Abstract:
A lighting device that enables use of one or more light-emitting diodes (LEDs) in combination with a reflector is described. The subject lighting device includes at least one LED on a supporting portion, such that the LED is located in front of and aimed toward a reflector. Light emitted from the LED is reflected by the reflector and travels past the LED to provide light. The light-emitting diode(s) may be substantially centrally located with respect to a central axis of a reflector. Focusability of the lighting device is achieved by adjusting the relative distance between the LED and reflector, or by other means.

Description:
[0001]     The present invention relates to the field of lighting devices. More specifically, the present invention relates to lighting devices utilizing light-emitting diodes as a light source. Some embodiments of the present invention relate to use in a flashlight, portable hand lantern or other similar portable lighting device, while other embodiments of the present invention relate to lighting devices that are permanently or semi-permanently installed in a location.  
       DESCRIPTION OF RELATED ART  
       [0002]     One problem with using LEDs as a light source is that the light emitted from LEDs travels in substantially one direction, with a majority of their light being spread at a fixed angle, usually between 5 and 50 degrees (typically greater than 10 degrees). Heretofore there has been no practical way of narrowing the beam spread to be less than 4-degrees, nor has there been a way for providing an adjustability to the beam spread of a LED lighting device. An incandescent light bulb, in comparison, will typically emit light in every direction (with the exception of the direction of its base). Similarly, fluorescent tubes emit light in virtually all directions, depending on their particular shape.  
         [0003]     As a result of the above drawbacks to using light-emitting diodes (LEDs), lighting devices utilizing LEDs as light sources typically are constructed so as to arrange LEDs in a direct-view manner. That is, when looking at typical LED devices, one will see light coming directly from the LEDs, or through a protective filter or cover, and otherwise directly from the LEDs. Due to the limitations of LEDs resulting from the substantially uni-directional light output and broad beam spread thereof, it has been necessary to manufacture LED flashlights and other portable LED-based lighting devices with one or a plurality of LEDs mounted on the device, with the LEDs projecting light directly or through a cover or filter. With these devices, however, instead of providing a bright “spot” pattern, they provide a more diffuse pattern that does not concentrate light in one small area, but across a wider area. This is often undesirable in instances where a user desires only to light a small area for viewing detail.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     One object of the subject lighting device is to overcome the drawbacks of other devices by providing a practical and economical means for applying LED technology to portable lighting devices. Another object of the subject lighting device is to provide a practical means for achieving a focusable lighting device using a LED as a light source, a focus being pre-selected prior to or at the time of manufacture, or alternatively, adjustable by a user following manufacture.  
         [0005]     Accordingly, the subject lighting device includes a structure that allows use of a reflector in adjusting a beam pattern. The beam spread or pattern may be adjusted to a predetermined size, in one embodiment, during the manufacture of the lighting device such as that of a relatively narrow-angle “spotlight,” or relatively wide-angle “floodlight,” is achieved. Additionally, a substantially rectangular pattern may be achieved using a condensing lens located in-front of the reflector. In another embodiment, the focus of the subject lighting device is manufactured so as to be user-adjustable. In still another embodiment, the focus is fixed during or following manufacture at a predetermined beam spread.  
         [0006]     Many embodiments of the subject lighting device incorporate the use of an LED light source mounted in front of a reflector or other reflecting surface, light being emitted from the LED, reflected off of the reflector or reflecting surface, then past the LED to provide a directed beam. The light source may, alternatively, be an incandescent, fluorescent or other light source. The light source may also comprise multiple lamps or LEDs (multiple individual light sources). As a further alternative, there may be a mix of types of lamps (LEDs and incandescent lamps, for example) for the purposes of tailoring the overall light quality (temperature, hue, etc.) to a particular application or to suit the preference of a user.  
         [0007]     Depending on the embodiment, the subject lighting device provides for focusability by adjusting the relative distance between the light source and a reflector and/or lens. Such focusability may be pre-selected during the manufacture of the subject lighting device or may be adjustable by a user (following manufacture).  
