WO2001037305A2

WO2001037305A2 - Monolithic multi-electrode grid structures for application in thin flat cathode ray array tubes

Info

Publication number: WO2001037305A2
Application number: PCT/US2000/042035
Authority: WO
Inventors: Frederick G. Oess
Original assignee: Mesa Vision
Priority date: 1999-11-15
Filing date: 2000-11-10
Publication date: 2001-05-25
Also published as: WO2001037305A3; AU3268601A

Abstract

A flat visual display device (100) comprises a cathode sector (20) including a backing electrode (12), a multi-electrode monolithic grid structures (50) and a face plate assembly (40). The multi-electrode monolithic grid structures (50) are applicable to array type thin planar vacuum tubes (100) utilizing planar virtual cathodes in close proximity to these grid structures. The grid structures incorporates selection, intensity control, modulation, focusing and in some cases all in single monolithic system.

Description

MONOLITHIC MULTI-ELECTRODE GRID STRUCTURES FOR

APPLICATION IN THIN FLAT CATHODE RAY ARRAY TUBES

FIELD OF THE INVENTION

The present invention relates generally to the electron optical and electrical connection systems in thin flat high density multi-beam cathode ray tubes; more particularly, the present invention relates to monolithic multi- electrode grid structures for use in thin flat cathode ray tubes.

BACKGROUND OF THE INVENTION

There are many approaches to optical and electrical connection systems in thin flat high density multi-beam cathode ray tubes. There are numerous approaches of such tubes, including an approach described in U.S. Patent No. 4,719,388.

One approach to designing electron optical assemblies that utilize various separate metallic structures to act as electrode arrays for various grid elements coupled with relatively large wide angle deflection systems, each of which covered a fairly large fraction of the total display area. Electrons emanated from different portions of thermionic wire emitters. A major shortcoming of this approach involves fairly deep envelopes, a mechanically complex grid structure to provide rigidity, and the need for extensive electronic corrections. The cost factors involved are extensive and the technology was recently abandoned because of these factors.

A second design approach uses metalized substrates (for example microsheet glass) for both conductors and optical control functions. The grid structure in the Northrop-TI approach comprises a stack of eleven apertured glass microsheets fritted together as a composite system in which five sheets were used as insulators with etched aperture holes and the remainder were aluminum metalized control plates. Electrons are extracted from thermal wire emitters at some distance from the first electrode or anode of the laminated grid stack operating at close to +100 volts. This led to a large number of basic problems leading to the failure of the display. First, the approach of electrons to the positive first anode could not be made sufficiently dense. Second, the electron approach density and angularity to the first anode could not be made uniform and resulted in display "washboarding" and low light output. Third, the electrode stack could only be assembled with great difficulty and was not very uniform in thickness. Fourth, since the aspect ratio of conductor height to diameter of the apertures was very low, relatively large voltages are required for selection (grid 2), modulation (grid 3), and focusing (grids 4, 5, and 6). Fifth, because of the large area positive anode (grid 1), electron bombardment heat losses are relatively high and are further complicated by voltage variations due to conductor resistance. Sixth, and by far the greatest problem resulted from electron secondary emission voltage variations at the insulator apertures especially since grid operation is near first cross-over level of the glass. To make matters worse, the metalization is aluminum which has a very high resistance oxidation layer and which also contributes to a secondary emission phenomenon. Seventh, pulsing of the active electrodes (grids 2 and 3) in conjunction with secondary emission made electrode voltage control more problematical due to high inter-electrode capacitance.

What is needed is an approach to electron optical and electrical connections systems that avoids one or more of these problems.

SUMMARY OF THE INVENTION

A display device is described. In one embodiment, the display device comprises a face plate assembly, an electron emitter subsystem, an accelerator, a grid assembly, an entrance plane, and an exit plane. The face plate assembly has an electrically positive screen on a face plate that causes an image to be displayed as a result of electron impingement thereon. The electron emitter subsystem establishes a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode. The accelerator in conjunction with the electron emitter subsystem creates at least one virtual cathode remotely located from the accelerator. The grid assembly is located between the face plate assembly and the remotely located virtual cathode and comprises multiple gun structures to select electrons from the remotely located virtual cathode to impinge the electrically positive screen. The entrance plane is located between the remote virtual cathode and the grid assembly to perform field shaping at the entrance to the grid assembly to aid in focusing. The exit plane is located between the face plate assembly and the grid assembly to perform field shaping at the exit of the grid assembly to aid in focusing and to reduce deflection caused by adjacent gun structures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only.

