Abstract:
A video display device is provided that naturally displays a video without blocking an observer&#39;s field of view, and includes the following: a display optical system that displays a video; an ocular optical system that guides video light emitted from the display optical system to the optical pupil of an observer; and a support that supports the ocular optical system upon the light path of video light emitted from the display optical system. The support includes a first support plate and a second support plate that face each other, and the ocular optical system is located between the first support plate and the second support plate. An opening through which the observer&#39;s line of sight passes is formed at least partially between the first support plate and the second support plate.

Description:
BACKGROUND 
     The present invention relates to an eyepiece image device installed in products such as head mount displays (HMDs). In a concrete sense, the image display device presented as the present invention is an optical device located in front of an eye of the observer, which guides image light projected from components such as a liquid crystal display (LCD) to an eye of the observer so that he or she visually recognizes an image. The present invention is mainly intended to achieve an eyepiece image device that does not block the field of vision of the observer while offering a natural wearability, and to decrease the size of the structure and achieve a stylish shape. 
     In recent years, demand is growing for wearable devices, defined as devices that can be attached to the body of users for use, such as HMDs used by attaching to the head. Furthermore, to name a few, various types of sensor devices and image display devices including LCDs have been downsized to a size installable in wearable devices; wearable devices coming with those devices are being developed at a rapid pace. 
     For example, conventional HMDs are disclosed in patent documents 1 through 3. The conventional HMDs disclosed in them have a common structure in which image light projected from the display element is propagated in the direction of the width of the eyes of the observer (horizontal direction) in the prism and guided to the optical pupils. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent document 1: Patent Application Publication No. 2004-317798 
     Patent document 2: Patent Application Publication No. 2008-165063 
     Patent document 3: Patent Application Publication No. 2010-122478 
     SUMMARY 
     Most conventional HMDs are the so-called “eyeglass-type”. Eye-glass HMDs have a structure in which lenses and a frame which supports the lenses are located in front of the eyes of the observer, and an image display device with components such as display elements are attached to these lenses or frame. With such eyeglass-type HMDs, because image display devices can be attached to eyeglass lenses or frame, these HMDs have been considered to allow relatively large image display devices to be safely attached. 
     However, wearing a conventional eyeglass-type HMD means that lenses and frame are constantly located in front of the eyes of the observer, which causes the observer to have a clear sense of wearing something. In other words, one problem with conventional HMDs is that the observer cannot escape from feeling the presence of the HMD because lenses and/or frames are unavoidably inside the field of vision of the observer. In addition, even persons with good eyesight must wear eyeglass-type devices, causing the appearance of such persons to be unnatural. 
     Furthermore, conventional eyeglass-type HMDs tend to come with relatively large image display devices. Therefore, in a normal design of conventional image display devices, a display optical system which displays images and an eyepiece optical system which guides image light from this display optical system to the eyes of the observer are stored in a single chassis. This chassis basically has only a window to allow image light projected from the eyepiece optical system to transmit, and the remaining part is shielded to prevent light from invading. If such an image display device chassis exists in front of the eyes of a wearer, that chassis frequently enters into the field of vision of the wearer. Therefore, with the structure of conventional image display devices, there is a problem that the field of vision of the wearer is limited, and the wearer feels unnatural or different. 
     As a result, currently, there is a need for technologies to downsize the structure of even such eyepiece image display devices installed in devices such as HMDs so that images can be displayed in a natural manner without blocking the field of vision of the observer. 
     In addition, currently, it can be said that not conventional eyeglass-type but stylishly designed HMDs that come with small image display devices are desired. 
     The inventor of the present invention, as a result of thoroughly considering means to solve the problem of the previous invention mentioned hereinbefore, gained knowledge that makes it possible to downsize the structure itself of image display devices and prevent the field of vision of the observer from being blocked to the extent possible, by supporting an eyepiece optical system on the optical path of the image light projected from the display optical system with the use of two support plates and by forming an opening between these two support plates that allows the line of sight of the observer looking into the eyepiece optical system to pass through. The present inventor realized that the problem of the prior art can be solved based on the knowledge above, and completed the present invention. The present invention has a structure that is described concretely as follows. 
     The present invention relates to an image display device. The image display device of the present invention has a display optical system  10 , an eyepiece optical system  20 , and a support  30 . The display optical system  10  includes a display element that displays images. The eyepiece optical system  20  guides image light projected from the display optical system  10  to the optical pupil of the observer. The support  30  supports the eyepiece optical system  20  on the optical path of image light projected from the display optical system  10 . The support  30  has the first support plate  31  and the second support plate  32  facing each other. The eyepiece optical system  20  is located between the first support plate  31  and the second support plate  32 . Between the first support plate  31  and the second support plate  32 , at least partly, an opening  33  is formed through which the line of sight of the observer passes. 
     As shown in the structure above, if the opening  33  is formed between the first support plate  31  and the second support plate  32  that supports the eyepiece optical system  20 , the observer can visually see the back side of the image display device through the opening  33 . In this structure, two support plates  31  and  32  are located in front of the eye of the observer; however, the observer visually recognizes only the thickness parts of the first support plate  31  and the second support plate  32 . Therefore, the present invention allows the observer to see images with as little as possible blocking the field of vision of the observer. In addition, the structure of the present invention basically supports the eyepiece optical system  20  with the two support plates  31  and  32  only, which makes it possible to downsize the structure of the entire image display device. As a result, the use of small image display devices covered by the present invention achieves more freedom in designing HMDs and expands the range of designs. Therefore, the present invention also makes it possible to create more stylishly designed HMDs different from conventional eyeglass-type HMDs. 
     In the image display device of the present invention, the support  30  preferably has the first storage chamber  34  and the second storage chamber  35 . The first storage chamber  34  stores the display optical system  10 , and has an exit window through which image light from the display optical system  10  passes. The second storage chamber  35  stores the eyepiece optical system  20 , and has an entrance window through which image light from the display optical system  10  passes and an eyepiece window through which light guided by the eyepiece optical system  20  passes. The first storage chamber  34  and the second storage chamber  35  are preferably connected by the first support plate  31  and the second support plate  32 . 
     As shown in the structure above, by storing the display optical system  10  and the eyepiece optical system  20  in the storage chamber  34  and the storage chamber  35 , respectively, and preventing outside light from directly entering into the display optical system  10  and the eyepiece optical system  20 , it becomes possible to prevent images from being displayed unclearly. In addition, by connecting the first storage chamber  34  and the second storage chamber  35  by the first support plate  31  and the second support plate  32 , it becomes possible to downsize the design of image display devices. 
     In the image display device of the present invention, the opening  33  is preferably formed between the first storage chamber  34  and the second storage chamber  35 . 
     As shown in the structure above, by forming the opening  33  between the first storage chamber  34  and the second storage chamber  35 , it becomes easier for the line of sight of the observer to pass through the opening  33 , which secures a wide field of vision for the observer. 
     In the image display device of the present invention, the first support plate  31  and the second support plate  32  preferably have an inclined part  31   a  and an inclined part  32   a  in a manner that the closer they get from the first storage chamber  34  to the second storage chamber  35 , the narrower the distance between them becomes. 
     As shown in the structure above, if the first support plate  31  and the second support plate  32  are inclined, the second storage chamber  35  becomes smaller than the first storage chamber  34 , which is located in front of the eye of the observer. Therefore, it is possible to prevent the second storage chamber  35  from blocking the field of vision of the observer. In addition, it has become clear that the two support plates  31  and  32  are less visible if the two support plates  31  and  32  extend at a slight incline rather than extending in parallel in the lateral direction (direction of the width of the eye). To that end, by forming the inclined part  31   a  and the inclined part  32   a  on the two support plates  31  and  32 , it becomes possible to provide the observer with a more natural field of vision. 
