Patent Publication Number: US-2006013001-A1

Title: Reflectors for condensed light beam distribution

Description:
This application claims benefits of the priority filing date for provisional patent No. 60/589/184 filed on Jul. 19, 2004 and titled “Improved Reflectors For Condensed Light Beam Distribution”.  
      References Cited: 
      U.S. Patent Documents     6,691,701     4,349,245   

    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to energy distribution, and in particular to illumination devices for concentrated or substantially collimated beam distribution of sunlight or artificial light.  
     BACKGROUND INFORMATION  
      Condensed beam distribution of daylight or artificial light is a conceived yet uncommercialized concept where a beam of concentrated light such as collected by a two axis sun-tracking collector and is distributed with stationary reflectors typically along a ceiling or roof, such as is described in U.S. Pat. No. 4,349,245 (Kliman). Successive portions of a concentrated beam in such a system can be re-directed typically in a downward fashion to provide for building illumination. Also described in U.S. Pat. No. 6,691,701 (Roth), proposed louver type reflectors for such a concept that progressively intersect the uppermost beam sections for this purpose may work adequately for high ceiling warehouses and for short distribution distances where the beam expands minimally, they are not ideal, nor practical for lower ceilings, and longer distance distribution applications.  
      When utilizing collector optics of practical and cost effective accuracy, the concentrated beam expands in diameter significantly over distance. Because of this expansion, both the beam and prior art reflectors designed to distribute portions of such a beam, both begin an undesirable and impractical incursion into the building workspace.  
      It is a principal object and advantage of the invention to allow improved distribution of light in a more confined space for a concentrated beam of sunlight or artificial light.  
     BRIEF SUMMARY OF THE INVENTION  
      The invention provides an improved means of re-directing and distributing light from a condensed beam of light in a confined space. Included are a series of reflectors where the reflector surfaces intersect a beam of light from at least two sides, and are oriented at an angle intersecting the cross section of the propagating beam. The reflectors are further characterized as having a configuration allowing passage of un-reflected portions of the beam to be successively re-directed by other reflectors along the path of propagation, and evenly distributing light over a given distance of beam propagation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an isometric view of the first reflector embodiment showing the vertical axis light rays.  
       FIG. 2  is an isometric view of a second reflector embodiment showing the vertical axis light rays.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIG. 1 , the figure shows a moderately expanding condensed light beam  2 , intersecting lateral reflector  6 . First reflector  4 , and aperture  12  are positioned intersecting a cross section of light beam  2 . Reflector  4  is positioned at preferably about 45 degrees facing toward the direction of propagation of light beam  2 , when downward distribution of the light is desired. Reflector  4  is preferably made of stamped aluminum, and preferably coated with semi gloss white paint. A white painted surface intersecting a beam of condensed light at substantially 45 degrees will evenly disperse the light in a direction generally perpendicular to the direction of light propagation. Other reflective surfaces, including specular, semi-specular and curved surfaces may be utilized, and their unique distribution characteristics derived from observation or state of the art optical engineering programs.  
      Light ray  14  re-directed from first reflector  4  propagates in a downward direction. Such reflectors  4 ,  8  and  16  can also be oriented to reflect the light horizontally etc. Portions of light beam  2  propagate through first reflector aperture  12 , and expand over distance. The expansion of the beam is an inherent characteristic of the optic errors from the collecting stage, and the subtended angle of the sun, or may be emphasized by intention in the optical design. The preferred beam expansion is about 1-6 degrees. Circumferential portions of light beam  2  intersect second reflector  8  and are re-directed in a downward direction. Where even spacing between reflectors is desired, reflector  8 , and a plurality of additional reflectors such as  16  have a greater utilized reflecting surface area than each preceding reflector in the propagation path of light beam  2 .  
      The greater and progressively increasing utilized reflective surface area of successive reflectors is useful and necessary to re-direct substantially the same amount of light as the preceding reflector where even spacing between reflectors is desired, because there is a lesser cross-sectional energy density of the beam as it expands over distance. The increased surface area of each successive reflector is a function of, and can be calculated by the increase in light beam  2  diameter at a given distance and spacing from the previous reflector, and compared to the diameter and energy density of the previous reflector (lumens/ reflector=reflector surface area×lumens/area of beam cross section). The optimal configuration can be determined by standard optical engineering programs, inputting the variables of an individual systems beam divergence, desired foot-candles of illumination, and the total desired number of reflectors and their spacing over distance. More generally speaking, for even distribution of light along a beams propagating path, there must be an increased total reflective surface area of a given number of reflectors over a given distance of beam propagation compared to a preceding and subsequent and equivalent given distance.  
       FIG. 2  shows a second embodiment where condensed beam  3  is progressively intersected by reflectors  18  and  20  above the beam, and reflectors  22  and  24  below the beam, each reflector preferably tilted at about 45 degrees toward the direction of the light beam propagation when downward distribution of the light is desired. Distributed light rays  26  and  28  are shown reflected from reflector  22  for example where they would illuminate a building workspace. Having two groups of tandem reflectors intersecting the beam from two sides both above and below the beam is crucial for keeping the reflectors and propagating beam from undesirable incursion into building space. If the propagating beam were intersected from only above the beam, the reflectors would progressively need to be positioned lower and lower into the building space to intersect the expanding beam, greatly limiting applications of such a distribution method because of the of impractical space requirements. As apparent, the utilized reflector surface area increases progressively as the condensed beam  3  propagates over a given distance  30  to provide substantially equal distribution of light as the cross-sectional energy density of propagating beam  3  decreases due to it&#39;s expansion over distance. These tandem reflector surfaces are preferably white substantially paint. Other reflective surfaces such as enhanced reflectivity aluminum, and or curved surfaces specular or semi-specular surfaces may also be utilized, and their unique distribution characteristics derived from state of the art optical engineering programs. It may also be desirable in some applications include additional reflectors oriented at approximately ninety degrees to the horizontal orientation of the reflectors to limit lateral expansion of the beam.