Abstract:
This invention relates to a microwave oven lighting assembly. The lighting assembly has a LED lamp and one or more light-guiding members to collect and to condense the light of the lamp; the lighting assembly is placed outside of the microwave oven cavity, casting the light into the cavity through holes on the cavity wall. The invention requires significantly less energy consumption and provides greatly enhanced oven cavity illumination.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    None. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates, in general, to a lighting assembly and a method for improving lighting of microwave ovens. More particularly, the present invention relates to improved lighting assemblies and the placement of said sources in microwave cavities for increased lighting intensity and improved viewing of the oven contents during cooking 
       BACKGROUND OF THE INVENTION 
       [0003]    Today, microwave ovens are a common household item found in nearly every home of the industrialized world and have become indispensible to our modern life. These household appliances have become popular because of their convenience and relative small sizes. Typically, a microwave oven comprises a cooking chamber (or oven cavity) for receiving food to be cooked and a door with a viewing window for monitoring the food during the cooking process. 
         [0004]    To monitor the food during cooking, the cooking chamber must be adequately illuminated. Prior art microwave ovens typically uses a tungsten filament appliance light bulb which provides poor illumination. In order for people to protect the filament from the microwave some structures such as an iron screen have to be installed between the bulb and the food chamber (or the microwave oven cavity), thus deteriorating the already poor viewing conditions. It is also impractical and expensive to simply adopt high power bulbs in conventional microwave ovens for daily use. 
         [0005]    U.S. Pat. No. 5,712,468 teaches an illuminating system that uses microwave-resistant quartz halogen lamps located in the food chamber. Halogen lamps must operate at higher temperatures, which makes their quartz envelope vulnerable to oils and other contaminants. Moreover, in order to achieve adequate lighting, the power required to drive the halogen lamp and the associated transformer are substantial, which reduces the amount of power available for cooking 
         [0006]    The known microwave oven illumination devices are not capable of providing sufficient light because of protective yet intrusive structures for the light bulbs while still suffering from low lighting efficiency. These problems have remained unsolved. Therefore, there still exists a need for an improved microwave illuminating system that is energy efficient and capable of providing adequate lighting to the cooking chamber (or the microwave oven cavity). 
       SUMMARY OF THE INVENTION 
       [0007]    The inventors of the present invention have recognized that what is needed in order to solve the above mentioned problem is to provide a differential high-illumination low energy-consumption light source and deliver the light from the light source efficiently into the microwave oven cavity. 
         [0008]    Accordingly, one aspect of the present invention is directed to a lighting assembly capable of efficiently collecting light from a light source and projecting the light to illuminate a designated surface area or volume of space in a microwave oven. Embodiments of lighting assemblies in accordance with this aspect of the present invention will generally include a lamp for generating light; and a lamp-front assembly comprising one or more light-guiding member(s) integrated for collecting, condensing, and distributing light generated by the lamp. In some preferred embodiments, the lamp-front assembly will have a light-receiving end, a light-exiting end, and a bulging section connecting the light-receiving end and the light-exiting-end. The lamp is embedded in the light-receiving-end of the lamp-front assembly, The portion of the lamp-front assembly from the light-receiving end to the bulging section is configured to collect light generated from the lamp, whereas the portion from the bulging section to the light-exiting end has a tapered shape to condense and distribute light to the designated surface area or volume of space. 
         [0009]    In a preferred embodiment, the lamp is a light emitting diode (LED). In other preferred embodiments, the light-guiding member(s) are single-piece lenses. In still some preferred embodiments, at least one of the single-piece lenses is a total internal reflection (TIR) lens. 
         [0010]    In some preferred embodiments, the light-exiting end of the lamp-front assembly has a concaved shape. In some other embodiments, the lamp-front assembly comprises a first lens forming the portion of the lamp-front assembly from the light-receiving end to the bulging section for light collection, and a second lens forming the portion of the lamp-front assembly from the bulging section to the light-exiting end, the second lens having a tapered shape for light condensing and distributing. The lenses are seamlessly connected to each other at the bulging section. 
         [0011]    Another aspect of the present invention is directed to a microwave oven equipped with one or more lighting assembly of the present invention as described above. Microwave ovens in accordance with this aspect of the present invention will generally have a cooking chamber defined by a top wall, a bottom wall, three side walls and a door; and one or more lighting assembly as described above. The lighting assemblies are each positioned behind an aperture disposed on the top wall allowing light to be projected therethrough into to the cooking chamber. 
