP0091170A1 (de
Inventor
David Lionel Emerson
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.)
Philips Electronics UK Ltd
Koninklijke Philips NV
Original Assignee
Philips Electronic and Associated Industries Ltd
Philips Electronics UK Ltd
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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Publication date
Application filed by Philips Electronic and Associated Industries Ltd, Philips Electronics UK Ltd, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Electronic and Associated Industries Ltd
Publication of EP0091170A1 publication Critical patent/EP0091170A1/de
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Publication of EP0091170B1 publication Critical patent/EP0091170B1/de
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    • 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
    • H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
    • H01J31/506—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output tubes using secondary emission effect
    • H01J31/507—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output tubes using secondary emission effect using a large number of channels, e.g. microchannel plates

Definitions

  • This invention relates to electron multipliers and more particularly to channel plate electron multipliers having continuous channel dynodes extending between input and output faces of the plate, and now referred to as channel plates.
  • channel plates are used in electronic image intensifier tubes where they are used to provide the major part of the image intensification.
  • a channel plate requires conducting electrodes on both the input and output faces of the plate. These electrodes must provide a reliable connection to the high resistance secondary emitting layer on the inside wall of each channel. A voltage can then be applied, via the electrodes, to all channels and a potential gradient established along the channels, needed for electron multiplication by secondary emission. Conventionally these electrodes are prepared by vacuum evaporation of a suitable conducting material, for example nichrome, onto each face. To ensure reliable connection to each channel, the geometry of the evaporation apparatus is generally arranged so that the electrode material penetrates a small distance into the channels. This arrangement also ensures that the secondary emitting layer deep within the channel is not contaminated by electrode material, which could occur if the evaporation source were positioned on the axis of the channels.
  • a suitable conducting material for example nichrome
  • channel plates and image intensifiers are described in British Patent Specification 1,164,894 in which a diode inverter intensifier is described in which an electron optical image inverting stage is placed between a photocathode and the channel plate.
  • the channel plate is a plane parallel-sided slab set normal to the intensifier axis.
  • the electron optical design of the inverter between the photocathode, which receives the input light image, and the input face of the channel plate, which receives the input image converted to photoelectrons, is such that the angle at which the primary photoelectrons land on the channel plate varies as a function of position across the input face of the channel plate. If the channels were normal to the input face, a significant proportion of the photoelectrons would penetrate far down the channels near the plate centre before they struck the channel walls and would not then be multiplied by secondary emission to the same extent had they struck the walls near the channel entrance. The gain provided by the channel plate for these electrons would be reduced.
  • the "black spot" can be avoided by cutting the channel plate so that the channels at the input face are at a bias angle to that face as described in British Patent Specification 1,164,894.
  • the incoming primary electrons then strike the channel walls near the entrance of each channel.
  • the penetration depth of the electrode material is substantially one channel diameter all around each channel entrance, a substantial proportion of the incoming primary electrons will strike channel walls where the secondary emissive layer is masked by the electrode material and will produce considerably fewer secondary electrons or none at all.
  • the mere loss of channel gain which then occurs could be restored by increasing the voltage applied to the channel plate. But the loss in signal-to-noise ratio which also occurs thereby at the input face cannot be restored by a gain increase. This loss reduces the reliability with which low contrast targets can be detected at low levels of scene illumination.
  • the channels may be tilted for another reason set out in British Patent Specification 1,064,073.
  • the effect of tilting is to reduce the strong dependence of channel gain on the length- to-diameter ratio of a channel by confining multiplication to one side of the channel and making the position of the opposite wall unimportant. The uniformity of channel gains is thereby improved.
  • a proportion of the incoming electrons therefore strike the channel walls immediately inside the end of the channels masked by the electrode material and by absorption.
  • the invention provides a channel plate secondary electron multiplier comprising, continuous dynode channels extending from an input face to an output face of the plate, and first and second conductive layers on the input and output faces forming the plate input and output electrodes respectively, said first layer penetrating inside the channel walls to a depth not substantially greater than the channel - width and which depth varies as a function of position around the wall of each channel, characterised in that the penetration depth is substantially zero on wall parts facing a predetermined direction in the input face so that electrons arriving at said input face at an angle to the channel axes at said face and from said predetermined direction land upon channel wall parts having a minimum area of secondary emitting surface obscured by said conductive layer.
