Abstract:
A projection display device comprises a main body cabinet, a projection lens section to which light modulated by a light modulating element entered, and a mirror section for reflecting the light emitted from the projection lens section to a projection plane. A level difference depending on an arrangement shift of the projection lens section and the mirror section is formed on a second side surface facing a first side surface having light projection port of the main body cabinet. Furthermore, the projection display device comprises a level difference correction section for directing the light from the mirror section in a desired direction by correcting the level difference, when the main body cabinet is planed on a plane to be placed, the second side surface facing the plane to be placed.

Description:
[0001]    This application claims priority under 35 U.S.C. Section 119 of Japanese Patent Application No. 2007-055979 filed Mar. 6, 2007, entitled “PROJECTION DISPLAY DEVICE” and Japanese Patent Application No. 2007-155098 filed Jun. 12, 2007, entitled “PROJECTION DISPLAY DEVICE”. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a projection display device for enlarging and projecting light modulated by a display element on a projection plane, and in particular, is preferably used for a projection display device in which an image on the display element is formed as an intermediate image between a projection lens section and a reflection mirror and this intermediate image is enlarged and projected by a reflection plane. 
         [0004]    2. Description of the Related Art 
         [0005]    Projection display devices (hereafter, referred to as “projectors”) for enlarging and projecting an image on a display element (liquid crystal panel, or the like) on a projection plane (screen, or the like) have been commercialized and widely used. In the projectors of this sort, it is desirable to reduce a distance between the screen and the projector body. 
         [0006]    To attain this, an arrangement for oblique projection may be used in which a projection optical system is wide-angled, and at the same time, a direction of projection light traveling is oblique to an optical axis of the projection optical system. For example, when a wide-angle lens with a large view angle is used as the projection optical system, and a display element and a screen are shifted in opposite directions to each other with regard to the optical axis of the projection optical system, a projection distance is shortened, and at the same time, oblique projection without distortion can be. achieved. However, with the arrangement as mentioned, a wider-angle lens with a larger view angle is necessary, and therefore, increased costs due to a large-sized lens and a large-sized projector body pose a problem. 
         [0007]    On the otherhand, for realization of the reduced projection distance, such an arrangement is also considered that a projection lens section and a mirror are used as a projection optical system, an image on a display element is formed as an intermediate image between the projection lens section and the mirror, and the intermediate image is then enlarged and projected by the mirror. 
         [0008]    With the projectors of this sort, various states in use as shown in  FIG. 18  are expected. With the latter arrangement, as shown in  FIG. 19 , since a light source, a projection lens section and a mirror are arranged in a same direction, although the light source directs in a horizontal direction for a ceiling mount type and a stationary type, the light source directs in a vertical direction for a desk mount type, thereby causing problems in a service life of the light source (burner). 
         [0009]    By the way, according to the arrangement shown in  FIG. 19 , light modulated by a panel is shifted in a direction getting away from the screen with regard to an optical axis of the projection lens section (refraction optical system), and the mirror (reflection plane) is shifted in a direction opposite to the direction getting away from the screen. However, contrary to this arrangement, when the panel is shifted in a direction approaching to the screen with regard to the optical axis of the projection lens section (refraction optical system), and the mirror (reflection plane) is shifted in the direction opposite to the direction approaching to the screen, a wider angle of projection light can be further promoted. 
         [0010]    However, with this arrangement, a level difference is created on a side surface of a main body cabinet due to shifting of the mirror with regard to the projection lens section. For this reason, when the side surface of the projector is placed on a plane to be placed (in the case of the stationary type shown in  FIG. 18B ), the projector will be oblique to a horizontal direction, thereby causing a problem that the light cannot be projected to the screen in a smooth manner. 
         [0011]    This problem can be eliminated by giving the above-mentioned side surface a uniform plane without any level difference. However, this attempt will create a dead space in the main body cabinet, and such a problem arises that the projector body is large-sized. 
