Abstract:
A light delivery system includes a light source. A first generally tubular, hollow coupling device with an interior light-reflective surface receives light from the source at an inlet and transmits it to an outlet. The coupling device increases in cross sectional area from inlet to outlet in such manner as to reduce the angle of light reflected from the surface as it passes through the device. A thermal-isolating region has an inlet positioned in proximity to an outlet of the coupling device and has an outlet for passing light to an optical member, the thermal-isolating region comprising one or more members. A waterproof container for the light source and coupling device has an aperture allowing light to pass out of the container. The aperture is sealed in part by a portion of a member of the thermal-isolating region. Advantageously, the system can be buried beneath the surface of the ground. This avoids the problem of people or equipment colliding with the system. The components in the sealed container are protected from intrusion by wildlife or deterioration from dirt and dust. In some embodiments, the container may be free of a fan, reducing the complexity and noise of the system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This invention is related to application Ser. No. 09/454,073, filed on Dec. 1, 1999, entitled “Efficient Arrangement for Coupling Light From a Light Source to a Light Guide,” by Roger F. Buelow et al. It is also related to application Ser. No. 09/470,156, filed Dec. 22, 1999, and entitled “Method of Making Optical Coupling Device,” by Juris Sulcs et al. The entirety of the disclosures of both these applications is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to systems for delivering light to one or more light guides, and, more particularly, to a waterproof system. 
     BACKGROUND OF THE INVENTION 
     Lighting fixtures adapted for operation in outdoor environments are commonly used to illuminate optical fibers. These systems mounted above ground, employ exterior shields to protect the internal components from rain and water splashed from adjacent pools or ponds. The optical fibers may be positioned in decorative arrays around a pool or pond, and also illuminate the pool. Often, a color wheel is interposed between the light source and the inlet ends of the optical fibers to enhance the visual effects with colored light from the fibers. Cooling air is drawn into the housing, circulated around the inlet ends of the optical fibers and the light source, and then channeled from the fixture under a pressure differential established by a fan positioned along the cooling path of air flowing through the fixture. 
     Various attempts have been made to configure these lighting fixtures with a low profile above the ground, and to prevent the internal light source from leaking (spurious) light from the light box to the adjacent area. However, such above-ground fixtures are vulnerable to collision with people and moving equipment such as carts and bicycles, and to associated damage from such collisions. They are also vulnerable to intrusion by wildlife such as insects or rodents that may disturb sensitive components, or to dirt and dust that accumulates over time on the optics to reduce their light output. 
     Another approach is to channel the spurious light into a translucent globe and so make the light box visible. See, for example, U.S. Pat. No. 5,779,353, entitled “Weather-Protected Lighting Apparatus and Method.” This approach, however, draws attention to the light source and away from the dramatic and aesthetically pleasing fiberoptic pool-lighting display. 
     It would be desirable to provide a lighting fixture with fiber connections that could be buried beneath the surface of the ground. This would require the lighting fixture to be completely sealed. This, in turn, would require the lighting fixture to be efficient enough to deliver ample illumination at a sufficiently low power to avoid the need for external cooling air. 
     SUMMARY OF THE INVENTION 
     In a preferred form, the invention provides a light delivery system including a light source. A first generally tubular, hollow coupling device with an interior light-reflective surface receives light from the source at an inlet and transmits it to an outlet. The coupling device increases in cross sectional area from inlet to outlet in such manner as to reduce the angle of light reflected from the surface as it passes through the device. A thermal-isolating region has an inlet positioned in proximity to an outlet of the coupling device and has an outlet for passing light to an optical member, the thermal-isolating region comprising one or more members. A waterproof container for the light source and coupling device has an aperture allowing light to pass out of the container. The aperture is sealed in part by a portion of a member of the thermal-isolating region. 
     Advantageously, the foregoing system can be buried beneath the ground. This avoids the problems of people or equipment colliding with the system. The components in the sealed container are protected from intrusion by wildlife or deterioration from dirt and dust. In some embodiments, the container may be free of a fan, reducing the complexity and noise of the system. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of several elements of a light delivery system in accordance with the invention. 
