Abstract:
A low profile module and frame assembly for arc lamps has been disclosed. In one embodiment, the arc lamp assembly includes an arc lamp, a first cooling fan coupled to a back of the arc lamp closer to a first side of the arc lamp, and a second cooling fan coupled laterally to the first cooling fan and to the back of the arc lamp closer to a second side of the arc lamp, the first side being opposite to the second side. Other embodiments have been described and claimed.

Description:
FIELD OF INVENTION 
     The present invention relates to arc lamps, and more particularly, to cooling an arc lamp. 
     BACKGROUND 
     In optical systems involving the generation and controlled radiation of long or continuous pulses of light, such as spectroscopy, or solar simulation, where high intensity, color correct illumination of sensitive working areas is required, such as in projection systems fiber optics illumination devices, it is advantageous to have a light source capable of producing the highest possible light flux density. Products utilized in such applications include short arc inert gas lamps, which may also be referred to as arc lamps. At least one conventional arc lamp includes a sealed chamber, which contains a gas pressurized to several atmospheres, and an opposed anode and cathode defining an arc gap. The conventional arc lamp further includes a window to provide for the transmission of the generated light and a reflector body surrounding the arc gap. The reflector body may be a ceramic reflector body. 
     During operation of the conventional arc lamp, the anode and the cathode generate a significant amount of heat. The anode and the cathode are inside the sealed chamber of the arc lamp. As a result, the reflector body is also subjected to high heat during operation of the arc lamp. Typically, heat is transferred from the sides of the arc lamp. The operating power of the arc lamp may be limited by how fast the reflector body cools off. The faster the reflector body cools off, the higher the operating power of the arc lamp may be. Furthermore, the reflector body is susceptible to cracking when operated at high temperatures over a long period of time. Cracking of the reflector body may cause the arc lamp to explode, leading to property damages and/or personal injuries. 
     One existing technique to cool off an arc lamp is to couple a single cooling fan to the back of the arc lamp. The cooling fan may be mounted to the back of a housing holding the arc lamp. However, the above technique is unsatisfactory because of several reasons. One reason is that the single cooling fan is usually too tall and bulky for tabletop mounting applications (e.g., in a tabletop video projection system) because a smaller fan would not be able to cool off the arc lamp to a safe temperature at an acceptable speed. Furthermore, the cooling fan is generally very noisy (e.g., having a noise level above approximately 36 dB) because of the size of the cooling fan. Thus, fan noise has frequently been an issue with arc lamp assemblies. The fan noise issue is particularly problematic for projection systems because such noise may distract the audience viewing a display by the projection system. 
     SUMMARY 
     A low profile module and frame assembly for arc lamps is described. In one embodiment, the arc lamp assembly includes an arc lamp, a first cooling fan coupled to a back of the arc lamp closer to a first side of the arc lamp, and a second cooling fan coupled laterally to the first cooling fan and to the back of the arc lamp closer to a second side of the arc lamp, the first side being opposite to the second side. 
     Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood more fully from the detailed description that follows and from the accompanying drawings, which however, should not be taken to limit the appended claims to the specific embodiments shown, but are for explanation and understanding only. 
         FIGS. 1A–1D  show one embodiment of an arc lamp assembly. 
         FIG. 2  shows one embodiment of an arc lamp assembly. 
         FIGS. 3A–3C  show one embodiment of an arc lamp assembly. 
         FIG. 4  shows one embodiment of an arc lamp assembly. 
         FIG. 5  shows one embodiment of a table top projection system 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known components, structures, and techniques have not been shown in detail in order not to obscure the understanding of this description. 
       FIG. 1A  illustrates a top view of one embodiment of an arc lamp assembly  100 . The arc lamp assembly  100  includes a frame  110 , a first cooling fan  120 , and a second cooling fan  130 . The first and the second cooling fans  120  and  130  are mounted side by side at the back of the frame  110 . 
       FIG. 1B  illustrates a back view of the arc lamp assembly  100 . The arc lamp assembly  100  further includes an arc lamp  140 . As shown in  FIG. 1B , the first cooling fan  120  is mounted to the back of the frame  110  and coupled to at least part of the back of the arc lamp  140 . Likewise, the second cooling fan  130  is mounted to the back of the frame  110  and coupled to at least part of the back of the arc lamp  140 . 
       FIG. 1C  illustrates a side view of the arc lamp assembly  100 . The second cooling fan  130  is shown mounted to the back of the frame  110 . 
       FIG. 1D  illustrates a front view of the arc lamp assembly  100 . The arc lamp  140  is mounted within the frame  110 . As shown in  FIG. 1D , the cathode  142  of the arc lamp  140  is mounted near the front of the arc lamp  140 . By using two cooling fans  120  and  130  to cool off the arc lamp  140 , the larger single cooling fan in many of the existing arc lamp assemblies can be eliminated. The smaller cooling fans  120  and  130  are shorter and less bulky, and thus, make the arc lamp assembly  100  more suitable for tabletop projection systems. For instance, the dimensions of a 500 Watt arc lamp assembly (including the arc lamp, the heat sinks, and a plastic holder) are about 2.25″ in height, 5.3″ in width, and 3.65″ in depth according to one embodiment of the present invention. Furthermore, the dimensions of a 750_Watt arc lamp assembly (including the arc lamp, the heat sinks, and a plastic holder) are about 2.6″ in height, 6.6″ in width, and 3.77″ in depth according to another embodiment of the present invention. In contrast, the dimensions of a typical conventional 500 Watt arc lamp assembly are about 3.7″ in height, 4″ in width, and 3.9″ in depth, while the dimensions of a typical conventional 750 Watt arc lamp assembly are about 4″ in height, 4″ in width, and 4.33″ in depth. Thus, there is a reduction of about 39% in the height of the 500 Watt arc lamp assembly and about 35% in the height of the 750_Watt arc lamp assembly according to some embodiments of the present invention. 
     Furthermore, the smaller cooling fans  120  and  130  have a lower combined noise level (e.g., less than approximately 36 dB) than the larger cooling fan in the existing arc lamp assemblies. Hence, the system incorporating the arc lamp assembly  100  is quieter than those incorporating the existing arc lamp assemblies. Lower noise level is advantageous for projection systems because quieter projection systems are less distracting for the audience viewing the display by the projection systems. 
       FIG. 2  shows one embodiment of an arc lamp assembly  200 . The arc lamp assembly  200  includes a frame  210 , two cooling fans  220  and  230 , two heat sinks  250  and  260 , and an arc lamp  240 . The two cooling fans  220  and  230  are mounted side by side to each other on the back of the frame  210 . The first cooling fan  220  is coupled to the back of the arc lamp  240  closer to a first side of the arc lamp  240 . The second cooling fan  230  is coupled to the back of the arc lamp  240  closer to a second side of the arc lamp  240 . The two sides of the arc lamp  240  are opposite to each other. 
     In one embodiment, the first heat sink  250  is coupled laterally to the first side of the arc lamp  240  while the second heat sink  260  is coupled laterally to the second side of the arc lamp  240 . Since heat generated during operation of the arc lamp  240  is typically transferred from the sides of the arc lamp  240 , the heat sinks  250  and  260  on the sides of the arc lamp  240  may effectively cool off the arc lamp  240 . Furthermore, the cooling fans  220  and  230  cause air to circulate more efficiently through the heat sinks  250  and  260 , respectively, and hence, help to cool off the arc lamp  240  faster. 
     By mounting the heat sinks  250  and  260  laterally to the arc lamp  240 , the height of the arc lamp assembly  200  is made smaller than many traditional arc lamp assemblies. Therefore, the arc lamp assembly  200  is more suitable for applications in systems that are limited in size, such as tabletop projection systems. 
       FIG. 3A  illustrates a front view of one embodiment of an arc lamp assembly. The arc lamp assembly  300  includes a first heat sink  310 , a second heat sink  320 , and an arc lamp  330 . The first heat sink  310  is coupled laterally to the arc lamp  330  on the left side in  FIG. 3A . Likewise, the second heat sink  320  is coupled laterally to the arc lamp  330  on the right side in  FIG. 3A . 
       FIG. 3B  shows a side view of the arc lamp assembly  300 . In one embodiment, the first heat sink  310  includes two pieces  310 A and  310 B. The piece  310 A may be coupled closer to the anode of the arc lamp  330  while the piece  310 B may be coupled closer to the cathode of the arc lamp  330 . Although only the left side view is shown in  FIG. 3B , it is apparent to one of ordinary skill in the art that the right side of the arc lamp assembly is substantially the same. 
       FIG. 3C  shows a top view of the arc lamp assembly  300 . In one embodiment, the second heat sink  320  includes two pieces  320 A and  320 B. The piece  320 A may be coupled closer to the anode of the arc lamp  330  while the piece  320 B may be coupled closer to the cathode of the arc lamp  330 . 
       FIG. 4  shows one embodiment of an arc lamp assembly. The arc lamp assembly  400  includes two heat sinks  410  and  420  and an arc lamp  430 . The heat sink  410  is coupled laterally to the left side of the arc lamp  430  and the heat sink  420  is coupled laterally to the right side of the arc lamp  430 . In one embodiment, the heat sink  410  includes two pieces  410 A and  410 B. Likewise, the heat sink  420  may include two pieces  420 A and  420 B. Both pieces  410 B and  420 B may be coupled closer to the anode of the arc lamp  430  while the other two pieces  410 A and  420 A may be coupled closer to the cathode of the arc lamp  430 . Since heat generated during operation of the arc lamp  430  is typically transferred from the side of the arc lamp  430 , the heat sinks  410  and  420  can effectively lower the temperature of the arc lamp  430 . Furthermore, by coupling two heat sinks  410  and  420  to the sides of the arc lamp  430  instead of a single heat sink as in some conventional designs, the heat sinks  410  and  420  may each be smaller than the single heat sink. The resultant arc lamp assembly  400  may be shorter and less bulky than the conventional design. Thus, the arc lamp assembly  400  is more suitable for application in smaller systems, such as a tabletop projection system. 
       FIG. 5  illustrates one embodiment of a tabletop projection system. The tabletop projection system  500  includes an arc lamp assembly  510  and a lens  520 . The arc lamp assembly  510  is optically coupled to the lens  520 . During operation, the arc lamp assembly  510  may generate a light ray  501 , which passes through the lens  520  to project onto a surface, such as a screen, a board, a wall, etc. Some embodiments of the arc lamp assembly  510  have been described above. 
     Note that the tabletop projection system  500  is described above as one example of the application of the improved arc lamp assembly. One of ordinary skill in the art would readily recognize other similar applications of the improved arc lamp based on the current disclosure. 
     The foregoing discussion merely describes some exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, the accompanying drawings and the claims that various modifications can be made without departing from the spirit and scope of the invention.