  • the axes of the channels at the input face are inclined at a common bias angle to the normal to the input face, said predetermined direction being the direction in which the angle between the channel axis and the input face is least.
  • the invention also provides an electronic imaging tube comprising, in order from the image input, a photocathode, an electron optical image inverting stage, a channel plate secondary electron multiplier comprising continuous dynode channels extending from an input face to an output face of the plate, first and second conductive layers on the input and output faces forming the plate input and output electrodes respectively, said first layer penetrating inside the channel walls to a depth not substantially greater than the channel width and which depth varies as a function of position around the wall of each channel characterised in that the penetration depth is substantially zero on wall parts facing a predetermined direction in the input face and in that the axes of the channels at the input face are inclined at a common bias angle to the input face, said predetermined direction being the direction in which the angle between the channel axes and the input face is least so that electrons arriving at said input face from the electron optical image inverting stage land upon channel wall parts having a minimum area of secondary emitting surface obscured by said conducting layer.
  • a micro-channel plate image intensifier 1 is shown in schematic cross- section.
  • a vacuum envelope 2 has a fibre optic input window 3 having a semi-transparent photoemissive layer 4 upon its interior surface 5.
  • An optical image 6, focused upon the exterior surface 7, is transferred by the optical fibres 9 to the interior surface 5 and to the photoemissive layer 4 where is gives rise to an electron image 8.
  • the axes of the channels 20 are inclined at a common bias angle to the normal to input face 12.
  • the output face 14 of plate 13 is held at a positive potential of 200 to 1000 volts, depending on the gain required, with respect to input face 12.
  • An intensified electron image 15 is proximity- focused onto a luminescent phosphor screen 16 on the interior surface of a fibre optic output window 17, which transfers a visible image 18 to the exterior surface 19 where it may be viewed with an eyepiece (not shown).
  • Such micro-channel plate image intensifiers are available commercially, for example Mullard (Trade Mark) Type No. XX1500, and will not be further described herein.
  • the magnified insert in Figure 1 shows a section of the channels 20 inclined at a common bias angle a, typically 14.5 degrees, to the normal to the input face 12.
  • the channel walls 21 are of conductive glass treated to emit secondary electrons.
  • a first conductive layer 22 of nichrome metal is laid down by vacuum evaporation from a direction 27 onto input face 12.
  • Layer 22 penetrates down the inside of the channel walls at 23 on the sides of channel walls facing into direction 27.
  • the opposite sides of the channel walls, facing a predetermined direction 26 in input face 12 corresponding to the evaporation direction 27, are masked by the channel ends during evaporation and the secondary emissive property of these side walls is not degraded.
  • Figure 2 shows in more detail the asymmetry in the penetration depth of the first conductive layer which is achieved by evaporation of the layer from direction 27.
  • the penetration varies from a maximum 23 round to zero on the opposite wall facing the predetermined direction 26.
  • the projected area of first conductive layer 22 is shown as two small areas 25 obscuring a minimum area of secondary emitting surface.
  • Incoming electrons 24 arriving normal to input face 12 will thus be incident almost entirely upon a good secondary emitter.
  • This may be compared to a channel plate having a bias angle of 14.5 degrees and the former symmetrical penetration by one channel diameter of the conductive layer in which 30% of primary electrons arriving normal to the channel plate surface will strike the conductive electrode material.
  • a 30% reduction in noise power factor is possible using the invention.
  • a reduction in noise power factor from 3.6 to 2.95 is obtained equivalent to a 20% increase in photocathode sensitivity.
  • the electrostatic field at the channel entrance is reduced owing to the presence of the conductive layer.
  • the extraction field for secondary electrons is not as favourable as it would have been without the penetrating layer.
  • the extraction field for first secondary electrons is asymmetric and is more favourable.
  • the channels are inclined to the input face to obtain the benefit of the invention. But if the incoming electrons arrive at an angle to the normal to the input face the channels may have zero bias angle provided that the direction of electron arrival is chosen in relation to the asymmetry of penetration so that the electrons land on the channel walls having least penetration of the conductive layer.
  • the channels may then be curved so that, for example, the output end of each channel is normal to the output face. In an image tube this may be desirable to avoid astigmatism in the image.
  • the invention is also applicable in non-imaging applications, for example in single channel electron multipliers used as electron detectors in mass spectrometers and space experiments.

