Patent Publication Number: US-8534877-B1

Title: Luminaire optical systems

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a nonprovisional application of Provisional Application Ser. No. 61/072,973, filed Apr. 3, 2008, upon which priority is claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to optical systems useful in industrial lighting applications and particularly to energy efficient and high performance luminaires incorporating such optical systems utilizing independent and concentrically aligned reflectors adjustable relative to each other and operating in tandem to produce a versatile range of tailored photometric distributions. 
     2. Description of the Prior Art 
     High bay luminaires have traditionally found particular use in warehouses, manufacturing facilities and increasingly in retail situations wherein ceiling heights require lighting adequate for illumination of particular areas within an overall space. Low bay luminaries of similar configuration find utility in lighting applications having differing lighting requirements. Conventional luminaires of these types typically provide uniform illumination over the distribution area of such facilities, such uniform illumination typically being less than adequate for at least certain areas in which a greater degree of light intensity is desirable, such as in an area in which an assembly line is located, as opposed to an area wherein a lesser degree of illumination is necessary such as walkways or the like where tasks requiring greater degrees of illumination are not performed. In typical warehouses, for example, luminaires are disposed between fifteen to seventy feet above floor level. In such situations, more light is desired at a working surface as opposed to upper portions of a storage rack or near ceiling levels. Even so, adequate illumination is necessary at these upper portions of storage racks and the like so that fork lift or “picking” operators can place and remove items from these racks. Typical high bay or low bay luminaires are incapable of providing adequate lighting levels at these spaced locations within the volumetric confines of a working space or the like without the use of high wattage lamping, thereby creating unnecessary illumination near ceilings in order to create adequate lighting near floor level. Such conventional luminaires typically use 400 watt lamps as well as lamping ranging up to 1000 watts in order to address these needs, the use of such lamps being extraordinarily wasteful of energy in the form of the electrical power necessary for operation of such lamping even without consideration for the additional energy required for space cooling due to the heat generated by this high wattage lamping. 
     The art has previously addressed certain of these failings through use of dual reflector lighting systems such as are disclosed by Thomas et al in U.S. Pat. No. 5,582,479; by Walker et al in U.S. Pat. No. 6,068,388 and by Splane, Jr. in U.S. Pat. Nos. 5,791,768; 6,273,590 and 6,464,377. In these patents, an inner reflector located within an outer reflector, such as is typically used as a sole reflector in a high bay luminaire or the like, can be displaced relative to the outer reflector and relative to lamping in order to produce a desired lighting distribution for any given luminaire in a building having a multiplicity of luminaires for illumination of the building. These luminaires function with lamping of a lower wattage to produce desired lighting distributions and illumination levels than would be expected given the performance of conventionally used high bay luminaires such as those disclosed in U.S. Pat. No. 3,401,258 to Guth and U.S. Pat. No. 4,173,037 to Henderson, Jr. et al, these and many other high bay luminaires being commonly used over at least the last fifty years. In these prior art luminaires, an opaque or transparent prismatic reflector typically having an inverted bowl shape houses an energy inefficient lamp in order to provide adequate illumination levels within a given volumetric space. Even though Henderson, Jr. et al disclose an outer reflector and an asymmetrical inner reflector, the inner reflector is mounted for rotational adjustment relative to the vertical axis of the disclosed luminaire and thus functions only to produce asymmetrical light distribution and does not permit energy efficiencies. Similarly, well known luminaires such as those disclosed by Cochran in U.S. Pat. No. 1,286,535 include dual reflectors incapable of displacement relative to each other to vary lighting distributions. 
     High bay luminaires are further disclosed by Jaffari et al in U.S. Pat. No. 6,478,454; by Burroughs in U.S. Pat. No. 6,494,596; by Sitzema, Jr., et al in U.S. Pat. No. 6,698,908; by Barnes et al in U.S. Pat. No. 4,839,781; by Taylor et al in U.S. Pat. No. 4,903,180; by Sales in U.S. Pat. No. 6,910,785 and by Leadford in U.S. Pat. No. 7,025,476. With the exception of Jaffari et al, these patents focus on transparent single reflector luminaires having prismatic structures which function to reflect light from lamping to illuminate a space. Jaffari et al disclose a metal primary or outer reflector capable of directing light upwardly of the luminaire. Burroughs treats a prismatic reflector on upper portions of inside surfaces in order to eliminate hot spots at nadir. Sitzema, Jr. et al provide a peened specular collar with a primary reflector to achieve a more narrow distribution in an acrylic high bay luminaire. Barnes et al disclose a commonly employed reflector/refractor used in luminaires and the like, such luminaires configured only with the reflector/refractor so disclosed being incapable of adjustment of light distribution characteristics along with an inability to provide desirable illumination levels with lamping of a lower wattage and thus greater energy efficiency than is possible in light of the disclosure provided herein. Sales and Leadford disclose single reflectors useable in high bay and similar luminaires, these reflectors being intended to utilize shaped prisms for direction of light from lamping housed within the reflectors. 
     Prismatic structures useable in luminaires such as high bay luminaires and the like are further described by Pearce in U.S. Pat. No. 5,416,684; by Shadwick in U.S. Pat. No. 3,800,138 and by Franck in U.S. Pat. No. 2,818,500. Franck discloses a number of basic lighting principles relating to prismatic structures formed of transparent materials such as high grade glass. Among these structures are radial scallops on interior surfaces of a reflector and configured to avoid light being incident on the valley and ridge radii of externally disposed prisms. Shadwick discloses scalloped structures that function to blur bleed-through lamp image viewed through a refractor functioning as a reflective structure. Pearce provides a fixed secondary metal reflector within an enclosing refractor in order to divert light away from a non-optical base of the refractor. Guth, previously mentioned, discloses in U.S. Pat. No. 3,401,258 faceted fluting in the form of radial scallops formed near the aperture of a metal or otherwise opaque reflector and used for glare control. Yet another prismatic reflector disclosed as a high bay luminaire is provided by Taylor et al in U.S. Pat. No. 4,903,180 with a transparent shroud for protection of the reflector from dust accumulation that degrades reflector performance. 
     The prior art fails to disclose optical systems particularly useful in high bay and similar luminaries as well as in luminaires capable of use in other lighting applications, which optical systems are capable of energy efficiencies and enhanced performance relative to presently available luminaires. Accordingly, a need for optical systems capable of energy efficiency and improved performance is long-felt and is addressed by the presently disclosed optical systems, said optical systems of the invention being characterized as dual reflector systems having precision optics utilizing highly specular reflective finishes particularly disposed on an inner reflector having radial waves or scallops either concave or convex, the assembly of the inner reflector and a clear point source lamp being displaceable relative to a prismatic outer reflector for maximization of optical control, tailoring of beam shape to optimally suit a variety of functions within a space to be illuminated, enhanced glare control and precision light placement as well as energy efficiencies afforded by the ability to use lower wattage lamping than has previously been necessary for suitable work plane illuminance for a given lighting application. The optical systems of the invention utilize two independent and concentrically aligned reflectors working in tandem to smoothly and efficiently produce a versatile range of tailored photometric distributions, the present systems being useful in lighting applications advantageously employing adjustable beams such as accent lighting, ellipsoidal downlighting, stage lighting, landscape lighting, aircraft and automotive reading lighting and even in flashlights as well as in high bay and low bay industrial and retail applications. The optical systems of the invention are now disclosed with particular reference to a high bay luminaire capable of exceptional performance with substantial energy efficiencies. 
     SUMMARY OF THE INVENTION 
     The invention provides optical systems useful in luminaires suitable in a variety of lighting applications wherein an adjustable beam is advantageous, these applications including but not being limited to industrial and retail lighting such as in warehouses, manufacturing facilities and retail establishments, particularly those establishments characterized by ceiling heights greater than approximately fifteen feet and which ordinarily are provided with luminaires commonly referred to as high bay luminaires. Other applications include but are not limited to accent lighting, ellipsoidal downlighting, stage lighting, landscape lighting, aircraft and automotive reading lighting, low bay lighting, task lighting and even “flash lights”. 
     The optical systems of the invention are particularly characterized in preferred embodiments by the use of at least two independent and concentrically aligned reflectors capable of tandem function to smoothly and efficiently produce a broad range of tailored photometric distributions. The present systems permit substantial increases in light output for a given energy expenditure, that is, for lamping of a given wattage, or substantial energy efficiencies for a given light output and utilization, that is, lamping of a lower wattage can be employed to provide lighting performance otherwise provided only by a higher wattage lamp operable with greater energy expenditure. The optical systems of the invention preferably employ clear point source lamping such as metal halide lamping including pulse-start metal halide and ceramic metal halide with clear outer glass envelopes, that is, non-phosphor coated bulbs or jackets. Use of such lamping in concert with the preferred precision optics of the invention permits maximization of optical control, tailoring of beam shape to optimally suit a variety of applications, enhanced glare control and precision light placement while taking full advantage of the long life, low maintenance, energy efficiency and high lumen output of the preferred lamping. 
     The optics of the present systems as are particularly embodied in luminaires such as high bay luminaires disclosed herein preferably include an outer or primary prismatic reflector having concentric scalloping and radial scalloping on interior surfaces, the intersections of such scalloping defining a multiplicity of optically efficient and visually appealing micro-regions. The preferred outer reflector houses an inner reflector movable in tandem with the preferred lamping to vary beam shape and thereby permit adjustability at anytime after original installation of individual luminaires to meet the requirements of a particular application. The inner reflector is preferably formed with radial scallops over its entire surface, preferred scalloping being convex as viewed from “inside” of the reflector. The scalloped inner reflector is preferably provided with a highly specular reflective finish to yield a specular reflectivity approaching 95%. Divergent and convergent profiling of the preferred inner reflector provides particularly improved performance especially with lamping such as high intensity discharge and the like that substantially functions as point source lamping. The inner reflector can be alternatively configured with a wave or concave pattern to provide desired performance. 
     Embodiments of the invention particularly useful as high bay luminaires are preferably configured with ventilation apertures formed in upper portions of the outer reflector in order to efficiently remove heat from the interior of the luminaire. Further, the high bay luminaires of the invention are preferably further provided with a prism shield surmounting the outer reflector and formed with ventilation apertures aligned with the ventilation apertures formed in the outer reflector so that ventilation is assured. The prism shield primarily functions to protect the outer reflector from dust accumulation that can degrade prism performance. 
     As will be appreciated with particular reference herein to high bay luminaire embodiments of the invention, the mounting of the inner reflector in fixed relation to the arc of the preferred lamping defines a “ceiling” of the optical system regardless of displacement or positional adjustment of the lamping and thus the inner reflector relative to the outer reflector to provide a desired lighting distribution on surfaces beneath the aperture of the outer reflector. This relationship between lamping, inner reflector and outer reflector plays a substantial role in the ability to provide the advantages of the invention as enumerated herein. 
     Accordingly, it is an object of the invention to provide optical systems particularly embodying multiple reflectors working in tandem to tailor photometric distribution to varying lighting applications while maximizing energy efficiencies. 
     It is another object of the invention to provide independent and concentrically aligned reflectors operable preferably with clear point source lamping, an inner reflector being fixed in relation to the lamping and being relatively displaceable with the lamping relative to an outer reflector to tailor beam shape and provide desired light outputs and distributions yielding improved performance with energy efficiencies. 
     It is a further object of the invention to provide an optical system having prismatic outer reflector housing an inner reflector having a divergent and convergent profile fixed positionally to a point source lamp, the inner reflector and lamp being displaceable relative to the outer reflector or vice versa to produce a versatile range of tailored photometric distribution while maximizing energy efficiencies. 
     Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a high bay luminaire having an adjustable dual reflector optical system configured according to a preferred embodiment of the invention; 
         FIG. 2  is a perspective view partially cut away of the high bay luminaire shown in  FIG. 1 ; 
         FIG. 3A  is a perspective view from beneath the luminaire shown in  FIG. 1 ; 
         FIG. 3B  is a detail view of a portion of inner surfaces of an outer reflector of the luminaire shown in  FIG. 3A ; 
         FIG. 3C  is a detail view of a portion of inner surfaces of an inner reflector of the luminaire shown in  FIG. 3A ; 
         FIG. 4  is a perspective view of an outer reflector configured according to a preferred embodiment of the invention; 
         FIG. 5  is a side elevational view in section of the outer reflector of  FIG. 4 ; 
         FIG. 6  is a detail view in section of a profile of the outer reflector of  FIG. 4 ; 
         FIG. 7  is a perspective view of a detail of the outer reflector of  FIG. 4 ; 
         FIGS. 8 through 11  are detail views of portions of the outer reflector of  FIG. 4 ; 
         FIG. 12  is a perspective view of an outer reflector of a high bay luminaire configured according to the invention and illustrating formation of concentric scalloping on inner surfaces of the reflector; 
         FIG. 13  is a schematic detail view of a portion of the inner surface of the reflector shown in  FIG. 12 ; 
         FIG. 14  is a perspective view of an outer reflector of a high bay luminaire configured according to the invention and illustrating formation of radial scalloping on inner surfaces of the reflector; 
         FIG. 15  is a perspective view of an outer reflector of a high bay luminaire configured according to the invention and illustrating a finished inner surface of said reflector having both concentric and radial scalloping of said inner surface; 
         FIG. 16  is a detail view of a portion of the inner surface of the reflector shown in  FIG. 15  and illustrating micro-regions defined by concentric and radial scalloping of said inner surface; 
         FIG. 17A  is a perspective view seen from beneath of an inner reflector of a high bay luminaire configured according to the invention and illustrating a convex radial scalloping of inner surfaces of the inner reflector; 
         FIGS. 17B through 17N  are various views of the inner reflector of  FIG. 17A ; 
         FIG. 18  is a perspective view seen from above the inner reflector of  FIG. 17A ; 
         FIG. 19  is a perspective view of an inner reflector of a high bay luminaire configured according to a further embodiment of the invention and illustrating a wave pattern formed in the inner reflector; 
         FIG. 20  is a perspective view of an inner reflector of a high bay luminaire configured according to another embodiment of the invention and illustrating a concave radial scalloping of surfaces of the reflector; 
         FIG. 21  is a perspective view of a prism shroud configured according to the invention and disposed over an outer reflector such as the reflector of  FIG. 4 ; 
         FIG. 22  is a side elevational view of the prism shroud of  FIG. 21 ; 
         FIG. 23  is a bottom view of the prism shroud of  FIG. 21 ; and, 
         FIG. 24  is a detail view of a portion of the prism shroud illustrating ventilation apertures inter alia. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The disclosures of U.S. Pat. Nos. 1,286,535; 2,818,500; 3,401,258; 3,800,138; 4,173,037; 4,839,781; 4,903,180; 5,416,684; 5,582,479; 5,791,768; 6,068,388; 6,273,590; 6,464,377; 6,478,454; 6,494,596; 6,698,908; 6,910,785 and 7,025,476 are incorporated hereinto by reference. 
     Referring now to the drawings and particularly to  FIGS. 1 through 3 , a high bay luminaire is seen generally at  10  to comprise a substantially bowl-shaped outer reflector  12  displaceable within the structure of the luminaire  10  by means of an adjustment mechanism  16 , the adjustment mechanism  16  comprising an annular base ring  18  fixed to the outer reflector  12 , the outer reflector  12  being displaceable along a threaded tubular adjustment member  20  received within a threaded central bore (not shown) of the base ring  18 . The tubular adjustment member  20  is fixedly mounted to a ballast housing  14 . Rotation of the outer reflector  12  about the tubular adjustment member  20  displaces the outer reflector  12  relative to an inner reflector  28  and a lamp  30  fixed relative to each other, thereby to vary beam spread of the light generated by the lamp  30  and exiting aperture  32  of the outer reflector  12 . The adjustment mechanism  16  functions similarly to a corresponding adjustment mechanism disclosed in U.S. Pat. No. 5,791,768, the disclosure of which patent is incorporated hereinto by reference. However, the position of the outer reflector  12  as seen in  FIGS. 1 and 2  is adjusted relative to the position of the fixed assembly of the lamp  30  and the inner reflector  28  according to preferred embodiments of the invention. However, it is to be understood that the lamp  30  and the inner reflector  28  can be caused to move relative to the outer reflector  12  through the agency of an adjustment mechanism (not shown) without departing from the scope of the invention. 
     The ballast housing  14  is essentially conventional in structure and operation and houses a ballast (not shown) which preferably comprises an energy efficient electronic ballast as well as other electrical components necessary for operation of the lamp  30 , the lamp  30  preferably being a clear point source lamp such as a high intensity discharge lamp having a clear glass envelope. A metal halide lamp such as a pulse-start metal halide or ceramic metal halide lamp is preferred due to inherent characteristics of such lamping such as high lumen output, long life, low maintenance and energy efficiency. Such lamping is typically characterized by an arc shape, proportion and location within the lamp envelope that, while not comprising a theoretical point source, functions essentially as a point source given the precision optics provided by the outer reflector  12  and the inner reflector  28  as will be disclosed hereinafter. 
     The high bay luminaire  10  is optionally provided with a prism shield  34  also seen in  FIGS. 21 through 24 . The structural details of the prism shield  34  will be provided hereinafter. The primary function of the shield  34  is to preclude dust accumulation on portions of the outer reflector  12  covered by the shield, thereby to prevent degradation of the performance of prismatic structures formed on covered portions of the outer reflector  12 . The shield  34  is further provided with ventilation apertures  36  which align with ventilation apertures  38  formed in the outer reflector  12 , heat produced by the lamp  30  within the interior of the luminaire  10  being vented through the aligned apertures  36  and  38 , when the shield is used, or through the apertures  38  to reduce the effect of heat on luminaire efficiency when the shield  34  is not employed. 
     With further reference to  FIGS. 4 through 16 , the outer reflector  12  is seen to be substantially shaped as a bowl that is inverted in a normal use situation. The reflector  12  is formed with an annular base  40  at an “upper” end and a perimetric rim  42  at the end thereof opposite the base  40 , the rim  42  defining the aperture  32  of the reflector  12 . As is conventional in luminaires of this and other types, the aperture  32  is the opening through which light generated and processed by luminaire optics is directed into a space and onto objectives within the space that are to be illuminated. The ventilation apertures  38  are formed in an annular apron  44  that extends about the periphery of the base  40  between the base  40  and major portions of the reflector  12  having prismatic structures generally represented as  46  in  FIG. 4  for general illustration. The outer reflector can advantageously be formed of conventional polymeric materials, particularly acrylics, as well as high grade glass as is also conventional in the art of manufacturing reflector and refractor structures. Acrylic materials are preferred due to cost, weight, appearance, flexibility and repeatability of injection molding processing of relatively large objects with precise and complex geometries. Prisms  48  formed on outer surfaces of the reflector  12  and best seen in  FIGS. 8 through 11  are traditional ninety-degree prisms long used in glass and “plastic” luminaire optics, such prisms being capable of the highly efficient optical phenomenon of total internal reflection at both prism faces as well as refraction, before and after, at inside surfaces. 
     The profile of the outer reflector  12  is best seen in  FIGS. 5 and 6  and is chosen to function with a clear lamp such as the lamp  30  which is preferred. Clear lamping typically produces greater light output than coated lamping and allows less light to be transmitted through prisms such as the prisms  48  due to lamp light origination close to the central axis of a reflective structure such as the reflector  12  with a resultant creation of favorable input angles into the prisms, reduction of prism transmission increasing the percentage of light in the 0-60 degree photometric range. Clear lamping further permits greater optical control. Such downwardly directed light is more efficient at providing illumination to lower, task-oriented objectives with a usual high bay application space relative to high angle light and up light resulting from prism leakage. 
     In the luminaire  10 , the outer reflector is displaced as noted above relative to the combination of the lamp  30  and the inner reflector  28  in order to adjust photometric distribution. However, in other embodiments, the combination of the lamp  30  and the inner reflector can be displaced relative to the outer reflector  12 . Accordingly, the highest angle light is advantageously caused to be more sensitive to lamp displacement with mid-angle light being made less so. In order to accomplish this result, bottom portions of the reflector  12  about the aperture  32  aims light to mid photometric angles. As the profile of the reflector  12  proceeds upwardly, light is reflected to higher vertical angles until a highest angle of the distribution is attained. Above this highest angle, light is aimed at progressively lower angles at a sufficiently rapid rate so that the lowest aiming angle is reached at the end of the profile contour. Accordingly, more useful light distributions are produced over a wide range of lamp displacements. The reflector  12  is thus shaped near bottommost portions thereof nearly conically, thereby providing a unique appearance relative to conventional high bay luminaires which are substantially vertical at bottom portions and curved over the outer profile. The profile of the reflector  12  further permits relatively deep scalloping especially near bottom portions thereof while providing adequate draft for injection molding. 
