CA1039872A - Cathodo-luminescent display panel - Google Patents
Cathodo-luminescent display panelInfo
- Publication number
- CA1039872A CA1039872A CA215,321A CA215321A CA1039872A CA 1039872 A CA1039872 A CA 1039872A CA 215321 A CA215321 A CA 215321A CA 1039872 A CA1039872 A CA 1039872A
- Authority
- CA
- Canada
- Prior art keywords
- electron
- multiplier
- electrons
- cathode
- anode
- 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
Links
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
- H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
- H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
- H01J31/128—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digitally controlled display tubes
-
- 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
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/467—Control electrodes for flat display tubes, e.g. of the type covered by group H01J31/123
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/04—Electron multipliers
- H01J43/06—Electrode arrangements
- H01J43/10—Dynodes
Landscapes
- Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This disclosure depicts cathodo-luminescent devices and luminescent panels employing X-Y matrices of such devices as the display elements. The cathodo-luminescent devices are depicted as each comprising a two-section cell containing an ionizable gas at very low pressure. The first section comprises an electron-multiplier serving as a controllable source of free electrons. Free electrons are drawn from the electron-multiplier and accelerated in the second section to high energies whereupon they collide with a light-emissive phosphor screen. Other structures including means for modulating the flow of electrons to the screen are disclosed.
This disclosure depicts cathodo-luminescent devices and luminescent panels employing X-Y matrices of such devices as the display elements. The cathodo-luminescent devices are depicted as each comprising a two-section cell containing an ionizable gas at very low pressure. The first section comprises an electron-multiplier serving as a controllable source of free electrons. Free electrons are drawn from the electron-multiplier and accelerated in the second section to high energies whereupon they collide with a light-emissive phosphor screen. Other structures including means for modulating the flow of electrons to the screen are disclosed.
Description
~03~87Z
13ack~round o` t~ xnven~lon Th~ evolut:ion o~ television and o-ther displays has ; been toward s-tructures which are capable o~ reproducing ever larger and brighter images, yet which are ever less bulk~ and ligirter. Because of seemingly inherent limitat,i.ons of cathode ray tubes t~hich prevent attairlment of compact larye screen television receivers, other approaches, many oE them rad.ically different from cathode ray tubes, have been investiyated.
It has been recognized that other avenue~ o~ investi~
gation, to be viable, must potentially lead to display structures capable of reproduc.ing images having adequate brightness and luminous efficiency and preferably having acceptable color rendition. A popular and widely investigated approach has utilized light-emissive elements arranged in X-Y matrices, selectively energized by means of row and column selectors and drivers. Light-emitting diodes, gas discharge devices and liquid crystal devices have been explored as possible display s elements for use in such matrix-type devices. ~he utilization ~
of display elements arranged in an X-Y matrix for row-column - ;
selection has imposed its own set of requirements, including the requirement that the indivi.dual picture elements be capable of individual control without partial energization of unselected - elements.
Prior Axt .
13ack~round o` t~ xnven~lon Th~ evolut:ion o~ television and o-ther displays has ; been toward s-tructures which are capable o~ reproducing ever larger and brighter images, yet which are ever less bulk~ and ligirter. Because of seemingly inherent limitat,i.ons of cathode ray tubes t~hich prevent attairlment of compact larye screen television receivers, other approaches, many oE them rad.ically different from cathode ray tubes, have been investiyated.
It has been recognized that other avenue~ o~ investi~
gation, to be viable, must potentially lead to display structures capable of reproduc.ing images having adequate brightness and luminous efficiency and preferably having acceptable color rendition. A popular and widely investigated approach has utilized light-emissive elements arranged in X-Y matrices, selectively energized by means of row and column selectors and drivers. Light-emitting diodes, gas discharge devices and liquid crystal devices have been explored as possible display s elements for use in such matrix-type devices. ~he utilization ~
of display elements arranged in an X-Y matrix for row-column - ;
selection has imposed its own set of requirements, including the requirement that the indivi.dual picture elements be capable of individual control without partial energization of unselected - elements.
Prior Axt .
2,868,994 Anderson
3,243,642 Gebel ''.'~.
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3,262,010 Ka~an 3,271,661 Goodrich et al 3,483,422 Novotny 3,492,523 Smith et al 3,519,870 Jensen 3,600,627 Goede et al 3,622,829 Watanabe ; 3,646,382 Goede et al 3,693,004 Sanford ` 10 3,725,731 Ka~an 3,771,008 Chen et al ~he present invention relates to a cathodo-luminescent devi~e including wall means defining an enclosure containing an ionizable gas at a predetermined low pressure~ An electron-multi-plier is located within the enclosure for creating at an output end thereof a source of electrons. The electron-multiplier in-~.
cludes cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, the elec-' tron-m~ltiplier generating positive gas ions as a result of col-, 20 lisions between electrons and the gas atoms, some of which ions i feed back to the cathode to cause the cathode to emit electrons.
Phosphor means are disposed at one end of the enclosure in spaced relation to the output end of the electron-multiplier for emitting light when bombarded by high energy electrons. Accelerating anode means are disposed at the phosphor means and are adapted to receive a predetermined accelerating voltage substantiall~ more positive than the voltage applied to the electron-multiplier means for drawing electrons Erom the electron-multiplier when the èlectron~multiplier is on and for accelerating them to hi~h energ:ies for impingement on the phosphor means, the predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in the device. Actlvating , xw/ ., .~ " , : : , . , , .:
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means are provided for driving the electron-multiplier between an "on" state associated with a predetermined high level of avail-able electron-multiplier cur~ent and an "off" state associated with negligible electron-multiplier ~urrent.
: Brief Description of the Drawings .
The features of the invention which are believed to be novel are set forth with particularity in the appended claims.
The invention, together with further objects and advantages there-of, may best be understood, however, be referencé to the following description taken in conjunction wi-th the accompanying drawings in which:
Figure 1 is a highly schematic view of a gas discharge diode of a type well known in the art;
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Figure 2 illu~tr~a~ n ~ ghly schematic form a low pres~ure gas cell containing an electron-multiplier;
~ igure 3 is a highly schematic view o~ a cathodo-luminescent device constructed in accordance with the principles of this invention;
Figure 4 is a fragmentary perspective view of a device similar to the Figure 3 device, shown in a more structural, less ~schematic representation;
Figure 5 shows in highly schematic form a television ; 10 display panel utilizing cathodo luminescent devices constructed to implement the teachings of this invention;
Figure 6 is a schematic fragmentary perspective view, broken away, of a display panel representing a preferred mode of :, execution of the invention;
Figure 7 is a sectioned ele~ational vieW of the panel ~;
shown in Figure 6, taken along lines 7-7 in Figure 6; and Figure 8, located on the third sheet of drawings, is an enlarged fragmentary sectional view taken along lines 8-8 in .-. Figure 7.
Descri~?tion of the Preferred Embod~ments The principles of this invention are preferably imp~nted in apparatus which employs a low pressure gas cell ~.
; containing an electron-multiplier which serves as an efficient source o~.free electrons and which has a threshold switching capability to enable mutually exclusive selection of elements in an X-Y matrix o f elements. The ~ree electrons generated in the electron-multiplier are accelerated in an accelerating stage into impingement with a cathodo-luminescent phosphor screen~
Be~ore discussing t.he details of a display panel constructed according to thls i.nvention, therP will be discussed certain ;.
basic principles underlying and cmployed in cathodo-luminescent de~ices according to this lnvention.
'~`~. ' .` ' .
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3,262,010 Ka~an 3,271,661 Goodrich et al 3,483,422 Novotny 3,492,523 Smith et al 3,519,870 Jensen 3,600,627 Goede et al 3,622,829 Watanabe ; 3,646,382 Goede et al 3,693,004 Sanford ` 10 3,725,731 Ka~an 3,771,008 Chen et al ~he present invention relates to a cathodo-luminescent devi~e including wall means defining an enclosure containing an ionizable gas at a predetermined low pressure~ An electron-multi-plier is located within the enclosure for creating at an output end thereof a source of electrons. The electron-multiplier in-~.
cludes cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, the elec-' tron-m~ltiplier generating positive gas ions as a result of col-, 20 lisions between electrons and the gas atoms, some of which ions i feed back to the cathode to cause the cathode to emit electrons.
Phosphor means are disposed at one end of the enclosure in spaced relation to the output end of the electron-multiplier for emitting light when bombarded by high energy electrons. Accelerating anode means are disposed at the phosphor means and are adapted to receive a predetermined accelerating voltage substantiall~ more positive than the voltage applied to the electron-multiplier means for drawing electrons Erom the electron-multiplier when the èlectron~multiplier is on and for accelerating them to hi~h energ:ies for impingement on the phosphor means, the predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in the device. Actlvating , xw/ ., .~ " , : : , . , , .:
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means are provided for driving the electron-multiplier between an "on" state associated with a predetermined high level of avail-able electron-multiplier cur~ent and an "off" state associated with negligible electron-multiplier ~urrent.
: Brief Description of the Drawings .
The features of the invention which are believed to be novel are set forth with particularity in the appended claims.
The invention, together with further objects and advantages there-of, may best be understood, however, be referencé to the following description taken in conjunction wi-th the accompanying drawings in which:
Figure 1 is a highly schematic view of a gas discharge diode of a type well known in the art;
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Figure 2 illu~tr~a~ n ~ ghly schematic form a low pres~ure gas cell containing an electron-multiplier;
~ igure 3 is a highly schematic view o~ a cathodo-luminescent device constructed in accordance with the principles of this invention;
Figure 4 is a fragmentary perspective view of a device similar to the Figure 3 device, shown in a more structural, less ~schematic representation;
Figure 5 shows in highly schematic form a television ; 10 display panel utilizing cathodo luminescent devices constructed to implement the teachings of this invention;
Figure 6 is a schematic fragmentary perspective view, broken away, of a display panel representing a preferred mode of :, execution of the invention;
Figure 7 is a sectioned ele~ational vieW of the panel ~;
shown in Figure 6, taken along lines 7-7 in Figure 6; and Figure 8, located on the third sheet of drawings, is an enlarged fragmentary sectional view taken along lines 8-8 in .-. Figure 7.
