US3624273A

US3624273A - Flat screen display devices using an array of charged particle sources

Info

Publication number: US3624273A
Application number: US778194A
Authority: US
Inventors: Alfred J Gale
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-11-22
Filing date: 1968-11-22
Publication date: 1971-11-30
Anticipated expiration: 1988-11-30
Also published as: DE1957247B2; FR2023892A1; SE370812B; NL6917565A; DE1957247A1; DE1966798A1; GB1267103A; DE1957247C3

Abstract

A display device utilizing an array of electron-emitting sources insulatively supported opposite a screen member so that each emitting source is in register with a selected area element of such screen member. Means are provided for sequentially controlling the emission of electrons from such sources so that the emitted electrons impinge in an appropriate sequence upon the selected area elements of the screen member to produce an image thereon. An appropriate stereoscopic display of such image may be provided by using optical filters adjacent each selected area element so that certain selected portions of the visible spectrum are transmitted to the receiver from each such element as a result of the impingement of electrons thereon.

Description

United States Patent PATENTEU Nuvao mn SHEET l UF 5 mvuNToR. A. JOHN GA/ E BY 000m AND oco/v/VEL L ATTORNEYS PATENIEU Nuvso 197| SHEET 2 UF 5 :NVLNTOR A. ./oH/v @ALE BY 0000/1 mvp 0c0/v/vELL "ATTORNEYS PATENTEDHuvsoIQn 3,624,273

SHEET s nF 5 Mo @W69 wm www@ we 6W ALB we w www@ @www gg@ mfg@ www @@ef Q Q Ww FLAT SCREEN DISPLAY DEVICES USING AN ARRAY OF CHARGED PARTICLE SOURCES This invention pertains generally to display devices and, more particularly, to a device adapted to provide a substantially flat screen display for use in television receivers, for example, wherein the depth of such device is substantially less than the width of the display screen.

In conventional television receivers the display component is in the form of a cathode-ray tube, the image being formed on the phosphor screen thereof. A normal characteristic of such a display tube is that the distance from the screen to the electron source, or gun, is approximately equal to the width of the picture which is presented on the screen. Consequently, relatively bulky cabinets, or housings, are required for such tubes, particularly in the larger picture sizes and particularly since the voltage potentials required to operate such tubes may be as high as 20,000volts or more.

One method which has been developed in an effort to reduce the size, and particularly the depth, of such display components has been to utilize a projection tube system wherein the image is formed on the phosphor screen of a relatively small cathode-ray tube and is thereupon optically amplified and projected onto a larger screen area. In a practical sense` however, such an approach does not measurably reduce the overall size and bulk of the display system and, moreover, the picture quality and brightness are degraded. Further, even higher voltage potentials are generally necessary for operating such a projection cathode-ray tube system.

Other attempts to reduce the size of the display component and to provide a substantially flat screen display system have included systems for causing an electron beam to travel essentially parallel to, rather than perpendicular to, the picture plane, the beam being deflected onto the picture plane only over the last portion of its path of travel. Such an approach does not measurably reduce the size of the electron beam tube involved and materially adds to the complexity of an already complicated system, particularly when such an approach is used for color television display.

This invention provides a system in which the depth of the display device is substantially less than the dimensions of the display screen on which the image is presented, such depth being approximately an order of magnitude less than the picture width, for example. Moreover, the overall display device of the invention is relatively lighter in weight than presently used display devices. A cathode-ray tube, for example, utilizes relatively heavy and thick glass, or other materials in order to safely support the evacuated tube against the external air pressure thereon. Such extreme glass weight and thickness is not required in the display device ofthe invention.

Moreover, in present day cathode-ray tubes the screen is generally curved, that is it can be represented as a portion of a sphere, particularly in large size cathode-ray tubes. This invention, however, provides a substantially planar, or flat, screen on which the image is presented and does not require excessively thick or heavy glass as is usually needed to support flat surfaces so as to prevent collapse due to external air pressure. Consequently, the internal reflections, which normally arise in thick glass systems, are avoided and the picture contrast is not degraded thereby.

Further, the voltage potentials used in operating the display device of the invention are relatively low in comparison to those potentials needed for cathode-ray tube structures. Thus, not only are electrical hazards avoided but also hazards due to X-radiation, which have been found to exist in present day cathode-ray tubes, are also eliminated.

The display device of the invention achieves these advantages by utilizing an array, or matrix, of charged-particle emitting sources, such as electron-emitting cathode structures, and a luminescent screen member, such as a phosphor screen, which responds to the impingement of such charged particles to produce an image thereon. Such sources and screen member are supported at either end of an appropriate insulative lattice structure so that each emitting source is oppositely disposed from and in register with a selected area of the luminescent screen. By appropriately controlling the emission of electrons from the emitting source in a desired sequence in accordance with a transmitted picture, for example, such electrons are caused to impinge in a suitable corresponding sequence upon the screen to produce the desired image thereon.

In the invention the distance from the emitting sources to the screen is substantially less than the dimensions of the screen, particularly being in the order of one-tenth, or less, of the screen width. Moreover, the voltage potentials required to energize the sources and to accelerate the electrons toward the luminescent screen are relatively small in comparison with present cathode-ray tube operating voltage potentials. The electron-emitting sources may be of various types, such as thin-film devices or other solid state structures, thermally emitting cathode structures, and field emission cathode structures, and the like.

The specific details of particular embodiments of the invention can be described more easily with the aid of the accompanying drawings wherein:

FIG. 1 shows generally a perspective outline drawing of the display device of the invention depicting the dimensional relationships therein;

FIG. 2 shows a sectional view along the direction of line 2- 2 of FIG. 1 showing a portion of one embodiment of the array of emitting sources;

FIG. 3 shows a sectional view along the direction of line 3 3 of FIG. l showing a portion of one embodiment of an array of screen elements;

FIG. 4 shows a sectional view along the direction of line 4- 4 of FIG. 1 showing the relationships between the emitting sources, the luminescent screen of FIGS. 2 and 3 and the sup port structures therefor;

FIG. 5 shows a more detailed view of one portion of the structure shown in FIG. 4;

FIG. 6 shows a sectional view of an alternative embodiment of the structure shown in FIG. 4;

FIG. 7 shows a sectional view of another alternative ernbodiment of the structure of FIG. 4;

FIG. 8 shows a sectional view of an alternative embodiment of the structure of FIG. 4 using a different form of emitting sources;

FIG. 9 shows another alternative embodiment of the structure of FIG. 4 utilizing another difference form of emitting sources;

FIG. l0 shows another alternative embodiment of the structure shown in FIG. 4 utilizing still another different form of emitting sources;

FIG. ll shows a more detailed view of one of the emitting sources shown in FIG. l0;

FIG. 12 shows a schematic diagram of a portion of the circuitry used to energize the emitting sources and adapted to be used with such sources as shown in FIG. 4 or the alternative embodiments of such sources as shown in FIGS. 8, 9 and 10;

FIG. 13 is a schematic diagram of an alternative arrangement of the circuitry of FIG. 10 adapted to be used for energizing the emitting sources of FIGS. 4, 8. 9 and 10;

FIG. 14 is a graph of the visible portion of the frequency spectrum which graph is useful in describing the application of the invention to stereoscopic displays;

FIG. 15 is a diagram illustrating one arrangement of the array of display area elements useful for stereoscopic displays; and

FIG. 16 is a diagram showing an alternative arrangement of the array of display area elements of FIG. l5.

