Patent Publication Number: US-2010118278-A1

Title: Diffuser driving device and projection-type image display apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a diffuser driving device driving a diffuser and a projection-type image display apparatus performing a display operation by projecting an image to a display unit such as a screen using the diffuser driving device. 
     2. Description of the Related Art 
     A projection-type image display apparatus such as a projector is known as an image display apparatus capable of magnifying and displaying an image. 
     The projection-type image display apparatus displays an image by projecting light from a light source to a screen. The projection-type image display apparatus is configured so that an observer can watch the image projected on the screen. 
     In the past, for example, a high-luminance projection tube was used as the light source of the projection-type image display apparatus. An image was projected on the screen by projecting light from the light source through a liquid crystal panel on which the image had been displayed, but the brightness or the color reproducibility was not satisfactory. Therefore, for the purpose of easy modulation based on an image signal, excellent color reproducibility, and guarantee of the brightness, a projection-type image display apparatus using color laser beams of red, green, and blue as a light source was suggested. 
     In such a projection-type image display apparatus using the laser beams as a light source, granular noise called speckle noise is generated on a screen, thereby markedly deteriorating the image quality. This is because a laser speckle phenomenon occurs due to a high coherence of the laser beams. For example, when the laser beams are applied to a rough surface of a screen or the like, granular or spot-like interference patterns are generated. 
     In the image display apparatus using the laser beams as a light source, a technique of reducing the speckle noise is described, for example, in Japanese Unexamined Patent Application Publication No. 6-208089. In Japanese Unexamined Patent Application Publication No. 6-208089, a rotatably-supported diffuser is disposed in an optical path of the laser beams. An image beam (two-dimensional intermediate image) is incident on the diffuser using the laser beams. In Japanese Unexamined Patent Application Publication No. 6-208089, temporally different speckle patterns are generated by rotating and driving the diffuser. Accordingly, the speckle noise may not be visible due to the average effect of eyes. 
     SUMMARY OF THE INVENTION 
     In the past, dust might be attached to the diffuser or a pattern defect might be generated. When the dust is attached to the diffuser or the pattern defect is generated, the dust or the pattern defect is displayed on the screen, thereby causing deterioration in image quality. Accordingly, so as not to allow a user to recognize the dust or the pattern defect, it is desirable to drive the diffuser in a track in which the diffuser does not pass through the same locus for a predetermined time (for example, 1 second). 
     However, in the technique of reducing the speckle noise described in Japanese Unexamined Patent Application Publication No. 6-208089, the diffuser is rotated in one direction. That is, a point of the diffuser described in Japanese Unexamined Patent Application Publication No. 6-208089 passes through the same locus in a very short period. Accordingly, the dust attached to the diffuser or the pattern defect draws the same locus in the two-dimensional intermediate image applied to the diffuser. As a result, the dust or the pattern defect is recognized by a user as a circular line on the screen to which the image is projected, thereby causing the deterioration in image quality. 
     The projection-type image display apparatus in which a diffuser is rotated uses a diffuser greater than the size of the image beam (two-dimensional intermediate image). Accordingly, the increase in size of the entire apparatus and the cost-up may be caused. When the diffuser is rotated and driven, a surface wobbling in the optical axis of the beam is caused in the diffuser. When the surface wobbling is caused in the diffuser, the further deterioration in image quality is caused. Therefore, the eccentricity adjustment is necessary for reducing the surface wobbling of the rotating diffuser and the assembly adjustment thus takes much time. 
     It is desirable to provide a diffuser driving device and a projection-type image display apparatus, which can suppress the influence of the deterioration in image quality due to dust attached to the diffuser or a pattern defect. 
     According to an embodiment of the invention, there is provided a diffuser driving device including: a moving frame mounted with a diffuser; a supporting frame movably supporting the moving frame; a drive unit driving the moving frame to vibrate in a first direction perpendicular to an optical axis of an image beam incident on the diffuser and a second direction perpendicular to the first direction and the optical axis; and a controller controlling the drive unit to change a phase difference between the vibration of the moving frame in the first direction and the vibration of the moving frame in the second direction and to move the moving frame at a moving speed higher than a predetermined value. 
     According to another embodiment of the invention, there is provided a projection-type image display apparatus including: an optical block forming and projecting an image beam; a projection lens magnifying and projecting the image beam to a display unit; and a diffuser driving device being disposed between the optical block and the projection lens and including a diffuser on which the image beam from the optical block is incident. 
     Here, the diffuser driving device includes a moving frame mounted with the diffuser, a supporting frame movably supporting the moving frame, a drive unit driving the moving frame to vibrate in a first direction perpendicular to the optical axis of the image beam incident on the diffuser and a second direction perpendicular to the first direction and the optical axis, and a controller controlling the driving unit to change a phase difference between the vibration of the moving frame in the first direction and the vibration of the moving frame in the second direction and to move the moving frame at a moving speed higher than a predetermined value. 
     In the diffuser driving device and the projection-type image display apparatus according to the embodiments of the invention, the phase difference between the vibration of the moving frame in the first direction and the vibration of the moving frame in the second direction is changed. Accordingly, it is possible to extend the interval between the times when a point of the diffuser passes through the same locus. That is, it is possible to drive the diffuser in the track not passing through the same locus for a predetermined time. As a result, since the dust attached to the diffuser or the pattern defect can hardly be recognized by a user, it is possible to suppress the influence of the deterioration in image quality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram schematically illustrating the configuration of a projection-type image display apparatus according to an embodiment of the invention. 
         FIG. 2  is a perspective view illustrating a diffuser driving device according to a first embodiment of the invention. 
         FIG. 3  is an exploded perspective view of the diffuser driving device according to the first embodiment of the invention as viewed from the front side. 
         FIG. 4  is an exploded perspective view of the diffuser driving device according to the first embodiment of the invention as viewed from the rear side. 
         FIG. 5  is a diagram illustrating a section of the diffuser driving device according to the first embodiment of the invention. 
         FIG. 6  is a plan view schematically illustrating the diffuser driving device according to the first embodiment of the invention. 