Descri~?tion of the Preferred Embod~ments The principles of this invention are preferably imp~nted in apparatus which employs a low pressure gas cell ~.
; containing an electron-multiplier which serves as an efficient source o~.free electrons and which has a threshold switching capability to enable mutually exclusive selection of elements in an X-Y matrix o f elements. The ~ree electrons generated in the electron-multiplier are accelerated in an accelerating stage into impingement with a cathodo-luminescent phosphor screen~
Be~ore discussing t.he details of a display panel constructed according to thls i.nvention, therP will be discussed certain ;.
basic principles underlying and cmployed in cathodo-luminescent de~ices according to this lnvention.
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~(~398~;Z
In a simple gas diode (see Figure 1), positive gas ions generated in the gas impinge upon the cathode, releasing secondary electr~ns. The electrons are accelerated toward the anode. The probability of interaction with a gas atom in the intervening space depends upon the cl~nsity (pressure) of gas molecules in that space and the length of the path. When an electron has gained sufficient energy in falling through the electric field along the cathode-to-anode path, it can ionize a gas atom, thus freeing an additional electron and creating a "feedback" ion. The two electrons (the oxiginal one plus the newly formed one) proceed toward the anode, perhaps creating additional ion/electron pairs on the way. Some ions and electrons will be lost to the walls. In general, each backwardly accelerated ion impinging upon the cathode will free an average lS of less than one electron ~- perhaps as few as 1 electron per 10 ions impinging. Hence, for a sustained discharge, each electron leaving the cathode must initiate an avalanche of -ion/electron pair generating collisions such that enough ions are generated on the average to satisfy wall losses and to generate collectively one new secondary electron at the cathode.
Obviously, if the density of gas is not sufficient to allow an adequate number of collisions along the cathode-to-anode path, a discharge cannot be maintained. Increasing the path length increases the probability of a collision at a given pressure. Raising the voltage difference helps in a marginal situation, primarily because the electrons will be accelerated to the minimum ionizing level sooner along the path (thus increasing the effective path length), and becausé occasionally more than one electron may be released per collision. On the other hand, high velocity electrons may ha~e reduced ionization probability. The net result is that if a path is too short, for a given gas density, a sel~-sustained discharge cannot be : ,. . .
103987;2 maintained everl when very high voltage dif~erences exist in the field-containing space. ~his circumstance is classically described by a Paschen curve. This curve and other principles and details of gas discharge devices and their operation are described in such works as "Gaseous Conductors", by ~ames Cobine, Dover Publications (1958).
The ~erm "gas discharge cell" or "gas discharge device"
; is herein intended to mean a cell or a device in which the electric fields differ significantly between the "on" state wherein a plasma is present and the "off" state wherein no current is flowing. Devices constructed in acco~d~nce ~ith this invention do not have the described characteristics o~ a gas discharge device. Rather, they may be aptly termed electro-static devices in w~ich the electric fields estab~ished within lS by application of voltages to its electrodes are not substantially and abruptly altered hy the presence of ions.
In a conventional gas discharge diode as sh~wn in Figure l, the design relationship between gas pressure "p" and the cathode-to-anode spacing "d", for minimum operating voltage, is given to excellent approximation by the Paschen similitude expression: p x d = K, where K is a constant which depends on cathode material, gas composition and tube geometry (but not tube siz~e). For usual discharge devices, K is generally equal to about one-half torr cm.
In the Figure l diode, electrons emitted from the cathode undergo ionizing collisions in the gas, resulting in an electron "avalanche" which multiplies the electron current as it approaches the anode. If the ion-electron secondary emission ratio is x (typically about .1), a gas-Plectron-avalan~he gain of at least x (where x is typically about lO) must be developed to establish an electron-ion loop gain of unity. Accordingly, the minimum breakdown voltage characterisitc for a given diode (revealed) ......
~03~87Z
by the well-known Paschen curve) i~ a measure of the ~econdary emission properties o~ the cathode of the diode, as well as a measure of the electron-avalanche properties of the ga3.
As will be explained in more detail hereinafte~, in accordance with the principles of this invention, an electron-multiplier, as shown schematically in Figure 2, is inserted between the cathode and the region where ions are to be generated.
The ill~strated Figure 2 device comprises an envelope 10 con-taining an ionizable gas such as hydrogen, helium, neon or other suitable gases or gas mixtures. A cathode 12 serves as an electron emit~er. ~ plurality of serially arranged, secondary-electron-emissive dynodes 14, 16, 18, 20, ~2 and 24 receive applied voltages ever-increasing in positive polarity in a direction ~way from the cathode 12. The voltages are shown as being provided by a tapped voltage divider 26. A final anode 28 collects the electrons from the last dynode 24.
Due to collisions between the electrons and the gas atoms within the envelope 10, positive gas ions 30 are generated.
J~ In accordance with this invention, as will be explained in more l~ 20 detail hereinafter, the dynodes 14-24 are arranged so as to 1: ~
permit t~e ions 30 to be accelerated directly to the cathode 12 to cause the cathode to emit additional free electrons 32.
For the Figure 2 device, the Paschen similitude expxession takes the general form:
p~l-g = K, where ~ is the efective length of the ion generation region and llgll is the gain of the electron-multiplier. The value of K
depends upon the efficiency with which positive ions are trans-p~rted back to the cathode and the ion-induced secondary electron amission coefficlent of the cathode~ This is true whether or not an electron-multiplier is included. K also depends upon the electron velocity in the ion generation region. In appro-. , ~3913~
¦ priately designed tubes, however, the value of K is not likely ¦ to differ greatly in general magnitude whether a multiplier is present or not. Hence it may be concluded that if an electron-multiplier o~ gain "g" is interposed, a discharge may be initiated at a pressure which is approximately l/g lower than if a multiplier is not interposed. This principle is basic to this invention.
By operating a tube at sufficiently low gas pressure~
ionizing collisions between gas atoms and electrons becomes a negligible effect so far as scattering of electrons is concerned.
Under such conditions a beam of electrons may be accelerated to high velocity with no significant energy loss and no concern about initiating an unwanted self sustained discharge between ~he high voltage anode and lower voltage electrodes in the tube.
Figure 3 illustrates in highly schematic form a cathodo-luminescent device containing basic components of devices constructed according to this invention. The Figure 3 device 34 is illustrated as comprising wall means in the form of an envelope 36 (typically glass) which defines an enclosure con-taining an ionizable gas such as helium, hydrogen, neon or other suitable gases or gas mixtures at a predetermined pre~sure sufficiently low to preclude establishment of a gas discharge in ~he devlce.
An electron-multiplier 38 located within the enclosure creates at an output end thereof a source o~ electrons~ The electxon-multiplier 38 includes a cathode 40, which may comprise, for example, an aluminumO magnesium or nickel strip. The electron-multiplier 38 is depicted as including a plurality of discrete dynodes 42, 44, 46, 48, 50 and 52. The dynodes 42-52 may be composed, ~ox example, of oxidized beryllium-copper alloy, cesium-a~timony alloy, silver-magnesium alloy, oxidized aluminum, or other suitable materials. The last dynode in the Figure 3 i , 1~39187;Z
7 embodiment (52~ and in later-described embodiments is also re~erred to herein as the "electron-multiplier anode~. As used, this term is intended to mean the highest voltage dynode ¦ in an electron-multiplier constituting a part of a light-emissive device constructed according to this invention, and is not f intended to mea.n a current-collecting electrode.
As in the Figure 2 device, the dynodes are adapted to receive voltages ever-increasing in positive polarity in a direction away from the cathode. 40, which pattern of voltages may be provided by a voltage divider, as shown at 26 in Figure 2.
This invention comprahends the use of an electron-multiplier of a type other than as shown, such as a channel plate multiplier, .
a Weis mesh multiplier, or a staggered plate multiplier; the illustrated shaped dynode structure is preferred however.
The electron-multiplier 38, of whatever form, generates positive gas ions 54 as a result of collisions between the f electrons and gas atoms within the multiplier. In accordance with this invention, as will be explained in more detail hereinafter, the dynodes 42-52 are arrange.d so as to permit the positive gas ions 54 to be accelerated to the cathode 40 to .:
cause the cathode to emit additional free electrons 56. The : additional electrons 56 emitted from the cathode 40 a~ a result of the ion bombardment are in turn multiplied in the electron-multiplier 38. The electron-multiplier 38 thus constitutes part of a regenerative electron-ion feedback loop.
Phosphor means in the form of a phosphor screen 58 is disposed at ona end of the enclosure in spacad relation to the ~utput end o~ the electron-multiplier 38 for emitting light when bombarded by high energy electrons. As will become evident as this description proceeds, tha phosphor material may be selected to emit white light for use in a one color display device or panel, or may be, fo.r example, red-emissive, blue-,`.'"` ' j emissive and green~emissive in arrays of devices designed to form ¦ color television pictures or other color displays. It should be I noted that only a small percentage of the multiplied electron beam is utilized to create positive gas ions, a very substantial part of the beam being available ~or acceleration to the phosphor screen 58.
An accelerating anode 60 is disposed at the phosphor screen 58 and is adapted to receive a predetermined accelerating voltage which is substantially higher than the voltage impressed .on the last dynode 52 (the electron-multiplier anode) o~ the : electron-multiplier 38. The accelerating anode 60 draws ; electrons from the electron-m~ltiplier when the electron-multiplieris in an active state and accelerates the electrons to hiqh .energies for impingement upon the phosphor screen 58.
.15 In the illustrated form of the invention, an ion -~
generation region or stage 62 is pro~ided between the last dynode 52 and the accelerating anode 60 to provide a maximized electron-gas interaction probabillty. Additional field.-forming electrodes may be provided in such a special ion-generating ; 20 -region to optimize the field characteristics for maximum ion generation. As described hereina~ter with respect to another embodiment of the invention, ion generation may, alternatively, .
be accomplished within the compass of the dynodes 42-52, thus obviating a separate ion generation region within the device.
The provision of a separate ion generation region i.mproves the efficiency of ion generation and ion feedback efficiency, but adds to the length of the cathodo-luminescent device and thus increases the front-to-back depth of a display panel made up of such devices.
In accordance with this invention, activating means are provided for selectively causing the loop yain of the electron-multiplier ~eedback loop to be less than unity when it ' ' . . .
~:)391~7Z
is desired to c~use tha electron-multiplier to asqume an inactive state, or for turning the electron-multiplier "on"
by causing the said loop gain to be unity or greater. In the illustrated preferred embodiment, the electron-multiplier is self-saturating due to space charge and other effects. Thus when the electron-multiplier is turned on, it is done so by causing the loop gain to momentarily exceed unity wherein the electron-multiplier saturates at a predetermined saturation current level and the gain becomes exactly unity. It is contemplated that devices may be built, however, which follow the teachings of this invention but which are not driven to saturation in the "on" state. - ~-By way of background, the "loop gain" is taken to bethe average number of electrons ultimately released from the cathode in a complete cycle by the action of a single electron starting from the cathode. The loop gain is thus e~ual to the -~
product of the following:
1) the gain of the electron-multiplier 38, 2~ the gas ionization probability due to a single output electron, 3~ the probability that an ion generated in the ion generation region will fall ba~k to the cathode, and 4) the secondary-electron-emission coefficient of the cathode upon ion bombardment.
Z5 If the loop gain exceeds unity, the current in the loop builds up exponentially until some saturation effect such as space - charge ~lters the electrical fields within the electron-multiplier and reduces the gain to unity. The loop current then stabiliæes at that level. If the loop gain is caused to fall below unity, the current exponentially falls towards zero.
Thus in the context of the preferrad Figure 3 self-saturating device, the device may be bi-stably driven between an ":: ' ' . ~ , , , ` .
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~ff state and an activated "on" state by selectively causing the loop gain to be either less than unity or, alternatively, unity or greater than unity. In Figure 3, the device activating means is illustrated as a switching mean~ ~or applying to the cathode 40 a positive voltage of such a value that th~ electron-multiplier gain drops below that level necessary to establish a loop gain of unity or greater. To turn the device on, a cathode voltage is selected which, in combination with the voltages applied to the dynodes 42-52, establishes a gain in the multiplier 38 which is adequate to cause the loop gain of the device to be unity or greater. ~-It is mani~est that by the expedient of a bi-stable switching mechanism which switches the loop gain between less than unity and unity or greater, the electron-multiplier 38 can be switched between "of~" and "on" states in a highly non-linear fashion.
It is contemplated that cathodo-luminescsnt devices constructed according to this invention may be employed as a self-contained cathodo-luminescent cell. Alternatively, the cells may be arrayed in a display panel having one output level, that is, a panel which is not capable of yielding a gray scale, but rather is either fully "on" or fully "o~f". An example of a commercially useful panel having one "on" level would be an alpha-numeric display panel, or the like, wherein alpha-numeric characters are displayed at one intensity levelO
It is contemplated however that the invention may be more usefully employed in applications wherein it is desired to have multiple :Light level rendition, that is, wherein it is possible to display a "gray scale". An example of an application contemplated in which a gray scale capability is necessary is a black and white or color television display panel. A television display panel may comprise an array or matrix of cathodo-luminescent c~115 according to this invention, each o~ which is capable of yielding a luminous output at any of a selected number of discrete output levels, or in a continuum of light output levels. To this end, it is desirable that control means be -provided which is responsive to an applied control voltage for modulating the flow of electrons ~rom the electron-multiplier 38 to the phosphor screen 58 and thus the amplitude of the light emitted by the screen. In the illustrated Figure 3 embodiment, control electrode means are shown schematically as taking the form of a control grid 63 flanked by apertured electrodes 64, 65. The electrodes 64, 65 serve to isolate the control grid 63 from fields in the electron-multiplier 38 and in the electron accelerating region of the device. The .
electrodes 64, 65 m~y have applied thereto a co~non voltage which is somewhat greater than the voltage applied to the last dynode 52. As will become evident hereinafter, electrodes 64, 65 may comprise windowed, electrically conductive plates.
It is also deemed to be desirable to provide baffle means between the electron-multiplier 38 and the accelerating - 20 anode 60 for blocking high energy electrons which might be emitted by the electron-multipliex 38 and for blocking passage to the cathode 40 of ions which might be generated in the region between the baffle means and the accelerating anode 60. In the Figure 3 representation, baffle means are illustrated in highly schematic orm as taking the form of a secondary-electron-emissive plate 66 having a surface angled with respect to the axis of the electron-multiplier 38 for blocking high speed electrons and an ion-blocking plate 68 for blocking the passage to the cathode 40 of ions generated in the electron accelerating region~ The function of the plates 66, 68 will become more apparent as other, more structural, embodiments are described hereinafter.
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¦ Figure 4 illuqtrates, in more structural form than I Figure 3, cathodo-luminescent devices according to this invention ¦ incorporated in a display panel 69. The panel 69 is illustrated~ as being bounded by a rear wall 70 and a faceplate 71. In the ¦ 5 panel 71, the cathodes are shown as horizontal cathode strips ~ 72. Five dynodes, constituting part of an electron-multiplier 1 74, are depicted at 76, 78, 80, 82 and 84. Voltages of ever-¦ increasing poten~ial are supplied to the dynodes 76-84 from a voltage divider 86.
Beam control means are illustrated as comprising.a pair . of electrically conductive grid--isolating electrodes 88, 90.
Windows 89 are provided for passing the electron beams. Sand-wiched between the electrodes 88, 90 is a control grid 91. The control grid 91 may take the'form of a dielectric support plate 92 containing conductively metalized apertured grid strips 93.
The discrete grid strips 93 are individually controlled by signals : .developed in signal processing and scan control circuitry~ repre-sented schematically at 94.
The Figure 4 embodiment includes baffle means for ~: 20 blocking the passage of high energy electrons from the electron- ~ :
~ - multiplier 7~ into the accelerating region o the device and for : ~preventing feedback of high energy ions to the cathode from theelectron accelerating region of the device. The accelerating region is the region between the beam contxol means and the ac-celerating electrode, preerably located on the back of the :~ faceplate 71. In the illustrated Figure 4 embodiment, the first-described baffling function is accomplished by a secondary-electron-emissive baffle plate 95. The latter baffling function is per-formed by electron-opaque areas 96 on the grid-isolating plate 90.
As noted above, it is contemplated that cathodo-luminescent devices constructed according to this invention may be incorpcrated in an image display panel such as a television . -14_ ' ' ' ' , ~' , ~
, ~1(339872 reproducer. Figure S is a hicJhly schematic p~rspectiv~ view of a television display pan~l 112 constituting a part of a television r~ceiver. The panel 112 incorporates an X~Y matrix of cathodo-luminescent devices according to this invention. The display panel 112 is illustrated as comprising a rear panel wall 114 on which is aisposed an array of horizontally`or'i-ented line or strip cathodes 116. At the forward end of the p`an~l 112 there is provided a transparent faceplate 118 on the back surface o~ which is disposed an array of sequentially repetitive, ver-tically oriented red-emissive, blue-emissive and green-emissive phosphor strips (not shown).
In Figure 5 there is illustrated a series of column leads 120 which lead from column current control circuitry 122 to control means such as the grid strips 93 in the Figure 4 embodiment. Row selection and drive circuitry, shown schematically at 124, along with the column control circuitry 122, provide a modulated raster scan of the panel 112.' The ro~ s~election and , ~ . . .
'~ drive circuitry 124 and the column circuitry 122 may'be constructed following principles well known to those skilled in the art.
In operation, the uppermost horizontally extending line of the cathodo luminescent devices is activated by application ; of appropriate potentials on'the uppermost cathode 116. A line o video information which has, for example, been received by an antenna I2'6, been processed appropriately in a processor 128 and been stored in a line storage memory 130, i~ applied in parallel to a fullirow or a portion of a full row of cathodo'-luminescent devices. The video information is applied, as described, to control grids within the cathodo-luminescent devices. The line o~ video information is maintained for a horizontal`line display period. In an allotted retrace time, typically 10 microseconds of the 63 microsecond line time, the first video line is de-activated and the next successive line or the line after that _15-~(~39872 (depending upon the means for effecting vertical rast~r interlace) is energized. A second line of video information which has been stored in the mèmory L30 is applied to the ~econd video line. A complete vertical scan of the panel to display a full video image is accompLished in this manner.
If satisfactory luminous intensity is developed in the cathodo-luminescent devices, the line of stored information can be displayed during the retrace interval. This mode of operation would require oneO rather than two, video storage memories. If insufficient intensity is obtained, the video information must be simultaneously written into one set of storage elements while another memory controls the display.
Vertical commutation may be accomplished using discrete or multi-phase scanning signals.
Flgures 6-8 illustrate a color television display panel representing a preferred embodiment of the-principles of this inventionO The Figures 6-8 embodiment is~ii~u`strated as comprising a faceplate 134 on the rear surface of which is disposed a vertically oriented, periodically repetitive sequence of red-emissive, blue-emissive and green-emissive phosphor ;-strips 1360 An accelerating anode 138 comprising a layer of electrically conductive material (aluminum, for example) is deposited over the phosphor strips 136 and is adapted to ~;
receive a relatively high applied voltage for accelerating the electron beams 139 (to be described) to high e~ergies for impingement on the phosphor strips 136.
The Figures 6-8 panel includes a rear enclosure plate 140 which may be composed of glass or othex suitable material, on which is deposited a series of horizontally arranged cathode strips 141. The cathode strips 141 function as cold cathodes and may be composed of a material such as aluminum or other suitable materials, certain of which ara suggested above. Each .. . . . . . .. . ... .. . . .. .. . . . ..
cathode strip 141 forms part of an electron-mulkiplier which includes a plurality of discrete, sexially a~ranged, secondary-electron-emissive dynodes 142, 144, 146, 148, 150, 152, lS~ and 155 for multiplying electrons emittecl from the cathode strips 141.
In the illustrated preferred Figures 6-8 embodiment, the dynodes 142-155 ~re illustrated as being foxmed from a series of spaced p~irs of dynode sheets 156, 158. The dynode sheets 156, 158 each comprise a sheet of electrically conductive material, preferably beryllium-copper, in which is integrally formed from the sheet material a matrix of flaps 160. The flaps 160 may be formed by photo-etch-ng away the flap boundaries and then stamping or pressing out the flaps. The dynode sheets 156, 158 are preferably formed simllar to each other except that the dynode flaps are deflected in opposite directions~
A dynode structure in the form of sheets with flaps bent out to form the secondary-electron-emissive elements and certain other stxuctural and fabrication principles embodied and revealed in the Figures 6-8 embodiment do not, per se, constitu'ce a part of ~his invention.
Whereas each of the flaps 160 may be formed to act as a dynode element for a singla horizontal image line element, as shown, it is preferable the flaps be wider so as to embrace a number of image line elements -- six for example. By this approach, fabrication of the flaps is vastly simplified, yet interstices are created between flaps ~or increasing the mechanical integrity o~ the panel structure.
The pairs of dynode sheets 156, 158 receive applied 28 voltages ever-ancreasing in positive polarity in a direction rw/~u .. . . . ~ .
''-''' :103~72 away from the cathod~ strips 141, which pattern of voltayes may be developed by the use of voltage divider means as shown at 86 in Figure 4. As shown by the electron paths in Figure 7, the first dynode 142 is not actually an electron-multiplying element, but rather serves as a fieLd-forming electrode which deflects the electrons emitted by the cathode strips to the second dynode 144. The pairs of dynode sheets 156, 158 are held in electrical union but are spaced each from each adjacent pair of sheets by means of spacers 162 which may, for example, be composed o~ glass or other suitable insulating material.
The spacers 162 may be fabricated as the vertically spaced bridges between panel-wide slit windows (aligned with the windows in sheets 156, 158) etched in a glass plate. The spacers are shielded from the electron beams by the dynodes 142,155 such that fields due to surface charges on the insulators do not substantially alter the charged particle trajectories.
The spacers 162 serve a number of functions. They control the spacing of the dynode sheets 156, 158 from neighboring dynode sheets~ Secondly, they provide periodic front-to-back support across the expanse of the panel. Thirdly, the spacers 162 prevent buckling or bending of the sheets to prevent electrical short circuit~g between adjacent sheet pairs.
A field-forming output electrode 164, including flaps 165, 166, is spaced beyond the last dynode sheet 158a and serves to form an electric field which guides the electron beam through t~e window formed between the flaps 165, 166 and into an electron control section or region of the panel, described below.
The Figures 6-8 electron-multiplier is illustrated as having the capability of a gain of approximately 1000. Suitable potentials which may be applied to the dynodes 142-155 and other electrodes in the panel are shown in Figure 7. By fabricating the electron-multiplier dynodes for the entire panel as flaps .; ' ~
1~39872 b~nt from electrlcally concluctive sheets stacked to form a multiple dynode electron-multiplier, very substantial economies in panel ~abrication are effected.
As in the above-described embodiments, the electron~
multiplier serves to establish a source of electrons for acceleration to high energies for bo~nbarding the phosphor strips 136. Control means for controlling the flow o~ electrons from the electron-multiplier to the phosphor strips 136 is illustrated in the preferred Figures 6-8 embodiment as taking the form of a stack of vertically oriented electrodes 168, 170, 171, 172, 174, 175 and 176. The electrodes 168-176 are divided into three functional groups by vertically oriented, horizontally spaced insulators 178, 180, which may, for example, comprise windowed glass plates. The first group of electrodes, comprising electrode 168, and the third group, comprising electrodes 174, 175 and 176, receive potentials effective to isolate the central group of control electrodes 170, 171, 172 from stray fields. See the exemplary potentials illustrated in Figure 7. The control electrodes receive a bias voltage on which is superimposed a modulating signal voltage which may, as shown in Figure 7, for the illustrated embodiment, take the form of a l900 volt bias modulated by a signal having a maximum peak-to-peak swing of 40 volts. The control electrodes 170-17~ are insulated from horizontally adjacent control electrodes by insulators 181.
~5 The electrodes 168, 174, 175 and 176 may be ~oxmed as physically and electrically united conductive plates (metalized glass plates or sheets of conductive materials, e.g.) having windows for passing the electron beams. One of such windows is shown in electrode 168 as 184. These electrodes preferably extend horizontally and vertically across the entire panel.
The insulators 178, 180 are also preferably formed as plates having beam-passing windows, except, of course, the . :
1~39872 insulators ar~ formed of an electrically non-conductive material such as glass. In outward appearance, the electrodes 168, 174, 175 and 176 and the insulators 178, 180 closely resemble the grid-isolating plates 188 and 190 co;nstituting part of the Figure 4 embodiment.
The beam control electrodes 170-172 must be individually controllable, column-by-column, since signal information to be imparted on the individual electron beams reaching the phosphor strips 136 is carried on these electrodes. The three electrodes 170-172 are preferably electrically~conductive strips which are physically and electrically united to act as a single control element. The electrodes 170-17~ also have windows for passing the electron beams. The electrodes 170-172 thus have the same function as the grid strips 93 in the Figure 4 embodiment and a similar construction, except for having three united electrodes operating as a single electrode, rather than a single electrode.
In order to insure that each of the triads o~ tied electrodes 170-172 are each isolated from their horizontally spac~d neighbors, vertically oriented insulators 181 are provided (see Figure 8). The insulators 181 preferably extend continuously from the top to the bottom of the panel and may be composed of glass or oth r suitable insulating material.
The beam-passing windows in the electrodes 168, 170-172, 174-176 and insulators 178, 180 are successively vertically offset such that they aggregatively define angled beam-conducting channels through the beam control means. The opaque portions 186 of the e}ectrode 184 act as a baffle which precludes entry into the beam accelerating region of high speed electrons generated in the electron-multiplier. Areas such as shown at 182 on ~he field-forming electrode 164 act to block the rearward passage of positive ions which might be genarated in the ~eam acceleration region~ Such baffling may not be necessary in all applications.
-20_ .... . . . .
~039872 Th~ electrodes ar~ spaced from the faceplate 62 by horizontally oriented, electrically insulative (glass, for example) spacers 198. The spacers 198 are preferably disposed between every other line (i.e., between each lace-interlace pair). Alternatively, other vertical separation distances may be employed, depending on the size of ~h~ panel and other electrical or structural considerations. In a small panel, simplified support structures may be employed.
Alternatively, vertically oriented, horizontally separated spacers may be used to provide the necessary structural rigidity for the panel~ These would preferably be disposed in the location of and in substitution for every other blue-emissive phosphor strip. Since the resolving ability of the human eye to blue-wavelength light images is relatively poor, the elimination of alternate blue-emissive phosphor strips will have a negligible effect on the perceived overall pict~re quality~ These spacers 198 serve also to periodically support the faceplate, preventing bending or breakage due to atmospheric `forces.
In order to precisely control the acceleration field in the acceleration region, it may be necessary to provide a series of electrically conductive ribbons, as shown at 202, on the sidewalls of the spacers 198. The ribbons 202 are adapted to receive a progression of voltages effective to achieve a satisfactory beam acceleration characteristic and to preclude interference with the beam by stray charge-generated fields or the like. An example of a voltage pattern suitable for applica-tion to the ribbons 202 is shown in Figure 7.
In accordance with an aspect of this invention, beam deflecting means may be provided for controlling the vertical position of the electron beams in the panel, for example to effect interlace of successive display fields. ~n the illustrated :, . ...
103~7~
embodim~nt, to deflect the electron beams for interlace purposes, a deflection voltage, generated, e.g., by deflection signal generator 203, may be applied to the first ribbons 202a, 202b.
See Figure 6. By application of an appropriate negative deflec-tion voltage to ribbons 202a (a few hundred volts, for example)and a complementary positive deflection voltage to ribbons 202b, the electron beams may be deflected downward during raster interlace. The interlace deflection signals must, of course, be synchronized with panel scan signals and synchroniza-tion signals.^ Figure 8 is a view of the control and accelerating regions of the device taken along section lines 8-8 in Figure 6. Electric fields which are established in the control and accelerating regions cause the electron beams to be converged or pinched horizontally such that the ultimate beam cross-- sectional configuration upon impingement with the phosphor ætrips 136 is horizontally narrowed. ` - ~ ~*1_ ~ Figure 8 illustrates a triad of luminescent devices or cells 204~ 206, 208, taken by way of example to be asso-ciated, respectively, with a red signal picture element, a blue signal picture element and a green signal picture element.
In the illustrated Figure 8 embodiment, by way of example, the control electrodes 170, 171, 172 controlling the red-associated cell 204 carry a signal voltage of minus 30 volts which is effective to completely shut off khe red-associated electron beam and thus prevent the luminescence of the red-emissive phosphor strip 136R. The control signal associated with blue infoxmation is applied to the electrodes 170, 171, 172 con-trolling ths blue-associated cell 206 and, in the illustrated embodiment, is shown as being of such a value (minus 25 volts, e.g.) as to admit passage of a relative~y low intensity electron beam 139B to the blue-emissive phosphor strip 136B. The green i. .
. ..~, . , .,.: , . . .
,, ~ ;,. . .. .
~ 039~3~2 information is shown as being a signal of greater value positive than that applied to elther the red-associated or blue-a~sociated cells 204, 206 (minus 20 volts, e.g.), permitting a relatively intense grPen-associated electron beam 139G to impinye upon S the green-emissive phosphor strip 136G. Thus the integrated luminous output of the triad of cells would be perceived as a predominantly green image somewhat desaturated by blue light.
~e invention is not limited to the particular details , of construction of the embodiments depicted and other modifica-1~0 tions and applications are contemplated. For example, rather than using control electrodes in the acceleration region, such ,as electrodes 170-172 in Figures 6-8 to modulate the flow of electrons to the phosphor strips 136, control s~ructures of other,,t~pes in ~he same or different regions of the device may be employed to control the flow of electrons from the electron-multiplier or to co~trol the output of the electron-multiplier itself. Rather than operating the electron-multiplier in a mode wherein it is either "off" or driven to saturation, the electron-multiplier may be activated in a non-saturated state at a predetermined intermediate level of output. If operated ,in a maximum output mode, it may be possible to avoid storing all or part of a line interval of information and display only in -,the retrace interval. Rather than switching the electron-multiplier by application of a switching voltage to the cathode, a switching voltage may be applied to other suitable electrodes ,within the device such as one of the dynodes~ It is,,,contemplated that the output beam may be deflecte,d on the phosphor screen, as by means of suitably structured and excited deflection electrodes, for purposes other than interlace scanning. Certain other changes may be made in the above-described apparatus without departing from the true spirit and scope of the inven-tion herein involved and it is intended that the subject : . . . .................... .
~ 03a~z matter in the above depiction shall be interpreted as illus-trative and not in a l.imiting sense.
; , ~.. ,.
.
~, ', ' ~'" ' .
., :" . . . : ~ .
~(~398~;Z
In a simple gas diode (see Figure 1), positive gas ions generated in the gas impinge upon the cathode, releasing secondary electr~ns. The electrons are accelerated toward the anode. The probability of interaction with a gas atom in the intervening space depends upon the cl~nsity (pressure) of gas molecules in that space and the length of the path. When an electron has gained sufficient energy in falling through the electric field along the cathode-to-anode path, it can ionize a gas atom, thus freeing an additional electron and creating a "feedback" ion. The two electrons (the oxiginal one plus the newly formed one) proceed toward the anode, perhaps creating additional ion/electron pairs on the way. Some ions and electrons will be lost to the walls. In general, each backwardly accelerated ion impinging upon the cathode will free an average lS of less than one electron ~- perhaps as few as 1 electron per 10 ions impinging. Hence, for a sustained discharge, each electron leaving the cathode must initiate an avalanche of -ion/electron pair generating collisions such that enough ions are generated on the average to satisfy wall losses and to generate collectively one new secondary electron at the cathode.
Obviously, if the density of gas is not sufficient to allow an adequate number of collisions along the cathode-to-anode path, a discharge cannot be maintained. Increasing the path length increases the probability of a collision at a given pressure. Raising the voltage difference helps in a marginal situation, primarily because the electrons will be accelerated to the minimum ionizing level sooner along the path (thus increasing the effective path length), and becausé occasionally more than one electron may be released per collision. On the other hand, high velocity electrons may ha~e reduced ionization probability. The net result is that if a path is too short, for a given gas density, a sel~-sustained discharge cannot be : ,. . .
103987;2 maintained everl when very high voltage dif~erences exist in the field-containing space. ~his circumstance is classically described by a Paschen curve. This curve and other principles and details of gas discharge devices and their operation are described in such works as "Gaseous Conductors", by ~ames Cobine, Dover Publications (1958).
The ~erm "gas discharge cell" or "gas discharge device"
; is herein intended to mean a cell or a device in which the electric fields differ significantly between the "on" state wherein a plasma is present and the "off" state wherein no current is flowing. Devices constructed in acco~d~nce ~ith this invention do not have the described characteristics o~ a gas discharge device. Rather, they may be aptly termed electro-static devices in w~ich the electric fields estab~ished within lS by application of voltages to its electrodes are not substantially and abruptly altered hy the presence of ions.
In a conventional gas discharge diode as sh~wn in Figure l, the design relationship between gas pressure "p" and the cathode-to-anode spacing "d", for minimum operating voltage, is given to excellent approximation by the Paschen similitude expression: p x d = K, where K is a constant which depends on cathode material, gas composition and tube geometry (but not tube siz~e). For usual discharge devices, K is generally equal to about one-half torr cm.
In the Figure l diode, electrons emitted from the cathode undergo ionizing collisions in the gas, resulting in an electron "avalanche" which multiplies the electron current as it approaches the anode. If the ion-electron secondary emission ratio is x (typically about .1), a gas-Plectron-avalan~he gain of at least x (where x is typically about lO) must be developed to establish an electron-ion loop gain of unity. Accordingly, the minimum breakdown voltage characterisitc for a given diode (revealed) ......
~03~87Z
by the well-known Paschen curve) i~ a measure of the ~econdary emission properties o~ the cathode of the diode, as well as a measure of the electron-avalanche properties of the ga3.
As will be explained in more detail hereinafte~, in accordance with the principles of this invention, an electron-multiplier, as shown schematically in Figure 2, is inserted between the cathode and the region where ions are to be generated.
The ill~strated Figure 2 device comprises an envelope 10 con-taining an ionizable gas such as hydrogen, helium, neon or other suitable gases or gas mixtures. A cathode 12 serves as an electron emit~er. ~ plurality of serially arranged, secondary-electron-emissive dynodes 14, 16, 18, 20, ~2 and 24 receive applied voltages ever-increasing in positive polarity in a direction ~way from the cathode 12. The voltages are shown as being provided by a tapped voltage divider 26. A final anode 28 collects the electrons from the last dynode 24.
Due to collisions between the electrons and the gas atoms within the envelope 10, positive gas ions 30 are generated.
J~ In accordance with this invention, as will be explained in more l~ 20 detail hereinafter, the dynodes 14-24 are arranged so as to 1: ~
permit t~e ions 30 to be accelerated directly to the cathode 12 to cause the cathode to emit additional free electrons 32.
For the Figure 2 device, the Paschen similitude expxession takes the general form:
p~l-g = K, where ~ is the efective length of the ion generation region and llgll is the gain of the electron-multiplier. The value of K
depends upon the efficiency with which positive ions are trans-p~rted back to the cathode and the ion-induced secondary electron amission coefficlent of the cathode~ This is true whether or not an electron-multiplier is included. K also depends upon the electron velocity in the ion generation region. In appro-. , ~3913~
¦ priately designed tubes, however, the value of K is not likely ¦ to differ greatly in general magnitude whether a multiplier is present or not. Hence it may be concluded that if an electron-multiplier o~ gain "g" is interposed, a discharge may be initiated at a pressure which is approximately l/g lower than if a multiplier is not interposed. This principle is basic to this invention.
By operating a tube at sufficiently low gas pressure~
ionizing collisions between gas atoms and electrons becomes a negligible effect so far as scattering of electrons is concerned.
Under such conditions a beam of electrons may be accelerated to high velocity with no significant energy loss and no concern about initiating an unwanted self sustained discharge between ~he high voltage anode and lower voltage electrodes in the tube.
Figure 3 illustrates in highly schematic form a cathodo-luminescent device containing basic components of devices constructed according to this invention. The Figure 3 device 34 is illustrated as comprising wall means in the form of an envelope 36 (typically glass) which defines an enclosure con-taining an ionizable gas such as helium, hydrogen, neon or other suitable gases or gas mixtures at a predetermined pre~sure sufficiently low to preclude establishment of a gas discharge in ~he devlce.
An electron-multiplier 38 located within the enclosure creates at an output end thereof a source o~ electrons~ The electxon-multiplier 38 includes a cathode 40, which may comprise, for example, an aluminumO magnesium or nickel strip. The electron-multiplier 38 is depicted as including a plurality of discrete dynodes 42, 44, 46, 48, 50 and 52. The dynodes 42-52 may be composed, ~ox example, of oxidized beryllium-copper alloy, cesium-a~timony alloy, silver-magnesium alloy, oxidized aluminum, or other suitable materials. The last dynode in the Figure 3 i , 1~39187;Z
7 embodiment (52~ and in later-described embodiments is also re~erred to herein as the "electron-multiplier anode~. As used, this term is intended to mean the highest voltage dynode ¦ in an electron-multiplier constituting a part of a light-emissive device constructed according to this invention, and is not f intended to mea.n a current-collecting electrode.
As in the Figure 2 device, the dynodes are adapted to receive voltages ever-increasing in positive polarity in a direction away from the cathode. 40, which pattern of voltages may be provided by a voltage divider, as shown at 26 in Figure 2.
This invention comprahends the use of an electron-multiplier of a type other than as shown, such as a channel plate multiplier, .
a Weis mesh multiplier, or a staggered plate multiplier; the illustrated shaped dynode structure is preferred however.
The electron-multiplier 38, of whatever form, generates positive gas ions 54 as a result of collisions between the f electrons and gas atoms within the multiplier. In accordance with this invention, as will be explained in more detail hereinafter, the dynodes 42-52 are arrange.d so as to permit the positive gas ions 54 to be accelerated to the cathode 40 to .:
cause the cathode to emit additional free electrons 56. The : additional electrons 56 emitted from the cathode 40 a~ a result of the ion bombardment are in turn multiplied in the electron-multiplier 38. The electron-multiplier 38 thus constitutes part of a regenerative electron-ion feedback loop.
Phosphor means in the form of a phosphor screen 58 is disposed at ona end of the enclosure in spacad relation to the ~utput end o~ the electron-multiplier 38 for emitting light when bombarded by high energy electrons. As will become evident as this description proceeds, tha phosphor material may be selected to emit white light for use in a one color display device or panel, or may be, fo.r example, red-emissive, blue-,`.'"` ' j emissive and green~emissive in arrays of devices designed to form ¦ color television pictures or other color displays. It should be I noted that only a small percentage of the multiplied electron beam is utilized to create positive gas ions, a very substantial part of the beam being available ~or acceleration to the phosphor screen 58.
An accelerating anode 60 is disposed at the phosphor screen 58 and is adapted to receive a predetermined accelerating voltage which is substantially higher than the voltage impressed .on the last dynode 52 (the electron-multiplier anode) o~ the : electron-multiplier 38. The accelerating anode 60 draws ; electrons from the electron-m~ltiplier when the electron-multiplieris in an active state and accelerates the electrons to hiqh .energies for impingement upon the phosphor screen 58.
.15 In the illustrated form of the invention, an ion -~
generation region or stage 62 is pro~ided between the last dynode 52 and the accelerating anode 60 to provide a maximized electron-gas interaction probabillty. Additional field.-forming electrodes may be provided in such a special ion-generating ; 20 -region to optimize the field characteristics for maximum ion generation. As described hereina~ter with respect to another embodiment of the invention, ion generation may, alternatively, .
be accomplished within the compass of the dynodes 42-52, thus obviating a separate ion generation region within the device.
The provision of a separate ion generation region i.mproves the efficiency of ion generation and ion feedback efficiency, but adds to the length of the cathodo-luminescent device and thus increases the front-to-back depth of a display panel made up of such devices.
In accordance with this invention, activating means are provided for selectively causing the loop yain of the electron-multiplier ~eedback loop to be less than unity when it ' ' . . .
~:)391~7Z
is desired to c~use tha electron-multiplier to asqume an inactive state, or for turning the electron-multiplier "on"
by causing the said loop gain to be unity or greater. In the illustrated preferred embodiment, the electron-multiplier is self-saturating due to space charge and other effects. Thus when the electron-multiplier is turned on, it is done so by causing the loop gain to momentarily exceed unity wherein the electron-multiplier saturates at a predetermined saturation current level and the gain becomes exactly unity. It is contemplated that devices may be built, however, which follow the teachings of this invention but which are not driven to saturation in the "on" state. - ~-By way of background, the "loop gain" is taken to bethe average number of electrons ultimately released from the cathode in a complete cycle by the action of a single electron starting from the cathode. The loop gain is thus e~ual to the -~
product of the following:
1) the gain of the electron-multiplier 38, 2~ the gas ionization probability due to a single output electron, 3~ the probability that an ion generated in the ion generation region will fall ba~k to the cathode, and 4) the secondary-electron-emission coefficient of the cathode upon ion bombardment.
Z5 If the loop gain exceeds unity, the current in the loop builds up exponentially until some saturation effect such as space - charge ~lters the electrical fields within the electron-multiplier and reduces the gain to unity. The loop current then stabiliæes at that level. If the loop gain is caused to fall below unity, the current exponentially falls towards zero.
Thus in the context of the preferrad Figure 3 self-saturating device, the device may be bi-stably driven between an ":: ' ' . ~ , , , ` .
.... .
~ ()3~87Z
~ff state and an activated "on" state by selectively causing the loop gain to be either less than unity or, alternatively, unity or greater than unity. In Figure 3, the device activating means is illustrated as a switching mean~ ~or applying to the cathode 40 a positive voltage of such a value that th~ electron-multiplier gain drops below that level necessary to establish a loop gain of unity or greater. To turn the device on, a cathode voltage is selected which, in combination with the voltages applied to the dynodes 42-52, establishes a gain in the multiplier 38 which is adequate to cause the loop gain of the device to be unity or greater. ~-It is mani~est that by the expedient of a bi-stable switching mechanism which switches the loop gain between less than unity and unity or greater, the electron-multiplier 38 can be switched between "of~" and "on" states in a highly non-linear fashion.
It is contemplated that cathodo-luminescsnt devices constructed according to this invention may be employed as a self-contained cathodo-luminescent cell. Alternatively, the cells may be arrayed in a display panel having one output level, that is, a panel which is not capable of yielding a gray scale, but rather is either fully "on" or fully "o~f". An example of a commercially useful panel having one "on" level would be an alpha-numeric display panel, or the like, wherein alpha-numeric characters are displayed at one intensity levelO
It is contemplated however that the invention may be more usefully employed in applications wherein it is desired to have multiple :Light level rendition, that is, wherein it is possible to display a "gray scale". An example of an application contemplated in which a gray scale capability is necessary is a black and white or color television display panel. A television display panel may comprise an array or matrix of cathodo-luminescent c~115 according to this invention, each o~ which is capable of yielding a luminous output at any of a selected number of discrete output levels, or in a continuum of light output levels. To this end, it is desirable that control means be -provided which is responsive to an applied control voltage for modulating the flow of electrons ~rom the electron-multiplier 38 to the phosphor screen 58 and thus the amplitude of the light emitted by the screen. In the illustrated Figure 3 embodiment, control electrode means are shown schematically as taking the form of a control grid 63 flanked by apertured electrodes 64, 65. The electrodes 64, 65 serve to isolate the control grid 63 from fields in the electron-multiplier 38 and in the electron accelerating region of the device. The .
electrodes 64, 65 m~y have applied thereto a co~non voltage which is somewhat greater than the voltage applied to the last dynode 52. As will become evident hereinafter, electrodes 64, 65 may comprise windowed, electrically conductive plates.
It is also deemed to be desirable to provide baffle means between the electron-multiplier 38 and the accelerating - 20 anode 60 for blocking high energy electrons which might be emitted by the electron-multipliex 38 and for blocking passage to the cathode 40 of ions which might be generated in the region between the baffle means and the accelerating anode 60. In the Figure 3 representation, baffle means are illustrated in highly schematic orm as taking the form of a secondary-electron-emissive plate 66 having a surface angled with respect to the axis of the electron-multiplier 38 for blocking high speed electrons and an ion-blocking plate 68 for blocking the passage to the cathode 40 of ions generated in the electron accelerating region~ The function of the plates 66, 68 will become more apparent as other, more structural, embodiments are described hereinafter.
" ~ . . . .
~03g87~
¦ Figure 4 illuqtrates, in more structural form than I Figure 3, cathodo-luminescent devices according to this invention ¦ incorporated in a display panel 69. The panel 69 is illustrated~ as being bounded by a rear wall 70 and a faceplate 71. In the ¦ 5 panel 71, the cathodes are shown as horizontal cathode strips ~ 72. Five dynodes, constituting part of an electron-multiplier 1 74, are depicted at 76, 78, 80, 82 and 84. Voltages of ever-¦ increasing poten~ial are supplied to the dynodes 76-84 from a voltage divider 86.
Beam control means are illustrated as comprising.a pair . of electrically conductive grid--isolating electrodes 88, 90.
Windows 89 are provided for passing the electron beams. Sand-wiched between the electrodes 88, 90 is a control grid 91. The control grid 91 may take the'form of a dielectric support plate 92 containing conductively metalized apertured grid strips 93.
The discrete grid strips 93 are individually controlled by signals : .developed in signal processing and scan control circuitry~ repre-sented schematically at 94.
The Figure 4 embodiment includes baffle means for ~: 20 blocking the passage of high energy electrons from the electron- ~ :
~ - multiplier 7~ into the accelerating region o the device and for : ~preventing feedback of high energy ions to the cathode from theelectron accelerating region of the device. The accelerating region is the region between the beam contxol means and the ac-celerating electrode, preerably located on the back of the :~ faceplate 71. In the illustrated Figure 4 embodiment, the first-described baffling function is accomplished by a secondary-electron-emissive baffle plate 95. The latter baffling function is per-formed by electron-opaque areas 96 on the grid-isolating plate 90.
As noted above, it is contemplated that cathodo-luminescent devices constructed according to this invention may be incorpcrated in an image display panel such as a television . -14_ ' ' ' ' , ~' , ~
, ~1(339872 reproducer. Figure S is a hicJhly schematic p~rspectiv~ view of a television display pan~l 112 constituting a part of a television r~ceiver. The panel 112 incorporates an X~Y matrix of cathodo-luminescent devices according to this invention. The display panel 112 is illustrated as comprising a rear panel wall 114 on which is aisposed an array of horizontally`or'i-ented line or strip cathodes 116. At the forward end of the p`an~l 112 there is provided a transparent faceplate 118 on the back surface o~ which is disposed an array of sequentially repetitive, ver-tically oriented red-emissive, blue-emissive and green-emissive phosphor strips (not shown).
In Figure 5 there is illustrated a series of column leads 120 which lead from column current control circuitry 122 to control means such as the grid strips 93 in the Figure 4 embodiment. Row selection and drive circuitry, shown schematically at 124, along with the column control circuitry 122, provide a modulated raster scan of the panel 112.' The ro~ s~election and , ~ . . .
'~ drive circuitry 124 and the column circuitry 122 may'be constructed following principles well known to those skilled in the art.
In operation, the uppermost horizontally extending line of the cathodo luminescent devices is activated by application ; of appropriate potentials on'the uppermost cathode 116. A line o video information which has, for example, been received by an antenna I2'6, been processed appropriately in a processor 128 and been stored in a line storage memory 130, i~ applied in parallel to a fullirow or a portion of a full row of cathodo'-luminescent devices. The video information is applied, as described, to control grids within the cathodo-luminescent devices. The line o~ video information is maintained for a horizontal`line display period. In an allotted retrace time, typically 10 microseconds of the 63 microsecond line time, the first video line is de-activated and the next successive line or the line after that _15-~(~39872 (depending upon the means for effecting vertical rast~r interlace) is energized. A second line of video information which has been stored in the mèmory L30 is applied to the ~econd video line. A complete vertical scan of the panel to display a full video image is accompLished in this manner.
If satisfactory luminous intensity is developed in the cathodo-luminescent devices, the line of stored information can be displayed during the retrace interval. This mode of operation would require oneO rather than two, video storage memories. If insufficient intensity is obtained, the video information must be simultaneously written into one set of storage elements while another memory controls the display.
Vertical commutation may be accomplished using discrete or multi-phase scanning signals.
