Abstract:
An illumination system for illuminating a surface includes an optical source for generating light. An asymmetric optic device generates output light by total internal reflection (TIR) of the light from the optical source, intensity of the output light being asymmetric with respect to an axis of the asymmetric optic device. A diffuser receives and diffuses the output light from the asymmetric optic device to generate diffused light. A cover lens receives the diffused light from the diffuser. The cover lens has an etched portion for scattering a portion of the diffused light to generate an output light pattern, the output light pattern having an intensity profile that is asymmetric with respect to the axis of the asymmetric optic device.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    This disclosure relates to lighting systems, and, more particularly, to wall wash lighting systems. 
         [0003]    2. Discussion of Related Art 
         [0004]    In interior and exterior lighting systems, it is often desirable to illuminate a vertical or nearly vertical wall. Such lighting systems, the goal of which is to provide uniform illumination of the vertical surface of the wall, are commonly referred to as “wall wash” systems. In typical conventional wall wash systems, a uniform distribution of light or illumination over the surface of the wall is difficult to obtain. 
       SUMMARY 
       [0005]    According to one aspect, an illumination system for illuminating a surface is provided. The illumination system includes an optical source for generating light. An asymmetric optic device generates output light by total internal reflection (TIR) of the light from the optical source, intensity of the output light being asymmetric with respect to an axis of the asymmetric optic device. A diffuser receives and diffuses the output light from the asymmetric optic device to generate diffused light. A cover lens receives the diffused light from the diffuser. The cover lens has an etched portion for scattering a portion of the diffused light to generate an output light pattern, the output light pattern having an intensity profile that is asymmetric with respect to the axis of the asymmetric optic device. 
         [0006]    In some exemplary embodiments, the illumination system is a wall wash illumination system. 
         [0007]    In some exemplary embodiments, the surface being illuminated is substantially parallel to the axis of the asymmetric optic device. 
         [0008]    In some exemplary embodiments, the surface being illuminated is a surface of a wall. The illumination system can be vertically located beneath ground level. The axis of the asymmetric optic device can be substantially perpendicular to a surface of the ground in which the illumination system is located. 
         [0009]    In some exemplary embodiments, the diffuser is an elliptical diffuser. 
         [0010]    In some exemplary embodiments, the optical source comprises a light-emitting diode (LED). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present disclosure is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the present disclosure, in which like reference numerals represent similar parts throughout the several views of the drawings. 
           [0012]      FIG. 1  includes a schematic cross-sectional view of a conventional wall wash lighting system. 
           [0013]      FIG. 2  includes a detailed schematic cross-sectional diagram of a symmetric TIR optic illustrated in  FIG. 1 . 
           [0014]      FIG. 3  includes a schematic cross-sectional view of a wall wash lighting system, according to some exemplary embodiments. 
           [0015]      FIG. 4  includes a detailed schematic cross-sectional diagram of an asymmetric TIR optic illustrated in  FIG. 3 , according to some exemplary embodiments. 
           [0016]      FIG. 5  includes a schematic cross-sectional view of a portion of the wall wash illumination system illustrated in  FIG. 3 , rotated 90 degrees from the view of  FIG. 3 , according to some exemplary embodiments. 
           [0017]      FIG. 6  includes a schematic diagram (ray trace) of a wall wash illumination system, according to some exemplary embodiments. 
           [0018]      FIGS. 7A and 7B  include schematic diagrams of a conventional wall wash illumination system and a wall wash system according to the exemplary embodiments, respectively, used to illuminate a wall. 
           [0019]      FIGS. 8A and 8B  include images which illustrate the wall wash illumination provided by a conventional wall wash illumination system and the wall wash illumination system according to the exemplary embodiments, respectively. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  includes a schematic cross-sectional view of a conventional wall wash lighting system  10 . Lighting system  10  includes a symmetric total internal reflection (TIR) optic  12 , which emits a light pattern  24  having a primary direction as illustrated by arrow  14  to illuminate a surface  20  of a wall  22 . Symmetric TIR optic  12  includes a light source  26 , which emits light  24  primarily along the direction indicated by arrow  14 . The light  24  emitted by TIR optic  12  passes through a glass cover lens  16 , which can include an etched portion  18 . Etched portion  18  of cover lens  16  diffuses the light  24  such that the light is emitted from glass cover lens  16  in light pattern  24  as shown in  FIG. 1 . 
         [0021]    Since wall  22  is located laterally some distance or setback from lighting system  10 , symmetric TIR optic  12  and cover lens  16  are tilted toward wall  22  as shown. This tilt is intended to provide additional illumination on wall  22 . However, in general, such conventional tilt systems provide wall wash illumination which is non-uniform both in the vertical dimension, i.e., up and down wall  22 , and the horizontal dimension, i.e., side-to-side on wall  22 . 
