Abstract:
A video display system utilizing a video source and an image intensifier having a substrate. A video image source positions at the substrate to provide a photon signal. A photocathode element at the substrate converts the photon signal into electrons. An optically transparent body having first and second surfaces is placed opposite the substrate spaced therefrom. A vacuum chamber is formed between the substrate and the first surface of the second optically transparent body. A fluorescing layer is positioned on said first surface of the second optically transparent body. A source of electrical power provides a voltage potential between the photocathode layer and said fluorescing layer. The intensified video image exits the second surface of the second optically transparent body for viewing.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation-in-part application of U.S. application Ser. No. 08/377,282, Filed Jan. 23, 1995, now is U.S. Pat. No. 5,543,862. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a novel and useful video display system. 
     Presently, producing video images is chiefly accomplished by the use of a cathode ray tube. Although successful in many aspects of the video technology, cathode ray tubes possess a number of disadvantages in that cathode ray tubes are not easily scaled upwardly in size. This is due to the fact that the weight of the vacuum tube becomes unmanageable with an increase in size, commensurate with a large increase in the cost of manufacture. However, cathode ray tubes produce a very high quality video image, via the fluorescing or phosphor display. Moreover, cathode ray tubes exhibit high brightness, speed, contrast, resolution, and color purity. 
     Liquid crystal displays (LCD) are lightweight and are capable of producing a video image on a flat screen. Unfortunately, the LCD technology produces a video image of low brightness, low efficiency, and low color purity, which has been described as a “washed-out” look. In addition, the LCD video image possesses low resolution and is not susceptible to wide-angle viewing since the Lambertian effect is not inherent in LCD displays. Moreover, LCDs are slow to display an image and are not cost effective. 
     Image intensifiers have been proposed such as that found in U.S. Pat. No. 5,029,009 where light is passed through a lens to focus the same onto a substrate having an array of gating electrodes, mounted thereupon. An electrode array and substrate are transparent to light in order to allow the light to pass to a photocathode. Thus, adaptive range gating is accomplished using a single imaging camera. 
     U.S. Pat. No. 3,864,595 describes an image intensifier tube having a photocathode element which converts incident radiation into corresponding electron images. A microchannel plate multiplies the electron image and sends the same to a phosphor screen to convert the electron image to a corresponding radiation image for viewing. The electron image is easily turned “on” and “off” by selectively applying a gating signal to the photocathode element. 
     U.S. Pat. No. 4,142,123 describes an image display device utilizing a photocathode, multiplier diodes, and an anode electrode in a cathode luminescent screen. The anode electrode is constructed of a material which exhibits slow fluorescence to permit emission of light energy after excitation has ceased. Electrons created in the discharge strike of the anode electrode are directed to the photocathode where they are converted into free electrons. Rapid initiation of subsequent electrical discharges is ensured by such free electrons. 
     U.S. Pat. No. 5,160,565 describes an image intensifier utilizing a fiber optic bundle which receives an image at one end and produces an intensified image at the other end of the bundle. 
     U.S. Pat. No. 3,742,285 teaches an image intensifier display system where a display tube having a fiber optic input window includes an electron emitting surface. Electrons impinge on a display window of larger diameter having a phosphor coated surface to provide a magnified image of a scene being viewed. 
     U.S. Pat. No. 4,694,171 describes an electron microscope imaging system which employs an image intensifier which receives light emitted from an image that is excited by an electron beam. 
     U.S. Pat. No. 4,213,055 shows an image intensifier tube which utilizes an entrance detection screen mounted in an envelope adjacent to an entrance window. An electron optical system also mounted in the envelope images electrons which pass to an exit screen in the envelope, resulting in a viewable video image. 
     U.S. Pat. No. 4,974,089 teaches a television camera in which an index rod lens is employed to relay a light image from an image intensifier to a filter which is coupled to a focal plane array assembly. 
     U.S. Pat. No. 3,757,351 illustrates an electrostatic printing system where light is reflected from a document, passed through a lens, and intensified by a container having a photocathode placed on a glass substrate. The cathode converts the photon image to an electron image which then passes through a microchannel plate and sends the image to a dielectric target in the form of an electro static charge. The electro static charge is then used to print a document. 
     A video display system which is capable of intensifying an image from a video source accurately and efficiently to produce a video display of very high quality would be a notable advance in the electronics field. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a novel and useful video display system is herein provided. 
     The video display system of the present invention utilizes a video image source which may take the form of a photocathode ray tube combined with an enlarging or focusing lens, a liquid crystal projector, and the like. Video image source may be monochromatic or simple non-color source. In addition, the video source may include video position data in the form of columns or rows, simple video intensity data, or a combination of any of these. 
