Patent Publication Number: US-9405121-B2

Title: Image display apparatus and head-mounted display

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation patent application of U.S. application Ser. No. 13/908,484 filed Jun. 3, 2013, which claims priority to Japanese Patent Application No. 2012-127450, filed Jun. 4, 2012 both of which are expressly incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an image display apparatus and a head-mounted display. 
     2. Related Art 
     For example, as an image display apparatus for displaying an image on a screen, there is a known configuration including a light source and an optical scanner that deflects light from the light source for two-dimensional scanning (see JP-A-2008-304726, for example). 
     The image display apparatus described in JP-A-2008-304726 includes a plurality of semiconductor lasers, a parallelizing lens that parallelizes a laser light flux from each of the semiconductor lasers, a polarizing beam splitter that combines the plurality of laser light fluxes, and a MEMS (optical scanner) that deflects the combined laser light flux from the polarizing beam splitter for two-dimensional scanning. A mirror provided in the MEMS is disposed to be perpendicular to a plane including the optical axis of the laser light flux from each of the semiconductor lasers, and the mirror is irradiated with the laser light flux traveling in a direction inclined to a normal to the mirror. In JP-A-2008-304726, the configuration described above is intended to reduce the size of the apparatus. 
     In the image display apparatus described in JP-A-2008-304726, the mirror is resonantly driven to swing in the in-plane direction in the plane at a large amplitude, whereas driven to swing in an out-of-plane direction (direction perpendicular to the plane) at an amplitude smaller than the amplitude in the in-plane direction. Since laser light LL is incident on the mirror in a direction inclined in the in-plane direction to a normal to the mirror as described above, the large amplitude of the mirror in the in-plane direction disadvantageously greatly distorts two ends of a drawable region S, which is a region of a screen, a wall surface, or any other object that can be scanned with the laser light, as shown in  FIG. 8B , resulting in a decrease in area of a rectangular effective drawing region (region actually irradiated with laser light for image display) S′ provided in the drawable region S. As a result, efficient laser light scanning cannot be made, or excellent image display characteristics cannot be achieved. 
     That is, the image display apparatus described in 
     JP-A-2008-304726 is problematic in that reduction in size of the apparatus and provision of excellent image display characteristics cannot be achieved at the same time. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide an image display apparatus capable of improving image display characteristics (enlarging effective drawing region, in particular) while reducing the size of the apparatus and a head-mounted display including the image display apparatus. 
     An image display apparatus according to an aspect of the invention includes a plurality of light source sections each of which emits a light flux, a light combining section that combines the light fluxes emitted from the plurality of light source sections, an optical scan section that swings around a first axis and a second axis perpendicular to the first axis to deflect a combined light from the light combining section for two-dimensional scanning, and a controller that controls an amplitude of a swing motion of the optical scan section around the first axis to be greater than the amplitude of the swing motion of the optical scan section around the second axis, an optical axis of each of the light fluxes emitted from the plurality of light source sections and directed through the light combining section toward the optical scan section and the first axis are present in a first plane, the optical scan section has a light reflection surface configured to be perpendicular to the first plane when the optical scan section is not driven, and the light reflection surface is irradiated with the combined light emitted from the light combining section and traveling in a direction inclined to a normal to the light reflection surface. 
     The image display apparatus described above has a small size and improved image display characteristics (enlarged effective drawing region, in particular). 
     In the image display apparatus according to the aspect of the invention, it is preferable that the optical scan section includes a movable portion having the light reflection surface, a frame that surrounds the movable portion, a support member that supports the frame, a first shaft that connects the movable portion to the frame in such a way that the movable portion is swingable around the first axis relative to the frame, and a second shaft that connects the frame to the support member in such a way that the frame is swingable around the second axis relative to the support member. 
     The optical scan section described above has a simple configuration. Further, using the two-dimensional-scanning optical scanner allows the size of the optical scan section to be reduced. 
     In the image display apparatus according to the aspect of the invention, it is preferable that a width of the frame in a direction perpendicular to the first plane is smaller than the width of the frame in an in-plane direction in the first plane. 
     The thickness of the image display apparatus can therefore be reduced. 
     In the image display apparatus according to the aspect of the invention, it is preferable that the optical scan section further includes a permanent magnet provided on the frame and a coil that faces the frame and produces a magnetic field that acts on the permanent magnet. 
     In the configuration described above, the thickness of the optical scan section in the direction of a normal to the light reflection surface increases, whereas the width of the optical scan section in the in-plane direction of the light reflection surface can be reduced. The thus shaped optical scan section is suitable for the image display apparatus according to the aspect of the invention. 
     In the image display apparatus according to the aspect of the invention, it is preferable that the light reflection surface resonantly swings around the first axis. 
     The light reflection surface can therefore be allowed to swing at a large amplitude around the first axis in a simple, reliable manner. 
     It is preferable that the image display apparatus according to the aspect of the invention further includes a prism that is provided on an optical path between the light combining section and the optical scan section, inclines an optical axis of the combined light from the light combining section, and changes a cross-sectional shape of the combined light. 
     Providing the prism increases the degree of freedom in arranging the components in the apparatus, and shaping the cross-sectional shape of the light improves the image display characteristics. 
     In the image display apparatus according to the aspect of the invention, it is preferable that the light flux emitted from each of the light source sections is linearly polarized light that behaves as s-polarized light with respect to a light incident surface of the prism. 
     In this way, for example, loss of the light flux produced when the light flux passes through the prism, which is an optical element, can be reduced. 
     In the image display apparatus according to the aspect of the invention, it is preferable that the prism changes the cross-sectional shape of the combined light from the light combining section by increasing a width of the combined light from the light combining section in an in-plane direction in the first plane. 
     An elliptical (or oval) cross-sectional shape of the light flux immediately after it is emitted from each light source can thus be changed to a substantially circular shape, whereby the image display characteristics can be improved. 
     In the image display apparatus according to the aspect of the invention, it is preferable that a light exiting surface of the prism is a light collecting lens surface. 
     In this way, when an image is displayed on an object located in a position in the vicinity of the focal point of the lens surface, better image display characteristics are provided. 
     It is preferable that the image display apparatus according to the aspect of the invention further includes a detector that detects an amount of light emitted from each of the light source sections and reflected off a light incident surface of the prism, and drive operation of the light source section is controlled based on the amount of light detected by the detector. 
     Light of a desired color and intensity can thus be produced, whereby excellent image display characteristics are provided. 
     In the image display apparatus according to the aspect of the invention, it is preferable that an angle of radiation of the light flux emitted from each of the plurality of light source sections and directed in a direction perpendicular to the first plane is set to be greater than the angle of radiation of the light flux emitted in an in-plane direction in the first plane. 
     A laser light flux emitted from a semiconductor laser, which is typically used as a light source, has a substantially elliptical intensity distribution. That is, the angle of radiation of the laser light flux in the direction of the major axis of the ellipse differs from the angle of radiation of the laser light flux in the direction of the minor axis of the ellipse. For example, setting the direction of the major axis, where the angle of radiation is larger, to be perpendicular to the first surface, allows the prism to be disposed in a horizontal attitude, whereby the size of the apparatus can be reduced. 
     In the image display apparatus according to the aspect of the invention, it is preferable that the plurality of light source sections, the light combining section, and the optical scan section are arranged in an in-plane direction in the first plane. 
     The size (thickness) of the image display apparatus can thus be reduced. 
