Patent Publication Number: US-7896522-B2

Title: Frontal illumination of a surface using LED lighting

Description:
PRIORITY CLAIM 
     This application claims the priority of U.S. Provisional Patent Application 61/029,952 filed on Feb. 20, 2008, entitled “Frontal Illumination Of A Surface Using Led Lighting” by Todd R. Heller and Dewey T. Pitts. The entirety of the above provisional application is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to lighting of billboards, signs, buildings, and other structures and, more particularly, relates to front illumination of surfaces using light emitting diodes (LEDs). 
     2. Description of the Related Art 
     Historically, light fixtures providing front illumination of large advertising billboards have utilized various types of illumination sources, including electro-florescent tubes and flood lights (incandescent, high energy discharge, projection lamps). The illumination source is enclosed in a fixture which is mounted on an extended arm, and the extended arm positions the illumination source, also referred to as a light source, far enough away from the billboard face to illuminate the image area (or “copy area”) for viewing in low light conditions. Typically, because of the beamwidth limitations of the light source, two or more light fixtures are needed to illuminate the copy area. The number of light fixtures needed thus depends upon the height and width of the copy area and the beamwidth of the light source. Also, in order to provide the desired dispersion of the light from the light sources, and to provide for relatively even illumination from top to bottom of the copy area, the light sources have to be set back from the billboard face, typically 6 to 8 feet. The fixture mounting system is typically attached to the billboard support structure, either at or near the top of, the bottom of, or both the top and the bottom of, the billboard face. The fixture mounting system therefore typically extends the light fixture in front of the billboard face. The mounting device for each fixture typically consists of a metal tube, arm, or conduit which is mounted to the billboard structure, and which extends out approximately 6 to 8 feet, the light source typically being attached at or near the end of the fixture. 
     A larger number of light sources provides for more even illumination of the copy area, but generally results in higher costs, more physical structures, higher wind loading, and more maintenance issues. Conversely, a lower number of light sources results in lower cost, fewer physical structures, lower wind loading, and fewer maintenance issues, but increases the likelihood that there will be noticeable and undesirable differences between better lit (lighter) areas and more poorly lit (darker) areas. As a compromise between these opposing goals and choices, a typical installation may use only a few light sources, spaced at intervals of 8 to 12 feet. To compensate for using a small number of light sources, the light sources are generally wide-angle light sources, so that the fields of illumination provided by the light sources overlap somewhat, thereby reducing the contrast between the differently-illuminated areas. The use of wide angle light sources, however, brings on other problems such as, but not limited to, (1) inefficiency because the use of wide-angle light sources causes a substantial amount of the light emitted to be spread outside the borders of the copy area; (2) undesired heat generation because more light output, and therefore more energy, is required so that the light which strikes the copy area is of sufficient intensity to properly illuminate the copy area; and (3) light pollution problems because the light which does not strike the copy area contributes to night sky light pollution. Night sky pollution has become such a severe problem in many large cities that only the brightest stars are visible at night. 
     Simply replacing the current light sources with LED light sources would seem to be a solution but, in reality, is not a solution because of several problems: (1) a large number of LEDs is required to provide the desired illumination, (2) the optics and lensing required to illuminate the copy area sufficiently is very complex, (3) the heat generated by a large number of LEDs in close proximity or clustered together causes the LEDs to quickly overheat and fail, and (4) cost, windloading, esthetic, maintenance, and other considerations. Thus, neither simply replacing conventional light sources with clustered LEDs, nor adding more projecting fixtures with fewer LEDs in a fixture, are viable options. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is an illustration of a billboard and shows the billboard face, the catwalk, and one possible LED lamp location. 
         FIG. 2  is an illustration of a billboard and shows the billboard face, the catwalk, and another possible LED lamp location. 