     The display system of the present invention also includes an image intensifier unto which the video image source is remotely projected or is transferred by close coupling. In the former case, projection may be accomplished by employing a cathode ray tube as the video image source. In addition, projecting of the video image may take place by employing a liquid crystal display spacial light modulator combined with a point source of light. Any other suitable projecting arrangement may be employed herewith. 
     The video intensifier of the system of the present invention may be constructed with a first optically transparent body or panel which may be constructed of glass, crystalline material, or any other suitable transparent substance. The optically transparent body would include a first side and a second side. The video image source would be delivered to the first side of the optically transparent body either by projecting the same or through close coupling. 
     A photocathode layer is placed or positioned on the second side of the first optically transparent body. The photocathode layer may be constructed of any material which will convert photons to electrons. For example, multi-alkali type material such as a sodium, potassium, antimony, cesium compounds, a cesium silver oxide compound, and the like. 
     Alternately, the photon signal may be converted into electrons by providing a substrate in association with a video image source. The substrate may be an optically opaque body. Photocathode elements or a photocathode layer are formed adjacent the video image source for converting the photon signal of the video image source to electrons. This arrangement may also include photon baffles and channel multipliers, which eliminates the need for metallic coating on the fluorescing layer. 
     The image intensifier is also provided with a second optically transparent body which may be of the same structure as the first optically transparent body. Of course, the second optically transparent body may comprise the sole optically transparent body when used with the opaque substrate. Likewise, the second optically transparent body possesses a first side and a second side. 
     A fluorescent layer, which may be a phosphor material, is positioned on the first side of the second optically transparent body. The fluorescing material forming the fluorescing layer is capable of transforming electrons, emanating from the photocathode layer positioned on the second side of the first optically transparent body or from the photocathode elements adjacent the video image source, into photons. Photons are then transmitted through the second optically transparent body for viewing. The fluorescing layer may be in the form of phosphor dots and include a protecting layer of metallic material, such as aluminum, to prevent photons from returning to the photocathode layer on the second side of the first optically transparent body. Although the image viewed on the second side of the second optically transparent body may be monochromatic, a suitably addressed color fluorescing type material on the first side of the second optically transparent body would create a color image employing methods known in the prior art. The aluminum layer on the second optically transparent body is not necessary where baffles and channel multipliers are employed with the photocathode elements and an opaque substrate. 
     Chamber means is also provided for forming a vacuum enclosure between the second side of the first optically transparent body and the first side of the second optically transparent body. Thus, electrons emanating from the photocathode layer may easily accelerate in the vacuum enclosure formed between the first and second optically transparent bodies. An insulating matrix may be employed to strengthen or reinforce the vacuum enclosure space to prevent collapse of the same under high vacuums. A seal would also be employed around the periphery of the vacuum enclosure as a portion of the chamber means. Such seal may be in the form of a frit seal. 
     A source of electrical power is also found in the present invention for applying a voltage potential between the photocathode layer of the first optically transparent body and the phosphor layer of the second optically transparent body. By this arrangement, the photocathode layer which serves as a cathode while the fluorescing or phosphor would serve as an anode. Such potential would intensify or provide a gain between the photocathode layer and the fluorescing layer. Moreover, grids or screens having a certain potential may be placed within the vacuum chamber and may be biased electrically to further influence electrons originating at the photocathode layer. A lesser amount of potential is required of the source of electrical power with the embodiment of the present invention using photocathode elements and an opaque substrate. 
     A color image viewed on the second side of the second optically transparent body may be obtained by projecting a color cathode ray tube image onto the first side of the first optically transparent body through a lens. The first side of the optically transparent body would include a plurality of color filters which would generate color image data of a particular hue at the photocathode layer found on the second side of the first optically transparent body. In addition, the fluorescing layer would include an array of fluorescing zones, each possessing the ability to stimulate the emission of a particular color therefrom. Thus, a color image would be derived from the second side of the second optically transparent body of greatly increased intensity. Of course, the color of such image would be commensurate with the color arrangement of the cathode ray tube, which is projected on the video intensifier. 
     In addition, a color image may be generated at the second side of the second optically transparent body using color data from a plurality of mono-chromatic cathode ray tubes and lenses. Thus, for example, red, blue and green data would be sent to the first side of the first optically transparent body of the image intensifier. An aperture mask would be placed on the first side of the image intensifier to intercept the distinct color data in order to separate the particular color rays at the photocathode layer on the second side of the first optically transparent body. At this point, color zones would be excited on the fluorescing layer on the first side of the second optically transparent body to produce the color image at the second side of the second optically transparent body. 
