Patent Publication Number: US-2022219538-A1

Title: Information display system and vehicle information display system using the same

Description:
TECHNICAL FIELD 
     The present invention relates to an information display system capable of displaying an image to inside or outside of a store (space) by reflecting on or transmitting through a transparent member that partitions the space such as a show window glass, and further relates to a vehicle information display system capable of displaying an image to inside or outside of an automobile, a train, an aircraft, or the like (hereinafter, collectively referred to as “vehicle”) by projecting image light onto a windshield, a rear glass, a side glass, or a combiner of the vehicle by using the information display system. 
     BACKGROUND ART 
     As this type of information display system, in general, displaying an image by using a transparent or reflection type screen has already been known, and for example, according to Patent Document 1 and Patent Document 2 below, a transparent or reflection type screen provided with a light diffusion layer containing a binder and fine particles has already been known. 
     On the other hand, as to an information display apparatus for use in a vehicle and an information display system using the same, a so-called head-up display (HUD) apparatus configured to display traffic information such as route information and traffic congestion information and vehicle information such as remaining fuel and cooling water temperature by projecting image light to form a virtual image on a windshield or a combiner of an automobile has already been known in, for example, Patent Document 3 below. In this type of information display apparatus, in general, in order to monitor the image information as a virtual image for the purpose of reducing the movement of the point of view of a driver, the configuration in which the image displayed on the image display apparatus is projected onto the point of view of the driver by using an optical system including a concave mirror (function of convex lens) has been adopted in many cases. 
     RELATED ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Patent No. 6133522 
         Patent Document 2: Japanese Patent No. 6199530 
         Patent Document 3: Japanese Unexamined Patent Application Publication No. 2015-194707 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in the above-mentioned magnification projection information display system or apparatus which is the conventional technology, consideration is not given to the improvement of the light utilization efficiency by efficient delivery of the image light to the observer, and as a result, there is the first problem that it is difficult to reduce the power consumption of the system and the image projection apparatus including the light source of the apparatus. 
     Further, in a vehicle information display apparatus represented by a head-up display or the like, AR (Augmented-Reality) information which is a virtual image is displayed so as not to obstruct the view outside the vehicle from the driver, but high resolution and high visibility are also required when displaying information such as a map. Therefore, a liquid crystal display element (liquid crystal display panel) is often used because a high-quality image can be easily obtained and it is inexpensive. On the other hand, since a small-sized liquid crystal display element is used in order to reduce the size of the set, the obtained resolution of the projection image is insufficient, and it poses the new second problem that it is not suitable for displaying a high-resolution image displayed on a smartphone or the like. 
     Further, in the conventional vehicle information display apparatus of the head-up display type, when the inclination angle of the windshield is large (close to vertical), since the place where the imaging apparatus is arranged is limited to the space between the steering and the windshield, the image light from the imaging apparatus is reflected in the direction in which the light cannot reach the eyes of the driver after the reflection on the windshield and the system cannot be established, so that the third problem that there is the restriction on the structure of the vehicle in which the apparatus is installed is clarified. 
     Further, the conventional vehicle information display apparatus of the head-up display type is not intended to display image information to the outside of the vehicle. Therefore, when it is desired to display image information to the outside of the vehicle, an image display apparatus such as a display is mounted inside the vehicle, and the image information is displayed through the glass of the vehicle. However, in that case, the image display apparatus obstructs the view of the driver, which is not preferable for safe driving. 
     In Patent Document 1 and Patent Document 2, which are conventional technologies, a reflection type screen or a transparent screen provided with a light diffusion layer containing a binder and fine particles used in an information display apparatus is disclosed, but no consideration is given to efficient delivery of image light to an observer, that is, improvement of light utilization efficiency, and there is no teaching on the application in vehicles and the specific method, form, and configuration for that purpose. 
     The present invention provides the information display system capable of displaying high-resolution image information even on a glass surface of a show window or the like and capable of significantly reducing the power consumption in the system and apparatus including the light source and the image projection apparatus by improving the light utilization efficiency by efficient delivery of the image light to the observer, and the vehicle information display system using the information display system, instead of the conventional information display system and apparatus. Also, the present invention aims to provide the vehicle information display system capable of performing the so-called unidirectional display in which the information can be visually confirmed by the passengers including the driver inside the vehicle but cannot be visually confirmed from the outside of the vehicle or the information can be visually confirmed from the outside of the vehicle but cannot be visually confirmed by the passengers inside the vehicle via the shield glass including a windshield, a rear glass, and a side glass of the vehicle, regardless of the inclination angle thereof, in addition to the reduction of the power consumption by the improvement of the light utilization efficiency. 
     Means for Solving the Problems 
     In the present invention, in order to achieve the above-mentioned objects, first, an information display system configured to unidirectionally display an image to inside or outside of a space via a transparent projected member that constitutes the space is provided. The information display system includes an image projection apparatus arranged inside the space and configured to generate and project image light by modulating a light flux from a light source, a transparent sheet provided on an inner surface of a display region set in a part of the projected member, and a light direction changing unit configured to direct a direction of the image light from the image projection apparatus to the transparent sheet in the display region, and the image projection apparatus includes an image light characteristic converting unit configured to convert the image light from the light source constituting the image projection apparatus into image light having a narrow diffusion angle and composed of a specific polarization component. 
     Also, in the present invention, in order to achieve the above-mentioned objects, a vehicle information display system configured to display information to inside or outside of a vehicle by using a part of a transparent projected member constituting the vehicle as a display region is provided. The vehicle information display system includes an image projection apparatus provided inside the vehicle and configured to project image light of the information, a transparent sheet provided on an inner surface of the display region set on a part of the projected member, and a light direction changing unit configured to change a direction of the image light from the image projection apparatus to the transparent sheet, and the image projection apparatus includes an image light characteristic converting unit for converting the image light from the light source constituting the image projection apparatus into image light having a narrow diffusion angle and composed of a specific polarization component. 
     Effect of the Invention 
     According to the present invention, it is possible to provide a new and highly usable information display system capable of displaying high-resolution image information even on a glass surface of a show window or the like and capable of significantly reducing power consumption by the improvement of the light utilization efficiency by efficient delivery of image light to an observer. Further, a vehicle information display system capable of significantly reducing power consumption is provided by using the information display system, and the vehicle information display system can perform the so-called unidirectional display in which the information can be visually confirmed by the passengers including the driver inside the vehicle but cannot be visually confirmed from the outside of the vehicle or the information can be visually confirmed from the outside of the vehicle but cannot be visually confirmed by the passengers inside the vehicle via the shield glass including a windshield, a rear glass, and a side glass of the vehicle. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         FIG. 1  is a diagram showing an example of an overall configuration of an information display system according to an embodiment of the present invention; 
         FIG. 2  is a diagram showing an example of a specific configuration of a light source apparatus constituting an image projection apparatus of the information display system; 
         FIG. 3  is a cross-sectional layout view for describing a configuration and operation of the light source to perform the polarization conversion in the image projection apparatus; 
         FIG. 4  is a cross-sectional layout view for describing a configuration and operation of the light source to perform the polarization conversion in the image projection apparatus; 
         FIG. 5  is a diagram showing an example of a configuration of a lenticular lens constituting the image projection apparatus of the information display system; 
         FIG. 6  is a diagram including graphs showing image light diffusion characteristics of an image display apparatus; 
         FIG. 7  is a diagram including graphs showing image light diffusion characteristics of an image display apparatus; 
         FIG. 8  is a cross-sectional view for describing the principle of a light direction changing panel constituting the image projection apparatus of the information display system; 
         FIG. 9  is a cross-sectional view showing an example of a schematic configuration of a protective cover constituting the image projection apparatus of the information display system; 
         FIG. 10  is a diagram showing a coordinate system to measure visual characteristics of a liquid crystal panel; 
         FIG. 11  is a diagram showing angular characteristics of luminance (up-down direction) in a general liquid crystal panel; 
         FIG. 12  is a diagram showing angular characteristics of contrast (up-down direction) in a general liquid crystal panel; 
         FIG. 13  is a diagram showing angular characteristics of luminance (left-right direction) in a general liquid crystal panel; 
         FIG. 14  is a diagram showing angular characteristics of contrast (left-right direction) in a general liquid crystal panel; 
         FIG. 15  is a cross-sectional view showing a configuration example of a light direction restriction panel provided in the image display apparatus of the information display system; 
         FIG. 16  is a cross-sectional view showing a configuration of a unidirectional transparent sheet (reflection type) (first example) constituting the image projection apparatus of the information display system; 
         FIG. 17  is a cross-sectional view showing a configuration of a unidirectional transparent sheet (reflection type) (second example) constituting the image projection apparatus of the information display system; 
         FIG. 18  is a cross-sectional view showing a configuration of a unidirectional transparent sheet (transmission type) (first example) constituting the image projection apparatus of the information display system; 
         FIG. 19  is a cross-sectional view showing a configuration of a unidirectional transparent sheet (transmission type) (second example) constituting the image projection apparatus of the information display system; 
         FIG. 20  is a diagram showing an example in which the information display system is applied to an automobile; 
         FIG. 21  is a diagram showing an example in which the image display apparatus of the information display system is installed on a ceiling portion of an automobile serving as a vehicle; 
         FIG. 22  is a diagram showing places where images are displayed on glass portions of an automobile when the image display apparatus of the information display system is installed on a ceiling portion of an automobile serving as a vehicle; 
         FIG. 23  is a diagram showing an example in which the image display apparatus of the information display system is installed on a ceiling portion of an automobile serving as a vehicle; 
         FIG. 24  is a diagram showing places where images are displayed on glass portions of an automobile when the image display apparatus of the information display system is installed on a ceiling portion of an automobile serving as a vehicle; 
         FIG. 25  is a diagram showing an example in which the information display system is applied to a bus serving as a vehicle; 
         FIG. 26  is a diagram showing an example in which the information display system is applied to a train serving as a vehicle; 
         FIG. 27  is a diagram including a graph showing a wavelength distribution of natural light such as sunlight; 
         FIG. 28  is a diagram including graphs showing reflectance of glass with respect to p-polarized light and s-polarized light of natural light such as sunlight; 
         FIG. 29  is a diagram showing an example of a specific configuration of the vehicle information display system in which the information display system is applied to a vehicle; 
         FIG. 30  is a diagram showing an example of a more specific configuration of the vehicle information display system in which the information display system is applied to a vehicle; 
         FIG. 31  is a diagram showing an example in which the information display system is applied to a vehicle; 
         FIG. 32  is a diagram showing an example of an arrangement of the vehicle information display system configured to display information to a driver via a windshield of a vehicle; 
         FIG. 33  is a diagram showing an example of an arrangement of the vehicle information display system configured to display information to a driver and an observer on a passenger seat via a windshield of a vehicle; 
         FIG. 34  is a diagram showing an example in which information is displayed to outside of a vehicle via a rear glass of a vehicle; 
         FIG. 35  is a diagram showing a relationship between a size of a virtual image obtained by the information display system and a position where the virtual image is generated; and 
         FIG. 36  is a diagram showing an example in which a light direction restriction panel provided in the image display apparatus of the information display system is installed in a vehicle together with the image display apparatus. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to drawings and the like. Note that the present invention is not limited to the following descriptions, and various changes and modifications can be made by a person having ordinary skill in the art within the scope of the technical idea disclosed in this specification. In addition, in all the drawings for describing the present invention, components having the same function are denoted by the same reference characters, and repetitive description thereof will be omitted in some cases. 
