Abstract:
A system for illuminating panels such as advertising display panels is provided. Such illuminated panels include at least one row of point light sources located substantially within the at least one illuminated frame member, a diffusion layer have a diffusion edge facing the at least one row of point light sources, a backscattering layer coupled to a back surface of the diffusion layer, and a dispersion layer coupled to a front surface of the diffusion layer. The diffusion layer has an edge with a surface roughness configured to diffuse light emitted by the at least one row of point light sources. In some embodiments, the light sources are dimmable Luxeon LEDs and can be activated by an infrared sensor. It is also possible to use ultraviolet to blue light sources for the panel and to include a phosphor in the dispersion layer of the panel for converting the ultraviolet to blue light into visible light.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of co-pending U.S. application Ser. No. 11/379,967 filed Apr. 24, 2006, entitled “System and Methods for Illuminating Panels”, which is hereby fully incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to illuminating panels. More particularly, this invention relates to cost effective systems and methods for using multiple point light sources such as light emitting diodes (LEDs) to illuminate panels. 
     Illuminated panels have many uses where evenly lit panels with neutral color temperature are used including advertising display panels, shopping mall directories, restaurant menus, event schedules, and navigational signboards. Other uses for illuminated panels include light-boxes for artists, photographers, architects, design engineers, general contractors and draftsmen. 
     These illuminated panels can be as small as six inches by six inches, and as large as four feet by eight to ten feet or more. Depending on their specific applications, weight, cost, panel thickness, and lamp-life, can all be crucial to the successful design, manufacture and marketing of these panels. In addition, environmental requirements such as vibration/shock resistance, impact resistance, operating temperature range, ease of maintenance and power consumption can also be important. 
     Fluorescent light tubes are used in most commercially available illuminated displays because of the inherent evenness of light output due to the tube&#39;s physical configuration. In addition, fluorescent lamp-life is significantly longer than incandescent bulbs, and fluorescent lights also consume significantly less power for the same light output. While fluorescent tubes are better than incandescent bulbs for illuminating panels, they also have many disadvantages including overall size and weight of the power supply, and fragility of the glass tube. For example, because most illuminated panels are less than one-half of an inch thick, the fluorescent tubes have to be equally skinny and very fragile. Accordingly, the fluorescent tubes are easily damaged during manufacture, transportation and installation. 
     In addition, although fluorescent tubes have longer lamp-life than incandescent bulbs, fluorescent tubes have a tendency to flicker depending on the frequency of the driving voltage. The light output of fluorescent tubes is also not easily adjusted to match ambient light conditions. Ballasts are also required for operation of the fluorescent tubes. Fluorescent tubes are also inefficient when operated under low temperatures. 
     There are also other disadvantages inherent with using single light sources, the most common of which are fluorescent tubes. Since fluorescent tubes are easily damaged when subjected to shock, when the single fluorescent tube fails, an entire side of the panel is not longer illuminated. 
     Previous attempts at replacing fluorescent tubes with point lights sources have failed because point light sources produce a “saw-tooth” effect in the light pattern. It is therefore apparent that an urgent need exists for improved illuminated panels using point light sources that are easy to manufacturer, easy to maintain, shock resistant, impact resistant, portable, cost effective, and have long lamp-life. 
     SUMMARY OF THE INVENTION 
     To achieve the foregoing and in accordance with the present invention, systems and methods for illuminating panels such as advertising display panels are provided. Such illuminators can be operated very efficiently, cost-effectively and with minimal maintenance once installed in the field. 
     In one embodiment of the invention, the illuminated panels include at least one row of point light sources located substantially within the at least one illuminated frame member, a diffusion layer have a diffusion edge facing the at least one row of point light sources, a backscattering layer coupled to a back surface of the diffusion layer, and a dispersion layer coupled to a front surface of the diffusion layer. The diffusion layer has an edge with a surface roughness configured to diffuse light emitted by the at least one row of point light sources. 
     In some embodiments, the light sources are dimmable Luxeon LEDs and can be activated by an infrared sensor so that the panel is appropriately illuminated when a potential viewer is in range, thereby conserving power. 
