IVI LLC EXHIBIT 2003
`XILINX V. IVI LLC
`Inter Partes Review Case 2013-00112
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`

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`US. Patent
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`Dec. 14, 1999
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`Sheet 1 of 9
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`6,002,207
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`20
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`U.S. Patent
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`6,002,207
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`U.S. Patent
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`Dec. 14, 1999
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`Sheet 3 of 9
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`6,002,207
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`51
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`U.S. Patent
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`Dec. 14,1999
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`Sheet 4 or 9
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`6,002,207
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`U.S. Patent
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`Dec. 14,1999
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`Sheet 5 of 9
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`6,002,207
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`U.S. Patent
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`Dec. 14,1999
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`Sheet 5 of 9
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`6,002,207
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`U.S. Patent
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`Dec. 14,1999
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`Sheet 7 of 9
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`6,002,207
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`U.S. Patent
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`Dec. 14, 1999
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`Sheet 8 of9
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`6,002,207
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`

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`U.S. Patent
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`Dec. 14, 1999
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`Sheet 9 of 9
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`6,002,207
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`F|G.1‘|
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`

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`6,002,207
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`1
`ELECTRON SOURCE WITH LIGHT
`SHUTTER DEVICE
`
`BACKGROUND OF THE INVENTION
`
`1. Technicai Field
`
`The present invention relates to a magnetic matrix elec-
`tron source.
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`10
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`A magnetic matrix eiectrort source of the present inven-
`tion is particularly although not exclusively useful in display
`applications, especially fiat panel display applications. Such
`applications include teievision receivers and visual display
`units for computers. especially although not exclttsively
`portabie computers. personal organizers. communications
`equipment, and the Like. Flat panel display devices based on
`a magnetic matrix electron source of the present invention
`will hereinafter by refened to as Magnetic Matrix Displays.
`2. Prior Art
`
`Conventional flat panel displays. such as liquid crystal
`display panels, and field emission displays. are complicated
`to manufacture because they each involve a relatively high
`Ievel of semiconductor fabrication, delicate materials, and
`high tolerances.
`
`SUMMARY OF THE INVENHON
`
`there is now
`in accordance with the present invention.
`provided an electron source comprising: photocathode
`means for emitting electrons on excitation by incident Eight
`radiation; a permanent magnet perforated by a plurality of
`channels extending between opposite poles of the magnet.
`the magnet generating, in each channel, a magnetic fieid
`which forms etectrons received from the photocathode
`means into an electron beam for guidance towards a target.
`Preferably, the electron source comprises shatter means
`having an array of addressable shutter elements each selec-
`tiveiy acrttable to filternateiy admit and bind: passage of
`light radiation onto the photocatttode means in response to
`an address signal.
`In preferred embodiments of the present invention, the
`shutter means comprises a liquid crystal shutter.
`Grid electrode means are preferably disposed between the
`cathode means and the rrtagrtet for controlling Flow of
`electrons from the cathode means into each channel. The
`
`grid eiectrode means may be disposed on the surface of the
`cathode means facing the magnet. Alternatively, the grid
`etectrode means may be disposed on the surface of the
`magnet facing the cathode means.
`The channets are preferably disposed in the magnet in a
`two dimensionai array of rows and txniunins. In preferred
`embodiments of the present invention,
`the grid electrode
`means comprises a plurality of parallel row conductors and
`a plurality of parallel column conductors arranged orthogo-
`nally to the tow conductom. each channel being located at a
`different
`intersection of a row conductor and a column
`conductor.
`
`Each channel may vary in cross-section along its length.
`Each channel is preferably tapered.
`The magnet preferably comprises ferrite. In preferred
`embodiments of the present inventiomthe magnet corn prises
`a binder. The binder may comprise silicon dioxide.
`In some embodiments of the present
`invention, each
`channel is quadrilateral in crosssection. In other en1bodi~
`merits of the present invention, each channel is circular is
`cross section. The corners and edges of each channel are
`preferabty radio:-used.
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`The magnet may comprise a stack of perforated
`laminations.
`the perforations in each lamination being
`aligned with the perforations in an adjacent lamination to
`continue the channel through the stack.
`Each lamination in the stack may be separated fI‘0ID an
`adjacent lamination by a spacer.
`In preferred embodiments of the present invention. anode
`means is disposed on the surface of the magnet remote from
`the cathode for accelerating eicctrons through the channels.
`The anode means preferably comprises a pluraiity of anodes
`extending parallel to the coiumns of chanoeis, the anodes
`comprising pairs of anodes each corresponding to a different
`co-ittrnrt of channels, each pair comprising first and second
`anodes respectiveiy extending aiong opposite sides of the
`corresponding column of anodes,
`the first anodes being
`interconnected and the second anodes being interconnected.
`The first and second anodesmay comprise Intern! formations
`surrounding corners of the channels. thtrtictzlarly preferred
`embodiments of the present invention comprise means for
`applying a defiection voltage across the first and second
`anodes to deflect eicctron beams emerging from the chan-
`nels.
`
`The present invention extends to a display device com-
`prising: an etectron source as hereinbefore described; a
`screen for receiving electrons from the electron source, the
`screen having a phosphor coating facing the side of the
`magnet remote frotltl the cathode; and means for stipplying
`control signals to the grid electrode means and the anode
`means to selectively control flow of electrons from the
`cathode to the phosphor coating via the channeis thereby to
`produce an image on the screen.
`The present invention aiso extends to a disptay device
`comprising: an electron source as hereinbeforc described; a
`screen for receiving electrons from the electron source, the
`screen having a phosphor coating facing the side of the
`magnet remote from the cathode.
`the phosphor coating
`comprising a plurality of groups of difierertt phosphors, the
`groups being arranged in a repetitive pattern, each group
`corresponding to a different channel; means for supplying
`control signals to the grid electrode means and the anode
`means to seieclively control flow of electrons from the
`cathode to the phosphor coating via the channels thereby to
`produce an image on the screen; and. deflectioo means for
`supplying deflection signals to the anode means to sequen-
`tially address etectroos emerging from the channels to
`different ones of the phosphors for the phosphor coating
`thereby to produce a color image on the screen. Preferably,
`the phosphors comprise Red. Green. and Blue phosphors. ln
`preferred embodiments of the present invention, the deflec«
`tiort means is arranged to address electrons emerging from
`the channels to riiifcreot ones of the phosphors in the
`repetitive sequence Red. Green, Red, Blue, . . .A finat anode
`layer is preferably disposed on the phosphor coating. The
`screen may be arcnate in at least one direction and each
`interconnection between adjacent first anodes and between
`adjacent second anodes comprises a resistive element.
`In
`preferred embodiments of the present
`invention there is
`provided means for dynamically varying a DC level applied
`to the anode means to align electrons emerging from the
`channels with the phosphor coating on the screen. An
`aluminum backing may be provided adjacent the phosphor
`coating.
`Viewing the present invention from another aspect, there
`is now provided a disptay device comprising: an electron
`source comprising: photocathude means for emitting trien-
`trons on excitation hy incident light radiation; a perrnanertl
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`6,002,207
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`3
`magnet perforated by a plurality of channels extending
`between opposite poles of the magnet.
`the magnet
`generating, in each channel, a magnetic field which forms
`electrons received from the photocathocle means into an
`electron beam; a screen for receiving electron beams from
`the electron source, the screen having a phosphor coating
`facing the side of the magnet remote from the cathode; and.
`shutter means having an array of addressable shutter ele-
`ments each selectively actuable in response to alternately
`admit and block passage of light radiation onto the photo-
`cathode means in response to an input video signal.
`The present
`invention further extends to a computer
`system comprising: memory means; data transfer means for
`transferring data to and from the memory means; processor
`means for processing data stored in the memory means; and
`a display device as hereinbefoze described for displaying
`data processed by the processor means.
`Flmherrnore, the present invention extends to a print-head
`comprising an electron source as hereinbeforc described.
`Still furthertnore, the present invention extends to document
`processing apparatus comprising such a print-head and
`means for supplying data to the prinbhead to produce a
`printed record in dependence on the data.
`Viewing the present invention from yet another aspect,
`there is now provided a method for generating electron
`beams comprising: exposing a photocatbode to incident
`light radiation to produce emission of electrons; generating.
`in each of a plurality of channels extending between oppo-
`site poles of a magnet. a magetic field which forms
`electrons received from the photocathode into an electron
`beam for guidance towards a target.
