Patent Publication Number: US-9429828-B2

Title: Image projection apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application of U.S. application Ser. No. 14/454,431, filed Aug. 7, 2014, which is a continuation of U.S. application Ser. No. 13/644,687, filed Oct. 4, 2012, which claims priority to Japanese Patent Application No. 2011-242923 filed in Japan on Nov. 4, 2011. The entire contents of each of the above are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image projection apparatus. 
     2. Description of the Related Art 
     Image projection apparatuses have been known that include digital mirror devices (DMDs) serving as image forming elements that modulate light on the basis of image data supplied from personal computers, for example, and image forming units having irradiation units irradiating the image forming elements by light from light sources, and in which the image forming units form images and the images formed by the image forming units are focused on projection planes using projection optical sections. 
     The image projection apparatuses use halogen lamps, metal halide lamps, or high-pressure mercury lamps as the light sources. These lamps reach a high temperature when emitting light. Japanese Patent Application Laid-open No. 2002-244210 and Japanese Patent Application Laid-open No. 2008-102374 disclose image projection apparatuses. In an example of the image projection apparatuses, ambient air is taken in from an intake port provided to the apparatus by an air supplying unit such as a blower or a fan, the air taken in is supplied to a light source to cool the light source, and air of which the temperature has increased by taking heat from the light source is discharged outside the apparatus via an exhaust port. 
     An operating unit serving as an input mechanism such as buttons for a user to operate the image projection apparatus is preferably disposed on the upper surface of the image projection apparatus for allowing the user to readily operate the image projection apparatus. 
     The temperature of the light source reaches up to about 1000° C. even though the light source is cooled by supplied air. As a result, air heated by the light source flows upward by air supplied from an air supplying unit and its ascending air current. In addition, heat from the light source is conducted toward the operating unit by thermal conduction. When the operating unit is disposed above or just above the light source, a problem arises in that air heated by the light source and flowing upward, heat by the thermal conduction, and heat by natural convention collide with the operating unit disposed above or just above the light source and the operating unit is heated by the heated air and the heat, thereby increasing the temperature of the operating unit. 
     Therefore, there is a need for an image projection apparatus capable of suppressing an increase in the temperature of an operating unit even when the operating unit is disposed above or just above a light source. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to at least partially solve the problems in the conventional technology. 
     According to an embodiment, there is provided an image projection apparatus for projecting an image using light. The image projection apparatus includes a light source configured to emit the light; and an operating unit configured to allow a user to operate the image projection apparatus, the operating unit being disposed above the light source when viewed from a placement surface on which a main body of the image projection apparatus is placed. The image projection apparatus also includes a first flow path in which air flows through the light source; and a second flow path different from the first flow path, the second flow path being formed between the light source and the operating unit. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a projector according to an embodiment of the invention and a projection plane; 
         FIG. 2  is a ray diagram from the projector to the projection plane; 
         FIG. 3  is a schematic perspective view illustrating an internal structure of the projector; 
         FIG. 4  is a schematic perspective view of a light source unit; 
         FIG. 5  is a perspective view illustrating optical system parts housed in a lighting unit and the other units; 
         FIG. 6  is a perspective view when the lighting unit, a projection lens unit, and an image forming unit are viewed from direction A of  FIG. 5 ; 
         FIG. 7  is a schematic diagram explaining an optical path of light in the lighting unit; 
         FIG. 8  is a perspective view of the image forming unit; 
         FIG. 9  is a perspective view illustrating a first optical system unit together with the lighting unit and the image forming unit; 
         FIG. 10  is a sectional view along line B-B of  FIG. 9 ; 
         FIG. 11  is a perspective view illustrating a second optical system held by a second optical system unit together with the projection lens unit, the lighting unit, and the image forming unit; 
         FIG. 12  is a perspective view illustrating the second optical system unit together with the first optical system unit, the lighting unit, and the image forming unit; 
         FIG. 13  is a perspective view illustrating an optical path from the first optical system to the projection plane; 
         FIG. 14  is a schematic diagram illustrating an arrangement of the units in the projector; 
         FIG. 15  is a schematic diagram illustrating an example of use of the projector in the embodiment; 
         FIG. 16  is a schematic diagram illustrating an example of use of a conventional projector; 
         FIG. 17  is a schematic diagram illustrating an example of use of a projector in which a light source and the lighting unit are arranged in a direction orthogonal to the projection plane; 
         FIG. 18  is a perspective view illustrating a placement surface side of the projector; 
         FIG. 19  is a perspective view illustrating the placement surface side of the projector when an open-close cover is removed from the projector; 
         FIG. 20  is a schematic diagram to explain an air flow in the projector; 
         FIG. 21  is a schematic diagram more specifically illustrating the structure illustrated in  FIG. 20 ; 
         FIG. 22  is a sectional view along line C-C of  FIG. 21 ; 
         FIG. 23  is a sectional view along line D-D of  FIG. 21 ; 
         FIG. 24  is a sectional view along line E-E of  FIG. 21 ; 
         FIG. 25  is a sectional view along line F-F of  FIG. 21 ; 
         FIG. 26  is a sectional view along line G-G of  FIG. 21 ; and 
         FIG. 27  is a schematic diagram to explain a modification of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiments of a projector that is an image projection apparatus to which the invention is applied is described below.  FIG. 1  is a perspective view illustrating a projector  1  according to an embodiment and a projection plane  101  such as a screen. The projector  1  is also referred to as the apparatus in the following description. In the following description, the normal line direction of the projection plane  101  is defined as an X direction, a short-axis direction (up-down direction) of the projection plane  101  is defined as a Y direction, and a long-axis direction (horizontal direction) of the projection plane  101  is defined as a Z direction. 
     As illustrated in  FIG. 1 , a transmissive glass  51  through which a projection image P is emitted is provided on an upper surface of the projector  1 . The projection image P emitted from the transmissive glass  51  is projected on the projection plane  101  such as a screen. 
     An operating unit  83  for a user to operate the projector  1  is also provided on the upper surface of the projector  1 . A focusing lever  33  for a focus adjustment is provided on a side surface of the projector  1 . Operating the operating unit  83  including a known input mechanism such as buttons, a user can adjust a tint and contrast of the projection image P and perform setting of a network such as Internet protocol address (IP address) setting. 
       FIG. 2  is a ray diagram from the projector  1  to the projection plane  101 . 
     The projector  1  includes a light source unit (not illustrated) provided with a light source and an image forming section  100 A that forms an image using light from the light source. The image forming section  100 A is made up of an image forming unit  10  provided with a digital mirror device (DMD)  12  and a lighting unit  20  that reflects light from the light source and irradiates the DMD  12  with the reflected light to cause the DMD  12  to produce an optical image. In addition, the projector  1  includes a projection optical section  100 B for projecting an image on the projection plane  101 . The projection optical section  100 B is made up of a first optical unit  30  including at least one transmissive refracting optical system and a coaxial first optical system  70  having positive power, and a second optical unit  40  including a reflection mirror  41  and a curved mirror  42  having positive power. 
     The DMD  12  is irradiated with light by the lighting unit  20  that reflects light from the light source (not illustrated), and produces an image by modulating light emitted from the lighting unit  20 . The image produced by the DMD  12  is projected on the projection plane  101  through the first optical system  70  of the first optical unit  30 , and the reflection mirror  41  and the curved mirror  42  of the second optical unit  40 . 
       FIG. 3  is a schematic perspective view illustrating an internal structure of the projector  1 . 
     As illustrated in  FIG. 3 , the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , and the second optical unit  40  are arranged in the Y direction, which is one of the directions parallel to the projection plane  101  and the image plane of the projection image P. A light source unit  60  is disposed on the right side of the lighting unit  20  in  FIG. 3 . 
