Abstract:
A projection apparatus for inexpensively adjusting the irradiating region of light on an image forming device to irradiate the light to the entire image forming surface of the image forming device is provided. 
     The projector including a light tunnel for passing the light emitted from a lamp and changing the light to condensed uniform light, a mirror for reflecting the light passed through the light tunnel, a DMD for reflecting the light at an image forming surface irradiated with the light reflected by the mirror and forming an image, a lens for projecting the image formed with the DMD, and a frame for attaching these components of an image projection optical system; further includes a rotation adjustment fixing mechanism for fixing the light tunnel to the frame with the rotation angle having the axis of the light tunnel as substantially the center adjusted with an incident port of light of the light tunnel facing the lamp and an exit port facing the mirror.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to projection apparatus that employ image forming devices such as DMD (Digital Micro-mirror Device), in particular, to a configuration of adjusting an irradiating region for irradiating the light from a light source to the image forming device. 
         [0003]    2. Description of the Related Art 
         [0004]      FIG. 1  is a view showing a schematic configuration of a projector  100  of DLP (Digital Light Processing) type. The projector  100  is one example of the projection apparatus. An illustrated image projection optical system unit is arranged inside the main body  1  of the projector  100 . An air conditioning system unit, a controlling system unit, a power supply system unit etc. (not shown) are also arranged inside the main body  1 . 
         [0005]    Reference numeral  3  is a lamp serving as a light source,  4  is a reflector, and  2  is a lamp case for holding the lamp  3  and the reflector  4 . Reference numeral  5  is a color wheel made of circular disc in which the color filters of red, green and blue are alternately arranged in the circumferential direction. The color wheel  5  that is rotated by a motor (not shown) transmits the white light emitted from the lamp  3  through one of the color filters, and separates the white light to red light, green light and blue light. Reference numeral  6  is an engine casting or a vertically separable frame made of magnesium. Components  7  to  11  of the image projection optical system described below are respectively assembled to the engine casting  6 . Reference numeral  7  is a light tunnel of square tube shape having a mirrored inner surface. The light entered from an incident port  7   a , which is an opening on one end side, is repeatedly reflected in the inside of the light tunnel  7 , and exit from an exit port  7   b , which is an opening on the other end side, thereby changing the light to a condensed uniform light in a short light path. Reference numeral  8  is a mirror for reflecting the light that has passed through the light tunnel  7 . The light path length is shortened and the image projection optical system is miniaturized through the use of the light tunnel  7  and the mirror  8 . Reference numeral  9  is a relay lens for aligning the light flux of the light reflected by the mirror  8 . 
         [0006]    Reference numeral  10  is a DMD (Digital Micro-mirror Device) in which several hundred thousand microscopic micro-mirrors (not shown) are integrated on a semiconductor memory, where each micro-mirror assigned with the memory cell configures the pixel. The DMD  10  is one example of the image forming device and is mounted on a circuit board (not shown) The micro-mirror of the DMD  10  that can be tilted in two directions at ±12° tilts to one direction by the electrostatic attraction force according to the memory value, and takes a binary state of ON/OFF depending on the tilted direction. Reference numeral  11  is a projection lens made up of a tube that is compressible in the axis direction, and a plurality of lenses etc. equipped inside of the tube. The projection lens  11  passes the light reflected by the DMD  10  and projects the light onto the screen  50 . 
         [0007]    As shown with an arrow, the white light emitted from the lamp  3  is passed through the opening  2   a  of the lamp case  2 , passed through one of the color filters of the color wheel  5 , and separated to the red light, green light and blue light. Each color light enters the inside through the opening  6   a  of the engine casting  6 , and passes through the light tunnel  7  to be condensed and uniformed. The light exit from the light tunnel  7  is passed through the lower side of the projection lens  11 , reflected upward at a predetermined angle by the mirror  8 , passed through the relay lens  9 , and irradiated onto the DMD  10 . In this case, when the micro-mirror of the DMD  10  is in the ON state, the light reflected by the mirror is taken into the projection lens  11  and projected onto the screen  50 . When the micro-mirror is in the OFF state, the light reflected by the mirror is not taken into the projection lens  11 , and thus is not projected onto the screen  50 . That is, the projector  100  forms the image with the DMD  10  by ON/OFF controlling the operation state of each micro-mirror of the DMD  10  based on the input video signal and the like, and projects the image onto the screen  50  through the projection lens  11 . 
