Abstract:
The purpose of the present invention is to efficiently orient image light toward an observer. A display device outputs projection light for displaying an image. A transmission type screen forms an image of the projection light and diffuses the same as image light. A projection lens enlarges projection light and forms the image on the transmission type screen. A light distribution adjustment means is disposed between the transmission type screen and the projection lens and adjusts the light distribution of the image light output by the transmission type screen for each region by refracting the projection light.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a head up display device for causing a virtual image superposed on a real view to be visually recognized. 
       BACKGROUND ART 
       [0002]    A conventional head up display (HUD) device is disclosed in PTL 1. As shown in  FIGS. 7 and 8 , such an HUD includes a projector  501  for emitting projection light beams L 1 , L 2 , and L 3 , a projection lens  502  for causing images of the projection light beams L 1 , L 2 , and L 3  to be formed on a transmission type screen  503 , the transmission type screen  503  having a back surface that receives the projection light beams L 1 , L 2 , and L 3  from the projection lens  502  and forms real images thereof and a front surface that diffuses and emits image light beams forming the real images, and a plane mirror  504  and a concave mirror  505  for directing image light beams M 1 , M 2 , and M 3  diffused on the transmission type screen  503  to a windshield (projection reflection surface)  510  of a vehicle. P 1 , P 2 , and P 3  shown in  FIGS. 7 and 8  indicate optical paths of the image light beams contributing to a viewer visually recognizing a virtual image. 
         [0003]    Projection light L directed from the projection lens  502  to the transmission type screen  503  is conically broadened toward the transmission type screen  503 . The projection light beam Li incident on the transmission type screen  503  is diffused by the transmission type screen  503  and is diffused as the image light beam M 1  having, as an optical axis, a light distribution axis M 1   a  having the same direction as that of the projection light beam L 1 . Similarly, the projection light beams L 2  and L 3  incident on the transmission type screen  503  are also diffused by the transmission type screen  503  and are diffused as the image light beams M 2  and M 3  having, as optical axes, light distribution axes M 2   a  and M 3   a  having the same directions as those of the projection light beams L 2  and L 3 . 
       CITATION LIST 
     Patent Literature 
       [0004]    PTL 1: JP-A-2004-126226 
       SUMMARY OF INVENTION 
     Technical Problem(s) 
       [0005]    However, in the case where the projection light L from the projection lens  502  is directly projected onto the transmission type screen  503  as in PTL 1, the directions of the light distribution axes M 1   a,  M 2   a,  and M 3   a  emitted from the transmission type screen  503  are substantially the same as those of the projection light beams L 1 , L 2 , and L 3 . Therefore, optical paths of the image light beams M 1  and M 3  emitted from predetermined regions of the transmission type screen  503  do not run along the optical paths P 1  and P 3  directed to a point of sight  520  of a viewer (the light distribution axes M 1   a  and M 3   a  do not match with the optical paths P 1  and P 3 ). Thus, an image light M reaching the point of sight  520  of the viewer is weak, and therefore luminance of a virtual image visually recognized by the viewer may be reduced. Further, the light distribution axes M 1   a  and M 3   a  of the image light beams M 1  and M 3  diffused in the respective regions of the transmission type screen  503  do not run along the optical paths P 1  and P 3  directed to the point of sight  520  of the viewer, and therefore light use efficiency of the image light beams M 1  and M 3  is reduced. 
         [0006]    The invention has been made in view of the above circumstances, and an object is to provide a head up display device capable of efficiently directing image light to a viewer. 
       Solution to Problem(s) 
       [0007]    In order to achieve the above object, a head up display device of a first invention includes: a projector for emitting projection light forming an image; a screen for allowing an image of the projection light to be formed and diffusing the projection light as image light; an imaging optical system for enlarging the projection light and forming the image of the projection light on the screen; and light distribution adjustment means for adjusting light distribution of the image light emitted from the screen in each region by refracting the projection light, the light distribution adjustment means being provided between the screen and the imaging optical system. 
         [0008]    A head up display device of a second invention is such that the light distribution adjustment means adjusts the image light so that the image light emitted from each region of the screen is directed to an optical axis of the projection light. 
         [0009]    A head up display device of a third invention is such that the light distribution adjustment means increases an adjustment amount of the projection light as the projection light is separated from an optical axis of the projection light in at least a first direction between the first direction and a second direction, the first direction extending in a direction vertical to the optical axis of the projection light and the second direction extending in a direction vertical to the optical axis of the projection light and orthogonal to the first direction. 
       Advantageous Effects of Invention 
       [0010]    According to the invention, it is possible to efficiently direct image light to a viewer. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a schematic configuration diagram of a head up display device in a first embodiment of the invention. 
           [0012]    In the above embodiment,  FIG. 2( a )  is a schematic configuration diagram of light distribution adjustment means seen from a second direction and  FIG. 2( b )  is a schematic configuration diagram of the light distribution adjustment means seen from a first direction. 
           [0013]    In a second embodiment,  FIG. 3( a )  is a schematic configuration diagram of light distribution adjustment means seen from a second direction and  FIG. 3( b )  is a schematic configuration diagram of the light distribution adjustment means seen from a first direction. 
           [0014]      FIG. 4  is a schematic configuration diagram of a head up display device in a third embodiment of the invention. 
           [0015]    In the above embodiment,  FIG. 5( a )  is a schematic configuration diagram of light distribution adjustment means seen from a second direction and  FIG. 5( b )  is a schematic configuration diagram of the light distribution adjustment means seen from a first direction. 
           [0016]      FIG. 6  is a schematic configuration diagram of light distribution adjustment means seen from a second direction in a modification example. 
           [0017]      FIG. 7  is a schematic configuration diagram of a head up display device in a conventional example. 
           [0018]      FIG. 8  is a schematic configuration diagram of light distribution adjustment means seen from a second direction in the conventional example. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       [0019]    A first embodiment of the invention will be described with reference to the drawings. 
         [0020]      FIG. 1  is a schematic configuration diagram showing a configuration of a head up display device (hereinafter, referred to as “HUD device”)  1  according to this embodiment. The HUD device  1  according to this embodiment is provided in a dashboard of a vehicle. The HUD device  1  emits an image light  200  toward a windshield  2  of the vehicle. The image light  200  reflected by the windshield  2  is directed to an eye box  3 . In the case where a user&#39;s point-of-sight position is in the eye box  3 , the user visually recognizes a virtual image having desired luminance generated by the image light  200 . The user recognizes the virtual image via the windshield  2  as if the virtual image is located in a distant place while the virtual image is being superposed on a real view in front of the vehicle. 
         [0021]    As shown in  FIG. 1 , the HUD device  1  includes a display device  10  for displaying a real image S 1  and emitting the image light  200  forming the real image S 1 , a first reflection unit  20  for reflecting the image light  200  emitted by the display device  10 , a second reflection unit  30  for enlarging the image light  200  reflected by the first reflection unit  20  and directing the image light  200  to the windshield  2 , a housing  40  storing the above members, and a control unit (not shown) for electrically controlling the HUD device  1 . 
       (Display Device  10 ) 
       [0022]    As shown in  FIG. 1 , the display device  10  includes a light source  11  for emitting irradiation light (not shown), light source mirrors  12 , a prism  13 , a reflection type display device  14 , a projection lens  15 , light distribution adjustment means  16 , and a transmission type screen  17 . The display device  10  forms the real image S 1  on the transmission type screen  17  and emits the image light  200  forming the real image S 1  toward the first reflection unit  20 . 
         [0023]    The light source  11  includes, for example, a plurality of LEDs capable of outputting light of red, blue, and green and emits the irradiation light of desired color with desired light intensity at a desired timing under the control of the control unit. The display device  10  in this embodiment employs a field sequential color driving method, and the light source  11  of each color emits the irradiation light in time division. 
