Abstract:
A projector light tunnel comprising an elongated transparent solid body having a light incident surface for facing toward a light source, a light emitting surface at an opposite side of the elongated transparent solid body to the light incident surface, for uniformly standardizing intensity distribution of light emitted from the light source, the light incident surface being configured as a curved surface.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a light tunnel and a projection apparatus with the same. And, particularly, to a light tunnel and a projection apparatus which improve the light intensity on the center area of the projector light tunnel and the light combination efficiency. 
       BACKGROUND 
       [0002]    Conventionally, a projection apparatus includes a light tunnel to convert a point light source generated by a lamp into a surface light source. The light generated by the lamp passes into the projector light tunnel and is reflected many time on an inner wall of the projector light tunnel, then the light is emitted from the projector light tunnel with uniform luminance and desired shape.  FIG. 6  illustrating a typical optical system of a projection apparatus includes a light source  100 , a solid light tunnel  120 , and a light filter  130 . The light source  100  has an arc lamp  101  and an elliptical reflective mirror  102 . The elliptical reflective mirror  102  defines a near focal point F 1  and a distant focal point F 2 . The arc lamp  101  is positioned at the near focal point F 1  and an end of the projector light tunnel  120  is positioned at the distant focal point F 2 . 
         [0003]    Accordingly, light coming from the arc lamp  101  located at the near focal point F 1  of the elliptical reflective mirror  102  is focused at the distant focal point F 2 . The light goes directly into the projector light tunnel  120  as a point light source and is emitted from the light  120  as a surface light source with uniform luminance after multiple internal reflections in the projector light tunnel  120 . The light emitted from the projector light tunnel  120  is projected through the light filter  130  to become red, green, and blue (RGB) components, then the RGB components are reflected by a digital micro-mirror device (DMD) controlled by a central processing unite (CPU) to form an image on a screen. 
         [0004]    Generally, the arc lamp  101  of the light source  100  has two electrodes spaced from each other for generating light between the electrodes by arc discharge. The light is reflected by the elliptical reflective mirror  102  of the light source  100  and focused at the distant focal point of the elliptical reflective mirror  102 . However, the electrodes of the arc lamp  101  are located in the light path, which blocks passage of some of the reflected light, as a result luminance at the center of the light emitted from the projector light tunnel  120  is lower than other areas. Additionally, some of the light is lost due to inadequate reflection angle within the tunnel. 
         [0005]    Therefore, a light tunnel and a projection apparatus with the same which can increase the luminance in the center area of emitting light and improve the light utilization factor are desired. 
       SUMMARY 
       [0006]    In one aspect, a projector light tunnel is provided. The projector light tunnel comprising an elongated transparent solid body having a light incident surface for facing toward a light source, a light emitting surface at an opposite side of the elongated transparent solid body to the light incident surface, for uniformly standardizing intensity distribution of light emitted from the light source, the light incident surface being configured as a curved surface. 
         [0007]    Those and other advantages and novel features will be more readily apparent from the following detailed description set forth below taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a light tunnel, according to a first preferred embodiment. 
           [0009]      FIG. 2  is a schematic drawing showing the operation of an illumination system having the projector light tunnel of  FIG. 1 . 
           [0010]      FIG. 3  is a graph of luminance of the light emitted from the projector light tunnel of  FIG. 1 ; 
           [0011]      FIG. 4  is a perspective view of a light tunnel, according to a second preferred embodiment; 
           [0012]      FIG. 5  is a schematic drawing showing operation of an illumination system having the projector light tunnel of  FIG. 4 ; 
           [0013]      FIG. 6  is a schematic, plan view of an illumination system of a projection apparatus, according to the related art; 
           [0014]      FIG. 7  is a graph of luminance of the illumination system of the  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Referring to  FIG. 1 , a projector light tunnel  220 , according to a first preferred embodiment, is an elongated transparent solid body, and includes a sidewall  222 , a concave light incident surface  224  for facing toward a light source, and an light emitting surface  226  at an opposite side of the elongated transparent solid body to the light incident surface. The light radiated from a light source enters into the projector light tunnel  220  through the light incident surface  224  and is reflected many times by the sidewall  222 , finally emitting as an uniform light from the light emitting surface  226  of the projector light tunnel  220 . 
         [0016]      FIG. 2  is an illumination system of a projection apparatus equipped with the projector light tunnel  220 . The illumination system includes a light source  100 , the projector light tunnel  220 , and a filter  130 . The light source  100  has an arc lamp  101  and an elliptical reflective mirror  102 . The elliptical reflective mirror  102  defines a near focal point F 1  and a distant focal point F 2 . 
