Abstract:
A digital micro-mirror assembly for an optical projection system includes a DMD module with a control board. The control board is provided with a first fixing member, and a DMD is mounted on one side of the control board. A DMD holder resiliently supports a perimeter of the DMD, and an optical holder is provided with a second fixing member to support the DMD module. A fastening member is engaged with the first and the second fixing members to integrally connect the DMD module and the optical holder.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 2005-29379, filed Apr. 8, 2005, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an optical projection system. More particularly, the present invention relates to a digital micro-mirror device (DMD) assembly for an optical projection system that has an improved structure.  
         [0004]     2. Description of the Related Art  
         [0005]     Optical projection systems are used to project a small image onto a relatively large, wide screen using an optical device. Optical projection systems can be generally divided into three types of systems: cathode ray tube (CRT) projection systems, a liquid crystal display (LCD) projection systems, and digital light processing (DLP) projection systems.  
         [0006]     The CRT projection system is the oldest type of system. It projects an enlarged image by using a mirror to reflect an image produced on a small high-definition CRT onto a screen. In an LCD projection system, an external reproduction image signal is transmitted to a projection TV, and a small LCD screen (approximately 4 inches in diameter) receives the external reproduction image signal in the projection TV to form an image. The image formed on the LCD screen is enlarged by irradiating a strong light from behind the LCD screen through a lens, reflected the light with a mirror, and projecting the reflected light onto a screen.  
         [0007]     A DLP projection system projects an externally input image signal using a DMD semiconductor chip in which hundreds of thousands of micro-mirrors are integrated. In the DLP projection system, an assembly comprising a heat sink, a DMD module (including a control board and a DMD) and an optical holder uses a flexible assembly system. The flexible assembly system restricts the arrangement of the heat sinks to prevent the heat sinks from applying excessive pressure to and damaging the DMD module.  
         [0008]     One flexible assembly system is disclosed in U.S. Pat. No. 6,791,838, which was filed on Sep. 15, 2004 and is assigned on its face to the Lite-On Technology Corporation. This patent is hereby incorporated by reference in its entirety.  
         [0009]      FIG. 1  shows the structure of the flexible assembly system disclosed in the U.S. Pat. No. 6,791,838. Referring to  FIG. 1 , the flexible assembly system comprises a heat sink  1 , a DMD module  2 , an optical holder  3 , a flexible element  4 , and a fastening element  5 .  
         [0010]     The heat sink  1  comprises a plurality of connection holes  10 , a thermal conductor  11  that protrudes from a lower portion of the heat sink, and a heat sink pin  12 .  
         [0011]     The DMD module  2  comprises a control board  20 , a DMD  21 , an upper cover  23  transmitting information from the control board  20  to the DMD  21 , and a fixing holder  22  disposed around the DMD  21 . The control board  20  has a board opening  200  and a first fastening hole  201   a . The upper cover  23  has a cover opening  230  formed to correspond to the thermal conductor  11  of the heat sink  1 . The thermal conductor  11  of the heat sink  1  penetrates the board opening  200  of the control board  200  and contacts a rear portion  210  of the DMD  21  which controls the angles of the plurality of micro-mirrors  211 .  
         [0012]     The optical holder  3  has a second fastening-hole  30   a  and an assembly interface  31   a  for assembling the DMD module  2 .  
         [0013]     The flexible element  4  comprises a plurality of compressing springs  4   a , whereas the fastening element  5  comprises a plurality of bolts  5   a.    
         [0014]      FIG. 2  illustrates the structure of another conventional DMD assembly.  
         [0015]     Referring to  FIG. 2 , the DMD assembly comprises the heat sink  1 , the DMD module  2 , the optical holder  3 , the flexible element  4  and the fastening element  5 . Since the DMD assembly is constructed similarly to the flexible assembly system of  FIG. 1 , the same elements will be cited by the same reference numerals and detailed description will not be repeated.  
         [0016]     In contrast to the DMD assembly of  FIG. 1 , the DMD assembly of  FIG. 2  has a flat spring  250  and a nut  260 . The flat spring  250  buffers pressure applied to the DMD module  2  when the assembly is connected to reduce damage to the DMD  21 . The nut  260  enhances the connection.  