FIG. l shows an outline perspective drawing depicting the relationships among the height, width and depth dimensions of a typical display device of the invention. As shown therein, the front planar surface 20 represents generally the plane of a luminescent display screen on which an image is presented. Such screen has a height h and width w as shown. An array of charged-particle emitting sources is mounted generally at the rear planar surface 21 of the device. The thickness, or depth, of the device, shown in the drawing as dimension d is substantially less than, and preferably of an order of magnitude approximately one-tenth of, the width w of the display screen at surface 20. The detailed structure of one particular embodiment of a display device conforming to the general outline configuration shown in FIG. 1 is discussed first with reference to FIGS. 2, 3 and 4.

FIG. 2 shows a view of a portion of the charged-particle emitting sources in the direction of the line 2-2 of FIG. l looking toward rear surface 21 thereof. An insulative lattice structure 22 forms an array of evacuated channels 23, as shown most clearly in FIG. 4. The rhombic cross section of each such channels confonns generally in its dimensions to the conventional widthzheightl ratio of the display screen at sur` face of FIG. l, such dimensions in accordance with normal television standards having a 4:3 ratio. Each channel is in register at one end with a specific area element of a luminescent display screen. More particularly, for color display purposes each channel is in register with a specific color area element thereof. For example, as shown in FIG. 2, channel 23a may be associated with the red content of a transmitted picture, channel 23b may be associated with the green content, thereof, and channel 23a` may be associated with the blue content, thereof. Although shown in rhombic cross section, the evacuated channels may be of other convenient configurations such as circular, for example.

Each evacuated channel 23 is in register at the other end with a separate electron-emitting source. Thus, the lattice structure provides for electrical and mechanical separation of the emitting sources at the cathode end as well as of the display screen area elements at the anode end, as described more clearly with reference to the subsequent figures.

For the particular embodiment described with reference to FIGS. 2, 3 andv4, a separate channel is shown as associated with each color element. However, since the electrons emitted from the cathode source end travel to the anode screen end with relatively small angular dispersion, such separate channels may not necessarily be required and each channel may be in register with more than one cathode source and corresponding anode display screen element. Enough insulative support material must be utilized, however, to withstand reliably the external air pressure on the substantially flat display and cathode surface planes of the device. In order to describe the operation of the device in a clearest manner, the discussion which follows considers an embodiment utilizing separate channels for each cathode and corresponding anode element combination, the overall de vice being described for use in generating a color picture.

As shown in FIGS. 2, 3 and 4, at the emitting or cathode end 24 of the display device, a plurality of conductors 26 form the upper electrodes of a suitable thin-film cathode structure 30 and a plurality of conductors 27 form the lower electrodes thereof. As seen in FIG. 2, conductor 26a is associated with channel 23a, conductor 26b is associated with channel 23b and conductor 26e` is associated with channel 23C, such triad sequence being repeated across the entire array. When a trio of adjacent conductors 26 (e.g., 26a, 26h and 26e) and a pair of adjacent conductors 27 are energized to cause electron flow, a specific triad of emitting sources, one source corresponding to each color, and only one specific triad is activated.

FIG. 3 shows the anode end 25 of the display device oppositely disposed with respect to the cathode end at the other end of insulative lattice structure 22. At such anode end an array of phosphor area elements 28 is shown associated with eachchannel 23. Each phosphor element is associated, as described below, with a specific color. Thus, phosphor element -28 1\for example, corresponds with the red content, phosphor element 28b.with the green content, and phosphor element-28C with theblue content.

FIGS. 4 and,5show in more detail the overall cathode and anode structures. In such figures, each of the thin-film cathodes 30 is formed on an insulator plate 29. Conductors 27, typically made of aluminum, form the lower electrodes of each of the rows of electron-emitting cathodes 30. An insulating compound layer 3l, typically made of silicon dioxide, is formed over conductors 27. In the region 32 of each cathode proper the thickness of the insulating compound layer 3l is less than that of the intervening regions 33. In a preferred embodiment, for example, the thickness of layer 3l in region 32 lies in the range from 0.03 to 0.3 micrometers and may typically be 0.1 micrometer. In the intervening regions 33 the insulating layer, for example, may be on the order of 1.0 micrometers thick, or greater.

Columns of conductors 26 are formed over silicon dioxide layer 31 such conductors being, for example, made of gold and formed in relatively thick layers, on the order of 0.l micrometer or greater, adjacent the region 33 where the insulator layer 31 is at its thickest. Conductors 26 are relatively thin where they are formed adjacent regions 32 of insulator layer 3l. In such regions, conductors 26 may be a few hun dredths of a micrometer thick, and typically may be 0.03 micrometer.

At the opposite end of insulative lattice structure 22 are the phosphor elements, or dots, 28 which elements are interconnected by a conductive film 34, both the phosphor elements and the interconnecting conductive lm adhering to a transparent face plate 35. An array of multidielectric filters 36, the purpose and more detailed description of which is discussed below, may optionally be interposed between the face plate 35 and the layer of phosphor elements and conductive lms as shown in FIG. 4.

