Patent Publication Number: US-8529102-B2

Title: Reflector system for lighting device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to reflector systems for lighting applications and, more particularly, to reflector systems for multi-element light sources. 
     2. Description of the Related Art 
     Light emitting diodes (LED or LEDs) are solid state devices that convert electric energy to light, and generally comprise one or more active regions of semiconductor material interposed between oppositely doped semiconductor layers. When a bias is applied across the doped layers, holes and electrons are injected into the active region where they recombine to generate light. Light is emitted from the active region and from surfaces of the LED. 
     In order to generate a desired output color, it is sometimes necessary to mix colors of light which are more easily produced using common semiconductor systems. Of particular interest is the generation of white light for use in everyday lighting applications. Conventional LEDs cannot generate white light from their active layers; it must be produced from a combination of other colors. For example, blue emitting LEDs have been used to generate white light by surrounding the blue LED with a yellow phosphor, polymer or dye, with a typical phosphor being cerium-doped yttrium aluminum garnet (Ce:YAG). The surrounding phosphor material “downconverts” some of the LED&#39;s blue light, changing its color to yellow. Some of the blue light passes through the phosphor without being changed while a substantial portion of the light is downconverted to yellow. The LED emits both blue and yellow light, which combine to provide a white light. 
     In another known approach light from a violet or ultraviolet emitting LED has been converted to white light by surrounding the LED with multicolor phosphors or dyes. Indeed, many other color combinations have been used to generate white light. 
     Because of the physical arrangement of the various source elements, multicolor sources often cast shadows with color separation and provide an output with poor color uniformity. For example, a source featuring blue and yellow sources may appear to have a blue tint when viewed head on and yellow tint when viewed from the side. Thus, one challenge associated with multicolor light sources is good spatial color mixing over the entire range of viewing angles. 
     One known approach to the problem of color mixing is to use a diffuser to scatter light from the various sources; however, a diffuser usually results in a wide beam angle. Diffusers may not be feasible where a narrow, more controllable directed beam is desired. 
     Another known method to improve color mixing is to reflect or bounce the light off of several surfaces before it is emitted. This has the effect of disassociating the emitted light from its initial emission angle. Uniformity typically improves with an increasing number of bounces, but each bounce has an associated loss. Many applications use intermediate diffusion mechanisms (e.g., formed diffusers and textured lenses) to mix the various colors of light. These devices are lossy and, thus, improve the color uniformity at the expense of the optical efficiency of the device. 
     Many modern lighting applications demand high power LEDs for increased brightness. High power LEDs can draw large currents, generating significant amounts of heat that must be managed. Many systems utilize heat sinks which must be in good thermal contact with the heat-generating light sources. Some applications rely on cooling techniques such as heat pipes which can be complicated and expensive. 
     SUMMARY OF THE INVENTION 
     One exemplary embodiment of a light emitting device according to the present invention comprises the following elements. A multi-element light source is mounted at the base of a secondary reflector. The secondary reflector is adapted to shape and direct an output light beam. A primary reflector is disposed proximate to the light source to redirect light from the source toward the secondary reflector. The primary reflector is shaped to reflect light from the multi-element source such that the light is spatially mixed prior to incidence on the secondary reflector. 
     One exemplary embodiment of a lamp device according to the present invention comprises the following elements. A protective housing surrounds a multi-element light source. The housing has an open end through which light may be emitted. A secondary reflector is disposed inside the housing and around the light source such that the light source is positioned at the center of the base of the secondary reflector. A primary reflector is disposed to reflect light emitted from the source toward the secondary reflector such that the light is spatially mixed prior to incidence on the secondary reflector. A lens plate is disposed over the open end of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a lamp device along its diameter according to one embodiment of the present invention. 
         FIG. 2  is a perspective view of a lamp device according to one embodiment of the present invention. 
         FIG. 3  is a top plan view of a light source according to one embodiment of the present invention. 
         FIG. 4  is a top plan view of a light source according to one embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of a light source and the tip section of a primary reflector according to one embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of a primary reflector according to one embodiment of the present invention. 
         FIG. 7  is a cross-sectional view of a primary reflector according to one embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of a lamp device along its diameter according to one embodiment of the present invention. 
         FIG. 9   a  is a cross-sectional view of a lamp device along its diameter according to one embodiment of the present invention. 