       SUMMARY OF THE INVENTION 
       [0012]    A projection display device according to an aspect of the present invention comprises a projection lens section to which light modulated by a light modulating element is entered; a mirror section for reflecting the light emitted from the projection lens section to a projection plane; a main body cabinet for accommodating the projection lens section and the mirror section, wherein a level difference depending on an arrangement shift of the projection lens section and the mirror section is formed on a second side surface facing a first side surface having a light projection port of the main body cabinet; and a level difference correction section for correcting the level difference to orient the light from the mirror section in a desired direction, when the main body cabinet is placed on a plane to be placed in a state that the second side surface faces the plane. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The foregoing and other objects and novel features of the present invention will be more fully understood by reading a description of preferred embodiments below with reference to the accompanying drawings as follows: 
           [0014]      FIG. 1  is a drawing (perspective view) illustrating an internal arrangement of the projector according to an embodiment; 
           [0015]      FIG. 2  is a drawing (top plan view) illustrating the internal arrangement of the projector according to the embodiment; 
           [0016]      FIG. 3  is a drawing (bottom plan view) illustrating the internal arrangement of the projector according to the embodiment; 
           [0017]      FIG. 4  is a drawing (right side view) illustrating the internal arrangement of the projector according to the embodiment; 
           [0018]      FIG. 5  is a drawing (left side view) illustrating the internal arrangement of the projector according to the embodiment; 
           [0019]      FIG. 6  is a drawing (front view) illustrating the internal arrangement of the projector according to the embodiment; 
           [0020]      FIG. 7  is a drawing (back view) illustrating the internal arrangement of the projector according to the embodiment; 
           [0021]      FIG. 8  is a drawing (perspective view) illustrating an arrangement of a projection optical system according to the embodiment; 
           [0022]      FIG. 9  is a drawing (cross-sectional view) illustrating the arrangement of the projection optical system according to the embodiment; 
           [0023]      FIG. 10  is a drawing illustrating an arrangement of an optical engine according to the embodiment; 
           [0024]      FIG. 11  is a drawing (perspective view) illustrating an external arrangement of the projector according to the embodiment; 
           [0025]      FIG. 12  is a drawing (right side view) illustrating the external arrangement of the projector according to the embodiment; 
           [0026]      FIG. 13  is a drawing (front view) illustrating the external arrangement of the projector according to the embodiment; 
           [0027]      FIG. 14  is a drawing (bottom plan view) illustrating the external arrangement of the projector according to the embodiment; 
           [0028]      FIG. 15  is a drawing illustrating an arrangement of an arm member and an adjusting screw according to the embodiment; 
           [0029]      FIG. 16  is a drawing illustrating a state in use (a stationary type) of the projector according to the embodiment; 
           [0030]      FIG. 17  is a drawing illustrating the state in use (the stationary type) of the projector according to the embodiment; 
           [0031]      FIG. 18A  is a drawing illustrating a state in use (a ceiling mount type) of the projector; 
           [0032]      FIG. 18B  is a drawing illustrating a state in use (the stationary type) of the projector; 
           [0033]      FIG. 18C  is a drawing illustrating a state in use (a desk mount type) of the projector; and 
           [0034]      FIG. 19  illustrates the prior art. 
       
    
    
       [0035]    The drawings are merely intended for illustration and do not set any limits to the scope of the present invention. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    Hereinafter, referring to the drawings, an arrangement of a projector according to the embodiment will be described. 
         [0037]      FIG. 1  through  FIG. 7  illustrate an internal arrangement of the projector in which an external cabinet is omitted. FIG.  1  is a perspective view of the internal arrangement showing an external appearance, and  FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5 ,  FIG. 6  and  FIG. 7  are respectively a top plan view, a bottom plan view, a right side view, a left side view, a front view, and a back view.  FIG. 2  through  FIG. 7  show the arrangement in a state that a main substrate  40  is removed.  FIG. 8  and  FIG. 9  are respectively a perspective view and a cross-sectional view (schematic view) of a projection optical system showing an external appearance. 
         [0038]    Referring now to  FIG. 1  through  FIG. 7 , the projector comprises an optical engine  10 , a projection optical system  20 , a power supply unit  30 , a main substrate  40 , an AV terminal section  50 , a suction fan  60 , an exhaust fan  70 , and an AC inlet  90 . Reference number  80   a  is a boss from a top face side of the cabinet, reference numeral  80   b  is a boss from a bottom face side of the cabinet, and reference numeral  80   c  is a bush for vibration absorption. 
