Patent Publication Number: US-2020284973-A1

Title: Illuminating device with multiple waveguides connected by a bridge

Description:
TECHNICAL FIELD 
     This invention relates to illuminating devices for distributing light from a light source. In particular, the illuminating device is manufactured as a single piece to ensure robust and consistent lighting output. 
     BACKGROUND ART 
     Current light-emitting diode (LED) lighting for automobile interiors, such as ceiling lights, generally includes an illuminating device for distributing the light. Typically, the illuminating device contains two waveguides: a first waveguide conducting light in a first direction and extracting the light in a second direction orthogonal to the first direction as the light travels in the first direction; and, a second waveguide receiving the extracted light from the first waveguide and forming an illuminating surface. An example of such a lighting assembly is disclosed, e.g. in U.S. Patent Application Publication No. 2010/0315833 to Holman et al. The two waveguides must be aligned within a tight tolerance for reliable and consistent lighting output. Current illuminating devices, however, are prone to misalignment of the waveguides, either during assembly or during use of the light, resulting in poor and inconsistent light output and distribution. 
     Therefore, there remains a need for an illuminating device that provides reliable and consistent lighting output and distribution, by providing robust alignment of the waveguides. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a light illuminating device containing a first waveguide and a second waveguide connected to the first waveguide by a bridge. The bridge is configured to align and to maintain the first waveguide and the second waveguide in spaced relation, such that an air gap exists between the first and second waveguides. The bridge aligns the first and second waveguides to ensure a consistent gap to provide reliable and consistent lighting output and distribution. The first waveguide is configured to receive light from a light source to a receiving end, conducting the light along its length in the x-direction, and reflecting the light in the y-direction toward the second waveguide. The second waveguide is configured to receive light from the first waveguide, conducting the light along its width in the y-direction, and reflecting the light in the z-direction through a bottom surface to illuminate a region below the second waveguide. 
     Another aspect of the present invention provides a lighting apparatus containing the illuminating device described above. The lighting apparatus may be used in interior lighting, such as for an automobile or a room 
     A further aspect of the present invention provides an automobile containing a lighting apparatus described above. 
     Methods for making and using the different aspects of the present invention are also provided. 
     Other aspects of the invention, including apparatuses, devices, kits, processes, and the like which constitute part of the invention, will become more apparent upon reading the following detailed description of the exemplary embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing background and summary, as well as the following detailed description, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG. 1  is perspective view of an illuminating device in accordance to the present invention; 
         FIG. 2  is a side view of the illuminating device; 
         FIG. 3  is a bottom view of the illuminating device; and 
         FIG. 4  is an alternate bottom view of the illuminating device. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The exemplary embodiment of the present invention will now be described with the reference to accompanying drawings. The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     For purposes of the following description, certain terminology is used in the following description for convenience only and is not limiting. The characterizations of various components and orientations described herein as being “front,” “back,” “vertical,” “horizontal,” “upright,” “right,” ‘left,” “side,” “top,” “bottom,” “above,” “below,” or the like designate directions in the drawings to which reference is made and are relative characterizations only based upon the particular position or orientation of a given component as illustrated. These terms shall not be regarded as limiting the invention. The words “downward” and “upward” refer to position in a vertical direction relative to a geometric center of the apparatus of the present invention and designated parts thereof. The terminology includes the words above specifically mentioned, derivatives thereof and words of similar import. 
     Referring to  FIGS. 1-2 , the illuminating device  100  contains a first waveguide  102  and a second waveguide  104  connected to the first waveguide  102  by a bridge  106 . The bridge  106  is configured to align the first waveguide  102  and the second waveguide  103  in spaced relation, such that an air gap  108  exists between the first and second waveguides  102  and  104 . 
     The first waveguide  102  is preferably an elongated bar having a length in the x-direction, a width in the y-direction, and a thickness in the z-direction, as noted in  FIG. 1 , where the x-, y-, and z-directions are orthogonal axes in a Cartesian coordinate frame. Preferably, the first waveguide  102  contains a pre-selected angular light distribution in each of the x-, y- and z-direction. The first waveguide  102  is configured to receive light from a light source to a receiving end  110 , conducting the light long its length in the x-direction, and extracting and directing the light in the y-direction toward the second waveguide  104 . The extracted light is emitted from an emitting surface  115  of the first waveguide  102  which faces the second waveguide  104 . 
     As one example, the light source is an LED-based light emitter. The LED emitter may contain a single LED having one or more LED chips coupled with appropriate optics designed to collect and transport the light efficiently from the LED emitter to the receiving end  110  of the first waveguide  102 . Preferably, the light entering the receiving end  110  is collimated in the x-direction. Other LED light emitters known in the art are also contemplated for use with the present invention. 
     The first waveguide  102  preferably has a substantially, square (or rectangular) cross-section and transmits input light flowing within the waveguide by total internal reflection. The side  112  of the first waveguide  102  (the side farthest from the second waveguide  104 ) contains one or more light extracting structures  114  for extracting a fraction of the light flowing within first waveguide  102  as the light strikes the light extracting structure  114  along the length of the first waveguide  102 , and redirecting the extracted light uniformly over the length of the first waveguide  102  substantially in the y-direction through the air gap  108  and to the second waveguide  104 . The light extracting structure  114  may be those known in the art, such as gratings, focusing lens, microprisms, other microoptical features, or combinations thereof, with microprisms being the preferred light extracting feature. One light extracting structure  114  is shown, e.g., in U.S. Patent Application Publication No. 2010/0315833, which is incorporated herein by reference. The light extracting structure  114  may be formed directly on the side  112  of first waveguide  102  or attached thereto, e.g. as a film layer. In an embodiment, the light extracting structure  114  may be in the form of a micro-patterned layer and/or having one or more reflecting surfaces (e.g. mirrors). In another embodiment, the extracting structure  114  may be a plurality of protruding structures on the side  112  of the first waveguide  102 . Preferably, the plurality of protruding structures may have a triangular cross-sectional shape forming a series of microprisms. Depending on the size of the light source, the first waveguide  102  may have a thickness of about 1 mm to about 5 mm, a width of about 1 mm to about 5 mm, and a length of about 10 to about 600 mm. For example, the first wave guide  102  may have a cross-section of about 2 mm×3 mm, about 3 mm×2 mm, about 4 mm×5 mm, etc. 
