Patent Grant
8344625
NOT APPLICABLE
NOT APPLICABLE
NOT APPLICABLE
The present invention relates generally to lighting techniques. In particular, the present invention provides a method and device using a plasma lighting device having a dielectric waveguide body having a shaped configuration. Merely by way of example, the invention can be applied to a variety of applications including a warehouse lamp, stadium lamp, lamps in small and large buildings, and other applications.
From the early days, human beings have used a variety of techniques for lighting. Early humans relied on fire to light caves during hours of darkness. Fire often consumed wood for fuel. Wood fuel was soon replaced by candles, which were derived from oils and fats. Candles were then replaced, at least in part by lamps. Certain lamps were fueled by oil or other sources of energy. Gas lamps were popular and still remain important for outdoor activities such as camping. In the late 1800, Thomas Edison, who is the greatest inventor of all time, conceived the incandescent lamp, which uses a tungsten filament within a bulb, coupled to a pair of electrodes. Many conventional buildings and homes still use the incandescent lamp, commonly called the Edison bulb. Although highly successful, the Edison bulb consumed much energy and was generally inefficient.
Fluorescent lighting replaced incandescent lamps for certain applications. Fluorescent lamps generally consist of a tube containing a gaseous material, which is coupled to a pair of electrodes. The electrodes are coupled to an electronic ballast, which helps ignite the discharge from the fluorescent lighting. Conventional building structures often use fluorescent lighting, rather than the incandescent counterpart. Fluorescent lighting is much more efficient than incandescent lighting, but often has a higher initial cost.
Shuji Nakamura pioneered the efficient blue light emitting diode, which is a solid state lamp. The blue light emitting diode forms a basis for the white solid state light, which is often a blue light emitting diode within a bulb coated with a yellow phosphor material. Blue light excites the phosphor material to emit white lighting. The blue light emitting diode has revolutionized the lighting industry to replace traditional lighting for homes, buildings, and other structures.
Another form of lighting is commonly called the electrode-less lamp, which can be used to discharge light for high intensity applications. Matt was one of the pioneers that developed an improved electrode-less lamp. Such electrode-less lamp relied upon a solid ceramic resonator structure, which was coupled to a fill enclosed in a bulb. The bulb was coupled to the resonator structure via rf feeds, which transferred power to the fill to cause it to discharge high intensity lighting. The solid ceramic resonator structure has been limited to a dielectric constant of greater 2. An example of such a solid ceramic waveguide is described in U.S. Pat. No. 7,362,056, which is hereby incorporated by reference herein. Although somewhat successful, the electrode-less lamp still had many limitations. As an example, electrode-less lamps have not been successfully deployed. Additionally, the conventional lamp also uses a high frequency and has a relatively large size, which is often cumbersome and difficult to manufacture and use. These and other limitations of the conventional lamp are described throughout the present specification and more particularly below.
From the above, it is seen that improved techniques for lighting are highly desired.
According to the present invention, techniques for lighting are provided. In particular, the present invention provides a method and device using a plasma lighting device having a dielectric waveguide body having a shaped configuration. Merely by way of example, the invention can be applied to a variety of applications including a warehouse lamp, stadium lamp, lamps in small and large buildings, and other applications.
In a specific embodiment, the present invention provides a plasma lamp apparatus. The lamp apparatus has a body comprising at least a dielectric material and having at least a main part with a first surface and a second surface opposed to the first surface. The apparatus has a feed inserted through the first surface into the main part of the body and configured to provide radio frequency energy to the body. In a preferred embodiment, a protruding portion of the dielectric material surrounding a periphery of a bulb. Preferably, the bulb has a first end, a second end, and a spatial region between the first end and the second end, and a predefined volume, the bulb enclosing a gas fill positioned to receive the radio frequency energy from the body such that a substantial portion of the electric field is provided within a vicinity of the spatial region. In a specific embodiment, the second surface is coated with an electrically conductive material. In a specific embodiment, the apparatus has at least a portion of the bulb enclosing the gas fill positioned above the main part of the body adjacent to the second surface and an rf power source coupled to the second surface to provide radio frequency energy to the body to cause the gas fill to emit a substantial portion of electromagnetic radiation of at least a determined amount of lumens per watt through a portion of the spatial region.
The present invention provides a dielectric support structure in which the bulb sits in. the bulb is supported in the structure through a protrusion that extends from the inner cavity of the support structure and makes contact around the periphery of the bulb. The protrusion extends from the support structure in a curved manner, thereby reducing the electric field that is generated at such protrusion. By reducing the electric field, the plasma is generated in the bulb at lower RF power levels, thereby increasing the lumens per watt characteristic of the lamp apparatus. Of course, there can be other variations, modifications, and alternatives.
Benefits are achieved over pre-existing techniques using the present invention. In a specific embodiment, the present invention provides a method and device having configurations of input, output, and feedback coupling elements that provide for electromagnetic coupling to the bulb whose power transfer and frequency resonance characteristics that are largely dependent upon a waveguide body having at least two materials. In a preferred embodiment, the present invention provides a method and configurations with an arrangement that provides for improved manufacturability as well as design flexibility. Other embodiments may include integrated assemblies of the output coupling element and bulb that function in a complementary manner with the present coupling element configurations and related methods for street lighting applications. In a specific embodiment, the present method and resulting structure are relatively simple and cost effective to manufacture for commercial applications. In a preferred embodiment, the invention provides a resulting device and method having a higher efficiency using rounded spatial features within one or more portions of the resonator structure to reduce electric fields and the like. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits may be described throughout the present specification and more particularly below.
The present invention achieves these benefits and others in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
According to the present invention, techniques for lighting are provided. In particular, the present invention provides a method and device using a plasma lighting device having a dielectric waveguide body having a shaped configuration. Merely by way of example, the invention can be applied to a variety of applications including a warehouse lamp, stadium lamp, lamps in small and large buildings, and other applications.
According to the present invention, techniques for lighting are provided. In particular, the present invention provides a method and device using a plasma lighting device having a dielectric waveguide of a dielectric constant of less than 2. More particularly, the present invention provides a method and apparatus having a plasma lighting device using a ceramic resonator structure of a dielectric constant of less than 2. Merely by way of example, the invention can be applied to a variety of applications including a warehouse lamp, stadium lamp, lamps in small and large buildings, and other applications.
Turning now to the drawings,
In a preferred embodiment referring to
In a preferred embodiment, the microwave radiation source 115 feeds the waveguide 103 microwave energy via the feed 117. The waveguide contains and guides the microwave energy to a cavity 105 preferably located on an opposing side of the waveguide 103 from the feed 117. Disposed within the cavity 105 is the bulb 107 containing the gas-fill. Microwave energy is preferably directed into the enclosed cavity 105, and in turn the bulb 107. This microwave energy generally frees electrons from their normal state and thereby transforms the noble gas into a plasma. The free electrons of the noble gas excite the light emitter. The de-excitation of the light emitter results in the emission of light. As will become apparent, the different embodiments of DWIPLs disclosed herein offer distinct advantages over the plasma lamps in the prior art, such as an ability to produce brighter and spectrally more stable light, greater energy efficiency, smaller overall lamp sizes, and longer useful life spans.
The microwave source 115 in
Depending upon the heat sensitivity of the microwave source 115, the microwave source 115 may be thermally isolated from the bulb 107, which during operation preferably reaches temperatures between about 700 Degree C. and about 1000 Degree C. Thermal isolation of the bulb 107 from the source 115 provides a benefit of avoiding degradation of the source 115. Additional thermal isolation of the microwave source 115 may be accomplished by any one of a number of methods commonly known in the art, including but not limited to using an insulating material or vacuum gap occupying an optional space 116 between the source 115 and waveguide 103. If the latter option is chosen, appropriate microwave feeds are used to couple the microwave source 115 to the waveguide 103.
In
Due to mechanical and other considerations such as heat, vibration, aging, or shock, when feeding microwave signals into a dielectric material, contact between the feed 117 and the waveguide 103 is preferably maintained using a positive contact mechanism 121. The contact mechanism 121 provides constant pressure between the feed 117 and the waveguide 103 to minimize the probability that microwave energy will be reflected back through the feed 117 and not transmitted into the waveguide 103. In providing constant pressure, the contact mechanism 121 compensates for small dimensional changes in the microwave feed 117 and the waveguide 103 that may occur due to thermal heating or mechanical shock. The contact mechanism may be a spring loaded device, such as is illustrated in
When coupling the feed 117 to the waveguide 103, intimate contact is preferably made by depositing a metallic material 123 directly on the waveguide 103 at its point of contact with the feed 117. The metallic material 123 eliminates gaps that may disturb the coupling and is preferably comprised of gold, silver, or platinum, although other conductive materials may also be used. The metallic material 123 may be deposited using any one of several methods commonly known in the art, such as depositing the metallic material 123 as a liquid and then firing it in an oven to provide a solid contact.
In
In one preferred embodiment, the waveguide body is approximately three inches or less with a dielectric constant of approximately 2 and less and operating frequency of approximately 400 MHz. Waveguide bodies, using the two dielectric materials, on this scale are significantly smaller than the waveguides in the conventional plasma lamps. As such, the waveguides in the preferred embodiments represent a significant advance over the conventional lamp because the smaller size allows the waveguide to be used in many applications, where waveguide size had previously prohibited such use or made such use wholly impractical. In a preferred embodiment, the present method and structure provides one or more benefits of a reduction in size, size reduction translates into a higher power density, lower loss, and thereby, an ease in igniting the lamp. Of course, there can be other variations, modifications, and alternatives.
Regardless of its shape and size, the waveguide 103 preferably has a body comprising a dielectric material which, for example, preferably exhibits the following properties; a dielectric constant preferably equal to or less than approximately 2; and a loss tangent preferably less than approximately 0.0001. In other embodiments, the dielectric constant is equal to or greater than 2. Of course, there can be other variations, modifications, and alternatives.
Certain ceramics, including alumina, zirconia, titanates, and variants or combinations of these materials, and silicone oil may satisfy many of the above preferences, and may be used because of their electrical and thermo-mechanical properties. In any event, it should be noted that the embodiments presented herein are not limited to a waveguide exhibiting all or even most of the foregoing properties. In preferred embodiments, the ceramic or dielectric includes one or more voids and/or air pockets that have an average dielectric constant of less than 2, but can be other materials. In other embodiments, the dielectric constant is equal to or greater than 2. Of course, there can be other variations, modifications, and alternatives.
In the various embodiments of the waveguide disclosed herein, such as in the example outlined above, the waveguide preferably provides a substantial thermal mass, which aids efficient distribution and dissipation of heat and provides thermal isolation between the lamp and the microwave source.
Alternative embodiments of DWIPLS 200, 220 are depicted in
As shown in
Returning to
Microwave leakage from the bulb cavity 105 may be significantly attenuated by having a cavity 105 that is preferably significantly smaller than the microwave wavelengths used to operate the lamp 101. For example, the length of the diagonal for the window is preferably considerably less than half of the microwave wavelength (in free space) used.
The bulb 107 is disposed within the bulb cavity 105, and preferably comprises an outer wall 109 and a window 111. In one preferred embodiment, the cavity wall of the body of the waveguide 103 acts as the outer wall of the bulb 107. The components of the bulb 107 preferably include one or more dielectric materials, such as ceramics and sapphires. In one embodiment, the ceramics in the bulb are the same as the material used in waveguide 103. Dielectric materials are preferred for the bulb 107 because the bulb 107 is preferably surrounded by the dielectric body of the waveguide 103 and the dielectric materials help ensure efficient coupling of the microwave energy with the gas-fill in the bulb 107.
The outer wall 109 is preferably coupled to the window 111 using a seal 113, thereby defining a bulb envelope 127 which contains the gas-fill comprising the plasma-forming gas and light emitter. The plasma-forming gas is preferably a noble gas, which enables the formation of a plasma. The light emitter is preferably a vapor formed of any one of a number of elements or compounds currently known in the art, such as sulfur, selenium, a compound containing sulfur or selenium, or any one of a number of metal halides, such as indium bromide (InBr3).
To assist in confining the gas-fill within the bulb 107, the seal 113 preferably comprises a hermetic seal. The outer wall 109 preferably comprises alumina because of its white color, temperature stability, low porosity, and thermal expansion coefficient. However, other materials that generally provide one or more of these properties may be used. The outer wall 109 is also preferably contoured to reflect a maximum amount of light out of the cavity 105 through the window 111. For instance, the outer wall 109 may have a parabolic contour to reflect light generated in the bulb 107 out through the window 111. However, other outer wall contours or configurations that facilitate directing light out through the window 111 may be used.
The window 111 preferably comprises sapphire for light transmittance and because it's thermal expansion coefficient matches well with alumina. Other materials that have a similar light transmittance and thermal expansion coefficient may be used for the window 111. In an alternative embodiment, the window 111 may comprise a lens to collect the emitted light.
As referenced above, during operation, the bulb 107 may reach temperatures of up to about 1000 Degrees Celsius, or slightly less. Under such conditions, the waveguide 103 in one embodiment acts as a heat sink for the bulb 107. By reducing the heat load and heat-induced stress upon the various components of the DWIPL 101, the useful life span of the DWIPL 101 is generally increased beyond the life span of typical electrodeless lamps. Effective heat dissipation may be obtained by preferably placing heat-sinking fins 125 around the outer surfaces of the waveguide 103, as depicted in
In another embodiment, the body of the waveguide 103 comprises a dielectric, such as a titanate, which is generally not stable at high temperatures. In this embodiment, the waveguide 103 is preferably shielded from the heat generated in the bulb 107 by placing a thermal barrier between the body of the waveguide 103 and the bulb 107. In one alternative embodiment, the outer wall 109 acts as a thermal barrier by comprising a material with low thermal conductivity such as NZP, commonly known as sodium zirconium phosphate. Other suitable material for a thermal barrier may also be used.
Embedded in the support 319 is an access seal 321 for establishing a vacuum within the gap 317 when the bulb 313 is in place. The bulb 313 is preferably supported by and hermetically sealed to the bulb support 319. Once a vacuum is established in the gap 317, heat transfers between the bulb 313 and the waveguide 311 are preferably substantially reduced.
