Display device and optical unit

Abstract

To increase the performance of image formation of a display unit.SOLUTION: A display unit 100 includes: a picture element 11; a prism mirror 22 for causing an image light ML emitted from the picture element 11 to enter from a light entrance surface 22a, be reflected by an inner reflection surface 22b, and be emitted from a light emission surface 22c so that the image light ML will go back in an inclined direction; a see-through mirror 23 for reflecting the image light ML emitted from the prism mirror 22 to a pupil position PP; and a basic aperture diaphragm 41 for limiting the light image ML entering the light entrance surface 22a of the prism mirror 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a see-through type display device and optical unit that enable the observation of a virtual image, and more particularly to a display device and optical unit of the type in which image light from an image source is incident on a see-through mirror and the reflected light from the see-through mirror is observed. [Background technology]

[0002] There exists a see-through display device in which a zigzag optical path is formed by two oblique incidence mirrors, and image light from a display element is made incident on a user's eyes via the zigzag optical path (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-34722 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a see-through display device such as that in Patent Document 1 mentioned above, the arrangement of optical components is restricted from the standpoint of securing an area for viewing the outside world and from the standpoint of increasing the freedom of appearance. In particular, the position of the intermediate pupil where the aperture diaphragm should be located is partially inside the optical element, making it impossible to install an aperture diaphragm. [Means for solving the problem]

[0005] A display device in one aspect of the present invention includes an image element, a projection lens that passes image light emitted from the image element, a prism mirror that causes the image light emitted from the projection lens to enter through a light entrance surface, reflect off an internal reflective surface, and exit from a light exit surface, thereby folding the image light back in an inclined direction, a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position, and a basic aperture diaphragm that limits the passage of the image light outside one of the light entrance surface and light exit surface of the prism mirror. [Brief description of the drawings]

[0006] [Figure 1] FIG. 2 is an external perspective view illustrating a mounting state of the display device according to the first embodiment. [Diagram 2] FIG. 2 is a side cross-sectional view illustrating the internal structure of the display device. [Diagram 3] 1A and 1B are a side cross-sectional view and a partial cross-sectional plan view of a display device. [Figure 4A] FIG. 4 is a front view illustrating the arrangement of a diaphragm member relative to a prism mirror. [Figure 4B] FIG. 4 is a perspective view illustrating the arrangement of a diaphragm member relative to a prism mirror. [Figure 4C] 13 is a bottom view illustrating the arrangement of the diaphragm member relative to the prism mirror. FIG. [Figure 5A] FIG. 4 is a conceptual cross-sectional view of a first aperture member. [Figure 5B] 1 is a conceptual diagram illustrating the state of a light beam passing through a basic aperture stop. [Figure 5C] 11 is a conceptual diagram illustrating the state of a light beam passing through an additional aperture stop. [Figure 6A] 10A and 10B are conceptual diagrams illustrating modified examples of a first aperture member which is a basic aperture stop. [Figure 6B] 13 is a conceptual diagram illustrating a modified example of the second aperture member which is an additional aperture stop. [Figure 7] 13 is a conceptual cross-sectional view illustrating another modified example of the second diaphragm member. FIG. [Figure 8] 1A and 1B are diagrams illustrating forced distortion of a display image formed on an image element. [Figure 9] FIG. 11 is a side cross-sectional view illustrating a display device according to a modified example. [Figure 10] 11A to 11C are side cross-sectional views and the like illustrating a structure of a display device according to a second embodiment. [Figure 11] FIG. 4 is a partially enlarged cross-sectional view illustrating an additional aperture stop formed on an internal reflection surface. [Figure 12] 11 is a conceptual diagram illustrating the state of a light beam passing through an additional aperture stop. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [First embodiment] Hereinafter, a display device according to a first embodiment of the present invention and an optical unit incorporated therein will be described with reference to FIGS. 1 to 3 and so on.

[0008] Fig. 1 is a diagram for explaining a wearing state of a head mounted display (hereinafter also referred to as HMD) 200, and the HMD 200 allows an observer or wearer US wearing the HMD 200 to recognize an image as a virtual image. In Fig. 1 and the like, X, Y, and Z are an orthogonal coordinate system, and the +X direction corresponds to the lateral direction in which the eyes EY of the observer or wearer US wearing the HMD 200 or the display device 100 are aligned, the +Y direction corresponds to the upward direction perpendicular to the lateral direction in which the eyes EY are aligned for the wearer US, and the +Z direction corresponds to the forward direction or front direction for the wearer US. The ±Y directions are parallel to the vertical axis or vertical direction.

[0009] The HMD 200 includes a first display device 100A for the right eye, a second display device 100B for the left eye, and a pair of temple-shaped support devices 100C that support the display devices 100A and 100B. The first display device 100A is composed of a display driver 102 arranged at the top and an exterior member 103 that is shaped like a pair of glasses and covers the front of the eyes. Similarly, the second display device 100B is composed of a display driver 102 arranged at the top and an exterior member 103 that is shaped like a pair of glasses and covers the front of the eyes. In the first display device 100A and the second display device 100B, the display driver 102 is the main part that forms an image, and the display driver 102 is also called the image source 10. The support device 100C supports the upper end side of the exterior member 103 via the display driver 102. The first display device 100A and the second display device 100B are optically reversed left and right, and hereinafter, the first display device 100A for the right eye will be described as the representative display device 100.

[0010] 2 is a side cross-sectional view illustrating the optical structure of the display device 100. As shown in the figure, the display device 100 includes an image element 11, an imaging optical system 12, and a display control circuit 13. However, in this specification, the display device 100 excluding the display control circuit 13 is also called the display device 100 from the viewpoint of achieving optical functions. The image element 11 and the display control circuit 13 are supported in a case 51 which is the outer frame of the display drive unit 102 shown in FIG. 1, and a part of the imaging optical system 12 is also housed and supported in the case 51 of the display drive unit 102.

[0011] The image element 11 is a self-luminous display device. The image element 11 is, for example, a micro LED display, and forms a color still image or video on a two-dimensional display surface 11a. The image element 11 is arranged along an xy plane that is slightly rotated and tilted around the X axis with respect to the XY plane. The image element 11 is driven by a display control circuit 13 to perform a display operation. The image element 11 is not limited to a micro LED display, and can be replaced with a display device using an organic EL (organic electroluminescence), inorganic EL, organic LED, laser array, quantum dot light-emitting element, or the like. The image element 11 is not limited to a self-luminous image light generating device, and may be composed of an LCD or other light modulation element, and may form an image by illuminating the light modulation element with a light source such as a backlight. Instead of an LCD, LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micromirror device, or the like can be used as the image element 11.

[0012] The imaging optical system 12 includes a projection lens 21, a prism mirror 22, and a see-through mirror 23, and a case 51 described later is a part of the imaging optical system 12. In this specification, the imaging optical system 12 is also referred to as an optical unit 16. In this embodiment, the optical path from the image element 11 to the prism mirror 22 is disposed above the upper end of the see-through mirror 23, but may be disposed at a position partially lower than the upper end of the see-through mirror 23 as long as it does not block the optical path of the image light ML incident on the eye EY. In other words, the image element 11, the projection lens 21, and the prism mirror 22 can be disposed at a position partially lower than the upper end of the see-through mirror 23 as long as it does not block the optical path of the image light ML incident on the eye EY.

