Abstract:
The exemplary embodiments herein provide an airguide backlight assembly having an anterior element, a reflective pan positioned posterior to the anterior element, and a light source positioned to direct light towards the reflective pan. A lens element may be placed in front of each light source. The reflective pan preferably contains a slope or curve so that light emitted from the light sources can be reflected and/or refracted to distribute the light uniformly to the anterior element. In some embodiments, blinders may be positioned between the light sources and the anterior element as well as between the light sources and the reflective pan.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/322,962 filed on Jul. 3, 2014, which claims priority to U.S. Provisional Patent Application No. 61/842,704 filed on Jul. 3, 2013, both of which are hereby incorporated by reference as if fully recited herein. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments generally relate to backlight assemblies. 
       BACKGROUND OF THE ART 
       [0003]    Backlight assemblies are used in a number of different applications, ranging from dynamic electronic displays (ex. liquid crystal displays) to static backlight displays (ex. a backlight positioned behind a poster or static graphic). Typically, for edge-lit assemblies (where the light source is placed around the outside edges of the assembly) a light guide is used to capture the light, homogenize, and out-couple the light from the light sources. 
       SUMMARY OF THE EXEMPLARY EMBODIMENTS 
       [0004]    Exemplary embodiments provide a backlight assembly using only air as the light guide (‘airguide’) where a lens is used to capture the light and a pan is used to homogenize and out-couple the light. The pan can have constant reflectivity, or reflectivity which changes based on the location within the pan. The pan can have features, including ramps, cylindrical curves, sinusoidal curves, arbitrarily optimized curves, or a hybrid of any of these shapes in order to homogenize and out-couple the light. In some embodiments, blinders may be positioned above and below the light sources to further control the emission and distribution of light. 
         [0005]    The various embodiments of the airguide backlight assembly described herein can be used with any device that requires a backlight, including but not limited to LCD displays and static displays. The light sources used with any of the embodiments herein can be any device for generating photons, including fluorescent tubes, LEDs, organic LEDs, or light emitting polymers. 
         [0006]    The foregoing and other features and advantages of the present invention will be apparent from the following more detailed description of the particular embodiments, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    A better understanding of an exemplary embodiment will be obtained from a reading of the following detailed description and the accompanying drawings wherein identical reference characters refer to identical parts and in which: 
           [0008]      FIG. 1  is a side elevation view of an exemplary embodiment of an airguide backlight assembly. 
           [0009]      FIG. 2  is a partial side elevation view of an embodiment of an airguide backlight assembly using a reflective pan having an optimized curvature. 
           [0010]      FIG. 3  is a partial side elevation view of an embodiment of an airguide backlight assembly using blinders around the light source. 
           [0011]      FIG. 4  is a partial side elevation view of an embodiment of an airguide backlight assembly showing the variables in the design which can be used for optimization. 
           [0012]      FIG. 5  is a partial side elevation view of an embodiment of an airguide backlight assembly showing further variables in the design, including a light source having its optical axis positioned at an angle relative to the display. 
           [0013]      FIG. 6  is a partial side elevation view of an embodiment of an airguide backlight assembly using a ramped reflective pan and a rod lens. 
           [0014]      FIG. 7  is a partial side elevation view of an embodiment of an airguide backlight assembly using a cylindrical reflective pan and a rod lens. 
           [0015]      FIG. 8  is a partial side elevation view of an embodiment of an airguide backlight assembly using a hybrid curved ramped reflective pan. 
           [0016]      FIG. 9  is an illustration of the light distribution generated by the embodiment shown in  FIG. 6 . 
           [0017]      FIG. 10  is an illustration of the light distribution generated by the embodiment shown in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. 
         [0019]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/ or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0020]    Embodiments of the invention are described herein with reference to illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
         [0021]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0022]      FIG. 1  is a side elevation view of an exemplary embodiment of an airguide backlight assembly. An anterior element  10  may be positioned at the front portion of the assembly (i.e. the anterior side of the backlight assembly that would face an intended observer) and may include any one or a combination of the following: clear or frosted glass or plastic, a diffusing element, brightness enhancing films, anti-reflective films, liquid crystal cells, posters/static graphics, etc. Preferably, the anterior element  10  is at least semi-transparent. The light source  15  is positioned along the edge of the assembly, preferably with another light source  15  on the opposing side. A lens  20  is preferably positioned in front of the light source  15  and may be used to at least partially collimate the light. 
         [0023]    There are no practical limits on the type of lens that may be used with the embodiments herein, assuming that a lens is required for the chosen light source. This may include convex-convex, plano-convex, cylindrical rods, gradient-index, and Fresnel lens. 
