Patent Publication Number: US-2011069286-A1

Title: Projection display apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-097490, filed on Apr. 13, 2009; and Japanese Patent Application No. 2009-179667, filed on Jul. 31, 2009; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a projection display apparatus which includes; a light source, a reflective light valve configured to modulate light emitted from the light source, and a projection unit configured to project light emitted from the reflective light valve on a projection plane. 
     2. Description of the Related Art 
     Recently, there has been known a projection display apparatus including a solid light source such as a laser light source, a light valve configured to modulate light emitted from the solid light source, and a projection unit configured to project the light outputted from the light valve on a projection plane. 
     A technique has been known in which a reflective light valve, such as a digital micromirror device (DMD), is used as the light valve. Another technique has been proposed in which an aperture shields light other than that forming an image, namely unwanted light, among light reflected by the reflective light valve (for example, Japanese Patent Application Publication No. 2002-122938). Specifically, the aperture is placed near the reflective light valve, and is configured to shield unwanted light reflected by the reflective light valve, near the reflective light valve. 
     As described above, near the reflective light valve, the aperture shields unwanted light reflected by the reflective light valve. Specifically, the aperture shields unwanted light near an object plane of a projection lens. In the projection display apparatus, when the aperture is away, even a little, from the reflective light valve placed at the object plane, unwanted light cannot be removed sufficiently. 
     SUMMARY OF THE INVENTION 
     A projection display apparatus of first aspect includes a housing case (housing case  200 ) housing a light source (red solid light sources  111 R, green solid light sources  111 G, blue solid light sources  111 B); a reflective light valve (DMD  500 R, DMD  500 G, DMD  500 B) configured to modulate light emitted from the light source; and a projection unit (projection unit  150 ) configured to project light emitted from the reflective light valve on a projection plane. The projection display apparatus is placed along a first placement face substantially parallel to the projection plane and along a second placement face substantially orthogonal to the first placement face. The housing case has a base plate (base plate  230 ) and a ceiling plate (ceiling plate  240 ), the base plate facing the second placement face, the ceiling plate being provided on an opposite side to the base plate. The ceiling plate is provided with a transmission area (transmission area  185 ) and a projection-plane-side shield plate (projection-plane-side shield plate  800 ). The transmission area is an area through which light emitted from the projection unit passes. The projection-plane-side shield plate is placed closer to the projection plane than the transmission area. The projection-plane-side shield plate is configured to shield unwanted light being other than light forming an image among light passed through the transmission area. 
     In the first aspect, the ceiling plate has a side shield plate (side shield plate  801 A, side shield plate  801 B) provided adjacently to the transmission area in a horizontal direction parallel to the projection plane. The side shield plate is configured to shield unwanted light being other than light forming an image among light passed through the transmission area. 
     In the first aspect, the projection-plane-side shield plate has a shape extending in a horizontal direction parallel to the projection plane. An area (neutral density filters  830 , diffuser plates  840 , small holes  850 ) having a predetermined transmittance is provided to each of end portions of the projection-plane-side shield plate in the horizontal direction parallel to the projection plane. 
     In the first aspect, the projection display apparatus further includes a support mechanism configured to support the projection-plane-side shield plate movable in an orthogonal direction to the projection plane. 
     In the first aspect, the projection display apparatus further includes a support mechanism configured to support the projection-plane-side shield plate movable in a direction orthogonal to both of a horizontal direction parallel to the projection plane and a direction normal to the projection plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a projection display apparatus  100  according to a first embodiment. 
         FIG. 2  is a view of the projection display apparatus  100  according to the first embodiment when viewed from side. 
         FIG. 3  is a view of the projection display apparatus  100  according to the first embodiment when viewed from above. 
         FIG. 4  is a view showing a light source unit  110  according to the first embodiment. 
         FIG. 5  is a view of a color separating-combining unit  140  and a projection unit  150  according to the first embodiment. 
         FIG. 6  is a view showing a ceiling plate  240  according to the first embodiment. 
         FIG. 7  is a view showing a ceiling plate  240  according to the first embodiment. 
         FIG. 8  is a view showing a ceiling plate  240  according to the first embodiment. 
         FIG. 9  is a view showing a projection-plane-side shield plate  800  according to the first embodiment. 
         FIG. 10  is a diagram illustrating unwanted-light shielding according to the first embodiment. 
         FIG. 11  is a diagram illustrating the unwanted-light shielding according to the first embodiment. 
         FIG. 12  is a diagram illustrating the unwanted-light shielding according to the first embodiment. 
         FIG. 13  is a view showing a projection-plane-side shield plate  800  according to Modification 1. 
         FIG. 14  is a view showing a projection-plane-side shield plate  800  according to Modification 1. 
         FIG. 15  is a view showing a projection-plane-side shield plate  800  according to Modification 1. 
         FIG. 16  is a diagram illustrating unwanted-light shielding according to Modification 1. 
         FIG. 17  is a view showing a projection-plane-side shield plate  800  according to Modification 2. 
         FIG. 18  is a view showing a projection-plane-side shield plate  800  according to Modification 2. 
         FIG. 19  is a view showing a projection-plane-side shield plate  800  according to Modification 2. 
         FIG. 20  is a perspective view showing a projection display apparatus  100  according to Modification 3. 
         FIG. 21  is a perspective view showing a projection display apparatus  100  according to Modification 4. 
         FIG. 22  is a view of a projection display apparatus  100  according to a second embodiment when viewed from side. 
         FIG. 23  is a view showing a first configuration example according to a third embodiment. 
         FIG. 24  is a view showing a support mechanism  900  of the first configuration example according to the third embodiment. 
         FIG. 25  is a view showing the support mechanism  900  of the first configuration example according to the third embodiment. 
         FIG. 26  is a view showing the support mechanism  900  of the first configuration example according to the third embodiment. 
         FIG. 27  is a view showing the support mechanism  900  of the first configuration example according to the third embodiment. 
         FIG. 28  is a view showing the support mechanism  900  of the first configuration example according to the third embodiment. 
         FIG. 29  is a view showing a second configuration example according to the third embodiment. 
         FIG. 30  is a view showing a support mechanism  900  of the second configuration example according to the third embodiment. 
         FIG. 31  is a view showing the support mechanism  900  of the second configuration example according to the third embodiment. 
         FIG. 32  is a view showing the support mechanism  900  of the second configuration example according to the third embodiment. 
         FIG. 33  is a view showing the support mechanism  900  of the second configuration example according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a projection display apparatus according to embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar reference signs are attached to the same or similar units and portions. 
     It should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is needless to say that the drawings also include portions having different dimensional relationships and ratios from each other. 
     Overview of Embodiments 
     A projection display apparatus of first aspect includes a housing case housing a light source; a reflective light valve configured to modulate light emitted from the light source; and a projection unit configured to project light emitted from the reflective light valve on a projection plane. The projection display apparatus is placed along a first placement face substantially parallel to the projection plane and along a second placement face substantially orthogonal to the first placement face. The housing case has a base plate and a ceiling plate, the base plate facing the second placement face, the ceiling plate being provided on an opposite side to the base plate. The ceiling plate is provided with a transmission area and a projection-plane-side shield plate. The transmission area is an area through which light emitted from the projection unit passes. The projection-plane-side shield plate is placed closer to the projection plane than the transmission area. The projection-plane-side shield plate is configured to shield unwanted light being other than light forming an image among light passed through the transmission area. 
     In the embodiments, the ceiling plate is provided with the projection-plane-side shield plate placed closer to the projection plane than the transmission area. The projection-plane-side shield plate is configured to shield light other than that forming an image, namely unwanted light, among light that has passed through the transmission area. In other words, near the projection plane where an image plane is formed, the projection-plane-side shield plate shields unwanted light. Accordingly, unwanted light reflected by the reflective light valve can be removed sufficiently, compared to the case where the unwanted light is shielded by an aperture placed near the reflective light valve in which an object plane is formed. 