[0013] The projection lens 21 passes the image light ML emitted from the image element 11 and makes it incident on the prism mirror 22. The projection lens 21 condenses the image light ML emitted from the image element 11 into a state close to a parallel light beam. The projection lens 21 is a single lens and has an entrance surface 21a and an exit surface 21b. The prism mirror 22 has a light entrance surface 22a, an inner reflection surface 22b, and a light exit surface 22c, and makes the image light ML emitted from the projection lens 21 incident on the light entrance surface 22a, totally reflects the image light ML at the inner reflection surface 22b, and makes the image light ML exit from the light exit surface 22c. At this time, the prism mirror 22 emits the image light ML incident from the front so as to be folded back in a direction inclined with respect to a direction in which the incident direction is reversed (the direction of the light source as seen from the prism mirror 22). In the case of an optical system decentered in the vertical direction as in this embodiment, the forward direction with respect to the optical path includes a direction within a range of about 45° above and below the +Z direction, and a direction inclined with respect to the forward direction (i.e., a direction in which the incident direction is reversed) includes a direction within a range of about 45° above and below the intermediate direction that forms 45° with the +Z direction and the -Y direction. The see-through mirror 23 reflects the image light ML emitted from the prism mirror 22 toward the pupil position PP. The pupil position PP is a position where the image light ML from each point on the display surface 11a is incident in a predetermined divergent or parallel state so as to overlap from an angular direction corresponding to the position of each point on the display surface 11a. The FOV (field of view) of the display device 100 including the illustrated imaging optical system 12 is, for example, 44°. The display area of ​​the virtual image by the display device 100 is rectangular, and the above 44° is a diagonal direction.

[0014] The imaging optical system 12, i.e., the optical unit 16, has a basic aperture stop 41 disposed between the projection lens 21 and the prism mirror 22, facing the light entrance surface 22a of the prism mirror 22. The optical unit 16 has an additional aperture stop 42 disposed between the prism mirror 22 and the see-through mirror 23, facing the light exit surface 22c of the prism mirror 22.

[0015] The basic aperture stop 41 is a part of the first aperture member 31 and is integrated with the first aperture member 31. The basic aperture stop 41 limits the image light ML incident on the light incident surface 22a of the prism mirror 22 to a necessary range. More specifically, the basic aperture stop 41 functions as an aperture stop in a first direction or a vertical direction parallel to a predetermined plane (a plane parallel to the YZ plane) including an optical axis portion AX1 of the image light ML incident on the prism mirror 22 and an optical axis portion AX2 of the image light ML emerging from the prism mirror 22. Here, the first direction approximately corresponds to a first direction D21 shown in FIG. 3 described later.

[0016] On the other hand, the additional aperture diaphragm 42 is a part of the second diaphragm member 32 and is integrated with the second diaphragm member 32. The additional aperture diaphragm 42 limits the image light ML emerging from the light exit surface 22c of the prism mirror 22 and entering the see-through mirror 23 to a necessary range. More specifically, the additional aperture diaphragm 42 functions as an aperture diaphragm in a second direction perpendicular to a predetermined plane (a plane parallel to the YZ plane) including an optical axis portion AX1 of the image light ML entering the prism mirror 22 and an optical axis portion AX2 of the image light ML emerging from the prism mirror 22, or in a horizontal direction. Here, the second direction corresponds to the horizontal X direction, and corresponds to a second direction D02 shown in FIG. 3 described later.

[0017] In the light path exemplified in this embodiment, the basic aperture stop 41 not only functions as an aperture stop in the first vertical direction, but also functions as an aperture stop in the second horizontal direction, although not fully, and is relatively important in terms of function. The additional aperture stop 42 complements the aperture function of the basic aperture stop 41, and can ultimately be omitted. From this perspective, the words "basic" and "additional" are added. Note that the aperture stop is a stop that determines the numerical aperture related to the resolution, and is generally arranged at the point where the chief rays intersect, and has the role of efficiently blocking unnecessary light that does not contribute to imaging while ensuring the passage of necessary light that contributes to imaging. However, when the points where the chief rays intersect are distributed to different positions along the optical axis AX as in the optical path of this embodiment, the imaging performance can be improved by providing aperture stops at multiple points where the chief rays intersect or in the vicinity thereof.

[0018] In the above, the basic aperture stop 41 is considered to be functionally important, and the additional aperture stop 42 is considered to be auxiliary or complementary. However, depending on the change in the light path, the aperture stop arranged at the position of the additional aperture stop 42 may be functionally important, and the aperture stop arranged at the position of the basic aperture stop 41 may be auxiliary or complementary. In such a case, the aperture stop arranged opposite the light exit surface 22c of the prism mirror 22 (the one arranged at the position of the additional aperture stop 42 shown in the figure) is called the basic aperture stop, and the aperture stop arranged opposite the light entrance surface 22a of the prism mirror 22 (the one arranged at the position of the basic aperture stop 41 shown in the figure) is called the additional aperture stop. Regarding the above aperture stops 41 and 42, the one located upstream of the light path is called the first aperture stop, and the one located downstream, i.e., at the rear of the light path, is called the second aperture stop, including the case where it is unclear which of the multiple aperture stops 41 and 42 is functionally important. Whether the first aperture stop or the second aperture stop is the basic aperture stop is determined in consideration of the degree to which unnecessary light that does not contribute to image formation is blocked, but it is not intended to make a strict distinction between them.

[0019] The projection lens 21 and the prism mirror 22 are housed in a case 51 together with the image element 11. The case 51 is a combination of a main body 52 and a holding member 30. The main body 52 is formed of a light-shielding material and supports a display control circuit 13 that operates the image element 11. The main body 52 is formed of a metal material or a resin material. In the case of a resin material, a black light-shielding material can be applied to the inner surface side. The main body 52 supports the image element 11, the projection lens 21, and the prism mirror 22 via the holding member 30. The holding member 30 is also formed of a light-shielding material. The case 51 has an opening 51a in the second diaphragm member 32 of the holding member 30, and enables the display drive unit 102 or the image source 10 to emit the image light ML toward the outside. The image light ML emitted outside the display drive unit 102 enters the inside of the see-through mirror 23.

[0020] In the illustrated example, display control circuit 13 is disposed inside case 51, but display control circuit 13 may also be disposed outside case 51. Image element 11 does not need to be disposed inside case 51 either. An opening for image element 11 may be provided in case 51, and image element 11 may be fixed to case 51 so that display surface 11a faces the inside of case 51 through this opening.

[0021] The case 51 supports the see-through mirror 23 via a support plate 61. In this case, the see-through mirror 23 is stably supported with respect to the prism mirror 22 and the like via the case 51. The see-through mirror 23 and the support plate 61 correspond to the exterior member 103 shown in FIG.