         FIG. 9   b  is a perspective view with an exposed cross-section of a lamp device according to one embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of a lamp device along its diameter according to one embodiment of the present invention. 
         FIG. 11  is a cross-sectional view of a lamp device along its diameter according to one embodiment of the present invention. 
         FIG. 12   a  is a perspective view of a secondary reflector according to an embodiment of the present invention. 
         FIG. 12   b  is a perspective view of a secondary reflector according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention provide a reflector system for lighting applications, especially multi-source solid state systems. The system works particularly well with multicolor light emitting diode (LED) arrangements to provide a tightly focused beam of white light with good spatial color uniformity. The sources can be chosen to produce varying shades of white light (e.g., warmer whites or cooler whites) or colors of light other than white. Applications range from commercial and industrial lighting to military, law enforcement and other specialized uses. 
     The system uses two reflective surfaces to redirect the light before it is emitted. This is sometimes referred to as a “double-bounce” configuration. The light source/sources are disposed at the base of the secondary reflector. The first reflective surface is provided by the primary reflector which is arranged proximate to the source/sources. The primary reflector initially redirects, and in some cases diffuses, light from the sources such that the different wavelengths of light are mixed as they are redirected toward the secondary reflector. The secondary reflector functions primarily to shape the light into a desired output beam. Thus, the primary reflector is used color mix the light, and the secondary reflector is used to shape the output beam. The reflector arrangement allows the source to be placed at the base of the secondary reflector where it may be thermally coupled to a housing or another structure to provide an outlet for heat generated by the sources. 
     It is understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. Furthermore, relative terms such as “inner”, “outer”, “upper”, “above”, “lower”, “beneath”, and “below”, and similar terms, may be used herein to describe a relationship of one element to another. It is understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. 
     Although the ordinal terms first, second, etc., may be used herein to describe various elements, components, regions and/or sections, these elements, components, regions, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, or section from another. Thus, unless expressly stated otherwise, a first element, component, region, or section discussed below could be termed a second element, component, region, or section without departing from the teachings of the present invention. 
     As used herein, the term “source” can be used to indicate a single light emitter or more than one light emitter functioning as a single source. For example, the term may be used to describe a single blue LED, or it may be used to describe a red LED and a green LED in proximity emitting as a single source. Thus, the term “source” should not be construed as a limitation indicating either a single-element or a multi-element configuration unless clearly stated otherwise. 
     The term “color” as used herein with reference to light is meant to describe light having a characteristic average wavelength; it is not meant to limit the light to a single wavelength. Thus, light of a particular color (e.g., green, red, blue, yellow, etc.) includes a range of wavelengths that are grouped around a particular average wavelength. 
       FIG. 1  and  FIG. 2  illustrate a lamp device  100  comprising a reflector system according to one embodiment of the present invention. 
       FIG. 1  is a cross-sectional view of the lamp device  100  along its diameter. A light source  102  is disposed at the base of a bowl-shaped region within the lamp  100 . Many applications, for example white light applications, necessitate a multicolor source to generate a blend of light that appears as a certain color. Because light within one wavelength range will trace out a different path than light within another wavelength range as they interact with the materials of the lamp, it is necessary to mix the light sufficiently so that color patterns are not noticeable in the output, giving the appearance of a homogenous source. 
     A primary reflector  104  is disposed proximate to the light source  102 . The light emitted from the source  102  interacts with the primary reflector  104  such that the color is mixed as it is redirected toward a secondary reflector  106 . The secondary reflector  106  receives the mixed light and shapes it into a beam having characteristics that are desirable for a given application. A protective housing  108  surrounds the light source  102  and the reflectors  104 ,  106 . The source  102  is in good thermal contact with the housing  108  at the base of the secondary reflector  106  to provide a pathway for heat to escape into the ambient. A lens plate  110  covers the open end of the housing  108  and provides protection from outside elements. Protruding inward from the lens plate  110  is a mount post  112  that holds the primary reflector  104  in place, proximate to the light source  102 . 