     An image display apparatus according to another aspect of the invention includes a plurality of light source sections each of which emits a light flux, a light combining section that combines the light fluxes emitted from the plurality of light source sections, and an optical scan section that swings around a first axis and a second axis perpendicular to the first axis to deflect a combined light from the light combining section for two-dimensional scanning, an optical axis of each of the light fluxes emitted from the plurality of light source sections and directed through the light combining section toward the optical scan section and the first axis are present in a first plane, the optical scan section has a light reflection surface configured to be perpendicular to the first plane when the optical scan section is not driven, the light reflection surface is irradiated with the combined light emitted from the light combining section and traveling in a direction inclined to a normal to the light reflection surface, and an amplitude of a swing motion of the optical scan section around the first axis is greater than the amplitude of the swing motion of the optical scan section around the second axis. 
     The image display apparatus described above has a small size and improved image display characteristics (enlarged effective drawing region, in particular). 
     A head-mounted display according to still another aspect of the invention includes a light reflector that reflects at least part of light incident thereon, and an image display apparatus that irradiates light to the light reflector, the image display apparatus including a plurality of light source sections each of which emits a light flux, a light combining section that combines the light fluxes emitted from the plurality of light source sections, an optical scan section that swings around a first axis and a second axis perpendicular to the first axis to deflect a combined light from the light combining section for two-dimensional scanning, and a controller that controls an amplitude of a swing motion of the optical scan section around the first axis to be greater than the amplitude of the swing motion of the optical scan section around the second axis, an optical axis of each of the light fluxes emitted from the plurality of light source sections and directed through the light combining section toward the optical scan section and the first axis are present in a first plane, the optical scan section has a light reflection surface configured to be perpendicular to the first plane when the optical scan section is not driven, and the light reflection surface is irradiated with the combined light emitted from the light combining section and traveling in a direction inclined to a normal to the light reflection surface. 
     A reliable head-mounted display can thus be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a plan view showing an image display apparatus according to a preferred embodiment of the invention. 
         FIG. 2  is a cross-sectional view of a laser light flux emitted from each laser light source shown in  FIG. 1 . 
         FIG. 3  is a side view of the image display apparatus shown in  FIG. 1 . 
         FIG. 4  is a plan view showing an optical scan section (optical scanner) provided in the image display apparatus shown in  FIG. 1 . 
         FIG. 5  is a cross-sectional view of the optical scanner shown in  FIG. 4 . 
         FIG. 6  is a block diagram of a voltage applying section provided in the optical scanner shown in  FIG. 4 . 
         FIGS. 7A and 7B  show examples of voltages generated by a first voltage generator and a second voltage generator shown in  FIG. 6 . 
         FIGS. 8A and 8B  show a difference in drawable region caused by how the optical scanner is disposed. 
         FIG. 9  is a perspective view showing a head-up display based on the image display apparatus according to the embodiment of the invention. 
         FIG. 10  is a perspective view showing a head-mounted display according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An image display apparatus and a head-mounted display according to preferred embodiments of the invention will be described below with reference to the accompanying drawings. 
     1. Image Display Apparatus 
       FIG. 1  is a plan view showing an image display apparatus according to a preferred embodiment of the invention.  FIG. 2  is a cross-sectional view of a laser light flux emitted from each laser light source shown in  FIG. 1 .  FIG. 3  is a side view of the image display apparatus shown in  FIG. 1 .  FIG. 4  is a plan view showing an optical scan section (optical scanner) provided in the image display apparatus shown in  FIG. 1 .  FIG. 5  is a cross-sectional view of the optical scanner shown in  FIG. 4 .  FIG. 6  is a block diagram of a voltage applying section provided in the optical scanner shown in  FIG. 4 .  FIGS. 7A and 7B  show examples of voltages generated by a first voltage generator and a second voltage generator shown in  FIG. 6 .  FIGS. 8A and 8B  show a difference in drawable region caused by how the optical scanner is disposed. In the following description, the upper side in  FIG. 5  is called “upper” and the lower side in  FIG. 5  is called “lower” for ease of description. Further, three axes perpendicular to each other are called an X axis, a Y axis, and a Z axis, as shown in  FIG. 1 . 
     The image display apparatus  1  shown in  FIG. 1  is an apparatus that scans an object  10 , such as a screen and a wall surface, with light to display an image. 
     The image display apparatus  1  includes a drawing light source unit  2 , which emits drawing laser light LL, a prism  3 , which inclines the optical axis of the drawing laser light LL and deforms the cross-sectional shape of the drawing laser light LL, an optical scan section  4 , which deflects the drawing laser light LL having passed through the prism  3  for scanning, a detector  5 , which detects the intensity of the drawing laser light LL, and a controller  6 , which controls the operation of the drawing light source unit  2  and the optical scan section  4 . 
     The image display apparatus  1  has an enclosure  9 , which has a small-aspect shape having relatively large dimensions in the XY plane and a height in the Z-axis direction, and the enclosure  9  accommodates the drawing light source unit  2 , the prism.  3 , the optical scan section  4 , and the detector  5  arranged in the XY plane. The enclosure  9  in this embodiment has a substantially rectangular exterior shape when viewed from above in the thickness direction of the enclosure  9 . The enclosure  9  further has a window  91  formed, for example, of a transparent member (made, for example, of glass or plastic), through which the drawing laser light LL being deflected by the optical scan section  4  for scanning exits out of the enclosure  9 . The controller  6  may be accommodated in the enclosure  9  as in this embodiment or may be provided external to the enclosure  9 . 
     The above components will be sequentially described below. 
     1-1. Drawing Light Source Unit 
     The drawing light source unit  2  includes laser light sources (light source sections)  21 R,  21 G, and  21 B for the following colors: red; green; and blue and collimator lenses  22 R,  22 G, and  22 B and dichroic mirrors  23 R,  23 G, and  23 B provided in correspondence with the laser light sources  21 R,  21 G, and  21 B, as shown in  FIG. 1 . 
     Each of the laser light sources  21 R,  21 G, and  21 B has a light source and a drive circuit (not shown). The laser light source  21 R emits a red laser light flux RR. The laser light source  21 G emits a green laser light flux GG. The laser light source  21 B emits a blue laser light flux BB. The laser light fluxes RR, GG, and BB are emitted in accordance with drive signals transmitted from the controller  6  and parallelized or substantially parallelized by the collimator lenses  22 R,  22 G, and  22 B, respectively. 
     In this embodiment, the laser light sources  21 R,  21 B, and  21 G are arranged in the -Y-axis direction in the order of the laser light source  21 R, the laser light source  21 B, and the laser light source  21 G and disposed in the enclosure  9  in a left end portion thereof in  FIG. 1 . The laser light sources  21 R,  21 G, and  21 B emit the laser light fluxes RR, GG, and BB, respectively, in the +X-axis direction. The thus arranged laser light sources  21 R,  21 G, and  21 B occupy a relatively small space, allowing the size of the image display apparatus  1  (enclosure  9 ) to be reduced. It is noted that the arrangement of the laser light sources  21 R,  21 G, and  21 B is not limited to the arrangement described above. 
     Each of the laser light sources  21 R,  21 G, and  21 B can, for example, be an edge-emitting semiconductor laser, a surface-emitting semiconductor laser, or any other suitable semiconductor laser. Using a semiconductor laser allows the size of each of the laser light sources  21 R,  21 G, and  21 B to be reduced. 
     When each of the laser light sources  21 R,  21 G, and  21 B is formed of a semiconductor laser, the optical intensity distribution of each of the laser light fluxes RR, GG, and BB emitted from the laser light sources  21 R,  21 G, and  21 B has in general a contour (what is called FFP: far field pattern) having a substantially elliptical shape. It is assumed in the following description that the “cross-sectional shape” of each of the laser light fluxes RR, GG, and BB has the same meaning as that of the “contour of the optical intensity distribution” of the corresponding one of the laser light fluxes RR, GG, and BB. That is, in this case, each of the laser light fluxes RR, GG, and BB emitted from the laser light sources  21 R,  21 G, and  21 B in other words has a substantially elliptical cross-sectional shape. The cross-sectional shape used herein is the shape of a cross section perpendicular to the optical axis of each of the laser light fluxes RR, GG, and BB. 
     The laser light sources  21 R,  21 G, and  21 B emit the laser light fluxes RR, GG, and BB, respectively, each of which has a substantially elliptical cross-sectional shape, as shown in  FIG. 2 . Each of the laser light sources  21 R,  21 G, and  21 B is so disposed in the enclosure  9  that the major axis of the ellipse substantially coincides with the Z axis (direction perpendicular to XY plane) and the minor axis of the ellipse substantially coincides with the Y axis (XY plane). In other words, each of the laser light fluxes RR, GG, and BB emitted from the laser light sources  21 R,  21 G, and  21 B has an angle of radiation in the Z-axis direction greater than the angle of radiation in the Y-axis direction (in-plane direction in XY plane). In this case, the three laser light sources  21 R,  21 G, and  21 B can be arranged in the Y-axis direction at narrower intervals than in a case where the angles of radiation are configured in a reversed manner (in a case where the angle of radiation in the Z-axis direction is smaller than the angle of radiation in the Y-axis direction), whereby the dimensions of the enclosure  9  in the XY plane can be reduced. The size of the image display apparatus  1  can therefore be reduced. 
     Each of the laser light fluxes RR, GG, and BB emitted from the laser light sources  21 R,  21 G, and  21 B is linearly polarized light. Further, the laser light fluxes RR, GG, and BB are s-polarized light, which is a light component polarized in a direction perpendicular to the reflection/transmission surfaces (light incident surfaces) of the dichroic mirrors  23 R,  23 G, and  23 B and the light incident surface of the prism  3 . That is, each of the laser light fluxes RR, GG, and BB emitted from the laser light sources  21 R,  21 G, and  21 B is polarized light oscillating (polarized) in the Z-axis direction and has an elliptical cross-sectional shape the major axis of which coincides with the oscillating direction. When each of the laser light fluxes RR, GG, and BB is s-polarized light, the amount of loss of the laser light fluxes RR, GG, and BB produced when they are incident on the dichroic mirrors  23 R,  23 G, and  23 B and the prism  3  can be reduced. 
     The dichroic mirror  23 R is characterized in that it reflects the laser light flux RR. The dichroic mirror  23 B is characterized in that it reflects the laser light flux BB and transmits the laser light flux RR. The dichroic mirror  23 G is characterized in that it transmits the laser light flux GG and reflects the laser light fluxes RR and BB. The dichroic mirrors  23 R,  23 G, and  23 B cause the optical axes of the color laser light fluxes RR, GG, and BB to coincide or substantially coincide (be combined) with each other so that the single drawing laser light LL is emitted in the +X-axis direction. That is, the dichroic mirrors  23 R,  23 G, and  23 B form a light combining section  23 , which combines the laser light fluxes RR, GG, and BB with each other. 
     In this embodiment, the dichroic mirror  23 R, the dichroic mirror  23 B, and the dichroic mirror  23 G are arranged in this order in the −Y-axis direction in correspondence with the arrangement of the laser light sources  21 R,  21 B, and  21 G. The dichroic mirror  23 R is so disposed that it reflects the laser light flux RR emitted in the +X-axis direction from the laser light source  21 R and causes the reflected light flux to travel in the −Y-axis direction. The dichroic mirror  23 B is so disposed that it not only reflects the laser light flux BB emitted in the +X-axis direction from the laser light source  21 B and causes the reflected light flux to travel in the −Y-axis direction but also transmits the laser light flux RR reflected off the dichroic mirror  23 R in the −Y-axis direction. Further, the dichroic mirror  23 G is so disposed that it not only transmits the laser light flux GG emitted in the +X-axis direction from the laser light source  21 G but also reflects the laser light fluxes RR and BB reflected in the −Y-axis direction off the dichroic mirrors  23 R and  23 B and causes the reflected light fluxes to travel in the +X-axis direction. The thus configured light combining section  23  outputs the drawing laser light LL in the +X-axis direction. 
     The dichroic mirrors  23 R,  23 G, and  23 B are preferably so disposed that a laser light flux of a shorter wavelength is incident on the prism  3  at a greater angle of incidence in consideration of dispersion resulting from the difference in refractive index among the wavelengths of the laser light fluxes. That is, the dichroic mirrors  23 R,  23 G, and  23 B are disposed with their reflection surfaces slightly shifted from each other around the Z axis so that the following relationship is achieved: the angle of incidence θ B  of the blue laser light flux BB&gt;the angle of incidence θ G  of the green laser light flux GG&gt;the angle of incidence θ R  of the red laser light flux RR. 
     1-2. Prism 
     The prism  3  is an optical element having a first function of inclining the optical axis of the drawing laser light LL, a second function of deforming the shape (cross-sectional shape) of the drawing laser light LL, and a third function of controlling the angle of radiation of the drawing laser light LL (collecting drawing laser light LL, for example). The prism  3  is a substantially colorless, transparent polyhedron made of glass or quartz. The prism  3  is not limited to a specific one as long as it has the functions described above and can, for example, be a triangular prism having a substantially triangular columnar shape. The angled portions of the triangular prism may, for example, be chamfered or otherwise rounded as long as the resultant shape does not affect the functions. 
     The first function will first be described. The prism  3  receives the drawing laser light LL incident through a light incident surface  31  and outputs the drawing laser light LL through a light exiting surface  32  in a direction inclined to the +X-axis direction toward the +Y-axis direction (direction toward inner portion of enclosure  9 ). That is, the prism  3  inclines the optical axis of the drawing laser light LL around the Z axis (in XY plane) . The thus configured prism  3  can direct the drawing laser light LL toward an inner portion of the enclosure  9 . The enclosure  9  therefore has a space large enough to place members along extensions of the optical axes of the light fluxes emitted from the laser light sources  21 R and  21 B, and the internal space of the enclosure  9  can be efficiently used by placing the optical scan section  4  in the space. That is, inclining the optical axis of the drawing laser light LL toward an inner portion of the enclosure  9  can reduce the volume of a dead space (unused space where no member is disposed) in the enclosure  9 , whereby the size of the image display apparatus  1  can be reduced. 
     The second function described above will next be described. The prism  3  changes the cross-sectional shape of the drawing laser light LL that is perpendicular to the optical axis thereof from the substantially elliptical shape to a substantially circular shape. Specifically, the prism  3  changes the cross-sectional shape of the drawing laser light LL to a substantially circular shape by increasing the width of the cross-sectional shape of the incident drawing laser light LL in the direction in which the XY plane extends with the width thereof in the Z-axis direction substantially unchanged. In other words, the prism  3  changes the cross-sectional shape of the drawing laser light LL in such a way that the length of the minor axis of the elliptical cross-sectional shape is increased to a point where the ratio between the minor axis and the major axis (aspect ratio) is substantially one. When the cross-sectional shape of the drawing laser light LL becomes a substantially circular shape as described above, the image display apparatus  1  can provide excellent image display characteristics. Further, when the cross-sectional shape of the drawing laser light LL before it is incident on the prism  3  has a substantially elliptical shape the major axis of which extends in the Z-axis direction as described above, the prism  3  only needs to be angularly shifted in the XY plane, whereby the prism  3  can be so disposed that the length of the enclosure  9  in the thickness direction (Z-axis direction) corresponding to the space where the prism  3  occupies is minimized. As a result, the size (thickness) of the image display apparatus  1  can be reduced. 
     The third function described above will next be described. The light exiting surface  32  of the prism  3  is formed of a curved convex surface (lens surface) and hence functions as a collector lens that collects (focuses) the drawing laser light LL incident in the form of parallelized light on the prism  3 . Focusing the drawing laser light LL as described above can increase the sharpness of an image displayed on the object  10  located in a position in the vicinity of the focal point (form an image having higher resolution). Further, the light exiting surface  32  having a function of a collector lens eliminates the necessity of separately providing a collector lens in addition to the prism  3 , whereby the number of parts can be reduced and the size of the image display apparatus  1  can be reduced. The light exiting surface  32  of the prism  3  is not limited to a convex surface (collector lens) as long as the light exiting surface  32  can control the angle of radiation of the light that exits through the light exiting surface  32  and can, for example, be a concave surface (lens that causes light to diverge). 
     The image display apparatus  1  does not necessarily use a prism but may use an optical element capable of providing the functions described above. 
     The drawing light source unit  2  and the prism  3  have been described in detail. In the image display apparatus  1 , the optical axes of the laser light fluxes RR, GG, and BB (drawing laser light LL) are present in the same XY plane (first plane F), as shown in  FIG. 3 . That is, the following actions are made in the plane F: The laser light sources  21 R,  21 G, and  21 B emit the laser light fluxes RR, GG, and BB; the light combining section  23  combines the laser light fluxes RR, GG, and BB and outputs the resultant drawing laser light LL; and the prism  3  inclines the optical axis of the drawing laser light LL in the XY plane. 
     1-3. Optical Scan Section 
     The optical scan section  4  has a function of deflecting the drawing laser light LL having passed through the prism  3  for two-dimensional scanning. The optical scan section  4  is not limited to a specific one and can be any device capable of deflecting the drawing laser light LL for two-dimensional scanning. For example, an optical scanner  40  having the following configuration can be used. 
     The optical scanner  40  includes a movable portion  41 , a pair of shafts  421  and  422  (first shafts), a frame  43 , two pairs of shafts  441 ,  442 ,  443 , and  444  (second shafts), a support member  45 , a permanent magnet  46 , a coil  47 , a magnet core  48 , and a voltage applying section  49 , as shown in  FIGS. 4 and 5 . 
     Among the components described above, the movable portion  41  and the pair of shafts  421  and  422  form a first oscillation system that swings (makes reciprocating motion) around the shafts  421  and  422  or a first axis J 1 . Further, the movable portion  41 , the pair of shafts  421  and  422 , the frame  43 , the two pairs of shafts  441 ,  442 ,  443 , and  444 , and the permanent magnet  46  forma second oscillation system that swings (makes reciprocating motion) around a second axis J 2 . The permanent magnet  46 , the coil  47 , and the voltage applying section  49  form a driver that drives the first and second oscillation systems described above. 
     The components of the optical scanner  40  will be sequentially described below in detail. 
     The movable portion  41  includes a base  411  and a light reflection plate  413  fixed to the base  411  via a spacer  412 , as shown in  FIGS. 4 and 5 . A light reflection portion  414 , which reflects light, is provided on the upper surface (one surface) of the light reflection plate  413 . The surface of the light reflection portion  414  forms a light reflection surface  414   a , which reflects the drawing laser light LL. The movable portion  41  swings around the first axis J 1  and the second axis J 2 , as described above. That is, it can be said that the base  411 , the spacer  412 , the light reflection plate  413 , and the light reflection surface  414   a , which form the movable portion  41 , also swing around the first axis J 1  and the second axis J 2 . 
     The light reflection plate  413  is so disposed that it is set apart from the shafts  421  and  422  in the thickness direction of the light reflection plate  413  but overlaps with the shafts  421  and  422  when viewed in the thickness direction (hereinafter also referred to as “plan view”). 
     The configuration described above allows the area of the plate surface of the light reflection plate  413  to be increased while allowing the distance between the shaft  421  and the shaft  422  to be shortened. Further, since the distance between the shaft  421  and the shaft  422  can be shortened, the size of the frame  43  can be reduced. Moreover, since the size of the frame  43  can be reduced, the distance between the shafts  441 ,  442  and the shafts  443 ,  444  can be shortened. As a result, the size of the optical scanner  40  can be reduced with the area of the plate surface of the light reflection plate  413  increased. 
     The light reflection plate  413  is further so formed that it covers the entire shafts  421  and  422  in the plan view. In other words, the shafts  421  and  422  are located inside the outer circumference of the light reflection plate  413  in the plan view. The area of the plate surface of the light reflection plate  413  is thus increased, resulting in an increase in the area of the light reflection portion  414 . The configuration further prevents unwanted light (light that has not been incident on light reflection portion  414 , for example) from being reflected off the shafts  421  and  422  to form stray light. 
     The light reflection plate  413  is further so formed that it covers the entire frame  43  in the plan view. In other words, the frame  43  is located inside the outer circumference of the light reflection plate  413  in the plan view. The area of the plate surface of the light reflection plate  413  is thus increased, resulting in an increase in the area of the light reflection portion  414 . The configuration further prevents the unwanted light from being reflected off the frame  43  to form stray light. 
     Further, the light reflection plate  413  is so formed that it covers the entire shafts  441 ,  442 ,  443 , and  444  in the plan view. The area of the plate surface of the light reflection plate  413  is thus increased, resulting in an increase in the area of the light reflection portion  414 . The configuration further prevents the unwanted light from being reflected off the shafts  441 ,  442 ,  443 , and  444  to form stray light. 
     In this embodiment, the light reflection plate  413  has a circular shape in the plan view. The light reflection plate  413  does not necessarily have a circular shape and can have an elliptical shape or a rectangular or any other polygonal shape in the plan view. 
     The thus shaped light reflection plate  413  has a hard layer  415  provided on the lower surface thereof (the other surface, the surface of the light reflection plate  413  that faces the base  411 ). 
     The hard layer  415  is made of a material harder than the material of which the body of the light reflection plate  413  is made, whereby the rigidity of the light reflection plate  413  can be increased. The thus increased rigidity prevents the light reflection plate  413  from being bent or suppresses the amount of bending when the light reflection plate  413  swings. The thickness of the light reflection plate  413  can also be reduced, whereby the moment of inertia of the light reflection plate  413  around the first and second axes J 1 , J 2  can be reduced when the light reflection plate  413  swings therearound. 
     The material of which the hard layer  415  is made is not limited to a specific one and can be any material harder than the material of which the body of the light reflection plate  413  is made, for example, diamond, quartz, sapphire, lithium tantalate, potassium niobate, or a carbon nitride film. It is, in particular, preferable to use diamond. The hard layer  415  is provided as necessary and can be omitted. 