     Further, a monochrome system may be used with registration of input pixels on the photocathode layer to output pixels from the fluorescing layer of the image intensifier. Color data would necessarily be assigned to one third of the pixels for each color of a three color system. 
     Moreover, a hybrid system may be employed in which lines, columns or matrixes of photocathodes are optically addressed on the second side of the first optically transparent body. However, the current through the cathode, i.e., the photocathode layer, is modulated using triode biasing techniques. In the hybrid design, the image intensifier is merged with a “cold cathode” field emission design to obtain the best features of each. 
     Such hybrid designs permit the turning on of a line of photocathodes with optical excitation one line at a time, and then biasing those elements one column at a time using control grids placed in the vacuum enclosure of the image intensifier of the present invention. In addition, a row of discrete photocathodes may be excited and modulated with respect to potential column-wise, using electrodes perpendicular to a large area grounded grid. In essence, column and row addressing lines of photocathodes by optical means, coupled with electronic biasing produces the desired result, in this aspect of the present invention. 
     It may be apparent that a novel and useful video display system has been described. 
     It is therefore an object of the present invention to provide a video display system which would employ a remote or close coupled video image source with a video image intensifier to produce a viewable image of high brightness and high resolution. 
     Another object of the present invention is to provide a video display system that operates at high efficiency and is capable of outputting a video image which is monochromatic or color with excellent color purity. 
     A further object of the present invention is to provide a video display system which is lightweight and may be formed into a viewing screen of minimal depth. 
     A further object of the present invention is to provide a video display system which is capable of intensifying a monochrome video image of low brightness to produce a viewable color image of high brightness. 
     Another object of the present invention is to provide a video display system which is relatively inexpensive to manufacture. 
     A further object of the present invention is to provide a video display system which intensifies a video image from any video source including a source with a restricted viewing angle and produces a video display having wide angle viewing characteristics through a high speed conversion process. 
     Yet another object of the present invention is to provide a video display system which utilizes a video source of low quality and intensifies such video source into a video display of very high quality. 
     Another object of the present invention is to provide a video display system having a photocathode element which function without layer thickness limitations. 
     Another object of the present invention is to provide a video intensifier that obviates the need for a metallic shield on the fluorescing layer. 
     The invention possesses other objects and advantages especially as concerns particular characteristics and features thereof which will become apparent as the specification continues. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic sectional view showing an embodiment of the present invention with the video image source depicted in block diagram. 
     FIG. 2 is a schematic sectional view taken along line  2 — 2  of FIG. 1 depicting another embodiment of the video display system of FIG. 1 utilizing electroluminescent display columns at the photocathode layer and phosphor domains on the fluorescing layer. 
     FIG. 3 is a side view of another embodiment of the present invention in which separating posts are employed in the vacuum gap. 
     FIG. 4 is a sectional view taken along line  4 — 4  of FIG.  3 . 
     FIG. 5 is a schematic view depicting a remote projection version of the present invention using a cathode ray tube as the video image source of the present invention. 
     FIG. 6 is a schematic view of a remote projecting embodiment of the present invention in which a liquid crystal display spacial light modulator is used in conjunction with a point source of light. 
     FIG. 7 is a schematic view depicting close coupling of the video image source to the image intensifier which employs a lambertian back light and a spatial light modulator. 
     FIG. 8 is a magnified view taken along line  8 — 8  of FIG. 7 depicting a column and row pixel video image source in the close coupling arrangement shown in FIG.  7 . 
     FIG. 9 represents a close coupled dynamic video image source in which the pixels are electroluminescent sources. 
     FIG. 10 is a schematic depicting the production of a color video display utilizing a plurality of color filters in conjunction with a plurality of color fluorescing domains. 
     FIG. 11 is a schematic of another embodiment of the present invention used to produce a color video display employing an aperture mask in conjunction with the intensifier depicted in FIG.  1 . 
     FIG. 12 is a sectional view taken along line  12 — 12  of FIG. 11 showing particulars of the aperture mask. 
     FIG. 13 is a elevational view of a hybrid system of the present invention utilizing lines of light in conjunction with ITO pixel strips. 
     FIG. 14 depicts a sectional view of an ITO pixel in conjunction with a photocathode strip employed with a grid to modulate electrons impinging on a fluorescing domain. 
     FIG. 15 is an isometric view of the photocathode strip and ITO strip depicted in FIG. 14 used in conjunction with the fluorescing domain found on a substrate. 
     FIG. 16 is a sectional view showing a photocathode system used in substitution for an FED display. 
     FIG. 17 is a schematic view depicting the possible combinations of optical and electrical data and line select combinations of the present invention. 
     FIG. 18 is a schematic view of ITO electrodes employed on the photocathode layer modulated by an electrical grid to selectively scan one row of color fluorescing domains at a time. 