     The light source  102  may comprise one or more emitters producing the same color of light or different colors of light. In one embodiment, a multicolor source is used to produce white light. Several colored light combinations will yield white light. For example, it is known in the art to combine light from a blue LED with wavelength-converted yellow light to create a white output. Both blue and yellow light can be generated with a blue emitter by surrounding the emitter with phosphors that are optically responsive to the blue light. When excited, the phosphors emit yellow light which then combines with the blue light to make white. In this scheme, because the blue light is emitted in a narrow spectral range it is called saturated light. The yellow light is emitted in a much broader spectral range and, thus, is called unsaturated light. Another example of generating white light with a multicolor source is combining the light from green and red LEDs. RGB schemes may be used to generate various colors of light. Sometimes an amber emitter is added for a RGBA combination. The previous combinations are exemplary; it is understood that many different color combinations may be used in embodiments of the previous invention. Several of these possible color combinations are discussed in detail in U.S. Pat. No. 7,213,940 to Van de Ven et al. which is commonly assigned with the present application to CREE LED LIGHTING SOLUTIONS, INC. and fully incorporated by reference herein. 
     Color combination can be achieved with a singular device having multiple chips or with multiple discreet devices arranged in proximity to each other. For example, the source  102  may comprise a multicolor monolithic structure (chip-on-board) bonded to a printed circuit board (PCB). In some embodiments, several LEDs are mounted to a submount to create a single compact optical source. Examples of such structures can be found in U.S. patent application Ser. Nos. 12/154,691 and 12/156,995, both of which are commonly assigned to CREE, INC., and both of which are fully incorporated by reference herein. In the embodiment shown in  FIG. 1 , the source  102  is protected by an encapsulant  114 . Encapsulants are known in the art and, therefore, only briefly discussed herein. The encapsulant  114  material may contain wavelength conversion materials, such as phosphors for example. 
     The encapsulant  114  may also contain light scattering particles to help with the color mixing process in the near field. Although light scattering particles dispersed within the encapsulant  114  may cause optical losses, it may be desirable in some applications to use them in concert with the reflectors  104 ,  106  so long as the optical efficiency is acceptable. 
     Color mixing in the near field may be aided by providing a scattering/diffuser material or structure in close proximity to the light sources. The diffuser is in, on, or remote from, but in close proximity to, the LED chips with the diffuser arranged so that the lighting/LED component can have a low profile while still mixing the light from the LED chips in the near field. By diffusing in the near field, the light may be pre-mixed to a degree prior to interacting with either reflector. 
     A diffuser can comprise many different materials arranged in many different ways. In some embodiments, a diffuser film can be provided on the encapsulant  114 . In other embodiments, the diffuser can be included within the encapsulant  114 . In still other embodiments, the diffuser can be remote from the encapsulant, but not so remote as to provide substantial mixing from the reflection of light external to the lens. Many different structures and materials can be used as a diffuser such as scattering particles, geometric scattering structures or microstructures, diffuser films comprising microstructures, or diffuser films comprising index photonic films. The diffuser can take many different shapes over the LED chips; it can be flat, hemispheric, conic, and variations of those shapes, for example. 
     The encapsulant  114  may also function as a lens to shape the beam prior to incidence on the primary reflector  104 . 
     Light emitted from the source is first incident on the primary reflector  104 . The primary reflector  104  is disposed proximate to the source  102  so that substantially all of the emitted light interacts with it. In one embodiment the mount post  112  supports the primary reflector  104  in position near the source  102 . A screw, an adhesive, or any other means of attachment may be used to secure the primary reflector  104  to the mount post  112 . Because the mounting post  112  is hidden behind the primary reflector  104  relative to the source  102 , the mounting post  112  blocks very little light as it exits through the lens plate  110 . 
     The primary reflector  104  may comprise a specular reflective material or a diffuse material. If a specular material is used, the primary reflector  104  may be faceted to prevent the source from imaging in the output. One acceptable material for a specular reflector is a polymeric material that has been vacuum metallized with a metal such as aluminum or silver. Another acceptable material would be optical grade aluminum that is shaped using a known process, such as stamping or spinning. The primary reflector  104  may be shaped from a material that is itself reflective, or it may be shaped and then covered or coated with a thin film of reflective material. If a specular material is used, the primary reflector  104  will preferably have a reflectivity of no less than 88% in the relevant wavelength ranges. 
     The primary reflector  104  may also comprise a highly reflective diffuse white material, such as a microcellular polyethylene terephthalate (MCPET). In such an embodiment, the primary reflector  104  functions as a reflector and a diffuser. 