         FIG. 7  is a block diagram illustrating the circuit configuration of a controller of the diffuser driving device according to the first embodiment of the invention. 
         FIG. 8  is a graph illustrating control signals output to a first drive unit and a second drive unit of the diffuser driving device according to the first embodiment of the invention. 
         FIG. 9  is a graph illustrating a phase difference between the control signals output to the first drive unit and the second drive unit of the diffuser driving device according to the first embodiment of the invention. 
         FIG. 10  is a diagram illustrating a driving locus of a point of a diffuser of the diffuser driving device according to the first embodiment of the invention. 
         FIG. 11  is a plan view schematically illustrating a diffuser driving device according to a second embodiment of the invention. 
         FIG. 12  is a diagram illustrating a partial section of the diffuser driving device according to the second embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described with reference to  FIGS. 1 to 12 . In the drawings, common elements are referenced by like reference numerals and signs. The invention is not limited to the embodiments. 
     1. First Embodiment 
     Configuration of Projection-Type Image Display Apparatus 
     A projection-type image display apparatus according to a first embodiment of the invention will be described now with reference to  FIG. 1 .  FIG. 1  is a diagram schematically illustrating the configuration of a projection-type image display apparatus according to an embodiment of the invention. 
     The projection-type image display apparatus shown in  FIG. 1  includes a one-dimensional light modulator  1 , an Offner relay  2 , a Galvano mirror  3 , a field curvature correcting optical system  4 , a diffuser driving device  5 , and a projection lens  6 . The one-dimensional light modulator  1  includes plural pixels arranged in a direction perpendicular to the paper plane. 
     A phase-reflecting diffraction grating such as a GLV (Grating Light Valve) device can be used as the one-dimensional light modulator  1 . When the GLV device is used, the device itself does not emit light and thus uses a light source and an optical system for projecting light from the light source to the device. Here, it is preferable that a coherent light source is used as the light source. The Offner relay  2  is disposed in a side to which the light is emitted from the one-dimensional light modulator  1 . 
     The Offner relay  2  is a relay optical system using a combination of reflecting mirrors. The Offner relay  2  serves to form an equivalent-magnification image of a one-dimensional image. The Offner relay  2  includes a primary mirror and a secondary mirror. 
     The primary mirror is a concave mirror of which the concave surface is directed to the one-dimensional light modulator  1  and takes charge of first and third reflections of the light from the one-dimensional light modulator  1 . The secondary mirror is a concave mirror of which the concave surface is directed to the primary mirror and takes charge of a second reflection. 
     The light incident on the Offner relay  2  from the one-dimensional light modulator  1  is first reflected by the primary mirror, arrives at the secondary mirror, is secondly reflected by the secondary mirror, and travels to the primary mirror again. The light thirdly reflected by the primary mirror travels to the Galvano mirror  3 . 
     The Galvano mirror  3  is a panel-like mirror and is disposed in front of an imaging position of the Offner relay  2 . The Galvano mirror  3  includes a light scanning unit for scanning the one-dimensional image in synchronization with an image signal. The Galvano mirror  3  can perform the scanning operation by rotating the panel-like mirror by the use of a driving mechanism (such as an actuator) not shown in the plane perpendicular to the arrangement direction of the one-dimensional light modulator  1 . 
     At this time, by modulating the light with the one-dimensional light modulator  1  on the basis of the image signal corresponding to a scanning angle of the Galvano mirror  3 , it is possible to obtain a two-dimensional image, which is formed by the scanning in the direction perpendicular to the plane including the one-dimensional image, from the one-dimensional image. The two-dimensional image is formed on a cylindrical surface centered on the rotational axis of the Galvano mirror  3 . 
     In this way, when the two-dimensional image formed on the cylindrical surface is projected without any change, it is not possible to correctly display an image on a planar screen. Therefore, the field curvature correcting optical system  4  is disposed at the position of the two-dimensional image formed by the Galvano mirror  3 . By allowing the two-dimensional image to pass through the field curvature correcting optical system  4 , it is possible to form a planar two-dimensional intermediate image. For example, the field curvature correcting optical system  4  can employ a cylindrical lens. 
     The one-dimensional light modulator  1 , the Offner relay  2 , the Galvano mirror  3 , and the field curvature correcting optical system  4  constitute an optical block  9 . The optical block  9  forms the two-dimensional intermediate image as an image beam as described above. The optical block  9  projects the formed two-dimensional intermediate image to the diffuser driving device  5  and the projection lens  6 . 
     The projection lens  6  serves to magnify and project the formed planar two-dimensional intermediate image onto the screen. The diffuser driving device  5  is disposed at a position where the planar two-dimensional intermediate image is formed between the field curvature correcting optical system  4  and the projection lens  6 . 
     Configuration of Diffuser Driving Device 
     A diffuser driving device according to a first embodiment (hereinafter, referred to as “this embodiment”) of the invention will be described now with reference to  FIGS. 2 to 6 .  FIG. 2  is a perspective view illustrating the diffuser driving device according to this embodiment,  FIGS. 3 and 4  are exploded perspective views illustrating the diffuser driving device according to this embodiment. FIG.  5  is a diagram illustrating a section of the diffuser driving device according to this embodiment.  FIG. 6  is a plan view schematically illustrating the diffuser driving device according to this embodiment. 
     As shown in  FIGS. 2 to 4 , the diffuser driving device  5  includes a fixing base  11 , a supporting frame  12 , a first moving frame  13 , a second moving frame  14 , a diffusing plate (hereinafter, referred to as “diffuser”)  16 , two drive units  17  and  18 , and a controller  7 . 
     The first moving frame  13  is supported by the supporting frame  12  so as to be movable in a first direction X perpendicular to a third direction Z parallel to the optical axis L of the optical system. The second moving frame  14  is supported by the first moving frame  13  so as to be movable in a second direction Y perpendicular to the third direction Z and the first direction X. That is, as shown in  FIGS. 2 and 5 , three members of the supporting frame  12 , the first moving frame  13 , and the second moving frame  14  are assembled in a tower shape in the third direction Z. 