     FIG. 19 is a graphical representation of quantum efficiency versus wave length depicting the disjointing of the video image source wavelengths from the phosphor emission wavelengths, thus illustrating the elimination of an aluminized coating on the fluorescing layer of the video intensifier where the photocathode layer is sensitive to ultraviolet radiation. 
     FIG. 20 is a schematic view of another embodiment of the system of the present invention. 
     FIG. 21 is a schematic sectional view showing another embodiment of the present invention. 
     FIG. 22 is a schematic sectional view of the substrate, video image source, and photocathode elements of the embodiment of FIG.  21 . 
     FIG. 23 is a sectional view taken along line  3 — 3  of FIG.  2 . 
     FIG. 24 is a schematic sectional view depicting the addition of photon baffle and channel multiplier means to the embodiment of FIG.  21 . 
    
    
     For a better understanding of the invention reference is made to the following detailed description of the preferred embodiments thereof which should be taken in conjunction with the hereinabove described drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is made to the following Detailed Description of the Preferred Embodiments thereof which should be taken in conjunction with the prior described drawings. 
     With respect to FIG. 1, the invention  10  is shown in its broadest format in which a video source  12  is projected onto a video image intensifier  14 . Although depicted schematically in the video display system  10 , the video source  12  may be a cathode ray tube, a liquid crystal display, and the like which would be projected remotely onto the video image intensifier  14 . In addition, the video image source  12  may be closely coupled to the video image intensifier  14 . That is to say, a spacial light modulator or video display, such as an electroluminescent panel, plasma display, or the like may be placed in close contact with the video image intensifier. In addition, the video image source may be formed on the outer surface  16  of the video image intensifier in several ways, which will be discussed hereinafter. In essence, video source  12  may take the form of video position data and/or video intensity data. 
     Referencing FIGS. 1 and 2, image intensifier  14  includes a first optically transparent body  18  having a first side or surface  16  and a second side  20 . The first optically transparent body  18  may be formed of glass, or other suitable crystalline material. Video source image  12  enters video image intensifier  14  through first outer surface  16 , represented by directional arrow  22 . 
     Second optically transparent body  24  includes a first surface  26  and a second opposite surface  28 . Again, second optically transparent body  24  may be formed of the same material as first optically transparent body  18 . Chamber means  30  is also included in the present invention for forming a vacuum space or enclosure  32  between first and second optically transparent bodies  18  and  24 . Chamber means  30  includes peripheral seals, which may be frit seals  34  and  36 . Vacuum enclosure  32  may be formed and sealed by optical bodies  18  and  24 , as well as by seals  34  and  36 , in order to create a relatively high vacuum in enclosure  32 , on the order of 10 −6  to 10 −10  Torr. 
     The video display system  10  also includes as one of its elements, a photocathode layer  38  which is placed on second surface or side  20  of first optically transparent body  18 . Photocathode layer  38  is capable of serving as a cathode for the purposes of emitting electrons through vacuum enclosure  32  upon the receipt of a photon signal from a video source  12 . Photocathode layer  38  may take the form of cesium iodide, a sodium potassium, antimony, cesium compound, a silver cesium oxide compound and the like, which are commonly known in the art. The thickness of photocathode layer  38  has been enlarged for the purposes of emphasis in FIG.  1 . 
     Fluorescing layer  40  is placed on first surface  26  of second optically transparent body  24 . Fluorescing layer  40  may be a phosphor type material which is capable of receiving electrons and transducing the same into photons which would be visible as a video image on second surface  28  of second optically transparent body  24 . Fluorescing layer  40  may be covered by a metallic coating  42  to prevent the return of photons from fluorescing layer  40  into vacuum enclosure  32 . It should be apparent that metallic coating  42  is capable of passing electrons from vacuum enclosure  32  to phosphor or fluorescing layer  42 . Fluorescing layer  40  and metallic coating  42  have likewise been enlarged on FIG. 1, for emphasis. Although depicted in its monochromatic format in FIG. 1, fluorescing layer  40  may include the provision of color video imagery, as will be discussed hereinafter. 