     The primary reflector  104  can be shaped in many different ways to reflect the light from the source  102  toward the secondary reflector  106 . In the embodiment shown in  FIG. 1 , the primary reflector  104  has a generally conic shape that tapers down to the edges. The shape of the primary reflector  104  should be such that substantially all of the light emitted from the source  102  interacts with the primary reflector  104  prior to interacting with the secondary reflector  106 . 
     The primary reflector  104  mixes the light and redirects it toward the secondary reflector  106 . The secondary reflector  106  may be specular or diffuse. Many acceptable materials may be used to construct the secondary reflector  106 . For example, a polymeric material which has been flashed with a metal may used. The secondary reflector  106  can also be made from a metal, such as aluminum or silver. 
     The secondary reflector  106  principally functions as a beam shaping device. Thus, the desired beam shape will influence the shape of the secondary reflector  106 . The secondary reflector  106  is disposed such that it may be easily removed and replaced with other secondary reflectors to produce an output beam having particular characteristics. In the embodiment shown in  FIG. 1 , the secondary reflector  106  has a substantially parabolic cross section with a truncated end portion that allows for a flat surface on which to mount the source  102 . Light redirected from the primary reflector  104  is incident on the surface of the secondary reflector  106 . Because the light has already been at least partially color-mixed by the primary reflector  104 , the designer has added flexibility in designing the secondary reflector  106  to form a beam having the desired characteristics. Thus, the reflector configuration provides a tailored output beam without sacrificing spatial color uniformity. The lamp device  100  features a bowl-shaped secondary reflector  106 ; however, other structure shapes are possible, a few examples of which are discussed below with reference to  FIGS. 12   a  and  12   b.    
     The secondary reflector  106  may be held inside the housing  108  using known mounting techniques, such as screws, flanges, or adhesives. In the embodiment of  FIG. 1 , the secondary reflector  106  is held in place by the lens plate  110  which is affixed to the open end of the housing  108 . The lens plate  110  may be removed, allowing easy access to the secondary reflector  106  should it need to be removed for cleaning or replacement, for example. The lens plate  110  may be designed to further tailor the output beam. For example, a convex shape may be used to tighten the output beam angle. The lens plate  110  may have many different shapes to achieve a desired optical effect. 
     The protective housing  108  surrounds the reflectors  104 ,  106  and the source  102  to shield these internal components from the elements. The lens plate  110  and the housing  108  may form a watertight seal to keep moisture from entering into the internal areas of the device  100 . A portion of the housing  108  may comprise a material that is a good thermal conductor, such as aluminum or copper. The thermally conductive portion of the housing  108  can function as a heat sink by providing a path for heat from the source  102  through the housing  108  into the ambient. The source  102  is disposed at the base of the secondary reflector  106  such that the housing  108  can form good thermal contact with the source  102 . Thus, the source  102  may comprise high power LEDs that generate large amounts of heat. 
     Power is delivered to the source  102  through a protective conduit  116 . The lamp device  100  may be powered by a remote source connected with wires running through the conduit  116 , or it may be powered internally with a battery that is housed within the conduit  116 . The conduit  116  may be threaded as shown in  FIG. 1  for mounting to an external structure. In one embodiment, an Edison screw shell may be attached to the threaded end to enable the lamp  100  to be used in a standard Edison socket. Other embodiments can include custom connectors such as a GU24 style connector, for example, to bring AC power into the lamp  100 . The device may also be mounted to an external structure in other ways. The conduit  116  functions not only as a structural element, but may also provide electrical isolation for the high voltage circuitry that it houses which helps to prevent shock during installation, adjustment and replacement. The conduit  116  may comprise an insulative and flame retardant thermoplastic or ceramic, although other materials may be used. 
       FIG. 2  is a perspective view of the lamp device  100 . The underside of the primary reflector  102  is visible through the transparent/translucent lens plate  110 . The mounting post  112  extends up from the lens plate  110  and holds the primary reflector  104  proximate to the source  102  (obscured in  FIG. 2 ). The lens plate  110  may be held in place with a flange or a groove as shown. Other attachment means may also be used. The inner surface of secondary reflector  106  is shown. In this embodiment, the secondary reflector  106  comprises a faceted surface; although in other embodiments the surface may be smooth. The faceted surface helps to further break up the image of the different colors from the source  102 . 