[0022] The imaging optical system 12 is an off-axis optical system 112 due to the see-through mirror 23 being a concave mirror. In this embodiment, the projection lens 21, the prism mirror 22, and the see-through mirror 23 are arranged non-axisymmetrically and have non-axisymmetric optical surfaces. The imaging optical system 12 being an off-axis optical system 112 means that the optical path is bent as a whole before and after the light ray is incident on at least one reflecting surface or refracting surface in the optical elements 21, 22, and 23 constituting the imaging optical system 12. In this imaging optical system 12, i.e., the off-axis optical system 112, the optical axis AX is bent so that the optical axis AX extends along an off-axis surface (a surface parallel to the YZ plane) corresponding to the paper surface. In this imaging optical system 12, the optical axis AX is bent within an off-axis surface parallel to the YZ plane, so that the optical elements 21, 22, and 23 are arranged along the off-axis surface. The imaging optical system 12 includes optical axis portions AX1, AX2, and AX3 that are arranged along an off-axis plane (a plane parallel to the YZ plane) that is a predetermined reference plane and are inclined to each other before and after the reflecting surface. The optical axis AX as a whole extends along the optical path of the chief ray emitted from the center of the image element 11 and passes through the eye ring ER corresponding to the eye point or the center of the pupil. When viewed in a cross section parallel to the YZ plane, the optical axis AX is arranged in a Z-shape by the multiple optical axis portions AX1, AX2, and AX3. That is, on the off-axis plane parallel to the YZ plane, the optical path P1 from the projection lens 21 to the internal reflecting surface 22b, the optical path P2 from the internal reflecting surface 22b to the see-through mirror 23, and the optical path P3 from the see-through mirror 23 to the pupil position PP are arranged to be folded back in two stages in a Z-shape. The imaging optical system 12 is arranged vertically. That is, the off-axis plane (a plane parallel to the YZ plane) that is a predetermined reference plane extends parallel to the vertical Y direction. In this case, the optical elements 21, 22, and 23 constituting the display device 100 are arranged at different height positions in the vertical direction, so that an increase in the width of the display device 100 can be prevented.

[0023] In the imaging optical system 12, the optical path P1 from the projection lens 21 to the internal reflection surface 22b is nearly parallel to the Z direction. That is, in the optical path P1, the optical axis portion AX1 extends substantially parallel to the Z direction or the front direction. As a result, the projection lens 21 is disposed between the prism mirror 22 and the imaging element 11 with respect to the Z direction or the front direction. It is desirable that the optical axis portion AX1 in the optical path P1 is within a range of about -30° to +30° on average, with the downward direction being negative, toward the Z direction. By making the optical axis portion AX1 of the optical path P1 downward at -30° or more toward the Z direction, it is possible to prevent the projection lens 21 and the imaging element 11 from interfering with the see-through mirror 23. In addition, by making the optical axis portion AX1 of the optical path P1 upward at +30° or less toward the Z direction, it is possible to prevent the projection lens 21 and the imaging element 11 from protruding upward and becoming conspicuous in appearance. In the optical path P2 from the inner reflection surface 22b to the see-through mirror 23, the optical axis portion AX2 is preferably within a range of about -70° to -45° on average in the Z direction, with the downward direction being negative. By making the optical axis portion AX2 of the optical path P2 downward at -70° or more in the Z direction, it is possible to prevent the overall inclination of the see-through mirror 23 from becoming excessively large, and it is easy to ensure a space for arranging an inner lens inside the see-through mirror 23. In addition, by making the optical axis AX of the optical path P2 downward at -45° or less in the Z direction, it is possible to prevent the prism mirror 22 from being disposed so as to protrude significantly in the -Z direction or in the back direction relative to the see-through mirror 23, and it is possible to prevent the thickness of the imaging optical system 12 from increasing. The optical path P3 from the see-through mirror 23 to the pupil position PP is nearly parallel to the Z direction. That is, in the optical path P3, the optical axis portion AX3 extends approximately parallel to the -Z direction or in the back direction.

[0024] The display driver 102 will be described in detail with reference to Fig. 3. In Fig. 3, an area AR1 shows a side cross-sectional view of the optical unit 16, i.e., the imaging optical system 12, and an area AR2 shows a partial planar structure of the imaging optical system 12. In the diagram of the planar structure shown in the area AR2, partial light rays traveling from the prism mirror 22 through the see-through mirror 23 toward the pupil position PP are shown.

[0025] The lateral end 11e of the image element 11 constituting the display drive unit 102 is held by a pair of support members 33 provided on a holding member 30 fixed in a case 51 shown by a dashed line. These support members 33 achieve alignment of the image element 11 in the case 51. The lateral end 21e of the projection lens 21 constituting the display drive unit 102 is also held by a pair of support members 33, and alignment of the projection lens 21 with respect to the case 51 is achieved. The lateral end 22e of the prism mirror 22 constituting the display drive unit 102 is also held by a pair of support members 33, and alignment of the prism mirror 22 with respect to the case 51 is achieved. In the illustrated example, the end 21e of the projection lens 21 is disposed in the case 51, but the end 21e may be exposed to the outside at a side wall of the case 51 or the main body 52. Similarly, end 22e of prism mirror 22 does not need to be disposed inside case 51, and end 22e may be exposed to the outside at a side wall of case 51 or main body 52. ​​Main body 52 of case 51 may be formed by combining frame members divided in half by a plane parallel to the YZ plane, for example, and when these frame members are joined together, imaging element 11, projection lens 21, etc. can be incorporated inside together with support member 33. Case 51 is not limited to being made up of two parts, but may be made up of three or more parts.

[0026] Although not shown in the figure, a first diaphragm member 31 disposed between the projection lens 21 and the prism mirror 22 is supported by the holding member 30 as a part of the holding member 30. A second diaphragm member 32 disposed on the light exit side of the prism mirror 22 is also supported by the holding member 30 as a part of the holding member 30.

[0027] The projection lens 21 is a single lens, and the entrance surface 21a and the exit surface 21b, which are optical surfaces constituting the projection lens 21, are asymmetric about the optical axis AX in first vertical directions D11, D12 that are parallel to the YZ plane and intersect with the optical axis AX, and are symmetric about the optical axis AX in a second horizontal direction D02 or the X direction that is perpendicular to the first directions D11, D12. The first vertical direction D11 with respect to the entrance surface 21a and the second vertical direction D12 with respect to the exit surface 21b form a predetermined angle.

[0028] The projection lens 21 is formed of, for example, resin, but may also be made of glass. The entrance surface 21a and the exit surface 21b of the projection lens 21 are, for example, free-form surfaces. The entrance surface 21a and the exit surface 21b are not limited to free-form surfaces, but may also be aspheric surfaces. In the projection lens 21, by making the entrance surface 21a and the exit surface 21b free-form or aspheric, aberration can be reduced. In particular, when a free-form surface is used, it becomes easy to improve the optical performance of the decentering system, so that it becomes easy to reduce the aberration of the imaging optical system 12, which is a non-coaxial off-axis optical system 112. Note that a free-form surface is a surface that does not have an axis of rotational symmetry, and various polynomials can be used as the surface function of the free-form surface. Also, an aspheric surface is a surface that has an axis of rotational symmetry and is expressed by a polynomial, but is a surface other than a parabolic surface or a spherical surface. Although detailed illustration is omitted, an anti-reflection film is formed on the entrance surface 21a and the exit surface 21b.

[0029] Prism mirror 22 is a refracting / reflecting optical member having a function of combining a mirror and a lens, and reflects while refracting image light ML from projection lens 21. More specifically, in prism mirror 22, image light ML enters the inside through light entrance surface 22a, which is a refracting surface, is totally reflected in a non-front direction by inner reflecting surface 22b, which is a reflective surface, and is emitted to the outside through light exit surface 22c, which is a refracting surface. Light entrance surface 22a and light exit surface 22c are optical surfaces made of curved surfaces, and contribute to improving resolution compared to the case where only the reflecting surfaces are present or the case where these are flat surfaces. The light entrance surface 22a, the internal reflection surface 22b, and the light exit surface 22c, which are the optical surfaces that constitute the prism mirror 22, are asymmetric about the optical axis AX in a first vertical direction D21, D22, D23 that is parallel to the YZ plane and intersects the optical axis AX, and are symmetric about the optical axis AX in a second horizontal direction D02 or the X direction that is perpendicular to the first directions D21, D22, D23.

