Patent Publication Number: US-2011063580-A1

Title: Projection display apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a projection display apparatus having a projection optical unit for projecting image light on a projection plane. 
     BACKGROUND ART 
     Conventionally, there has been known a projection display apparatus having: a light valve for modulating the light emitted from a light source; and a projection lens for projecting the light emitted from the light valve on a projection plane (screen). 
     Hence, a long distance between the projection lens and the screen needs to be assured for displaying a large-size image on the screen. In contrast to this, a projection display system has been proposed which aims to shorten a distance between the projection display apparatus and the screen by using a reflection mirror for reflecting the light emitted from the projection lens, toward the screen side (for example, Japanese Patent Application Publication No. 2006-235516). 
     With the aim of shortening the distance between the projection display apparatus and the screen, the projection display apparatus becomes in proximity to the screen, and the projection display apparatus becomes within a user&#39;s field of view. Thus, there is a need to perform vertically or laterally oblique projection of the screen. For example, in the above-described projection display system, a projection distance is shortened and oblique projection is performed by shifting a positional relationship between a light valve and an optical axis of the projection optical unit in a vertical direction and employing a concave mirror as a reflection mirror. 
     Incidentally, as a method of setting up a projection display apparatus, there is considered a method of setting up a projection display apparatus on a floor surface or the him (hereinafter, referred to as a floor-placed setup) or a method of setting up a projection display apparatus on a ceiling or the like (hereinafter, referred to as a ceiling-suspended setup). On the other band, the disposition precision of a reflection mirror is a very important factor for appropriately displaying an image to be projected on a projection plane. 
     In the floor-placed setup and ceiling-suspended setup, the top and bottom of the projection display apparatus need to be inverted. That is, the direction of gravity applied to the reflection mirror provided at the projection display apparatus is reversed. Therefore, the disposition precision of the reflection mirror can be lowered owing to self-weight of the reflection mirror. 
     Specifically in a case where the reflection mirror is disposed while with the floor-placed setup being dealt as a target, the disposition precision of the reflection mirror lowers in the ceiling-suspended setup. Conversely, in a case where the reflection mirror is disposed with the ceiling-suspended setup being dealt as a target, the disposition precision of the reflection mirror lowers in the floor-placed setup. 
     DISCLOSURE OF THE INVENTION 
     A first aspect of a projection display apparatus, includes: an image light generating unit (image light generating unit  200 ) configured to generate image light; and a projection optical unit (projection optical unit  300 ) configured to project the image light on a projection plane. The projection optical unit has a reflection mirror (reflection mirror  320 ) configured to reflect the image light emitted from the image light generating unit. The projection optical unit is configured to project the image light in a plurality of directions without changing disposition of the projection display apparatus. 
     A second aspect of a projection display apparatus, includes: an image light generating unit (image light generating unit  200 ) configured to generate image light; and a projection optical unit (projection optical unit  300 ) configured to project the image light on a projection plane. The projection optical unit has a reflection mirror (reflection mirror  320 ) configured to reflect the image light emitted from the image light generating unit. The projection display apparatus includes a support mechanism (support mechanism  500 ) configured to support a reflection optical element (reflection optical element  330 ) while a first state and a second state can be switched as a state of the reflection optical element, the reflection optical element configured to reflect the image light reflected by the reflection mirror. The first state is a state in which the reflection optical element is disposed on an optical path of the image light reflected by the reflection mirror. The second state is a state in which the reflection optical element is caused to come off from a course of the optical path of the image light reflected by the reflection mirror. The projection optical unit projects on the projection plane the image light reflected by the reflection optical element in the first state, and projects on the projection plane the image light reflected by the reflection mirror in the second state. 
     According to the second aspect, the support mechanism supports a reflection optical element while the first state and the second state can be switched from each other. The projection optical unit projects the image light reflected by the reflection optical element, in the first state, and projects the image light reflected by the reflection mirror, in the second state. 
     In this manner, floor-placed setup and ceiling-suspended setup can be switched from each other without inverting the top and bottom of the projection display apparatus. That is, the disposition precision of the reflection mirror can be appropriately maintained, since the direction of gravity applied to the reflection mirror provided to reduce a distance between the projection display apparatus and the projection plane is not reversed. 
     In the second aspect, the projection display apparatus includes a protection cover (protection cover  400 ) provided on an optical path of the image light reflected by the reflection mirror. The protection cover has an opening portion configured to transmit the image light. The opening portion includes a first opening portion (first opening portion  410 ) configured to transmit the image light on a side of the projection plane in the first state, and a second opening portion (second opening portion  420 ) configured to transmit the image light on the side of the projection plane in the second state. 
     In the second aspect, the projection display apparatus includes an opening control section (open/close mechanism control section  255 , the open/close mechanism  600 ) configured to control the opening portion. The opening portion has an opening (opening  411 , opening  421 ) configured to transmit the image light and a capping member (capping member  412 , capping member  422 ) configured to close the opening. The opening control section controls whether or not the opening is dosed by the capping member, in accordance with a state of the reflection optical element. 
     In the second aspect, the projection display apparatus includes an image control section (image control section  253 ) configured to control an image displayed on the projection plane. The image control section controls an orientation of the image displayed on the projection plane, in accordance with the state of the reflection optical element. 
     In the second aspect, the reflection mirror focuses the image light between the reflection optical element and the projection plane in the first state, and focuses the image light between the reflection mirror and the projection plane in the second state. The first opening portion and the second opening portion are disposed in proximity to a position at which the image light is focused. 
     A third aspect of a projection display apparatus, includes an image light generating unit (image light generating unit  200 ) configured to generate image light; and a projection optical unit (projection optical unit  300 ) configured to project the image light on a projection plane. The projection optical unit has a reflection mirror (reflection mirror  320 ) configured to reflect the image light emitted from the image light generating unit and a half mirror (half mirror  350 ) provided on the optical path of the image light reflected by the reflection mirror. The reflection mirror focuses the image light emitted from the image light generating unit. The half mirror reflects one portion of the image light reflected by the reflection mirror, and transmits another portion of the image light reflected by the reflection mirror. 
     According to the third aspect, the half mirror reflects one portion of the image light reflected by the reflection mirror and transmits another portion of the image light reflected by the reflection mirror. Therefore, images can be displayed on two sites by means of one projection display apparatus. 
     Further, the reflection mirror focuses the image light emitted from the image light generating unit, and the half mirror is provided on the optical path of the image light reflected by the reflection mirror. Therefore, upsizing of the projection display apparatus can be restrained. 
     In this manner, in a case in which images are displayed on a plurality of projection plane, even where an attempt is made to reduce a distance between the projection display apparatus and each of the projection planes, upsizing of the projection display apparatus can be restrained. 
     In the third aspect, the projection display apparatus includes a protection cover (protection cover  400 ) provided on an optical path of the image light reflected by the reflection mirror. The protection cover has a transmissive region for transmitting the image light. The transmissive region includes a first transmissive region (transmissive region  480 ) for transmitting one portion of the image light reflected by the reflection mirror; and a second transmissive region (transmissive region  440 ) for transmitting another portion of the image light reflected by the reflection mirror. The projection optical unit configured to project, on a first projection plane (projection plane  210 ), the one portion of the image light transmitted through the first transmissive region, and to project, on a second projection plane (projection plane  220 ), the another portion of the image light transmitted through the second transmissive region. 
     In the third aspect, the half mirror is the second transmissive region. 
     In the third aspect, the reflection mirror focuses the one portion of the image light emitted from the image light generating unit between the half mirror and the first projection plane. The first transmissive region is disposed in proximity to a position at which the image light is focused. 
     In the third aspect, the reflection mirror focuses the another portion of the image light emitted from the image light generating unit between the half mirror and the second projection plane. The second transmissive region is disposed in proximity to a position at which the image light is focused. 
     In the third aspect, the reflection mirror focuses the image light emitted from the image light generating unit between the half mirror and the second projection plane. The half mirror is disposed in proximity to a position at which the image light is focused. 
     In the third aspect, the protection cover has opening communicating from the reflection mirror to the projection plane. The transmissive region is the opening. 
     In the third aspect, at least part of the protection cover is comprised of a light-transmissive member. The transmissive region is comprised of the light-transmissive member. 
     A forth aspect of a projection display apparatus, includes: an image light generating unit (image light generating unit  200 ) having display element (display element  40 ) configured to generate image light; and a projection optical unit (projection optical unit  300 ) configured to project the image light on a projection plane. The projection optical unit has a reflection mirror (reflection mirror  320 ) configured to reflect the image light emitted from the image light generating unit. The reflection mirror focuses the image light emitted from the image light generating unit. The display element has a first display region (display region  45 ) and a second display region (display region  46 ). The reflection mirror has a first reflective region (first reflective region  321 ) and a second reflective region (second reflective region). The first reflective region reflects a first image light emitted from the first display region and focuses the first image light emitted from the first display region. The second reflective region reflects a second image light emitted from the second display region and focuses the second image light emitted from the second display region. 
     According to the forth aspect, the display element has the first display region and the second display region, and the reflection mirror has the first reflective region and the second reflective region. Therefore, images can be displayed at two sites by means of one projection display apparatus. 
     Further, the first reflective region focuses the first image light emitted from the first display region. The second reflective region focuses the second image light emitted from the second display region. Therefore, upsizing of the projection display apparatus can be restrained. 
     In this manner, in a case in which images are displayed on a plurality of projection planes, even where an attempt is made to reduce a distance between the projection display apparatus and each of the projection planes, upsizing of the projection display apparatus can be restrained. 
     Further, the display element has the first display region for emitting the first image light and the second display region for emitting the second image light. Therefore, different images can be displayed on the plurality of projection planes. 
     In the forth aspect, the projection display apparatus includes a protection cover (protection cover  400 ) provided on an optical path of the image light reflected by the reflection mirror. The protection cover has a transmissive region for transmitting the image light. The transmissive region includes a first transmissive region (transmissive region  430 ) for transmitting the first image light reflected by the first reflective region; and a second transmissive region (transmissive region  440 ) for transmitting the second image light reflected by the second reflective region. The projection optical unit configured to project, on a first projection plane, the first image light transmitted through the first transmissive region, and to project, on a second projection plane, the second image light transmitted through the second transmissive region. 
     In the forth aspect, the projection optical unit has a first half mirror (first half mirror  351 ) provided on the optical path of the first image light reflected by the first reflective region. The first transmissive region includes a first transmissive region (a) and a first transmissive region (b). The first half mirror reflects one portion of the first image light to the first transmissive region (a) side, and transmits the another portion of the first image light to the first transmissive region (b) side. 
     In the forth aspect, the projection optical unit has a second half mirror (second half mirror  352 ) provided on the optical path of the second image light reflected by the second reflective region. The second transmissive region includes a second transmissive region (a) and a second transmissive region (b). The second half mirror reflects one portion of the second image light to the second transmissive region (a) side, and transmits the another portion of the second image light to the second transmissive region (b) side. 
     In the forth aspect, the first reflective region focuses the first image light emitted from the first display region between the first reflective region and the first projection plane. The first half mirror is disposed in proximity to a position at which the first image light is focused. 
     In the forth aspect, the second reflective region focuses the second image light emitted from the second display region between the second reflective region and the second projection plane. The second half mirror is disposed in proximity to a position at which the second image light is focused. 
     In the forth aspect, the fast reflective region focuses the first image light emitted from the first display region between the first reflective region and the first projection plane. The first transmissive region is disposed in proximity to a position at which the first image light is focused. 
     In the forth aspect, the second reflective region focuses the second image light emitted from the second display region between the second reflective region and the second projection plane. The second transmissive region is disposed in proximity to a position at which the second image light is focused. 
     In the forth aspect, the protection cover has opening communicating from the reflection mirror to the projection plane. The transmissive region is the opening. 
     In the forth aspect, at least part of the protection cover is comprised of a light-transmissive member. The transmissive region is comprised of the light-transmissive member. 
     A fifth aspect of a projection display apparatus, includes: an image light generating unit (image light generating unit  200 ) having display element (display element  40 ) configured to generate image light; and a projection optical unit (projection optical unit  300 ) configured to project the image light on a projection plane. The projection display apparatus includes a polarization adjusting element (polarization adjusting element  60 ) provided on the optical path of the image light emitted from the display element. The projection optical unit has a reflection mirror (reflection mirror  320 ) configured to reflect the image light emitted from the display element, and a reflective polarization plate (reflective polarization plate  360 ) provided on the optical path of the image light reflected by the reflection mirror. The reflection mirror focuses the image light emitted from the image light generating unit. The display element displays a first image and a second image in time division. The polarization adjusting element adjusts first image light which corresponds to the first image, into first polarization, and adjusts second image light which corresponds to the second image, into second polarization, of the image light emitted from the display element. The reflective polarization plate reflects the first image light adjusted into the first polarization, and transmits the second image light adjusted into the second polarization. 
     According to the fifth aspect, the polarization adjusting element adjusts the first image light into the first polarization and adjusts the second image light into the second polarization. The reflective polarization plate reflects the first image light adjusted into the first polarization. On the other hand, the reflective polarization plate transmits the second image light adjusted into the second polarization. Therefore, images can be displayed at two sites by means of one projection display apparatus. 
     In addition, the reflection mirror focuses the image light emitted from the image light generating unit. Therefore, upsizing of the projection display apparatus can be restrained. 
     In this manner, in a case in which images are displayed on a plurality of projection planes, even where an attempt is made to reduce a distance between the projection display apparatus and each of the projection planes, upsizing of the projection display apparatus can be restrained. 
     Further, the display element displays the first image and the second image in time division. Therefore, different images can be displayed on the plurality of projection planes. 
     In the fifth aspect, the projection display apparatus includes a protection cover (protection cover  400 ) provided on an optical path of the image light reflected by the reflection mirror. The protection cover has a transmissive region for transmitting the image light. The transmissive region includes a first transmissive region (transmissive region  430 ) for transmitting the first image light adjusted into the first polarization; and a second transmissive region (transmissive region  440 ) for transmitting the second image light adjusted into the second polarization. The projection optical unit configured to project, on a first projection plane, the first image light transmitted through the first transmissive region, and to project, on a second projection plane, the second image light transmitted through the second transmissive region. 
     In the fifth aspect, the reflective polarization plate is the second transmissive region. 
     In the fifth aspect, the reflection mirror focuses the first image light emitted from the image light generating unit between the reflective polarization plate and the first projection plane. The first transmissive region is disposed in proximity to a position at which the first image light is focused. 
     In the fifth aspect, the reflection mirror focuses the second image light emitted from the image light generating unit between the reflective polarization plate and the second projection plane. The second transmissive region is disposed in proximity to a position at which the second image light is focused. 
     In the fifth aspect, the reflection mirror focuses the image light emitted from the image light generating unit between the reflective polarization plate and the second projection plane. The reflective polarization plate is disposed in proximity to a position at which the image light is focused. 
     In the fifth aspect, the protection cover has opening communicating from the reflection mirror to the projection plane. The transmissive region is the opening. 
     In the fifth aspect, at least part of the protection cover is comprised of a light-transmissive member. The transmissive region is comprised of the light-transmissive member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing a projection display apparatus  100  according to a first embodiment. 
         FIG. 2  is a view showing the projection display apparatus  100  according to the first embodiment. 
         FIG. 3(A)  and  FIG. 3(B)  are views showing a support mechanism  500  according to the first embodiment. 
         FIG. 4(A)  and  FIG. 4(B)  are views showing the support mechanism  500  according to the first embodiment. 
         FIG. 5  is a view showing a configuration of an image light generating unit  200  according to the first embodiment. 
         FIG. 6  is a view showing a projection display apparatus  100  according to a second embodiment. 
         FIG. 7  is a view showing the projection display apparatus  100  according to the second embodiment. 
         FIG. 8(A)  and  FIG. 8(B)  are views showing a support mechanism  500  according to the second embodiment. 
         FIG. 9(A)  and  FIG. 9(B)  are views showing the support mechanism  500  according to the second embodiment. 
         FIG. 10  is a view showing a projection display apparatus  100  according to a third embodiment. 
         FIG. 11  is a view showing the projection display apparatus  100  according to the third embodiment. 
         FIG. 12(A)  and  FIG. 12(B)  are views showing a support mechanism  500  according to the third embodiment. 
         FIG. 13(A)  and  FIG. 13(B)  are views showing the support mechanism  500  according to the third embodiment. 
         FIG. 14  is a view showing a projection display apparatus  100  according to a fourth embodiment. 
         FIG. 15  is a view showing the projection display apparatus  100  according to the fourth embodiment. 
         FIG. 16(A)  and  FIG. 16(B)  are views showing a first opening portion  410  and a second opening portion  420 , according to the fourth embodiment. 
         FIG. 17(A)  and  FIG. 17(B)  are views showing the first opening portion  410  and the second opening portion  420 , according to the fourth embodiment. 
         FIG. 18  is a view showing a support mechanism  500  and an open/close mechanism  600 , according to a fifth embodiment. 
         FIG. 19  is a view showing the support mechanism  500  and the open/close mechanism  600 , according to the fifth embodiment. 
         FIG. 20  is a block diagram depicting a control unit  250  according to a sixth embodiment. 
         FIG. 21  is a view showing a projection display apparatus  100  according to a seventh embodiment. 
         FIG. 22  is a view showing a display example according to the seventh embodiment. 
         FIG. 23  is a view showing the display example according to the seventh embodiment. 
         FIG. 24  is a view showing a setup example according to the seventh embodiment. 
         FIG. 25  is a view showing the setup example according to the seventh embodiment. 
         FIG. 26  is a view showing a projection display apparatus  100  according to an exemplary modification of the seventh embodiment. 
         FIG. 27  is a view showing the projection display apparatus  100  according to an eighth embodiment. 
         FIG. 28  is a view showing a display example according to the eighth embodiment. 
         FIG. 29  is a view showing a projection display apparatus  100  according to a ninth embodiment. 
         FIG. 30  is a view showing a display example according to the ninth embodiment. 
         FIG. 31  is a view showing the display example according to the ninth embodiment. 
         FIG. 32  is a view showing a projection display apparatus  100  according to a tenth embodiment. 
         FIG. 33  is a view showing a display example according to the tenth embodiment. 
         FIG. 34  is a view showing the display example according to the tenth embodiment. 
         FIG. 35  is a view showing a setup example according to the tenth embodiment. 
         FIG. 36  is a view showing the setup example according to the tenth embodiment. 
         FIG. 37  is a view showing a projection display apparatus  100  according to an exemplary modification of the tenth embodiment. 
         FIG. 38  is a view showing a projection display apparatus  100  according to an eleventh embodiment. 
         FIG. 39  is a view showing a display example according to the eleventh embodiment. 
         FIG. 40  is a view showing a projection display apparatus  100  according to a twelfth embodiment. 
         FIG. 41  is a view showing a configuration of an image light generating unit  200  according to the twelfth embodiment. 
         FIG. 42  is a view showing a reflective polarization plate  360  according to the twelfth embodiment. 
         FIG. 43(A)  and  FIG. 43(B)  are views showing a polarization adjusting element  60  according to the twelfth embodiment. 
         FIG. 44  is a view showing a display example according to the twelfth embodiment. 
         FIG. 45  is a view showing the display example according to the twelfth embodiment. 
         FIG. 46  is a view showing a setup example according to the twelfth embodiment. 
         FIG. 47  is a view showing the setup example according to the twelfth embodiment. 
         FIG. 48  is a view showing a projection display apparatus  100  according to an exemplary modification of the twelfth embodiment. 
         FIG. 49  is a view showing a projection display apparatus  100  according to a thirteenth embodiment. 
         FIG. 50  is a view showing a display example according to the thirteenth embodiment. 
         FIG. 51  is a view showing a projection display apparatus  100  according to a fourteenth embodiment. 
         FIG. 52  is a view showing a display example according to the fourteenth embodiment. 
         FIG. 53  is a view showing the display example according to the fourteenth embodiment. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, a projection display apparatus according to the 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, as a matter of course, the drawings also include portions having different dimensional relationships and ratios from each other. 
     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 the drawings.  FIG. 1  and  FIG. 2  are views showing a configuration of a projection display apparatus  100  according to the first embodiment.  FIG. 1  shows an example of floor-placed setup, and  FIG. 2  shows an example of ceiling-suspended setup. 
     As shown in  FIG. 1  and  FIG. 2 , a projection display apparatus  100  has an image light generating unit  200 , a projection optical unit  300 , and a protection cover  400 . 
     The image light generating unit  200  generates image light. Specifically, the image light generating unit  200  has at least a display element  40  for emitting image light. The display element  40  is provided at a position which is shifted relative to an optical axis L of the projection optical unit  300 . The display element  40  is a reflective liquid crystal panel, a transmissive liquid crystal panel, a DMD (Digital Micromirror Device) or the like, for example. A detailed description of the image light generating unit  200  will be given later (see  FIG. 5 ). 
     The projection optical unit  300  projects image light emitted from the image light generating unit  200 . Here, the projection optical unit  300  projects the image light on a projection plane  210 . Specifically, the projection optical unit  300  has a projection lens  310 , a reflection mirror  320 , and a reflection optical element  330 . 
     The projection lens  310  emits the image light emitted from the image light generating unit  200  to the side of the reflection mirror  320 . 
     The reflection mirror  320  reflects the image light emitted from the projection lens  310 . The reflection mirror  320  widely angles the image light after focusing the image light. For example, the reflection mirror  320  is a non-spherical mirror having a concave face on the side of the image light generating unit  200 . 
     The reflection optical element  330  is a reflection mirror for reflecting the image light reflected by the reflection mirror  320 . As states of the reflection optical element  330 , there can be considered a state shown in  FIG. 1  (hereinafter, referred to as a first state) and a state shown in  FIG. 2  (hereinafter, referred to as a second state). 
     The first state is a state in which the reflection optical element  330  is disposed on an optical path of the image light reflected by the reflection mirror  320 . That is, in the first state, as shown in  FIG. 1 , the reflection optical element  330  is mounted on an optical path of the image light reflected by the reflection mirror  320 . 
     On the other hand, the second state is a state in which the reflection optical element  330  is caused to come off from the course of the optical path of the image light reflected by the reflection mirror  320 . That is, in the second state, as shown in  FIG. 2 , the reflection optical element  330  is caused to come off from the course of the optical path of the image light reflected by the reflection mirror  320 . 
     In the first embodiment, the reflection optical element  330  is removably configured. Although not shown in  FIG. 1  and  FIG. 2 , the projection display apparatus  100  has a support mechanism (support mechanism  500  to be described later) supporting the reflection optical element  330  while the first and second states can be switched from each other. A detailed description of the support mechanism will be given later (see  FIG. 3(A) ,  FIG. 3(B) ,  FIG. 4(A)  and  FIG. 4(B) ). 
     The protection cover  400  is a cover for protecting the reflection mirror  320 . The protection cover  400  is provided on the =optical path of the image light reflected by the reflection mirror  320 . Specifically, the protection cover  400 , as shown in  FIG. 1 , has a first opening portion  410  for transmitting the image light reflected by the reflection optical element  330 , in the first state. The protection cover  400 , as shown in  FIG. 2 , has a second opening portion  420  for transmitting the image light reflected by the reflection mirror  320 , in the second state. In the first embodiment, the first opening portion  410  is provided on a side face of the protection cover  400  opposite to the second opening portion  420 . 
     In this manner, the projection optical unit  300  projects the image light transmitting the first opening portion  410 , on the projection plane  210 , in the first state. The projection optical unit  300  projects the image light transmitting the second opening portion  420 , on the projection plane  210 , in the second state. 
     (Configuration of Support Mechanism) 
     Hereinafter a configuration of a support mechanism according to the first embodiment will be described with reference to the drawings.  FIG. 3(A)  and  FIG. 3(B)  are views showing a support mechanism  500  according to the first embodiment (first state).  FIG. 4(A)  and  FIG. 4(B)  are other views showing the support mechanism  500  according to the first embodiment (second state). 
     In the first embodiment, as described above, the reflection optical element  330  is removably configured. That is, the support mechanism  500  removably supports the reflection optical element  330 . 
     As shown in  FIG. 3(A) , the reflection optical element  330  is mounted to a base  331 . The base  331  has a pair of guide pins (guide pin  332   a  and guide pin  332   b ) and a fixing screw  333 . 
     As shown in  FIG. 4(A) , the support mechanism  500  has: a pair of outer frames (outer frame  511  and outer frame  512 ), which are compatible with outer frames of the protection cover  400 ; and a pair of arm members (arm member  513  and arm member  514 ). The outer frame  511  has a guide groove  511   a  into which a guide pin  332   a  is to be inserted and a guide groove  511   b  into which a guide pin  332   b  is to be inserted. The outer frame  512  has a screw hole  512   a  into which a fixing screw  333  is to be turned. The arm member  513  and the arm member  514  define a position of the base  331  and support the base  331 . 
     As shown in  FIG. 3(A)  and  FIG. 3(B) , in the first state, the base  331  to which the reflection optical element  330  is mounted is further mounted to the support mechanism  500 . Specifically, the guide pin  332   a  and the guide pin  332   b  that are provided at the base  331  are firstly inserted into the guide groove  511   a  and the guide groove  511   b  that are provided at the support mechanism  500 , respectively. The fixing screw  333  that is provided at the base  331  is secondly turned into a screw hole  512   a  which is provided at the support mechanism  500 . 
     As shown in  FIG. 4(A)  and  FIG. 4(B) , in the second state, the base  331  to which the reflection optical element  330  is mounted is removed from the support mechanism  500 . 
     It is preferable that the support mechanism  500  is integrated with the protection cover  400 . That is, it is preferable that the protection cover  400  has the support mechanism  500 . 
     (Configuration of Image Light Generating Unit) 
     Hereinafter, a configuration of the image light generating unit according to the first embodiment will be described with reference to the drawings.  FIG. 5  is a view mainly showing an image light generating unit  200  according to the first embodiment. The image light generating unit  200  has a power circuit (not shown), an image signal processing circuit (not shown) or the like in addition to the constituent elements shown in  FIG. 5 . Here is illustrated a case in which the display element  40  is a transmissive light crystal panel. 
     The image light generating unit  200  has a light source  10 , a fly-eye lens unit  20 , a Polarizing Beam Splitter (PBS) array  30 , a plurality of liquid crystal panels  40  (liquid crystal panel  40 R, liquid crystal panel  40 G, liquid crystal panel  40 B), and a cross-dichroic prism  50 . 
     The light source  10  is a UHP lamp or the like comprised of a burner and a reflector. The light emitted from the light source  10  includes red component light, green component light, and blue component light. 
     The fly-eye lens unit  20  uniformizes the light emitted from the light source  10 . Specifically, the fly-eye lens unit  20  is comprised of a fly-eye lens  20   a  and a fly-eye lens  20   b.    
     The fly-eye lens  20   a  and the fly-eye lens  20   b  are comprised of a plurality of micro-lenses, respectively. Each micro-lens focuses the light emitted from the light source  10  so that the light emitted from the light source  10  is irradiated all over the liquid crystal panel  40 . 
     The PBS array  30  coordinates a polarization state of the light emitted from the fly-eye lens unit  20 . In the first embodiment, the PBS array  30  coordinates the light emitted from the fly-eye lens  20  with P-polarization. 
     The liquid crystal panel  40 R modulates red component light by rotating the polarization direction of the red component light. An incidence-side polarization plate  41 R for transmitting the light having one polarization direction (for example, P-polarization) and interrupting the light having the other polarization direction (for example, S-polarization) is provided on the light-incidence plane side of the liquid crystal panel  40 R. An emission-side polarization plate  42 R for interrupting the light having one polarization direction (for example, P-polarization) and transmitting the light having the other polarization direction for example, S-polarization) is provided on the light-emission plane side of the liquid crystal panel  40 R. 
     Similarly, the liquid crystal panel  40 G and the liquid crystal panel  40 B modulate green component light and blue component light by rotating the polarization direction of the green component light and the blue component light, respectively. The incidence-side polarization plate  41 G is provided on the light-incidence plate side of the liquid crystal panel  40 G and an emission-side polarization plate  42 G is provided on the light-emission plane side of the liquid crystal panel  40 G. An incidence-side polarization plate  41 B is provided on the light-incidence plane side of the liquid crystal panel  40 B and an emission-side polarization plate  42 B is provided on the light-emission plane side of the liquid crystal panel  40 B. 
     The cross-dichroic prism  50  combines the light emitted from the liquid crystal panel  40 R, the liquid crystal panel  40 G, and the liquid crystal panel  40 B with each other. The cross-dichroic prism  50  emits the combined light to the side of the projection lens  310 . 
     In addition, the image light generating unit  200  has: a mirror group (dichroic mirror  111 , dichroic mirror  112 , reflection mirror  121  to reflection mirror  123 ); and a lens group (condenser lens  131 , condenser lens  140 R, condenser lens  140 G, condenser lens  140 B, relay lens  151  and relay lens  152 ). 
     The dichroic mirror  111  transmits red component light and green component light of the light emitted from the PBS array  30 . The dichroic mirror  111  reflects blue component light of the light emitted from the PBS array  30 . 
     The dichroic mirror  112  transmits red component light of the light transmitting the dichroic mirror  111 . The dichroic mirror  112  reflects green component light of the light transmitting the dichroic mirror  111 . 
     The reflection mirror  112  reflects blue component light and guides the reflected light to the side of the liquid crystal panel  40 B. The reflection mirror  122  and the reflection mirror  123  reflect red component light, and guide the reflected light to the side of the liquid crystal panel  40 R. 
     The condenser lens  131  is a lens for focusing incandescent light emitted from the light source  10 . 
     The condenser lens  140 R substantially collimates red component light so that the liquid crystal panel  40 R is irradiated with the red component light. The condenser lens  140 G substantially collimates green component light so that the liquid crystal panel  40 G is irradiated with the green component light. The condenser lens  140 B substantially collimates blue component light so that the liquid crystal panel  40 B is irradiated with the blue component light. 
     The relay lens  151  and the relay lens  152  substantially form an image with red component light on the liquid crystal panel  40 R while restraining expansion of the red component light. 
     (Function(s) and Effect(s)) 
     In the first embodiment, the support mechanism  500  supports a reflection optical element  330  while the first state and the second state can be switched from each other. The projection optical unit  300  projects the image light reflected by the reflection optical element  330 , in the first state, and projects the image light reflected by the reflection mirror  320 , in the second state. 
     In this manner, floor-placed setup and ceiling-suspended setup can be switched from each other without inverting the top and bottom of the projection display apparatus  100 . That is, the disposition precision of the reflection mirror  320  can be appropriately maintained, since the direction of gravity applied to the reflection mirror  320  provided to reduce a distance between the projection display apparatus  110  and the projection plane is not reversed. 
     In the first embodiment, the protection cover  400  is provided on the optical path of the image light reflected by the reflection mirror  320 . Therefore, an angle or the like of the reflection mirror  320  can be restrained from being varied by a user touching the reflection mirror  320 . In addition, the protection cover  400  has opening portions (first opening portion  410  and second opening portion  420 ) for transmitting the image light reflected by the reflection mirror  320 . Accordingly, the image light with which the projection plane  210  is irradiated is never interrupted by the protection cover  400 . In this manner, the disposition precision of the reflection mirror  320  provided to reduce a distance between the projection display apparatus  100  and the projection plane can be appropriately maintained. 
     Second Embodiment 
     Hereinafter, a second embodiment will be described with reference to the drawings. Hereinafter, differences between the first embodiment and the second embodiment will be mainly described. 
     Specifically, in the first embodiment, a reflection optical element  330  is removably configured. In contrast, in the second embodiment, reflection optical element  330  is turnably configured. 
     (Configuration of Projection Display Apparatus) 
     Hereinafter, a configuration of a projection display apparatus according to the second embodiment will be described with reference to the drawings.  FIG. 6  and  FIG. 7  are views showing a configuration of a projection display apparatus  100  according to the second embodiment.  FIG. 6  shows an example of floor-placed setup and  FIG. 7  shows an example of ceiling-suspended setup. In  FIG. 6  and  FIG. 7 , like constituent elements shown in  FIG. 1  and  FIG. 2  are designated by like reference numerals. 
     A first state, like the first embodiment, is a state in which the reflection optical element  330  is disposed on an optical path of image light reflected by a reflection mirror  320 . That is, in the first state, as shown in  FIG. 6 , the reflection optical element  330  turns on the optical path of the image light reflected by the reflection mirror  320 . 
     On the other hand, a second state, like the first embodiment, is a state in which the reflection optical element  330  is caused to come off the course of the optical path of the image light reflected by the reflection mirror  320 . That is, in the second state, as shown in  FIG. 7 , the reflection optical element  330  turns so as to come off from the course of the optical path of the image light reflected by the reflection mirror  320 . 
     (Configuration of Support Mechanism) 
     Hereinafter, a configuration of a support mechanism according to the second embodiment will be described with reference to the drawings.  FIG. 8(A)  and  FIG. 8(B)  are views showing a support mechanism  500  according to the second embodiment (first state).  FIG. 9(A)  and  FIG. 9(B)  are other views showing the support mechanism  500  according to the second embodiment (second state). 
     In the second embodiment, as described above, the reflection optical element  330  is turnably configured. That is, the support mechanism  500  turnably supports the reflection optical element  330 . 
     As shown in  FIG. 8(A)  and  FIG. 9(A) , the reflection optical element  330  is mounted to a base  331 . The base  331  is mounted to a turn shaft  524  which is provided at the support mechanism  500 . 
     As shown in  FIG. 8(A) ,  FIG. 8(B) ,  FIG. 9(A) , and  FIG. 9(B) , the support mechanism  500  has an eccentric cam  521 , a cam shaft  522 , a motor mechanism  523 , a turn shaft  524 , and a guide mechanism  525 . 
     The eccentric cam  521  turns around the cam shaft  522 . The eccentric cam  521  supports the base  331  to which the reflection optical element  330  is mounted. The cam shaft  522  turns owing to the drive force generated by the motor mechanism  523 . The cam shaft  522  is provided at a position coming off from the center of the eccentric cam  521 . The turn shaft  524  turnably supports the base  331  to which the reflection optical element  330  is mounted. The guide groove  525  is a groove taken along an arc drawn by the base  331  turning around the turn shaft  524 . The guide groove  525  aids in turning of the base  331  to which the reflection optical element  330  is mounted. 
     In this manner, owing to the drive force generated by the motor mechanism  523 , the base  331  to which the reflection optical element  330  is mounted turns along the guide groove  525  around the turn shaft  524 . The guide groove  525  may specify a turn range of the base  331 . 
     As shown in  FIG. 8(A)  and  FIG. 8(B) , in the first state, the base  331  to which the reflection optical element  330  is mounted turns on the optical path of the image light reflected by the reflection mirror  320 , owing to the rotation of the cam shaft  522 . On the other hand, as shown in  FIG. 9(A)  and  FIG. 9(B) , in the second state, the base  331  to which the reflection optical element  330  is mounted turns so as to come off from the course of the optical path of the image light reflected by the reflection mirror  320 , owing to the rotation of the cam shaft  522 . 
     Third Embodiment 
     Hereinafter, a third embodiment will be described with reference to the drawings. Hereinafter, differences between the first embodiment and the third embodiment will be mainly described. 
     Specifically, in the first embodiment, the reflection optical element  330  is removably configured. On the other hand, in the third embodiment, the reflection optical element  330  is slidably configured. 
     (Configuration of Projection Display Apparatus) 
     Hereinafter, a configuration of a projection display apparatus according to the third embodiment will be described with reference to the drawings.  FIG. 10  and  FIG. 11  are views showing a configuration of the projection display apparatus  100  according to the third embodiment.  FIG. 10  shows an example of floor-placed setup, and  FIG. 11  shows an example of ceiling-suspended setup. In  FIG. 10  and  FIG. 11 , like constituent elements shown in  FIG. 1  and  FIG. 2  are designated by like reference numerals. 
     A first state, like the first embodiment, is a state in which the reflection optical element  330  is disposed on an optical path of image light reflected by the reflection mirror  320 . That is, in the first state, as shown in  FIG. 10 , the reflection optical element  330  slides on the optical path of the image light reflected by the reflection mirror  320 . 
     On the other hand, a second state, like the first embodiment, is a state in which the reflection optical element  330  is caused to come off from the course of the optical path of the image light reflected by the reflection mirror  320 . That is, in the second state, as shown in  FIG. 11 , the reflection optical element  330  slides so as to come off from the course of the optical path of the image light reflected by the reflection mirror  320 . 
     (Configuration of Support Mechanism) 
     Hereinafter, a configuration of a support mechanism according to a third embodiment will be described with reference to the drawings.  FIG. 12(A)  and  FIG. 12(B)  are views showing a support mechanism  500  according to the third embodiment (first state).  FIG. 13(A)  and  FIG. 13(B)  are other views showing the support mechanism  500  according to the third embodiment (second state). 
     In the third embodiment, as described above, the reflection optical element  330  is slidably configured. That is, the support mechanism  500  slidably supports the reflection optical element  330 . 
     As shown in  FIG. 12(A)  and  FIG. 13(B) , the reflection optical element  330  is mounted to a base  331 . The base  331  is fixed to an arm member  532  which is provided at the support mechanism  500 . 
     As shown in  FIG. 12(A) ,  FIG. 12(B) ,  FIG. 13(A) , and  FIG. 13(B) , the support mechanism  500  has a pair of guide rails  531  (guide ran  531   a  and guide rail  531   b ), an arm member  532 , a gear  533 , and a motor mechanism  534 . 
     The guide rail  531  is a rail for slidably supporting the arm member  532 . The gear  533  rotates owing to the drive force generated by the motor mechanism  534 . That is, the base  331  fixed to the arm member  532  slides on the guide rail  531 , owing to the drive force generated by the motor mechanism  534 . 
     (As shown in  FIG. 12(A)  and  FIG. 12(B) , in the first state, the base  331  to which the reflection optical element  330  is mounted slides on the optical path of the image light reflected by the reflection mirror  320 , owing to the rotation of the gear  533 . On the other hand, as shown in  FIG. 13(A)  and  FIG. 13(B) , in the second state, the base  331  to which the reflection optical element  330  is mounted slides so as to come off from the course of the optical path of the image light reflected by the reflection mirror  320 , owing to the rotation of the gear  533 . 
     Fourth Embodiment 
     Hereinafter, a fourth embodiment will be described with reference to the drawings. Hereinafter, differences between the first embodiment and the fourth embodiment will be mainly described. 
     Specifically, in the fourth embodiment, an opening portion is comprised of an opening and a capping member. The fourth embodiment illustrates a case in which the support mechanism  500  shown in the second embodiment is employed. 
     (Configuration of Projection Display Apparatus) 
     Hereinafter, a configuration of a projection display apparatus according to the fourth embodiment will be described with reference to the drawings.  FIG. 14  and  FIG. 15  are views showing a configuration of the projection display apparatus  100  according to the fourth embodiment.  FIG. 14  shows an example of floor-placed setup, and  FIG. 15  shows an example of ceiling-suspended setup. In  FIG. 14  and  FIG. 15 , like constituent elements shown in  FIG. 1  and  FIG. 2  are designated by like reference numerals. 
     As shown in  FIG. 14  and  FIG. 15 , a first opening portion  410  has a first opening  411  and a first capping member  412 . The first opening  411  transmits image light. The first capping member  412  can close the first opening  411 . For example, the first capping member  412  slides, thereby enabling the first opening  411  to be closed by the first capping member  412 . Similarly, the first capping member  412  slides thereby enabling the first opening  411  to be exposed therefrom. 
     A second opening portion  420  has a second opening  421  and a second capping member  422 . The second opening  421  transmits image light. The second capping member  422  can close the second opening  421 . The second capping member  422  slides thereby enabling the second opening  421  to be dosed by the second capping member  422 , for example. Similarly, the second capping member  422  slides thereby enabling the second opening  421  to be exposed therefrom. 
     As shown in  FIG. 14  and  FIG. 16(A) , in the first state, the first opening portion  410  allows the first opening  411  to be exposed owing to the slide of the first capping member  412 . On the other hand, as shown in  FIG. 14  and  FIG. 16(B) , in the first state, the second opening portion  420  allows the second opening  421  to be closed by the second capping member  422  owing to the slide of the second capping member  422 . 
     As shown in  FIG. 15  and  FIG. 17(A) , in the second state, the first opening portion  410  allows the first opening  411  to be closed by the first capping member  412  owing to the slide of the first capping member  412 . As shown in  FIG. 15  and  FIG. 17(B) , in the second state, the second opening portion  420  allows the second opening  421  to be exposed owing to the slide of the second capping member  422 . 
     (Function(s) and Advantageous Effect(s)) 
     In the fourth embodiment, the first opening portion  410  and the second opening portion  420  have the first capping member  412  and the second capping member  422 , respectively. Therefore, an opening which is not employed in projection of image light is closed by a capping member, and the entry of foreign object such as dust and grime into equipment through the opening can be restrained. 
     Fifth Embodiment 
     Hereinafter, a fifth embodiment will be described with reference to the drawings. Hereinafter, differences between the first embodiment and the fifth embodiment will be mainly described. 
     Specifically, in the fifth embodiment, an opening portion is comprised of an opening and a capping member. The fifth embodiment illustrates a case in which the support mechanism  500  shown in the third embodiment is employed. In addition, the capping member operates in conjunction with the support mechanism  500 . 
     (Operation of Reflection Optical Element and Capping Member) 
     Hereinafter, operations of a reflection optical element and a capping member according to the fifth embodiment will be described with reference to the drawings.  FIG. 18  and  FIG. 19  are views for explaining the operations of the reflection optical element and the capping member according to the fifth embodiment.  FIG. 18  shows an example of floor-placed setup, and  FIG. 19  shows an example of ceiling-suspended setup. In  FIG. 18  and  FIG. 19 , like constituent elements shown in  FIG. 12(A) ,  FIG. 12(B) ,  FIG. 13(A)  and  FIG. 13(B)  are designated by like reference numerals. 
     As shown in  FIGS. 18 and 19 , a first opening portion  410  has a first opening  411  and a first capping member  412 . The first opening  411  transmits image light. The first capping member  412  can close the first opening  411 . A second opening portion  420  has a second opening  421  and a second capping member  422 . The second opening  421  transmits image light. The second capping member  422  can close the second opening  421 . 
     A projection display apparatus  100  has an open/close mechanism  600  of operating the first capping member  412  that is provided at the first opening portion  410  and the second capping member  422  that is provided at the second opening portion  420 . 
     The open/close mechanism  600  has a first arm member  611 , a first gear  612 , a second arm member  621 , and a second gear  622 . 
     The first arm member  611  is mounted to the first capping member  412  and the first gear  612 . The first gear  612  is meshed with a gear  533  and turns in conjunction with the gear  533 . The second arm member  621  is mounted to the second capping member  422  and a second gear  622 . The second gear  622  is meshed with the gear  533  and turns in conjunction with the gear  533 . 
     As shown in  FIG. 18 , in a first state, a base  331  to which a reflection optical element  330  is mounted slides on an optical path of image light reflected by a reflection mirror  320 , owing to the rotation of the gear  533 . In conjunction with this slide, the first capping member  412  slides so as to expose the first opening  411 , owing to the turning movement of the gear  533  and the first gear  612 . The second capping member  422  slides so as to close the second opening  421 , owing to the turning movement of the gear  533  and the second gear  622 . 
     On the other hand, as shown in  FIG. 19 , in a second state, the base  331  to which the reflection optical element  330  is mounted slides so as to come off from the course of the optical path of the image light reflected by the reflection mirror  320 , owing to the rotation of the gear  533 . In conjunction with this slide, the first capping member  412  slides so as to close the first opening  411 , owing to the turning movement of the gear  533  and the first gear  612 . The second capping member  422  slides so as to expose the second opening  412 , owing to the turning movement of the gear  533  and the second gear  622 . 
     In this manner, in accordance with a state of the reflection optical element  330 , the support mechanism  500  and the open/close mechanism  600  operate in conjunction with each other. That is, the reflection optical element  330 , the first capping member  412 , and the second capping member  422  appropriately operate in accordance with the state of the reflection optical element  330 . 
     (Function(s) and Advantageous Effect(s)) 
     In the fifth embodiment, the first opening portion  410  and the second opening portion  420  have the first capping member  412  and the second capping member  422 , respectively. The open/close mechanism  600  closes an opening, which is not employed in projection of image light, by means of a capping member, in conjunction with the state of the reflection optical element  330 . In this manner, the entry of foreign matter such as dust and grime into equipment through the opening can be automatically restrained. 
     Sixth Embodiment 
     Hereinafter, a sixth embodiment will be described with reference to the drawings. Hereinafter, differences between the first embodiment and the sixth embodiment will be mainly described. 
     Specifically, the sixth embodiment describes a case of controlling constituent elements (for example, liquid crystal panel  40 , support mechanism  500 , and open/close mechanism  600 ), in accordance with the state of a reflection optical element  330 . 
     (Function of Projection Display Apparatus) 
     Hereinafter, functions of a projection display apparatus according to the sixth embodiment will be described with reference to the drawings.  FIG. 20  is a block diagram depicting a control unit  250  provided in a projection display apparatus  100  according to the sixth embodiment. 
     As shown in  FIG. 20 , a control unit  250  has an input interface  251 , a receiving section  252 , an image control section  253 , a support mechanism control section  254 , and an open/close mechanism control section  255 . 
     The input interface  251  accepts a variety of information from an operational interface (touch panel or switches) which a user operates. For example, the input interface  251  accepts specific information for specifying a method of setting up the projection display apparatus  100 . The items of specific information are information for specifying floor-placed setup and information for specifying ceiling-suspended setup, etc. 
     The receiving section  252  receives a variety of information from a remote controller for remotely operating the projection display apparatus  100 . The receiving section  252  receives specific information for specifying a method of setting up the projection display apparatus  100 , for example. 
     The image control section  253  controls an image displayed on a projection plane  210 . That is, the image control section  253  controls a display element  40  (liquid crystal panel  40 R to liquid crystal panel  40 B). 
     Specifically, the image control section  253  controls an orientation of the image displayed on the projection plane  210 , in accordance with the method of setting up the projection display apparatus  100 . 
     Let us consider a case in which, where the setup method is floor-placed setup, for example, the image control section  253  is set so that the orientation of the image displayed on the projection plane  210  is appropriate. In such a case, where the setup method is ceiling-suspended setup, if image control is not performed in particular, the top and bottom of the image displayed on the projection plane  210  are inverted. Therefore, in a case where the setup method is ceiling-suspended setup, the image control section  253  inverts the top and bottom of the image displayed on the display element  40 . That is, in a case where a state of the reflection optical element  330  is the second state, the image control section  253  inverts the top and bottom of the image displayed on the display element  40 . 
     Let us also consider a case in which, where the setup method is ceiling-suspended setup, the image control section  253  is set so that the orientation of the image displayed on the projection plane  210  is appropriate. In such a case, where the setup method is floor-placed setup, if image control is not performed in particular, the top and bottom of the image displayed on the projection plane  210  are inverted. Therefore, in a case where the setup method is floor-placed setup, the image control section  253  inverts the top and bottom of the image displayed on the display element  40 . That is, in a case where the state of the reflection optical element  330  is the first state, the image control section  253  inverts the top and bottom of the image displayed on the display element  40 . 
     The support mechanism control section  254  controls a support mechanism  500 . Specifically, the support mechanism control section  254  controls the support mechanism  500  in accordance with the setup method of the projection display apparatus  100 . 
     In a case where the setup method is floor-placed setup, for example, the support mechanism control section  254  controls the state of the reflection optical element  330  to enter the first state. That is, the support mechanism control section  254  disposes the reflection optical element  330  on the optical path of the image light reflected by the reflection mirror  320 . 
     On the other hand, in a case where the setup method is ceiling-suspended setup, the support mechanism control section  254  controls the state of the reflection optical element  330  to enter the second state. That is, the support mechanism control section  254  causes the reflection optical element  330  to come off from the course of the optical path of the image light reflected by the reflection mirror  320 . 
     The open/close mechanism control section  255  controls the open/dose mechanism  600 . Specifically, the open/close mechanism control section  255  controls the open/close mechanism  600  in accordance with the setup method of the projection display apparatus  100 . 
     In a case where the setup method is floor-placed setup, for example, the open/close mechanism control section  255  operates a first capping member  412  so as to expose a first opening  411  and operates a capping member  422  so as to dose a second opening  421 . That is, the open/close mechanism control section  255  exposes the first opening  411  and closes the second opening  421 , in the first state. 
     On the other hand, in a case where the setup method is ceiling-suspended setup, the open/close mechanism control section  255  operates a first capping member  412  so as to close the first opening  411  and operates the second capping member  422  so as to expose the second opening  421 . That is, the open/dose mechanism control section  255  closes the first opening  411  and exposes the second opening  421 , in the second state. 
     As shown in the fifth embodiment, in a case where the support mechanism  500  and the open/close mechanism  600  move in conjunction with each other, the support mechanism control section  254  and the open/close mechanism control section  255  may be comprised of one control section. 
     Further, as the support mechanism  500  employed in the sixth embodiment, for example, any of the support mechanisms  500  according to the first to third embodiments described above may be employed. 
     While, in the sixth embodiment, the setup method of the projection display apparatus  100  is specified in accordance with specific information acquired from the input interface  251  or receiving section  252 , a means for specifying the setup method of the projection display apparatus  100  is not limitative thereto. For example, with a sensor such as an acceleration sensor being incorporated in the projection display apparatus  100 , the setup method of the projection display apparatus  100  may be specified according to a detection result of the sensor. 