     Creation of the interior topography of the inner surfaces of the outer reflector  12  is best understood with reference to  FIGS. 12 through 14 , a series of concentric scallops  50  being shown in  FIG. 12  without the complication of illustration of radial scallops  52 , seen for illustration in  FIG. 14 , being overlaid on the concentric scallops  50 . The concentric scallops  50  primarily function to vertically diffuse reflected light to assure a smooth distribution without bright or dark rings on illuminated surfaces, thereby providing a result not otherwise readily accomplished with the use of a clear lamp together with the specularly reflecting nature of acrylic prisms. Further, this vertical diffusion thus provided produces a spreading of the reflected image or flash as viewed from the inside of the reflector  12 , thereby reducing the potential for glare due to the reflected light. Still further, the concentric scallops  50  vertically diffuse light that bleeds through the prisms  48  such as through ridge and valley radii of said prisms such that a lamp image band, that is, a band due to the horizontal spreading of light by the prism radii seen through the reflector  12  is spread in the vertical dimension as well as tapers in perceived brightness from its center outwardly to top and bottom edges. These affects reduce the potential for glare and any visual distraction caused by any bleed-through band. The concentric scallops  50  are chosen to be concave as viewed from the interior of the reflector  12  in spite of a manufacturing advantage in the forming of convex scalloping. While convex scalloping can be employed, light coming into and then out of convex concentric scalloping when formed in the reflector  12 , or reflection from the prisms  48 , can produce a Moiré interference resulting in less smooth distribution of light in the vertical dimension. The concentric scalloping employed in the reflector  12  produces along with the vertical optical profile of the reflector  12  desired photometric distributions. The concentric scallops  50  maintain a given depth over the full extent of said scallops  50  to the aperture  32  of the reflector  12  while maintaining necessary draft angles for part removal from tooling, thereby causing the optical benefits thus detailed to be manifest over the entirety of the inner surfaces of the reflector  12  over which the scallops  50  are formed. The shape of the concentric scallops  50  can further be appreciated with reference to  FIG. 13 . The concentric scallops  50  per se can be advantageously employed in a further embodiment of the invention, that is, the outer reflector  12  can be employed essentially as shown in  FIG. 12 . 
     Radial scallops  52  are seen in  FIG. 14  without overlay or incorporation of the concentric scallops  50  for purposes of illustration. The radial scallops  52  are formed on interior surfaces of the reflector  12  as are the concentric scallops  50 , the radial scallops  52  being essentially orthogonal to the concentric scallops  50  as seen in  FIG. 15 . A primary function of the radial scallops  52  is reduction of light leakage from the prisms  48 , the radial scallops  52  diverting light from the lamp  30  toward central areas of flat central portions of prism faces via refraction, this function being accomplished by the convex shaping of the radial scallops  52  as viewed from interiorly of the reflector  12 . Two radial scallops  52  are preferably provided for each of the externally disposed prisms  48  so that both prism valleys and ridges are avoided in order not to increase light transmission through the prisms  48 . Cusps between adjacent radial scallops  52  are precisely aligned in the same vertical plane as either a prism valley or ridge. The number and width of the radial scallops  52  thus varies according to the width and number of the exteriorly disposed prisms  48 . 
     Reduction of prism leakage through the agency of the radial scallops  52  also decreases perceived brightness of any bleed-through lamp image as viewed from outside of the lamping  10  and looking through the reflector  12 . Reduction of prism leakage also causes less light to be sent upwardly or at high vertical angles, thereby improving light delivery efficiency into that space below the luminaire  10 . The radial scallops  52  also horizontally disperse light bleeding through the prisms  48  although such light is dispersed widely in the horizontal sense due to refraction at ridge and valley radii of the prisms  48 . The radial scallops  52  also spread the reflected/flashed image over the interior surfaces of the reflector  12 , thereby reducing perceived brightness and associated glare. While the concentric scallops  50  spread reflected image in the vertical dimension, the radial scallops  52  spread the reflected image in the horizontal dimension. In combination, the scallops  50  and  52  produce comprehensive beam homogeneity via the orthogonal affects of said scallops. The radial scallops  52  also stabilize the amount of light output at and near nadir to enable the use of effectively deep shaping of the concentric scallops  50  without causing a spike in output around nadir that would otherwise arise when vertically dispersing light to near nadir angles from large portions of the reflector profile. 