         [0017]     The conventional DMD assemblies described above have complicated structures, comprising the flexible element  4 , the compressing springs  4   a , the flat spring  250  and special screws such as the bolts  5   a . As a consequence, the manufacturing process is relatively complicated. Further, adjusting the position of the DMD  21  is difficult with these conventional structures. Also, in these structures, the DMD  21  can be exposed to dust, and image quality may deteriorate.  
         [0018]     Accordingly, there is a need for a simpler structure for a digital micro-mirror device (DMD) assembly for an optical projection system that is easier to manufacture, easier to adjust, and minimizes exposure to dust.  
       SUMMARY OF THE INVENTION  
       [0019]     An aspect of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a digital micro-mirror device (DMD) assembly for an optical projection system that has an an improved structure for simpler manufacturing.  
         [0020]     Another aspect of the present invention is to provide a DMD assembly for an optical projection system that is prevents the deterioration of image quality by adding a substantially dustproof structure.  
         [0021]     In accordance with an exemplary embodiment of the present invention, a DMD assembly comprises a DMD module with a control board that has a first fixing member. A DMD is mounted on one side of the control board, and a DMD holder resiliently supports a perimeter of the DMD. An optical holder is provided with a second fixing member to support the DMD module. A fasteninig member is engaged with the first and the second fixing members to integrally connect the DMD module and the optical holder.  
         [0022]     The DMD holder may have a DMD holder opening in the center thereof, and the DMD holder opening may be provided with a plurality of decentralizing holes.  
         [0023]     The control board may be provided with a bracket plate on the side opposite to the side where the DMD is mounted. The bracket plate may have a third fixing member to integrally connect the bracket plate, the DMD module and the optical holder through the fastening member.  
         [0024]     The fastening member may comprise a plurality of screws. The first fixing member may comprise a plurality of board connection holes formed on the control board for engagement with the screws. The third fixing member may comprise a plurality of bracket plate connection holes formed on the bracket plate. The DMD holder may be provided with a plurality of via-holes for penetration of the screws.  
         [0025]     The bracket plate is preferably made of aluminum. The bracket plate may be connected with a heat sink by a heat sink supporting unit and may be provided with a bracket plate opening so that a rear portion of the DMD can contact with the heat sink.  
         [0026]     The heat sink supporting unit may comprise a plurality of hooks formed on a peripheral end of the bracket plate. A flat spring may support the heat sink and have hook recesses at opposite ends for engaging the hooks.  
         [0027]     The heat sink may be further provided with a cooling fan on one side which is supported by a fan supporting unit. The fan supporting unit may comprise a cooling fan supporting boss protruding from the bracket plate, a fan holder inserted in the cooling fan supporting boss, and a fan bracket engaged with the fan holder at opposite ends of the bracket and connected to a bottom of the cooling fan.  
         [0028]     A substantially dustproof unit may be provided between the DMD holder and the optical holder. The substantially dustproof unit may comprise a gasket that surrounds the DMD holder opening of the DMD holder. The gasket may be formed of resilient material. At least one of the optical holder and the DMD holder may be provided with a groove for receiving the gasket.  
         [0029]     The DMD assembly may further comprise a housing that encloses the DMD module and the DMD holder. The holder may have a plurality of housing connection holes thereon, and wherein the optical holder may further comprise a housing boss having boss holes corresponding to the housing connection holes, so that the housing and the optical holder can be integrally connected with each other. The housing may comprise a plurity of cooling holes. The housing is preferably formed of metal so as to shield electromagnetic interference (EMI). The housing connection holes may be formed larger than the boss holes so that the position of the housing can be adjusted.  
         [0030]     According to the above-described DMD assembly of the optical projection system in accordance with an exemplary embodiment of the present invention, the assembly of the DMD is easier because dedicated structures such as a flat spring and a special screw for connection are omitted.  
         [0031]     Furthermore, since foreign substances such as dust are prevented from flowing into the DMD by the substantially dustproof unit, image quality can be improved.  
         [0032]     In addition, the position of the DMD can be adjusted easily by varying the fastening position of the housing which includes the DMD.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0033]     The above and other objects, features, and advantages of certain embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
         [0034]      FIG. 1  is an exploded view of the structure of a flexible assembly system disclosed in U.S. Pat. No. 6,791,838;  
         [0035]      FIG. 2  is an exploded view of the structure of another conventional digital micro-mirror device (DMD) assembly;  
         [0036]      FIGS. 3 and 4  are perspective views of the structure of an optical engine using a DMD assembly according to an exemplary embodiment of the present invention;  
         [0037]      FIG. 5  is an exploded, perspective view of the structure of the DMD assembly according to an exemplary embodiment of the present invention;  
         [0038]      FIG. 6  is a partially enlarged view of a DMD holder according to an exemplary embodiment of the present invention, viewed in the direction of the arrow A in  FIG. 5 ;  
         [0039]      FIG. 7  is a front view illustrating the structure of a bracket plate according to an exemplary embodiment of the present invention, viewed in the direction of the arrow B of  FIG. 5 ;  
         [0040]      FIG. 8  is an enlarged view of the portion ‘V’ of  FIG. 5 ;  
         [0041]      FIG. 9  shows a heat sink being connected, according to an exemplary embodiment of the present invention; and  
         [0042]      FIG. 10  is an enlarged view of a portion ‘VI’ of  FIG. 5  that shows a substantially dustproof unit applied in accordance with an exemplary embodiment of the present invention. 
     
    
       [0043]     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0044]     The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
         [0045]      FIG. 3  is a perspective view showing the structure of an optical engine with a digital micro-mirror device (DMD) assembly according to an exemplary embodiment of the present invention. Referring to  FIG. 3 , an optical engine  500  comprises a base  501 , a lighting unit  510 , a DMD assembly  600 , and a projection lens unit  530 . A light projected from the lighting unit  510  is reflected from a DMD of the DMD assembly  530  toward the projection lens unit  530 . The DMD will be described in detail later. An image light reflected to the projection lens unit  530  is projected onto a projection surface such as a screen (not shown).  
         [0046]      FIG. 4  is a perspective view illustrating the structure of the DMD assembly  600  according to an exemplary embodiment of the present invention. Referring to  FIG. 4 , an optical holder  610  which forms part of the DMD assembly  600  is erected on the base  501 . The optical holder  610  includes a DMD module which will be described later. A housing  660 , which is connected with a heat sink  630  and a cooling fan  650 , is attached on the outside of the optical holder  610 .  
         [0047]      FIG. 5  is an exploded, perspective view showing the structure of the DMD assembly  600 .  FIG. 6  is an enlarged view of a DMD holder according to an exemplary embodiment of the present invention.  
         [0048]     Referring to  FIG. 5 , the DMD assembly  600  comprises the optical holder  610 , the heat sink  630 , the cooling fan  650 , the housing  660 , the DMD module  670 , and a fastening member  680 .  
         [0049]     The housing  660  encloses the DMD module  670 . To this end, the housing  660  comprises a pair of square boxes, that is, first and second square boxes  661  and  663 . The first square box  661  includes a connection piece  661   a  that extends from a peripheral end of the housing  600  and has a plurality of housing connection holes  661   a ′. The second square box  663  forming the housing  660  has a plurality of cooling holes  663   c  to emit heat generated from the DMD module  670  formed therein. The housing  660  is preferably formed of metal so as to effectively shield electromagnetic interference (EMI).  
         [0050]     The DMD module  670  comprises a control board  671 , a socket  673  mounted on one side of the control board  671 , a DMD  674  in which numerous micro-mirrors are arranged, and a DMD holder  675  resiliently surrounding and supporting the DMD  674 . Here, the DMD holder  675  decentralizes a force applied to the DMD  674  during assembly of the DMD assembly  670 .  
         [0051]     The socket  673  and the control board  671  respectively have a socket opening  673   a  and a board opening  671   a  to allow the rear portion of the DMD  674  to penetrate through. Additionally, the control board  671  is provided with a first fixing member  67  l b , such as a plurality of board connection holes  671   b’ , to fix the fastening member  680 .    
         [0052]     Referring to  FIG. 6 , the DMD holder  675  has a DMD holder opening  675   a  in its center portion and a plurality of decentralizing holes  675   b  for evenly dividing the force applied to the DMD  674  by resiliently supporting the DMD  674 . Additionally, the DMD holder  675  has via-holes  675   c  to allow the fastening member  680  to pass through.  
