Patent Document

BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a light source of a projector, and more particularly, to a light source having a plurality of beam generators for enhancing brightness of a projection image of a projector.  
           [0003]    2. Description of the Prior Art  
           [0004]    With the progress of optics, projectors have found broad use in many applications. Generally speaking, projected light intensity is usually an important factor while designing a projector, as the projection quality improves with greater intensities of the projected light.  
           [0005]    Please refer to FIG. 1. FIG. 1 is a schematic diagram of a projector  10  according to the prior art. The projector  10  comprises a light source  12 , a color wheel  14 , a light pipe  16 , and an image device  18 . The light source  12  is used to generate a light beam  22  and to project the light beam  22  through the color wheel  14  to the light pipe  16 . The color wheel  14  is positioned between the light source  12  and the light pipe  16 . The color wheel  14  rotates round an axle  15  and outputs red, green, and blue polarized beams  24  by turning after filtering the light beam  22  via different filters so that the image device  18  can process the input beams according to their specific color. The light pipe  16  uniformizes the beams  24  to outputs a uniformized beam  26  to the image device  16 . The image device  18  processes the uniformized beam  26  to modulate an image into the uniformized beam  26  to form an image beam  28 . The image beam  28  is projected to a screen  20  to form a projection image. The light source  12  is composed of a bulb  17  for generating light and a lampshade  19  for collecting the light generated by the bulb  17  to form the light beam  22 . Because the projector  10  comprises only one bulb  17  as a lighting device to provide light to the projector  10 , the power of the bulb  17  should be raised when enhancing the brightness of the projection image of the projector  10 . However, this method of enhancing the brightness of the projection image of the projector  10  is improper. For example, when the power of the bulb  17  is raised, the waste heat of the bulb  17  increases correspondingly, increasing the operational temperature of the projector  10 . Further, if the bulb  17  becomes too hot, the bulb  17  could burn out.  
         SUMMARY OF INVENTION  
         [0006]    It is therefore a primary objective of the claimed invention to provide a light source having a plurality of beam generators for enhancing brightness of a projection image of a projector to solve the above-mentioned problem.  
           [0007]    In an embodiment of the present invention, a light source is disclosed. The light source comprises a prism for refracting and reflecting light beams, and a plurality of beam generators. Each of the beam generators is used to generate a light beam and to project the light beam to the prism. The light beams enter the prism with a first refraction, and then leave the prism with a second refraction and are collected to form an enhanced light beam after total reflection in the prism.  
           [0008]    In another embodiment of the present invention, another light source is disclosed. The light source comprises a prism for reflecting light beams, and a plurality of beam generators. Each of the beam generators is used to generate a light beam and to project the light beam to the prism. The light beams are reflected by the prism to form an enhanced light beam.  
           [0009]    These and other objectives and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]    [0010]FIG. 1 is a schematic diagram of a projector according to the prior art.  
         [0011]    [0011]FIG. 2 is a schematic diagram of a projector using a first embodiment light source according to the present invention.  
         [0012]    [0012]FIG. 3 is a schematic diagram of a prism of the light source shown in FIG. 2.  
         [0013]    [0013]FIG. 4 indicates traveling paths of light beams in the prism shown in FIG. 2.  
         [0014]    [0014]FIG. 5 is a schematic diagram of a second embodiment light source according to the present invention.  
         [0015]    [0015]FIG. 6 is a schematic diagram of a prism of the light source shown in FIG. 5.  
         [0016]    [0016]FIG. 7 is a schematic diagram of a third embodiment light source according to the present invention.  
         [0017]    [0017]FIG. 8 is a schematic diagram of a prism of the light source shown in FIG. 7.  
         [0018]    [0018]FIG. 9 is a schematic diagram of a projector using a fourth embodiment light source according to the present invention.  
         [0019]    [0019]FIG. 10 is a schematic diagram of a fifth embodiment light source according to the present invention.  
         [0020]    [0020]FIG. 11 is a schematic diagram of a sixth embodiment light source according to the present invention.  
         [0021]    [0021]FIG. 12 is a schematic diagram of a projector using a seventh embodiment light source according the present invention.  
         [0022]    [0022]FIG. 13 is a schematic diagram of the light source shown in FIG. 12.  
         [0023]    [0023]FIG. 14 is a schematic diagram of the prism shown in FIG. 13 rotated by 60 degrees.  
         [0024]    [0024]FIG. 15 is a schematic diagram of the prism shown in FIG. 13 rotated by 120 degrees.  
