Patent Publication Number: US-7902766-B2

Title: Plasma lighting system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma lighting system using electromagnetic wave, and more particularly, to a dielectric mirror for a plasma lighting system. 
     2. Description of the Background Art 
     Generally, an optical source for illumination is divided into an incandescent lamp using heat radiation, a fluorescent lamp using a fluorescent body at a discharge pipe, a high intensity discharge lamp (HID lamp) using luminance by a discharge of gas of a high pressure or vapor, and a plasma lighting system using an electrodeless discharge. 
     The incandescent lamp has a high color rendering, a small size, a simple lighting circuit, and a low price. However, the incandescent lamp has a low optical efficiency and a short life span. The fluorescent lamp has an optical efficiency higher than that of the incandescent lamp and a life span longer than that of the incandescent lamp. However, the fluorescent lamp has a relatively large size and requires an additional lighting circuit. The HID lamp has a high optical efficiency and a long life span. However, the HID lamp requires time in lighting and re-lighting and needs an additional lighting circuit. The PLS lamp has a life span longer than any other lamp and a highest optical efficiency. However, the PLS lamp has a large consumption power and a high price, and requires an additional lighting circuit. 
     The PLS lamp is recognized as a new optical source. A plasma lighting system using the PLS lamp emits light of a high optical amount without an electrode by making a discharge material inside a bulb into plasma by electromagnetic wave generated from a magnetron of a microwave oven and thereby continuously emitting light by a metal compound. 
     The bulb of the plasma lighting system contains a main discharge material such as a metal, a halogen-based compound, sulfur, or selenium for emitting light by forming a plasma, an initial discharge material such as Ar, Xe, Kr, etc. for forming plasma inside a light emitting portion at the time of an initial luminance, and a discharge catalyst material such as Hg for facilitating lighting by an initial discharge or controlling a light spectrum. 
       FIG. 1  is a longitudinal section view showing one example of a plasma lighting system in accordance with the conventional art, and  FIG. 2  is a perspective view showing a dielectric mirror in the plasma lighting system in accordance with the conventional art. 
     As shown, the conventional plasma lighting system comprises a magnetron  20  mounted in a casing  10  and generating electromagnetic wave, a high voltage generator  30  for supplying alternating current (AC) power to the magnetron  20  by boosting into a high voltage, a wave guide  40  connected to an outlet of the magnetron  20  for transmitting electromagnetic wave generated from the magnetron  20 , a resonator  50  connected to an outlet of the wave guide  40  for resonating the electromagnetic wave passing through the wave guide  40 , a bulb  60  disposed in the resonator  50  for emitting light by making the discharge materials filled therein into plasma by electromagnetic wave, a reflector  70  containing the resonator  50  therein for forwardly reflecting light generated from the bulb  60 , a dielectric mirror  80  mounted in the resonator  50  positioned at a rear side of the bulb  60  for passing electromagnetic wave and reflecting light, and an electromagnetic wave guiding plate  90  covering the outlet of the wave guide  40  and having an electromagnetic wave passing hole  91  for connecting the wave guide  40  and the resonator  50  to each other. 
     The bulb  60  comprises a light emitting portion  61  having an inner volume and a sphere shape formed of a quartz material, disposed outside the casing  10 , and having a discharge material, a discharge catalyst material, etc. therein for emitting light by making the inner materials into plasma; and a supporting portion  62  integrally extending from the light emitting portion  61  and supported in the casing  10 . 
     As shown in  FIG. 2 , the dielectric mirror  80  comprises a glass plate  81  formed of a quartz material so as to be endurable against a high temperature, and a reflection coating layer  82  coated at one side of the glass plate  81  for reflecting light generated from the bulb  60  in a forward direction. 
     The electromagnetic wave guiding plate  90  is provided with the electromagnetic wave passing hole  91  for guiding electromagnetic wave to the resonator  50  by connecting the wave guide  40  and the resonator  50  to each other at the center thereof. Also, a fixing portion  92  having the electromagnetic wave passing hole  91  for fixing the reflector  70  at an outer circumferential surface thereof and fixing the dielectric mirror  80  thereon is formed at one side of the electromagnetic wave guiding plate  90 . The fixing protrusion  92  has a height not to cover the light emitting portion  61  of the bulb  60 . 
     An unexplained reference numeral  11  denotes an air inlet,  12  denotes an air outlet,  13  denotes an air flow path, F denotes a cooling fan, M 1  denotes a bulb motor for rotating the bulb, and M 2  denotes a fan motor for rotating the cooling fan. 
     An operation of the conventional plasma lighting system will be explained as follows. 
     When a driving signal is inputted to the high voltage generator  30  by a controller, the high voltage generator  30  boosts alternating current (AC) power thus to supply it to the magnetron  20 . Then, the magnetron  20  is oscillated by the high voltage thus to generate electromagnetic wave having a high frequency. The electromagnetic wave is emitted into the resonator  50  through the wave guide  40 , and continuously excites the discharge material and the discharge catalyst material contained in the bulb  60  into a plasma state. As the result, light having a specific emission spectrum is generated, and the light is forwardly reflected by the reflector  70  and the dielectric mirror  80  thus to illuminate a space. 
     However, the conventional plasma lighting system has the following problem. When the reflection coating layer  82  is formed at the glass plate  81  formed of a quartz material in order to fabricate the dielectric mirror  80 , the reflection coating layer  82  is degraded by heat of a high temperature thus to be damaged. As the result, when the reflection coating layer  82  is used for a long time, a reflection efficiency is lowered. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a plasma lighting system capable of preventing a reflection efficiency of a dielectric mirror from being lowered. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a plasma lighting system, comprising: a resonator; a bulb received in the resonator and containing a discharge material therein for emitting light by making the discharge material into plasma; and a dielectric mirror disposed at one side of the bulb and formed of a spontaneous reflective material for spontaneously reflecting light generated from the bulb. 
     According to another aspect of the present invention, there is provided a plasma lighting system comprising: a magnetron; a wave guide connected to the magnetron for guiding electromagnetic wave; a resonator connected to the wave guide for resonating electromagnetic wave; a bulb received in the resonator and containing a discharge material therein for emitting light as the discharge material becomes a plasma state by an electric field; a reflector containing the resonator and the bulb therein for reflecting light generated from the bulb; an electromagnetic wave guiding plate disposed between the wave guide and the resonator and having an electromagnetic wave passing hole to connect the wave guide and the resonator to each other at a surface that covers an outlet of the wave guide; and a dielectric mirror disposed at the electromagnetic wave guiding plate and formed of a spontaneous reflective material for spontaneously reflecting light generated from the bulb. 
     According to still another aspect of the present invention, there is provided a plasma lighting system comprising: a magnetron; a wave guide connected to the magnetron for guiding electromagnetic wave; a resonator connected to the wave guide for resonating electromagnetic wave; a bulb received in the resonator and containing a discharge material therein for emitting light as the discharge material becomes a plasma state by an electric field; a reflector containing the resonator and the bulb therein for reflecting light generated from the bulb; and an electromagnetic wave guiding plate disposed between the wave guide and the resonator and having an electromagnetic wave passing hole to connect the wave guide and the resonator to each other at a surface that covers an outlet of the wave guide, for reflecting light generated from the bulb. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a longitudinal section view showing one example of a plasma lighting system in accordance with the conventional art; 
         FIG. 2  is a perspective view showing a dielectric mirror in the plasma lighting system in accordance with the conventional art; 
         FIG. 3  is a longitudinal section view showing one example of a plasma lighting system according to the present invention; 
         FIG. 4  is a perspective view showing a dielectric mirror in the plasma lighting system according to the present invention; 
         FIG. 5  is a longitudinal section view showing a plasma lighting system according to another embodiment of the present invention; and 
         FIG. 6  is a sectional view showing a modification example of a main part of the plasma lighting system according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     Hereinafter, a plasma lighting system according to the present invention will be explained in more detail with reference to the attached drawings. 
       FIG. 3  is a longitudinal section view showing one example of a plasma lighting system according to the present invention, and  FIG. 4  is a perspective view showing a dielectric mirror in the plasma lighting system according to the present invention. 
     As shown, the plasma lighting system according to the present invention comprises a magnetron  120  mounted in a casing  110  and generating electromagnetic wave, a high voltage generator  130  for supplying alternating current (AC) power to the magnetron  120  by boosting into a high voltage, a wave guide  140  connected to an outlet of the magnetron  120  for transmitting electromagnetic wave generated from the magnetron  120 , a resonator  150  connected to an outlet of the wave guide  140  for resonating the electromagnetic wave passing through the wave guide  140 , a bulb  160  disposed in the resonator  150  for emitting light by making the discharge materials filled therein into plasma by electromagnetic wave, a reflector  170  containing the resonator  150  therein for forwardly reflecting light generated from the bulb  160 , a dielectric mirror  180  mounted in the resonator  150  positioned at a rear side of the bulb  160  for passing electromagnetic wave and reflecting light, and an electromagnetic wave guiding plate  190  covering the outlet of the wave guide  140  and having an electromagnetic wave passing hole  191  for connecting the wave guide  140  and the resonator  150  to each other. 
     The bulb  160  comprises a light emitting portion  161  having an inner volume and a sphere shape formed of a quartz material, disposed outside the casing  110 , and containing a discharge material therein, a discharge catalyst material, etc. therein for emitting light by making the inner materials into plasma; and a supporting portion  162  integrally extending from the light emitting portion  161  and supported in the casing  110 . 
     As shown in  FIG. 3 , the dielectric mirror  180  has a disc shape so as to be inserted into the cylindrical resonator  150  to be fixed. Preferably, the dielectric mirror  180  is formed of a ceramic material endurable to a high temperature and having a high diffusion reflection ratio for visible rays so as to smoothly reflect light generated form the bulb  160  without a reflection coating layer. 
