Abstract:
A lighting system and process for lighting objects particularly art works such as paintings and sculptures, comprising a diffusing film that scatters the light such that the object is illuminated substantially uniformly. The preferred embodiment employs one row of such lighting sources for small objects, and two or more rows for larger objects. The inner row is directed towards the top portion of the object and the outer row is directed towards the bottom portion of the object. The rows need not be placed next to each other. For 3-dimensional objects, one row may be below the object and the other row above to eliminate shadows.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
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     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
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     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of lighting systems, and more particularly to a 1- or multi-array of lights with each row having different intensities, different angles, different secondary optics, and different diffusion films to scatter the light towards an object—typically an art work—to achieve substantially uniform lighting of the object. 
     2. Background Art 
     Paintings, sculptures and other art works are typically illuminated by one or more lights directed generally towards the center of the art work. This causes a hot spot of intense light at that area, and increasingly dimmer lighting towards the periphery of the work. This greatly detracts from the aesthetic perception and enjoyment of the art work. 
     Some adjustable multi-light arrays improve this deficiency, but they still create two or more hot spots, leaving non-uniform lighting of the art work. Lights are typically placed immediately above the art work, or in the ceiling, leaving the top portion of the work significantly brighter than the bottom portion due to attenuation and disbursement of the light over a greater distance towards the bottom, along with greater intensity in the center of the horizontal axis than at the sides. 
     One device disclosed in U.S. Pat. No. 7,070,293 B2 shows a 2- to 3-row overhead array of lights spanning the width of the art work in which each row of lights has a different intensity and angle towards the art work. One row is aimed towards the top portion of the art work having lower intensity than the row (or rows) angled towards the lower portion or portions of the art work. One embodiment shows the use of optical attenuators to provide a relatively even gradient of light from the top to the bottom of the art work, away from the light feature. 
     Attenuators, however, are inefficient as they block a portion of the light, requiring greater intensity of light. They work by either absorbing the light, or reflecting it back towards the light source, where it is dissipated. Graduated attenuators, such as a Benday screen, are suggested in the &#39;293 patent to block a greater amount of light that is aimed at the top-most portion of the art work, and less light as the angle moves down the art work. Benday screens are comprised of opaque dots on a transparent film, with a greater density of dots positioned on the screen in the areas greater attenuation is desired. In practice, such attenuators have produced a somewhat uniform lighting system, but fail short of producing a uniform light. 
     It would be beneficial to have a system for directing and disbursing the light without the use of attenuators such that the art work is uniformly lit, and one that is inexpensive to make. It would be further beneficial to have a small, unobtrusive fixture to illuminate the art work. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention solves these problems by using a diffusing film to scatter the light directed towards an object, typically an art work. Diffusing film is comprised of a thin piece of material—typically plastic—that scatters light as it passes through it. Specialized films can diffuse light in a specified manner, such as 5 degrees, or 30 degrees, enabling the light to be disbursed in an even and controlled fashion even with multiple light sources. 
     In the preferred embodiment, for small art works—about 16 inches in height or less—one row of lights spanning the width of the art work is sufficient to light it evenly so that human eye cannot detect differences in intensity over the vast majority of the art work. The threshold for avoiding human detection of different illumination levels is within about 50 percent intensity throughout the art work. 
     For larger art works, two rows of lights are positioned atop the art work—typically a painting—generally spanning the width of the art work. The inner-most row, or first module, is directed towards the top portion of the art work, and the outer row, or second module, is directed further down the art work. The light sources are preferably light-emitting diodes (“LEDs”). 
     The light sources on inner-most row—which is designated as module one or the first module—are focused by parabolic reflectors and directed towards the art work. Parabolic reflectors create a secondary ring of more intense light around the central hot spot generated by the light source. Diffusers take advantage of this phenomenon to scatter the light in a more uniform manner. Diffusers may also be used to scatter the light horizontally, thereby avoiding the need to have a continuous row of lights extend completely across the horizontal length of the art work. 
     The outer-most row of lights (module two) preferably has total internal reflection (TIR) lenses instead of parabolic reflectors, which are larger, less efficient and more costly than TIR lenses. Because of the greater distance from the targeted area of illumination, the light need not be scattered with as much of a scattering effect as with the inner-most row of lights (module one). In other words, module two does not require the benefits from the secondary ring effect because of it has a smaller angle of its propagation field due to its greater distance from the light source. 
     Diffusing films are preferably used for each module. Diffusing films comprise a thin film having a texture embossed on the film to scatter the light. In one embodiment, embossed diffusing film is used, which is also known as holographic diffusing film. 