     &lt;Information Display System&gt; 
       FIG. 1  shows an overall configuration of an information display system according to an embodiment of the present invention. For example, in a store or the like, a space is partitioned by a show window (also referred to as “window glass”)  220  which is a translucent member such as glass, and according to the information display system of the present embodiment, it is possible to unidirectionally display an image to inside or outside of the store (space) by reflecting on or transmitting through the transparent member. In  FIG. 1 , the inside of the show window  220  (inside the store) is shown as a far side in the depth direction, and the outside thereof (for example, the sidewalk) is shown a near side. 
     More specifically, as shown in  FIG. 1 , though described later in detail, an image display apparatus  48  provided with a light source and configured to generate and project image light to be displayed is arranged above the show window  220  which is a transparent member such as glass, and the image light generated by the image display apparatus  48  is unidirectionally displayed to inside or outside selectively by the function of a light direction changing panel  54  and a transparent sheet (film)  51  attached to the show window  220  also described later in detail. Accordingly, it is possible to display various kinds of information to inside or outside of the show window  220  by using it, and it is possible to remarkably improve the utilization efficiency of the show window. 
     Next,  FIG. 2  shows a more specific configuration of the above-mentioned information display system, and an image display element  52  constituting the above-mentioned image display apparatus  48  is composed of a relatively large-sized liquid crystal display panel with a screen size of more than 6 inches. Further, in order to perform correction at a level of causing no problem in practical use by distortion correction, the resolution of the panel is preferably 1280×720 dots or more. 
     Also, the image display apparatus  48  further includes a light source apparatus  101  constituting a light source thereof together with the above-mentioned liquid crystal display panel  52 , and the light source apparatus  101  is shown in a developed perspective view together with the above-mentioned liquid crystal display panel  52  in  FIG. 2 . 
     Though described later in detail, as indicated by arrows  30  in  FIG. 2 , the liquid crystal display panel (element)  52  obtains an illumination light flux having characteristics similar to laser light with strong directivity (straightness) and polarization plane aligned in one direction, by the light from the light source apparatus  101  which is a backlight apparatus, and emits the image light modulated in accordance with an input image signal to the transparent sheet  51  provided on a surface of the window glass  220 . 
     Also, in  FIG. 2 , the information display system is shown together with the liquid crystal display panel  52  constituting the image display apparatus  48 . Also, as shown below, it further includes the light direction changing panel  54  configured to control the directional characteristics of the light flux emitted from the light source apparatus  101  and a narrow-angle diffusion plate (not shown) as needed. Namely, polarization plates are provided on both surfaces of the liquid crystal display panel  52 , and the image light having a specific polarization is emitted with the light intensity modulated by the image signal (see arrows  30  in  FIG. 2 ). 
     Consequently, a desired image is projected as specific polarized light having high directivity (straightness) toward the window glass  220  via the light direction changing panel  54 , and it is reflected by or transmits through the transparent sheet  51  provided on the surface thereof toward the eyes (not shown) of the observer inside or outside the store (space). Note that a protective cover (not shown) may be provided on the surface of the above-mentioned light direction changing panel  54 . 
     In this embodiment, in order to significantly reduce the power consumption by improving the utilization efficiency of the light flux  30  emitted from the light source apparatus  101 , in the image display apparatus  48  including the light source apparatus  101  and the liquid crystal display panel  52 , high directivity is given by an optical component such as a lenticular lens described below to the luminance of the image light which is the light from the light source apparatus  101  (see arrows  30  in  FIG. 2 ) and is transmitted through or diffused by the transparent sheet  51  provided on the surface of the window glass  20  as described below. According to this, the image light from the image display apparatus  48  efficiently reaches an observer inside the show window  220  (inside the store) or an observer outside it (for example, on a sidewalk) with high directivity (straightness) like a laser beam, and as a result, a high-quality image can be displayed with high resolution and the power consumption by the image display apparatus  48  including an LED element  201  serving as a light source can be remarkably reduced. 
     &lt;Embodiment of Image Display Apparatus&gt; 
       FIG. 3  shows a specific configuration of the light source apparatus  101  described above. In  FIG. 3 , the liquid crystal display panel  52  and the light direction changing panel  54  arranged on the image display apparatus  48  including the light source apparatus  101  in  FIG. 2  are shown. The light source apparatus  101  is formed into a case made of plastic or the like as shown in  FIG. 2 , and is configured such that the LED element  201  and a light guide body  203  described later in detail are housed in the case. On an end surface of the light guide body  203 , in order to convert the divergent light from each of the LED elements  201  into substantially parallel light flux as shown in  FIG. 2 , a lens shape whose cross-sectional area gradually increases toward a light receiving portion and which functions to gradually reduce a divergence angle by total reflection plural times when propagating inside is provided. On an upper surface thereof, the liquid crystal display panel  52  constituting the image projection apparatus  48  is attached. 
     Further, on one side surface (left end surface in the example of  FIG. 3 ) of the case of the light source apparatus  101 , the LED (Light Emitting Diode) element  201  which is a semiconductor light source and an LED board  202  on which the control circuit thereof is mounted are attached, and a heat sink which is a member for cooling the heat generated by the LED element and the control circuit is attached to an outer surface of the LED board  202  in some cases. 
     On the other hand, on a frame (not shown) of the liquid crystal display panel attached to the upper surface of the case of the light source apparatus  101 , the liquid crystal display panel  52  attached to the frame, an FPC (Flexible Printed Circuits: Flexible Wiring Board) (not shown) electrically connected to the liquid crystal display panel, and the like are attached. Namely, though described in detail later, the liquid crystal display panel  52  which is a liquid crystal display element generates the display image by modulating the intensity of transmitted light based on the control signal from the control circuit (not shown here) constituting an electronic apparatus together with the LED element  201  which is a solid light source. At this time, since the image light to be generated has a narrow diffusion angle and includes only a specific polarization component, a novel and non-conventional image display apparatus that is close to a surface-emitting laser image source driven by an image signal can be obtained. 
     At present, a laser light flux having the same size as the image obtained by the above-mentioned image display apparatus  48  cannot be obtained by using the laser apparatus also from the viewpoint of safety. Therefore, in this embodiment, for example, the light close to the above-mentioned surface-emitting laser image light is obtained from a light flux from a general light source provided with an LED element. 
     &lt;Lenticular Lens&gt; 
     In order to control the diffusion distribution of the image light from the liquid crystal display panel  52 , the unidirectional emission characteristics (image light in the x-axis direction in the drawing) can be controlled by optimizing the lens shape by providing a lenticular lens  800  shown in  FIG. 5  between the above-mentioned light source apparatus  101  and the liquid crystal display panel  52  or on the surface of the liquid crystal panel  52 . Further, by arranging the microlens array in a matrix shape, the emission characteristics of the image light flux from the image projection apparatus  48  can be controlled in the x-axis direction and the y-axis direction, and as a result, an image display apparatus having desired diffusion characteristics can be obtained. 
     Subsequently, the configuration of the optical system housed in the case of the light source apparatus  101  will be described in detail below with reference to  FIG. 4  together with  FIG. 3  described above. 
     Since  FIG. 3  and  FIG. 4  are cross-sectional views, only one of the plurality of LED elements  201  constituting the light source is shown, and these are converted to substantially collimated light by the shape of alight receiving end surface  203   a  of the light guide body  203  as described above. Therefore, the light receiving portion on the end surface of the light guide body and the LED element are attached so as to keep a predetermined positional relationship. 
     Each of the light guide bodies  203  is made of a translucent resin such as acrylic resin. Also, the LED light receiving surface at the end of the light guide body has a conical convex outer peripheral surface obtained by, for example, rotating a paraboloid cross section, has at the top thereof a concave portion in which a convex portion (that is, a convex lens surface) is formed at the center thereof, and has a convex lens surface projecting outward (or a concave lens surface recessed inward) in the central portion of the flat surface portion thereof (not shown). The outer shape of the light receiving portion of the light guide body to which the LED element  201  is attached has a parabolic shape forming a conical outer peripheral surface, and it is set within an angular range capable of totally reflecting the light emitted in the peripheral direction from the LED element therein or has a reflection surface formed thereon. 
     On the other hand, the LED element  201  is arranged at a predetermined position on the surface of the so-called LED board  202  which is the circuit board thereof. The LED board  202  is arranged and fixed with respect to the LED collimator (light receiving end surface  203   a ) such that the LED element  201  on the surface thereof is located at the central portion of the concave portion described above. 
     With the configuration described above, the light emitted from the LED element  201  can be taken out as substantially parallel light by the shape of the light receiving end surface  203   a  of the light guide body  203  described above, and the utilization efficiency of the generated light can be improved. 
     As described above, the light source apparatus  101  is configured by attaching the light source unit, in which a plurality of LED elements  201  as a light source is arranged, on the light receiving end surface  203   a  serving as a light receiving portion provided on the end surface of the light guide body  203 . The divergent light flux from the LED element  201  is converted to substantially parallel light by the lens shape of the light receiving end surface  203   a  on the end surface of the light guide body, is guided inside the light guide body  203  as indicated by arrows (horizontal direction in the drawing), and is then emitted to the liquid crystal display panel  52  arranged approximately parallel to the light guide body (vertical direction in the drawing) by a light flux direction changing unit  204 . By optimizing the distribution (density) of the light flux direction changing unit  204  by the internal shape or the surface shape of the light guide body, the uniformity of the light flux incident on the liquid crystal display panel  52  can be controlled. 
       FIG. 3  is a cross-sectional layout view for describing the configuration and operation of the light source of the present embodiment to perform the polarization conversion in the light source apparatus  101  including the light guide body  203  and the LED element  201  described above. In  FIG. 3 , the light source apparatus  101  includes the light guide body  203  having the light flux direction changing unit  204  provided on its surface made of plastic or the like or in its inside, the LED element  201  as a light source, a reflection sheet  205 , a retardation plate  206 , the above-mentioned lenticular lens  800 , and the like, and the liquid crystal display panel  52  having a polarization plate provided on a light source light incident surface and an image light emission surface is attached on its upper surface as the image projection apparatus  48 . 
     Further, a film or sheet-shaped reflection type polarization plate  49  is provided on the light source light incident surface (lower surface in the drawing) of the liquid crystal display panel  52  corresponding to the light source apparatus  101 , by which one polarized wave (for example, P wave)  212  of the natural light flux  210  emitted from the LED light source  201  is selectively reflected, and the reflected light is reflected by the reflection sheet  205  provided on one surface (lower part of the drawing) of the light guide body  203  and is directed again toward the liquid crystal display panel  52 . 
     Then, by providing a retardation plate (λ/4 plate)  206  between the reflection sheet  205  and the light guide body  203  or between the light guide body  203  and the reflection type polarization plate  49 , the light is reflected by the reflection sheet  205  and is transmitted twice to convert the reflection light flux from p-polarized light to s-polarized light, so that the utilization efficiency of the light source light as the image light is improved. Since the image light flux whose light intensity is modulated by the image signal in the liquid crystal display panel  52  (arrows  213  in  FIG. 3 ) is incident on the window glass  220  at a large incident angle as shown in  FIG. 1 , the reflectance at the transparent sheet  51  is increased, and favorable diffusion characteristics for monitoring inside or outside the store (space) can be obtained. 
       FIG. 4  is a cross-sectional layout view for describing the configuration and operation of the light source of the present embodiment to perform the polarization conversion in the light source apparatus  101  including the light guide body  203  and the LED element  201  similarly to  FIG. 3 . The light source apparatus  101  of  FIG. 4  also includes the light guide body  203  having the light flux direction changing unit  204  provided on its surface made of plastic or the like or in its inside, the LED element  201  as a light source, the reflection sheet  205 , the retardation plate  206 , the above-mentioned lenticular lens  800 , and the like, and the liquid crystal display panel  52  having a polarization plate provided on a light source light incident surface and an image light emission surface is attached on its upper surface as the image projection apparatus  48 . 
     Further, the film or sheet-shaped reflection type polarization plate  49  is provided on the light source light incident surface (lower surface in the drawing) of the liquid crystal display panel  52  corresponding to the light source apparatus  101 , by which one polarized wave (for example, S wave)  211  of the natural light flux  210  emitted from the LED light source  201  is selectively reflected, and the reflected light is reflected by the reflection sheet  205  provided on one surface (lower part of the drawing) of the light guide body  203  and is directed again toward the liquid crystal display panel  52 . By providing a retardation plate (λ/4 plate) between the reflection sheet  205  and the light guide body  203  or between the light guide body  203  and the reflection type polarization plate  49 , the light is reflected by the reflection sheet  205  and is transmitted twice to convert the reflection light flux from s-polarized light to p-polarized light, so that the utilization efficiency of the light source light as the image light is improved. Even when the image light flux whose light intensity is modulated by the image signal in the liquid crystal display panel  52  (arrows  214  in  FIG. 4 ) is incident on the window glass  220  at a large incident angle as shown in  FIG. 1 , the reflection on the surface is reduced, and the image light can be efficiently diffused to the outside by the transparent sheet  51 . 
     Here, the function of the lenticular lens  800  shown in  FIG. 5  will be described. The lenticular lens  800  makes it possible to efficiently reflect or diffuse the light emitted from the image display apparatus  48  described above on the transparent sheet  51  on the window glass  220  by optimizing the lens shape. Namely, for example, as shown in  FIG. 6( a )  and  FIG. 6( b ) , by arranging two lenticular lenses in combination or microlens array in a matrix shape with respect to the image light from the image projection apparatus  48  and providing a sheet for controlling diffusion characteristics, the luminance (relative luminance) of the image light can be controlled in accordance with its reflection angle (0 degrees in the vertical direction) in the X-axis direction and the Y-axis direction. 
     In this embodiment, by the lenticular lens  800  mentioned above, the luminance characteristics in the vertical direction are made steeper as shown in  FIG. 6( b )  and further the light luminance (relative luminance) by the reflection and diffusion is increased by changing the balance of the directional characteristics in the vertical direction (positive and negative directions of the y-axis) as compared with the conventional case, whereby the image light having a narrow diffusion angle (high straightness) and including only a specific polarization component like the image light from the surface-emitting laser image source is obtained, and is efficiently delivered to the eyes of the observer. 
     Also, by achieving the directional characteristics having significantly narrower angle in both the x-axis direction and the y-axis direction shown as the first embodiment and the second embodiment by the above-mentioned light source apparatus, as compared with the diffusion characteristics of the emission light (referred to as conventional in  FIG. 6 ) from the general liquid crystal panel shown in  FIG. 6( a )  and  FIG. 6( b ) , the image display apparatus capable of emitting light of a specific polarization which emits an image light flux almost parallel to a specific direction can be realized. 
       FIG. 7  shows an example of the characteristics of the lenticular lens used in this embodiment. In this example, in particular, the characteristics in the X direction (vertical direction) are shown, and a characteristic O shows a luminance characteristic in which the peak in the light emission direction is at an angle of about 30 degrees upward from the vertical direction (0 degrees) and is vertically symmetrical. Also, characteristics A and B in  FIG. 7  further show examples of the characteristics in which the image light above the peak luminance is condensed at around degrees to increase the luminance (relative luminance). Therefore, in these characteristics A and B, the luminance (relative luminance) of light is sharply reduced at the angle exceeding 30 degrees as compared with the characteristic O. 
     Namely, with the above-mentioned optical system including the lenticular lens, the image light from the image projection apparatus  48  can be reflected and diffused while increasing (emphasizing) the luminance thereof in a specific direction via the transparent sheet  51  on the window glass  220  described below. Consequently, the image light from the image projection apparatus  48  can be efficiently delivered to the eyes of the observer inside or outside the room as the light having a narrow diffusion angle (high straightness) and including only a specific polarization component like the image light from the surface-emitting laser image source. According to this, even if the intensity (luminance) of the image light from the image projection apparatus  48  is reduced, the observer can accurately recognize the image light and obtain information. In other words, it is possible to realize the information display system with lower power consumption by further reducing the output of the image projection apparatus  48 . 
     &lt;Light Direction Changing Panel&gt; 
       FIG. 8  is a schematic explanatory diagram for describing the principle of the light direction changing panel  54  constituting a part of the information display system of the present embodiment and provided on the upper surface of the image display apparatus  48  described above. The light flux from the light guide body  203  of the light source apparatus  101  described above is incident from the incident surface (lower surface in the drawing) of the light direction changing panel  54 , and is refracted in a desired direction θ 3  by the lens function of the linear Fresnel lens provided on the emission surface (upper surface in the drawing). At this time, the desired direction θ 3  is uniquely derived from Snell&#39;s law by the incident angle θ 2  of the light flux to the Fresnel lens, the Fresnel angle θ 0  of the Fresnel lens, and the refractive index n of the base material. 
     As a result, the directivity in a desired direction can be given to the substantially parallel light flux from the light guide body. Namely, the image light emitted from the liquid crystal display panel  52  constituting the image display apparatus  48 , which has high straightness and includes only a specific polarization component, is directed to the transparent sheet  51  provided on the window glass  220  described later without being visually recognized by an observer inside or outside the store (space). Thereafter, the image light is unidirectionally reflected and diffused by the transparent sheet  51 , and the reflected image is visually recognized by the observer. 
     Namely, by the light direction changing panel  54 , the image light itself from the image display apparatus  48  (see  FIG. 1 ) is not visually recognized directly inside the space and thus does not disturb the observer in the store, and only the reflected image of the reflected light will be monitored by the observer. By providing a light-absorbing paint or pigment on a connecting surface  88  of the Fresnel lens, the generation of light other than the light flux traveling in a desired direction is suppressed. As a result, unnecessary light is not mixed with the image light reflected by the window glass  220 , so that the imaging performance is not impaired. 
     &lt;Protective Cover&gt; 
       FIG. 9  is a cross-sectional view showing a schematic configuration of a protective cover  50  provided on the upper surface of the above-mentioned light direction changing panel  54 . Black stripes  59  are provided on a part of the light emission side of a substantially transparent base material  56 . In order to reduce the surface reflection of external light including sunlight, a black paint such as a paint containing carbon black is preferably used as the black stripe  59 . Further, by providing an antireflection film for suppressing surface reflection on the portion where the black stripe is not provided, the external light reflection on the surface of the protective cover  50  is significantly reduced, and the hindrance due to the external light reflection is reduced. On the other hand, in order to enhance the light-shielding performance against sunlight, it is preferable to make the antireflection film have a property of reflecting near-infrared light and infrared light. 
     On the other hand, on the light incident side (lower side of the drawing) of the substantially transparent base material  56 , a film  50   a  that absorbs or reflects the P wave component of the solar light flux is formed or adhered. As a result, since the P wave component of sunlight and the like do not enter the image projection apparatus  48 , the reliability regarding light resistance and heat resistance is greatly improved. On the other hand, since it also has the characteristics of a filter that selectively transmits the S-polarized image light output from the image projection apparatus  48 , the contrast performance of the obtained image is significantly improved. 
     By the way, in a general TFT (Thin Film Transistor) liquid crystal panel, luminance and contrast performances differ depending on the light emission direction due to the mutual characteristics of the liquid crystal and the polarization plate. In the evaluation under the measurement environment shown in  FIG. 10 , the characteristics of the luminance and the viewing angle in the up-down direction of the panel are excellent at the angle slightly deviated (+5 degrees in this embodiment) from the emission angle vertical to the panel surface (emission angle: 0 degrees) as shown in  FIG. 11 . This is because the characteristics of twisting light in the up-down direction of the liquid crystal do not become 0 degrees when the applied voltage is maximum. 
     On the other hand, as shown in  FIG. 12 , the contrast performance in the up-down direction is excellent in the range of −15 degrees to +15 degrees, and the use in the range of ±10 degrees centered on 5 degrees can obtain the best characteristics when combined with the luminance characteristics. 
     Also, as shown in  FIG. 13 , the characteristics of the luminance and the viewing angle in the left-right direction of the panel are excellent at the emission angle vertical to the panel surface (emission angle: 0 degrees). This is because the characteristics of twisting light in the left-right direction of the liquid crystal become 0 degrees when the applied voltage is maximum. 
     Similarly, as shown in  FIG. 14 , the contrast performance in the left-right direction is excellent in the range of −5 degrees to −10 degrees, and the use in the range of ±5 degrees centered on −5 degrees can obtain the best characteristics when combined with the luminance characteristics. Therefore, by making the light enter the liquid crystal panel from the direction in which the most excellent characteristics can be obtained by the light flux direction changing unit  204  provided in the light guide body  203  of the light source apparatus  101  described above and performing the light modulation by the image signal, the image quality and performance of the image display apparatus  48  can be improved. 
     In order to bend the image light from the liquid crystal panel as the image display element in a desired direction, it is preferable to provide the light direction changing panel  54  on the emission surface of the liquid crystal panel. 
     &lt;Image Light Control Film&gt; 
       FIG. 15  is a cross-sectional view of an image light control film  70  having a function of restricting the emission direction of the image light. The image light control film  70  is provided on, for example, the upper surface of the image display apparatus  48  and emits the image light from the liquid crystal display panel  52  in a specific direction (in the direction of the white arrow in the drawing). Also, since a black portion  70   b  of the image light control film  70  blocks a part of the light, the light does not directly enter the observer&#39;s eyes, and it is thus possible to prevent the hindrance due to the direct light from the image display apparatus  48  entering the observer&#39;s eyes. 
     The image light control film  70  has a function of preventing the image light from directly directing to the observer, while the image light passes through a transparent portion  70   a  and is reflected by a windshield  6  or the like and can be recognized by the driver who is the observer. As the image light control film  70 , for example, a viewing angle control film (VCF: View Control Film) of Shin-Etsu Polymer Co., Ltd. is suitable, and since the structure thereof is such that transparent silicon and black silicon are alternately arranged and a synthetic resin is arranged on a light incident/emission surface to form a sandwich structure, the same effect as that of the image light control film  70  of the present embodiment can be expected. 
     It is desirable that a pitch h of the transparent portion  70   a  and the black portion  70   b  of the viewing angle control film described above is ⅓ or less with respect to the pixels of the image to be displayed. At this time, when the viewing angle α is desired to be larger than 90 degrees, a thickness W should be set such that h/w becomes larger than 1.0, and when the viewing angle α is desired to be smaller than 90 degrees, the thickness W should be set such that h/w becomes smaller than 1.0. On the other hand, there is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  is 10% or less, but it is preferably 4% or less. 
     &lt;Unidirectional Transparent Sheet: First Example of Reflection Type&gt; 
     Next, in the overall configuration of the information display system according to the present embodiment, in particular, the configuration and function of the transparent sheet  51  will be described with reference to  FIG. 16 . Here, the S polarized wave of the sunlight incident on the window glass  220  from an oblique direction is reflected, and the P polarized wave is transmitted and directed to the transparent sheet  51 . The transparent sheet  51  is composed of a polarization plate  57  that transmits S waves, a transparent diffusion sheet material  55 , and a retardation plate  58 . 
     For this transparent sheet  51 , a film obtained by melting and stretching a thermoplastic polymer in which zirconium nanoparticles and diamond nanoparticles having a large refractive index are dispersed, for example, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. can be used (see Patent Document 3 mentioned above). Consequently, the display which is transparent and does not prevent the observer from monitoring the scenery of the outside world (outside the store) when the image is not displayed and the display which diffuses and reflects the image light such that the observer inside or outside the store (space) can visually recognize the image information when the image is displayed, that is, the unidirectional display can be realized. At this time, there is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  is 10% or less, but it is preferably 4% or less. 
     Since the image light from the image projection apparatus  48  is S-polarized wave, it scatters inside the transparent diffusion sheet material  55  described above and is emitted toward the observer in a state where the reflectance in the oblique incidence is high. On the other hand, a part of the image light whose polarization direction is disturbed due to the scattering diffuses and transmits through the transparent diffusion sheet material  55 , and is emitted toward the window glass  220 . Since the difference in refractive index is small on the incident surface of the window glass  220 , the level of the double image generated by the reflected light is low. 
     On the other hand, since the intensity of the reflected light generated on the emission surface (the surface in contact with the outside world) of the window glass  220  is mostly the S polarization component, the reflectance is large. Since the image light reflected on this surface passes through the polarization plate  57  again after reflection and is then absorbed, it does not return to the observer side. Therefore, since the light intensity of the double image generated by the reflected image of the window glass  220  can be significantly reduced, the image quality is greatly improved. Similarly, it goes without saying that the same effect can be obtained by attaching the above-mentioned transparent sheet  51  to the combiner instead of the window glass  220  as the image reflection surface. 
     With the transparent sheet  51  described above, the sunlight component of the P-polarized light that has passed through the window glass  220  (passed through also the combiner afterward in the combiner method) under predetermined conditions in the daytime is absorbed in front of the information display system and the light direction changing panel  54  and the protective cover  50  provided on the upper surface thereof, so that it is possible to prevent it from returning to the liquid crystal display panel and the polarization plate. 
     &lt;Unidirectional Transparent Sheet: Second Example of Reflection Type&gt; 
     The second example of the reflection type unidirectional transparent sheet will be described with reference to  FIG. 17 . In this example, the image light control film  70  shown in  FIG. 15  is further added on the transparent sheet  51  described above to form an external light control film (hereinafter, denoted by reference numeral  70 ). 
     As described above, the S polarized wave of sunlight incident on the window glass  220  from an oblique direction is reflected, and the P polarized wave thereof is transmitted and directed to the transparent sheet  51 . At this time, it is absorbed by the black region  70   b  (shown in gray in  FIG. 17 ) provided in the external light control film  70 , and does not reach the inside of the room or the vehicle in which the image display apparatus is arranged. 
     Further, since it is not mixed with the image light from the image display apparatus  48 , deterioration of the image quality is prevented. The transparent sheet  51  is made of the transparent diffusion sheet material  55 . For this transparent sheet  51 , a film obtained by melting and stretching a thermoplastic polymer in which zirconium nanoparticles and diamond nanoparticles having a large refractive index are dispersed, for example, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. can be used (see Patent Document 3 mentioned above). Consequently, the display which is transparent and does not prevent the observer from monitoring the scenery of the outside world (outside the store) when the image is not displayed and the display which diffuses and reflects the image light such that the observer inside or outside the store (space) can visually recognize the image information when the image is displayed, that is, the unidirectional display can be realized. 
     Further, the above-mentioned external light control film  70  does not obstruct the monitoring of the scenery of the outside world because the light of the outside world passes through the transparent portion  70   a  when the observer monitors the scenery of the outside world. As this external light control film  70 , for example, a viewing angle control film (VCF: View Control Film) of Shin-Etsu Polymer Co., Ltd. is suitable, and since the structure thereof is such that transparent silicon and black silicon are alternately arranged and a synthetic resin is arranged on a light incident/emission surface to form a sandwich structure, the same effect as that of the external light control film of the present embodiment can be expected. It is desirable that a pitch h of the transparent portion  70   a  and the black portion  70   b  of the viewing angle control film described above is ⅓ or less with respect to the pixels of the image to be displayed. At this time, when the viewing angle α is desired to be larger than 90 degrees, a thickness W should be set such that h/w becomes larger than 1.0, and when the viewing angle α is desired to be smaller than 90 degrees, the thickness W should be set such that h/w becomes smaller than 1.0. 
     On the other hand, there is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  is 10% or less, but it is preferably 4% or less. In addition, the total transmittance of 75% or more is required when it is attached to a windshield for use in a vehicle. 
     Since the image light from the image projection apparatus  48  is S-polarized wave, it scatters inside the transparent diffusion sheet material  55  described above and is emitted toward the observer in a state where the reflectance in the oblique incidence is high. On the other hand, a part of the image light whose polarization direction is disturbed due to the scattering diffuses and transmits through the transparent diffusion sheet material  55 , and is emitted toward the window glass  220 . Since the difference in refractive index is small on the incident surface of the window glass  220 , the level of the double image generated by the reflected light is low. 
     On the other hand, since the intensity of the reflected light generated on the emission surface (the surface in contact with the outside world) of the window glass  220  is mostly the S polarization component, the reflectance is large. Since the image light reflected on this surface passes through the external light control film  70  again after reflection and is then absorbed in the black region  70   b , it does not return to the observer side. Therefore, since the light intensity of the double image generated by the reflected image of the window glass  220  can be significantly reduced, the image quality is greatly improved. Similarly, it goes without saying that the same effect can be obtained by attaching the above-mentioned transparent sheet  51  to the combiner instead of the window glass  220  as the image reflection surface. 
     With the unidirectional transparent sheet  51  described above, the sunlight component of the P-polarized light that has passed through the window glass  220  (passed through also the combiner afterward in the combiner method) under predetermined conditions in the daytime is absorbed in front of the information display system and the light direction changing panel  54  and the protective cover  50  provided on the upper surface thereof, so that it is possible to prevent it from returning to the liquid crystal display panel and the polarization plate. 
     &lt;Unidirectional Transparent Sheet: First Example of Transmission Type&gt; 
       FIG. 18  shows a configuration of a transparent sheet  51 ′ that diffuses the image light flux to the outside of the vehicle or the outside of the room. The polarization plate  57  that transmits P waves and the retardation plate  58  are provided on the image light flux incident surface of the transparent diffusion sheet material  55 , and the image light flux reflected by the transparent diffusion sheet material  55  is prevented from returning to the inside of the room (space in which the information display apparatus is installed). As a result, the image projected on the window glass  220  does not hinder the observer. As the optimum phase difference of the retardation plate  58  provided between the polarization plate  57  and the transparent diffusion sheet material  55 , an optimal value is preferably selected in accordance with the diffusion characteristics of the transparent diffusion sheet. When the diffusion angle is large, it is preferably close to λ/4, and when the diffusion angle is small, better conversion performance can be obtained by combining with a λ/8 plate or the like. 
     Also, it can be confirmed that, by providing a sheet to which the reflection enhanced coating whose reflectance of a specific polarized wave is increased is applied instead of the above-mentioned transparent diffusion sheet material  55  or applying the reflection enhanced coating to the surface of the polarization plate, the reflectance of the image light flux can be increased and simultaneously the intensity of the double image generated by the reflected image of the window glass  220  can be significantly reduced, that is, it can be confirmed that the same effect as the above-mentioned technique can be obtained. 
     Further, it is preferable that, by using, for example, PDLC (Polymer Dispersed Liquid Crystal) of Santech Display Co., Ltd. instead of the transparent diffusion sheet material  55  described above, the image light is dispersed without applying a voltage in the image display state and it is used instead of the transparent sheet by turning it to a transparent state by applying a voltage in the image non-display state. Also, the inventors have revealed by the experiment that it is possible to realize a screen having a novel function capable of controlling the diffusion characteristics by changing the voltage applied to the above-mentioned PDLC and capable of controlling the transmittance in accordance with the image by modulating the applied voltage in synchronization with the ON/OFF or the intensity of the image signal. 
     &lt;Unidirectional Transparent Sheet: Second Example of Transmission Type&gt; 
       FIG. 19  shows a configuration in which the image light control film  70  shown in  FIG. 15  is used as the external light control film (hereinafter, denoted by a reference numeral  70 ) in addition to the transparent sheet  51 ′ that diffuses the image light flux to the outside of the vehicle or the outside of the room. As described above, the S polarized wave of sunlight incident on the window glass  220  from an oblique direction is reflected, and the P polarized wave thereof is transmitted and directed to the transparent sheet  51 . At this time, it is absorbed by the black portion  70   b  (shown in gray in  FIG. 19 ) provided in the external light control film  70 , and does not reach the inside of the room or the vehicle in which the image display apparatus is arranged. In addition, since it is not mixed with the image light from the image display apparatus  48 , deterioration of the image quality is also prevented. The transparent sheet  51 ′ is made of the transparent diffusion sheet material  55 . 
     For this transparent sheet  51 ′, a film obtained by melting and stretching a thermoplastic polymer in which zirconium nanoparticles and diamond nanoparticles having a large refractive index are dispersed, for example, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. can be used (see Patent Document 3 mentioned above). Consequently, the display which is transparent and does not prevent the observer from monitoring the scenery of the outside world (outside the store) when the image is not displayed and the display which diffuses and reflects the image light such that the observer outside the store (space) can visually recognize the image information when the image is displayed, that is, the unidirectional display can be realized. 
     Further, in the above-mentioned external light control film  70 , the image light incident on the window glass  220  from an oblique direction is hardly blocked by the black portion  70   b  and passes through the transparent portion  70   a , and is thus diffused by the transparent sheet  51 ′, which enables the image display to the outside world (to the outside of the vehicle or outside of the store). As the external light control film  70 , for example, a viewing angle control film (VCF: View Control Film) of Shin-Etsu Polymer Co., Ltd. is suitable, and since the structure thereof is such that transparent silicon and black silicon are alternately arranged and a synthetic resin is arranged on a light incident/emission surface to form a sandwich structure, the same effect as that of the external light control film of the present embodiment can be expected. 