         [0024]    The light source mirror  12  is, for example, a dichroic mirror for reflecting light having a specific wavelength and transmitting light having the other wavelengths. The light source mirror  12  aligns courses of light of red, blue, and green emitted from the plurality of light sources  11  to direct the courses thereof to the prism  13  and causes the irradiation light from the light source  11  to be incident on the prism  13  at a proper angle. 
         [0025]    The prism  13  is provided between the light source mirror  12  and the reflection type display device  14  and has an inclined plane that is inclined at a predetermined angle with respect to an optical axis of the irradiation light incident from the light source mirror  12 . The irradiation light incident on the inclined plane from the light source mirror  12  is transmitted through the inclined plane and is incident on the reflection type display device  14 . Then, projection light  100  emitted from the reflection type display device  14  is incident on the prism  13  again and is reflected by the inclined plane toward the projection lens  15 , and the projection light  100  is emitted from a projection surface  13   a.    
         [0026]    The reflection type display device  14  is, for example, a reflection type display device such as a DMD (Digital Micromirror Device) or an LCOS (registered trademark: Liquid Crystal On Silicon). The reflection type display device  14  converts the irradiation light incident from the prism  13  into the projection light  100  for displaying a virtual image under the control of the control unit and reflects the projection light toward the prism  13 . 
         [0027]    The projection lens  15  is made up of, for example, a convex lens having a spherical surface and enlarges the projection light  100  incident from the prism  13  and emits the projection light  100  toward the light distribution adjustment means  16 . The projection lens  15  is an imaging optical system for receiving the projection light  100  from the reflection type display device  14  and forming the real image S 1  on the transmission type screen  17  described below. 
         [0028]    As shown in  FIG. 2 , the light distribution adjustment means  16  is a biconvex lens having free-form surfaces whose curvatures are different between a first direction X extending in a direction vertical to an optical axis ( 102 ) of the projection light and a second direction Y orthogonal to this first direction X and is provided on an optical path of the projection light  100  directed from the projection lens  15  to the transmission type screen  17 . The light distribution adjustment means  16  adjusts light distribution of the image light  200  emitted from regions of the transmission type screen  17  by refracting the projection light  100  directed from the projection surface  13   a  to the transmission type screen  17 . Specific effects of the light distribution adjustment means  16  will be described in detail below. 
         [0029]    The transmission type screen  17  is, for example, a diffusion film made of resin such as polycarbonate. The transmission type screen  17  allows an image of the projection light  100  emitted from the projection lens  15  to be formed as the real image S 1  and emits the image light  200  diffused in a constant distribution. Note that light distribution of the image light  200  emitted from the transmission type screen  17  is adjusted in each region of the transmission type screen  17  by effects of the light distribution adjustment means  16 . 
         [0030]    In the display device  10  described above, the reflection type display device  14  generates the projection light  100  and emits the projection light  100  through the projection surface  13   a,  and the projection lens  15  forms an image of the projection light  100  on the transmission type screen  17  as the real image S 1 . Then, the light distribution adjustment means  16  refracts the projection light  100  directed from the projection lens  15  to the transmission type screen  17 , thereby adjusting light distribution of the image light  200  emitted from the regions of the transmission type screen  17 . Thus, it is possible to efficiently direct the image light  200  in a direction of the eye box  3 . 
         [0031]    The first reflection unit  20  is a plane mirror and is obtained by forming a reflective film on a surface of a base made of, for example, a synthetic resin material or glass material by using depositing or other means. The first reflection unit  20  reflects the image light  200  diffused by and transmitted through the transmission type screen  17  toward the second reflection unit  30  described below. 