     First Embodiment 
     (Configuration of Projection Display Apparatus) 
     Hereinafter, a configuration of a projection display apparatus according to a first embodiment will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a perspective view of a projection display apparatus  100  according to the first embodiment.  FIG. 2  is a view of the projection display apparatus  100  according to the first embodiment when viewed from side. 
     As shown in  FIGS. 1 and 2 , the projection display apparatus  100  includes a housing case  200  and is configured to project an image on a projection plane  300 . The projection display apparatus  100  is arranged along a first placement surface (a wall surface  420  shown in  FIG. 2 ) and a second placement surface (a floor surface  410  shown in  FIG. 2 ) substantially orthogonal to the first placement surface. 
     Here, the first embodiment is illustrated for a case where the projection display apparatus  100  projects image light on the projection plane  300  provided on a wall surface (wall surface projection). An arrangement of the housing case  200  in this case is referred to as a wall surface projection arrangement. In the first embodiment, the first placement surface substantially parallel to the projection plane  300  is the wall surface  420 . 
     In the first embodiment, a horizontal direction parallel to the projection plane  300  is referred to as “a width direction”, a orthogonal direction to the projection plane  300  is referred to as “a depth direction”, and an orthogonal direction to both of the width direction and the depth direction is referred to as “a height direction”. 
     The housing case  200  has a substantially rectangular parallelepiped shape. The size of the housing case  200  in the depth direction and the size of the housing case  200  in the height direction are smaller than the size of the housing case  200  in the width direction. The size of the housing case  200  in the depth direction is almost equal to a projection distance from a reflection mirror (a concave mirror  152  shown in  FIG. 2 ) to the projection plane  300 . In the width direction, the size of the housing case  200  is almost equal to the size of the projection plane  300 . In the height direction, the size of the housing case  200  is determined depending on a position where the projection plane  300  is provided. 
     Specifically, the housing case  200  includes a projection-plane-side sidewall  210 , a front-side sidewall  220 , a base plate  230 , a ceiling plate  240 , a first-lateral-surface-side sidewall  250 , and a second-lateral-surface-side sidewall  260 . 
     The projection-plane-side sidewall  210  is a plate-shaped member facing the first placement surface (the wall surface  420  in the first embodiment) substantially parallel to the projection plane  300 . The front-side sidewall  220  is a plate-shaped member provided on the side opposite from the projection-plane-side sidewall  210 . The base plate  230  is a plate-shaped member facing the second placement surface (a floor surface  410  in the first embodiment) other than the first placement surface substantially parallel to the projection plane  300 . The ceiling plate  240  is a plate-shaped member provided on the side opposite from the base plate  230 . The first-lateral-surface-side sidewall  250  and the second-lateral-surface-side sidewall  260  are plate-shaped members forming both ends of the housing case  200  in the width direction. 
     The housing case  200  houses a light source unit  110 , a power supply unit  120 , a cooling unit  130 , a color separating-combining unit  140 , a projection unit  150 . The projection-plane-side sidewall  210  includes a projection-plane-side recessed portion  160 A and projection-plane-side recessed portion  160 B. The front-side sidewall  220  includes front-side protruding portion  170 . The ceiling plate  240  includes a ceiling-plate recessed portion  180  and a projection-plane-side shield plate  800 . The first-lateral-surface-side sidewall  250  includes cable terminals  190 . 
     The light source unit  110  is a unit including multiple solid light sources (solid light sources  111  shown in  FIG. 4 ). Each of the solid light sources  111  is a light source such as a laser diode (LD). In the first embodiment, the light source unit  110  includes red solid light sources (red solid light sources  111 R shown in  FIG. 4 ) configured to emit red component light R, green solid light sources (green solid light sources  111 G shown in  FIG. 4 ) configured to emit green component light G, and blue solid light sources (blue solid light sources  111 B shown in  FIG. 4 ) configured to emit blue component light B. The light source unit  110  will be described in detail below (see  FIG. 4 ). 
     The power supply unit  120  is a unit to supply power to the projection display apparatus  100 . The power supply unit  120  supplies power to the light source unit  110  and the cooling unit  130 , for example. 
     The cooling unit  130  is a unit to cool the multiple solid light sources provided in the light source unit  110 . Specifically, the cooling unit  130  cools each of the solid light sources by cooling jackets (cooling jackets  131  shown in  FIG. 4 ) on which the solid light source is mounted. 
     The cooling unit  130  may be configured to cool the power supply unit  120  and a light valve (DMDs  500  which will be described later) in addition of the solid light sources. 
     The color separating-combining unit  140  combines the red component light R emitted from the red solid light sources, the green component light G emitted from the green solid light sources, and the blue component light B emitted from the blue solid light sources. In addition, the color separating-combining unit  140  separates combined light including the red component light R, the green component light G, and the blue component light B, and modulates the red component light R, the green component light G, and the blue component light B. Moreover, the color separating-combining unit  140  recombines the red component light R, the green component light G, and the blue component light B, and thereby emits image light to the projection unit  150 . The color separating-combining unit  140  will be described in detail later (see  FIG. 5 ). 
     The projection unit  150  projects the light (image light) outputted from the color separating-combining unit  140  on the projection plane  300 . Specifically, the projection unit  150  includes a projection lens group (a projection lens group  151  shown in  FIG. 5 ) configured to project the light outputted from the color separating-combining unit  140  on the projection plane  300 , and a reflection mirror (a concave mirror  152  shown in  FIG. 5 ) configured to reflect the light, outputted from the projection lens group, to the projection plane  300 . The projection unit  150  will be described in detail later. 
     The projection-plane-side recessed portion  160 A and the projection-plane-side recessed portion  160 B are provided in the projection-plane-side sidewall  210 , and each have a shape recessed inward of the housing case  200 . The projection-plane-side recessed portion  160 A and the projection-plane-side recessed portion  160 B extend to the respective ends of the housing case  200 . The projection-plane-side recessed portion  160 A and the projection-plane-side recessed portion  160 B are each provided with a vent hole through which the inside and the outside of the housing case  200  are in communication with each other. 
     In the first embodiment, the projection-plane-side recessed portion  160 A and the projection-plane-side recessed portion  160 B extend in the width direction of the housing case  200 . For example, the projection-plane-side recessed portion  160 A is provided with an air inlet as the vent hole for allowing the air outside the housing case  200  to flow into the inside of the housing case  200 . The projection-plane-side recessed portion  160 B is provided with an air outlet as the vent hole for allowing the air inside the housing case  200  to flow out into the outside of the housing case  200 . 
     The front-side protruding portion  170  is provided in the front-side sidewall  220 , and has a shape protruding to the outside of the housing case  200 . The front-side protruding portion  170  is provided at a substantially center portion of the front-side sidewall  220  in the width direction of the housing case  200 . A space formed by the front-side protruding portion  170  inside the housing case  200  is used for placing the projection unit  150  (the concave mirror  152  shown in  FIG. 5 ). 
     The ceiling-plate recessed portion  180  is provided in the ceiling plate  240 , and has a shape recessed inward of the housing case  200 . The ceiling-plate recessed portion  180  includes an inclined surface  181  extending downwardly toward the projection plane  300 . The inclined surface  181  has a transmission area  185  through which light outputted from the projection unit  150  is transmitted (projected) toward the projection plane  300 . 
     The projection-plane-side shield plate  800  is provided on the ceiling plate  240 , at a position closer to the projection plane  300  than the transmission area  185 . The projection-plane-side shield plate  800  has a shape extending in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). 
     The cable terminals  190  are provided to the first-lateral-surface-side sidewall  250 , and are terminals such as a power supply terminal and an image signal terminal. Here, the cable terminals  190  may be provided to the second-lateral-surface-side sidewall  260 . 
     (Arrangement of Units in Housing Case in Width Direction) 
     Hereinafter, arrangement of the units in the width direction in the first embodiment will be described with reference to  FIG. 3 .  FIG. 3  is a view of the projection display apparatus  100  according to the first embodiment when viewed from above. 
     As shown in  FIG. 3 , the projection unit  150  is arranged in a substantially center of the housing case  200  in a horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). 
     The light source unit  110  and the cooling unit  130  are arranged in the line with the projection unit  150  in the width direction of the housing case  200 . Specifically, the light source unit  110  is arranged in the line at one of the sides of the projection unit  150  in the width direction of the housing case  200  (the side extending toward the second-lateral-surface-side sidewall  260 ). The cooling unit  130  is arranged in the line at the other side of the projection unit  150  in the width direction of the housing case  200  (the side extending to the first-lateral-surface-side sidewall  250 ). 
     The power supply unit  120  is arranged in the line, with the projection unit  150  in the width direction of the housing case  200 . Specifically, the power supply unit  120  is arranged in the line at the same side of the projection unit  150  as the light source unit  110  in the width direction of the housing case  200 . The power supply unit  120  is preferably arranged between the projection unit  150  and the light source unit  110 . 
     (Configuration of Light Source Unit) 
     Hereinafter, a configuration of the light source unit according to the first embodiment will be described with reference to  FIG. 4 .  FIG. 4  is a view showing the light source unit  110  according to the first embodiment. 
     As shown in  FIG. 4 , the light source unit  110  includes multiple red solid light sources  111 R, multiple green solid light sources  111 G and multiple blue solid light sources  111 B. 
     The red solid light sources  111 R are red solid light sources, such as LDs, configured to emit red component light R as described above. Each of the red solid light sources  111 R includes a head  112 R to which an optical fiber  113 R is connected. 
     The optical fibers  113 R connected to the respective heads  112 R of the red solid light sources  111 R are bundled by a bundle unit  114 R. In other words, the light beams emitted from the respective red solid light sources  111 R are transmitted through the optical fibers  113 R, and thus are gathered into the bundle unit  114 R. 
     The red solid light sources  111 R are mounted on respective cooling jackets  131 R. For example, the red solid light sources  111 R are fixed to respective cooling jackets  131 R by screwing. The red solid light sources  111 R are cooled by respective cooling jackets  131 R. 
     The green solid light sources  111 G are green solid light sources, such as LDs, configured to emit green component light G as described above. Each of the green solid light sources  111 G includes a head  112 G to which an optical fiber  113 G is connected. 
     The optical fibers  113 G connected to the respective heads  112 G of the green solid light sources  111 G are bundled by a bundle unit  114 G. In other words, the light beams emitted from all the green solid light sources  111 G are transmitted through the optical fibers  113 G, and thus are gathered into the bundle unit  114 G. 
     The green solid light sources  111 G are mounted on respective cooling jackets  131 G. For example, the green solid light sources  111 G are fixed to respective cooling jackets  131 G by screwing. The green solid light sources  111 G are cooled by respective cooling jackets  131 G. 
     The blue solid light sources  111 B are blue solid light sources, such as LDs, configured to emit blue component light B as described above. Each of the blue solid light sources  111 B includes a head  112 B to which an optical fiber  113 B is connected. 
     The optical fibers  113 B connected to the respective heads  112 B of the blue solid light sources  111 B are bundled by a bundle unit  114 B. In other words, the light beams emitted from all the blue solid light sources  111 B are transmitted through the optical fibers  113 B, and thus are gathered into the bundle unit  114 B. 
     The blue solid light sources  111 B are mounted on respective cooling jackets  131 B. For example, the blue solid light sources  111 B are fixed to respective cooling jackets  131 B by screwing. The blue solid light sources  111 B are cooled by respective cooling jackets  131 B. 
     (Configurations of Color Separating-Combining Unit and Projection Unit) 
     Hereinafter, configurations of the color separating-combining unit and the projection unit according to the first embodiment will be described with reference to  FIG. 5 .  FIG. 5  is a view showing the color separating-combining unit  140  and the projection unit  150  according to the first embodiment. The projection display apparatus  100  based on the DLP (Digital Light Processing) technology (registered trademark) is illustrated in the first embodiment. 
     As shown in  FIG. 5 , the color separating-combining unit  140  includes a first unit  141  and a second unit  142 . 
     The first unit  141  is configured to combine the red component light R, the green component light G, and the blue component light B, and to output the combine light including the red component light R, the green component light G, and the blue component light B to the second unit  142 . 
     Specifically, the first unit  141  includes multiple rod integrators (a rod integrator  10 R, a rod integrator  10 G, and a rod integrator  10 B), a lens group (a lens  21 R, a lens  21 G, a lens  21 B, a lens  22 , and a lens  23 ), and a mirror group (a mirror  31 , a mirror  32 , a mirror  33 , a mirror  34 , and a mirror  35 ). 
     The rod integrator  1 OR includes a light incident surface, a light output surface, and a light reflection side surface provided between an outer circumference of the light incident surface and an outer circumference of the light output surface. The rod integrator  10 R uniformizes the red component light R outputted from the optical fibers  113 R bundled by the bundle unit  114 R. More specifically, the rod integrator  10 R makes the red component light R uniform by reflecting the red component light R with the light reflection side surface. 
     The rod integrator  10 G includes a light incident surface, a light output surface, and a light reflection side surface provided between an outer circumference of the light incident surface and an outer circumference of the light output surface. The rod integrator  10 G uniformizes the green component light G outputted from the optical fibers  113 G bundled by the bundle unit  114 G. More specifically, the rod integrator  10 G makes the green component light G uniform by reflecting the green component light G with the light reflection side surface. 
     The rod integrator  10 B includes a light incident surface, a light output surface, and a light reflection side surface provided between an outer circumference of the light incident surface and an outer circumference of the light output surface. The rod integrator  10 B uniformizes the blue component light B outputted from the optical fibers  113 B bundled by the bundle unit  114 B. More specifically, the rod integrator  10 B makes the blue component light B uniform by reflecting the blue component light B with the light reflection side surface. 
     Incidentally, each of the rod integrator  10 R, the rod integrator  10 G, and the rod integrator  10 B may be a hollow rod including a mirror surface as the light reflection side surface. Instead, each of the rod integrator  10 R, the rod integrator  10 G, and the rod integrator  10 B may be a solid rod formed of a glass. 
     Here, each of the rod integrator  10 R, the rod integrator  10 G, and the rod integrator  10 B has a columnar shape extending in a horizontal direction substantially parallel to the projection plane  300  (in the width direction of the housing case  200 ). In other words, the rod integrator  10 R is arranged so that the longitudinal direction of the rod integrator  10 R can extend substantially in the width direction of the housing case  200 . Similarly, the rod integrator  10 G and the rod integrator  10 B are arranged so that the respective longitudinal directions of the rod integrator  10 G and the rod integrator  10 B can extend substantially in the width direction of the housing case  200 . The rod integrator  10 R, the rod integrator  10 G, and the rod integrator  10 B are arranged in the line on a single horizontal plane substantially orthogonal to the projection plane  300  (a plane parallel to the ceiling plate  240 ). 
     The lens  21 R is a lens configured to make the red component light R substantially parallel so that the substantially parallel red component light R can enter a DMD  500 R. The lens  21 G is a lens configured to make the green component light G substantially parallel so that the substantially parallel green component light G can enter a DMD  500 G. The lens  21 B is a lens configured to make the blue component light B substantially parallel so that the substantially parallel blue component light B can enter onto a DMD  500 B. 
     The lens  22  is a lens configured to cause the red component light and the green component light G to substantially form images on the DMD  500 R and the DMD  500 G, respectively, while controlling the expansion of the red component light R and the green component light G. The lens  23  is a lens configured to cause the blue component light B to substantially form an image on the DMD  500 B while controlling the expansion of the blue component light B. 
     The mirror  31  reflects the red component light R outputted from the rod integrator  10 R. The mirror  32  is a dichroic mirror configured to reflect the green component light G outputted from the rod integrator  10 G, and to transmit the red component light R. The mirror  33  is a dichroic mirror configured to transmit the blue component light B outputted from the rod integrator  10 B, and to reflect the red component light R and the green component light G. 
     The mirror  34  reflects the red component light R, the green component light G, and the blue component light B. The mirror  35  reflects the red component light R, the green component light G, and the blue component light B to the second unit  142 . Here,  FIG. 5  shows the configurations in a plan view for simplification of the description; however, the mirror  35  actually reflects the red component light R, the green component light G, and the blue component light B obliquely in the height direction. 
     The second unit  142  separates the red component light R, the green component light G, and the blue component light B from each other, and modulates the red component light R, the green component light G, and the blue component light B. Subsequently, the second unit  142  recombines the red component light R, the green component light G, and the blue component light B, and outputs the image light to the projection unit  150 . 
     Specifically, the second unit  142  includes a lens  40 , a prism  50 , a prism  60 , a prism  70 , a prism  80 , a prism  90 , and multiple digital micromirror devices (DMDs: a DMD  500 R, a DMD  500 G and a DMD  500 B). 
     The lens  40  is a lens configured to make the light outputted from the first unit  141  substantially parallel so that the substantially parallel light of each color component can enter the DMD of the same color. 
     The prism  50  is made of a light transmissive material, and includes a surface  51  and a surface  52 . An air gap is provided between the prism  50  (the surface  51 ) and the prism  60  (a surface  61 ), and an angel (incident angle) at which the light outputted from the first unit  141  enters the surface  51  is larger than a total reflection angle. For this reason, the light outputted from the first unit  141  is reflected by the surface  51 . On the other hand, an air gap is also provided between the prism  50  (the surface  52 ) and the prism  70  (a surface  71 ), and an angel (incident angle) at which the light outputted from the first unit  141  enters the surface  52  is smaller than the total reflection angle. Thus, the light reflected by the surface  51  passes through the surface  52 . 
     The prism  60  is made of a light transmissive material, and includes the surface  61 . 
     The prism  70  is made of a light transmissive material, and includes a surface  71  and a surface  72 . An air gap is provided between the prism  50  (the surface  52 ) and the prism  70  (the surface  71 ), and an angle (incident angle) at which each of the blue component light B reflected by the surface  72  and the blue component light B outputted from the DMD  500 B enters the surface  71  is larger than the total reflection angle. Accordingly, the blue component light B reflected by the surface  72  and the blue component light B outputted from the DMD  500 B are reflected by the surface  71 . 
     The surface  72  is a dichroic mirror surface configured to transmit the red component light R and the green component light G and to reflect the blue component light B. Thus, in the light reflected by the surface  51 , the red component light R and the green component light G pass through the surface  72 , but the blue component light B is reflected by the surface  72 . The blue component light B reflected by the surface  71  is again reflected by the surface  72 . 
     The prism  80  is made of a light transmissive material, and includes a surface  81  and a surface  82 . An air gap is provided between the prism  70  (the surface  72 ) and the prism  80  (the surface  81 ). Since an angle (incident angle) at which each of the red component light R passing through the surface  81  and then reflected by the surface  82 , and the red component light R outputted from the DMD  500 R again enters the surface  81  is larger than the total reflection angle, the red component light R passing through the surface  81  and then reflected by the surface  82 , and the red component light R outputted from the DMD  500 R are reflected by the surface  81 . On the other hand, since an angle (incident angle) at which the red component light R outputted from the DMD  500 R, reflected by the surface  81 , and then reflected by the surface  82  again enters the surface  81  is smaller than the total reflection angle, the red component light R outputted from the DMD  500 R, reflected by the surface  81 , and then reflected by the surface  82  passes through the surface  81 . 
     The surface  82  is a dichroic mirror surface configured to transmit the green component light G and to reflect the red component light R. Hence, in the light passing through the surface  81 , the green component light G passes through the surface  82 , whereas the red component light R is reflected by the surface  82 . The red component light R reflected by the surface  81  is reflected by the surface  82 . The green component light G outputted from the DMD  500 G passes through the surface  82 . 
     Here, the prism  70  separates the blue component light B from the combine light including the red component light R and the green component light G by means of the surface  72 . The prism  80  separates the red component light R and the green component light G from each other by means of the surface  82 . In short, the prism  70  and the prism  80  function as a color separation element to separate the color component light by colors. 
     Note that, in the first embodiment, a cut-off wavelength of the surface  72  of the prism  70  is set at a value between a wavelength range corresponding to a green color and a wavelength range corresponding to a blue color. In addition, a cut-off wavelength of the surface  82  of the prism  80  is set at a value between a wavelength range corresponding to a red color and the wavelength range corresponding to the green color. 
     Meanwhile, the prism  70  combines the blue component light B and the combine light including the red component light R and the green component light G by means of the surface  72 . The prism  80  combines the red component light R and the green component light G by means of the surface  82 . In short, the prism  70  and the prism  80  function as a color combining element to combine color component light of all the colors. 
     The prism  90  is made of a light transmissive material, and includes a surface  91 . The surface  91  is configured to transmit the green component light G. Here, the green component light G entering the DMD  500 G and the green component light G outputted from the DMD  500 G pass through the surface  91 . 
     The DMD  500 R, the DMD  500 G and the DMD  500 B are each formed of multiple movable micromirrors. Each of the micromirrors corresponds to one pixel, basically. The DMD  500 R changes the angle of each micromirror to switch whether or not to reflect the red component light R toward the projection unit  150 . Similarly, the DMD  500 G and the DMD  500 B change the angle of each micromirror to switch whether or not to reflect the green component light G and the blue component light B toward the projection unit  150 , respectively. 
     The projection unit  150  includes a projection lens group  151  and a concave mirror  152 . 
     The projection lens group  151  outputs the light (image light) outputted from the color separating-combining unit  140  to the concave mirror  152 . 
     The concave mirror  152  reflects the light (image light) outputted from the projection lens group  151 . The concave mirror  152  collects the image light, and then scatters the image light over a wide angle. For example, the concave mirror  152  is an aspherical mirror having a surface concave toward the projection lens group  151 . 
     The image light collected by the concave mirror  152  passes through the transmission area provided in the inclined surface  181  of the ceiling-plate recessed portion  180  formed in the ceiling plate  240 . The transmission area provided in the inclined surface  181  is preferably provided near a place where the image light is collected by the concave mirror  152 . 
     The concave mirror  152  is housed in the space formed by the front-side protruding portion  170 , as described above. For example, the concave mirror  152  is preferably fixed to the inside of the front-side protruding portion  170 . In addition, the inner surface of the front-side protruding portion  170  preferably has a shape along the concave mirror  152 . 
     (Configuration of the Ceiling Plate) 
     Hereinafter, a configuration of the ceiling plate according to the first embodiment will be described with reference drawings.  FIGS. 6 to 8  are views each showing the ceiling plate  240  according to the first embodiment. 
     Specifically,  FIG. 6  is a view of the projection display apparatus  100  seen from the ceiling plate  240  side.  FIG. 7  is a view of the projection display apparatus  100  seen in a direction C in  FIG. 6 .  FIG. 8  is a view of the projection display apparatus  100  seen in a direction D in  FIG. 6 . 
     As  FIGS. 6 to 8  show, the ceiling plate  240  is provided with the ceiling-plate recessed portion  180 . In addition to the inclined surface  181  described above, the ceiling-plate recessed portion  180  has an inclined surface  182 , an inclined surface  183 , and an inclined surface  184 . 
     The inclined surface  181  is provided on the front side of the ceiling-plate recessed portion  180 , and has a shape inclining downward toward the projection plane  300 . As described above, the inclined surface  181  is provided with the transmission area  185  through which light emitted from the projection unit  150  passes toward the projection plane  300 . 
     The inclined surface  182  is provided on the projection plane  300  side of the ceiling-plate recessed portion  180 , and has a shape inclining downward toward the front side. 
     The inclined surface  183  and the inclined surface  184  are provided respectively on both sides of the ceiling-plate recessed portion  180  in the width direction of the housing case  200 . The inclined surface  183  and the inclined surface  184  each have a shape inclining toward the center of the ceiling-plate recessed portion  180 . 
     The projection-plane-side shield plate  800  is placed closer to the projection plane  300  than the transmission area  185 . Specifically, the projection-plane-side shield plate  800  has a curved shape bulging over the inclined surface  182 . The projection-plane-side shield plate  800  is formed of a shielding member, and is configured to shield light other than that forming an image, namely unwanted light, among light that has passed through the transmission area  185 . 
     (Configuration of the Projection-Plane-Side Shield Plate) 
     Hereinafter, a projection-plane-side shield plate according to the first embodiment will be described with reference to the drawing.  FIG. 9  is a view showing the projection-plane-side shield plate  800  according to the first embodiment. 
     As  FIG. 9  shows, the projection-plane-side shield plate  800  has a curved portion  810 . As described above, the projection-plane-side shield plate  800  is placed such that the curved portion  810  may bulge over the inclined surface  182 . The entire projection-plane-side shield plate  800  is formed of a shielding member  820 . For example, the shielding member  820  is a black sheet metal or a black acrylic sheet. 
     (Shielding of Unwanted Light) 
     Hereinafter, a shielding of unwanted light according to the first embodiment will be described with reference to the drawings.  FIG. 10  is a diagram showing a luminous flux pattern of image light  700  near the concave mirror  152  according to the first embodiment.  FIGS. 11 and 12  are diagrams each showing a luminous flux pattern of the image light  700  on the projection plane  300  according to the first embodiment. 
     Note that, since the concave mirror  152  and the projection plane  300  face each other, the luminous flux pattern of the image light  700  on the projection plane  300  (see  FIGS. 11 and 12 ) and the luminous flux pattern of the image light  700  near the concave mirror  152  (see  FIG. 10 ) are mirror-reversed. 
     First, referring to  FIG. 10 , a description is given of the luminance flux pattern of the image light  700  near the concave mirror  152 . In the projection display apparatus  100  according to the embodiment, an aspheric mirror is used as the concave mirror  152 . Accordingly, as  FIG. 10  shows, the image light  700  forming an image forms a distorted pattern near the concave mirror  152 . 
     A lower edge of the image light  700  curves upward. Unwanted light  710  exists along the lower edge of the image light  700 . Side edges of the image light  700  curve inward, and expand upward. Unwanted light  720  and unwanted light  730  exist along the respective side edges of the image light  700 . An upper edge of the image light  700  curves upward. Unwanted light  740  exists along the upper edge of the image light  700 . 
     In the projection display apparatus  100  according to the embodiment, to reduce the distance between the concave mirror  152  and the projection plane  300 , the DMD  500  is placed such that the center of the DMD  500  is shifted upward of the center of the optical axis of the projection lens group  151 . It is known that the intensity of light passing near the center of the optical axis of the projection lens group  151  is larger than the intensity of light passing through a peripheral area of the projection lens group  151 . 
     For that reason, it should be noted that, in the luminance flux pattern of the light image  700  near the concave mirror  152 , the intensity of light at a lower part of the pattern is larger than that at an upper part of the pattern. In other words, the unwanted light  710  has a larger intensity than the unwanted light  740 . 
     Second, referring to  FIG. 11 , a description is given of the luminous flux pattern of the image light  700  on the projection plane  300 . Note that  FIG. 11  shows a case where the projection-plane-side shield plate  800  is not provided. 
     As  FIG. 11  shows, the image light  700  has a rectangular shape on the projection plane  300 . The unwanted light  710 , the unwanted light  720 , the unwanted light  730 , and the unwanted light  740  exist around the image light  700 . Here, the unwanted light includes light with an intensity a, light with an intensity b, light with an intensity c, and light with intensity d, from the lower part to the upper part. Here, the intensities a, b, c, and d satisfy the following relationship: intensity a&gt;intensity b&gt;intensity c&gt;intensity d. In other words, the intensity of the unwanted light decreases gradually from the lower part of the image light  700  to the upper part of the image light  700 . Note that the unwanted light  710  includes an area having the intensity a which is the largest. 
     Third, referring to  FIG. 12 , a description is given of a pattern formed on the projection plane  300  by light projected from the projection display apparatus  100 . Note that  FIG. 12  shows a case where the projection-plane-side shield plate  800  is provided. 
     As  FIG. 12  shows, the unwanted light  710  existing along the lower edge of the image light  700  is shielded. Since the projection-plane-side shield plate  800  is placed near the projection plane  300 , the unwanted light  710  can be removed sufficiently by being shielded by the projection-plane-side shield plate  800 . In other words, light having the intensity a, which is the largest, is removed. 
     (Advantageous Effects) 
     In the first embodiment, the ceiling plate  240  is provided with the projection-plane-side shield plate  800  which is placed closer to the projection plane  300  than the transmission area  185 . The projection-plane-side shield plate  800  is configured to shield light other than that forming an image, namely unwanted light (unwanted light  710 ), among light that has passed through the transmission area  185 . 
     The projection plane  300 , in which an image plane is formed, is much larger than the reflective light valve (DMD  500 ) placed at an object plane of the projection lens group  151 . An aperture placed near a reflective light valve (DMD  500 ) on which irradiation light is incident obliquely would need to have an opening larger than the reflective light valve. Accordingly, even when the projection-plane-side shield plate  800  is somewhat away from the projection plane  300 , unwanted light reflected by the reflective light valve can be removed sufficiently, compared to the case where the unwanted light is shielded by the aperture placed near the reflective light valve. 
     It should be noted that it is effective to remove the unwanted light  710  existing along the lower edge of the image light  700  on the projection plane  300  because the unwanted light  710  is light passing near the center of the optical axis of the projection lens group  151 , and therefore has an intensity larger than the other unwanted light. Moreover, it should be noted that there is less need to remove the unwanted light  740  existing along the upper edge of the image light  700  because the unwanted light  740  is light passing through a peripheral area of the projection lens group  151 , and therefore has an intensity smaller than the other unwanted light. 
     [Modification 1] 
     Modification 1 of the first embodiment will be described below with reference to the drawings. Differences from the first embodiment will be mainly described below. 
     Specifically, in the first embodiment, the entire projection-plane-side shield plate  800  is formed of the shielding member  820 . In modification 1, on the other hand, the projection-plane-side shield plate  800  is provided with an area having a predetermined transmittance and extending in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). 
     (Configuration of the Projection-Plane-Side Shield Plate) 
     Hereinafter, a configuration of a projection-plane-side shield plate according to modification 1 will be described with reference to the drawings.  FIGS. 13 to 15  are diagrams each showing a projection-plane-side shield plate  800  according to modification 1. 
     As  FIG. 13  shows, the projection-plane-side shield plate  800  may be formed of the shielding member  820  and neutral density filters  830 . The neutral density filters  830  are provided on the respective end portions of the projection-plane-side shield plate  800  in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). Each of the neutral density filters  830  is a member configured to reduce the intensity of light to be transmitted, and forms an area having a predetermined transmittance. The transmittance of each shield filter  830  increases gradually toward a corresponding end of the projection-plane-side shield plate  800 . Specifically, a transmittance a, a transmittance b, and a transmittance c satisfy the following relationship: transmittance a&gt;transmittance b&gt;transmittance c. 
     As  FIG. 14  shows, the projection-plane-side shield plate  800  may be formed of the shielding member  820  and diffuser plates  840 . The diffuser panels  840  are provided on the respective end portions of the projection-plane-side shield plate  800  in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). Each of the diffuser plates  840  is a member configured to diffuse light, and forms an area having a predetermined transmittance. The diffusivity of each diffuser plate  840  decreases gradually toward a corresponding end of the projection-plane-side shield plate  800 . Accordingly, a diffusivity a, a diffusivity b, and a diffusivity c satisfy the following relationship: diffusivity a&lt;diffusivity b&lt;diffusivity c. 
     As  FIG. 15  shows, the projection-plane-side shield plate  800  may be formed of the shielding member  820  having small holes  850 . The small holes  850  are formed in each of its end portions of the projection-plane-side shield plate  800  in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). Each small hole  850  is an aperture configured to allow light to pass through, and an area of the small hole  850  forms an area having a predetermined transmittance. The number of the small holes  850  increases toward a corresponding end of the projection-plane-side shield plate  800 . 