     Since LEDs are not operating most efficiently when emitting white light, it is also possible to use ultraviolet to blue light sources for the panel, and to include a phosphor in the dispersion layer of the panel for converting the ultraviolet to blue light into visible light. 
     These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the present invention may be more clearly ascertained, one embodiment will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1A  is a front view of one embodiment of the present invention; 
         FIG. 1B  is a cross-sectional view  1 B- 1 B of  FIG. 1A ; 
         FIG. 1C  is a cross-sectional view of a variant of the embodiment of  FIG. 1 ; 
         FIG. 2  is a front view of another variant of the embodiment of  FIG. 1 ; 
         FIG. 3  is a front view of yet another variant of the embodiment of  FIG. 1 ; 
         FIG. 4A  is a front view of another embodiment of the invention; 
         FIG. 4B  is a cross-sectional view  4 B- 4 B of  FIG. 4A ; 
         FIG. 5A  is a front view of yet another embodiment of the invention; 
         FIG. 5B  is a cross-sectional view  5 B- 5 B of  FIG. 5A ; and 
         FIGS. 6A-6C  are cross-sectional views illustrating several variants of an illuminated display for the embodiments of  FIGS. 4A and 5A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in detail with reference to several embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention. The features and advantages of the present invention may be better understood with reference to the drawings and discussions that follow. 
       FIG. 1A  is a front view showing one embodiment of an illuminated panel  100  in accordance with the present invention. Panel  100  includes frame members  110 ,  120 ,  130 ,  140 . To facilitate discussion, the front portion of top frame member  110  and the front portion of bottom frame member  130  have cutaways exposing a top row of point light sources  155   a ,  155   b ,  155   c  . . .  155   y  and a bottom row of point light sources  165   a ,  165   b ,  165   c  . . .  165   y , respectively. 
     The top row of point light sources  155   a ,  155   b ,  155   c  . . .  155   y  are mounted a light base  150  which functions as a mounting support and also as means for providing power and control to light sources  155   a ,  155   b ,  155   c  . . .  155   y . Similarly, the bottom row of point light sources  165   a ,  165   b ,  165   c  . . .  165   y  are mounted a light base  160  which functions as a mounting support and also as means for providing power and control to light sources  165   a ,  165   b ,  165   c  . . .  165   y . Depending on the overall panel dimensions and cost, weight, and/or power constraints of panel  100 , one member, two members (as shown in this example), three members or all four members of frame members  110 ,  120 ,  130 ,  140  can be illuminated. In addition, power and control circuitry for panel  100  can either be internal, external, or combinations thereof, with respect to frame members  110 ,  120 ,  130 ,  140 . 
     In this embodiment, point light sources  155   a ,  155   b ,  155   c  . . .  155   y  and  165   a ,  165   b ,  165   c  . . .  165   y  can be low-wattage light emitting diodes (LEDs) commercially available from www.nichia.com, www.cree.com or www.lumileds.com. LEDs  155   a ,  155   b ,  155   c  . . .  155   y  and  165   a ,  165   b ,  165   c  . . .  165   y  are spaced about one-quarter of an inch apart from each other, resulting in about forty-eight LEDs per linear foot of light bases  150 ,  160 , respectively. Each LED consumes about 20 mA and emits about 5 candela of visible light. LEDs  155   a ,  155   b ,  155   c  . . .  155   y  and  165   a ,  165   b ,  165   c  . . .  165   y  can be powered and controlled using commercially available constant-current power supplies, e.g., M/W model number TSU 66A-3 which provides 12V DC @5.5 A, or MWS model number 122500UC which provides 12V DC @250 mA. Another manufacturer of DC power supplies is XP Power (www.xpplc.com). 
       FIG. 1B  is a cross-sectional view  1 B- 1 B of panel  100  showing top frame member  110 , light source  155   m  attached to light base  150 , and an illuminated display comprising a transparency  190 , a diffusion layer  170  and a back-scattering layer  180 . Transparency  190  can be merely in contact with diffusion layer  170  so that transparency  190  can be easily replaced by a new or different transparency. Alternatively, transparency  190  can be permanently attached to diffusion layer  170  using a suitable adhesive or process. 