         [0022]      FIG. 2  includes a detailed schematic cross-sectional diagram of symmetric TIR optic  12  illustrated in  FIG. 1 . Referring to  FIG. 2 , symmetric TIR optic  12  includes light source  26 , which emits light into symmetric TIR optic  12 . By reflection of the emitted light from inner walls  25  of symmetric TIR optic  12 , light pattern  24  is generated and emitted from symmetric TIR optic  12 . As illustrated in  FIG. 2 , the light pattern  24  emitted by symmetric TIR optic  12  propagates with equal intensity in the direction toward wall  22  and in the direction away from wall  22  toward an “observer” some distance away from wall  22 . The light toward the observer, referred to as “glare,” is light that is not directed onto the target surface. Thus, in these conventional systems, the coefficient of utilization, which is related to the ratio of the light onto the wall to the total light out of the illumination system, is relatively low. 
         [0023]    According to exemplary embodiments described in detail herein, a wall wash illumination system which achieves a more uniform illumination of a wall is provided.  FIG. 3  includes a schematic cross-sectional view of a wall wash lighting system  110 , according to some exemplary embodiments. Referring to  FIG. 3 , wall wash lighting system  110  includes an asymmetric total internal reflection (TIR) optic  112 , in contrast with the symmetric TIR optic  12  of the conventional system  10  illustrated in  FIGS. 1 and 2 . Asymmetric TIR optic  112  emits a light pattern  124  having a primary direction as illustrated by arrow  114  to illuminate surface  20  of wall  22 . Asymmetric TIR optic  112  includes a light source  126 , such as an LED light source, which emits light  124  primarily along the direction indicated by arrow  114 . The light emitted by TIR optic  12  passes through a diffuser  127 , which in some exemplary embodiments is an elliptical diffuser. Diffuser  127  diffuses light  124  in both the vertical and horizontal dimensions such that a more uniform illumination of surface  20  in both dimensions is achieved. Light from diffuser  127  passes through a glass cover lens  116 , which can include an etched portion  118 . Etched portion  118  of cover lens  116  diffuses the light such that the light is emitted from system  110  in light pattern  124 . The etched portion  118  of cover lens  116  primarily directs a portion of the light out of system  110  toward the portion of the wall closest to system  110 . That is, in the exemplary illustration in which system  110  is located near a lower portion of wall  22 , etched portion  118  of cover lens  116  directs a portion of the light out of system  110  primarily toward the bottom portion of wall  22 , thus eliminating dark spots near the bottom of wall  22 . 
         [0024]    According to the exemplary embodiments, the asymmetric TIR optic  112 , elliptical diffuser  127  and partially etch cover lens  116  provide illumination more suitable to providing uniform illumination of surface  20  of wall  22  than prior systems, such as system  10  illustrated in  FIGS. 1 and 2 . According to the exemplary embodiments, this improved illumination profile is achieved without the need to tilt any of the system components, as is commonly done in conventional wall wash illumination systems. Furthermore, a higher portion of the output light from the illumination system  110  is directed onto the wall. That is, an increased coefficient of utilization is realized by illumination system  110  of the present disclosure. 
         [0025]      FIG. 4  includes a detailed schematic cross-sectional diagram of asymmetric TIR optic  112  illustrated in  FIG. 3 . Referring to  FIG. 4 , asymmetric TIR optic  112  includes light source  126 , which in some exemplary embodiments is an LED light source. Light source  126  emits light into asymmetric TIR optic  112 . By reflection of the emitted light from inner walls  125  of asymmetric TIR optic  112 , light pattern  124  is generated and emitted from asymmetric TIR optic  112 . As illustrated in  FIG. 4 , the light pattern  124  emitted by asymmetric TIR optic  112  is asymmetric in that more of the light  124  propagates in the direction toward wall  22  than in the direction away from wall  22  toward an “observer” some distance away from wall  22 . 
         [0026]      FIG. 5  includes a schematic cross-sectional view of a portion of the wall wash illumination system  110  illustrated in  FIG. 3 , rotated 90 degrees from the view of  FIG. 3 , according to some exemplary embodiments. Referring to  FIG. 5 , light from the plurality of asymmetric TIR optics  112  is diffused by diffuser  127 , as illustrated by the light ray arrows in  FIG. 5 . As described above, diffuser  127  diffuses light  124  in both the vertical Z dimension and the horizontal Y dimension, such that a more uniform illumination of surface  20  in both dimensions is achieved. 
         [0027]    In some exemplary embodiments, diffuser  127  is an elliptical diffuser. As such, the amount of diffusion or diffusion angle in each dimension provided by diffuser  127  can be different and can be selected as needed for the particular wall wash illumination application. That is, given a particular wall height and setback, i.e., lateral distance between system  110  and wall  22 , characteristics of diffuser  127  and, therefore, the amount of diffusion in each dimension, are selectable according to the desired wall wash illumination effect. 
         [0028]    For example, one particular exemplary elliptical diffuser  127  may be a 50×3 diffuser, in which the diffusion angle in the Y dimension, i.e., side-to-side on the wall, is 50 degrees and the diffusion angle in the Z dimension, i.e., up and down the wall, is 3 degrees. In certain applications, i.e., wall height, setback, etc. this elliptical diffuser might provide light that is spread evenly across the wall horizontally. The 3-degree Z dimension would also help to improve the light uniformity up and down the wall. However, such a distribution may only be ideal for one particular setback and one particular wall height. For example, for a shorter wall, with this diffuser, more light might be lost or might illuminate a ceiling or other surface or object above the wall. Also, if the setback is greater, then there may not be enough light at the base of the wall. 