         [0012]    In a preferred embodiment, the microwave oven has two light assemblies each configured to project a spot light. The light assemblies are positioned on the opposite ends of the top wall and angled towards the center of the cooking chamber such that the spot lights from each of the two lighting assemblies substantially overlap so as to substantially eliminate shadows casted by each other when an object is placed in the region illuminated by the spot lights. 
         [0013]    Yet another aspect of the present invention is directed to a method of forming a microwave oven with improved illumination for its cooking chamber. Microwave ovens formed by methods of the present invention will generally have a cooking chamber defined by a top wall, a bottom wall, three side walls and a door. Methods in accordance with this aspect of the invention will generally include the steps of placing a lighting assemblies behind an aperture disposed on one of the walls of the microwave oven&#39;s cooking chamber. The lighting assemblies used are as described above. In a preferred embodiment, the method further includes a step of angling the lighting assembly towards the center of the bottom wall. In another preferred embodiment, the method further includes a step of forming two apertures positioned on the opposite ends of the top wall; and place a light assembly as described above behind each of the aperture. In still another preferred embodiment, the method further include a step of configuring the light assembly to cast a spot light towards the center of the cooking chamber. 
         [0014]    One advantage of the present invention is that because the lamp is included in the lighting assembly, and the lighting assembly is placed outside of the microwave oven cavity, the lamp is prevented from being exposed to microwaves which obviates the need for a protective metal mesh as required in prior art devices. At the same time, the light can be directed from the lamp into the cooking chamber in any desired angles without structural hindrance. Such a lighting assembly is also referred to herein as a “focalizer” and the light-guiding members as “lenses”. 
         [0015]    The focalizer form a stand-alone optical design capable of accommodating any kind of lamp commonly known in the art, but is preferably coupled with a light emitting diode (LED) as the lighting source. 
         [0016]    The focalizer can have any desired number of lenses. Two lenses, one for light collecting and the other for light condensing and distributing, have proven to be advantageous, however. The lens for light collecting is referred to hereinafter as a “collector lens” and the lens for light condensing and distributing as “a condenser lens”. 
         [0017]    In particular embodiments of the invention, the collector lens may be a total internal reflection (TIR) lens and the condenser lens may be cone-shaped with a flat-top tip. The two lenses are placed in tandem so the light is collected by the TIR lens and conveyed to the condenser lens and then distributed through the flat-top surface. The flat-top surface of the condenser lens may be advantageously concave, to better distribute the light. 
         [0018]    In other particular embodiments of the invention, the collector lens and the condenser lens can be molded into one integral piece in order to minimize the light loss during the conveyance from one lens to another. 
         [0019]    The focalizer can illuminate the microwave oven cavity from any location of the oven walls. An overhead installation of the focalizer right above the microwave door is most advantageous, however. The focalizer can be tilted towards the center of the cavity floor. Any desirable number of focalizers can be adopted for a microwave oven but two focalizers are found to be advantageous. 
         [0020]    Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  shows a prior art microwave equipped with a conventional incandescent lamp located in the cavity behind a protective metal mesh. 
           [0022]      FIG. 2  shows a schematic view of one embodiment of the lighting assembly. 
           [0023]      FIG. 3  A-B show the back view, and the front view, respectively, of one embodiment of the lighting assembly. 
           [0024]      FIG. 4  shows light paths and range of illuminating angle emanating from one embodiment of the lighting assembly. 
           [0025]      FIG. 5  shows a schematic view of a second embodiment of the lighting assembly. 
           [0026]      FIG. 6  shows an exemplary positioning configuration of one embodiment of the lighting assembly in a microwave oven cooking chamber. 
           [0027]      FIG. 7  shows a front perspective view of the positioning configuration of one embodiment of the lighting assembly in a microwave oven cooking chamber. 
           [0028]      FIG. 8  shows the enlarged positioning configuration of the embodiment of the lighting assembly in the microwave oven cooking chamber. 