         [0032]    The second reflection unit  30  is a concave mirror and is obtained by forming a reflective film on a surface of abase made of, for example, a synthetic resin material by using depositing or other means. The second reflection unit  30  has a reflection surface having a concave free-form surface, and a detailed shape of the surface thereof is calculated on the basis of a positional relationship with the transmission type screen  17 , the first reflection unit  20 , the windshield  2  (reflection-transmission surface), and the eye box  3 , a curvature of the windshield  2 , a required imaging distance of the virtual image, an angle of view of the HUD device  1  visually recognized by the user, and the like. The second reflection unit  30  can be designed so that distortion of the virtual image is minimized. Further, the second reflection unit  30  enlarges the image light  200  reflected by the first reflection unit  20  and reflects the image light  200  toward the windshield  2 . 
         [0033]    The second reflection unit  30  includes an actuator  30   a  capable of adjusting an angle of the second reflection unit  30 . The actuator  30   a  can direct the image light  200  to the eye box  3  by rotating the second reflection unit  30  in accordance with a viewer&#39;s point-of-sight position detected by point-of-sight position detection means (not shown) made up of a camera or the like. The actuator  30   a  may rotate the second reflection unit  30  in accordance with operation of an operation unit (not shown). 
         [0034]    Hereinabove, the configuration of the HUD device  1  in this embodiment has been described. Hereinafter, effects of the light distribution adjustment means  16  will be described with reference to  FIG. 2 .  FIG. 2( a )  is a schematic configuration diagram of the light distribution adjustment means  16  seen from the second direction Y, and  FIG. 2( b )  is a schematic configuration diagram of the light distribution adjustment means  16  seen from the first direction X. 
       (Effects of Light Distribution Adjustment Means  16 ) 
       [0035]    An effect of the light distribution adjustment means  16 , which is obtained by seeing the light distribution adjustment means  16  from the second direction Y, will be described with reference to  FIG. 2( a ) . Note that the projection light  100  (projection light  101 , projection light  102 , and projection light  103 ) emitted from the projection surface  13   a  shown in  FIG. 2( a )  is light forming a vertical direction of the virtual image visually recognized by the viewer. The projection light  101  forms a lower end of the virtual image, the projection light  102  forms a part in the vicinity of the vertical center of the virtual image, and the projection light  103  forms an upper end of the virtual image. 
         [0036]    The projection light  100  (projection light  101 , projection light  102 , and projection light  103 ) emitted from the regions of the projection surface  13   a  is incident on the light distribution adjustment means  16  via the projection lens  15 . The light distribution adjustment means  16  refracts the projection light  101 , the projection light  102 , and the projection light  103  incident on the transmission type screen  17  so that a light distribution axis  201   a,  a light distribution axis  202   a,  and a light distribution axis  203   a  of image light  201 , image light  202 , and image light  203  emitted from the transmission type screen  17  substantially run along an optical path P 1 , an optical path P 2 , and an optical path P 3  directed to the eye box  3 . 
         [0037]    In the first direction X, the light distribution adjustment means  16  largely refracts the projection light  100  (projection light  101  and projection light  103 ) incident on positions apart from an optical axis of the light distribution adjustment means  16  and emits the projection light  100  toward the transmission type screen  17 . Specifically, the light distribution adjustment means  16  inclines the projection light  101  by an angle θ 1  and the projection light  103  by an angle θ 3  toward the optical axis of the light distribution adjustment means  16  and emits the projection light  101  and the projection light  103 . Note that the projection light  102  along the optical axis of the light distribution adjustment means  16  forms an image on the transmission type screen  17  without being refracted by the light distribution adjustment means  16  (without being adjusted by the light distribution adjustment means  16  in terms of light distribution thereof) and is emitted as the image light  202 . The light distribution adjustment means  16  increases an adjustment amount (angle to be inclined) of the projection light  100  as the projection light  100  is separated from the optical axis of the light distribution adjustment means  16 . 
         [0038]    Next, an effect of the light distribution adjustment means  16 , which is obtained by seeing the light distribution adjustment means  16  from the first direction X, will be described with reference to  FIG. 2( b ) . Note that the projection light  100  (projection light  104 , projection light  105 , and projection light  106 ) emitted from the projection surface  13   a  shown in  FIG. 2( b )  is light forming a horizontal direction of the virtual image visually recognized by the viewer. The projection light  104  forms a right end of the virtual image, the projection light  105  forms a part in the vicinity of the horizontal center of the virtual image, and the projection light  106  forms a left end of the virtual image. 