     The fixing base  11  is formed substantially in a panel shape having a rectangular plane portion. The fixing base  11  is fixed to the main body of the projection-type image display apparatus  10  by a fixing method using plural fixing screws  19  and the like. A positioning base  21  is formed on the planar portion of the fixing base  11  in an overlapping manner. 
     The positioning base  21  has substantially a panel shape. The positioning base  21  are provided with plural fixing holes. Although not shown in the drawings, the plural fixing holes are longitudinal holes having an elliptical shape. The positioning base  21  is fixed to the fixing base  11  by a fixing method using fixing screws  19 . The positioning base  21  is provided with a fixing portion  22  substantially having an L shape. The fixing portion  22  is fixed to the positioning base  21  by a fixing method using fixing screws  19  or the like. The supporting frame  12  is fixed to the fixing portion  22  by a fixing method using fixing screws or the like. 
     The positioning base  21  can adjust the initial position in the third direction Z of the supporting frame  12  using the longitudinal fixing holes. The positioning base  21  can adjust the initial positions of a rotation angle X-ro of the supporting frame  12  about the first direction X and a rotation angle Y-ro about the second direction Y by the use of the fixing portion  22  having an L shape. As a result, by disposing the positioning base  21  between the fixing base  11  and the supporting frame  12 , the positioning and the angle adjustment between the pattern plane of the diffuser  16  and the two-dimensional intermediate image projected from the field curvature correcting optical system  4  can be carried out. 
     The supporting frame  12  is formed substantially of a rectangular panel. A substantially rectangular opening  23  is formed at the center of the supporting frame  12 . The opening area of the opening  23  is substantially equal to or slightly greater than the size of the two-dimensional intermediate image. The supporting frame  12  is fixed to the fixing portion  22  of the positioning base  21  in such a manner that the longitudinal direction is parallel to the first direction X. Accordingly, as shown in  FIGS. 3 and 4 , the open side of the opening  23  of the supporting frame  12  is directed to the third direction Z. 
     The supporting frame  12  includes two rail members  24 A and  24 B and four magnets  26 . The two rail members  24 A and  24 B support the first moving frame  13  so as to move (vibrate) parallel to the first direction X. The two rail members  24 A and  24 B have a section of an U shape. Sliding members  32 A and  32 B to be described later and attached to the first moving frame  13  slidably engage with the concave portions of the U shapes of the two rail members  24 A and  24 B. 
     As shown in  FIGS. 3 and 6 , the first rail member  24 A is disposed on one side in the short-side direction of the planar portion of the supporting frame  12  and one side in the longitudinal direction. The longitudinal direction of the first rail member  24 A is substantially parallel to the longitudinal direction of the supporting frame  12 , that is, the first direction X. 
     The second rail member  24 B is disposed on the other side in the short-side direction of the planar portion of the supporting frame  12  and the other side in the longitudinal direction. That is, the second rail member  24 B is disposed at a diagonal corner of the supporting frame  12  relative to the first rail member  24 A. The longitudinal direction of the second rail member  24 B is substantially parallel to the longitudinal direction of the supporting frame  12 , that is, the first direction X. In this way, the first rail member  24 A and the second rail member  24 B are disposed outside the opening  23  in the longitudinal direction and the short-side direction. 
     As shown in  FIG. 3 , the four magnets  26  are arranged so that two magnets are disposed on both sides of the longitudinal direction of the opening  23 , respectively, with the opening  23  interposed therebetween. The magnets  26  are interposed between the supporting frame  12  and the first moving frame  13 . The magnets  26  serve to reduce the vibration in the third direction Z of the first moving frame  13  at the time of driving by means of their attractive forces. Accordingly, it is possible to suppress the surface wobbling in the third direction Z parallel to the optical axis L at the time of driving, thereby obtaining an excellent focus of a projection image. 
     The first moving frame  13  is formed substantially of a rectangular panel-like member. Both ends of the first moving frame  13  in the short-side direction are substantially bent perpendicularly. Both upper ends of the first moving frame  13  are provided with a first upper locking hole  15   a  and a second upper locking hole  15   b . Both lower ends of the first moving frame  13  are provided with lower locking holes  15   c.    
     A first opening window  27  substantially having a rectangular shape is substantially formed at the center of the first moving frame  13 . The opening area of the first opening window  27  is substantially equal to or slightly greater than the opening area of the opening  23  formed in the supporting frame  12 . As shown in  FIG. 5 , when the first moving frame  13  and the supporting frame  12  overlap with each other, the first opening window  27  is opposed to the opening  23  of the supporting frame  12 . The first moving frame  13  includes a first attachment piece  28  at one end in the longitudinal direction thereof. The first attachment piece  28  has a tongue shape and protrudes from the substantial center of the short side of the first moving frame  13 . 
     The first moving frame  13  includes two rail members  31 A and  31 B and two sliding members  32 A and  32 B. The two rail members  31 A and  31 B has a section of an U shape, similarly to the two rail members  24 A and  24 B of the supporting frame  12 . Sliding members  37 A and  37 B to be described attached to the second moving frame  14  slidably engage with the concave portions of the U shapes of the two rail members  31 A and  31 B. 
     As shown in  FIGS. 3 and 6 , the third rail member  31 A and the fourth rail member  31 B are disposed on both sides in the longitudinal direction of the first opening window  27  with the first opening window  27  interposed therebetween. The third rail member  31 A is disposed on one side in the longitudinal direction of the first opening window  27 . The fourth rail member  31 B is disposed on the other side in the longitudinal direction of the first opening window  27 . The longitudinal directions of the third rail member  31 A and the fourth rail member  31 B are substantially parallel to the short-side direction of the first moving frame  13 , that is, the second direction Y. 
     The two sliding members  32 A and  32 B are formed substantially in a rectangular hexahedral shape. The two sliding members  32 A and  32 B are attached to the rear surface of the first moving frame  13  which is the opposite of the surface to which the two rail members  31 A and  31 B are attached. The first sliding member  32 A is disposed on one side in the short-side direction of the rear surface of the first moving frame  13  and one side in the longitudinal direction thereof. The longitudinal direction of the first sliding member  32 A is substantially parallel to the longitudinal direction of the first moving frame  13 , that is, the first direction X. The first sliding member  32 A is fixed to the first moving frame  13  by a fixing method using fixing screws or the like. 
