Abstract:
A light source unit and a projector apparatus secure a certain light quantity by improving the utilization efficiency of light, and thereby realize miniaturization. The light source unit includes a reflector having an opening for housing a lamp and an opening for radiating light, the reflector having an inner surface subjected to mirror surface working to be shaped in a polynomial surface, a light source equipped with a bulb and an electrode introducing unit guiding an electrode to the bulb, the bulb being inserted into the reflector from the opening and being disposed so that a focus position of the light reflected by an inner wall of the reflector is not located on the electrode introducing unit, and a condenser lens condensing the light emitted from the reflector, the condenser lens disposed so as to be located on an optical axis of light emitted from the light source.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a light source unit and a projector apparatus equipped with the light source unit, and more particularly to a light source unit miniaturized without decreasing the utilization efficiency of light from a light source and a projector apparatus equipped with the light source unit. 
     2. Description of the Related Art 
     A projector apparatus is configured to display an image on a screen by making the light that has outgone from a light source unit be incident into a mirror tunnel to make the light having a uniform intensity distribution after making the light pass through a color wheel, and by projecting the light with the light quantity being switched at each pixel with a micro-mirror device, a liquid crystal display device or the like. 
     As shown in  FIG. 9 , a light source unit  50  is composed of a light source  51  radiating light, a convex lens  52 , which is disposed on an optical axis K for condensing the light emitted form the light source  51 , and a mirror tunnel  53 , into which the light that has outgone from the convex lens  52  is made to be incident (see JP Hei 06-51401A). 
     The light source  51  is composed of a reflector  54  and a lamp  55  inserted into the reflector  54 . The lamp  55  is composed of a bulb  56  and electrode introducing units  59 , and the lamp  55  is inserted so that the bulb  56  may be located in the reflector  54 . In addition, the color wheel is omitted in  FIG. 9 . 
     Here, a part of the light that has been emitted from the bulb  56  and has been reflected by the inner wall of the reflector  54  strikes the electrode introducing unit  59 , and the light quantity of the light is attenuated. Moreover, the convex lens  52  cannot sufficiently radiate the light reflected by the reflector  54  onto the incidence plane  53   a  of the mirror tunnel  53 . 
     Accordingly, in order to secure a certain light quantity, it becomes necessary for the light source unit  50  to have a size equal to a certain size or more, and a projector apparatus having the light source unit  50  built therein has a tendency to become large in size. Consequently, the projector apparatus is not always easy to carry and to install. 
     Although the size of a light source unit is more preferable to be smaller from the viewpoint of miniaturizing the whole body, it has been necessary for the size of the lamp of the light source unit to be a certain size or more from the viewpoint of securing a light quantity. 
     SUMMARY OF THE INVENTION 
     A preferable aspect of the present invention is a light source unit including: a reflector having an opening for housing a lamp and an opening for radiating light, the reflector having an inner surface subjected to mirror surface working to be shaped in a polynomial surface; a light source equipped with a bulb emitting light and an electrode introducing unit guiding an electrode to the bulb, the bulb being inserted into the reflector from the opening for housing the lamp and being disposed so that a focus position of the light emitted from the bulb and reflected by an inner wall of the reflector is not located on the electrode introducing unit; and a condenser lens condensing the light emitted from the reflector, the condenser lens disposed so as to be located on an optical axis of light emitted from the light source. 
     Moreover, another preferable aspect of the present invention is a projector apparatus including: a light source unit composed of a reflector having an opening for housing a lamp and an opening for radiating light, the reflector having an inner surface subjected to mirror surface working to be shaped in a polynomial surface, a light source equipped with a bulb emitting light and an electrode introducing unit guiding an electrode to the bulb, the bulb being inserted into the reflector from the opening for housing the lamp and being disposed so that a focus position of the light emitted from the bulb and reflected by an inner wall of the reflector is not located on the electrode introducing unit, and a condenser lens condensing the light emitted from the reflector, the condenser lens disposed so as to be located on an optical axis of light emitted from the light source; a mirror tunnel guiding light that has outgone from the condenser lens; a lens condensing light that has outgone from the mirror tunnel; a micro-mirror device receiving light that has outgone from the lens to project an image; and a projector lens expanding the image projected from the micro-mirror device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of the inner part of a projector apparatus according to an embodiment of the present invention; 
         FIG. 2  is a schematic configuration diagram of an optical system according to the projector apparatus of the present embodiment; 
         FIG. 3  is a schematic sectional view of a light source unit; 
         FIGS. 4A ,  4 B and  4 C are schematic views showing a lamp used for the present invention; 
         FIG. 5  is a schematic perspective view of a condenser lens according to the present embodiment; 
         FIG. 6  is a sectional view taken along a line VI-VI of the condenser lens shown in  FIG. 5 ; 
         FIG. 7  is a schematic front view of the lens surface on the light source side of the condenser lens according to the present embodiment; 
         FIG. 8  is a schematic view showing a positional relation between the members constituting the light source unit; and 
         FIG. 9  is a sectional view of a conventional light source unit. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, an embodiment of the present invention is described by reference to the drawings. However, the range of the invention is not limited to the shown example. 
       FIG. 1  is a top view showing the inner part of a projector apparatus according to an embodiment of the present invention.  FIG. 2  is a schematic configuration diagram of the optical system according to the projector apparatus of the present embodiment.  FIG. 3  is a schematic sectional view of a light source unit. In addition, the illustration of a color wheel  20  is omitted in  FIG. 3 . 
     As shown in  FIG. 1 , a projector apparatus  1  is provided with a case  2 . A power source substrate  3  for controlling the whole body of the projector apparatus  1  is disposed in the inner part of the case  2 . On the power source substrate  3  a not shown power source is attached. Near the central portion in the case  2 , a light source unit  4  controlled by the power source substrate  3  is disposed. 
     As shown in  FIGS. 2 and 3 , the light source unit  4  is composed of a light source  5  and a condenser lens  6 . As shown in  FIG. 3 , the light source  5  is composed of a reflector  9  and a lamp  10  housed in the reflector  9 . 
     The reflector  9  is formed into a polynomial surface shape. The polynomial surface shape of the reflector  9  is a form expressed by the formula obtained by substituting a value shown in Table 1 for each parameter of the following Formula (1). 
     
       
         
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 (1) 
               
               
                 
                   
                     
                       
                         z 
                         = 
                         
                           
                             
                               cr 
                               2 
                             
                             
                               1 
                               + 
                               
                                 
                                   1 
                                   - 
                                   
                                     
                                       ( 
                                       
                                         1 
                                         + 
                                         k 
                                       
                                       ) 
                                     
                                     ⁢ 
                                     
                                       c 
                                       2 
                                     
                                     ⁢ 
                                     
                                       r 
                                       2 
                                     
                                   
                                 
                               
                             
                           
                           + 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             r 
                           
                           + 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               2 
                             
                           
                           + 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               3 
                             
                           
                           + 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             4 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               4 
                             
                             ⁢ 
                             ⋯c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             10 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               10 
                             
                           
                         
                       
                     
                   
                 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 DIAMETER OF OPENING FOR 
                 33.12 
               
               
                   
                 RADIATING LIGHT (mm) 
               
               
                   
                 DIAMETER OF OPENING FOR 
                 11 
               
               
                   
                 HOUSING LAMP (mm) 
               
               
                   
                 CONIC CONSTANT: k 
                 −0.47973 
               
               
                   
                 CURVATURE: c 
                 0.0837149 
               
               
                   
                 COEFFICIENT: c1 
                  9.29227E−02 
               
               
                   
                 COEFFICIENT: c2 
                 −3.764339E−02 
               
               
                   
                 COEFFICIENT: c3 
                  7.347004E−03 
               
               
                   
                 COEFFICIENT: c4 
                 −5.758458E−04 
               
               
                   
                 COEFFICIENT: c5 
                 −1.368030E−06 
               
               
                   
                 COEFFICIENT: c6 
                  2.231387E−06 
               
               
                   
                 COEFFICIENT: c7 
                 −2.921644E−08 
               
               
                   
                 COEFFICIENT: c8 
                 −1.982415E−09 
               
               
                   
                 COEFFICIENT: c9 
                 −2.136231E−10 
               
               
                   
                  COEFFICIENT: c10 
                  1.042357E−11 
               
               
                   
                   
               
             
          
         
       
     
     In Formula (1), the letter z denotes an axis in an optical axis direction (the traveling direction of light is supposed to be positive); the letter c denotes a radius of curvature; the letter k denotes a conic constant; and the letter r (mm) denotes the length of a perpendicular line when the perpendicular line is let fall from the edge portion of an opening for radiating light  11 , which will be described later, to the optical axis K. 
     Moreover, the opening for radiating light  11  is formed on the reflector  9  for making light outgo. Furthermore, an opening for housing a lamp  12  is also formed at the base of the reflector  9 , and the lamp  10  is housed from the opening for housing a lamp  12 . 
     As shown in  FIG. 4A , the lamp  10  is composed of a bulb  13  making light outgo and electrode introducing units  14  provided on both the ends of the bulb  13  in the longitudinal direction thereof for introducing electrodes into the bulb  13 . Moreover, in the bulb  13 , an arc  15  carrying out discharges is provided. The bulb  13  is disposed near the opening for housing a lamp  12  in the reflector  9  so that the focus position of emitted light emitted from the bulb  13  to be reflected by the inner wall of the reflector  9  may be formed at a position farther than the electrode introducing unit  14  on the side of the traveling direction of the emitted light. 
     As a concrete shape of the bulb  13  used for the present invention, for example, the following shape can be cited. 
     First, as shown in  FIG. 4B , an ellipse A having a conic coefficient of −0.91508, the radius of curvature of 4.175964 mm, a semimajor axis of 49.17239 mm and a semiminor axis of 14.32976 mm is located so that the major axis L of the ellipse A may cross at right angles with the optical axis K. At this time, the optical axis K is disposed so that the optical axis K may cross at right angles with the major axis L of the ellipse A at a position distant by 5.25 mm from a point Q at one end on the major axis L of the ellipse A to the side of a point R at the other end on the major axis L of the ellipse A (hereinafter, the point where the optical axis K crosses at right angles with the major axis L of the ellipse A is referred to as a “point S”). 
     Next, an ellipse B is disposed so that the central point U of the ellipse B may be located at a position distant by 24.77409 mm from the central point T of the ellipse A on the side of the point Q on the major axis L and so that the minor axis N of the ellipse B may be parallel to the minor axis M of the ellipse A. The ellipse B has a conic coefficient of −0.85721, the radius of curvature of 110047 mm, a semimajor axis of 21.7811 mm and a semiminor axis of 8.230445 mm. 
     Next, the ellipses A and B are rotated around the optical axis K. Thereupon, a solid spindle C shown in  FIG. 4C  is formed by an arc O of the ellipse A, which is located nearer to the point Q than the optical axis K and rotates around the optical axis K. 
     The outer edge portion of the solid spindle C corresponds to the periphery of the bulb used for the present embodiment. Moreover, the space in the inside of a spindle D formed by the rotation of an arc P of the ellipse B, which is located nearer to the point Q than the optical axis K, around the optical axis K corresponds to the space in which the arc  15  is housed in the bulb. 
     Then, the shape of the space between the spindles C and D corresponds to the shape of a glass member for housing the arc, and the point S corresponds to the position of the arc housed in the bulb. By attaching the electrode introducing units  14  supplying electric power to the arc on both the ends of the bulb  13 , which has the shape mentioned above, in the longitudinal direction of the bulb  13  as shown in  FIG. 4A , the lamp  10  used for the present invention is formed. 
     The condenser lens  6  is disposed in the traveling direction of the light that has outgone from the opening for radiating light  11  of the reflector  9 . The shape of the condenser lens  6  is not limited as long as the condenser lens  6  can sufficiently condense the light that has outgone from the opening for radiating light  11  to make the condensed light outgo into the traveling direction of the light. An example of a lens capable of being used as the condenser lens is shown in the following. 
       FIG. 5  is a schematic perspective view of an example of the condenser lens  6 , and  FIG. 6  is a sectional view taken along the line VI-VI of the condenser lens  6  shown in  FIG. 5 . 
     As shown in  FIGS. 5 and 6 , a lens surface  16  on the side on which the light that has outgone from the opening for radiating light  11  of the reflector  9  is radiated is formed into a concave, and the lens surface  16  is formed to be most depressed in the central portion of the lens surface  16 . Moreover, a lens surface  17  on the side from which the light of the condenser lens  6  outgoes is formed into a convex, and is formed so that the central portion of the lens surface  17  may evaginate. In addition, although the central portion of the lens surface  16  of the condenser lens  6  is formed so as to be depressed and the central portion of the lens surface  17  of the condenser lens  6  is formed so as to evaginate, the lens surface  16  may be simply formed into a concave and the lens surface  17  may be also simply formed into a convex. 
     The condenser lens  6  is disposed so that the lens surface  16  may be opposed to the opening for radiating light  11  of the reflector  9  of the light source  5  and the lens surface  17  may be opposed to the incidence surface  21   a  of a mirror tunnel  21 , which will be described later. Moreover, the condenser lens  6  is disposed so that the center of the lens surface  16  and the center of the lens surface  17  may be located on the optical axis K. 
     The shape of the lens surface  16  on the side of the light source  5  of the condenser lens  6  and the shape of the lens surface  17  on the side of the mirror tunnel  21  are expressed by the formulae obtained by substituting each parameter of the following Formula (2) for a value shown in Table 2. 
     
       
         
               
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                   
                 (2) 
               
               
                 
                   
                     
                       
                         z 
                         = 
                         
                           
                             
                               cr 
                               2 
                             
                             
                               1 
                               + 
                               
                                 
                                   1 
                                   - 
                                   
                                     
                                       ( 
                                       
                                         1 
                                         + 
                                         k 
                                       
                                       ) 
                                     
                                     ⁢ 
                                     
                                       c 
                                       2 
                                     
                                     ⁢ 
                                     
                                       r 
                                       2 
                                     
                                   
                                 
                               
                             
                           
                           + 
                           
                             
                               c 
                               1 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             r 
                           
                           + 
                           
                             
                               c 
                               2 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               2 
                             
                           
                           + 
                           
                             
                               c 
                               3 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               3 
                             
                           
                           + 
                           
                             
                               
                                 c 
                                 ⁢ 
                                 
                                     
                                 
                               
                               4 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               4 
                             
                           
                         
                       
                     
                   
                 
               
               
                   
               
             
          
           
               
                   
                 LENS SURFACE 16 
                 LENS SURFACE 17 
               
               
                   
                   
               
             
          
           
               
                 CONIC CONSTANT: k 
                 −1 
                 −1 
               
               
                 RADIUS OF 
                 INFINITY 
                 INFINITY 
               
               
                 CURVATURE: c 
               
               
                 COEFFICIENT: c1 
                 −8.124720E−01 
                  1.535353E−01 
               
               
                 COEFFICIENT: c2 
                  1.777498E−01 
                 −8.654634E−02 
               
               
                 COEFFICIENT: c3 
                 −2.406356E−02 
                 −1.362107E−03 
               
               
                 COEFFICIENT: c4 
                  1.099373E−03 
                  2.023045E−04 
               
               
                   
               
             
          
         
       
     
     In Formula (2), the letter z denotes an axis in an optical axis direction (the traveling direction of light is supposed to be positive); the letter c denotes a radius of curvature; and the letter k denotes a conic constant. Moreover, the letter r (mm) denotes the length of a perpendicular line Z when the perpendicular line Z is let fall from a point V, which is a point on the edge portion of the condenser lens  6 , to the optical axis K, as shown in  FIG. 6 . 
     The lens surface  16  on the side of the light source  5  of the condenser lens  6  can be divided into the range (hereinafter referred to as an “effective range”) that condenses radiated light to introduce the condensed light to the lens surface  17  on the side of the mirror tunnel  21  and the other range. For example, in case of a condenser lens having the radius of 10 mm, as shown in  FIG. 7 , the effective range  19  is the range on the outside of the range within 1.5 mm from the central point X and on the inside of the range within 9 mm from the central point X. Then, the distance from a point W to the central point X is 3.4 mm, and the distance from the central point X to a point Y, where the optical axis K and the lens surface  17  are crossed with each other, is 6.51 mm. 
     As shown in  FIGS. 1 and 2 , in the outgoing direction of light of the condenser lens  6 , the color wheel  20 , which converts the light that has outgone from the condenser lens  6  into each color of red (R), green (G) and blue (B), is disposed. The mirror tunnel  21  is disposed in the traveling direction of the light that has been transmitted through the color wheel  20 , and an image unit  22  for projecting an image on a screen is disposed in the outgoing direction of light of the mirror tunnel  21 . In addition, the color wheel  20  may be disposed on the side of the outgoing direction of light of the mirror tunnel  21 . 
     The color wheel  20  is a circular rotation plate, and is equipped with the color filters of a red (R) one, a green (G) one and a blue (B) one, which are arranged in the circumferential direction. The color wheel  20  is disposed so that the central axis of rotation is laterally shifted from the optical axis K. 
     The mirror tunnel  21  is a transparent rectangular column, and is provided to be arranged along the optical axis K. The mirror tunnel  21  introduces the incidence light from the incidence surface  21   a  into the optical axis direction, making the incidence light carry out the total reflections thereof at the interface between the side surface of the mirror tunnel  21  and the outside air layer. Then, the mirror tunnel  21  makes the guided light outgo from the exit surface  21   b  of the mirror tunnel  21  as a light flux having a uniform intensity distribution. In addition, a rectangular cylinder in which a reflection film is provided on the whole inner circumferential surface thereof may be used as the mirror tunnel  21 . 
     As shown in  FIGS. 1 and 2 , the image unit  22  is disposed in the direction in which light is made to outgo from the mirror tunnel  21 . As shown in  FIG. 2 , the image unit  22  is composed of, for example, a lens  23  irradiated by the light that has been made to outgo from the mirror tunnel  21 , a micro-mirror device  24  irradiated by the light that has been made to outgo from the lens  23 , and a projector lens  25  on which the light that has been reflected by the micro-mirror device  24  is projected. 
     The lens  23  projects the light that has been made to outgo from the mirror tunnel  21  on the micro-mirror device  24 . Although the lens  23  is illustrated as a single lens in  FIG. 2 , the lens  23  may be composed of a plurality of lenses. 
     The micro-mirror device  24  forms each pixel of a display image by a plurality of micro-mirrors, and switches the light and darkness of the pixels by switching the inclination directions of these micro-mirrors to project the image. The micro-mirrors are formed of ultra-thin pieces of metal such as the pieces of aluminum, and each of the micro-mirrors has a vertical width and a horizontal width, each within a range of from 10 μm to 20 μm. Each of these micro-mirrors is formed on each of a plurality of mirror driving devices (not shown) such as CMOS&#39;s arranged in a matrix in row directions and column directions. 
     The projector lens  25  expands the reflected light from the micro-mirror device  24  to project the expanded light onto the screen (not shown). In addition, although the projector lens  25  is illustrated as a single lens in  FIG. 2 , the projector lens  25  may be composed of a plurality of lenses. 
     As shown in  FIG. 1 , a sirocco fan  26  making cooling air flow into the inside of the light source  5  in order to cool the light source  5  is disposed between the case  2  and the mirror tunnel  21 . Moreover, an axial flow fan  29  for exhausting the air that has been made to flow into the light source  5  is disposed in the direction of the opening for housing a lamp  12  of the reflector  9 . 
     Here, an example of the positional relation of the light source unit  4  used in the present embodiment is described. In addition, the above exemplified sizes of the reflector, the lamp and the condenser lens are used as those in the description here.  FIG. 8  is a schematic sectional view of the light source unit  4  showing the positional relation of the members constituting the light source unit  4 . In addition, in order to clarify the positional relation, the illustration of the color wheel  20  is omitted in  FIG. 8 . 
     The arc  15  is disposed so as to be located at a position distant from the base of the reflector  9  by 5.794 mm on the optical axis K. The condenser lens  6  is disposed so that the center of the lens surface  16  on the side of the light source  5  may be located at a position distant from the arc  15  by 33.34 mm. Moreover, the mirror tunnel  21  is disposed so that the distance from the arc  15  to the point where the incidence surface  21   a  and the optical axis K cross at right angles may be 47.5 mm. 
     Next, the operation of the embodiment of the present invention is described. 
     When the projector apparatus  1  is driven, light is emitted from the bulb  13  of the light source  5 , and most of the emitted light is radiated onto the inner wall of the reflector  9 , on which mirror surface working is performed. 
     At this time, as shown in  FIG. 3 , the bulb  13  of the light source  5  is disposed near to the opening for housing a lamp  12  in the reflector  9  so that the focus position of emitted light that has been emitted from the bulb  13  and has been reflected by the inner wall of the reflector  9  may be formed at a position farther than the end of the electrode introducing unit  14  on the side of the condenser lens  6  in the traveling direction of the reflected light. Consequently, most of the reflected light is radiated to the portions other than the central portion of the lens surface  16  of the condenser lens  6 . The light radiated into the effective range  19  in the light radiated onto the lens surface  16  of the condenser lens  6  is condensed before being radiated from the lens surface  17  into the color wheel  20 . 
     After the light that has been radiated into the color wheel  20  is converted into three colors of red, green and blue by the filter of each color of the red (R), the green (G) and the blue (B), respectively, the converted light is radiated onto the incidence surface  21   a  of the mirror tunnel  21 . The light that has been incident into the mirror tunnel  21  is guided into the optical axis direction, being subjected to the total reflection at the interface between the side surface in the mirror tunnel  21  and the outside air layer as shown in  FIG. 3 . Then, the guided light is radiated into the lens  23  after having been made to outgo from the exit surface  21   b.    
     The light flux of the light that has been radiated on the lens  23  is expanded by the lens  23 , and then the expanded light is radiated onto the micro-device  24 . Then, the light reflected by the micro-mirror device  24  is expanded by the projector lens  25  to be projected onto the not shown screen. 
     As described above, according to the present invention, because the focus position of the emitted light that has been emitted from the bulb  13  and has been reflected by the reflector  9  does not exist on the electrode introducing unit  14 , most of the emitted light does not strike the electrode introducing unit  14  of the lamp. Consequently, the emitted light does not attenuate to be radiated onto the lens. Thus, the loss of the emitted light can be reduced, and then the utilization efficiency of the emitted light emitted from the light source  5  can be improved. Consequently, it becomes possible to miniaturize the reflector  9 , and to miniaturize the whole body of the light source unit  4  in comparison with the conventional light source unit. 
     Moreover, because the light source unit  4  is miniaturized, the projector apparatus  1 , which installs the miniaturized light source unit  4 , can be miniaturized itself.