     It is desirable that a pitch h of the transparent portion  70   a  and the black portion  70   b  of the viewing angle control film described above is ⅓ or less with respect to the pixels of the image to be displayed. At this time, when the viewing angle α is desired to be larger than 90 degrees, a thickness W should be set such that h/w becomes larger than 1.0, and when the viewing angle α is desired to be smaller than 90 degrees, the thickness W should be set such that h/w becomes smaller than 1.0. Also, the energy loss can be reduced by matching an inclination angle γ of the black portion with the incident angle of the image light determined by the mounting positions of the image display apparatus  48  and the window glass. 
     On the other hand, there is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  is 10% or less, but it is preferably 4% or less. Also, it can be confirmed that, by providing a sheet to which the reflection enhanced coating whose reflectance of a specific polarized wave is increased is applied instead of the above-mentioned transparent diffusion sheet material  55 , the reflectance of the image light flux can be increased and simultaneously the intensity of the double image generated by the reflected image of the window glass  220  can be significantly reduced, that is, it can be confirmed that the same effect as the above-mentioned technique can be obtained. 
     Further, it is preferable that, by using, for example, PDLC (Polymer Dispersed Liquid Crystal) of Santech Display Co., Ltd. instead of the transparent diffusion sheet material  55  described above, the image light is dispersed without applying a voltage in the image display state and it is used instead of the transparent sheet by turning it to a transparent state by applying a voltage in the image non-display state. Also, the inventors have revealed by the experiment that it is possible to realize a screen having a novel function capable of controlling the diffusion characteristics by changing the voltage applied to the above-mentioned PDLC and capable of controlling the transmittance in accordance with the image by modulating the applied voltage in synchronization with the ON/OFF or the intensity of the image signal. 
     Since the image source constituting the image projection apparatus  48  described above is a liquid crystal panel, when the observer wears polarized sunglasses, a problem that a specific polarized wave is blocked and the observer cannot see the image occurs. In order to prevent this, a film  50   a  such as a λ/4 plate, a λ/8 plate, or a λ/16 plate is arranged between the film  50   a  for absorbing or reflecting the P wave component of the solar light flux provided on the light incident side surface of the protective cover  50  provided on the light emitting side of the image projection apparatus  48  described above and the base material  56 . By providing the wave plate  50   b , preferably, the polarization direction of the light flux is aligned in a specific direction, the image light is made to have the optimum polarization angle, and the polarization direction of the polarized sunglasses and the polarization axis are shifted from each other by a desired amount. 
     On the other hand, even with the same polarization, by rotating the absorption axis so as to shift the absorption axis of the polarization plate on the light emission side of the liquid crystal panel by 30 degrees or more with respect to the absorption axis of the polarized sunglasses, the absorption becomes about 50%, so that the problem that the image cannot be seen can be solved. 
     Further, when the polarization axis is rotated to be approximated to circular polarization, the polarization axis of the image light from the information display system is rotated from S-polarized light. Thus, since the reflectance by the window glass  220  is lowered and the brightness of the image is lowered, the balanced selection therebetween is preferable. 
     In the information display system according to the present embodiment described above in detail, since the image light from the image projection apparatus  48  has a narrow diffusion angle (high straightness) and includes only a specific polarization component like the image light from the surface-emitting laser image source, various information can be displayed inside or outside the space by using, for example, the show window  220  that constitutes the space, the utilization efficiency of the show window can be greatly improved, high-quality images can be displayed with high resolution, and power consumption can be significantly reduced by improving the utilization efficiency of the light emitted from the light source. 
     Further, when displaying a larger image, a large-sized liquid crystal display panel  52  obtained by combining a plurality of relatively inexpensive liquid crystal display panels by making the joints thereof continuous may be adopted as the liquid crystal display panel  52  that is an image display element constituting the image projection apparatus  48  together with the light source apparatus  101 . In this case, by directing the light flux from the above-mentioned light source apparatus  101  to the transparent sheet  51  parallelly provided on the window glass  220  and unidirectionally reflecting/diffusing it by the transparent sheet  51 , more expanded image information can be displayed while significantly reducing the power consumption. 
     In the above description, an example in which the information display system is applied to a store which is a space partitioned by a show window which is a transparent member such as glass and information is unidirectionally displayed to the inside or outside thereof by using the show window  220  has been described, but the present invention is not limited to this example. Namely, the information display system according to the present invention can unidirectionally display the information to the inside or outside of the space by using the transparent member that partitions the space as long as the space is partitioned by using a transparent member such as glass, and other examples of the information display system will be described below. 
     &lt;Vehicle Information Display System&gt; 
     In the information display system according to the above-described embodiment, (1) the image light generated from the image projection apparatus  48  and emitted toward the show window  220  which is a member to which the light is projected (referred to as a projected member) is converted to image light having a narrow diffusion angle (high straightness) and including only a specific polarization component like the image light from the surface-emitting laser image source, so that high-quality images can be displayed with high resolution and power consumption can be significantly reduced by improving the utilization efficiency of the emitted light, and (2) the overall outer shape of the apparatus can be formed to be flat (panel-like) shape as is apparent from the component parts described above. Therefore, various examples of the so-called vehicle information display systems in which the information display system according to the above-described embodiment is applied by utilizing these features to a vehicle such as an automobile, a train, and an aircraft instead of a space such as a store mentioned above will be described in detail below. 
       FIG. 20  shows an example in which a vehicle information display system is mounted on an ordinary passenger car. In this example, image information is displayed on some or all of a part of the windshield  6  (upper part of a steering  43 ), a rear glass, a part of a side glass  6 ″ (gray part), and the like by the vehicle information display panel  100  according to the present embodiment. 
     As a specific configuration for displaying an image on (a part or all of) the window glass of an automobile, for example, as shown in  FIG. 21 , the image projection apparatus  48  including a large-sized liquid crystal panel  52   a  (see also reference numeral  52  in  FIG. 2 ) is installed on a ceiling portion of a vehicle body  1 , and a plurality of light guide bodies  203   a ,  203   b ,  203   c ,  203   d ,  203   e ,  203   f , and  203   g  (see also reference numerals  101  and  203  in  FIG. 2 ) constituting the light source apparatus  101  is provided on a part of the back surface of the liquid crystal panel as the light source apparatus  101 , so that the image light each having a narrow diffusion angle (high straightness) and an aligned polarization plane like the light from the surface-emitting laser light source can be obtained as indicated by the white arrows in the drawing. 
     These light fluxes are further projected to the windshield  6 , the rear glass  6 ′, and the side glass  6 ″ serving as projected surfaces of the image information by the light direction changing panels (not shown here, see reference numeral  54  in  FIG. 2 ) provided so as to correspond to each of the light guide bodies  203   a  to  203   g , and the image is unidirectionally displayed to the inside or outside of the vehicle  1 . At this time, as shown in  FIG. 22 , at the positions of the liquid crystal panels constituting the image projection apparatus  48 , the images corresponding to them are separately displayed, respectively. Also, since the distances from the image display apparatus to the window glasses and the shapes of the window glasses are different, the original image is distorted such that the projected images are displayed in the correct shape. As the resolution of the large-sized liquid crystal panel  52   a , about 8 k is sufficient. 
     Alternatively, as shown in  FIG. 23  and  FIG. 24 , it is also possible to display the image to each of the window glasses by installing a plurality of image display apparatuses  48   a ,  48   b ,  48   c ,  48   d ,  48   e , and  48   f  on a ceiling portion of a vehicle body instead of the image projection apparatus  48  composed of the large-sized liquid crystal panel  52   a  described above. Also at this time, since the distances from the image display apparatuses to the window glasses and the shapes of the window glasses are different, the original image is preferably distorted such that the projected images are displayed in the correct shape. 
     In the above, an example in which various images are displayed on the image display region in which the transparent sheet  51  is attached to the window glass  6  by the vehicle information display system has been described. However, the present invention is not limited to this, and it can be confirmed that, by providing the reflection enhanced coating whose reflectance of a specific polarized wave is increased instead of the above-mentioned transparent diffusion sheet material, the reflectance of the image light flux can be increased and simultaneously the intensity of the double image generated by the reflected image of the window glass  6  can be significantly reduced, and thus the same effect as the above-mentioned technique can be obtained. 
       FIG. 25  and  FIG. 26  are external views showing the case where the vehicle information display system is mounted on a commercial vehicle such as a bus or a train. The windshield  6 , the rear glass  6 ′ (not shown), the side glass  6 ″, and the like (collectively referred to as “shield glass”) as the transparent projected members on which the image light is projected and displayed are present in the vehicle body  1 . In particular, the windshield  6  in front of the driver&#39;s seat of the vehicle body  1  has different inclination angles to the vehicle body depending on the types of the vehicle. The inventors have studied the radius of curvature thereof in order to realize the optimum virtual image optical system. As a result, it has been found that the windshield  6  of a bus, a railroad vehicle, and the like has the following relationship between the radius of curvature Rh in the horizontal direction horizontal to the ground contact surface of the vehicle and the radius of curvature Rv in the direction vertical to the horizontal axis, and the radius of curvature Rh in the horizontal direction is close to a flat surface in many cases. 
       Rh&gt;Rv 
     This vehicle information display system is configured to unidirectionally display the image information to the inside or the outside of the vehicle by using the windshield  6 , the rear window  6 ′, and/or the side glass  6 ″ which are the translucent member partitioning the space in the vehicle and serve as the projected member constituting a part of the vehicle, and it relates to the system capable of displaying the image information to the driver and the passenger in the vehicle when the driver is driving the own vehicle and capable of displaying the image information also to the outside of the vehicle. Consequently, the driver and the passenger can monitor the necessary information displayed on a display region such as the windshield  6  inside the vehicle as appropriate, but the information cannot be monitored from the outside. Alternatively, the image information can be displayed also to the outside of the vehicle via the rear glass  6 ′ or the side glass  6 ″ (and the windshield  6 ), and this displayed information can be monitored from the outside but cannot be monitored from the inside, so that it does not obstruct the monitoring of the outside scenery by the driver and the passenger and does not hinder the driving. 
     Further, in the vehicle information display system, since the vehicle itself is exposed to natural light including sunlight, it is necessary to take some measures for sunlight. However, as shown in  FIG. 27 , natural light such as sunlight is not only the light of the wide wavelength range from the ultraviolet to the infrared but also exists in the state where the lights of two types of polarization directions such as the light in the vibration direction perpendicular to the traveling direction of the light and the light in the horizontal direction (hereinafter, referred to as S-polarized light and P-polarized light) are mixed. In particular, in the region in which the incident angle on the windshield  6  is larger than 50 degrees, as shown in  FIG. 28 , the reflectance on the glass surface varies depending on the S-polarized light, the P-polarized light, and the incident angle, respectively. 
     Therefore, in the present embodiment, based on the above-mentioned findings by the inventors, that is, considering that most of the sunlight entering through the windshield  6  is a P-polarized light component, it has been confirmed that it is particularly effective to reduce the P wave component in order to suppress external light including sunlight entering the information display apparatus. In addition, it has been confirmed that it is effective to use the S wave component as the image light to be emitted from the information display apparatus and reflected in the vehicle and monitored by the driver and the passenger serving as the observers. 
     &lt;First Specific Configuration Example of Vehicle Information Display System&gt; 
     Subsequently, another vehicle information display system in which the information display system according to the present embodiment is applied to a vehicle and a specific configuration thereof will be described in detail with reference to  FIG. 29  and  FIG. 30 . 
       FIG. 29  and  FIG. 30  show the overall configuration of the vehicle information display system in which the information display system according to the present embodiment is applied to the vehicle and the image information is displayed in a part of the outside scenery monitored by the driver via the windshield  6  which is a transparent projected member constituting a part of the vehicle. Here, the windshield  6  is divided into a plurality of regions, the image light from the image projection apparatus  48  is diffused and reflected in a part of the regions (in this example, the upper part of the windshield  6 ), and the reflected image is unidirectionally monitored by the driver and the passengers directly. As a result, the driver and the passenger can monitor the necessary information displayed in the display region of the windshield  6  as appropriate, but on the other hand, the information cannot be visually recognized from the outside of the vehicle. 
     In this vehicle information display system, as shown in FIG.  29 , the image projection apparatus  48  projects the high-resolution map information from the smartphone  300  or the like (image of a large-sized high-resolution image display apparatus) onto the inner surface of the windshield  6  via the light direction changing panel  54  and the protective cover  50  (hereinafter, the light source apparatus  101  serving as a backlight apparatus, the image projection apparatus  48 , the light direction changing panel  54 , and the protective cover  50  constituting the information display system according to the present embodiment are collectively referred to as the “information display apparatus”  100 ) though described later in detail, so that the image is reflected via the transparent sheet  51  provided on the surface of the windshield  6  to the eyes  8  of the observer (driver), thereby displaying the image on the windshield  6 . 
     Note that an example of the case of using the smartphone  300  which is a high-performance mobile terminal device equipped with a navigation function that provides map information and the like is shown here, and the display screen from the smartphone  300  is input through a wired connection terminal or by a wireless connection such as Bluetooth (registered trademark) or Wifi (registered trademark) so as to be able to display the image thereof, so that the driver can monitor the high-resolution image information by using the vehicle information display system. Although not shown here, it is natural that the smartphone is provided with a controller composed of a CPU (Central Processing Unit) and various solid-state memories such as RAM and ROM functioning as work memory and information storage like the image projection apparatus  48  described above, and has a function of generating and displaying the necessary image on the display apparatus (liquid crystal display) thereof. 
     Further, a more specific configuration of the vehicle information display system will be described. The image display element  52  constituting the image projection apparatus  48  of the information display apparatus  100  is composed of, for example, a relatively large liquid crystal display panel having a screen size of more than 6 inches. In general, since the radius of curvature of the windshield  6  is partially different in many cases, non-uniform (longitudinal and lateral) distortions occur in the displayed image depending on the place where the image is reflected. Therefore, distortion correction is required to obtain a correct image when the reflected image is viewed from the monitoring direction. In order to perform correction at a level that does not cause a problem in practical use by this distortion correction, the resolution of the panel needs to be 1280×720 dots or more. 
     Also, the image display apparatus  48  further includes the light source apparatus  101  constituting a light source thereof together with the above-mentioned liquid crystal display panel  52 , and the light source apparatus  101  is shown above the liquid crystal display panel  52  in  FIG. 29 . 
     The liquid crystal display panel (element)  52  obtains an illumination light flux having strong directivity by the light source apparatus  101  which is a backlight apparatus and emits the image light modulated in accordance with an input image signal to the transparent sheet  51  provided on the windshield  6  as shown  FIG. 29 . Also, in  FIG. 29 , the vehicle information display system further includes the light direction changing panel  54  configured to control the directional characteristics of the light flux  30  emitted from the light source apparatus  101  and a narrow-angle diffusion plate (not shown) as needed together with the image display apparatus  48  including the light source apparatus  101  and the liquid crystal display panel  52 . Namely, polarization plates are provided on both surfaces of the liquid crystal display panel  52 , and the image light having a specific polarization is emitted with the light intensity thereof modulated by the image signal. Consequently, the high-resolution image from the smartphone  300  or the like (image of large-sized high-resolution image display apparatus) is projected toward the windshield  6  via the light direction changing panel  54 , and it is reflected toward the eyes  8  of the observer (driver) via the transparent sheet  51  provided on the surface thereof. 
     Note that the image projection apparatus  48  constituting the vehicle information display system includes the light source apparatus  101 , the liquid crystal display panel  52 , and the like as shown in the drawing, and the configuration and operation of the image projection apparatus  48  including the light source apparatus  101  have already been described above as the embodiment of the image display apparatus and are not described in detail here. However, almost all the light generated by the LED can be taken out as parallel light, and the utilization efficiency of the generated light can be improved. Further, it is also possible to improve its uniform illumination characteristics, and at the same time, it is possible to manufacture it in a small size and at low cost including a modularized light source apparatus of the S-polarized light. 
     Though not shown here, with the image light having a narrow diffusion angle (high straightness) and including only a specific polarization component like the image light from the surface-emitting laser image source obtained by adopting the lenticular lens or the microlens array sheet (not shown) whose configurations and characteristics are shown in  FIG. 5  to  FIG. 7 , the image light from the image projection apparatus  48  is efficiently delivered to the eyes  8  of the observer inside or outside the room, so that it is possible to realize the vehicle information display system in which the high-quality image can be displayed with high resolution and the power consumption can be reduced by reducing the output of the image projection apparatus  48 . 
     In addition, the light direction changing panel  54  provided on the lower surface of the image projection apparatus  48  described above is also the same as that described above with reference to  FIG. 8  and others, and the configuration and operation thereof are not described in detail here. However, the image light which is emitted from the liquid display panel  52  constituting the image projection apparatus  48  of the vehicle information display system is directed to the transparent sheet  51  provided on the windshield  6  without being visually recognized by the driver and the passenger in the vehicle, and then, the image light is unidirectionally reflected and diffused by the transparent sheet  51  and the reflected image is visually recognized by the driver. Namely, with this light direction changing panel  54 , the image light itself from the image projection apparatus  48  is not visually recognized directly from the inside of the vehicle and thus does not obstruct the driving, and only the reflected image by the reflected light thereof is monitored by the driver and the passenger. 
     Also, the protective cover  50  arranged in contact with the ceiling surface of the vehicle and provided on the upper surface of the light direction changing panel  54  described above is also the same as that described above with reference to  FIG. 9  and others, and the configuration and operation thereof are not described in detail here. However, in the vehicle information display system, in particular, the hindrance due to the reflection of external light at the time when the driver drives the vehicle can be reduced. 
     In addition, the S-polarized wave of the sunlight incident on the windshield  6  from an oblique direction is reflected, and the P-polarized wave thereof is transmitted and directed to the transparent sheet  51 . As described above with reference to  FIG. 16  and others, the transparent sheet  51  is composed of the polarization plate  57  that transmits the S waves and the transparent diffusion sheet material  55 , is transparent when the image is not displayed, and does not prevent the driver from monitoring the scenery of the outside world (outside the vehicle). On the other hand, the transparent sheet  51  diffuses and reflects the image light when the image is displayed, so that the unidirectional display in which the driver and the passenger can visually recognize the image information can be realized. 
     Further, it has already been described that the same effect can be obtained also in the configuration shown in  FIG. 17 . At this time, there is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  is 10% or less, but it is preferably 4% or less. Meanwhile, the HAZE of window glass for automobiles is 2% or less. 
     On the other hand, since the image light from the image projection apparatus  48  constituting the vehicle information display system is S-polarized wave, it scatters inside the transparent diffusion sheet material  55  constituting the transparent sheet  51  described above and is emitted toward the observer in a state where the reflectance in the oblique incidence is high. On the other hand, a part of the image light whose polarization direction is disturbed due to the scattering diffuses and transmits through the transparent diffusion sheet material  55 , and is emitted toward the windshield  6 . Since the difference in refractive index is small on the incident surface of the windshield  6 , the level of the double image generated by the reflected light is low. 
     On the other hand, since the intensity of the reflected light generated on the emission surface (the surface in contact with the outside world) of the windshield  6  is mostly the S polarization component, the reflectance is large. Since the image light reflected on this surface passes through the polarization plate  57  again after reflection and is then absorbed, it does not return to the observer side. Therefore, since the double image caused by the reflected image of the windshield  6  is not generated, the image quality is greatly improved. Similarly, it goes without saying that the same effect can be obtained by attaching the above-mentioned transparent sheet  51  to the combiner instead of the windshield  6  as the image reflection surface. 
     With the transparent sheet  51  described above, as is clear from  FIG. 16  and  FIG. 17 , the sunlight component of the P-polarized light that has passed through the windshield  6  (passed through also the combiner afterward in the combiner method) under predetermined conditions in the daytime is absorbed in front of the image projection apparatus  48  including the light source apparatus  101  and the liquid crystal panel  52  constituting the vehicle information display system, the apparatus including the light direction changing panel  54 , and the protective cover  50  provided on the upper surface thereof, so that it is possible to prevent it from returning to the liquid crystal display panel and the polarization plate. 
     In the above example, the case in which the reflection type transparent sheet  51  is adopted as the unidirectional transparent sheet  51  provided on the windshield  6  has been described, but also by adopting the transmission type transparent sheet  51 ′ described with reference to  FIG. 18  instead of it, the image light flux can also be diffused unidirectionally, that is, to the outside of the vehicle. In that case, a polarization plate that transmits P waves and a retardation plate are provided on the image light flux incident surface of the transparent diffusion sheet material  55  constituting the transparent sheet  51 ′, and the image light flux reflected by the transparent diffusion sheet material  55  is prevented from returning to the inside of the vehicle (the space where the vehicle information display system is installed). As a result, the driving of the driver is not obstructed by the image projected on the windshield  6 . 
     As the optimum phase difference of the retardation plate  58  provided between the polarization plate  57  and the transparent diffusion sheet material  55 , an optimal value is preferably selected in accordance with the diffusion characteristics of the transparent diffusion sheet. When the diffusion angle is large, it is preferably close to λ/4, and when the diffusion angle is small, better conversion characteristics can be obtained by combining with a λ/8 plate or the like. Further, the same effect can be obtained also in the second example of the unidirectional transparent sheet described with reference to  FIG. 19 . 
     In the vehicle information display system including the image projection apparatus  48  having the light source apparatus  101  and the liquid crystal display panel  52 , the light direction changing panel  54 , and the like described above in detail, as shown by the arrows in  FIG. 29 , the large-sized high resolution image projection apparatus  48  is provided at the position (ceiling surface) corresponding to the image display region of the upper region of the windshield  6  which is the transparent member partitioning the space inside the vehicle, and the display image thereof is reflected on the windshield, so that the reflected image thereof can be directly monitored by the driver and the passenger. At that time, a high-quality image can be displayed with high resolution by the image light having a narrow diffusion angle (high straightness) and including only a specific polarization component like the image light from the surface-emitting laser image source, and power consumption can be significantly reduced by improving the utilization efficiency of the emitted light. 
     &lt;Second Specific Configuration Example of Vehicle Information Display System&gt; 
     In the above, the vehicle information display system configured to display an image by the image projection apparatus  48 , the light direction changing panel  54 , and the like by using the window glasses including the windshield  6  and the side glass  6 ″ partitioning the space in the vehicle has been described, but the present invention is not limited to this. For example, an image can be displayed also by using a rear glass, or a head-up display (HUD) type information display apparatus (hereinafter referred to as “HUD apparatus”) can also be mounted and used at the same time, and the example in such a case will be described below. 
     Subsequently,  FIG. 31  shows an example in which the vehicle information display system is mounted on an ordinary passenger vehicle whose appearance is shown in  FIG. 30  instead of the above-mentioned large vehicle, and an image is unidirectionally displayed on a part of the windshield  6  (upper part of the steering  43 ) and a part of the side glass  6 ″ to the inside or outside of the vehicle by an image display apparatus  704  and a light source apparatus  710  of the HUD apparatus  700  provided instead of the image projection apparatus  48  and the light direction changing panel  54  described above. 
     Here, as the HUD apparatus, a known general apparatus can be adopted, and the outline thereof will be schematically described below as an example. 
       FIG. 31  is a schematic configuration diagram showing the HUD apparatus  700  including its peripheral device configuration. Here, in order to form a virtual image V 1  in front of the own vehicle in the line of sight (eye point) of the driver  8 , various information reflected by the projected member  6  (inner surface of the windshield) is diffused and reflected by the transparent sheet  51  provided on the windshield  6  to the inside of the vehicle and is displayed as a real image. 
     The above-mentioned HUD apparatus  700  includes the image display apparatus  704  that corresponds to the image projection apparatus  48  described above and generates the image light of the information to be displayed and the light source apparatus  710  that corresponds to the light source apparatus  101  described above and supplies the light to the image display apparatus  704 . In order to control the diffusion distribution of the image light from the image display apparatus  704 , the unidirectional control can be achieved by optimizing the lens shape by providing a lenticular lens on a part of the surface of the image display apparatus  704  in the same manner as above. 
     Further, the image light flux from the HUD apparatus  700  is emitted from an opening (not shown) toward the windshield  6 . Namely, by adopting the image light having a narrow diffusion angle (high straightness) and including only a specific polarization component like the image light from the surface-emitting laser image source obtained by adopting the lenticular lens or the microlens array sheet described above in the HUD apparatus  700  constituting the vehicle information display system, the image light can be efficiently delivered to the eyes  8  of the observer inside or outside the room, and as a result, the vehicle information display system capable of displaying the high-quality image with high resolution and reducing the power consumption by reducing the output of the HUD apparatus  700  can be realized. 
     In addition, the HUD apparatus  700  includes a controller  740  that controls the backlight thereof. The image display apparatus  704  and the optical components including the backlight reflect and diffuse the display image of the image display apparatus  704  on the transparent sheet  51  attached to the windshield  6 , thereby directing it toward the driver&#39;s line of sight  8 . As the image display apparatus  704 , for example, an LCD (Liquid Crystal Display) having a backlight can be presented. 
     The controller  740  in the drawing constituting the HUD apparatus acquires, from a navigation system  761 , various information such as the speed limit and the number of lanes of the road corresponding to the current position where the vehicle is traveling, the planned route of the own vehicle set in the navigation system  761 , and others as foreground information (that is, information displayed in front of the own vehicle by the above-mentioned virtual image). 
     Also, a driving support ECU  762  is a controller for realizing driving support control by controlling the drive system and the control system in accordance with the obstacle detected as a result of the monitoring by a peripheral monitoring device  763 . Such driving support control includes well-known techniques such as cruise control, adaptive cruise control, pre-crash safety, and lane keeping assist. The peripheral monitoring device  763  in the drawing is configured to monitor the situation around the own vehicle, and is, for example, a camera that detects an object existing in the vicinity of the own vehicle based on an image taken around the own vehicle, a searching device that detects an object existing around the own vehicle based on the result of transmitting and receiving searching waves, and the like. 
     The controller  740  of the HUD apparatus described above acquires information from the driving support ECU  762  (for example, the distance to the preceding vehicle, the orientation of the preceding vehicle, the position where an obstacle or a sign exists, etc.) as foreground information. Further, an ignition (IG) signal and own vehicle state information are input to the controller  740 . The own vehicle state information thereof is information acquired as vehicle information and does not require high-resolution display, and includes, for example, warning information indicating that the predetermined abnormal condition has occurred such as the remaining amount of fuel of the internal combustion engine and the temperature of cooling water. 
     It also includes the operation result of the direction indicator, the traveling speed of the own vehicle, the shift position information, and the like. The controller  740  described above is activated when an ignition signal is input. Further, the projected member  6  may be any member such as a combiner on which information can be projected other than the windshield described above, and any member can be adopted as long as the real image can be formed in front of the own vehicle in the driver&#39;s line of sight  8  so as to be visually recognized by the driver. 
     Subsequently,  FIG. 32  shows an example of the arrangement in the cockpit of the automobile in which the above-mentioned image projection apparatus  48 , the transparent sheet  51 , and/or the HUD apparatus  700  are mounted.  FIG. 32 ( a )  shows the arrangement of the system corresponding to the automobile having the steering arranged on the left side, and  FIG. 32 ( b )  shows the arrangement of the system corresponding to the automobile having the steering arranged on the right side. 
     In an HUD image display region ( 1   a ) of  FIG. 32 , the image information is reflected and displayed on the windshield  6  by using the HUD apparatus  700  shown above. Also, in an image display region (lb) (corresponding to a region where the transparent sheet  51  is attached), image information is reflected on the windshield  6  by using the apparatus (here, “vehicle information display apparatus” denoted by reference numeral  100 ) including the image projection apparatus  48  having the light source apparatus  101  and the liquid crystal display panel  52  and the light direction changing panel  54 , and the reflected image thereof is monitored by the driver. At that time, as shown in the drawing, it is preferable that the image display region (lb) is set in the upper part of the windshield  6  and the HUD image display region ( 1   a ) is set in a range or region which does not obstruct the monitoring of the scenery outside the vehicle for the driver, for example, in the range where the bonnet of the own vehicle is monitored. 
     As shown in  FIG. 32 , the vehicle information display apparatus  100  described above is arranged on the ceiling surface of the vehicle, while the HUD apparatus  700  is arranged inside the dashboard  47  between the windshield  6  and the steering  43  so as to be directed toward the steering  43  at the position continuous to the windshield  6 . As a result, it is possible to provide the vehicle information display system, in which when the driver drives his/her own vehicle, the image of the large-sized high resolution image display apparatus is reflected on the windshield  6  by the vehicle information display apparatus  100  and the reflected image thereof can be monitored by the driver or the passenger on the outside scenery monitored through the windshield  6 , that is, in a part of the region of the windshield  6  or the information from the HUD apparatus  700  can also be displayed as needed. 
     Namely, in the image display region (lb) in which the transparent sheet  51  is attached to the windshield  6 , the image light from the vehicle information display apparatus  100  is reflected and monitored by the driver. At that time, the augmented reality can be realized in a pseudo manner by, for example, superimposing the image display region (lb) on the scenery monitored by the driver while driving. The image projected at this time is preferably set in a range or region that does not obstruct the monitoring of the scenery outside the vehicle for the driver. 
     For example, by providing a camera  72  configured to monitor the state of the driver and the state in the vehicle on a rear-view mirror  71  shown in  FIG. 32 , it is also possible to control the emission direction of the image light from the vehicle information display apparatus  100  so as to be matched with the height of eyes of the driver. 
     &lt;Modification of Vehicle Information Display System: Display to Outside&gt; 
     According to the embodiment described above in detailed, when the driver drives his/her own vehicle, the necessary image information can be unidirectionally displayed with high resolution so as to be monitored by the driver and the passenger in the vehicle via the windshield  6  as the projected member which is the shield glass constituting the vehicle. 
     At that time, the information cannot be monitored from the outside of the vehicle. However, the vehicle information display system according to the present invention is not limited to the above-described embodiment, and it is also possible to display the image information to the outside of the vehicle. Namely, the image information can be displayed to the inside or the outside of the vehicle not only via the windshield  6  described above but also via the rear glass  6 ′ and the side glass  6 ′ which are shield glasses in the same manner as above. 
     For example, in the system of this embodiment, it is possible to display information indicating the state of a vehicle such as “vacant” on a part of the windshield  6  of a taxi and further on the rear glass  6 ′ or the side glass  6 ″. Alternatively, it is also possible to display other information such as promotion and advertisement to the outside of the vehicle. Also, in a vehicle such as a bus or a train, information such as the route and the destination can be unidirectionally displayed on the windshield, the rear glass, the side glass, and others to the outside of the vehicle. The configuration of the vehicle information display system when displaying information to the outside will be described below. 
       FIG. 33  shows a system in which necessary image information is unidirectionally displayed with high resolution to the outside of the vehicle via the windshield  6  as a projected member so as to be monitored from the outside. More specifically, an example of displaying the state of a taxi (such as “vacant”) on the windshield of a taxi is shown here. In this example, in the configuration shown in  FIG. 32 , the image light from the vehicle information display apparatus  100 ′ is diffused and transmitted on transparent sheet  51 ′ (see  FIG. 18 ) provided on the surface of the windshield  6 , and the image thereof is transmitted and displayed to the outside of the vehicle as indicated by arrows in  FIG. 18  and the like such that a pedestrian or the like can monitor it. As a result, although the driver or the passenger can display the necessary information on the windshield  6  in a relatively large size to the outside of the vehicle, the display does not obstruct the monitoring of the scenery outside the vehicle to be monitored from the inside of the vehicle and does not hinder the driving of the driver. 
     Further, by providing a reflection enhanced coating whose reflectance of a specific polarized wave is increased instead of the above-mentioned transparent diffusion sheet material  55  of the transparent sheet  51 ′, the reflectance of the image light flux can be increased and simultaneously the intensity of the double image generated by the reflected image of the windshield  6  can be significantly reduced. Namely, it can be confirmed that the same effect as the above-mentioned technique can be obtained. 
     Further, it is preferable that, by using, for example, PDLC (Polymer Dispersed Liquid Crystal) of Santech Display Co., Ltd. instead of the above-mentioned transparent diffusion sheet material  55  of the transparent sheet  51 ′, the image light is dispersed without applying a voltage in the image display state and it is used instead of the transparent sheet by turning it to a transparent state by applying a voltage in the image non-display state. 
     Similarly to the above, the transparent sheet  51 ′ is composed of the polarization plate  57  that transmits S waves and the transparent diffusion sheet material  55 , and by using a film obtained by melting and stretching a thermoplastic polymer in which zirconium nanoparticles and diamond nanoparticles having a large refractive index are dispersed, for example, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. (see Patent Document 2), it is transparent when the image is not displayed and it diffuses and transmits the image light when the image is displayed. Consequently, the image information can be displayed to the outside in the state where the image information is not visually recognized by driver and the passenger and the monitoring of the outside scenery is not obstructed. 
     The function of the transparent sheet  51 ′ in this case will be described. The transparent sheet  51 ′ is composed of the polarization plate  57 , the transparent diffusion sheet material  55 , and the retardation plate  58 , and reduces the illuminance of the sunlight incident from an oblique direction by reflecting the S polarized wave of thereof and transmitting the P polarized wave thereof similarly to the above. At this time, apart of the sunlight is absorbed by the polarization plate by rotating the polarization axis of P-polarized light by the retardation plate  58 . As a result, the damage that the image projection apparatus  48  receives due to the sunlight can be dispersed. 
