Abstract:
A narrow angle LED illuminated spotlight in which the light-emitting output of an LED light source is coupled with an optic element, in the form of a focusing reflector or focusing lens, and a masking element is interposed between the light source and the optic element to partially mask off the output area of the light source and significantly reduce the area of the emitted light reaching the optic element. This enables the light passed by the masking element to be concentrated into a, narrow beam (i.e., 18° or less) using an optic element of much smaller size than otherwise, thus making the use of an LED light source module a practical source of light for narrow beam spotlights.

Description:
FIELD OF THE INVENTION 
     This invention relates to commercial and stage lighting fixtures and more particularly to improvements in such fixtures of the type incorporating LED elements as a light source. 
     BACKGROUND OF THE INVENTION 
     Light emitting diodes (LEDs) are increasingly being utilized as a light source in various lighting fixtures because of their inherently high efficiency in converting electrical power to light. Although LED elements are relatively expensive, compared to incandescent and other forms of light sources, the initial cost is recovered over time through energy conversion efficiencies. A typical LED light source suitable for commercial and theatrical lighting can be comprised of a plurality of individual LED elements arranged in an enclosed housing to discharge light through an output lens or window of a predetermined size and shape. A representative such light source is shown in, for example, the Harbers et al U.S. Pat. No. 7,988,336, assigned to Xicato, Inc., the content of which is incorporated herein by reference. 
     A frequent requirement of commercial and theatrical lighting is to be able to confine light output of a luminaire or light fixture to a relatively narrow beam, for example as narrow as 8 degrees, so that a particular object can be highlighted in relation to its immediate surroundings. With available commercial LED illumination modules, such as the shown in the before mentioned Harbers et al patent, the light output lens or window covers a plurality of LED elements and accordingly is of relatively large diameter. The emitted light is somewhat diffused in that it originates from a plurality of sources and confinement of the light into a tight beam requires reflectors, typically of a compound parabolic configuration, to be undesirably long in an axial direction. Conventional reflectors thus tend to a compromise, combining a somewhat shorter reflector with a wider-than-desired beam concentration. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a narrow beam spot light, incorporating an LED illumination module as the light source, in combination with a beam concentrator in the form of a reflector or lens. For this purposes of this invention and this application, a narrow beam is considered to be 18 degrees or less. Pursuant to the invention, a masking element is interposed between the illumination module and the concentrator. The masking element has an aperture which is of substantially smaller area than the illumination output area of the LED module. The arrangement is such that only the light passing through the aperture of the masking element reaches the concentrator. This allows the light to be concentrated into a narrow beam with a concentrator of much smaller size than is normally required, and renders the use of an LED illumination module as a practical source of light for a narrow beam luminaire of reasonable size. Heretofore, the use of LED modules has required the use of concentrators of such large size as to be unsuitable for many practical applications. 
     For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment of the invention and also to the accompanying drawings illustrating the same. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a narrow beam luminaire according to the invention, illustrating an LED illumination module and a reflector associated therewith. 
         FIG. 2  is a side elevational view of the luminaire of the invention. 
         FIG. 3  is a longitudinal cross sectional view of a narrow beam reflector as shown in  FIGS. 1 and 2 , in which a masking element according to the invention is integrally incorporated. 
         FIG. 4  is a bottom plan view of the reflector of  FIG. 3 . 
         FIG. 5  is an enlarged, fragmentary cross sectional view illustrating the assembled association of the LED illumination module of  FIG. 1  with the reflector of  FIG. 3 . 
         FIG. 6  is a longitudinal cross sectional view of a reflector of prior art design that typically would be associated with an LED illumination module of the type shown in  FIG. 1 . 
         FIG. 7  is an isometric view, from below, of a beam-concentrating lens adapted for mounting on an LED illumination module as shown in  FIG. 1  and incorporating a masking element formed with a center aperture for limiting the area of the illumination module that can pass light to the lens. 