     The second waveguide  104  is preferably a flat, square (or rectangular) plate having a length in the x-direction, a width in the y-direction, and a thickness in the z-direction, as noted in  FIG. 1 . The second waveguide  104  is configured to receive light from the first waveguide  102  to a receiving edge  116 , conducting the light long its width in the y-direction, and extracting and directing the light in the z-direction through the bottom surface  118 . Preferably, the second waveguide.  104  contains a preselected angular light distribution in each of the x-, y-, and z-direction. The second waveguide  104  transmits the light flowing therein by total internal reflection in the y-direction. As the light is being conducted in the y-direction, a fraction of the light is extracted and directed in the z-direction by one or more light extracting structures  119  present on the top surface  120  of the second waveguide.  104 . The light extracting structure  119  may be the same or different than those on the first wave guide  102  and may be, but is not limited to, gratings, focusing lens, microprisms, other microoptical features, or combinations thereof, with microprisms or other microoptical features being preferred. Preferably, the light extracting structure  119  is configured to redirect the extracted light uniformly over the surface of the first waveguide  102  substantially in the z-direction. Depending on the application, the second waveguide  104  may have a thickness of about 1 mm to about 5 mm, a width of about 10 mm to about 600 min, and a length of about 10 mm to about 600 min. Preferably, the lengths of the first and second waveguides  102  and  104  are the same. 
     The first and second waveguides  102  and  104  are aligned relative to each other, so that the air gap  108  separates the two waveguides. In proper alignment, the receiving surface  116  of the second waveguide  103  faces the emitting surface  115  of the first waveguide  102 , with the gap  108  separating the two surfaces  115  and  116 . Preferably, the gap  108  is made as small as possible and is usually limited by production methods. Depending on the application of the illuminating device  100 , the gap  108  may be from about 0.8 mm to about 1.5 mm. The width of the gap  108  may vary along the length of the waveguides  102  and  104 ; however, preferably, the width of the gap  108  is the same along the length of the waveguides  102  and  104 . 
     To properly align the first and second waveguides  102  and  104 , the bridge  106  is used to connect the two waveguides  102  and  104  and to rigidly hold them apart. The bridge  106  provides a robust mechanism to align the first and second waveguides  102  and  104  to control the width of the gap  108 . The bridge  106  contains a first end  122  attached to the bottom surface  124  of the first waveguide  102  and a second end  126  attached to the bottom surface  118  of the second waveguide  104 . Importantly, the bridge  106  does not intrude into the gap  108 , so that it does not interfere with the light transmission through the gap  108 . As such, as shown in  FIGS. 1-2 , the bridge arches over and does not protrude into the gap  106 . As shown in  FIG. 3 , the illuminating device  100  may contain a single bridge  106  that spans the whole length, or a majority of the length of, the first and second waveguides  102  and  104 . Alternatively, as shown in  FIG. 4 , illuminating device  100  may contain two or more bridges along the lengths of the waveguides  102  and  104 . Furthermore, although the drawings show the bridge connecting the bottom surfaces  124  and  118  of the first and second waveguides  102  and  104 , respectively, it is also possible for the bridge  106  to connect the top surfaces  128  and  120  or the first and second waveguides  102  and  104 , respectively. 
     The waveguides  102  and  104  may be made of a transparent material, e.g., an optically transparent material. For example, the (optically) transparent material may be optically transmissive to an electromagnetic radiation of the visible light spectrum emitted from the light source. The material is preferably an optically transparent plastic, preferably polymethyl methacrylate acrylate (PMMA), polycarbonate, or combinations thereof. The waveguides  102  and  104  and the bridge  106  may be formed by injection molding, a technique known in the art, of the optical transparent plastic. Preferably, the waveguides  102  and  104  and the bridge  106  are form, e.g. molded, from the same material as a single piece. 
     In use, the illuminating device  100  receives light from the light source and distributes the light through the bottom surface  118  of the second waveguide  104  to provide illumination in the region below the second waveguide  104 . In doing so, the first wave guide  102  receives light from the light source at the receiving end  110 , and conducts the light along its length in the x-direction. As the light is being conducted in the first waveguide  102 , the light is extracted and directed in the y-direction toward the second waveguide  104  due to the light extracting structure  114  on the first waveguide  102 . The reflected light traverses the gap  108  and enters the second waveguide  104  at the receiving edge  116 . The second waveguide  104  conducts the light along its width in the y-direction. As the light is being conducted in the first waveguide  102 , the light is extracted and directed in the z-direction due to the light extracting structure  119  on the second waveguide.  104 . The extracted light exits the second waveguide  104  at its bottom surface  118 , to illuminate in the region below the second waveguide  104 . The disclosed illuminating device  100  may be used in lighting assembly to provide aesthetically pleasing, sturdy, cost effective lighting for use in interior lighting, such as for an automobile or a room. 
     Although certain presently preferred embodiments of the invention have been specifically described herein, it will be apparent to those skilled in the art to which the invention pertains that variations and modifications of the various embodiments shown and described herein may be made without departing from the spirit and scope of the invention.