     FIG. 2 is a side plan view, partially in section and partially cut away, showing arrangements for sealing a thermal-isolating member to a waterproof container and for sealing a termination of a light guide. 
     FIG. 3 is a side plan view, partially in cross section and partially cut away, of the structure shown in FIG.  2 . 
     FIGS. 4A and 4B are side plan views, in simplified form, an arrangement for sealing a thermal-isolating region to a waterproof container when a light coupling device and an elliptical reflector are respectively used to deliver light to such region. 
     FIGS. 4C and 4D are side plan views, in simplified form, an arrangement for sealing another thermal-isolating region to a waterproof container when a light coupling device and an elliptical reflector are respectively used to deliver light to such region. 
     FIG. 5 is an exploded view of a framework for holding the light coupling devices and lamp of FIG.  1 . 
     FIGS. 6A and 6B are front and side view respectively of a wave washer used in the framework of FIG.  5 . 
     FIG. 7 is an assembled view, in perspective, of the framework of FIG.  5 . 
     FIG. 8 is a side plan view of a lamp used in the framework of FIG.  5 . 
     FIG. 9 is a simplified, perspective view of a light-coupling device in accordance with the invention. 
     FIG. 10 is a view of a light delivery system using principles of the coupling device of FIG. 9, partially shown in block diagram form. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is an exploded view of several elements of a light delivery system in accordance with the invention. A light source or lamp  12 , shown partially cut away, has upper and lower legs  12   a  and  12   b,  and a central, bulbous portion  12   c.  When lamp  12  comprises a metal halide gas discharge lamp, for instance, the bulbous portion  12   c  contains electrodes  14   a  and  14   b.  These electrodes are connected to in-leads  16   a  and  16   b  respectively, which, in turn, are connected to foil in-leads  18   a  and  18   b,  respectively. Lamp  12  may alternatively comprise a formed halogen or other filament-type lamp (not shown), for instance, or an electrodeless lamp (not shown). 
     In a preferred arrangement, light from lamp  12  is captured by optical devices  20  and  22 , and directed through thermal-isolating members  24  and  26 , respectively, to respective light guides (not shown) for distribution to remote locations. Members  24  and  26  (and other “thermal-isolating members” described herein) are necessary to thermally isolate temperature-sensitive light guides (not shown) from the heat of lamp to prevent premature deterioration of the light guides. Plastic light guides are typically thermally sensitive, as well as glass light guides including thermally sensitive glue or other components. Each of devices  20  and  22  has an inlet facing the lamp, and an outlet facing a respective one of thermal-isolating members  24  and  26 . The interior surface of each device is reflective to light from the lamp. Each coupling device increases in cross sectional area from inlet to outlet in such manner as to reduce the angles of light reflected from the inner surface as it passes through the device. It is preferred that substantially all cross-sectional segments along the interior of each coupling device taken through a central axis of light propagation  28  be substantially parabolic, or substantially conform to a CPC shape. CPC is a specific form of an angle-to-area converter, as described in detail in, for instance, W. T. Welford and R. Winston, High Collection Nonimaging Optics, New York: Academic Press, Inc. (1989), chapter 4 (pp. 53-76). 
     The inlet of coupling device  20  has recesses  30   a  and  30   b,  and similarly the inlet of coupling device  20  has recesses  32   a  and  32   b.  These recesses receive respective portions of upper and lower legs  12   a  and  12   b  of the lamp, and enable the coupling devices to hold the lamp. In the case of an electrodeless lamp (not shown), the recesses could receive a gas probe of a starting aid projecting from one side of a bulbous portion of the lamp and another projection from another side of the bulbous portion. 
     The outlet of coupling device  20  has recesses  34   a,    34   b,    34   c  and  34   d,  and similarly the outlet of coupling device  22  has recesses  36   a,    36   b,    36   c  and  36   d.  These recesses may be used to align the coupling devices with a framework (not shown), as will be described below. 