           [0029]      FIG. 9  illustrates an exemplary illumination pattern in the positioning configuration of one embodiment of the lighting assembly in a microwave oven cooking chamber. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1  shows an example of a prior art lighting devices for microwave ovens. The device is a typically small, tungsten filament appliance light bulb (about 25 watts) which radiates about 200 lumens. The life expectancy of such light bulbs are normally around 200 hours. However, these light bulbs are vulnerable to microwaves because microwave energy is capable of heating the tungsten filament to destructive levels. For example, in a typical 25 watt light bulb operating on 120 volts AC, it will draw about 0.2 amperes. But when the light bulb&#39;s filament is exposed to microwaves, additional current may be induced, which can push the total current flowing through the filament to exceed its rated value, causing the filament to quickly burn out. This problem is made worse if the bulb is used in one of the newer combination microwave/convection ovens in which the temperature within the oven can rise to as high as 400° F. At this temperature, the heating effects of the microwave in addition to the heating effects of the AC current supply can quickly raise the filament temperature above its rated value. 
         [0031]    As illustrated in  FIG. 1 , to address this problem prior art microwaves hide the appliance light bulb in a small cavity formed in one of the walls of the cooking chamber and cover it with a screen to prevent microwave energy from reaching the bulb filament. Unfortunately, such a placement of the bulb causes a severe reduction in the amount of illumination reaching the cooking chamber. For example, only a small fraction of the generated light from the bulb will actually reach the screen. The protective shield will further cut the amount of transmitted light to about half of the light that falls on the screen. As a result, only about four percent of the light generated from the light bulb actually reaches the oven cavity. Much of this remaining light is lost in the cavity via absorption by the oven walls and oven contents so that the result is a very dimly lit cavity. To make the matter worse, viewing windows provided on the access doors for microwave ovens also are equipped with microwave-impervious screens, which further reduce the amount of the light that can pass through the window for viewing. The end result is that in a typical prior art oven employing a 25 watt light bulb, only less than 0.3 foot-candles of light will actually exit the oven through the oven window. This level of light is far below the minimum required for a user to accurately discern forms and colors. 
         [0032]    To achieve good color rendition, a light source should produce a spectral continuum with visual intensities of about 10 candle power. Although high temperature incandescent light bulbs are capable of producing this level under normal conditions, when light intensity is low, true colors cannot be detected by human eyes. In particular, when the light intensity is below 10 foot-candles of light, human vision becomes unable to detect true colors. At about 0.5 foot-candles, human vision is essentially color blind. 
         [0033]    U.S. Pat. No. 5,712,468 issued to Ace (1998) discloses a system that uses quartz halogen lamps located at the front of the oven or near the top instead of in a separate chamber. It also proposes using lamps with shorter and thicker filaments that can withstand exposure to microwave or filament-less lamps such as point-source gas discharge or arc lamps. However, halogen lamps must operate at higher temperatures which makes their quartz envelope vulnerable to oils and other contaminants. For example, oil from human fingertips or food can create a hot spot on the bulb surface when the bulb is turned on. The localized hot spot will cause the quartz to change from its vitreous form into a weaker crystalline form that leaks gas. To avoid contamination, additional protected shields must be used, which in turn reduces the efficacy of the lamps&#39; illuminating power, rendering the device more complex and expensive to manufacture. Moreover, in order to achieve adequate lighting, the power required to drive the halogen lamp and the associated transformer are substantial, which reduces the amount of power available for cooking 
         [0034]    The known microwave oven lighting devices are not capable of providing sufficient light because of protective yet intrusive structures for the light bulbs, as well as their low lighting efficiency. As noted above, it remained for the present invention to recognize the need to make microwave oven lighting devices more powerful without the increasing expense of extra electricity usage and whose manufacture provides numerous benefits, as detailed hereinabove. Indeed, the incandescent light bulb in  FIG. 1  consumes 20 watts and radiates only 200 lumens and of that amount, only a remnant (4%) reaches the oven cavity. 
       FIG.  2 - 4 —A First Preferred Embodiment 
       [0035]      FIG. 2  depicts an exemplary lighting assembly, or “focalizer,”  24 .  FIG. 7  illustrates the usage of said focalizer, embodying the principles of the present invention that provide a light source of high-illumination and low energy-consumption, and a high-efficiency light-delivering system for conveying the light into the microwave oven cavity via an aperture on the wall. Our assembly brings much more light into the oven cavity compare to those of prior art lighting assemblies and is easy to manufacture. It essentially prevents the lamp from being exposed to microwaves and obviates the need for a protective metal mesh. 
         [0036]    As shown in  FIG. 2 , the focalizer  24  comprises an LED  22 , a light-collecting lens (or collector lens)  21 , and a light-distributing lens (or condenser lens)  23 . The collector lens  21  and the condenser lens  23  form a lamp-front assembly. The focalizer  24  has a generally streamlined shape like a fish where the LED  22  is the mouth, the collector lens  21  the rest of the head, and the condenser lens  23  the body. The three parts are connected in tandem closely. 
         [0037]    In this embodiment, the LED  22  is a lamp with 100 lumens output and operational at 3.2-3.6V, 350 mA, 1W. Most of the LED  22  body is enveloped by the collector lens  21  for maximal light collection but the basal part of the LED  22  is exposed outside for heat dissipation. 
         [0038]    The collector lens  21  is a bowl-shaped lens and has a base  27  and a distant end  29  with bigger diameter. The distant end  29  has a round flat surface. The collector lens base  27  is a light-receiving end, configured to accommodate and attach the LED  22 . The LED  22  is simply clipped onto the base  27  without the need for extra materials. The bulb of the LED  22  is entirely enveloped by the collector lens  21 . In this way the light leakage from the assembly is minimized. Viewed from outside, only the rear end of the LED  22  is exposed for heat dissipation, as shown in  FIG. 3A . 
         [0039]    The surrounding side surface of the collector lens  21  has a property of total internal reflection (TIR), and the collector lens  21  is a total internal reflection (TIR) lens. The collector lens  21  can reduce light from escaping and direct the received light with an efficiency of over 96%. One of skill in the art would recognize that a TIR lens may be constructed using the techniques currently used in optics design. 
         [0040]    The condenser lens  23  is a cone-shaped lens but the tip of the cone is cut. The condenser lens  23  comprises a base  31  and a discharging end  25 . The base  31  has a round flat surface with the same area with the distal end  29  of the collection lens  21 , which enables the base  31  to exactly match with the distal end  29  of the collection lens  21 . In this way the condenser lens  23  is seamlessly coupled (or integrated) with the distal end  29  of the collection lens  21 . 
         [0041]    The discharging end  25  is a light-exiting end for distributing the light into the microwave oven cavity. To protect the LED  22  from microwaves, the discharging end  25  has a substantially small surface (only one quarter of the plane area of the base  31 ), as shown in  FIG. 3B . The small surface of the discharging end  25  greatly decreases the microwave leakage. Additionally, the surface of the discharging end  25  is a round concave surface, in order for the light to be fanned out maximally. 
         [0042]    In this embodiment, the collector lens  21  and the condenser lens  23  are made of Poly(methyl methacrylate) (PMMA), a transparent thermoplastic. The lenses are single-piece constructions molded, cast, or machined from PMMA. With the disclosure, one of skill in the art would construct the lenses using the techniques currently used in the art. 
         [0043]    The three parts of the focalizer  24 , e.g. the LED  22 , the collector lens  21  and the condenser lens  23 , are bonded together tightly. Since the collector lens base  27  is configured to attach to the LED  22 , the LED  22  simply clips on to the collector lens  21 . The collector lens distant end  29  and the condenser lens base  31  can be permanently glued together. There is nothing substantial in the interface of the two lenses  21  and  23 . 
         [0044]      FIG. 4  shows the light path of the focalizer  24  in this embodiment. As the light rays emanate from the LED  22  and enter the collector lens  21  through the base  27 , the surrounding side surface of collector lens  21  takes advantage of its TIR properties to collect the light rays. After that, the light rays are reflected towards the distant end  29  and enter the condenser lens  23  through the base  31 . The light rays are condensed to some degree in the distribution lens  23  before passing through the discharging end  25 . Lastly the light rays enter the microwave cavity and are distributed at an approximate angle of 90°. 
       FIG.  5 —A Second Preferred Embodiment 
       [0045]    In a second exemplary embodiment of the lighting assembly, the focalizer has one integral lens in order to minimize any loss during the light relaying process, as well as to make simpler the manufacture of the lighting assembly. 