     
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       [0008]      FIG. 1  is a partial cross-sectional view of one embodiment of the subject lighting device;  
         [0009]      FIG. 2  illustrates a second embodiment of the subject lighting device;  
         [0010]      FIG. 3  illustrates a third embodiment of the subject lighting device;  
         [0011]      FIG. 4  illustrates an alternate embodiment of a reflector of the subject lighting device;  
         [0012]      FIGS. 5A and 5B  illustrate one embodiment of a supporting portion of the subject lighting device;  
         [0013]      FIG. 6  illustrates a second embodiment of a supporting portion of the subject lighting device;  
         [0014]      FIG. 7  illustrates a third embodiment of a supporting portion of the subject lighting device;  
         [0015]      FIGS. 8A-8E  illustrate paths of example light rays emanating from locations at selected distances from a parabolic reflector. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]      FIG. 1  is a partial cross-sectional view of one embodiment of the subject lighting device  100 . A housing  110 , a portion the lighting device  100 , houses a reflector  120  secured to the housing  110 , a lens or filter  150 , which in conjunction with the housing  110 , acts to protect a space defined by the housing  110  and filter  150 , in which the reflector  120  and other components are arranged. In-front of the reflector  120 , with respect to a longitudinal axis of the housing  100 , is a LED light source  130 , which may comprise a single LED or a plurality of LEDs. For the purposes of simplifying this discussion, the LED light source  130  will simply be referred to in the singular, but it should be understood that a plurality of LEDs may be incorporated. In this embodiment, the LED  130  is oriented in-front of the reflector, and arranged so as to direct a majority of the light output therefrom toward the reflector  120 . In other embodiments, it may be preferable to include a plurality of reflectors, at least some of which are not directly behind the LED  130 .  
         [0017]     In this embodiment, the LED  130  is mounted on a supporting frame  140 . The supporting frame suspends the LED  130  in a position relative to the reflector that produces a desired beam spread (wide-angle/flood, narrow-angle/spot). The beam spread may be predetermined during the manufacture or user-adjustable.  
         [0018]     Focusability of light in the subject lighting device  100  may be achieved in a variety of manners. In one embodiment, the LED is suspended above the reflector on a flexible support frame  140 . A screw  157  behind the LED  130 , when turned, applies a force on a LED base plate  145  or on the back of the flexible support frame  140 , which moves the LED toward or away from the reflector. The screw  157  may be held by a grommet  155  to reinforce the lens/filter  150 . As shown in  FIG. 2 , an alternate means for achieving axial translation of the LED  130  relative to the reflector  120  and/or housing  110  includes providing the lighting device  100  with a helical groove  270  in which the supporting frame  240  sits, as may be seen in  FIG. 2 . When desired, the LED  130  and the supporting frame  240  may be turned, in this embodiment, by screw  257 . Thereby, the axial position of the LED  130  is adjusted. As shown in  FIG. 3 , if the LED  130  is mounted to the lens/ filter  350 , then the entire lens/filter  350  may be rotated to bring about axial translation of the LED  130 .  
         [0019]     In any embodiment in which the LED  130  itself rotates, power may be supplied in any known means. A power supply may be in the base  160  of the lighting device  100 , elsewhere in the lighting device, or may be supplied from an external source, such as a vehicle power supply. Because LEDs typically require a lower voltage than other light sources, a transformer, resistor or other voltage reducing circuitry will typically be required, unless run off of a battery power supply with an appropriate voltage output.  
         [0020]     Power supply wires (not shown) may be provided with enough slack that a maximum number of turns of the LED  130  will not damage the wires. Alternatively, contacts may be placed within the housing  110  and on moving parts so that as the LED  130  rotates, conduction may continuously occur.  