When a positive potential difference exists from the relevant conductor 26 to a corresponding relevant conductor 27, a particular cathode structure will emit electrons into a corresponding vacuum channel 23, the value of the potential difference needed for this purpose being dependent on the dimensions of the cathode structure. Typically for a silicon dioxide layer 3l of approximately 0.1 micrometer this potential difference is in the order of 200 volts. In the quiescent, or nonemitting,

state conductors

26 and 27 are held at approximately equal potentials relatively close to ground. In synchronism with the transmitted picture information each conductor 27 (or conductor pair in the case of a color display) is sequentially switched to a negative potential equal to the threshold for electron emission between it and the quiescent conductor 26. Depending on the brightness content, or luminance, of the picture of the transmitted picture information, positive potentials are applied sequentially, and in synchronism with the transmitted picture, to conductors 26 so that each cathode structure is caused to emit electrons in short bursts, the number of electrons being determined by the luminance information of the transmitted picture element. ln the case of a color display, the conductors 26 are arranged in triads, each member of the triad receiving a voltage potential determined by the luminance (or brightness) and chrominance (or color) information in the transmitted signal. In a typical operation the switching signals applied to conductors 27 may be in the range of -50 to -500 volts and the modulating signals applied to conductors 26 may lie in the range from 0 to 100 volts.

The electrons so emitted by each cathode structure during such operation are accelerated with a relatively small angular dispersion toward the anode plane 25 which for such purposes may be held at a voltage potential in the order of 5,000 volts or higher. The electrons accelerated from each cathode structure 30 impinge upon the corresponding oppositely disposed phosphor dot 28 exciting it to luminescence. For monochrome display a substantially white light emitting phosphor element is selected for each phosphor dot. Alternatively, the dot configuration for monochrome operation may be preferably and more economically replaced by a continuous thin layer of phosphor material, in which case each evacuated channel lies opposite to and in register with a selected area element thereof.

In the case of a color display, the materials of each of the phosphor dots 28 are selected to emit the appropriate hues. Alternatively, for color operation the phosphor may be selected to emit substantially white light, either a continuous thin layer of phosphor material or as a dot configuration, which white light upon luminescence is filtered through appropriate multilayer dielectric, or other, filters 36, as optionally shown for this purpose. The filters are appropriately designed to transmit the desired color portions (i.e., red, green, or blue) of the visible spectrum through transparent face plate 35.

Embodiments of the circuitry required to provide the appropriate sequence of operations for reproducing an overall image on the phosphor display screen are discussed below with reference to FIGS. 12 and 13. Before describing such circuitry, however, alternative embodiments of the electron emitting sources are first described with reference to FIGS. 6-1 1.

In FIG. 6 a structure similar to that shown in FIG. 4 is illustrated, with like reference numerals referring to like portions thereof. ln FIG. 6, however, the insulative lattice structure 22 is replaced by two

insulative lattice structures

37 and 38 between which are placed a plurality of apertured vertical conductors, or grids, 39 having apertures 40. The overall structure shown in FIG. 6 is, therefore, in the nature of a triode configuration, several modes of operation of which are possible. For example, in one mode conductors 26 are all connected together, preferably to a ground potential, and conductors 27 (or appropriate conductor pairs for color display as discussed above) are sequentially switched in the manner described above with reference to FIG. 4 to a voltage which provides a sufficiently high potential difference between

conductors

26 and 27 to permit maximum electron emission and flow therefrom. Thus, the potential difference applied thereto is greater than that discussed with reference to FIG. 4 wherein a potential difference related to the threshold value of electron emission was used.

A modulating bias voltage is thereupon sequentially applied to the grid structure 39 in appropriate synchronism with the transmitted picture information thereby permitting a suitable fractional portion (or all, if necessary) of the electrons emitted from the cathode structures 30 to flow through aperture 40 and thereby be accelerated to the anode plane 25. An advantage of utilizing such a grid or triode configuration over the diode configuration in FIG. 4 is that the capacitance of the individual grids 39 to other parts of the system is considerably less than that of the conductors 26 of FIG. 4. The system of grids can therefore be driven with considerably less power, and thus, more economically than the system utilizing merely the thin-film cathode 30 in the previous figure.

In FIG. 7 a structure similar to those shown in FIGS. 4 and 6 is illustrated, with like reference numerals referring to like portions thereof. In FIG. 7 the insulative lattice structure is formed in three

sections

41, 42 and 43. A plurality of apertured horizontal conductors, or grids, 44 having apertures 45 is mounted between sections 4l and 42, such grids being arranged in rows in a horizontal configuration. A plurality of vertically oriented grids 46 having apertures 47 are placed between

sections

42 and 43, such grids being substantially the same as grids 39 described above with reference to FIG. 6. Several alternative modes of operation of the configuration shown in FIG. 7 are possible. In one such mode, all ofthe conductors 26 of cathode 30 are connected together to a common voltage potential so that all of the cathodes continuously emit electrons. Conductors, or grids, 44 are normally held at a voltage potential which prevents electron flow through apertures 45 and are sequentially switched in synchronism with the transmitted picture signal information t0 permit a substantial fraction of the electrons from each cathode to be accelerated through apertures 45. The grids 46 are sequentially biased in synchronism with such transmitted picture signal information to modulate the quantity of electrons which are ultimately accelerated to the anode end for impingement upon phosphor elements 28. An advantage of the arrangement in FIG. 7 is that the capacitance associated with the individual conductors 44 is considerably less than that associated with the individual conductors 27.

Having thus described various particular embodiments of the invention utilizing the cathode structure of FIG. 5, either in diode configuration, triode configuration, or tetrode configuration as in FIGS. 4, 6 and 7, respectively, FIGS. 8-11 are now used to describe similar structures utilizing other forms of cathode structures. In comparing FIGS. 8-11 with FIGS. 2-7, it should be noted that like reference numerals refer to like elements thereof.

In FIG. 8 an alternative fonn of a solid state cathode 48 is shown. The array of cathodes used therein comprises a set of vertical conductors 49 contiguous to the insulative structure 29 together with a set of horizontal conductors 50. Typically, conductors 49 and 50 are of metal of which gold, silver, and aluminum have been found suitable. Between conductors 49 and 50, in the region of each cathode source 48, a film of semiconductor compound 51 is placed, such compound, for example, typically being composed of tin oxide. Projections 52 placed on a portion of conductors 49 rise to the surface of the semiconductor film 5l. Electrons are emitted from the metal semiconductor junctions when a voltage potential difference is applied from conductor 50 to conductor 49 across semiconductor film 51. In operation, conductors 50 are sequentially switched in synchronism with the transmitted picture signal information to a voltage potential, relative to the quiescent condition of conductors 49, which is the threshold voltage for electron emission. Typically such voltage potential is in the order of 200 volts. Additional modulating voltage potentials are sequentially applied to the vertical conductors 49 to control the number of electrons emitted from each cathode in accordance with the point-by-point luminance and chromnance values of the transmitted picture content. The remaining details of the image formation at the anode plane are substantially similar to those described in conjunction with FIG. 4, for example, and such details are not repeated here.