       FIG. 3  is a top plan view of the source  102  according to one embodiment of the present invention. As discussed above, many different light source combinations may be used. In this particular embodiment, the source  102  comprises a singular device having four colored chips, namely a red emitter, two green emitters and a blue emitter. This arrangement is typical in RGB color schemes. All of the emitters  302 ,  304 ,  306  are disposed underneath an encapsulant  308 . In this embodiment the encapsulant  308  is hemispherical. The encapsulant  308  may be shaped differently to achieve a desired optical effect. Light scattering particles or wavelength conversion particles may be dispersed throughout the encapsulant. The source  102  and the encapsulant  308  are arranged on a surface  310 . The surface  310  may be a substrate, a PCB or another type of surface. The backside of the source  102  is in good thermal contact with the housing  108  (not shown in  FIG. 3 ). 
     The physical arrangement of the emitters  302 ,  304 ,  306  on the surface  310  will cause some non-uniform color distribution (i.e., imaging) in the output if the colors are not mixed prior to escaping the lamp device  100 . The double bounce from the primary reflector  102  to the secondary reflector  106  mixes the colors and prevents imaging of the LED arrangement in the output. The color of the output light is controlled by the emission levels of the individual emitters  302 ,  304 ,  306 . A controller circuit may be employed to select the emission color by regulating the current to each of the emitters  302 ,  304 ,  306 . 
       FIG. 4  is a top plan view of the source  102  according to an embodiment of the present invention. In the embodiment shown, two discrete emitters are used. A green emitter  402  and a red emitter  404  are disposed underneath an encapsulant  406  on a surface  408 . In combination green and red light can produce white light. In other embodiments, blue LEDs and red LEDs may be combined to output white light. A portion of the light from the blue LEDs is downconverted to yellow (“blue-shifted yellow) and combined with the red light to yield white. Uniform color in the output is important in white light applications where color imaging is noticeable to the human eye. The discreet emitters  402 ,  404  may be manufactured separately and then mounted on the surface  408 . The electrical connection is provided with traces to the bottom side of the emitters  402 ,  404 . 
       FIG. 5  is a cross-sectional view of the source  102  according to one embodiment of the present invention. An emitter  502  is arranged on a surface  504 . The emitter  502  comprises a singular blue LED. An encapsulant  506  surrounds the emitter  502 . In this embodiment, wavelength conversion particles  508  are dispersed throughout the encapsulant  506 . The wavelength conversion material may also be disposed in a conformal layer over the emitter  502 . In other embodiments, the phosphor can be disposed remotely relative to the emitter  502 . For example, the remote phosphor may be concentrated in a particular area of an encapsulant, or it may be included in a conformal layer that is not adjacent to the emitter  502 . The emitter  502  emits blue light, a portion of which is then yellow-shifted by the wavelength conversion particles  508 . This conversion process is known in the art. The unconverted blue light and the converted yellow light combine to produce a white light output. After the light leaves the encapsulant  508  it is incident on the primary reflector  104  (only the tip of the reflector  104  is shown in  FIG. 5 ). The remote phosphor configuration can be used with many different color combinations as discussed above. For example, one or more blue LEDs may be used to a combination of blue and blue-shifted yellow, or one or more blue LEDs may combined with red LEDs to emit blue, blue-shifted yellow, and red. These colors may combine to emit white light. 
       FIG. 6  is a cross-sectional view of a primary reflector  600  according to one embodiment of the present invention. This particular reflector  600  has a faceted surface  602 . The facets on the surface  602  break up the image of the multicolor source  102 . The facets shown in  FIG. 6  are relatively large so that they can easily be observed in the figure; however, the facets can be any size with miniature facets producing a more dramatic scattering effect. 
       FIG. 7  is a cross-sectional view of a primary reflector  700  according to one embodiment of the present invention. Unlike the primary reflector  600  shown in  FIG. 6 , the primary reflector  700  has a smooth surface  702 . The contour of the surface  702  is designed to redirect substantially all of the light emitted from the source  102  toward the secondary reflector (not shown in  FIG. 7 ) The primary reflector  700  has a generally conic shape with the tapered edge regions. Many different surface contours are possible. 
