Abstract:
Disclosed is a light diffusing panel, a light diffusing module and a traffic sign incorporating the light diffusing module. A front face of the panel has a plurality of linear disruptions, which disruptions redirect the light to emit from the front face of the panel in a broad diffuse emission. The plurality of linear disruptions extends as a series of parallel lines across the front face. A second plurality of linear disruptions extends as a series of parallel lines across the front face, with the first plurality of linear disruptions forming a grid across the front face. The light diffusing module adds to the light diffusing panel, a reflective sheet adjacent to the rear face of the light diffusing panel and light sources along an edge of the light diffusing panel. The traffic sign adds a message panel to the light diffusing module as well as a power supply.

Description:
FIELD OF INVENTION 
       [0001]    The present invention is in the field of light diffusing panels and assemblies of light diffusing modules, and the use of light diffusing modules for signs, in particular traffic signs. 
       BACKGROUND 
       [0002]    Light is electromagnetic energy transmitting with the characteristics of both particles and waves. The intensity of visible light can be modified by a diffuser, as is known in the art. 
         [0003]    Light emitting diodes (LEDs) are used in an increasing amount as alternates to other, more traditional, lighting sources, such as incandescent and fluorescent lights. For the same power utilization, LEDs emit far more light than the more traditional lighting sources, and use far less power for the same amount of light. LEDs have a longer operational lifespan, and may be used in environmental conditions that do not permit long use of traditional lighting sources. 
         [0004]    LEDs present a number of disadvantages that have prevented them from being adopted as replacements for traditional lighting sources. LEDs are discrete sources of light, producing intense light within the narrow beam of their output, and dim light outside of that beam. This problem is known as the point source problem of LED lighting. 
         [0005]    LEDs provide only point source illumination, not uniform planar illumination. It is consequently necessary to somehow distribute the light emitted by one or more LEDs so as to uniformly illuminate a plane. LEDs are often set in a row or array to increase overall light output and attempt to provide a broader beam of light. 
         [0006]    It is known to add a diffuser to one or more LEDs to alleviate the point source problem, distributing the point source light to a broader distribution. Prior art diffusers include a frosted or abraded surface, a particulate medium, prisms or lenses on a diffuser panel surface, raised protrusions on a diffuser panel surface, coatings, reflective surfaces and combinations of one or more of the foregoing. Microelectromechanical systems have also been used for diffusing or redirecting LED light sources, primarily in liquid crystal display systems. 
         [0007]    Prior art edge lit diffusing panels have provided a variety of surface disruptions to reflect LED light, including frosted or abraded surfaces, dot or circle disruptions, and lines. Prior art diffusing panels have disclosed varying the size and depth of the surface disruptions as a way of providing uniform light intensity over an area. 
         [0008]    The present invention has a specific utilization for traffic signs and signaling apparatus. Prior art traffic signs provide a reflective surface allowing for greater visibility of the signs at night or in reduced lighting conditions. However, the reflective surface relies upon an external light source, such as that of an oncoming vehicle or a fixed mounted light, and the visibility of the traffic sign and its reflective surface is dependent upon the brightness and angle of the external light source relative to the desired viewer of the traffic sign. Where a vehicle may not have fully operational forward facing lights, the available light for reflection would be reduced, thereby reducing the effective visibility of the traffic sign. 
         [0009]    The invention is specifically designed for use in traffic signs, providing a greater visibility than available by reflecting an external light. Providing an internal illumination for traffic signs will result in greater efficiency and safer conditions for motor vehicle operators and pedestrians alike. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention is a light diffusing panel and light diffusing module incorporating the light diffusing panel. The light diffusing panel allows light to enter from distinct light sources, preferably LEDs, at an edge of the panel. A front face of the panel is comprised of a plurality of etched linear disruptions. The plurality of etched linear disruptions extends as a series of parallel lines across the front face. Preferably, a second plurality of etched linear disruptions extends as a series of parallel lines across the front face, perpendicular to the first plurality of etched linear disruptions, forming a grid across the front face. The rear face of the panel is preferably smooth, allowing light to reflect toward the front face. The linear disruptions on the front face increase the redirection of light to emit from the front face of the panel in a broad diffuse emission. 
         [0011]    The light diffusing module is comprised of the light diffusing panel, a reflective sheet adjacent to the rear face of the light diffusing panel, and a plurality of light sources along an edge of the light diffusing panel. 