         [0029]    According to the exemplary embodiments, this diffuser  127  can be switched for a different diffuser with wider diffusion in the small, i.e., vertical Z, dimension. For example, the 50×3 diffuser may be replaced with a 50×5 or a 50×10 diffuser. The result would be to move the region of the highest illuminance up and down the wall. 
         [0030]    Thus, according to the present disclosure, optimal wall wash illumination is achieved by system  110  for virtually any wall wash application. That is, virtually every wall wash configuration, with wide ranges of wall heights and/or setbacks, is accommodated by the system  110  of the present disclosure by changing out different diffusers  127 . 
         [0031]      FIG. 6  includes a schematic diagram (ray trace) of wall wash illumination system  110 , according to some exemplary embodiments. Referring to  FIG. 6 , light source  126  provides light into asymmetric TIR optic  112 , which, by internal reflection, provides an asymmetric light pattern to diffuser  127 . Based on the selected characteristics of diffuser  127 , as described above in detail, diffuse light passes through cover lens  116 . The portion of the light which passes through the etched portion  118  of cover lens  116  is further scattered. The resulting asymmetric light pattern emitted by system  110  has greater intensity in the direction toward the wall than in the direction away from the wall. As a result, improved, more uniform wall wash illumination is achieved. 
         [0032]      FIGS. 7A and 7B  include schematic diagrams of a conventional wall wash illumination system and a wall wash system according to the present disclosure, respectively, used to illuminate a wall. Specifically,  FIG. 7A  illustrates a conventional symmetric TIR “tilt” optic system, such as system  10  illustrated in  FIG. 1 , installed in the ground at a setback distance from wall  22 . Specifically,  FIG. 7A  illustrates three systems  10  being used to provide wall wash illumination on wall  22 .  FIG. 7B  illustrates a true asymmetric TIR optic system of the present disclosure, such as system  110  illustrated in  FIGS. 3-6  and described above in detail, installed in the ground at a setback distance from wall  22 . Specifically,  FIG. 7B  illustrates three systems  110  being used to provide wall wash illumination on wall  22 . It will be understood that, although the schematic illustrations of  FIGS. 7A and 7B  show systems  110  in the ground and emitting light primarily vertically, the present disclosure is completely applicable to any other configuration. For example, systems  110  need not be located in the ground. Also, the systems  110  may be located anywhere along the wall  22  and may direct light anywhere, as needed. For example, systems  110  could also be located at or near the top of wall  22  and may direct light primarily in the downward direction to illuminate wall  22 .  FIGS. 7A and 7B  are intended to illustrate any other orientations. 
         [0033]    As noted from  FIG. 7A , the conventional systems  10  provide wall wash illumination which is not uniform and which casts shadows of some wall features onto other portions of the wall  22 . In contrast, as noted from  FIG. 7B , the systems  110  of the present disclosure provide a more uniform wall wash illumination. Shadows and dark regions are eliminated, to the point that the wall  22  of  FIG. 7B  takes on a two-dimensional flat appearance. 
         [0034]      FIGS. 8A and 8B  include images which illustrate the wall wash illumination provided by the conventional wall wash illumination system  10  and the wall wash illumination system  110  according to the present disclosure, respectively. Referring to  FIG. 8A , the tilted-symmetric-optic-based illumination creates “hot spot” regions of high intensity on the wall and leaves dark spots on the upper portion of the wall and at the base of the wall. Referring to  FIG. 8B , the asymmetric-optic-based system  110  of the present disclosure creates an evenly illuminated wall with a majority of the light on the target surface. The asymmetric TIR optic  112  directs light toward the top of the wall, the elliptical diffuser  127  spreads it along the wall, and the partially etched portion  118  of the cover lens  116  gets light to the base of the wall. 
         [0035]    It is noted that the exemplary embodiments of the wall wash illumination system  110  of the present disclosure are described in detail herein as being configured as one or more linear arrays of light sources in one or more fixtures which are disposed in the ground and which illuminate a nearly vertical wall adjacent to the one or more fixtures, the longitudinal axis of the one or more fixtures being oriented substantially parallel to the surface of the wall being illuminated. It will be understood that this configuration is exemplary only and is used for the purpose of conveying an understanding of the principles of the disclosure. The present disclosure contemplates and is intended to cover other configurations. For example, the illumination system including the one or more fixtures need not be located in the ground. They also need not be located at the base or bottom of the illuminated surface. They may be located anywhere along the illuminated surface, including but not limited to, near the top of a wall, with the light being emitted from the illumination system including the one or more fixtures in the downward direction. Furthermore, the present disclosure also contemplates and is intended to cover any number of light sources, including a single light source, arranged in any configuration, i.e., not necessarily as a plurality of sources in a linear array. 
         [0036]    Whereas many alterations and modifications of the disclosure will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. Further, the subject matter has been described with reference to particular embodiments, but variations within the spirit and scope of the disclosure will occur to those skilled in the art. It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present disclosure. 
         [0037]    While the present inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims.