Abstract:
There are provided a light source unit which realizes the reduction in size thereof while securing a certain quantity of light by increasing the utilization efficiency of light and a projector system utilizing the light source unit. A light source unit which includes a reflector of which an internal surface is planished to provide a mirror reflection effect and in which a lamp accommodation opening and a light emitting opening are formed, a light source in which a lamp including a bulb which radiates light and electrode introducing portions which guide electrodes into the bulb is inserted into the interior of the reflector from the lamp accommodation opening and is disposed in such a manner that a focal point position of the radiated light that is radiated from the bulb and reflected on an internal wall of the reflector is not positioned on the electrode introducing portion, and a condenser lens including a recess portion at a central portion of at least one of lens surfaces thereof which lies on an optical axis of the light radiated from the lamp and which is adapted to gather the light radiated from the lamp that is reflected on the reflector.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a light source unit and a projector system including the light source unit, and more particularly to a light source unit that is made smaller in size without reducing the utilization efficiency of light from a light source and a projector system including the light source unit.  
         [0002]     Projector systems are such that light emitted from a light source unit is passed through a color wheel, is thereafter caused to enter a mirror tunnel so as to be made into light having a uniform luminous intensity distribution and is then projected on a screen while the quantity of light of each pixel is being changed over by a micro mirror device or a liquid crystal display element, so that an image is displayed on the screen.  
         [0003]     As shown in  FIG. 14 , a light source unit  40  is made up of a light source  41  which emits light, a convex lens  42  disposed on an optical axis K for gathering light emitted from the light source  41  and a mirror tunnel  43  which light emerging from the convex lens  42  is made to enter to shine thereon (refer to Patent Document No.  1 ).  
         [0004]     The light source  41  is made up of a reflector  44  and a lamp  45  inserted into the reflector  44 . The lamp  45  is made up of a bulb  46  and electrode introducing portions  49 ,  49 , and the bulb  46  is inserted so as to be positioned within the reflector  44 . Note that the illustration of a color wheel is omitted in  FIG. 14 .  
         [0005]     Here, part of the light that is emitted from the bulb  46  and is then reflected on an internal wall of the reflector  44  impinges on the electrode introducing portion  49 , whereby the quantity of light is dampened. In addition, the convex lens  42  cannot sufficiently illuminate a light incident surface  43   a  of the mirror tunnel  43  with the light reflected by the reflector  44 .  
         [0006]     Due to this, the light source unit  40  needs to have a certain size or larger in order to secure a certain quantity of light, and hence, a projector system incorporating the light source unit  40  so enlarged tends to be enlarged, resulting in a problem that the projector system is not necessarily easy to carry and set.  
         [0007]     While the light source unit is preferred to be small in the light of making small the whole of the projector system, it is a conventional idea that the lamp in the light source unit must have a certain size or lager in the light of securing a necessary quantity of light.  
         [0008]     [Patent Document No. 1] Japanese Unexamined Patent Publication No. 6-51401  
       SUMMARY OF THE INVENTION  
       [0009]     According to a preferred aspect of the invention, there is provided a light source unit including a reflector of which an internal surface is planished to provide a mirror reflection effect and in which a lamp accommodation opening and a light emitting opening are formed, a light source in which a lamp including a bulb which radiates light and electrode introducing portions which guide electrodes into the bulb is inserted into the interior of the reflector from the lamp accommodation opening and is disposed in such a manner that a focal point position of the radiated light that is radiated from the bulb and reflected on an internal wall of the reflector is not positioned on the electrode introducing portion, and a condenser lens including a recess portion at a central portion of at least one of lens surfaces thereof which lies on an optical axis of the light radiated from the lamp and which is adapted to gather the light radiated from the lamp that is reflected on the reflector.  
         [0010]     In addition, according to another preferred aspect of the invention, there is provided a projector system including a light source unit including, in turn, a reflector of which an internal surface is planished to provide a mirror reflection effect and in which a lamp accommodation opening and a light emitting opening are formed, a light source in which a lamp including a bulb which radiates light and electrode introducing portions which guide electrodes into the bulb is inserted into the interior of the reflector from the lamp accommodation opening and is disposed in such a manner that a focal point position of the radiated light that is radiated from the bulb and reflected on an internal wall of the reflector is not positioned on the electrode introducing portion, and a condenser lens including a recess portion at a central portion of at least one of lens surfaces thereof which lies on an optical axis of the light radiated from the lamp and which is adapted to gather the light radiated from the lamp that is reflected on the reflector, a mirror tunnel which guides light that emerges from the condenser lens, a lens which gathers light that emerges from the mirror tunnel, a micro mirror device which receives light that emerges from the lens so as to project an image, and a projection lens which enlarges the image projected by the micro mirror device.  
         [0011]     Furthermore, according to a further aspect of the invention, there is provided a condenser lens used in a light source unit including a reflector of which an internal surface is planished to provide a mirror reflection effect and in which a lamp accommodation opening and a light emitting opening are formed, and a light source in which a lamp including a bulb which radiates light and electrode introducing portions which guide electrodes into the bulb is inserted into the interior of the reflector from the lamp accommodation opening and is disposed in such a manner that a focal point position of the radiated light that is radiated from the bulb and reflected on an internal wall of the reflector is not positioned on the electrode introducing portion, the condenser lens including a recess portion at a central portion of at least one of lens surfaces thereof which lies on an optical axis of the light radiated from the lamp and which is adapted to gather the light radiated from the lamp that is reflected on the reflector. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a plan view of a projector system according to a first embodiment of the invention with an upper surface removed to shown an inside configuration thereof.  
         [0013]      FIG. 2  is a schematic diagram which shows the configuration of the projector system according to the invention.  
         [0014]      FIG. 3  is a longitudinal sectional view of a light source unit according to the invention.  
         [0015]      FIG. 4  is a front view of a condenser lens.  
         [0016]      FIG. 5  is a sectional view of the condenser lens shown in  FIG. 4  taken along the line A-A′ in the same figure.  
         [0017]      FIG. 6  is a front view of a condenser lens.  
         [0018]      FIG. 7  is a sectional view of the condenser lens shown in  FIG. 6  taken along the line B-B′ in the same figure.  
         [0019]      FIG. 8  is a front view of a condenser lens.  
         [0020]      FIG. 9  is a sectional view of the condenser lens shown in  FIG. 8  taken along the line C-C′ in the same figure.  
         [0021]      FIG. 10  is a front view of a side A of a condenser lens.  
         [0022]      FIG. 11  is a front view of a side B of the condenser lens.  
         [0023]      FIG. 12  is diagram which shows reference lines drawn on the sectional view taken along the line A-A′ of the condenser lens.  
         [0024]      FIG. 13  is an exemplary diagram which shows a positional relationship between members making up a light source unit.  
         [0025]      FIG. 14  is a sectional view of a related-art light source unit. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]     Next, an embodiment of the invention will be described by reference to the accompanying drawings. However, note that claims are not limited by what is illustrated in the drawings.  
         [0027]     As shown in  FIG. 1 , a projector system  1  includes a case  2 , and a power supply circuit board  3  having a power supply mounted thereon is disposed in the case  2  for controlling the whole of the projector system  1 . A light source  5  that is to be controlled by the power supply circuit board  3  is disposed in the case  2  at a position near a central portion thereof, and a condenser lens  6  is disposed in a traveling direction of light emitted from the light source  5 . A color wheel  9  is disposed in a traveling direction of light that emerges from the condenser lens  6  for converting the light emerging from the condenser lens  6  into respective colors of red (R), green (G) and blue (B). A mirror tunnel  10  is disposed in a traveling direction of light that has transmitted through the color wheel  9 , and a projection unit  11  is disposed in a traveling direction of light that emerges from the mirror tunnel  10  for projecting an image on to a screen. In addition, a multiblade fan  13  for sending cooling air into the light source unit  5  to cool the light source  5  and an axial fan  12  for discharging the air sent into the light source  5  by the multiblade fan  13  from the interior of the projector system  1  are provided in the projector system.  
         [0028]      FIG. 2  is a schematic diagram which shows the configuration of the projector system  1 . A light source unit  4  is provided in the interior of the projector system  1 , and the light source unit  4  is made up of the light source  5  which radiates light and a condenser lens  6  which gathers the light radiated from the light source  5 .  
         [0029]     The condenser lens  6  is provided in the traveling direction of light emitted from the light source  5  for gathering the light so emitted, and the color wheel  9  is disposed in the traveling direction of light that emerges from the condenser lens  6  for converting the light emerging from the condenser lens  6  into the respective colors of R, G and B. The mirror tunnel  10  is disposed in the traveling direction of light that has transmitted through the color wheel  9 . The projection unit  11  is disposed in the traveling direction of light that emerges from the mirror tunnel  10 , and a lens  21  and a micro mirror device  22  which makeup the projection unit  11  are disposed on an optical axis K of light that emerges from the mirror tunnel  10 , the micro mirror device  22  being disposed in a traveling direction of light that emerges from the lens  21  in such a manner as not to oppositely face the lens  21 . A projection lens  23  is disposed in a traveling direction of light that is reflected by the micro mirror device  22 . Note that the color wheel  9  may be disposed on a light emerging side of the mirror tunnel  10  from which light emerges.  
         [0030]      FIG. 3  is a schematic longitudinal sectional view of the light source unit  4 . Note that the illustration of the color wheel  9  is omitted in  FIG. 3 .  
         [0031]     The light source  5  is made up of a reflector  24  and a lamp  29  accommodated within the reflector  24 .  
         [0032]     The reflector  24  is formed into a semi-spherical shape and an internal surface thereof is planished so as to provide a mirror reflection effect, an opening (hereinafter, referred to as a “light emitting opening  25 ”) being provided on a color wheel  9  side thereof. In addition, an opening is provided in a proximal portion of the reflector  24  (hereinafter, the opening formed in the proximal portion of the reflector  24  will be referred to as a “lamp accommodation opening  26 ”), so that the lamp  29  is made to be accommodated into the reflector  24  from the lamp accommodation opening  26 .  
         [0033]     The lamp  29  is made up of a bulb  30  which emits light and electrode introducing portions  31 ,  31  provided at both ends of the bulb  30  through which electrodes are introduced into the interior of the bulb  30 . In addition, an arc  32  is provided in the interior of the bulb  30  for generating an electric discharge. The bulb  30  is disposed near the lamp accommodation opening  26  in the reflector  24  in such a manner that a focal point position of light radiated from the bulb  30  and reflected by an internal wall of the reflector  24  is formed further forward in a traveling direction of the reflected light than the electrode introducing portion  31 .  
         [0034]     The condenser lens  6  for gathering reflected light is disposed along the optical axis K in the traveling direction of light reflected by the reflector  24 .  FIG. 4  is a front view which shows one of lens surfaces of the condenser lens  6 , and  FIG. 5  is a sectional view of the condenser lens  6  shown in  FIG. 4  taken along the line A-A′ in the same figure. As shown in  FIGS. 4 and 5 , the condenser lens  6  is a convex lens in which recess portions are provided at central portions of light gathering convex surfaces on both sides of the condenser lens  6 .  
         [0035]     The area of a light gathering surface (hereinafter, referred to as an “effective range”) on the lens surface of the condenser lens  6  which faces the light source  5  is made to become larger than that of a light emerging surface (hereinafter, referred to as an “effective range”) of the lens surface of the condenser lens  6  which faces the color wheel  9 .  
         [0036]     Note that a condenser lens  7  may be used which has, as shown in  FIGS. 6 and 7 , a normal convex surface on one lens surface and a convex surface with a recess portion provided at a central portion thereof on the other lens surface thereof. This condenser lens  7  may be disposed with either of the lens surfaces thereof directed towards the light source  5 .  
         [0037]     In addition, a condenser lens  8  may be used which has, as shown in  FIGS. 8 and 9 , a flat surface on one lens surface and a convex surface with a recess portion provided at a central portion thereof on the other lens surface thereof. This condenser lens  8  may be disposed with either of the lens surfaces thereof directed towards the light source.  
         [0038]     The mirror tunnel  10  is a transparent prism and is provided along the optical axis K. This mirror tunnel  10  is made such that incident light from a light incident surface  10   a  is guided in the optical axis direction while totally reflected on an interface between sides of the mirror tunnel  10  and an outside air layer so as to be allowed to emerge from a light emerging surface  10   b  as a bundle of rays in which luminous intensity distribution is uniform. Note that an angular tube in which a reflecting film is provided on the entirety of an inner circumferential surface thereof may be used as the mirror tunnel like this.  
         [0039]     The color wheel  9  is a circular rotary disc and includes color filters of red, blue and green which are arranged in a circumferential direction. The color wheel  9  is disposed with its rotating central axis X made to deviate to a side of the optical axis K.  
         [0040]     The lens  21  is such as to project light that emerges from the mirror tunnel  10  on to the micro mirror device  22 . In  FIG. 2 , while the lens  21  is illustrated as a single lens element, the lens  21  may be made up of a plurality of lens elements.  
         [0041]     The micro mirror device  22  is such as to form individual pixels for an image to be displayed by a plurality of micro mirrors and then change over light and shade of the pixels by changing over the inclination of the micro mirrors so as to project the image.  
         [0042]     The micro mirrors are formed of extremely thin metallic pieces such as aluminum pieces and have vertical and horizontal widths which range from 10 μm to 20 μm. These micro mirrors are provided, respectively, on a plurality o mirror drive elements (not shown) such as CMOS which are formed into a matrix-like arrangement in row and column directions.  
         [0043]     The projection lens  23  is such as to enlarge and project reflected light from the micro mirror device  22  on to a screen (not shown). In  FIG. 2 , note that the projection lens  23  is illustrated as a single lens element, the projection lens  23  may be made up of a plurality of lens elements.  
         [0044]     Note that an example of dimensions and positional relationships of the members making up the light source unit in this embodiment will be described.  
         [0045]     When a reflector is used which has a Korenick constant of −0.55106, a radius of curvature of 10.97669, a light emitting opening whose radius is 32.5 mm and a lamp accommodation opening whose radius is 11 mm, a condenser lens  6  will be used which has the following dimensions.  
         [0046]      FIG. 10  is a front view of a light source  5  side (hereinafter, appropriately referred to as a “side A”) of the condenser lens  6 . The radius of this lens surface is 8.3 mm. As shown in  FIG. 10 , an effective range X of the lens surface on the side A is within a range which is outside a range defined by a circle centered at the center point of the recess portion and having a radius of 1.5 mm and inside a range defined by a circle centered at the center point of the recess portion and having a radius of 7.8 mm+/−0.1 mm.  FIG. 11  is a front view of a mirror tunnel  10  side (hereinafter, appropriately referred to as a “side B”) of the condenser lens  6 . As shown in  FIG. 11 , an effective range Y of the lens surface on the side B is a range which is outside a range defined by a circle centered at the center point of the recess portion and having a radius of 0.8 mm and inside a range defined by a circle centered at the center point of the recess portion and having a radius of 7.0 mm.  
         [0047]      FIG. 12  shows a sectional view of the condenser lens  6 , and in order to make clear the dimensions of the condenser lens  6  below, firstly, how to draw reference lines will be described using  FIG. 12 .  
         [0048]     A reference line C, which intersects with the optical axis K at right angles, is drawn in such a manner as to pass through the center of the recess portion on the lens surface on the side A of the condenser lens  6 , and a reference line D is drawn in such a manner as to intersect with the optical axis K at right angles at a position  4 mm apart from the reference line C along the optical axis K towards the side B.  
         [0049]     Next, draw reference lines E, F, respectively, from apex portions of convex portions on the lens surface on the side B of the condenser lens  6  to the reference line D in such a manner as to be parallel to the optical axis K. In addition, draw reference lines G, H, respectively, also from apex portions of convex portions on the lens surface on the side A of the condenser lens  6  similarly in such a manner as to be parallel to the optical axis K.  
         [0050]     An arc L, which has a radius equal to a distance from a point I where the reference line D intersects with the reference line E at right angles to an end portion J of a circumferential edge portion of the condenser lens  6  and which is centered at the point I, is formed from the end portion J towards the optical axis K.  
         [0051]     In addition, an arc O, which has a radius equal to a distance from a point M where the reference line D intersects with the reference line F at right angles to an end portion N of a circumferential edge portion of the condenser lens  6  and which is centered at the point M, is formed from the end portion N towards the optical axis K. Then, a point where the arc L intersects with the arc O constitutes a central portion of the recess portion on the lens surface on the side A.  
         [0052]     In addition, an arc R, which has a radius equal to a distance from a point P where the reference line C intersects with the reference line G at right angles to an end portion Q of a circumferential edge portion of the condenser lens  6  and which is centered at the point P, is formed from the end portion Q towards the optical axis K.  
         [0053]     Additionally, an arc U, which has a radius equal to a distance from a point S where the reference line C intersects with the reference line H at right angles to an end portion T of a circumferential edge portion of the condenser lens  6  and which is centered at the point S, is formed from the end portion T towards the optical axis K. Then, a point where the arc R intersects with the arc U constitutes a central portion of the recess portion on the lens surface on the side B.  
         [0054]     Next, the dimensions of respective portions of the condenser lens  6  will be described in detail. The distance of a line which connects the point I and the point M together is 7 mm and the distance of a line which connects the point P and the point S together is  6 mm. In addition, the radii of the arc L and the arc O are 5.5 mm, respectively, and the radii of the arc R and the arc U are 6.4 mm, respectively.  
         [0055]      FIG. 13  is a longitudinal sectional view of the light source unit  4  which illustrates positional relationships of the members which make up the light source unit  4 . Note that in  FIG. 13 , the illustration of the color wheel  9  is omitted in order to make clear the positional relationships.  
         [0056]     The ark  32  is disposed in such a manner as to lie on the optical axis K at a position 5.6 mm apart from a proximal portion of the reflector  24 . The condenser lens  6  is disposed in such a manner that a point where a line which connects together the convex portions on the lens surface on the side A intersects with the optical axis K at right angles lies at a position 30.5 mm apart from the arc  32 . In addition, the mirror tunnel  10  is disposed in such a manner that a distance from the arc  32  to a point where the light incident surface  10   a  intersects with the optical axis K equals to a distance of not more than 44.5 mm.  
         [0057]     Next, the function of the embodiment of the invention will be described.  
         [0058]     When the projector system  1  is activated, light is radiated from the bulb  30  of the light source  5 , and most of the light so radiated illuminates the internal wall of the reflector  24  to which a planishing treatment is applied to provide a mirror reflection effect.  
         [0059]     As this occurs, as shown in  FIG. 3 , since the bulb  30  of the light source  5  is disposed near the lamp accommodation opening  26  within the reflector  24  in such a manner that the focal point position of the radiated light radiated from the bulb  30  and reflected by the internal wall of the reflector  24  is formed further forward in the reflected light traveling direction than a distal end portion of the electrode introducing portion  31  which faces the condenser lens  6 , most of the reflected light is made to illuminate portions of the condenser lens  6  other than the central portion thereof where the recess portion is provided so as to be gathered.  
         [0060]     The light, which has been made to illuminate the condenser lens  6  so as to be gathered, is then made to illuminate the color wheel  9  so as to be converted into three colors of red, green and blue and thereafter is made to illuminate the light incident surface  10   a  of the mirror tunnel  10 .  
         [0061]     The light that has emerged from the mirror tunnel  10  is made to illuminate the micro mirror device  22  after a bundle of rays thereof has been enlarged by the lens  21 . Then, the light, which has been reflected by the micro mirror device  22 , is then enlarged by the projection lens  23  so as to be projected on to a screen, not shown.  
         [0062]     Thus, according to the invention, since the focal point position of the radiated light that is radiated from the bulb  30  and is reflected by the reflector  24  does not lie on the electrode introducing portion  31 , there occurs no case where most of the radiated light impinges on the electrode introducing portion  31  of the lamp to thereby be dampened, and hence, the loss of the radiated light that illuminates the lens can be reduced, so that the utilization efficiency of radiated light that is radiated from the light source  5  can be enhanced, whereby the reflector  24  can be made smaller in size. Thus, the whole of the light source unit  4  can be made smaller in size than the related art light source unit.  
         [0063]     In addition, since the light source unit  4  is made smaller in size in this way, the projector system  1  itself, which incorporates therein the light source unit  4 , can be made smaller in size.