Abstract:
A light bulb having anti-reflective coatings on an inner surface and/or an outer surface of the shell of the light bulb. The anti-reflective coatings reduce light loss due to reflections at the interfaces between the interior of the bulb and the shell and between the shell and the exterior of the bulb. The light source may be either incandescent, fluorescent or LED.

Description:
BACKGROUND 
     1. Field 
     The present invention relates to reducing optical losses of bulbs used for lighting, and more particularly, to the use of anti-reflective coatings on the inner and outer surfaces of the shells of the bulb in order match the index of refraction of the shell material to the indices of refraction of the inside/inner portion of the bulb and outside/ambient surroundings of the bulb, thus increasing the light output of the bulb being replaced. 
     2. Description of Related Art 
     There are several types of light bulb now in use. The most common is still the incandescent bulb, formed by surrounding a very hot filament in a partial vacuum with a glass shell. Another common type is the fluorescent bulb, formed by surrounding a plasma column with a glass shell containing a phosphor, the phosphor serving to convert the ultraviolet radiation emitted by the plasma into visible light. Another type of bulb, rapidly gaining in popularity, is the LED (light emitting diode) bulb. One popular method of forming an LED bulb is to surround the LEDs with air or a fluid, gel or plastic, and encase the LEDs inside a plastic shell. 
     All of these bulbs share in common the fact that their light source is surrounded, either immediately or with an intermediate, by a shell. The shell provides physical protection to the light source from the surrounding ambient air, as neither the partial vacuum of an incandescent filament, nor the plasma column of a fluorescent, nor the fluid, gel or plastic of an LED bulb will normally withstand direct exposure to ambient air (or ambient surroundings). In the case of air surrounding the LEDs in an LED bulb, the shell provides physical isolation of the LEDs from physical damage. While the shell provides physical isolation for the internal components of the bulb, it has the drawback that the commonly used shell materials, glass or plastic, have a different index of refraction than does the surrounding ambient air (or ambient surroundings). Further, in the case of the LED bulb using a fluid, gel or plastic, the index of refraction of the shell does not match that of the internal fluid, gel or plastic either. This mismatch of index of refraction creates reflection of the impinging light at the material interface, resulting in loss of light output. 
     This invention has the object of developing a light emitting apparatus, such that the above-described primary problem is effectively solved. In accordance with an exemplary embodiment, the light emitting apparatus provides a bulb constructed similarly to that of currently available bulbs, but without the light losses associated with reflections from the shell enclosing the bulb. In accordance with an embodiment, the bulb includes a shell, constructed of glass or plastic. The shell has an anti-reflective coating on the inside (i.e., an inner surface) and/or outside (i.e., an outer surface) of the shell. In accordance with an exemplary embodiment, the anti-reflective coatings are designed such that reflections from the interfaces from the inside to the shell, and from the shell to the ambient air or ambient surroundings are minimized. 
     BRIEF SUMMARY 
     In accordance with one embodiment, an incandescent bulb comprises: an incandescent filament; a partially evacuated glass shell surrounding the filament, the shell being potentially filled with a gas; an anti-reflective coating on the inside (or an inner surface) of the shell to match the index of refraction of the interior partial vacuum to that of the glass; and/or an anti-reflective coating on the outside (or an outer surface) of the shell to match the index of refraction of the glass shell to that of the ambient air or surroundings. 
     In accordance with another embodiment, a fluorescent bulb comprises: a partially evacuated glass tube; the glass tube being potentially filled with a gas; the glass tube also being filled with a material suitable for causing ultraviolet emissions; a phosphorescent material lining the inside (or inner surface) of the glass tube to convert the ultraviolet emissions to visible light; and an anti-reflective coating on the outside (or outer surface) of the glass tube to match the index of refraction of the glass tube to that of the ambient air or surroundings. 
     In accordance with a further embodiment, an LED bulb comprises: at least one LED; a glass or plastic shell surrounding the at least one LED, the shell being potentially filled with air, fluid, gel or plastic; an anti-reflective coating on the inside (or inner surface) of the shell to match the index of refraction of the interior air, fluid, gel or plastic to that of the glass or plastic; and/or an anti-reflective coating on the outside (or outer surface) of the shell to match the index of refraction of the glass or plastic shell to that of the ambient air or surroundings. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a cross-sectional view of a light bulb having a shell, and showing anti-reflective coatings on the interior (or inner) and exterior (or outer) surfaces of the shell. 
         FIG. 2  is a perspective view of a fluorescent light bulb, which includes a phosphorescent material lining the inside of the tube that converts the fluorescent radiation into visible radiation, and an anti-reflective coating on an outer surface of the tube. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. According to the design characteristics, a detailed description of each preferred embodiment is given below. 
       FIG. 1  shows a cross-sectional view of a light bulb  10  showing the shell  20  enclosing a light source  50  according to one embodiment. The light bulb  10  includes a screw-in base  12 , which includes a series of screw threads  14  and a base pin  16 . The screw-in base  12  is configured to fit within and make electrical contact with a standard electrical socket. The electrical socket is preferably dimensioned to receive an incandescent or other standard light bulb as known in the art. However, it can be appreciated that the screw-in base  12  can be modified to fit within any electrical socket, which is configured to receive an incandescent bulb, such as a bayonet style base. The screw-in base  12  makes electrical contact with the AC power in a socket through its screw threads  14  and its base pin  16 . 
     In accordance with various embodiments, the light source  50  can be an incandescent filament, a plasma column of a fluorescent bulb, or a LED (light emitting diode). For example as shown in  FIG. 1 , the light bulb  10  includes an inner anti-reflective coating  30  and an outer anti-reflective coating  40 , which are on the inner or interior surface  32  and the outer or exterior surface  42 , respectively, of the shell  20 . The inner anti-reflective coating  30  is of such a thickness  34  that the index of refraction of the shell  20  and/or shell material  21  is substantially matched to the index of refraction of the inner portion  70  of the bulb  10  and/or a material  60  within the inner portion  70  of the bulb  10 . In an alternative embodiment, the outer anti-reflective coating  40  is of such a thickness  44  that the index of refraction of the shell  20  and/or shell material  21  is substantially matched to the index of refraction of the external atmosphere  80  (or ambient surroundings) of the shell  20 . It can be appreciated that the shell  20  (or enclosure) may be any shape, or any of the other conventional or decorative shapes used for bulbs, including but not limited to spherical, cylindrical, and “flame” shaped shells  20 . Alternatively, the shell  20  could be a tubular element, as used in fluorescent lamps or other designs and shown in  FIG. 2 . 
     In accordance with an exemplary embodiment, the light bulb  10  includes at least one LED  52 , and a glass or plastic outer shell  20  surrounding an interior or an inner portion  70  of the bulb  10 , which houses the at least one LED  52 . The inner portion  70  of the shell  20  can be filled or partially filled with a material  60  such as air, fluid, gel and/or a plastic or plastic material. In accordance with an exemplary embodiment, an anti-reflective coating  30  can be placed or applied to the inside  32  (or inner surface) of the shell  20  to match the index of refraction of the interior (or an inner portion)  70  of the bulb  10  to that of the glass or plastic shell  20 . In addition, an anti-reflective coating  30  can be placed or applied to the inside  32  (or inner surface) of the shell  20  to match the index of refraction of the material  60 . Alternatively, the interior  70  of the shell  20  can be fully evacuated or partially evacuated, and an anti-reflective coating  30  can be placed or applied to the inside  32  (or inner surface) of the shell  20  to match the index of refraction of the full or partial vacuum thus created. In accordance with another exemplary embodiment, an anti-reflective coating  40  can be placed or applied to the outside  42  (or outer surface) of the shell  20  to match the index of refraction of the glass or plastic shell  20  to that of the ambient air or surroundings  80 . 
     In accordance with another exemplary embodiment, as shown in  FIG. 2 , the light bulb  10  is a fluorescent bulb  100 , which includes a tube  110 , one or more substances  120  inside the tube  110 , and wherein at least one of the one or more substances  120  fluoresces when properly excited. For example, the tube  110  can be partially evacuated and filled with a gas or material suitable for causing ultraviolet emissions. In accordance with an exemplary embodiment, the bulb  10  includes one or more substances  120  in the form of a phosphorescent material  130  lining the inside or inner surface  112  of the tube  110  that converts the fluorescent radiation (or ultraviolet emissions) into visible radiation (or visible light). 
     In accordance with another exemplary embodiment, an anti-reflective coating  140  can be applied or placed on an outer surface  114  of the tube  110 . The anti-reflective coating  140  matches an index of refraction of an external atmosphere  150  with an index of refraction of the tube  110  and/or tube material  111 . The tube  110  is preferably made of glass; however, other suitable materials can be used. In addition, the tube  110  is preferably partially evacuated. 
     As shown in  FIG. 2 , the light bulb  10  also includes a screw-in base  12 , which includes a series of screw threads  14  and a base pin  16  The screw-in base  12  is configured to fit within and make electrical contact with a standard electrical socket. The electrical socket is preferably dimensioned to receive an incandescent or other standard light bulb as known in the art. However, it can be appreciated that the screw-in base  12  can be modified to fit within any electrical socket, which is configured to receive an incandescent bulb, such as a bayonet style base. The screw-in base  12  makes electrical contact with the AC power in a socket through its screw threads  14  and its base pin  16 . 
     It can be appreciated that the light bulb as shown in  FIGS. 1 and 2  is shown as a replacement bulb for standard incandescent bulbs, however, the bulb  10  can be adapted to usage with any other powering system or configuration, and can be used for any lighting system, including incandescent bulbs, flashlights, headlights for automobiles or motorcycles, and lanterns. 
     It will be apparent to those skilled in the art that various modifications and variation can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.