Projection apparatus

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.

BACKGROUND OF THE INVENTION

1. Field of the Invention

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.

2. Description of the Related Art

FIG. 1is a view showing a schematic configuration of a projector100of DLP (Digital Light Processing) type. The projector100is one example of the projection apparatus. An illustrated image projection optical system unit is arranged inside the main body1of the projector100. An air conditioning system unit, a controlling system unit, a power supply system unit etc. (not shown) are also arranged inside the main body1.

Reference numeral3is a lamp serving as a light source,4is a reflector, and2is a lamp case for holding the lamp3and the reflector4. Reference numeral5is 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 wheel5that is rotated by a motor (not shown) transmits the white light emitted from the lamp3through one of the color filters, and separates the white light to red light, green light and blue light. Reference numeral6is an engine casting or a vertically separable frame made of magnesium. Components7to11of the image projection optical system described below are respectively assembled to the engine casting6. Reference numeral7is a light tunnel of square tube shape having a mirrored inner surface. The light entered from an incident port7a, which is an opening on one end side, is repeatedly reflected in the inside of the light tunnel7, and exit from an exit port7b, which is an opening on the other end side, thereby changing the light to a condensed uniform light in a short light path. Reference numeral8is a mirror for reflecting the light that has passed through the light tunnel7. The light path length is shortened and the image projection optical system is miniaturized through the use of the light tunnel7and the mirror8. Reference numeral9is a relay lens for aligning the light flux of the light reflected by the mirror8.

Reference numeral10is 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 DMD10is one example of the image forming device and is mounted on a circuit board (not shown) The micro-mirror of the DMD10that 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 numeral11is 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 lens11passes the light reflected by the DMD10and projects the light onto the screen50.

As shown with an arrow, the white light emitted from the lamp3is passed through the opening2aof the lamp case2, passed through one of the color filters of the color wheel5, and separated to the red light, green light and blue light. Each color light enters the inside through the opening6aof the engine casting6, and passes through the light tunnel7to be condensed and uniformed. The light exit from the light tunnel7is passed through the lower side of the projection lens11, reflected upward at a predetermined angle by the mirror8, passed through the relay lens9, and irradiated onto the DMD10. In this case, when the micro-mirror of the DMD10is in the ON state, the light reflected by the mirror is taken into the projection lens11and projected onto the screen50. When the micro-mirror is in the OFF state, the light reflected by the mirror is not taken into the projection lens11, and thus is not projected onto the screen50. That is, the projector100forms the image with the DMD10by ON/OFF controlling the operation state of each micro-mirror of the DMD10based on the input video signal and the like, and projects the image onto the screen50through the projection lens11.

FIG. 14is a view showing a conventional irradiating state of the light on the DMD10. Rectangle10ashown with a solid line is the image forming surface of the DMD10arranged on the side to be irradiated with light. The image forming surface10aconsists of above-described micro-mirrors. The light emitted from the lamp3is passed through the light tunnel7and the like, reflected by the mirror8, and irradiated onto the DMD10, as described above. In this case, the light is narrowed according to the diameter of the light tunnel7of square tube shape, and the light path is bent by the reflection at the mirror8, and thus the irradiating region of the light irradiated on the DMD10becomes a square shape tilted (sometimes deformed) with respect to the image forming surface10aas shown with10bin a dot-dash line inFIG. 14, and the light may not be irradiated to one part, as indicated by the shaded area, of the image forming surface10a. If the image is formed with the DMD10and projected onto the screen50in this state, the image quality may degrade such as the projected image may become dark.

Therefore, the attachment angle and position of the mirror8with respect to the engine casting6have been adjusted in the prior art to adjust the irradiating region of the light on the DMD10so that light is irradiated to the entire image forming surface10a. Furthermore, the irradiating region of the light on the DMD10sometimes cannot be adequately adjusted so that light is irradiated on the entire image forming surface10aonly by adjusting the attachment of the mirror8, in which case, the size of the diameter of the light tunnel7is changed to larger size, which enlarges the irradiating region of the light to10c, as shown with a dot-dot-dash line inFIG. 14, in the prior art. However, the optical specification must be changed if the size of the light tunnel7is changed, which leads to adverse effects such as lowering in energy of the light per unit area to be irradiated on the DMD10, and re-designing etc. of the image projection optical system may become necessary, which is very troublesome. Furthermore, various light tunnels7of different sizes must be manufactured and prepared, which is very costly.

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 DMD10, and is also costly since a great number of motors and switches are used.

SUMMARY OF THE INVENTION

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

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 ofFIG. 1described in the Background of the Invention section, and thusFIG. 1will be cited for the embodiment of the present invention, and redundant description will be omitted. The projector100shown inFIG. 1is one example of the projection apparatus according to the embodiment of the present invention.