The overall display device and the grid structures which constitute the actual disclosures will be described in more detail hereinafter in conjunction with the drawings wherein:

Figure 1 is a partial break away, exploded perspective view of a flat visual display device designed to incorporate a grid structure;

Figure 2 is a diagrammatic illustration, in side elevation, of the device of Figure 1;

Figure 3 diagrammatically illustrates operational aspects of the device of Figures 1 and 2; Figure 4A diagrammatically illustrates a side cross-section through a basic aperture design of a grid stack element (electron optical gun) using a single substrate;

Figure 4B and Figure 4C diagrammatically illustrate electron optical aspects of Figure 4A;

Figure 5A diagrammatically illustrates a side cross-section through an aperture design of a grid stack incorporating entrance and exit electrodes using a single substrate;

Figure 5B diagrammatically illustrates electron optical aspects of Figure

5A;

Figure 6A diagrammatically illustrates a side cross-section of the aperture design of an assembled dual substrate grid stack incorporating entrance and exit electrodes and centrally located grid one and grid two conductor delineations;

Figure 6B diagrammatically illustrates a break away view of Figure 6A showing an alternative approach of electrically and mechanically separating the grid one or grid two electrodes from their respective electrodes;

Figure 7A is a perspective view of the basic aperture conductor delineations which are used orthogonally in grids one and two of Figures 1 through 7; and

Figure 7B perspective view of an improved conductor delineation system incorporating both conductor and entrance /exit electrode surfaces for application in the designs of Figures 1 through 4 at both grid one and orthogonally at grid two.

DETAILED DESCRIPTION

A display device is described. In the following description, numerous details are set forth. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

Note that in the following disclosure, like components are designated by the same reference numerals throughout all figures.

Overview

In one embodiment, a flat visual display device is disclosed herein and includes a flat face plate having a front face and opposite back plate and electrically positive receptor on the latter which as a result of impingement of the electrons thereon, provides a visual image through the front face of the face plate. The device establishes a uniformly dense planar space charge cloud of free electrons, which is also a remote virtual cathode, within a planar band parallel with and rearward of the back face of the display faceplate. The device includes an apertured address plate disposed in spaced-apart confronting relationship with the back face of the faceplate between the latter and in very close proximity of the uniform planar virtual cathode to act on the electrons within the virtual cathode in a controlled way to cause the electrons acted upon to impinge on specific areas of the electrically positive receptor of the display faceplate in order to produce a desired image through the transparent face plate's front face.

Figures 1 and 2 illustrate one embodiment of a display device 100, such as may be found in a thin flat cathode ray array tube. Display device 100 is a vacuum device and may be designed in accordance with the teachings of U.S. Patent No. 4,719,388, entitled "Flat Electron Control Device Utilizing a Uniform Space-Charge Cloud of Free Electrons as a Virtual Cathode," issued January 12,

1988 and/or the teachings of U.S. Patent Application Serial No. , entitled "Segmented Virtual Cathode," filed concurrently herewith on , incorporated herein by reference. As details have been extensively discussed therein, only the major components, assemblies, and spatial relations are noted in Figures 1 and 2 of this disclosure.

In one embodiment, the planar receptor comprises a face plate assembly having a front face and a coated electrically positive back face and a mechanism on the latter which, as a result of impingement of electrons thereon, provides a corresponding visual image as viewed from the face plate's front face. The planar receptor need not be a visual display screen. It could be, for example, an end plane of individual electronic leads to activate other devices such as, for example, a liquid crystal display. However, for purposes of discussion, the receptor will be described as a display screen and the overall device will be referred to as a flat visual display device.

The display device also includes a grid stack which may be identical to grid stack assembly 50 forming part of display device 100 in Figure 1 or an arrangement which only includes the apertured address plate. The grid stack assembly 50 may incorporate address electrodes and a supply of free electrons for use by the address electrodes. In one embodiment, the electrodes forming part of the grid stack assembly 50 or any other electrodes do not draw any appreciable power from the free electrons during operation of the device.

In addition and in accordance with the present invention, the flat visual display device disclosed herein utilizes an electron emitter mechanism for establishing a uniformly dense space-charge cloud of free electrons within a planar band parallel with and just rearward of the back side of the first address grid so that each and every aperture in the address plate sees and acts upon a reasonably uniform or nearly equal supply of electrons during operation of the device. The addressed apertures of the grid stack assembly 50 as shown in Figure 1 pass a similar number of electrons for a given increment of time, thereby effectively eliminating or substantially reducing the non-uniformity or washboarding effect described above.

In one embodiment, the above noted dense planar space charge cloud forms a virtual cathode, i.e., the density of the cloud may be such that the electrical field within the cloud at some plane (e.g., within the band referred to above) drops to slightly below emitter potential. The virtual cathode potential is very slightly, less than 1 (one) volt, below the emitter potential due to the thermal energy of the electrons emitted by the emitter. In most devices using free electrons, space-charge limited emission or temperature- limited emission may be used. In one embodiment, this device only uses space charge limited emission. This means that more electrons are thermally ejected into the virtual cathode than are subsequently used by the device. The excess electrons in the virtual cathode fall back into the emitter due to the increasing thermal injection of electrons as well as any decreases in electrons used by the device.

In one embodiment, the uniformly dense space-charge cloud of free electrons or "virtual cathode" is established in part by use of a backing electrode and an accelerator electrode in combination with the previously described first address electrode of the device's grid stack, all three acting on electrons supplied by suitable electron emitter mechanism such as emitter array 20 in Figure 1. These three components cooperate with one another in order to cause free electrons emitted by the emitter to oscillate back and forth in a pendulum-like fashion between two planar bands, one essentially coplanar with and incorporating the emitter plane and the other one behind and adjacent to the first address electrode. In other words, the backing electrode, electron emitter mechanism (array) and the accelerator are involved in simultaneously establishing uniform and planar space-charge clouds of free electrons functioning as a proximity virtual cathode and a remotely located virtual cathode. Thus, at least one embodiment of a flat high vacuum visual display device has been described which is not subject to the non-uniformity or washboarding effects discussed above nor excessively sensitive to magnetic fields. Also, at least one embodiment of a flat visual display device is energy efficient in operation.

In Figures 1 and 2, the backplate 11 and the faceplate 42 constitute respectively the back and front envelope components of the display device 100.

The cathode sector 20 comprises a sequence of spaced apart and mutually parallel components. The cathode sector 20 includes a metal layer forming the backing electrode 12. The metal layer is deposited on or applied to the backplate 11. In one embodiment, the back plate 11 comprises an insulator, such as, for example, glass, and a metal layer. The cathode sector 20 also includes a spaced apart planar array of thermionic emitter electrodes (wires) 21 followed by an accelerator 22. In one embodiment, accelerator 22 comprises a spaced apart planar high transmission mesh which transmits greater than 90 percent of the electrons that flow from the proximity cathode. In one embodiment, the accelerator 22 comprises tungsten, tungsten 4% rhenium, molybdenum, etc. The entire cathode sector 20 extends in the direction of the vertical (Z-axis) space between the backplate 11 and a location slightly below the grid stack assembly 50 which constitutes the grid sector.

The various structural and electron optical aspects of the grid stack assembly 50 will be discussed in further detail.

The post grid assembly acceleration sector (space) 30 begins following the grid stack assembly 50 and terminates at the [anode]view screen 41 of the faceplate assembly 40. In one embodiment, the view screen 41 comprises an aluminized screen. Any type of material regularly used for a view screen may be used.

The faceplate 42 is a transparent glass plate allowing the image formed at the view screen 41 to be transmitted to the observer. Figure 3 is identical to Figure 2 but includes the operational aspects of the grid sector. Details of the structure are provided in U.S. Patent No.

4,719,388 and U. S. Patent Application Serial No. , entitled

"Segmented Virtual Cathode," filed concurrently herewith on , and incorporated herein by reference. Referring to Figure 3, oscillatory paths of the electrons 23 are shown between the proximity virtual cathode 24 and the remote virtual cathode 25. The remote virtual cathode 25 supplies all the beam current utilized by the grid stack assembly 50 and the view screen 41. In one embodiment, the electron density is far in excess of what is required by the grid stack assembly 50 and the view screen 41.

The cathode sector 20 also compensates for the current used by the remainder of the gun structures in the grid stack assembly 50 and maintains a constant voltage level at the remote virtual cathode 25. This compensation is achieved by the emitter electrodes 21 inputting more electrons into the cathode sector 20 as electrons are drawn out of the cathode sector 20 to create an image on the face plate 42. The energy consumption of the virtual cathode system may be reduced by synchronizing a narrow segment of the virtual cathode with the beam addressing sector of the first grid of the grid stack assembly 50 as shown in United States Patent Application Serial No. , entitled

"Segmented Virtual Cathode," and concurrently filed herewith on

In one embodiment, voltages and voltage differences between electrodes in cathode sector 20 in its operating mode are less than 100 volts for all elements and less than one hundred volts in the grid stack assembly 50. In one embodiment, the view screen 41 may be operated at values from about 5 kilovolts to 25 kilovolts. In one embodiment, the vertical (i.e., Z) dimension inside of the envelope members is less than one inch. The Grid Stack Assembly

One embodiment of a grid stack assembly 50 is shown in Figures 2, 3, and 4A.

Figure 4A illustrates a side cross-section through one aperture design of a grid stack element or electron gun using a single substrate 51. In one embodiment, the substrate 51 may comprise glass, urethane, a laminate, etc. The properties of substrate 51 may include the ability to support the gun structures while not being susceptible to secondary emission effects and not creating outgassing in a vacuum. In an alternative embodiment, a substrate may not be necessary.

The grid stack assembly 50 includes multiple apertures. An exemplary aperture, aperture 73, comprises a first grid cylinder 52, a second grid cylinder 53, and a separation 56 between them. The first grid cylinder 52 and the second grid cylinder 53 are preferably coaxially aligned. In one embodiment, the grid cylinders are designed to assure that all addressed apertures pass a similar number of electrons in similar increments of time in the operating modes of the individual apertures.

The first grid cylinder 52 and the second grid cylinder 53 are extensions of grid conductors. That is, the first grid conductors (address electrodes) 54 and second grid conductors (address electrodes) 55 extend into the aperture. The separation between the individual conductors in each of the first grid conductors 54 and second grid conductors 55 is referred to herein as a delineation. The first grid conductors are disposed in the X direction (or in rows) and the second grid conductors are disposed in the Y direction (or in columns). This system will be used for convenience throughout the discussion. As a general rule, rows and columns may be interchanged. The first grid conductors 54 represent the delineated grid conductors nearest to the remote virtual cathode 25, and the second grid conductors 55 represent the delineated second grid conductors. Although first grid conductors 54 and first grid cylinders 52 are discussed as being distinct, the two may be part of the same physical conductor structure with the first grid cylinders 52 representing that portion of the physical conductor structure within the apertures. The same is true of the relationship between second grid conductors 55 and second grid cylinders 53.

In one embodiment, the grid cylinders may be other shapes that permit the passage of electrons from the remote virtual cathode 25 to the face plate 42, such as, for example, conical, ovals, rectangular, square, etched profile (epitaxial), or eliptical.

The field gradient created by a voltage applied to each active first grid cylinder 52 in cooperation with the remote virtual cathode 25 operates as an electron optical lens. Similarly, the field gradient created by a voltage applied to each second grid cylinder 53 in cooperation with the accelerating field of the space 30 between the second grid cylinder 53 and the face plate 40 acts as an electron optical lens. Although the first grid cylinder 52 and the second grid cylinder 53 extend into the same aperture, they are isolated from each other by separation 56, and the field gradient created by the voltage differential between the first grid cylinder 52 and the second grid cylinder 53 also acts as an electron optical lens. Such combinations of electron optical lenses found with the first grid cylinder 52 and second grid cylinder 53 create electric fields that together operate as an electron gun structure.

In one embodiment, the ratio of aperture height to diameter is about two to one or may be somewhat higher for reasons of lens separation or beam distance needed for electron optical consideration, to reduce voltage differentials, or to control lens power. The lens separation 56 needs to be as uniform and narrow as possible (e.g., 0.001" to 0.005" wide) in all lenses of the single substrate 51 remaining nearly identical within close ranges to reduce differences in secondary emission charging effects of the insulator substrates, thereby affecting the lenses between the first and second grid conductors. The orthogonality of the plane of separation 56 relative to the aperture axis is also of major importance to ensure proper functioning of the grid structures.

If a change in aperture height is made, a change may be made to the voltage that is applied to the grid conductors. Similarly, if there is a change in the voltage that is applied to the grid conductors, then the aperture height may be changed. By making such changes, the resolution and focusing capabilities of the gun structures, along with the ability to avoid cross talk, is maintained.

The view screen 41 in a planar shape and the remote virtual cathode 25 in a planar shape are also shown in Figure 4A. Figure 4 A also shows the distance from the remote virtual cathode 25 to the aperture under grid structure quiescent conditions in which no electrons are being drawn from the remote virtual cathode.

Figures 4B and 4C indicate the electron optical conditions if voltage is applied to both the first and second grid structure and the gun structure. Normally under cutoff conditions, the first grid cylinder 52 and remaining portion of the first grid conductors 54 are very slightly negative relative to the remote virtual cathode 25 such that a small spacing 57 exists and no current will flow into the first grid cylinder 52.

If only a first grid electrode received a positive voltage, then electron current will flow through the gap 57 into the aperture formed by the first grid cylinder 52 and conductive current flows in the first grid conductor 54. For practical reasons, including the physical strength of the assembly and an advantageous aperture size, the ratio of non-aperture (or conductor) area to aperture area at the surface of the substrate is in the order of two to one. This means that the conductor surface area connecting the first grid cylinders 52 absorbs at least two times as much electron current as is available for the electron beam and additionally the electron current absorbed and conducted by the first grid conductor 54 and first grid cylinder 52 will in this case produce both heat and capacitive effects in the conductor elements. These, in turn, produce voltage variations along the path of the first grid conductors 54 and therefore voltage variations at the apertures. Although under most circumstances the system still functions satisfactorily, the above conditions are not desirable. The electron flow through gap 57 is space charge limited and follows the Child Langmuir equation for planar diodes.

If an entrance electrode is included (as described in detail below) between the remote virtual cathode and the first grid conductors 54, the entrance electrode repels electrons in the remote virtual cathode. Consequently, the first grid conductors 54 will have little or no absorption of electrons. In such a case, only the sidewalls of the first grid cylinder 52 and the second grid cylinder 53 tend to absorb electrons.

In one embodiment as shown in Figures 4B and 4C, if both the first grid cylinder 52 and the second grid cylinder 53 are electrically positive relative to the remote virtual cathode 33, an electron beam flows through the aperture 73. Three electron lenses form (as a result of the voltage applied to the grid conductors and grid cylinders) to control the beam. The first lens, entrance lens 80, is at the entrance of the first grid conductors 54, which tends to be weak and slightly divergent, thereby causing some of the electron beam to be absorbed by the walls of the first grid cylinder 52.