         FIG. 3  is an illustration of a billboard and shows the billboard face, the catwalk, another possible LED lamp location, and the preferred light dispersion characteristic. 
         FIG. 4  is an illustration of one embodiment of a lamp array. 
         FIG. 5  is an illustration of another embodiment of a lamp array. 
         FIG. 6  is a side elevation cutaway view of an embodiment of a lamp array, and shows a typical position for the power supply and an individual LED cell. 
         FIGS. 7 and 8  are photographs of an embodiment of a lamp array and show LED cells, both with and without optical lenses. 
         FIGS. 9 and 10  are photographs of an embodiment of a lamp array and show the protective cover in place. 
         FIGS. 11A-11E  are illustration of various LED cell configurations and various optical lensing arrangements. 
         FIG. 12  is a photograph showing the light distribution provided by the LED lamp array of one embodiment. 
         FIG. 13  is a photograph illustrating one method of connecting lamp arrays. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-3  illustrate embodiments of various billboard installations and some location possibilities for LED lamp arrays.  FIG. 1  is an illustration of one embodiment of a billboard  10  and shows the billboard face  12 , the catwalk  14 , and one possible location  16  for lamp arrays  30 A- 30 N.  FIG. 2  is an illustration another embodiment of a billboard  10 , and shows the billboard face  12 , the catwalk  14 , and another possible location  16  for the lamp arrays  30 .  FIG. 3  is an illustration of another embodiment of a billboard  10  and shows the billboard face  12 , the catwalk  14 , another possible location  16  for the lamp arrays  30 , and the preferred light dispersion characteristic  20 . 
     The front illuminated sign has a plurality of LED lamp arrays  30 A- 30 N, also referred to herein as light fixtures, preferably mounted to the service access catwalk  14  kickrail, and parallel to the advertising sign face  12 . An adjustable mounting bracket  15  accommodates various relationships between the advertising sign face  12  and the location of the service access catwalk  14  toe and kick rails  14 A,  14 B, such as differences in the locations of the catwalk kickrails in relationship to the sign face. Each LED light fixture is preferably long and rectangular in shape, and has either a single row or multiple rows of LED lamps. The fixtures are mounted on the service access catwalk kickrail, running horizontally along most of the length of the kickrail. Optical lens on the LED lamps selectively and purposefully distribute light vertically and horizontally across the copy area. Preferably, different lens with different light distribution patterns are used for the various LEDs. Even spacing of LED lamps, placed horizontally along the catwalk kickrail, and directed towards the face of the billboard, results in consistent illumination of the copy area. 
     The illustrated embodiments provide a visually appealing method of illuminating the copy area of a billboard face from the front. There are no protruding light fixtures at the top or the bottom of the billboard. There is no need to obtain extended property line set back permission to accommodate the protruding light fixtures because the LED lights preferably occupy the same latitudinal space as the catwalks present on most billboards. Such catwalks are typically present to provide access for installation and changing of the advertising message, changing light bulbs, general servicing of the billboard, etc. More uniform horizontal illumination can be obtained as a result of evenly spacing LED fixtures along the catwalk kickrail, as opposed to adding and positioning protruding light fixtures. In addition to providing for more even illumination, evenly spacing LED fixtures along the catwalk kickrail eliminates the need for large clusters of LEDs. LED fixtures, especially those intended to be direct replacements for conventional light fixtures typically have large clusters of LEDs, which generate excessive heat build-up, resulting in premature LED failure. The use of the evenly spaced horizontal LED fixtures described herein provides for less power consumption, longer operating lifetimes, cooler operating temperatures, and considerably smaller fixtures than flood lights, electro-fluorescent tubes, or clustered LED fixtures. 
     The illustrated embodiments provide for front illumination of advertising billboards and other vertical surfaces by using a plurality of horizontally oriented, preferably evenly spaced, LED light fixtures which are mounted to the service access catwalk kickrail parallel to the billboard or sign face. 
     The illustrated embodiments also provide for an efficient layout of the LEDs, which simplifies cooling and efficiently distributes light in order to illuminate the copy area over a long horizontal distance. The LED fixtures are preferably evenly-spaced horizontally along the front of the sign face, and are preferably mounted in one, two, or three rows to avoid the build-up of heat, which buildup can reduce LED longevity. A buildup of heat is typical of spotlight-type fixtures, including cluster LED fixtures. 