     In a single-module configuration for art works no more than 16 inches high, the module may be pivoted along the horizontal axis to provide the user control to aim the light onto the art work. A dimmer switch is also used to adjust the intensity of the light. In a two-module configuration, each module may independently pivot along the horizontal axis, with each module including a dimmer switch to independently adjust the intensity of the light. The ability to adjust the angle and intensity of each module enables the user to tailor the lighting system to the particularly sized art work to ensure substantially uniform light at the desired illumination level. In addition, a “global” dimming feature is provide to allow the entire fixture (both modules) to be dimmed and turned on and off in unison. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings illustrate the invention, where like reference numerals indicate the same feature throughout the drawings: 
         FIG. 1  shows an exploded view of a generic module of the present invention, along with the module itself; 
         FIG. 2  shows a side and center view of the lighting system as assembled on the top portion of a painting; 
         FIG. 3  shows a 3-dimensional view of the lighting system attached to a painting with the two modules removed to show the relative angles of each module; and 
         FIG. 4  shows a side view of the lighting system as assembled on the top portion of a painting along with the angle of projection and the portion of the painting illuminated by each module. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     1. Definitions 
     In this specification and the claims that follow, the phrases “illuminated substantially uniformly” and “illuminating the object substantially uniformly,” and like designations, shall mean to illuminate an object such that the art work or other object is illuminated sufficiently uniformly that, for at least 75 percent of the front surface of the object, the human eye cannot reasonably detect a difference in illumination intensity from one point on the art work or object to another point. 
     The human eye cannot typically dissociate between illumination intensity unless the intensity exceeds about 50 percent difference from one area to another. Consequently, “illuminated substantially uniformly” and “illuminating the object substantially uniformly” shall mean up to about 50 percent difference in illumination intensity, with the actual percentage being the amount in which an average person cannot dissociate between the illumination intensity from one area to another over at least 75 percent of the surface of the object. The “about 50 percent” shall be no less than 50 percent difference in illumination intensity, but no greater than the percent difference that an average person cannot detect a difference in illumination level with the naked eye. 
     For the portion of the art work that is not illuminated within this about 50 percent difference, that is, less than 25 percent of the art work, for an object “illuminated substantially uniformly,” the illumination intensity of any particular area shall not differ by more than 100 percent of the average illumination level of the first area (the first area being the portion of the art work that has an illumination level within about 50 percent difference). In all of these cases, the percent difference shall be calculated by the percent increase of the lower or lowest illumination level. 
     In this specification and the claims that follow, the phrase “an object” or “the object” shall mean either a single object or a plurality of objects that collectively are generally adjacent or in proximity to each other, such that the collection of objects can be deemed a single entity comprised of individual objects. (For example, an object may comprise two distinct paintings adjacent to each other, or a multi-piece sculpture.) The phrase “an object” or “the object” shall also be limited to an object, or collection of distinct objects, that are at least nine inches (9″) in the dimension orthogonal to the light fixture. 
     In this specification and the claims that follow, the word “height” refers to the dimension along the side of the object or art work that is in the line of sight of a viewer and is perpendicular to the longitudinal axis of the row of light sources; that is, it is in the direction that the light is projected across the object or art work. The terms “width” and “side” is the dimension parallel to the longitudinal axis of the row of light sources, and perpendicular to the “height” of the object or art work. 
     2. Preferred Embodiment 
     The drawings are for illustrative purposes of the preferred embodiment of the present invention, shown for a painting. The same design characteristics apply to other art works—such as a sculpture—and to any object for which one desires uniform lighting, such as historical or valuable documents. The substitution of various objects would be obvious to one ordinarily skilled in the art. 
     In  FIG. 1 , a single generic module is shown along with its housing. Generic module  100  is shown in its configured state at the bottom of the drawing, and an exploded view showing the various internal layers, housing and hardware is shown above. Housing  10  is at the top of generic module  100 , and serves both as a top housing structure and a heat sink to dissipate heat generated by light-emitting diodes  210  (“LED  210 ”). Thermally conductive pad  20  is located immediately below housing  10  to provide electrical isolation and facilitate the transfer of heat to housing  10 . A plurality of holes  44  are positioned to line up with fasteners  40 , which screw into threaded holes in housing  10  (not shown in the drawings) to hold the various layers of generic module  100  together. Holes  44  are in-line with holes  41 ,  42 ,  43  on various other layers such that fasteners  40  may be inserted. 
     Circuit board  200  is positioned immediately below thermally conductive pad  20 . Circuit board  200  is comprised of driver electronics, local dimming control  220 , and a plurality of LEDs  210 . Dimming control  220 , which controls the illumination intensity of LEDs  210 , is positioned on one side of circuit board  200 . Holes  43  are present in circuit board  200  through which fasteners  40  extend. In the preferred embodiment, high brightness, surface mount, high color rendering, white LEDs are used. Circuit board  200  and dimmer switch  220  are well known to those skilled in the art. 
