Patent Publication Number: US-2022236578-A1

Title: Image display device

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-011759, filed Jan. 28, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an image display device that enables observation of a virtual image, and particularly relates to an image display device in which an optical system is partially accommodated in an exterior member. 
     2. Related Art 
     As an image display device, a head-mounted display (hereinafter also referred to as “HMD”) having a structure in which a housing accommodating an optical system that guides imaging light in a vertical direction is covered by an external cover, and the external cover is attached to a frame for head mounting (JP-A-2017-212475). In this HMD, a separation surface of the housing is waterproofed by disposing and sandwiching a seal member that covers the entire circumference at the separation surface of the housing, which accommodates an optical component and is separated into a half body, as well as a base end portion of an image display member. 
     In the HMD of JP-A-2017-212475, the housing accommodating the optical system is waterproofed and the housing is attached to the frame via the external cover, therefore, there is a problem in that the overall device becomes larger and heavier in weight than the housing accommodating the optical system. 
     SUMMARY 
     An image display device according to one aspect of the present disclosure includes a first display unit that includes: a first optical system that emits an imaging light toward a pupil position, and a first frame that supports the first optical system, a first cover member that accommodates the first optical system and that exposes a portion of the first frame, an exterior member that accommodates the first cover member, and a sheet-shaped member that has flexibility and that includes: a first portion that is sandwiched by the exterior member, and a second portion that is sandwiched between the first frame and the first cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external perspective view illustrating a wearing state of an image display device according to a first exemplary embodiment. 
         FIG. 2  is a plan view, front view, side view, and bottom view of the image display device. 
         FIG. 3  is a front view, side view, perspective view, etc. illustrating an interior of the image display device with an exterior member removed. 
         FIG. 4  is an exploded perspective view of the remainder of the portion where the exterior member is removed from the image display device. 
         FIG. 5  is a plan view and a bottom view of an optical unit at which left and right display units are combined. 
         FIG. 6  is a perspective view describing a coupling between a first frame and a fixing member, a perspective view describing a positional relationship between the fixing member and a first cover member, and a perspective view describing a positional relationship between the first frame, the fixing member, and the first cover member. 
         FIG. 7  illustrates a bottom view of an upper exterior member and a plan view of a lower exterior member. 
         FIG. 8  is a conceptual side cross-sectional view illustrating an optical system inside the image display device. 
         FIG. 9  is a diagram illustrating distortion correction of a display image. 
         FIG. 10  is a plan view illustrating a sealing member. 
         FIG. 11  is a conceptual side view illustrating a sealing structure of the image display device. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, a structure, operation, manufacturing method, etc. of an image display device according to the present disclosure will be described with reference to  FIGS. 1 to 3 , etc. 
       FIG. 1  is a diagram illustrating a wearing state of an image display device  200 . The image display device  200  is a head-mounted display, i.e., HMD  201 , and causes an observer or a wearer US who wears the head-mounted display  201  to recognize an image as a virtual image. In  FIG. 1 , etc., X, Y, and Z correspond to an orthogonal coordinate system, a +X direction corresponds to a lateral direction in which the two eyes EY of the observer or wearer US who is wearing the image display device  200  or HMD  201  are arranged, a +Y direction corresponds to an upward direction orthogonal to the lateral direction in which the two eyes EY of the wearer US are arranged, and a +Z direction corresponds to a direction to the front or a forward direction for the wearer US. A ±Y direction is parallel to a vertical axis or a vertical direction. 
     The image display device  200  includes a main body  200   a  disposed to cover the front of the wearer US and a pair of temple support devices  200   b  that support the main body  200   a . The main body  200   a , when functionally viewed, includes a first display device  100 A for the right eye and a second display device  100 B for the left eye. The first display device  100 A includes a display driving unit  102  disposed at an upper portion thereof, and a combiner  103   a  that is shaped like a spectacle lens and covers the front of the eye. Similarly, the second display device  100 B includes a display driving unit  102  disposed at an upper portion thereof, and a combiner  103   b  that is shaped like a spectacle lens and covers the front of the eye. 
     The appearance of the main body  200   a  of the image display device  200  will be described with reference to  FIG. 2 . In  FIG. 2 , a region AR 1  is a plan view of the main body  200   a , a region AR 2  is a front view of the main body  200   a , a region AR 3  is a right side view of the main body  200   a , and a region AR 4  is a bottom view of the main body  200   a . A pair of the display driving units  102  disposed on the +Y side or the upper side of the main body  200   a  are coupled and integrated, and are covered by a dome-shaped upper exterior member  107   a  elongated in the lateral direction and a flat plate-shaped lower exterior member  107   b . A combination of the upper exterior member  107   a  and the lower exterior member  107   b  is referred to as an exterior member  107 . The first combiner  103   a  and the second combiner  103   b  have a shape such that an upper portion of a hemisphere protruding in the forward or the +Z direction is cut, and is disposed so as to protrude downward from the lower exterior member  107   b.    
     With reference to  FIG. 3 , an overview of an internal structure in which the upper exterior member  107   a  and the lower exterior member  107   b  have been removed from the main body  200   a  illustrated in  FIG. 2  will be described. In  FIG. 3 , a region BR 1  is a front view with an upper portion of the main body  200   a  exposed, a region BR 2  is a right side view with the upper portion of the main body  200   a  exposed, a region BR 3  is a perspective view with the upper portion of the main body  200   a  exposed, and a region BR 4  is a perspective view with an internal optical system of the main body  200   a  exposed. The first display device  100 A for the right eye includes a first display element  11   a , a first optical system  12   a , and the first combiner  103   a , as the first display unit  100   a . A first frame  61   a  described below is also an element of the first display unit  100   a . The first optical system  12   a  is covered with a first cover member  71   a , which is an inner cover. The first display element  11   a  is disposed so as to close an opening  710  of the first cover member  71   a , and is fixed to an outer frame of the first optical system  12   a  via a first holder  72   a  having a rectangular frame shape. 
     As illustrated in  FIG. 4 , the first optical system  12   a  is fixed to an upper surface of the plate-shaped first frame  61   a  by adhesion, etc., and the first combiner  103   a  is fixed to the front half of the periphery of the first frame  61   a  by adhesion, etc. at an upper end thereof. 
     Referring back to  FIG. 3 , the second display device  100 B includes a second display element lib, a second optical system  12   b , and the second combiner  103   b , as the second display unit  100   b . A second frame  61   b  described below is also an element of the second display unit  100   b . The second optical system  12   b  is covered with a second cover member  71   b , which is an inner cover. The second display element  11   b  is disposed so as to close the opening  710  of the second cover member  71   b , and is fixed to an outer frame of the second optical system  12   b  via the second holder  72   b  having a rectangular frame shape. The second display device  100 B for the left eye has the same structure and function as the first display device  100 A for the right eye. In other words, the second display element  11   b  is the same as the first display element  11   a , the second optical system  12   b  is the same as the first optical system  12   a , and the second combiner  103   b  is the same as the first combiner  103   a . However, in a case where the first optical system  12   a , the first combiner  103   a , etc. have asymmetry with respect to the left and right X direction, the second optical system  12   b , the second combiner  103   b , etc. are obtained by laterally inverting the first optical system  12   a , the first combiner  103   a , etc. 
     As illustrated in  FIG. 4 , the second optical system  12   b  is fixed to an upper surface of the plate-shaped second frame  61   b  by adhesion, etc., and the second combiner  103   b  is fixed to the front half of the periphery of the second frame  61   b  by adhesion, etc. at an upper end thereof. 
     Referring back to  FIG. 3 , the first display device  100 A and the second display device  100 B are coupled via a fixing member  78  therein. The fixing member  78  is a rod-shaped metal member, and is formed from, for example, a magnesium alloy. By forming the fixing member  78  from the magnesium alloy, the first frame  61   a  and the second frame  61   b  can be cooled by heat dissipation. The fixing member  78  fixes the first display unit  100   a  and the second display unit  100   b  relative to each other at both ends thereof. The fixing member  78  is a member corresponding to an arm of a balance, and supports a pair of the display units  100   a ,  100   b  corresponding to a pair of plates in the center. The fixing member  78  has a shape that allows the first optical system  12   a  and the second optical system  12   b  to rotate in rotational directions along two or more axes when the first display unit  100   a  and the second display unit  100   b  are aligned prior to fixing. 
     The support of the first display unit  100   a  and the second display unit  100   b  by the fixing member  78  will be described with reference to  FIGS. 4 to 6 . In  FIG. 5 , a region CR 1  is a plan view of an optical unit OU coupled to the left and right display units  100   a ,  100   b , and a region CR 2  is a bottom view of the optical unit OU. In  FIG. 6 , a region DR 1  is a perspective view describing a coupling between the first frame  61   a  and the fixing member  78 , a region DR 2  is a perspective view describing a positional relationship between the fixing member  78  and the first cover member  71   a , and a region DR 3  is a perspective view describing a positional relationship between the first frame  61   a , the fixing member  78 , and the first cover member  71   a . Fixing portions  81   a ,  82   a , which are spherical members, are formed at both ends of the fixing member  78 . After the first display unit  100   a  and the second display unit  100   b  are aligned, these fixing portions  81   a ,  82   a  are attached to concave portions  81   b ,  82   b , which are hemispherical indentation members provided at the inner ends of the display units  100   a ,  100   b  or the frame  61   a ,  61   b  by an adhesive material, etc., whereby the rotation is stopped. A coupling member  81  that combines the fixing portion  81   a  and the concave portion  81   b  has a ball joint type bearing structure, and is covered by an extending portion  71   c  of the first cover member  71   a . A bearing-shaped coupling member  82  that combines the fixing portion  82   a  and the concave portion  82   b  also has a ball joint type bearing structure, and is also covered by an extending portion  71   c  of the second cover member  71   b . One of the coupling members  81  is provided between the fixing portion  81   a  and the first display unit  100   a , namely, the first frame  61   a , and has rotational degrees of freedom around three axes. The other coupling member  82  is provided between the fixing portion  82   a  and the second display unit  100   b , namely, the second frame  61   b , and has rotational degrees of freedom around three axes. By using such coupling members  81 ,  82 , the degree of freedom of relative positioning between the first display unit  100   a  and the second display unit  100   b  can be increased. 