         [0039]    In the projection optical system  20 , plate-like sections  202   a  and  205   a  shown in  FIG. 8  are sandwiched between the bosses  80   a  and  80   b  via two bushes  80   c  as shown in  FIG. 1 ,  FIG. 2 , and  FIG. 3  to be mounted in the cabinet. Since the projection optical system  20  is sandwiched via the bush  80   c  for vibration absorption, shock is hardly conveyed to the projection optical system  20 . The projection optical system  20  is supported by the boss  80   a  from the top face side of the cabinet and the boss  80   b  from the bottom face side of the cabinet via the bush  80   c  for vibration absorption, thereby improving supporting strength. 
         [0040]    The optical engine  10  separates white light from a light source  101  into light in a blue wavelength band, light in a green wavelength band, and light in a red wavelength band, and at the same time, modulates the light in respective wavelength bands by a corresponding display element (liquid crystal panel) Furthermore, the optical engine  10  executes color synthesis of the modulated light in the respective wavelength bands by a dichroic prism, and emits the synthesized light to the projection optical system  20 . As shown in  FIG. 2 , the light source  101  is disposed so as to illuminate the light in a direction of an X-axis. Furthermore, the projection optical system  20  is disposed so that the optical axis may be positioned in a direction of a Y-axis. An arrangement of the optical engine  10  and a positional relationship between the optical engine  10  and the projection optical system  20  will be described later, referring to  FIG. 10 . 
         [0041]    The power supply unit  30  supplies electric power to the light source  101  and a main circuit  40 . AC voltage is input to the power supply unit  30  via an AC inlet  90 . The main circuit  40  is a circuit for driving and controlling the projector. As shown in  FIG. 1 , a circuit substrate for holding the main circuit  40  is disposed on the top face of the optical engine  10  to cover a part of the optical engine  10 . Furthermore, an AV (Audio Visual) signal is input to the main circuit  40  via the AV terminal section  50 . 
         [0042]    As shown in  FIG. 1  and  FIG. 3 , three suction fans  60  are disposed on the bottom face side of the optical engine  10 . Air sucked by these suction fans  60  is exhausted by an exhaust fan  70  (see  FIG. 5 ) disposed on a left side surface of the optical engine  10  and an exhaust fan  70  (see  FIG. 7 ) disposed on a rear surface of the optical engine  10 . Disposition of the suction fans  60  and exhaust fans  70  as mentioned above allows the air sucked by the suction fan  60  to flow passing through an optical system of the optical engine  10 , the light source  101 , and the power supply unit  30 . Furthermore, as shown in  FIG. 2 ,  FIG. 3 , and  FIG. 6 , the sucked air is guided to a side surface of the light source  101  via a duct  61  and flows from the side surface of the light source  101  to the exhaust fan  70 . Such air flow removes heat generated in these members. 
         [0043]      FIG. 8  and  FIG. 9  are respectively a perspective view and a cross-sectional view of the projection optical system showing the external appearance.  FIG. 9  schematically illustrates an A-A′ section in  FIG. 8 . 
         [0044]    In  FIG. 8  and  FIG. 9 , reference number  201  denotes a projection lens unit, reference number  202  denotes a housing, reference number  203  denotes a dust cover, reference number  204  denotes a reflection mirror, reference number  205  denotesa mirror cover, and reference number  206  denotes a light beam passing window. 
         [0045]    The projection lens unit  201  comprises a group of lenses for image formation of the projection light onto an intermediate image formation plane, and an actuator for adjusting a focus state of the projected image by displacing a part of the group of lenses in a direction of an optical axis. Here, focus adjustment of the projection lens unit  201  is carried out by rotating a lever  201   a  around the optical axis of the projection lens unit  201 . As shown in  FIG. 8 , the lever  201   a  is disposed to protrude from a side surface of the projection lens unit  201  without blocking the projection light from the light beam passing window  206 . 
         [0046]    The reflection mirror  204  has a reflection plane having an aspheric shape, widens an angle of the projection light entered from the projection lens unit  201 , and projects it from the light beam passing window  206  to a projection plane (screen). 
         [0047]    The projection lens unit  201  is accommodated in the housing  202 , and further, is covered by the dust cover  203 . The reflection mirror  204  is attached to the housing  202  and is also covered by the mirror cover  205 . 