     Diffusion layer  170  can be made from acrylic or another suitable plastic or polymer with the required light transmitting properties available from Mitsubishi. Back-scattering layer  180  can be made from a suitable highly reflective polymer such as Styrene or vinyl, available from 3M Corporation. Back-scattering layer  180  can either in contact with diffusion layer  170 , or back-scattering layer  180  can be permanently bonded to diffusion layer  170  by a suitable adhesive. 
     The internal reflective characteristics of the frame members of panel  100  can be enhanced by incorporating a suitable frame profile thereby increasing the effectiveness of the illumination produced by LED  155   m . For example, as shown in  FIG. 1C , frame member  111  has parabolic surfaces  111   d ,  111   e  to better focus the light from LED  155   m  into diffusion layer  170 . 
     The internal reflective characteristics of frame member  110  and frame member  111  can be further enhanced by incorporating a suitable surface polish to inner surfaces  110   a ,  110   b ,  110   c  and surfaces  111   d ,  111   e , respectively. It is also possible to apply a reflective layer in the form of coating or chemical processing including painting, electro-plating or anodizing to the inner surfaces  110   a ,  110   b ,  110   c ,  110   d ,  111   e . Light base  150  can be recessed into frame member  111  to better position LED  155   m  relative to parabolic surfaces  111   d ,  111   e  so that more light can be reflected into diffusion layer  170 . 
     In order to minimize the saw-tooth problem due to the increased LED spacing, surface  175  of diffusion layer  170  has a surface roughness designed to diffuse the light emitted by LEDs  155   a ,  155   b ,  155   c  . . .  155   y  as the light enters diffusion layer  170 . Since diffusion layer  170  can be cut to the appropriate size using several well known techniques such as band saws and circular saws, by leaving surface  175  unpolished with saw cut marks intact or by sanding using grit #2000 or lower, ensuring that the light entering diffusion layer  170  is sufficiently diffused to mitigate the saw-tooth problem. 
     Other modifications to the illuminated panels of the present invention are also possible. For example, the front portion of frame member  110  can be hinged so that transparency  190  can be easily replaced and also to provide easy access to light sources  155   a ,  155   b ,  155   c  . . .  155   y.    
     Another advantage of using point light sources is the increased variety of potential panel shapes.  FIG. 2  is a cutaway front view of an octagonal panel  200  which includes frame members  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280 , and light bases  212 ,  232 ,  252 ,  272  inside frame members  210 ,  230 ,  250 ,  270 , respectively. Similarly, the cutaway front view of  FIG. 3  illustrates a semi-circular panel  300  having a curved frame member  310  with curved light base  312 , straight frame member  320 , straight frame member  330  with straight light base  332 , and straight frame member  340 . 
     Referring now to  FIG. 4A , a cutaway front view illustrating another embodiment of the present invention, illuminated panel  400  includes frame members  410 ,  420 ,  430 ,  440 , with the front portion of top frame member  410  and the front portion of bottom frame member  430  exposed to show a top row of point light sources  455   a ,  455   b ,  455   c ,  455   d ,  455   e  and a bottom row of point light sources  465   a ,  465   b ,  465   c ,  465   d ,  465   e , respectively. The top row of point light sources  455   a ,  455   b ,  455   c ,  455   d ,  455   e  are mounted on light base  450  which provides structural support and power to light sources  455   a ,  455   b ,  455   c ,  455   d ,  455   e . Similarly, the bottom row of point light sources  465   a ,  465   b ,  465   c ,  465   d ,  465   e  are mounted on powered light base  460 . 
     In this embodiment, point light sources  455   a ,  455   b ,  455   c ,  455   d ,  455   e  and  465   a ,  465   b ,  465   c ,  465   d ,  465   e  can be 3-Watt front-emitting Luxeon LEDs. LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e ,  465   a ,  465   b ,  465   c ,  465   d ,  465   e  are spaced about 1 to 2 inches apart from each other, resulting in approximately 6 Luxeon LEDs per linear foot of their respective light bases  450 ,  460 . In this example, each 3-Watt Luxeon LED emits about 60 lumens of visible light. This arrangement should be sufficient to accomplish sufficient penetration of up to two feet into diffusion layer  470  while maintaining light variation within 20% so that the variation of intensity on the surface of panel  400  is not noticeable to the average human eye. 
     Suitable front-emitting Luxeon LEDs are commercially available in 1-Watt, 3-Watt, 5-Watt, and other higher wattage LED modules from www.luxeon.com, for example Lumineds Lambertian LXHL PW09 white Luxeon LED. Other commercial sources of higher wattage LEDs include www.edison-opto.com.tw. 
     Because higher wattage Luxeon LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e ,  465   a ,  465   b ,  465   c ,  465   d ,  465   e  generate a significant amount of heat, light bases  450 ,  460  also function as heat sinks for Luxeon LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e  and  465   a ,  465   b ,  465   c ,  465   d ,  465   e , respectively. Light bases  450 ,  460  in turn conduct heat to their respective frame members  410 ,  430 . 
     Luxeon LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e ,  465   a ,  465   b ,  465   c ,  465   d ,  465   e  can be powered and controlled using a constant-current power supply, such as the AED Series 36-100 Watt power supply available from www.xppower.com. 
       FIG. 4B  is a cross-sectional view  4 B- 4 B of panel  400  showing top frame member  410 , light source  455   c  attached to light base  450 , and an illuminated display comprising a transparency  490 , a diffusion layer  470  and a back-scattering layer  480 . Because brighter Luxeon LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e  and  465   a ,  465   b ,  465   c ,  465   d ,  465   e  can be spaced further apart from each other than lower power point light sources, the saw-tooth problem associated with all point light sources is more pronounced. In accordance with one aspect of the invention, surface  475  of diffusion layer  470  has a suitable surface roughness of approximately 2000 grit and courser in order to diffuse the light emitted by LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e  as the light enters diffusion layer  470 . This surface roughness can be accomplished by for example by cutting with a saw having about 80-100 teeth per inch. 
     In addition to being reflective, the inner surfaces  410   a ,  410   b ,  410   c  of frame member  410  can also be made to diffusively reflect light emitted by LEDs  455   a ,  455   b ,  455   c ,  455   d ,  455   e  by, for example, incorporating small dimples into reflective surfaces  410   a ,  410   b ,  410   c.    
       FIG. 5A  is a cutaway front view showing yet another embodiment of the invention. An illuminated panel  500  includes frame members  510 ,  520 ,  530 ,  540 , with the front portion of top frame member  510  and the front portion of bottom frame member  530  exposed to show a top row of point light sources  555   a ,  555   b ,  555   c ,  555   d ,  555   e  and a bottom row of point light sources  565   a ,  565   b ,  565   c ,  565   d ,  565   e , respectively. The top row of point light sources  555   a ,  555   b ,  555   c ,  555   d ,  555   e  are mounted on light base  550  which provides structural support and power to light sources  555   a ,  555   b ,  555   c ,  555   d ,  555   e . Similarly, the bottom row of point light sources  565   a ,  565   b ,  565   c ,  565   d ,  565   e  are mounted on powered light base  560 . 
     Side-emitting Luxeon LEDs are commercially available in 1-Watt, 3-Watt, 5-Watt, and other higher wattage modules from www.luxeon.com. Because higher wattage Luxeon LEDs  555   a ,  555   b ,  555   c ,  555   d ,  555   e ,  565   a ,  565   b ,  565   c ,  565   d ,  565   e  generate a significant amount of heat, light bases  350 ,  360  also dissipate heat from LEDs  555   a ,  555   b ,  555   c ,  555   d ,  555   e  and  565   a ,  565   b ,  565   c ,  565   d ,  565   e  to frame members  510 ,  530 , respectively. Light bases  550 ,  560  in turn conduct heat to their respective frame members  510 ,  530 . Power and control circuitry for panel  500  is similar to that described above for panel  400 . 