As with the thin-film cathodes of FIGS. 4-7, a triode configuration similar to that described in conjunction with FIG. 6 and a multielectrode configuration similar to that described with reference to FIG. 7 can be used as further alternative embodiments to the diode configuration of FIG. 8. Consequently, such structures are not further illustrated in detail here.

FIG. 9 shows an alternative embodiment utilizing different electron-emitting sources. In such figure a reflective film 53 of silver, or other metal chosen for maximum reflectivity in the red and infrared portions of the optical spectrum, is deposited on insulator 29. A layer 54 of transparent insulating material, typically aluminum oxide, or other high-temperature insulator chosen for maximum transparency in the red and infrared portions of the optical spectrum, is deposited over reflective film 53. Layer 54 is in the order of a few micrometers thick, typically being approximately 2.0 micrometers. A plurality of thin-film heaters 55, typically of carbon or tungsten or other high-temperature conductive material, are deposited on insulating layer 54, interconnections between the heaters being also deposited on insulating layer 54 so that the heaters are connected in series in rows. A further layer 56 of high-temperature insulative materials, such as aluminum oxide, is deposited over the heaters and heater interconnections as well as portions of layer 54. Electron-emitting cathodes 57, typically of lanthanum hexaboride or other low work function material, are deposited on high-temperature insulative layer 56. Cathodes 57 are interconnected in columns, or alternatively in rows, depending on the electrical functions associated with the apertured grid structures 58 as discussed below. To prevent chemical reactions between the cathodes 57 and the insulative layer 56, and also to provide maximum radiation absorption from the heaters 55, thin layers of carbon (not shown) may be deposited on the insulating layer 56 prior to the deposition of cathodes 57.

A grid structure 58 is mounted between two

insulative lattice structures

59 and 60 in a manner similar to that described above with reference to FIG. 6, such grids 58 having apertures 6l as shown.

ln one mode of operation of the embodiment shown in FIG. 9, the grid structures 58 are held at a constant potential and the cathodes 57 are interconnected in columns. The rows of heaters 55 are sequentially switched in synchronism with the transmitted picture signal information. The thennal inertia of such heater/cathode structures is so low that sufficiently fast switching times are obtainable, particularly when bias power is applied to the heater rows elevating all of cathodes 57 to a temperature just below the threshold for significant electron emission in the quiescent condition. Modulating voltage potentials in confonnity and synchronism with the transmitted picture infomation are sequentially applied to the columns of cathodes 57 so that the quantities of electron flow through the apertures 6l of grids 58 are controlled by the point-to-point luminance (and chrominance) content of the picture. The further details of picture formation are substantially similar to that discussed with respect to the descriptions of the previous embodiments described above. Y

In another mode of operation of the particular embodiment shown in FIG. 9, cathodes 57 are interconnected in rows and the grid structures 58 are arranged in columns substantially similar to grids 39 of FIG. 6. In such arrangement, fast switching of the heater rows is not required. In the quiescent condition the cathode rows are held at a positive voltage potential relative to the grid structure 58 thereby preventing electron flow through the aperture 6l. The rows of cathodes are sequentially switched in synchronism with the transmitted picture information to a threshold voltage potential for electron flow through aperture 61 of grid structure S8. Modulation potentials are sequentially applied to the grid columns in accordance with the luminance (and chrominance) content of the picture.

FIGS. l and l1 show an alternative embodiment of the invention utilizing a difference form of cathode electron emitting structure. ln such figures a film 62 of aluminum oxide is deposited on insulator 29. A plurality of conductors 63, typically made of molybdenum, are deposited in a set of rows on aluminum oxide film 62. In a preferred embodiment the thickness of conductors 63 may be in the order of 0.2 micrometers. Over the rows of conductors 63 a further layer 64 of aluminum oxide, in a preferred embodiment being approximately 1.0 micrometer thick, is further deposited. A set of conductors 65 arranged in columns, such conductors being typically made of molybdenum, are then deposited on layer 64. Conductors 65 in a preferred embodiment are typically on the order of 0.2 micrometers thick. At each cathode 68 an opening, or hole 67 which in a preferred embodiment may be circular and have a diameter in the order of 2.0 micrometers is etched into conductors 65 and film 64 so as to provide a suitable aperture in conductors 65 and to remove a portion of the aluminum oxide film 64 in the region immediately beneath such aperture. A cone 66 of molybdenum is deposited on conductors 63 within the etched hole as shown. A voltage potential in the range of 50 to 500 volts between conductor 65 and conductor 63, with conductor 65 being positive relative to conductor 63, produces an electron flow from the field emission point of cone 66. Electrons flow through opening 67 and are further accelerated to the phosphor anode screen structure at the other end of channels 23.

In operation, the horizontal conductors 63 are sequentially switched synchronously with the transmitted picture information to a threshold voltage potential for electron emission from the field emission points of cones 66. Additional modulation voltage potentials are sequentially applied to the conductors 65 synchronously and in accordance with the luminance (and chrominance) content of the transmitted picture information.

In an alternative arrangement of the embodiment in FIG. 10, an additional apertured electrode, similar to thc apertured grid electrodes shown in FIGS. 6 and 9, may be situated between field emission cathodes 68 and the anode/phosphor screen structure in the neighborhood of cathodes 68. Such apertured electrode may be held at a positive voltage potential in the range from about 50 to about 500 volts, a primary purpose of such electrode being to isolate the somewhat critical field emission cathodes from variations in the anode potential and to prevent possible charge accumulation on the adjacent insulator.

FIGS. 4-11 have described various embodiments of the cathode structures and FIGS. l2 and 13 are now used to show a portion of the switching circuitry utilized to operate such previously described structures. The circuitry of FIG. 12 is depicted as used with the cathode structure of FIG. 4, for example, and in FIG. 12 the vertical conductors 26 and horizontal conductors 27 of thin film cathodes 30 are shown. For line sequencing each horizontal conductor 27 is connected to one of a plurality of semiconductor switches, such as 69a 69b 69e` and each trio of semiconductor switches is connected to a single terminal point. For example, switches 69a, and 69b and 69t` are each connected to terminal point 70a and subsequent trios of switches are connected to terminals 70b, 70C, etc. The tenninals 70a, 70b, 70C, etc. are sequentially switched in synchronism with the transmitted picture information through additional semiconductor switches (not shown) to a voltage potential providing the threshold voltage for electron emission from thin-film cathodes 30. In alternate frames, either all the switches 69h or all the switches 69a` are held open thereby preventing emission from the connected cathodes 30 and providing for the interlacing of alternate frames. In either state switches 69a remain closed in such interlacing process. Although switches 69a may be omitted they are preferably included to provide matched impedance elements in the switching circuitry associated with each of the conductors 27.

One conductor of each trio of adjacent vertical conductors 26 is connected as shown to one of a trio of transistors 71a, 7lb and 71C which may be, for example, well-known metal oxide semiconductor field effect transistors, although other switching or modulating semiconductor devices may a|ternatively be used. All gates of transistors 71a are connected together to a terminal 72a. Similarly, all gates of transistors 71b are connected to terminal 72b and all gates of transistors 71C are connected to terminal 72C. Chrominance signals are applied to the terminals 72a, 72b and 72C. The emitters of transistors 71a, 7lb and 71C are connected as shown to the collectors of another set of transistors 73a, 73b, and 73L` arranged in sets of three as shown. The emitters of all transistors 73 are connected together via terminal 74 to a common voltage potential which is positive relative to that which is switchably applied to terminals 70a, 70b, 70C, etc. The gates of transistors 73a 73band 73C are connected together in triplets as shown to

terminals

75a, 75b and 75e. Normallyl transistors 73 are nonconducting. A signal proportional to the luminance content of the transmitted picture is sequentially applied in synchronism with the transmitted picture information to

terminals

75a, 75b, 75C, etc., causing each of the sets of transistors 73a, 73b, 73C, etc. to conduct in turn. This current flow is divided through transistors 72a, 72b, and 72C, etc. in accordance with the chrominance signal applied to the gates of those transistors.

The arrangement of FIG. l2, though somewhat complex with respect to the switching circuitry, is utilized to minimize the total number of cathode structures required in the array of emitting structures utilized in the invention while at the same time retaining the full transmitted picture definition. As presently envisioned with respect to the known state of the art relative to the elements utilized in the invention, such arrangement appears to give the greatest overall economy.

A simpler arrangement of switching circuitry is shown in FIG. 13, such arrangement requiring somewhat more cathode structures than that shown in FIG. 12. In the modulation sequencing switching arrangement of FIG. 13 each triplet of transistors 73a, 73b and 73e of FIG. 12 is replaced by a single transistor 76a, 76b, 76C, etc. the collectors of which are connected as shown to transistors 71a, 7Ib and 71C. The emitters of transistors 76 are connected together and to terminal 74 while the gates of transistors 76a, 76h, 76e, etc. are connected to the

modulating terminals

75a, 75b, 75C, etc. Closer inspection of FIGS. l2 and 13 shows that approximately 50 percent more vertical conductors 26 are required for the switching circuitry of FIG. 13 than for that shown in FIG. l2.

In FIG. 13 an alternative arrangement for the line sequencing is also shown with respect to the horizontal conductors 27. Each conductor 27 is connected to a separate switching transistor 79 and through it only to one of the terminals 70a, 70b, 70C, etc. The operation of switching transistors 79 for providing the interlacing of alternate frames is substantially the same as that described with reference to switching transistors 69 in FIG. I2. The degree of overlap between adjacent lines of succeeding frames is thereby reduced at the expense of an additional 50 percent more conductors 27. Therefore, for FIG. 13 approximately 125 percent more cathode structures 30 are required than for FIG. l2. The line sequencing arrangement of FIG. l2 may alternatively be used with the modulation sequencing arrangement of FIG. 13 and vice versa. Moreover, the alternative overall sequencing arrangements shown and discussed above with reference to both figures may be used also with each of the different cathode structures, such as are shown in FIGS. 8, 9 and l0.

As discussed above, particular embodiments of the invention may employ multidielectn'c, or other type, filters 36 discussed above as being optionally useful and shown in the anode portions of the display device of FIGS. 4, 6, 7, 8, 9 and l0. Such embodiments are particularly adaptable to stereoscopic display presentation. The principles of such stereoscopic displays are explained with reference to FIGS. 14, l and 16 and, although described in relation to the particuiar embodiments of the invention discussed above, such principles are also adaptable to other forms of television display devices, including conventional cathode-ray tubes.

FIG. 14 is a representation of the visible spectrum indicating visibility as a function of wavelength. ln such figure, the visible spectrum 80 is arbitrarily divided into six regions labeled RR, RR, GR, GR, BR, and BR. Each filter of the array of filters 36 is arranged either to transmit one of these six regions of the spectrum or the complete red, green, and blue portions, (RR RR), (GR GR), and (BR BR), respectively, of the spectrum in a manner to be described in conjunction with FIG. 15, for example. FIG. l5 is a schematic representation of the display screen ofa display device of the invention, or other conventional cathode-ray tube, with the transmission band of the filter associated with each area element of the screen indicated by the appropriate reference letters. In the figure, R indicates that the filter transmits the complete red portion (RR RR), G indicates transmission of the complete green portion (GR GB) and B indicates transmission of the complete blue portion (BR BR). With reference to FIG. 12 it will be observed that in the line sequencing switching arrangement the lines are scanned in pairs. In FIG. 15 a line pair arbitrarily designated as lines L1 scans over the filters RB, GR, and BR as well as the set of filters immediately above them identified as R, B, and G. Line pair L2 scans over the filters RR, GR, and BR and the filters R, B, and G immediately above it. Similarly, alternate frame line pair ALI scans over filters RR, GR, and BR and the filters R, B, and G immediately below it, while alternate frame line pair AL2 scans over the filters RR, GR, and BR and the filters R, B, and G immediately below it. When line pairs denoted by odd numbers (i.e., L1, L3, etc. and ALl, AL3, etc.) are taken from one camera and the line pairs denoted by even numbers (i.e., L2, L4, etc. and AL2, AL4, etc.) are taken from an adjacent camera focused on the same scene, stereoscopic information is conveyed to the viewer in the display. The stereoscopic scene is viewed through filters RR, GR, and BR for the one eye and filters RR, GR, and BR for the other eye. Preferably a neutral filter of approximately 50 percent light attenuation is associated with each of the filters R, G, and B on the display tube so that the light flux transmitted through them is approximately equal to that through the filters, RR, GH, BR, RR, GR, and BR. Such an arrangement makes the stereoscopic light flux dominant when the display is 5 observed through the appropriate filters and the light flux uniform when the display is directly observed. Thus, this stereoscopic system is compatible with existing monochrome and color transmission systems and standards.