     On the other hand, the image light diffused to the outside of the vehicle by the function of the transparent diffusion sheet material  55  (see  FIG. 18 ) is reflected by the rear glass  6 ′ or the like and returns to the inside of the vehicle. This light obstructs the driver&#39;s field of view and thus hinders the driving. Therefore, in this embodiment, the retardation plate  58  is arranged between the rear glass  6 ′ and the like and the polarization plate  57  to absorb the reflected light by the polarization plate, so that the information by the image light is unidirectionally displayed to the outside of the vehicle without being visually recognized by the driver and the passenger in the vehicle. 
     Needless to say, the same effect can be obtained also in the second example of the unidirectional transparent sheet shown in  FIG. 19 . At that time, the information by the image light does not obstructs the monitoring of the outside scenery by the driver or the passenger in the vehicle and does not hinder the driving. There is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  mentioned above is 10% or less, but it is preferably 4% or less. Meanwhile, the HAZE of window glass for automobiles is 2% or less. 
     As described above, the display of information to the outside of the vehicle by using a part of shield glasses such as the windshield  6 , the rear glass, and the side glass would be particularly suitable for displaying the above-mentioned information such as “vacant” indicating the vacant state of the taxi to pedestrians on the street. Further, as described above, the vehicle information display system according to the present embodiment not only unidirectionally displays image information on the windshield, but also can display various information including promotion, advertisement, and notification even in a large vehicle such as a bus or a train by using the projected member such as the rear glass  6 ′ and the side glass  6 ″ (see  FIG. 25 ,  FIG. 26 , and others) which are the shield glasses constituting the vehicle. In the following, the configuration and operation of the vehicle information display system in the case of displaying information to the outside of the vehicle will be described below. 
       FIG. 34  shows an example in which information is displayed to, for example, a pedestrian or the like outside the vehicle via the rear glass  6 ′ constituting a part of the vehicle serving as the projected member. As a result, the driver and the passenger can monitor the necessary information on the windshield  6  described above (see  FIG. 25  and the like), and at the same time, information can be displayed also to the outside of the vehicle by the rear glass  6 ′. Note that the driver and the passenger cannot monitor the information displayed to the outside, and thus, the driver&#39;s field of view is not obstructed. Namely, the display of information to the outside of the vehicle does not obstruct the monitoring of the outside scenery by the driver and the passenger inside the vehicle. 
     In this example, the vehicle information display apparatus  100 ′ is arranged above the rear glass  6 ′ which is the projected member constituting a part of the vehicle, and the image information is displayed by projecting the image light thereof to the image display region ( 1   e ) set on the entire surface or a part of the surface of the rear glass  6 ′. 
     Also in this example, it is natural that the transparent sheet  51 ′ shown in  FIG. 18  and  FIG. 19  described above is provided in the image display region of the rear glass  6 ′. In addition, the projected member that unidirectionally displays the image information to the outside of the vehicle is not limited to the windshield  6  and the rear glass  6 ′ described above, and the side glass  6 ″ that constitutes the side surface of the vehicle (see  FIG. 25 ,  FIG. 26 ,  FIG. 31 , etc.) can also be used. In this case, though not shown here, it is natural that the vehicle information display apparatus  100 ′ is arranged on a member in the vicinity of the side glass  6 ″ (for example, a part of adjacent ceiling surface or window frame) and the transparent sheet  51 ′ shown in  FIG. 18  and  FIG. 19  described above is provided in the image display region ( 1   d ) of the side glass  6 ″. 
     The display of the information on the side glass  6 ″ may be suitable for displaying a message such as “Thank you for waiting” or “Please board” in, for example, a taxi to the passenger or the like on the street. 
     In addition, in the above example, the image vehicle information display apparatuses  100  and  100 ′ in which the information is unidirectionally displayed to the inside or the outside of the vehicle via the windshield  6 , the rear glass  6 ′, and the side glass  6 ″ which are the projected members constituting the vehicle have been described. However, the present invention is not limited to these, and for example, the vehicle information display apparatus  100  that displays information to the inside of the vehicle and the vehicle information display apparatus  100 ′ that displays information to the outside of the vehicle can be combined as appropriate. 
     According to this, for example, when applied to public transportation such as a bus and a train, various types of information including promotion, advertisement, notification, and others can be displayed to the public outside the vehicle via the rear glass  6 ′ and the side glass  6 ′ (in this case, it is possible to control the display so as not to be visually recognized from the inside of vehicle), and information can be effectively displayed to the public. Further, as described above, it is also possible to simultaneously mount and use the head-up display (HUD)  700  as the vehicle information display apparatus. 
     Further, by using, for example, PDLC (Polymer Dispersed Liquid Crystal) of Santech Display Co., Ltd. instead of the transparent diffusion sheet material  55  described above to form a film that absorbs or reflects the specific polarized wave on the image light incident side, the image light can be displayed to the inside and the outside of the vehicle by turning it to a white state without applying a voltage in the image display state. It is preferable that it is used instead of the transparent sheet by turning it to a transparent state by applying a voltage in the image non-display state. When the driver needs to see the rear scenery, for example, when a shift lever is shifted to a back gear or it is confirmed by a driver surveillance camera that the point of view has been moved to a side mirror or a rear-view mirror, the rear visibility is ensured by applying a voltage to a part of the PDLC to make the entire surface or a part of the PDLC transparent. The return of the image light to the driver side is reduced by the sheet or the film mentioned above, thereby preventing the hindrance of the driving. 
     Further, it is also possible to display the image from the HUD apparatus  700  described above on the window glass  6  by using the display apparatus including the image projection apparatus  48  and the light direction changing panel  54  described above, and  FIG. 29  and  FIG. 31  show an example thereof. The configuration and operation of the HUD apparatus  700  are the same as above, and the configuration and operation of the vehicle information display apparatus  100  are also the same as above. Also in this case, similarly to the above, it is possible to improve the utilization efficiency of the generated light and to improve the uniform illumination characteristics, and at the same time, it is possible to manufacture it in a small size and at low cost including a modularized light source apparatus of the S-polarized wave. 
     In addition, when displaying a larger image via the windshield  6 , the rear glass  6 ′ and the side glass  6 ′ which are projected members constituting the vehicle, a large-sized liquid crystal display panel  52  obtained by combining a plurality of relatively inexpensive liquid crystal display panels by making the joints thereof continuous may be adopted as the image display element  52  that constitutes the image projection apparatus  48  together with the light source apparatus  101  in the vehicle information display apparatuses  100  and  100 ′. In this case, by emitting the light flux from the above-mentioned light source apparatus  101  to the transparent sheet  51  parallelly provided on the window glass  6  and unidirectionally reflecting and diffusing it by the transparent sheet  51 , the vehicle information display system capable of displaying more expanded image information can be realized relatively easily and at low cost while significantly reducing the power consumption. 
     In the vehicle image display system of the HUD apparatus type according to the present invention described above, when the image light from the image display apparatus  48  is parallel and the distance from the window glass to the eyes  8  of the observer is 80 cm, the relative size of the reflected image (virtual image) shown on the window glass in the case where the screen horizontal size of the image display apparatus  48  is 10 to 20 inches is obtained by calculation using the distance at which the virtual image can be seen (position reflected on the window glass) as a parameter.  FIG. 35  shows the result thereof. 
     When a virtual image is formed above an axis L-L′ horizontal to the eyes of the observer, the virtual image appears in the air, and the observer causes motion sickness when the car fluctuates up and down. Therefore, the virtual image should be displayed on or below the horizontal line L-L′, and the experiments by the inventors have revealed that an angle β formed between the virtual image and the horizontal axis is preferably in the range of 0 to 8 degrees, and is more preferably in the range of 0 to 4 degrees when realizing augmented reality. The virtual image distance when β is 4 degrees is 20 m, and the virtual image obtained by the reflection on the window is about 250 inches when the horizontal size of the image display apparatus is 10 inches and it is about 500 inches when it is 20 inches. 
     Further,  FIG. 36  is a cross-sectional view showing an example in which the image display apparatus  48  provided with the above-mentioned image light control film  70  (see  FIG. 15 ) having the function of restricting the emission direction of the image light is mounted in an automobile. In  FIG. 36 , similarly to  FIG. 3  and  FIG. 4  above, the light source apparatus  101  includes, for example, the light guide body  203  having the light flux direction changing unit  204  provided on its surface made of plastic or the like or in its inside, the LED element  201  as a light source, the reflection sheet  205 , the retardation plate  206 , and the like, and the liquid crystal display panel  52  having the polarization plate  49  provided on alight source light incident surface and an image light emission surface is attached on its upper surface as the image projection apparatus  48  and the image light control film  70  shown in  FIG. 15  is provided on its uppermost portion. Since the image light from the liquid crystal panel  52  is emitted to a specific direction (toward windshield  6  in the drawing) and a part of the light is blocked by the black portion  70   b , the light does not directly enter the eyes of the observer and the direct light from the image display apparatus  48  does not hinder the driving. 
     The image light control film  70  has a function of preventing the image light from directly directing to the observer, while the image light passes through the transparent portion  70   a  and is reflected by the windshield  6 , so that the driver who is the observer can recognize it. As the image light control film  70 , for example, a viewing angle control film (VCF: View Control Film) of Shin-Etsu Polymer Co., Ltd. is suitable, and since the structure thereof is such that transparent silicon and black silicon are alternately arranged and a synthetic resin is arranged on a light incident/emission surface to form a sandwich structure, the same effect as that of the image light control film  70  of the present embodiment can be expected. 
     It is desirable that a pitch h of the transparent portion  70   a  and the black portion  70   b  of the viewing angle control film described above is ⅓ or less with respect to the pixels of the image to be displayed. At this time, when the viewing angle α is desired to be larger than 90 degrees, a thickness W should be set such that h/w becomes larger than 1.0, and when the viewing angle α is desired to be smaller than 90 degrees, the thickness W should be set such that h/w becomes smaller than 1.0. On the other hand, there is no practical problem if the haze (HAZE) defined by the ratio of the diffusion transmittance and the parallel light transmittance of the transparent sheet  51  is 10% or less, but it is preferably 4% or less. 
     In the foregoing, the various embodiments have been described above. However, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above embodiments have described the entire system in detail in order to make the present invention easily understood, and the present invention is not necessarily limited to those having all the described configurations. Also, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment, and the configuration of one embodiment may be added to the configuration of another embodiment. Furthermore, another configuration may be added to a part of the configuration of each embodiment, and a part of the configuration of each embodiment may be eliminated or replaced with another configuration. 
     REFERENCE SIGNS LIST 
       1  . . . automobile (vehicle) body,  6  . . . windshield,  6 ′ . . . rear glass,  6 ″ . . . side glass,  100  . . . vehicle information display apparatus,  101  . . . light source apparatus,  48  . . . image projection apparatus,  49  . . . reflection type polarization plate,  52  . . . liquid crystal display panel (element),  50  . . . protective cover,  51  . . . unidirectional transparent sheet,  54  . . . light direction changing panel,  55  . . . transparent diffusion sheet material,  57  . . . polarization plate,  58  . . . retardation plate,  70   a  . . . transparent portion,  70   b  . . . black portion,  202  . . . LED board,  203  . . . light guide body,  205  . . . reflection sheet,  220  . . . show window (window glass),  300  . . . smartphone