     The lower surface of the light reflection plate  413  is fixed to the base  411  via the spacer  412 . The light reflection plate  413  can therefore swing around the first axis J 1  without the lower surface of the light reflection plate  413  coming into contact with the shafts  421 ,  422 , the frame  43 , or the shafts  441 ,  442 ,  443 ,  444 . 
     Further, the base  411  is located inside the outer circumference of the light reflection plate  413  in the plan view. Moreover, the area of the base  411  in the plan view is preferably minimized to the extent that the base  411  can support the light reflection plate  413  via the spacer  412 . In this case, the distance between the shaft  421  and the shaft  422  can be reduced, while the area of the plate surface of the light reflection plate  413  is increased. 
     The frame  43 , which has a frame-like shape, is so disposed that it surrounds the base  411  of the movable portion  41  described above. In other words, the base  411  of the movable portion  41  is disposed inside the frame  43 , which has a frame-like shape. The frame  43  is supported by the support member  45  via the shafts  441 ,  442 ,  443 , and  444 . The base  411  of the movable portion  41  is supported by the frame  43  via the shafts  421  and  422 . 
     The length of the frame  43  in the direction along the second axis J 2  is shorter than the length thereof in the direction along the first axis J 1 . That is, a&gt;b is satisfied, where “a” represents the length of the frame  43  in the direction along the first axis J 1 , and “b” represents the length of the frame  43  in the direction along the second axis J 2 . The length of the optical scanner  40  in the direction along the second axis J 2  can be therefore reduced, while the length necessary for the shafts  421  and  422  is ensured. Since the optical scanner  40  is so disposed in the enclosure  9  that the second axis J 2  is parallel to the Z axis as will be described later, the thickness of the enclosure (length in Z-axis direction) can be reduced when the relationship a&gt;b is satisfied as described above. 
     Further, the frame  43  has a shape that follows the exterior shape of a structure formed of the base  411  of the movable portion  41  and the pair of shafts  421  and  422  in the plan view. The thus shaped frame  43  can be compact while allowing the first oscillation system formed of the movable portion  41  and the pair of shafts  421  and  422  to oscillate, that is, the movable portion  41  to oscillate around the first axis J 1 . The shape of the frame  43  is not limited to the illustrated shape but can be any frame-like shape. 
     Each of the shafts  421  and  422  and the shafts  441 ,  442 ,  443 , and  444  is elastically deformable. The shafts  421  and  422  connect the movable portion  41  to the frame  43  in such a way that the movable portion  41  is swingable around the first axis J 1 . Further, the shafts  441 ,  442 ,  443 , and  444  connect the frame  43  to the support member  45  in such a way that the frame  43  is swingable around the second axis J 2 , which is perpendicular to the first axis J 1 . 
     The shafts  421  and  422  are disposed on opposite sides of the base  411  of the movable portion  41 . Further, each of the shafts  421  and  422  has an elongated shape extending in the direction along the first axis J 1 . Each of the shafts  421  and  422  has one end connected to the base  411  and the other end connected to the frame  43 . Each of the shafts  421  and  422  is further so disposed that the central axis thereof coincides with the first axis J 1 . The thus configured shafts  421  and  422  are torsionally deformed when the movable portion  41  swings around the first axis J 1 . 
     The shafts  441 ,  442  and the shafts  443 ,  444  are disposed on opposite sides of the frame  43 . Each of the shafts  441 ,  442 ,  443 , and  444  has an elongated shape extending in the direction along the second axis J 2 . Further, each of the shafts  441 ,  442 ,  443 , and  444  has one end connected to the frame  43  and the other end connected to the support member  45 . Further, the shafts  441  and  442  are disposed on opposite sides of the second axis J 2 . Similarly, the shafts  443  and  444  are disposed on opposite sides of the second axis J 2 . The shafts  441 ,  442 ,  443 , and  444  are so configured that the shafts  441  and  442  as a whole and the shafts  443  and  444  as a whole are torsionally deformed when the frame  43  swings around the second axis J 2 . 
     As described above, the movable portion  41  swingable around the first axis J 1  and the frame  43  swingable around the second axis J 2  allow the movable portion  41  (that is, light reflection plate  43 ) to swing around the two axes perpendicular to each other, the first and second axes J 1 , J 2 . 
     The shapes of the shafts  421  and  422  and the shafts  441 ,  442 ,  443 , and  444  are not limited to those described above, and each of them may, for example, have a bent or curved portion or a branch in at least one position along the shaft. 
     The base  411 , the shafts  421  and  422 , the frame  43 , the shafts  441 ,  442 ,  443 , and  444 , and the support member  45  described above are formed integrally with each other. 
     In this embodiment, the base  411 , the shafts  421  and  422 , the frame  43 , the shafts  441 ,  442 ,  443 , and  444 , and the support member  45  are formed by etching an SOI substrate formed of a first Si layer (device layer), an SiO 2  layer (box layer), and a second Si layer (handle layer) stacked in this order. The configuration described above provides the first and second oscillation systems with excellent oscillation characteristics. Further, forming the base  411 , the shafts  421  and  422 , the frame  43 , the shafts  441 ,  442 ,  443 , and  444 , and the support member  45  by using the SOI substrate, which allows etching-based micro-processing, not only provides excellent precision in their dimensions but also reduces the size of the optical scanner  40 . 
     The first Si layer of the SOI substrate forms the base  411 , the shafts  421  and  422 , and the shafts  441 ,  442 ,  443 , and  444 . The shafts  421  and  422  and the shafts  441 ,  442 ,  443 , and  444  therefore have excellent elasticity. Further, the base  411  will not come into contact with the frame  43  when the base  411  pivots around the first axis J 1 . 
     Each of the frame  43  and the support member  45  is formed of the SOI substrate or the stacked member formed of the first Si layer, the SiO 2  layer, and the second Si layer, whereby the frame  43  and the support member  45  have excellent rigidity. Further, the SiO 2  layer and the second Si layer of the frame  43  not only function as a rib that increases the rigidity of the frame  43  but also have a function of preventing the movable portion  41  from coming into contact with the permanent magnet  46 . 
     The upper surface of each of the shafts  421  and  422 , the shafts  441 ,  442 ,  443 , and  444 , the frame  43 , and the support member  45 , which are located outside the light reflection plate  413  in the plan view, preferably undergoes antireflection processing, which prevents unwanted light incident on portions other than the light reflection plate  413  from forming stray light. The antireflection processing is not limited to specific one and can, for example, be formation of an antireflection film (dielectric multilayer film), surface roughing, and surface blackening. 
     The materials of which the base  411 , the shafts  421  and  422 , and the shafts  441 ,  442 ,  443 , and  444  are made and the method for forming these components described above are presented by way of example and are not necessarily used in the invention. 
     Further, in this embodiment, the spacer  412  and the light reflection plate  413  are also formed by etching the SOI substrate. The spacer  412  is formed of a stacked member of the SiO 2  layer and the second Si layer of the SOI substrate. The light reflection plate  413  is formed of the first Si layer of the SOI substrate. The spacer  412  and the light reflection plate  413  bonded to each other can thus be manufactured in a simple, highly precise manner by forming the spacer  412  and the light reflection plate  413  based on the SOI substrate as described above. 