         [0048]    As shown in  FIG. 9 , synthesized light generated by the optical engine  10  is entered to the projection lens unit  201  at a position spaced from the optical axis of the projection lens unit  201  in a direction of a Z-axis. The synthesized light entered as mentioned is subjected to a lens action by the projection lens unit  201  and is entered to the reflection mirror  204 . Following this, the angle of the synthesized light is widened by the reflection mirror  204  and is projected on the projection plane (screen) via the light beam passing window  206 . 
         [0049]    As mentioned above, the synthesized light from the optical engine  10  is entered to the projection lens unit  201  at the position shifted from the optical axis of the projection lens unit  201  in the direction of the Z-axis. Therefore, the reflection mirror  204  is disposed to be shifted from the optical axis of the projection lens unit  201  in the direction opposite to the direction of the synthesized light being shifted, as shown in  FIG. 9 . Here, since the reflection mirror  204  has a larger reflection plane than a lens surface of each of the lenses constituting the projection lens unit  201 , an amount of shifting the reflection mirror  204  with regard to the optical axis of the projection lens unit  201  becomes comparatively larger. For this reason, a comparatively large space G is created on the bottom face side of the projector as shown in  FIG. 4  and  FIG. 5 . 
         [0050]    Next, referring to  FIG. 10 , a principal arrangement of the optical engine  10  will be described. 
         [0051]    The light source  101  comprises a burner and a reflector and emits approximately parallel light to an illumination optical system  102 . The light source  101  includes, for example, an extra high pressure mercury lamp. The illumination optical system  102  comprises a fly-eye integrator, a PBS (polarization beam splitter) array and a condenser lens. The illumination optical system  102  uniformizes distribution of light quantity of the light of the respective colors when the light are entered to the display elements (liquid crystal panels)  106 ,  109 , and  115 , and arranges a direction of polarization of the light traveling to a dichroic mirror  103  in one direction. The light source  101  may be a single light type equipped with only one lamp comprising a burner and a reflector, or a multiple light type equipped with a plurality of lamps. 
         [0052]    The dichroic mirror  103  reflects only the light in the blue wavelength band (hereafter, referred to as “B-light”),among the light entered from the illumination optical system  102 , and transmits the light in the red wavelength band (hereafter, referred to as “R-light”), and the light in the green wavelength band (hereafter, referred to as “G-light”). Amirror  104  reflects the B-light reflected by the dichroic mirror  103  to a direction to a condenser lens  105 . 
         [0053]    The condenser lens  105  gives a lens action to the B-light so that the B-light is entered to the display element  106  in a state of parallel light. The display element  106  is driven in response to an image signal for a blue color and modulates the B-light in response to a driven state of the display element  106 . A polarization plate (not shown) is disposed at an incident side and emitting side of the display element  106 . 
         [0054]    A dichroic mirror  107  reflects the G-light only of the R-light and G-light transmitted through the dichroic mirror  103 . A condenser lens  108  gives a lens action to the G-light so that the G-light is entered to the display element  109  in a state of parallel light. The display element  109  is driven in response to an image signal for a green color and modulates the G-light in response to a driven state of the display element  109 . A polarization plate (not shown) is disposed at an incident side and emitting side of the display element  109 . 
         [0055]    Relay lenses  110  and  112  give a lens action to the R-light so that an incident state of the R-light with regard to the display element  115  becomes identical with incident states of the B-light and G-light with regard to the display elements  106  and  109 . Mirrors  111  and  113  change the optical path of the R-light so as to guide the R-light transmitted through the dichroic mirror  107  to the display element  115 . 
         [0056]    A condenser lens  114  gives a lens action to the R-light so that the R-light is entered to the display element  115  in a state of parallel light. The display element  115  is driven in response to an image signal for a red color and modulates the R-light in response to a driven state of the display element  115 . A polarization plate (not shown) is disposed at an incident side and emitting side of the display element  115 . 
         [0057]    For the B-light, G-light, and R-light modulated by the display element  106 ,  109 , and  115 , a dichroic prism  116  reflects the B-light and R-light, and at the same time, transmits the G-light, thereby performing color synthesis of the B-light, G-light, and R-light. As mentioned above, the color synthesized light (synthesized light) is entered to the projection lens unit  201  in the projection optical system  20 . Then, an angle of the synthesized light is widened by the reflection mirror  204 , and the synthesized light is projected to the projection plane (screen) via the light beam passing window  206 . 