     The second sliding member  32 B is disposed on the other side in the short-side direction of the rear surface of the first moving frame  13 , that is, on the other side in the longitudinal direction thereof. That is, the second sliding member  32 B is disposed at a diagonal corner of the first moving frame  13  relative to the first sliding member  32 A. The longitudinal direction of the second sliding member  32 B is substantially parallel to the longitudinal direction of the first moving frame  13 , that is, the first direction X. The second sliding member  32 B is fixed to the first moving frame  13  by a fixing method using fixing screws or the like. The fixing method of the first and second sliding members  32 A and  32 B is not limited to the method using the fixing screws. For example, the first and second sliding members  32 A and  32 B may be fixed by welding. 
     When the supporting frame  12  overlaps with the first moving frame  13 , the first sliding member  32 A slidably engages with the first rail member  24 A disposed in the supporting frame  12 . The first rail member  24 A and the first sliding member  32 A constitute a specific example of the guide member in the claims. Similarly, the second sliding member  32 B slidably engages with the second rail member  24 B disposed in the supporting frame  12 . The second rail member  24 B and the second sliding member  32 B constitute a specific example of the guide member in the claims. Accordingly, the first moving frame  13  is guided by the first rail member  24 A and the second rail member  24 B so as to move substantially parallel to the first direction X. 
     The second moving frame  14  is formed substantially of a rectangular panel-like member. Both ends of the second moving frame  14  in the longitudinal direction are substantially bent perpendicularly. Both upper ends of the second moving frame  14  are provided with upper locking holes  25   a . Both lower ends of the second moving frame  14  are provided with lower locking holes  25   b.    
     Similarly to the first moving frame  13 , the second opening window  34  substantially having a rectangular shape is substantially formed at the center of the second moving frame  14 . The opening area of the second opening window  34  is substantially equal to the opening area of the first opening window  27 . As shown in  FIG. 5 , when the supporting frame  12 , the first moving frame  13 , and the second moving frame  14  overlap with each other, the second opening window  34  is opposed to the opening  23  and the first opening window  27 . The second moving frame  14  includes a second attachment piece  36  at one end in the short-side direction thereof. The second attachment piece  36  has a tongue shape and protrudes from the substantial center of the long side of the second moving frame  14 . 
     The second moving frame  14  includes two sliding members  37 A and  37 B and plural fasteners  38 . The two sliding members  37 A and  37 B are substantially formed in a rectangular hexahedral shape. When the second moving frame  14  overlaps with the first moving frame  13 , the two sliding members  37 A and  37 B are attached to the rear surface of the second moving frame  14  opposed to the first moving frame  13 . 
     The third sliding member  37 A and the fourth sliding member  37 B are disposed on both sides in the longitudinal direction of the second opening window  34  with the second opening window  34  interposed therebetween. The third sliding member  37 A is disposed on one side in the longitudinal direction of the second opening window  34 . The fourth sliding member  37 B is disposed on the other side in the longitudinal direction of the second opening window  34 . The longitudinal directions of the third sliding member  37 A and the fourth sliding member  37 B are substantially parallel to the short-side direction of the second moving frame  14 , that is, the second direction Y. 
     The third sliding member  37 A and the fourth sliding member  37 B are fixed to the first moving frame  13  by a fixing method using fixing screws or the like. The fixing method of the third and fourth sliding members  37 A and  37 B is not limited to the method using the fixing screws. For example, the third and fourth sliding members  37 A and  37 B may be fixed by welding. 
     When the second moving frame  14  overlaps with the first moving frame  13 , the third sliding member  37 A slidably engages with the third rail member  31 A disposed in the first moving frame  13 . The third rail member  31 A and the third sliding member  37 A constitute a specific example of the guide member in the claims. Similarly, the fourth sliding member  37 B slidably engages with the fourth rail member  31 B disposed in the first moving frame  13 . The fourth rail member  31 B and the fourth sliding member  37 B constitute a specific example of the guide member in the claims. Accordingly, the second moving frame  14  is guided by the third rail member  31 A and the fourth rail member  31 B so as to move substantially parallel to the second direction Y. 
     In this embodiment, the rail members and the sliding members are used as a specific example of the guide member guiding the first moving frame  13  and the second moving frame  14 . However, the guide member guiding the first moving frame  13  and the second moving frame  14  is not limited to the rail members and the sliding members. For example, the guide member may include a sliding shaft formed of a rod-like member and a bearing guiding the sliding shaft to be slidable. 
     The plural fasteners  38  are disposed around the second opening window  34 . The diffuser  16  is fixed, for example, by a fixing method using fixing screws or the like, so as to cover the second opening window  34  with the plural fasteners  38 . That is, the diffuser  16  is substantially perpendicular to the third direction Z. The method of fixing the diffuser  16  is not limited to the fixing screws, but for example, may employ an adhesive. 
     The diffuser  16  is substantially a rectangular panel-like member. As shown in  FIG. 6 , the surface area of the diffuser  16  is set to be slightly greater than the area of the two-dimensional intermediate image M. The diffuser  16  has plural concave and convex portions on the surface thereof. In this way, by forming the concave and convex patterns on the surface of the diffuser  16 , the light passing through the diffuser  16  is subjected to the spatial phase modulation corresponding to the concave and convex patterns. The speckle noise pattern of a projected image projected onto the screen varies depending on the phase of the light. Therefore, temporally varying phase modulation can be realized by driving (moving) the diffuser  16 . Accordingly, since the speckle pattern on the screen varies, it is possible to reduce the noise by the average effect of human eyes. 
     The diffuser  16  can be manufactured by employing a transparent material such as a glass substrate and forming repeated concave and convex patterns by photolithography. 
     As shown in  FIGS. 5 and 6 , the two-dimensional intermediate image from the field curvature correcting optical system  4  passes through the opening  23 , the first opening window  27 , and the second opening window  34  along the optical axis L. The two-dimensional intermediate image is projected on the diffuser  16  and the two-dimensional intermediate image M is formed on the patterned plane of the diffuser  16 . 
     Here, as shown in  FIG. 6 , the first rail member  24 A and the first sliding member  32 A are disposed to avoid the upside of the opening  23  and the first opening window  27 . The third and fourth rail members  31 A and  31 B and the third and fourth sliding members  37 A and  37 B are disposed on both ends of the first opening window  27  and the second opening window  34 . That is, the sliding mechanism guiding the first moving frame  13  and the second moving frame  14  are disposed to avoid the upside (the upper portion in the gravitational direction) in the optical path. Accordingly, when the rail members and the sliding members slide relative to each other to generate abrasion particles, it is possible to suppress or prevent the abrasion particles from being dropped to the optical path. As a result, it is possible to prevent the abrasion particles from being attached to the patterned surface of the diffuser  16  and to form a clear two-dimensional intermediate image M on the patterned surface of the diffuser  16 . 
     Two drive units  17  and  18  will now be described. The two drive units  17  and  18  have the same configuration. The two drive units  17  and  18  employ a voice coil motor (hereinafter, referred to as “VCM”) method. 
     The first drive unit  17  includes a first coil  41 , two magnets  42   a  and  42   b , and a first yoke  43 . The first drive unit  17  drives the first moving frame  13  to move (vibrate) in the first direction X. 
     As shown in  FIGS. 3 and 4 , the first coil  41  is formed of a flat coil which is wound substantially two-dimensionally in an elliptical shape and which includes substantially a rectangular space at the center thereof. As shown in  FIG. 2 , the first coil  41  is disposed in the first attachment piece  28  of the first moving frame  13  with a flexible circuit board  49  interposed therebetween. The first coil  41  is attached by a fixing mechanism such as soldering to form a body with the flexible circuit board  49 . Accordingly, the first coil  41  is electrically connected to the wiring patterns disposed in the flexible circuit board  49 . 
     Here, in the first coil  41 , two linear portions on the long sides opposed to each other in the width direction serve to a thrust generator generating a thrust force of an actuator. In the first coil  41  of the first drive unit  17 , the extending direction of the thrust generator is perpendicular to the first direction X. 
     The first yoke  43  is formed of a flat cylindrical member. The first yoke  43  includes a first yoke member  44  and a second yoke  46 . The first yoke member  44  is formed substantially in an U shape. The first yoke member  44  includes two opposed pieces  44   a  and  44   a  opposed to each other and a connection piece  44   c  connecting both opposed pieces  44   a  and  44   a . Engaging claws  45  are formed in both opposed pieces  44   a  and  44   a  in the first yoke member  44 , respectively. The first magnet  42   a  is integrally fixed to the connection piece  44   c  of the first yoke member  44  by a fixing method using an adhesive or the like. 
     On the contrary, the second yoke member  46  has a panel shape. Engaging portions  48  engaging with the two engaging claws  45  of the first yoke member  44  are formed at both ends in the longitudinal direction of the second yoke member  46 . The second magnet  42   b  is integrally fixed to the second yoke member  46  by a fixing method using an adhesive or the like. A fixing member  47  for fixation to the supporting frame  12  is attached to the opposite surface of the surface, in which the second magnet  42   b  is disposed, in the second yoke member  46 . The fixing member  47  is fixed to one side in the longitudinal direction of the supporting frame  12  by a fixing method using fixing screws or the like. 
     When the engaging claws  45  of the first yoke member  44  engage with the engaging portions  48  of the second yoke member  46 , the first magnet  42   a  is opposed to the second magnet  42   b . At this time, the first magnet  42   a  and the second magnet  42   b  have different magnetic polarities. As shown in  FIGS. 2 and 5 , the first coil  41  attached to the first moving frame  13  is disposed in the space between the first magnet  42   a  and the second magnet  42   b.    
     In this way, the magnetic force due to the first magnet  42   a  and the second magnet  42   b  acts in a direction perpendicular to the first coil  41 . As a result, when current flows in the first coil  41 , a thrust force directed to the first direction X is generated in the first drive unit  17  by the Fleming&#39;s left-hand rule. 
     The second drive unit  18  includes a second coil  51 , two magnets  52   a  and  52   b , and a second yoke  53 . The second drive unit  18  drives the second moving frame  14  to move (vibrate) in the second direction Y. 
     As shown in  FIGS. 3 and 4 , similarly to the first coil  41 , the second coil  51  is formed of a flat coil which is wound substantially two-dimensionally in an elliptical shape and which includes substantially a rectangular space at the center thereof. As shown in  FIG. 2 , the second coil  51  is disposed in the second attachment piece  36  of the second moving frame  14  with a flexible circuit board  49  interposed therebetween. The second coil  51  is attached by a fixing mechanism such as soldering to form a body with the flexible circuit board  49 . Accordingly, the second coil  51  is electrically connected to the wiring patterns disposed in the flexible circuit board  49 . 
     Here, similarly to the first coil  41 , in the second coil  51 , two linear portions on the long sides opposed to each other in the width direction serve to a thrust generator generating a thrust force of an actuator. In the second coil  51  of the second drive unit  18 , the extending direction of the thrust generator is perpendicular to the second direction Y. 
     The second yoke  53  is formed of a flat cylindrical member. The second yoke  53  includes a first yoke member  54  and a second yoke member  56 . The first yoke member  54  is formed substantially in an U shape. The first yoke member  54  includes two opposed pieces  54   a  and  54   a  opposed to each other and a connection piece  54   c  connecting both opposed pieces  54   a  and  54   a . Engaging claws  55  are formed in both opposed pieces  54   a  and  54   a  in the first yoke member  54 , respectively. The first magnet  52   a  is integrally fixed to the connection piece  54   c  of the first yoke member  54  by a fixing method using an adhesive or the like. 