     The first frame  61   a  is a semi-circular plate-shaped metal member, and is formed, for example, from a magnesium alloy. By forming the first frame  61   a  from the magnesium alloy, heat dissipation efficiency of heat generated by the display element  11   a , etc. can be increased. The concave portions  81   b  are formed at both the left and right ends of the first frame  61   a , but only one of the concave portions  81   b  is used for coupling with the fixing member  78 . An optical aperture OA is formed at the first frame  61   a , and a plate-shaped optical element  28  that seals the optical aperture OA is disposed. The plate-shaped optical element  28  is part of the first optical system  12   a . The second frame  61   b  is a semi-circular metal member, and is formed, for example, from a magnesium alloy. By forming the second frame  61   b  from the magnesium alloy, heat dissipation efficiency of heat generated by the display element  11   b , etc. can be increased. The concave portions  82   b  are formed at both the left and right ends of the second frame  61   b , but only one of the concave portions  82   b  is used for coupling with the fixing member  78 . An optical aperture OA is also formed at the second frame  61   b , and a plate-shaped optical element  28  that seals the optical aperture OA is disposed. 
     The upper exterior member  107   a  and the lower exterior member  107   b  will be described with reference to  FIG. 7 . In  FIG. 7 , a region ER 1  is a bottom view illustrating the inside of the upper exterior member  107   a , and a region ER 2  is a plan view illustrating the inside of the lower exterior member  107   b . The upper exterior member  107   a  and the lower exterior member  107   b  are formed from a resin material. An outer edge  7   a  of the upper exterior member  107   a  and an outer edge  7   b  of the lower exterior member  107   b  have the same shape. By abutting them, a space for accommodating the first optical system  12   a  and the second optical system  12   b  illustrated in  FIG. 3  can be formed. The upper exterior member  107   a  and the lower exterior member  107   b  are fixed using fastening portions  7   f ,  7   g , which are screw holes, etc. The lower exterior member  107   b  has a pair of openings OP 1 , and the first frame  61   a  and the second frame  61   b  can be disposed at the openings OP 1 , as indicated by a dotted lines. Gaps GP are provided between the openings OP 1  and the frames  61   a ,  61   b , and allows the frames  61   a ,  61   b  to shift in position with respect to the X-Y plane or the Y direction within the openings OP 1 . That is, the first display unit  100   a  and the second display unit  100   b  illustrated in  FIG. 3 , etc. are fixed to the lower exterior member  107   b  while remaining aligned with each other, and even in a state of being accommodated in the upper exterior member  107   a  and the lower exterior member  107   b , the positional relationship between the display units  100   a ,  100   b  upon completion of positioning is maintained. Screwing hole  7   j  are formed at the lower exterior member  107   b  and can be fixed by screwing to a pair of fastening portions  78   z  provided at a bridge  78   a  of the fixing member  78 . 
     Referring to  FIGS. 3 and 4 , an sealing member  75  is disposed above the first frame  61   a  and the second frame  61   b . The sealing member  75  is a rubber-like elastic sheet or waterproof sheet, and has flexibility. The sealing member  75  is interposed between the first frame  61   a  and the second frame  61   b , and the upper exterior member  107   a  and the lower exterior member  107   b  illustrated in  FIG. 2 , to maintain an internal space IS of the exterior member  107  in a liquid-tight or air-tight manner. Here, the sealing by the sealing member  75  is not limited to complete air tightness, and also includes a level such as a drop or dust prevention. 
     With reference to  FIG. 3 , a rectangular plate-shaped circuit board  91  is disposed above the fixing member  78  between the left and right display units  100   a ,  100   b . The circuit board  91  includes a control device  92  that controls display operation of the first display element  11   a  and the second display element  11   b . The control device  92  outputs a drive signal corresponding to the display image to the left and right display elements  11   a ,  11   b  to control the display operation of the left and right display elements  11   a ,  11   b . The control device  92  includes, for example, an IF circuit, a signal processing circuit, etc., and causes the left and right display elements  11   a ,  11   b  to display a two-dimensional image according to the image data or the image signal received from the outside. Although not shown, the control device  92  includes a main board that controls the operation of the first display device  100 A and the operation of the second display device  100 B. The main substrate may have, for example, an interface function that communicates with an external device (not shown) and performs signal conversion on a signal received from the external device, and an integrated function that links between the display operation of the first display device  100 A and the display operation of the second display device  100 B. In order to draw a communication line extending from the circuit board  91  to the outside, a conductive opening (not illustrated) is produced at an appropriate position on the upper exterior member  107   a , and the periphery of an insertion opening is also liquid-tightly sealed. 
     The circuit board  91  is supported on the fixing member  78  by a substrate support portion  74 . The circuit board  91  is fixed at the substrate support portion  74 . The substrate support portion  74  is a member made of resin covering the fixing member  78  from the upper, front, and rear, and is detachable from the fixing member  78  together with the circuit board  91  by a snap fit using a fitting portion  51 . 