`BRIEF DESCRIPTION OF THE‘. DRAWINGS
`
`Preferred embodiments of the present invention will now
`be described, by way of example only, with reference to the
`accompanying drawings. in which:
`FIG. 1 is an exploded diagram of display apparatus
`embodying the present invention;
`FIG. 2A is a cross-section view through a well of an
`electron source embodying the present invention to show
`magnetic field orientation;
`FIG. 2B is a cross~section view through a well of an
`electron source embodying the present invention to show
`electric field orieotatiort;
`FIG. 3 is an isometric view of a well of an electron source
`embodying the present invention;
`FIG. 4A is a plan view of a well of an electron source
`embodying the present invention:
`FIG. 4B is a plan view of a plurality of wells of an electron
`source embodying the present invention;
`FIG. 5A is a cross section of a stack of magnets of an
`electron source embodying the present invention:
`FIG. 53 is a cross section of another stack of magnets of
`an electron source embodying the present invention;
`FKG. GA,
`is a plan view of a display embodying the
`present invention;
`FIG. 6B. is a cross section through the display of FIG. 6A;
`HG. 7. is a block diagram of an addressing system for a
`display embodying the present invention;
`FIG. 8 is a timing diagram corresponding to the address-
`ing system of FIG. 7;
`FIG. 9 is a cross section through a display embodying the
`present invention:
`FIG. 1!) is a block diagram of a display embodying the
`present invention having a photncathode; and,
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`4
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`FIG. 11 is a block diagram of a display embodying the
`present invention having a photocathode and a shutter.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODZMETNS OF THE
`ll."W}?.N'I'lON
`
`Referring first to FIG. 1, a color magnetic matrix display
`of the present invention comprises: a tirst glass plate 10
`carrying a cathode 20 and a second glass plate 98 carrying
`a coating of sequentially arranged red, green and blue
`phosphor stripes 88 facing the cathode 28. The phosphors
`are preferably high voltage phosphors. A final anode layer
`{not shown) is disposed on the phosphor coating 80. A
`permanent magnet 68 is disposed between glass plates 90
`and 10. The magnet is perforated by a two dimension matrix
`of perforation or "pixel wells“ 19. An array of anodes 50 are
`formed on the surface of the magnet 60 facing the phosphors
`30. For the purposes of explanation of the operation of the
`display, this surface will be referred to as the top of the
`magnet 60. There is a pair of anodes 59 amocieted with each
`column of the matrix of pixel wells 70. The anode of each
`pair extend along opposite sides of the corresponding col-
`umn of pixel wells 78. A control grid 49 is formed on the
`surface of the magnet 68 facing the cathode 20. For the
`purposes of explanation of the operation of the display, this
`surface will be referred to as the bottom of the magnet 60.
`The control grid 40 comprises a first group of parallel
`control grid conductors extending across the magnet surface
`in a column direction and a second group of parallel control
`grid conductors extending across the magnet surface in a
`row direction so that each pixel well ‘It! is situated at the
`intersection of different coortbinatiou of a row grid conductor
`and a column grid conductor. As will be described later.
`plates 10 and 90. and magnet 60 are brought together, sealed
`and then the whole is evacuated. In operation, electrons are
`released from the cathode and attracted towards control grid
`40. Control grid 40 provides a rowicoluntn tnatrix address-
`ing rnechanisrn for selectively admitting electrons to each
`pixel well 70. Electrons pass through grid 40 into an
`addressed pixel well 70. In each pixel well 70. there is an
`intense magnetic field. The pair of anodes so at the top of
`pixel well 70 accelerate the electrons through pixel well 79
`and provide selective sideways deflection of the emerging
`electron beam 3|]. Electron beam 36 is then accelerated
`towards a higher voltage anode formed on glass plate 90 to
`produce a high velocity electron beam 30 having sulficient
`energy to penetrate the anode and reach the underlying
`phosphors 80 resulting ion light output. The higher voltage
`anode may typically be held at 10 k\/.