         [0024]    A reflective pan  30  is positioned behind the anterior element  10  and within the path of the light passing through the lens  20 . In this embodiment, the reflective pan  30  has a simple ramp design where two primary variables control the performance of the reflective pan  30 : a Center Gap (CG) and an Edge Gap (EG). The Center Gap (CG) may be defined as the distance from the pan  30  to the rear surface of the anterior element  10 , when measured along the Centerline (CL). The Edge Gap (EG) may be defined as the distance from the pan  30  to the rear surface of the anterior element  10 , when measured at the edge of the pan  30  and anterior element  10  where the light source  15  is positioned. By way of example, the CG distance is often on the order of 60-90% of the EG distance. 
         [0025]      FIG. 2  is a partial side elevation view of an embodiment of an airguide backlight assembly using a reflective pan  31  having an optimized curvature  32 . An optimized curvature would generally serve to transform the distribution of light as it exits the light source  20  to the desired distribution of light over the viewing area, which is typically a uniform distribution. The distribution of light as it exits the light source at  20  is generally not uniform. Thereby, the shape of the pan  32  is designed to compensate for the nonuniformity of the light source while simultaneously and conveniently reflecting the light in a predominately outward direction through anterior element  10 . Clearly, the complexity of the shape of the pan  32  depends on: 1) the nonuniformity of the light exiting the light source at  20  that must be compensated, and 2) the degree to which the desired viewing area distribution is satisfied. More specifically, the pan may intrinsically reflect more light outward where the light striking it from the light source is weaker, and vice versa. Alternatively and/or simultaneously, in areas where the light striking the pan  32  is relatively stronger the pan  32  may direct light to regions of the viewing area that would otherwise be relatively weaker. A similar effect may be obtained by varying the reflectivity of the pan  32  at different locations along the pan  32 . 
         [0026]    Clearly, there is a very large degree of optimization that is potentially possible by the shape of the pan  32 . Although the shape of the pan  32  is shown as being contiguous, this is not strictly a requirement. In other words, the shape may have discontinuities such as bent edges, or even formed in discrete sections. 
         [0027]    The surface texture of the pan  32  is another variable that can be used to optimize the distribution of light at the viewing area. A smoother texture will tend to ‘specularly’ reflect light like a common mirror does, while a rougher texture will ‘broadcast’ the light over a wider range of angles. The surface texture may also vary at different locations along the pan  32 . 
         [0028]      FIG. 3  is a partial side elevation view of an embodiment of an airguide backlight assembly using blinders  100  around the light source  15 . The blinders  100  are preferably placed above and below the light source  15  and lens  20 . In other words, a top blinder may be positioned between the anterior element  10  and the light source  15  while a bottom blinder may be positioned between the pan  31  and the light source  15 . The blinders  100  may have any value of reflectivity, from 0-100%, which serves to aid in the desired distribution of light at the viewing area. A preferred use of blinders  100  is to selectively control stray light as it exits the light source at  20 . 
         [0029]      FIG. 4  is a partial side elevation view of an embodiment of an airguide backlight assembly showing the variables in the design which can be used for optimization. 
         [0030]      FIG. 5  is a partial side elevation view of an embodiment of an airguide backlight assembly showing further variables in the design, including a light source  15  having its optical axis positioned at an angle relative to the anterior element  10 . 
         [0031]      FIG. 6  is a partial side elevation view of an embodiment of an airguide backlight assembly using a simple ramped reflective pan  30  and a simple rod that serves as the lens  50 . This embodiment illustrates, by way of example, the invention in perhaps its most simplistic form. 
         [0032]      FIG. 7  is a partial side elevation view of an embodiment of an airguide backlight assembly using a cylindrical reflective pan  35  and a rod lens  50 . 
         [0033]      FIG. 8  is a partial side elevation view of an embodiment of an airguide backlight assembly using a hybrid curved ramped reflective pan  36 , which begins with a ramp section  37  and transitions to a curved section  38  as you approach the centerline of the backlight assembly. 
         [0034]      FIG. 9  is an illustration of the light distribution generated by the embodiment shown in  FIG. 6 . This illustration was produced using light modeling software ASAP, which is available from Breault Research Organization. This simulation was performed with no diffuser placed into the model. 
         [0035]      FIG. 10  is an illustration of the light distribution generated by the embodiment shown in  FIG. 7 . This simulation was performed with no diffuser placed into the model. 
         [0036]    Having shown and described a preferred embodiment of the invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention and still be within the scope of the claimed invention. Additionally, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims.