Abstract:
Provided is a projection video display device with which precision of location of each component of the optical engine and the projection optical assembly is maintained and display video quality not impaired even if exterior force is sustained. A projection video display device comprises an optical engine ( 2 ) which projects light which is emitted from a light source ( 21 ) upon a liquid-crystal panel ( 231 ) and forms a video, and a projection optical assembly ( 3 ) which projects an enlargement of the video which is emitted from the optical engine ( 2 ). The projection optical assembly ( 3 ) and the optical engine ( 2 ) are configured to be anchored to a common base ( 4 ) which retains these in an integrated manner, with the common base ( 4 ) being attached to the casing of the device.

Description:
TECHNICAL FIELD 
     The present invention relates to a projection video display device. 
     BACKGROUND 
     Projection video display devices such as a liquid crystal projector irradiate a display element such as a liquid crystal panel with light emitted from a light source such as a mercury lamp, and enlarges and projects a video formed by the display element with a projection lens onto a screen. The configuration of an optical system of the device includes an optical unit from irradiation with light emitted from the light source on the liquid crystal panel to formation of the video (hereinafter, referred to as an optical engine) and a projection optical system which enlarges and projects the video formed by the liquid crystal panel with the projection lens. In an optical engine of a color video display device, three liquid crystal panels for three primary colors (RGB) as display elements, a color separation system for irradiation light, and a color synthesis system for respective video colors are provided. Moreover, for adjusting a video-displaying position on the screen, a lens shifting mechanism is provided in the projection optical system which can move a projection lens in a direction perpendicular to an optical axis. 
     The optical engine and the projection optical system are positioned with respect to each other and are accommodated in a case of the device. In a conventional accommodating method, as described in Patent Literature 1, for example, respective components of the optical engine including the light source are accommodated and arranged in a light guide as an optical components case, and the light guide is fixed to the case of the device. The projection optical system is configured to be joined and fixed to an outgoing end portion of the light guide. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Application Laid-Open No. 2004-240024 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional structure such as the one of Patent Literature 1, the respective components of the optical engine are fixed to the case while being accommodated in the light guide as the optical components case. The light guide has a complicated internal structure corresponding to the shape of the respective components which are to be accommodated therein, and is generally formed of synthetic resin material by injection molding, for example. Therefore, the light guide itself has limitation on strength and can be easily deformed, as compared with metal material. Moreover, since the light guide is fixed to the case of the device, when the case is deformed by an external force, the deformation may extend to the light guide. As a result, positional accuracy between the respective optical components accommodated in the light guide may deteriorate, and, further by positional displacement with respect to the projection optical system, the quality of a video displayed on a screen may deteriorate (luminance unevenness, color shift or the like may occur). 
     It is therefore an object of the present invention to provide a projection video display device which can maintain positional accuracy of respective components of an optical engine and a projection optical system even when an external force is applied, and can prevent deterioration of the quality of a displayed video. 
     Solution to Problem 
     According to the present invention, in a projection video display device which projects a video formed by a display element, an optical engine which radiates light emitted from a light source on the display element to form the video and a projection optical system which enlarges and projects the video emitted from the optical engine are provided. The optical engine and the projection optical system are fixed to a common base which holds those integrally, and the common base is attached to a case of the device. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to maintain positional accuracy of respective optical components even when an external force or the like is applied, and prevent deterioration of the quality of a video to be displayed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an entire structure of a projection video display device according to this example. 
         FIG. 2  is a diagram showing an optical engine and a projection optical system. 
         FIG. 3  is a diagram showing a state in which the optical engine and the projection optical system are detached from a common base. 
         FIG. 4  is a perspective view showing a shape of the common base. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described below, referring to the drawings. 
       FIG. 1  is a diagram showing the entire structure of a projection video display device of this example, and shows an internal structure of the display device when a case top cover is removed. In a case  1 , an optical engine  2  which emits light from a light source and radiates the light onto a liquid crystal panel as a display element to form a video, and a projection optical system  3  which enlarges and projects the video formed by the liquid crystal panel with a projection lens are accommodated. In addition to those, a power supply unit  6  and a cooling unit  7 , and a video signal circuit, a control circuit, and the like which are not shown are also accommodated. 
       FIG. 2  and  FIG. 3  are diagrams showing the structures of the optical engine  2  and the projection optical system  3 . 
       FIG. 2  shows a diagram showing a state in which the optical engine  2  and the projection optical system  3  are taken out of the case  1 . The optical engine  2  and the projection optical system  3  are mounted on a common base  4  and are fixed thereto. 
       FIG. 3  shows a diagram showing a state in which the optical engine  2  and the projection optical system  3  are detached from the common base  4 . Please note that the projection lens  31  is not shown in  FIG. 3 . 
     The optical engine  2  includes a light source portion  21 , a color separation optical system  22 , and a color synthesis optical system  23 . Those components are accommodated in a tube-shaped light guide  20  and are fixed at predetermined positions. A light source such as an ultra-high pressure mercury lamp is used in the light source portion  21 , and emits approximately white light. The color separation optical system  22  separates the approximately white light into light of RGB three primary colors and guides the light of three primary colors to respective liquid crystal panels corresponding thereto. The color synthesis optical system  23  includes R, G, and B liquid crystal panels  231  and a cross dichroic prism  232 , and forms respective videos based on R, G, and B signals and performs color synthesis for those videos. 
     The projection optical system  3  is formed by a projection lens  31  and a lens shifting mechanism  32 . Video light emitted from the color synthesis optical system  23  is enlarged and projected onto a screen or the like by the projection lens  31 . The lens shifting mechanism  32  holds the projection lens  31  and moves it in two axial directions perpendicular to an optical axis (projection direction), and includes a horizontal direction (X direction) driving portion  32   x  and a vertical direction (Y direction) driving portion  32   y . To a lens attaching surface  32   a  of the lens shifting mechanism  32 , the projection lens  31  is fixed. Thus, a position of an image projected onto the screen can be moved and adjusted in the horizontal direction and the vertical direction. 
     In this example, the optical engine  2  and the projection optical system  3  are attached to the case  1  while being integrally fixed to the common base  4 . More specifically, an outgoing end portion of the tube-shaped light guide  20  and the color synthesis optical system  23  of the optical engine  2  are fixed to the common base  4 . Also, the lens shifting mechanism  32  of the projection optical system  3  is fixed to the common base  4 . 
       FIG. 4  is a perspective view showing the shape of the common base  4 . The common base  4  includes a fixing frame  41  standing in a central portion and pedestal portions  42  and  43  on both sides thereof, and is formed by aluminum die casting, for example, as a member which has high rigidity and is hardly deformable. The fixing frame  41  has an opening  44  through which video light from the optical engine  2  passes. The optical engine  2  is mounted on the pedestal portion  42 , the lens shifting mechanism  32  of the projection optical system  3  is mounted on the pedestal portion  43 , and they are integrally fixed. 
     More specifically, as for the optical engine  2  mounted on the pedestal portion  42 , what is fixed to the pedestal portion  42  is limited to the outgoing end portion of the light guide  20  and the color synthesis optical system  23 , and those are screwed to be fixed to fixing portions  51  (at three positions in this example). The reason for this is the following. The optical engine  2  has a number of optical components from the light source portion  21  to the color synthesis optical system  23 , and the dimensions (an optical path length) of the light guide  20  for accommodating those components becomes large. In a case of fixing the whole, the common base  4  increase in size, it is difficult to ensure the rigidity, and the mass increases simultaneously. Therefore, it is unwise to fix the whole optical engine  2  (light guide  20 ) to the pedestal portion  42 . 
     Moreover, as for the projection optical system  3  mounted on the pedestal portion  43 , an incident side of the lens shifting mechanism  32  is fixed to the standing fixing frame  41 , while the projection lens  31  is held by the lens attaching surface  32   a  on an outgoing side of the lens shifting mechanism  32 . 
     On the bottom surface of the common base  4 , fixing portions  50  for attaching the common base  4  to the case  1  are provided (at five positions in the example of  FIG. 4 ). Those fixing portions  50  are provided near a leg portion of the deformable fixing frame  41  for the purpose of preventing the deformation of the case  1  from extending to the optical engine  2  and the color synthesis optical system  23 . 
     The pedestal portion  42  of the common base  4  is provided with fixing portions  51  for attaching the end portion of the light guide  20  (at three positions in the example of  FIG. 4 ) and fixing portions  52  for attaching the color synthesis optical system  23  (at two positions in the example of  FIG. 4 ). Moreover, the fixing frame  41  of the common base  4  is provided with fixing portions  53  for attaching the lens shifting mechanism  32  (at four positions in the example of  FIG. 4 ). 
     According to the above structure, the optical engine  2  and the projection optical system  3  are integrally fixed to the common base  4 , and only the common base  4  is attached to the case  1 . In other words, the optical engine  2  and the projection optical system  3  are not fixed directly to the case  1 . Therefore, even when the case  1  has been deformed by an external force, deformation is prevented by the common base  4  having high rigidity, and the optical engine  2  and the projection optical system  3  are not directly affected by the deformation of the case  1 . Moreover, since the optical engine  2  (light guide  20 ) to be fixed to the common base  4  is limited to the outgoing end portion only, an external force is hardly applied to the main body of the light guide  20  and the respective optical components accommodated in the light guide  20  are maintained at predetermined positions with predetermined accuracy. Furthermore, since the optical engine  2  and the projection optical system  3  are fixed to the common base  4  having high rigidity, the positional relationship between both cannot be displaced. Thus, according to the structure of this example, even when an external force or the like is applied, it is possible to maintain the positional accuracy of the respective optical components and prevent deterioration of the quality of a video to be displayed (e.g., occurrence of luminance unevenness, color shift or the like). 
     REFERENCE SIGN LIST 
       1  . . . case, 
       2  . . . optical engine, 
       3  . . . projection optical system, 
       4  . . . common base, 
       20  . . . light guide, 
       21  . . . light source portion, 
       22  . . . color separation optical system 
       23  . . . color synthesis optical system, 
       231  . . . liquid crystal panel, 
       232  . . . cross dichroic prism, 
       31  . . . projection lens, 
       32  . . . lens shifting mechanism, 
       32   a  . . . lens attaching surface, 
       41  . . . fixing frame, 
       42 ,  43  . . . pedestal portion, 
       44  . . . opening, 
       50  to  53  . . . fixing portion.