         [0046]      FIG. 5  shows a schematics illustration of a focalizer  100  according to the second embodiment of the lighting assembly. The focalizer  100  differs from the focalizer  24  in the first embodiment in that the lens is molded in one piece and functions as a combination of the collector lens  21  and the condenser lens  23  of the first preferred embodiment. Specifically, the focalizer  100  comprises a LED  122  and a lens  133 . The LED  122  is a lamp with 100 lumens output and operational at 3.2-3.6V, 350 mA, 1W. Most of the body of LED  122  is enveloped by the lens  133  for maximal light collection but the basal part of the LED  122  is exposed for heat dissipation 
         [0047]    The lens  133  is a stand-alone lamp-front assembly and spindle-shaped. It has a base  127  and a discharging end  125 , with a bulging section  135  in the middle. The portion from the base  127  to the bulging section  135  is gradually bulging out for collecting the light, identical to the collector lens  21  in the focalizer  24 . The portion from the bulging section  135  to the discharging end  125  is tapering for condensing and distributing the light, identical to the condenser lens  23  in the focalizer  24 . 
         [0048]    Identical to the base  27  in the focalizer  24 , the base  127  is a light-receiving end, configured to accommodate and attach the LED  122  so that the bulb of the LED  122  is entirely enveloped by the lens  133 . The LED  122  is simply clipped onto the base  127  without the need for extra materials. In this way the light leakage from the assembly is minimized. Viewed from the outside, only the rear end of the LED  122  is exposed for heat dissipation. 
         [0049]    For the part from the base  127  to the bulging section  135 , the surrounding side surface has a property of total internal reflection (TIR), identical to the collector lens  21 . One of skill in the art would recognize that such a feature as TIR may be constructed into the lens using the techniques currently used in the art. 
         [0050]    For the part from the bulging section  135  to the discharging end  125 , the lens is tapered, i.e. gradually becoming narrower. Identical to the discharging end  25  in the focalizer  24 , the discharging end  125  is a light-exiting end for distributing the light into the microwave oven cavity, and has a relatively small surface area (approximately one quarter of the plane area of the bulging section  135 ). The small surface area of the discharging end  25  advantageously decreases the microwave leakage around it. Identical to the discharging end  25  in the focalizer  24 , the surface of the discharging end  125  is a round concave surface, in order for the light to be maximally fanned out. 
         [0051]    Identical to the collector lens  21  and the condenser lens  23  in the focalizer  24 , the lens  133  is made of PMMA. The lens can be molded, cast, or machined from a single-piece construction of PMMA. With the disclosure, one of skill in the art would construct the lenses using the techniques currently used in the art. 
         [0052]    The light path of the focalizer  100  (omitted in the drawings) is identical to that of the focalizer  24 . As the light rays emanate from the LED  122  and enter the lens  121  through the base  127 , the surrounding side surface of collector lens  121  acts with TIR properties and is able to collect the light rays. After that, the light rays are reflected towards the discharging end  125 . The light rays are condensed to some degree in the lens  133  as the lens  133  gradually tapers before passing through the discharging end  125 . Lastly the light rays enter the microwave cavity and are distributed at an approximate angle of 90°. 
       FIG.  6 - 8 —Operation 
       [0053]    The positioning configuration and the illumination pattern of conventional incandescent bulbs in the microwave oven cavity are shown in  FIG. 1 . The conventional incandescent bulb used in the microwave oven is placed inside the side walls, covering by a metal mesh, so the illuminating angle is limited and the brightness is largely reduced. Due to the position of the light bulb, the illuminated area is limited in area and typically does not cover the whole oven. 
         [0054]    A cooking chamber (or microwave oven cavity) typically has a top wall, a bottom wall, three side walls and a door. In preferred embodiments, the focalizer is connected with electrical wires (omitted in the drawings), put behind the side wall of the microwave oven, and shoots light beams into the cooking chamber through a small hole (or an aperture) in the oven.  FIGS. 6-8  show one embodiment of the invention, which has two focalizers  24 , located within a microwave oven  26 . The microwave oven  26  has a door  28 , a top wall  37 , and a bottom wall  39 . The top wall  37  has an aperture  40 , behind which the focalizer  24  is installed. For this particular embodiment, the discharging end of the focalizer  24  is in the cooking chamber; the LED is behind the aperture  40 ; the body is fixed to the aperture  40  with permanent glue. The focalizers  24  are close to and overhead of the microwave door  28 , directing the light towards the center of the bottom wall (or the oven cavity floor)  39 . 
         [0055]    As shown in  FIGS. 6-8 , the light can be directed from the focalizers  24  into the microwave oven cavity in any desired angles without structural hindrance. The illumination pattern of this embodiment is shown in  FIG. 9 . The lightened area of the microwave cavity walls are roughly divided into three partitions: a first bright area  36 A, a second bright area  36 B, and an enhanced bright area  38 . The light rays emitted from two focalizers  24  are illuminating the target walls, each of them bringing brightness to the first bright area  36 A or to the second bright area  36 B. In the middle part of the oven cavity, however, the light rays overlap and then produce the enhanced bright area  38 , resulting in higher brightness. The light angle of this invention can be adjusted according to the size of the oven, thereby solving the problem of the single angle and small emitting angle of lighting systems in conventional microwave ovens. 