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Electron Tubes For Measurement (AREA)

Claims (6)

1. Elektronenvervielfacher vom Kanal plattentyp mit durchgehenden und von einer Eingangsfläche zu einer Ausgangsfläche der Platte sich erstrekkenden Dynodenkanälen und mit ersten und zweiten Leitschichten auf den Eingangs- und Ausgangsflächen, die die Platteneingangs- und Plattenausgangselektroden bilden, wobei die erste Leitschicht in die Kanalwände bis zu einer Tiefe eindringt, die im wesentlichen nicht grösser als die Kanalbreite ist und wobei diese Tiefe abhängig von der Position um die Wand jedes Kanals variiert, dadurch gekennzeichnet, dass die Eindringtiefe im wesentlichen Null auf Wandteilen beträgt, die in einer vorgegebenen Richtung der Eingangsfläche zugewandt sind, so dass Elektronen die bei dieser Eingangsfläche unter einem Einfallswinkel zu den Kanalachsen und aus der vorgegebenen Richtung an dieser Fläche ankommen, Kanalwandteile mit einem minimalen Gebiet an sekundäremittierender Fläche erreichen, die von der erwähnten Leitschicht bedeckt ist.
2. Elektronenvervielfacher vom Kanalplattentyp nach Anspruch 1, dadurch gekenzeichnet, dass die Kanalachsen an der Eingangsfläche unter einem gemeinsamen Vorgabewinkel zur Normalen zur Eingangsfläche geneigt sind, wobei die vorgegebene Richtung die Richtung ist, in der der Winkel zwischen den Kanalachsen und der Eingangsflächen am kleinsten ist.
3. Elektronenvervielfacher vom Kanalplattentyp nach einem oder mehreren der vorangehenden Ansprüche, dadurch gekennzeichnet, dass sich die durchgehenden Dynodenkanäle in einer Kurve zwischen den Eingangs- und Ausgangsflächen erstrecken.
4. Elektronenbildwiedergaberöhre mit einer Photokathode zur Bildung des Bildeingangs, mit einer Umkehrstufe für das optische Elektronenbild, mit einem Elektronenvervielfacher vom Kanalplattentyp mit durchgehenden Dynodenkanälen von einer Eingangsfläche zu einer Ausgangsfläche der Platte, mit ersten und zweiten Leitschichten an den Eingangs- und Ausgangsflächen, die die Platteneingangs- bzw. die Plattenausgangselektroden bilden, wobei die erste Leitschicht innerhalb der Kanalwänden bis zu einer Tiefe eindringt, die im wesentlichen nicht grösser als die Kanalbreite ist und wobei diese Tiefe abhängig von der Position um die Wand jedes Kanals variiert, dadurch gekennzeichnet, dass die Eindringtiefe im wesentlichen auf Wandteilen Null beträgt, die einer vorgegebenen Richtung in der Eingangsfläche zugewandt sind, und dass die Kanalachsen an der Eingangsfläche unter einem gemeinsamen Vorgabewinkel zur Eingangsfläche geneigt sind, wobei die vorgegebene Richtung die Richtung ist, in der der Winkel zwischen den Kanalachsen und der Eingangsfläche am kleinsten ist, so dass bei der genannten Eingangsfläche ankommende Elektronen aus der Umkehrstufe für das optische Elektronenbild bei den Kanalwandteilen mit einem Mindestgebiet ankommen, das eine von der erwähnten Leitschicht bedeckte Sekundärelektronenerzeugungsfläche hat.
5. Elektronenbildwiedergaberöhre nach Anspruch 5, dadurch gekennzeichnet, dass sich die durchgehenden Dynodenkanäle in einer Kurve zwischen den Eingangs- und Ausgangsflächen erstrecken.
6. Elektronenbildwiedergaberöhre nach Anspruch 4, oder Anspruch 5 in Form einer Bildverstärkerröhre oder einer Bildwandlerröhre mit einem lumineszierenden Sichtschirm an der Ausgangsseite der Kanalplatte.
EP19830200464 1982-04-05 1983-03-31 Elektronenvervielfacher vom Kanalplattentyp und mit einem derartigen Elektronenvervielfacher versehene Bildröhre Expired EP0091170B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB08210029A GB2118358B (en) 1982-04-05 1982-04-05 Channel plate electron multipliers
GB8210029 1982-04-05

Publications (2)

Publication Number Publication Date
EP0091170A1 EP0091170A1 (de) 1983-10-12
EP0091170B1 true EP0091170B1 (de) 1986-06-11

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EP19830200464 Expired EP0091170B1 (de) 1982-04-05 1983-03-31 Elektronenvervielfacher vom Kanalplattentyp und mit einem derartigen Elektronenvervielfacher versehene Bildröhre

Country Status (3)

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EP (1) EP0091170B1 (de)
DE (1) DE3364048D1 (de)
GB (1) GB2118358B (de)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1154515A (en) * 1967-05-15 1969-06-11 Mullard Ltd Improvements in or relating to Image Intensifiers
US3974411A (en) * 1970-09-20 1976-08-10 Rca Corporation Channel plate electron multiplier tube having reduced astigmatism
US4153855A (en) * 1977-12-16 1979-05-08 The United States Of America As Represented By The Secretary Of The Army Method of making a plate having a pattern of microchannels

Also Published As

Publication number Publication date
GB2118358A (en) 1983-10-26
DE3364048D1 (en) 1986-07-17
GB2118358B (en) 1986-01-02
EP0091170A1 (de) 1983-10-12

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