       FIG. 8  is a side cross-sectional view illustrating an optical structure of the first display unit  100   a . The first display unit  100   a  includes the first display element  11   a  and an imaging optical system  20 . The imaging optical system  20  is also referred to as a light guide optical device. The imaging optical system  20  includes a projection lens  21 , a prism mirror  22 , the plate-shaped optical element  28 , and a see-through mirror  23 . The projection lens  21 , the prism mirror  22 , and the plate-shaped optical element  28  of the imaging optical system  20  correspond to the first optical system  12   a  illustrated in  FIG. 3 , etc., and the see-through mirror  23  corresponds to the first combiner  103   a . The first optical system  12   a  cooperates with the first combiner  103   a  to emit imaging light ML toward a pupil position PP. The first display element  11   a , the projection lens  21 , and the prism mirror  22  are fixed to the first frame  61   a  in a state of being aligned with each other by a frame body (not illustrated), and is accommodated in a space SP 1  sandwiched between the first cover member  71   a  and the first frame  61   a . The plate-shaped optical element  28  is disposed so as to be fitted into a step formed at the optical aperture OA of the first frame  61   a , and the periphery of the optical aperture OA is kept airtight state. 
     The first display element  11   a  is a spontaneous light emission type display device. The first display element  11   a  is, for example, an organic EL (Organic Electro-luminescence) display, and forms a color still image or moving image on a two-dimensional display surface  11   d . The first display element  11   a  is disposed along the X-Y plane that is inclined by being rotated about the X-axis with respect to an X-Y plane. The first display element  11   a  is driven by the control device  92  provided at the circuit board  91  to perform display operation. The first display element  11   a  is not limited to the organic EL display, and can be replaced with a micro LED display or a display device using an inorganic EL, an organic LED, a laser array, a quantum dot light emitting element, etc. The first display element  11   a  is not limited to a spontaneous light emission type imaging light generation device, and may include an LCD and another light modulation element, and may form an image by illuminating the light modulation element with a light source such as a backlight. As the first display element  11   a , a LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micro-mirror device, etc. may be used instead of an LCD. 
     The projection lens  21  causes the imaging light ML emitted from the first display element  11   a  to pass therethrough and then to be incident on the prism mirror  22 . The projection lens  21  includes a first lens  21   p  and a second lens  21   q , and focuses the imaging light ML emitted from the first display element  11   a  into a state close to a parallel luminous flux. The prism mirror  22  has an inner reflection surface  22   b , and causes the imaging light ML emitted from the projection lens  21  to be incident on a light incident surface  22   a , to be totally reflected by the inner reflection surface  22   b , and to be emitted from a light emission surface  22   c . At this time, the prism mirror  22  emits the imaging light ML incident from the front such that it is bent in a direction inclined with respect to a direction in which an incident direction is reversed (a direction of the light source seen from the prism mirror  22 ). The plate-shaped optical element  28  causes the imaging light ML from the prism mirror  22  to pass therethrough while refracting it, and then to be incident on the see-through mirror  23 . 
     The see-through mirror  23  is a curved plate-shaped optical member that serves as a concave surface mirror, and reflects the imaging light ML incident from the prism mirror  22  via the plate-shaped optical element  28  toward a pupil position PP. The pupil position PP is a position at which the imaging light ML from each of points on the display surface  11   d  is incident so as to be overlapped from an angular direction corresponding to a position of each of points on the display surface  11   d  in a predetermined divergent state or a parallel state. The see-through mirror  23  covers the pupil position PP at which the eye EY or the pupil is disposed, has a concave shape toward the pupil position PP, and has a convex shape toward the outside. The see-through mirror  23  is a mirror plate having a structure in which a mirror film  23   c  is formed at a front surface or a back surface of a plate-shaped body  23   b . The reflection surface  23   a  of the see-through mirror  23  has transmissive properties. The external light OL that has passed through the see-through mirror  23  and a support plate  41  therearound is also incident on the pupil position PP. In other words, the wearer US wearing the image display device  200  can observe a virtual image of the imaging light ML in a state in which the imaging light ML overlaps with the external image. 
     In the above, optical surfaces constituting the projection lens  21 , the prism mirror  22 , the plate-shaped optical element  28 , and the see-through mirror  23  includes a free-form surface, and at least some of the optical surfaces may be replaced with an aspheric surface or a spherical surface. 
     The imaging optical system  20  is an off-axis optical system OS due to the see-through mirror  23  being a concave mirror, etc. In the case of the present exemplary embodiment, the projection lens  21 , the prism mirror  22 , the plate-shaped optical element  28 , and the see-through mirror  23  are disposed non-axisymmetric and have a non-axisymmetric optical surface. In the imaging optical system  20 , that is, the off-axis optical system OS, an optical axis AX is bent so that the optical axis AX extends along an off-axis surface (a surface parallel to the Y-Z surface) corresponding to a plane of the drawing. In the imaging optical system  20 , the optical elements  21 ,  22 , and  23  are arranged along the off-axis surface by bending the optical axis AX in the off-axis plane parallel to the Y-Z plane. The imaging optical system  20  includes optical axis portions AX 1 , AX 2 , and AX 3  that are disposed along the off-axis surface (a surface parallel to the Y-Z plane) which is a reference surface extending in the longitudinal direction and are inclined with respect to each other before and after the reflection surface. The optical axis AX as a whole extends along an optical path of the main rays emitted from the center of the display element  11   a  and passes through the center of the eye ring ER or the pupil corresponding to an eye point. The optical axis AX is disposed in a Z shape by the plurality of optical axis portions AX 1 , AX 2 , and AX 3  when seen in a transverse cross section parallel to the Y-Z plane. In other words, in the off-axis surface parallel to the Y-Z plane, an optical path P 1  from the projection lens  21  to an inner reflection surface  22   b , an optical path P 2  from the inner reflection surface  22   b  to the see-through mirror  23 , and an optical path P 3  from the see-through mirror  23  to the pupil position PP are arranged to be bent in a Z shape in two stages. 