`What
`follows is a description of the device physics
`associated with a display of the present invention. in which
`the following quantities and equations are used:
`Charge on an electron: l.6xl(}"°(I
`Energy of 1 electron-volt: l.t3xl0‘“'}
`Rest mass of 1 electron: 9.lOBxlU"“I{g
`Electron velocity: v-(2eWm)"" rnls
`Electron kinetic energy: rnvz.-"2
`Electron momentum: rnv
`Cyclotron frequency: f-«qB;"{1.pi.m} Hz
`FIG. 2A shows a simplified representation of rnagrtetic
`fields with associated electron trajectories priming though
`pixel well 70. FIG. 213 shows a representation of electro-
`static fields with associated electron trajectories passing
`through pixel well 78. Au electrostatic potential is applied
`between the top and bottom of magnet 60 which has the
`eifect of attracting electrons through the magnetic field
`shown at 18%}.
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`Al the bottom of the magnetic field 190. by the entrance
`to pixel well 70, the electron velocity is relatively low (1 eV
`above It: cathode work function repraents an electron
`velocity of around 6:10’ Inls). Elcctrom 30' in this region
`can be considered as forming a cloud, with each electron
`t.ravel.il:tg in its own random direction. As the electrons are
`attracted by the electrostatic field their vertical velocity
`increases. If an electron is moving in exactly the same
`direction as the magnetic field 100 there will be on lateral
`force exerted upon it. The electron will
`therefore rise
`through the vacuum following the electric field lines.
`However. in the more general case the electron directionwill
`not be in the direction of the magnetic field.
`Refening now to FIG. 2B, magnetic force acting on a
`moving electron is perpendicular to both the magnetic field
`and the velocity of the electron (Fleming: right hand rule or
`F-e(E+vxB). Thus. in the case of a uniform magnetic field
`only, the election will describe a circular path. However.
`when the electron is also being accelerated by an electric
`held, the path becomes helical with the diameter of the helix
`being controlled by the magnetic field strength and the
`electrons x,y velocity. The periodicity of the helix is con-
`trolled by the electrons vertical velocity. A good analogy of
`this behavior is that of a nod: to a whirlpool or dust in a
`tornado.
`
`By way of summary. electrons enter magnetic field B 100
`at the bottom of magnet 60, accelerate through well 7|) in
`magnet 60, and emerge at the top of magnet 60 in a narrovr
`but diverging beam.
`Considering now the display as whole rather than a single
`pixeL tin magnetic field B llll shown in FIG. 2A is formed
`by a channel or pixel well 70 through a permanent magnet
`6-0. Each pixel requires a separate pixel well 10. Magnet 60
`is the size oftbc display area and is perforated by a plurality
`of pixel welh 70.
`Referring now to FIG. 3, the magnetic field intensity in
`well '70 is relatively high; the only path for the flux lines to
`close is either at the edge of magnet 60 or through wells 70.
`Wells 70 may be tapered. with the narrow end of the taper
`adjacent cathode 20. It is in this region that the magnetic
`field is strongest and the electron velocity lowest. Thus
`eflicient electron collection is obtained.
`Referring hack to FIG. 2B. electron beam 30 is shown
`entering an electrostatic field E. As an electron in the beam
`moves through the field, it gains velocity and momentum.
`The significance of this increase in the electrons momentum
`will be discussed shortly. When the electron nears the top of
`magnet 60. it enters a region influenced by deflectioo anodes
`50. Assuming an anode voltage of 1 kV and a cathode
`voltage nf0V. the electron velocity at this point is l.B7Sxl0"
`tn.-is or approximately 6% of the speed of light. Al the final
`anode. where the electron velocity is s.93xto" mls or 0.2 c.
`since the electron has then moved through 10 RV. Anodes 51
`and 52 on either side of the exit from the pixel well 70 may
`be iodividtrally controlled Referring now to FIGS. IIA and
`4B, am. 51 and 52 are preferably arranged in a comb
`configuration in the interests of easing fabrication. Anodes
`51and.'t2areseparatedfrornwell7tIandgr-id-I0by
`insulating regions 53. There are four possible states for
`anodes 51 and 52. as follows.
`l.Anode5l is0FF;Anode 52 isCll'*'l-': lntbiscase thcreis
`no accelerating voltage Va between the cathode 20 and the
`anodes 51 and 52. This state is not used in normal
`operation of the display.
`2. Anode 51 is ON; Anode 52 is ON: In this case there is
`accelerating voltage V, symmetrically about the electron
`beam. The electron beam path is unchanged. When leav-
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`ing the control mode region the electrons continue until
`they strilee the Green phosphor.
