Abstract:
An electrodeless lamp ( 10 ) for producing an intense beam of light includes a concave lamp body ( 11 ) that surrounds the lamp interior. A gas, such as sulfur or selenium or compounds thereof, is contained within the lamp body ( 11 ) for forming a plasma light source. The concave lamp body ( 11 ) has a reflecting surface ( 12 ). Electrodes ( 27, 28 ) are disposed external to the lamp body for producing radio frequency energy exciting the gas. A heat resistant glass plate ( 20 ) seals the concave lamp body ( 11 ). A frit seal ( 23 ) can be used for forming a pressure and temperature resistant seal between the concave lamp body ( 11 ) and the glass plate ( 20 ). The light beam generated by the plasma exists through the glass plate ( 20 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a national stage application of PCT/US97/22304, filed Dec. 16, 1997, and a con of U.S. application Ser. No. 08/771,757, filed Dec. 20, 1996, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a high temperature, high efficiency lamp apparatus with an improved, frit sealed ceramic housing that produces a beam of light using a fill contained under pressure within the lamp housing interior that is energized with externally placed electrodes for vaporizing the gas to form a plasma. More particularly, the present invention relates to a projecting system that features a high temperature electrodeless lamp in which light energy is generated by a plasma contained inside a frit sealed ceramic body or housing that has a concave reflector surface surrounding the lamp body interior. 
     2. Description of the Related Art 
     High power lamps are used for illumination applications beyond typical incandescent and fluorescent lamps. One type of lamp known as a high intensity discharge (HID) lamp consists of a glass envelope which contains electrodes and a fill which vaporizes and becomes a gas when the lamp is operated. 
     Recently, a patent issued for a high power lamp that utilizes a lamp fill containing sulfur or selenium or compounds of these substances. U.S. Pat. No. 5,404,076, issued to Dolan, et al., and entitled “Lamp Including Sulfur” discloses an electrodeless lamp utilizing an excited fill. The Dolan, et al., U.S. Pat. No. 5,404,076 is incorporated herein by reference. 
     Projecting systems are used to display images on large surfaces, such as movie or television screens and computer displays. For example, in a front projection system, an image beam is projected from an image source onto the front side of a reflection-type angle transforming screen, which then reflects the light toward a viewer positioned in front of the screen. In a rear projection system, the image beam is projected onto the rear side of a transmission-type angle transforming screen and transmitted toward a viewer located in front of the screen. 
     In prior co-pending U.S. patent application Ser. No. 08/581,108, entitled “Projecting Images,” to Knox, filed Dec. 29, 1995, now abandoned there is disclosed a method of displaying an optical image by projecting the image along an optical path and at an optical device interposed across the optical path, at one time reflecting the image from the optical device and at a different time permitting the image to pass through the optical device to be displayed. U.S. patent application Ser. No. 08/581,108, filed Dec. 29, 1995, now abandoned is incorporated herein by reference. A projection system for such a display is disclosed in U.S. application Ser. No. 08/730,818, entitled “Image Projection System Engine Assembly,” to Knox, filed Oct. 17, 1996, which is hereby incorporated by reference. 
     The image source for a projection system employs a light that must be of high intensity and preferably very efficient. Such a light is disclosed in U.S. patent application Ser. No. 08/747,190, entitled “High Efficiency Lamp Apparatus for Producing a Beam of Polarized Light,” to Knox, et al., filed Nov. 12, 1996, now U.S. Pat. No. 5,833,360 which is hereby incorporated by reference. If an optical image is to be displayed by projection, it sometimes passes through an optical device interposed across the optical path. In the projection system of prior co-pending application Ser. No. 08/581,108, filed Dec. 29, 1995, one or more optical devices reflect the image at one time from the optical device and at a different time permit the image to pass through the optical device to be displayed. There will be a decrease in light intensity once the optical image strikes the optical device interposed across the optical path. Therefore, in projection systems where an optical device is interposed across the optical path there is a need for a projection engine with a high intensity light of improved efficiency. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved high efficiency lamp apparatus for producing an intense beam of light using a plasma light source. The apparatus includes an electrodeless lamp body, preferably of ceramic or like heat resistant material. The lamp body has a concavity that surrounds a lamp interior. 
     A clear glass plate seals one end portion of the housing. A fill is contained within the lamp body interior. The fill is preferably sulfur or selenium or a combination thereof that can be excited to form a plasma light source. 
     The lamp body provides a concavity with a reflective surface thereon. Electrodes are positioned externally of the lamp body for producing radio frequency (or RF or Microwave) energy that enables the gas in the lamp body cavity to be excited and form the plasma light source that generates intense heat (about 800° C. to 1200° C.) and an intense light beam. As used herein, the term radio frequency means a frequency range sufficient to excite a fill in the bulb (e.g., about 150 MegaHertz to about 10 GigaHertz, or other suitable frequency. 
     The clear (e.g., glass, quartz, sapphire, or any optically clear material) plate seals the gas within the interior of the housing and allows light to escape the housing. 
     A frit seal can be used for a connection between the lamp body at its peripheral edge and the periphery of the glass lens. The glass lens is preferably a quartz plate or like material that is clear and which can withstand high temperature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein: 
     FIG. 1 is a sectional elevational view of a first embodiment of the lamp apparatus of the present invention; 
     FIG. 2 is a sectional elevational view of a second embodiment of the lamp apparatus of the present invention; 
     FIG. 3 is a sectional elevational view of a third embodiment of the lamp apparatus of the present invention; 
     FIG. 4 is sectional elevational view of a fourth embodiment of the lamp apparatus of the present invention; 
     FIG. 5 is a partial perspective view of the fourth embodiment of the lamp apparatus of the present invention; 
     FIGS. 6-7 are sectional elevational views of the fifth and sixth embodiment of the apparatus of the present invention showing additional seal geometries; 
     FIGS. 8A and 8B are a sectional elevational view showing an alternative seal; and 
     FIGS. 9 and 10 are side views of a system suitable for use of the apparatus according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows generally the first embodiment of the apparatus of the present invention designated generally by the numeral  10 . Lamp apparatus  10  includes housing or body  11  having inner concave surface  12  and outer convex surface  13 . Housing  11  provides an open end portion surrounded by annular flange  14  having inner flat surface  15  and outer surface  16 . Annular shoulder  17  extends from annular flange  14 . Annular shoulder  17  has inner surface  18  and outer surface  19 . Housing  11  is preferably ceramic. 
     Clear circular plate  20  is preferably of an optically clear material that is heat resistant such as glass, quartz, or sapphire. Plate  20  is connected to lamp housing  11  at annular flange  14  and annular shoulder  17 . Circular plate  20  has inner surface  21  and outer surface  22 . 
     The connection between lamp housing  11  and circular plate  20  is perfected using frit seal  23  that is positioned in between annular flange  14  at surface  15  and circular plate  20  as shown in FIG. 1. A frit seal is a seal made by fusing together glass powders with a glass binder. However, seal  23  can also be a brazing seal or a direct bond type seal  120  (see FIG.  8 A), melting the glass or a clear ceramic such as sapphire to the ceramic. Seal  23  could also be formed by metalizing that portion of the ceramic housing  11  and that portion of the plate  20  at the joint, then welding metal  121  to metal  122  at the metalized coatings (see FIG.  8 B). A connection  30  is formed between plate  20  and housing  11 . 
     An interior space  24  is defined by the concavity of housing  11  and circular plate  20 . Interior  24  contains a fill medium such as a sulfur or selenium fill, or compounds of these substances. The gas contained within interior  24  is a fill that can be excited using radio frequency energy, for example, to form a plasma light source  25 . 
     Electrodes  27  and  28  are shown in FIG. 1, positioned externally of lamp housing  11  and spaced away from the outer surface  13  of housing  11 . Electrodes  27 ,  28  are thus not subjected to the intense heat of plasma light source  25 . 
     Reflecting surface  12  can be a high reflectivity ceramic surface, preferably a diffuse reflection (e.g., white ceramic). This produces a collimating lamp apparatus  10  that generates light rays  29  that are generally parallel. A variety of shapes are possible other than the curved shape of housing  11  and square shape of housing  32  of FIG.  2 . Different shapes can be employed to force the plasma itself into different shapes or to provide different sealing properties between the clear material and the ceramic. 
     FIG. 2 discloses a second embodiment of the lamp apparatus of the present invention, designated generally by the numeral  31 . Lamp apparatus  31  provides a housing  32  that has cylindrically shaped side wall  33  and flat circular end wall  34  that are integrally formed. Housing  32  can be of a heat resistant material such as ceramic. 
     Inside flat surface  35  is provided at circular end wall  34 . Cylindrical shaped inner surface  36  is formed at cylindrically side wall  33 . Outer surfaces  37 ,  38  are also shown in FIG. 2 as being respectively circular and cylindrical in shape. 
     Lamp housing  32  has an open end  39  that is covered with a circular filter  40 , such as a polarizing filter. Circular filter  40  has a peripheral surface  41  that forms a connection at  42  with lamp housing  32 . Filter  40  has an inside surface  43  and an outer surface  44 . Inside surface  43  connects to peripheral surface  41  of housing  32  at connection  42 . Connection  42  preferably includes a frit seal. However, seal  42  can also be a brazing seal or a direct bond type seal, melting the glass to the ceramic. Seal  42  could also be formed by metalizing that portion of the ceramic housing  32  and that portion of the filter  40  at the joint, then welding metal to metal at the metalized coatings. A connection  30  is formed between filter  40  and housing  32 . 
     A second plate  45  is positioned in between a plasma light source  47  and a filter  43 . Plate  45  is preferably an optically clear plate of high temperature resistant material, such as quartz, sapphire, or the like. Connection  46  designates a connection between plate  45  and cylindrical inner surface  36  of housing  32 . 
     Plasma light source  47  is formed within an interior  51  of housing  32 . Interior  51  contains a fill (such as sulfur, selenium, or compounds thereof) that can be excited to form plasma light source  47 . Plasma light source  47  is not a well defined ball, but occupies the central area of interior  51 . 
     A pair of electrodes  49 ,  50  provide radio frequency energy that can excite the gas with interior  51  to form plasma light source  47 . Interior  52  of housing  32  is that space between filter  43  and glass plate  45 . Interior  52  is filled with a gaseous substance that forms an insulation layer between plate  45  and plate  43 . 
     Plate  43  can be a polarizing film filter that may not be able to withstand the intense heat generated within interior  51  of lamp housing  32 . Therefore, insulating gaseous layer  52  is provided in between plates  43  and  45  to prevent heat damage to film plate  43 . Light rays  53  are shown in FIG. 2 as being emitted from lamp housing  32 , passing through glass plate  45  and filter  43 . In the embodiment of FIG. 2, the light  53  is polarized having passed through the polarizing filter  43 . 
     In FIG. 3, a third embodiment of the apparatus of the present invention is shown, designated by the numeral  54 . Lamp apparatus  54  has cylindrical housing  55 , that includes flat circular end wall  56 , inside flat surface  57 , inside cylindrical surface  58 , and outer surface  59 . The surfaces  57 ,  58  define with circular plate  62  an interior  60  for containing a fill that can be excited (such as sulfur or selenium gas or compounds thereof) to form plasma light source  73 . Lamp housing  55  has open end  61  that is covered by circular plate  62 . Plate  62  has inner surface  70  and outer surface  71 . 
     Housing  55  provides peripheral flange  63  and annular shoulder  64 . Flange  63  has inner surface  65  and outer surface  66 . Annular shoulder  64  has outer surface  67  and inner surface  68 . Frit seal  69  forms a seal in between plate  62  and annular flange  63 . A connection  72  is formed in between the annular shoulder  64  and plate  62 . 
     Plasma light source  73  is formed within gas containing interior  60  by energy from electrodes  75 ,  76 . Electrodes  75  and  76  are shown in FIG. 3 positioned externally of the lamp interior so that they are not subjected to the intense heat generated by plasma light source  73 . Light rays  77  are shown exiting lamp apparatus  54 . 
     In FIGS. 4 and 5, a fourth embodiment of the apparatus of the present invention is shown designated by the numeral  78 . Lamp apparatus  78  includes a housing or body (preferably ceramic)  79  having a concave reflective surface  80 , an outer convex surface  81  and an interior  82 . Interior  82  contains a fill medium such as sulfur, selenium, or compounds thereof, that can be excited to form a plasma light source  83 . 
     Electrodes  85  and  86  are positioned externally of lamp housing  79  so that they are not subjected to the intense heat of plasma heat source  83 . Peripheral flange  87  is provided having outer surface  88  and inner surface  89 . Clear plate  90  can be of a heat resistant glass such as quartz. Plate  90  has outer surface  91  and inner surface  92 . Peripheral edge  93  of clear plate  90  forms a connection at  94  with lamp housing  79 . Frit seal  95  is positioned in between lamp housing  79  and plate  90  as shown in FIG.  4 . Lamp housing  79  provides flat peripheral surface  96  that forms a connection with reflector  97 . Reflector  97  also has a flat corresponding surface  98  that forms a connection with flat surface  96 . Reflector  97  has peripheral edge  99  with recess  100  that receive filter  101 . Filter  101  has peripheral edge  102  that forms a connection with shade  97  at recess  100 . 
     FIGS. 6 and 7 show additional geometries for the frit seal type seal of FIG.  3 . In FIG. 6, an alternate version of the apparatus  54  of FIG. 3 is shown with a different seal configuration. Lamp  104  is constructed as lamp  54  in FIG. 3 but for the seal geometry. In FIG. 6, housing  105  is shaped as housing  55  in FIG.  3 . However, the members  63 ,  64  differ in geometry. Housing  105  has a seal arrangement that includes a frit seal  110  positioned in between the plate  109  in FIG. 6 (that corresponds to the plate  62  of FIG. 3) and the plurality of flanges  106 ,  107 ,  108 . The flanges  106 ,  107 ,  108  form a C-shaped annular member that receives the seal  110 . 
     In FIG. 7, plate  116  corresponds to the plate  62  in FIG.  3 . The housing  113  corresponds to the housing  55  of FIG. 3, but differs in geometry at the seal  116 . In the embodiment of FIG. 7, lamp  112  includes a housing  113  having annular flanged portions  114 ,  115  that intersect at about ninety degrees relative to one another. A seal  117  can be a frit seal positioned in between annular edge  118  of annular flange  115  and the peripheral edge  119  of plate  116 . Each of the seals of FIGS. 6 and 7 can be frit seals or brazed or welded. If welded, the surfaces of housings  105 ,  113  and the surfaces  109 ,  116  are first metalized so that metal to metal surfaces are provided for welding. 
     FIGS. 9 and 10 show a rear projection video system  260  that includes a linear reflecting polarizer  262  and an achromatic retarder  264  that allow light in a projected image  266  to reflect from a display screen  268  at one instance and to pass through the screen  268  at another instance. This allows for “optical folding,” which allows the video system  260  to be very shallow yet project a large image, as described in the previously incorporated U.S. patent application entitled “Projecting Images.” For the video system  260  to work properly, the image source  276  must produce polarized light. A wide variety of other types of video systems employ polarization in image formation. 
     Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.