     Each of thermal-isolating members  24  and  26  may comprise a single device, or it may comprise multiple devices such as a pair of semi-cylindrical devices (not shown) or four quarter-cylindrical devices (not shown). Each of members  24  and  26  or any of its included devices could be hollow if desired. Quartz may be used for member  24  or  26 , although other refractory materials that can withstand the heat from lamp  12  without degrading the lamp or light guide can be used, such as high temperature borosilicate glass. Alternatively, each of members  24  and  26  may comprise an extension (not shown) of its associated coupling device with a cross section in the direction of light propagation that may be substantially constant, as opposed to the changing cross sections of members  24  and  26  as shown. 
     FIG. 2 shows a waterproof container  40  having an aperture  42  through which a portion of thermal-isolating member  24  extends. Aperture  42 , which allows light to pass outside of the container, is sealed in part by thermal-isolating member  24 . It is further is sealed by a sealing arrangement including a first hub member  44  and a second hub member  46 . Hub member  44  may be sealed to the left-shown side of container  40  by a ring-like seal  48 . Second hub member  46  is coupled to the first hub member, preferably by threads as shown, and together press a ring-like seal  50  against the circumference of thermal-isolating member  24 . To minimize surface contact between seal  50  and member  24 , the thickness of the seal is preferably small, such as 1 mm where member  24  has a diameter of 19 mm. This minimizes light leakage from member  24 . To further reduce light leakage, the exterior of seal  50  preferably comprises material with a substantially lower index of refraction (e.g., 1.3) than that of region  24  (e.g., 1.5). Such low index material may comprise a fluoroelastomer from the family of copolymers and terpolymers made with tetra-fluro-ethylene and hexa-fluro propylene. One such material is sold by DuPont Corp. of Wilmington, Delaware, under the trademark TEFLON. 
     For compactness, a third hub member  52  (FIG. 2) may be coupled to second hub member  50  for scaling a termination  54  of a light guide  56  against water, etc. Where light guide  56  is stranded, as shown, its termination  54  may take the form of a nipple as shown. In contrast, a solid-core light guide (not shown) does not typically require additional structure such as a nipple at its termination; it may properly terminate simply by being cut to a desired length. Hub members  50  and  52  cooperate to press a ring-like seal  57  against the outer circumference of termination  54 . 
     FIG. 3 shows a side view of first hub member  44  mounted on container  40 , with third hub member  52  coupled to second hub member  46 . Termination  54  surrounds fibers  56 , which are shown in cross section. To secure the first hub member to the container, bolts  58   a  and  58   b  (shown in phantom) may pass through holes  59   a  and  59   b  in the first hub member and corresponding holes (not shown) in container  40 . 
     First hub member  44  may include partial holes  60  so that a bolt  61  (shown in phantom) may pass between outward projections  46   a  and  46   b  of hub member  46  and into one of such a holes for locking the position of such hub member. 
     The features of FIGS. 2 and 3 regarding thermal-isolating member  24  and light guide  56 , for instance, are preferably duplicated for thermal-isolating member  26  (FIG. 1) and a further light guide (not shown). 
     FIG. 4A shows in simplified form various parts of a light delivery system, to illustrate different sealing arrangements. Thermal-isolating member  26  passes through aperture  42  of container wall  40  and through a hub arrangement  62  representing a simplified view of the hub arrangement of FIG. 2 that comprises first and second hub members  44  and  46 . Ring-like seals  48  and  50  may be the same as those shown in FIG.  2 . Lamp  12  provides light that is directed through coupling device  22  and an air gap  63  to reach thermal-isolating member  26 , where it is then passed to a light guide  64 , shown in simplified form. Collectively, air gap  63  and thermal-isolating member  26  form a thermal-isolating region  65 , which isolate the typically thermally sensitive light guide  64  from the heat of lamp  12 . 
     In the embodiment of FIG. 4A, the ratio of the average diameter of the main light-transmitting portion of aperture  42  (e.g.,  66 ) to the average (i.e., left-to-right shown) length of the main light-transmitting portion of member  26  is less than one. 
     FIG. 4B is substantially similar to FIG. 4A except for the use of a lamp  67  whose rays  68  are directed by a generally semi-spherical, elliptical reflector  69  to the left-shown side of member  26 . Lamp  67  may be substantially similar to lamp  12  of the various figures herein. In FIG. 4B, the thermal-isolating region includes an air gap  71  between reflector  69  and member  26 , in addition to member  26  itself. The foregoing ratio mentioned in connection with FIG. 4A also applies to FIG.  4 A. 
     FIG. 4C shows a further variation on a light delivery system in which a thermal-isolating region  200  includes a member in the form of a plate  202  sealed to container wall  40  by a ring-like seal  204 . The mechanical details of placing seal  204  under pressure, which will be routine to those of ordinary skill in the art, have been omitted. Thermal-isolating region  200  additionally includes a cylindrical extension  206  of a coupling device  208 , which otherwise may be similar to coupling device  22  of FIG. 1, and also includes an air gap  210 . 
     In the embodiment of FIG. 4C, the ratio of the average diameter of the main light-transmitting portion of aperture  42  (e.g.,  212 ) to the average length of a main light-transmitting portion of thermal-isolating member  202  (e.g.,  214 ) most proximate the aperture is greater than one. 
     FIG. 4D is substantially similar to FIG. 4C except for showing a lamp  67  and reflector  69  (as in FIG. 4B) focusing rays  68  from lamp  67  onto the right-shown surface of light guide  64 . Lamp  67  may be substantially similar to lamp  12  of the various figures herein. Additionally, a thermal-isolating region  215  includes an air gap  216  between reflector  69  and thermal-isolating member  202 , and an air gap  218  between member  202  and light guide  64 . The foregoing ratio mentioned in connection with FIG. 4C also applies to FIG.  4 D. 
     Preferably, the inside of container  40  is free of a fan. This can result from one or more of: (1) isolating the temperature-sensitive, typically plastic light guide (e.g.,  56 , FIG. 2) from the heat of the lamp by use of a thermal-isolating region including a thermal-isolating member (e.g.,  24  or  26 , FIG.  1 ); (2) using light coupling devices as described above, which are highly efficient; (3) using an electronic ballast (not shown) mounted in a separate chamber (not shown) from the lamp and coupling devices; (4) forming container  40  of a thermally conductive material, such as aluminum, so that its large surface area radiates a substantial portion of the heat produced by the lamp; and (5) designing components within the container to operate in a high ambient temperature without lowering their expected life; for example, for the lamp, increasing the length of its foil in-leads so that heat from its environment and from its arc source does not cause such leads to destructively oxidize. 
     FIG. 5 shows an exploded view of a framework including frame members  70  and  72  of zinc, for instance, for holding coupling devices  20  and  22  (FIG. 1) and lamp  12 . One or more wave washers  76  and  78 , or other resilient means, are used to achieve an arrangement for holding the coupling devices in a manner allowing considerable manufacturing tolerances in their length, for instance. 
     A supporting wall  80  of frame member  72  supports the right-hand shown side of wave washer  78 , which may have the shape of a cross-section of a clamshell, i.e., a shape formed by joining two arcs each of less than 180 degrees. A lateral support wall  82  maintains proper rotational alignment of the wave washer by, for instance, also having the shape of a cross-section of a clamshell, as shown. Washer  78  has inward projections  84  for being received by recesses  36   a - 36   d  of coupling device  22 . This limits axial movement of the device along a main axis of light propagation, while also maintaining proper rotational alignment of the coupling device. FIGS. 6A and 6B respectively show a front view and a side view of washer  78  to better illustrate projections  84  and preferred bends in the washer that flatten to accommodate manufacturing tolerances in the axial length of coupling device  22 , for instance. Similarly, frame member  70  has a supporting wall  86  (shown in dashed lines) and a lateral support wall  88  corresponding to the like-named walls of frame member  72  for interacting in a similar manner with wave washer  76  and coupling device  20 . 