         [0056]    There are two main benefits of this design. First, it is easy to control illumination angles and light paths so that more light can reach desired areas, which results in high light energy utilization and an even illuminating effect, Second, light transmission is completed effectively in this way. Therefore, preferred embodiments can provide a method to illuminate regions where adequate lighting is difficult to achieve with conventional incandescent lamps due to constraints of the intended environment. 
         [0057]    A microwave with conventional incandescent bulbs as in  FIG. 1  may also be retrofitted with the lighting assemblies of this invention, positioning them at the two top corners near the access door. The two lights are placed in a crossfire pattern, emitting light to the center of the cavity floor (or the bottom wall). 
       Other Exemplary Embodiments 
       [0058]    In one or more embodiments according to the invention, other LED lamps are used, which have different output and are operational at certain voltages. Also used are other kinds of lamps or combination of other lamps, such as tungsten halogen lamps, xenon short arc lamps, metal halide lamps and derivatives of these technologies. These other lamp types can be used because the lighting devices of the present invention more efficiently provide light to the microwave oven cavity. Additionally, in one or more embodiments the base around the lamp (such as the bases  27  or  127  in the preferred embodiments) is enlarged and a plurality of lamps can be attached to the light-collecting lens. 
         [0059]    In one or more embodiments according to the invention, the focalizer has three or more lenses. The lenses are seamlessly attached with each other (or integrated) and work collectively for initial light-collecting and then light-condensing before casting the light into the microwave oven cavity. The lenses are bonded together with glue or using some means for physical binding. 
         [0060]    In one or more embodiments according to the invention, metallic reflectors are used for light-collecting and light-condensing, or in combination with the TIR or the condenser lenses in the preferred embodiments. 
         [0061]    In other embodiments in accordance with the invention, the material of the lenses is glass, polycarbonate, polystyrene, or some other kind of acrylic. The material should have high transmittance characteristics. The lenses are molded, cast, or machined in any desired way. 
         [0062]    In other particular embodiments in accordance of the invention, the surface of the discharging end (such as the discharging ends  25  or  125  in the preferred embodiments) is formed so that the light rays enter the microwave cavity and are distributed at an angle of any desired degree. 
         [0063]    In one or more embodiments according to the invention, other focalizers are used, such as the focalizer  100 . 
         [0064]    In one or more embodiments according to the invention, two focalizers are installed behind the walls as in the embodiment shown in  FIG. 7  but installed on the opposite positions of each other with the center of the oven cavity in the middle. The two focalizers are facing each other and the center of the cavity is the common focus of them so that the food placed on the cavity floor can be brightly illuminated and the shadows are eliminated. 
         [0065]    In one or more embodiments according to the invention, only one focalizer is used to illuminate the microwave oven cavity. The focalizer is placed in the middle of the space right above the cavity door. In other embodiments, more than two focalizers are used to illuminate the oven cavity. They are installed behind the surrounding walls and illuminate the cavity from multiple angles. The installation pattern can be modern and stylish. 
         [0066]    Each of these details provides particular advantages and can be implemented independently of the others. 
       Advantages 
       [0067]    The description above makes evident a number of main advantages of our high-efficiency low-energy-consumption lighting device for illuminating the microwave oven cavity: 
         [0068]    (a) The use of single-piece lenses makes the structure simple, the illuminating efficiency high, and the lighting pattern design adjustable, all of which can better light the microwave oven cavity and reduce the cost of the microwave oven manufacture. 
         [0069]    (b) The use of the LED as the light source in the preferred embodiments, provides high and even brightness of light and various lighting angles; high light energy efficiency, and effective energy saving; easy installation; compact size, simple structure, applicable to lighting the microwave oven of different sizes; the embodiments not only enable the microwave oven to have a better lighting distribution, but also decreases the complexity of the lighting subsystem. 
         [0070]    Although the present invention has been described in terms of specific exemplary embodiments and examples, it will be appreciated that the embodiments disclosed herein are for illustrative purposes only and various modifications and alterations might be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims