Patent Publication Number: US-2007121084-A1

Title: Projector with a plurality of light sources

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a projector, and more particularly, to a projector with a plurality of light sources.  
      2. Description of the Prior Art  
      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 intensity of the projected light.  
      Please refer to  FIG. 1  .  FIG. 1  is a schematic diagram of a projector  10  in the prior art. The projector  10  includes 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 output a uniformized beam  26  to the image device  18 . 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  30  for generating light and a lampshade  32  for collecting the light generated by the bulb  30  to form the light beam  22 .  
      Because the projector  10  includes only one bulb  30  as a lighting device to provide light to the projector  10 , the power of the bulb  30  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  30  is raised, the waste heat of the bulb  30  increases correspondingly, increasing the operational temperature of the projector  10 . Further, if the bulb  30  becomes too hot, the bulb  30  could burn out.  
     SUMMARY OF THE INVENTION  
      It is therefore a primary objective of the claimed invention to provide a projector with a plurality of light sources for solving the above-mentioned problem.  
      According to the claimed invention, a projector includes a housing, a first light source installed inside the housing for generating light beams, a second light source installed inside the housing for generating light beams, a first refractive element installed inside the housing for refracting the light beams generated by the first light source, a second refractive element installed inside the housing for refracting the light beams generated by the second light source to a direction parallel to a direction of the light beams refracted by the first refractive element substantially, a light pipe installed inside the housing for uniformizing light beams from the first refractive element and the second refractive element, and an image device installed inside the housing for processing the uniformized light from the light pipe and for projecting the processed light to form an image.  
      These and other objectives 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 THE DRAWINGS  
       FIG. 1  is a schematic diagram of a projector in the prior art.  
       FIG. 2  is a schematic diagram of a projector of a first embodiment according to the present invention.  
       FIG. 3  is a schematic diagram of a projector of a second embodiment according to the present invention. 
    
