Abstract:
An optical projection device including a light source, a housing, an imaging unit, a projection lens and a dust protection device is provided. The light source is adopted for providing a light beam. The housing has a projection-lens-assembling opening. The imaging unit is disposed in the housing, and on the transmission path of the light beam. In addition, the projection lens in the housing, and exposed by the projection-lens-assembling opening. The dust protection device is disposed between the projection lens and the projection-lens-assembling opening. The optical projection device is thus protected from dust and displaying quality thereof is excellent.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the priority benefit of Taiwan application serial no. 93138331, filed on Dec. 10, 2004. All disclosure of the Taiwan application is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical projection device. More particularly, the present invention relates to a dust protection device for the optical projection device. 
   2. Description of Related Art 
   In general, conventional optical projection device is mainly constructed by light source, imaging unit and projection lens. The imaging unit includes a non-direct view display device such as silicon-based liquid crystal panel, high temperature polycrystalline silicon liquid crystal panel or digital micromirror device (DMD), and an optical lens set constructed by reflection mirrors and lens. The light source is adopted for providing a light beam into the imaging unit. The optical lens set is adopted for transmitting the light beam into the display device. The display device receives the light beam and generates an image, and then the image is transmitted to the projection lens via the optical mirror set. Finally, the image is projected to a projection screen by the projection lens. 
   In general, the resolution of the display device optical projection device has high resolution. The higher image quality of the projected and the enlarged image can be achieved. However, it is noted that the image is enlarged several times in the optical projection device. Therefore, if the display device or the optical lens set is covered with dust or other contaminations, the display device is damaged. In addition, the interference due to the dust or the contaminations is also simultaneously enlarged with the image during being projected to the projection screen. Therefore, the quality of the image displayed is adversely affected. 
   Accordingly, a dust protection device is developed for the internal optical lens set and the display device in a conventional optical projection device.  FIG. 1A  is a perspective view of a conventional optical projection device.  FIG. 1B  is a top view of the optical projection device shown in  FIG. 1A . It is noted that, parts of the housings are shown in  FIG. 1B . Referring to  FIG. 1B , the projection lens  130  is mounted on the housing  110 . The terminal of the projection lens  130  is connected to a barrel (not shown), thus the terminal of the projection lens  130  cannot be lengthened or shortened. A DMD  122  and an optical lens set are installed in the housing  110 , wherein the optical lens set generally includes a relay lens  124  and other optical lens (not shown). Generally, in order to protect the DMD  122  from the dust or the contaminants, conventionally the relay lens  124  is installed outside of the DMD  122  and over the projection lens  130 . Therefore, the DMD  122  is surrounded and sealed by the relay lens  124  and the barrel for mounting, so that the DMD  122  is protected from dust. 
   However, as the demand of the display quality and the magnifying power of the image increase gradually, the size of the projection lens is also increased. For this reason, the optical path among the projection lens is also lengthened. Therefore, the terminal of the projection lens cannot be mounted in the barrel, and thus the relay lens and barrel cannot be sealed from the dust. In summary, the conventional optical projection device cannot be adopted for high magnification projection lens. In addition, the conventional dust protection mechanism has to be modified corresponding to the development of optical system. 
   SUMMARY OF THE INVENTION 
   The present invention provides a dust protection device for an optical projection device. 
   According to one embodiment of the present invention, an optical projection device including a light source, a housing, an imaging unit, a projection lens and a dust protection device is provided. The light source is adopted for providing a light beam. The housing has a projection-lens-assembling opening. The imaging unit is disposed in the housing, and on the transmission path of the light beam. In addition, the projection lens in the housing, and exposed by the projection-lens-assembling opening. The dust protection device is disposed between the projection lens and the projection-lens-assembling opening. The optical projection device is thus protected from dust and displaying quality thereof is excellent. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1A  is a perspective view of a conventional optical projection device. 
       FIG. 1B  is a top view of the optical projection device shown in  FIG. 1A . 
       FIG. 2A  is a perspective view of an optical projection device according to one embodiment of the present invention. 
       FIG. 2B  is a top view of the optical projection device shown in  FIG. 2A . 
       FIG. 2C  is a cross-sectional view of  FIG. 2B  along line A-A′. 
   

   DESCRIPTION OF EMBODIMENTS 
   The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention could, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     FIG. 2A  is a perspective view of an optical projection device according to one embodiment of the present invention.  FIG. 2B  is a top view of the optical projection device shown in  FIG. 2A , wherein the second shell of the housing is not shown.  FIG. 2C  is a cross-sectional view of  FIG. 2B  along line A-A′. Referring to  FIGS. 2A to 2C , an optical projection device  200  comprises, for example, a housing  210 , an imaging unit  220 , a projection lens  230 , a dust protection device  240  and a light source (not shown). The imaging unit  220  is disposed in the housing  210 , and the imaging unit  220  comprises a display device  222  and an optical lens set  224 . In one embodiment of the present invention, the display device  222  comprises a non-direct view display device such as a silicon-based liquid crystal panel, a high temperature polycrystalline silicon liquid crystal panel or a digital micromirror device (DMD). The optical lens set  224  comprises optical mirror or lens sheet such as relay lens  224   a,  collector lens  224   b,  and/or reflection mirror  224   c.    
   Referring to  FIGS. 2A to 2C , the housing  210  comprises, a first shell  212  having, for example, a first rib  216   a  disposed thereon and a second shell  214  having, for example, a second rib disposed thereon. The first shell  212  is assembled with the second shell  214  such that the first rib  216   a  is assembled with second rib  216   b  to form the projection-lens-assembling opening  210   a.  Thus, the first rib  216   a  and the second rib  216   b  are assembled to construct a rounded rib  216  to define the projection-lens-assembling opening  210   a.    
   Referring to  FIGS. 2A to 2C , the projection lens  230  is assembled within the projection-lens-assembling opening  210   a  of the housing  210  and is exposed by the projection-lens-assembling opening  210   a.  The rounded rib  216  constructed by the first rib  216   a  on the first shell  212  and the second rib  216   b  on the second shell  214  surrounds the boundary of the projection lens  230 . In one embodiment of the present invention, according to the design of the system and the requirement of the application, for example, almost all the projection lens  230  is extended out from the housing  210 , or almost all the projection lens  230  is confined within the housing  210 . Therefore, the adjustable length for lengthening or shortening the projection lens may be increased. In addition, the light beam (not shown) emitted by the light source (not shown) sequentially passes the collector lens  224   b,  the reflection mirror  224   c  and the relay lens  224   a  to the display device  220  to form an image on the display device  220 . Then the image passes the relay lens  224   a  and then projects via the projection lens  230 . 
   As shown in  FIGS. 2A to 2C , in one embodiment of the present invention, the dust protection device  240 , which is disposed between the projection-lens-assembling opening  210   a  and the projection lens  230 , is in the housing  210  for protecting the imaging unit  220  of the display device  222  and the optical lens set  224  disposed in the housing  210  from dust. Wherein, the material of the dust protection device  240  comprises, for example, rubber material or foaming material. The dust protection device  240  is positioned surrounding the projection lens  230  corresponding to the projection-lens-assembling opening  210   a.  When the projection lens  230  is assembled with housing  210 , the dust protection device  240  leans against the rounded rib  216  on the housing  210 . Therefore, the interior of the housing  210  is sealed by the combination of the dust protection device  240  and the rounded rib  216  on the housing  210 . In this way, the display device  222  and the optical lens set  224  disposed in the housing  210  can be effectively protected from dust. 
   It is noted that, in one embodiment of the present invention, the length of the second rib  216   b  is three times the length of the first rib  216   a.  In other words, the second rib  216   b  disposed on the second shell  212  constitute ¾th circumference of the projection lens  230  and, the first rib  216   a  disposed on the first shell  214  constitute the remaining ¼th circumference of the projection lens  230 . Hence, a stable mounting can be achieved. In addition, in another embodiment of the present invention, the lengths of the first rib  216   a  and the second rib  216   b  could be the same or different according to the design or the requirements. 
   Referring to  FIGS. 2A to 2C , the projection lens  230  is assembled within the projection-lens-assembling opening  210   a  of the housing  210  and is exposed by the projection-lens-assembling opening  210   a.  The rounded rib  216  constructed by the first rib  216   a  on the first shell  212  and the second rib  216   b  on the second shell  214  surrounds the boundary of the projection lens  230 . In one embodiment of the present invention, according to the design of the system and the requirement of the application, for example, almost all the projection lens  230  is extended out from the housing  210 , or almost all the projection lens  230  is confined within the housing  210 . Therefore, the adjustable length for lengthening or shortening the projection lens may be increased. In addition, the light beam (not shown) emitted by the light source (not shown) sequentially passes the collector lens  224   b,  the reflection mirror  224   c  and the relay lens  224   a  to the display device  222  to form an image on the display, device  222 . Then the image passes the relay lens  224   a  and then projects via the projection lens  230 . 
   The foregoing description of the embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure intends to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.