     On the contrary, the second yoke member  56  has a panel shape. Engaging portions  58  engaging with the two engaging claws  55  of the first yoke member  54  are formed at both ends in the longitudinal direction of the second yoke member  56 . The second magnet  52   b  is integrally fixed to the second yoke member  56  by a fixing method using an adhesive or the like. A fixing member  57  for fixation to the supporting frame  12  is attached to the opposite surface of the surface, in which the second magnet  52   b  is disposed, in the second yoke member  56 . The fixing member  57  is fixed to one side in the short-side direction of the supporting frame  12  by a fixing method using fixing screws or the like. Two locking holes  59  are formed in the fixing member  57 . 
     When the engaging claws  55  of the first yoke member  54  engage with the engaging portions  58  of the second yoke member  56 , the first magnet  52   a  is opposed to the second magnet  52   b . At this time, the first magnet  52   a  and the second magnet  52   b  have different magnetic polarities. As shown in  FIGS. 2 and 5 , the second coil  51  attached to the first moving frame  13  is disposed in the space between the first magnet  52   a  and the second magnet  52   b.    
     In this way, the magnetic force due to the first magnet  52   a  and the second magnet  52   b  acts in a direction perpendicular to the second coil  51 . As a result, when current flows in the second coil  51 , a thrust force directed to the second direction Y is generated in the second drive unit  18  by the Fleming&#39;s left-hand rule. 
     In this embodiment, the VCM method is used as the driving method of the first drive unit  17  and the second drive unit  18 , but the driving method is not limited to the VCM method. For example, a piezoelectric device, a shape-memory alloy, or an eccentric cam mechanism may be employed as the driving method of the first drive unit  17  and the second drive unit  18 . 
     The first drive unit  17  and the second drive unit  18  having the above-mentioned configuration are electrically connected to the controller  7  via the flexible circuit board  49 . 
     As shown in  FIG. 2 , the supporting frame  12  and the first moving frame  13  are connected to each other with two tension coil springs  61  as a specific example of the urging member. Ends in the longitudinal direction of the two tension coil springs  61  are locked to the first upper locking holes  15   a  formed at both upper ends of the first moving frame  13 . The other ends in the longitudinal direction of the two tension coil springs  61  are locked to the locking holes  59  of the fixing member  57  fixed to the supporting frame  12 . 
     The two tension coil springs  61  urge the first moving frame  13  to the supporting frame  12 . Accordingly, the first and second rail members  24 A and  24 B and the first and second sliding members  32 A and  32 B are typically urged in the third direction Z during the driving. Accordingly, it is possible to suppress or prevent the surface wobbling of the first moving frame  13  in the third direction Z which is the optical axis direction at the time of driving. 
     The first moving frame  13  and the second moving frame  14  are connected to each other with four tension coil springs  62 A,  62 B,  62 C, and  62 D. The first tension coil spring  62 A and the second tension coil spring  62 B are disposed at one end in the longitudinal direction of the first moving frame  13  and the second moving frame  14 . The third tension coil spring  62 C and the fourth tension coil spring  62 D are disposed at the other end in the longitudinal direction of the first moving frame  13  and the second moving frame  14 . 
     One end in the longitudinal direction of the first tension coil spring  62 A is locked to the second upper locking hole  15   b  disposed in the upper portion of the first moving frame  13 . The other end in the longitudinal direction of the first tension coil spring  62 A is locked to the lower locking hole  25   b  of the second moving frame  14 . One end in the longitudinal direction of the second tension coil spring  62 B is locked to the upper locking hole  25   a  of the second moving frame  14 . The other end in the longitudinal direction thereof is locked to the lower locking hole  15   c  of the first moving frame  13 . That is, the first tension coil spring  62 A and the second tension coil spring  62 B intersect each other on one side in the longitudinal direction of the first moving frame  13  and the second moving frame  14 . 
     Similarly, the third tension coil spring  62 C and the fourth tension coil spring  62 D intersect each other on the other side in the longitudinal direction of the first and second moving frames  13  and  14 . 
     The four tension coil springs  62 A,  62 B,  62 C, and  62 D urge the second moving frame  14  to the first moving frame  13 . Accordingly, the third and fourth rail members  31 A and  31 B and the third and fourth sliding members  37 A and  37 B are typically urged in the third direction Z during the driving. Accordingly, it is possible to suppress or prevent the surface wobbling of the second moving frame  14  in the third direction Z at the time of driving, similarly to the first moving frame  13 . As a result, it is possible to reduce the surface wobbling in the direction perpendicular to the diffuser  16  with a very simple configuration, thereby acquiring an excellent image. 
     In this way, in the diffuser driving device  5  according to this embodiment, the tension coil springs  61  and  62 A to  62 D are disposed in the first direction X and the second direction Y. Accordingly, when the two drive units  17  and  18  are not driven, it is possible to return the first moving frame  13  and the second moving frame  14  to the vicinity of the stroke center by means of the elastic forces of the tension coil springs  61  and  62 A to  62 D. The elastic forces of the tension coil springs  61  and  62 A to  62 D assist the vibration driving of the first drive unit  17  and the second drive unit  18 . As a result, it is possible to reduce the power consumption of the first drive unit  17  and the second drive unit  18 . 
     In this embodiment, the tension coil springs are used as the urging member, but the invention is not limited to the tension coil springs. For example, by employing magnets as the urging member, the first moving frame  13  and the second moving frame  14  may be urged to the supporting frame  12  by means of the attractive force of the magnets. 
     Configuration of Diffuser Driving Device 
     The circuit configuration of the diffuser driving device will be described now with reference to  FIG. 7 .  FIG. 7  is a block diagram illustrating the control concept of the diffuser driving device  5 . The controller  7  includes a central processing unit (micro computer)  71 , two amplifiers (AMP)  72 A and  72 B, and two low-pass filters (LPF)  73 A and  73 B. The central processing unit  71  is electrically connected to the first drive unit  17  via the first amplifier  72 A and the first low-pass filter  73 A. The central processing unit  71  is electrically connected to the second drive unit  18  via the second amplifier  72 B and the second low-pass filter  73 B. The central processing unit  71  outputs control signals to be described later to the first drive unit  17  and the second drive unit  18 . 
     Driving Example of Controller and Operation of Diffuser Driving Device 
     The driving control of the controller  7  on the first drive unit  17  and the second drive unit  18  will be described now with reference to  FIGS. 7 and 10 . 