    
     DETAILED DESCRIPTION  
      Please refer to  FIG. 2 .  FIG. 2  is a schematic diagram of a projector  50  of a first embodiment according to the present invention. The projector  50  includes a housing  52 , and a first light source  54  installed inside the housing  52 . The first light source  54  includes a light device  56   a  for generating light and a light collector  58   a  for collecting the light generated by the light device  56   a  to form a light beam  60   a . The light collector  58   a  includes a parabolic mirror  62   a . The light device  56   a  is positioned on a focus of the parabolic mirror  62   a . The light collector  58   a  further includes a positive lens  64   a  and a negative lens  66   a . The projector  50  further includes a second light source  68  installed inside the housing  52  and on a side opposite to the first light source  54 . The second light source  68  includes a light device  56   b  for generating light and a light collector  58   b  for collecting the light generated by the light device  56   b  to form a light beam  60   b . The light collector  58   b  includes a parabolic mirror  62   b . The light device  56   b  is positioned on a focus of the parabolic mirror  62   b . The light collector  58   b  further includes a positive lens  64   b  and a negative lens  66   b . Each of the light device  56   a  and the light device  56   b  can be a bulb. Each of the positive lens  64   a  and the positive lens  64   b  can be a plano-convex lens or a biconvex lens. Each of the negative lens  66   a  and the negative lens  66   b  can be a plano-concave lens or a biconcave lens. The projector  50  further includes a first refractive element  70  and a second refractive element  72 . The first refractive element  70  and the second refractive element  72  can be prisms for refracting the light beam  60   a  and the light beam  60   b  so as to form condensed beams  71   a ,  71   b . The first refractive element  70  and the second refractive element  72  are not connected.  
      The projector  50  further includes a focusing lens assembly  74  for focusing the condensed beams  71   a ,  71   b  from the first refractive element  70  and the second refractive element  72 , and a color wheel  76  for filtering a light beam  78  via different filters to output red, green, and blue beams by turning. The focusing lens assembly  74  focuses the light beam  78  to an entrance of a light pipe  80 . The light pipe  80  can uniformize the light beam  78  to output a uniformized beam  82 . The projector  50  further includes an image device  84  for processing the uniformized beam  82  to modulate an image into the uniformized beam  82  to form an image beam  86 . The image beam  86  is projected to a screen  90  to form a projection image.  
      The optical paths of the light from the first light source  54  and the second light source  68  to the screen  90  are described in detail as follows. First the light devices  56   a ,  56   b  are positioned on the focuses of the parabolic mirrors  62   a ,  62   b  respectively, so the light emitted from the light devices  56   a ,  56   b  is reflected as two parallel beams  92   a ,  92   b  by the parabolic mirrors  62   a ,  62   b . The positive lenses  64   a ,  64   b  can refract and condense the parallel beams  92   a ,  92   b , and then the negative lenses  66   a ,  66   b  can refract the light refracted by the positive lenses  64   a ,  64   b  as the light beams  60   a ,  60   b . That is, the combination of the positive lenses  64   a ,  64   b  and the negative lenses  66   a ,  66   b  can condense light so that the light can be condensed to emit to the first refractive element  70  and the second refractive element  72 . Then the first refractive element  70  and the second refractive element  72  deflect the light beams  60   a ,  60   b  to form the condensed beams  71   a ,  71   b . The focusing lens assembly  74  focuses the condensed beams  71   a ,  71   b  to form the light beam  78 . The color wheel  76  filters the light beam  78  via different filters to output red, green, and blue beams by turning. The focusing lens assembly  74  focuses the light beam  78  to the entrance of the light pipe  80 . The light pipe  80  uniformizes the light beam  78  to output the uniformized beam  82 . At last the image device  84  processes the uniformized beam  82  to modulate an image into the uniformized beam  82  to form the image beam  86 . The image beam  86  is projected to the screen  90  to form a projection image.  
      The first refractive element  70  and the second refractive element  72  can change the optical paths of the light generated by the first light source  54  and the second light source  68  so as to condense the light emitted from the first light source  54  and the second light source  68 . The light from the light source can be condensed to output to the lens of the projector  50  so as to enhance the brightness and uniformity of the projection image of the projector  50 . In addition, the distance between the first light source  54  and the second light source  68  can be increased so as to prevent the concentrated heat generated by the light device  56   a ,  56   b  because the first refractive element  70  and the second refractive element  72  can focus the light emitted from the first light source  54  and the second light source  68  to the focusing lens assembly  74 .  
      Please refer to  FIG. 3 .  FIG. 3  is a schematic diagram of a projector  100  of a second embodiment according to the present invention. The difference between the projector  50  and the projector  100  is the light collector. The projector  100  includes a first light source  104 . The first light source  104  includes the light device  56   a  for generating light and a light collector  108   a  for collecting the light generated by the light device  56   a  to form a light beam  110   a . The light collector  108   a  includes an ellipsoid mirror  112   a . The light device  56   a  is positioned on a focus of the ellipsoid mirror  112   a . The light collector  108   a  further includes a negative lens  116   a . The projector  100  further includes a second light source  118  installed on a side opposite to the first light source  104 . The second light source  118  includes a light device  56   b  for generating light and a light collector  108   b  for collecting the light generated by the light device  56   b  to form a light beam  110   b . The light collector  108   b  includes an ellipsoid mirror  112   b . The light device  56   b  is positioned on a focus of the ellipsoid mirror  112   b . The light collector  108   b  further includes a negative lens  116   b . Each of the light device  56   a  and the light device  56   b  can be a bulb. Each of the negative lens  116   a  and the negative lens  116   b  can be a plano-concave lens or a biconcave lens. The projector  100  further includes the first refractive element  70  and the second refractive element  72 . The first refractive element  70  and the second refractive element  72  can be prisms for refracting the light beam  110   a  and the light beam  110   b  so as to form condensed beams  121   a ,  121   b . The focusing lens assembly  74  of the projector  100  can focus the condensed beams  121   a ,  121   b . The color wheel  76  filters a light beam  128  via different filters to output red, green, and blue beams by turning. The focusing lens assembly  74  focuses the light beam  128  to an entrance of the light pipe  80 . The light pipe  80  can uniformize the light beam  128  to output a uniformized beam  132 . The image device  84  processes the uniformized beam  132  to modulate an image into the uniformized beam  132  to form an image beam  136 . The image beam  136  is projected to the screen  90  to form a projection image.  
      The light devices  56   a ,  56   b  are positioned on the focuses of the ellipsoid mirrors  112   a ,  112   b  respectively, so the light emitted from the light devices  56   a ,  56   b  is reflected as two condensed beams  142   a ,  142   b  by the ellipsoid mirrors  112   a ,  112   b . The negative lenses  116   a ,  116   b  can refract the condensed beams  142   a ,  142   b  as the light beams  110   a ,  110   b . That is, the combination of the ellipsoid mirrors  112   a ,  112   b  and the negative lenses  116   a ,  116   b  can condense and parallelize light so that the light can be condensed to emit to the first refractive element  70  and the second refractive element  72 . Then the first refractive element  70  and the second refractive element  72  deflect the light beams  110   a ,  110   b  to form the condensed beams  121   a ,  121   b . The focusing lens assembly  74  focuses the condensed beams  121   a ,  121   b  to form the light beam  128 . The color wheel  76  filters the light beam  128  via different filters to output red, green, and blue beams by turning. The focusing lens assembly  74  focuses the light beam  128  to the entrance of the light pipe  80 . The light pipe  80  uniformizes the light beam  128  to output the uniformized beam  132 . At last the image device  84  processes the uniformized beam  132  to modulate an image into the uniformized beam  132  to form the image beam  136 . The image beam  136  is projected to the screen  90  to form a projection image.  
      In contrast to the conventional projector with one light device, the projector according to the present invention includes a plurality of light sources so as to enhance the brightness of the projection image. In addition, the refractive elements can condense the light generated by the light sources to form a condensed beam so as to concentrate the light to output to the lens of the projector, increasing light efficiency and uniformity of the light sources. In addition, the distance between the light sources can be increased so as to prevent the concentrated heat generated by the light sources.  
      Those skilled in the art will readily observe that numerous modifications and alterations of the device and method 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.