         [0053]     Referring back to the  FIG. 5 , the optical holder  610  has an optical holder opening  611  and a plurality of connection bosses  613   a  to form a second fixing member  613  to fix the fastening member  680 . In addition, a housing boss  615   a  is provided around the optical holder  610 , which has a boss holes  615   a ′ corresponding to the housing connection holes  661   a ′ formed on the connection piece  661   a , so as to integrate the housing  660  and the optical holder  610 . Preferably, the housing connection holes  661   a ′ are larger than the boss holes  615   a’ so that the housing  660  can move vertically or horizontally, thereby positioning the DMD  674  built in the housing  660 .    
         [0054]     The fastening member  680  comprises screws  681  for engagement with the board connection holes  671   b ′ (which are the first fixing member  671   b ) and with the connection bosses  613   a  (which are the second fixing member  613 ). Accordingly, the fastening member  680  integrates the DMD module  670  (including the control board  671 , the socket  673  and the DMD  674 ), with the optical holder  610 .  
         [0055]     A bracket plate  690  may be further provided on an opposite side of the control board  671  to the side where the DMD  674  is mounted.  
         [0056]      FIG. 7  is a front view of the bracket plate  690  according to one exemplary embodiment of the present invention. Referring to  FIG. 7 , the bracket plate  690  has a bracket plate opening  691  and a third fixing member  693  for engagement with the screws  681  (which are the fastening member  680 ). The third fixing member  693  comprises a plurality of bracket plate connection holes  693   a  to allow the screws  681  to pass through. Accordingly, the optical holder  610 , the DMD module  670 , the control board  671  and the bracket plate  690  can all lie integrated by the screws  681 .  
         [0057]     The bracket plate  690  is structured to mount an air-expelling device such as the heat sink  630  and the cooling fan  650 . The mounting structure of such an air-expelling device will now be described in greater detail.  
         [0058]      FIG. 8  is an enlarged view of a portion ‘V’ of  FIG. 5 , and  FIG. 9  shows the heat sink  630  when it is connected.  
         [0059]     Referring to FIGS.  7  to  9 , the bracket plate  690  is partly exposed to the outside of the second square box  663  of the housing  660  and is connected with the heat sink  630  through a heat sink supporting unit  710 . The heat sink supporting unit  710  comprises hooks  695  formed on a peripheral end of the bracket plate  690 , and a flat spring  713  supporting one side of the heat sink  630  by crossing under the heat sink  630  and having hook recesses  713   a  for engagement with the hooks  695  at opposite ends thereof. The heat sink  630  comprises a plurality of protruding cooling fins  631 .  
         [0060]     With reference to  FIGS. 5 and 8 , the cooling fins  631  are mounted on one side of the heat sink  630  through a fan supporting unit  750 . The fan supporting unit  750  comprises a fan supporting boss  697  protruding from the bracket plate  690 , a fan holder  753  inserted in the fan supporting boss  697 , and a fan bracket  755  connected to a bottom of the cooling fan  631  and engaged with the fan holder  753  at opposite ends of the fan holder. The bracket plate  690  is preferably made of aluminum due to its superior thermal conductivity. One end of the fan holder  753  is inserted in the fan supporting boss  697  while the other end is exposed to the outside of the fan supporting boss  697  and fit into a damper  753   a.    
         [0061]     Additionally, a substantially dustproof unit  770  is provided to the DMD  674  to block foreign substances and prevent them from flowing into the DMD  674 .  
         [0062]      FIG. 10  is an enlarged view of a portion ‘VI’ of  FIG. 5  that illustrates a substantially dustproof unit applied in accordance with an exemplary embodiment of the present invention.  
         [0063]     Referring to  FIGS. 5 and 10 , the substantially dustproof unit  770  comprises a gasket  771  formed as a substantially square frame for surrounding the DMD holder opening  675   a  of the DMD holder  675 . The gasket  771  is preferably formed of resilient material. To mount the gasket  771 , at least one of the optical holder  610  or the DMD holder  675  is provided with a groove  617  for insertion of the gasket  771 . In the drawing, by way of example, the optical holder  610  has the groove  617 . According to this structure, foreign substances such as dust can be effectively prevented from flowing into the DMD  674 .  
         [0064]     While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.