     Another aspect of the present invention is a HMD that comes with the image display device above. 
     Effect of the Invention 
     As described hereinbefore, the present invention can downsize the structure of even eyepiece image display devices installed in devices such as HMDs so that images can be displayed in a natural manner without blocking the field of vision of the observer. As a result, installing small image display devices covered by the present invention in HMDs can allow more freedom in designing HMDs and expand the range of designs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an example appearance of the image display device covered by the present information. 
         FIG. 2( a )  is a front view of the image display device and  FIG. 2( b )  is a plane view of the image display device. 
         FIG. 3  schematically shows a condition in which the image display device is located in front of the optical pupil of the observer. 
         FIG. 4  is a block view of an example optical system installed in the image display device. 
         FIG. 5  is a perspective view of an example design of a HMD coming with the image display device. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment for working the present invention is described using drawings. The present invention is not limited to the embodiment described hereinafter, but includes amendments thereto made as needed by those skilled in the art to the extent obvious. In the figures prepared for the claimed invention, an XYZ orthogonal coordinate system is defined for the purpose of clearly showing the three-dimensional directions of the device. In the specifications of the claimed invention, for convenience purposes, the X-axis direction is set as the lateral direction, the Y-axis as the vertical direction, and the Z-axis as the depth direction. In addition, in the specifications of the claimed invention, “A˜B” basically means “A or higher but below B”. 
       FIG. 1  is an external perspective view of an example embodiment of the image display device  100  covered by the present information.  FIG. 1  particularly shows the appearance of the support  30  that comprises the image display device  100 . The support  30  is a tool that supports the display optical system  10  which displays images and the eyepiece optical system  20  which guides image light projected from the display optical system  10  to the optical pupil of the observer. The support  30  supports the eyepiece optical system  20  on the optical path of image light projected from the display optical system  10 . In addition,  FIG. 2( a )  is a front view of the image display device  100  seen from the front (X-Y surface), and  FIG. 2( b )  is a planar view of the image display device  100  seen from the planar surface (X-Z surface) 
     As shown in  FIG. 1  and  FIG. 2 , the support  30  has two support plates  31  and  32  which face each other in the vertical direction (Y-axis direction). In the specifications of the claimed invention, the two support plates are called the first support plate  31  and the second support plate  32 , respectively. In the embodiment of the claimed invention, the first support plate  31  is located on the lower side, and the second support plate  32  is located on the lower side. 
     As shown in  FIG. 1 , at the base end side of the two support plates  31  and  32 , the first storage chamber  34  is formed. The first storage chamber  34  is a chamber comprising the upper surface formed by part of the first support plate  31 , the bottom surface formed by part of the second support plate  32 , and the side wall  34   a  vertically standing in the vertical direction (Y-axis direction) and connecting the first support plate  31  and the second support plate  32 . The first storage chamber  34  stores the display optical system  10  which has components such as an image element for displaying images. In addition, as shown in  FIG. 1 , on the side wall  34   a  of the first storage chamber  34 , an exit window  34   b  through which optical images projected from the display optical system  10  passes and an insertion window  34   c  through which various cables are inserted for connection to the display optical system  10 . To the display optical system  10 , control cables for controlling the function of the display optical system  10  (not shown) and power cables for supplying power to the display optical system  10  (not shown) can be connected. 
     As shown in  FIG. 1 , at the head end side of the two support plates  31  and  32 , the second storage chamber  35  is formed. The second storage chamber  35  is a chamber comprising the upper surface formed by part of the first support plate  31 , the bottom surface formed by part of the second support plate  32 , and the side wall  35   a  vertically standing in the vertical direction (Y-axis direction) and connecting the first support plate  31  and the second support plate  32 . The second storage chamber  35  stores the eyepiece optical system  20  including a prism which guides image light projected from the display optical system  10  to the optical pupil of the observer. On the side wall  35   a  of the second storage chamber  35 , an entrance window  35   b  through which image light projected from the display optical system  10  enters and an eyepiece window  35   c  through which image light projected from the eyepiece optical system  20  passes are formed. 
     As shown in  FIG. 1 , there is open space between the first storage chamber  34  and the second storage chamber  35 . Thus, image light projected from the display optical system  10  reaches this space through the exit window  34   b  of the first storage chamber  34 . Subsequently, the image light that passed through the exit window  34   b  enters into the eyepiece optical system  20  via this space after passing through the entrance window  35   b  of the second storage chamber  35 . After that, the image light is guided to the optical pupil of the observer by the eyepiece optical system  20 . 
     In addition, as shown in  FIG. 1 , the opening  33  through which the line of sight of the observer passes is formed at least partly between the first support plate  31  and the second support plate  32 . To describe this more in detail, the opening  33  is that through which the line of sight of the observer passes when the optical pupil of the observer is in a position facing the eyepiece window  35   c . That is to say, as shown in  FIG. 1 , the opening  33  constitutes the part between the first support plate  31  and the second support plate  32  in which no side wall standing vertically in the vertical direction (Y-axis direction) is formed. As shown in  FIG. 1 , the opening  33  is preferably formed at a position corresponding to the space between the first storage chamber  34  and the second storage chamber  35 , in the lateral direction (X-axis direction). 
       FIG. 3  schematically shows the image display device  100  having the opening  33 , located in front of an optical pupil E of the observer. As shown in  FIG. 3 , by forming the opening  33  on the support  30  of the image display device  100 , it becomes possible to lessen the degree to which the image display device  100  blocks the field of vision of the observer. That is to say, because the image display device  100  no longer enters into the field of vision of the observer, a natural range of field of vision of the observer can be maintained even when images are displayed for the observer. In addition, forming the opening  33  on the image display device  100  also lessens the degree to which the face of the observer is covered by the image display device  100 . Therefore, it becomes possible to mitigate the unnaturalness of the appearance of the observer wearing a device equipped with the image display device  100 , such as an HMD. 
     Next, the structure of the support  30  of the image display device  100  is described more concretely with reference to  FIG. 2 . 
     As shown in  FIG. 2( a ) , in the vertical direction (Y-axis direction), the height of the first storage chamber  34  and that of the second storage chamber  35  are different. That is to say, the height of the second storage chamber  35  (H 2 ) is lower than the height of the first storage chamber  34  (H 1 ) (H 2 &lt;H 1 ). For example, provided that the height of the first storage chamber  34  (H 1 ) is 100%, the height of the second storage chamber  35  (H 2 ) is preferably 80% or less, 60% or less, or 40% or less. Concretely, the height of the second storage chamber  35  (H 2 ) is preferably in the range of 10%˜80%, 20%˜60%, or 30%˜50% relative to the height of the first storage chamber  34  (H 1 ). Because the second storage chamber  35  is what is located in front of the eye of the observer, it is preferably smaller than the first storage chamber  34 . 
     The first support plate  31  and the second support plate  32  connect the first storage chamber  34  and the second storage chamber  35 , which have a different height from each other. Therefore, the inclined part  31   a  and the inclined part  32   a  are located on the first support plate  31  and the second support plate  32  so that the height of the first storage chamber  34  matches the height of the second storage chamber  35 . That is to say, the inclined part  31   a  and the inclined part  32   a  are inclined so that the closer they get from the first storage chamber  34  to the second storage chamber  35 , the narrower the distance between them becomes. Particularly, as shown in  FIG. 1  and  FIG. 2 , the inclined part  31   a  and the inclined part  32   a  are preferably formed on the part on which the opening  33  is formed. It has become clear that, as described hereinbefore, by making the first support plate  31  and the second support plate  32  inclined on the part through which the line of sight of the observer passes (opening  33 ), there is less chance for the observer to visually recognize the two support plates  31  and  32 . That is to say, there is less chance for the observer to visually recognize the support plates  31  and  32  if they extend diagonally inclined than if they extend linearly. Therefore, by forming the inclined part  31   a  and the inclined part  32   a  on the first support plate  31  and the second support plate  32 , it becomes possible to secure an even better field of vision of the observer. 
     The angle θ of inclination of the support plates  31  and  32  relative to the optical axis of image light extending to the lateral direction (X-axis direction) of the image display device  100  may be, for example, 5˜60 degrees, 10˜45 degrees, or 15˜30 degrees. In the embodiment shown in  FIG. 2( a )  and other figures, the angle of inclination of the first support plate  31  and the angle of inclination of the second support plate  32  are configured in the same range. However, the angle of inclination of the first support plate  31  and the angle of inclination of the second support plate  32  may be different from each other. Furthermore, although not shown using figures, both the first support plate  31  and the second support plate  32  do not necessarily need to have an inclined part. For example, only either the first support plate  31  or the second support plate  32  may have an inclined part. 
       FIG. 2( a )  also shows the length of the support  30  in the lateral direction (X-axis direction) with the sign EL, and the length of the opening  33  in the lateral direction (X-axis direction) with the sign AL. The length AL of the opening  33  is preferably 20% or higher, 30% or higher, or 40% or higher, provided that the length EL of the support  30  is 100%. Concretely, the length AL of the opening  33  is preferably in the range of 20%˜90%, 30%˜80%, or 40%˜70% relative to the length EL of the support  30 . As shown hereinbefore, by arranging the area of the opening  33  to be large, it becomes possible to secure a wide field of vision for the observer. 
       FIG. 2( a )  also shows the thickness of the first support plate  31  and the second support plate  32  on the part in which the opening  33  is formed, with the sign T. For example, the thickness T of the support plates  31  and  32  is preferably 5 mm or less. Concretely, the thickness T of the support plates  31  and  32  is preferably 0.1 mm˜0.5 mm, and more preferably 0.5 mm˜3 mm or 1 mm˜2 mm. The present invention is configured to support the eyepiece optical system  20  by the two support plates  31  and  32 . Therefore, the eyepiece optical system  20  can still be supported sufficiently strongly, even if the thickness of the support plates  31  and  32  is decreased. In addition, by decreasing the thickness of the support plates  31  and  32 , there is less chance for the observer to visually recognize the support plates  31  and  32 . As a result, it becomes possible to achieve a natural field of vision of the observer. 
     Next, the optical systems installed in the image display device  100  are described more in detail with reference to  FIG. 4 .  FIG. 4  is a view of the inside of the image display device  100  seen from the planar surface (X-Z surface). As shown in  FIG. 4 , the image display device  100  comes with the display optical system  10  which displays images and the eyepiece optical system  20  which guides image light projected from the display optical system  10  to the optical pupil E of the observer. As described hereinbefore, the display optical system  10  is stored in the first storage chamber  34  and the eyepiece optical system  20  is stored in the second storage chamber  35 . The optical systems shown in  FIG. 4  are merely an embodiment of the present invention. In the present invention, not only the optical systems shown in  FIG. 4  but also other publicly known systems can be adopted as needed. 
     As shown in  FIG. 4 , the display optical system  10  has a source of light  11 , a collecting lens  12 , and a display element  13 . The source of light  11  is preferably one that emits colors in R (red), G (green), and B (blue). The source of light  11  is preferably configured by an RGB-integrated LED panel. The source of light  11  may be one that emits a single color light or white light. The collecting lens  12  collects light from the source of light  11  and provides it to the display element  13 . The display element  13  is a component that displays images by modulating the incident light depending on image data. The display element  13  is preferably configured by, for example, a transmission-type liquid crystal display in which pixels that serve as regions through which light passes are arranged in a matrix. To that end, a liquid crystal display (LCD) is used in the display optical system  10 . 
     Next, the eyepiece optical system  20  is an optical system that guides image light from the display element  13  described above to the optical pupil E. The eyepiece optical system  20  has a prism  21 , an eyepiece lens  22 , and a correction lens  23 . The prism  21  is a light guiding component that internally guides image light from the display element  13 . The prism  21  is shaped to have an entrance surface  21   a , a total reflection surface  21   b , and an exit surface  21   c  for image light. The prism  21  may be configured by a single prism or in combination of multiple prisms. The eyepiece lens  22  has axially asymmetric and positive power and collects image light totally reflected by the total reflection surface  21   b  to the optical pupil E. The eyepiece lens  22  is integrated with the prism  21  by being jointed to the exit surface  21   c  of the prism  21 . The correction lens  23  is a lens for correcting optical aberration occurring at components such as the eyepiece lens  22 . The eyepiece lens  22  is integrated with the prism  21  by being joined to the entrance surface  21   a  of the prism  21 . 
     Here, the configuration of the prism  21  is concretely described. The entrance surface  21   a  of the prism  21  is formed in the depth direction (Z-axis direction) which vertically crosses with the optical axis of image light progressing in the lateral direction (X-axis direction). The exit surface  21   c  is formed facing the optical pupil E of the observer. The total reflection surface  21   b  is, for example, rectangular (oblong) and functions as a means to perpendicularly refract the optical path of image light. Concretely, the total reflection surface  21   b  totally reflects in the Z-axis direction the image light that enters the prism via the entrance surface  21   a  and progresses in the X-axis direction. 
     According to the configuration above, light projected from the source of light  11  is collected by the collecting lens  12  and then enters into the display element  13 . This light is modulated by the display element  13  into image light. Subsequently, the image light projected from the display element  13  enters into the eyepiece optical system  20 . In the eyepiece optical system  20 , the image light enters into the prism  21  via the correction lens  23  and the entrance surface  21   a . After that, the image light progresses inside the prism  21  in the lateral direction (X-axis direction), and changes its direction with the optical path refracted by the total reflection surface  21   b  and progresses in the depth direction (Y-axis direction). As a result, the image light is guided to the optical pupil E of the observer via the exit surface  21   c  of the prism  21  and the eyepiece lens  22 . The observer can see an enlarged virtual image displayed by the display element  13  at the position of the optical pupil E. 
       FIG. 5  is an example design of a head mount display (HMD)  200  equipped with the image display device  100 . As shown in  FIG. 5 , the image display device  100  can be extremely downsized and installed on the eyepiece part of the HMD  200 . As is shown, the image display device  100  of the present invention makes it possible to achieve stylishly designed HMDs that are different from conventional eyeglass-type HMDs. 
     So far, in the specifications of the claimed invention, an embodiment was described with reference to drawings, in order to express the content of the present invention. However, the present invention is not limited to the embodiment described hereinbefore, and encompasses obvious modifications and improvements made by those skilled in the art based on the matters described in the specifications of the claimed invention. 
     The present invention relates to an eyepiece image device installed in products such as HMDs. Therefore, the present invention is suitable and useful in the industry of manufacturing wearable devices. 
     DESCRIPTION OF THE NUMERALS 
       10 : Display optical system  11 : Source of light  12 : Collecting lens  13 : Display element  20 : Eyepiece optical system  21 : Prism  21   a : Entrance surface  21   b : Total reflection surface  21   c : Exit surface  22 : Eyepiece lens  23 : Correction lens  30 : Support  31 : First support plate  32 : Second support plate  31   a ,  32   a : Inclined parts  33 : Opening  34 : First storage chamber  34   a : Side wall  34   b : Exit window  34   c : Insertion window  35 : Second storage chamber  35   a : Side wall  35   b : Entrance window  35   c : Eyepiece window  100 : Image display device  200 : Head mount display