         FIG. 8  is a longitudinal cross sectional view of the lens of  FIG. 7  illustrating the association of the masking element and its aperture with the illumination output of the LED module. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and initially to the embodiment shown in  FIGS. 1-5  thereof, the reference numeral  20  designates generally an LED illumination module, preferably but not necessarily of the type marketed by Xicato, Inc of San Jose, Calif., under its product designation XSM  80  LED Module. Such a module is illustrated in the before mentioned U.S. Pat. No. 7,988,336. The module  20  includes a base  21  housing an array of a plurality of LED elements  22  ( FIG. 5 ). Preferably and in the illustration of  FIGS. 1 ,  2  and  5 , the base  21  is of circular form with circular internal walls  23  forming a confined circular area  24  for the LED elements, which are spaced somewhat uniformly over the circular area  24 . A window or lens  25  is secured to the base  21  over the opening at the top of the confined circular area  24 , as shown in  FIGS. 1 and 5 . The circular internal walls  23  of the base define the illumination output aperture  26  of the module  20 . Light emitted by the several LED elements  22  is directed upwardly out of the aperture  26 , through the lens  25 , which can be formed or treated to color and/or diffuse the light passing through it. 
     Commercially available LED illumination modules, such as the illustrated Xicato module, because they utilize a number of LED elements to produce the desired light output, tend to have illumination output apertures of considerable size. In the case of the Xicato XSM  80  module shown as an example, the illumination output aperture is approximately 22 mm in diameter. 
     Many applications of commercial and theatrical lighting require a rather concentrated beam of light in order to highlight an object or person in relation to the immediate surroundings. For example, an 8° beam concentration is a common requirement. This has created a problem when using commercially available LED modules, however, in that a conventional, prior art concentrating reflector  26 , shown in  FIG. 6 , formed with a base opening  27 , of a diameter corresponding to that of the illumination output aperture of the LED module, must be excessively large in order to achieve the desired level of beam concentration. By way of example, a prior art reflector of the type shown, with a conventional 22 mm opening at its base to correspond with the 22 mm illumination output of the LED module, requires a reflector of 86 mm length (measured axially) and 134 mm in diameter at the outer end, in order to concentrate the beam to 12°. An even larger size would be required to achieve an 8° concentration. There are very few circumstances where a reflector of such a large size would be accepted in a commercial luminaire. As a result, an unsatisfactory compromise has been accepted heretofore, wherein the reflector has been provided in an acceptable physical size (e.g., 70 mm outer end diameter and 42 mm length), and the end user has accepted a maximum beam concentration of only about 20°. 
     Utilizing the principles of the invention, however, a reflector of acceptable physical dimensions (e.g., a body of revolution of about 42 mm in length and about 70 mm in outer end diameter), can be utilized in combination with commercially available LED modules to achieve a desired beam concentration of 8°. This is accomplished in a surprising way, by interposing an opaque masking element  28  between the illumination output  26  and the concentrating reflector  29 . In the illustrated embodiment of the invention, the masking element  28  is molded integrally with the side walls of the reflector  29 . Theoretically, however, the masking element and reflector could be formed as a separate element. 
     According to the invention, the masking element  28  is of a size to cover the entire illumination output  26  of the LED module  20 , and is provided with an aperture  30 , preferably aligned with the axis of the reflector, that is significantly smaller in diameter than the illumination output  26 . In one preferred and exemplary embodiment, a masking element aperture of 10 mm is used in a luminaire driven by an LED module  20  with a 22 mm illumination output  26 . The area of such an aperture  30  is less than 23% of the total area of the illumination output. 
     When a masking element or component  28  with a restrictive aperture  30  is utilized, a reflector  29  of conventional configuration and acceptable physical dimensions can effectively concentrate the emitted LED light into a narrow beam of, for example, 8°. The concentrator itself may be of conventional configuration, for example a compound parabolic internal contour. 