     The spacer  412  is bonded to the base  411  with an adhesive, a wax material, or any other suitable bonding material (not shown). 
     The permanent magnet  46  is bonded to the lower surface of the frame  43  described above. A method for bonding the permanent magnet  46  to the frame  43  is not limited to a specific one and can, for example, be a bonding method using an adhesive. The permanent magnet  46  is magnetized in a direction inclined to the first and second axes J 1 , J 2  in the plan view. 
     In this embodiment, the permanent magnet  46  has an elongated shape (rod-like shape) extending in a direction inclined to the first and second axes J 1 , J 2 . The permanent magnet  46  is magnetized in the elongated direction. That is, the permanent magnet  46  is so magnetized that one end thereof forms an S pole and the other end thereof forms an N pole . Further, the permanent magnet  46  is so disposed that it is symmetrical with respect to the intersection of the first axis J 1  and the second axis J 2  in the plan view. 
     The inclination angle θ of the direction in which the permanent magnet  46  is magnetized (direction in which permanent magnet  46  extends) with respect to the second axis J 2  is not limited to a specific value but is preferably greater than or equal to 30° but smaller than or equal to 60°, more preferably greater than or equal to 45° but smaller than or equal to 60°, still more preferably 45°. The thus disposed permanent magnet  46  allows the movable portion  41  to swing around the second axis J 2  in a smooth, reliable manner. 
     The permanent magnet  46  can preferably be, for example, a neodymium magnet, a ferrite magnet, a samarium cobalt magnet, an Alnico magnet, or a bonded magnet. The permanent magnet  46  is a magnetized hard magnetic material and formed, for example, by placing a hard magnetic material not yet having been magnetized on the frame  43  and magnetizing the entire structure. The reason for this is that an attempt to place the permanent magnet  46 , which has been magnetized, on the frame  43  may not result in successful placement of the permanent magnet  46  in a desired position in some cases because magnetic fields produced by objects outside the apparatus and other parts in the apparatus affect the placement of the permanent magnet  46 . 
     The coil  47  is disposed immediately below the permanent magnet  46 , whereby a magnetic field produced by the coil  47  can act on the permanent magnet  46  in an efficient manner. As a result, the electricity consumption and the size of the optical scanner  40  can be reduced. The coil  47  is wound around the magnetic core  48 . The magnetic field produced by the coil  47  can thus act on the permanent magnet  46  in an efficient manner. The magnetic core  48  may be omitted. 
     The thus configured coil  47  is electrically connected to the voltage applying section  49 . When the voltage applying section  49  applies a voltage to the coil  47 , the coil  47  produces a magnetic field having a magnetic flux perpendicular to the first and second axes J 1 , J 2 . 
     The voltage applying section  49  includes a first voltage generator  491  that generates a first voltage V 1  for causing the movable portion  41  to pivot around the first axis J 1 , a second voltage generator  492  that generates a second voltage V 2  for causing the movable portion  41  to pivot around the second axis J 2 , and a voltage superimposing section  493  that superimposes the first voltage V 1  and the second voltage V 2  on each other, and the superimposed voltage from the voltage superimposing section  493  is applied to the coil  47 , as shown in  FIG. 6 . 
     The first voltage V 1  (voltage for primary scan), which is generated by the first voltage generator  491 , periodically changes at a period T 1 , as shown in  FIG. 7A . The first voltage V 1  has a sinusoidal waveform. The frequency of the first voltage V 1  (1/T 1 ) preferably ranges, for example, from 10 to 40 kHz. In this embodiment, the frequency of the first voltage V 1  is set to be equal to a torsional resonant frequency (f1) of the first oscillation system formed of the movable portion  41  and the pair of shafts  421  and  422 , whereby the angle of pivotal motion of the movable portion  41  around the first axis J 1  can be increased. 
     On the other hand, the second voltage V 2  (voltage for secondary scan), which is generated by the second voltage generator  492 , periodically changes at a period T 2  different from the period T 1 , as shown in  FIG. 7B . The second voltage V 2  has a saw-toothed waveform. The frequency of the second voltage V 2  (1/T 2 ) only needs to differ from the frequency of the first voltage V 1  (1/T 1 ) and preferably ranges, for example, from 30 to 80 Hz (about 60 Hz). In this embodiment, the frequency of the second voltage V 2  is adjusted to be a frequency different from a torsional resonant frequency (resonant frequency) of the second oscillation system formed of the movable portion  41 , the pair of shafts  421  and  422 , the frame  43 , the two pairs of shafts  441 ,  442 ,  443 , and  444 , and the permanent magnet  46 . 
     The thus set frequency of the second voltage V 2  is preferably lower than the frequency of the first voltage V 1 . In this case, the movable portion  41  is allowed to swing not only around the first axis J 1  at the frequency of the first voltage V 1  but also around the second axis J 2  at the frequency of the second voltage V 2  in a more reliable, smoother manner. 
     Now, let f1 [Hz] be the torsional resonant frequency of the first oscillation system and f2 [Hz] be the torsional resonant frequency of the second oscillation system, and f1 and f2 preferably satisfy f2&lt;f1, more preferably 10×f2≦f1. Satisfying the relationship described above allows the movable portion  41  to pivot not only around the first axis J 1  at the frequency of the first voltage V 1  but also around the second axis J 2  at the frequency of the second voltage V 2  in a smoother manner. On the other hand, when f1≦f2, the first oscillation system can oscillate at the frequency of the second voltage V 2 . 
     The thus configured first voltage generator  491  and second voltage generator  492  are connected to the controller  6  and driven based on signals from the controller  6 . The voltage superimposing section  493  is connected to the first voltage generator  491  and the second voltage generator  492 . 
     The voltage superimposing section  493  includes an adder  493   a  for applying a voltage to the coil  47 . The adder  493   a  receives the first voltage V 1  from the first voltage generator  491 , receives the second voltage V 2  from the second voltage generator  492 , superimposes the voltages on each other, and applies the resultant voltage to the coil  47 . 
     A description will next be made of a method for driving the optical scanner  40 . It is assumed that the frequency of the first voltage V 1  is set to be equal to the torsional resonant frequency of the first oscillation system, and that the frequency of the second voltage V 2  is set to be not only different from the torsional resonant frequency of the second oscillation system but also smaller than the frequency of the first voltage V 1  (for example, the frequency of the first voltage V 1  is set at 15 kHz, and the frequency of the second voltage V 2  is set at 60 Hz). 
     For example, when the voltage superimposing section  493  superimposes the first voltage V 1  shown in  FIG. 7A  and the second voltage V 2  shown in  FIG. 7B  on each other and applies the superimposed voltage to the coil  47 , the first voltage V 1  produces the following alternately switching magnetic fields: a magnetic field that causes the one end (N pole) of the permanent magnet  46  to be attracted to the coil  47  and the other end (S pole) of the permanent magnet  46  to be repulsed from the coil  47  (the magnetic field is referred to as “magnetic field A 1 ”); and a magnetic field that causes the one end (N pole) of the permanent magnet  46  to be repulsed from the coil  47  and the other end (S pole) of the permanent magnet  46  to be attracted to the coil  47  (the magnetic field is referred to as “magnetic field A 2 ”). 