     (Shielding of Unwanted Light) 
     Hereinafter, a shielding of unwanted light according to modification 1 will be described with reference to the drawings.  FIG. 16  is a diagram showing a luminous flux pattern of the image light  700  on the projection plane  300  according to Modification 1. Note that  FIG. 16  shows a case where the projection-plane-side shield plate  800  shown in any of  FIGS. 13 to 15  is provided. 
     As  FIG. 16  shows, in the case where the projection-plane-side shield plate  800  shown in any of  FIGS. 13 to 15  is provided, the unwanted light  710  existing along the lower edge of the image light  700  is shielded. Since the projection-plane-side shield plate  800  shown in any of  FIGS. 13 to 15  has an area having a predetermined transmittance on both end portions thereof in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ), portions of the unwanted light  710  are left at lower parts of the unwanted light  720  and the unwanted light  730 , respectively (a boundary portion  710 A and a boundary portion  710 B). Accordingly, light-dark boundaries are not noticeable at the lower ends of the unwanted light  720  and the unwanted light  730 , respectively. 
     (Advantageous Effects) 
     In modification 1, the projection-plane-side shield plate  800  has an area having a predetermined transmittance at each of its end portions in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). Accordingly, it is possible to make unnoticeable the light-dark boundaries at the lower ends of the unwanted light  720  and the unwanted light  730 , respectively. 
     [Modification 2] 
     Modification 2 of the first embodiment will be described below with reference to the drawings. Differences from the first embodiment are mainly described below. 
     Specifically, in modification 2, the ceiling plate  240  is provided with an enlarged recessed portion having a substantially horizontal bottom face. The ceiling-plate recessed portion  180  is provided in the bottom face of the enlarged recessed portion. 
     (Configuration of the Ceiling Plate) 
     Hereinafter, a configuration of the ceiling plate according to Modification 2 will be described with reference to the drawings.  FIGS. 17 to 19  are views showing a ceiling plate  240  according to modification 2. 
     Specifically,  FIG. 17  is a view of the projection display apparatus  100  seen from the ceiling plate  240  side.  FIG. 18  is a view of the projection display apparatus  100  seen in a direction C in  FIG. 17 .  FIG. 19  is a view of the projection display apparatus  100  seen in a direction D in  FIG. 17 . 
     As  FIGS. 17 to 19  show, the ceiling plate  240  is provided with an enlarged recessed portion  600  having a substantially horizontal bottom face  601 . The ceiling-plate recessed portion  180  described above is provided in the bottom face  601  of the enlarged recessed portion  600 . Side faces forming walls around the enlarged recessed portion  600  preferably incline at a substantially right angle to the bottom face  601 . 
     The configuration of the ceiling-plate recessed portion  180  is the same as that in the first embodiment, and therefore the description therefore is omitted here. 
     The projection-plane-side shield plate  800  is provided on the bottom face  601  of the enlarged recessed portion  600 . Further, as in the first embodiment, the projection-plane-side shield plate  800  has a curved shape bulging over the inclined surface  182 . 
     [Modification 3] 
     Modification 3 of the first embodiment will be described below with reference to the drawing. Differences from the first embodiment are mainly described below. 
     Specifically, in modification 3, the ceiling plate  240  is provided with not only the projection-plane-side shield plate  800 , but also side shield plates that are placed adjacently to the transmission area  185  in the horizontal direction parallel to the projection plane  300 . 
     (Configuration of the Projection Display Apparatus) 
     Hereinafter, a configuration of the projection display apparatus according to modification 3 will be described with reference to the drawings.  FIG. 20  is a perspective view showing a projection display apparatus  100  according to modification 3. 
     As  FIG. 20  shows, in addition to the projection-plane-side shield plate  800 , the ceiling plate  240  includes a side shield plate  801 A and a side shield plate  801 B. 
     The side shield plate  801 A and the side shield plate  801 B are placed adjacently to the transmission area  185  (not shown in  FIG. 20 ) in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). The side shield plate  801 A and the side shield plate  801 B each have a shape extending in the orthogonal direction to the projection plane  300  (the depth direction of the housing case  200 ). 
     The side shield plate  801 A and the side shield plate  801 B are each formed of a shielding member (e.g., a black sheet metal or a black acrylic sheet), and configured to shield light other than that forming an image, namely unwanted light (the unwanted light  720  and the unwanted light  730  described above), among light that has passed through the transmission area  185 . 
     In addition, the side shield plate  801 A and the side shield plate  801 B each have a curved shape bulging toward the inside of the ceiling-plate recessed portion  180  so as to shield the unwanted light  720  and the unwanted light  730 . 
     (Advantageous Effects) 
     In modification 3, the ceiling plate  240  is provided with the side shield plate  801 A and the side shield plate  801 B placed adjacently to the transmission area  185  in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). The side shield plate  801 A and the side shield plate  801 B are configured to shield light other than that forming an image, namely unwanted light (the unwanted light  720  and the unwanted light  730 ), among light that has passed through the transmission area  185 . Accordingly, near the projection plane  300  where an image plane is formed, the side shield plate  801 A and the side shield plate  801 B shield unwanted light. Thus, compared to a case where an aperture, provided near a reflective light valve in which an object plane is formed, is used to shield unwanted light, the projection-plane-side shield plate  800  and the side shield plates  801 A and  801 B can sufficiently remove unwanted light reflected by the reflective light valve. 
     [Modification 4] 
     Modification 4 of the first embodiment will be described below with reference to the drawing. Differences from the first embodiment and modification 3 are mainly described below. 
     Specifically, in the first embodiment and modification 3, the projection-plane-side shield plate  800 , the side shield plate  801 A, and the side shield plate  801 B are placed bulging toward the inside of the ceiling-plate recessed portion  180 . In contrast, in modification 4, the projection-plane-side shield plate  800 , the side shield plate  801 A, and the side shield plate  801 B are placed protruding upward of the ceiling plate  240 . 
     (Configuration of the Projection Display Apparatus) 
     Hereinafter, a configuration of the projection display apparatus according to modification 4 will be described with reference to the drawings.  FIG. 21  is a perspective view showing a projection display apparatus  100  according to modification 4. 
     As  FIG. 21  shows, like modification 3, the ceiling plate  240  includes the projection-plane-side shield plate  800  as well as the side shield plate  801 A and the side shield plate  801 B. 
     The side shield plate  801 A and the side shield plate  801 B are placed adjacently to the transmission area  185  (not shown in  FIG. 21 ) in the horizontal direction parallel to the projection plane  300  (in the width direction of the housing case  200 ). The side shield plate  801 A and the side shield plate  801 B each have a shape extending in the orthogonal direction to the projection plane  300  (the depth direction of the housing case  200 ). 
     The side shield plate  801 A and the side shield plate  801 B are each formed of a shielding member (e.g., a black sheet metal or a black acrylic sheet), and configured to shield light other than that forming an image, namely unwanted light (the unwanted light  720  and the unwanted light  730  described above), among light that has passed through the transmission area  185 . 
     In modification 4, the side shield plate  801 A and the side shield plate  801 B are placed protruding upward of the ceiling plate  240 . Further, the side shield plate  801 A and the side shield plate  801 B each have a curved shape bulging upward of the ceiling-plate recessed portion  180  so as to shield the unwanted light  720  and the unwanted light  730 . 
     Second Embodiment 
     Hereinafter, a second embodiment will be described with reference to the drawings. Differences from the first embodiment will be mainly described below. 
     Specifically, the first embodiment has been illustrated for the case where the projection display apparatus  100  projects image light onto the projection plane  300  provided to the wall surface. In contrast, the second embodiment will be illustrated for a case where a projection display apparatus  100  projects image light onto a projection plane  300  provided on a floor surface (floor surface projection). An arrangement of a housing case  200  in this case is referred to as a floor surface projection arrangement. 
     (Configuration of Projection Display Apparatus) 
     Hereinafter, description will be provided for a configuration of a projection display apparatus according to the second embodiment with reference to  FIG. 22 .  FIG. 22  is a view of a projection display apparatus  100  according to the second embodiment when viewed from side. 
