Abstract:
Methods and apparatus are provided for increasing the luminous output of a fluorescent lamp suitable for use as a backlight in an avionics or other liquid crystal display (LCD). The apparatus includes a channel configured confine a vaporous material that produces an ultra-violet light when electrically excited. A layer of light-emitting material disposed within at least a portion of the channel is responsive to the ultra-violet light to produce the visible light emitted from the lamp. To increase the luminous output of the lamp, the surface area of the light-emitting material is increased through the presence of one or more grooves. The grooves may be longitudinal or transverse with respect to the channel.

Description:
TECHNICAL FIELD  
       [0001]     The present invention generally relates to fluorescent lamps, and more particularly relates to techniques and structures for improving the luminescence of fluorescent lamps such as those used in liquid crystal displays.  
       BACKGROUND  
       [0002]     A fluorescent lamp is any light source in which a fluorescent material transforms ultraviolet or other energy into visible light. Typically, fluorescent lamps include a glass or plastic tube that is filled with argon or other inert gas, along with mercury vapor or the like. When an electrical current is provided to the contents of the tube, the resulting arc causes the mercury gas within the tube to emit ultraviolet radiation, which in turn excites phosphors located inside the lamp wall to produce visible light. Fluorescent lamps have provided lighting in numerous home, business and industrial settings for many years.  
         [0003]     More recently, fluorescent lamps have been used as backlights in liquid crystal displays such as those used in computer displays, cockpit avionics, and the like. Such displays typically include any number of pixels arrayed in front of a relatively flat fluorescent light source. By controlling the light passing from the backlight through each pixel, color or monochrome images can be produced in a manner that is relatively efficient in terms of physical space and electrical power consumption. Despite the widespread adoption of displays and other products that incorporate fluorescent light sources, however, designers continually aspire to improve the amount of light produced by the light source, to extend the life of the light source, and/or to otherwise enhance the performance of the light source, as well as the overall performance of the display.  
         [0004]     Accordingly, it is desirable to provide a fluorescent lamp and associated methods of building and/or operating the lamp that improve the performance and lifespan of the lamp. Other desirable features and characteristics will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.  
       BRIEF SUMMARY  
       [0005]     In various embodiments, methods and apparatus are provided for increasing the luminous output of a fluorescent lamp suitable for use as a backlight in an avionics or other liquid crystal display (LCD). The apparatus includes a channel configured to confine a vaporous material that produces an ultra-violet light when electrically excited. A layer of light-emitting material disposed within at least a portion of the channel is responsive to the ultra-violet light to produce the visible light emitted from the lamp. To increase the luminous output of the lamp, the surface area of the light-emitting material is increased through the presence of one or more grooves. The grooves may be longitudinal or transverse with respect to the channel.  
         [0006]     In another embodiment, a method of making a fluorescent lamp suitable for use in a liquid crystal display includes the broad steps of deforming the surface of the channel to thereby increase the surface area of the channel, and then forming a layer of phosphor material within at least a portion of the channel to thereby create a light-emitting layer having a plurality of grooves corresponding to the deformed surface of the channel.  
         [0007]     Other embodiments include other lamps or displays incorporating structures and/or techniques described herein. Additional detail about various exemplary embodiments is set forth below.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and  
         [0009]      FIG. 1  is an exploded perspective view of an exemplary flat panel display;  
         [0010]      FIG. 2  is a cross-sectional side view of an exemplary fluorescent lamp with a protective coating provided over a light-emitting layer;  
         [0011]      FIG. 3  is a cross-sectional side view of an exemplary fluorescent lamp showing a light-emitting layer with longitudinal grooves to increase surface area; and  
         [0012]      FIG. 4  is a cross-sectional view of an exemplary fluorescent lamp showing a light-emitting layer with transverse grooves.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.  