       FIG. 5B  is a cross-sectional view  5 B- 5 B of panel  500  showing top frame member  510 , light source  555   c  attached to light base  550 , and an illuminated display comprising a transparency  590 , a diffusion layer  570  and a back-scattering layer  580 . In this embodiment, point light sources  555   a ,  555   b ,  555   c ,  555   d ,  555   e ,  565   a ,  565   b,    565   c ,  565   d ,  565   e  can be 3-Watt side-emitting Luxeon LEDs. Accordingly, LEDs  555   a,    555   b ,  555   c ,  555   d ,  555   e ,  565   a ,  565   b ,  565   c ,  565   d ,  565   e  are oriented so the light is emitted substantially in the same plane as diffusion layer  570 . 
     The higher wattage Luxeon LEDs  555   a ,  555   b ,  555   c ,  555   d ,  555   e ,  565   a,    565   b ,  565   c ,  565   d ,  565   e  of panel  300  are spaced about 1 to 2 inches apart from each other, resulting in approximately 6 LEDs per linear foot of their respective light bases  550 ,  560 . In this example, each 3-Watt Luxeon LED emits about 60 lumens of visible light. Suitable side-emitting Luxeon LEDs are commercially available from www.luxeon.com such as the Lumineds LXHL DW09 white LED. 
     As discussed above, in order to minimize the saw-tooth problem due to the increased LED spacing, surface  575  of diffusion layer  570  has a suitable surface roughness designed to diffuse the light emitted by LEDs  555   a ,  555   b ,  555   c ,  555   d ,  555   e  as the light enters diffusion layer  570 . This surface roughness can be accomplished by for example a sand-blasting medium that can penetrate surface  570   a  using multiple blasting heads to cause a varied density pattern thereby enabling panel  500  to output a more even light intensity. 
     In this embodiment, because a significant amount of light from LEDs  555   a,    555   b ,  555   c ,  555   d ,  555   e  is initially emitted in a direction away from diffusion layer  570 , the inner surfaces  510   a ,  510   b ,  510   c  of frame member  510  should be designed to efficiently and diffusively reflect light emitted by LEDs  555   a ,  555   b ,  555   c ,  555   d ,  555   e  toward surface  575  of diffusion layer  570 . Techniques such as profiling, polishing and dimpling of reflective surface  510   a ,  510   b ,  510   c  described above can be employed to better utilize the higher order indirect light emitted by LEDs  555   a ,  555   b ,  555   c ,  555   d ,  555   e.    
     Hence in accordance with another aspect of the invention as illustrated by the cross-sectional views  FIGS. 6A and 6B  of display panel  600 , a dispersion layer  675  is positioned in front of diffusion layer  670 . The inclusion of dispersion layer  675  improves the overall light transmission efficiency of panel  600  by increasing the transmission of higher-order light rays from point light source  655   c  and also from additional point light sources (not shown) inside frame member  610 , through diffusion layer  670 , dispersion layer  675  and transparency  690 . Note that light source  655   c  can be attached to frame member  610  via any of surfaces  610   a ,  610   b ,  610   c.    
     In this embodiment, backscattering layer  680  is approximately several microns to about 3 mm in thickness, and should be opaque, and diffusive with high reflectance, preferably over 90%. Suitable materials for back-scattering layer  680  include aluminum oxide and titanium oxide, any suitable rare earth coating, or a highly reflective diffusive plastic sheet. 
     Diffusion layer  670  can be about 5 to 10 mm thick and should be as optically transparent as possible. Ideally, diffusion layer  670  should not have scattering materials impregnated since that will cause absorption of the light. In addition, surface  670   a  of diffusion layer  670  should be roughened in the manner described above in order to minimize the saw-tooth effect. 
     Dispersion layer  675  can be about 3 to 10 microns with mode optical scattering properties. Layer  675  can be a lower index layer relative to diffusion layer  670 . In addition, dispersion layer  675  may have a scattering medium that has a different refractive index impregnated to provide even scattering relative to the total area of panel  600 . 