FIG. 2is a perspective view showing a lower side frame6A of the engine casting6. The engine casting6is assembled by fitting the lower side frame6A and an upper side frame (not shown) and tightening the frames with a screw and the like. The lower side frame6A is integrally formed with an assembling part61for assembling the projection lens11; an assembling part62for assembling the mirror8; an assembling part63for assembling the relay lens9; an assembling part64for assembling the DMD10, a circuit board (not shown) mounted with the DMD10, and a heat sink (not shown) for cooling the DMD10; and an assembling part60for assembling the assembling component20including the light tunnel7shown inFIG. 4. The assembling part60and the assembling component20are 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 part60to64.

The assembling component20is configured by the light tunnel7, fixture21, base22, pin23, coil spring24, round machine screw with cross-shaped groove25, and screw26with a hexagonal hole, as shown inFIG. 4. The light tunnel7has a square tube shape as shown inFIG. 10, and has a mirrored inner surface. InFIG. 10A, a state in which the light tunnel7is viewed diagonally from the incident port7aside is shown. InFIG. 10B, a state viewed diagonally from the exit port7bside is shown. The fixture21is formed by bending a sheet metal, as shown inFIG. 11AtoFIG. 1C. InFIG. 11A, a state in which the fixture21is viewed diagonally from above is shown. InFIG. 11B, a state viewed diagonally from the side is shown. InFIG. 11C, a state viewed diagonally from below is shown. An opening21ais formed on the front surface of the fixture21, as shown inFIG. 11B. The opening21ahas the same size as the incident port7a, the exit port7b, and the inner diameter of the light tunnel7. Pressing parts21bare formed at the center of each side surface of rectangular shape having a large width, and hook parts21c,21dare formed at the ends.

The base22is made of metal and is formed into a shape such as shown inFIG. 12AandFIG. 12B. As shown inFIG. 12A, a substantially V-shaped groove22ais formed across the longitudinal direction of the base22at the center on one surface side of the base22. Projection type supporting parts22b,22efor supporting the light tunnel7are formed on the inner side of the groove22a. As shown inFIG. 12B, a convex part22mis formed on the side surface of the base22on the supporting part22eside. Holes22c,22dfor inserting the hook parts21c,21dof the fixture21are formed on both sides of the groove22a. The light tunnel7is fitted into the groove22aof the base22, and the side surface of the light tunnel7is supported at the supporting part22band the end of the exit port7bside is supported at the supporting part22e, and thereafter, the hook parts21c,21dof the fixture21are inserted to the holes22c,22dof the base22, respectively, whereby the hook parts21c,21delastically deform to be hooked at the edge of the holes22c,22d, and the fixture21is attached to the base22, as shown inFIG. 4andFIGS. 8A,8B.FIG. 8AandFIG. 8Bshow a state in which the assembling component20is seen from the opening21aside of the fixture21. In this state, the light tunnel7is fixed to the base22while being supported by the pressing part21band the front surface of the fixture21and the supporting parts22b,22eof the base22, and the incident port7aand the exit port7bof the light tunnel7and the opening21aof the fixture21are lined in the axial direction of the light tunnel7, as shown with a dot-dash line inFIG. 4.

As shown inFIGS. 12A and 12B, the center on the other surface side of the base22is projected across the longitudinal direction of the base22to form the bottom of the groove22a, and an engaging part22fof circular arc shape is formed at both ends at the distal end. The center of the circular arc of the engaging part22fis set so as to substantially coincide with the axis (dot-dash line ofFIG. 4) of the light tunnel7fixed to the base22. Holes22g, through which two pins23are passed respectively, are each formed at one end22xof the base22in a direction perpendicular to the axis of the light tunnel7inFIG. 4. An inclined surface22his formed around each hole22gso as to incline while rising in the axial direction from the incident port7atowards the exit port7bof the light tunnel7. The coil spring24is arranged around each pin23so as to contact the inclined surface22h. The diameter of each hole22gof the base22is larger than the diameter of the middle part23bof each pin23, and is smaller than the diameter of each coil spring24. A cross-shaped groove is formed at the head23aof each pin23, and a collar23cis arranged immediately under the head23a. The diameter of each collar23cis larger than the diameter of each coil spring24. A screw part23dhaving a diameter smaller than the middle part23bis formed at the lower part of each pin23.

A hole22j(FIGS. 12A,12B) for passing one machine screw25and a hole22kfor screw fitting one screw26are formed at the other end22yof the base22in a direction perpendicular to the axis of the light tunnel7inFIG. 4. The diameter of the hole22jis larger than the diameter of the screw part25dof the machine screw25, and smaller than the diameter of the head25a. The diameter of the head26aof the screw26is substantially the same as the diameter of the screw part26dat the middle. A tapered inclined part26bis formed at the distal end of the screw26.

FIG. 3is an enlarged view of the assembling part60of the lower side frame6A. An opening6ais formed in the side surface6bon the right side of the assembling part60of the lower side frame6A so as to face the assembling part60, as shown inFIG. 6. The color filter5and the lamp case2are arranged on the external side (right side inFIG. 2andFIG. 3) of the side surface6b, as shown inFIG. 1. In the arrangement state ofFIG. 1, the opening6aof the lower side frame6A and the opening2aof the lamp case2are lined in the optical axis direction of the light emitted from the lamp3.

A dent6cis formed in the assembling part60. A supporting part6din the form of inclined surface and a side wall6eare formed on the inner side of the dent6cso that the light emitted from the lamp3and passed through the openings2a,6ais not shielded from entering the mirror8assembled to the assembling part62, as shown inFIG. 1toFIG. 3andFIG. 6. The base22is fitted to the dent6c, as shown inFIG. 5. When the base22is fitted to the dent6cas shown inFIG. 5with the light tunnel7fixed to the base22by means of the fixture21, as shown inFIG. 4, the incident port7aof the light tunnel7faces the lamp3, and the exit port7bfaces the mirror8of the assembling part62, so the axis of the light tunnel7substantially coincide with the optical axis of the light from the lamp3, whereby the light from the lamp3passes through the light tunnel7and becomes able to enter the mirror8, as shown inFIG. 1. Furthermore, the engaging part22fof the base22is supported by the supporting part6don the inner side of the dent6cas shown inFIG. 8AandFIG. 8B, so that the base22becomes rotatable with the axis of the light tunnel7as substantially the center. InFIG. 8AandFIG. 8B, the cross mark indicated on the inner side of the opening21aof the fixture21and the inner side of the incident port7aof the light tunnel7is the axis of the light tunnel7and is the center of rotation of the base22.

A screw hole6ffor screw fitting the screw part23dof the pin23and a screw hole6gfor screw fitting the screw part25dof the machine screw25are formed on the upper part of the dent6c, as shown inFIG. 3. An inclined surface6hthat engages the inclined part26bof the distal end of the screw26is formed in the vicinity of the screw hole6g. The inclined surface6his formed so as to incline while rising in the optical axis direction of the light of the lamp3from the side wall6etowards the opening6a, that is, in the axial direction from the exit port7btowards the incident port7aof the light tunnel7fixed to the base22in the state ofFIG. 5.

In the above configuration, in order to assemble the light tunnel7to the lower side frame6A, the light tunnel7is first fitted to the groove22aof the base22, as described above, and fixed with the fixture21, as shown inFIG. 4. The base22is then fitted to the dent6cof the assembling part60of the lower side frame6A and the engaging part22fis supported by the supporting part6d. The coil spring24is then arranged around the middle part23bof each pin23, the screw part23dand the middle part23bare passed through the hole22gat the end22xof the base22, as shown inFIG. 4, and the screw part23dis screwed into each screw hole6fusing a screwdriver and the like to attach each pin23to the lower side frame6A, as shown inFIG. 7. InFIG. 7, the illustration of the light tunnel7and the fixture21is omitted.

When each pin23is attached to the lower side frame6A as described above, the end22xof the base22is supported by each pin23swingably. Furthermore, each coil spring24contacts each inclined surface22hof the base22, whereby the force F acting towards the side wall6eside of the lower side frame6A is applied to each inclined surface22h, the end22xof the base22is moved towards the side wall6e, and the side wall of each hole22gis pushed against the middle part23bof each pin23. Furthermore, the force W acting towards the supporting part6dside of the lower side frame6A is applied from each coil spring24to each inclined surface22h, whereby the base22rotates in the clockwise direction with the axis of the light tunnel7as substantially the center, as shown inFIG. 8A, and the end22yrises from the lower side frame6A with respect to the end22x. In this state, the end22xof the base22is held at a plural points by two pins23, two coil springs24, and the lower side frame6A, and thus shake of the base22is suppressed, whereby subsequent attachment work is facilitated.

Next, the screw25is passed through the hole22jat the end22yof the base22, and screwed into the screw hole6gof the lower side frame6A using the screwdriver and the like. The end22yof the base22is then pushed against the supporting part6dside of the lower side frame6A with the head25aof the screw25, whereby the base22rotates in the counterclockwise direction with the axis of the light tunnel7as substantially the center, as shown inFIG. 8B. Thus, the distance between the ends22x,22yof the base22and the lower side frame6A can be changed by changing the screw-fit depth of the screw25with respect to the screw hole6gof the lower side frame6A, and the rotation angle of the light tunnel7is adjusted with the base22. In this state, the base22is supported from both upper and lower surfaces by the coil spring24, the screw25, and the lower side frame6A, and thus the shake in the rotating direction of the base22and the light tunnel7is suppressed, and subsequent attachment work is facilitated.