The arrangement of FIG. 15 in conjunction with the switching circuitry shown in FIG. l2 minimizes the number of elements required in the display tube. Alternative arrangements requiring more picture tube elements may also be devised. One example thereof is given in FIG. 16 wherein line l5 pairs L1, L2, etc. and alternating frame line pairs ALI, AL2,

etc. scan only filters RR, GR, BR for the odd numeral lines i.e., Lll, L3, etc. and ALl, AL3, etc.) and only RR, GR, BR for the even numbered lines (i.e., L2, L4, etc. and AL2, AL4, etc.) The circuitry of FIG. 13 may be used in conjunction with the 20 display arrangement of FIG. 16. Other alternative arrangements may occur to those in the art wherein, for example, the optical spectrum is divided into more than six regions, such as an arrangement utilizing nine arbitrarily divided regions, each color being divided into three regions, the outer portions of which are scanned for presentation to one eye and the central portion of which is scanned for presentation to the other eye.

The invention, therefore, is not to be construed as limited to the particular embodiments described herein except as defined by the appended claims.

What is claimed is:

1. A display device comprising a two-dimensional array of charged-particle emitting sources;

a screen member responsive to the impingement of charged sources is in register so as to produce an image on said screen member.

2. A display device in accordance with claim l wherein said charged particles are electrons and said screen member is luminescent.

0 3. A display device in accordance with claim 2 wherein said supporting means includes an insulative lattice structure disposed between said array of sources and said screen member for producing an array of channels, at least one emitting source being oppositely disposed at one end of each said channels in register with a selected area element of said luminescent screen member at the other end of said channel.

4. A display device in accordance with claim 2 wherein each of said emitting sources is a thin-film device which comprises a first conductor deposited on an insulating base;

an insulating layer deposited on said base and on said first conductor;

a second conductor being deposited on said insulating layer at a region thereof opposite said first conductor; and

6 5 means for providing a voltage potential across said first and second conductors thereby causing electrons to be emitted from said thin-film device.

5. A display device in accordance with claim 4 wherein said first conductor is aluminum, said second conductor is gold,

and said insulating layer is silicon dioxide.

6. A display device in accordance with claim 4 wherein said insulating layer between said first conductor and the region of said second conductor opposite thereto has a thickness within the range from approximately 0.03

micrometers to 0.3 micrometers; and

the region of said second conductor opposite said first conductor has a thickness within the range from approximately 0.01 micrometers to 0.1 micrometers.

7. A display device in accordance with claim 4 wherein the thickness of said insulating layer in the region between said first conductor and the region of said second conductor opposite thereto has a thickness of approximately 0.1 micrometer; and

said voltage potential is approximately 200 volts.

8. A display device in accordance with claim 2 wherein each of said emitting sources comprises a first conductor deposited on an insulator base;

a film of semiconductor compound deposited over a first portion of said first conductor;

a second conductor deposited on and projecting from a second portion of said first conductor adjacent said semiconductor film;

a third conductor deposited on a portion of said semiconductor compound; and

means for supplying operating voltage potentials to said conductors for causing electrons to be emitted from said emitting source.

9. A display device in accordance with claim 8 wherein said first, second and third conductors are formed of material taken from the group consisting of gold, silver and aluminum; and

said film of semiconductor compound is formed of tin oxide.

l0. A display device in accordance with claim 8 wherein said voltage potential supplying means includes means for supplying a voltage potential between said first and said second conductor of approximately 200 volts; and

means for supplying a modulating voltage potential to said third conductor.

ll. A display device in accordance with claim 2 wherein each of' said emitting sources comprises a metal film having optically reflective characteristics deposited on an insulator base;

a first layer of transparent high-temperature insulating material deposited on said reflective film;

a thin-film heater element deposited on a portion of said high-temperature insulating layer;

interconnecting means deposited on said insulating layer for connecting the thin-film heater elements of each of said emitting sources in series in rows upon said first high-temperature insulating layer;

a second layer of high-temperature insulating material deposited on said heaters and said heater interconnec` tions;

a low work function cathode material deposited on a portion of said second high temperature insulating layer at a region opposite each of said thin-film heater elements;

means for supplying a heater voltage potential to said thin film heater elements to heat said elements to a temperature approximately at or below the threshold temperature required for significant emission of electrons, and

means for supplying a modulating voltage potential to said low work function cathode material for causing electrons to be emitted from said emitting source.

l2. A display device in accordance with claim l1 wherein said first layer of transparent high-temperature insulating material is chosen to provide maximum transparency in the red and infrared portions of the frequency spectrum.

13. A display device in accordance with claim l2 wherein said first and second layers of high-temperature insulating material are aluminum oxide;

Said thin-film heater elements are made of a material taken from the class consisting of carbon and tungsten; and

said low work function cathode material is lanthanum hexaboride.

14. A display device in accordance with claim ll and further including a layer of carbon is deposited between said second insulating layer and said low work function material to prevent chemical reaction between said layer and said material and to provide maximum radiatron absorption from said thin-film heater elements.

l5. A display device in accordance with claim ll and further including an apertured grid structure mounted adjacent said emitting source whereby electrons emitted from said source pass through the aperture of said grid structure.

16. A display device in accordance with claim l5 and further including means for supplying a substantially constant voltage potential to said thin-film heater element whereby said emitting sources are elevated to a temperature approximately at or below the threshold temperature required for significant electron emission; and

means for supplying a modulating voltage potential to said low work cathode material to cause electrons to be emitted from said emitting source to pass through the aperture of said grid structure.

17. A display device in accordance with claim 2 wherein each of said emitting sources comprises a first layer of insulative material deposited on an insulator base;

a first conductor deposited on a portion of said first insulative layer;

a second layer of insulative material deposited on said first conductor and on a portion of said first insulative layer;

a second conductor forming a layer deposited on said second layer of insulative material;

an opening etched in said second conductor and said second layer of insulative material at a region opposite said first conductor whereby at least a portion of said first cond uctor is thereby exposed;

a third conductor forming a cone of conductive material deposited on said first conductor in said exposed region thereof, the apex of said cone thereby forming a field emission point; and

means for supplying operating voltage potentials to said first, second and third conductors for causing electron emission from said emitting source.

18. A display device in accordance with claim 17 wherein said first and second layers of insulating material are aluminum oxide; and

said first, second and third conductors are molybdenum.

19. A display device in accordance with claim 17 wherein said rst conductor is approximately 0.2 micrometers thick;

said second layer of insulating material is approximately 1.0

micrometers thick;

said second conductor layer is approximately 0.2 micrometers thick; and

said etched opening is circular and has a diameter of approximately 2.0 micrometers.