       FIG. 3  also illustrates legs  32   a   1  and  32   a   2  of a lens holder  32  (refer to  FIG. 9 ) of the first optical unit  30 , and screw fixing portions  26   g  that fix the image forming unit  10  to the lighting unit  20  with screws. 
     The structure of each unit is described in detail below. 
     The structure of the light source unit  60  is described below. 
       FIG. 4  is a schematic perspective view of the light source unit  60 . 
     The light source unit  60  has a light source bracket  62 . A light source  61  such as a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp is mounted above the light source bracket  62 . The light source bracket  62  is provided with a connector  62   a  that connects to a power source side connector (not illustrated) connected to a power source unit  80  (refer to  FIG. 14 ). 
     A holder  64  that holds a reflector (not illustrated), for example, is fixed with screws to a light emission side of the light source  61 , which is mounted above the light source bracket  62 . An emission window  63  is provided on a surface opposite the surface on which light source  61  is provided of the holder  64 . Light emitted from the light source  61  is converged to the emission window  63  by the reflector (not illustrated) held by the holder  64 , and emitted from the emission window  63 . 
     Light source positioning portions  64   a   1  to  64   a   3  are provided on the upper surface of the holder  64  and on the lower surface of the holder  64  at both ends in the X direction, and used for positioning the light source unit  60  to a lighting bracket  26  (refer to  FIG. 6 ) of the lighting unit  20 . The light source positioning portion  64   a   3  provided on the upper surface of the holder  64  is formed in a projection shape while the light source positioning portions  64   a   1  and  64   a   2  provided on the lower surface of the holder  64  are formed as holes. 
     A light source air intake port  64   b  through which air flows to cool the light source  61  is provided on a side surface of the holder  64  while a light source air exhaust port  64   c  through which air heated by the light source  61  is discharged is provided on the upper surface of the holder  64 . 
     The light source bracket  62  is provided with a passage  65  through which air sucked in by an air intake blower  91  (e.g., refer to  FIG. 21 ) flows, which is described later. An opening  65   a  is provided on an air flow-in side of the passage  65 , i.e., on the lower left side in  FIG. 4 . The opening  65   a  allows part of air flowing through the passage  65  to flow between the light source unit  60  and an open-close cover  54  (refer to  FIG. 18 ), which is described later. Cooling of the light source unit  60  is described later. 
     A planar section  64   d   2  on which the light source positioning portion  64   a   3  is provided and a planar section  64   d   1  on which the light source positioning portions  64   a   1  and  64   a   2  are provided, both of which are illustrated in  FIG. 4 , are abutting sections that abut the lighting bracket  26  when being pushed by a pushing unit of the open-close cover  54 . 
     The lighting unit  20  is described below. 
       FIG. 5  is a perspective view illustrating optical system parts housed in the lighting unit  20  and the other units. 
     As illustrated in  FIG. 5 , the lighting unit  20  includes a color wheel  21 , a light tunnel  22 , two relay lenses  23 , a cylinder mirror  24 , and a concave mirror  25 , which are held by the lighting bracket  26 . The lighting bracket  26  has a housing-like section  261  in which the two relay lenses  23 , the cylinder mirror  24 , and the concave mirror  25  are housed. The housing-like section  261  only has a side surface on the right side in  FIG. 5 . The other three sides of the housing-like section  261  are open. An OFF light plate  27  (refer to  FIG. 6 ) is attached to an opening provided on the side surface on a far side in the X direction while a cover member (not illustrated in all of the drawings) is attached to an opening provided on the side surface on a near side in the X direction. As a result, the two relay lenses  23 , the cylinder mirror  24 , and the concave mirror  25  housed in the housing-like section  261  of the lighting bracket  26  are covered with the lighting bracket  26 , the OFF light plate  27  (refer to  FIG. 6 ), and the cover member which is not illustrated in all of the drawings. 
     The housing-like section  261  of the lighting bracket  26  has, on the lower surface thereof, an irradiation through-hole  26   d  out of which the DMD  12  is exposed. 
     The lighting bracket  26  has three legs  29 . The legs  29  abut a base member  53  (refer to  FIG. 13 ) and support the weights of the first optical unit  30  and the second optical unit  40  that are stacked and fixed on the lighting bracket  26 . In addition, the legs  29  thus provided form a space through which ambient air flows to a heat sink  13  (refer to  FIG. 6 ) serving as a cooling unit that cools the DMD  12  of the image forming unit  10 , which is described later. 
       FIG. 5  also illustrates legs  32   a   3  and  32   a   4  of the lens holder  32  of the first optical unit  30 , and a screw fixing portion  45   a   3  of the second optical unit  40 . 
       FIG. 6  is a perspective view when the lighting unit  20 , a projection lens unit  31 , and the image forming unit  10  are viewed from direction A of  FIG. 5 . 
     An upper surface  26   b  orthogonal to the Y direction is provided on the housing-like section  261  of the lighting bracket  26 . A through-hole is provided at each of the four corners of the upper surface  26   b  (in  FIG. 6 , only through-holes  26   c   1  and  26   c   2  are illustrated and the other through-holes  26   c   3  and  26   c   4  are not illustrated). Screws for fixing the first optical unit  30  are inserted in the through-holes. Positioning holes  26   e   1  and  26   e   2  for positioning the first optical unit  30  to the lighting unit  20  are provided adjacent to the through-holes  26   c   1  and  26   c   2 , respectively, located on the near side in the X direction. In the two positioning holes provided on the near side in the X direction, the positioning hole  26   e   1  on the color wheel  21  side is a primary reference for the positioning and formed as a round hole while the positioning hole  26   e   2  on a side away from the color wheel  21  is a secondary reference for the positioning and formed as an elongate hole extending in the Z direction. The surrounding area of each of the through-holes  26   c   1  and  26   c   2  is protruded from the upper surface  26   b  of the lighting bracket  26  and serves as a positioning protrusion  26   f  for positioning the first optical unit  30  in the Y direction. When positioning accuracy in the Y direction is intended to be increased without the positioning protrusions  26   f , flatness of the whole upper surface of the lighting bracket  26  needs to be increased, resulting in high costs. In contrast, by the positioning protrusions  26   f  thus provided, the flatness of the positioning protrusions  26   f  only needs to be increased. As a result, costs can be reduced and the positioning accuracy in the Y direction can be increased. 
     A light shielding plate  262  to which the lower portion of the projection lens unit  31  is fitted is provided to an opening on the upper surface  26   b  of the lighting bracket  26 . The light shielding plate  262  prevents light from entering the housing-like section  261  from above. 
     An area between the through-holes  26   c   1  and  26   c   2  of the upper surface  26   b  of the lighting bracket  26  is notched so as not to hinder the fixing of the second optical unit  40  to the first optical unit  30  with screws, which is described later. 
     A light source positioning receiving portion  26   a   3  having a tubular shape is provided at an end on the color wheel  21  side of the lighting bracket  26  (on the near side in the Z direction). The light source positioning receiving portion  26   a   3  has a through-hole in the up-down direction in which the light source positioning portion  64   a   3  having a protrusion shape provided on the upper surface of the holder  64  of the light source unit  60  (refer to  FIG. 4 ) is fitted. Under the light source positioning receiving portion  26   a   3 , two light source positioning receiving portions  26   a   1  and  26   a   2  having a protrusion shape are provided in which the light source positioning portions  64   a   1  and  64   a   2  that are formed as holes and provided on the light source bracket  62  side of the holder  64  are fitted. The light source positioning portions  64   a   1  to  64   a   3  of the holder  64  are fitted in the light source positioning receiving portions  26   a   1  to  26   a   3  provided to the lighting bracket  26  of the lighting unit  20 , resulting in the light source unit  60  being positioned and fixed to the lighting unit  20  (refer to  FIG. 3 ). 
     A lighting cover  28  that covers the color wheel  21  and the light tunnel  22  is attached to the lighting bracket  26 . 
       FIG. 7  is a schematic diagram to explain an optical path L of light in the lighting unit  20 . 
     The color wheel  21 , which has a discoid shape, is fixed to a motor shaft of a color motor  21   a . The color wheel  21  has filters of red (R), green (G), and blue (B) provided in a rotational direction thereof, for example. Light converged by the reflector (not illustrated) provided to the holder  64  of the light source unit  60  passes through the emission window  63  and reaches a circumferential edge of the color wheel  21 . Light having reached the circumferential edge of the color wheel  21  is divided into light components of R, G, and B by the rotation of the color wheel  21  in a time division manner. 
     The light components divided by the color wheel  21  enter the light tunnel  22 . The light tunnel  22  has a square tubular shape and an inner circumferential surface of the light tunnel  22  is a mirror surface. Light having entered the light tunnel  22  becomes a uniform surface light source while repeating reflection on the inner circumferential surface of the light tunnel  22  a plurality of times and is emitted toward the relay lenses  23 . 
     Light after passing through the light tunnel  22  travels through the two relay lenses  23 , and is reflected by the cylinder mirror  24  and the concave mirror  25 , and converged on an image forming surface of the DMD  12 . 
     The image forming unit  10  is described below. 
       FIG. 8  is a schematic perspective view of the image forming unit  10 . 
     As illustrated in  FIG. 8 , the image forming unit  10  includes a DMD board  11  to which the DMD  12  is attached. The DMD  12  is attached to a socket  11   a  provided on the DMD board  11  such that the image forming surface, on which micro mirrors are arranged in matrix, faces upward. The DMD board  11  is provided with a driving circuit that drives the DMD mirrors, for example. The heat sink  13  serving as the cooling unit cooling the DMD  12  is fixed to a rear surface (a surface opposite the surface on which the socket  11   a  is provided) of the DMD board  11 . A portion to which the DMD  12  is attached of the DMD board  11  is formed as a through-hole (not illustrated). The heat sink  13  has a protrusion  13   a  (refer to  FIG. 7 ) that is inserted in the through-hole. The tip of the protrusion  13   a  has a planer shape. The protrusion  13   a  is inserted in the through-hole (not illustrated) and the planar surface of the tip of the protrusion  13   a  is abutted to the rear surface (the surface opposite the image forming surface) of the DMD  12 . An elastically formable heat-transfer sheet may be attached to the planar surface or the area to which the heat sink  13  is abutted of the rear surface of the DMD  12  so as to enhance adhesiveness and thermal conductivity between the planar surface of the protrusion  13   a  and the rear surface of the DMD  12 . 
     The heat sink  13  is pushed and fixed to the surface opposite the surface on which the socket  11   a  is provided of the DMD board  11  by a fixing member  14 . The fixing member  14  has platy fixing sections  14   a  on the rear surface of the DMD board  11  on the right side and the left side in  FIG. 8 . Pushers  14   b  are provided near one end and the other end of the respective fixing sections  14   a  in the X direction so as to connect the fixing sections  14   a.    
     The heat sink  13  is pushed and fixed to the surface opposite the surface on which the socket  11   a  is provided of the DMD board  11  by the fixing members  14  when the image forming unit  10  is fixed to the lighting bracket  26  (refer to  FIG. 6 ) with screws. 
     The fixing of the image forming unit  10  to the lighting bracket  26  is described below. First, the image forming unit  10  is positioned to the lighting bracket  26  such that the DMD  12  faces the opening of the irradiation through-hole  26   d  provided to the lower surface of the lighting bracket  26  of the lighting unit  20 , which is illustrated in  FIG. 5 . Then, screws are inserted in through-holes (not illustrated) provided to the fixing sections  14   a  and through-holes  15  of the DMD board  11  from below and screwed in tapped holes provided to the lower surfaces of the screw fixing portions  26   g  (refer to  FIG. 3 ) provided to the lighting bracket  26  so as to fix the image forming unit  10  to the lighting bracket  26 . As the screws are screwed in the screw fixing portions  26   g  provided to the lighting bracket  26 , the pushers  14   b  push the heat sink  13  toward the DMD board  11 . As a result, the heat sink  13  is pushed and fixed to the surface opposite the surface on which the socket  11   a  is provided of the DMD board  11  by the fixing member  14 . 
     In this way, the image forming unit  10  is fixed to the lighting bracket  26  and the three legs  29  illustrated in  FIG. 3  also support the weight of the image forming unit  10 . 
     A plurality of moveable micro mirrors are arranged in matrix on the image forming surface of the DMD  12 . Each micro mirror can slant a mirror surface thereof at a certain angle around a torsion axis to be set to two states of “ON” and “OFF”. When set to the “ON” state, the micro mirror reflects light from the light source  61  toward the first optical system  70  (refer to  FIG. 2 ) as illustrated as an arrow L 2  in  FIG. 7 . When set to the “OFF” state, the micro mirror reflects light from the light source  61  toward the OFF light plate  27  held on the side surface of the lighting bracket  26  illustrated in  FIG. 6  (refer to an arrow L 1  in  FIG. 7 ). Accordingly, projection of light can be controlled for each pixel of image data by driving each mirror individually, thereby enabling an image to be produced. 
     Light reflected toward the OFF light plate  27  (not illustrated in  FIG. 7 ) is absorbed as heat and cooled by an outside air flow. 
     The first optical unit  30  is described below. 
       FIG. 9  is a perspective view illustrating the first optical unit  30  together with the lighting unit  20  and the image forming unit  10 . 
     As illustrated in  FIG. 9 , the first optical unit  30  is disposed on the lighting unit  20  and includes the projection lens unit  31  holding the first optical system  70  made up of a plurality of lenses (refer to  FIG. 2 ) and the lens holder  32  holding the projection lens unit  31 . The lens holder  32  is provided with four legs  32   a   1  to  32   a   4  extending downward (in  FIG. 9 , only the legs  32   a   2  and  32   a   3  are illustrated, and as for the legs  32   a   1  and  32   a   4 , refer to  FIGS. 3 and 4 , respectively). Tapped holes are formed on the bottom surfaces of the legs  32   a   1  to  32   a   4  and used for fixing the lens holder  32  to the lighting bracket  26  with screws. 
     The projection lens unit  31  is provided with a focusing gear  36 , with which an idler gear  35  engages. A lever gear  34  engages with the idler gear  35 . The focusing lever  33  is fixed to the rotational shaft of the lever gear  34 . A tip portion of the focusing lever  33  is exposed out of the apparatus body (main body) as illustrated in  FIG. 1 . 
     With the movement of the focusing lever  33 , the focusing gear  36  is rotated through the lever gear  34  and the idler gear  35 . With the rotation of the focusing gear  36 , the lenses included in the first optical system  70  in the projection lens unit  31  are moved in respective certain directions, resulting in a focus of a projection image being adjusted. 
     The lens holder  32  has four screw through-holes  32   c   1  to  32   c   4  through which screws  48  used for fixing the second optical unit  40  to the first optical unit  30  are inserted (in  FIG. 9 , three screw through-holes  32   c   1  to  32   c   3  and tip portions of the screws  48  inserted in the screw through-holes are illustrated). Second optical unit positioning projections projected from the surface of the lens holder  32  are formed around the respective screw through-holes  32   c   1  to  32   c   4  (in  FIG. 9 , only second optical unit positioning projections  32   d   1  to  32   d   3  are illustrated). 
       FIG. 10  is a sectional view along line B-B of  FIG. 9 . 
     As illustrated in  FIG. 10 , the legs  32   a   1  and  32   a   2  are provided with positioning receiving projections  32   b   1  and  32   b   2 , respectively. The positioning receiving projection  32   b   1  on the right side in  FIG. 10  is inserted in the positioning hole  26   e   1  that is formed as a round hole on the upper surface  26   b  of the lighting bracket  26  and serves as the primary reference for the positioning, resulting in the lens holder  32  being positioned in the Z-axis direction. The positioning receiving projection  32   b   2  on the left side in  FIG. 10  is inserted in the positioning hole  26   e   2  that is formed as an elongate hole on the upper surface  26   b  of the lighting bracket  26  and serves as the secondary reference for the positioning, resulting in the lens holder  32  being positioned in the X-axis direction. Thereafter, screws  37  are inserted in the through-holes  26   c   1  to  26   c   4  provided on the upper surface  26   b  of the lighting bracket  26  and screwed in the tapped holes provided to the legs  32   a   1  to  32   a   4  of the lens holder  32 , resulting in the first optical unit  30  being fixed to the lighting unit  20 . 
     An upper portion of the projection lens unit  31  with regard to the lens holder  32  is covered by a mirror holder  45  (refer to  FIG. 12 ) of the second optical unit  40 , which is described later. As illustrated in  FIG. 10 , the projection lens unit  31  is exposed between the lower surface of lens holder  32  and the upper surface  26   b  of the lighting bracket  26  of the lighting unit  20 . However, no light enters an optical path of an image from the exposed portion because the projection lens unit  31  is fitted in the lens holder  32 . 
     The second optical unit  40  is described below. 
       FIG. 11  is a perspective view illustrating a second optical system included in the second optical unit  40 , the projection lens unit  31 , the lighting unit  20 , and the image forming unit  10 . 
     As illustrated in  FIG. 11 , the second optical unit  40  includes the reflection mirror  41  and the curved mirror  42  having a concave shape that constitute the second optical system. A light-reflecting surface of the curved mirror  42  may be formed in a spherical surface, a rotationally symmetric aspheric surface, or a free-form surface, for example. 
       FIG. 12  is a perspective view illustrating the second optical unit  40  together with the first optical unit  30 , the lighting unit  20 , and the image forming unit  10 . 
     As illustrated in  FIG. 12 , the second optical unit  40  also includes the transmissive glass  51  through which an optical image reflected from the curved mirror  42  passes and that protects the optical parts in the apparatus from dust. 
     The second optical unit  40  includes a mirror bracket  43  holding the reflection mirror  41  and the transmissive glass  51 , a free mirror bracket  44  holding the curved mirror  42 , and the mirror holder  45  to which the mirror bracket  43  and the free mirror bracket  44  are attached. 
     The mirror holder  45  has a boxy shape and areas corresponding to the upper surface, the lower surface, and a surface on the far side in the X direction in  FIG. 12  are open. That is, the mirror holder  45  has approximately a c-shape from top view. Edge sections located on the near side and the far side in the Z direction of the upper opening of the mirror holder  45  extend in the X direction, and each edge section has a slanted section and a parallel section. The slanted section ascends as it extends from an edge on the near side to the far side in the X direction while the parallel section extends in parallel with the X direction. The slanted section is located on the near side in the X direction with regard to the parallel section. The other edge section located on the near side in the X direction of the upper opening of the mirror holder  45  extends in the Z direction in parallel with the Z direction. 
     The mirror bracket  43  is mounted on the mirror holder  45 . The mirror bracket  43  has a slanted surface  43   a  and a parallel surface  43   b . The slanted surface  43   a  abuts the slanted sections of the edge sections of the upper opening of the mirror holder  45  and ascends as it extends from the edge on the nearside to the far side in the X direction. The parallel surface  43   b  abuts the parallel sections of the edge sections of the upper opening of the mirror holder  45  and is in parallel with the X direction. Each of the slanted surface  43   a  and the parallel surface  43   b  has an opening. The reflection mirror  41  is held so as to cover the opening of the slanted surface  43   a  while the transmissive glass  51  is held so as to cover the opening of the parallel surface  43   b.    
     The reflection mirror  41  is positioned to and held by the slanted surface  43   a  of the mirror bracket  43  with mirror pushing members  46  having a plate spring shape that push both ends of the reflection mirror  41  in the Z direction to the slanted surface  43   a  of the mirror bracket  43 . One end of the reflection mirror  41  in the Z direction is fixed by the two mirror pushing members  46  and the other end of the reflection mirror  41  in the Z direction is fixed by one mirror pushing member  46 . 
     The transmissive glass  51  is positioned and fixed to the mirror bracket  43  with glass pushing members  47  having a plate spring shape that push both ends of the transmissive glass  51  in the Z direction to the parallel surface  43   b  of the mirror bracket  43 . The transmissive glass  51  is held by the glass pushing member  47  at each end in the Z direction. 
     The free mirror bracket  44  holding the curved mirror  42  has arms  44   a  on the near side and the far side in the Z-axis direction. The arm  44   a  descends as it extends from the far side to the near side in the X direction in  FIG. 12 . The free mirror bracket  44  has a connector  44   b  that connects the two arms  44   a  at the upper portions of the arms  44   a . The arms  44   a  of the free mirror bracket  44  are attached to the mirror holder  45  such that the curved mirror  42  covers the opening of the mirror holder  45  on the far side in the X direction. 
     The curved mirror  42  is pushed to the connector  44   b  of the free mirror bracket  44  by a free mirror pushing member  49  having a plate spring shape at approximately a central portion of the edge thereof on the transmissive glass  51  side. Both ends of the curved mirror  42  on the first optical system  70  side in the Z-axis direction are fixed to the arms  44   a  of the free mirror bracket  44  with screws. 
     The second optical unit  40  is mounted on and fixed to the lens holder  32  of the first optical unit  30 . Specifically, the mirror holder  45  has at the lower end thereof a lower surface  451  facing the upper surface of the lens holder  32 . The lower surface  451  is provided with four screw fixing portions having a tubular shape used for fixing the mirror holder  45  to the first optical unit  30  with screws (in the four screw fixing portions, as for screw fixing portions  45   a   1  and  45   a   2 , refer to  FIG. 11 , as for the screw fixing portion  45   a   3 , refer to  FIG. 5 , and the other screw fixing portion is not illustrated). The screws  48  (refer to  FIG. 9 ) are inserted in the respective screw through-holes  32   c   1  to  32   c   3  provided to the lens holder  32  of the first optical unit  30  and screwed to the respective screw fixing portions  45   a   1  to  45   a   3 , resulting in the second optical unit  40  being fixed to the first optical unit  30  with the screws  48 . Meanwhile, the lower surface  451  of the mirror holder  45  of the second optical unit  40  abuts the second optical unit positioning projections  32   d   1  to  32   d   4 , resulting in the second optical unit  40  being positioned and fixed in the Y direction. 
     As the result of the mounting and fixing of the second optical unit  40  to the lens holder  32  of the first optical unit  30 , the upper portion of the projection lens unit  31  with regard to the lens holder  32  is housed in the mirror holder  45  of the second optical unit  40  as illustrated in  FIG. 9 . When the second optical unit  40  is mounted on and fixed to the lens holder  32 , a gap is formed between the curved mirror  42  and the lens holder  32 , and the idler gear  35  (refer to  FIG. 9 ) is disposed in the gap. 
       FIG. 13  is a perspective view illustrating an optical path from the first optical system  70  to the projection plane  101  (screen). 
     A light beam after passing through the projection lens unit  31  included in the first optical system  70  forms a conjugate intermediate image to an image produced by the DMD  12  between the reflection mirror  41  and the curved mirror  42 . The intermediate image is focused as a curved image between the reflection mirror  41  and the curved mirror  42 . The light beam dispersed after focusing of the intermediate image, enters the curved mirror  42  having a concave shape and becomes a convergent light beam. The intermediate image is changed to a “further enlarged image”, projected, and focused on the projection plane  101  by the curved mirror  42 . 
     As described above, a projection optical system is made up of the first optical system  70  and the second optical system, and the intermediate image is formed between the first optical system  70  and the curved mirror  42  of the second optical system, and enlarged and projected by the curved mirror  42 . As a result, a projection distance can be shortened, thereby enabling the projector  1  to be used in a small meeting room, for example. 
     As illustrated in  FIG. 13 , the first optical unit  30  and the second optical unit  40  are mounted on and fixed to the lighting bracket  26 . The image forming unit  10  is also fixed to the lighting bracket  26 . As a result, the legs  29  of the lighting bracket  26  receive the weights of the first optical unit  30 , the second optical unit  40 , and the image forming unit  10  and are fixed to the base member  53 . 
       FIG. 14  is a schematic diagram illustrating an arrangement of the units in the apparatus. 
     As illustrated in  FIG. 14 , the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , and the second optical unit  40  are arranged in a layered manner in the Y direction, which is the short-axis direction of the projection plane  101 , while the light source unit  60  is disposed in the Z direction, which is the long-axis direction of the projection plane  101 , relative to the layered body in which the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , and the second optical unit  40  are arranged in a layered manner. In the embodiment, the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , the second optical unit  40 , and the light source unit  60  are disposed in the Y direction or the Z direction that is the direction in parallel with a projection image and the projection plane  101  as described above. More specifically, the light source unit  60  is connected to the image forming section  100 A made up of the image forming unit  10  and the lighting unit  20  in a direction orthogonal to a direction in which the image forming section  100 A and the projection optical section  100 B made up of the first optical unit  30  and the second optical unit  40  are arranged in a layered manner. The image forming section  100 A and the light source unit  60  are arranged on a straight line parallel to the base member  53 . The image forming section  100 A and the projection optical section  100 B are arranged in this order from the base member  53  on a straight line perpendicular to the base member  53 . As a result, an installation space of the apparatus can be suppressed from being taken in a direction orthogonal to a plane of a projection image projected on the projection plane  101 . Consequently, when the image projection apparatus is used while placed on a desk, for example, the apparatus can be prevented from hindering the arrangement of the desk and chairs in a small room. 
     In the embodiment, the power source unit  80  supplying power to the light source  61  and the DMD  12  is disposed above the light source unit  60  in a layered manner. The light source unit  60 , the power source unit  80 , the image forming section  100 A, and the projection optical section  100 B are housed in a housing of the projector  1 . The housing includes the upper surface of the projector  1 , the base member  53 , and an outer packaging cover  59  (refer to  FIGS. 18 and 19 ) covering around the projector  1 , which is described later. 
       FIG. 15  is a schematic diagram illustrating an example of use of the projector  1  of the embodiment.  FIG. 16  is a schematic diagram illustrating an example of use of a conventional projector  1 A.  FIG. 17  is a schematic diagram illustrating an example of use of a projector  1 B in which the light source unit  60  and the lighting unit  20  are arranged in a direction orthogonal to the projection plane  101 . 
     As illustrated in  FIGS. 15 to 17 , each of the projectors  1 ,  1 A, and  1 B is placed on a table  200  and used for projecting an image on the projection plane  101  such as a whiteboard when used in a meeting room, for example. 
     As illustrated in  FIG. 16 , in the conventional projector  1 A, the DMD  12  (image forming element), the lighting unit  20 , the first optical system  70 , and the second optical system (the curved mirror  42 ) are arranged in series in a direction orthogonal to the plane of a projection image projected on the projection plane  101 . As a result, the projector  1 A is long in the direction orthogonal to the projection plane  101  (the X direction) and takes space in the direction orthogonal to the projection plane  101 . In general, chairs on which viewers who watch images projected on the projection plane  101  sit and desks used by the viewers are arranged in the direction orthogonal to the projection plane  101 . Therefore, when the projector takes space in the direction orthogonal to the projection plane, a space for arranging the chairs and the desks is limited due to the space taken by the projector, thereby lowering convenience. 
     In the projector  1 B illustrated in  FIG. 17 , the DMD  12  (image forming element), the lighting unit  20 , and the first optical system  70  are arranged in series in a direction parallel to the plane of a projection image projected on the projection plane  101 . Accordingly, the length of the projector  1 B in the direction orthogonal to the projection plane  101  can be shortened with regard to that of the projector  1 A illustrated in  FIG. 16 . The projector  1 B illustrated in  FIG. 17 , however, cannot sufficiently shorten the length thereof in the direction orthogonal to the projection plane  101  because the light source  61  is disposed in the direction orthogonal to the projection plane  101  relative to the lighting unit  20 . 
     In contrast, in the projector  1  of the embodiment illustrated in  FIG. 15 , the image forming section  100 A made up of the image forming unit  10  and the lighting unit  20  and the projection optical section  100 B made up of the first optical unit  30  and the reflection mirror  41  are arranged in series in the Y direction, which is one of the directions parallel to the projection plane  101  and the image plane of a projection image projected on the projection plane  101 . In addition, the light source unit  60  and the lighting unit  20  are arranged in series in the Z direction, which is one of the directions parallel to the plane of a projection image projected on the projection plane  101 . That is, in the projector  1  of the embodiment, the light source unit  60 , the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , and the reflection mirror  41  are arranged in the direction parallel to the plane of a projection image projected on the projection plane  101  (the Z direction or the Y direction), and each of the light source unit  60 , the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , and the reflection mirror  41  is disposed in parallel with the projection plane  101  and the image plane of a projection image. Because the light source unit  60 , the image forming unit  10 , the lighting unit  20 , the first optical unit  30 , and the reflection mirror  41  are arranged in the direction parallel to the plane of a projection image projected on the projection plane  101  (the Z direction or the Y direction) as described above, the length of the projector  1  in the direction orthogonal to the projection plane  101  (the X direction) can be shortened with regard to those of the projectors illustrated in  FIGS. 16 and 17 . As a result, the projector  1  can be prevented from causing a space for arranging chairs and desks to be reduced, thereby enabling the projector  1  to provide higher convenience. 
     In the embodiment, as illustrated in  FIG. 14 , the power source unit  80  supplying power to the light source  61  and the DMD  12  is disposed above the light source unit  60  in a layered manner. As a result, the length in the Z direction of the projector  1  is also reduced. 
     Although the second optical system includes the reflection mirror  41  and the curved mirror  42  in the embodiment, the second optical system may include only the curved mirror  42 . The reflection mirror  41  may be a planar mirror, a mirror having positive refractive power, or a mirror having negative refractive power. Although the concave mirror is used as the curved mirror  42  in the embodiment, a convex mirror can be used as the curved mirror  42 . In this case, the first optical system  70  is structured such that no intermediate image is formed between the first optical system  70  and the curved mirror  42 . 
     The light source  61  needs to be periodically replaced with a new one because its life span ends after being used for a certain period of time. Therefore, the light source unit  60  is attached to the apparatus body in a detachable manner in the embodiment. 
       FIG. 18  is a perspective view illustrating a placement surface side of the projector  1 . 
     As illustrated in  FIG. 18 , the base member  53  included in the bottom surface of the projector  1  is provided with the open-close cover  54 , which is provided with a rotational operating unit  54   a . When the rotational operating unit  54   a  is rotated, fixing between the open-close cover  54  and the apparatus body is released and the open-close cover  54  can be removed from the apparatus body. The base member  53  is provided with a power source air intake port  56  at a position adjacent to the open-close cover  54  in the X direction. 
     As illustrated in  FIG. 18 , an air intake port  84  and an external input unit  88  to which image data is input from an external apparatus such as a personal computer are provided to one Y-X plane of the outer packaging cover  59  of the projector  1 . 
       FIG. 19  is a perspective view illustrating the placement surface side of the projector  1  when the open-close cover  54  is removed from the apparatus. 
     As illustrated in  FIG. 19 , a surface opposite the side to which the light source  61  is attached of the light source bracket  62  of the light source unit  60  is exposed when the open-close cover  54  is removed. A handgrip  66  is attached to the light source bracket  62  so as to be rotatable to the light source bracket  62  around O 1  indicated with the dashed line in  FIG. 19  as a rotational center. 
     To remove the light source unit  60  from the apparatus body, the light source unit  60  is removed through an opening of the apparatus body by rotating the handgrip  66  to grip the handgrip  66 , and pulling the handgrip  66  to the near side in  FIG. 19 . When the light source unit  60  is attached to the apparatus body, the light source unit  60  is inserted in the opening of the apparatus body. The light source unit  60  inserted in the apparatus body is connected to a power source side connector (not illustrated) of the apparatus body with the connector  62   a  illustrated in  FIG. 4 . The light source positioning portions  64   a   1  to  64   a   3  of the holder  64  illustrated in  FIG. 4  are fitted in the light source positioning receiving portions  26   a   1  to  26   a   3  provided to the lighting bracket  26  of the lighting unit  20  illustrated in  FIG. 6 , resulting in the light source unit  60  being positioned to the apparatus body. As a result, the attachment of the light source unit  60  is completed. Then, the open-close cover  54  is attached to the base member  53 . Although the handgrip  66  is provided to the light source unit  60  in the embodiment, the passage  65  that protrudes on the open-close cover  54  side as illustrated in  FIG. 19  may be used as the handgrip. 
     The base member  53  is provided with three legs  55 . A projecting amount from the base member  53  is changed by rotating the legs  55 , thereby enabling an adjustment in a height direction (the Y direction). 
     As illustrated in  FIG. 19 , an exhaust port  85  is provided to the other Y-X plane of the outer packaging cover  59 . 
       FIG. 20  is a schematic diagram to explain an air flow in the projector  1  of the embodiment.  FIG. 20  illustrates the projector  1  viewed from the direction orthogonal to the projection plane  101  (the X direction).  FIG. 21  illustrates the components in the embodiment corresponding to the numerals in  FIG. 20  with the same numerals. In  FIGS. 20 and 21 , the arrows indicate air flow directions.  FIG. 22  is a sectional view along line C-C of  FIG. 21 .  FIG. 23  is a sectional view along line D-D of  FIG. 21 .  FIG. 24  is a sectional view along line E-E of  FIG. 21 .  FIG. 25  is a sectional view along line F-F of  FIG. 21 .  FIG. 26  is a sectional view along line G-G of  FIG. 21 . 
     As illustrated in  FIG. 20 , the air intake port  84  that takes ambient air into the inside of the projector  1  is provided to one side surface (the left side in  FIG. 20 ) of the projector  1  while the exhaust port  85  that discharges air inside the projector  1  is provided to the other side surface (the right side in  FIG. 20 ) of the projector  1 . An exhaust fan  86  is provided so as to face the exhaust port  85 . 
     Parts of the exhaust port  85  and the air intake port  84  are provided so as to be between the light source unit  60  and the operating unit  83  when the projector  1  is viewed from the direction orthogonal to the projection plane  101  (the X direction). As a result, ambient air taken in from the air intake port  84  flows in the Z-Y plane of the mirror holder  45  and the rear surface of the curved mirror  42  in the second optical unit  40  illustrated in  FIG. 12  and toward the air intake port  84  along the mirror holder  45  and a curved surface of the rear surface of the curved mirror  42  (refer to  FIGS. 22, 24, and 26 ). The power source unit  80  disposed above the light source unit  60  has an arch-like shape when viewed from the Z direction. Air flowing from the air intake port  84  along the mirror holder  45  and the curved surface of the rear surface of the curved mirror  42  flows in a space surrounded by the power source unit  80 , and is discharged from the exhaust port  85 . The curved mirror  42  has a concave shape and the positive power as described above. The rear surface of the curved mirror  42  has a convex shape approximately conforming to the shape of the front surface of the curved mirror  42 . The exhaust port  85 , the air intake port  84 , and the curved mirror  42  are arranged on a straight line. 
     The arrangement of the exhaust port  85  and part of the air intake port  84  provided so as to be between the light source unit  60  and the operating unit  83  when the projector  1  is viewed from the direction orthogonal to the projection plane  101  (the X direction) enables an air flow to be produced that passes through the space between the light source unit  60  and the operating unit  83  and is discharged from the exhaust port  85 . In addition, a space in which air can flow is provided between the curved mirror  42  and the outer packaging cover  59  (refer to  FIGS. 22, 24, and 26 ) and ambient air taken in from the air intake port  84  flows along the rear surface of the curved mirror  42 , i.e., the curved surface of the surface that is not used as a reflection surface, and reaches the exhaust port  85 . This structure has a cooling effect on the curved mirror  42  and also achieves a flow path having a very low loss in flow rate. 
     In  FIG. 22 , the three arrows illustrate an air flow between the outer packing cover  59  and the rear surface of the curved mirror  42 . This air flow is also above the light source unit  60  (obscured in  FIG. 22 , but whose location is clear in  FIG. 20  and  FIG. 21 ) and below the operating unit  83 . 
     A light source blower  95  is disposed at such a position that the light source blower  95  can take in air surrounding the color motor  21   a  (refer to  FIG. 5 ) rotating the color wheel  21  of the lighting unit  20  (refer to  FIG. 25 ). As a result, an air flow produced by air sucked in by the light source blower  95  can cool the color motor  21   a.    
     Air taken in by the light source blower  95  flows through a light source duct  96  and flows in the light source air intake port  64   b  of the holder  64  (refer to  FIG. 4 ). Part of air having flowed in the light source duct  96  flows through an opening  96   a  formed on a surface facing the outer packaging cover  59  (refer to  FIG. 19 ) of the light source duct  96  through the space between a light source housing  97  and the outer packaging cover  59 . 
     Air flowing in the space between the light source housing  97  and the outer packaging cover  59  through the opening  96   a  of the light source duct  96  cools the light source housing  97  and the outer packaging cover  59 , and thereafter is discharged from the exhaust port  85  by the exhaust fan  86 . 
     Air flowing in the light source air intake port  64   b  flows in the light source  61 , cools the light source  61 , and thereafter is discharged from the light source air exhaust port  64   c  provided on the upper surface of the holder  64 . Air discharged from the light source air exhaust port  64   c  flows through an opening on the upper surface of the light source housing  97  toward the exhaust port  85  along a fluid guide  87 . Thereafter, the air mixes with low temperature air flowing in the space surrounded by the power source unit  80  after flowing through the second optical unit  40 , and is then discharged from the exhaust port  85  by the exhaust fan  86 . In this way, high temperature air discharged from the light source air exhaust port  64   c  mixes with ambient air before being discharged, thereby enabling air discharged from the exhaust port  85  to be prevented from reaching high temperature. The fluid guide  87  is not always required. Without the fluid guide  87 , high temperature air discharged from the light source air exhaust port  64   c  is discharged from the exhaust port  85  by air flowing toward the exhaust port  85  from the air intake port  84  through the rear surface of the curved mirror  42 , in a space surrounded by a main PFC power source board  80   a  and a sub PFC power source board  80   b , which are described later. However, the use of the fluid guide  87  can prevent high temperature air discharged from the light source air exhaust port  64   c  from flowing directly to the main PFC power source board  80   a  and flowing in the vicinity of the sub PFC power source board  80   b . However, when the fluid guide  87  is used for flowing all high temperature air off the main PFC power source board  80   a  and the sub PFC power source board  80   b , all high temperature air does not mix with air flowing on the rear surface of the curved mirror  42 , i.e., the temperature is not lowered, and is discharged from the exhaust port  85 , resulting in the temperature of the exhaust port  85  being increased. Accordingly, in a case in which some of the air that is discharged from the light source air exhaust port  64   c  and flows through the fluid guide  87  flows through the space surrounded by the main PFC power source board  80   a  and the sub PFC power source board  80   b , the air can reliably mix with air flowing on the rear surface of the curved mirror  42  from the air intake port  84  and toward the exhaust port  85 , which is safe for a user. 
     The operating unit  83  for a user to operate the apparatus is preferably provided on the upper surface of the apparatus for allowing the user to readily operate the apparatus. In the embodiment, the transmissive glass  51  used for projecting an image on the projection plane  101  is provided on the upper surface of the projector  1 . Because of the structure, the operating unit  83  needs to be provided such that part of the operating unit  83  overlaps with the light source unit  60  when the projector  1  is viewed from the Y direction, i.e., from top view of the projector  1 . That is, when the operating unit  83  is assumed as an operation plane having a certain area, the light source unit  60  is disposed on the normal line of any area of the operation plane. It can be also said that the light source unit  60  and the operating unit  83  are disposed on the normal line extended from the base member  53  having a platy shape. 
     In the embodiment, air having high temperature after cooling the light source  61  is discharged toward the exhaust port  85  by an air flow flowing from the air intake port  84  toward the exhaust port  85  in the space between the light source unit  60  and the operating unit  83 , thereby enabling high temperature air to be prevented from flowing to the operating unit  83 . As a result, an increase in the temperature of the operating unit  83  due to air having high temperature after cooling the light source  61  can be suppressed. In addition, part of air flowing from the air intake port  84  toward the exhaust port  85  through the second optical unit  40  flows directly under the operating unit  83  and cools the operating unit  83 . This air flow can also suppress an increase in the temperature of the operating unit  83 . 
     Air suction by the exhaust fan  86  causes ambient air to be sucked in from the power source air intake port  56  provided to the base member  53  illustrated in  FIG. 18 . A ballast substrate  3   a  (refer to  FIGS. 24 and 25 ) that supplies stable power (current) to the light source  61  is disposed on the far side in the X-direction in  FIG. 21  with regard to the light source housing  97 . Ambient air taken in from the power source air intake port  56  cools the ballast substrate  3   a  while flowing upward in the space between the light source housing  97  and the ballast substrate  3   a . Thereafter, the air flows in the space surrounded by the power source unit  80  disposed above the ballast substrate  3   a  and is then discharged from the exhaust port  85  by the exhaust fan  86 . 
     In the embodiment, a fan that generates an air flow flowing from the air intake port  84  toward the exhaust port  85  is provided on the exhaust side as the exhaust fan  86 , thereby enabling a supplying amount of air supplied to the inside of the apparatus from the air intake port  84  to be further increased than a case when the fan is provided to the air intake port  84 . When the fan is provided to the air intake port  84 , the volume of ambient air supplied from the fan to the inside of the apparatus is reduced by the second optical unit  40  because the second optical unit  40  is disposed in a direction in which the fan sends air. In contrast, when the fan is disposed on the exhaust port  85  side as the exhaust fan  86 , the volume of air discharged by the exhaust fan  86  is not reduced because no obstacles are usually disposed on an air exhaust side of the exhaust port  85 . Accordingly, air of the same amount as air discharged by the exhaust fan  86  is taken in from the air intake port  84 , resulting in a supplying amount of air supplied from the air intake port  84  to the inside of the apparatus not being reduced. As a result, air can flow at a certain pressure from the air intake port  84  toward the exhaust port  85 , thereby enabling heated air ascending from the light source  61  to be well directed toward the exhaust port  85  by the air flow flowing from the air intake port  84  to the exhaust port  85 . 
     On the lower left side of the apparatus body in  FIG. 20 , a cooling section  120  is disposed that cools the heat sink  13  of the image forming unit  10  and the light source bracket  62  of the light source unit  60 , for example. The cooling section  120  includes the air intake blower  91 , a vertical duct  92 , and a horizontal duct  93 . 
     The air intake blower  91  is disposed under the air intake port  84  so as to face the air intake port  84 . The air intake blower  91  sucks in ambient air through the air intake port  84  from a surface thereof facing the air intake port  84  and sucks in air inside the apparatus from another surface opposite the surface facing the air intake port  84 , and supplies the sucked air to the vertical duct  92  disposed below the air intake blower  91 . Air flowing in the vertical duct  92  flows downward and to the horizontal duct  93  connected to the downward portion of the vertical duct  92 . 
     In the horizontal duct  93 , the heat sink  13  is disposed. The heat sink  13  is cooled by air flowing in the horizontal duct  93 . The heat sink  13  cooled in this way can efficiently cool the DMD  12  and prevent the DMD  12  from reaching high temperature. 
     Air after flowing in the horizontal duct  93  flows through the passage  65  or the opening  65   a  provided to the light source bracket  62  of the light source unit  60  illustrated in  FIG. 4 . Air after flowing in the opening  65   a  flows in the space between the open-close cover  54  and the light source bracket  62 , and cools the open-close cover  54 . 
     On the other hand, air flowing through the passage  65  cools the light source bracket  62  and thereafter flows in a space opposite the emission side of the light source  61  to cool a side opposite the reflection surface of the reflector of the light source  61 , thereby cooling the reflector of the light source  61 . That is, air flowing through the passage  65  takes away heat from both the light source bracket  62  and the light source  61 . Air passed through the vicinity of the reflector flows through an exhaust duct  94  that guides air existing from the level of the light source bracket  62  to approximately the lower portion of the exhaust fan  86 , and thereafter mixes with air discharged from the light source air exhaust port  64   c  and reaches the exhaust port  85  through the fluid guide  87 . Then, the air is discharged via the exhaust port  85  by the exhaust fan  86 . Air flowing in the space between the open-close cover  54  and the light source bracket  62  through the opening  65   a  cools the open-close cover  54  and thereafter flows in the inside of the apparatus and is discharged from the exhaust port  85  by the exhaust fan  86 . 
     In the projector  1  of the embodiment, the image forming section  100 A (the image forming unit  10  and the lighting unit  20 ) and the projection optical section  100 B (the first optical unit  30  and the second optical unit  40 ) are disposed in the Y direction (up-down direction) in a layered manner, and an image is projected from the upper surface of the projector  1  toward the projection plane  101 . In addition, the light source unit  60  is disposed in the Z direction relative to the lighting unit  20 , thereby shortening the length of the projector  1  in the direction orthogonal to the projection plane  101  (the X direction). The operating unit  83  for a user to operate the apparatus is preferably provided on the upper surface of the projector  1  for allowing the user to readily operate the apparatus. In the embodiment, the transmissive glass  51  used for projecting an image on the projection plane  101  is provided on the upper surface of the projector  1 . Because of the structure, the operating unit  83  needs to be provided in such a position that the operating unit  83  overlaps with the light source  61  when the projector  1  is viewed from the Y direction. 
     When the operating unit  83  is disposed in such a position that the operating unit  83  overlaps with the light source  61  when the projector  1  is viewed from the Y direction as described above, air heated by the light source  61  ascends to and collides with the operating unit  83 , and the operating unit  83  may reach high temperature. 
     In the embodiment, ascending air heated by the light source  61  is discharged toward the exhaust port  85  by an air flow flowing from the air intake port  84  toward the exhaust port  85  in the space between the light source unit  60  and the operating unit  83  as describe above, thereby enabling the heated air to be prevented from colliding with the operating unit  83  and the operating unit  83  from reaching high temperature. Even if the ascending air collides with the operating unit  83 , air heated by the light source  61  mixes with low temperature air taken in from the air intake port  84 , resulting in the temperature being lowered, and collides with the operating unit  83 . As a result, an increase in the temperature of the operating unit  83  can be suppressed. In addition, part of air flowing from the air intake port  84  toward the exhaust port  85  cools the operating unit  83  while flowing directly under the operating unit  83 . This air flow can also suppress an increase in the temperature of the operating unit  83 . 
     Air heated through the light source housing  97  by thermal conduction and radiation heat from the light source  61  also ascends toward the operating unit  83  disposed above the light source  61 . The heated air can also flow toward the exhaust port  85  by the air flow flowing from the air intake port  84  to the exhaust port  85 . As a result, the collision of the heated air with the operating unit  83  is suppressed, thereby enabling an increase in the temperature of the operating unit  83  to be suppressed. 
     As illustrated in  FIG. 27 , a mixing duct  98  that receives air discharged from the light source and ascending from the light source housing  97  and mixes the discharged air with low temperature air flowing from the air intake port  84  may be provided between the light source  61  and the operating unit  83 . 
     As illustrated in  FIG. 27 , the ends of the mixing duct  98  on the near side and the far side in the Z-axis direction are open. The light source housing  97  is provided with a light source exhaust duct  99  that forms a flow path guiding air discharged from the light source upward in the vertical direction and causes the discharged air to flow in the mixing duct  98 . One end of the light source exhaust duct  99  is connected to an opening of the light source housing  97  formed just above the light source air exhaust port  64   c  of the holder  64  while the other end of the light source exhaust duct  99  is connected to an opening provided to a lower surface of the mixing duct  98 . 
     Air temperature which is increased by taking heat of the light source  61  discharged from the light source air exhaust port  64   c  of the holder  64  ascends in the light source exhaust duct  99  by its ascending air current, suction power of the exhaust fan  86 , and wind pressure of the light source blower  95 , for example, and collides with an upper surface serving as a wall surface of the mixing duct  98 . 
     Air after the collision with the upper surface of the mixing duct  98  mixes with low temperature air flowing in the mixing duct  98  through an inflow vent  98   a  opened on the left side of the mixing duct  98  in  FIG. 27  from the air intake port  84  and through the second optical unit  40 . As a result, the temperature of air discharged from the light source is lowered and the air flows toward the exhaust fan  86 . The air of which the temperature is lowered flows out from an outflow vent  98   b  opened on the exhaust fan  86  side of the mixing duct  98 . The outflow mixes with air flowing from an outer circumference of the mixing duct  98  and the temperature of mixed air is further lowered, and thereafter the mixed air is discharged outside the apparatus by the exhaust fan  86 . 
     The mixing duct  98  thus provided can prevent air heated by the light source  61  from colliding with the operating unit  83 . 
     The descriptions above are represented by way of example, and the invention provides particular effects in the following aspects (1) to (3). 
     (1) In the image projection apparatus including the light source unit  60 , the image forming section  100 A that forms an image using light from the light source unit  60  (in the embodiment, the image forming section  100 A is made up of the image forming unit  10  and the lighting unit  20 ), the curved mirror  42  having a concave shape, the projection optical section  100 B that projects the image (in the embodiment, made up of the first optical unit  30  and the second optical unit  40 ), and the operating unit  83  for a user to operate the apparatus, the operating unit  83  is disposed on the upper surface of the apparatus and above the light source unit  60 . The apparatus further includes the air intake port  84  that takes ambient air into the inside of the apparatus, the exhaust port  85  that discharges air inside the apparatus, and the air supplying unit such as the exhaust fan  86  that supplies air by sucking in ambient air from the air intake port  84  and supplying air so as to exhaust air from the exhaust port  85 . At least part of the air intake port  84  and at least part of the exhaust port  85  are disposed so as to be between the light source unit  60  and the operating unit  83 . The curved mirror  42  having a concave shape is disposed such that air flowing from the air intake port  84  toward the exhaust port  85  flows along the rear surface of the curved mirror  42 . 
     This structure produces an air flow flowing from the air intake port toward the exhaust port in the space between the light source unit  60  and the operating unit  83  as described in the embodiment. This air flow enables ascending air heated by heat of the light source unit  60  to flow toward the exhaust port  85  and to be discharged. As a result, the collision of air heated by the light source unit  60  with the operating unit  83  disposed above the light source unit  60  can be suppressed and an increase in the temperature of the operating unit  83  can be suppressed. In addition, the curved mirror  42  having a concave shape is disposed such that air flowing from the air intake port  84  toward the exhaust port  85  flows along the rear surface of the curved mirror  42  having a concave shape, enabling ambient air taken in from the air intake port  84  to flow in the space between the light source  61  in the apparatus and the operating unit  83  while maintaining its momentum when taken in and discharged from the exhaust port  85 . Air heated by the light source  61  mixes with low temperature air and is discharged from the exhaust port  85  as describe above, thereby enabling air discharged from the exhaust port  85  to be prevented from reaching high temperature. 
     (2) In the image projection apparatus according to the first aspect, the air supplying unit is provided to the exhaust port  85  side. 
     This structure enables a supplying amount of air capable of being taken into the inside of the apparatus to be further increased than a case when the air supplying unit is provided to the air intake port  84  side as described in the embodiment. As a result, air heated by the light source  61  can be well transferred to the exhaust port  85  by the air flow flowing from the air intake port  84  toward the exhaust port  85 . 
     (3) In the image projection apparatus according to any one of the first and the second aspects, the projection optical section  100 B is disposed on the image forming section  100 A while the light source  61  and the image forming section  100 A are arranged in a direction in parallel with a plane of a projection image projected on the projection plane  101  and the apparatus body, and the image is projected from the upper surface of the apparatus toward the projection plane  101 . 
     This structure enables the length of the apparatus in a direction orthogonal to the projection plane  101  to be shortened. As a result, an installation space of the apparatus can be prevented from being largely taken in the direction orthogonal to the plane of a projection image projected on the projection plane  101 . Consequently, when the image projection apparatus is used while placed on a desk, for example, the apparatus can be prevented from hindering the arrangement of the desk and chairs in a small room. 
     According to the embodiments, air that is heated by the light source and ascends in the apparatus and heated air are caused to flow toward the exhaust port through a second flow path formed between the light source and the operating unit, thereby enabling the operating unit to be further suppressed from being heated than in conventional ways. Air that is heated by heat conducted from the light source by thermal conduction and the light source and ascends in the apparatus mixes with air flowing in the second flow path different from a first flow path, thereby lowering the temperature of the air. Consequently, an increase in the temperature of the operating unit can be suppressed even when the operating unit is disposed above the light source when viewed from the placement surface on which the apparatus body is placed. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.