         [0014]     Various techniques for improving the efficiency, luminescence and/or other performance aspect of a fluorescent light source are described herein. These techniques include, for example, increasing the surface area of the light-producing material through the addition of grooves, indentations and/or the like. Each of the various techniques and structures described herein may be readily applied to all types of fluorescent light sources, including so-called “aperture lamps”, “flat lamps”, fluorescent bulbs, and the like.  
         [0015]     Turning now to the drawing figures and with initial reference to  FIG. 1 , an exemplary flat panel display  100  suitably includes a backlight assembly with a substrate  104  and a faceplate  106  confining appropriate materials for producing visible light within one or more channels  108 . Typically, materials present within channel(s)  108  include argon (or another relatively inert gas), mercury and/or the like. To operate the lamp, an electrical potential is created across the channel  108  (e.g. by coupling electrodes  102 ,  103  to suitable voltage sources and/or driver circuitry), the gaseous mercury is excited to a higher energy state, resulting in the release of a photon that typically has a wavelength in the ultraviolet light range. This ultraviolet light, in turn, provides “pump” energy to phosphor compounds and/or other light-emitting materials located in the channel to produce light in the visible spectrum that propagates outwardly through faceplate  106  toward pixel array  110 .  
         [0016]     The light that is produced by backlight assembly  104 / 106  is appropriately blocked or passed through each of the various pixels of array  110  to produce desired imagery on the display  100 . Conventionally, display  100  includes two polarizing plates or films, each located on opposite sides of pixel array  110 , with axes of polarization that are twisted at an angle of approximately ninety degrees from each other. As light passes from the backlight through the first polarization layer, it takes on a polarization that would ordinarily be blocked by the opposing film. Each liquid crystal, however, is capable of adjusting the polarization of the light passing through the pixel in response to an applied electrical potential. By controlling the electrical voltages applied to each pixel, then, the polarization of the light passing through the pixel can be “twisted” to align with the second polarization layer, thereby allowing for control over the amounts and locations of light passing from backlight assembly  104 / 106  through pixel array  110 . Most displays  100  incorporate control electronics  105  to activate, deactivate and/or adjust the electrical parameters  109  applied to each pixel. Control electronics  105  may also provide control signals  107  to activate, deactivate or otherwise control the backlight of the display. The backlight may be controlled, for example, by a switched connection between electrodes  102 ,  103  and appropriate power sources. While the particular operating scheme and layout shown in  FIG. 1  may be modified significantly in some embodiments, the basic principals of fluorescent backlighting are applied in many types of flat panel displays  100 , including those suitable for use in avionics, desktop or portable computing, audio/video entertainment and/or many other applications.  
         [0017]     Fluorescent lamp assembly  104 / 106  may be formed from any suitable materials and may be assembled in any manner. Substrate  104 , for example, is any material capable of at least partially confining the light-producing materials present within channel  108 . In various embodiments, substrate  104  is formed from ceramic, plastic, glass and/or the like. The general shape of substrate  104  may be fashioned using conventional techniques, including sawing, routing, molding and/or the like. Further, and as described more fully below, channel  108  may be formed and/or refined within substrate  104  by sandblasting in some embodiments.  
         [0018]     Channel  108  is any cavity, indentation or other space formed within or around substrate  104  that allows for partial or entire confinement of light-producing materials. In various embodiments, lamp assembly  104 / 108  may be fashioned with any number of channels, each of which may be laid out in any manner. Serpentine patterns, for example, have been widely adopted to maximize the surface area of substrate  104  used to produce useful light. U.S. Pat. No. 6,876,139, for example, provides several examples of relatively complicated serpentine patterns for channel  108 , although other patterns that are more or less elaborate could be adopted in many alternate embodiments.  
         [0019]     With reference now to  FIG. 2 , channel  108  in substrate  104  is suitably provided with a light-emitting material  202  and a protective layer  204 . Channel  108  is appropriately formed in substrate  104  by milling, molding or the like, and light-emitting material  202  is applied though spraying or any other conventional technique. Light-emitting material  202  is typically a phosphorescent compound capable of producing visible light in response to “pump” energy (e.g. ultraviolet light) emitted by vaporous materials confined within channel  108 . Various phosphors used in fluorescent lamps include any presently known or subsequently developed light-emitting materials, which may be individually or collectively employed in a wide array of alternate embodiments. Light emitting layer  202  may be applied or otherwise formed in channel  108  using any technique, such as conventional spraying or the like.  
         [0020]     An optional protective layer  204  may be provided on light-emitting layer  202  to prevent argon, mercury or other vapor molecules from diffusing into the phosphor or other light-emitting material. When used, protective layer  204  may be made up of any conventional coating material such as aluminum oxide or the like. Alternatively, various embodiments could include a protective layer  204  that includes fused silica (“quartz glass”) or a similar material to prevent mercury penetration into light emitting layer  102 .  
         [0021]     With reference now to  FIG. 3 , one technique for improving the efficiency of the fluorescent lamp suitably involves creating one or more grooves in the surface of light-emitting material  202 . “Groove” in this context refers to any regular or irregular variation that increases the surface area of light-emitting layer  202 . The exemplary embodiment shown in  FIG. 3 , for example, shows various grooves  302 ,  304 ,  306  created in the longitudinal direction with respect to channel  108 , although alternate embodiments may provide any sort of transverse, longitudinal, oblique, irregular or other grooves along some or all of channel  108 .  FIG. 4 , for example, shows various grooves  402 ,  404  formed in a transverse direction with respect to channel  108 . By increasing the surface area of the light emitting layer  102  facing toward channel  108 , the amount of light produced by the layer can be substantially increased. That is, the presence of one or more grooves  302 ,  304 ,  306 ,  402 ,  404  in light-emitting layer  202  increases the amount of light emitting material  202  exposed to pump radiation from vaporous materials in channel  108 , thereby increasing the amount of visible light produced within channel  108 .  
         [0022]     In various embodiments, then, a fluorescent lamp assembly  104 / 106  may be made by simply forming a substrate  104  with one or more channels  108  of appropriate size and shape, applying the light emitting layer  202  within channel(s)  108 , and then applying a suitable layer  204  of protective material on at least a portion of the light emitting material  202 . Substrate  104  may be formed and shaped by molding, milling, sandblasting and/or other techniques. Light emitting layer  202  may be applied on the grooved substrate  104  by spraying or otherwise applying a layer of phosphor or other material. Finally, optional protective layer  204  may be applied by sputtering, deposition and/or any other suitable technique.  
         [0023]     Grooves  302 ,  304 ,  306  may be created in any manner. In an exemplary embodiment, such grooves are created by deforming the surface of substrate  104  by molding, for example, or by milling, sandblasting or otherwise processing substrate  104  after molding in any appropriate manner. The various grooves can be readily sandblasted into the upper surface of substrate  104  facing into channel  108 , for example, such that corresponding grooves form in light-emitting layer  202  when the layer is sprayed or otherwise applied in channel  108 . Alternatively, light-emitting layer  202  may be processed after application to create regular or irregular surface deformities as appropriate. As noted above,  FIG. 4  shows a fluorescent lamp  100  that includes several transverse-oriented grooves  402 ,  404  in light-emitting layer  202 .  
         [0024]      FIG. 4  also shows the placement of a faceplate or cover  106  with respect to channel  108 . Cover  106  is typically made of glass, ceramic glass or plastic, and is suitably attached to substrate  104  by glass fritting or the like in a manner that seals the vaporous materials within channel  108 . In various embodiments, a reflective coating  406  is suitably applied to the internal or external face of cover  106  to further increase the efficiency of lamp  100 . Reflective coating  406  is designed to reflect light of certain wavelengths while transmitting light of other wavelengths; for example, coating  406  may be designed to reflect ultraviolet light back toward channel  108  while allowing visible light to transmit through cover  106 , toward pixel array  110  ( FIG. 1 ). Various layers of metals, for example, could provide such functionality, although the particular coatings used to implement reflective layer  406  vary from embodiment to embodiment.  
         [0025]     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.