     In addition, lamp arrays  30 A- 30 N may be stacked so as to achieve more luminosity, and the rows may be offset from one another so as to achieve a more uniform illumination across the copy area. 
       FIGS. 4-6  illustrate embodiments of various LED lamp array configurations.  FIG. 4  is an illustration of one embodiment of a lamp array  30  and shows a housing  32 , a plurality of LEDs  34 A- 34 N and a plurality of lens elements  36 A- 36 M, where M is less than or equal to N, and, preferably, a cover  38  to protect the LEDs  34  and lens  36  from the environment. 
       FIG. 5  is an illustration of another embodiment of a lamp array  30  and shows a housing  32  and, preferably, a cover  38 . The LEDs  34  and lens  36  are present but are not shown in this view. 
       FIG. 6  is a side elevation cutaway view of the embodiment of the lamp array  30 , such as the embodiment of  FIG. 4 , and shows the housing  32 , a typical position for the power supply  40 , and one LED  34 /lens  36  combination. 
       FIGS. 7-10  are photographs of exemplary lamp arrays  30 .  FIG. 7  shows an exemplary embodiment of a lamp array  30  with an LED cell  34  covered by an optical lens  36 .  FIG. 8  shows an exemplary embodiment of a lamp array  30  with an LED cell  34  which is not covered by an optical lens. 
       FIGS. 9 and 10  show an exemplary embodiment of a lamp arrays  30  from two different perspectives, and show the protective cover  38  in place. 
     As shown in  FIGS. 1-3 , the lamp arrays  30 A- 30 N are lined up, end to end, at the desired position with respect to the catwalk  14 , some but not all of which positions are shown. As can be seen, all LEDs  34  of the lamp arrays  30  preferably lie along the same line or axis, and are generally evenly spaced along the length of the catwalk  14 . The lamp arrays  30  are preferably mounted just outside the catwalk area  14 , which provides for ease of maintenance, such as replacing a cracked protective cover  38 . 
       FIGS. 11A-11E  illustrate some exemplary LED cell  34  configurations for a lamp array  30 . The LEDs  34  are spaced approximately 4 inches apart, which distance is preferred, but is not critical. The spacing is based on a tradeoff between, for example, the acceptable difference in the illumination levels in adjacent or even non-adjacent sections of the copy area, the minimum amount of lighting required, and the cost tradeoffs between higher power, but fewer, LEDs, and fewer lens, versus lesser power, but more, LEDs, and more lens, etc. 
       FIG. 11A  illustrates an embodiment wherein lenses  36  are used on all of the LEDs  34 . The various lenses  36  may be the same type or may be different types depending upon the uniformity of illumination desired or acceptable, color(s) desired, cost considerations, etc. 
     It will be appreciated that light from a light source spreads as the light gets farther away from the light source, so an area at one distance will receive a different amount of light than the same size area at a different distance. Further, it will be appreciated that a surface which receives light from a light source shining directly at the surface will have a higher level of illumination per area of surface than if that same surface were turned at an angle to the light source. To compensate for these effects, for example, when the LED arrays are mounted toward the bottom of the billboard face such as on the catwalk, then more of the light is directed toward the upper portion of the copy area, because the upper portion is farther away from the LED arrays than the bottom portion and is at a greater angle with respect to the LED arrays than the bottom portion. 
       FIG. 11B  shows an embodiment wherein different lenses  36  are used on some of the LEDs  34  and, preferably, no lenses are used on other LEDs  34 . The designations “TOP”, “MIDDLE”, and “FILLER” indicate the general vertical position on the copy area where the light from that particular LED  34  strikes the copy area. For example, for a billboard which has a copy area height of approximately 14 feet, a TOP area is preferably, but not necessarily, an oval area, approximately 2.5 feet high by 5 feet wide, the center of this TOP area being approximately 1.25 feet from the top edge of the copy area. A MIDDLE area is preferably, but not necessarily, a circular area, approximately 5 feet high by 5 feet wide, the center of this MIDDLE area being approximately 7 feet from the top edge of the copy area. Although the TOP and MIDDLE areas could overlap, an overlap is not necessary so, in this embodiment, these areas do not overlap. It will be appreciated that the illumination outside of an area does not abruptly fall to zero outside of the area, but tapers off. Thus, a TOP position LED will provide some illumination outside of the TOP area, and a MIDDLE position LED will provide some illumination outside of the MIDDLE area. These outside-area illuminations therefore combine and enhance the uniformity of the illumination. 