The second lens, central lens 81, in Figure 4B is convergent due to the fact that the second grid cylinder 53 is more positive than the first grid cylinder 52 (shown by "++" and "+" in Figure 4B). In Figure 4C, the central lens 82 is divergent and tends to spread the beam further, which may cause electrons to be collected at the walls of the second grid cylinder 53.

Exit lens 83 shown in both Figures 4B and 4C is formed by the positive voltage gradient established by the second grid cylinder 53 combined with the second grid conductors 55 and the view screen 41. Exit lens 83 is convergent and its strength depends on the voltage on view screen 41 and the spacing between the second grid cylinder 53 and the view screen 41. Once focus is established at the view screen 41, changing the distance to the view screen 41 will not appreciably alter the screen focus conditions since increasing or decreasing this distance changes the lens strength in nearly the same proportion and retains the same general focus conditions at the view screen 41.

This permits the use of a curved screen in conjunction with a flat grid structure.

To establish focus in the general configuration of Figures 4B and 4C, the central lens 81 or 82 are dominant in accomplishing overall focusing. This function depends mainly on the voltage differential between the first and second grid cylinders since neither the entrance lens 80 nor the exit lens 83 produces major focus alterations.

Thus, the display system provides electron optical structures with aperture diameter to height ratio sufficient to prevent undesirable interactions of lens functions in the same aperture (beam) system, to reduce voltage differentials required for lens strength and to increase distances over which the beam can become wider or more concentrated.

The grid structure design format shown in Figures 5A and 5B differ considerably from those of Figures 4 A, 4B, and 4C. Referring to Figures 5 A and 5B, entrance electrode 58 and exit electrode 59 have been added to the assembly as additional surfaces. These surfaces are insulated from the grid conductors 54 and 55 by insulators 60. In one embodiment, the entrance electrode 58 and exit electrode 59 are part of aperture arrays of the electrodes and their insulators are aligned with those of the insulator substrate 51. Similarly, the entrance electrode 58 and the exit electrode 59 include apertures that are aligned with the apertures of the gun structures.

In one embodiment, the stack created by inclusion of the entrance electrode 58 and the exit electrode 59 with respect to the grid conductor electrodes 54 and 55, respectively, is a layered structure that includes the entrance /exit electrode, and its respective grid conductor electrodes with an isolation region in between.

Under quiescent conditions at the grid stack assembly 50, the voltages of the entrance electrode 58 and the first grid cylinder 52 can be adjusted to just cutoff conditions so that no or negligible electron current flows to the entrance electrode 58 or the first grid cylinder 52. At this point, the spacing 57 is near zero. It is also possible to use voltages at the entrance electrode 58 somewhat more positive (i.e., less negative relative to the accelerator potential) to increase spacing 57 and thus alter the entrance lens 80, thereby altering the focus of the overall system. The voltage of the remote virtual cathode 25, which is also the reference potential for all elements forward of the remote virtual cathode 25, remains as before.

The entrance electrode 58 permits the elimination of electron current from reaching the first grid conductors 54, thereby considerably reducing electron current and resistive losses due to conduction. Electron current is also reduced in the first grid cylinder 52 due to the now convergent configuration of entrance lens 80 when the second grid cylinder 53 is operational. During operation, this leaves only capacitive currents resulting from the activation of the second grid conductors and electron currents from the first grid conductors when the second grid conductors are cut off.

Therefore, in one embodiment, purposes for using an entrance electrode 58 include:

1) Reduce loss of electron current from the remote virtual cathode 25 by the conduction strips of the first grid conductors 54. In one embodiment, the entrance electrode 58 shields these areas by its continuous unipotential surface, typically fixed at a cut off potential. Thus, the entrance electrode 58 provides isolation of the remote virtual cathode 25 from the first grid conductors 54 to shield conductors and prevent electron absorption.

2) Reduce voltage variations across the grid stack assembly 50 at the first grid conductors 54 due to current.

3) Reduce lens distortions at the entrance lenses to the first grid conductors 54 during operation resulting from field distortion caused by the conduction strips of first grid conductors 54. 4) Reduce electron flow into the surfaces of the first grid conductors 54 by avoiding electron collection at the conduction strips and also at the first grid aperture electrodes during active operation due to the now convergent configuration of the entrance lenses.

5) Provide field shaping control upon the entrance lenses to aid in focussing.

6) Aid in control of the location of the remote virtual cathode 25. Thus, the entrance electrode 58 may be controlled in order to perform these functions in a manner not performed in the prior art.

The central lens 81 or 82 in Figure 5B perform the same functions as in Figures 4B and 4C.

A purpose of the exit electrode 59 is to reduce, and even minimize, deflection caused by adjacent gun structures. That is, the exit electrode 59 isolates the field effects created between adjacent columns of second grid conductors 55, particularly during differential pulsing when different intensities at adjacent pixels exist. By isolating field effects, minor beam distortions or deflections may be avoided, such as due to capacitive coupling. Again without the exit electrode 59, beam distortions can exist because of different lens effects caused by the dominance of the second grid conductors 55 which tend to be somewhat dominant in the vertical, or Z, direction.

In one embodiment, the entrance electrode 58 and the exit electrode 59 are held at different potentials, although it is not necessary to do so. Also the potential at which each is held is the same across the entire surface of the electrode.

Thus, the exit electrode 59, similar in location to electrode 28 of Figure 1, may be controlled to provide the following functionality:

1) isolation to prevent cross talk between adjacent apertures in grid stack assembly 50,

2) field shaping to aid in focusing, and 3) Prevent lens distortions at the exit lenses to the second grid conductors 55 during operation resulting from field distortion caused by the conduction strips of second grid conductors 55.

Thus, embodiments of the display system described herein provide isolation via entrance and exit electrodes at the inputs and outputs of the grid stack assembly, respectively, to perform isolation and other functions such as virtual cathode stand-off control, current control and focus control for the first grid cylinder 52, and aid in the exit lens formation at the second grid cylinder

53 of the stack.

Figure 6A illustrates an alternative embodiment of a grid stack assembly

50, including a method of construction, which differs from Figure 5A mainly in that it uses two insulator substrates 64 and 65 rather than the single substrate

51 of the previous embodiments. The first and second grid substrates 64 and 65 are joined into a monolithic structure by insulative material 66, which may be made of, for example, glass frit or any suitable dielectric material that is vacuum compatible. In one embodiment, the insulative material 66 may be an adhesive material.

The insulative material 66 maintains a separation which may be in part a vacuum between the substrates. In one embodiment, the insulative material 66 maintains the separation as nearly the same as possible between the substrates throughout the monolithic grid structure. The insulative material 66 may be applied in spots, strips, lines, or in general areas located across the substrates.

Note that the insulative material 66 may be located between every aperture in the substrate or located at a predetermined number of apertures away from each other.

In terms of mechanical construction, it simplifies manufacturing processes by separating the metalization of the first grid cylinder 52 and the second grid cylinder 53, thereby simplifying the manufacturing process. It also eliminates the need for isolation coating between the arrays of grid electrodes and their respective entrance /exit electrodes. In addition, there is more capacitive isolation electrically and electronically between the grid electrode arrays and their entrance/exit electrodes. Since the dielectric constant between the first and second grid conductors 54 and 55 is low due to vacuum separation, and since in most cases only one first grid electrode (line) is active at a time, capacitive coupling problems do not increase. Thus, embodiments described herein improve the capacitive coupling between active elements, thereby preventing undesirable voltage variability in the operation of adjacent elements particularly during pulsing.

Figure 6B illustrates a simple modification of Figure 6A that provides a simpler grid to electrode separation when two or more substrates are used by having conductors on the inside. Referring to Figure 6B, the metalization can cover the entire outer surface of each substrate, then grid electrodes and the entrance /exit electrodes can be separated. In one embodiment, the grid electrodes and the entrance /exit electrodes are separated by grinding or lapping. In one embodiment, each of the electrodes has a separate substrate associated with it.

Thus, embodiments described herein include improved electrical connections that reduce, and may even minimize, current and power losses.

Figure 7A illustrates a basic grid conductor delineation system as may be used in the display devices of Figures 1 through 5B. To avoid insulator secondary emission charging, the separation lines are made as narrow as possible (e.g., 0.001" to 0.003") as is the case with all insulator separation areas subject to electron bombardment and particularly where voltages at the conductors are below first cross-over or vary across first cross-over.

Figure 7B represents a grid electrode delineation system that can be used as an alternate to that shown in Figures 5A and 5B which incorporated both the grid electrodes and the isolation electrode planes. In one embodiment, the entrance /exit electrodes interconnected at a peripheral edge of the display device. In one embodiment, the grid electrode areas exposed to the outer surface are small compared to the entrance/exit electrode areas. Provided conductivity of the first grid conductor is adequate, losses in the display device due to the first grid electron bombardment and resulting resistive conduction losses will also be low.

The display system includes a high density multi-electron gun array of electron beams (based on a high density uniform remote virtual cathode system) which provides a uniform bright flat display having controlled focus capabilities. Embodiments of the display system includes an electron optical system of having an array of gun structures based on one or two insulator substrates in a monolithic, reliable, and low cost assembly which includes the functions of selection, intensity control, modulation, and focusing.

The operation of the electrodes in the display device described herein throughout are controlled using a controller that controls which electrodes have potentials applied to them and the amount of the potential that is applied.

Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims which in themselves recite only those features regarded as essential to the invention.

Thus, a display device has been described.

Claims

CLAIMSI claim:

1. A display device comprising: a face plate assembly having an electrically positive screen on a face plate that causes an image to be displayed as a result of electron impingement thereon; an electron emitter subsystem to establish a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode; an accelerator to operate in conjunction with the electron emitter subsystem to create a virtual cathode remotely located from the accelerator; a grid assembly located between the face plate assembly and the remotely located virtual cathode, the grid assembly comprising a plurality of gun structures to select electrons from the at least one remotely located virtual cathode to impinge the electrically positive screen; and an entrance plane located between the remote virtual cathode and the grid assembly to perform field shaping at the entrance to the grid assembly to aid in focusing; and an exit plane located between the face plate assembly and the grid assembly to perform field shaping at the exit to the grid assembly to aid in focusing and to reduce deflection caused by adjacent gun structures.

2. The display device defined in Claim 1 wherein each of the entrance plane and the exit plane are held at individual potentials across their entire surface.

3. The display device defined in Claim 1 wherein each of the plurality of gun structures comprises an aperture, and further wherein each of the entrance and the exit planes include an aperture aligned with one of the apertures of the plurality of gun structures.

4. The display device defined in Claim 1 wherein the entrance plane also reduces absorption by electrodes of the grid assembly.

5. The display device defined in Claim 1 wherein each of the entrance and exit planes comprises an isolation electrode.

6. The display device defined in Claim 1 wherein a potential on the entrance plane creates a uniform field between the at least one remotely located virtual cathodes and the grid assembly.

7. The display device defined in Claim 1 wherein the exit plane reduces capacitive coupling between at least a pair of the plurality of gun structures.

8. The display device defined in Claim 1 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element, and further wherein the isolation plane comprises an exit electrode, the potential applied to the exit electrode and the active second grid element being nearly equal.

9. The display device defined in Claim 1 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element, and further wherein the entrance plane comprises an entrance electrode, the potential applied to the entrance electrode is less than that applied to the first grid element.

10. The display device defined in Claim 1 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element, and further wherein the grid assembly further comprises an entrance electrode in proximity to and electrically isolated from the first grid element for each of the plurality of apertures.

11. The display device defined in Claim 10 wherein the grid assembly and the entrance electrodes are integrated into a monolithic multi-electrode grid structure.

12. The display device defined in Claim 10 wherein the entrance electrode repels electrons except electrons passing through at the entrance to active first grid element apertures in the grid assembly.

13. The display device defined in Claim 10 wherein the flow of electrons through an aperture is based on voltages applied to the entrance electrode and the first grid elements.

14. The display device defined in Claim 10 wherein the grid assembly further comprises a first insulator between the entrance electrode and the first grid element.

15. The display device defined in Claim 10 wherein the grid assembly further comprises a first separation between the entrance electrode and the first grid element.

16. The display device defined in Claim 1 wherein each of the plurality of gun structures has a plurality of grid cylinders having a length that is longer than a distance across at its narrowest point.

17. The display device defined in Claim 16 wherein the length is at least two times longer than the distance across its narrowest point.

18. The display device defined in Claim 1 further comprising an isolator coupled between the entrance plane and a plurality of electrodes on the grid assembly.

19. The display device defined in Claim 1 wherein the exit plane comprises an exit electrode that isolates field effects created between adjacent apertures.

20. The display device defined in Claim 1 wherein the exit plane electrode causes changes in shaping an electron beam.

21. The display device defined in Claim 1 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element coupled together with a separation region that comprises a single substrate.

22. The display device defined in Claim 1 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element coupled together with insulative material.

23. The display device defined in Claim 22 wherein the insulative material couples the first and second grid elements using adhesive.

24. The display device defined in Claim 22 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element with a vacuum space between substrates of the grid assembly.

25. A method for controlling a display device comprising: establishing a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode; activating portions of a segmented backing electrode to create at least one remotely located virtual cathode at a first location using an accelerator positioned a first distance from the proximity virtual cathode, the first location being a second distance from the accelerator; activating first and second grid elements located within apertures in a grid stack assembly to select electrons from the at least one remotely located virtual cathode to impinge an electrically positive screen of a face plate assembly; and reducing electron beam deflection caused by adjacent apertures while activating first and second grid elements.

26. The method defined in Claim 25 further comprising applying different voltages to the first and second grid elements to permit flow through of electrons through the grid stack assembly.

27. The method defined in Claim 25 further comprising applying a first voltage to the second grid element and a second voltage to the first grid element to permit electron flow through the grid stack assembly, where the first voltage is greater than the second voltage.

28. The method defined in Claim 25 further comprising applying a first voltage to the second grid element and a second voltage to the first grid element to permit electron flow through the grid stack assembly, where the first voltage is less than or equal to the second voltage.

29. The method defined in Claim 25 wherein reducing electron beam deflection caused by adjacent apertures comprises applying a potential to an exit electrode between the grid stack assembly and the face plate assembly

30. The method defined in Claim 29 wherein applying a potential comprises applying substantially the same potential to the exit electrode as to an active second grid element.