         [0017]    The projector light tunnel  220  is positioned on the front of the arc lamp  101  and a center point of the light incident surface  224  is located between the near focal point F 1  and the distant focal point F 2  of the arc lamp  101 . The arc lamp  102  radiates light l that is reflected by the elliptical reflective mirror  102  to the projector light tunnel  220 . Meanwhile, the angle formed between light l and a center axis of the projector light tunnel  220  becomes small when light l enters into the projector light tunnel  220  via penetrating the concave light incident surface  224  which can change the traveling direction of light l. Accordingly, the incident angle γ of light l entering the projector light tunnel  220  becomes greater. Therefore the projector light tunnel  220  can receive more effective light than the conventional light tunnel  120 , because of the concave light incident surface  224  changing the light traveling direction when it passes into the tunnel  220 . 
         [0018]    The brightness of the center area of light emitted from the projector light tunnel  220  is increased, because the distance light travels between reflections from the sidewall  222  will be increased with the increasing of the incident angle and as a result there is more light at the center axis of the projector light tunnel  220 . 
         [0019]      FIG. 3  shows of the projector light tunnel  220 , wherein the abscissa indicates the angle formed between the light emitted from the projector light tunnel  220  and the center axis of the projector light tunnel  220 , and the ordinate indicates the luminance of the light emitted from the projector light tunnel  220 . It is obvious that the brightness on center area of the light emitted from the projector light tunnel  220  is higher than in the conventional light tunnel as shown in  FIG. 7 . 
         [0020]    Referring to  FIG. 4 , a light tunnel  320 , according to second preferred embodiment, is an elongated transparent solid body, and includes a sidewall  322 , an convex light incident surface  324  for facing toward a light source, and an opposite light emitting surface  326  at an opposite side of the elongated transparent solid body to the light incident surface. The light radiated from a light source enters into the projector light tunnel  320  through the light incident surface  324  and reflected many times by the sidewall  322 , finally emitting as an uniform light from the light emitting surface  326  of the projector light tunnel  320 . 
         [0021]    As illustrated in  FIG. 5 , is an illumination system of a projection apparatus equipped with the projector light tunnel  320 . The illumination system includes a light source  100 , the projector light tunnel  320  and a filter  130 . The light source  100  has an arc lamp  101  and an elliptical reflective mirror  102 . The elliptical reflective mirror  102  defines a near focal point F 1  and a distant focal point F 2 . 
         [0022]    The projector light tunnel  320  is positioned on the front of the arc lamp  101  and a top center point of the light incident surface  324  is located beyond the distant focal point F 2  of the arc lamp  101 . The arc lamp  102  radiates light l that is reflected by the elliptical reflective mirror  102  to the projector light tunnel  320 . Meanwhile, the angle formed between light l and a center axis of the projector light tunnel  320  becomes small when light l enters into the projector light tunnel  320  via penetrating the convex light incident surface  324  which changes the traveling direction of light l. Accordingly, the incident angle γ of light l entering in the projector light tunnel  320  becomes greater. Therefore the projector light tunnel  320  can receive more effective light than conventional light tunnel  120 , because of the convex light incident surface  324  thereof changing the light traveling direction when it passes into the tunnel  220  from air. 
         [0023]    The brightness of the center area of light emitted from the projector light tunnel  320  is increased, because the distance light travels between reflections from the sidewall  322  will be increased with the increasing of the incident angle and as a result there is more light at the center axis of the projector light tunnel  320 . Understandably, the shape of a cross section of the projector light tunnel may be configured as a square shape for getting a squarely emitting light emitted from the projector light tunnel, in addition the shape of the cross section of the projector light tunnel may be designed as a trapezoid surface, a circular surface or a ellipse surface and so on for getting different shaped emitting light. 
         [0024]    Understandably, the light incident surface  324  of the projector light tunnel  320  may be configured as a spherical surface or an aspheric surface for matching the luminosity curve of the light source  100  for receiving more useable light irradiated from the light source. The location of the light incident surface of the projector light tunnel is positioned between the near focal point F 1  and the distant focal point F 2  or beyond the focal point F 2  fully depending on the shape of light incident surface. When the light incident surface is configured as a concave surface which can make the light divergence should be positioned between the near focal point F 1  and the distant focal point F 2  of the elliptical reflective mirror  102 . When the light incident surface is configured as a convex surface which can make the light convergence should be positioned beyond the distant focal point F 2  of the elliptical reflective mirror  102 . 
         [0025]    Understandably, the light emitting surface  326  of the projector light tunnel  320  may be configured as a curved surface corresponding to the light incident surface  324  of the projector light tunnel  320 . The light emitting surface  326  of the projector light tunnel  320  is matched to the light incident surface  324  of the projector light tunnel  320  for getting a matched optical characteristics. The projector light tunnel  320  can receive more light reflected from the light filter by the curved light emitting surface  326 . The light received by the projector light tunnel  320  can be reflected by the elliptical reflective mirror  102  and be reused to increase the brightness of the light emitting from the projector light tunnel  320 . 
         [0026]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.