     Source of electrical power  44  places a potential between photocathode layer  38  (the cathode) and fluorescing or phosphor layer  40  (the anode). The effect of such a potential is to greatly accelerate electrons through vacuum enclosure  32  to the speed of approximately 10,000 electron volts. Source of electrical power  44  may be on the order of 1,000 to 10,000 volts. Grids may be placed in vacuum enclosure  32  to further bias the pull of electrons from photocathode layer  38  to fluorescing layer  40 . A typical gain across vacuum enclosure  32  is one hundred or more based on a quantum efficiency of ten to fifty percent of the photocathode layer  38 . Thus, one photon impinging on photocathode layer  38  will induce the emission of ten to several hundred photons at anode fluorescing layer  40 . Although not absolutely necessary, the gain characteristic of the present invention is an important aspect, since the light production efficiency by electrons impacting fluorescing layer  42  is very high, typically 30 to 50 lumens per watt. This level of light production compares favorably with liquid crystal displays (1-5 lumens/watt) electroluminescent displays (1-5 lumens/watt) and other types of displays. By using a low brightness image source  12  and multiplying this source by several hundred times with intensifier  14 , a very high overall efficiency of system  10  is obtained. Also, system  10  is relatively simple and inexpensive to build since an image source of high brightness and efficiency is not required in system  10 . Combined with intensifier  14  a low cost, high brightness, and highly efficient display system  10  results. 
     Turning to FIG. 2, it may be observed that a detail is depicted in which an alternate intensifier embodiment  14 A is shown having identical first and second optically transparent bodies  18  and  24 . The embodiment in FIG. 2 is intended to produce a color image on second surface  28  of second optically transparent body  24 . In this regard, a metallic (aluminum) back electrode layer  46  is depicted on surface  24  of body  18 . Monochromatic electroluminescent phosphor  48  lies between aluminum back electrode  46  and indium tin oxide (ITO) electrodes  50 , which are electronically color designated. It should be noted that the upper case letters R, B and G represent red, blue and green in FIG.  2 . Dielectric layer  52  covers plurality of ITO electrodes  50 , and is itself overlain by photocathode layer  54 . Photoelectrons, directional arrows  56 , impinge and pass through metallic layer  58 , fluorescing plurality of phosphor dots  60  labeled R, B and G. Thus, a color image passes through second optically transparent body  24  for viewing. 
     FIGS. 3 and 4 represent a video image intensifier  14 B having first and second optically transparent bodies  62  and  64 , respectively. The photocathode and fluorescing layers have been omitted from FIG. 3 for the sake of simplicity. However, a plurality of ribbons  66  lies within vacuum enclosure  68  and spans the distance between first and second optically transparent bodies  62  and  64 . Ribbons  66  protects video image intensifier  14   b  against bowing or collapse due to the vacuum within vacuum enclosure  68 . Ribbons or spacers  66  may take the form of glass or similar dielectric material. For example, an artificial mica sold as “Cogemicanite”, available from Cogebi of Dovers New Hampshire would suffice in this regard. This structure is particularly important when video image intensifier is large. 
     With reference to FIG. 5, it may be observed that the video image source  12 A may be a cathode ray tube  70  which may project directly onto video intensifier  72 , which is similar to video image intensifier  14 , but will be detailed hereinafter with respect to FIG.  10 . Cathode ray tube  70  may also project photons through lens  74  to enlarge the image on back surface  76  of video intensifier  72 . 
     Turning now to FIG. 6, it may be observed that another structure projecting video source  12 B on intensifier  72  is depicted. The video source  12   b  is a point source of light  78  which is passed through a spacial light modulator  80  and then impinges on surface  76  of video intensifier  72 . similarly, lens  82  may collate or focus the light from point source  78  prior to impinging on spacial light modulator  80 . In either FIG. 5 or  6 , the video image may be viewed on back surface  84  of intensifier  72 . 
     Referencing now FIG. 7, a structure for close coupling video source  12 C to video intensifier  86  is depicted. Video source  12   c  includes a spacial light modulator (LCD)  88  which is sandwiched between a Lambertian back light  90  and the surface  92  of video intensifier  86 . FIG. 8 depicts a detail of the close coupling depicted in FIG. 7 in which a “dynamic” display system is shown. In other words, light is generated by pixels rather than being modulated by a liquid crystal display. For example, in FIG. 8, pixel column pixel electrode  94  is depicted as being positioned against a transparent back plate  96 . Plurality of row pixel electrodes  98  are fixed against a thin glass member  100  whose outer surface marks the line of demarcation between the video source  12 C and intensifier  86 . Thin glass plate  100  may be very thin, on the order of 2 mils. Thin glass plate  100  may also take the form of a fiber optic member. Moreover, the row and column addressing by row and column electrodes  94  and  98  may be a gas plasma display, or an electroluminescent display, of either a thin film AC, a thin film DC, or a thick film type. 
     With respect to FIG. 9, close coupling is again illustrated in which video intensifier  104  is placed against thin glass plate  106 , similar to thin glass plate  100  of FIG. 8, in which row of pixels  108  is placed against one side thereof. Line  110  marks the border between intensifier  104  and video source  12 D. 