31. The method defined in Claim 29 wherein applying a potential comprises applying a potential to the exit electrode that is different than the potential applied to an active second grid element.

32. An apparatus for controlling a display device comprising: means for establishing a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode; means for activating portions of a segmented backing electrode to create at least one remotely located virtual cathode at a first location using an accelerator positioned a first distance from the proximity virtual cathode, the first location being a second distance from the accelerator; means for activating first and second grid elements located within apertures in a grid stack assembly and separated by a separation region to select electrons from the at least one remotely located virtual cathode to impinge an electrically positive screen of a face plate assembly; and means for reducing electron beam deflection caused by adjacent apertures while activating first and second grid elements.

33. The apparatus defined in Claim 32 wherein the means for reducing deflection comprises an exit electrode.

34. The apparatus defined in Claim 32 further comprising means for applying a first voltage to the second grid elements and a second voltage to the first grid elements to permit electron flow through the grid stack assembly.

35. The apparatus defined in Claim 32 further comprising means for applying voltages to an entrance electrode and the first grid element to form a first lens in an aperture in the grid stack assembly.

36. The apparatus defined in Claim 35 further comprising means for applying voltages to an exit electrode and the second grid element to form an exit lens in the aperture in the stack grid assembly.

37. A display device comprising: a face plate assembly having an electrically positive screen on the face plate that causes an image to be displayed as a result of electron impingement thereon; an electron emitter array to establish a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode; an accelerator creating at least one virtual cathode remotely located from the accelerator; and a grid assembly located between the face plate assembly and the remotely located virtual cathode, the grid assembly creating a plurality of gun structures to select electrons from the at least one remotely located virtual cathode to impinge the electrically positive screen, wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element coupled together with insulative material.

38. The display device defined in Claim 37 wherein the pair of insulative material maintains a vacuum between substrates of the grid assembly.

39. The display device defined in Claim 37 wherein the insulative material couples the first and second grid elements using adhesive.

40. A display device comprising: a face plate assembly having an electrically positive screen on the face plate that causes an image to be displayed as a result of electron impingement thereon; an electron emitter array to establish a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode; an accelerator creating at least one virtual cathode remotely located from the accelerator; and a grid assembly creating a plurality of gun structures to select electrons from the at least one remotely located virtual cathode to impinge the electrically positive screen, wherein the grid assembly comprises a first and second substrates electrically isolated from each other via a separation region, the first and second substrates having a plurality of first electrodes and a plurality of second electrodes, respectively, with a plurality of apertures therein, at least one electrode electrically isolated from at least one of the plurality of first or second electrodes via a portion of the first or second substrates respectively.

41. The display device defined in Claim 40 wherein the at least one electrode comprises an entrance electrode electrically isolated from at least one of the plurality of first electrodes via a portion of the first substrate.

42. The display device defined in Claim 40 wherein the at least one electrode comprises an exit electrode electrically isolated from at least one of the plurality of second electrodes via a portion of the second substrate.

43. A display device comprising: a face plate assembly having an electrically positive screen on the face plate that causes an image to be displayed as a result of electron impingement thereon; an electron emitter array to establish a uniform space-charge cloud of free electrons functioning as a proximity virtual cathode; an accelerator creating at least one virtual cathode remotely located from the accelerator; and a grid assembly located between the face plate assembly and the remotely located virtual cathode, the grid assembly creating a plurality of gun structures to select electrons from the at least one remotely located virtual cathode to impinge the electrically positive screen, wherein length of each of the plurality of gun structures is longer than a distance across its narrowest point.

44. The display device defined in Claim 43 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element.

45. The display device defined in Claim 43 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element, and further wherein the grid assembly further comprises an entrance electrode in proximity to and electrically isolated from the first grid element for each of the plurality of apertures.

46. The display device defined in Claim 45 wherein the grid assembly and the entrance electrode are integrated into a monolithic multi-electrode grid structure.

47. The display device defined in Claim 46 wherein the entrance electrode repels electrons.

48. The display device defined in Claim 46 wherein the flow of electrons through an aperture is based on a voltage applied to the entrance electrode.

49. The display device defined in Claim 46 wherein the grid assembly further comprises a first isolator coupled between the entrance electrode and the first grid element.

50. The display device defined in Claim 43 further comprising an exit electrode that isolates field effects created between adjacent apertures.

51. The display device defined in Claim 43 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element coupled together with a separation region that comprises a single substrate.

52. The display device defined in Claim 38 wherein the grid assembly comprises a plurality of first electrodes and a plurality of second electrodes with a plurality of apertures therein, each of the apertures comprising a first grid element and a second grid element coupled together with a separation region, the separation region comprising an insulative material.

53. The display device defined in Claim 52 wherein the insulative material maintains a vacuum between substrates in the grid assembly.

54. The display device defined in Claim 53 wherein the pair of isolator spots couple the first and second grid elements using adhesive.