       FIG. 8  is a diagram illustrating the control signals output to the first drive unit and the second drive unit at a certain instant,  FIG. 9  is a diagram illustrating a phase difference between the control signals output to the first drive unit and the second drive unit, and  FIG. 10  is a diagram illustrating the driving locus of a point in the diffuser. 
     When dust is attached to the diffuser  16  or a pattern defect is generated, it is necessary to drive the diffuser  16  in such a track that the diffuser does not pass through the same locus for a predetermined time, so as not to allow a user to recognize the dust or the pattern defect. Therefore, in the diffuser driving device  5  according to this embodiment, the controller  7  controls the first drive unit  17  and the second drive unit  18  to drive the diffuser  16  as follows. 
     The central processing unit  71  of the controller  7  shown in  FIG. 7  calculates a voltage value or a current value Vx using Expression 1 and outputs the calculated voltage value or current value Vx to the first drive unit  17 . Here, Ax represents the maximum value of the voltage or current applied to the first drive unit  17  and Tx represents the period of a basic vibration of the first drive unit  17 . In addition, t represents the time and P represents the phase difference given for the control of the first drive unit  17  and the second drive unit  18 . 
         Vx=Ax ×sin(2 π×t/Tx+P )  Expression 1 
     Similarly, the central processing unit  71  calculates a voltage value or a current value Vy using Expression 2 and outputs the calculated voltage value or current value Vy to the second drive unit  18 . Here, Ay represents the maximum value of the voltage or current applied to the second drive unit  18  and Ty represents the period of a basic vibration of the second drive unit  18 . 
         Vy=Ay ×cos(2 π×t/Ty−P )  Expression 2 
     That is, the driving waveforms shown in  FIG. 8  are output to the first drive unit  17  and the second drive unit  18  from the controller  7  at a certain instant. 
     Here, since the magnetic forces of the two magnets  42   a  and  42   b  of the first drive unit  17  are constant, the speed in the first direction X of the first moving frame  13  is correlated with the voltage value or the current value Vx applied to the first drive unit  17 . The driving force to one side of the first direction X is generated in the first moving frame  13  when the voltage value or current value Vx is +, and the driving force to the other side in the first direction X is generated when the voltage value or current value Vx is −. Accordingly, the first moving frame  13  vibrates in the first direction X with a period of Tx. 
     Similarly, since the magnetic forces of the two magnets  52   a  and  52   b  of the second drive unit  18  are constant, the speed in the second direction Y of the second moving frame  14  is correlated with the voltage value or the current value Vy applied to the second drive unit  18 . The driving force to one side in the second direction Y is generated in the second moving frame  14  when the voltage value or current value Vy is +, and the driving force to the other side in the second direction Y is generated when the voltage value or current value Vy is −. Accordingly, the second moving frame  14  vibrates in the second direction Y with a period of Ty. 
     The phase difference P given for the control of the first drive unit  17  and the second drive unit  18  is calculated, for example, using Expression 3. Here, Tp represents the repeated period (period) of a dynamic phase difference, Pa represents the maximum value of the dynamic phase difference, and Pp represents a static phase difference. 
         P=Pa ×sin(2 π×t/Tp )+ Pp   Expression 3 
     In this way, the controller  7  sequentially changes the phase difference P given for the control of the first drive unit  17  and the second drive unit  18  at every time t. Here, as described above, the voltage value or current value Vx applied to the first drive unit  17  is proportional to the speed of the first moving frame  13 . The voltage value or current value Vy applied to the second drive unit  18  is proportional to the speed of the second moving frame  14 . As a result, by changing the phase difference between the signals applied to the first drive unit  17  and the second drive unit  18 , the phase difference between the vibration of the first moving frame  13  in the first direction X and the vibration of the second moving frame  14  in the second direction Y is also changed. 
     By synthesizing the vibration of the first moving frame  13  in the first direction X and the vibration of the second moving frame  14  in the second direction Y, a point of the diffuser  16  draws the driving locus shown in  FIG. 10 . 
     As shown in  FIG. 10 , by changing the phase difference P between the vibration in the first direction X and the vibration in the second direction Y, the length of the track drawn by a point of the diffuser  16  can be extended. As a result, compared with the case where the diffuser is rotated and driven, it is possible to extend the interval (hereinafter, referred to as “driving period”) between the times when a point of the diffuser  16  passes through the same locus. 
     Therefore, compared with the case where the diffuser  16  is rotated, it is possible to reduce the number of times (the number of times of passing through the same driving locus) of passing through the same area per a predetermined time. That is, since the diffuser  16  is driven in the track not passing through the same locus for a predetermined time, it is possible to allow a user hardly to recognize the dust attached to the diffuser  16  or the pattern defect. Accordingly, it is possible to suppress deterioration in image quality due to the attachment of dust or the pattern defect. 
     When the driving speed of the diffuser  16  is slowed down, a user can easily recognize the dust attached to the patterned surface of the diffuser  16  or the pattern defect. Accordingly, the controller  7  controls the first drive unit  17  and the second drive unit  18  to drive the diffuser  16  at a speed greater than a predetermined speed (speed at which the attached dust or the pattern defect is not recognized by the user). 
     For example, when the size of the two-dimensional intermediate image is 18 mm×32 mm and the dust or the pattern defect with a diameter of 50 μm is intended not to influence the image quality, it is necessary to set the driving speed of the diffuser  16  equal to or greater than 100 mm/s. Accordingly, the phase difference is changed by 10° in the range of ±20° by allowing the first moving frame  13  and the second moving frame  14  to vibrate with an amplitude of 4 mm and a frequency of 5 Hz. Therefore, it is possible to allow a user hardly to recognize the dust or the pattern defect, thereby preventing or suppressing the deterioration in image quality. 