         [0021]     Instead of or in addition to an axially translating LED  130 , the reflector  120  may also translate along the longitudinal axis of the housing  110 . As seen in  FIG. 4 , to achieve a axially translating reflector, the housing  110 , for example, may have one or more linear guides  410  on its interior surface along which the reflector may travel. Alternatively, the reflector  120  may simply move linearly via a screw-type interface or another means.  
         [0022]     Moreover if an optical lens  150  is incorporated into the lighting device instead of a simple filter, the lens  150  may translate along the longitudinal axis of the housing  110 , in order to achieve an adjustable beam spread. Such an adjustable lens  150  may be in addition to or in place of a translating or shape-changing reflector  120 , 420 , and may be embodied with an interface similar to the rotating/ axially translating filter shown in  FIG. 3 .  
         [0023]     By adjusting the relative position between the LED  130  and the reflector  120 , either a relatively narrow or relatively wide beam spread may be achieved, depending on the relative position of the LED  130  and reflector  120 .  
         [0024]     The supporting frame  140  may comprise a shaped flexible material, in-particular a plastic, in-particular a see-through plastic. Alternatively, the supporting frame  140  may be made from a metal.  FIGS. 5A and 5B  illustrate the supporting portion  540  as having three substantially flat prongs  545 . In the embodiment shown in  FIG. 1 , the prongs sit on the surface of the reflector, typically near the top of the reflector  120  near its upper edge. Typically, the supporting frame  140  will be arranged in such a manner that unless an external force is applied to the supporting frame  140 , it will hold the LED  130  at a neutral, resting position. As described above, there are a number of ways to achieve an axial translation of the LED  130  relative to the reflector  120 . In the embodiment of  FIG. 1 , however, typically a force is applied from the adjusting screw  157  to deflect the supporting frame  140  and LED  130  toward the reflector.  
         [0025]      FIG. 6  illustrates an alternate type of LED supporting frame  140 , comprising resilient cylindrical prongs  610 . These prongs  610  act similarly to the prongs shown in  FIG. 5 , to support the LED  130  in the space in-front of the reflector  120 . The prongs  610 , in this embodiment, may be made from a plastic or a metal, such as a spring steel, but may be manufactured of another suitable material. The prongs  610  ride on the reflector  120  or another guide and are thereby provided support. The LED  130  and its base  145 , are either held in position by the rigidity of the supporting frame  610 , through a permanent deformation of the supporting frame  610 , or through the influence of a secondary force, such as that from the adjusting screw  157  or a non-adjustable, permanently fixed secondary support (not shown) for urging the LED  130  into a desired position. In this or other embodiments, when the supporting frame  140  is manufactured out of a conductive material, the supporting frame  140  may conduct the power to the LED  130  necessary for operation.  
         [0026]     Alternatively, if the supporting frame  140  is made from a material with a suitable surface area, conductors may be applied to one or more surfaces thereof. For example, a thin, conductive metal strip with an adhesive backing may be applied to the supporting frame  140 , or conductors may be silk-screened onto the supporting frame  140 . As described above, the power may be carried to the LED  130  by way of wires (not shown).  
         [0027]     In an alternate embodiment shown in  FIG. 7 , the LED  130  is supported by a supporting frame  740  that is oriented substantially along the central axis of the reflector  120  and housing  110 . The LED  130  is oriented so as to emit a majority of its light toward the reflector  120 . The supporting frame  740  may be user-adjustable or may be fixed at a pre-determined position during manufacture to achieve a desired beam spread. If adjustable, the supporting frame  740  may be provided with teeth  747  that mesh with a gear  775 . The gear  775  may be powered by a motor  770  or by manual means. Alternatively, relative linear movement between the supporting frame  740  and reflector  120  may be achieved in another manner. Further, in this embodiment, power may be supplied to the LED  130  through the supporting frame  740 .  