     Axial movement of coupling device  22  can also be achieved other than by using recesses  36   a - 36   b.  For instance, the outer perimeter of the outlet of such device can be configured with radially outward facing bumps (not shown) that cooperate with inward projections (not shown) of wave washer  78  that may be generally similar to projections  84 . If desired to maintain proper rotational alignment of the coupling device, one or more inward projections can be each configured to partially wrap around both sides of an associated bump along a main axis of light propagation. 
     If desired, one of the wave washers may be omitted. Alternatively, a wave washer may be replaced by other resilient means, such as a plurality of small coil springs (not shown) for pressing against a plurality of points of the outlet of an adjacent coupling device. 
     Arms  92  of frame member  72  preferably join respective arms  94  of frame member  70  in a non-telescoping manner as results, for instance, from the configuration of the ends of such arms as shown. This assures that the resilient force placed on coupling devices  20  and  22  is governed by the wave washers (or alternative resilient means) rather than by any additional resilient force (not shown) pressing together the frame members. Such additional resilient force may be provided by upper and lower coil springs  96  and  98 , respectively, as shown in the assembled view of frames  70  and  72  in FIG.  7 . 
     As shown in FIG. 5, both foil in-leads  18   a  and  18   b  of the lamp incorporate bends, as well as in-lead portions  90   a  and  90   b.  FIG. 8 shows these bends in more detail. Thus, bends  110   a  and  100   b  in in-leads  18   a  and  18   b  result in a compact profile for the lamp. In-lead portion  90   a  incorporates “knee”-type (or generally orthogonal) bends  102  and  104 , while in-lead portion  90   b  incorporates knee-type bends  106 ,  108 ,  108  and  112 . The foregoing bends allow in-leads  90   a  and  90   b  to flex relative to the vitreous-covered in-lead portions  18   a  and  18   b  (e.g., by 4 mm) so that the coupling of these leads to respective female conductors (not shown) will not dislodge the lamp from a desired position supported, for instance, by coupling members  20  and  22  (e.g., FIG.  7 ). 
     Alignment structure  114   a  and  114   b  (FIG. 7) may be provided for aligning in-leads  90   a  and  90   b.    
     Example of Forming Coupling Device 
     Coupling devices having a circular cross-section along a main axis of light propagation provide good results. However, because the thermal isolating device (e.g., a quartz rod) receives only a portion of the output, a design that has a smaller output area while giving the same or better angular transformation would be more efficient. 
     In order to decrease the output area without harming the angular transformation, the input area must be decreased. This is not possible with a circular cross-sectioned device, but is possible with a modified coupling device (or angle-to area converter) with a clamshell shaped (or oblong) cross section that more closely matches the shape of the arc chamber. FIG. 9 shows such a design for a coupling device  120 , simplified to omit recesses at either end. 
     One way to make an oblong cross section is to brine together two arc-shaped segments of less than 180 degrees. If two 142° segments of a 14 mm diameter circle are brought together the resulting shape is 13.25 mm tall by 9.5 mm wide, large enough to accept a 68-watt metal halide DC arc lamp. 
     The shape of an oblong coupling device (or angle-to-area converter) was constructed by first designing a device with a 14 mm input and a 38 degree output. This shape was then sectioned and replicated such that its input was the union of two 142° arc segments  122  and  124  of a 14 mm input circle (not shown). 
     In order to make sure that the angular conversion of the device was at most 38 degrees, the angle of the segment  122  or  124  of each section was increased as the diameter increased. This translates to greater area and therefore conversion to even lower angles. 
     The output of the oblong angle-to-area converter is the union of two  156 ° segments  126  and  128  of a 22.8 mm diameter circle (not shown). Coupling device  120  works in much the same manner as a device defining a compound parabolic concentrator (CPC). The shape of each of the two sections follows the equations for a CPC as described by the above-cited Winston and Welford reference except for the location of the optical axis. The majority of the light (e.g., more than 75%) reflects from a wall only once. For these single-reflection rays, the oblong device acts exactly as it would in the case of a true CPC that the section emulates. The oblong device gives increased efficiency over the true CPC because: 
     1. The ratio of output area to input area is greater in the oblong converter described here, resulting in light converted to lower angles; 
     2. The output area of the CPC is 15% larger than the oblong converters. Since our thermal isolator collects only a set area of the output, and this area is a greater percentage of the smaller oblong converter, the isolator therefore collects more light. 
     Oblong device  120  formed according to the foregoing principles has an output  126 ,  128  with a ratio of minor axis  130  to major axis  132  that substantially exceeds the ratio of minor axis  134  to  136  of its input  122 ,  124 . Preferably, the increase in such ratios from input to output causes substantially all light to be received by a first light guide (not shown) having a first acceptance angle (e.g., 38 degrees) while ensuring that a second, alternative light guide (not shown) having a substantially lower acceptance angle (e.g., 30 degrees) receives a substantial (i.e., useful) amount of light. More preferably, the increase in such ratios is sufficient to maximize the amount of light received by the second light guide. In this way, a single coupling device can efficiently accommodate either the first or second light guides, which may typically be a solid-core light guide and a stranded-core light guide, respectively. 
     FIG. 10 shows a light delivery system including a light source  300 , light-coupling devices  302  and  304 , thermal-isolating regions  306  and  308 , and light guides  310  and  312 . These parts are like the like-named parts above. The system provides a useful light level to both light guides  310  and  312  when they are of the stranded-core and solid-core types, respectively, and when devices  302  and  304  are substantially identical to each other and made according to the principles of FIG.  9 . Alternatively, the system provides a useful light level to light guide  310 , for instance, whether embodied as a stranded-core or a solid-core fiber, when light-coupling device is made according to the principles of FIG.  9 . 
     When made of ceramic, casting can form a coupling device. When made of quartz or other vitreous material, a coupling device can be formed by blow molding in a similar way as a quartz arc tube with a bulbous region (not shown) along a main axis of the arc tube. The bulbous region typically has a maximum diameter at its midpoint along the axis, and tapers in diameter towards both of its axial ends. A respective coupling device can be cut from each tapered section, with its interior made reflective. 
     For either circular or non-circular cross-sectioned devices, an outwardly extending ridge (not shown) preferably extends around the bulbous region at the midpoint to facilitate alignment of a cutting instrument and to reduce the chance of fracturing the bulbous region during cutting. The ridge can be formed by applying a narrow zone of heat to the region in a special gathering step. 
     In making coupling devices, reference can generally be made to prior art techniques for making arc tubes for forming a structure similar to an arc tube with a bulbous region. Additionally, manufacturing tolerances should be kept especially low to substantially achieve an optically desired shape. Maintaining an accurate mold shape, accurately centering a tube of quartz, etc., and accurately positioning the mold on the tube can accomplish this, for instance. These measures will be routine to those of ordinary skill in the art from the present specification. 
     A special consideration arises when making devices with non-circular (e.g., oblong) cross sections along the central axis of light propagation. Since a mold directly shapes only the exterior of the device whereas only the interior surface is used for reflection, the bulbous region is varied in thickness to result in a desired interior surface topology. 
     When forming coupling devices from the foregoing molding process, the thickness of the device wall will typically be greater at its inlet than at its outlet. 
     The foregoing describes a process of producing an arc tube-like structure. Cutting the structure at axial points can then produce axial sections of such structure. This is preferably accomplished with a cutting device, such as a diamond wheel, preferably wet, or a laser. Alternatively, by way of example, the technique of score-snapping can be used by circumferentially scoring, or scratching, the structure at an axial point, and then bending the ends of the structure about such point. 
     Cuts may and then be made in the resulting axial sections to form the various recesses described above, e.g., recesses  32   a,    32   b  and  36   a - 36   b  of coupling device  22  shown in FIG.  1 . The cutting may be made by a diamond wheel (not shown), preferably wet, used in the manner of a radial arm saw; that is, with the wheel in the plane of the central longitudinal access (not shown) of the structure. Such diamond wheel is preferably shaped to conform to the desired shape of a recess. Thus, for a round recess, the tip of the wheel is preferably rounded in cross section taken transverse to its axis. 
     While the invention has been described with respect to specific embodiments by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true scope and spirit of the invention.