     Row of pixels  108  represent electronic addressing which derives from a monochromatic source. Such monochromatic source may be coupled in a 1 to 1 registration with color phosphor elements  112  found within intensifier  104 . By way of example, the row of pixels or pixel dots  108  and phosphor columns or dots  112  are labeled with the upper case letter representations R, B, and G, to represent red, blue, and green. Again, pixels  108  may take the form of a gas plasma display, an electroluminescent (EL) panel, and the like. By using a gas plasma video image source, an ultraviolet light image generator would be formed in the embodiment shown in FIG. 9, if a suitable gas is chosen for the plasma display. A color video display result may be obtained in similar ways using the system of the present invention. The photons emitted by the photocathode layer  105  of intensifier  104  will be propelled directly to opposing anode pixel dots  112  since the random energy of photoelectrons streaming from photocathode layer  105  is less than one electron volt. Moreover, such photoelectrons experience an electric field of about 50,000 volts per centimeter directed perpendicularly to photocathode layer  105 . Thus, alignment of the photons from image source  12  (by close coupling FIGS.  7 - 9 ), the corresponding photoelectron color domains of photocathode layer  105 , and the corresponding color phosphor dots  112  is easily accomplished. In other words, a one-to-one registration between input pixels on photocathode layer  105  and output pixels  112  results. This occurs even at very high resolutions, e.g., 50 line pairs per millimeter or greater. 
     The present system  10  may produce a color video image in several ways, FIGS. 10-12. FIG. 10 represents a light source  12 E that impinges on a plurality of color filters  114  placed against surface  116  of glass plate  118  which would serve as the first optically transparent body of intensifier  120 . Line  122  marks the outer boundary of video intensifier  120 . It should be noted that plurality of filters  114  are labeled Y, B, and G to represent colors yellow, blue, and green. Colors  114  are embedded in a film or other suitable holder  124 . Photocathode layer  126  of intensifier  120  emits the photoelectrons and includes the same acceleration mechanism as shown with respect to video image intensifier  14  of FIG.  1 . Pixels  128  are depicted in the form of phosphor dots labeled R, G, and B for the colors red, green, and blue. Phosphor pixels  128  lie on the surface of second optically transparent body  130  which corresponds to second optically transparent body  124  of FIG.  1 . Thus, color image source  12 E, such as that from a color cathode ray tube, passes through plurality of color filters  114  such that color image data from the plurality of filters  114  are transformed in to photoelectrons that hit the particular color photocathode phosphor dots or pixels, directly across vacuum space  32 , on optically transparent body  130 . Thus, color photon emission is stimulated, such that such photons pass through optical body  30  for viewing. 
     FIG. 11 represents another method of producing a color output from the system of the present invention in which an aperture mask  132  is employed. Plurality of CRTs  134  generate monochrome color data labeled R, B, and G for red, blue, and green. Multiplicity of lenses  136  intercept such light and create, for example, an all yellow light which passes through aperture mask  132  and then to a video intensifier  138  similar to intensifier  120  depicted in FIG.  10 . Photocathode layer  140  emits photoelectrons which are accelerated directly to oppositely placed phosphor dots or pixels  142  on second optically transparent body  144 . 
     FIGS. 13-14 represent a hybrid video display system  10 A. FIG. 13 shows a flat panel display  146  in which optically transparent electrodes such as ITO electrodes covered by photocathode material are shown in columns  148  arranged vertically in FIG. 13 with optically emitting rows  150  arranged horizontally in FIG.  13 . Such optically emitting rows  150  may take the form of electroluminescent devices, plasma devices, and the like, which are close coupled to column electrodes  148 . In such a hybrid system  10 A, enabling of lines of photocathodes is accomplished optically, but the resulting cathode current is modulated using triode biasing techniques. In such hybrid designs, there is a merger of the image intensifier design of FIG. 1 with cold cathode field emission designs, known in the art, to obtain the best features of each. For example, a group of photocathodes such as columns  148  may be optically excited, not over their overall dimension but one row at a time and then biased column-by-column with video data using voltage control. In addition, row  150  strips are excited to optically emit photons and the resulting photocathode currents are modulated column-wise using the perpendicular column electrodes  148  relative to a large area grounded grid. Moreover, pixel  152  illustrated in FIG. 13 represents the conflux of the optically transparent column electrodes (ITO electrodes)  148  coated with photocathode material and the optically emitting rows  150 . FIG. 15 shows a detail of a pixel for hybrid system  10 A in which photocathode strip  154  lies atop ITO strip  156 . Perpendicular to the combined ITO and photocathode strips is a dielectric strip  158  underlain by photo emitting strip  160  to provide line addressing. With reference to FIG. 14, grid  162  is illustrated schematically. Plurality of arrows  164  represent photons from photo emitting strip  160  which impinges on ITO strip  156  and cathode  154  which, in turn, is driven with video data information as a low voltage. In this regard, each pixel formed by the combination depicted in FIG. 15 may be driven by low voltage, devices such as a CMOS driver. Phosphor domain or dot  166  is biased as an anode. When photocathode  154  is biased with respect to grid  162  in the plus direction, little current flows between cathode  154  and anode  168 . However, when cathode element  154  is biased in a negative voltage with respect to grid  162  current copiously flows between photocathode  154  and anode  168 , but only if strip  160  emits photons. The grid not shown in FIG. 13 or  15  would be a large area screen interposed anode and cathode, and is shown schematically in FIG.  14 . Of course, the system depicted in FIG. 14 may be enlarged such that line addressing may include 500 electroluminescent, or plasma display drive circuits for the rows while column electrodes driven with video data by CMOS sample and hold elements may number 1500 columns. 