         [0025]    [0025]FIG. 16 is a schematic diagram of the prism shown in FIG. 13 rotated by 180 degrees.  
         [0026]    [0026]FIG. 17 is a schematic diagram of an eighth embodiment light source according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0027]    Please refer to FIG. 2, which is a schematic diagram of a projector  30  using a first embodiment light source  50  according to the present invention. The main difference between the projector  10  and the projector  30  is that the light source  50  replaces the light source  12  to provide light to the projector  30 . The projector  30  also comprises a color wheel  14 , a light pipe  16 , and an image device  18  where the characteristics of these elements are the same as those installed in the projector  10 . The light source  50  comprises a prism  60  for reflecting and refracting light, and a plurality of beam generators  70 . Each of the beam generators  70  is used to generate a light beam  76  and to project the light beam  76  to the prism  60 . Each of the beam generators  70  comprises a light device  72  for radiating light and a collector  74 , where the light device  72  can be a bulb, a tube, or another device capable of generating light, and the light collector  74  is a parabolic mirror for collecting the light generated by the light device  72  to form the light beam  76 . The prism  60  guides the light beams  76  to the light pipe  16  by refracting and totally reflecting the light beams  76  to form an enhanced light beam  80 . In contrast to the prior art light source  12 , if the brightness of one light beam  76  generated by one of the beam generators  70  is the same as the brightness of the light beam  22  generated by the light source  12 , because the light source  50  has two of the beam generator  70 , the brightness of the projection image projected by the projector  30  is greater than the brightness of the projection image projected by the projector  10 . Moreover, similar to the projector  10 , the color wheel  14  rotates round an axle  15  and outputs red, green, and blue beams  81  via different color filters by turning after filtering the enhanced light beam  80 . The image device  18 , thus, can process the input beams according to their specific color. The light pipe  16  uniformizes the beams  81  to output a uniformized beam  82  to the image device  18 . The image device  18  processes the uniformized beam  82  to modulate an image into the uniformized beam  82  to form an image beam  84  and to project the image beam  84  to the screen  20  to form a projection image.  
         [0028]    To describe the operations of the light source  50  in more detail, please refer to FIG. 2- 4 . FIG. 3 is a schematic diagram of the prism  60 . FIG. 4 indicates traveling paths of the light beams  76 . The prism  60  is made of transparent material, such as glass, and has a refractive index N 1 . The prism  60  comprises a first optical plane  62 , a second optical plane  64 , and a third optical plane  66 . In this embodiment, the three optical planes  62 ,  64 , and  66  are three rectangles having the same width and length. Two sides of each optical plane  62 ,  64 , or  66  are respectively adjacent to the sides of the other two optical planes so that two equilateral triangles are formed at the two ends of the prism  60 . The two beam generators  70  respectively face toward the first optical plane  62  and the second optical plane  64 . The light beams  76  generated by the beam generators  70  enter the prism  70  respectively through the first optical plane  62  and the second optical plane  64 , and then are redirected to leave the prism  60  through the third optical plane  66 . When the two light beams  76  enter the prism  60 , a first refraction occurs. Suppose that the refractive index of the air is N 2 , then incident angles α, X, and refraction angles a″, X″ have following relationship:  
         N1   N2     =         sin                 α       sin                   α   ′         =       sin                 x       sin                   x   ′                                 
 
         [0029]    Because the refractive index N 1  is greater than the refractive index N 2 , the paths of the two light beams  76  are shifted toward the normal vectors of the two optical planes  62  and  64 . This means that the refraction angle α″ is less than the incident angle a and that the refraction angle X″ is less than the incident angle X. After the first refraction, the two light beams  76  are respectively totally reflected at the first optical plane  62  and the second optical plane  64  and are redirected to the third optical plane  66 , where the reflection angles θ and y have following relationship:  
           sin                 θ     ≥     N2   N1       ,       sin                 y     ≥     N2   N1                             
 
         [0030]    After the total reflection in the prism  60 , the light beams  76  leave the prism  60  with a second refraction. The incident angles β″, Z″, and the refraction angles β, Z have following relationship:  
         N1   N2     =         sin                 β       sin                   β   ′         =       sin                 z       sin                   z   ′                                 
 
         [0031]    Similarly, because the refractive index N 1  is greater than the refractive index N 2 , the paths of the two light beams  76  stray from the normal of the third optical planes  66 . This means that the refraction angle β is greater than the incident angle β″ and that the refraction angle z is greater than the incident angles z″. Finally, the two light beams  76  leave the prism  60  through the third optical plane  66  and then are collected to from the enhanced light beam  80 .  