     Also, a reflection surface of the dielectric mirror  180  is precisely processed by a polishing method, etc. so that light generated from the bulb  160  can be evenly reflected in a forward direction. 
     The electromagnetic wave guiding plate  190  is provided with the electromagnetic wave passing hole  191  for guiding electromagnetic wave to the resonator  150  by connecting the wave guide  140  and the resonator  150  to each other at the center thereof. Also, a fixing portion  192  having the electromagnetic wave passing hole  191  for fixing the reflector  170  at an outer circumferential surface thereof and fixing the dielectric mirror  180  thereon is formed at one side of the electromagnetic wave guiding plate  190 . The fixing portion  192  has a height not to cover the light emitting portion  161  of the bulb  60 . 
     The same reference numerals are given to the same parts of the present invention as those of the conventional art. 
     An unexplained reference numeral  111  denotes an air inlet,  112  denotes an air outlet,  113  denotes an air flow path, F denotes a cooling fan, M 1  denotes a bulb motor for rotating the bulb, and M 2  denotes a fan motor for rotating the cooling fan. 
     An operation of the plasma lighting system according to the present invention will be explained as follows. 
     When a driving signal is inputted to the high voltage generator  130  by a controller, the high voltage generator  130  boosts alternating current (AC) power thus to supply it to the magnetron  120 . Then, the magnetron  120  is oscillated by the high voltage thus to generate electromagnetic wave having a high frequency. The electromagnetic wave is emitted into the resonator  150  through the wave guide  140 , and continuously excites the discharge material and the discharge catalyst material filled in the bulb  160  into a plasma state. As the result, light having a specific emission spectrum is generated, and the light is forwardly reflected by the reflector  170  and the dielectric mirror  180  thus to illuminate a space. 
     The dielectric mirror  180  is formed of a ceramic material having a high diffusion reflection ratio for visible rays without a reflection coating layer. Accordingly, light generated from the bulb  160  is effectively reflected, and the dielectric mirror  180  is not damaged by heat of a high temperature. As the result, an optical efficiency of the dielectric mirror  180  is not degraded even if it is used for a long time. 
     The dielectric mirror may not be provided at all. In this case, the resonator positioned at a rear side of the bulb or a surface of the wave guide received in the resonator is partially polished precisely so as to effectively reflect light generated from the bulb. 
     As shown in  FIG. 5 , instead of using the dielectric mirror for forwardly reflecting light generated from the bulb  260  in a backward direction, an electromagnetic wave guiding plate  290  is used as a reflection surface thereby to forwardly reflect light generated from the bulb  260  in a backward direction. 
     The electromagnetic wave guiding plate  290  is provided with an electromagnetic wave passing hole  291  for connecting the wave guide  240  and the resonator  250  to each other at a center thereof. Also, a fixing portion  292  having the electromagnetic wave passing hole  291  and protruding with a certain height so as to fix the reflector  270  at an outer circumferential surface thereof is formed at the electromagnetic wave guiding plate  290 . 
     The electromagnetic wave passing hole  291  can be formed so that an outer circumferential surface thereof can be in contact with an inner circumferential surface of the fixing portion  292 . Also, as shown in  FIG. 5 , the electromagnetic wave passing hole  290  can be formed so that an outer circumferential surface thereof can be further provided with a reflection surface  293  having a certain width at an inner circumferential surface of the fixing portion  292  so as to forwardly guide light reflected to a lower end of the fixing portion  292 . As shown in  FIG. 5 , the reflection surface  293  can be formed to be perpendicular to the fixing portion  292 . 
     Also, as shown in  FIG. 6 , the reflection surface  293  can be formed to be inclined with the fixing protrusion with a certain inclination angle so as to control a reflection angle of light. That is, the electromagnetic wave guiding plate  290  includes a covering portion  294  that covers the outlet of the wave guide  240  and the fixing portion  292  extending from an upper surface of the fixing portion  294  by a predetermined height with a ring shape so as to accommodate the electromagnetic wave passing hole  291  therein, and having the resonator  250  coupled thereto. The reflection surface  293  is integrally formed between an upper surface of the covering portion  294  and an inner circumferential surface of the fixing portion  292  so as to forwardly reflect light backwardly generated from the bulb  260 , and the reflection surface  293  is formed with an inclination toward the upper surface of the covering portion  294  from the inner circumferential surface of the fixing portion  292 . 
     An unexplained reference numeral  210  denotes a casing,  211  denotes an air inlet,  212  denotes an air outlet,  213  denotes an air flow path,  220  denotes a magnetron,  230  denotes a high voltage generator,  261  denotes a light emitting portion,  262  denotes a supporting portion, F denotes a cooling fan, M 1  denotes a bulb motor, and M 2  denotes a fan motor. 
     As aforementioned, in the present invention, the electromagnetic wave guiding plate is used to in order to forwardly reflect light generated from the bulb in a backward direction instead of the dielectric mirror. Accordingly, a production cost and an assembly cost for the dielectric mirror can be saved. Also, the size of the plasma lighting system can be reduced by lowering the height of the fixing protrusion. 
     As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.