Patent Publication Number: US-9416952-B2

Title: Lighting apparatus with a light source comprising light emitting diodes

Description:
This application is a continuation of commonly-owned application Ser. No. 13/189,052, filed on 22 Jul. 2011 (now allowed), which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The subject matter of the present disclosure relates to lighting and lighting devices and, more particularly, to embodiments of a lighting apparatus using light-emitting diodes (LEDs), wherein the embodiments exhibit an optical intensity distribution consistent with common incandescent lamps. 
     Incandescent lamps (e.g., integral incandescent lamps and halogen lamps) mate with a lamp socket via a threaded base connector (sometimes referred to as an “Edison base” in the context of an incandescent light bulb), a bayonet-type base connector (i.e., bayonet base in the case of an incandescent light bulb), or other standard base connector. These lamps are often in the form of a unitary package, which includes components to operate from standard electrical power (e.g., 110 V and/or 220 V AC and/or 12 VDC). In the case of incandescent and halogen lamps, these components are minimal, as the lamp comprises an incandescent filament that operates at high temperature and efficiently radiates excess heat into the ambient. Many incandescent lamps are omni-directional light sources. These types of lamps provide light of substantially uniform optical intensity distribution (or, “optical intensity”). Such lamps find diverse applications such as in desk lamps, table lamps, decorative lamps, chandeliers, ceiling fixtures, and other applications where a uniform distribution of light in all directions is desired. 
     Solid-state lighting technologies such as LEDs and LED-based devices often have performance that is superior to incandescent lamps. This performance can be quantified by its useful lifetime (e.g., its lumen maintenance and its reliability over time). For example, whereas the lifetime of incandescent lamps is typically in the range about 1000 to 5000 hours, lighting devices that use LED-based devices are capable of operation in excess of 25,000 hours, and perhaps as much as 100,000 hours or more. 
     Unfortunately, LED-based devices are highly directional by nature. Common LED devices are flat and emit light from only one side. Thus, although superior in performance, the optical intensity of many commercially-available LED lamps intended as incandescent replacements is not consistent with the optical intensity of incandescent lamps. 
     Yet another challenge with solid-state technology is the need to adequately dissipate heat. LED-based devices are highly temperature-sensitive in both performance and reliability as compared with incandescent or halogen filaments. These features are often addressed by placing a heat sink in contact with or in thermal contact with the LED device. However, the heat sink may block light that the LED device emits and hence further limits the ability to generate light of uniform optical intensity. Physical constraints such as regulatory limits that define maximum dimensions for all lamp components, including light sources, further limit that ability to properly dissipate heat. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure describes embodiments of a lighting apparatus with an optical intensity consistent with an incandescent lamp and with adequate heat dissipation to avoid problems with excess heat. Other features and advantages of the disclosure will become apparent by reference to the following description taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made briefly to the accompanying drawings, in which: 
         FIG. 1  depicts a schematic diagram of a side view of one exemplary embodiment of a lighting apparatus; 
         FIG. 2  depicts a perspective view of another exemplary embodiment of a lighting apparatus; 
         FIG. 3  depicts a side view of the lighting apparatus of  FIG. 2 ; 
         FIG. 4  depicts a side view of the lighting apparatus of  FIG. 2  compared to an example of an industry standard lamp profile; 
         FIG. 5  depicts a cross-section, side view of the lighting apparatus taken along line A-A of  FIG. 2 ; 
         FIG. 6  depicts a side view of the lighting apparatus of  FIG. 2 ; 
         FIG. 7  depicts a top view of the lighting apparatus of  FIG. 2 ; 
         FIG. 8  depicts a plot of an optical intensity distribution profile for an embodiment of a lighting apparatus such as the lighting apparatus of  FIGS. 1, 2, 3, 4, 5, 6, and 7 ; and 
         FIG. 9  depicts a plot of LED board temperature profiles for two embodiments of a lighting apparatus such as the lighting apparatus of  FIGS. 1, 2, 3, 4, 5, 6, and 7 . 
     
    
    
     Where applicable like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. 
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
       FIG. 1  illustrates an exemplary embodiment of a lighting apparatus  100 . The lighting apparatus  100  comprises a base  102 , a center axis  104 , a north pole  106 , and a south pole  108 . The north pole  106  and the south pole  108  form a coordinate system that is useful to describe the spatial distribution of illumination that the lighting apparatus generates. The coordinate system is typically of the spherical coordinate system type, which in the present example comprises an elevation or latitude coordinate θ and an azimuth or longitude coordinate φ. For purposes of the discussion below, the latitude coordinate θ=0° at the north pole  106  and the latitude coordinate φ=180° at the south pole  108 . 
     The lighting apparatus  100  also comprises a light diffusing assembly  110 , a heat dissipating assembly  112 , and a light source  114  which generates light. The light diffusing assembly  110  has an envelope  116 , which in one example comprises light-transmissive material. The envelope  116  has an outer surface  118 , an inner surface  120 , and an interior volume  122 . Inside of the interior volume  122 , the light diffusing assembly  110  comprises a reflector element  124  with an outer reflective portion  126  and an inner transmissive portion  128 . 
     At a relatively high level, embodiments of the lighting apparatus  100  generate light with a relative optical intensity distribution (or “optical intensity”) at a level of about 100±20% over values of the latitude coordinate θ of about 0° to about 135° or greater. In one embodiment, the lighting apparatus  100  maintains a relative optical intensity at a level of about 100±20% at values of the latitude coordinate θ of about 0° to about 150° or greater. In another embodiment, the lighting apparatus  100  maintains a relative optical intensity at a level of about 100±10% at values of the latitude coordinate θ of about 0 to about 150° or greater. These characteristics comply with target values for optical intensity that the Department of Energy defines for solid-state lighting products as well as other industry standards and ratings (e.g., Energy Star). For example, levels of optical intensity that the lighting apparatus  100  provides are suitable to replace common, incandescent light bulbs. Moreover, physical characteristics of the lighting apparatus  100  are consistent with the physical lamp profile of such incandescent light bulbs, where the outer dimension defines boundaries in which the lighting apparatus  100  must fit. Examples of this outer dimension meets one or more regulatory limits (e.g., ANSI, NEMA, etc.). 
     The envelope  116  can be substantially hollow and have a curvilinear geometry, e.g., spherical, spheroidal, ellipsoidal, toroidal, ovoidal, etc, that diffuses light. In some embodiments, the envelope  116  comprises a glass element, although this disclosure contemplates a variety of light-transmissive material such as diffusive plastics (e.g., diffusing polycarbonate) and/or diffusing polymers that diffuse light. Materials of the envelope  116  may be inherently light-diffusive (e.g., opal glass) or can be made light-diffusive in various ways such as by frosting and/or other texturing of the inside surface (e.g., the inner surface  120 ) and/or the outer surface (e.g., the outer surface  118 ) to promote light diffusion. In one example, the envelope  116  comprises a coating (not shown) such as enamel paint and/or other light-diffusive coating (available, for example, from General Electric Company, New York, USA). Suitable types of coatings are found on glass bulbs of some incandescent or fluorescent light bulbs. In still other examples, manufacturing techniques may embed light-scattering particles or fibers or other light scattering media in the material of the envelope  116 . 
     The reflector element  124  fits within the envelope  116  in a position to intercept light from the light source  114 . Fasteners such as adhesive can secure the peripheral edge of the reflector element  124  to the inner surface  120 . In some embodiments, the inner surface  120  and the reflector element  124  can comprise one or more complimentary features (e.g., a boss and/or a ledge), the combination of which secure the reflector element  124  in position. These features may form a snap-fit or have another mating configuration that prevents the reflector element  124  from moving. 
     The inner transmissive portion  128  is proximate the center axis  104 . Materials for the inner transmissive portion  128  may be a light diffuser comprising glass, plastic, ceramic, or surface diffusers and like materials that promote the scattering and transmission of light therethrough. Materials for the inner transmissive portion  128  may also be a light transmitter having minimal or no scattering, comprising glass, plastic, ceramic, or other optically transparent material. The inner transmissive portion  128  may also be an open aperture allowing light to transmit through without modification. The inner transmissive portion  128  may also be omitted. 
     In the present example, the outer reflective portion  126  bounds the inner transmissive portion  128  and has optical properties that reflect or transmit or scatter light or combination of reflection, transmission, and scattering of light. These optical properties may result from materials used to construct the reflector element  124  including the inner transmissive portion  128 . In some examples, the outer reflective potion  126  comprises an optically opaque and highly reflective material such as a solid polymer, ceramic, glass, or metal, or a reflective coating, or laminate on a substrate, etc. The reflected light may be specularly reflected, or diffusely reflected, or a combination of specularly and diffusely reflected. In one example, both sides of the reflector element  124  comprise a coating/laminate to form the outer reflective portion  126 . In some other examples, the outer reflective portion  126  comprises an optically reflective and transmissive material such as a solid polymer, ceramic, glass, or a reflective coating or laminate on a substrate, etc., that can reflect a portion of light and transmit a portion of light. The transmitted portion of light may be scattered or partially scattered or not scattered. The reflected portion of light may be specularly reflected, or diffusely reflected, or a combination of specularly and diffusely reflected. In still other examples, in lieu of distinctly arranged transmissive and reflective portions (e.g., the outer reflective portion  126  and the inner transmissive portion  128 ), the reflector element  124  can have a pattern of one or more reflective elements and/or transmissive elements that cause the reflector element  124  to both transmit and reflect light. 
     Turning next to  FIGS. 2, 3, 4, 5, 6, and 7  another exemplary embodiment of a lighting apparatus  200  is shown.  FIG. 2  depicts a perspective view of the lighting apparatus  200  and  FIGS. 3, 4 and 6  illustrate a side view of the lighting apparatus  200 .  FIG. 5  illustrates a cross-section of the lighting apparatus  200  taken along line A-A ( FIG. 2 ).  FIG. 7  illustrates a top view of the lighting apparatus  200 . Like numerals are used to identify like components as between  FIG. 1  and  FIGS. 2, 3, 4, 5, 6 and 7 , except that the numerals are increased by 100 (e.g., 100 in  FIG. 1  is now 200 in  FIGS. 2,3, 4, 5, 6, and 7 ). For example, embodiments of the lighting apparatus  200  comprise a center axis  204 , a light diffusing assembly  210 , a heat dissipating assembly  212 , and a light source  214 . The light diffusing assembly  210  comprises an envelope  216  with an outer surface  218  and an inner surface  220 . 
     In  FIG. 2 , the light source  214  comprises a solid-state device  230  with one or more light-emitting elements  232 , e.g., light-emitting diodes (LEDs). The reflector element  224  comprises a cone element  234  and an aperture element  238 . The heat dissipating assembly  212  comprises a base element  240 , in thermal contact with the light source  214 , and one or more heat dissipating elements  242  coupled to the base element  240 . The heat dissipating elements  242  promote conduction, convection, and radiation of heat away from the light source  214 . For example, the heat dissipating elements  242  have an element body  244  with a tip end  246  and a base end  248  that can conduct thermal energy from the base element  240 . 
     The solid-state device  230  can comprise a planar LED-based light source that emits light into a hemisphere having a nearly Lambertian intensity distribution, compatible with the light diffusing assembly  210  for producing omni-directional illumination distribution. In one embodiment, the planar LED-based Lambertian light source includes a plurality of LED devices (e.g., LEDs  232 ) mounted on a circuit board (not shown), which is optionally a metal core printed circuit board (MCPCB). The LED devices may comprise different types of LEDs. For example, the solid-state device  230  may comprise one or more first LED devices and one or more second LED devices having respective spectra and intensities that mix to render white light of a desired color temperature and color rendering index (CRI). In one embodiment, the first LED devices output white light, which in one example has a greenish rendition (achievable, for example, by using a blue- or violet-emitting LED chip that is coated with a suitable “white” phosphor). The second LED devices output red and/or orange light (achievable, for example, using a GaAsP or AlGaInP or other epitaxy LED chip that naturally emits red and/or orange light). The light from the first LED devices and second LED devices blend together to produce improved color rendition. In another embodiment, the planar LED-based Lambertian light source can also comprise a single LED device or an array of LED emitters incorporated into a single LED device, which may be a white LED device and/or a saturated color LED device and/or so forth. In another embodiment, the LED emitter are organic LEDs comprising, in one example, organic compounds that emit light. 
     As best shown in  FIG. 3 , the element body  244  of the heat dissipating elements  242  has a peripheral edge  250  that forms the outer periphery or shape of the heat dissipating elements  242 . Each of the heat dissipating elements  242  have an element surface  252  on the front and back of the element body  244 . The peripheral edge  250  comprises an outer peripheral edge  254  and an inner peripheral edge  256  proximate the outer surface  218  of the envelope  216 . A gap  260  separates the inner peripheral edge  256  from the outer surface  218  of the envelope  216 . 
     The gap  260  spaces the tip end  246  of the heat dissipating elements  242  away from the outer surface  218  of the envelope  216 . Generally the gap  260  is smaller at tip end  246  than at the base end  248 . Surprisingly, this configuration improves heat dissipation and reduces the LED board temperature by about 5° C. at least as compared to other designs in which all or a portion of the heat dissipating element  242  nearly contacts the envelope  216 . It is believed that the gap  260  provides space between the inner peripheral edge  256  and the outer surface  218  to facilitate air flow and convection currents. The space effectively reduces friction and drag on the air, which improves air flow over the outer surface  218  of the envelope  216 , the front and back faces of the element body  244 , and the inner peripheral edge  256 . The improved flow of air increases the rate of convection and the rate of heat dissipation. In one embodiment, the gap  260  at the tip end  246  is from about 1.75 mm to about 3 mm, about 2 mm or greater and, in one example, the gap  260  is about 3 mm or more. In one embodiment the gap  260  at the base end  248  is greater than the gap  260  at the tip end  246 , where the gap  260  can be from about 3 mm to about 10 mm or more. 
     In addition to the lighting apparatus  200 ,  FIG. 4  shows that the outer peripheral edge  254  fits within a lamp profile  262 , the extent of which is defined by an outer dimension D, which can be from about 60 mm (e.g., typical of a GE A19 incandescent lamp) to about 69.5 mm (e.g., the maximum diameter allowed by ANSI for an A19 lamp. Embodiments of the lighting apparatus  200  are amenable to many other examples of the lamp profile  262 . Some examples include A-type (e.g., A15, A19, A21, A23, etc.) and G-type (e.g., G20, G30, etc.) as well as other profiles that various industry standards known and recognized in the art define. 
     In designing the heat dissipating assembly  212 , the limiting thermal impedance in a passively cooled thermal circuit is typically the convective impedance to ambient air (that is, dissipation of heat into the ambient air). It is generally simpler to optimize the thermal conduction through the bulk of the heat dissipating assembly  212  than it is to optimize the convention and radiation to ambient from the heat dissipating assembly  212 . Furthermore, the convective heat transfer to ambient from the heat dissipating assembly  212  is generally much greater than the radiative heat transfer to ambient from the heat dissipating assembly  212 . So, to achieve the most effective cooling of the LEDs, it is required to minimize the thermal impedance of the convective heat transfer to ambient from the heat dissipating assembly  212 . 
     This convective impedance is generally proportional to the surface area of the heat dissipating assembly  212 . In the case of a replacement lamp application, where the lighting apparatus  200  must fit into the same space as the traditional Edison-type incandescent lamp being replaced (e.g., into the lamp profile  262 ), there is a fixed limit on the available amount of surface area of the imaginary outside element profile. Therefore, it is advantageous to increase the available surface area that is in contact with ambient air as much as possible for heat dissipation into the ambient, such as by placing the heat dissipating elements  242  or other heat dissipating structures around or adjacent to the light source  214 , and by maximizing the surface area of each of the heat dissipating elements  242 , and by maximizing the number of heat dissipating elements  242 , while maintaining a minimal blockage of light from the envelope  116 . Functionally, however, the configuration of the heat dissipating elements  242  may be required to vary to meet not only the physical lamp profile (e.g., the lamp profile  262 ) of current regulatory limits (ANSI, NEMA, etc.), but also to satisfy consumer aesthetics or manufacturing constraints as well. 
     Thermal properties of the heat dissipating elements  242  can have a significant effect on the total energy that the heat dissipating assembly  212  dissipates and, accordingly, the temperature of the solid-state device  230  and any corresponding driver electronics. Since the performance and reliability of the solid-state device  230  and driver electronics is generally limited by operating temperature, it is critical to select one or more materials with appropriate properties. The thermal conductivity of a material defines the ability of a material to conduct heat. Since the solid-state device  230  may have a very high heat density, the heat dissipating assembly  212  should preferably comprise materials with high thermal conductivity so that the generated heat can be conducted through a low thermal resistance away from the solid-state device  230 . 
     In general, metallic materials have a high thermal conductivity, with common structural metals such as alloy steel, cast aluminum, extruded aluminum, copper, or engineered composite materials such as thermally-conductive polymers. Exemplary materials can exhibit thermal conductivities of about 50 W/m-K, from about 80 W/m-K to about 100 W/m-K, 170 W/m-K, 390 W/m-K, and from about 1 W/m-K to about 30 W/m-K, respectively. A high conductivity material will allow more heat to move from the thermal load to ambient and result in a reduction in temperature rise of the thermal load. The heat dissipating assembly  212  (e.g., the base element  240  and the heat dissipating elements  242 ) can comprise one or more high thermal conductivity materials including metals (e.g., aluminum), plastics, plastic composites, ceramics, ceramic composite materials, nano-materials, such as carbon nanotubes (CNT) or CNT composites. 
     Practical considerations, such as manufacturing process or cost, may affect the selection of materials and the effective thermal properties. For example, cast aluminum, which is generally less expensive in large quantities, has a thermal conductivity value approximately half of extruded aluminum. It is preferred for ease and cost of manufacture to use predominantly one material for the majority of the heat dissipating assembly  212  (e.g., the base element  240  and the heat dissipating elements  242 ), but combinations of cast/extrusion methods of the same material or even incorporating two or more different materials into construction of the heat dissipating assembly  212  to maximize cooling are also possible. 
     Embodiments of the lighting apparatus  200  can comprise 3 or more heat dissipating elements  242  arranged radially about the center axis  204 . The heat dissipating elements  242  can be equally spaced from one another so that adjacent ones of the heat dissipating elements  242  are separated by at least about 45° for an 8-fin apparatus and 22.5° for an 18-fin apparatus measured along the longitude coordinate (p. Physical dimensions (e.g., width, thickness, and height) can also determine the necessary separation between the heat dissipating elements  242  as well as other physical aspects of the lighting apparatus  200 . 
     Moreover, the physical dimensions, placement, and configuration of the heat dissipating elements  242  may also impact a variety of lighting characteristics, including the optical intensity of the lighting apparatus  200 . For example, the width of the heat dissipating elements  242  affects primarily the latitudinal uniformity of the light distribution, the thickness of the heat dissipating elements  242  affects primarily the longitudinal uniformity of the light distribution, and the height of the heat dissipating elements  242  affects how much of the latitudinal uniformity is disturbed. In general terms, in order to minimize the distortion of the light intensity distribution the same fraction of the emitted light should interact with the heat dissipating elements  242  at all angles θ. In functional terms, to maintain the existing light intensity distribution of the light diffusing assembly  210 , the area of the element surfaces  252  in view of the light source  214  created by the width and thickness of the heat dissipating elements  242  should stay in a constant ratio with the surface area of the emitting light surface that they encompass. 
     The heat dissipating assembly  212  can also have optical properties that affect the resultant optical intensity. When light impinges on a surface, it can be absorbed, transmitted, or reflected. In the case of most engineering thermal materials, they are opaque to visible light, and hence, visible light can be absorbed or reflected from the surface. In consideration of optical properties, selection and design of the light apparatus  200  should contemplate the optical reflectivity efficiency, optical specularity, and the size and location of the heat dissipating elements  242 . As discussed hereinbelow, concerns of optical efficiency, optical reflectivity, and intensity will refer herein to the efficiency and reflectivity the wavelength range of visible light, typically about 400 nm to about 700 nm. 
     The absolute reflectivity of the surface of the heat dissipating elements  242  will affect the total efficiency of the lighting apparatus  200  as well as the intrinsic light intensity distribution of the light source  214 . Though only a small fraction of the light emitted from the light source  214  may impinge the heat dissipating assembly  212  with heat dissipating elements  242  arranged around the light source  214 , if the reflectivity is very low, a large amount of flux will be lost on the element surfaces  252  of the heat dissipating elements  242 , and reduce the overall efficiency of the lighting apparatus  200 . 
     The optical intensity is affected by both the redirection of emitted light from the light source  214  and also absorption of flux by the heat dissipating assembly  212 . In one embodiment, if the reflectivity of the heat dissipating elements  242  is kept at a high level, such as greater than 70%, the distortions in the optical intensity can be minimized. Similarly, the longitudinal and latitudinal intensity distributions can be affected by the surface finish of the thermal heat sink and surface enhancing elements. Smooth surfaces with a high specularity (mirror-like) distort the underlying intensity distribution less than diffuse (Lambertian) surfaces as the light is directed outward along the incident angle rather than perpendicular to the surface of the heat dissipating elements  242 . 
     The thermal emissivity, or efficiency of radiation in the far infrared region (approximately 5-15 μm) of the electromagnetic radiation spectrum, is also an important property for the surfaces of the heat dissipating elements  242 . Generally, very shiny metal surfaces have very low emissivity, on the order of 0.0-0.2. Hence, some sort of coating or surface finish may be desirable, such as paints (0.7-0.95) or anodized coatings (0.55-0.85). A high emissivity coating on the heat dissipating elements  242  may dissipate approximately 40% more heat than bare metal with low emissivity. Selection of a high-emissivity coating must also take into account the optical properties of the coating, as low reflectivity or low specularity in the visible wavelength can adversely affect the overall efficiency and light distribution of the lighting apparatus  100 . 
     A range of surface finishes, varying from a specular (reflective) to a diffuse (Lambertian) surface can be selected for the heat dissipating elements  242 . The specular designs can be a reflective base material or an applied highly specular coating. The diffuse surface can be a finish on the heat dissipating elements  242 , or an applied paint or powder coating or foam or fiber mat or other diffuse coating. Each provides certain advantages and disadvantages. For example, a highly reflective surface may have the ability to maintain the light intensity distribution, but may be thermally disadvantageous due to the generally lower emissivity of bare metal surfaces. Or a highly diffuse, high-reflectivity coating may require a thickness that provides a thermally insulating barrier between the heat dissipating elements  242  and the ambient air. 
     In addition, highly specular surfaces may be difficult to maintain over the life of the lighting apparatus  200 , which is typically 25,000-50,000 hours. A visibility transparent coating may be applied over the specular surface to improve the resistance to abrasion and oxidation of the surface. Further if the visibly transparent coating has a high emittance in the infrared, then the thermal radiation may be desirably enhanced. In one embodiment, the heat diffusing elements  242  can comprise a diffuse surface. The maintenance of the diffuse surface might be robust over the life of the lighting apparatus than a specular surface, and can also provide a visual appearance that is similar to existing incandescent omnidirectional light sources. A diffuse finish might also have an increased thermal emissivity compared to a specular surface which will increase the heat dissipation capacity of the heat sink, as described above. In one example, the coating will possess a highly specula surface and also a high emissivity, examples of which would be highly specular paints, or high emissivity coatings over a highly specular finish or coating. 
     The cross-section of  FIG. 5  and the top view of  FIG. 6  shows one configuration of the reflector element  224 . In  FIG. 5 , the cone element  234  has a frusto-conical member  264  with a thin-wall profile  266 , an upper surface  268 , and a lower surface  270 . The frusto-conical member  264  forms an angle β with the center axis  204 . In one embodiment, the angle β may be less than 90°, in which case the frusto-conical member  264  has its larger diameter at the bottom and its smaller diameter at the top, as shown in  FIG. 5 . In one embodiment, the angle β may be 90°, in which case the frusto-conical member  264  simplifies to a flat circle and, in construction, the flat circuit comprises an aperture at the center. In another embodiment, the angle β may be greater than 90°, so that the frusto-conical member  264  is inverted. In yet another embodiment, the frusto-conical member  264  might be a combination of multiple frusto-conical members, one or more of which has different angle β and joined together, e.g., at their edges. An example of this multiple-member construction is shown in  FIG. 6 , wherein the frusto-conical member  264  comprises a plurality of members  274  with edges  276  abutting adjacent members. 
     Referring back to  FIG. 5 , the aperture element  238  comprises a circular member  278  that is aligned with the center axis  204 . The specific dimensions of each optical element (e.g., the frusto-conical member  264 , the circular member  278 , the lighting assembly  210 , etc.) to be used for any target relative optical distribution will depend on a combination (1) LED light source (or “engine”) size and native optical distribution determined by standard source imaging goniometers, and (2) optical properties (e.g., scattering, transmittance, reflectance, absorption, etc.) of the envelop, cone element and surface, annular surface, and coatings on the heating dissipating element. In one example, where a low loss surface diffuser is used in the annulus the circular member  278  can have a diameter of about 10 mm to about 20 mm or greater, as measured about the center axis  204 . In other examples, the diameter can range from about 1 mm to about 60 mm. Other shapes (other than circular) are also possible for the aperture element  238  including square, rectangular, polygonal, annular, etc. In another embodiment, the circular member  278  may be three-dimensional with a surface geometry such as a frusto-conical, conical, hemispherical, and the like. 
     The thin-wall profile  266  can have thickness from about 0.5 mm to about 3 mm or more and/or, for example, of suitable thickness to provide the relative optical intensity as described above. In one embodiment, one or more of the upper surface  268  and the lower surface  270  can have a coating disposed thereon. Values for the angle β can be from about 45° to about 135°, and in one example from about 55° to about 75° and, in another example the angle β is 65° or greater. 
     In  FIG. 7 , the frusto-conical member  264  comprises a plurality of slots  280  found between the peripheral edge of the frusto-conical member  264  and the inner surface  220  of the envelope  216 . In one embodiment, the frusto-conical member  264  includes the slots  280  to provide the lighting apparatus  200  with a more appealing and/or aesthetically pleasing appearance by allowing light to illuminate the envelope  216  near the edge of the frusto-conical member  264  to reduce the bright-dark contrast that otherwise is visible at the edge. The slots  274  can be spaced radially about the center axis  204 . Each of the slots  274  can have a radial length (R L ), which can vary as desired. For example, the radial length (R L ) can vary from slot-to-slot, or the slots  274  can be configured so the radial length (R L ) is uniform among the plurality of slots  274 . In one embodiment, the slots  274  comprise about 2% (slot width/cone diameter) and/or about 10% of the total area of the frusto-conical member  264 . 
     The slots  280  may be in any other geometric shape or size of opening so as to provide a region within the frusto-conical member  264  where light is transmitted through to the envelope  216 . This feature can enhance the light intensity distribution near the north pole (e.g., the north pole  106  ( FIG. 1 )) or to provide a more uniformly lit appearance on the surface of the envelope  216 . For example, the slots  280  might be circles, ellipses, polygons, or any other shape. The slots  280  may be positioned at or near the edge of the frusto-conical member  264  or at or near the circular member  272 , or anywhere in between. The slots  280  may be voids of air, or may be filled with any of the materials that are available for use in the circular member  272  which allow transmission of light. 
     The following example further illustrates various aspects and embodiments of the present invention. 
     EXAMPLE 
     In one embodiment, a lighting apparatus (e.g., the lighting apparatus  100 ,  200  of  FIGS. 1, 2, 3, 4, 5, 6, and 7 ) comprises the following: 
     An example of an envelope (e.g., the envelope  116 ,  216  of  FIGS. 1, 2, 3, 4 , and  5 ) comprising a Teijin ML5206 low loss diffuser having a spheriodal shape with dimensions of 53 mm×53 mm×39 mm. 
     An example of a reflector element (e.g., the reflector element  124 ,  224  of  FIGS. 1, 2, 3, 4, 5, 6, and 7 ). The reflector element comprises a cone element (e.g., the cone element  234  of  FIGS. 4, 5, 6, and 7 ) comprising a slotted polycarbonate cone with high-reflectance paint and/or high-reflectance self-adhesive laminates and/or integral molded high-reflectance white plastics. The reflector element also comprises an aperture element (e.g., the aperture element  238  of  FIGS. 3, 4, 5, 6, and 7 ) comprising an 80° surface diffuser center aperture, wherein 80° is the full-width at half-maximum (FWHM) of the intensity distribution of light scattered by the diffuser. 
     An example of a light source (e.g., the light source  114 ,  214  of  FIGS. 1 and 2 ) comprises a circular LED package on board assembly. 
     An example of a heat dissipating assembly (e.g., the heat dissipating assembly  112 ,  212  of  FIGS. 1 and 2 ) comprises eight (8) heat dissipating elements (e.g., the heat dissipating elements  242  of  FIGS. 2, 3, and 4 ) comprising Al 6061, wherein each of the heat dissipating elements comprises a high reflectance outdoor coating and/or high-reflectance powder coating. 
       FIG. 8  illustrates a plot  300  of an optical intensity distribution profile  302  (or “optical intensity” profile  302 ). Data for the plot  300  was gathered using a Mirror Goniometer from the embodiment of the lighting apparatus having features described above. As the optical intensity profile  302  illustrates, the lighting apparatus achieves a mean optical intensity  304  of about 100±10% at an angle (e.g., the latitude coordinate θ of  FIG. 1 ) up to at least 150°. 
       FIG. 9  illustrates a plot  400  of thermal profiles  402  comprising an 8-fin profile  404  and a 12-fin profile  406 . The thermal profiles  402  also comprise an ambient profile  408 . Data for the plot  400  was gathered using a thermocouple secured to one of the heat dissipating elements on the embodiment of the lighting apparatus having features described above. As the 8-fin profile  404  illustrates, the lighting apparatus achieves a mean temperature of 62° C. when measured in a 25° C. ambient. 
     Table 1 below summarizes data for color uniformity for the embodiment of the lighting apparatus having features described above. The data was gathered using a Mirror Goniometer. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Du‘v’ 
               
            
           
           
               
               
               
               
               
            
               
                 θ 
                 0 
                 90 
                 180 
                 270 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 0 
                 0.0016 
                 0.0018 
                 0.0018 
                 0.0019 
               
               
                 10 
                 0.0020 
                 0.0020 
                 0.0019 
                 0.0019 
               
               
                 20 
                 0.0017 
                 0.0019 
                 0.0017 
                 0.0016 
               
               
                 30 
                 0.0016 
                 0.0019 
                 0.0016 
                 0.0012 
               
               
                 40 
                 0.0013 
                 0.0017 
                 0.0016 
                 0.0011 
               
               
                 50 
                 0.0010 
                 0.0013 
                 0.0019 
                 0.0009 
               
               
                 60 
                 0.0010 
                 0.0009 
                 0.0023 
                 0.0015 
               
               
                 70 
                 0.0014 
                 0.0014 
                 0.0024 
                 0.0020 
               
               
                 80 
                 0.0018 
                 0.0024 
                 0.0025 
                 0.0021 
               
               
                 90 
                 0.0017 
                 0.0026 
                 0.0018 
                 0.0014 
               
               
                 100 
                 0.0018 
                 0.0027 
                 0.0014 
                 0.0011 
               
               
                 110 
                 0.0016 
                 0.0024 
                 0.0011 
                 0.0011 
               
               
                 120 
                 0.0015 
                 0.0020 
                 0.0008 
                 0.0010 
               
               
                 130 
                 0.0013 
                 0.0017 
                 0.0006 
                 0.0005 
               
               
                 140 
                 0.0012 
                 0.0018 
                 0.0004 
                 0.0003 
               
               
                 150 
                 0.0009 
                 0.0016 
                 0.0004 
                 0.0005 
               
               
                   
               
            
           
         
       
     
     Note the color uniformity that the data of Table 1 illustrates. 
     A sample of embodiments of a lighting apparatus is provided below in which: 
     In embodiment A, a lighting apparatus, comprising a light diffusing assembly comprising an envelope and a reflector element; and a light source comprising a solid-state device, wherein the light diffusing assembly can disperse light from the solid-state device with an optical intensity distribution of 100±20% over a latitude coordinate θ of 135° or better. 
     The lighting apparatus of embodiment A, further comprising a plurality of heat dissipating elements disposed radial about the envelope. 
     The lighting apparatus of embodiment A, wherein the envelope comprises a spheroid shape. 
     The lighting apparatus of embodiment A, wherein the reflector element comprises an outer reflective portion and an inner transmissive portion. 
     In embodiment B, a lamp, comprising an envelope from which light can be emitted; and a plurality of heat dissipating elements disposed radially about the envelop, the heat dissipating elements having a tip end spaced apart from the envelope to form an air gap, wherein light from the envelope exhibits an optical intensity of 100±20% over a latitude coordinate θ of 135° or better. 
     The lamp of embodiment B, wherein the air gap is at least 3 mm. 
     The lamp of embodiment B, wherein the heat dissipating elements fit within a form factor defined by ANSI standard for A19 lamps. 
     The lamp of embodiment B, wherein the heat dissipating elements are equally-spaced radially apart from one another. 
     The lamp of embodiment B, wherein the heat dissipating elements comprise a reflective coating. 
     The lamp of embodiment B, further comprising a light source in thermal contact with the heat dissipating elements, wherein the light source comprises a plurality of light emitting diodes. 
     This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.