20. A display device in accordance with claim 17 wherein said operating voltage potential supplying means includes means for supplying a voltage potential between said second and said first conductor the value of which is in the range from approximately 50 volts to approximately 500 volts, the potential at said second conductor being positive relative to that of said first conductor, whereby electrons are caused to flow from said field emission point of said conductor cone through said etched opening.

2l. A display device in accordance with claim 17 wherein said operating voltage potential supplying means includes means for providing a voltage potential to said first conductor to maintain said emitting source at a threshold voltage for electron emission from said field emission point of said conductor cone; and

means for supplying a modulation voltage potential to said second conductor.

22. A display device in accordance with claim 17 and further including an apeitured electrode mounted adjacent said electronemitting source between said source and said screen member;

means for supplying a positive voltage potential the value of which is in the range from approximately 50 volts to ap proximately 500 volts to said apertured electrode for isolating said emitting source from said screen member and for preventing charge accumulation on said second insulating layer. 23. A display device in accordance with claim 4 and further including a first apertured grid structure mounted adjacent said emitting source between said source and said screen member the aperture of said grid structure being opposite said emitting source.

24. A display device in accordance with claim 23 and further including a second apertured grid structure mounted adjacent said first apertured grid structure between said first grid structure and said screen member, the aperture of said second grid structure being opposite the aperture of said first grid structure.

25. A display device in accordance with claim 8 and further including a first apertured grid structure mounted adjacent said emitting source between said source and said screen member the aperture of said grid structure being opposite said emitting source.

26. A display device in accordance with claim 25 and further including a second apertured grid structure mounted adjacent said first apertured grid structure between said first grid structure and said screen member, the aperture of said second grid structure being opposite to the aperture of said first grid structure.

27. A display device in accordance with claim 2 wherein said luminescent screen member has a height h and a width w and the distance from said emitting source to said screen member is substantially less than said width w of said screen member.

28. A display device in accordance with claim 27 wherein said distance is approximately one-tenth of said width w 29. A display device in accordance with claim 4 and adapted for displaying a color image wherein said controlling means for sequentially controlling electron emission includes line and frame sequencing control means comprising first switching means connected to a line voltage potential for switchably applying said line voltage potential to adjacent pairs of said first conductors of said emitting sources in a controlled sequence during a first plurality of frames and for applying said line voltage potential to interlaced adjacent pairs of said first conductors during a second plurality of alternate frames; and

modulation sequencing control means comprising a plurality of second switching means each connected to a second conductor of'said emitting sources;

third switching means connected to said second switching means for controlling the operation of said second switching means in response to a luminance signal whereby said luminance signal is sequentially switched to adjacent groups of three switches of said second switch means;

means for applying chrominance signals to said second switching means in synchronism with said sequentially applied luminance signals;

whereby the operation of said line sequencing control means and said modulation sequencing control means provides for the luminescence of said area elements of said screen member to produce a color image.

30. A display device in accordance with claim 29 wherein each of said switching means comprises semiconductor switching elements.

3l. A display device in accordance with claim l wherein said screen member includes an array of optical filter means, one of each of said optical filter means positioned adjacent to one of each said area elements, whereby each said area element is adapted to transmit a selected color portion of the optical spectrum, said area elements thereby being caused to transmit said selected color portions sequentially to produce said 32|.migdeisplay device in accordance with claim 3l wherein alternate lines of said area elements are adapted to transmit the complete red, green and blue portions of the optical spectrum in sequence across the width of said screen member; and

intermediate lines are adapted to transmit selected regions of said complete red, green, and blue portions of said optical spectrum. 33. A display device in accordance with claim 32 and further including a plurality of neutral filters mounted adjacent each of those filters which are adapted to transmit the complete red, blue and green portions of the optical spectrum, said neutral filters arranged to provide approximately 50 percent attenuation of the optical signal transmitted there through.

34. A display device in accordance with claim 3l wherein alternate lines of said area elements are adapted to transmit first selected regions of said complete red, green and blue portions 0f` said optical spectrum; and

intermediate lines are adapted to transmit second selected regions of said complete red, green, and blue portions of said optical spectrum.

ik Ik

Claims

1. A display device comprising a two-dimensional array of charged-particle emitting sources; a screen member responsive to the impingement of charged particles thereon for producing an image; means for insulatively supporting said array and said screen member opposite each other so that each of said charged particle emitting sources is in register with a selected area element of said screen member; and means for sequentially controlling the emission of charged particles from said emitting sources whereby said emitted charged particles sequentially impinge upon said area elements of said screen member with which each of said sources is in register so as to produce an image on said screen member.

2. A display device in accordance with claim 1 wherein said charged particles are electrons and said screen member is luminescent.

3. A display device in accordance with claim 2 wherein said supporting means includes an insulative lattice structure disposed between said array of sources and said screen member for producing an array of channels, at least one emitting source being oppositely disposed at one end of each said channels in register with a selected area element of said luminescent screen member at the other end of said channel.

4. A display device in accordance with claim 2 wherein each of said emitting sources is a thin-film device which comprises a first conductor deposited on an insulating base; an insulating layer deposited on said base and on said first conductor; a second conductor being deposited on said insulating layer at a region thereof opposite said first conductor; and means for providing a voltage potential across said first and second conductors thereby causing electrons to be emitted from said thin-film device.

5. A display device in accordance with claim 4 wherein said first conductor is aluminum, said second conductor is gold, and said insulating layer is silicon dioxide.

6. A display device in accordance with claim 4 wherein said insulating layer between said first conductor and the region of said second conductor opposite thereto has a thickness within the range from approximately 0.03 micrometers to 0.3 micrometers; and the region of said second conductor opposite said first conductor has a thickness within the range from approximately 0.01 micrometers to 0.1 micrometers.

7. A display device in accordance with claim 4 wherein the thickness of said insulating layer in the region between said first conductor and the region of said second conductor opposite thereto has a thickness of approximately 0.1 micrometer; and said voltage potential is approximately 200 volts.

8. A display device in accordance with claim 2 wherein each of said emitting sources comprises a first conductor deposited on an insulator base; a film of semiconductor compound deposited over a first portion of said first conductor; a second conductor deposited on and projecting from a second portion of said first conductor adjacent said semiconductor film; a third conductor deposited on a portion of said semiconductor compound; and means for supplying operating voltage potentials to said conductors for causing electrons to be emitted from said emitting source.