     As illustrated in  FIG. 9 , the display image formed at the display surface  11   d  of the first display element  11   a  is set to a modified image DA 1  having a distortion such as trapezoidal distortion. That is, since the imaging optical system  20  is the off-axis optical system OS, it is not easy for the optical system itself to remove distortion such as trapezoidal distortion. In this way, a pixel array of a projected image IG 1  of the virtual image observed at the pupil position PP via the imaging optical system  20  can be made into a grid pattern corresponding to an original display image DA 0 , and the outline thereof can be made rectangular by causing the image displayed on the first display element  11   a  to have reverse distortion that cancels out the distortion formed by the projection lens  21 , the prism mirror  22 , the plate-shaped optical element  28 , and the see-through mirror  23 . In other words, the first display element  11   a  corrects the distortion formed by the projection lens  21 , the prism mirror  22 , the plate-shaped optical element  28 , and the see-through mirror  23 . As a result, aberrations can be suppressed as a whole including the first display element  11   a  while allowing the distortion generated by the see-through mirror  23 , etc. Thus, the degree of freedom in the arrangement and size of optical elements such as the prism mirror  22  is increased, and it is possible to easily secure the optical performance of the first display unit  100   a  while achieving miniaturization of the first display unit  100   a.    
     Although the first display unit  100   a  has been described above, the second display unit  100   b  has a similar structure to that of the first display unit  100   a , and thus a description of the specific structure thereof will be omitted. 
     Hereinafter, the sealing member  75  will be described with reference to  FIG. 10 . The sealing member  75  has an outline shape similar to that of the exterior member  107  as seen in plan view, and extends elongated in the lateral X direction. The sealing member  75  is a waterproof sheet formed of an independent foam material such as “PORON®” and has a uniform thickness. The sealing member  75  has cushioning properties and is elastically deformable. The thickness of the sealing member  75  is set to approximately 0.5 mm, for example, but is not limited thereto. By making the sealing member  75  elastically deformable, the tolerance of adjusting the positions of the first frame  61   a  and the second frame  61   b  with respect to the exterior member  107  can be increased. A pair of openings OP 21  and OP 22  are formed at the sealing member  75 . An outer circumferential portion  75   o  of the sealing member  75  functions as an outer first sealing portion  75   f , as illustrated in a fine dot pattern in the drawings. The outer circumferential portion  75   o  is sandwiched between the outer edges  7   a  and  7   b  of the exterior member  107 , and is fixed in close contact with the exterior member  107 . Two second sealing portions  75   s  are provided between the outer circumferential portion  75   o  of the sealing member  75  and the openings OP 21 , OP 22 , in other words, on the inner side of the first sealing portion  75   f , as illustrated by a fine dot pattern in the drawing. The two second sealing portions  75   s  correspond to the outer peripheries of the first frame  61   a  and the second frame  61   b , and are attached to the outer peripheral upper surfaces of the both frames  61   a ,  61   b.    
     After assembly, the first frame  61   a  and the second frame  61   b  are disposed on the underside or −Y side of the sealing member  75 , and the periphery of the openings OP 21 , OP 22  is supported at the first frame  61   a  and the second frame  61   b . At this time, the first optical system  12   a  protrudes and is exposed on the opposite side or the +Y side of the first frame  61   a  via the opening OP 21 . Furthermore, the second optical system  12   b  protrudes and is exposed on the opposite side or the +Y side of the second frame  61   b  via the opening OP 22 . The first cover member  71   a  is disposed on the upper surface side or the +Y side of the sealing member  75  to cover the first optical system  12   a , and the second cover member  71   b  is disposed on the upper surface side or the +Y side of the sealing member  75  to cover the second optical system  12   b . An insertion hole  8   g  corresponding to the fastening portion  7   f , etc. formed at the upper exterior member  107   a  illustrated in  FIG. 7  is formed around the sealing member  75 , and an insertion hole  8   j  corresponding to the screwing hole  7   j  of the lower exterior member  107   b  illustrated in  FIG. 7  is formed in the center of the sealing member  75 . 
     The sealing in the image display device  200  will be described with reference to  FIG. 11 . The first sealing portion  75   f  formed outside of the sealing member  75  performs sealing between the first sealing portion  75   f  and the exterior member  107 . The first sealing portion  75   f  is sandwiched between the upper exterior member  107   a  and the lower exterior member  107   b  constituting the exterior member  107 , and is fixed to the exterior member  107 . An outward step  7   p  is formed at the outer edge  7   a  of the upper exterior member  107   a , an inward step  7   q  is formed at the outer edge  7   b  of the lower exterior member  107   b , and the upper exterior member  107   a  and the lower exterior member  107   b  are engaged with each other by the fitting of these steps  7   p ,  7   q . A gap G 1  is formed at the steps  7   p ,  7   q  abutted, and the first sealing portion  75   f  is elastically deformed and tightly sandwiched in the gap G 1 . As illustrated in  FIG. 10 , the first sealing portion  75   f  is provided in an annular shape along the outer periphery of the upper exterior member  107   a  and the lower exterior member  107   b.    
     The second sealing portion  75   s  formed inside the first sealing portion  75   f  in the sealing member  75  performs sealing between the second sealing portion  75   s  and the first frame  61   a . The second sealing portion  75   s  is attached and fixed to an upper surface  61   m  of an outer peripheral region of the first frame  61   a  via an adhesive layer  93 . In other words, the adhesive layer  93  is provided between the first frame  61   a  and an main body  75   z  of the sealing member  75 . Here, the adhesive layer  93  functions as part of the second sealing portion  75   s , and the second sealing portion  75   s  is fixed in a state of being attached to the first frame  61   a  via the adhesive layer  93 . The second sealing portion  75   s  and the adhesive layer  93  are provided in an annular shape along the outer periphery of the first frame  61   a  (see  FIG. 10 ). Note that, in the sealing member  75 , the inner circumferential portion  75   i  corresponding to the edge of the opening OP 21  or the vicinity thereof is pressed by a lower end  71   e  of the first cover member  71   a.    
     An intermediate region  75   t  of the sealing members  75 , which is sandwiched between the first sealing portion  75   f  and the second sealing portion  75   s  and extends in the lateral direction, couples the first sealing portion  75   f  and the second sealing portion  75   s  to seal the internal space IS of the exterior member  107 . Since the intermediate region  75   t  is elastically deformed, the first frame  61   a  is allowed to shift slightly with respect to the lower exterior member  107   b , etc., which allows positioning of the first frame  61   a  or the first display unit  100   a  that does not refer to the exterior member  107 . Note that the exterior member  107  is manufactured by a technique that does not require relatively precise shape; however, when the exterior member  107  is manufactured with high precision, the positioning can be achieved by directly fixing the first display unit  100   a  to the exterior member  107  without interposing the fixing member  78 . 
     By using the sealing member  75 , the first frame  61   a  is disposed like a lid that covers the opening OP 1  of the exterior member  107 , while the gap GP can be ensured between the both, and sealing in the exterior member  107  can be achieved. 
     In the above, sealing around the first display unit  100   a  of the image display device  200  has been described, but the same applies to the sealing around the second display unit  100   b . Of the sealing of the second display unit  100   b , the portion relative to the exterior member  107  is common to the first display unit  100   a , and uses the first sealing portion  75   f  of the sealing member  75 . Of the sealing of the second display unit  100   b , the portion relative to the second frame  61   b  uses the second sealing portion  75   s  provided surrounding the opening OP 22  of the sealing member  75 . 
     The outer shape of the sealing member  75  is greater than the plate-shaped outer shape of the first frame  61   a  and the second frame  61   b , and the first sealing portion  75   f  is disposed outside the two second sealing portions  75   s  so as to collectively surround the two second sealing portions  75   s  (see  FIG. 10 ). In the center of the sealing member  75 , the sealing member  75  is disposed on the lower side of the fixing member  78  coupled to the first frame  61   a  and the second frame  61   b  (see  FIG. 3 ). In other words, the sealing member  75  is sandwiched between the fixing member  78  and the first frame  61   a  of the first display unit  100   a , and is sandwiched between the fixing member  78  and the second frame  61   b  of the second display unit  100   b . By disposing the sealing member  75  in this manner, the periphery of the fixing member  78  can be sealed, and the fluid tightness or air tightness in the space SP 1  can be maintained. When the lower exterior member  107   b  is fixed to the fixing member  78 , the periphery of the insertion hole  8   j  and the fixing member  78  is kept in a liquid-tight or air-tight manner and sealed. The insertion hole  8   g  for fixing the upper exterior member  107   a  to the lower exterior member  107   b  is also sealed by the fastening portion  7   f  and the surrounding members. 
     While detailed illustration is omitted, the internal space IS of the exterior member  107  is in communication with the space SP 1  sandwiched between the first cover member  71   a  and the first frame  61   a , and is not completely separated. By forming the lower end of the first cover member  71   a  in an annular shape and fixing it to the upper surface  61   m  of the first frame  61   a  so as to press the sealing member  75 , the internal space IS and the space SP 1  can be separated. 
     Hereinafter, the manufacturing or assembling of the image display device  200  will be described. First, the first optical system  12   a  and the first combiner  103   a  are fixed to the first frame  61   a , and the display element  11   a  is fixed while being positioned with respect to the first optical system  12   a  using the first holder  72   a , etc. This results in a right eye unit RU including the first display unit  100   a  (see  FIG. 4 ). In parallel, the second optical system  12   b  and the second combiner  103   b  are fixed to the second frame  61   b , and the display element  11   b  is fixed while being positioned with respect to the second optical system  12   b  using the second holder  72   b , etc. This results in a left eye unit LU including the second display unit  100   b  is obtained (see  FIG. 4 ). Thereafter, the right eye unit RU and the left eye unit LU are set in a two-lineage measurement device, and the sealing member  75  is fixed on the first frame  61   a  and the second frame  61   b . At this time, the second sealing portion  75   s  of the sealing member  75  is attached to both of the frames  61   a ,  61   b  via the adhesive layer  93 . As a result, the OP 21 , OP 22  inside the sealing member  75  are sealed by the first frame  61   a  and the second frame  61   b . Furthermore, the first fixing portion  81   a  of the fixing member  78  is fitted into the first concave portion  81   b  of the first frame  61   a , and the second fixing portion  82   a  of the fixing member  78  is fitted into the second concave portion  82   b  of the second frame  61   b . The stage of the two-lineage measurement device is then utilized to precisely adjust the angle and arrangement of the right eye unit RU and the left eye unit LU. At this time, the right eye unit RU and the left eye unit LU can independently rotate in the R1 direction about the X-axis, the R2 direction about the Y-axis, and the R3 direction about the Z-axis, in a state where the right eye unit RU and the left eye unit LU are coupled by the fixing member  78  (see  FIG. 4 , etc.). Note that the sealing member  75  is elastically deformed, and relative displacement of both frames  61   a ,  61   b  is allowed. After the position adjustment is complete, the adhesive supplied in advance between the first fixing portion  81   a  and the first concave portion  81   b  is cured, and the adhesive supplied in advance between the second fixing portion  82   a  and the second concave portion  82   b  is cured. This completes alignment of the right eye unit RU and the left eye unit LU. Thereafter, the first cover member  71   a  is covered so as to cover the first optical system  12   a  from above the first frame  61   a , and the extending portion  71   c  provided thereon is screwed into the first concave portion  81   b  side of the first frame  61   a  via the screwing hole formed therein and the first fixing portion  81   a . As a result, the fixing of the first cover member  71   a  with respect to the first frame  61   a  is completed. The method of fixing the second cover member  71   b  to the second frame  61   b  is the same as the method of fixing the first cover member  71   a  to the first frame  61   a , so that description thereof is omitted. Next, the circuit board  91  is attached to the fixing member  78  using the substrate support portion  74 , and the FPC extending from the display elements  11   a ,  11   b  is coupled to the circuit board  91 . Finally, the lower exterior member  107   b  is fixed to the fixing member  78  using the pair of fastening portions  78   z  provided at the fixing member  78 , and then the upper exterior member  107   a  is fixed to the lower exterior member  107   b . At this time, the first frame  61   a  and the second frame  61   b  are allowed to shift slightly with respect to the lower exterior member  107   b , and the positioning of the first display unit  100   a  and the first display unit  100   b  with respect to the fixing member  78  is maintained. Furthermore, by sandwiching the outer circumferential portion  75   a , that is, the first sealing portion  75   f , of the sealing member  75  between the outer edge  7   a  of the upper exterior member  107   a  and the outer edge  7   b  of the lower exterior member  107   b , sealing is achieved therebetween. That is, the internal space IS of the exterior member  107  is sealed. 
     The image display device  200  according to the exemplary embodiment described above includes the display units  100   a ,  100   b  including the optical systems  12   a ,  12   b  configured to emit the imaging light ML toward the pupil position PP, and the frames  61   a ,  61   b  configured to support the optical systems  12   a ,  12   b , the exterior member  107  configured to accommodate the optical systems  12   a ,  12   b  of the display units  100   a ,  100   b  in the internal space IS, and partially exposes the frames  61   a ,  61   b , and the sheet-shaped sealing member  75  having flexibility configured to seal the internal space IS of the exterior member  107 , wherein the sealing member  75  includes the outer first sealing portion  75   f  configured to perform sealing between the sealing member  75  and the exterior member  107 , and the inner second sealing portion  75   s  configured to perform sealing between the sealing member  75  and the frames  61   a ,  61   b . As a result, the inside and outside of the exterior member  107  can be separated by the frame  61   a ,  61   b , and the liquid tightness or air tightness of the internal space IS that accommodates the optical systems  12   a ,  12   b  can be maintained, whereby reliable sealing of the internal space IS can be achieved while reducing the size and weight of the exterior member  107 . At this time, due to the flexibility of the sealing member  75 , the positions of the frames  61   a ,  61   b , that is, the display units  100   a ,  100   b , can be adjusted with respect to the exterior member  107 . 
     Modified Examples and Others 
     The present disclosure is described according to the above-described embodiments, but the present exemplary disclosure is not limited to the above-described embodiments. The present exemplary disclosure may be carried out in various modes without departing from the gist of the present disclosure, and, for example, the following modifications may be carried out. 
     The image display device  200  may be a single eye display device. In other words, it can be used as a display device including only the first display unit  100   a , omitting the second display unit  100 . In this case, the exterior member  107  is small in which only the first display unit  100   a  is accommodated. 
     The first sealing portion  75   f  of the sealing member  75  is not limited to being sandwiched and fixed between the upper exterior member  107   a  and the lower exterior member  107   b , but can be fixed to the exterior member  107  by adhesion. In addition, the second sealing portion  75   s  is not limited to being attached to the first frame  61   a , but can be sandwiched and fixed between the first frame  61   a  and the associated part (for example, the first cover member  71   a ). The sealing member  75  need not be an integral product, and for example, the first sealing portion  75   f  and the second sealing portion  75   s  can be attached to the inside and outside of the sheet-shaped member. While it is desirable that the first sealing portion  75   f  and the second sealing portion  75   s  achieve sealing that is formed in an annular shape without cuts, but the sealing may be partially formed with cuts or discontinuities to an extent which does not cause problems with waterproof or anti-drop specifications. 
     The imaging optical system  20  incorporated into the first display unit  100   a  is not limited to that illustrated, and may have various configurations. Specifically, the imaging optical system  20  described above is the off-axis optical system OS that is asymmetric in the Y direction or the longitudinal direction, but may also be an off-axis optical system that is asymmetric in the X direction or the lateral direction. The optical elements constituting the imaging optical system  20  are merely exemplary in  FIG. 8 , and changes can be made, such as increasing or decreasing the number of lenses, adding a light-guiding member, etc. 
     A light control device that controls light by limiting the transmitted light of the combiners  103   a ,  103   b  can be attached on an external side of the combiners  103   a ,  103   b . The light control device adjusts a transmittance, for example, electrically. Mirror liquid crystals, electronic shades, etc. may be used as the light control device. The light control device may adjust a transmittance according to outside light brightness. 
     The combiner  103   a ,  103   b  may be replaced with a mirror having light blocking properties. In this case, the optical system is a non-see-through type optical system that does not assume direct observation of an external image. 
     The first frame  61   a , the second frame  61   b , and the fixing member  78  are not limited to being formed from a metal material, and may be formed from fiber-reinforced plastic (FRP). 
     The sealing member  75  can be formed from an independent foam material, but is not limited to this, and can be formed from various elastic resin materials. 
     The structure of the coupling members  81 ,  82  is not limited to one having a ball joint shape, and can be replaced with various mechanisms having increased rotational degrees of freedom around two or more axes. 
     In the description above, although it was assumed that the image display device  100  was worn on the head and is used, the image display device  100  may also be used as a handheld display that is not worn on the head and is to be looked into like binoculars. In other words, the head-mounted display also includes a hand-held display in the present disclosure. 
     An image display device according to a specific aspect includes a display unit including an optical system configured to emit imaging light toward a pupil position, and a frame configured to support the optical system, an exterior member configured to accommodate the optical system of the display unit in an internal space and partially exposes the frame, and a sheet-shaped sealing member having flexibility configured to seal the internal space of the exterior member, wherein the sealing member includes an outer first sealing portion configured to perform sealing between the sealing member and the exterior member, and an inner second sealing portion configured to perform sealing between the sealing member and the frame. 
     In the image display device described above, in the sealing member, the first sealing portion performs sealing between the sealing member and the exterior member, and the second sealing portion performs sealing between the sealing member and the frame. Thus, the liquid tightness or air tightness of the internal space in which the optical system is accommodated can be maintained while separating the inside and outside of the exterior member by the frame. At this time, due to the flexibility of the sealing member, the position of the frame, that is, the display unit, can be adjusted with respect to the exterior member. 
     In a specific aspect, the first sealing portion is sandwiched between an upper exterior member and a lower exterior member constituting the exterior member, and is fixed. In this case, the fixing of the first sealing portion to the exterior member is simple and reliable. 
     In a specific aspect, the first sealing portion is provided in an annular shape along an outer periphery of the upper exterior member and the lower exterior member. In this case, the sealing member has the first sealing portion as an annular outer circumferential portion. 
     In a specific aspect, the second sealing portion is fixed to the frame via an adhesive layer. In this case, it is not necessary to particularly provide a structure that fixes the second sealing portion to the frame, and it is easy to simplify and reduce the weight of the frame. 
     In a specific aspect, an outer shape of the sealing member is greater than an outer shape of the frame, and the first sealing portion is disposed outside of the second sealing portion. In this case, the first sealing portion is disposed outside the outer shape of the frame, making it easy to assemble the frame like a lid covering the opening of the exterior member. 
     In a specific aspect, the sealing member is disposed at the frame, and the adhesive layer is provided between the frame and a main body of the sealing member. In this case, the adhesive layer is provided in an annular shape at the upper surface of the frame, and the sealing member is disposed entirely on the internal space side of the exterior member. 
     In a specific aspect, the sealing member includes an opening disposed on inner side of an outer periphery of the frame. In this case, an optical system, etc. can be fixed in the frame region corresponding to the opening of the sealing member. 
     In a specific aspect, the second sealing portion is provided in an annular shape along the outer periphery of the frame. In this case, sealing is performed at the outer periphery of the frame. 
     In a specific aspect, the sealing member is an elastically deformable waterproof sheet. In this case, the tolerance of adjusting the position of the frame or display unit with respect to the exterior member can be increased. 
     In a specific aspect, the display unit includes a first display unit and a second display unit each having the optical system and the frame, and the sealing member adheres to the frame of the first display unit and the frame of the second display unit at the second sealing portion on the inner side. In this case, a type of the image display device that emits the imaging light into the left and right eyes can be obtained by the first display unit and the second display unit. 
     In a specific aspect, a fixing member configured to relatively fix the first display unit and the second display unit with respect to each other is included, and the sealing member is sandwiched between the fixing member and the frame of the first display unit, and between the fixing member and the frame of the second display unit. In this case, the first display unit and the second display unit can be positioned and fixed to the sealing member, and the periphery of the fixing member can be sealed. 
     In a specific aspect, bearing-shaped coupling members are provided between the fixing member and the first display unit, and between the fixing member and the second display unit, respectively, each of the bearing-shaped coupling members having rotational degrees of freedom around three axes. In this case, the degree of freedom of relative positioning between the first display unit and the second display unit can be increased.