         [0012]    The invention is specifically designed for incorporation into traffic signs, providing a traffic sign capable of being visible at greater distances than by mere reflection of oncoming vehicle lights. As a traffic sign, the light diffusing module is placed behind an informative signage or graphic, providing a back lighting effect for the signage and increasing the visibility thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a front perspective exploded view of the light diffusing panel of the present invention. 
           [0014]      FIG. 2  is a front plan view of the light diffusing panel of the present invention. 
           [0015]      FIG. 3  is cross-sectional side view along line B-B of  FIG. 2 . 
           [0016]      FIG. 4  is a cross-sectional side view along line A-A of  FIG. 2 . 
           [0017]      FIG. 5  is a front perspective exploded view of a light diffusing module of the present invention. 
           [0018]      FIG. 6  is a front plan view of a traffic sign incorporating the light diffusing module of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    The invention preferably consists of a light diffusing panel  100  formed of a plane of transparent or nearly transparent material. The light diffusing panel  100  has front and rear planar surfaces ( 101 ,  102 ). The front planar surface  101  has a first plurality of linear disruptions  120  extending along its surface. In a preferred embodiment, there is a second plurality of linear disruptions  110  extending perpendicular to the first plurality of linear disruptions  120 , forming a grid  150  on the front planar surface  101 . 
         [0020]    The linear disruptions ( 110 ,  120 ) on the front planar surface  101  are preferably uniform in depth and width. The linear disruptions ( 110 ,  120 ) on the front planar surface  101  are preferably formed by laser etching, which is known to create uniform lines. Linear disruptions ( 110 ,  120 ) are interruptions in the front planar surface  101 , which otherwise has a smooth and even surface. 
         [0021]    Light diffusing panel  100  is capable of receiving light emanating from a light source, where the light is initially directed at an oblique angle relative to the front planar surface  101 . Preferably, the light source generates beams of light directed perpendicular to the front planar surface. At least part of the light entering light diffusing panel  100  will interact with the linear disruptions, causing refraction toward and outward from the front planar surface  101 . Other components of the light entering light diffusing panel  100  will reflect off of the interiors of front planar surface  101  and rear planar surface  102 , eventually emanating outward through front planar surface  101 . 
         [0022]    Light diffusing panel  100  may be comprised of glass, acrylic or plastic, or any material capable of allowing light to transmit there through. The thickness of light diffusing panel  100  may vary, but is preferably wider than the width of a light source used with the light diffusing panel to ensure efficient light diffusion. Where the light source is a plurality of LEDs, known for being small point sources of light, the panel width may be less than a quarter of an inch. 
         [0023]    A reflective coating  200  is applied to the rear planar surface  102  of the light diffusing panel  100 , redirecting light toward the front planar surface  101 . Reflective coating  200  is preferably white or light colored to provide additional diffusion to the reflected light, although a mirrored or other surface capable of reflecting light may also serve the function of reflecting the light toward front planar surface  101 . 
         [0024]    One embodiment of the invention provides light sources  400  along at least one edge of the light diffusing panel. In a preferred embodiment, at least one channel  220  at or near an edge of light diffusing panel  100  may be provided for placement of light sources  400 , the light sources  400  being LEDs. For the light diffusing module of the present invention, channel  220  with LED light sources  400  is provided as part of light diffusing panel  100 . In  FIG. 3 , channel  220  is shown with a dashed line, being visible through transparent light diffusing panel  100 . In a preferred embodiment, LED light sources  400  would be sealed within channel  220 , preventing the entry of water or dirt from coming into channel  220 , and potentially interfering with the operation of LED light sources  400 . 
         [0025]    For light diffusing panels with larger surfaces, the light sources may be placed along additional or all edges of light diffusing panel  100 , or may be placed within additional channels at locations remote from edges of light diffusing panel  100 . For efficient operation, the width of the light sources is preferably no wider than the width of light diffusing panel  100 , namely the distance between front planar surface  101  and rear planar surface  102  of light diffusing panel  100 . 
         [0026]    LEDs are preferred for use as light sources as LEDs draw lower power than incandescent or fluorescent light sources. With the lower power requirement, LED light sources can be used with solar power and have a longer life span on battery power. LEDs are often small point sources, allowing for use in small locations. LEDs can be used in a variety of temperature ranges, making them more suited for outdoor applications. 
