Virtual image display device and optical unit

Abstract

To achieve downsizing of a virtual image display device, and improve utilization efficiency of light.SOLUTION: A virtual image display device comprises: a display panel 11a which emits moving image light ML; a projection optical system 20 which collimates the moving image light ML from the display panel 11a; and a light guide member 50 which includes a light guide plate 51a which guides the moving image light ML, an incident part DI which allows the moving image light ML to be incident to the light guide plate 51a, a relay part DE which guides the moving image light ML having passed the incident part DI and magnifies a pupil in a first direction, and an emission part DO which guides the moving image light ML having passed the relay part DE, magnifies the pupil in a second direction orthogonal to the first direction, and emits the light from the light guide plate 51a, where an exit pupil Lx of the projection optical system 20 has a shape in which a vertical width He is larger than a lateral width We, the incident part DI has a shape in which a vertical width Hn is larger shape than a lateral width Wn corresponding to the shape of the exit pupil Lx.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a virtual image display device and an optical unit that enable viewing of a virtual image. [Background technology]

[0002] As a display device that enables the observation of a virtual image, there is one that includes a light guide member into which the image light emitted from the image light generating device is incident, a first diffraction element provided on the incident side of the light guide member, a second diffraction element provided on the exit side of the light guide member, and a mirror provided at the end of the incident side of the light guide member (Patent Document 1). In the device of Patent Document 1, the image light that has passed through the first diffraction element is reflected by the mirror and propagates within the light guide member, and the image light that has passed through the second diffraction element is emitted toward the eye. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-156995 Summary of the Invention [Problem to be solved by the invention]

[0004] In the display device of Patent Document 1, if the size of the image light generating device is reduced in order to miniaturize the device, the luminance efficiency may decrease. [Means for solving the problem]

[0005] A virtual image display device or optical unit in one aspect of the present invention includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, and a light guide member including an entrance portion that causes the image light to enter the light guide plate, a relay portion that guides the image light that has passed through the entrance portion and expands the pupil in a first direction, and an exit portion that guides the image light that has passed through the relay portion and expands the pupil in a second direction perpendicular to the first direction and emits it from the light guide plate, wherein the exit pupil of the projection optical system has a shape in which the vertical width is greater than the horizontal width, and the entrance portion has a shape in which the vertical width is greater than the horizontal width corresponding to the shape of the exit pupil. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a plan view illustrating a state in which an HMD according to a first embodiment is worn. [Diagram 2] FIG. 2 is a side view for explaining the arrangement of an optical system that constitutes the virtual image display device. [Diagram 3] FIG. 2 is a plan view for explaining the arrangement of an optical system that constitutes the virtual image display device. [Figure 4] FIG. 2 is a front view illustrating a light-guiding optical system or a light-guiding member. [Diagram 5] 4 is a conceptual plan view illustrating the optical system of the first display driver. FIG. [Figure 6] 4 is a conceptual side view illustrating the optical system of the first display driver. FIG. [Figure 7] 4 is a conceptual perspective view illustrating an optical system of a first display driving section. FIG. [Figure 8] FIG. 2 is a plan view illustrating a display surface of a display panel. [Figure 9] 4 is a conceptual diagram illustrating the angular characteristics etc. of a first display driving section. FIG. [Figure 10] 13 is a light path diagram illustrating a modified example of the optical system of the first display driving section. FIG. [Figure 11] FIG. 11 is a conceptual plan view illustrating an optical system in a second embodiment. [Figure 12] FIG. 11 is a conceptual side view illustrating an optical system in the second embodiment. [Figure 13] 13A to 13C are diagrams illustrating an example and a comparative example of the optical system of the second embodiment. [Figure 14] FIG. 11 is a light path diagram showing an example of light rays in the optical system of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [First embodiment] Hereinafter, a first embodiment of a virtual image display device according to the present invention will be described with reference to FIGS.

[0008] Fig. 1 is a diagram for explaining the wearing state of a head mounted display device (hereinafter also referred to as a head mounted display or HMD) 200, in which the observer or wearer US wearing the HMD 200 recognizes an image as a virtual image. In Fig. 1 etc., X, Y, and Z are an orthogonal coordinate system, the +X direction corresponds to the lateral direction in which the eyes EY of the observer or wearer US wearing the HMD 200 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 virtual image display device 100A for the left eye, a second virtual image display device 100B for the right eye, a pair of temple-shaped support devices 100C for supporting the virtual image display devices 100A and 100B, and a user terminal 90 that is an information terminal. The first virtual image display device 100A functions as an HMD by itself, and is composed of a first display drive unit 102a arranged at the top, and a first light guide optical system 103a that is shaped like a pair of glasses and covers the front of the eyes. The second virtual image display device 100B also functions as an HMD by itself, and is composed of a second display drive unit 102b arranged at the top, and a second light guide optical system 103b that is shaped like a pair of glasses and covers the front of the eyes. The support device 100C is a mounting member that is mounted on the head of the wearer US, and supports the upper end sides of the pair of light guide optical systems 103a and 103b via the display drive units 102a and 102b that are integrated in appearance. The first virtual image display device 100A and the second virtual image display device 100B are optically reversed from left to right, and a detailed description of the second virtual image display device 100B will be omitted.

[0010] Fig. 2 is a side view specifically explaining the first display driving unit 102a and the first light guiding optical system 103a of the first virtual image display device 100A. Fig. 3 is a plan view specifically explaining the first display driving unit 102a and the first light guiding optical system 103a. Fig. 4 is a front view mainly explaining the first light guiding optical system 103a.