     It is preferable that the frequency at which the first moving frame  13  and the second moving frame  14  are driven by the first drive unit  17  and the second drive unit  18  is set to be lower than the resonance frequency of the tension coil springs  61  and  62 A to  62 D. For example, when the resonance frequency of the tension coil springs  61  and  62 A to  62 D is 8 Hz, the driving frequency is set to 5 Hz. Accordingly, even in use for a long time, it is possible to prevent or suppress the two moving frames  13  and  14  from resonating with the tension coil springs  61  and  62 A to  62 D to collide with a stopper or the like during the driving. As a result, it is possible to extend the lifetime of the sliding mechanism of the diffuser driving device  5  and also to reduce the noise or the power consumption. 
     When the driving frequency is set to be higher than the resonance frequency of the tension coil springs  61  and  62 A to  62 D, it is possible to obtain the speckle reducing effect or the effect of suppressing the deterioration in image quality due to the dust or the pattern defect, similarly to the case where the driving frequency is lower than the resonance frequency. 
     The driving frequency may be set to be equal to the resonance frequency of the tension coil springs  61  and  62 A to  62 D. Accordingly, it is possible to further reduce the power consumption by using the resonance with the tension coil springs  61  and  62 A to  62 D. When the driving frequency is set to be equal to the resonance frequency of the tension coil springs  61  and  62 A to  62 D, it is necessary to control the resonance amplitude so as to prevent the two moving frames  13  and  14  from colliding with the stopper or the like during the driving. 
     To more accurately control the driving locus of the diffuser  16 , a position detecting sensor for detecting the sliding positions of the first moving frame  13  and the second moving frame  14  may be provided. For example, a hole device or an optical position sensor such as a linear encoder and a PSD (Position Sensitive Detector) may be used as the position detecting sensor. The position detecting sensor is electrically connected to the controller  7  and outputs the position information of the first moving frame  13  and the second moving frame  14  to the controller  7 . Then, the controller  7  controls the voltage value or current value applied to the first coil  41  of the first drive unit  17  and the second coil  51  of the second drive unit  18  on the basis of the input position information. Accordingly, it is possible to accurately control the driving locus of the diffuser  16  depending on the position thereof. 
     2. Second Embodiment 
     Configuration of Diffuser Driving Device 
     A diffuser driving device according to a second embodiment of the invention will be described now with reference to  FIGS. 11 and 12 .  FIG. 11  is a plan view schematically illustrating a diffuser driving device according to the second embodiment of the invention and  FIG. 12  is a diagram illustrating a part of the diffuser driving device according to the second embodiment of the invention. 
     In the diffuser driving device  105  according to the second embodiment, the moving frames for holding the diffuser  16  are combined into one body. As shown in  FIG. 11 , the diffuser driving device  105  includes a supporting frame  112 , a moving frame  113  holding the diffuser  16 , two drive units  117  and  118 , and three spherical members  119 . 
     The moving frame  113  is supported by the supporting frame  112  with the three spherical members  119  interposed therebetween as another specific example of the guide member so as to move in two directions (the first direction X and the second direction Y) perpendicular to the third direction Z which is parallel to the optical axis of the optical system. The moving frame  113  can be made to move in the first direction X by the first drive unit  117  and can be made to move in the second direction Y by the second drive unit  118 . The moving frame  113  is urged to the supporting frame  112  by three spring members  121 . 
     As shown in  FIG. 12 , spherical member holding portions  122  for holding the spherical members  119  are formed in the supporting frame  112 . The spherical member holding portions  122  are formed as circular concave portions with a diameter greater than the spherical members  119 . The three spherical members  119  are rotatably held in the spherical member holding portions  122  formed in the supporting frame  112 . The three spherical members  119  are interposed between the supporting frame  112  and the moving frame  113  in a state where they are held in the spherical member holding portions  122 . Accordingly, it is possible to greatly reduce the frictional resistance among the moving frame  113 , the spherical members  119 , and the supporting frame  112 . As a result, the drive units  117  and  118  can allow the moving frame  113  to satisfactorily vibrate with a small driving force. Since the spherical members  119  or the portions contacting with the spherical members  119  can easily be abraded to cause the deterioration or the generation of dust, it is preferable that they are formed of a material such as ceramics resistant to the abrasion. 
     Other configurations and operations are the same as the diffuser driving device  5  according to the first embodiment, description thereof is omitted. According to the diffuser driving device  105  having the above-mentioned configuration, it is possible to obtain the same operations and advantages as the diffuser driving device  5  according to the first embodiment. 
     In the diffuser driving device  105  according to the second embodiment, it is possible to reduce the number of components of the second moving frame in comparison with the diffuser driving device  5  according to the first embodiment, thereby reducing the entire size of the apparatus. 
     As described above, in the diffuser driving device according to the embodiments of the invention, the phase difference between the vibration of the moving frame holding the diffuser in the first direction and the vibration of the moving frame in the second direction is changed. Accordingly, it is possible to extend the driving period of the diffuser, compared with the case where the diffuser is rotated. That is, it is possible to drive the diffuser in the track not passing through the same locus for a predetermined time. The diffuser is driven at a speed greater than the speed at which the dust attached to the diffuser or the pattern defect is not recognized by a user. As a result, it is possible to allow a user hardly to recognize the dust attached to the diffuser or the pattern defect, thereby suppressing the deterioration in image quality due to the attached dust or the pattern defect. 
     By providing the urging member urging the moving frame to the supporting frame, it is possible to reduce the surface wobbling of the diffuser in the optical axis direction during the driving, thereby obtaining an excellent focus of a projected image. By setting the size of the diffuser to be slightly greater than the surface size of the two-dimensional intermediate image, it is possible to reduce the cost of the diffuser, compared with the case where the diffuser is rotated. 
     The invention is not limited to the embodiments shown in the drawings, but may be modified in various forms without departing from the spirit and scope of the appended claims. For example, the configuration of the optical block forming and projecting the image beam (two-dimensional intermediate image) is not limited to the above-mentioned embodiments. That is, an optical block using plural light-emitting portions or another laser as a light source may be employed. 
     The diffuser and the moving frame may be formed in a body, a coil or the like constituting the drive unit may be fixed to the diffuser, and then the diffuser may be driven. 
     The present application contains subject matter related to that disclosed in Japanese Priority Patent Application No. 2008-290394 filed in the Japan Patent Office on Nov. 12, 2008, the entire content of which is hereby incorporated by reference. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.