         [0027]    With an edge-lit light diffusing panel, light emanating from the LEDs is spread through the panel by internal reflection. Disruptions formed on or in one surface of the panel scatter the LED light, re-directing the light to emit through the surface of the panel. In a preferred embodiment of the present invention, the linear disruptions ( 110 ,  120 ) in the panel surface (front planar surface  101 ) are laser-etched into the surface of the panel, as laser etching provides an accurate and consistent surface disruption for the LED light scattering function. Alternate etching techniques may be used, where such alternate etching techniques produce consistent surface disruptions. 
         [0028]    It is preferred that the linear disruptions  110  be in a parallel arrangement to other linear disruptions  110  and of uniform spacing. Similarly, it is preferred that linear disruptions  120  be in a parallel arrangement to each other and also of uniform spacing. Where linear disruptions  110  and  120  are provided, with linear disruptions  120  being perpendicular to linear disruptions  110 , a grid  150  of linear disruptions is formed on front planar surface  101 . 
         [0029]    The reflected and refracted light emanating from the front planar surface has a uniform brightness. For applications involving long distances from the light source to areas on the front planar surface, the intensity of the light may be increased through the use of additional light sources on other edges of light diffusing panel  100 , or within light diffusing panel  100 . 
         [0030]    The light diffusing module of the present invention is particularly suited for use in traffic signs and messaging.  FIG. 5  shows the assembly of a light diffusing module, and  FIG. 6  shows an example representation of a stop sign incorporating the light diffusing module of the present invention. The term “traffic sign” is used herein as representative of any exterior sign or indicator used for control, regulation and information of and for any type of vehicles, including land, water and air vehicles, as well as pedestrians. 
         [0031]    In a traffic sign assembly, the light diffusing module is constructed as described above. The traffic sign will add a message panel  500 , which is placed in front of front planar surface  101 . Message panel  500  is comprised of transparent or translucent material, allowing the diffused light emanating from front planar surface  101  to be visible there-through. As is known in the art, the nature of the material comprising message panel  500  is compliant with government regulations for visible color and size. In operation, the light emanating from front planar surface  101  provides a back lit effect for message panel  500 , resulting in greater visibility of message panel  500 . 
         [0032]    In a preferred embodiment, anti-glare coating  600  is placed between front planar surface  101  and message panel  500 . As is known in the traffic sign industry, it may not be permitted to cover message panel  500  with any materials other than those approved for use with traffic signs. 
         [0033]    A frame  710  may be placed around the formed light diffusing module, to seal the light diffusing module against the effects of weather, and to support the light diffusing module. As the light diffusing module has no moving parts, and LEDs have long life spans, maintenance of the present invention incorporated into a traffic sign may be limited to replacing the light diffusing module and/or light diffusing panel  100  from a traffic sign with a new light diffusing module or light diffusing panel  100 . 
         [0034]    The light sources of the light diffusing module of the present invention may be powered by any power source. It is anticipated that for incorporating the present invention in existing traffic sign installations, such as free standing road side signs, the power source to be used will incorporate a rechargeable battery or power storage module and a solar panel for providing a charge to the rechargeable power storage module. In  FIG. 6 , solar panel  800  is shown mounted on stop sign embodiment. Solar panel  800  is preferably electrically connected to a rechargeable battery which is electrically connected to and powers light sources  400 . 
         [0035]    Light sources  400  can be powered by any source, as known in the art, but for outdoor implementation of the present invention, a preferred power source is solar energy. Utilizing solar panels or other solar energy capturing devices, the LED light sources can be powered in remote locations, allowing for the use of traffic signs incorporating the light diffusing module of the present invention in any location, regardless of proximity to a utility line or other power source. When using solar energy, an additional battery or other power storage module would be needed for night operation of the light diffusing module. 
         [0036]    The light diffusing panel and module of the present invention may be used for any type of traffic or road sign, including warning signs, construction signs, street signs, speed limit signs, traffic control signs, regulatory signs, directional or wayfinding signs, or other signs as are known in the art. The light diffusing panel and module of the present invention may be used in a variety of different types of sign mountings, including poles, overhead mast arm signs, temporary signs, hanging signs, or other mountings as are known in the art. 
         [0037]    The light diffusing panel and module of the present invention may be used for billboards, advertising signage or other similar uses as are known in the art or may be developed. 
         [0038]    While certain novel features of the present invention have been shown and described, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing from the spirit of the invention.