     A “FILLER” (or “BOTTOM”) area is preferably, but not necessarily, approximately the bottom half of the copy area, such as from the bottom edge of the copy area to approximately 9 feet from the bottom edge of the copy area. The FILLER area may be determined by focusing the light output from a FILLER LED, such as by using a lens, or may be determined by the characteristics of the particular LED device used. Although the MIDDLE and FILLER areas could overlap, an overlap is not necessary so, in this embodiment, these areas do not overlap. It will be appreciated, as mentioned above, that the illumination outside of an area does not abruptly fall to zero outside of the area, but tapers off. 
     The TOP and MIDDLE areas are obtained by the use of focusing lenses and, in one embodiment, the focusing lens for a TOP LED has a beamwidth of 23 degrees by 50 degrees, and the focusing lens for a MIDDLE LED has a beamwidth of 45 degrees. The FILLER LED preferably, but not necessarily, does not use a focusing lens. As used herein, the term “focus” is not limited to the narrowing of a beam of light from an LED but also includes broadening of a beam and adjusting the pattern of a beam. 
     In operation of a preferred embodiment, the TOP LEDs will illuminate the uppermost portions of the copy area. Preferably, the illumination footprints provided by the TOP LEDs in the same lamp array will overlap, and the illumination footprints provided by the TOP LEDs in adjacent arrays will overlap. The MIDDLE LEDs will illuminate the middle portions of the copy area. Also, preferably, the illumination footprints provided by the MIDDLE LEDs in the same lamp array will overlap, the illumination footprints provided by the MIDDLE LEDs in adjacent arrays will overlap. The FILLER LEDs preferably illuminate at least the bottom portion of the copy area. Preferably, the illumination footprints provided by the FILLER LEDs in the same lamp array will overlap, and the illumination footprints provided by the FILLER LEDs in adjacent arrays will overlap. The overlap, or near overlap, between different footprints serves to make the illumination more uniform across the billboard and to reduce contrast between adjacent areas. Too little overlap can cause darker areas to appear, while too much overlap can cause brighter areas to appear, as well as increasing the cost of operation. 
       FIG. 11C  is an illustration of one LED cell configuration, such as might be used in  FIGS. 11A and 11B , but without the lenses. 
       FIGS. 11D and 11E  show two alternative LED cell configurations wherein the LEDs are grouped. One situation in which these configurations may be used is, for example, when additional lighting is required so that the billboard face can be seen from a greater distance or in conditions other than near or total darkness. Another situation in which they may be used is, for example, to provide different colors or color effects. For example, all LEDs in a group may have the same color (but preferably different lens), and different groups may have different colors. As another example, the LEDs in a group may have different colors (and preferably similar or identical lens), and different groups may have lens with different characteristics. 
     In one embodiment, the LEDs are type Xlamp™ XR-E manufactured by Cree™ of Durham, N.C., and have an output of 100 Lumens at 350 milliamps (ma). These LEDs are rated at a current input of up to 1000 ma and, in one embodiment, the current input is 950 ma, which provides a light output of 180 Lumens. In another embodiment, the LEDs are type XLamp 7090 XR, also manufactured by Cree. 
     In one embodiment, such as when the above-mentioned Cree LEDs are used, the lens is an “FC Lens”, sold by Fraen™ Corporation, Reading, Mass. In another embodiment, the lens is a “CRS Square Lenses”, for CREE XR-E LEDs, sold by Marubeni America™ Corporation, Santa Clara, Calif. In one embodiment, the lens used for the “TOP” position LEDs is a type CRS-O manufactured by Ledil Oy™, Salo, Finland, which has a vertical beamwidth of 28 degrees and a horizontal beamwidth of 12 degrees, and the lens used for the “MIDDLE” position LEDs is a type FC-W2-XR79-HRF manufactured by Fraen Corporation, and has a beamwidth (horizontal and vertical) of 41 degrees. 
     In another embodiment, rather than there being a single row of LEDs in a lamp array  30 , there are two or more rows of LEDs in an array. The LEDs in the different rows may be in a vertical column, or they may be offset, if desired, so as to further and more evenly distribute the light shining on the copy area. For example,  FIG. 11D  shows a lamp array which has two rows of LEDs in a vertical column, and  FIG. 11E  shows a lamp array which may be considered to have three rows, the center row being offset horizontally from the other two rows. Other embodiments are also possible such as, for example, where the top row in  FIG. 11D  is offset, with respect to the bottom row, by one-half of the distance between the elements in the bottom row. 