`3.Anode51 'n0F'F;Aoode£is0N: lo Iltisclsetbere is
`an asymmetrical control anode voltage V,.’1'he electrons
`are attracted towards the energized anode 52 (which is
`still providing an accelerating voltage relative to the
`cathode 20). The electrons bean: is thus eleclrostatically
`deflected towards the Red phosphor.
`4.Anode51is ON;Anode 52 isOFF:This islheopposite
`to 3. above. In this case, the electron beam is deflected
`towards the Blue phosphor.
`it will be appreciated that other sequences of phosphors
`may be deposited on the screen with corresponding data
`re-ordering.
`the above deflection
`It should also be appreciated that
`technique does not change the magnitude of the electron
`energy.
`As described above. electron beam 30 is formed as
`electrons move through magnet 60. The magnetic field B
`lill. although decreasing in intensity still exists above the
`magnet and in the region of anodes 50. Thus. operation of
`anodes 50 also requires that they have sufiicient efiect to
`drive electron beam 30 at an angle through magnetic field B
`It'll. The momentum change of the electron between the
`bottom atai top of well 70 is of the order of 32:: (for a l KV
`anode voltage). Tb: elIecI of the divergent magnetic field E
`III] may be reduced between the bottom and top by a similar
`amount.
`
`Individual electrons tend to continue traveling in a
`straight line. However,
`there are three forum tending to
`disperse electron beam 30. as follows:
`1. The diverging magnetic field B 100 tends to cause
`electron beam 30 to diverge due to the v_, distribution;
`2. The electrostatic field E tends to hflect electron beam 30
`towards itself; and.
`3. Space charge elfects within beam 30 itself cause some
`divergence.
`in a modification to the
`Referring now to FIG. 5A.
`example of the preferred embodiment of the present inven-
`tion hereinhefore described, magnet 60 is replarxd by a stack
`61 of magnets 60 with like poles facing each other. This
`produces rt magnetic lens in each well 70, thereby aiding
`beam collimation prior to defleotion. This provides addi-
`tional electron beam focusing. Furthermore. providing the
`stack 61 consists of one or more pairs of magnets. the helical
`motion of the electrons is canceled. in some embodiments of
`the present invention, spacers 604: [(not shown)] may be
`inserted between magnets 60 to improve the lens effect of
`stack 61.
`As mentioned earlier. the display has cathode means 20.
`grid or gate electrodes 40, and an anode. The arrangement
`can thus be regarded as a triode structure. Electron flow from
`cathode means 2|) is regulated by grid «I-I) thereby controlling
`the current flowing to the anode. It should he noted that the
`brightness of the display cbes not depend on the velocity of
`the elections but on the quantity of electrons striking phnrr
`phor 810.
`As mentioned above, magnet 60 acts as a substrate onto
`which the various conductors required to form the tried: are
`deposited. Deflection anodes 50 are deposited on the top
`face of magnet 60 and control grid 40 is fabricated on the
`bottom surface of the magnet 60. Referring back to HG. 3.
`it will be appreciated that the dirnensiorts of these conduc-
`tors are relatively large compared with those employed in
`current flat panel technologies such as liquid crystal or [icld
`emission displays for example. The conductors may advan-
`tageously be deposited on magnet ill by conventional screen
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`6,002,207
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`7
`printing techniques, thereby leading to lower cost manufac-
`ture compared with current fiat panel technologies
`Referring back to FIG. 4A, deflection anodes 50 are
`placed on either side of well 71). In the example hereinbefore
`described. an anode thickness of 0.01 mm provided accept»
`able defiection. However, larger dimensions may be used
`with lower deflection voltages. Defiecrioe anodes 50 may
`also be deposited to extend at {east partially into pixel well
`70. It will be appreciated that. in a monochrome example of
`a display device of the present invention. anode switching or
`modulation is not required. The anode width is selected to
`avoid capacitive effects introducing discernible time delays
`in anode switching across the display. Another factor affect-
`ing anode width is current carrying capacity, which is
`preferably sufficient that a flash-over does not fuse adiacent
`anodes together and thus damage the display.