[0011] 2 and 3, the first display driving unit 102a includes an image light generating device 10, a projection optical system 20, and a driving circuit member 88. The image light generating device 10 is an optical engine including a display panel 11a. The projection optical system 20 is a collimator including a plurality of lens elements 21. The image light ML generated by the image light generating device 10 is collimated by the projection optical system 20 and coupled to the first light guiding optical system 103a, which is a light guiding member 50. Collimation refers to optically adjusting diffused light to be in a parallel state by an optical element, to make it into collimated light, that is, parallel light. The driving circuit member 88 causes the display panel 11a to perform a display operation. Note that in the first virtual image display device 100A, an optical device excluding the driving circuit member 88 is called an optical unit 100. The first virtual image display device 100A guides the image light ML to the eye EY of the wearer US, thereby allowing the wearer US to view a virtual image.

[0012] With reference to FIG. 4, the first light guide optical system 103a is a light guide member 50 that enables color display, and extends approximately parallel to the XY plane. The first light guide optical system 103a has a light guide plate 51a, an incident diffraction layer 51b, a pupil enlargement grating layer 51e, and an exit diffraction layer 51c. The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e diffract the image light ML according to the wavelength of the image light ML. The incident diffraction layer 51b is an entrance portion DI, which guides the collimated image light ML from the first display driving unit 102a (see FIG. 2) into the light guide plate 51a and propagates it laterally. The pupil enlargement grating layer 51e is a relay portion DE, which propagates the image light ML propagating laterally in the light guide plate 51a downward while expanding the pupil size of the image light ML. The exit diffraction layer 51c is the exit section DO, which expands the pupil size of the image light ML propagating downward within the light guide plate 51a, and emits the image light ML toward a pupil position PP (see Figure 2) set inside where the eye EY (see Figure 2) is located.

[0013] 5 and 6 are conceptual plan and side views for explaining the optical system of the first display driving unit 102a. FIG. 7 is a conceptual perspective view for explaining the optical system of the first display driving unit 102a. In the first display driving unit 102a, the image light generating device 10 includes only one display panel 11a. That is, the display panel 11a includes pixels of three colors, RGB, and the pixels of each color are two-dimensionally arranged in the display panel 11a. The projection optical system 20 includes a plurality of lens elements 21. The display panel 11a and the projection optical system 20 are fixed in a state in which they are positioned relative to each other by a lens barrel 30. The lens barrel 30 is supported together with the driving circuit member 88 by a holder 71 (see FIG. 2) that also serves as a cover in a state in which they are positioned relative to each other, and is fixed to the first light guiding optical system 103a.

[0014] The display panel 11a is a display element or display device that emits image light ML to form an image corresponding to a virtual image. Specifically, the display panel 11a is a display of various light-emitting element arrays such as OLED (Organic Light Emitting Diode), micro OLED, organic EL (Organic Electro-Luminescence), inorganic EL, LED (Light Emitting Diode), and micro LED, and forms a still image or a moving image on a two-dimensional display surface 11d parallel to the XY plane. Note that OLED is included in organic EL elements. The display panel 11a has a light-emitting element 14a. The light-emitting element 14a is a multiplicity of pixels two-dimensionally arranged on a substrate along the XY plane. When the display panel 11a is an OLED display, each pixel constituting the light-emitting element 14a includes, in order from the substrate side, a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and a transparent electrode layer.

[0015] The display panel 11a is not limited to a self-luminous image light generating device, but may be a display 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 background. Instead of an LCD, the display panel 11a may be an LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micromirror device (specifically, DLP, a registered trademark), a laser beam scan, or the like.

[0016] FIG. 8 is a plan view illustrating the display surface 11d of the display panel 11a. The display surface 11d of the display panel 11a has a horizontally elongated shape in which the horizontal width Wp is larger than the vertical width Hp. Accordingly, the display panel 11a also has a horizontally elongated shape. In this embodiment, the horizontal width Wp is the length in the horizontal or left-right direction, that is, the X direction, and the vertical width Hp is the length in the vertical or up-down direction, that is, the Y direction. The horizontal direction is the direction in which the positions where the eyes EY are arranged are lined up, and the direction in which the light guide plate 51a extends. The vertical direction is the direction perpendicular to the horizontal direction. When the image light generating device 10 is composed of only one display panel 11a, the display panel 11a two-dimensionally arranges the RGB sub-pixels Pr, Pg, Pb that display each color of RGB as one pixel Px (pixel element). That is, the display panel 11a has a three-color stripe structure by the sub-pixels Pr, Pg, Pb. The sub-pixels Pr, Pg, and Pb have a vertically long shape. Therefore, the display panel 11a has a wide viewing angle characteristic in the vertical direction, that is, the Y direction. Here, the viewing angle characteristic means a property in which the contrast ratio, the appearance of colors, etc. differ depending on the direction (angle) from which the screen is viewed.

[0017] FIG. 9 is a conceptual diagram for explaining the angular characteristics of the first display driving unit 102a. In FIG. 9, the symbol FOV indicates the viewing angle. In the display panel 11a having the pixels Px with the vertical stripe structure described above, the viewing angle characteristics in the vertical direction are wider, so that the swallow angle θ of the image light ML emitted from the display panel 11a is also larger in the vertical direction than in the horizontal direction (see FIG. 6 and FIG. 8). Therefore, the amount of irradiated light flux at the exit pupil position of the projection optical system 20 can be increased, and the light utilization efficiency of the entire optical system can be improved. Here, the swallow angle θ means an angle at which the projection optical system 20 can swallow the image light ML emitted from the display panel 11a (the angle of the incident light with respect to the optical axis AX of the projection optical system 20).