[0030] Prism mirror 22 is made of, for example, resin, but can also be made of glass. The refractive index of the body of prism mirror 22 is set to a value that achieves total reflection on the inner surface, taking into consideration the reflection angle of image light ML. It is desirable to set the refractive index and Abbe number of the body of prism mirror 22 in consideration of its relationship with projection lens 21. In particular, by increasing the Abbe numbers of prism mirror 22 and projection lens 21, the remaining color dispersion as a whole can be reduced.

[0031] The optical surfaces of the prism mirror 22, that is, the light entrance surface 22a, the inner reflection surface 22b, and the light exit surface 22c, are, for example, free-form surfaces. The light entrance surface 22a, the inner reflection surface 22b, and the light exit surface 22c are not limited to free-form surfaces, but may be aspheric surfaces. In the prism mirror 22, by making the optical surfaces 22a, 22b, and 22c free-form or aspheric, it is possible to reduce aberrations, and in particular, when free-form surfaces are used, it is easy to improve the optical performance of the decentering system. In other words, it is easy to reduce the aberrations of the imaging optical system 12, which is the non-coaxial off-axis optical system 112, and it is possible to improve the resolution. The inner reflection surface 22b is not limited to a surface that reflects the image light ML by total reflection, but may be a reflection surface made of a metal film or a dielectric multilayer film. In this case, a reflection film made of a single layer film or a multilayer film made of a metal such as Al or Ag is formed on the inner reflection surface 22b by deposition or the like, or a sheet-like reflection film made of a metal is attached. Although not shown in detail, an anti-reflection film is formed on the light incident surface 22a and the light exit surface 22c.

[0032] 4A to 4C, the shapes and arrangements of the first iris aperture member 31 and the second iris aperture member 32 will be described. Fig. 4A is a front view from the +Z side mainly illustrating the first iris aperture member 31, Fig. 4B is a perspective view from the +Z and -Y sides mainly illustrating the first iris aperture member 31 and the second iris aperture member 32, and Fig. 4C is a bottom view from the -Y side mainly illustrating the second iris aperture member 32.

[0033] The first aperture member 31 has a first aperture AP1 disposed near the light incidence surface 22a of the prism mirror 22, and the periphery of the first aperture AP1 functions as a basic aperture stop 41. The first aperture member 31 is formed of a resin material or a metal material. The first aperture AP1 is elliptical rather than circular. By making it elliptical in this way, the necessary image light ML can be efficiently passed without waste, and the passage of unnecessary light can be prevented as much as possible. A slope 31j is formed on the basic aperture stop 41 around the first aperture AP1, preventing the necessary light from being blocked. In the first aperture member 31, the upper part 31p is a part for attaching the first aperture member 31 to the holding member 30 shown in FIG. 3.

[0034] The second aperture member 32 has a second aperture AP2 disposed near the light exit surface 22c of the prism mirror 22, and the periphery of the second aperture AP2 functions as an additional aperture stop 42. The second aperture member 32 is formed of a resin material or a metal material. The second aperture AP2 is not circular but is a pentagon with rounded corners. The additional aperture stop 42 or the second aperture AP2 has an asymmetric shape that changes when inverted with respect to a first direction (here, the Z direction). Specifically, when the second aperture AP2 is rotated 180° around a rotation axis extending in the X direction perpendicular to the first direction with the center of the second aperture AP2 fixed, the width in the X direction is reversed. The size of the ray bundle of the image light ML to pass through the additional aperture stop 42 changes depending on the position in the first direction, and by making the pentagon asymmetric with respect to the first direction in this way, the necessary image light ML can be passed efficiently without waste, and the passage of unnecessary light can be prevented as much as possible. That is, the pentagonal additional aperture stop 42 enables finer blocking of image light ML. Slopes 32j are formed on the additional aperture stop 42 around the second aperture AP2 to prevent necessary light from being blocked. The second aperture member 32 is made of a material that is thicker than the first aperture member 31. In the second aperture member 32, the outer circumferential portion 32p is a portion for attaching the second aperture member 32 to the holding member 30 shown in FIG.

[0035] As shown in FIG. 5A, the first aperture member 31 is a wedge-shaped member and has a first aperture AP1 that is open around the optical axis AX. The first aperture member 31 is not limited to a wedge-shaped member, and can have various shapes including a parallel plate. In the first aperture member 31, the inner edge IE that defines the first aperture AP1 has a thickness t of 1 mm or less. As shown in the figure, the generation of stray light can be suppressed by providing a slope 31j and reducing the thickness t of the edge IE. The first aperture member 31 can be formed of a light-absorbing base material, but when it is formed of a light-transmitting base material, a light-absorbing coating can be applied to the surface. The coating is formed by coating, vapor deposition, plating, or the like. The surface 31s of the first aperture member 31 can also be processed to enhance scattering properties. The basic aperture stop 41 including the edge IE may be a separate member that is attached to the main body of the first aperture member 31 or inserted into a gap in the main body of the first aperture member 31.

[0036] The image light ML passing through the first aperture member 31 will be described with reference to Fig. 5B. A ray bundle of the image light MLa emitted from the center of the display surface 11a of the image element 11 passes through a region near the center of the elliptical first opening AP1, a ray bundle of the image light MLb emitted from the right end of the display surface 11a of the image element 11 as viewed from the +Z side passes through a region on the right side of the elliptical first opening AP1, and a ray bundle of the image light MLc emitted from the left end of the display surface 11a of the image element 11 as viewed from the +Z side passes through a region on the left side of the elliptical first opening AP1. As a result, when considering a cross section that crosses the center of the display surface 11a in the X direction, a ray bundle that contributes to imaging from each point on the display surface 11a passes through the basic aperture stop 41 without being blocked by the basic aperture stop 41. On the other hand, the envelope of a series of ray bundles of the image lights MLa, MLb, MLc, etc. is a similar ellipse slightly smaller than the first aperture AP1, and the basic aperture stop 41 blocks almost all of the rays that do not contribute to image formation. However, the basic aperture stop 41 allows some unnecessary light in the horizontal direction to pass through. That is, a gap GA exists between the first aperture AP1 and the left and right outer sides, i.e., the outer sides in the ±Z direction, of the ray bundle of the image light MLa. Similarly, a gap exists between the first aperture AP1 and the left outer side, i.e., the outer side in the -Z direction, of the ray bundle of the right image light MLb, and a gap exists between the first aperture AP1 and the right outer side, i.e., the outer side in the +Z direction, of the ray bundle of the left image light MLc. In order to reduce the influence of such a gap GA, the second aperture member 32 shown in FIG. 4C and the like is provided, so that the unnecessary light in the horizontal direction that has passed through the first aperture AP1 can be cut.