         [0039]    The projection light  100  (projection light  104 , projection light  105 , and projection light  106 ) emitted from the regions of the projection surface  13   a  is incident on the light distribution adjustment means  16  via the projection lens  15 . The light distribution adjustment means  16  refracts the projection light  104 , the projection light  105 , and the projection light  106  incident on the transmission type screen  17  so that a light distribution axis  204   a,  a light distribution axis  205   a,  and a light distribution axis  206   a  of image light  204 , image light  205 , and image light  206  emitted from the transmission type screen  17  substantially run along an optical path P 4 , an optical path P 5 , and an optical path P 6  directed to the eye box  3 . 
         [0040]    In the second direction Y, the light distribution adjustment means  16  largely refracts the projection light  100  (projection light  104  and projection light  106 ) incident on positions apart from the optical axis of the light distribution adjustment means  16  and emits the projection light  100  toward the transmission type screen  17 . Specifically, the light distribution adjustment means  16  inclines the projection light  104  by an angle θ 4  and the projection light  106  by an angle θ 6  toward the optical axis of the light distribution adjustment means  16  and emits the projection light  104  and the projection light  106 . Note that the projection light  105  along the optical axis of the light distribution adjustment means  16  forms an image on the transmission type screen  17  without being refracted by the light distribution adjustment means  16  (without being adjusted by the light distribution adjustment means  16  in terms of light distribution thereof) and is emitted as the image light  205 . The light distribution adjustment means  16  increases an adjustment amount (angle to be inclined) of the projection light  100  as the projection light  100  is separated from the optical axis of the light distribution adjustment means  16 . Note that the angle θ 1  and the angle θ 3  (adjustment amounts) at which the image light  201  and the image light  203  distributed in a vertical direction of the eye box  3  are refracted by the light distribution adjustment means  16  are larger than the angle θ 4  and the angle θ 6  (adjustment amounts) at which the image light  204  and the image light  206  distributed in a horizontal direction of the eye box  3  are refracted. 
         [0041]    As described above, according to the HUD device  1  in this embodiment, light distribution of the image light  200  emitted from the regions of the transmission type screen  17  can be adjusted by the light distribution adjustment means  16 , and therefore it is possible to efficiently direct the image light  200  to the eye box  3 . 
       Second Embodiment 
       [0042]    Hereinafter, effects of light distribution adjustment means  16   a  in a second embodiment will be described with reference to  FIG. 3 .  FIG. 3( a )  is a schematic configuration diagram of the light distribution adjustment means  16   a  seen from the second direction Y, and  FIG. 3( b )  is a schematic configuration diagram of the light distribution adjustment means  16   a  seen from the first direction X. Note that, in  FIG. 3 , configurations the same as the configurations in the above first embodiment are denoted by the same reference signs, and description thereof will be omitted. 
         [0043]    The HUD device  1  in the second embodiment is different in that the HUD device  1  includes the light distribution adjustment means  16   a  having a characteristic different from that of the light distribution adjustment means  16  in the above first embodiment. The light distribution adjustment means  16   a  in the second embodiment is a cylindrical lens that has power to refract the projection light  100  in the first direction X and does not have power to refract the projection light  100  in the second direction Y. 
         [0044]    An effect of the light distribution adjustment means  16 , which is obtained by seeing the light distribution adjustment means  16   a  in the second embodiment from the first direction X, will be described with reference to  FIG. 3( b ) . 