[0018] The projection optical system 20 includes a first lens 21a and a second lens 21b as lens elements 21 that collimate, i.e., parallelize, the incident light. The projection optical system 20 has a function substantially equivalent to that of a single lens 20i, and collimates the image light ML emitted from the display surface 11d of the display panel 11a to a state having a predetermined light beam width, and emits the image light ML toward the incident diffraction layer 51b. The projection optical system 20 may include optical elements such as a reflecting mirror in addition to one or more lens elements made of resin or glass. The optical surfaces of the optical elements constituting the projection optical system 20 may be any of spherical, aspherical, and free-form surfaces.

[0019] Light guide plate 51a is a member formed from a parallel plate, and has first total reflection surface 51i and second total reflection surface 51o, which are a pair of flat surfaces extending in the XY plane.

[0020] Returning to Fig. 4, in the first light guiding optical system 103a or the light guiding member 50, the incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are formed on the second total reflection surface 51o of the light guiding plate 51a. That is, the incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are disposed on the external side, i.e., the +Z side, of the light guiding plate 51a. The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are designed to function as a reflective diffraction grating that partially transmits external light.

[0021] The incident diffraction layer 51b is an input diffractive optical element that is an incident portion DI, and folds back the image light ML that is emitted from the display panel 11a of the image light generating device 10 and enters through the lens element 21 of the projection optical system 20 so as to propagate inside the light guide member 50. The image light ML that is collimated about an optical axis AX (see FIG. 2) perpendicular to the light guide plate 51a is incident on the incident diffraction layer 51b. The incident diffraction layer 51b is formed with a diffraction pattern that extends linearly in the vertical Y direction and is periodically repeated in the horizontal X direction.

[0022] The pupil enlargement grating layer 51e is a pupil enlargement diffractive optical element that is a relay unit DE, and is provided on the -X side of the incident diffraction layer 51b, and bends the optical path of the image light ML that is guided into the light guide plate 51a and travels in the -X direction as a whole so that it travels in the -Y direction as a whole. In the example of this embodiment, the relay unit DE is an element that converts the propagation guide direction of the image light ML from the horizontal direction to the vertical direction. The pupil enlargement grating layer 51e does not substantially lose angular information of the image light ML in the left and right X direction and angular information of the image light ML in the up and down Y direction while switching the diffraction direction. The pupil enlargement grating layer 51e guides the image light ML guided from the incident diffraction layer 51b into the light guide plate 51a to the exit diffraction layer 51c, while enlarging the pupil of the exit diffraction layer 51c. More specifically, the pupil enlargement grating layer 51e is interposed between the incident diffraction layer 51b and the exit diffraction layer 51c, and divides the light while guiding the image light ML in a direction (-Y direction) intersecting the diffraction direction (-X direction) of the incident diffraction layer 51b, and has a role of expanding the width of the light in the horizontal direction. In other words, the pupil enlargement grating layer 51e expands the pupil in the horizontal direction, which is the first direction. The pupil enlargement grating layer 51e is formed with a diffraction pattern that extends linearly in the oblique DS1 direction parallel to the XY plane and is periodically repeated in the DS2 direction parallel to the XY plane and perpendicular to the DS1 direction. The DS1 direction is rotated 45° counterclockwise with respect to the +Y direction, and is an intermediate direction between the -X direction and the +Y direction. The grating period or pitch in the X and Y directions of the pattern formed on the pupil enlargement grating layer 51e matches the grating period in the X direction of the pattern formed on the incident diffraction layer 51b, and also matches the grating period in the Y direction of the pattern formed on the exit diffraction layer 51c.

[0023] The exit diffraction layer 51c is an output diffractive optical element that is an exit portion DO, and divides the light beam while guiding the image light ML in the -Y direction, and has a role of expanding the light beam width in the vertical direction. That is, the exit diffraction layer 51c expands the pupil in the vertical direction, which is the second direction perpendicular to the first direction. As a result, the light beam width in the X direction and the Y direction of the image light ML incident on the pupil position PP shown in FIG. 2 has a spread corresponding to the exit diffraction layer 51c, and the pupil size in the vertical direction and the horizontal direction increases through the pupil expansion grating layer 51e, the exit diffraction layer 51c, etc. From the exit diffraction layer 51c, the image light ML that is collimated with the exit optical axis OX (see FIG. 2) perpendicular to the light guide plate 51a as the center is output. The image light ML output from the exit diffraction layer 51c is about ±25° with the exit optical axis OX as the reference. That is, the angle of view of the first virtual image display device 100A is about 50°. The emission diffraction layer 51c is formed with a diffraction pattern that extends linearly in the horizontal X direction and is periodically repeated in the vertical Y direction.

[0024] The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are formed, for example, from a surface relief type diffraction element. The surface relief type diffraction element is formed by nanoimprinting, but is not limited to this, and can also be formed by etching the surface of the light guide plate 51a, or a diffraction element may be attached. The material of the diffraction grating is a nanoimprint material when it is produced by nanoimprinting, and is the same material as the light guide plate 51a when it is produced by etching. The material of the light guide plate 51a is, for example, glass, resin, etc.

[0025] The shapes and dimensions of the display panel 11a, the projection optical system 20, and the incident diffraction layer 51b will be described below with reference to FIGS.

[0026] The display surface 11d of the display panel 11a has a horizontally elongated shape with a horizontal width Wd larger than a vertical width Hd corresponding to the exit pupil Lx. The sub-pixels Pr, Pg, and Pb for each color in the display panel 11a have a vertically elongated shape with a vertical width Hp larger than a horizontal width Wp corresponding to the exit pupil Lx (see FIG. 8). That is, the viewing angle characteristic of the image light ML has an angular characteristic in which the vertical direction is wider than the horizontal direction corresponding to the exit pupil Lx. This angular characteristic can be realized by providing vertically elongated sub-pixels in the display panel 11a or by providing a vertically elongated lens in the lens element 21 as described later. The exit pupil Lx of the projection optical system 20 has a vertically elongated shape with a vertical width He larger than a horizontal width We. The shape of the exit pupil Lx is the contour shape of the image light ML on a plane perpendicular to the optical axis AX. The shape of the exit pupil Lx mainly depends on the light distribution characteristics of the pixels of the display panel 11a, assuming that the projection optical system 20 superimposes the collimated image light ML on the pupil position, and is influenced by the optical element acting on the characteristics when an optical element acting on the light distribution characteristics exists, and is influenced by the aperture shape of the projection optical system 20 and the size of the display panel 11a. In addition, the lenses 21a and 21b of the lens element 21 have a vertically elongated shape in which the vertical width is larger than the horizontal width corresponding to the exit pupil Lx. That is, the lenses 21a and 21b have a vertically elongated shape. The entrance diffraction layer 51b, which is the entrance portion DI, has a vertically elongated shape in which the vertical width Hn is larger than the horizontal width Wn corresponding to the exit pupil Lx. The size of the entrance diffraction layer 51b is the same as the size of the exit pupil Lx, but may be slightly larger than the size of the exit pupil Lx. As a result, the entrance diffraction layer 51b can reduce the optical loss of the image light ML from the projection optical system 20.

[0027] In order to miniaturize the projection optical system 20, the incident diffraction layer 51b needs to be small. Specifically, the width Wn of the incident diffraction layer 51b is, for example, about 1 mm, and the length Hn is, for example, about 2 mm. The exit pupil Lx of the projection optical system 20 has a width We of, for example, about 1 mm, and a length He of, for example, about 2 mm, so as to correspond to the incident diffraction layer 51b. This allows the width of the projection optical system 20 to be reduced, and AR (Augmented Reality) glasses that are similar in shape to glasses can be realized.

[0028] In the above, when the incident diffraction layer 51b is vertically long, it is preferable to first guide the light by folding it back in the horizontal direction, which is the short side direction of the incident diffraction layer 51b. This is because when the light is guided by the light guide plate 51a, loss occurs if the light re-enters the incident diffraction layer 51b.

[0029] The virtual image display devices 100A and 100B of the first embodiment include a display panel 11a that emits image light ML, a projection optical system 20 that collimates the image light ML from the display panel 11a, a light guide plate 51a that guides the image light ML, an entrance section DI that causes the image light ML to enter the light guide plate 51a, a relay section DE that guides the image light ML that has passed through the entrance section DI and expands the pupil in a first direction, and an exit section DO that guides the image light ML that has passed through the relay section DE, expands the pupil in a second direction perpendicular to the first direction, and emits it from the light guide plate 51a, and the exit pupil Lx of the projection optical system 20 has a shape in which the vertical width He is greater than the horizontal width We, and the entrance section DI has a shape in which the vertical width Hn is greater than the horizontal width Wn corresponding to the shape of the exit pupil Lx.

[0030] In the virtual image display devices 100A and 100B, the exit pupil Lx when the light guide plate 51a is irradiated by the projection optical system 20 is larger in the vertical direction than in the horizontal direction, so that the width of the projection optical system 20 can be reduced and the amount of irradiated light flux can be increased. As a result, the virtual image display devices 100A and 100B can improve the luminance of the light emitted from the light guide member 50 or the light guide plate 51a and improve the light utilization efficiency while approaching the shape of glasses by reducing the size of the projection optical system 20.

[0031] Fig. 10 is a light path diagram for explaining a modified example of the optical system of the first display driver 102a. In Fig. 10, an area AR1 shows a cross section of the optical system of the first display driver 102a, and an area AR2 shows a vertical section of the optical system of the first display driver 102a. As shown in Fig. 10, the optical system of the first display driver 102a in this embodiment is not limited to a telecentric optical system, and may be a non-telecentric optical system. However, a telecentric optical system is optimally designed depending on conditions such as the viewing angle FOV and the panel size of the display panel 11a.

[0032] Second Embodiment Hereinafter, a virtual image display device according to a second embodiment of the present invention will be described. Note that the virtual image display device of the second embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of the common parts will be omitted.

[0033] 11 and 12 are conceptual plan and side views illustrating the optical system of the first display driver 102a. In the first display driver 102a, the image light generation device 10 of the first display driver 102a includes three display panels 11r, 11b, and 11g, and a cross dichroic prism 18. The projection optical system 20 is a collimator including a plurality of lenses 21a and 21b, which are lens elements 21.

[0034] The red display panel 11r is a first display panel and emits red image light MLr, which is a first image light. The display panel 11r is, for example, a micro OLED display, forms a still image or a moving image on a two-dimensional display surface 11d parallel to the YZ plane, and emits red image light MLr.

[0035] The blue display panel 11b is a second display panel, and emits blue image light MLb, which is the second image light. The display panel 11b is, for example, a micro OLED display, similar to the red display panel 11r, and forms a still image or a moving image on a two-dimensional display surface 11d parallel to the YZ plane, and emits blue image light MLb. The light emitting element 14a incorporated in the blue display panel 11b has a different emission wavelength from the light emitting element 14a of the red display panel 11r. In other words, the blue image light MLb, which is the second image light, and the red image light MLr, which is the first image light, have different wavelength ranges.

[0036] The green display panel 11g is a third display panel and emits green image light MLg, which is the third image light. The display panel 11g is, for example, a micro OLED display, similar to the red display panel 11r, and forms a still image or a moving image on a two-dimensional display surface 11d parallel to the XY plane, and emits green image light MLg. The light emitting element 14a incorporated in the green display panel 11g has a different emission wavelength from the light emitting element 14a of the red and blue display panels 11r and 11b. In other words, the green image light MLg, which is the third image light, has a different wavelength range from the red image light MLr, which is the first image light, and the blue image light MLb, which is the second image light.

[0037] The light emitting element 14a incorporated in the display panels 11r, 11b, and 11g is a micro OLED display with a first-order resonant cavity. Therefore, the orientation characteristics of the display panels 11r, 11b, and 11g are such that the light intensity is high in the front direction parallel to the optical axis AX, and the light intensity drops rapidly in a direction slightly tilted from the front direction. The angle at which the light intensity is half-maximum is defined as the radiation angle, and the radiation angle from the pixel of the red image light MLr, the radiation angle from the pixel of the blue image light MLb, and the radiation angle from the pixel of the green image light MLg are within about 20°. The dichroic mirrors 18r and 18b of the cross dichroic prism 18 described later are designed based on these radiation angles of the image lights MLr, MLb, and MLg.

[0038] The red display panel 11r is fixed so as to be attached to the first light incident surface 18ib of the cross dichroic prism 18. The first red display panel 11r causes red image light MLr, which is the first image light, to enter the cross dichroic prism 18 from the first light incident surface 18ib. The blue display panel 11b is fixed so as to be attached to the second light incident surface 18ic of the cross dichroic prism 18. The second blue display panel 11b causes blue image light MLb, which is the second image light, to enter the cross dichroic prism 18 from the second light incident surface 18ic. The green display panel 11g is fixed so as to be attached to the third light incident surface 18ia of the cross dichroic prism 18. The third green display panel 11g causes green image light MLg, which is the third image light, to enter the cross dichroic prism 18 from the third light incident surface 18ia.

[0039] The cross dichroic prism 18 is formed by joining four right-angled triangular prisms made of glass or the like so that their right-angled edges coincide with each other, and has a structure in which two dichroic mirrors 18r, 18b perpendicular to the joining portion are embedded. One dichroic mirror 18r is disposed at an angle of 45° with the first light incident surface 18ib. The dichroic mirror 18r forms a surface that connects the diagonal corners of the square outline when viewed from the direction of the cross axis CX of the cross dichroic prism 18. The other dichroic mirror 18b is disposed at an angle of 45° with the second light incident surface 18ic. The dichroic mirror 18b forms a surface that connects the diagonal corners of the square outline when viewed from the direction of the cross axis CX of the cross dichroic prism 18.

[0040] The red image light MLr incident on the first light incident surface 18ib of the cross dichroic prism 18 from the first display panel 11r for red is reflected by the dichroic mirror 18r and bent toward the exit side, i.e., the projection optical system 20, and is emitted from the light exit surface 18o in the +Z direction to the outside. The blue image light MLb incident on the second light incident surface 18ic of the cross dichroic prism 18 from the second display panel 11b for blue is reflected by the dichroic mirror 18b and bent toward the exit side, i.e., the projection optical system 20, and is emitted from the light exit surface 18o in the +Z direction to the outside. The green image light MLg incident on the third light incident surface 18ia of the cross dichroic prism 18 from the third display panel 11g for green passes through the dichroic mirrors 18r and 18b without being reflected by them and toward the projection optical system 20, and is emitted from the light exit surface 18o in the +Z direction to the outside. That is, the cross dichroic prism 18 transmits the green image light MLg. As a result, the cross dichroic prism 18 synthesizes an image in which the red image light MLr, the green image light MLg, and the blue image light MLb are superimposed, and the image light is emitted as image light ML and can be incident on the projection optical system 20.

[0041] In the cross dichroic prism 18, the cross axis CX extends along the intersection line between the two dichroic mirrors 18r, 18b and is parallel to the Y direction. The optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 extends in the horizontal direction perpendicular to the light guide plate 51a, that is, in the Z direction.

[0042] The projection optical system 20 is an optical system that is approximately telecentric with respect to the display panels 11r, 11b, and 11g, which are the object side. That is, the main ray of the image light 11r, 11b, and 11g emitted from each part of the light emitting element 14a, which is the display surface 11d of each display panel 11r, 11b, and 11g, passes through the light entrance surfaces 18ib, 18ic, and 18ia of the cross dichroic prism 18 in a state approximately parallel to the optical axis AX, enters the cross dichroic prism 18, and is emitted from the cross dichroic prism 18 approximately parallel to the optical axis AX. As a result, the red image light MLr, the green image light MLg, and the blue image light MLb within a predetermined angle range are incident on the dichroic mirrors 18r and 18b, and light loss due to the dichroic mirrors 18r and 18b can be suppressed.

[0043] The arrangement of the display panels 11r, 11b, and 11g can be changed as appropriate.

[0044] The angular characteristics of the dichroic mirrors 18r and 18b are wide in accordance with the exit pupil Lx or the long side of the incident diffraction layer 51b. The cross axis CX of the dichroic mirrors 18r and 18b is along the vertical direction of the light guide member 50 or the light guide plate 51a. In the cross dichroic prism 18, the traveling direction of the image light ML before being bent by the dichroic mirrors 18r and 18b coincides with the horizontal direction of the incident diffraction layer 51b. In other words, the length of the traveling direction of the image light ML before being bent by the dichroic mirrors 18r and 18b corresponds to the horizontal width Wn of the incident diffraction layer 51b. When mounted, the short side direction of the incident diffraction layer 51b is horizontal.

[0045] In an optical system that combines light with a plurality of display panels 11r, 11b, 11g and dichroic mirrors 18r, 18b, a monochromatic light source is used for each panel, so that the light-emitting layer can be made monochromatic, unlike an optical system that displays three colors with one panel. In addition, the optical system that combines the above-mentioned light can achieve high brightness because there is no reduction in the amount of light due to a color filter, and is effective for producing practical brightness even in an optical system with low brightness efficiency such as an optical system using a pupil enlargement light guide plate having a diffraction element as in this embodiment. The cross dichroic prism 18 for three-color combination has a characteristic of reflecting and transmitting light in different wavelength regions for each color of RGB as the characteristic of the dichroic mirrors 18r, 18b. In general, the reflection and transmission characteristics and the wavelength characteristics shift depending on the angle of light incident on the dichroic mirrors 18r, 18b, so that for a light source having a somewhat broad light such as an organic light-emitting diode, it is necessary to limit the angle of incidence to some extent. For example, in the red-reflecting dichroic mirror 18r, the transmission / reflection switching region (specifically, the switching region between green transmission and red reflection) needs to be within the range of 550 nm to 630 nm in all angle ranges. For example, in the blue-reflecting dichroic mirror 18b, the transmission / reflection switching region (specifically, the switching region between blue reflection and green transmission) needs to be within the range of 470 nm to 530 nm in all angle ranges. To satisfy this condition, the condition of the angle of incidence of the red image light MLr or the blue image light MLb on the dichroic mirrors 18r, 18b needs to be ±7° or less with respect to the tilt angle of the dichroic mirrors 18r, 18b.

[0046] 9, when the field of view of the projection optical system 20 is FOV, the exit pupil size is EPD, the panel size is D, the focal length of the projection optical system 20 is f, and the acceptance angle (half angle) of the light emitted from the display panel 11a is θ, the following relational expression is established. Note that the panel size D is the size of the display surface 11d of the display panel 11a. f=EPD / 2tanθ f=D / 2tan(FOV / 2) tan(FOV / 2)=Dtanθ / EPD

[0047] According to the above relational expression, when there is a limit to the swallow angle θ, it is necessary to increase the panel size D or decrease the exit pupil size EPD. If the panel size D is increased, the size of the cross dichroic prism 18, which is a composite prism, also increases, so that the entire projection optical system 20 becomes larger. In this case, it is necessary to arrange the projection optical system 20 so as not to interfere with the face of the wearer US, and the width of the first virtual image display device 100A increases, resulting in deviation from the design of the HMD 200, an increase in weight, and other effects. In addition, if the exit pupil size EPD is decreased, the projection optical system 20 can be made smaller, but the amount of irradiated light flux at the exit pupil position decreases, and the luminance of the optical system decreases.

[0048] From the above, in order to achieve both the glasses-shaped design and the luminance efficiency of the HMD 200, it is necessary to increase the exit pupil Lx while maintaining the size of the width of the display panels 11r, 11b, and 11g and the width of the projection optical system 20. As described above, the cross dichroic prism 18 has a restriction on the incidence angle, and the reflection angle is basically 45°. In other words, the principal ray angle of each field angle is based on the panel normal direction. In addition, since the light is basically incident on the light guide plate 51a as parallel light, the projection optical system 20 is made to be a one-sided telecentric optical system. To realize the above configuration, the vertical width He of the exit pupil Lx is made larger than the horizontal width We, and the vertical width Hn of the incident diffraction layer 51b of the light guide plate 51a is made larger than the horizontal width Wn.

[0049] As shown in FIG. 11 and FIG. 12, the display surface 11d of the display panel 11g has a horizontally elongated shape in which the horizontal width Wd is larger than the vertical width Hd. In this embodiment, the vertical width Hd and horizontal width Wd of the display surface 11d of the display panel 11g are based on the third display panel 11g for green arranged opposite the light guide member 50. The first display panel 11r for red and the second display panel 11b for blue are shaped similarly to the third display panel 11g for green. The dichroic mirrors 18r and 18b are arranged to be inclined at 45° in the horizontal direction with respect to the optical axis AX. The allowable range of the angle of incidence on the dichroic mirrors 18r and 18b is 45±7° or less within the medium of the cross dichroic prism 18. The projection optical system 20 is designed to be one-sided telecentric. The chief ray emerging from the display panels 11r, 11b, and 11g is perpendicular to the display surfaces 11d of the display panels 11r, 11b, and 11g. If the angle of incidence exceeds 45±7°, some wavelengths of light that would normally be reflected or transmitted are not reflected or transmitted, resulting in a significant change in color and a significant decrease in brightness in the peripheral area of ​​the exit pupil Lx of the projection optical system 20.

[0050] Here, if the horizontal field of view angle is large, the size of the cross dichroic prism 18 will increase, which will have a significant effect on the size of the projection optical system 20 itself. Therefore, by making the exit pupil Lx larger in the vertical direction so that a larger vertical field of view angle FOV is used than in the horizontal direction, it is possible to prevent the cross dichroic prism 18 from becoming enlarged, reduce the back focus of the projection optical system 20, and reduce the size of the projection optical system 20.

[0051] FIG. 13 is a diagram for explaining a design example of the exit pupil size EPD when the angle of incidence on the dichroic mirrors 18r, 18b in the cross dichroic prism 18 needs to be suppressed to ±7°. FIG. 13 shows a calculation example comparing the difference in size of the cross dichroic prism 18 between a vertically elongated elliptical exit pupil Lx as an embodiment and a circular exit pupil Lx as a comparative example. The panel size D is 0.3 inches, and the viewing angle FOV is 60°. According to the calculation result, by making the shape of the exit pupil Lx a vertically elongated ellipse, the horizontal size of the cross dichroic prism 18 can be reduced from 10.2 mm to 9.6 mm. This makes it possible to achieve weight reduction by reducing the prism size, and the size of the projection optical system 20 can also be reduced by shortening the distance to the lens element 21.

[0052] FIG. 14 is a light path diagram showing an example of a specific light beam of the optical system of the first display driver 102a in this embodiment. In FIG. 14, region BR1 shows a cross section of the optical system of the first display driver 102a, and region BR2 shows a vertical section of the optical system of the first display driver 102a. The aspect ratio of the lenses 21a and 21b of the projection optical system 20 changes depending on conditions such as the viewing angle FOV and the panel size D of the display panel 11a. For example, depending on conditions such as the viewing angle FOV and the panel size D of the display panel 11a, the aspect ratio of the second lens 21a on the display panel 11a side may be approximately the same. In addition, the optical system using the cross dichroic prism 18 can be in a non-telecentric state inclined inward depending on the design conditions such as the panel size D and the viewing angle FOV, and the allowable conditions of the incident angle of the light beam due to the design of the dichroic mirrors 18r and 18b. This allows the cross dichroic prism 18 to be configured to be more compact.

[0053] [Other matters] The above-described structure is merely an example, and various modifications can be made within the scope of achieving the same function.

[0054] The light guide member 50 may be a stack of multiple light guides arranged in parallel. In this case, each of the light guides may correspond to, for example, three colors, R, G, and G. Each light guide includes a light guide plate 51a, an entrance diffraction layer 51b, an exit diffraction layer 51c, and a pupil enlargement grating layer 51e.

[0055] The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are not limited to diffraction elements, and may be formed from volume holograms. The incident section DI, the relay section DE, and the exit section DO are not limited to those that diffract the image light ML, and may be deflection branching sections that change the direction of the image light ML. As a specific example, the incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e may be a dielectric multilayer mirror or a metal mirror. The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are not limited to those that are made of a single layer, and may be those that are made by laminating multiple functional layers that are adapted to the wavelength, etc., of the image light ML.

[0056] The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e may be formed on the first total reflection surface 51i of the light guide plate 51a. In this case, the incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are designed to function as a transmission type diffraction grating.

[0057] In the above, the virtual image display devices 100A, 100B can be used as HMDs, but the present invention is not limited to this and can be applied to various optical devices. For example, the present invention can be applied to a head-up display (HUD).

[0058] In a specific embodiment, the virtual image display device includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, and a light guide member including an entrance portion for causing the image light to enter the light guide plate, a relay portion for guiding the image light that has passed through the entrance portion and expanding the pupil in a first direction, and an exit portion for guiding the image light that has passed through the relay portion and expanding the pupil in a second direction perpendicular to the first direction and causing it to exit the light guide plate, wherein the exit pupil of the projection optical system has a shape in which the vertical width is greater than the horizontal width, and the entrance portion has a shape in which the vertical width is greater than the horizontal width corresponding to the shape of the exit pupil.

[0059] In the virtual image display device, the exit pupil when the light guide plate is irradiated by the projection optical system is larger in the vertical direction than in the horizontal direction, so that the width of the projection optical system can be reduced and the amount of irradiated light flux can be increased. As a result, the virtual image display device can improve the luminance of the light emitted from the light guide member or the light guide plate and improve the light utilization efficiency while approaching the shape of glasses by reducing the size of the projection optical system.

[0060] In a specific embodiment of the virtual image display device, the first direction is the horizontal direction, the second direction is the vertical direction, the vertical width is the size in the second direction, and the horizontal width is the size in the first direction. When the incident portion has a vertically long shape, the loss of the guided light can be suppressed by first folding back the light in the horizontal direction, which is the short side direction of the incident portion, and guiding the light.

[0061] In a virtual image display device according to a specific embodiment, the entrance section, the exit section, and the relay section are formed of any one of a diffraction element, a volume hologram, a dielectric multilayer mirror, and a metal mirror.

[0062] In a virtual image display device according to a specific embodiment, the viewing angle characteristic of the image light emerging from the display panel has an angle characteristic in which the vertical direction is wider than the horizontal direction in correspondence with the exit pupil.

[0063] In a specific embodiment of the virtual image display device, the projection optical system has a lens having a shape whose vertical width is greater than its horizontal width in correspondence with the exit pupil, whereby the size of the projection optical system can be reduced.

[0064] In a specific embodiment of the virtual image display device, the sub-pixels for each color on the display panel have a shape in which the vertical width is greater than the horizontal width in correspondence with the exit pupil, whereby the viewing angle characteristic of the display panel becomes wider in the vertical direction.

[0065] In a specific embodiment, the virtual image display device includes a first display panel that is a display panel that emits a first image light of the image light, a second display panel that emits a second image light having a wavelength range different from that of the first image light, a third display panel that emits a third image light having a wavelength range different from that of the first image light and the second image light, and a cross dichroic prism that combines the first image light, the second image light, and the third image light. In this way, by combining the first image light, the second image light, and the third image light, a high-luminance virtual image can be displayed.

[0066] In a specific embodiment of a virtual image display device, the angular characteristics of the dichroic mirror of the cross dichroic prism are wide corresponding to the long side of the exit pupil, the cross axis of the dichroic mirror is along the vertical direction of the light-guiding member, and in the cross dichroic prism, the length of the traveling direction of the image light before being bent by the dichroic mirror corresponds to the horizontal width of the entrance portion.

[0067] In a specific embodiment of the virtual image display device, the display panel is any one of an organic electroluminescence display, a micro LED display, a reflective liquid crystal display, and a digital micromirror device.

[0068] In a specific embodiment, the optical unit includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, and a light guide member including an entrance portion that causes the image light to enter the light guide plate, a relay portion that guides the image light that has passed through the entrance portion and expands the pupil in a first direction, and an exit portion that guides the image light that has passed through the relay portion and expands the pupil in a second direction perpendicular to the first direction and emits it from the light guide plate, wherein the exit pupil of the projection optical system has a shape in which the vertical width is greater than the horizontal width, and the entrance portion has a shape in which the vertical width is greater than the horizontal width corresponding to the shape of the exit pupil. [Explanation of symbols]

[0069] 10...image light generating device, 11a, 11r, 11b, 11g...display panel, 18...cross dichroic prism, 20...projection optical system, 21...lens element, 30...lens barrel, 50...light guiding member, 51a...light guiding plate, 51b...entrance diffraction layer, 51c...exit diffraction layer, 51e...pupil enlargement grating layer, 88...driving circuit member, 90...user terminal, 100...optical unit, 100A, 100B...virtual image display device, 100C...support device, 102a, 102b...display driving unit, 103a, 103b...light guiding optical system, AX...optical axis, CX...cross axis, DE...relay unit, DI...entrance unit, DO...exit unit, EY...eye, Lx...exit pupil, ML...image light, PP...pupil position, Pr, Pg, Pb...subpixel, Px...pixel, US...wearer

Claims

1. A display panel that emits image light; a projection optical system that collimates the image light from the display panel; a light guide member including a light guide plate that guides the image light, an entrance portion that causes the image light to enter the light guide plate, a relay portion that guides the image light that has passed through the entrance portion and expands a pupil in a first direction, and an exit portion that guides the image light that has passed through the relay portion and expands the pupil in a second direction perpendicular to the first direction and causes the image light to exit from the light guide plate; Equipped with an exit pupil of the projection optical system has a shape in which the vertical width is greater than the horizontal width; The entrance portion has a shape in which a vertical width is greater than a horizontal width in accordance with the shape of the exit pupil. Virtual image display device.

2. The first direction is a horizontal direction and the second direction is a vertical direction; The vertical width is the size in the second direction, and the horizontal width is the size in the first direction. The virtual image display device according to claim 1 .

3. the incident portion, the exit portion, and the relay portion are formed of any one of a diffraction element, a volume hologram, a dielectric multilayer mirror, and a metal mirror; The virtual image display device according to claim 1 .

4. The viewing angle characteristic of the image light emitted from the display panel has an angle characteristic in which the vertical direction is wider than the horizontal direction in correspondence with the exit pupil. The virtual image display device according to claim 1 .

5. the projection optical system has a lens having a shape in which a vertical width is greater than a horizontal width in correspondence with the exit pupil, The virtual image display device according to claim 1 .

6. The sub-pixels for each color in the display panel have a shape in which the vertical width is greater than the horizontal width in correspondence with the exit pupil. The virtual image display device according to claim 1 .

7. a first display panel that emits a first image light out of the image light; a second display panel that emits second image light having a wavelength range different from that of the first image light; a third display panel that emits third image light having a wavelength range different from those of the first image light and the second image light; a cross dichroic prism that combines the first image light, the second image light, and the third image light. The virtual image display device according to claim 1 .

8. The angular characteristics of the dichroic mirror of the cross dichroic prism are wide in correspondence with the long side of the exit pupil, The cross axis of the dichroic mirror is aligned along the vertical direction of the light guide member, In the cross dichroic prism, the length of the image light in the traveling direction before being bent by the dichroic mirror corresponds to the width of the entrance portion. The virtual image display device according to claim 7 .

9. The display panel is any one of an organic electroluminescence display, a micro LED display, a reflective liquid crystal display, and a digital micromirror device. The virtual image display device according to claim 1 .

10. A display panel that emits image light; a projection optical system that collimates the image light from the display panel; a light guide member including a light guide plate that guides the image light, an entrance portion that causes the image light to enter the light guide plate, a relay portion that guides the image light that has passed through the entrance portion and expands a pupil in a first direction, and an exit portion that guides the image light that has passed through the relay portion and expands the pupil in a second direction perpendicular to the first direction and causes the image light to exit from the light guide plate; Equipped with an exit pupil of the projection optical system has a shape in which the vertical width is greater than the horizontal width; The entrance portion has a shape in which a vertical width is greater than a horizontal width in accordance with the shape of the exit pupil. Optical unit.

Images