     When the magnetic field A 1  and the magnetic field A 2  are alternately switched from each other as described above, oscillation having a torsional oscillation component around the first axis J 1  is excited in the frame  43 , and the oscillation causes the shafts  421  and  422  to be torsionally deformed and hence the movable portion  41  to swing around the first axis J 1  at the frequency of the first voltage V 1 . Since the frequency of the first voltage V 1  is equal to the torsional resonant frequency of the first oscillation system, the resonance action (resonant oscillation) allows the movable portion  41  to swing at a large amplitude. That is, even when the oscillation produced in the frame  43  and having a torsional oscillation component around the first axis J 1  has a small amplitude, the angle of swing motion of the movable portion  41  around the first axis J 1  produced by the oscillation can be increased. 
     On the other hand, the second voltage V 2  produces the following alternately switching magnetic fields: a magnetic field that causes the one end (N pole) of the permanent magnet  46  to be attracted to the coil  47  and the other end (S pole) of the permanent magnet  46  to be repulsed from the coil  47  (the magnetic field is referred to as “magnetic field B 1 ”); and a magnetic field that causes the one end (N pole) of the permanent magnet  46  to be repulsed from the coil  47  and the other end (S pole) of the permanent magnet  46  to be attracted to the coil  47  (the magnetic field is referred to as “magnetic field B 2 ”). 
     When the magnetic field B 1  and the magnetic field B 2  are alternately switched from each other as described above, the shafts  441 ,  442  and the shafts  443 ,  444  are torsionally deformed and the frame  43  along with the movable portion  41  swings around the second axis J 2  at the frequency of the second voltage V 2 . Since the frequency of the second voltage V 2  is set to be greatly lower than the frequency of the first voltage V 1  and the torsional resonant frequency of the second oscillation system is set to be lower than the torsional resonant frequency of the first oscillation system as described above, the pivotal motion of the movable portion  41  around the first axis J 1  will not occur at the frequency of the second voltage V 2 . 
     As described above, when the first voltage V 1  and the second voltage V 2  superimposed on each other are applied to the coil  47  in the optical scanner  40 , the movable portion  41  can pivot not only around the first axis J 1  at the frequency of the first voltage V 1  but also around the second axis J 2  at the frequency of the second voltage V 2 . The thus configured optical scanner  40  allows the cost and size of the apparatus to be reduced and causes the movable portion  41  to swing around the first and second axes J 1 , J 2  based on the electro-magnetic drive method (moving magnet method), whereby the drawing laser light LL reflected off the light reflection portion  414  can be deflected for two-dimensional scanning. Further, since the number of parts that form the drive source (permanent magnet and coil) can be reduced, the resultant configuration can be simple and compact. Moreover, since the coil  47  is set apart from the oscillation systems of the optical scanner  40 , heat generated by the coil  47  will not adversely affect the oscillation systems. 
     The configuration of the optical scanner  40  has been described above in detail. According to the gimbal-type, two-dimensional-scanning optical scanner  40  described above, which is alone capable of deflecting the drawing laser light LL for two-dimensional scanning, the size of the optical scan section  4  can be reduced and alignment adjustment thereof can be readily made as compared, for example, with a configuration in which two one-dimensional-scanning optical scanners are combined with each other to deflect the drawing laser light LL for two-dimensional scanning. 
     The optical scanner  40  is an electro-magnetically driven optical scanner driven by using the permanent magnet  46  and the coil  47 . The thus configured optical scanner  40  requires the permanent magnet  46  and the coil  47  to face each other as shown in  FIG. 5 , which increases the thickness of the optical scanner  40  (length in the direction of an axis J 3  that intersects the intersection of the first and second axes J 1 , J 2  and is perpendicular to the two axes). However, the size of the optical scanner  40  in the in-plane direction in the plane including the first and second axes J 1 , J 2  can be reduced. As described above, the optical scanner  40 , the size of which in the in-plane direction described above is reduced instead of the size in the thickness direction, can form an optical scanner suitable for the image display apparatus  1 . 
     The optical scanner  40  having the configuration described above is so disposed in the enclosure  9  that the light reflection portion  414  is perpendicular to the XY plane when the optical scanner  40  is not driven (when no voltage is applied to the coil  47 ) as shown in  FIGS. 1 and 3 . In other words, the optical scanner  40  is so disposed in the enclosure  9  that the plane including the first and second axes J 1 , J 2  is perpendicular to the XY plane (the axis J 3  is present in the plane F). Since the optical scanner  40  has a small size in the in-plane direction in the plane including the first and second axes J 1 , J 2  as described above, disposing the optical scanner  40  as described above allows the size (thickness) of the image display apparatus  1  (enclosure  9 ) to be reduced. Although the optical scanner  40  is not so thin in the direction of the axis J 3  but is so disposed in the image display apparatus  1  that the axis J 3  is present in the plane F, an increase in the size of the apparatus resulting from the thickness in the direction of the axis J 3  is minimized. 
     Further, the drawing laser light LL having passed through the prism  3  is incident on the light reflection portion  414  in a direction inclined to the axis J 3 . When the drawing laser light LL is incident on the light reflection portion  414  in a direction inclined to the axis J 3  (normal to light reflection surface  414   a ), the drawing laser light LL deflected by the optical scanner  40  for scanning can exit out of the enclosure  9  without interfering with other members (prism  3 , for example) in the enclosure  9 . It is therefore not necessary to provide a flat mirror, a prism, or any other optical component for changing the optical path of the drawing laser light LL deflected by the optical scanner  40  for scanning, whereby the size of the image display apparatus  1  can be reduced. 
     Further, in the optical scanner  40 , the amplitude of the oscillation (angle of swing motion) of the resonantly driven movable portion  41  around the first axis J 1  is greater than the amplitude of the oscillation (angle of swing motion) of the non-resonantly driven movable portion  41  around the second axis J 2 . The thus configured optical scanner  40  is so disposed that the amplitude in the Z-axis direction is greater than the amplitude in the in-plane direction in the XY plane. That is, the optical scanner  40  is so disposed that the first axis J 1  is parallel to the in-plane direction in the XY plane (coincides with the first plane F) and the second axis J 2  is parallel to the Z axis. Disposing the optical scanner  40  as described above provides the following advantageous effects. 
     Since the drawing laser light LL is incident on the light reflection portion  414  in a direction inclined to the axis J 3  as described above, the drawable region S irradiated with the drawing laser light LL deflected by the light reflection portion  414  for two-dimensional scanning is shaped as shown in  FIGS. 8A and 8B .  FIG. 8A  shows a drawable region produced when the optical scanner  40  is so disposed that the first axis J 1  is parallel to the in-plane direction in the XY plane and the second axis J 2  is parallel to the Z axis as described in this embodiment of the invention, and  FIG. 8B  shows a drawable region produced when the optical scanner  40  is so disposed that the first axis J 1  is parallel to the Z axis and the second axis J 2  is parallel to the in-plane direction in the XY plane as in the related art. 
     As shown in  FIGS. 8A and 8B , the distortion of the drawable region S in  FIG. 8A , which shows this embodiment of the invention, is smaller than in  FIG. 8B , which shows related art, whereby this embodiment of the invention provides a larger effective rectangular drawing region (region actually irradiated with the drawing laser light LL for image display) S′ ensured in the drawable region S. Therefore, the drawable region S can be used more effectively in  FIG. 8A  than in  FIG. 8B , and a more efficient, larger image can be drawn. 