     Although the embodiments are depicted on billboards which have catwalks, the LED arrays can also be used on billboards which do not have catwalks. One could use, for example, a plurality of mounting arms to support the arrays. One could also, for example, provide a railing, set out from the bottom of the billboard, and held in place by a plurality of mounting arms, and fasten the arrays to the railing. Also, although the embodiments shown have the LED arrays mounted toward the bottom of the billboard, pointing generally upwardly, the LED arrays can, instead, be mounted toward the top of the billboard, and generally pointing downward. Top mounting of the arrays may be accomplished, for example, by a plurality of mounting arms as mentioned above, or by a railing set out from the top billboard and held in place by a plurality of mounting arms. Also, if there are two billboards which are stacked, then the arrays could be mounted to the catwalk of the upper billboard and, in this case, the catwalk on the upper billboard may serve for mounting of the light arrays for both the upper billboard and the lower billboard. In addition, if exceptional uniformity of illumination is desired, or if exceptional luminance is desired, then two sets of LED arrays could be used, one mounted toward the bottom of the billboard, pointing generally upwardly, and the other mounted toward the top of the billboard, and generally pointing downward. 
     For convenience of discussion below, it is assumed that the copy area has a size of 12 feet×24 feet. Thus, the copy area could be considered to be a 12 foot by 24 foot matrix of light surfaces. Also for convenience, Table I and Table II have both been broken into two table segments, with the top segment of the table representing the left one-half of the copy area, and the bottom part representing the right one-half of the copy area. 
     Table I shows the illumination across a 12 foot by 24 foot panel, which is illuminated by a typical four-projection arm and light source array. The total power provided to the four High Intensity Discharge lamps (HID) is 432 watts (3.6 amps at 120 VAC), and the four arrays produce an illumination of 42,000 Lumens. The panel is divided into 1 foot squares, but measurements were not taken on the leftmost, rightmost, topmost, or bottommost squares. Accordingly, measurements were conducted on 220 (10×22) squares. The numbers show the illumination in foot-candles for each square and are actual measurements, except that the values for squares A6-A22, B6-B22, and C16-C22 are estimates. From this, it can be seen that the total copy area illumination is 11152 footcandles, the average illumination is 50.60 footcandles, and the low and high illuminations are 16 and 124 footcandles, respectively. As the arrays produce 42000 lumens, and only 11152 lumens strike the board, this means that up to 30848 lumens are not used, contributing nothing to the illumination of the copy area, but contributing to night sky pollution. In other words, only about 26.55% of the illumination strikes the copy area, and the other 73.45% is effectively wasted. 
     Table II similarly shows the illumination across a 12 foot by 24 foot panel, which is illuminated by an embodiment using LEDs. The total power provided to the LEDs is 240 watts (2.0 amps at 120 VAC), and the LEDs produce an illumination of 13,500 Lumens. The numbers show the illumination in foot-candles for each square and are actual measurements, except that the values for squares A6-A22, B6-B22, and C6-C22 are estimates. From this, it can be seen that the total copy area illumination is 10747.6 footcandles, the average illumination is 48.85 footcandles, and the low and high illuminations are 12.6 and 99 footcandles, respectively. As the arrays produce 13500 lumens, and 10747.6 lumens strike the board, this means that only 2752.4 lumens are not used. In other words, about 79.61% of the illumination strikes the desired areas of the copy area, and only 20.39% is wasted. 
     Therefore, the efficiency of the LED fixture, as compared to the High Density fixture, has been increased almost three-fold, from 26.55% to 79.61%. Further, the power consumption has been reduced by over 40% but the total light striking the copy area has decreased by less than 4%. 
       FIG. 12  is a photograph showing the light distribution provided by the LED lamp array of one embodiment. 
       FIG. 13  is a photograph illustrating one method of connecting lamp arrays  30  in an end-to-end configuration. The lamp arrays  30  have end caps  40 , and are held together by mounting hardware  42 , such as, but not limited to, a bolt and a nut. The method of connecting the lamp arrays  30  is not critical and other techniques may be used. 
     