     As shown in  FIG. 22 , the projection display apparatus  100  projects image light onto the projection plane  300  provided on the floor surface (floor surface projection). In the second embodiment, a floor surface  410  is a first placement surface substantially parallel to the projection plane  300 , and a wall surface  420  is a second placement surface substantially orthogonal to the first placement surface. 
     In the second embodiment, a horizontal direction parallel to the projection plane  300  is referred to as “a width direction”, an orthogonal direction to the projection plane  300  is referred to as “a height direction”, and an orthogonal direction crossing both the width direction and the height direction is referred to as “a depth direction”. 
     In the second embodiment, the housing case  200  has a substantially rectangular parallelepiped shape as similar to the first embodiment. The size of the housing case  200  in the depth direction and the size of the housing case  200  in the height direction are smaller than the size of the housing case  200  in the width direction. The size of the housing case  200  in the height direction is almost equal to a projection distance from a reflection mirror (the concave mirror  152  shown in  FIG. 2 ) to the projection plane  300 . In the width direction, the size of the housing case  200  is almost equal to the size of the projection plane  300 . In the depth direction, the size of the housing case  200  is determined depending on a distance from the wall surface  420  to the projection plane  300 . 
     A projection-plane-side sidewall  210  is a plate-shaped member facing the first placement surface (the floor surface  410  in the second embodiment) substantially parallel to the projection plane  300 . A front-side sidewall  220  is a plate-shaped member provided on the side opposite from the projection-plane-side sidewall  210 . A ceiling plate  240  is a plate-shaped member provided on the side opposite from a base plate  230 . The base plate  230  is a plate-shaped member facing the second placement surface (the wall surface  420  in the second embodiment) different from the first placement surface substantially parallel to the projection plane  300 . A first-lateral-surface-side sidewall  250  and a second-lateral-surface-side sidewall  260  are plate-shaped members forming both ends of the housing case  200  in the width direction. 
     Third Embodiment 
     A third embodiment will be described below with reference to the drawings. Differences from the first embodiment are mainly described below. Specifically, in the third embodiment, the position and the angle of the projection-plane-side shield plate  800  are adjustable. 
     For example, the position and the angle of the projection-plane-side shield plate  800  are adjustable as follows. (1) The position of the projection-plane-side shield plate  800  is adjustable in the orthogonal direction to the projection plane  300  (in the depth direction). (2) The angle of the projection-plane-side shield plate  800  is adjustable around an axis extending in the horizontal direction parallel to the projection plane  300  (in the width direction). (3) The position of the projection-plane-side shield plate  800  is adjustable in the direction (the height direction) orthogonal to both of the horizontal direction parallel to the projection plane  300  (the width direction) and the orthogonal direction to the projection plane  300  (the depth direction). 
     Note that any one of, or more than one of, the positions and the angle in (1) to (3) may be adjusted. 
     FIRST CONFIGURATION EXAMPLE 
     Hereinafter, a first configuration example for adjusting the position and the angle of the projection-plane-side shield plate  800  with reference to the drawings.  FIG. 23  is a view showing the first configuration example for adjusting the position and the angle of the projection-plane-side shield plate  800 . Specifically,  FIG. 23  is an enlarged view of an area around the projection-plane-side shield plate  800 . 
     As  FIG. 23  shows, the projection display apparatus  100  includes a support mechanism  900  configured to support the projection-plane-side shield plate  800 . 
     The support mechanism  900  is configured to support the projection-plane-side shield plate  800  movable in the orthogonal direction to the projection plane  300  (in the depth direction). Moreover, the support mechanism  900  is configured to support the projection-plane-side shield plate  800  rotatable around the axis extending in the horizontal direction parallel to the projection plane  300  (in the width direction). 
     The support mechanism  900  is provided to the ceiling plate  240  of the housing case  200 . For example, the support mechanism  900  is placed inside the ceiling-plate recessed portion  180  of the ceiling plate  240 . 
     Here, details of the first configuration example of the support mechanism  900  are described with reference to  FIGS. 24 to 27 .  FIG. 24  is a perspective view of the support mechanism  900 .  FIG. 25  is a view of the support mechanism  900  seen from the front side thereof.  FIG. 26  is a view of the support mechanism  900  seen from the upper side thereof.  FIG. 27  is a view of the support mechanism  900  seen from a lateral side thereof. 
     As  FIGS. 24 to 27  show, the support mechanism  900  includes a base  910 , rails  920 , a first cam mechanism  930 , a feed screw  940 , a rotary shaft  950 , and a second cam mechanism  960 . 
     The base  910  has a shape extending in the horizontal direction parallel to the projection plane  300  (in the width direction). Widthwise end portions of the base  910  are fitted into the respective rails  920 . 
     A base  910 A and a base  910 B are provided on the respective widthwise end portions of the base  910 . The base  910 A and the base  910 B are configured to rotatably support the rotary shaft  950  extending in the horizontal direction parallel to the projection plane  300  (in the width direction). As will be described later, the projection-plane-side shield plate  800  is fixed to the rotary shaft  950 . Accordingly, the base  910 A and the base  910 B support the projection-plane-side shield plate  800  around the rotary shaft  950 . 
     One of the widthwise end portions of the base  910  (the end portion where the base  910 B is provided) has a screw hole which receives the feed screw  940 . The screw hole has a spiral concave portion that engages with a spiral convex portion provided to the feed screw  940 . 
     Each of the rails  920  has a groove that slidably supports the corresponding end portion of the base  910 . The groove provided in the rail  920  extends in the orthogonal direction to the projection plane  300  (in the depth direction). 
     The first cam mechanism  930  is fixed to one of the rails  920 . The first cam mechanism  930  is connected to the feed screw  940 . Note that the first cam mechanism  930  is connected to a focus adjustment mechanism and a zoom adjustment mechanism of the projection unit  150  (both not shown), and is configured to rotate the feed screw  940  in conjunction with focus adjustment and zoom adjustment by the projection unit  150 . 
     The feed screw  940  has the spiral convex portion. The feed screw  940  is screwed into the screw hole provided in the one end portion of the base  910 . Meanwhile, the feed screw  940  is connected to the first cam mechanism  930 . 
     According to the rotation amount of the feed screw  940 , the base  910  described above moves along the rails  920 , namely, in the orthogonal direction to the projection plane  300  (in the depth direction). In other words, according to the rotation amount of the feed screw  940 , the projection-plane-side shield plate  800  supported by the base  910  moves in the orthogonal direction to the projection plane  300  (in the depth direction). 
     The rotary shaft  950  has a shape extending in the horizontal direction parallel to the projection plane  300  (in the width direction). The rotary shaft  950  is fixed to the projection-plane-side shield plate  800 , and is rotatably supported by the base  910 A and the base  910 B. 
     The second cam mechanism  960  is provided on one of the end portions of the base  910  (the end portion where the base  910 B is provided). More specifically, as  FIG. 28  shows, the second cam mechanism  960  is formed of multiple cams. The multiple cams include a cam configured to engage with the spiral convex portion provided to the feed screw  940 . Further, the multiple cams include a cam configured to rotate around the rotary shaft  950 . Accordingly, the projection-plane-side shield plate  800  fixed to the rotary shaft  950  rotates around the rotary shaft  950  in conjunction with the rotation of the feed screw  940 . 
     As described, in conjunction with the projection-plane-side shield plate  800  moving in the orthogonal direction to the projection plane  300  (in the depth direction), the projection-plane-side shield plate  800  rotates around the rotary shaft  950 . 
     The second cam mechanism  960  is configured to adjust the move amount and the rotation amount of the projection-plane-side shield plate  800  so as to shield unwanted light (unwanted light  710 ) which is other than light constructing an image. 
     Specifically, in conjunction with focus adjustment and zoom adjustment by the projection unit  150 , the first cam mechanism  930  rotates the feed screw  940 . Thereby, adjustments are made on the position of the projection-plane-side shield plate  800  in the depth direction and the rotation angle of the projection-plane-side shield plate  800  rotating around the rotary shaft  950 . 