     FIG. 16 represents a field emission device (FED) type system of video production in which a photocathode  170  has been substituted for a typical FED. Large area back light  172  represented by a plurality of arrows is directed toward photocathode  170  which is recessed in a substrate  174 . Grid  176  is modulated for appropriate video column data. In addition, phosphor dots  178  are modulated electrically for a particular line select capability. 
     FIG. 17 shows the various combinations of optical and electrical video column data and line selecting. T he systems described in FIGS. 1-12 would be represented by box  180 , because all of the video data is applied optically, i.e., one could view the image source as it appears either projected or close coupled to the photocathode of the intensifier. Box  184  would represent the system depicted in FIGS. 13-15, because line select data is inputted to the photocathode optically while column intensity data is introduced as a cathode bias voltage with respect to a grounded grid, while the combination shown in box  186  is the FED system of FIG. 16 with substituted photocathode  170 . Box  183  is not shown herein, but would be an alternate version of the system of FIGS. 13-15 having the video data replaced by line select data and the line select data replaced by video data. 
     In FIG. 19 where the aluminum coating  42  is removed from fluorescing layer  40  of FIG. 1, it is possible to choose a photocathode layer  40  which is sensitive outside the visible range of light, i.e., red, blue, or green light. In other words, photocathode layer  40  could be sensitive to ultraviolet light. For example, by employing a cesium iodide photocathode layer  40  of FIG. 1, photocathode layer may be operated at a much lower anode voltage, since electrons would not need to penetrate the aluminum. This structure also eliminates the problem of light leakage through pin holes in the removed aluminum coating  42 . Since, the photocathode material  40  is blind to the photons depicted in FIG. 2, leaving surface  28  of second optically transparent body  24 . The ultraviolet light sensitive cathode  40  of FIG. 19 is physically durable, not being susceptible to chemical aging. 
     Referring now to FIGS. 21-24, another embodiment  10 A of the present invention is depicted. Embodiment  10 A includes a photocathode apparatus  210  which differs from embodiment  10  depicted in FIG.  1 . Photocathode apparatus includes a backing or substrate  212  which may be a metallic member, such as a woven stainless steel screen coated with cesiated antimony. Substrate  212  may also take the form of semitransparent photocathodes of the thin film type. That is to say, substrate  212  may be a glass material upon which a thin film of cesium has been evaporated. A photocathode coating  214  may be placed on backing member  12 . Photons representing the video image may be directed toward layer  214  to produce electrons that are accelerated across vacuum chamber  216 , similar to chamber enclosure  32 , FIG.  1 . The designation “e” represents the electrons produced by photocathode layer  214 . The designation “p” represents photons of a video image source. It should be noted that fluorescing layer  218  is also shown. Photocathode layer or coating  214  may take the form of a plated coating of antimony or an antimony based alloy, i.e., antimony steel, antimony silver, and the like. In addition, an antimony layer may react with cesium vapor to produce a cesium-antimony alloy. It should be noted that layer  214  need not be homogenous as is the case with embodiment  10  depicted in FIG.  1 . In certain cases, the antimony or antimony alloy may be formed directly as substrate  212 , i.e., a unitary member. 
     As noted above, fluorescing layer  218  is also found within chamber  16  and lies atop optically transparent body  220  which permits viewing on side  222  thereof. The source of electrical power  224  produces a voltage potential between photocathode layer  214  and fluorescing layer  218 . Such voltage may be in the range of 1-30 kilo volts. 