Embodiments of the DWIPLs thus far described preferably operate at a microwave frequency in the range of 0.5-10 GHz. The operating frequency preferably excites one or more resonant modes supported by the size and shape of the waveguide, thereby establishing one or more electric field maxima within the waveguide. When used as a resonant cavity, at least one dimension of the waveguide is preferably an integer number of half-wavelengths long.
In each of the DWIPLs and corresponding modes depicted in
Other modes may also be excited within a cylindrical prism-shaped waveguide. For example,
As another example,
Using a dielectric waveguide has several distinct advantages. First, as discussed above, the waveguide may be used to help dissipate the heat generated in the bulb. Second, higher power densities may be achieved within a dielectric waveguide than are possible in the plasma lamps with air cavities that are currently used in the art. The energy density of a dielectric waveguide is greater, depending on the dielectric constant of the material used for the waveguide, than the energy density of an air cavity plasma lamp.
Referring back to the DWIPL 101 of
Once the plasma is formed in the DWIPL and the incoming power is absorbed, the waveguide's Q value drops due to the conductivity and absorption properties of the plasma. The drop in the Q value is generally due to a change in the impedance of the waveguide. After plasma formation, the presence of the plasma in the cavity makes the bulb cavity absorptive to the resonant energy, thus changing the overall impedance of the waveguide. This change in impedance is effectively a reduction in the overall reflectivity of the waveguide. Therefore, by matching the reflectivity of the feed close to the reduced reflectivity of the waveguide, a sufficiently high Q value may be obtained even after the plasma formation to sustain the plasma. Consequently, a relatively low net reflection back into the energy source may be realized.
Much of the energy absorbed by the plasma eventually appears as heat, such that the temperature of the lamp may approach 1000 Degrees Celsius, or slightly less. When the waveguide is also used as a heat sink, as previously described, the dimensions of the waveguide may change due to its coefficient of thermal expansion. Under such circumstances, when the waveguide expands, the microwave frequency that resonates within the waveguide changes and resonance is lost. In order for resonance to be maintained, the waveguide preferably has at least one dimension equal to an integer multiple of the half wavelength microwave frequency being generated by the microwave source.
One preferred embodiment of a DWIPL that compensates for this change in dimensions employs a waveguide comprising a dielectric material having a temperature coefficient for the refractive index that is approximately equal and opposite in sign to its temperature coefficient for thermal expansion. Using such a material, a change in dimensions due to thermal heating offsets the change in refractive index, minimizing the potential that the resonant mode of the cavity would be interrupted. Such materials include Titanates. A second embodiment that compensates for dimensional changes due to heat comprises physically tapering the walls of the waveguide in a predetermined manner.
In another preferred embodiment, schematically shown in
The first feed 613 may generally operate as described above in other embodiments. The second feed 615 may probe the waveguide 611 to sample the field (including the amplitude and phase information contained therein) present and provide its sample as feedback to an input of the energy source 617 or amplifier. In probing the waveguide 611, the second feed 615 also preferably acts to filter out stray frequencies, leaving only the resonant frequency within the waveguide 611.
In this embodiment, the first feed 613, second feed, 615 and bulb cavity 619 are each preferably positioned with respect to the waveguide 611 at locations where the electric field is at a maximum. Using the second feed 615, the energy source 617 amplifies the resonant energy within the waveguide 611. The source 617 thereby adjusts the frequency of its output to maintain one or more resonant modes in the waveguide 611. The complete configuration thus forms a resonant oscillator. In this manner, automatic compensation may be realized for frequency shifts due to plasma formation and thermal changes in dimension and the dielectric constant.
The dielectric resonant oscillator mode also enables the DWIPL 610 to have an immediate re-strike capability after being turned off. As previously discussed, the resonant frequency of the waveguide 611 may change due to thermal expansion or changes in the dielectric constant caused by heat generated during operation. When the DWIPL 610 is shutdown, heat is slowly dissipated, causing instantaneous changes in the resonant frequency of the waveguide 611.
However, as indicated above, in the resonant oscillator mode the energy source 617 automatically compensates for changes in the resonant frequency of the waveguide 611. Therefore, regardless of the startup characteristics of the waveguide 611, and providing that the energy source 617 has the requisite bandwidth, the energy source 617 will automatically compensate to achieve resonance within the waveguide 611. The energy source immediately provides power to the DWIPL at the optimum plasma-forming frequency.
While embodiments and advantages of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.
While embodiments and advantages of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.
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| Number | Date | Country | |
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| Number | Date | Country | |
|---|---|---|---|
| Parent | 12484174 | Jun 2009 | US |
| Child | 12824441 | US |