       
         
           
               
             
               
                 TABLE I 
               
               
                   
               
               
                 HID LIGHTING 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
               
               
                   
               
               
                 A 
                 18 
                 21 
                 23 
                 26 
                 28 
                 28 
                 29 
                 32 
                 32 
                 31 
                 30 
               
               
                 B 
                 19 
                 24 
                 28 
                 31 
                 36 
                 37 
                 36 
                 39 
                 41 
                 40 
                 38 
               
               
                 C 
                 20 
                 26 
                 33 
                 39 
                 43 
                 46 
                 46 
                 48 
                 50 
                 50 
                 49 
               
               
                 D 
                 19 
                 25 
                 36 
                 46 
                 51 
                 57 
                 58 
                 57 
                 60 
                 61 
                 58 
               
               
                 E 
                 19 
                 26 
                 35 
                 45 
                 60 
                 67 
                 72 
                 69 
                 69 
                 70 
                 67 
               
               
                 F 
                 17 
                 24 
                 33 
                 49 
                 62 
                 73 
                 78 
                 82 
                 80 
                 80 
                 77 
               
               
                 G 
                 16 
                 20 
                 29 
                 41 
                 61 
                 72 
                 79 
                 85 
                 93 
                 100 
                 103 
               
               
                 H 
                 17 
                 21 
                 27 
                 35 
                 48 
                 66 
                 73 
                 83 
                 101 
                 114 
                 124 
               
               
                 I 
                 19 
                 22 
                 29 
                 35 
                 44 
                 54 
                 69 
                 82 
                 98 
                 107 
                 109 
               
               
                 J 
                 18 
                 23 
                 28 
                 38 
                 41 
                 49 
                 47 
                 60 
                 82 
                 95 
                 86 
               
               
                   
               
               
                   
                 12 
                 13 
                 14 
                 15 
                 16 
                 17 
                 18 
                 19 
                 20 
                 21 
                 22 
               
               
                   
               
               
                 A 
                 30 
                 31 
                 32 
                 32 
                 29 
                 28 
                 28 
                 26 
                 23 
                 21 
                 18 
               
               
                 B 
                 38 
                 40 
                 41 
                 39 
                 36 
                 37 
                 36 
                 31 
                 28 
                 24 
                 19 
               
               
                 C 
                 49 
                 50 
                 50 
                 48 
                 46 
                 46 
                 43 
                 39 
                 33 
                 25 
                 20 
               
               
                 D 
                 58 
                 61 
                 60 
                 57 
                 58 
                 57 
                 51 
                 46 
                 36 
                 25 
                 19 
               
               
                 E 
                 67 
                 70 
                 69 
                 69 
                 72 
                 67 
                 60 
                 45 
                 35 
                 26 
                 19 
               
               
                 F 
                 77 
                 80 
                 80 
                 82 
                 78 
                 73 
                 62 
                 49 
                 33 
                 24 
                 17 
               
               
                 G 
                 103 
                 100 
                 96 
                 85 
                 79 
                 72 
                 61 
                 41 
                 29 
                 20 
                 16 
               
               
                 H 
                 124 
                 114 
                 101 
                 83 
                 73 
                 66 
                 48 
                 35 
                 27 
                 21 
                 17 
               
               
                 I 
                 109 
                 107 
                 98 
                 82 
                 69 
                 54 
                 44 
                 35 
                 29 
                 22 
                 19 
               
               
                 J 
                 86 
                 86 
                 95 
                 82 
                 60 
                 47 
                 49 
                 41 
                 38 
                 26 
                 23 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE II 
               
               
                   
               
               
                 LED LIGHTING 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
               
               
                   
               
               
                 A 
                 16.5 
                 18 
                 19 
                 25 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
               
               
                 B 
                 19.9 
                 21.5 
                 24.3 
                 30 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
               
               
                 C 
                 25.9 
                 29.9 
                 32.4 
                 39.5 
                 49 
                 49 
                 49 
                 49 
                 49 
                 49 
                 49 
               
               
                 D 
                 33.8 
                 39.3 
                 44.6 
                 51.8 
                 60.7 
                 62 
                 66 
                 60 
                 50 
                 57 
                 64 
               