     LEDs  210  are inserted into secondary optics  300 , which reflect the light generated by LEDs  210  in the general direction opposite housing  10 . Such secondary optics  300  are well known in the art. In first module  110 , which is directed towards the top portion of the painting, secondary optics  300  are preferably parabolic reflectors. Parabolic reflectors take advantage of the phenomenon that they create a secondary ring of intense light a radial distance from and around the central hot spot generated by the light source. In second module  120 , which is directed towards the bottom portion of the painting, secondary optics  300  are preferably total internal reflection (TIR) lenses. 
     Below secondary optics  300  is diffusing film  400 , which is a thin film that scatters light in a controlled manner as the light passes through it. Diffusing films comprise a thin film having a texture embossed on the film to scatter the light. In one embodiment, embossed diffusing film is used, which is also known as holographic diffusing film. Other types of diffusing film may also scatter the light sufficiently, such as a proprietary diffusing film disclosed at http://www.fusionoptix.com/products/materials/diffusion.htm. Holes  42  are positioned on diffusing film  400  in line with fasteners  40 . 
     The assembly described above is housed beneath by cover  30 , which has holes  41  in line with fasteners  40 . Cover  30  is secured to housing  10  by fasteners  40 , which extend through holes  41 ,  42 ,  43 ,  44  and is attached to threaded holes in housing  10 . Other forms of securing cover  30  to housing  10  may alternately be used. 
     The result of the above components so assembled forms generic module  100 , which is shown at the bottom of  FIG. 1 . First and second modules  110 ,  120  are identical except that optics  300  are parabolic reflectors in first module  110  and total internal reflective lenses in second module  120 , and diffusing film  400  has a larger angle of diffusion than the diffusing film in second module  120 . Alternately, other types of optics and diffusing film may be used for either module. 
     As shown in  FIG. 2 , for a one-row assembly for use with small paintings, only first module  110  is used. It is housed in module housing  70 , shown in  FIG. 2 . End caps  60  are secured on both ends of housing  70 . First module  110  is mounted to end caps  60  such that it may pivot along the longitudinal axis, that is, horizontally, to enable the user to aim first module  110  onto painting  80  so that it lights the entire surface. Module housing  70  is attached to assembly  50 , which is secured to painting  80  by adjustable brackets  55 , which allows the assembly to be raised and lowered by the user. 
     As shown in  FIGS. 3 and 4 , for a two-row assembly first module  110  and second module  120  are employed. They are housed in module housing  70 . ( FIG. 3  shows modules  110 ,  120  removed from module housing  70  to better illustrate the relative longitudinal angle between each of modules  110 ,  120 ; and  FIG. 4  shows modules  110 ,  120  inside housing  70 , with an enlargement of the modules.) Each of first module  110  and second module  120  are mounted to end caps  60  such that they may independently pivot along the longitudinal axis, that is, horizontally, to enable the user to aim the light onto painting  80 . When properly orientated, or angled, first module  110  projects light from LEDs  210  onto painting  80  in propagation field  115 , and second module  120  projects light from its LEDs  210  onto painting  80  in propagation field  125 . Note that each module  110 ,  120  should be angled such that propagation fields  115 ,  125  have minimal to no overlap, that is, the lower boundary of propagation field  115  is substantially in the same location as the top boundary of propagation field  125 . 
     The width of modules  110 ,  120  (along the longitudinal or horizontal axis) is preferably the width of painting  80 , but may be less than the width if diffusing film  400  is designed to scatter the light horizontally outward onto painting  80  from the outer-most LEDs  210 . 
     While the preferred embodiments shown in the various drawings depict one- and two-module lighting fixtures, three or may be used for a particularly tall object or art work. In such event, module two would be used for the third module, which would project light farther away from the lighting fixture than the first and second modules. In such event, the third and any subsequent modules for the preferred embodiment, the TIR lenses would be employed for optics  300 . 
     Alternately, a one- or two-module lighting fixture may be positioned on each of the top and bottom of the object or art work, or on each side. For configurations with two one-module fixtures positioned opposite each other, in the preferred embodiment, parabolic reflectors would be used. For configurations with one or two two-module fixtures positioned opposite each other—such as for use in a relatively tall art work—parabolic reflectors would preferably be used for the first module, and where a two-module fixture is used, TIR lenses would preferably be used for the second module. 
     The one- and two-module lighting fixtures are also shown being attached to the object itself, but may instead be mounted directly to a wall or on the ceiling or floor, and may be located many feet from the object that it illuminates. 
     The two-module configuration may instead be placed in a single module having two sets of LEDs, where each set is directed at a different angle of propagation towards the object, typically in an alternating fashion. For multi-module configurations, one or more modules may have two such sets of LEDs. 
     For any configuration, the light sources need not be LEDs, but other conventional light sources, or any light source that may later be conceived. 
     Various other modifications may be made to that depicted in the various drawings of the preferred embodiment of the present invention without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited by the preferred embodiment shown in the various drawings and described herein, but by the scope of the claims.