         [0008]      FIG. 14  is a view showing a conventional irradiating state of the light on the DMD  10 . Rectangle  10   a  shown with a solid line is the image forming surface of the DMD  10  arranged on the side to be irradiated with light. The image forming surface  10   a  consists of above-described micro-mirrors. The light emitted from the lamp  3  is passed through the light tunnel  7  and the like, reflected by the mirror  8 , and irradiated onto the DMD  10 , as described above. In this case, the light is narrowed according to the diameter of the light tunnel  7  of square tube shape, and the light path is bent by the reflection at the mirror  8 , and thus the irradiating region of the light irradiated on the DMD  10  becomes a square shape tilted (sometimes deformed) with respect to the image forming surface  10   a  as shown with  10   b  in a dot-dash line in  FIG. 14 , and the light may not be irradiated to one part, as indicated by the shaded area, of the image forming surface  10   a . If the image is formed with the DMD  10  and projected onto the screen  50  in this state, the image quality may degrade such as the projected image may become dark. 
         [0009]    Therefore, the attachment angle and position of the mirror  8  with respect to the engine casting  6  have been adjusted in the prior art to adjust the irradiating region of the light on the DMD  10  so that light is irradiated to the entire image forming surface  10   a . Furthermore, the irradiating region of the light on the DMD  10  sometimes cannot be adequately adjusted so that light is irradiated on the entire image forming surface  10   a  only by adjusting the attachment of the mirror  8 , in which case, the size of the diameter of the light tunnel  7  is changed to larger size, which enlarges the irradiating region of the light to  10   c , as shown with a dot-dot-dash line in  FIG. 14 , in the prior art. However, the optical specification must be changed if the size of the light tunnel  7  is changed, which leads to adverse effects such as lowering in energy of the light per unit area to be irradiated on the DMD  10 , and re-designing etc. of the image projection optical system may become necessary, which is very troublesome. Furthermore, various light tunnels  7  of different sizes must be manufactured and prepared, which is very costly. 
         [0010]    Patent document 1; Japanese Patent Application Laid-Open No. 2000-155373 discloses a technique of adjusting the image displaying position on the screen by arranging a motor for rotating the projection lens with the optical axis as the center, a motor for operating a zoom mechanism of the projection lens, and a motor for moving a liquid crystal panel, DMD etc. in the X direction perpendicular to the optical axis and the Y direction in a rear projection television etc., and operating each motor through switch operation. However, such technique is difficult to apply to the adjustment of the irradiating region of the light on the DMD  10 , and is also costly since a great number of motors and switches are used. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention, in view of solving the above problems, aims to provide a projection apparatus for inexpensively adjusting the irradiating region of the light on the image forming device to irradiate the light to the entire image forming surface of the image forming device. 
         [0012]    The present invention relates to a projection apparatus including a light tunnel for passing light emitted from a light source and changing the light to condensed uniform light, a mirror for reflecting the light passed through the light tunnel, an image forming device for reflecting the light at an image forming surface irradiated with the light reflected by the mirror and forming an image, a lens for projecting the image formed with the image forming device, and a frame for attaching these components of an image projection optical system; the apparatus further including a rotation adjustment fixing mechanism for fixing the light tunnel to the frame with the rotation angle adjusted with the incident port of light of the light tunnel facing the light source and the exit port facing the mirror. 
         [0013]    Accordingly, the irradiating region of the light on the image forming device can be adjusted with a change of tilt or position by adjusting the rotation angle of the light tunnel by means of the rotation adjustment fixing mechanism, whereby the light can be irradiated to the entire image forming surface of the image forming device. As a result, the image quality can be prevented from degrading such as the projected image from becoming dark when the image formed with the image forming device is projected by the lens. Furthermore, the optical specification is not changed since the size of the light tunnel does not need to be changed as in the prior art, and thus the trouble of redesigning image projection optical system, and the cost for preparing the light tunnel of different sizes etc. can be saved. 
         [0014]    In the present invention, the rotation adjustment fixing mechanism is configured by a base having the light tunnel fixed at one surface side at the center by means of a fixture and the other surface side rotatably supported at a supporting part formed in the frame with the incident port of light of the light tunnel facing the light source and the exit port facing the mirror; a pin, passed through a hole formed at one end of the base in a direction perpendicular to the axis of the light tunnel and attached to the frame, for supporting the one end swingably; a spring for biasing the one end of the base towards the supporting part of the frame; a screw, passed through a hole formed on the other end of the base in a direction perpendicular to the axis of the light tunnel and screwed into a screw hole formed in the frame, for pressing the other end towards the supporting part of the frame with a head; and a vis, screwed into a screw hole formed in the base to pass through the base and engaged to an inclined surface formed in the frame so as to incline in the axial direction of the light tunnel, for pressing the base against the side wall of the frame in the axial direction of the light tunnel. 