     Turning now to FIG. 22, it may be observed that substrate  212  may include a photocathode apparatus  224  having a plurality of photon producing elements comprising the video image source  228 . For example, plurality of elements  226  may take the form of an electroluminescent phosphor of zinc sulfide material doped with manganese. In addition, elements  226  may be formed of gas plasma envelopes. Of course, the photon producing elements  226  are electronically linked to a video image such as video source  12 , FIG. 1. A plurality of photocathode elements  230  are also shown in FIG.  22 . Each photocathode element of plurality of photocathode elements  230  essentially convert photons from any photon producing element  226  into an electron which is accelerated across chamber  216 . Each photocathode element may take the form of an antimony-based material similar to photocathode coating  214  of FIG.  21 . Each photocathode element may be constructed of such material or be composed of a base material having a coating of photocathode material thereover. With reference to FIG. 23 it may be observed that plurality of photon producing elements  226  and photocathode elements  230  are formed into a “Swiss cheese” type of arrangement. In such case, photocathode elements  230  would be a contiguous member. 
     With reference to FIG. 24, a typical photon producing element  232  is shown. Photon producing element  232  is used in conjunction with baffles  234  and channel multipliers  236 , known in the prior art. Dynodes  238 ,  239 , and  240  include end surfaces, such as end surface  242  and  244 , which shelter photon producing elements  232  from returning photons from fluorescing layer  218  of FIG.  21 . Directional arrow  246  represents such returning photons. Photocathode material, e.g., cesium-antimony, are coated on the ends of dynodes  238 ,  239 , and  240  to convert photons emanating from photon producing element  232  into primary electrons, denoted with a “1” having a circle about it on FIG.  24 . Secondary electrons, denoted by the number “2” with a circle about it, are also produced in this arrangement. Typical potentials are shown in FIG. 24 for dynodes  238 ,  239 , and  240 . The use of the baffles  234  and channel multiplier means  236  eliminates the need for a metallic coating on phosphor layer or screen  218 . Also, voltage source  224  between photocathode coating  214  of FIG. 21 or photocathode elements  230  of FIG. 22, and fluorescing layer  218  is relatively low, since the electrons bridging the gap of vacuum chamber  216  need not be propelled through metallic material or a metallic mirror overlying fluorescing layer  218 . Also, positive ions returning from the phosphor screen  218  will not damage the photocathode element  230  by impact. 
     In operation, the user utilizes a video source  12 , by remote projection or by close coupling, which may be the output of a cathode ray tube, liquid crystal display (LCD) and the like onto a video image intensifier  14  such as that shown in FIG.  1 . The photons of the video source impinge on video image intensifier  14 . The video image intensifier is motivated by a potential in the form of a source of electrical power  44  to accelerate photoelectrons across a gap or vacuum enclosure  32 . Photons from video source  12  are transduced into such photoelectrons by photocathode layer  38  found first optically transparent body of video image intensifier  14 . The embodiment  10 A, generates photoelectrons from a video source  12  using an opaque substrate  212 . Fluorescing layer  40  on second optically transparent body  24  of video image intensifier  14  receives the greatly accelerated photoelectrons and produces a video image which is viewable on second surface  28  of se con d optically transparent body  24 . The system of the present invention may be employed to intensify monochromatic video sources, to produce a color image from a color coded monochromatic video source, or a color video source. System  10  may be employed to produce a flat panel display exhibiting the Lambertian characteristics of a cathode ray tube, without the disadvantage of depth required for the cathode ray tube, i.e., a flat panel display. 
     FIG. 20 represents a system  10 B in which a high resolution color image is obtained using a low resolution light modulator in conjunction with three point light sources  192 , each of different color, labeled R, G, &amp; B for red, green, and blue. Point light sources represent light emitting diodes (LEDS) in the embodiment of FIG.  20 . Collimating lens  194  passes light from LEDS  194  to a monochrome light modulator (LCD)  196  of low resolution. Pixels  198 ,  200 , and  202  each represent one pixel of the monochrome light modulator  196 . Intensifier  14 A is similar in construction to intensifier  14  accepting the inclusion of a plurality of color filters  204 , labeled R, G, or B in accordance with the colors of point light sources  192 . Three sequential screens are created in the system  10 B by sequentially shining the red, green, and blue light video data portions from sources  192 . During each color frame, modulator  196  is driven with color data for a particular color frame. Wrong data is prevented from reaching the photocathode of intensifier  14 A by plurality of color filters  204 , which are arranged in triads of color (R, B, and G) in front of each pixel  198 ,  200 , and  202  of LCD  196 . In FIG. 20, only green light of the video data is shown to reach intensifier  14 A. The same is true for red and blue light of the video data from sources  197 . Of course, the colors red, blue, and green (R, B, and G) are arbitrarily chosen in FIG.  20 . 
     While in the foregoing, embodiments of the present invention have been set forth in considerable detail for the purposes of making a complete disclosure of the invention, it may be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and principles of the invention.