     In the specifically illustrated example, shown in  FIGS. 1-5 , the diameter of the reflector at its base  31  can be considerably greater than that of the aperture  30 . By way of example and not of limitation, the diameter at the base may be about 22 mm, generally consistent with the base diameter of the conventional reflector shown in  FIG. 6  and with the illumination output  26  of the LED module. With such a configuration, the opaque portions of the integral masking element  28  extend radially inward from the base  31  to the aperture  30 . The reflector base may also be of larger or smaller size, as long as the masking element  28  serves to mask off the illumination output of the LED module and confine its actual output to the aperture  30  of a predetermined smaller diameter than that of the illumination output  26 . 
     The illustrated form of LED module  26  incorporates a mounting collar  35  having three radially spaced slots  36  and associated flanges  37 . The reflector  29  is accordingly provided with three angularly spaced, radially projecting mounting members  38 , which allow the reflector to be easily coupled with the LED module by way of a twist-lock action. When the masking element  28  is integral with the body of the reflector, as illustrated, a single twist-lock action mounts both the reflector and its associated masking element. The geometry of the components is such that the twist-lock mounting of the reflector positions and maintains the masking element  28  and its aperture  30  in close-coupled relation with the output lens  25  of the LED module, such that light discharged from the LED module is substantially exclusively through the restricted aperture  30 . 
     The invention is in no way restricted to the particular dimensional relationships heretofore described. The underlying principle is that of restricting the output of light generated by an LED module to an area less than the intended illumination output area, and in conjunction therewith using a concentrator of reduced physical dimensions to achieve beam concentrations otherwise obtainable only from the use of concentrators of excessively large and unsuitable sizes. In the example given above, the use of a masking element with a 10 mm aperture, in connection with a 22 mm LED illumination output, enabled an 8° beam to be achieved with a reflector of 42 mm in length and 70 mm in diameter, whereas without masking the output of the LED module, a reflector 86 mm long and 134 mm wide was required to concentrate the beam in a wider 12° angle. Within the teachings of the invention, greater and lesser amounts of masking can be employed with a given LED illumination output, depending upon the desired level of concentration and the physical limitations imposed by other factors on the length and diameter of the reflector. A person skilled in the art can readily vary the extent of masking required or desired to achieve a given degree of beam concentration using a reflector of the desired size. The principles of the invention are useful to advantage to achieve beam concentrations over a range of 6° to 18°. 
     The invention is also not limited to the use of reflectors as beam concentrators but also is applicable to luminaires incorporating concentrating lenses. Such an arrangement is illustrated in  FIGS. 7 and 8  in which an optical lens  40  is joined at its base  41  with a masking element  42  provided with a central aperture  43 . The masking element  42  is formed with integral, radially extending mounting members  44  positioned for engagement with the mounting collar  35  of the LED module  20 . When the masking element  42  is secured to the mounting collar, the bottom surface of the masking element is seated tightly against the upper surface of the lens  25  of the LED module, in the same manner as the masking element  28  of the embodiment of  FIGS. 1-5 . In the illustrative but non-limiting example of  FIGS. 7-8 , the aperture  43  may have a diameter of 10 mm, for use with an LED module  20  having an illumination output of 22 mm. Larger or smaller apertures  43  may be utilized, depending on the objectives of the designer. The aperture  43 , by reducing the area of light that can be emitted by the LED module  20 , enables the lens  40  to concentrate the light to a narrower beam than otherwise. In the illustration of  FIGS. 7 and 8 , a lens of about 27 mm in diameter, formed of clear acrylic, can be employed to achieve a beam concentration of 8°. 
     Although the form of the invention specifically disclosed herein utilizes an LED module having a circular illumination output, it is noted that some commercially available LED modules have differently shaped illumination outputs, such as square and rectangular. The underlying principles of the invention are also applicable to such differently shaped illumination outputs. 
     It will thus be understood that the specific embodiments of the invention herein illustrated and described are intended to be representative only and that many variations may be made therein within the broad teachings of the invention and the disclosure thereof. Accordingly, reference should be made to the following claims in determining the full scope of the invention.