`In an embodiment of the present invention preferred for
`simplicity. beam indexing is implemented by aiternately
`switching drive voitages to deflection anodes 50. Improved
`performance is obtained in another embodiment of the
`present
`invention by imposing a moduiatiou voltage on
`dellcction anodes 50. The modulation voltage waveform can
`be one of many dilferent shapes. However, a sine wave is
`preferable to reduce back emf effects due to the presence of
`the magnetic field.
`Cathode means 29 may include an array of fieid emission
`tips or field emission sheet emitters (am orphotts diamond or
`silicon for example). In such cases, the control grid 40 may
`be formed on the field emission device substrate.
`Alternativety, cathode means 20 may include plasma or hot
`area cathodes, in which cases control grid 40 may be formed
`on the bottom surface of the magnet as hereinbefore
`described. An advantage of the ferrite block magnet is that
`the ferrite block can act as a carrier and support for all the
`structures of the dimiay that need precision alignment. and
`that these structures can be deposited by low grade photo-
`lithography or screen printing. In yet another alternative
`embodiment of the premnt invention, cathode means 20
`comprises a photocalhode.
`As mentioned above, control grid 40 controls the beam
`current and hence the brightness. In some embodiments of
`the present
`invention,
`the display may be responsive to
`digital video alone, i.e.: pixels either on or off with no grey
`scale. In such cases, a single grid 4|] provides adequate
`control ofbeatn current. The application ofstrch displays are
`however limited and, generaliy. some form oi analog. or
`grey scale. control is desirable. Thus, in other embodiments
`of the present invention, two grids are provided; one for
`setting the black level or biasing, and the other for setting the
`brightness of the individual pixeis. Such a double grid
`arrangement may aiso perform tnatzix addressing of pixets
`where it may be diificoit to modulate the cathode.
`A display of the present invention differs from a convert-
`tional CRT dispiay in that, whereas in a CRT display only
`one pixel at a time is lit, in a display of the present invention
`a whole row or column is lit. Another benefit of the display
`of the present invention resides in the utilization of row and
`column drivers. Whereas a typical LCD requires a driver for
`each of the Red. Green and Biue channels of the display, a
`display of the present invention uses a single pixei weli 70
`(and hence grid) for all three colors. Cornbined with the
`aforemerttioned beam indexing. this means that the driver
`requirement is reduced by a factor of 3 relative to a com-
`parable LCD. A further advantage is that. in active LCDS,
`conductive tracks must pass between semiconductor
`switches fabricated on the screen. Since the tracks do not
`emit light, their size must be limited so as not to be visible
`
`to a user. In displays of the present invention, all tracks are
`hidden either beneath phosphor 80 or on the underside of
`magnet 60. Due to the relatively large spaces between
`adjacent pixel welis 70, the tracks can be made relatively
`large. Hence capacitance elfects can be easiiy overcome.
`The retative eificiencies of phosphors 89 at least partially
`determines the drive characteristics of the gate stnrcture.
`One way to reduce the voltages involved in operating a beam
`indexed system is to change the scanning convention. In a
`preferred embodiment of the present invention. rather than
`theusualscanofll G ERG B, .. . ,thescan isorganized
`so that the most inefficient phosphor is pieced in between the
`two more eiiicient phosphors in a phosphor stripe pattern.
`Thus. if the roost ineificient phosphor is, for exarrzpie, Red.
`lhescat1followsthepatternBRG RBR GR . ..
`In a preferred embodiment of the resent invention, a
`standing DC potential dilference is introduced across deflec-
`tion anodes 58. The potential can be varied by potentiometer
`adjustrncot to permit correction of any rcsiduai misalign-
`ment between phosphors 89 and pixel wells 1'0. A two
`dimensional misalignment can be compensated by applying
`a varying modulation as the row scan proceeds from top to
`bottom.
`
`ID
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`21}
`
`Referring now to FIG. 6A, in a preferred embodiment of
`the present invention. resistive elements 53 between det1ec-
`lion anodes 59 are made resistive. This introduces a siightly
`different DC potential from the center to the edge of the
`display. The eiectron trajectory thus varies gradttalty in
`aogte as shown in FIG. 6B. This permits a {let magnet St) to
`be combined with non-fiat giass 90 and,
`in particular,
`cylindrical glass. Cyiindrical ghtss is preferable to flat glass
`because it relieves mechanical stress under atmospheric
`pressure. Flat screens tend to demand extra implosion pro-
`tection when used in vacuum tubes.