9. A display device in accordance with claim 8 wherein said first, second and third conductors are formed of material taken from the group consisting of gold, silver and aluminum; and said film of semiconductor compound is formed of tin oxide.

10. A display device in accordance with claim 8 wherein said voltage potential supplying means includes means for supplying a voltage potential between said first and said second conductor of approximately 200 volts; and means for supplying a modulating voltage potential to said third conductor.

11. A display device in accordance with claim 2 wherein each of said emitting sources comprises a metal film having optically reflective characteristics deposited on an insulator base; a first layer of transparent high-temperature insulating material deposited on said reflective film; a thin-film heater element deposited on a portion of said high-temperature insulating layer; interconnecting means deposited on said insulating layer for connecting the thin-film heater elements of each of said emitting sources in series in rows upon said first high-temperature insulating layer; a second layer of high-temperature insulating material deposited on said heaters and said heater interconnections; a low work function cathode material deposited on a portion of said second high temperature insulating layer at a region opposite each of said thin-film heater elements; means for supplying a heater voltage potential to said thin film heater elements to heat said elements to a temperature approximately at or below the threshold temperature required for significant emission of electrons, and means for supplying a modulating voltage potential to said low work function cathode material for causing electrons to be emitted from said emitting source.

12. A display device in accordance with claim 11 wherein said first layer of transparent high-temperature insulating material is chosen to provide maximum transparency in the red and infrared portions of the frequency spectrum.

13. A display device in accordance with claim 12 wherein said first and second layers of high-temperature insulating material are aluMinum oxide; Said thin-film heater elements are made of a material taken from the class consisting of carbon and tungsten; and said low work function cathode material is lanthanum hexaboride.

14. A display device in accordance with claim 11 and further including a layer of carbon is deposited between said second insulating layer and said low work function material to prevent chemical reaction between said layer and said material and to provide maximum radiatron absorption from said thin-film heater elements.

15. A display device in accordance with claim 11 and further including an apertured grid structure mounted adjacent said emitting source whereby electrons emitted from said source pass through the aperture of said grid structure.

16. A display device in accordance with claim 15 and further including means for supplying a substantially constant voltage potential to said thin-film heater element whereby said emitting sources are elevated to a temperature approximately at or below the threshold temperature required for significant electron emission; and means for supplying a modulating voltage potential to said low work cathode material to cause electrons to be emitted from said emitting source to pass through the aperture of said grid structure.

17. A display device in accordance with claim 2 wherein each of said emitting sources comprises a first layer of insulative material deposited on an insulator base; a first conductor deposited on a portion of said first insulative layer; a second layer of insulative material deposited on said first conductor and on a portion of said first insulative layer; a second conductor forming a layer deposited on said second layer of insulative material; an opening etched in said second conductor and said second layer of insulative material at a region opposite said first conductor whereby at least a portion of said first conductor is thereby exposed; a third conductor forming a cone of conductive material deposited on said first conductor in said exposed region thereof, the apex of said cone thereby forming a field emission point; and means for supplying operating voltage potentials to said first, second and third conductors for causing electron emission from said emitting source.

18. A display device in accordance with claim 17 wherein said first and second layers of insulating material are aluminum oxide; and said first, second and third conductors are molybdenum.

19. A display device in accordance with claim 17 wherein said first conductor is approximately 0.2 micrometers thick; said second layer of insulating material is approximately 1.0 micrometers thick; said second conductor layer is approximately 0.2 micrometers thick; and said etched opening is circular and has a diameter of approximately 2.0 micrometers.

21. A display device in accordance with claim 17 wherein said operating voltage potential supplying means includes means for providing a voltage potential to said first conductor to maintain said emitting source at a threshold voltage for electron emission from said field emission point of said conductor cone; and means for supplying a modulation voltage potential to said second conductor.

22. A display device in accordance with claim 17 and further including an apertured electrode mounted adjacent said electron-emitting source between said source and said screen member; means for supplying a positive voltage potential the value of which is in the range from approximately 50 volts to approximately 500 volts to said apertured electrode for isolating said emitting source from said screen member and for preventing charge accumulation on said second insulating layer.

23. A display device in accordance with claim 4 and further including a first apertured grid structure mounted adjacent said emitting source between said source and said screen member the aperture of said grid structure being opposite said emitting source.

27. A display device in accordance with claim 2 wherein said luminescent screen member has a height h and a width w; and the distance from said emitting source to said screen member is substantially less than said width w of said screen member.

28. A display device in accordance with claim 27 wherein said distance is approximately one-tenth of said width w.

29. A display device in accordance with claim 4 and adapted for displaying a color image wherein said controlling means for sequentially controlling electron emission includes line and frame sequencing control means comprising first switching means connected to a line voltage potential for switchably applying said line voltage potential to adjacent pairs of said first conductors of said emitting sources in a controlled sequence during a first plurality of frames and for applying said line voltage potential to interlaced adjacent pairs of said first conductors during a second plurality of alternate frames; and modulation sequencing control means comprising a plurality of second switching means each connected to a second conductor of said emitting sources; third switching means connected to said second switching means for controlling the operation of said second switching means in response to a luminance signal whereby said luminance signal is sequentially switched to adjacent groups of three switches of said second switch means; means for applying chrominance signals to said second switching means in synchronism with said sequentially applied luminance signals; whereby the operation of said line sequencing control means and said modulation sequencing control means provides for the luminescence of said area elements of said screen member to produce a color image.

31. A display device in accordance with claim 1 wherein said screen member includes an array of optical filter means, one of each of said optical filter means positioned adjacent to one of each said area elements, whereby each said area element is adapted to transmit a selected color portion of the optical spectrum, said area elements thereby being caused to transmit said selected color portions sequentially to produce said image.

32. A display device in accordance with claim 31 wherein alternate lines of said area elements are adapted to transmit the complete red, green and blue portions of the optical spectrum in sequence across the width of said screen member; and intermediate lines are adapted to transmit selected regions of said complete red, green, and blue portions of said optical spectrum.

33. A display device in accordance with claim 32 and further including a plurality of neutral filters mounted adjacent each of those filters which are adapted to transmit the complete red, blue and green portions of the optical spectrum, said neutral filters arranged to provide approximately 50 percent attenuation of the optical signal transmitted there through.

34. A display device in accordance with claim 31 wherein alternate lines of said area elements are adapted to transmit first selected regions of said complete red, green and blue portions of said optical spectrum; and intermediate lines are adapted to transmit second selected regions of said complete red, green, and blue portions of said optical spectrum.