Flgures 6-8 illustrate a color television display panel representing a preferred embodiment of the-principles of this inventionO The Figures 6-8 embodiment is~ii~u`strated as comprising a faceplate 134 on the rear surface of which is disposed a vertically oriented, periodically repetitive sequence of red-emissive, blue-emissive and green-emissive phosphor ;-strips 1360 An accelerating anode 138 comprising a layer of electrically conductive material (aluminum, for example) is deposited over the phosphor strips 136 and is adapted to ~;
receive a relatively high applied voltage for accelerating the electron beams 139 (to be described) to high e~ergies for impingement on the phosphor strips 136.
The Figures 6-8 panel includes a rear enclosure plate 140 which may be composed of glass or othex suitable material, on which is deposited a series of horizontally arranged cathode strips 141. The cathode strips 141 function as cold cathodes and may be composed of a material such as aluminum or other suitable materials, certain of which ara suggested above. Each .. . . . . . .. . ... .. . . .. .. . . . ..
cathode strip 141 forms part of an electron-mulkiplier which includes a plurality of discrete, sexially a~ranged, secondary-electron-emissive dynodes 142, 144, 146, 148, 150, 152, lS~ and 155 for multiplying electrons emittecl from the cathode strips 141.
In the illustrated preferred Figures 6-8 embodiment, the dynodes 142-155 ~re illustrated as being foxmed from a series of spaced p~irs of dynode sheets 156, 158. The dynode sheets 156, 158 each comprise a sheet of electrically conductive material, preferably beryllium-copper, in which is integrally formed from the sheet material a matrix of flaps 160. The flaps 160 may be formed by photo-etch-ng away the flap boundaries and then stamping or pressing out the flaps. The dynode sheets 156, 158 are preferably formed simllar to each other except that the dynode flaps are deflected in opposite directions~
A dynode structure in the form of sheets with flaps bent out to form the secondary-electron-emissive elements and certain other stxuctural and fabrication principles embodied and revealed in the Figures 6-8 embodiment do not, per se, constitu'ce a part of ~his invention.
Whereas each of the flaps 160 may be formed to act as a dynode element for a singla horizontal image line element, as shown, it is preferable the flaps be wider so as to embrace a number of image line elements -- six for example. By this approach, fabrication of the flaps is vastly simplified, yet interstices are created between flaps ~or increasing the mechanical integrity o~ the panel structure.
The pairs of dynode sheets 156, 158 receive applied 28 voltages ever-ancreasing in positive polarity in a direction rw/~u .. . . . ~ .
''-''' :103~72 away from the cathod~ strips 141, which pattern of voltayes may be developed by the use of voltage divider means as shown at 86 in Figure 4. As shown by the electron paths in Figure 7, the first dynode 142 is not actually an electron-multiplying element, but rather serves as a fieLd-forming electrode which deflects the electrons emitted by the cathode strips to the second dynode 144. The pairs of dynode sheets 156, 158 are held in electrical union but are spaced each from each adjacent pair of sheets by means of spacers 162 which may, for example, be composed o~ glass or other suitable insulating material.
The spacers 162 may be fabricated as the vertically spaced bridges between panel-wide slit windows (aligned with the windows in sheets 156, 158) etched in a glass plate. The spacers are shielded from the electron beams by the dynodes 142,155 such that fields due to surface charges on the insulators do not substantially alter the charged particle trajectories.
The spacers 162 serve a number of functions. They control the spacing of the dynode sheets 156, 158 from neighboring dynode sheets~ Secondly, they provide periodic front-to-back support across the expanse of the panel. Thirdly, the spacers 162 prevent buckling or bending of the sheets to prevent electrical short circuit~g between adjacent sheet pairs.
A field-forming output electrode 164, including flaps 165, 166, is spaced beyond the last dynode sheet 158a and serves to form an electric field which guides the electron beam through t~e window formed between the flaps 165, 166 and into an electron control section or region of the panel, described below.
The Figures 6-8 electron-multiplier is illustrated as having the capability of a gain of approximately 1000. Suitable potentials which may be applied to the dynodes 142-155 and other electrodes in the panel are shown in Figure 7. By fabricating the electron-multiplier dynodes for the entire panel as flaps .; ' ~
1~39872 b~nt from electrlcally concluctive sheets stacked to form a multiple dynode electron-multiplier, very substantial economies in panel ~abrication are effected.
As in the above-described embodiments, the electron~
multiplier serves to establish a source of electrons for acceleration to high energies for bo~nbarding the phosphor strips 136. Control means for controlling the flow o~ electrons from the electron-multiplier to the phosphor strips 136 is illustrated in the preferred Figures 6-8 embodiment as taking the form of a stack of vertically oriented electrodes 168, 170, 171, 172, 174, 175 and 176. The electrodes 168-176 are divided into three functional groups by vertically oriented, horizontally spaced insulators 178, 180, which may, for example, comprise windowed glass plates. The first group of electrodes, comprising electrode 168, and the third group, comprising electrodes 174, 175 and 176, receive potentials effective to isolate the central group of control electrodes 170, 171, 172 from stray fields. See the exemplary potentials illustrated in Figure 7. The control electrodes receive a bias voltage on which is superimposed a modulating signal voltage which may, as shown in Figure 7, for the illustrated embodiment, take the form of a l900 volt bias modulated by a signal having a maximum peak-to-peak swing of 40 volts. The control electrodes 170-17~ are insulated from horizontally adjacent control electrodes by insulators 181.
~5 The electrodes 168, 174, 175 and 176 may be ~oxmed as physically and electrically united conductive plates (metalized glass plates or sheets of conductive materials, e.g.) having windows for passing the electron beams. One of such windows is shown in electrode 168 as 184. These electrodes preferably extend horizontally and vertically across the entire panel.
The insulators 178, 180 are also preferably formed as plates having beam-passing windows, except, of course, the . :
1~39872 insulators ar~ formed of an electrically non-conductive material such as glass. In outward appearance, the electrodes 168, 174, 175 and 176 and the insulators 178, 180 closely resemble the grid-isolating plates 188 and 190 co;nstituting part of the Figure 4 embodiment.
The beam control electrodes 170-172 must be individually controllable, column-by-column, since signal information to be imparted on the individual electron beams reaching the phosphor strips 136 is carried on these electrodes. The three electrodes 170-172 are preferably electrically~conductive strips which are physically and electrically united to act as a single control element. The electrodes 170-17~ also have windows for passing the electron beams. The electrodes 170-172 thus have the same function as the grid strips 93 in the Figure 4 embodiment and a similar construction, except for having three united electrodes operating as a single electrode, rather than a single electrode.
In order to insure that each of the triads o~ tied electrodes 170-172 are each isolated from their horizontally spac~d neighbors, vertically oriented insulators 181 are provided (see Figure 8). The insulators 181 preferably extend continuously from the top to the bottom of the panel and may be composed of glass or oth r suitable insulating material.
The beam-passing windows in the electrodes 168, 170-172, 174-176 and insulators 178, 180 are successively vertically offset such that they aggregatively define angled beam-conducting channels through the beam control means. The opaque portions 186 of the e}ectrode 184 act as a baffle which precludes entry into the beam accelerating region of high speed electrons generated in the electron-multiplier. Areas such as shown at 182 on ~he field-forming electrode 164 act to block the rearward passage of positive ions which might be genarated in the ~eam acceleration region~ Such baffling may not be necessary in all applications.
-20_ .... . . . .
~039872 Th~ electrodes ar~ spaced from the faceplate 62 by horizontally oriented, electrically insulative (glass, for example) spacers 198. The spacers 198 are preferably disposed between every other line (i.e., between each lace-interlace pair). Alternatively, other vertical separation distances may be employed, depending on the size of ~h~ panel and other electrical or structural considerations. In a small panel, simplified support structures may be employed.
Alternatively, vertically oriented, horizontally separated spacers may be used to provide the necessary structural rigidity for the panel~ These would preferably be disposed in the location of and in substitution for every other blue-emissive phosphor strip. Since the resolving ability of the human eye to blue-wavelength light images is relatively poor, the elimination of alternate blue-emissive phosphor strips will have a negligible effect on the perceived overall pict~re quality~ These spacers 198 serve also to periodically support the faceplate, preventing bending or breakage due to atmospheric `forces.
In order to precisely control the acceleration field in the acceleration region, it may be necessary to provide a series of electrically conductive ribbons, as shown at 202, on the sidewalls of the spacers 198. The ribbons 202 are adapted to receive a progression of voltages effective to achieve a satisfactory beam acceleration characteristic and to preclude interference with the beam by stray charge-generated fields or the like. An example of a voltage pattern suitable for applica-tion to the ribbons 202 is shown in Figure 7.
In accordance with an aspect of this invention, beam deflecting means may be provided for controlling the vertical position of the electron beams in the panel, for example to effect interlace of successive display fields. ~n the illustrated :, . ...
103~7~
embodim~nt, to deflect the electron beams for interlace purposes, a deflection voltage, generated, e.g., by deflection signal generator 203, may be applied to the first ribbons 202a, 202b.
See Figure 6. By application of an appropriate negative deflec-tion voltage to ribbons 202a (a few hundred volts, for example)and a complementary positive deflection voltage to ribbons 202b, the electron beams may be deflected downward during raster interlace. The interlace deflection signals must, of course, be synchronized with panel scan signals and synchroniza-tion signals.^ Figure 8 is a view of the control and accelerating regions of the device taken along section lines 8-8 in Figure 6. Electric fields which are established in the control and accelerating regions cause the electron beams to be converged or pinched horizontally such that the ultimate beam cross-- sectional configuration upon impingement with the phosphor ætrips 136 is horizontally narrowed. ` - ~ ~*1_ ~ Figure 8 illustrates a triad of luminescent devices or cells 204~ 206, 208, taken by way of example to be asso-ciated, respectively, with a red signal picture element, a blue signal picture element and a green signal picture element.