`In a preferred embodiment of the present invention. color
`selection is performed by beam indexing. To facilitate such
`bean: indexing, the line rate is 3 titnes faster than normal and
`the R. G. and B line is multiplexed sequentially.
`Aiternatively. the frame rate may be 3 times faster than usual
`and field sequential color is employed. It shouid he appre-
`ciated that field-sequerttial scanning may produce objection-
`able visual effects to an observer moving relative to the
`display.
`Important features of a display of the present
`invention include the following.
`1. Each pixel is generated by a single pixel well 70.
`2. The color of a pixel is determined by a relative drive
`intensity applied to each of the three primary colors.
`3. Phosphor 80 is deposited on faceptate 90 in stripes.
`4. Primary coiors are scanned via a beam index system
`which is synchronized to the grid control.
`5. An electron beam is used to excite high voltage phos-
`phors.
`6. Gt’cy~ttt:ale is achieved by crmtrtrl of the grid voltage at the
`bottom of each pixel well (and hence the electron beam
`density).
`7. An entire row or coturno is addressed simultaneously.
`8. If required, the least eflicient phosphor 80 can be double
`scanned to ease grid drive rcquitcrnents.
`9. Phosphor 80 is held at a constant DC voltage.
`The above features may provide one or more of the
`following advantages over conventional flat panel disptays.
`I. The pixel well concept reduces overall complexity of
`display fabrication.
`2. Whereas in a CRT displ ay, only about 11% of the electron
`beam current exits the shadow mask to excite the phos-
`phor triads,
`in a display of the present
`invention the
`electron hearrt current at or near to 300% of the beam
`
`45
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`SE]
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`55
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`68
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`65
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`

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`6,002,207
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`9
`current is utilized for each phosphor stripe it is directed at
`by the beam indexing system. An overall beam current
`utilization of 33% is achievable, 3 times that achievable
`in a conventional CRT display.
`3. Striped phosphors prevent Moire interference occurring in
`the direction of the stripes.
`4. Control structures and tracks for the heart: index system
`can be easily accommodated in a readily available area on
`top of the magnet, thereby overcoming a requirement for
`narrow and precise photolithogaphy as is inherent in
`conventional i_CDs.
`
`5. High voltage phosphors are well understood and readily
`available.
`6. The grid voltage controls an analog system. Thus the
`effective number of bits for each color is limited only by
`the DAC used to drive grid 40. Since only one DAC per
`pixel well row is involved, and the tirne available for
`digital to analog conversion is very long, higher resolu-
`tion in terms of grey«scale granularity is cootrnereially
`feasible. Thus, the generation of "true color" (24 bits or
`more) is realizable at relatively low cost.
`7. As with conventional Mills, a display of the present
`invention uses a row/coiutnn addressing technique.
`Unlike conventional CRT displays however, the excita-
`tion time of the phosphor is elfeetively one third of the
`line period. e.g.: between 200 and 530 times longer than
`that 501' a CRT display Eur between 600 and 1600 pixels
`per
`line resolution. Even greater ratios are possible.
`especially at higher resolutions. The reason for this is that
`line and frame fiyback time necessary when considering
`conventional CRT display are not needed for displays of
`the present invention. The line fiybaok time alone for a
`conventional CRT display is typically 20% of the total
`line period. Furthermore front and back porch times are
`redundant in displays of the present invention, thereby
`leading to additional advantage. Farther benefits include:
`a) Oniy one driver per rowfcolumn is required ( conven-
`tionai color LCDS need three);
`b) wry high light outputs are possible. In a conventional
`CRT display.
`the phosphor excitation time is much
`shorter than it‘s decay time. This means that only one
`photon per site is emitted during each frame scan. In a
`display of the present invention, the excitation time is
`longer than the decay period and m multiple photons
`per site are emitted during each scan. Thus. a much
`greater luminous output can be achieved. This is attrac-
`tive both for projection applications and for displays to
`be viewed in direct sunlight.
`c) The grid switching speeds are fairly low. It will be
`appreciated that. in a display of the present invention,
`the conductors formed on the magnet are operating in
`a magnetic field. Thus. the conductor inductance gives
`rise to an unwanted EMF. Reducing the switching
`speeds reduces the EMF, and also reduces stray mag-
`netic and electric fields.
`8. The grid drive voltage is rela