         [0058]    As illustrated, the light source  101  is disposed so that a direction of light illumination directs in a direction of the X-axis. With this arrangement of the light source  101 , the light source  101  is positioned to illuminate light in the horizontal direction even when the projector is used in any state in use, i.e., used as the ceiling mount type, the stationary type, or the desk mount type. Accordingly, reduction in the service life of the light source  101  due to disposition of the light source  101  in the vertical direction can be suppressed. 
         [0059]      FIG. 11  is a drawing (perspective view) illustrating an external appearance of the projector where an internal structure of the projector shown in  FIG. 1  is accommodated in the cabinet.  FIG. 12 ,  FIG. 13 , and  FIG. 14  are respectively a right side view, a back view, and a bottom plan view. 
         [0060]    As illustrated, to correct the level difference created depending on the above-mentioned space G (see  FIG. 4  and  FIG. 5 ), an arm member  400  is attached to the bottom face of the main body cabinet  300 . Furthermore, two adjusting screws  500  are attached to the arm member  400  so that end portions of the screws may penetrate through the arm member  400 . 
         [0061]    An operation button section  301  is disposed on the top face of the main body cabinet  300 . A protrusion  302  having a circular arc shape is disposed on the bottom face of the main body cabinet  300  at a position where the reflection mirror  204  is disposed. 
         [0062]      FIG. 15  illustrates a state that the adjusting screw  500  is attached to the arm member  400 . The arm member  400  is formed by molding a resin onto a sheet metal as shown in a right upper area in  FIG. 15 . In the arm member  400 , four holes  401  for securing the arm member  400  by screws to the bottom face of the main body cabinet  300  are formed. A position where the adjusting screws  500  is attached has a structure shown in an enlarged cross-sectional view in  FIG. 15 . 
         [0063]    In the enlarged cross-sectional view, reference number  403  denotes a core sheet metal, and reference numbers  402  and  404  respectively denote a resin molded to a bottom face side of the core sheet metal  403  and a resin molded to a top face side of the core sheet metal  403 . A screw hole is integrally formed in the resin  402  at a bottom face side, and a screw member  501  of the adjusting screw  500  is threaded into this hole. 
         [0064]    The adjusting screw  500  comprises the screw member  501  and an adjustment dial  502  secured to the screw member  501  by a fixing screw  503 . A cushion  504  is attached to an end portion of the screw member  501 . An appearance of the adjusting screw  500  is shown at a left end part (side view) in  FIG. 15 . 
         [0065]    The arm member  400  is attached, as shown in  FIG. 14 , by aligning the holes  401  shown in  FIG. 15  to four screw holes  303   a  through  303   d  among the screw holes  303   a  through  303   i  formed in the bottom face of the main body cabinet  300 , and in this state, threading the screws into the screw holes  303   a  through  303   d . The screw holes  303   a  through  303   i  all have an insert nut in which as shown in a right lower area in  FIG. 14 , a nut  305  made of a metal is inserted into a boss hole  304 . 
         [0066]    When the projector is used for ceiling mount shown in  FIG. 18A , the main body cabinet  300  is secured to a mounting mechanism for ceiling mount using all the screw holes  303   a  through  303   i . In this case, the arm member  400  is removed from the main body cabinet  300 . 
         [0067]      FIG. 16  is a drawing showing a state when the bottom face of the projector is placed on the plane to be placed (stationary mount). In this state, the protrusion  302  having the circular arc shape disposed at the bottom face of the main body cabinet  300  and the end portions of the two adjusting screws  500  attached to the arm member  400  contact with the plane to be placed. In this state, an amount of protrusion of the adjusting screw  500  with regard to the bottom face of the arm member  400  is at the minimum. In this state, the top face of the main body cabinet  300  is being rotated counterclockwise in the figure by a predetermined angle with regard to the horizontal state. 
         [0068]    When the adjusting screw  500  is rotated from the state shown in the figure and the adjusting screw  500  is further protruded from the bottom face of the arm member  400 , the projector rotates clockwise, the protrusion  302  acting as the fulcrum point. Due to this rotation, an orientation of the projection light rotates from the state shown in the figure to the clockwise direction.  FIG. 17  illustrates a state when an amount of protrusion of the adjusting screw  500  with regard to the bottom face of the arm member  400  is at the maximum. 