     Both layers  670  and  675  can be made of a suitable acrylic material, e.g. polymethamethacrylate. In this example, layer  670  has a refractive index N of about 1.47 to 1.49 and layer  675  has a refractive index N of about 1.33 to 1.35. 
     Referring to both  FIGS. 6A and 6B , an exemplary higher-order light ray  692  from light source  655   c  enters surface  670   a  and is reflected in a scattered pattern by backscattering layer  680  into rays  694   a ,  694   b ,  694   c ,  694   d  directed towards dispersion layer  675 . Note that reflected ray  694   d  arrives at steeper angle at dispersion layer  675  than rays  694   a ,  694   b ,  694   c , and hence ray  694   d  is further scattered by dispersion layer  675  as rays  696   a ,  696   b  and  696   c  through transparency  690 . In this example, although ray  694   d  is reflected off backscattering layer  680 , ray  694   d  can also depict similarly-angled rays directly generated by light source  655   c . Ideally, light transmission at the interface between diffusion layer  670  and dispersion layer  675  should be greater than 90% with minimal Fresnel losses. 
     Further, in order to minimize variation of light intensity over panel  600 , a variable pattern of reflectance can be incorporated into the back surface of layer diffusion layer  670  so that the reflectance increases in a direction away from LED  655   c.    
     The resulting multi-layer sandwich comprising of dispersion layer  675 , diffusion layer  670  and backscattering layer  680  can be manufactured using a cast layering process, an enclosed liquid polymerization extrusion process, or a combination thereof, using techniques known to one skilled in the plastics manufacturing arts. Alternatively, backscattering layer  680  be evaporated on, bonded to or attached to the back surface of diffusion layer  670  with a suitable adhesive. 
     Many modifications and variations are possible. For example, panels  100 ,  200 ,  300 ,  400 ,  500  and  600  can be dimmable by adding a variable current control circuitry. An infrared red sensor can also be added to the control circuitry of panels  100 ,  200 ,  300 ,  400 ,  500  and  600 , so that the panels are triggered when a potential customer enters the detection field thereby dimming or turning on and off in an appropriate manner. 
     In some applications as illustrated by embodiment  600 C of FIG  6 C, in addition to the edge lights described in the above embodiments, panels  100 ,  200 ,  300 ,  400 ,  500 ,  600  can also be back-lighted by additional light source(s)  620 . Accordingly, dispersion layers and/or backscattering layers, e.g., layers  670 ,  680 , can be opaque in order to diffuse the back lighting. 
     Further, since white LEDs are not the most efficient emitter of light, it is also possible for LED  655   c  to transmit light in the substantially blue-to-ultraviolet range into diffusion layer  670 , to include phosphors in dispersion layer  675  or back-scattering layer  680  or combinations thereof, and to convert the blue-to-ultraviolet light into white light or any colored light within the visible spectrum. 
     Other modifications and variations are also possible. For example, other higher intensity point light sources for illuminating panels  400 ,  500  include high intensity discharge (HID) lights and halogen lights. The present invention will also improve the quality and quantity of light transmitted by other non-point light sources such as neon and fluorescent light sources. 
     In the above described embodiments, frame members of panels  100 ,  200 ,  300 ,  400 ,  500  and  600  can be manufactured from aluminum extrusions. The use of any other suitable rigid framing materials including other metals, alloys, plastics and composites such as steel, bronze, wood, polycarbonate, carbon-fiber, and fiberglass is also possible. 
     In sum, the present invention provides an improved illuminator using light sources such as LEDs for evenly illuminating panels that is easy to manufacturer, easy to maintain, shock resistant, impact resistant, portable, cost effective, and have long lamp-life, while minimizing the “saw-tooth” effect in the emitted light pattern. 
     While the present invention has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the inventive scope is not so limited. In addition, the various features of the present invention can be practiced alone or in combination. Alternative embodiments of the present invention will also become apparent to those having ordinary skill in the art to which the present invention pertains. Such alternate embodiments are considered to be encompassed within the spirit and scope of the present invention. Accordingly, the scope of the present invention is described by the appended claims and is supported by the foregoing description.