In the illustrated Figure 8 embodiment, by way of example, the control electrodes 170, 171, 172 controlling the red-associated cell 204 carry a signal voltage of minus 30 volts which is effective to completely shut off khe red-associated electron beam and thus prevent the luminescence of the red-emissive phosphor strip 136R. The control signal associated with blue infoxmation is applied to the electrodes 170, 171, 172 con-trolling ths blue-associated cell 206 and, in the illustrated embodiment, is shown as being of such a value (minus 25 volts, e.g.) as to admit passage of a relative~y low intensity electron beam 139B to the blue-emissive phosphor strip 136B. The green i. .
. ..~, . , .,.: , . . .
,, ~ ;,. . .. .
~ 039~3~2 information is shown as being a signal of greater value positive than that applied to elther the red-associated or blue-a~sociated cells 204, 206 (minus 20 volts, e.g.), permitting a relatively intense grPen-associated electron beam 139G to impinye upon S the green-emissive phosphor strip 136G. Thus the integrated luminous output of the triad of cells would be perceived as a predominantly green image somewhat desaturated by blue light.
~e invention is not limited to the particular details , of construction of the embodiments depicted and other modifica-1~0 tions and applications are contemplated. For example, rather than using control electrodes in the acceleration region, such ,as electrodes 170-172 in Figures 6-8 to modulate the flow of electrons to the phosphor strips 136, control s~ructures of other,,t~pes in ~he same or different regions of the device may be employed to control the flow of electrons from the electron-multiplier or to co~trol the output of the electron-multiplier itself. Rather than operating the electron-multiplier in a mode wherein it is either "off" or driven to saturation, the electron-multiplier may be activated in a non-saturated state at a predetermined intermediate level of output. If operated ,in a maximum output mode, it may be possible to avoid storing all or part of a line interval of information and display only in -,the retrace interval. Rather than switching the electron-multiplier by application of a switching voltage to the cathode, a switching voltage may be applied to other suitable electrodes ,within the device such as one of the dynodes~ It is,,,contemplated that the output beam may be deflecte,d on the phosphor screen, as by means of suitably structured and excited deflection electrodes, for purposes other than interlace scanning. Certain other changes may be made in the above-described apparatus without departing from the true spirit and scope of the inven-tion herein involved and it is intended that the subject : . . . .................... .
~ 03a~z matter in the above depiction shall be interpreted as illus-trative and not in a l.imiting sense.
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Claims (11)
1. A cathodo-luminescent device comprising:
wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;
an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons;
phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons;
accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons from said electron-multiplier when aid electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device; and activating means for driving said electron-multiplier between an "on" state associated with a predetermined high level of available electron-multiplier current and an "off" state associated with negligible electron-multiplier current.
wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;
an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons;
phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons;
accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons from said electron-multiplier when aid electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device; and activating means for driving said electron-multiplier between an "on" state associated with a predetermined high level of available electron-multiplier current and an "off" state associated with negligible electron-multiplier current.
2. The device defined by claim 1 wherein said electron-multiplier comprises a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode means and said electron-multiplier anode means and adapted to receive applied voltages ever-increasing in positive polarity in a direction away from said cathode, but substantially less than the voltage applied to said accelerating anode means, said electron-multiplier including an ion-generation region in which said positive gas ions are generated, said dynodes being arranged so as to permit some of said positive gas ions generated in said electron-multiplier to be accelerated to said cathode means to cause said cathode means to emit additional free electrons.
3. The device defined by claim 1 including control means responsive to an applied control voltage for modulating the flow of electrons to said phosphor means and thus the amplitude of the light emitted by said phosphor means.
4. The device defined by claim 1 wherein said device includes baffle means disposed between said electron-multiplier and said accelerating anode means for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode means of ions which might be generated in the region between said baffle means and said accelerating anode means.
5. A cathodo-luminescent device comprising:
wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;
an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop;
phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons;
accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device;
activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier "on" by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation currant level; and control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means.
wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;
an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop;
phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons;
accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device;
activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier "on" by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation currant level; and control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means.
6. The device defined by claim 5 wherein said device includes baffle means disposed between said electron-multiplier and said accelerating anode for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode of ions which might be generated in the region between said baffle means and said accelerating anode.
7. Television display panel for reproducing an image carried by an input video signal, comprising:
an array of cathodo-luminescent elements discretely excitable by row-column selective addressing, each element comprising:
wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier "on" by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level, and control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means; and means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude.
an array of cathodo-luminescent elements discretely excitable by row-column selective addressing, each element comprising:
wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means adapted to receive a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier "on" by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level, and control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means; and means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude.
8. The device defined by claim 7 wherein said panel includes baffle means disposed between said electron-multiplier and said accelerating anode for blocking high energy electrons which might be emitted by said electron-multiplier and for blocking the passage to said cathode of ions which might be generated in the region between said baffle means and said accelerating anode.
9. A luminescent panel for displaying alpha-numeric characters or other light representations carried by an input signal, comprising:
an array of discretely excitable cathodo-luminescent elements, each element comprising:
wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multi-plier anode means adapted to receive an applied potential dif-ference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier anode means for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, and activating means for driving said electron-multiplier between an "on" state associated with a predetermined maximum available electron multiplier current and an "off"
state associated with negligible electron-multiplier current;
and means responsive to the input signal and coupled to said electron-multiplier of each of said elements for applying the input signal to said array of elements to cause the input signal to be reproduced on the panel as a light representation spatially varying in amplitude.
an array of discretely excitable cathodo-luminescent elements, each element comprising:
wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multi-plier anode means adapted to receive an applied potential dif-ference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier anode means for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, and activating means for driving said electron-multiplier between an "on" state associated with a predetermined maximum available electron multiplier current and an "off"
state associated with negligible electron-multiplier current;
and means responsive to the input signal and coupled to said electron-multiplier of each of said elements for applying the input signal to said array of elements to cause the input signal to be reproduced on the panel as a light representation spatially varying in amplitude.
10. A cathodo-luminescent device comprising:
wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;
an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons;
phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device;
activating means for driving said electron-multiplier between an "on" state associated with a predetermined high level of available electron-multiplier current and an "off"
state associated with negligible electron multiplier current;
and beam deflecting means responsive to an applied deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means.
wall means defining an enclosure containing an ionizable gas at a predetermined low pressure;
an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier including cathode means and electron-multiplier anode means adapted to receive an applied potential difference thereacross, said electron-multiplier generating positive gas ions as a result of collisions between electrons and the gas atoms, some of which ions feed back to said cathode to cause said cathode to emit electrons;
phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons accelerating anode means disposed at said phosphor means and adapted to receive a predetermined accelerating voltage substantially more positive than the voltage applied to said electron-multiplier means for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device;
activating means for driving said electron-multiplier between an "on" state associated with a predetermined high level of available electron-multiplier current and an "off"
state associated with negligible electron multiplier current;
and beam deflecting means responsive to an applied deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means.
11. Television display panel for reproducing an image carried by an input video signal, comprising:
an array of cathodo-luminescent elements discretely excitable by row-column selective addressing, each element comprising:
wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means adapted to receive .
a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier "on" by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level, control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means, and beam deflecting means responsive to an applied interlace deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means to effect interlace of successively displayed fields; and means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude.
an array of cathodo-luminescent elements discretely excitable by row-column selective addressing, each element comprising:
wall means defining at least a portion of an enclosure containing an ionizable gas at a predetermined low pressure, an electron-multiplier located within said enclosure for creating at an output end thereof a source of electrons, said electron-multiplier comprising a cathode and an electron-multiplier anode adapted to receive an applied potential difference thereacross, said electron-multiplier including a plurality of discrete, serially arranged, secondary-electron-emissive dynodes disposed between said cathode and said anode and adapted to receive applied voltages ever-increasing in a positive polarity in a direction away from said cathode, said electron-multiplier including an ion-generation region in which positive gas ions are generated as a result of collisions between electrons and said gas, said dynodes being arranged so as to permit said positive gas ions to be accelerated to said cathode to cause said cathode to emit additional free electrons and thereby complete a regenerate electron-ion feedback loop, phosphor means disposed at one end of said enclosure in spaced relation to said output end of said electron-multiplier for emitting light when bombarded by high energy electrons, accelerating anode means adapted to receive .
a predetermined accelerating voltage substantially higher than the voltage applied to said electron-multiplier anode for drawing electrons from said electron-multiplier when said electron-multiplier is on and for accelerating them to high energies for impingement on said phosphor means, the said predetermined gas pressure being sufficiently low as to preclude the establishment of a gas discharge in said device, activating means for selectively causing the loop gain of said electron-multiplier feedback loop to be less than unity to cause said electron-multiplier to assume an inactive state or for turning said electron-multiplier "on" by causing said loop gain to be unity or greater wherein said electron-multiplier saturates at a predetermined saturation current level, control means including a control electrode located within said enclosure between said electron-multiplier and said accelerating anode, said control means being responsive to an applied control voltage for modulating the flow of electrons from said electron-multiplier to said phosphor means and thus the amplitude of the light emitted by said phosphor means, and beam deflecting means responsive to an applied interlace deflection voltage for vertically deflecting the electron beam to a different vertical location on said phosphor means to effect interlace of successively displayed fields; and means responsive to the input signal and coupled to both said control means and to said activating means associated with each of said elements for storing a predetermined interval of said input signal and for subsequently applying the stored information in parallel to appropriate elements in said array of elements such that said input signal is reproduced on the panel as a light image spatially varying in amplitude.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US433186A US3904923A (en) | 1974-01-14 | 1974-01-14 | Cathodo-luminescent display panel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039872A true CA1039872A (en) | 1978-10-03 |
Family
ID=23719163
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA215,321A Expired CA1039872A (en) | 1974-01-14 | 1974-12-05 | Cathodo-luminescent display panel |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US3904923A (en) |
| CA (1) | CA1039872A (en) |
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- 1974-01-14 US US433186A patent/US3904923A/en not_active Expired - Lifetime
- 1974-12-05 CA CA215,321A patent/CA1039872A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3904923A (en) | 1975-09-09 |
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