         [0069]    Furthermore, the projector can be rotated in an in-plane direction of an X-Z plane by making the amounts of protrusion of the two adjusting screws  500  different, and with this rotation, the orientation of the projection light can be similarly rotated in the in-plane direction of the X-Z plane. Therefore, by properly adjusting the amounts of protrusion of the two adjusting screws  500 , a rotational position of the projector can be finely adjusted in both the in-plane direction of the Y-Z plane and the in-plane direction of the X-Z plane. This allows fine adjustment of the orientation of the projection light to an appropriate position in both the in-plane direction of the Y-Z plane and the in-plane direction of the X-Z plane. 
         [0070]    According to the present embodiment, when the main body cabinet  300  is placed on the plane to be placed, the bottom face of the main body cabinet facing the plane to be placed, the level difference created on the bottom face side of the main body cabinet  300  is corrected by the arm member  400 , and therefore, the projection light can be properly oriented in a direction to projection plane also in the case of stationary mount. 
         [0071]    Furthermore, according to the present embodiment, a projecting direction of light can be finely adjusted by properly adjusting the adjusting screws  500 , and an image can be properly projected. Since adjustment of the projecting direction of the light can be performed by turning the adjusting screws  500 , the adjustment can be performed by an easy and simple operation. Furthermore, according to the present embodiment, since points of action of the two adjusting screws  500  and the protrusion  302  are arranged at apexes of a triangle, the orientation of the projection light can be finely adjusted in a two-dimensional direction, as mentioned above. 
         [0072]    Furthermore, according to the present embodiment, since the screw holes  303   a  through  303   d  for attaching the arm member  400  are commonly used as the screw holes for ceiling mount, the space on the bottom face of the main body cabinet  300  can be effectively used. Besides, the arm member  400  is unnecessary for ceiling mount, these screw holes  303   a  through  303   d  can be used as the screw holes for ceiling mount by removing the arm member  400 . 
         [0073]    With the present embodiment, since the arm member  400  is formed with a sheet metal, when the arm member  400  is held by chance while carrying the projector, the arm member will not be damaged. Furthermore, since the arm member  400  is attached by threading the arm member to the insert nut having sufficient mechanical strength as previously mentioned, even when the projector is taken up by grasping the arm member  400 , the arm member  400  will not be removed and dropped from the projector. In this way, according to the present embodiment, the mechanical strength of the arm member  400  and mounting means thereof is enhanced, damage or accident attributable to direct grasping of the arm member  400  can be obviated. 
         [0074]    The embodiment of the present invention has been described as described above, while the present invention is not limited by above-mentioned embodiment. It should be understood that various other modifications and variations may be made to the embodiment of the present invention. 
         [0075]    For example, although, in the above-mentioned embodiment, the B-light, G-light, and R-light are modulated by the display elements, and the light after modulated are synthesized by the dichroic prism, such an alternative may be used that light in a wavelength band other than in these wavelength bands is further modulated by a corresponding display element, the light after modulated is synthesized together with the B-light, G-light, and R-light and the synthesized light is entered to the projection optical system  20 . For example, in a case where there is a spectral component in a yellow wavelength band (hereafter, referred to as “Ye-light”) in the light emitted by the light source  101  in addition to the B-light, G-light, and R-light, the Ye-light is guided to the corresponding display element, and the Ye-light modulated by the display element is synthesized by the dichroic prism together with the B-light, G-light, and R-light. 
         [0076]    Besides, although a transmission type display element is used as an element for modulating the light of each color in the above-mentioned embodiment, the present invention can be applied to the projector using a reflection type display element. For an issue from which plane of the dichroic prism  116  the light of the respective colors are entered, modifications may be appropriately made in addition to the above-mentioned method. 
         [0077]    Furthermore, in the example of the arrangement shown in  FIG. 1 , although a fly-eye integrator is used as means for giving uniformity to the light, a rod integrator may be used instead. 
         [0078]    In the embodiment mentioned above, although the projector using the liquid crystal panels is shown, the present invention can be applied to a projection display device equipped with other image light generation system, e.g., a projector based on the DLP (Digital Light Processing, a trademark of Texas Instruments (TI) Incorporated). 
         [0079]    Various modifications and variations may be appropriately applied to the embodiment of the present invention within the technical concepts defined in the scope of claims.