               
                 E 
                 41.7 
                 50.7 
                 53.8 
                 57 
                 71.7 
                 71 
                 71 
                 62 
                 53 
                 65 
                 76 
               
               
                 F 
                 39.1 
                 50.1 
                 59.2 
                 65.6 
                 74.5 
                 80.1 
                 79 
                 65 
                 60 
                 76 
                 83 
               
               
                 G 
                 27.7 
                 38 
                 50 
                 62 
                 70 
                 82 
                 84 
                 70 
                 66 
                 83 
                 92 
               
               
                 H 
                 21.3 
                 33.8 
                 43.6 
                 53.1 
                 63.2 
                 77 
                 84 
                 67 
                 63.5 
                 87.3 
                 94.1 
               
               
                 I 
                 17.6 
                 30.3 
                 41.8 
                 45.8 
                 47.6 
                 54 
                 57 
                 80 
                 48 
                 69 
                 68 
               
               
                 J 
                 13 
                 20 
                 26 
                 27 
                 27 
                 29 
                 29 
                 27 
                 29 
                 34 
                 37 
               
               
                   
               
               
                   
                 12 
                 13 
                 14 
                 15 
                 16 
                 17 
                 18 
                 19 
                 20 
                 21 
                 22 
               
               
                   
               
               
                 A 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 31.6 
                 25 
                 19 
                 18 
                 16.5 
               
               
                 B 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 39.5 
                 30 
                 24.3 
                 21.5 
                 19.9 
               
               
                 C 
                 49 
                 49 
                 49 
                 49 
                 49 
                 49 
                 49 
                 39.5 
                 32.4 
                 29.9 
                 25.9 
               
               
                 D 
                 63 
                 55 
                 57 
                 64 
                 62 
                 53 
                 46 
                 45 
                 44 
                 34 
                 16.5 
               
               
                 E 
                 72 
                 61 
                 65 
                 68 
                 66 
                 58 
                 51 
                 53 
                 50 
                 40 
                 17 
               
               
                 F 
                 78 
                 65 
                 71.2 
                 74 
                 73 
                 64 
                 53 
                 56 
                 57 
                 41 
                 18 
               
               
                 G 
                 87 
                 71 
                 80 
                 81 
                 80 
                 72 
                 65 
                 63 
                 64 
                 49 
                 17.8 
               
               
                 H 
                 99 
                 70.1 
                 82 
                 84 
                 78 
                 69.9 
                 66.8 
                 65.5 
                 65.1 
                 47.9 
                 18.6 
               
               
                 I 
                 71 
                 58 
                 59 
                 60 
                 61 
                 57 
                 58 
                 56 
                 54 
                 38 
                 16 
               
               
                 J 
                 35 
                 32 
                 31 
                 34 
                 34 
                 34 
                 35 
                 37 
                 34 
                 25 
                 12.6 
               
               
                   
               
            
           
         
       
     
     It will be appreciated that the individual LEDs may be individually focused onto the copy area at the desired location and with the desired beamwidth. It will also be appreciated that if top mounting of the light array is desired, then some mounting mechanism must be provided to replace the catwalk used for bottom mounting of the light array. Even in such a case, however, the light array will still be closer to the copy area than in conventional technology, and there will not be the long projection arms used by conventional technology. 
     The housing may be secured to the catwalk, or to another available mounting surface, by any convenient technology, such as, but not limited to, bolts, clamps, straps, and welding. Also, although not shown, it will be appreciated that electrical power must be provided to the light arrays in some manner, such as by conventional wiring. 
     In addition to billboards, the LED arrays may be used to illuminate the side of a building, such as for esthetic purposes. The LED arrays can be, if desired, mounted using supports extending from the sides of the building, or may be mounted on, for example, existing ledges of the building. The LED arrays may also be used to light highway and roadway signs, from above or from below, or both. 
     Various advantages and benefits result from the above. Although each embodiment provides at least one advantage or benefit, there is no requirement that any embodiment must provide all benefits, as tradeoffs are to be expected. Therefore, it is expected that one of ordinary skill in the art can and will choose among the various characteristics and features of the various embodiments to achieve the desired illumination result.