     (Function(s) and Advantageous Effect(s)) 
     In the sixth embodiment, the image control section  253  controls the orientation of the image displayed on the projection plane  210 , in accordance with the setup method of the projection display apparatus  100  (i.e., the state of the reflection optical element  330 ). Therefore, even in a case where floor-placed setup and ceiling-suspended setup are switched from each other, an appropriate image can be displayed on the projection plane  210 . 
     In the sixth embodiment, the open/close mechanism control section  255  controls the open/close mechanism  600  in accordance with the setup method of the projection display apparatus  100  (i.e., the state of the reflection optical element  330 ). That is, the open/dose mechanism control section  255  controls the open/close mechanism  600  so as to close an opening, which is not employed in projection of image light, by means of a capping member. In this manner, the entry of foreign matter such as dust or grime into equipment through the opening can be automatically restrained. 
     Seventh Embodiment 
     Configuration of Projection Display Apparatus 
     Hereinafter a configuration of a projection display apparatus according to a seventh embodiment will be described with reference to the drawings.  FIG. 21  is a view showing a configuration of a projection display apparatus  100  according to the seventh embodiment. 
     As shown in  FIG. 21 , the projection display apparatus  100  has an image light generating unit  200 , a projection optical unit  300 , and a protection cover  400 . 
     The image light generating unit  200  generates image light. Specifically, the image light generating unit  200  has at least a display element  40  for emitting image light. The display element  40  is provided at a position which is shifted relative to an optical axis L of the projection optical unit  300 . The display element  40  is a reflective liquid crystal panel, a transmissive liquid crystal panel, a DMD (Digital Micromirror Device) or the like, for example. The image light generating unit  200  has a configuration which is similar to that of  FIG. 5 . 
     The projection optical unit  300  projects the image light emitted from the image light generating unit  200 . Here, the projection optical unit  300  projects the image light on a plurality of projection planes (projection plane  210  and projection plane  220 ). Specifically, the projection optical unit  300  has a projection lens  310 , a reflection mirror  320 , and a half mirror  350 . 
     The projection lens  310  emits the image light emitted from the image light generating unit  200  to the side of the reflection mirror  320 . 
     The reflection mirror  320  reflects the image light emitted from the projection lens  310 . The reflection mirror  320  widely angles the image light after focusing the image light. For example, the reflection mirror  320  is a non-spherical mirror having a concave face on the side of the image light generating unit  200 . 
     The half mirror  350  is provided on the optical path of the image light reflected by the reflection mirror  320 . The half mirror  350  reflects one portion of the image light reflected by the reflection mirror  320  to the side of the projection plane  210 . On the other hand, the half mirror  350  transmits another portion of the image light reflected by the reflection mirror  320  to the side of the projection plane  220 . 
     The protection cover  400  is a cover for protecting the reflection mirror  320 . The protection cover  400  is provided at least on the optical path of the image light reflected by the reflection mirror  320 . The protection cover  400  has a transmissive region for transmitting image light. Specifically, the protection cover  400  has a transmissive region  430  for transmitting one portion of the image light reflected by the reflection mirror  320 ; and a transmissive region  440  for transmitting another portion of the image light reflected by the reflection mirror  320 . In the seventh embodiment, the transmissive region  430  is provided on a side face of the protection cover  400  opposite to the transmissive region  440 . 
     That is, the transmissive region  430  transmits one portion of the image light reflected by the half mirror  350  to the side of the projection plane  210 . The transmissive region  440  transmits another portion of the image light transmitted the half mirror  350  to the side of the projection plane  220 . 
     In this manner, the projection optical unit  300  projects one portion of the image light transmitting the transmissive region  430 , on the projection plane  210 . The projection optical unit  300  projects another portion of the image light transmitting the transmissive region  440 , on the projection plane  220 . 
     Here, the projection plane  210  functions as a transmissive screen for displaying an image through transmission of image light, for example. The projection plane  220  functions as a reflective screen for displaying an image by reflection of image light, for example. 
     Here, it is merely described that in a case where screens is of same type (transmissive or reflective screens) the orientation of the image displayed on the projection plane  210  is laterally inverted relative to that of the image displayed on the projection plane  220 . Therefore, the projection plane  210  may be a reflective screen, whereas the projection plane  220  may be a transmissive screen. 
     (Image Display Example(s)) 
     Hereinafter, image display examples according to the seventh embodiment will be described with reference to the drawings.  FIG. 22  and  FIG. 23  are views showing the image display examples according to the seventh embodiment. 
     Here, the orientations of images displayed on the projection plane  210  and the projection plane  220  are changed according to the dispositions of the projection display apparatus  100  and the display element  40 . Here is illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the left and right sides of the projection display apparatus  100 . 
     As shown in  FIG. 22 , in a case in which the display element  40  is provided so as to be longer in a vertical direction than in a horizontal direction, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     On the other hand, as shown in  FIG. 23 , in a case in which the display element  40  is provided so as to be longer in a horizontal direction than in a vertical direction, longer images in a horizontal direction than in a vertical direction are displayed on the projection plane  210  and the projection plane  220 . 
     (Function(s) and Advantageous Effect(s)) 
     In the seventh embodiment, the half mirror  350  reflects one portion of the image light reflected by the reflection mirror  320  to the side of the projection plane  210  and transmits another portion of the image light reflected by the reflection mirror  320  to the side of the projection plane  220 . Therefore, images can be displayed on two sites by means of one projection display apparatus  100 . 
     Further, the reflection mirror  320  focuses the image light emitted from the image light generating unit  200 , and the half mirror is provided on the optical path of the image light reflected by the reflection mirror  320 . Therefore, upsizing of the projection display apparatus  100  can be restrained. 
     In this manner, in a case in which images are displayed on a plurality of projection plane (projection plane  210  and projection plane  220 ), even where an attempt is made to reduce a distance between the projection display apparatus  100  and each of the projection planes, upsizing of the projection display apparatus  100  can be restrained. 
     In the seventh embodiment, the protection cover  400  is provided on the optical path of the image light reflected by the reflection mirror  320 . Therefore, an angle or the like of the reflection mirror  320  can be restrained from being varied by a user touching the reflection mirror  320 . Further, the protection cover  400  has transmissive regions (transmissive region  430  and transmissive region  440 ) for transmitting the image light reflected by the reflection mirror  320 . Accordingly, the image light with which the projection planes (projection plane  210  and projection plane  220 ) are irradiated is never interrupted by the protection cover  400 . In this manner, the disposition precision of the reflection mirror  320  provided to reduce a distance between the projection display apparatus  100  and each of the projection planes can be appropriately maintained. 
     As a setup site of the projection display apparatus  100 , as shown in  FIG. 24 , there is considered a ceiling (floor) which is provided between an upper floor and a lower floor. In this manner, images can be displayed on the wall surfaces of the upper floor and the lower floor, respectively. 
     As a setup site of the projection display apparatus  100 , as shown in  FIG. 25 , there is considered a wall which is provided between a plurality of passageways. In this manner, images can be displayed on the floor surfaces of these passageways, respectively. 
     As a setup site of the projection display apparatus  100 , there is considered the inside of a display window which is provided at a shop. In this manner, an image can be shown to customers in the shop or pedestrians outside the shop. 
     Exemplary Modification of the Seventh Embodiment 
     Hereinafter, an exemplary modification of the seventh embodiment will be described with reference to the drawings. Hereinafter, differences from the seventh embodiment will be mainly described. Specifically, in the exemplary modification of the seventh embodiment, as shown in  FIG. 26 , a half mirror  350  is a transmissive region  440 . That is, the half mirror  350  is employed as the transmissive region  440 . 
     (Function(s) and Advantageous Effect(s)) 
     In the exemplary modification of the seventh embodiment, the half mirror  350  is employed as the transmissive region  440 . Therefore, the number of parts in the projection display apparatus  100  can be reduced and the projection display apparatus  100  can be downsized. 
     Eighth Embodiment 
     Hereinafter, an eighth embodiment will be described with reference to the drawings. Hereinafter, differences between the seventh embodiment and the eighth embodiment will be mainly described. 
     Specifically, in the eighth embodiment, as shown in  FIG. 27 , a half mirror  350  is employed as a transmissive region  440 , like the exemplary modification of the seventh embodiment. 
     A projection optical unit  300  has a reflection mirror  340  provided on an optical path of the image light transmitting the half mirror  350  (transmissive region  440 ). The reflection mirror  340  is provided on the optical path of the image light transmitting the half mirror  350  (transmissive region  440 ). The reflection mirror  340  reflects the image light transmitting the half mirror  350  (transmissive region  440 ) to the side of a projection plane  220 . It is preferable that the reflection mirror  340  is provided as part of the protection cover  400 . 
     Here, even in a case where screens are of same type (transmissive or reflective screens), the orientation of the image displayed on the projection plane  210  is not laterally inverted relative to that of the image displayed on the projection plane  220 . Therefore, screens of same type (transmissive or reflective screens) can be employed as the projection plane  210  and the projection plane  220 . 
     (Image Display Example(s)) 
     Hereinafter, an image display example according to the eighth embodiment will be described with reference to the drawings.  FIG. 28  is a view showing the image display example according to the eighth embodiment. 
     Here is illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the left and right sides of the projection display apparatus  100 . Here is also illustrated a case in which the display element  40  is disposed so as to be longer in a vertical direction than in a horizontal direction. 
     As shown in  FIG. 28 , screens of same type (reflective screens) can be employed as the projection plane  210  and the projection plane  220 . Further, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     (Function(s) and Advantageous Effect(s)) 
     In the eighth embodiment, the reflection mirror  340  reflects the image light transmitting the half mirror  350  (transmissive region  440 ) to the side of the projection plane  220 . Therefore, screens of same type (transmissive or reflective screens) can be employed as the projection plane  210  and the projection plane  220 . 
     In a case where the projection plane  210  and the projection plane  220  function as reflective screens, the center of a passageway is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed on both wall surfaces of the passageway. 
     In a case where the projection plane  210  and the projection plane  220  function as reflective screens, a revolving shaft of a revolving door is considered as a setup site of the projection display apparatus  100 . In this manner, images can be shown to a plurality of pedestrians passing through the revolving door. 
     In a case where the projection plane  210  and the projection plane  220  function as transmissive screens, a wall interior having its thickness which is capable of housing the projection display apparatus  100  is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed at the front and back faces of wall. 
     Ninth Embodiment 
     Hereinafter, a ninth embodiment will be described with reference to the drawings. Hereinafter, differences between the seventh embodiment and the ninth embodiment will be mainly described. 
     Specifically, in the ninth embodiment, as shown in  FIG. 29 , a transmissive region  430  is provided on a side face of a protection cover  400  in the same manner as that in a transmissive region  440 . 
     The half mirror  350  has an inclination which is substantially vertical relative to a side face of the protection cover  400  on which the transmissive region  430  and the transmissive region  440  are provided. The inclination of the half mirror  350  is not limitative to being substantially vertical relative to the side face of the protection cover  400  on which the transmissive region  430  and the transmissive region  440  are provided. The inclination of the half mirror  350  may be a given inclination. 
     Like the seventh embodiment, the transmissive region  430  transmits one portion of the image light reflected by the half mirror  350  to the side of the projection plane  210 . The transmissive region  440  transmits another portion of the image light transmitting the half mirror  350  to the side of the projection plane  220   
     Here, the projection plane  210  functions as a transmissive screen for displaying an image by way of transmission of image light, for example. The projection plane  220  functions as a reflective screen for displaying an image by way of reflection of image light, for example. 
     Here, it is merely described here that in a case where screens are of same type (transmissive or reflective screens), the orientation of the image displayed on the projection plane  210  is laterally inverted relative to that of the image displayed on the projection plane  220 . Therefore, the projection plane  210  may be a reflective screen, whereas the projection plane  220  may be a transmissive screen. 
     (Image Display Example(s)) 
     Hereinafter, image display examples according to the ninth embodiment will be described with reference to the drawings.  FIG. 30  and  FIG. 31  are views showing the image display example(s) according to the ninth embodiment. Here is illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the lower side of the projection display apparatus  100 . 
     As shown in  FIG. 30 , in a case in which the display element  40  is provided so as to be longer in a horizontal direction than in a vertical direction, longer images in a horizontal direction than in a vertical direction are displayed on the projection plane  210  and the projection plane  220 . 
     On the other hand, as shown in  FIG. 31 , in a case in which the display element  40  is provided so as to be longer in a vertical direction than in a horizontal direction, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     The ninth embodiment illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at a lower side of the projection display apparatus  100 . However, the disposition of the projection display apparatus  100  is not limitative thereto. For example, the projection display apparatus  100  may be disposed so that the transmissive region  430  and the transmissive region  440  are provided at an upper side of the projection display apparatus  100 . The projection display apparatus  100  may also be disposed so that the transmissive region  430  and the transmissive region  440  are provided at a lateral side of the projection display apparatus  100 . 
     (Function(s) and Advantageous Effect(s)) 
     In the ninth embodiment, the transmissive region  430  is provided on a side face of the protection cover  400  in the same manner as that in the transmissive region  440 . In this manner, images can be displayed in two sites at the lower, upper, or lateral side of the projection display apparatus  100 . 
     In a case where the transmissive region  430  and the transmissive region  440  are provided at the lower side of the projection display apparatus  100 , a building&#39;s ceiling is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed on a plurality of walls provided in building. 
     In a case where the transmissive region  430  and the transmissive region  440  are provided at the upper side of the projection display apparatus  100 , a building&#39;s floor is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed on a plurality of walls provided in building. 
     Tenth Embodiment 
     Configuration of Projection Display Apparatus 
     Hereinafter, a configuration of a projection display apparatus according to a tenth embodiment will be described with reference to the drawings.  FIG. 32  is a view showing a configuration of a projection display apparatus  100  according to the tenth embodiment. 
     As shown in  FIG. 32 , the projection display apparatus  100  has an image light generating unit  200 , a projection optical unit  300 , and a protection cover  400 . 
     The image light generating unit  200  generates image light. Specifically, the image light generating unit  200  has at least a display element  40  for emitting image light. The display element  40  is a reflective liquid crystal panel, a transmissive liquid crystal panel, a DMD (Digital Micromirror Device) or the like, for example. The image light generating unit  200  has a configuration which is similar to that of  FIG. 5 . 
     Here, the display element  40  has: a first display region  45  for emitting first image light corresponding to a first image; and a second display region  46  for emitting second image light corresponding to a second image. The first image and the second image may be identical to each other or may be different therefrom. Further, in order to separate the first image light and the second image light from each other, a separation region  47  is provided between the first display region  45  and the second display region  46 . It is preferable that the separation region  47  is configured so as not to emit light. That is, it is preferable that a black image is displayed on the separation region  47 . 
     Here, the first display region  45  and the second display region  46  are provided at positions which are shifted relative to an optical axis L of the projection optical unit  300 . Here, the first display region  45  is provided at a position which is shifted upside relative to the optical axis L of the projection optical unit  300 . The second display region  46  is provided at a position which is shifted downside relative to the optical axis L of the projection optical unit  300 . 
     The projection optical unit  300  projects the image light emitted from the image light generating unit  200  (first image light and second image light), on a plurality of projection planes. Here, the projection optical unit  300  projects the first image light on a projection plane  210  and projects the second image light on a projection plane  220 . Specifically, the projection optical unit  300  has a projection lens  310  and a reflection mirror  320 . 
     The projection lens  310  emits the image light (first image light and second image light) emitted from the image light generating unit  200  to the side of the reflection mirror  320 . 
     The reflection mirror  320  reflects the image light (first image light and second image light) emitted from the projection lens  310 . The reflection mirror  320  widely angles the first image light and the second image light, respectively, after focusing the first image light and the second image light, respectively. For example, the reflection mirror  320  is a non-spherical mirror having a concave face on the side of the image light generating unit  200 . 
     Here, the reflection mirror  320  has: a first reflective region  321  for reflecting the first image light emitted from the first display region  45  and focusing the first image light; and a second reflective region  322  for reflecting the second image light emitted from the second display region  46  and focusing the first image light. 
     Here, the first reflective region  321  and the second reflective region  322  are provided at positions which are shifted relative to the optical axis L of the projection optical unit  300 . Specifically, since the first display region  45  is provided at a position which is shifted upside relative to the optical axis L, the first image light is emitted in an obliquely downward direction. Therefore, the first reflective region  321  is provided at a position which is shifted downside relative to the optical cods L of the projection optical unit  300 . On the other hand, since the second display region  46  is provided at a position which is shifted downside relative to the optical axis L, the second image light is emitted in an obliquely upward direction. Accordingly, the second reflective region  322  is provided at a position which is shifted upside relative to the optical axis L of the projection optical unit  300 . 
     The protection cover  400  is a cover for protecting the reflection mirror  320 . The protection cover  400  is provided at least on the optical path of the image light reflected by the reflection mirror  320 . The protection cover  400  has a transmissive region for transmitting image light. Specifically, the protection cover  400  has: a transmissive region  430  for transmitting the first image light reflected by a first reflective region  321 ; and a transmissive region  440  for transmitting the second image light reflected by a second reflective region  322 . In the tenth embodiment, the transmissive region  430  is provided on a side face of the protection cover  400  opposite to the transmissive region  440 . 
     In this manner, the projection optical unit  300  projects the first image light transmitting the transmissive region  430 , on the projection plane  210 . The projection optical unit  300  projects the second image light transmitting the transmissive region  440 , on the projection plane  220 . 
     Here, the projection plane  210  is a reflective screen for displaying an image by way of reflection of image light, for example. The projection plane  220  is a reflective screen for displaying an image by way of reflection of image light, for example. 
     However, a first image displayed in the first display region  45  or a second image displayed in the second display region  46  is laterally inverted, whereby the orientation of the images displayed on the projection plane  210  and the projection plane  220  can be coordinated. Therefore, screens of given type (reflective or transmissive screens) can be employed as the projection plane  210  and the projection plane  220 . 
     (Image Display Example(s)) 
     Hereinafter, image display examples according to the tenth embodiment will be described with reference to the drawings.  FIG. 33  and  FIG. 34  are views showing the image display examples according to the tenth embodiment. 
     Here, the images displayed on the projection plane  210  and the projection plane  220  are changed depending upon dispositions of the projection display apparatus  100  and the display element  40 . Here is illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the left and right sides of the projection display apparatus  100 . 
     As shown in  FIG. 33 , in a case in which the display element  40  is provided so that the first display region  45  and the second display region  46  are longer in a vertical direction than in a horizontal direction, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     On the other hand, as shown in  FIG. 34 , in a case in which the display element  40  is provided so that the first display region  45  and the second display region  46  are longer in a horizontal direction than in a vertical direction, longer images in a horizontal direction than in a vertical direction are displayed on the projection plane  210  and the projection plane  220 . 
     (Function(s) and Advantageous Effect(s)) 
     In the tenth embodiment, the display element  40  has the first display region  45  and the second display region  46 , and the reflection mirror  320  has the first reflective region  321  and the second reflective region  322 . Therefore, images can be displayed at two sites by means of one projection display apparatus  100 . 
     Further, the first reflective region  321  focuses the first image light emitted from the first display region  45 . The second reflective region  322  focuses the second image light emitted from the second display region  46 . Therefore, upsizing of the projection display apparatus  100  can be restrained. 
     In this manner, in a case in which images are displayed on a plurality of projection planes (projection plane  210  and projection plane  220 ), even where an attempt is made to reduce a distance between the projection display apparatus  100  and each of the projection planes, upsizing of the projection display apparatus  100  can be restrained. 
     Further, the display element  40  has the first display region  45  for emitting the first image light and the second display region  46  for emitting the second image light. Therefore, different images can be displayed on the projection plane  210  and the projection plane  220 . 
     In the tenth embodiment, the protection cover  400  is provided on the optical path of the image light reflected by the reflection mirror  320 . Therefore, an angle or the like of the reflection mirror  320  can be restrained from being varied by a user touching the reflection mirror  320 . In addition, the protection cover  400  has transmissive regions (transmissive region  430  and transmissive region  440 ) for transmitting the image light reflected by the reflection mirror  320 . Accordingly, the image light with which the projection planes (projection plane  210  and projection plane  220 ) are irradiated is never interrupted by the protection cover  400 . In this manner, disposition precision of the reflection mirror  320  provided to reduce a distance between the projection display apparatus  100  and each of the projection planes can be appropriately maintained. 
     As a setup site of the projection display apparatus  100 , there is considered a ceiling (floor) which is provided between an upper floor and a lower floor, as shown in  FIG. 35 . In this manner, images can be displayed on wall surfaces of the upper floor and the lower floor respectively. 
     As a setup site of the projection display apparatus  100 , there is considered a wall which is provided between a plurality of passageways, as shown in  FIG. 36 . In this manner, images can be displayed on the floor surfaces of the passageways, respectively. It should be noted that the top and bottom of the second image displayed in the second display region  46  are inverted relative to the first image displayed in the first display region  45 . 
     The inside of a display window which is provided at a shop is considered as a setup site of the projection display apparatus  100 . In this manner, an image can be shown to customers in the shop or pedestrians outside the shop. 
     Exemplary Modification of the Tenth Embodiment 
     Hereinafter, an exemplary modification of the tenth embodiment will be described with reference to the drawings. Hereinafter, differences from the tenth embodiment will be mainly described. Specifically, in the exemplary modification of the tenth embodiment, as shown in  FIG. 37 , display elements  40  include a first display element  141  having a first display region  45  and a second display element  142  having a second display region  46 . 
     (Function(s) and Advantageous Effect(s)) 
     In the exemplary modification of the tenth embodiment, the first display region  45  and the second display region  46  are provided in separate display elements  40  (the first display element  141  and the second display element  142 ). Therefore, there is no need to, provide the abovementioned separation region  47  at the display element  40 . In addition, images of different resolutions or images of different sizes can be displayed on the projection plane  210  and the projection plane  220 . 
     Eleventh Embodiment 
     Hereinafter, an eleventh embodiment will be described with reference to the drawings. Hereinafter, differences between the tenth embodiment and the eleventh embodiment will be mainly described. 
     Specifically, in the eleventh embodiment, as shown in  FIG. 38 , a projection optical unit  300  has a first half mirror  351  and a second half mirror  352 . A transmissive region  430  has a transmissive region  430   a  and a transmissive region  430   b . A transmissive region  440  has a transmissive region  440   a  and a transmissive region  440   b.    
     The first half mirror  351  is provided on an optical path of the first image light reflected by a first reflective region  321 . The first half mirror  351  reflects one portion of the first image light to the side of the transmissive region  430   a  and transmits one portion of the first image light to the side of the transmissive region  430   b . Here, the first half mirror  351  has a substantially vertical inclination relative to the transmissive region  430 . This half mirror is also provided at a boundary between the transmissive region  430   a  and the transmissive region  430   b.    
     The second half mirror  352  is provided on an optical path of the second image light reflected by a second reflective region  322 . The second half mirror  352  reflects one portion of the second image light to the side of the transmissive region  440   a  and transmits one portion of the second image light to the side of the transmissive region  440   b . Here, the second half mirror  352  has an inclination which is substantially vertical relative to the transmissive region  440 . This half mirror is also provided at a boundary between the transmissive region  440   a  and the transmissive region  440   b.    
     The projection optical unit  300  projects one portion of the first image light reflected by the first half mirror  351 , on a projection plane  210   a  via the transmissive region  430   a , and projects another portion of the first image light transmitting the first half mirror  351 , on a projection plane  210   b  via the transmissive region  430   b.    
     The projection optical unit  300  projects one portion of the second image light reflected by the second half mirror  352 , on the projection plane  220   a  via the transmissive region  440   a , and projects another portion of the second image light transmitting the second half mirror  352 , on the projection plane  220   b  via the transmissive region  440   b.    
     (Image Display Example(s)) 
     Hereinafter, an image display example according to the eleventh embodiment will be described with reference to the drawings.  FIG. 39  is a view showing the image display example according to the eleventh embodiment. 
     Here, the orientations of the images that are displayed on the projection plane  210   a  and the projection plane  210   b  are changed according to the dispositions of the projection display apparatus  100  and the display element  40 . Similarly, the orientations of the images that are displayed on the projection plane  220   a  and the projection plane  220   b  are changed according to the dispositions of the projection display apparatus  100  and the display element  40 . 
     Here is illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the left and right sides of the projection display apparatus  100 . 
     It should be noted that the orientation of a first image which is displayed in a first display region  45  is laterally inverted relative to that of a second image which is displayed in a second display region  46  in  FIG. 39 . As shown in  FIG. 39 , the projection plane  210   a  and the projection plane  220   b  function as screens of same type (reflective screens). On the other hand, the projection plane  210   b  and the projection plane  220   a  function as screens of same type (transmissive screens). 
     Here, let us consider that the orientation of the first image that is displayed in the first display region  45  is identical to that of the second image that is displayed in the second display region  46 . In such a case, the projection plane  210   a  and the projection plane  220   a  function as screens of same type (reflective or transmissive screens). On the other hand, the projection plane  210   a  and the projection plane  220   b  function as screens of same type (reflective or transmissive screens). 
     (Function(s) and Advantageous Effect(s)) 
     In the eleventh embodiment, the projection optical unit  300  has the first half mirror  351  and the second half mirror  352 . Therefore, more images can be displayed by one projection display apparatus  100 . 
     Twelfth Embodiment 
     Configuration of Projection Display Apparatus 
     Hereinafter, a configuration of a projection display apparatus according to a twelfth embodiment will be described with reference to the drawings.  FIG. 40  is a view showing a configuration of a projection display apparatus  100  according to the twelfth embodiment. 
     As shown in  FIG. 40 , the projection display apparatus  100  has an image light generating unit  200 , a projection optical unit  300 , and a protection cover  400 . 
     The image light generating unit  200  generates image light. Specifically, the image light generating unit  200  has at least a display element  40  emitting image light. The display element  40  is provided at a position which is shifted relative to an optical axis L of the projection optical unit  300 . The display element  40  is a reflective liquid crystal panel, a transmissive liquid crystal panel, a DMD (Digital Micromirror Device) or the like, for example. 
     Here, the display element  40  displays a first image and a second image alternately in time division. The first image and the second image may be identical to each other or may be different therefrom. As described later, the first image light corresponding to the first image is adjusted into the first polarization (for example, P-polarization or S-polarization) by means of a polarization adjusting element  60 . On the other hand, the second image light corresponding to the second image is adjusted into the second polarization (for example, S-polarization or P-polarization) by means of a polarization adjusting element  60 . A detailed description of the image light generating unit  200  will be given (see  FIG. 41 ). 
     The projection optical unit  300  projects the image light emitted from the image light generating unit  200 , on a plurality of projection planes. Here, the projection optical unit  300  projects the first image light on the projection plane  210  and projects the second image light on the projection plane  220 . Specifically, the projection optical unit  300  has a projection lens  310 , a reflection mirror  320 , and a reflective polarization plate  360 . 
     The projection lens  310  emits the image light (first image light and second image light) emitted from the image light generating unit  200  to the side of the reflection mirror  320 . 
     The reflection mirror  320  reflects the image light (first image light and second image light) emitted from the projection lens  310 . The reflection mirror  320  widely angles the first image light and the second image light, respectively, after focusing the first image light and the second image light, respectively. For example, the reflection mirror  320  is a non-spherical mirror having a concave face on the side of the image light generating unit  200 . 
     The reflective polarization plate  360  is provided on the optical path of the image light (first image light and second image light) reflected by the reflection mirror  320 . The reflective polarization plate  360 , as shown in  FIG. 42 , reflects the first polarization (for example, S-polarization) and transmits the second polarization (for example, P-polarization). Specifically, the reflective polarization plate  360  reflects the first image light adjusted into the first polarization to the side of the projection plane  210  and transmits the second image light adjusted into the second polarization to the aide of the projection plane  220 . 
     The protection cover  400  is a cover for protecting the reflection mirror  320 . The projection cover  400  is provided at least on the optical path of the image light reflected by the reflection mirror  320 . The protection cover  400  has a transmissive region for transmitting image light. Specifically, the protection cover  400  has: a transmissive region  430  for transmitting the first image light reflected by the reflection mirror  320 ; and a transmissive region  440  for transmitting the second image light reflected by the reflection mirror  320 . In the twelfth embodiment, the transmissive region  430  is provided on a side face of the protection cover  400  opposite to the transmissive region  440 . 
     That is, the transmissive region  430  transmits the first image light reflected by the reflective polarization plate  360  to the side of the projection plane  210 . The transmissive region  440  transmits the second image light transmitting the reflective polarization plate  360  to the side of the projection plane  220 . 
     In this manner, the projection optical unit  300  projects the first image light transmitting the transmissive region  430 , on the projection plane  210 . The projection optical unit  300  projects the second image light transmitting the transmissive region  440 , on the projection plane  220 . 
     Here, the projection plane  210  is a transmissive screen for displaying an image by means of transmission of image light, for example. The projection plane  220  is a reflective screen for displaying an image by means of reflection of image light, for example. 
     By laterally inverting the first image or the second image that a liquid crystal panel  40  displays, the orientations of the images that are displayed on the projection plane  210  and the projection plane  220  can be adjusted into each other. Therefore, screens of given type (reflective or transmissive screens) can be employed as the projection plane  210  and the projection plane  220 . 
     (Configuration of Image Light Generating Unit) 
     Hereinafter, a configuration of an image light generating unit according to the twelfth embodiment will be described with reference to the drawings.  FIG. 41  is a view mainly showing an image light generating unit  200  according to the twelfth embodiment. In  FIG. 41 , like constituent elements shown in  FIG. 5  are designated by like reference numerals. The image light generating unit  200  has a power circuit (not shown) and an image signal processing circuit (not shown) in addition to the constituent elements shown in  FIG. 41 . Here is illustrated a case in which a display element  40  is a transmissive liquid crystal panel. 
     The image light generating unit  200  has a polarization adjusting element  60  in addition to the constituent elements shown in  FIG. 5 . 
     The polarization adjusting element  60  is a liquid crystal modulation element or the like for switching a polarization state of light transmitting its own element at a high speed with a given timing by means of electrical control. For example, as shown in  FIG. 48(A) , the polarization adjusting element  60  transmits incident light while polarization of the incident light is left as it is, in a state in which no voltage is applied to its own element (OFF state). On the other hand, as shown in  FIG. 43(B) , the polarization adjusting element  60  transmits incident light while polarization of the incident light is rotated at an angle of substantial 90 degrees, in a state in which a voltage is applied to its own element (ON state). 
     Specifically, out of the image light emitted from a cross-dichroic prism  50 , the polarization adjusting element  60  adjusts the first image light, which corresponds to the first image, into the first polarization and adjusts the second image light, which corresponds to the second image, into the second polarization. 
     Here, the first image light is reflected by the reflective polarization plate  360 , as described above. Therefore, it is preferable that the polarization adjusting element  60  adjusts polarization of the first image light so as to become S-polarization in the reflective polarization plate  360 . On the other hand, the second image light transmits the reflective polarization plate  360 , as described above. Therefore, it is preferable that the polarization adjusting element  60  adjusts polarization of the second image light so as to become P-polarization in the reflective polarization plate  360 . 
     In a case where the polarization of each color component light emitted from the cross-dichroic prism  50  is incomplete, the polarization adjusting element  60  may be combined with a narrow-band phase difference plate for coordinating only polarization of light having a specific wavelength band. In addition, the polarization adjusting element  60  may be a liquid crystal modulation element for selectively coordinating the wavelength band of each color component light to a given polarization. 
     While the polarization adjusting element  60  is provided at the light emission side of the cross-dichroic prism  50 , disposition of the polarization adjusting element  60  is not limitative thereto. For example, the polarization adjusting element  60  may be provided at the light emission side of each liquid crystal panel  40  independently. 
     (Image Display Example(s)) 
     Hereinafter, image display examples according to the twelfth embodiment will be described with reference to the drawings.  FIG. 44  and  FIG. 45  are views showing the image display examples according to the twelfth embodiment. 
     Here, the orientations of the images displayed on the projection plane  210  and the projection plane  220  are changed depending upon the dispositions of the projective display apparatus  100  and the display element  40 . Here is illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the left and right sides of the projection display apparatus  100 . 
     As shown in  FIG. 44 , in a case in which the display element  40  is provided to be longer in a vertical direction than in a horizontal direction, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     On the other hand, as shown in  FIG. 45 , in a case in which the display element  40  is provided to be longer in a horizontal direction than in a vertical direction, longer images in a horizontal direction than in a vertical direction are displayed on the projection plane  210  and the projection plane  220 . 
     (Function(s) and Advantageous Effect(s)) 
     In the twelfth embodiment, the polarization adjusting element  60  adjusts the first image light into the first polarization and adjusts the second image light into the second polarization. The reflective polarization plate  360  reflects the first image light adjusted into the first polarization. On the other hand, the reflective polarization plate  360  transmits the second image light adjusted into the second polarization. Therefore, images can be displayed at two sites by means of one projection display apparatus  100 . 
     In addition, the reflection mirror  320  focuses the image light emitted from the image light generating unit  200 . Therefore, upsizing of the projection display apparatus  100  can be restrained. 
     In this manner, in a case in which images are displayed on a plurality of projection planes (projection plane  210  and projection plane  220 ), even where an attempt is made to reduce a distance between the projection display apparatus  100  and each of the projection planes, upsizing of the projection display apparatus  100  can be restrained. 
     Further, the display element  40  displays the first image and the second image in time division. Therefore, different images can be displayed on the projection plane  210  and the projection plane  220 . 
     In the twelfth embodiment, the protection cover  400  is provided on the optical path of the image light reflected by the reflection mirror  320 . Therefore, an angle or the like of the reflection mirror  320  can be restrained from being varied by a user touching the reflection mirror  320 . In addition, the protection cover  400  has transmissive regions (transmissive region  430  and transmissive region  440 ) for transmitting the image light reflected by the reflection mirror  320 . Therefore, the image light with which the projection planes (projection plane  210  and projection plane  220 ) are irradiated is never interrupted by the protection cover  400 . In this manner, disposition precision of the reflection mirror  320  provided to reduce a distance between the projection display apparatus  100  and each of the projection planes can be appropriately maintained. 
     As a setup site of the projection display apparatus  100 , there is considered a ceiling (floor) which is provided between an upper floor and a lower floor, as shown in  FIG. 46 . In this manner, images can be displayed on the wall surfaces of the upper floor and the lower floor respectively. 
     As a setup site of the projection display apparatus  100 , there is considered a wall which is provided between a plurality of passageways, as shown in  FIG. 47 . In this manner, images can be displayed on the floor surfaces of the passageways, respectively. 
     As a setup site of the projection display apparatus  100 , there is considered the inside of a display window which is provided at a shop. In this manner, an image can be shown to customers in the shop or pedestrians outside the shop. 
     Exemplary Modification of Twelfth Embodiment 
     Hereinafter, an exemplary modification of the twelfth embodiment will be described with reference to the drawings. Hereinafter, differences from the twelfth embodiment will be mainly described. Specifically, in the exemplary modification of the twelfth embodiment, as shown in  FIG. 48 , a reflective polarization plate  360  is a transmissive region  440 . That is, the reflective polarization plate  360  is employed as the transmissive region  440 . 
     (Function(s) and Advantageous Effect(s)) 
     In the exemplary modification of the twelfth embodiment, the reflective polarization plate  360  is employed as the transmissive region  440 . Therefore, it is possible to reduce the number of parts in the projection display apparatus  100  and downsize the projection display apparatus  100 . 
     Thirteenth Embodiment 
     Hereinafter, a thirteenth embodiment will be described with reference to the drawings. Hereinafter, differences between the twelfth embodiment and the thirteenth embodiment will be mainly described. 
     Specifically, in the thirteenth embodiment, as shown in  FIG. 49 , a reflective polarization plate  360  is employed as a transmissive region  440 , like the exemplary modification of the twelfth embodiment. 
     The projection optical unit  300  has a reflection mirror  340  provided on an optical path of image light transmitting the reflective polarization plate  360  (transmissive region  440 ). The reflection mirror  340  is provided on the optical path of the image light transmitting the reflective polarization plate  360  (transmissive region  440 ). The reflection mirror  340  reflects the image light transmitting the reflective polarization plate  360  (transmissive region  440 ) to the side of a projection plane  220 . It is preferable that the reflection mirror  340  is provided as part of the protection cover  400 . 
     (Image Display Example(s)) 
     Hereinafter, an image display example according to the thirteenth embodiment will be described with reference to the drawings.  FIG. 50  is a view showing the image display example according to the thirteenth embodiment. 
     Here is illustrated a case in which a projection display apparatus  100  is disposed so that a transmissive region  430  and a transmissive region  440  are provided at the left and right sides of the projection display apparatus  100 . In addition, there is illustrated a case in which a display element  40  is disposed so as to be longer in a vertical direction than in a horizontal direction. 
     As shown in  FIG. 50 , screens of same type (reflective screens) can be employed as the projection plane  210  and the projection plane  220 . In addition, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     (Function(s) and Advantageous Effect(s)) 
     In the thirteenth embodiment, the reflection mirror  340  reflects the image light transmitting the reflective polarization plate  360  (transmissive region  440 ) to the side of the projection plane  220 . Therefore, as the projection plane  210  and the projection plane  220 , screens of given type can be employed on different planes irrespective of whether they are of transmissive or reflective type. In addition, different images can be displayed on the projection plane  210  and the projection plane  220 . 
     A center of a passageway is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed on both wall faces of the passageway. 
     A revolving shaft of a revolving door is considered as a setup site of the projection display apparatus  100 . In this manner, an image can be shown to a plurality of pedestrians passing through the revolving door. 
     A wall interior having its thickness which is capable of housing the projection display apparatus  100  is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed at the front and back faces of wall. 
     Fourteenth Embodiment 
     Hereinafter, a fourteenth embodiment will be described with reference to the drawings. Hereinafter, differences between the twelfth embodiment and the fourteenth embodiment will be mainly described. 
     Specifically, in the fourteenth embodiment, as shown in  FIG. 51 , a transmissive region  430  is provided on a side face of a protection cover  400  in the same manner as that in a transmissive region  440 . 
     A reflective polarization plate  360  has an inclination which is substantially vertical relative to the side face of the protection cover  400  on which a transmissive region  430  and a transmissive region  440  are provided. The inclination of the reflective polarization plate  360  is not limitative to being substantially vertical relative to the side face of the protection cover  400  on which a transmissive region  430  and a transmissive region  440  are provided. The inclination of the reflective polarization plate  360  may be a given inclination. 
     Like the twelfth embodiment, the transmissive region  430  transmits the first image light reflected by the reflective polarization plate  360  to the side of the projection plane  210 . The transmissive region  440  transmits the second image light transmitting the reflective polarization plate  360  to the side of the projection plane  220 . 
     Here, the projection plane  210  is a transmissive screen for displaying an image by way of transmission of image light, for example. The projection plane  220  is a reflective screen for displaying an image by way of reflection of image light, for example. 
     However, a first image or a second image that a liquid crystal panel  40  displays is laterally inverted, whereby the orientations of images displayed on the projection plane  210  and the projection plane  220  can be coordinated. Therefore, screens of given type (reflective or transmissive screens) can be employed as the projection plane  210  and the projection plane  220 . 
     (Image Display Example(s)) 
     Hereinafter, image display examples according to the fourteenth embodiment will be described with reference to the drawings.  FIG. 52  and  FIG. 53  are views showing the image display examples according to the fourteenth embodiment. Here is illustrated a case in which a projection display apparatus  100  is disposed so that a transmissive region  430  and a transmissive region  440  are provided at the lower side of the projection display apparatus  100 . 
     As shown in  FIG. 52 , in a case in which a display element  40  is provided so as to be longer in a horizontal direction than in a vertical direction, longer images in a horizontal direction than in a vertical direction are displayed on the projection plane  210  and the projection plane  220 . 
     On the other hand, as shown in  FIG. 53 , in a case in which the display element  40  is provided so as to be longer in a vertical direction than in a horizontal direction, longer images in a vertical direction than in a horizontal direction are displayed on the projection plane  210  and the projection plane  220 . 
     The fourteenth embodiment illustrated a case in which the projection display apparatus  100  is disposed so that the transmissive region  430  and the transmissive region  440  are provided at the lower side of the projection display apparatus  100 . However, the disposition of the projection display apparatus  100  is not limitative thereto. The projection display apparatus  100  may be disposed so that the transmissive region  430  and the transmissive region  440  are provided at the upper side of the transmissive display apparatus  100 , for example. The projection display apparatus  100  may also be disposed so that the transmissive region  430  and the transmissive region  440  are provided at the lateral side of the transmissive display apparatus  100 . 
     (Function(s) and Advantageous Effect(s)) 
     In the fourteenth embodiment, the transmissive region  430  is provided at the side face of the protection cover  400  in the same manner as that in the transmissive region  440 . In this manner, images can be displayed in two sites on different planes at the lower side, the upper side, or the lateral side of the projection display apparatus  100 . Different images can also be displayed on the projection plan  210  and the projection plane  220 . 
     In a case where the transmissive region  430  and the transmissive region  440  are provided at the lower side of the projection display apparatus  100 , a building&#39;s ceiling is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed on a plurality of walls provided in building. 
     In a case where the transmissive region  430  and the transmissive region  440  are provided at the upper side of the projection display apparatus  100 , a building&#39;s floor is considered as a setup site of the projection display apparatus  100 . In this manner, images can be displayed on a plurality of walls provided in building. 
     Other Embodiments 
     While the present invention has been described by way of the foregoing embodiments, it should not be understood that the statements and drawings forming a part of this disclosure limit the invention. From this disclosure, a variety of alternative embodiments, examples, and applicable techniques would have been apparent to one skilled in the art. 
     Although not set forth in the foregoing embodiments in particular, a reflection mirror  320  focuses image light between a reflection optical element  330  and a projection plane  210 , in a first state. It is preferable that a first opening portion  410  is provided in proximity to a position at which image light is to be focused by the reflection mirror  320 . Similarly, the reflection mirror  320  focuses image light between the reflection mirror  320  and the projection plane  210 , in a second state. It is preferable that a second opening portion  420  is provided in proximity to a position at which image light is to be focused by the reflection mirror  320 . 
     While the foregoing embodiments illustrated a case in which a non-spherical mirror is employed as a reflection mirror  320 , the reflection mirror  320  is not limitative thereto. For example, a free curved mirror may be employed as the reflection mirror  320 , for example. A spherical mirror may be employed as the reflection mirror  320  as long as any contrivance is made as to aberration or resolution. 
     While the foregoing embodiments illustrate a case in which a plurality of display elements  40  (triple-plate system) are employed as constituent elements shown in an image light generating unit  200 , the constituent elements shown in the image light generating unit  200  are not limitative thereto. A single display element  40  (single-plate system) may be employed as a constituent element of the image light generating unit  200 . 
     While the foregoing embodiments illustrated a case in which a reflection optical element  330  is a reflection mirror, the reflection optical element  330  is not limitative thereto. The reflection optical element  330  may be a half mirror for reflecting one portion of image light and transmitting another portion of the image light. The reflection optical element  330  may be a reflective polarization plate for reflecting image light having the first polarization and transmitting light having the second polarization. 
     In such a case, if a state of the reflection optical element  330  is a first state, the reflection optical element  330  may be adapted to reflect image light of one portion to the side of the first opening portion  410  and transmit image light of another portion to the side of the second opening portion  420 , out of the image light reflected by the reflection mirror  320 . In this manner, an image is displayed on a first projection plane by means of the image light of one portion transmitting the first opening portion  410 , whereas an image is displayed on a second projection plane by means of the image light of another pardon transmitting the second opening portion  420 . That is, the projection display apparatus  100  can display images at two sites. 
     In the foregoing embodiments, in a case where the projection display apparatus  100  is of floor-placed setup type, the state of the reflection optical element  330  corresponds to a first state, and in a case where the projection display apparatus  100  is of ceiling-suspended setup type, the state of the reflection optical element  300  corresponds to a second state. However, depending upon the configuration of the projection display apparatus  100 , the state of the reflection optical element  330  may correspond to the second state in the case where the projection display apparatus  100  is of floor-placed setup type, whereas the state of the reflection optical element  330  may correspond to the first state in the case where the projection display apparatus  100  is of ceiling-suspended setup type. 
     Although not set forth in the foregoing embodiments, a projection plane  210  may be any plane as long as image light is projected thereon. Therefore, the projection plane  210  may not be a screen used exclusively for a projection display apparatus. For example, the projection plane  210  may be a wall surface, a floor surface, a ceiling, a glass window or the like. 
     According to each of the embodiments, as described above, a distance between a projection display apparatus and a projection plane is shortened by providing a reflection mirror  320 . Therefore, image light can be restrained from being interrupted by a person or the like standing between the projection display apparatus and the projection plane. In addition, in a case where a laser diode (LD) is employed as a light source  10 , a possibility that a person is irradiated with laser beam (image light) can be reduced. 
     Although not set forth in the foregoing embodiment in particular, at least a part of the protection cover  400  may be comprised of an optically transmissive member such as a transmissive resin or a glass. A transmissive region  430  may be comprised of such an optically transmissive member. Similarly, a transmissive region  440  may be comprised of such an optically transmissive member. 
     Although not set forth in the foregoing embodiments in particular, the reflection mirror  320  focuses one portion of the image light emitted from the image light generating unit  200  between the half mirror  350  and the projection plane  210 . It is preferable that the transmissive region  430  is provided in proximity to a position at which one portion of the image light is focused by the reflection mirror  320 . Similarly, the reflection mirror  320  focuses another portion of the image light emitted from the image light generating unit  200  between the half mirror  350  and the projection plane  220 . It is preferable that the transmissive region  440  is provided in proximity to a position at which another portion of the image light is focused by the reflection mirror  320 . According to the exemplary modification of the seventh embodiment, it is preferable that the half mirror  350  is provided in proximity to a position at which image light is focused by the reflection mirror  320 . 
     Although not set forth in the foregoing embodiments, as the half mirror  350 , a half mirror in which a relationship between a reflection index and a transmission factor is not one-to-one may be employed in a visible light region. 
     Although not set forth in the foregoing embodiments in particular, as the half mirror  350 , there may be employed a dichroic mirror or the like for reflecting light having a wavelength band of one portion and transmitting light having the wavelength band of another portion, of the wavelength band that the image light has. In addition, as the half mirror  350 , there may be employed a reflective polarization plate or the like, for reflecting light having one polarization and transmitting light having the other polarization, of the image light. As a case of employing a dichroic mirror or a reflective polarization plate as the half mirror  350 , there is considered a case of displaying images of different colors on the projection plane  210  and the projection plane  220 . 
     Although not set forth in the foregoing embodiments in particular, the first reflective region  321  focuses the first image light emitted from the image light generating unit  200  between the first reflective region  321  and the projection plane  210 . It is preferable that the transmissive region  430  is provided in proximity to a position at which the first image light is focused by the first reflective region  321 . Similarly, the second reflective region  322  focuses the second image light emitted from the image light generating unit  200  between the second reflective region and the projecting plane  220 . It is preferable that the transmissive region  440  is provided in proximity to a position at which the second image light is focused by the second reflective region  322 . 
     According to the eleventh embodiment, it is preferable that a first half  351  is provided in proximity to a position at which the first image light is focused by the first reflective region  321 . It is preferable that a second half mirror  352  is provided in proximity to a position at which the second image light is focused by the second reflective region  322 . 
     Although not set forth in the foregoing embodiments in particular, a protection cover  400  may have an opening communication from the reflective polarization plate  360  to the side of the projection plane  210 . The transmissive region  430  may be such an opening. Similarly, the protection cover  400  may have an opening communicating from the reflective polarization plate  360  to the side of the projection plane  220 . The transmissive region  440  may be such an opening. 
     Although not set forth in the foregoing embodiments in particular, at least part of the protection cover  400  may be comprised of an optically transmissive member such as a transmissive resin or a glass. The transmissive region  430  may be comprised of such an optically transmissive member. Similarly, the transmissive region  440  may be comprised of such an optically transmissive member. 
     Although not set forth in the foregoing embodiments in particular, the reflection mirror  320  focuses the first image light emitted from the image light generating unit  200  between the reflective polarization plate  360  and the projection plane  210 . It is preferable that the transmissive region  430  is provided in proximity to a position at which the first image light is focused by the reflection mirror  320 . Similarly, the reflection mirror  320  focuses the second image light emitted from the image light generating unit  200  between the reflective polarization plate  360  and the projection plane  220 . It is preferable that the transmissive region  440  is provided in proximity to a position at which the second image light is focused by the reflection mirror  320 . According to the exemplary modification of the twelfth embodiment, it is preferable that the reflective polarization plate  360  is provided in proximity to a position at which the image light is focused by the reflection mirror  320 . 
     While, in the foregoing embodiments, a polarization adjusting element  60  is provided in an image light generating unit  200 , the disposition of the polarization adjusting element  60  is not limitative thereto. For example, the polarization adjusting element  60  may be provided before image light is incident to the reflective polarization plate  360 , on the optical path of the image light emitted from the image light generating unit  200 . 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, there can be provided a projection display apparatus which is capable of appropriately maintaining disposition precision of a reflection mirror provided to reduce a distance between the projecting display apparatus and a projection plane.