         [0028]     The beam spread of the subject lighting device  100  is dependent on the specific embodiment. That is, there are a number of variables that are typically selected prior to manufacture, including the precise type of reflector  120 . The shape of the reflector  120  will inpart determine the behavior of the light output from the lighting device  100 . Naturally, the nearer the LED  130  to the focus of the mirror, the more the beam spread will approach a spot pattern, as all light rays will be leave the reflector approximately parallel to each other and to a central axis of the lens.  
         [0029]     FIGS.  8 A-E illustrate example paths that light rays emitted from the LED  130  may take, depending on the position of the LED relative to the reflector  120 . In FIGS.  8 A-E, rays emanating from only for one side of the of the LED are depicted to facilitate understanding by the reader.  
         [0030]      FIG. 8A  illustrates the position of the focus F of the particular cross-section of the parabolic reflector illustrated in FIGS.  8 A-E. Light hitting the reflector perpendicular to the central axis of the reflector will be reflected to the focus F. Similarly, light emitted from a LED  130  arranged about the focus F will be reflected and will leave the lighting device  100  substantially perpendicularly to the axis of the reflector  120 .  
         [0031]     However, with the LED  130  located at the focus F and arranged such that it is directed substantially downward toward the bottom-most point of the reflector, current LEDs would not be able to emit a substantial amount of light in the direction of ray  810   a  or even  810   b  or  810   c.  One of the limitations of LEDs set forth above in the Background of the Invention section, is that they typically emit light in a substantially uni-directional manner. As such, a typical LED will not be able to project much light beyond the angles and outside of the area defined by lines  820   a  and  820   b.  FIGS.  8 B-E, however, illustrate the behavior of the light when the LED is placed further from the reflector  120  than the Focus F.  
         [0032]     The specific size of an area lighted by the lighting device  100  depends in part on the distance the lighting device  100  is located from the area to be lighted, since if the light rays are not perfectly parallel to the axis, they will ultimately diverge from the central axis and create a wider beam as they travel further from the lighting device  100 . For example, the position of the LED  130  in  FIG. 8B  yields two example rays  830   a  and  830   b  that diverge from the center axis as they leave the reflector area.  FIG. 8C  illustrates example rays  840   a - 840   c  that diverge from the central axis at an even greater angle than rays  830   a  and  830   b  of  FIG. 8B . However,  FIG. 8D  illustrates a position of the LED  130  that yields a substantially converging set of rays  850 . Rays  850   b  and  850   c,  upon leaving the reflector area are clearly angled toward the central axis of the reflector  120 . Ray  850   a,  however, has missed the reflector and diverges from the central axis. If, however, the reflector were larger than that illustrated here, this ray  850   a  too, would be angled toward the central axis.  FIG. 8E  illustrates a LED  130  position that results in an more marked convergence of the rays upon leaving the reflector area.  
         [0033]     As stated above, however, if the rays are not parallel upon leaving the reflector, they will ultimately diverge. In the case of the position of the LED  130  shown in  FIGS. 8D and 8E , prior to diverging, the rays will converge and form a spot pattern at a distance from the lighting device  100 . Since the position of the LED  130  may be adjustable, the distance at which a spot pattern is formed may also be adjustable.  
         [0034]     In alternate embodiments, the subject lighting device may be affixed in a permanent or semi-permanent manner, such as in a building for general or accent lighting, in special-effect displays, in outdoor lighting fixtures, warning beacons on vehicles for interior lighting, headlights or warning beacons on the vehicle.  
         [0035]     When used as a warning beacon, the lighting device  100  may be arranged on a rotating or oscillating base or frame, such that at least the reflector  120  and LED  130  rotate or oscillate as a unit, thereby providing a flashing effect from the perspective of a viewer, alerting the viewer to the presence of the beacon and a thereby providing a warning of a potential hazard.  
         [0036]     It is to be understood that though specific embodiments and examples are set forth herein, that the spirit of the invention may be applied in situations and embodiments not specifically set forth herein.