         [0045]    The projection light  100  (projection light  104 , projection light  105 , and projection light  106 ) emitted from the regions of the projection surface  13   a  is incident on the light distribution adjustment means  16   a  via the projection lens  15 . The light distribution adjustment means  16   a  emits the projection light  104 , the projection light  105 , and the projection light  106  toward the transmission type screen  17  without changing directions of the projection light  104 , the projection light  105 , and the projection light  106 . The transmission type screen  17  emits the image light  204 , the image light  205 , and the image light  206  having the light distribution axis  204   a,  the light distribution axis  205   a,  and the light distribution axis  206   a  whose directions are substantially the same as those of the projection light  104 , the projection light  105 , and the projection light  106  incident on a back surface thereof. Note that projection angles of the projection light  104 , the projection light  105 , and the projection light  106  from the projection lens  15  are set so that the light distribution axis  204   a,  the light distribution axis  205   a,  and the light distribution axis  206   a  run along the optical path P 4 , the optical path P 5 , and the optical path P 6  directed to the eye box  3 . 
         [0046]    Also in such a configuration, light distribution of the image light  200  emitted from the regions of the transmission type screen  17  can be adjusted by the light distribution adjustment means  16   a,  and therefore it is possible to efficiently direct the image light  200  to the eye box  3 . Further, the light distribution adjustment means  16   a  has power to refract the projection light  100  only in one axial direction (first direction X), and therefore it is possible to facilitate an optical design of the light distribution adjustment means  16   a.    
       Third Embodiment 
       [0047]    The HUD device  1  in a third embodiment is different in that the image light  201 , the image light  202 , and the image light  203  emitted from the regions of the transmission type screen  17  intersect with one another and form an intermediate image S 2  at a predetermined position. Hereinafter, the third embodiment of the invention will be described with reference to  FIGS. 4 and 5 .  FIG. 4  is a schematic configuration diagram of the HUD device  1  in the third embodiment.  FIG. 5( a )  is a schematic configuration diagram of light distribution adjustment means  16   b  seen from the second direction Y, and  FIG. 5( b )  is a schematic configuration diagram of the light distribution adjustment means  16   b  seen from the first direction X. 
         [0048]    The light distribution adjustment means  16   b  in the third embodiment is, for example, a cylindrical lens, and an optical region that receives the projection light  100  and emits the refracted projection light  100  toward the transmission type screen  17  is formed to be larger than a region where the transmission type screen  17  forms the real image S 1 . 
       (Effects of Light Distribution Adjustment Means  16   b ) 
       [0049]    An effect of the light distribution adjustment means  16   b,  which is obtained by seeing the light distribution adjustment means  16   b  from the second direction Y, will be described with reference to  FIG. 5( a ) . 
         [0050]    The projection light  100  (projection light  101 , projection light  102 , and projection light  103 ) emitted from the regions of the projection surface  13   a  is incident on the light distribution adjustment means  16   b  via the projection lens  15 . The light distribution adjustment means  16   b  refracts the projection light  101 , the projection light  102 , and the projection light  103  so that the light distribution axis  201   a,  the light distribution axis  202   a,  and the light distribution axis  203   a  of the image light  201 , the image light  202 , and the image light  203  emitted from the transmission type screen  17  substantially run along the optical path P 1 , the optical path P 2 , and the optical path P 3  directed to the eye box  3  and emits the projection light  101 , the projection light  102 , and the projection light  103  toward the transmission type screen  17 . 
         [0051]    In the first direction X, the projection light  100  (projection light  101  and projection light  103 ) incident on positions apart from an optical axis of the light distribution adjustment means  16   b  is largely refracted and is emitted toward the transmission type screen  17 . Specifically, the light distribution adjustment means  16   b  inclines the projection light  101  and the projection light  103  so that the projection light  101  and the projection light  103  are directed to the optical axis of the light distribution adjustment means  16   b  and emits the projection light  101  and the projection light  103 . With this, the whole image light  200  is directed to the first reflection unit  20  while being converged, and therefore a small first reflection unit  20  can receive the image light  200 . The light distribution adjustment means  16   b  increases an adjustment amount (angle to be inclined) of the projection light  100  as the projection light  100  is separated from the optical axis of the light distribution adjustment means  16   b.    
         [0052]    In the HUD device  1  in the third embodiment, the first reflection unit  20   b  is made up of a concave mirror in order to form the intermediate image S 2  with the image light  200  emitted from the transmission type screen  17 . The first reflection unit  20  forms the image light  200  of the real image S 1  formed on the transmission type screen  17  as the intermediate image S 2  between the first reflection unit  20  and the second reflection unit  30 . An imaging position of the intermediate image S 2  is set to be closer to the second reflection unit  30  than a focal length of the second reflection unit  30  and be in the vicinity of the focal length of the second reflection unit  30 . This makes it possible to cause a viewer to visually recognize a high-magnification virtual image. 
         [0053]    As described above, the HUD device  1  in the third embodiment directs a light distribution axis  200   a  of the image light  200  emitted from each region of the transmission type screen  17  to the optical axis of the light distribution adjustment means  16   b  by using the light distribution adjustment means  16   b,  and therefore it is possible to efficiently generate the intermediate image S 2  with the small first reflection unit  20 . 
         [0054]    The invention is not limited by the above embodiments and the drawings. It is possible to make modification (including deletion of constituent elements) as appropriate without deviating from the scope of the present invention. Hereinafter, modification examples will be described. 
         [0055]    In the above embodiments, the light distribution adjustment means  16  for refracting the projection light  100  from the projection lens  15  is a free-form surface lens or a cylindrical lens. However, the light distribution adjustment means  16  is not limited thereto and may be a rotationally symmetric lens or a toroidal lens having a spherical or aspherical surface as appropriate. 
         [0056]    In the above embodiments, the light distribution adjustment means  16  is made up of a lens. However, the light distribution adjustment means  16  may be made up of a mirror having a concave surface. 
         [0057]    In the above embodiments, the transmission type screen  17  is a diffusion film. However, the transmission type screen  17  may be made up of a microlens array. When the transmission type screen  17  is made up of a microlens array, a magnitude of a light distribution angle and a light distribution direction of the image light  200  emitted from each region of the transmission type screen  17  can be adjusted in each region of the transmission type screen  17 . Therefore, it is possible to direct the image light  200  to a viewer more efficiently. 
         [0058]    In the above embodiments, the transmission type screen  17  is provided to be vertical to the optical axis of the light distribution adjustment means  16 . However, as shown in  FIG. 6 , the transmission type screen  17  may be inclined with respect to the optical axis of the light distribution adjustment means  16  in the first direction X or/and the second direction Y. With this configuration, it is possible to prevent sunlight entering from the outside of the HUD device  1  from being transmitted through the transmission type screen  17  to be propagated to the light source mirror  12  and the light source  11 . 
         [0059]    The reflection-transmission surface onto which the image light  200  is projected is not limited to the windshield  2  of the vehicle. The reflection-transmission surface onto which the image light  200  is projected may be, for example, a combiner member provided dedicatedly. 
         [0060]    In the above description, in order to easily understand the invention, description of publicly-known unimportant technical matters has been omitted as appropriate. 
       Industrial Applicability 
       [0061]    The invention relates to a head up display device for causing a virtual image superposed on a real view to be visually recognized and is suitable as, for example, a display device for emitting image light toward a windshield of a vehicle, the display device being provided in a dashboard of the vehicle. 
       Reference Signs List 
       [0062]      1  HUD device (head up display device) 
         [0063]      2  windshield (reflection-transmission surface) 
         [0064]      3  eye box 
         [0065]      10  display device 
         [0066]      11  light source 
         [0067]      12  light source mirror 
         [0068]      13  prism 
         [0069]      14  reflection type display device (projector) 
         [0070]      15  projection lens (imaging optical system) 
         [0071]      16  light distribution adjustment means 
         [0072]      17  transmission type screen (screen) 
         [0073]      20  first reflection unit 
         [0074]      30  second reflection unit 
         [0075]      40  housing 
         [0076]      100  projection light 
         [0077]      200  image light