         [0015]    In such configuration, when the base fixed with the light tunnel by the fixture is supported at the supporting part of the frame, the pin is passed through the hole at one end of the base and attached to the frame, and the one end of the base is biased towards the supporting part with a spring, the base rotates and the other end rises from the frame with respect to the one end, and the base is held by the frame. If the screw is passed through the hole on the other end of the base and screwed into the screw hole of the frame in such state, the other end of the base is pressed towards the supporting part side of the frame with the head of the screw, and the base gradually rotates. Thus, the rotation angle of the light tunnel is adjusted with the base by changing the screw-fit depth of the screw with respect to the screw hole of the frame. When the vis is screwed into the screw hole of the base and engaged to the inclined surface of the frame, a force acting towards the supporting part side is applied to the inclined surface of the frame from the vis, and a force acting towards the side wall side of the frame is applied to the vis from the inclined surface of the frame as reactive force, whereby the other end of the base is pressed against the side wall of the frame, and the base and the light tunnel are fixed to the frame without shaking in the axial direction and the rotating direction. Therefore, the rotation angle of the light tunnel is easily adjusted with a tightening task of screw, vis and the like, whereby the irradiating region of the light on the image forming surface is adjusted and the light can be irradiated to the entire image forming surface of the image forming device. Furthermore, the optical specification is not changed since the size of the light tunnel does not need to be changed as in the prior art, and thus the trouble and cost can be saved. 
         [0016]    In the present invention, the spring contacts one surface of the base and presses one end towards the supporting part of the frame, and an inclined surface is formed at the area contacting the spring of the base so as to incline in a direction opposite the inclined surface of the frame. 
         [0017]    According to this, the one end of the base is biased towards the supporting part side and the side wall side of the frame since the inclined surface of the base is pressed by the spring, whereby the base and the light tunnel are more reliably fixed to the frame without shaking in the axial direction and the rotating direction. 
         [0018]    Furthermore, in a typical embodiment of the present invention, a projection apparatus includes a light tunnel of square tube shape for passing light emitted from a light source and changing the light to condensed uniform light, a mirror for reflecting the light passed through the light tunnel, a DMD (Digital Micro-mirror Device) for reflecting the light at an image forming surface irradiated with the light reflected by the mirror and forming an image, a lens for projecting the image formed with the DMD, and a frame for attaching these components of an image projection optical system; the projection apparatus further including a rotation adjustment fixing mechanism configured by, base having the light tunnel fixed at one surface side at the center by means of a fixture and the other surface side rotatably supported with the axis of the light tunnel as substantially the center at a supporting part formed in the frame with an incident port of light of the light tunnel facing the light source and an exit port facing the mirror; a plurality of pins, each passed through a plurality of holes formed at one end of the base in a direction perpendicular to the axis of the light tunnel and attached to the frame, for supporting the one end swingably; a spring, arranged around each pin, for pressing an inclined surface formed so as to incline in the axial direction of the light tunnel around each hole of the base towards the supporting part side of the frame; a screw, passed through a hole formed on the other end of the base in a direction perpendicular to the axis of the light tunnel and screwed into a screw hole formed in the frame, for pressing the other end towards the supporting part of the frame with a head; and a vis, screwed into a screw hole formed in the other end of the base to be passed through the base and engaged to an inclined surface formed in the frame so that an inclined part formed at the distal end inclines in the direction opposite the inclined surface of the base, for pressing the base against the side wall of the frame in the axial direction of the light tunnel; the rotation adjustment fixing mechanism fixing the light tunnel to the frame with the rotation angle having the axis of the light tunnel as substantially the center adjusted with the whole base by changing the screw-fit depth of the screw with respect to the screw hole of the frame, and screwing the vis into the screw hole of the base to engage the inclined surface of the frame. 
         [0019]    In such configuration, when the base fixed with the light tunnel by the fixture is supported at the supporting part of the frame, and each pin, around which the spring is arranged, is passed through each hole at one end of the base and attached to the frame, each spring contacts the inclined surface around each hole of the base, and forces acting toward the supporting part and the side wall of the frame are applied to the inclined surface, whereby the base rotates with the axis of the light tunnel as substantially the center, the other end rises from the frame with respect to the one end, the one end moves towards the side wall side and the side wall of each hole at the one end is pressed against the side surface of each pin. In this state, the one end of the base is held at a plurality of points by a plurality of pins, a plurality of springs, and the frame, and thus shake of the base is suppressed, and subsequent attachment work is facilitated. The screw is then passed through the hole of the other end of the base and screwed into the screw hole of the frame, whereby the other end of the base is pressed against the supporting part side of the frame with the head of the screw, and the base gradually rotates with the axis of the light tunnel as substantially the center. Thus, the rotation angle of the light tunnel is adjusted with the base by changing the screw-fit depth of the screw with respect to the screw hole of the frame. In this state, the shake in the rotating direction of the base and the light tunnel is suppressed since the base is supported from both surfaces by the springs, the screws and the frame, and subsequent attachment work is facilitated. When the vis is screwed into the screw hole of the other end of the base, the inclined part at the distal end of the vis smoothly engages the inclined surface of the frame, whereby a force acting towards the supporting part side is applied to the inclined surface of the frame from the inclined part of the vis and a force acting towards the side wall side of the frame is applied to the inclined part of the vis from the inclined surface of the frame as reactive force. Thus, the base is thereby moved towards the side wall side of the frame and pushed against thereto, and the base and the light tunnel are fixed to the frame without shaking in the axial direction and the rotating direction. In this state, the base is supported by the springs, the screws, the vis, and the frame, and thus the shake in the axial direction and the rotating direction of the base and the light tunnel is almost completely suppressed, and a stable fixed state can be maintained. 
         [0020]    Therefore, the rotation angle of the light tunnel is easily adjusted by the tightening task of the screw, vis and the like, whereby the irradiating region of the light on the DMD is adjusted and the light can be irradiated to the entire image forming surface of the DMD. In particular, if the rotation angle of the light tunnel is adjusted and the attachment of the mirror is adjusted, the adjustable range of the irradiating region of the light on the DMD is extended, and the light is more reliably irradiated to the entire image forming surface of the DMD. As a result, the image quality is prevented from degrading such as the projected image from becoming dark when the image formed with the DMD is projected by the lens. The optical specification is not changed since the size of the light tunnel does not need to be changed as in the prior art, and thus the trouble and cost can be saved. Moreover, the adjustment of the irradiating region of the light on the DMD is appropriately performed even if the same type of light tunnel is used indifferent types of projection apparatus, thereby standardizing the components, and further reducing the cost. 
         [0021]    According to the present invention, the irradiating region of the light on the image forming device is adjusted by adjusting the rotation angel of the light tunnel by means of the rotation adjustment fixing mechanism, and the light can be irradiated on the entire image forming surface of the image forming device, and furthermore, the trouble and cost are saved since the size of the light tunnel does not need to be changed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a configuration view of a projector serving as one example of a projection apparatus according to the present invention; 
           [0023]      FIG. 2  is a perspective view of a lower side frame in the projector; 
           [0024]      FIG. 3  is an enlarged view of the main parts of the lower side frame; 
           [0025]      FIG. 4  is a perspective view of assembling components including a light tunnel; 
           [0026]      FIG. 5  is a view showing the attachment state of the assembling components with respect to the lower side frame; 
           [0027]      FIG. 6  is a perspective view showing the side surface of the lower side frame; 
           [0028]      FIG. 7  is a view showing the attachment state of one end of a base with respect to the lower side frame; 
           [0029]      FIG. 8  is a view showing the attachment state of the assembling component with respect to the lower side frame; 
           [0030]      FIG. 9  is a view showing the attachment state of the other end of the base with respect to the lower side frame; 
           [0031]      FIG. 10  is a perspective view of the light tunnel; 
           [0032]      FIG. 11  is a perspective view of a fixture; 
           [0033]      FIG. 12  is a perspective view of the base; 
           [0034]      FIG. 13  is a view showing the irradiating state of light on a DMD according to the present invention; and 
           [0035]      FIG. 14  is a view showing an irradiating state of the light on a DMD in prior art. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    The embodiments of the present invention will now be described with reference to the drawings. The schematic configuration of the projection apparatus according to the embodiment of the present invention is similar to that of  FIG. 1  described in the Background of the Invention section, and thus  FIG. 1  will be cited for the embodiment of the present invention, and redundant description will be omitted. The projector  100  shown in  FIG. 1  is one example of the projection apparatus according to the embodiment of the present invention. 
         [0037]      FIG. 2  is a perspective view showing a lower side frame  6 A of the engine casting  6 . The engine casting  6  is assembled by fitting the lower side frame  6 A and an upper side frame (not shown) and tightening the frames with a screw and the like. The lower side frame  6 A is integrally formed with an assembling part  61  for assembling the projection lens  11 ; an assembling part  62  for assembling the mirror  8 ; an assembling part  63  for assembling the relay lens  9 ; an assembling part  64  for assembling the DMD  10 , a circuit board (not shown) mounted with the DMD  10 , and a heat sink (not shown) for cooling the DMD  10 ; and an assembling part  60  for assembling the assembling component  20  including the light tunnel  7  shown in  FIG. 4 . The assembling part  60  and the assembling component  20  are main components of a rotation adjustment fixing mechanism in the present embodiment. Screw, vis, spring and the like are used to assemble each component of the image projection optical system to each assembling part  60  to  64 . 
         [0038]    The assembling component  20  is configured by the light tunnel  7 , fixture  21 , base  22 , pin  23 , coil spring  24 , round machine screw with cross-shaped groove  25 , and vis  26  with hexagonal hole  26 , as shown in  FIG. 4 . The light tunnel  7  has a square tube shape as shown in  FIG. 10 , and has a mirrored inner surface. In  FIG. 10A , a state in which the light tunnel  7  is viewed diagonally from the incident port  7   a  side is shown. In  FIG. 10B , a state viewed diagonally from the exit port  7   b  side is shown. The fixture  21  is formed by bending a sheet metal, as shown in  FIG. 11A  to  FIG. 1C . In  FIG. 11A , a state in which the fixture  21  is viewed diagonally from above is shown. In  FIG. 11B , a state viewed diagonally from the side is shown. In  FIG. 11C , a state viewed diagonally from below is shown. An opening  21   a  is formed on the front surface of the fixture  21 , as shown in  FIG. 11B . The opening  21   a  has the same size as the incident port  7   a , the exit port  7   b , and the inner diameter of the light tunnel  7 . Pressing parts  21   b  are formed at the center of each side surface of rectangular shape having a large width, and hook parts  21   c ,  21   d  are formed at the ends. 
         [0039]    The base  22  is made of metal and is formed into a shape such as shown in  FIG. 12A  and  FIG. 12B . As shown in  FIG. 12A , a substantially V-shaped groove  22   a  is formed across the longitudinal direction of the base  22  at the center on one surface side of the base  22 . Projection type supporting parts  22   b ,  22   e  for supporting the light tunnel  7  are formed on the inner side of the groove  22   a . As shown in  FIG. 12B , a convex part  22   m  is formed on the side surface of the base  22  on the supporting part  22   e  side. Holes  22   c ,  22   d  for inserting the hook parts  21   c ,  21   d  of the fixture  21  are formed on both sides of the groove  22   a . The light tunnel  7  is fitted into the groove  22   a  of the base  22 , and the side surface of the light tunnel  7  is supported at the supporting part  22   b  and the end of the exit port  7   b  side is supported at the supporting part  22   e , and thereafter, the hook parts  21   c ,  21   d  of the fixture  21  are inserted to the holes  22   c ,  22   d  of the base  22 , respectively, whereby the hook parts  21   c ,  21   d  elastically deform to be hooked at the edge of the holes  22   c ,  22   d , and the fixture  21  is attached to the base  22 , as shown in  FIG. 4  and  FIGS. 8A ,  8 B.  FIG. 8A  and  FIG. 8B  show a state in which the assembling component  20  is seen from the opening  21   a  side of the fixture  21 . In this state, the light tunnel  7  is fixed to the base  22  while being supported by the pressing part  21   b  and the front surface of the fixture  21  and the supporting parts  22   b ,  22   e  of the base  22 , and the incident port  7   a  and the exit port  7   b  of the light tunnel  7  and the opening  21   a  of the fixture  21  are lined in the axial direction of the light tunnel  7 , as shown with a dot-dash line in  FIG. 4 . 
         [0040]    As shown in  FIGS. 12A and 12B , the center on the other surface side of the base  22  is projected across the longitudinal direction of the base  22  to form the bottom of the groove  22   a , and an engaging part  22   f  of circular arc shape is formed at both ends at the distal end. The center of the circular arc of the engaging part  22   f  is set so as to substantially coincide with the axis (dot-dash line of  FIG. 4 ) of the light tunnel  7  fixed to the base  22 . Holes  22   g , through which two pins  23  are passed respectively, are each formed at one end  22   x  of the base  22  in a direction perpendicular to the axis of the light tunnel  7  in  FIG. 4 . An inclined surface  22   h  is formed around each hole  22   g  so as to incline while rising in the axial direction from the incident port  7   a  towards the exit port  7   b  of the light tunnel  7 . The coil spring  24  is arranged around each pin  23  so as to contact the inclined surface  22   h . The diameter of each hole  22   g  of the base  22  is larger than the diameter of the middle part  23   b  of each pin  23 , and is smaller than the diameter of each coil spring  24 . A cross-shaped groove is formed at the head  23   a  of each pin  23 , and a collar  23   c  is arranged immediately under the head  23   a . The diameter of each collar  23   c  is larger than the diameter of each coil spring  24 . A screw part  23   d  having a diameter smaller than the middle part  23   b  is formed at the lower part of each pin  23 . 
         [0041]    A hole  22   j  ( FIGS. 12A ,  12 B) for passing one machine screw  25  and a hole  22   k  for screw fitting one vis  26  are formed at the other end  22   y  of the base  22  in a direction perpendicular to the axis of the light tunnel  7  in  FIG. 4 . The diameter of the hole  22   j  is larger than the diameter of the screw part  25   d  of the machine screw  25 , and smaller than the diameter of the head  25   a . The diameter of the head  26   a  of the vis  26  is substantially the same as the diameter of the screw part  26   d  at the middle. A tapered inclined part  26   b  is formed at the distal end of the vis  26 . 
         [0042]      FIG. 3  is an enlarged view of the assembling part  60  of the lower side frame  6 A. An opening  6   a  is formed in the side surface  6   b  on the right side of the assembling part  60  of the lower side frame  6 A so as to face the assembling part  60 , as shown in  FIG. 6 . The color filter  5  and the lamp case  2  are arranged on the external side (right side in  FIG. 2  and  FIG. 3 ) of the side surface  6   b , as shown in  FIG. 1 . In the arrangement state of  FIG. 1 , the opening  6   a  of the lower side frame  6 A and the opening  2   a  of the lamp case  2  are lined in the optical axis direction of the light emitted from the lamp  3 . 
         [0043]    A dent  6   c  is formed in the assembling part  60 . A supporting part  6   d  in the form of inclined surface and a side wall  6   e  are formed on the inner side of the dent  6   c  so that the light emitted from the lamp  3  and passed through the openings  2   a ,  6   a  is not shielded from entering the mirror  8  assembled to the assembling part  62 , as shown in  FIG. 1  to  FIG. 3  and  FIG. 6 . The base  22  is fitted to the dent  6   c , as shown in  FIG. 5 . When the base  22  is fitted to the dent  6   c  as shown in  FIG. 5  with the light tunnel  7  fixed to the base  22  by means of the fixture  21 , as shown in  FIG. 4 , the incident port  7   a  of the light tunnel  7  faces the lamp  3 , and the exit port  7   b  faces the mirror  8  of the assembling part  62 , so the axis of the light tunnel  7  substantially coincide with the optical axis of the light from the lamp  3 , whereby the light from the lamp  3  passes through the light tunnel  7  and becomes able to enter the mirror  8 , as shown in  FIG. 1 . Furthermore, the engaging part  22   f  of the base  22  is supported by the supporting part  6   d  on the inner side of the dent  6   c  as shown in  FIG. 8A  and  FIG. 8B , so that the base  22  becomes rotatable with the axis of the light tunnel  7  as substantially the center. In  FIG. 8A  and  FIG. 8B , the cross mark indicated on the inner side of the opening  21   a  of the fixture  21  and the inner side of the incident port  7   a  of the light tunnel  7  is the axis of the light tunnel  7  and is the center of rotation of the base  22 . 
         [0044]    A screw hole  6   f  for screw fitting the screw part  23   d  of the pin  23  and a screw hole  6   g  for screw fitting the screw part  25   d  of the machine screw  25  are formed on the upper part of the dent  6   c , as shown in  FIG. 3 . An inclined surface  6   h  that engages the inclined part  26   b  of the distal end of the vis  26  is formed in the vicinity of the screw hole  6   g . The inclined surface  6   h  is formed so as to incline while rising in the optical axis direction of the light of the lamp  3  from the side wall  6   e  towards the opening  6   a , that is, in the axial direction from the exit port  7   b  towards the incident port  7   a  of the light tunnel  7  fixed to the base  22  in the state of  FIG. 5 . 
         [0045]    In the above configuration, in order to assemble the light tunnel  7  to the lower side frame  6 A, the light tunnel  7  is first fitted to the groove  22   a  of the base  22 , as described above, and fixed with the fixture  21 , as shown in  FIG. 4 . The base  22  is then fitted to the dent  6   c  of the assembling part  60  of the lower side frame  6 A and the engaging part  22   f  is supported by the supporting part  6   d . The coil spring  24  is then arranged around the middle part  23   b  of each pin  23 , the screw part  23   d  and the middle part  23   b  are passed through the hole  22   g  at the end  22   x  of the base  22 , as shown in  FIG. 4 , and the screw part  23   d  is screwed into each screw hole  6   f  using a screwdriver and the like to attach each pin  23  to the lower side frame  6 A, as shown in  FIG. 7 . In  FIG. 7 , the illustration of the light tunnel  7  and the fixture  21  is omitted. 
         [0046]    When each pin  23  is attached to the lower side frame  6 A as described above, the end  22   x  of the base  22  is supported by each pin  23  swingably. Furthermore, each coil spring  24  contacts each inclined surface  22   h  of the base  22 , whereby the force F acting towards the side wall  6   e  side of the lower side frame  6 A is applied to each inclined surface  22   h , the end  22   x  of the base  22  is moved towards the side wall  6   e , and the side wall of each hole  22   g  is pushed against the middle part  23   b  of each pin  23 . Furthermore, the force W acting towards the supporting part  6   d  side of the lower side frame  6 A is applied from each coil spring  24  to each inclined surface  22   h , whereby the base  22  rotates in the clockwise direction with the axis of the light tunnel  7  as substantially the center, as shown in  FIG. 8A , and the end  22   y  rises from the lower side frame  6 A with respect to the end  22   x . In this state, the end  22   x  of the base  22  is held at a plural points by two pins  23 , two coil springs  24 , and the lower side frame  6 A, and thus shake of the base  22  is suppressed, whereby subsequent attachment work is facilitated. 
         [0047]    Next, the screw  25  is passed through the hole  22   j  at the end  22   y  of the base  22 , and screwed into the screw hole  6   g  of the lower side frame  6 A using the screwdriver and the like. The end  22   y  of the base  22  is then pushed against the supporting part  6   d  side of the lower side frame  6 A with the head  25   a  of the screw  25 , whereby the base  22  rotates in the counterclockwise direction with the axis of the light tunnel  7  as substantially the center, as shown in  FIG. 8B . Thus, the distance between the ends  22   x ,  22   y  of the base  22  and the lower side frame  6 A can be changed by changing the screw-fit depth of the screw  25  with respect to the screw hole  6   g  of the lower side frame  6 A, and the rotation angle of the light tunnel  7  is adjusted with the base  22 . In this state, the base  22  is supported from both upper and lower surfaces by the coil spring  24 , the screw  25 , and the lower side frame  6 A, and thus the shake in the rotating direction of the base  22  and the light tunnel  7  is suppressed, and subsequent attachment work is facilitated. 
         [0048]    Next, the vis  26  is screwed into the screw hole  22   k  of the end  22   y  of the base  22  using a wrench and the like, whereby the inclined part  26   b  of the distal end of the vis  26  smoothly engages the inclined surface  6   h  of the lower side frame  6 A, as shown in  FIG. 9 .  FIG. 9  shows only the vicinity of the end  22   y  of the base  22 . When the inclined part  26   b  of the vis  26  engages the inclined surface  6   h  of the lower side frame  6 A, the force W′ acting towards the supporting part  6   d  side of the lower side frame  6 A is applied to the inclined surface  6   h  from the inclined part  26   b , and the force F′ acting towards the side wall  6   e  of the lower side frame  6 A is applied to the inclined part  26   b  from the inclined surface  6   h  as one component of reactive force. The base  22  is thereby moved towards the side wall  6   e , the convex part  22   m  ( FIG. 12B ) of the base  22  is pressed against the side wall  6   e , and the base  22  and the light tunnel  7  are fixed to the lower side frame  6 A without shaking in the axial direction and the rotating direction. The fixed state of the base  22  at this point is the same as the state shown in  FIG. 5 . In  FIG. 5 , the illustration of the light tunnel  7  and the fixture  21  is omitted. When fixed in the above manner, the shake in the axial direction and the rotating direction of the base  22  and the light tunnel  7  are almost completely suppressed and a stable fixed state can be maintained since the base  22  is supported at both upper and lower surfaces and both ends  22   x ,  22   y  with forces W, W′, F, F′ etc. by the coil spring  24 , the screw  25 , the vis  26 , and the lower side frame  6 A. 
         [0049]    After the other components  8  to  11  of the image projection optical system are assembled to other assembling parts  61  to  64  of the lower side frame  6 A, the upper side frame is fitted to the lower side frame  6 A to assemble the engine casting  6 , and the engine casting  6  is installed in the main body  1  of the projector  100  as shown in  FIG. 1 . In such installation state, the light emitted from the lamp  3  passes through the opening  2   a  of the lamp case  2 , the color wheel  5 , and the opening  6   a  of the engine casting  6 , enters the light tunnel  7 , and then condensed and uniformed in the light tunnel  7 . The light which exit from the light tunnel  7  is reflected by the mirror  8 , passed through the relay lens  9 , and irradiated onto the DMD  10 . Furthermore, the image is formed at the DMD  10  by ON/OFF operating each micro-mirror of the DMD  10 , and the image is projected onto the screen  50  through the projection lens  11 . 
         [0050]      FIG. 13  is a view showing the irradiation state of the light on the DMD  10  of the projector  100  of the present embodiment installed with each component as described above. The rectangular shape  10   a  shown with a solid line is the image forming surface of the DMD  10  arranged on the side irradiated with the light. The image forming surface  10   a  consists of above-described micro-mirrors, and is covered with a cover glass (not shown).  10   x  shown with a dot-dash line is the irradiating region of the light of before adjustment that is irradiated on the DMD  10 . That is, the irradiating region  10   x  is one example of the irradiating region of the light irradiated on the DMD  10  when the light tunnel  7  and the like are vaguely attached to the lower side frame  6 A without performing rotation adjustment. The irradiating region  10   x  is a square shape slanted and slightly deformed with respect to the image forming surface  10   a , and thus the light is not irradiated to one part, as indicated by the shaded area, of the image forming surface  10   a.    
         [0051]    The upper side frame of the engine casting  6  is detached from the lower side frame  6 A, and the tightening degree of the vis  26 , the screw  25  and the like (pin  23  in some cases) assembled to the assembling part  60  is changed to adjust the rotation angle of the light tunnel  7  with the whole base  22 , thereby rotating the irradiating region  10   x  of the light on the DMD  10  of  FIG. 13  and changing the tilt or position as in the irradiating region  10   x ′ shown with a dot-dot-dash line so that the light can be irradiated on the entire image forming surface  10   a . Furthermore, by adjusting the rotation angle of the light tunnel  7 , and adjusting the attachment angle or position of the mirror  8  with respect to the lower side frame  6 A, the adjustable range of the irradiating region of the light on the DMD  10  is extended so that the light can be more reliably irradiated on the entire image forming surface  10   a.    
         [0052]    As a result, the image quality is prevented from degrading such as the projected image from becoming dark when the image formed with the DMD  10  is projected onto the screen  50  through the projection lens  11 . The adjustment of the rotation angle of the light tunnel  7  and the adjustment of the irradiating region of the light on the DMD  10  are easily performed with a simple task such as tightening the vis  26 , the screw  25  etc., and thus the working time can be shortened. Furthermore, the optical specification is not changed since the size of the light tunnel  7  does not need to be changed as in the prior art, and thus the trouble of redesigning the image projection optical system, and the cost for preparing the light tunnel  7  of different sizes etc. can be saved. Moreover, the adjustment of the irradiating region of the light on the DMD  10  can be appropriately performed even by using the same type of light tunnel  7  in different types of projector  100 , thereby standardizing the components, and further reducing the cost. 
         [0053]    The present invention may adopt various forms other than the above described embodiment. For instance, an example in which one end  22   x  of the base  22  is supported swingably using two pins  23  has been described in the above embodiment, but the present invention is not limited thereto. One end  22   x  of the base  22  may be supported using one or three or more pins. 
         [0054]    Also, an example in which one end  22   x  of the base  22  is pressed towards the supporting part  6   d  side of the lower side frame  6 A using two coil springs  24  has been described in the above embodiment, but the present invention is not limited thereto. One end  22   x  of the base  22  may be pressed using one or three or more of other types of spring such as blade spring. 
         [0055]    Furthermore, an example in which the present invention is applied to the projector  100  has been described in the above embodiment, but the present invention is also applicable to projection apparatus such as DLP type rear projection television, for example.