       FIG. 8  shows a cross-sectional view of a lamp device  800  along a diameter. The device  800  includes similar elements as the lamp device  100  of  FIG. 1 . This particular embodiment features a secondary reflector  802  that is defined by two different parabolic sections. A first parabolic section  804  is disposed closer to the base of the secondary reflector  802 . The second parabolic section  806  defines the outer portion of the secondary reflector  802  that is closer to the housing opening through which light is emitted. These parabolic sections  804 ,  806  are shaped to achieve an output beam with particular characteristics and may be defined by curves having various shapes. Although secondary reflector  802  is shown having two curved segments, it is understood that other embodiments may include more than two curved segments. 
       FIGS. 9   a  and  9   b  show two views of a lamp device  900 .  FIG. 9   a  shows a cross-sectional view of the lamp device  900  along a diameter.  FIG. 9   b  shows a perspective view of the lamp device  900  with the cross-section cutaway shown. The device  900  includes similar elements as the lamp device  100  of  FIG. 1 . This particular embodiment includes a tube element  902  that surrounds the light source  102  and extends from the base of the secondary reflector  106  to the primary reflector  904 . The light source  102  in this embodiment comprises multiple discreet LEDs  906  that are mounted to the base of the secondary reflector  106 . Each of these LEDs  906  has its own encapsulant. As discussed above, these LEDs may be different colors which are combined using the double-bounce structure to yield a desired output color. 
     The tube element  902  may be cylindrical as shown in  FIG. 9  or it may be another shape, for example, elliptical. The tube element comprises an aggressive diffuser. The diffusive material may be dispersed throughout the volume of the tube, or it may be coated on the inside or outside surface. As light is emitted from the LEDs  908 , the tube element  902  guides the light toward the primary reflector  904  while, at the same, time mixing the colors. The added optical guidance helps to prevent light from spilling out around the edges of the primary reflector  904 . The tube element  902  may also include a wavelength conversion material such as a phosphor. Phosphor particles may be dispersed throughout the volume of the tube element  902 , or they may be coated on the inside or outside surface. In this way the tube element  902  may function to convert the wavelength of a portion of the emitted light. The tube element may be made from many materials including, for example, silicone, glass, or a transparent polymeric material such as poly(methyl methacrylate) (PMMA) or polycarbonate. 
     In this embodiment, the primary reflector has a notch  908  around the perimeter of the substantially conic structure. The tube element  902  cooperates with the notch  908  such that the inside surface of the tube element  902  abuts the circumferential outer surface of the notch  908 . The tube element  902  may have an inner diameter such that it fits snugly over the notch  908 , aligning and stabilizing the adjoined elements. The notch  908  functions not only as an alignment mechanism, it also reduces the amount of light that bleeds out between tube element  908  and the primary reflector  904  by effectively shielding the joint from the emitted light. 
       FIG. 10  shows a cross-sectional view an embodiment of a lamp device  1000  along its diameter. In this particular embodiment the primary reflector  1002  has a cross-section defined by two linear segments. The first segment  1004  has a slope that is closer to normal with respect to an axis running longitudinally through the center of the device. The second segment  1006  has a more aggressive slope as shown. The tube element  1008  has an outer diameter that is just large enough to surround the encapsulant  114  and the first segment  1004  of the primary reflector  1002 . Although not shown in  FIG. 10 , it is understood that a notch feature similar to the one shown in lamp device  900  may be included in any of the various primary reflector designs. 
       FIG. 11  shows a cross-sectional view of an embodiment of a lamp device  1100 . Lamp device  1100  is similar to lamp device  1000  of  FIG. 10  and contains several common elements. In this particular embodiment, the tube element  1102  has a large diameter which almost spans the entire width of the primary reflector  1002 . Increasing the distance from the light source  102  and the tube element  1102  improves the color mixing and provides a more even distribution. Although the large diameter works well for these reasons, other diameters may be used to achieve a particular output profile. 
       FIGS. 12   a  and  12   b  show two perspective views of an embodiment of a secondary reflector  1200 . Unlike the smooth bowl-shape of the secondary reflector  106  shown in  FIG. 1 , the secondary reflector  1200  features a segmented structure with a plurality of adjoined panels  1202 . The panels  1202  may be smooth or faceted. They may formed of a material that is itself reflective or coated or covered with a reflective material. 
     Although the present invention has been described in detail with reference to certain preferred configurations thereof, other versions are possible. For example, embodiments of the lamp device may include various combinations of primary and secondary reflectors discussed herein. Therefore, the spirit and scope of the invention should not be limited to the versions described above.