     Referring again to  FIG. 15  as well as to  FIG. 16 , contours of multiple lens structures  54  formed by the intersections of the concentric and radial scallops  50  and  52  can best be seen, the lens structures  54  existing in a grid. The very large number of the lens structures  54  have a mixed curvature similar to a “saddle” shape generally. The lens structures  54  thus formed by intersections of the concentric and radial scallops  50  and  52  preserve the independent functionalities of both the concentric and radial scallops  50  and  52  due to the mutual orthogonal orientation of the scallops  50  and  52 . Exemplary of the dimensions of the lens structures  54 , the lens structures  54  typically and preferably exhibit 20 degrees of arc along arcuate lines  56  with vertical dimensions being normally 0.10″ and in horizontal dimensions from 0.12″ at the bottom of the reflector  12  near the aperture  32  to 0.05″ near the top of the reflector  12 . The invention is not limited to these dimensions nor to a specific number of the scallops  50  and  52 . 
     As disclosed above, the inner reflector  28  is mounted in fixed relation to the lamp  30  so that displacement of the outer reflector  12  relative the fixed combination of the lamp  30  and thus the inner reflector  28  varies the position of the arc of the lamp  30  relative to the reflector  12  to produce differing photometric distributions. A single dimensional adjustment therefore achieves different distributions and renders feasible user adjustment in a use environment such as becomes desirable when changes occur in space usage, such as the movement of an assembly line in an industrial facility. Multiple photometric distributions can thus be achieved with a single optical system as disclosed herein. In particular, a fixed mounting of the inner reflector  28  relative to the lamp  30  permits a substantial photometric contribution to light distribution near nadir without instabilities associated with highly specular optics, high specularity being preferred in forming of the inner reflector  28 . In the present optical systems, the fixed combination of the lamp  30  and the inner reflector  28  produces a fixed output useful within the entire range of desired total distributions. Accordingly, the fixed lamp/reflector combination produces no more light at nadir than is required by the widest producible distribution and also does not direct light to an angle than is higher than required by the most narrow distribution. In practice, the distribution of the inner reflector  28  and the lamp  30  falls essentially linearly as the lamp/reflector combination moves out from nadir. The outer reflector  12  has a complementary distribution that falls off linearly toward nadir and superimposes nearly additive light to produce desired net photometric distributions. The two overlapping linearly tapering distributions created by the luminaire  10  combine smoothly over a wide lamp/reflector displacement range to provide multiple desirable distributions that vary smoothly between limits of displacement of the outer reflector  12  relative to the fixed lamp  30  and inner reflector  28  combination. 
     A preferred embodiment of the inner reflector  28  is best seen in  FIGS. 2 ,  3 A,  3 C,  17 A through  17 N and  18 , the reflector  28  having radial scallops  58  that are convex as viewed from inside of the reflector  28 . The optical profile of the inner reflector  28  provides illumination from nadir outwardly to approximately forty degrees from nadir, the profile being particularly useful with a lamp having a clear envelope such as the lamp  30  and thereby provides a greater degree of optical control and increased lumen rating relative to a coated lamp of the same wattage. The inner portion of the reflector  28  is divergent in that light is reflected away from a centerline of the luminaire  10  drawn between zenith and nadir. Outer portions of the reflector  28  are convergent and reflect light across the centerline, the combination of divergent and convergent characteristics of the optical profile allowing the reflector  28  to provide reflected output over the desired angular range while minimizing flux reflected back onto the envelope of the lamp  30  and onto the outer reflector  12 . Thus, one bounce and out is assured for reflected light with improvement of output efficiency and reduction of heat and degradation of the lamp  30  as well as other components of the luminaire  10 . Further, the profile allows reflected flash and lamp image associated with light output at nadir to be located at the center of the reflector  28  and thus to cover a large radial range. The radial scallops  58  significantly reduce nadir output sensitivity relative to lamp placement and orientation characteristics to thereby allow a single optical system to provide similar photometric characteristics using a broad range of point light sources having differing geometries and photometric distribution. The inner reflector  28  is dimensioned to capture and efficiently redirect a significant portion of upwardly directed flux likely to leak out through the prisms  48  formed on exterior surfaces of the outer reflector  12 . 