[0037] The image light ML passing through the second aperture member 32 will be described with reference to Fig. 5C. A ray bundle of the image light MLa emitted from the center of the display surface 11a of the image element 11 passes through a region near the center of the pentagonal second opening AP2, a ray bundle of the image light MLf emitted from the lower end as viewed from the +Z side of the display surface 11a of the image element 11 passes through a region on the front or +Z side of the second opening AP2, and a ray bundle of the image light MLg emitted from the upper end as viewed from the +Z side of the display surface 11a of the image element 11 passes through a region on the rear or -Z side of the second opening AP2. As a result, when considering a vertical cross section cutting the center of the display surface 11a in the X direction, a ray bundle contributing to image formation from each point on the display surface 11a passes through the additional aperture stop 42 without being blocked by the additional aperture stop 42. On the other hand, the envelope of a series of ray bundles of the image lights MLa, MLf, MLg, etc. has a similar shape to that of the second aperture AP2 but is slightly smaller, and the additional aperture stop 42 blocks many of the rays that do not contribute to image formation. However, the additional aperture stop 42 allows a significant amount of unnecessary light in the vertical direction to pass through. In other words, a significant gap exists between the series of ray bundles of the image lights MLa, MLf, MLg, etc. and the second aperture AP2, but the rays that pass through such a gap are cut off in advance by the first aperture member 31 or the basic aperture stop 41 and hardly reach the second aperture member 32.

[0038] Fig. 6A is a diagram illustrating a modified example of the first diaphragm member 31 shown in Fig. 5B. In this case, the first diaphragm member 31 or the basic aperture diaphragm 41 has a rectangular first aperture AP1. Although not shown, the first aperture AP1 may be elliptical. The shape of the first aperture AP1 can be set appropriately according to the size and arrangement of the image lights MLa, MLf, MLg.

[0039] Fig. 6B is a diagram illustrating a modified example of the second diaphragm member 32 shown in Fig. 5C. In this case, the second diaphragm member 32 or the additional aperture diaphragm 42 has a trapezoidal second aperture AP2. The additional aperture diaphragm 42 or the second aperture AP2 has an asymmetric shape with respect to the first direction (here, the Z direction).

[0040] FIG. 7 is a diagram for explaining another modified example of the second aperture member 32. In this case, the second aperture member 32 has a light-shielding mask 32r formed on a light-transmitting flat plate 32q, and a window 32s provided in the mask 32r is used as the second opening AP2. The second aperture member 32 is airtightly adhered to an attachment hole (not shown) of the case 51 or the main body 52. ​​This seals the internal space of the case 51 from the outside, and prevents the light exit surface 22c of the prism mirror 22 from being exposed to the outside world. As a result, it is possible to prevent not only the light exit surface 22c of the prism mirror 22, but also the light entrance surface 22a, the entrance surface 21a and the exit surface 21b of the projection lens 21, etc. from being contaminated by dust or dirt that has entered from the outside, or from having water droplets adhere thereto, and it is possible to suppress deterioration of optical performance due to use. The mask 32r may be a three-dimensional, thick mask that extends over the entire thickness of the second aperture member 32.

[0041] Returning to FIG. 3, the see-through mirror 23 is a plate-shaped optical member that functions as a concave surface mirror and reflects the image light ML from the prism mirror 22. That is, the see-through mirror 23 reflects the image light ML from the emission area of ​​the image source 10 toward the pupil position PP. The see-through mirror 23 covers the pupil position PP where the eye EY or pupil is located, has a concave shape toward the pupil position PP, and has a convex shape toward the outside world. The see-through mirror 23 is a concave transmissive mirror that covers the entire effective area of ​​the screen in the field of view. The see-through mirror 23 is a collimator with a converging function, and converges the chief ray of the image light ML emitted from each point on the display surface 11a and once spreads due to imaging near the emission area of ​​the image source 10 to the pupil position PP. The see-through mirror 23 is a mirror plate having a structure in which a mirror film 23c is formed on the front or back surface of a plate-shaped body 23b. The reflecting surface 23a of the see-through mirror 23 has transparency. The see-through mirror 23 and the reflecting surface 23a are asymmetric about the optical axis AX in a first vertical direction D31 that is parallel to the YZ plane and intersects the optical axis AX, and are symmetric about the optical axis AX in a second horizontal direction D02 or the X direction that is perpendicular to the first direction D31.

[0042] The reflecting surface 23a of the see-through mirror 23 is, for example, a free-form surface. The reflecting surface 23a is not limited to a free-form surface, but can also be an aspheric surface. By making the see-through mirror 23 a free-form surface or an aspheric surface, aberration can be reduced, and in particular, when a free-form surface is used, it becomes easier to reduce aberration in the imaging optical system 12, which is an off-axis optical system or a non-coaxial optical system. Regardless of whether the reflecting surface 23a of the see-through mirror 23 is a free-form surface or an aspheric surface, the see-through mirror 23 has a shape in which the origin of the curved surface formula is shifted toward the projection lens 21 side or the image element 11 side from the effective area of ​​the see-through mirror 23. In this case, the inclined surface of the see-through mirror that realizes a Z-shaped optical path can be set without placing an excessive burden on the design of the optical system.

[0043] The see-through mirror 23 is a transmissive reflecting element that transmits a portion of light when reflected, and the mirror film 23c of the see-through mirror 23 is formed of a semi-transparent reflecting layer. As a result, the outside light OL passes through the see-through mirror 23, making it possible to see through the outside world, and a virtual image can be superimposed on the outside world image. In this case, if the plate-like body 23b is thin, such as a few mm or less, the magnification change of the outside world image can be kept small. The reflectance of the mirror film 23c to the image light ML and the outside world light OL is set to 10% or more and 50% or less in the assumed range of the incidence angle of the image light ML, from the viewpoint of ensuring the brightness of the image light ML and facilitating the observation of the outside world image by the see-through. The plate-like body 23b, which is the base material of the see-through mirror 23, is formed of, for example, resin, but can also be made of glass. The plate-like body 23b is formed of the same material as the support plate 61 that supports it from the periphery, and has the same thickness as the support plate 61. The mirror film 23c is formed of, for example, a dielectric multilayer film consisting of a plurality of dielectric layers whose thicknesses are adjusted. The mirror film 23c may be a single layer film or a multilayer film of a metal such as Al or Ag whose thicknesses are adjusted. The mirror film 23c can be formed by laminating, but can also be formed by attaching a sheet-like reflective film. An anti-reflection film is formed on the outer surface 23o of the plate-like body 23b.

[0044] In this imaging optical system 12, a vertical intermediate pupil IPa is disposed at or near the light entrance surface 22a of the prism mirror 22. The vertical intermediate pupil IPa refers to a location where the image lights MLa, MLb, and MLc (see FIG. 5B) from each point on a vertical line segment extending from the center of the display surface 11a of the image element 11 in the ±y direction spread vertically and overlap with each other, and is disposed at a conjugate point of the eye ring ER or pupil position PP. The vertical intermediate pupil IPa is a location where the chief rays Pa (see FIG. 2) of the image lights MLa, MLb, and MLc intersect. As described above, the first aperture member 31 or the first aperture AP1 of the basic aperture stop 41 is disposed near this vertical intermediate pupil IPa, and functions as an aperture stop in the vertical direction.

[0045] A horizontal intermediate pupil IPb is disposed at or near the light exit surface 22c of the prism mirror 22. The horizontal intermediate pupil IPb refers to a location where the image lights MLa, MLf, and MLg (see FIG. 5C) from each point on a horizontal line segment extending from the center of the display surface 11a in the ±x direction spread horizontally and overlap relatively a lot with each other, and is disposed at a conjugate point of the eye ring ER or pupil position PP. The horizontal intermediate pupil IPb is a location where the chief ray Pb (see the area AR2 in FIG. 3) of the image lights MLa, MLf, and MLg intersect. As described above, the second aperture AP2 of the second aperture member 32 or the additional aperture stop 42 is disposed near this horizontal intermediate pupil IPb, and functions as an aperture stop in the horizontal direction.

[0046] As described above, in the display device 100 of this embodiment, the position where one principal ray Pa intersects with the position where the other principal ray Pb intersects with respect to different directions perpendicular to the optical axis, i.e., the first vertical direction parallel to the YZ plane and the second horizontal direction parallel to the X axis, are different positions spaced apart along the optical axis AX. Here, the first vertical direction corresponds to the first directions D21, D23 at the entrance / exit surfaces 22a, 22c of the prism mirror 22, and the second horizontal direction corresponds to the second direction D02 at the entrance / exit surfaces 22a, 22c of the prism mirror 22. Among the different positions where the principal rays Pa, Pb intersect with respect to different vertical and horizontal directions, the first diaphragm member 31 or the basic aperture diaphragm 41 is disposed at or near the first position upstream in the optical path, and the second diaphragm member 32 or the additional aperture diaphragm 42 is disposed at or near the second position downstream in the optical path. In other words, the multiple aperture stops 41, 42 are disposed at or near different positions where the chief rays intersect in different directions perpendicular to the optical axis AX.

[0047] The intermediate image IM is formed between the prism mirror 22 and the see-through mirror 23. The intermediate image IM is formed closer to the prism mirror 22 than the see-through mirror 23. In this way, by forming the intermediate image IM closer to the prism mirror 22 than the see-through mirror 23, the burden of magnification by the see-through mirror 23 can be reduced and the aberration of the observed virtual image can be suppressed. The intermediate image IM is a real image formed in a position upstream of the eye ring ER in the optical path and conjugate with the display surface 11a, and has a pattern corresponding to the display image on the display surface 11a, but does not need to be a sharp image and may exhibit various aberrations such as field curvature and distortion aberration.

[0048] Regarding the optical path, the image light ML from the image element 11 enters the projection lens 21 and is emitted in a substantially collimated state. The image light ML that passes through the projection lens 21 enters the prism mirror 22 via the basic aperture stop 41, passes through the light entrance surface 22a while being refracted, is reflected by the internal reflection surface 22b with a high reflectance close to 100%, and is refracted again at the light exit surface 22c. The image light ML from the prism mirror 22 enters the see-through mirror 23 via the additional aperture stop 42, and is reflected by the reflection surface 23a with a reflectance of about 50% or less. The image light ML reflected by the see-through mirror 23 enters the pupil position PP where the eye EY or pupil of the wearer US is located. External light OL that passes through the see-through mirror 23 and the support plate 61 around it also enters the pupil position PP. In other words, the wearer US wearing the display device 100 can observe a virtual image by the image light ML superimposed on the external image.

[0049] As shown in FIG. 8, the original projected image IG0 showing the image formed by the imaging optical system 12 has a relatively large distortion. That is, the imaging optical system 12 forms a distortion. Since the imaging optical system 12 is an off-axis optical system 112, it is not easy to completely remove distortion such as keystone distortion. Therefore, even if distortion remains in the imaging optical system 12, when the original display image is DA0, the display image formed on the display surface 11a is a corrected image DA1 that has a distortion such as keystone distortion in advance. That is, by making the image displayed on the image element 11 have an inverse distortion that cancels out the distortion formed by the projection lens 21, the prism mirror 22, and the see-through mirror 23, the pixel arrangement of the projected image IG1 of the virtual image observed at the pupil position PP through the imaging optical system 12 can be a lattice pattern corresponding to the original display image DA0, and the outline can be made rectangular. As a result, it is possible to suppress aberration as a whole including the image element 11 while allowing distortion aberration generated by the see-through mirror 23, etc. As a result, the degree of freedom in the arrangement and size of optical elements such as the prism mirror 22 is increased, and the optical performance of the display device 100 can be easily ensured while achieving a compact size of the display device 100.

[0050] As shown in FIG. 9, the optical axis portion AX3 of the optical path P3 can be set to about -10° in the +Z direction, with the downward direction being negative. In this case, in order to set the virtual image display or field of view in a direction tilted downward, the entire optical system shown in FIG. 2 is rotated about 10° around the X axis. In this way, by making the optical axis portion AX3 face downward in the +Z direction with the central axis HX as a reference, the human line of sight is stabilized in a slightly downcast state in which it is tilted about 10° downward from the horizontal direction. Note that the central axis HX extending horizontally with respect to the pupil position PP is assumed to be in a state in which the wearer US wearing the display device 100 is in an upright position, relaxed, facing forward, and gazing at the horizontal direction or the horizontal line. The shape and posture of the head, including the arrangement of the eyes and ears, of each wearer US wearing the display device 100 are various, but by assuming the average head shape or head posture of the wearer US, the average central axis HX can be set for the display device 100 of interest.

[0051] The display device 100 of the first embodiment described above is provided with a basic aperture stop 41 that limits the passage of image light ML outside the light incident surface 22a of the prism mirror 22, so that it is possible to selectively pass the image light ML necessary for imaging while blocking light that degrades imaging, thereby improving the imaging performance of the display device 100.

[0052] Second Embodiment Hereinafter, a display device according to a second embodiment of the present invention will be described. Note that the display device according to the second embodiment is a partial modification of the display device according to the first embodiment, and a description of common parts will be omitted.

[0053] A display device according to the second embodiment will be described with reference to Fig. 10. In Fig. 10, region BR1 shows a side cross-sectional view of imaging optical system 12, and region BR2 shows a partial planar structure of imaging optical system 12.

[0054] In the case of the display device 100 of this embodiment, the optical path in plan view shown in region BR2 in Fig. 10 is modified so that the chief ray Pb in the horizontal direction intersects near the internal reflection surface 22b of the prism mirror 22, and an intermediate pupil IPb is formed at this position. Correspondingly, an additional aperture stop 42 in the horizontal direction is formed at the position of the internal reflection surface 22b of the prism mirror 22. Note that in the holding member 30, an opening 30s is formed at the location where the second diaphragm member 32 was formed, and functions as a light blocking diaphragm.

[0055] As shown in FIG. 11, the internal reflection surface 22b has a reflection mirror 22y formed in an effective area EA that is surrounded by a light-shielding area OA and allows the image light ML to propagate and corresponds to the optical surface area. The reflection mirror 22y is formed on a surface 22s of a base material 22z of the prism mirror 22 that corresponds to the optical surface area. In this case, the reflection mirror 22y can be indirectly made to function as an additional aperture stop 42 by arranging the reflection mirror 22y in a minimum necessary area. Around the reflection mirror 22y, a mask 42r having a light-shielding property is formed on the base material 22z of the prism mirror 22 as an absorption structure AS provided in the light-shielding area OA. The mask 42r is formed by attaching a sheet-like light-shielding body on the surface 22s, but is not limited to this, and may be formed by applying or depositing a light-shielding paint or a light-shielding substance. The absorption structure AS can suppress unintended stray light formed in the light-shielding area around the reflection mirror 22y. Furthermore, a scattering structure SS is formed around the reflection mirror 22y as a base for the absorption structure AS. The scattering structure SS is a roughened surface 22s of the light-shielding area OA provided outside the effective area EA of the base material 22z of the prism mirror 22, and has fine random unevenness. In this case, the scattering structure SS can suppress unintended stray light formed in the light-shielding area OA around the reflection mirror 22y. Note that, although a bend is formed at the boundary between the effective area EA and the light-shielding area OA in the drawing, these boundaries can also be smoothly curved.

[0056] In the above, the absorbing structure AS and the scattering structure SS are provided in the light-shielding area OA, but only one of the absorbing structure AS and the scattering structure SS may be provided. The reflecting mirror 22r may be a total reflection surface without a reflecting member such as a metal film.

[0057] 12 is a conceptual diagram illustrating the state of image light passing through the additional aperture diaphragm 42. In this case, the additional aperture diaphragm 42 has a second aperture AP2 having a shape obtained by cutting an arched portion that is a part of a circle.

[0058] In this embodiment, the first diaphragm member 31 or the basic aperture diaphragm 41 can be formed on the light incident surface 22a of the prism mirror 22, similarly to the additional aperture diaphragm 42. In this case as well, something similar to the mask 42r can be formed on the base material 22z of the prism mirror 22 outside the effective area EA for the light incident surface 22a.

[0059] As in this embodiment, when the image light ML converges near the light incident surface 22a of the prism mirror 22 in a first direction around the optical axis AX (corresponding to the vertical Y direction here), unwanted light can be blocked by the basic aperture stop 41 arranged there, and when the image light ML converges near the internal reflective surface 22b of the prism mirror 22 in a second direction around the optical axis AX (corresponding to the horizontal direction here), unwanted light can be blocked by the additional aperture stop 42 arranged there.

[0060] [Variations and Others] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0061] In the display device 100 of the above embodiment, the additional aperture diaphragm 42 is provided separately from the basic aperture diaphragm 41. However, if the optical path is designed so that the horizontal chief ray Pb intersects with the light entrance surface 22a of the prism mirror 22 or at a position not far from the light entrance surface 22a, the intersection points of the vertical and horizontal chief rays Pa and Pb become close to each other, so that the additional aperture diaphragm 42 can be omitted and the basic aperture diaphragm 41 alone can function as a normal aperture diaphragm. Conversely, if the optical path is designed so that the vertical chief ray Pa intersects with the light exit surface 22c of the prism mirror 22 or at a position not far from the light entrance surface 22c, the intersection points of the vertical and horizontal chief rays Pa and Pb become close to each other, so that the basic aperture diaphragm 41 can be omitted and the additional aperture diaphragm 42 alone can function as a normal aperture diaphragm. In this way, when an aperture diaphragm is incorporated alone at the position of the additional aperture diaphragm 42, the aperture diaphragm incorporated alone at the position of the additional aperture diaphragm 42 is called a basic aperture diaphragm.

[0062] The projection lens 11 is not limited to being made up of a single lens, but can be made up of a plurality of lenses.

[0063] The basic aperture diaphragm 41 and the additional aperture diaphragm 42 may be provided in two stages. In other words, the basic aperture diaphragm 41 can be incorporated as a plurality of diaphragms arranged at different positions along the optical path direction, and the additional aperture diaphragm 42 can also be incorporated as a plurality of diaphragms arranged at different positions along the optical path direction.

[0064] In the display device 100 of the above embodiment, a self-luminous display device such as an organic EL element, an LCD, or other light modulation elements are used as the image element 11, but instead of this, a configuration using a laser scanner combining a laser light source and a scanner such as a polygon mirror is also possible. In other words, the present invention can also be applied to a laser retinal projection type head mounted display.

[0065] A dimming device that adjusts light by limiting the light transmitted through the see-through mirror 23 can be attached to the outside world side of the see-through mirror 23. The dimming device adjusts the transmittance electrically, for example. As the dimming device, a mirror liquid crystal, an electronic shade, etc. can be used. The dimming device may adjust the transmittance according to the illuminance of outside light.

[0066] In the above description, it is assumed that the display device 100 is used by being mounted on the head, but the display device 100 can also be used as a handheld display that is not mounted on the head and is peered at like binoculars. In other words, in the present invention, the head mounted display also includes a handheld display.

[0067] In a specific embodiment, the display device includes an image element, a projection lens that passes image light emitted from the image element, a prism mirror that causes the image light emitted from the projection lens to enter through a light entrance surface, reflect off an internal reflective surface, and exit from a light exit surface, thereby folding the image light back in an inclined direction, a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position, and a basic aperture diaphragm that limits the passage of the image light outside one of the light entrance surface and light exit surface of the prism mirror.

[0068] The above-mentioned display device is provided with a basic aperture diaphragm that limits the passage of image light outside the light entrance surface or light exit surface of the prism mirror, so that it is possible to selectively pass the image light necessary for imaging while blocking light that degrades imaging, thereby improving the imaging performance of the display device.

[0069] In a specific aspect, the basic aperture stop is disposed between the projection lens and the prism mirror, where it is easy to secure a space and to dispose the basic aperture stop.

[0070] In another aspect, the optical system further includes an additional aperture stop arranged opposite the light exit surface of the prism mirror. When the position where the image light emitted from the image element is collected varies depending on the direction around the optical axis, the basic aperture stop and the additional aperture stop can be combined to provide a function similar to that of a general aperture stop. Specifically, when the image light is collected near the light entrance surface of the prism mirror in a specific direction around the optical axis, the basic aperture stop arranged there can block unnecessary light, and when the image light is collected near the light exit surface of the prism mirror in another direction around the optical axis, the additional aperture stop arranged there can block unnecessary light.

[0071] In another aspect, the optical system further includes an additional aperture stop formed at the position of the internal reflection surface of the prism mirror. When image light is focused in the vicinity of the light incident surface of the prism mirror in a specific direction around the optical axis, unnecessary light can be blocked by the basic aperture stop arranged there, and when image light is focused in the vicinity of the internal reflection surface of the prism mirror in another direction around the optical axis, unnecessary light can be blocked by the additional aperture stop arranged there.

[0072] In another aspect, the internal reflection surface has a reflection mirror formed in an effective area that is surrounded by a light-shielding area and allows the image light to propagate. In this case, the reflection mirror can be arranged in a minimum necessary area so that it can indirectly function as an additional aperture stop.

[0073] In another aspect, the reflecting mirror has an absorbing structure provided in a light-shielding region around the reflecting mirror, and unintended stray light formed in the light-shielding region around the reflecting mirror can be suppressed by the absorbing structure.

[0074] In another aspect, the reflecting mirror has a scattering structure provided in a light-shielding region around the reflecting mirror, and unintended stray light formed in the light-shielding region around the reflecting mirror can be suppressed by the scattering structure.

[0075] In another aspect, the basic aperture stop functions as an aperture stop in a first direction parallel to a predetermined plane including an optical axis of the image light entering the prism mirror and an optical axis of the image light exiting from the prism mirror, the first direction corresponding to a direction in which the optical axis is deviated by the prism mirror.

[0076] In another aspect, the basic aperture stop is arranged to correspond to an intermediate pupil position in the first direction. The basic aperture stop does not need to be exactly aligned with the designed intermediate pupil position, and may be arranged at a position slightly shifted therefrom.

[0077] In another aspect, the intermediate pupil position is a position where a plurality of chief rays emitted from different pixel positions in the first direction intersect.

[0078] In another aspect, the additional aperture stop functions as an aperture stop in a second direction perpendicular to a predetermined plane including the optical axis of the image light entering the prism mirror and the optical axis of the image light exiting from the prism mirror, the second direction corresponding to a direction perpendicular to the direction in which the optical axis is deflected by the prism mirror.

[0079] In another aspect, the additional aperture stop is disposed corresponding to an intermediate pupil position with respect to the second direction.

[0080] In another aspect, the additional aperture stop has an asymmetric shape with respect to a first direction parallel to the predetermined plane. The size of the ray bundle of the image light to be passed through the additional aperture stop may vary depending on the position in the first direction. In such a case, the necessary image light can be passed efficiently without waste.

[0081] In another aspect, the basic aperture stop is a part of a holding member that supports the prism mirror. In this case, the prism mirror and the basic aperture stop can be supported together in alignment by the holding member. The holding member can also support an additional aperture stop.

[0082] In another aspect, the projection lens has a free-form surface, and the light entrance surface, the internal reflection surface, and the light exit surface of the prism mirror are free-form surfaces. By including the free-form surfaces in the display device, it becomes easier to improve the optical performance.

[0083] In another aspect, the image source is an off-axis optical system that includes optical axis portions disposed along a predetermined reference plane and inclined relative to each other before and after the reflecting surface.

[0084] In another aspect, the predetermined reference plane extends in a vertical direction.

[0085] In another aspect, an optical system including a prism mirror and a see-through mirror forms distortion. In this case, the degree of freedom in the arrangement and size of optical elements such as the prism mirror is increased, and it is possible to easily ensure the optical performance of the display device while achieving a compact display device.

[0086] Another display device in a specific aspect includes an image element, a projection lens that passes image light emitted from the image element, a prism mirror that causes the image light emitted from the projection lens to enter through a light entrance surface, reflect off an internal reflection surface, and emit from a light exit surface, thereby folding the image light back in an inclined direction, and a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position, and has a plurality of aperture stops that are arranged at or near the different positions where chief rays intersect along the optical axis in different directions perpendicular to the optical axis.

[0087] An optical unit in one aspect of the present invention includes a projection lens that passes image light emitted from an image element, a prism mirror that causes the image light emitted from the projection lens to enter through a light entrance surface, reflect off an internal reflective surface, and exit from a light exit surface, thereby folding the image light back in an inclined direction, a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position, and a basic aperture diaphragm that limits the passage of the image light outside one of the light entrance surface and light exit surface of the prism mirror. [Explanation of symbols]

[0088] 10...image source, 11...image element, 12...imaging optical system, 13...display control circuit, 16...optical unit, 21...projection lens, 21a...entrance surface, 21b...exit surface, 22...prism mirror, 22a...light entrance surface, 22b...internal reflection surface, 22c...light exit surface, 23...see-through mirror, 23a...reflection surface, 23o...exterior surface, 30...holding member, 31...first aperture member, 32...second aperture member, 41...basic aperture stop, 42...additional aperture stop, 32r...mask, 32s...window, 33...support Support member, 41...first aperture, 42...second aperture, 42r...mask, 51...case, 100A, 100B...display device, 100C...support device, 102...display drive unit, 112...off-axis optical system, AX...optical axis, AX1, AX2, AX3...optical axis portion, ER...eye ring, IPa, IPb...intermediate pupil, ML...image light, MLa, MLb, MLc...image light, MLa, MLf, MLg...image light, OL...external light, P1, P2, P3...optical path, PP...pupil position, Pa, Pb...chief ray

Claims

1. An imaging element; a projection lens that transmits image light emitted from the image element; a prism mirror that causes the image light emitted from the projection lens to enter from a light incident surface, reflects the image light on an internal reflection surface, and emits the image light from a light exit surface, thereby folding the image light in an inclined direction; a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position; a basic aperture stop that limits passage of the image light on the outer side of one of the light entrance surface and the light exit surface of the prism mirror; and an additional aperture stop formed at the position of the internal reflection surface of the prism mirror.

2. The display device according to claim 1 , wherein the basic aperture stop is disposed between the projection lens and the prism mirror.

3. The display device according to claim 1 , wherein the internal reflection surface has a reflection mirror formed in an effective area that is surrounded by a light-shielding area and allows the image light to propagate.

4. The display device according to claim 3 , further comprising an absorbing structure provided in the light-shielding region around the reflective mirror.

5. The display device according to claim 3 , further comprising a scattering structure provided in the light-shielding region around the reflective mirror.

6. A display device according to any one of claims 1 to 5, wherein the basic aperture stop functions as an aperture stop in a first direction parallel to a predetermined plane including an optical axis of the image light incident on the prism mirror and an optical axis of the image light emerging from the prism mirror.

7. The display device according to claim 6 , wherein the basic aperture stop is arranged in correspondence with an intermediate pupil position in the first direction.

8. The display device according to claim 7 , wherein the intermediate pupil position is a position where a plurality of chief rays emitted from different pixel positions in the first direction intersect.

9. 9. The display device according to claim 6, wherein the additional aperture stop functions as an aperture stop in a second direction perpendicular to the predetermined plane.

10. The display device according to claim 9 , wherein the additional aperture stop is arranged to correspond to an intermediate pupil position in the second direction.

11. The display device according to claim 9 , wherein the additional aperture stop has an asymmetric shape with respect to the first direction.

12. 12. The display device according to claim 1, wherein the basic aperture stop is a part of a holding member that supports the prism mirror.

13. the projection lens has a free-form surface; 13. The display device according to claim 1, wherein the light entrance surface, the internal reflection surface, and the light exit surface of the prism mirror are free-form surfaces.

14. The display device according to any one of claims 1 to 13, wherein the image element, the projection lens and the prism mirror are off-axis optical systems arranged along a predetermined reference plane and including optical axis portions that are inclined relative to each other in front of and behind the reflective surface.

15. The display device according to claim 14 , wherein the predetermined reference surface extends in a vertical direction.

16. 16. The display device according to claim 1, wherein an optical system including the prism mirror and the see-through mirror forms a distortion.

17. An imaging element; a projection lens that transmits image light emitted from the image element; a prism mirror that causes the image light emitted from the projection lens to enter from a light incident surface, reflects the image light on an internal reflection surface, and emits the image light from a light exit surface, thereby folding the image light in an inclined direction; a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position, for different directions perpendicular to the optical axis, the chief rays intersect at different locations spaced along said optical axis; a plurality of aperture stops each disposed at or near the different positions; A display device, wherein the multiple aperture stops are a basic aperture stop that limits the passage of the image light outside one of the light entrance surface and the light exit surface of the prism mirror, and an additional aperture stop that is formed at the position of the internal reflection surface of the prism mirror.

18. A projection lens that passes image light emitted from an image element; a prism mirror that causes the image light emitted from the projection lens to enter from a light incident surface, reflects the image light on an internal reflection surface, and emits the image light from a light exit surface, thereby folding the image light in an inclined direction; a see-through mirror that reflects the image light emitted from the prism mirror toward a pupil position; a basic aperture diaphragm for restricting the image light incident on the light incident surface of the prism mirror; an additional aperture stop formed at the position of the internal reflection surface of the prism mirror.

Images