     Since the length “b” of the frame  43  along the second axis J 2  is shorter than the length “a” of the frame  43  along the first axis J 1  as described above, disposing the optical scanner  40  in the enclosure  9  as described above reduces the length of the optical scanner  40  in the Z-axis direction, whereby the thickness of the image display apparatus  1  can be reduced. 
       1 - 4 . Detector 
     The detector  5  has a function of detecting the intensity of the drawing laser light LL (each of the laser light fluxes RR, GG, and BB). The thus configured detector  5  includes a light receiving device  51 , such as a photodiode, disposed in the enclosure  9 . The light incident surface  31  of the prism  3  is configured to slightly (at a reflectance of about 0.1%, for example) reflect the laser light fluxes RR, GG, and BB, and the light receiving device  51  is located on the optical paths of the reflected light fluxes. The light receiving device  51  outputs a signal (voltage) having a magnitude according to the intensity of each of the received reflected light fluxes, and the intensity of each of the laser light fluxes RR, GG, and BB can be detected based on the signal. 
     Information on the detected intensities of the laser light fluxes RR, GG, and BB is sent to the controller  6 , which then controls the drive operation of the laser light sources  21 R,  21 G, and  21 B based on the received information. 
     Specifically, the reflectance and transmittance representing how much the collimator lenses  22 R,  22 G, and  22 B and the dichroic mirrors  23 R,  23 G, and  23 B reflect and transmit the laser light fluxes RR, GG, and BB and the reflectance representing how much the light incident surface  31  reflects the laser light fluxes RR, GG, and BB are measured in advance, and the measurement information is stored in a memory (not shown) in the controller  6 . 
     Subsequently, for example, before image drawing is initiated, the controller  6  sends a drive signal of a predetermined magnitude (voltage) to the drive circuit associated with the laser light source  21 R, which then emits the laser light flux RR. Part of the laser light flux RR is then reflected off the light incident surface  31  of the prism  3 , and the light receiving device  51  receives the reflected light and detects the intensity thereof. The actual intensity of the laser light flux RR emitted from laser light source  21 R is then determined based on the reflectance stored in the memory described above and representing how much each of the portions described above reflects the laser light flux RR. The relationship between the intensity of the laser light flux RR and the magnitude (voltage value) of the drive signal is thus determined, and the magnitude of the drive signal necessary to provide the laser light flux RR of a predetermined intensity is found. 
     The relationship is stored in the memory described above. To draw an image, the controller  6  sends the drive circuit a desired drive signal that causes the laser light source  21 R to emit a laser light flux RR of a desired intensity based on the relationship. The same holds true for the laser light fluxes GG and BB. Specifically, the relationship between the intensity of each of the laser light fluxes GG and BB and the magnitude of the corresponding drive signal is determined, and the controller  6  sends the drive circuit desired drive signals that cause the laser light sources  21 G and  21 B to emit laser light fluxes GG and BB of desired intensities based on the determined relationships. 
     Drawing laser light LL of a desired color and luminance can thus be produced, and the image display characteristics are improved. 
     The above description has been made with reference to the case where the relationship between the intensity of the laser light flux RR and the magnitude (voltage value) of the drive signal is provided before image drawing is initiated. The relationship is not necessarily provided before image drawing is initiated and may, for example, be provided in the course of image drawing. The effective drawing region S′ in the drawable region S is irradiated with the drawing laser light LL, whereas the other region (non-drawing region S″) is not irradiated therewith, as described above. In view of the fact described above, the relationship between the intensity of the laser light flux RR and the magnitude (voltage value) of the drive signal may alternatively be provided as described above during a period when an image is being drawn but the movable portion  41  (light reflection portion  414 ) faces the non-drawing region S″ and no drawing laser light LL is outputted. 
       1 - 5 . Controller 
     The controller  6  has a function of controlling the operation of the drawing light source unit  2  and the light scan section  4 . Specifically, the controller  6  drives the optical scanner  40  to cause the movable portion  41  to swing around the first and second axes J 1 , J 2  and drives the drawing light source unit  2  to emit the drawing laser light LL in synchronization with the swing motion of the movable portion  41 . The controller  6  drives the laser light sources  21 R,  21 G, and  21 B to emit laser light fluxes RR, GG, and BB of predetermined intensities at predetermined timings based, for example, on image data sent from an external computer so that the drawing laser light LL of a predetermined color and intensity (luminance) is emitted at a predetermined timing. As a result, an image according to the image data is displayed on the object  10 . 
     The configuration of the image display apparatus  1  has been described in detail. 
     In the image display apparatus  1  described above, the members thereof, that is, the laser light sources  21 R,  21 G, and  21 B, the collimator lenses  22 R,  22 G, and  22 B, the dichroic mirrors  23 R,  23 G, and  23 B, the prism  3 , the optical scanner  40 , and the light receiving device  51  are arranged in a flat plane (the same plane) extending in the direction in which the XY plane extends. The optical axes of the laser light fluxes RR, GG, and BB emitted from the laser light sources  21 R,  21 G, and  21 B and the optical axis of the drawing laser light LL, which is the combination of the laser light fluxes RR, GG, and BB, are present in the same plane (first plane F) parallel to the XY plane until the drawing laser light LL is incident on the optical scanner  40 . 
     Further, in the image display apparatus  1 , since the prism  3  inclines the optical axis of the drawing laser light LL within the first plane F, the components of the image display apparatus  1  (optical scanner  40 , in particular) can be arranged in the flat plane. In this case, the components of the image display apparatus  1  can be aligned with each other in the flat plane, whereby the image display apparatus  1  can be readily assembled. Further, in the image display apparatus  1 , since the prism  3  shapes the drawing laser light LL, excellent image display characteristics are provided. 
     2. Head-up Display 
     A description will next be made of the configuration of a head-up display based on the image display apparatus according to the embodiment of the invention. 
       FIG. 9  is a perspective view showing a head-up display based on the image display apparatus according to the embodiment of the invention. 
     In a head-up display system  200 , the image display apparatus  1  is accommodated in a dashboard of an automobile to form a head-up display  210 , as shown in  FIG. 9 . The head-up display  210  can display a predetermined image, such as a displayed image that guides a driver to a destination, on a windshield  220 . The head-up display system  200  is not necessarily used with an automobile but may be used, for example, with an airplane and a ship. 
     3. Head-mounted Display 
     A description will next be made of a head-mounted display based on the image display apparatus according to the embodiment of the invention (head-mounted display according to an embodiment of the invention). 
       FIG. 10  is a perspective view showing a head-mounted display according to an embodiment of the invention. 
     A head-mounted display  300  includes glasses  310  and the image display apparatus  1  mounted on the glasses  310 , as shown in  FIG. 10 . The image display apparatus  1  displays a predetermined image in a display section (light reflector)  320  provided in a portion of the glasses  310  that originally functions as a lens, and the image is viewed with one of the eyes. 
     The display section  320  may be transparent or opaque. When the display section  320  is transparent, information from the image display apparatus  1  can be superimposed on information from the real world and the superimposed information can be viewed. Further, the display section  320  only needs to reflect at least part of light incident thereon and can, for example, be a half-silvered mirror. 
     The head-mounted display  300  may alternatively be provided with two image display apparatus  1 , and two display sections display images viewed with both eyes. 
     The image display apparatus and the head-mounted display according to the embodiments of the invention have been described with reference to the drawings, but the invention is not limited thereto. The configuration of each of the components can be replaced with an arbitrary configuration having the same function. Further, other arbitrary components may be added to the embodiments of the invention.