     The convergent and divergent profile of the inner reflector  28  couples functionally with the geometry of the radial scallops  58  to produce desired light output distributions. The radial scallops  58  can be varied in depth in relation to curvature changes along the optical profile of the inner reflector  28 , the relationship minimizing stretching and thus degradation of a reflection-enhancing thin film coating  60  formed on the reflector  28  during forming, the coating conveniently being the MiroPress material produced by Alanod. The macro “bowl” shape of the inner reflector  28  would tend to result in excess material when sheet material is formed into the bowl shape if the scallops  58  were not formed in the reflector  28 . The width of the radial scallops  58  and number of scallops can be selected for aesthetic affect. While optical properties of the scalloping can be achieved with a wave conformation as seen in  FIG. 19  in wave-shaped scallops  62  formed in an inner reflector  27  or in  FIG. 20  in concave scallops  64  formed in an inner reflector  29 , the convex radial scallops  58  formed in the inner reflector  28  are preferred for various practical reasons including reflector rigidity and reduction of glare by the breaking of flashed image into smaller, more spatially dispersed, distinct images. 
     The use of a highly specular coating on the inner reflector  28  is permitted by the ability of the reflector  28  to diffuse light by virtue of its profile and formation with radial scalloping, the usual sensitivities associated with highly specular surface coatings in conjunction with clear envelope lamping being greatly reduced. Use of the highly specular coating  60  permits greater optical control and application efficiency. The inner reflector  28  can thus be formed of pre-anodized aluminum sheet with the coating  60  to provide a specular reflectivity of approximately 95%. 
     Referring now to  FIGS. 21 through 24 , the opaque prism shield  34  also seen in  FIGS. 1 and 2  is seen to be shaped congruently with upper portions of the outer reflector  12  surmounted by the shield  34 . As previously noted, the shield  34  functions to prevent dust from collecting on the prisms  48  located on upper and outer portions of the outer reflector  12 , those portions of the reflector  12  being more prone to dust collection and thus potential degradation of optical performance due to a more horizontal orientation of said upper portions relative to lower portions of the reflector  12 . The shield  34  is preferably formed of a polymeric material with inner surfaces of said shield  34  being a bright white to ensure efficient return of any light leakage through the prisms  48 . 
     When the shield  34  covers upper portions of the outer reflector  12 , the aligned apertures  36  and  38  formed respectively in the outer reflector  12  and the prism shield  34  permit a chimney effect ventilation of heat occasioned by vertical hot air movement from the interior of the outer reflector  12  to cool the luminaire  10 . This air movement also functions to reduce the opportunity for dust to settle and accumulate on optical surfaces. When the shield  34  is not utilized, ventilation through the apertures  36  reduces heat loads internally of the outer reflector  12 . The apertures  36  do not degrade efficiency since the inner reflector  28  serves to block light from incidence on the apertures  36  in any location of the lamp  30  and the inner reflector  28  fixed positionally relative to the lamp  30 . The shield  34  also provides an appealing appearance. 
     The outer reflector  12  is further seen such as in  FIG. 7  inter alia to terminate in the rim  42  as aforesaid, the rim  42  being essentially “flangeless” relative to flange-like structures such as are commonly employed in high bay reflectors. The rim  42  is seen to terminate in a decorative trim lip  43 , the surface of which is preferably textured to diffuse lamp light reflected through it thereby reducing the potential for glare and to provide a glow at high vertical angles for decorative appeal and for a higher perception of environmental brightness. 
     The invention can be practiced other than as explicitly disclosed herein, the principles herein disclosed being applicable to a variety of luminaire structures useful in a variety of applications. As one example, a high bay luminaire can be configured according to an embodiment of the invention through substitution of the outer reflector  12  with the reflector disclosed in U.S. Pat. No. 4,839,781, the disclosure of which patent being incorporated hereinto by reference. While the reflector of this patent will not provide the totality of the advantages provided by the luminaire  10  explicitly disclosed herein, substantial advantages are realized even though only the fixed relationships between the lamp  30  and the inner reflector  28  is embodied in a luminaire. Further advantages accrue in such a luminaire when the particular structure of the inner reflector  28  as disclosed herein is employed.