Next, the screw26is screwed into the screw hole22kof the end22yof the base22using a wrench and the like, whereby the inclined part26bof the distal end of the screw26smoothly engages the inclined surface6hof the lower side frame6A, as shown inFIG. 9.FIG. 9shows only the vicinity of the end22yof the base22. When the inclined part26bof the screw26engages the inclined surface6hof the lower side frame6A, the force W′ acting towards the supporting part6dside of the lower side frame6A is applied to the inclined surface6hfrom the inclined part26b, and the force F′ acting towards the side wall6eof the lower side frame6A is applied to the inclined part26bfrom the inclined surface6has one component of reactive force. The base22is thereby moved towards the side wall6e, the convex part22m(FIG. 12B) of the base22is pressed against the side wall6, and the base22and the light tunnel7are fixed to the lower side frame6A without shaking in the axial direction and the rotating direction. The fixed state of the base22at this point is the same as the state shown inFIG. 5. InFIG. 5, the illustration of the light tunnel7and the fixture21is omitted. When fixed in the above manner, the shake in the axial direction and the rotating direction of the base22and the light tunnel7are almost completely suppressed and a stable fixed state can be maintained since the base22is supported at both upper and lower surfaces and both ends22x,22ywith forces W, W′, F, F′ etc. by the coil spring24, the screw25, the screw26, and the lower side frame6A.

After the other components8to11of the image projection optical system are assembled to other assembling parts61to64of the lower side frame6A, the upper side frame is fitted to the lower side frame6A to assemble the engine casting6, and the engine casting6is installed in the main body1of the projector100as shown inFIG. 1. In such installation state, the light emitted from the lamp3passes through the opening2aof the lamp case2, the color wheel5, and the opening6aof the engine casting6, enters the light tunnel7, and then condensed and uniformed in the light tunnel7. The light which exit from the light tunnel7is reflected by the mirror8, passed through the relay lens9, and irradiated onto the DMD10. Furthermore, the image is formed at the DMD10by ON/OFF operating each micro-mirror of the DMD10, and the image is projected onto the screen50through the projection lens11.

FIG. 13is a view showing the irradiation state of the light on the DMD10of the projector100of the present embodiment installed with each component as described above. The rectangular shape10ashown with a solid line is the image forming surface of the DMD10arranged on the side irradiated with the light. The image forming surface10aconsists of above-described micro-mirrors, and is covered with a cover glass (not shown).10xshown with a dot-dash line is the irradiating region of the light of before adjustment that is irradiated on the DMD10. That is, the irradiating region10xis one example of the irradiating region of the light irradiated on the DMD10when the light tunnel7and the like are vaguely attached to the lower side frame6A without performing rotation adjustment. The irradiating region10xis a square shape slanted and slightly deformed with respect to the image forming surface10a, and thus the light is not irradiated to one part, as indicated by the shaded area, of the image forming surface10a.

The upper side frame of the engine casting6is detached from the lower side frame6A, and the tightening degree of the screw26, the screw25and the like (pin23in some cases) assembled to the assembling part60is changed to adjust the rotation angle of the light tunnel7with the whole base22, thereby rotating the irradiating region10xof the light on the DMD10ofFIG. 13and changing the tilt or position as in the irradiating region10x′ shown with a dot-dot-dash line so that the light can be irradiated on the entire image forming surface10a. Furthermore, by adjusting the rotation angle of the light tunnel7, and adjusting the attachment angle or position of the mirror8with respect to the lower side frame6A, the adjustable range of the irradiating region of the light on the DMD10is extended so that the light can be more reliably irradiated on the entire image forming surface10a.

As a result, the image quality is prevented from degrading such as the projected image from becoming dark when the image formed with the DMD10is projected onto the screen50through the projection lens11. The adjustment of the rotation angle of the light tunnel7and the adjustment of the irradiating region of the light on the DMD10are easily performed with a simple task such as tightening the screw26, the screw25etc., and thus the working time can be shortened. Furthermore, the optical specification is not changed since the size of the light tunnel7does 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 tunnel7of different sizes etc. can be saved. Moreover, the adjustment of the irradiating region of the light on the DMD10can be appropriately performed even by using the same type of light tunnel7in different types of projector100, thereby standardizing the components, and further reducing the cost.

The present invention may adopt various forms other than the above described embodiment. For instance, an example in which one end22xof the base22is supported swingably using two pins23has been described in the above embodiment, but the present invention is not limited thereto. One end22xof the base22may be supported using one or three or more pins.

Also, an example in which one end22xof the base22is pressed towards the supporting part6dside of the lower side frame6A using two coil springs24has been described in the above embodiment, but the present invention is not limited thereto. One end22xof the base22may be pressed using one or three or more of other types of spring such as blade spring.

Furthermore, an example in which the present invention is applied to the projector100has 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.