     SECOND CONFIGURATION EXAMPLE 
     Hereinafter, a second configuration example for adjusting the position and the angle of the projection-plane-side shield plate  800  with reference to the drawings.  FIG. 29  is a view showing the second configuration example for adjusting the position of the projection-plane-side shield plate  800 . Specifically,  FIG. 29  is an enlarged view of an area around the projection-plane-side shield plate  800 . 
     As  FIG. 29  shows, the projection display apparatus  100  includes a support mechanism  900  configured to support the projection-plane-side shield plate  800 . 
     The support mechanism  900  is configured to support the projection-plane-side shield plate  800  movable in the orthogonal direction to the projection plane  300  (in the depth direction). Moreover, the support mechanism  900  is configured to support the projection-plane-side shield plate  800  movable in the direction (the height direction) orthogonal to both of the horizontal direction parallel to the projection plane  300  (the width direction) and the orthogonal direction to the projection plane  300  (the depth direction). 
     As in the first configuration example, the support mechanism  900  is provided to the ceiling plate  240  of the housing case  200 . For example, the support mechanism  900  is placed inside the ceiling-plate recessed portion  180  of the ceiling plate  240 . 
     Here, details of the second configuration example of the support mechanism  900  are described with reference to  FIGS. 30 to 32 .  FIG. 30  is a perspective view of the support mechanism  900 .  FIG. 31  is a view of the support mechanism  900  seen from the front side thereof.  FIG. 32  is a view of the support mechanism  900  seen from the upper side thereof. 
     As  FIGS. 30 to 32  show, the support mechanism  900  includes the base  910 , the rails  920 , the first cam mechanism  930 , the feed screw  940 , and a stage  970 . Since the configurations of the base  910 , the rails  920 , the first cam mechanism  930 , and the feed screw  940  are the same as those in the first configuration example, the descriptions therefore are omitted here. 
     The stage  970  is placed at a substantially center portion of the base  910  in the horizontal direction parallel to the projection plane  300  (in the width direction). Further, the stage  970  is configured to move the projection-plane-side shield plate  800  in the direction (the height direction) orthogonal to both of the horizontal direction parallel to the projection plane  300  (the width direction) and the orthogonal direction to the projection plane  300  (the depth direction). 
     Here, details of the stage  970  are described with reference to  FIG. 33 .  FIG. 33  is a cross-sectional view taken along an A-A line shown in  FIG. 31 . 
     As  FIG. 33  shows, the stage  970  includes a first stage  971  and a second stage  972 . The first stage  971  has an inclined surface  971 A that inclines with respect to a plane P orthogonal to the projection plane  300 . Similarly, the second stage  972  has an inclined surface  972 A that inclines with respect to the plane P orthogonal to the projection plane  300 . The inclined surface  971 A and the inclined surface  972 A face each other. The first stage  971  is configured to be slidable along the interface between the inclined surface  971 A and the inclined surface  972 A. 
     The first stage  971  is fixed to the base  910 , and moves along with the base  910  in the orthogonal direction to the projection plane  300  (in the depth direction). Meanwhile, the second stage  972  is fixed to the housing case  200  and the like, and does not move in the orthogonal direction to the projection plane  300  (in the depth direction). Further, the second stage  972  supports the projection-plane-side shield plate  800 . 
     As described, as the first stage  971  moves in the orthogonal direction to the projection plane  300  (in the depth direction), the first stage  971  slides along the interface between the inclined surface  971 A and the inclined surface  972 A. This moves the second stage  972  in the direction (the height direction) orthogonal to both of the horizontal direction parallel to the projection plane  300  (the width direction) and the orthogonal direction to the projection plane  300  (the depth direction), and thereby also moves the projection-plane-side shield plate  800  supported by the second stage  972 . 
     In the second configuration example, the projection-plane-side shield plate  800  has a rectangular plate shape. Further, the projection-plane-side shield plate  800  has a shape whose center portion in the horizontal direction parallel to the projection plane  300  (in the width direction) curves upward. As in the first embodiment, the projection-plane-side shield plate  800  having such shape can shield the unwanted light  710  existing along the lower edge of the image light  700  even if the projection-plane-side shield plate  800  does not have the curved shape bulging over the inclined surface  182 . 
     (Advantageous Effects) 
     In the first configuration example of the third embodiment, the support mechanism  900  supports the projection-plane-side shield plate  800  movable in the orthogonal direction to the projection plane  300  (in the depth direction), and to rotate around the rotary shaft  950  extending in the horizontal direction parallel to the projection plane  300  (the width direction). 
     In the second configuration example of the third embodiment, the support mechanism  900  supports the projection-plane-side shield plate  800  movable in the orthogonal direction to the projection plane  300  (in the depth direction), and to move in the direction (the height direction) orthogonal to both of the horizontal direction parallel to the projection plane  300  (the width direction) and the orthogonal direction to the projection plane  300  (the depth direction). 
     Accordingly, the unwanted light  710  existing along the lower edge of the image light  700  can be appropriately shielded, even when the light path of the unwanted light  710  to be shielded by the projection-plane-side shield plate  800  changes as a result of, for example, focus adjustment or zoom adjustment by the projection unit  150 . 
     Other Embodiments 
     As described above, the details of the present invention have been described by using the embodiments of the present invention. However, it should not be understood that the description and drawings which constitute part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be easily found by those skilled in the art. 
     In the first embodiment, the projection plane  300  is provided on the wall surface  420  on which the housing case  200  is arranged. However, an embodiment is not limited to this case. The projection plane  300  may be provided in a position behind the wall surface  420  in a direction away from the housing case  200 . 
     In the second embodiment, the projection plane  300  is provided on the floor surface  410  on which the housing case  200  is arranged. However, an embodiment is not limited to this case. The projection plane  300  may be provided in a position lower than the floor surface  410 . 
     In the embodiments, a DMD (a digital micromirror device) has been used merely as an example of the light valve. The light valve may be a reflective liquid crystal panel. 
     In the embodiments, as an example, a laser diode (LD) is used as the light source. However, the light source is not limited to an LD, and may be, for example, a light emitting diode (LED), a UHP lamp, a xenon lamp, or the like. 
     In the embodiments, as an example of a method of cooling the light source, liquid cooling is used. However, the method of cooling the light source is not limited to the liquid cooling method, and may be, for example, air cooling method. 
     In the embodiments, light beams having been emitted from the LDs and passed through the optical fibers are collected at the bundle unit, and the rod integrator is used as means to equalize the light beams. However, the embodiments are not limited to this case. For example, when fly-eye lenses are used as the means for equalizing the light beams, the optical fibers and the bundle unit may be omitted. 
     Although not particularly mentioned in the embodiments, the projection-plane-side shield plate  800 , the side shield plate  801 A, and the side shield plate  801 B may be configured so that the arrangement of the projection-plane-side shield plate  800 , the side shield plate  801 A, and the side shield plate  801 B can be adjusted. Specifically, the projection-plane-side shield plate  800  may be configured to be movable in the orthogonal direction to the projection plane  300  (e.g., in the depth direction). Further, the side shield plate  801 A and the side shield plate  801 B each may be configured to be movable in the horizontal direction substantially parallel to the projection plane  300  (in the width direction of the housing case  200 ). 
     In the third embodiment, the position or the angle of the projection-plane-side shield plate  800  is controlled in conjunction with focus adjustment or zoom adjustment by the projection unit  150 . However, the embodiments are not limited to such case. The position or the angle of the projection-plane-side shield plate  800  may be adjusted manually. 
     In the first configuration example of the third embodiment, the position and the angle of the projection-plane-side shield plate  800  are adjusted in conjunction with each other. However, the embodiments are not limited to such case. The position and the angle of the projection-plane-side shield plate  800  may be adjusted independent from each other. 
     In the second configuration example of the third embodiment, the position of the projection-plane-side shield plate  800  in the depth direction and that in the height direction are adjusted in conjunction with each other. However, the embodiments are not limited to such case. The position of the projection-plane-side shield plate  800  in the depth direction and that in the height direction may be adjusted independent from each other. 
     The term “substantially” allows a margin of ±10%, when the term “substantially” is used for structural meaning. On the other hand, The term “substantially” allows a margin of ±5%, when the term “substantially” is used for optical meaning.