         [0032]    Please refer to FIG. 5 and FIG. 6. FIG. 5 is a schematic diagram of a second embodiment light source  85  according to the present invention. FIG. 6 is a schematic diagram of a prism  90  of the light source  85 . Both of the two light sources  50  and  85  are used to provide light to a corresponding projector. The main differences between the two light sources  50  and  85  are the shape of their prism and the amount of beam generators  70 . The prism  90  of the light source  85  comprises four equilateral triangular optical planes: a first optical plane  92 , a second optical plane  94 , a third plane  96 , and a fourth optical plane  98 . The light source  85  comprises three beam generators  70  for generating light beams  76  and for respectively projecting the light beams  76  to the first optical plane  92 , the second optical plane  94 , and the third optical plane  96 . The three light beams  76  are respectively totally reflected at the first optical plane  92 , the second optical plane  94 , and the third optical plane  96 , and then are emitted out from the prism  90  through a fourth optical plane  98  of the prism  90  and are collected into an enhanced light beam. Moreover, the fourth optical plane  98  is positioned toward to the image device of the projector so that the light pipe is capable of receiving light from the light source  85 .  
         [0033]    Please refer to FIG. 7 and FIG. 8. FIG. 7 is a schematic diagram of a third embodiment light source  95  according to the present invention. FIG. 8 is a schematic diagram of a prism  100  of the light source  95 . The main difference between the light source  95  and the light source  85  is the amount of beam generators  70 . The light source  95  comprises four beam generators  70  for respectively outputting light beams  76  to a first optical plane  102 , a second optical plane  104 , a third optical plane  106 , and a fourth optical plane  108  of the prism  100 . The four light beams  76  are totally reflected in the prism  100  and then are collected into an enhanced light beam after leaving the prism  100  through a fifth optical plane  110  of the prism  100 . Furthermore, the fifth optical plane  110  is positioned toward the light pipe of the projector to receive the light from the light source  95 .  
         [0034]    It is noted that the amount of beam generators  70  of the light source and the shape of the prisms in above embodiments should not be construed as limiting the present invention. The present invention can be applied to other applications that use a plurality of beams generators  70  for enhancing brightness of projection images and a prism for collecting light beams by total reflection.  
         [0035]    Please refer to FIG. 9, which is a schematic diagram of a projector  120  using a fourth embodiment light source  125  according to the present invention. The only difference between the projector  120  and the projector  30  is that the light source  125  replaces the light source  50  to provide light to the projector  120 . The light source  125  comprises a prism  130  for reflecting light and two beam generators  70  for generating light beams  76 . The two light beams  76  are respectively reflected at a first optical plane  132  and a second optical plane  134  of the prism  130 , and then are collected into an enhanced light beam  136 . The enhanced light beam  136  passes through the color wheel  14  into the light pipe  16 , and then is inputted to the image device  18  after being uniformized by the light pipe  16 .  
         [0036]    Please refer to FIG. 10, which is a schematic diagram of a fifth embodiment light source  140  according to the present invention. Similar to the light source  130 , the light source  140  is used to provide light to a projector. The main differences between the two light sources  130  and  140  are the shape of their prisms and the amount of beam generators  70 . The shape of the prism  150  of the light source  140  is the same as the shape of the prism  90  shown in FIG. 6. The prism  150  comprises three optical planes for reflecting light: a first optical plane  152 , a second optical plane  154 , and a third optical plane  156 . The three optical planes  152 ,  154 , and  156  connected to each other at an apex  158 , and the prism  150  is positioned in the projector such that the apex  158  faces toward the light pipe of the projector. The light source  140  further comprises three beam generators  70  for generating three light beams  76  and respectively projecting the three light beams  76  to the first optical plane  152 , the second optical plane  154 , and the third optical plane  156 . Finally, the three light beams  76  are reflected at the first optical plane  152 , the second optical plane  154 , and the third optical plane  156  to be collected and inputted to the light pipe of the projector.  
         [0037]    Please refer to FIG. 11, which is a schematic diagram of a sixth embodiment light source  155  according to the present invention. The difference between the two light sources  155  and  140  is the amount of beam generators  70 . The light source  150  comprises four beam generators  70 . The four light beams  76  generated by the four beam generators  70  are respectively projected to a first optical plane  162 , a second optical plane  164 , a third optical plane  166 , and a fourth optical plane  168  of a prism  160  of the light source  155 . Finally, the four light beams  76  are reflected at the first optical plane  162 , the second optical plane  164 , the third optical plane  166 , and the fourth optical plane  168  to be collected and inputted to the light pipe of the projector.  
         [0038]    Please refer to FIG. 12 and FIG. 13. FIG. 12 is a schematic diagram of a projector  170  using a seventh embodiment light source  175  according the present invention. FIG. 13 is a schematic diagram of the light source  175 . The main difference between the two projectors  170  and  120  is that the light source  175  replaces both the light source  125  and the color wheel  14  to provide light to the projector and to filter light. The light source  175  comprises a prism  180  for reflecting light and two beam generators  70 . The prism  180  is placed in the projector  170  in a rotatable manner and comprises two first reflective filtering areas R, two second reflective filtering areas G, and two third reflective filtering areas B. Each of the reflective filtering areas R, G, and B is used for filtering and reflecting light. The first reflective filtering areas R filter the red light out of the light beams  76  and reflect the red light. The second reflective filtering areas G filter the green light out of the light beams  76  and reflect the green light. The third reflective filtering areas B filter the blue light out of the light beams  76  and reflect the blue light. When the prism  180  rotates clockwise at an angular velocity w, the two light beams  76  illuminate two of the reflective filtering areas R, G, or B that have the same filtration characteristic. Then, the two light beams  76  are filtered and reflected by the reflective filtering areas R, G, or B and are collected to form an enhanced light beam  76  which is projected to the light pipe  16 . Finally, the image device  18  can process the enhanced light beam  76  to form an image beam.  
         [0039]    The operations of the light source  175  are described in detail referencing FIG. 13 to FIG. 16. FIG. 14 is a schematic diagram of the prism  180  when rotated by 60 degrees. FIG. 15 is a schematic diagram of the prism  180  when rotated by 120 degrees. FIG. 16 is a schematic diagram of the prism  180  when rotated by 180 degrees. As previously mentioned, the prism  180  rotates clockwise at an angular velocity ω. When the prism  180  rotates to 0 degrees as shown in FIG. 13, the two light beams  76  are projected to the first reflective filtering areas R so that the enhanced light beam  76  is a red monochromatic light beam. When the prism  180  rotates to 60 degrees as shown in FIG. 14, the two light beams  76  are projected to the second reflective filtering areas G so that the enhanced light beam  76  is a green monochromatic light beam. When the prism  180  rotates to 120 degrees as shown in FIG. 15, the two light beams  76  are projected to the third reflective filtering areas B so that the enhanced light beam  76  is a blue monochromatic light beam. When the prism  180  rotates to 180 degrees as shown in FIG. 16, the two light beams  76  are projected to the first reflective filtering areas R again. Therefore, the light source  175  periodically outputs the red, green, and blue enhanced light beams at a period (180°/ω).  
         [0040]    Please refer to FIG. 17, which is a schematic diagram of an eighth embodiment light source  185  according to the present invention. The operations of the light source  185  are very similar with the operations of the light source  175 . The main differences between the two light sources  175  and  185  are the amount of beam generators  70  and the amount of the reflective filtering areas of the prisms. The light source  185  comprises four of the light beam generators  70  and a prism  190 . The prism  190  comprises four first reflective filtering areas R, four second reflective filtering areas G, and four third reflective filtering areas B shown as FIG. 17. The prism  190  rotates clockwise at an angular velocity ω so that the light beams  76  are projected to four of the reflective filtering areas R, G, or B that have the same filtration characteristic. Therefore, the light source  185  outputs red, green, and blue monochromatic light beams by turning.  
         [0041]    It is noted that the amount of reflective filtering areas in the above embodiments should not be construed as limiting the present invention. The present invention can be applied to other applications that use a plurality of the beams generators  70  for enhancing projection images and a prism for collecting light beams by reflection.  
         [0042]    In contrast to the prior art, the present invention provides a light source that has a plurality of beam generators for generating light beams and a prism for collecting the light beams by reflection or refraction to form an enhanced light beam. Therefore, a projector comprising the light source according to the present invention can project images having greater brightness than other prior art projectors. In addition, the prism can comprises a plurality of reflective filtering areas for filtering and reflecting light to output red, green, and blue monochromatic light beams by turning so that a color wheel of the projector can be omitted to effectively use the limited space inside the projector.  
         [0043]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Technology Category: 3