Virtual image display device and optical unit

Abstract

To reduce the size of an optical system.SOLUTION: A virtual image display device comprises: a first display panel 11r that emits first video light; a second display panel 11b that emits second video light having a different wavelength region; and a third display panel 11g that emits third video light having a different wavelength region; a cross dichroic prism 18 that has a first light incident surface 18ib for the first video light, a second light incident surface 18ic for the second video light, and a third light incident surface 18ia for the third video light, and that synthesizes the first video light to the third video light; a projection optical system 20 including an optical path bending prism 21 having a first transmission surface S1 on which the video light ML from the cross dichroic prism 18 is made incident, a first reflection surface S2 that reflects the video light ML, a second reflection surface that reflects the video light ML again, and a second transmission surface that emits the video light ML reflected by the second reflection surface; and a light-guiding optical system 103a, 103b, which is a light-guiding member 50 that guides the video light ML emitted from the projection optical system 20 to a pupil position PP.SELECTED DRAWING: Figure 2

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] A known display device that enables the observation of virtual images is one in which the display light emitted from three display panels is combined using a combining optical system equipped with two intersecting dichroic mirrors, and the combined light is made to enter one end of a plate-shaped light-guiding section and exit from the other end (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-205451 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the display device shown in the above Patent Document 1, a prism-shaped synthetic optical system is used, so the size of the optical system up to the light guide unit is likely to become large, and the light guide unit also becomes large, resulting in increased weight and design restrictions, which are undesirable for the user. In particular, when the light guide unit is of a diffractive type, it is not easy to arrange the synthetic optical system inclined outward or toward the ear rather than perpendicularly to the light guide plate that constitutes the light guide unit, and restrictions on the arrangement and size of the light guide plate become large. [Means for solving the problem]

[0005] A virtual image display device or an optical unit in one aspect of the present invention has a first display panel that emits a first 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, a first light incident surface through which the first image light is incident, a second light incident surface through which the second image light is incident, and a third light incident surface through which the third image light is incident, The projection optical system includes a cross dichroic prism that combines image light and emits the combined image light from a light exit surface, a projection optical system including an optical path bending prism having a first transmitting surface onto which the image light from the cross dichroic prism is incident, a first reflecting surface and a second reflecting surface that reflect the image light that has transmitted through the first transmitting surface, and a second transmitting surface from which the image light reflected at the second reflecting surface is emitted, and a light guiding member that guides the image light emitted from the projection optical system to a pupil position where the eye is positioned. [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. 4 is a rear view illustrating a light-guiding optical system or a light-guiding member. [Diagram 5] 3A and 3B are side and rear views illustrating the optical system of the first display driving section. [Figure 6] FIG. 2 is a perspective view showing the appearance of an optical path bending prism. [Figure 7] FIG. 13 is a plan view illustrating a virtual image display device according to a modified example. [Figure 8] 13A and 13B are a side view and a rear view illustrating an optical system in a second embodiment. [Figure 9] 13A and 13B are a side view and a rear view illustrating an optical system in a third embodiment. [Figure 10] FIG. 10 is a perspective view illustrating an optical block shown in FIG. [Figure 11]FIG. 13 is a side view illustrating an optical system according to a modified example. 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 a wearing state of a head mounted display device (hereinafter also referred to as a head mounted display or HMD) 200, and the HMD 200 allows an observer or wearer US wearing the device to recognize an image as a virtual image. In FIG. 1 and the like, X, Y, and Z are Cartesian coordinate systems, and the +X direction corresponds to the horizontal 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 horizontal 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. The +Y direction or upward direction corresponds to the direction from the chin of the face toward the center of the forehead when the HMD 200 is worn by the wearer US.

[0009] The HMD 200 includes a first virtual image display device 100A for the right eye, a second virtual image display device 100B for the left 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, and Fig. 4 is a rear 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 cross prism type image light emitting unit 11. The projection optical system 20 is a collimator including an optical path bending prism 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 the light guiding member 50. In the first virtual image display device 100A, the optical device excluding the driving circuit member 88 is called an optical unit 100. The image unit 30 which combines the image light generating device 10 and the projection optical system 20 is disposed inside the first light guiding optical system 103a where the eye EY of the wearer US is located. The image unit 30 is disposed in the upper part of the first light guiding optical system 103a and on the outer corner side of the eye. Here, the upper part of the first light guiding optical system 103a means the upper side (edge ​​in the +Y direction) of the rectangle, and the outer corner of the first light guiding optical system 103a means the lateral outer side (edge ​​in the +X direction) of the rectangle. As a result, the image unit 30 is disposed at a position close to the connection part between the support device 100C and the first virtual image display device 100A.

[0012] 4, the first light guide optical system 103a is a diffractive light guide member that enables three-color display of RGB, 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 guides the collimated image light ML from the first display driver 102a into the light guide plate 51a and propagates it laterally, the pupil enlargement grating layer 51e propagates the image light ML propagating laterally in the light guide plate 51a while expanding the pupil size of the image light ML propagating laterally in the light guide plate 51a, and the exit diffraction layer 51c expands the pupil size of the image light ML propagating downward in the light guide plate 51a and causes the image light ML to exit toward a pupil position PP (see FIG. 2) set inside where the eye EY (see FIG. 2) is present.

[0013] FIG. 5 is a diagram for explaining the optical system of the first display driving unit 102a. In FIG. 5, an area AR1 is a side view of the optical system constituting the first display driving unit 102a, and an area AR2 is a rear view of the optical system constituting the first display driving unit 102a. In the first display driving unit 102a, the image light exiting unit 11 includes three display panels 11r, 11b, and 11g, and a cross dichroic prism 18. The projection optical system 20 includes a light path bending prism 21 having a positive power, and an aperture stop 25. The image light exiting unit 11, which is an integral part of the display panels 11r, 11b, and 11g and the cross dichroic prism 18, and the light path bending prism 21 are supported in a mutually positioned state by a holder 71 (see FIG. 2) which also serves as a cover, and are fixed on the -Z side, which is the inside, with respect to the first light guiding optical system 103a. The optical path bending prism 21 and the light exit unit 11 are arranged vertically side by side, and the optical path bending prism 21 is arranged above the image light exit unit 11 and the cross dichroic prism 18 incorporated therein.

[0014] 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, an organic EL (organic electro-luminescence) display, forms a still image or a moving image on a two-dimensional display surface parallel to the XY plane, and emits red image light MLr. The red display panel 11r includes a light-emitting element 14a and a transparent cover 14b. The light-emitting element 14a is a multiplicity of pixels arranged two-dimensionally along the XY plane on a substrate, and each pixel has a structure similar to that of a general organic EL element (not shown), and 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 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 an organic EL display similar to the red display panel 11r, and forms a still image or a moving image on a two-dimensional display surface parallel to the XY plane, and emits red image light MLr. The blue display panel 11b includes a light-emitting element 14a and a transparent cover 14b. In the blue display panel 11b, the light-emitting element 14a is a multiplicity of pixels arranged two-dimensionally along the XY plane. The light-emitting element 14a incorporated in the blue display panel 11b has a similar structure to the light-emitting element 14a incorporated in the red display panel 11r, but has a different emission wavelength from the light-emitting element 14a of the red display panel 11r.

[0016] 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 an organic EL display similar to the red display panel 11r, and forms a still image or a moving image on a two-dimensional display surface parallel to the XZ plane, and emits green image light MLg. The green display panel 11g includes a light-emitting element 14a and a transparent cover 14b. In the green display panel 11g, the light-emitting element 14a is a multiplicity of pixels arranged two-dimensionally along the XZ plane. The light-emitting element 14a incorporated in the green display panel 11g has a similar structure to the light-emitting element 14a incorporated in the red display panel 11r, but has a different emission wavelength from the light-emitting element 14a of the red display panel 11r.

[0017] The radiation angle from a pixel of red image light MLr, the radiation angle from a pixel of blue image light MLb, and the radiation angle from a pixel of green image light MLg are assumed to be within approximately 20°, and the dichroic mirrors 18r, 18b of the cross dichroic prism 18 described below are designed based on this premise, but the present invention is not limited to this.

[0018] The transparent cover 14b of 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 transparent cover 14b of 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 transparent cover 14b of 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 display panel 11g for green causes green image light MLg, which is the third image light, to enter the cross dichroic prism 18 from a third light incident surface 18ia.

[0019] The cross dichroic prism 18 is a rectangular prism-shaped member, and has three light incident surfaces 18ia, 18ib, and 18ic and one light exit surface 18o as side surfaces of the rectangular prism. The opposing first light incident surface 18ib and second light incident surface 18ic extend parallel to each other, and the opposing third light incident surface 18ia and light exit surface 18o extend parallel to each other. The opposing first light incident surface 18ib and second light incident surface 18ic extend perpendicular to the third light incident surface 18ia provided between them.

[0020] The cross dichroic prism 18 is formed by joining four right-angled triangular prisms 18a 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 are embedded at right angles to the boundaries or joints of the four right-angled triangular prisms 18a. One dichroic mirror 18r extends perpendicular to a reference direction D1 that is parallel to the YZ plane and forms an angle of 45° with the Y and -Z directions. In other words, the dichroic mirror 18r is disposed at an angle of 45° with the first entrance surface 18ib. The dichroic mirror 18r forms a surface that connects the diagonals 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 extends perpendicular to a reference direction D2 perpendicular to the reference direction D1, which is parallel to the YZ plane and at an angle of 45° to the Y and -Z directions. In other words, the dichroic mirror 18b is disposed at an angle of 45° with the second entrance surface 18ic. The dichroic mirror 18b forms a surface that connects the diagonals of the square outline when viewed from the direction of the cross axis CX of the cross dichroic prism 18.

[0021] The red image light MLr incident on the first entrance 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 optical axis AX side, and is emitted from the light exit surface 18o in the +Y direction to the outside. The blue image light MLb incident on the second entrance 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 optical axis AX side, and is emitted from the light exit surface 18o in the +Y direction to the outside. The green image light MLg incident on the third entrance surface 18ia of the cross dichroic prism 18 from the third display panel 11g for green passes through the optical axis AX side without being reflected by the dichroic mirrors 18r and 18b, and is emitted from the light exit surface 18o in the +Y 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.

[0022] In the cross dichroic prism 18, the cross axis CX extends along the intersection line of the two dichroic mirrors 18r, 18b and is parallel to the X direction. A first optical axis X1 extending from the center of the first display panel 11r for red to the cross axis CX of the cross dichroic prism 18 is parallel to the Z direction. A second optical axis X2 extending from the center of the display panel 11b for blue to the cross axis CX of the cross dichroic prism 18 is parallel to the Z direction. A third optical axis X3 extending from the center of the display panel 11g for green to the cross axis CX of the cross dichroic prism 18 is parallel to the Y direction. An optical axis AX extending from the center of the cross axis CX to the light exit surface 18o of the cross dichroic prism 18 is on an extension of the third optical axis X3 and extends parallel to the Y direction.

[0023] In the above, the optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 extends in the vertical direction, i.e., the Y direction, parallel to the light guide plate 51a. As a result, the projection optical system 20 including the light path bending prism 21 and the cross dichroic prism 18 can be arranged along the light guide plate 51a, and the height of the optical system protruding from the light guide plate 51a can be reduced. In addition, the cross axis CX of the cross dichroic prism 18 extends parallel to the light guide plate 51a. In this case, the display panels 11r, 11b, and 11g have a horizontal aspect ratio and are relatively large in size in the X direction parallel to the cross axis CX, so that the cross dichroic prism 18 can have a small cross-sectional size as viewed from the X direction, and it becomes easy to bring the cross dichroic prism 18 closer to the light guide plate 51a.

[0024] The light-path bending prism 21 of the projection optical system 20 is an optical member having a refracting and reflecting function that has a function combining a mirror and a lens, and reflects while refracting the image light ML emitted from the cross dichroic prism 18 of the image light emitting unit 11. The light-path bending prism 21 has, as optical surfaces, a first transmitting surface S1 which is a convex refracting surface, a first reflecting surface S2 which is a concave reflecting surface, a second reflecting surface S3 which is a concave reflecting surface, and a second transmitting surface S4 which is a flat refracting surface. An aperture stop 25 is provided in association with this second transmitting surface S4.

[0025] 6 is a perspective view of the appearance of the light path bending prism 21. The light path bending prism 21 has a pentagonal prism shape that is long in the X direction. In the light path bending prism 21, the inclined surface 22c that connects the first reflecting surface S2 and the second reflecting surface S3 is a connection surface CS that does not function optically, and may be a flat surface or a curved surface. The light path bending prism 21 has a pair of side surfaces 22d at both ends in the horizontal direction. The light path bending prism 21 has a relatively horizontally long outline corresponding to the aspect ratio of the display panels 11r, 11b, and 11g.

[0026] Returning to FIG. 5, the optical path bending prism 21 emits the image light ML incident from below where the image light emitting unit 11 is disposed, so as to bend it forward. The first transmitting surface S1, the first reflecting surface S2, and the second reflecting surface S3 constituting the optical path bending prism 21 have positive power. The first transmitting surface S1, the first reflecting surface S2, and the second reflecting surface S3 are asymmetric about the optical axis AX in the vertical direction parallel to the YZ plane and intersecting the optical axis AX, and are symmetric about the optical axis AX in the horizontal direction or X direction. The first transmitting surface S1, the first reflecting surface S2, and the second reflecting surface S3 are, for example, free-form surfaces. The first transmitting surface S1, the first reflecting surface S2, and the second reflecting surface S3 are not limited to free-form surfaces, and may be aspheric surfaces. The optical path bending prism 21 is made of glass or resin. The first and second reflecting surfaces S2 and S3 can be configured to reflect the image light ML by total reflection, but can also be configured to be reflecting surfaces made of a metal film or a dielectric multilayer film. In this case, a reflective film made of a single layer or multilayer film made of a metal such as Al or Ag is formed on the first and second reflecting surfaces S2 and S3 by deposition or the like. Although not shown in detail, an anti-reflection film can be formed on the first and second transmitting surfaces S1 and S4.

[0027] The reflecting surfaces S2 and S3 may be structural reflecting surfaces such as wire grids, or may be reflective polarizing films. As a structural reflecting surface, for example, a wire grid polarizer having a fine aluminum wire grid structure formed on a resin film substrate can be used. A reflective polarizing film is a multi-layered polarization separation film formed on a resin film substrate. In other words, the reflecting surface of the light path bending prism 21 can be of various types, such as a structure in which multiple metal films or dielectrics are laminated, or a structure having a fine structure on the surface.

[0028] The optical axis AX passing through the second transmitting surface S4 of the light path bending prism 21 is the optical axis on the exit side of the projection optical system 20, and extends perpendicular to the light guide plate 51a. Furthermore, the optical axis AX passing through the first transmitting surface S1 of the light path bending prism 21 and the optical axis AX passing through the second transmitting surface S4 of the light path bending prism 21 are perpendicular and perpendicular to each other. In this case, the optical path is bent by 90° before and after passing through the light path bending prism 21, and the cross dichroic prism 18 can be disposed along the light guide plate 51a. The optical axis AX on the entrance side passing through the first transmitting surface S1 of the light path bending prism 21 and the optical axis AX on the exit side passing through the second transmitting surface S4 can be made to be in a state other than perpendicular by adjusting the angular relationship of the first reflecting surface S2, the second reflecting surface S3, etc. When the angle φ between the optical axis AX passing through the first transmitting surface S1 and the optical axis AX passing through the second transmitting surface S4 is, for example, an obtuse angle, the cross dichroic prism 18 is disposed at a position shifted in the -Z direction from the light path bending prism 21 and at a position relatively far from the light guide plate 51a, so that the distance from the light guide plate 51a can be adjusted. In this way, the light path bending prism 21 not only bends the light path to substantially shorten it, but also functions like a joint with respect to the light path, so that the degree of freedom in the arrangement of the cross dichroic prism 18 can be increased.

[0029] In the optical path bending prism 21, the angle between the optical axis AX before and after reflection by the first reflecting surface S2 is α, and the angle between the optical axis AX before and after reflection by the second reflecting surface S3 is β. The angles α and β are substantially equal to prevent excessive off-axis and difficult aberration correction. In addition, the reference axis RX2 of the first reflecting surface S2 corresponding to the bisector of the optical axis AX before and after reflection by the first reflecting surface S2 and the reference axis RX3 of the second reflecting surface S3 corresponding to the bisector of the optical axis AX before and after reflection by the second reflecting surface S3 form an obtuse angle γ with respect to the inward direction. This means that the first reflecting surface S2 and the second reflecting surface S3 are arranged in a state where they face each other at an acute angle rather than being perpendicular as a whole, and it is possible for the optical axis AX incident on the first reflecting surface S2 and the optical axis AX emerging from the second reflecting surface S3 to intersect.

[0030] The optical path bending prism 21 is an optical system that is approximately telecentric with respect to the image light emitting unit 11 side, which is the object side. That is, the main rays of the image lights MLg, MLr, and MLb emitted from each part of the display surface of each display panel 11b, 11r, and 11g pass through the light entrance surfaces 18ib, 18ic, and 18ia of the cross dichroic prism 18 in a state approximately parallel to the optical axes X1, X2, and X3, and are emitted from the cross dichroic prism 18 approximately parallel to the optical axis AX. As a result, the red image light MLr, green image light MLg, and 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.

[0031] The optical path bending prism 21 collimates the image light MLg, MLr, MLb emitted from the display surface of each display panel 11b, 11r, 11g and causes the image light MLg, MLr, MLb to be collected and incident on the central region of the incident diffraction layer 51b of the light guide plate 51a. At this time, the image light MLg, MLr, MLb passes through the aperture 25a of the aperture stop 25. The aperture stop 25 suppresses the generation of stray light.

[0032] Returning to Fig. 4, in the first light guiding optical system 103a or the light guiding member 50, the incident diffraction layer 51b is a first diffraction element and is formed with a diffraction pattern that extends linearly in the vertical Y direction and repeats periodically in the horizontal X direction. The exit diffraction layer 51c is a second diffraction element and is formed with a diffraction pattern that extends linearly in the horizontal X direction and repeats periodically in the vertical Y direction. The pupil enlargement grating layer 51e is a third diffraction element and is provided on the +X side of the incident diffraction layer 51b to bend the optical path of the image light ML that is guided into the light guiding plate 51a and travels in the +X direction as a whole so that it travels in the -Y direction as a whole.

[0033] The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e diffract light in accordance with the wavelengths of the image light MLg, MLr, and MLb, and 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 incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e may be formed from a volume hologram. The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are not limited to being made of a single layer, and may be a laminate of multiple functional layers adapted to the wavelength and angle of view direction of the image light ML. The light guide plate 51a is formed of plastic or glass, and when made of plastic, it can have a thickness of, for example, about 1 mm, and when made of glass, it can have a thickness of, for example, about 0.3 to 0.4 mm.

[0034] The pupil enlargement grating layer 51e does not substantially impair the angular information of the image light ML in the left and right X direction and the 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 is interposed between the incident diffraction layer 51b and the exit diffraction layer 51c, and divides the light beam 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 beam in the horizontal direction. The pupil enlargement grating layer 51e is formed with a diffraction pattern that extends linearly in the oblique DS2 direction parallel to the XY plane and is periodically repeated in the DS1 direction parallel to the XY plane and perpendicular to the DS2 direction. The DS1 direction is rotated 45° clockwise 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 direction and the Y direction of the pattern formed on the pupil enlargement grating layer 51e is consistent with the grating period in the X direction of the pattern formed on the entrance diffraction layer 51b, and is consistent with the grating period in the Y direction of the pattern formed on the exit diffraction layer 51c. The exit diffraction layer 51c 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. 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 enlargement grating layer 51e, the exit diffraction layer 51c, etc. From the exit diffraction layer 51c, the image light ML collimated with the exit optical axis OX (see FIG. 2) perpendicular to the light guide plate 51a is emitted. The image light ML emitted from the exit diffraction layer 51c is within a range of about ±25° with respect to the exit optical axis OX. In other words, the angle of view of the first virtual image display device 100A is about 50°.

[0035] In the above description, the optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 extends in the vertical Y direction, but the optical axis AX passing through the light exit surface 18o may extend in the horizontal X direction. In this case, the optical path bending prism 21 and the cross dichroic prism 18 are arranged in the horizontal X direction along the light guide plate 51a.

[0036] In the above description, the optical axis AX passing through the second transmitting surface S4 of the light path bending prism 21 extends perpendicular to the light guide plate 51a, but the optical axis AX emerging from the light path bending prism 21 can be tilted from a perpendicular state to the light guide plate 51a. For example, by adjusting the angular relationship between the second reflecting surface S3 and the second transmitting surface S4 constituting the light path bending prism 21 shown in Fig. 6 etc., it is possible to adjust the direction of the optical axis AX emerging from the second transmitting surface S4 to be tilted in a desired direction and angle with respect to the normal direction thereof.

[0037] The display panels 11b, 11r, and 11g are not limited to organic EL, but may be replaced with display devices using LED arrays, laser arrays, quantum dot light-emitting elements, or the like.

[0038] A polarizing plate or a filter can be sandwiched between the transparent covers 14b of the display panels 11b, 11r, and 11g and the light entrance surfaces 18ib, 18ic, and 18ia of the cross dichroic prism 18.

[0039] The light guide plate 51a or the incident diffraction layer 51b does not need to be spaced apart from the second transmitting surface S4 of the light path bending prism 21, and they can be placed in close contact with each other.

[0040] 7, the shape of the light path bending prism 21 is adjusted to tilt the optical axis AX emerging from the projection optical system 20 toward the nose side or the -X side on the projection optical system 20 side or the upstream side with respect to the state perpendicular to the light guide plate 51a as a reference. This allows the emerging optical axis OX to be tilted toward the ear side or the +X side on the pupil side, and the light guide plate 51a can be rotated and tilted counterclockwise with respect to the vertical Y axis as a reference, so that the arrangement of the light guide plate 51a can be made to fit the face. As shown in the figure, in order to tilt the optical axis AX emerging from the projection optical system 20 in the Y axis direction or when viewed from above, the optical unit 100 or the image unit 30 is rotated integrally around an axis parallel to the Y axis.

[0041] The virtual image display devices 100A and 100B of the first embodiment include a first display panel 11r that emits red image light MLr as the first image light, a second display panel 11b that emits blue image light MLb as the second image light having a wavelength range different from that of the first image light, a third display panel 11g that emits green image light MLg as the third image light having a wavelength range different from that of the first image light and the second image light, a first light incident surface 18ib that allows the red image light MLr as the first image light to be incident, a second light incident surface 18ic that allows the blue image light MLb as the second image light to be incident, and a third light incident surface 18ia that allows the green image light MLg as the third image light to be incident, and the first image light, the second image light, and the third image light are incident on the first display panel 11r and the second display panel 11b. The projection optical system includes a cross dichroic prism 18 that combines image light and emits the combined image light ML from a light emission surface, a projection optical system 20 including an optical path bending prism 21 having a first transmitting surface S1 on which the image light ML from the cross dichroic prism 18 is incident, a first reflecting surface S2 that reflects the image light ML transmitted through the first transmitting surface S1, a second reflecting surface S3 that reflects the image light ML reflected by the first reflecting surface S2, and a second transmitting surface S4 that emits the image light ML reflected by the second reflecting surface S3, and light guiding optical systems 103a, 103b that are light guiding members 50 that guide the image light ML emitted from the projection optical system 20 to a pupil position PP where the eye is located.

[0042] In the above virtual image display devices 100A and 100B, the light path bending prism 21 included in the projection optical system 20 has a first transmission surface S1 on which the image light ML from the cross dichroic prism 18 is incident, a first reflection surface S2 which reflects the image light ML transmitted through the first transmission surface S1, a second reflection surface S3 which reflects the image light ML reflected by the first reflection surface S2, and a second transmission surface S4 which emits the image light ML reflected by the second reflection surface S3, so that the light path is bent in the light path bending prism 21, the light path can be increased, and it becomes easy to improve the imaging performance. In addition, as a result of being able to provide a desired angle difference between the optical axis AX incident on the light path bending prism 21 and the optical axis AX emerging from the light path bending prism 21, the degree of freedom in the arrangement of the cross dichroic prism 18 is increased, and the optical system as a whole can be made compact.

[0043] 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 common parts will be omitted.

[0044] Fig. 8 is a diagram illustrating a virtual image display device according to a second embodiment. In Fig. 8, area BR1 is a side view of the optical system constituting the first display driving unit 102a, and area BR2 is a rear view of the optical system constituting the first display driving unit 102a.

[0045] As shown in the figure, in the virtual image display device of the second embodiment, the projection optical system 20 of the first display driving unit 102a has an optical path bending prism 221 that has no power and a lens group 23. The optical path bending prism 221 has, as optical surfaces, a first transmitting surface S1 that is a flat refracting surface, a first reflecting surface S2 that is a flat reflecting surface, a second reflecting surface S3 that is a flat reflecting surface, and a second transmitting surface S4 that is a flat refracting surface. The lens group 23 has positive power as a whole and has a first lens 23a, a second lens 23b, and a third lens 23c. These lenses 23a, 23b, and 23c each have positive power. The angular relationship between the surfaces S1, S2, S3, and S4 is not limited to that shown in the figure and can be changed. This allows the direction of the optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 to be freely adjusted relative to the light guide plate 51a, and the protruding direction of the cross dichroic prism 18 from the light guide plate 51a to be freely adjusted.

[0046] The number of lenses constituting the lens group 23 is not limited to three, but may be one, two, or four or more.

[0047] Third Embodiment Hereinafter, a virtual image display device according to a third embodiment of the present invention will be described. Note that the virtual image display device of the third embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of common parts will be omitted.

[0048] Fig. 9 is a diagram for explaining a virtual image display device of the second embodiment. In Fig. 9, a region CR1 is a side view of the optical system constituting the first display drive unit 102a, and a region CR2 is a plan view of the optical system constituting the first display drive unit 102a. Fig. 10 is a perspective view of the optical system constituting the first display drive unit 102a.

[0049] As shown in the figure, in the virtual image display device of the third embodiment, the projection optical system 20 of the first display driving unit 102a is composed of only an optical path bending prism 321 having a positive power. The optical path bending prism 321 has, as optical surfaces, a first transmitting surface S1 which is a flat refracting surface, a first reflecting surface S2 which is a concave reflecting surface, a second reflecting surface S3 which is a concave reflecting surface, and a second transmitting surface S4 which is a flat refracting surface. Here, the first reflecting surface S2 and the second reflecting surface S3 have positive power. The first transmitting surface S1 of the optical path bending prism 321 is a flat surface and is joined to the light exit surface 18o of the cross dichroic prism 18. In other words, the cross dichroic prism 18 and the optical path bending prism 321 are integrated and can be treated as one block. Furthermore, by abutting the first transmitting surface S1 and the light exit surface 18o, the optical path bending prism 321 can be positioned with respect to rotation around the X-axis and rotation around the Z-axis with respect to the cross dichroic prism 18 and can be fixed with high precision, making it easier to achieve miniaturization and high precision of the first display driving unit 102a.

[0050] In the present embodiment, the image light ML is likely to pass through the cross dichroic prism 18 to the optical path bending prism 321. Therefore, when the divergence angle component of the image light ML from each pixel is large, it may be better to separate the second transmission surface S4 of the optical path bending prism 321 from the light guide plate 51a or the incident diffraction layer 51b.

[0051] [Other matters] The above-described structure is merely an example, and various modifications can be made within the scope of achieving the same function.

[0052] The optical path bending prism 21 is not limited to having a first transmitting surface S1 through which the image light ML is incident, a first reflecting surface S2 that reflects the image light ML that has transmitted through the first transmitting surface S1, a second reflecting surface S3 that reflects the image light ML reflected by the first reflecting surface S2, and a second transmitting surface S4 that emits the image light ML reflected by the second reflecting surface S3, but may also be provided with a third reflecting surface that causes the image light ML reflected by the first reflecting surface S2 to be incident on the second reflecting surface S3.

[0053] The aperture stop 25 provided in association with the second transmitting surface S4, which is the exit surface of the path-bending prism 21, is not essential.

[0054] By slightly shifting the display panels 11b, 11r, and 11g in the vertical and horizontal directions, the exit pupils of the light path bending prism 21 can be arranged differently for each color. In this case, the aperture stop 25 can be provided with a plurality of apertures 25a suitable for each color, shifted in the X direction or the Y direction. In this case, the incident diffraction layer 51b can be provided for each aperture 25a of each color, or to cover all the apertures 25a. The light guide member 50 may be a stack of a plurality of light guide plates or light guides in parallel, and for example, the first light guide plate can be used for RG and the second light guide plate can be used for BG. In this case, the first light guide plate and the second light guide plate have an area of ​​the incident diffraction layer provided so as to face the opening 25a for G color.

[0055] When the angle φ between the optical axis AX passing through the first transmitting surface S1 of the light path bending prism 21 and the optical axis AX passing through the second transmitting surface S4 of the light path bending prism 21 is an obtuse angle, the cross dichroic prism 18 tends to protrude more than the light path bending prism 21 with respect to the light guide plate 51a, but it becomes easier to secure space to accommodate the display panels 11b, 11r, 11g and their associated driving circuits.

[0056] The light-guiding member 50 is not limited to including the incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e, and may, for example, omit the pupil enlargement grating layer 51e. In this case, the incident diffraction layer 51b guides the collimated image light ML into the light-guiding plate 51a and causes it to propagate laterally, and the exit diffraction layer 51c causes the image light ML propagating laterally in the light-guiding plate 51a to be emitted toward a pupil position PP inside the image light ML.

[0057] The light guide member 50 may be a stack of multiple light guides 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.

[0058] 11, the light-guiding member 50 may be provided with an entrance diffraction layer 51b, an exit diffraction layer 51c, and a pupil enlargement grating layer 51e on the external side of a light-guiding plate 51a. In this case, the entrance diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are all reflective diffraction elements.

[0059] With regard to the optical path bending prism 221 shown in FIG. 8, among the optical surfaces constituting it, for example, the first transmitting surface S1 can be a convex refracting surface, or the first reflecting surface S2, the second reflecting surface S3, etc. can be concave reflecting surfaces.

[0060] In the first display driver 102a, the optical system combining the cross dichroic prism 18 and the optical path bending prism 21 is not limited to one that couples the image light ML to the first light guide optical system 103a, which is a diffractive light guide member, but may be one that couples the image light ML to various non-diffractive light guide plates or one that couples the image light ML to a birdbath-type light guide member. As various non-diffractive light guide plates, for example, a region in which a large number of split mirrors are embedded is provided in a single light guide plate at a location corresponding to a diffractive element to couple the image light ML.

[0061] 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).

[0062] In a specific aspect, the virtual image display device includes a first display panel that emits a first 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, a cross dichroic prism that has a first light incident surface for allowing the first image light to be incident, a second light incident surface for allowing the second image light to be incident, and a third light incident surface for allowing the third image light to be incident, and that combines the first image light, the second image light, and the third image light and emits the combined image light from the light exit surface, a projection optical system including an optical path bending prism that has a first transmitting surface for allowing the image light from the cross dichroic prism to be incident, a first reflecting surface and a second reflecting surface for reflecting the image light transmitted through the first transmitting surface, and a second transmitting surface for exiting the image light reflected at the second reflecting surface, and a light guiding member that guides the image light emitted from the projection optical system to a pupil position where the eye is positioned.

[0063] In the above virtual image display device, the light-path bending prism included in the projection optical system has a first transmitting surface through which the image light from the cross dichroic prism is incident, a first reflecting surface and a second reflecting surface that reflect the image light transmitted through the first transmitting surface, and a second transmitting surface through which the image light reflected at the second reflecting surface is emitted, so that the light path is bent in the light-path bending prism, the light path can be increased, and it is easy to improve the imaging performance. In addition, as a result of being able to provide a desired angle difference between the optical axis entering the light-path bending prism and the optical axis exiting the light-path bending prism, the degree of freedom in the arrangement of the cross dichroic prism is increased, and the optical system as a whole can be made compact.

[0064] In a specific embodiment of the virtual image display device, the optical path bending prism has a positive power. In this case, the optical path bending prism contributes to the formation of a part of the collimator, and it becomes easy to reduce the number of optical members that make up the projection optical system.

[0065] In a specific embodiment of the virtual image display device, the first reflecting surface has a positive power.

[0066] In a specific embodiment of the virtual image display device, the second reflecting surface has a positive power, which can reduce the need to incorporate a lens into the projection optical system.

[0067] In a specific embodiment of the virtual image display device, the first transmitting surface has a positive power, which can reduce the need to incorporate a lens into the projection optical system.

[0068] In a virtual image display device according to a specific embodiment, the first transmitting surface is a plane and is bonded to the light exit surface of the cross dichroic prism, which makes it easy to position the cross dichroic prism and the path bending prism.

[0069] In a specific embodiment of the virtual image display device, the projection optical system includes a lens disposed between the cross dichroic prism and the optical path bending prism.

[0070] In a specific embodiment of the virtual image display device, the optical axis passing through the first transmitting surface of the light-path bending prism and the optical axis passing through the second transmitting surface of the light-path bending prism form a perpendicular or obtuse angle. In this case, the optical path can be appropriately bent before and after passing through the light-path bending prism, and it becomes easy to arrange the cross dichroic prism close to the light guide member.

[0071] In a specific embodiment of the virtual image display device, the light guide member includes a flat light guide plate, an incident diffraction layer provided in association with the light guide plate, and an exit diffraction layer provided in association with the light guide plate at a location different from the incident diffraction layer. In this case, the light guide member can propagate image light from the incident diffraction layer to the exit diffraction layer while enlarging the pupil.

[0072] In a specific embodiment of the virtual image display device, the optical axis on the exit side of the projection optical system extends perpendicular to the light guide plate.

[0073] In a specific embodiment of the virtual image display device, the optical axis passing through the light exit surface of the cross dichroic prism extends parallel to the light guide plate. In this case, the optical path bending prism and the cross dichroic prism can be disposed along the light guide plate, and the height of the optical system protruding from the light guide plate can be reduced.

[0074] In a specific embodiment of the virtual image display device, the optical path bending prism is disposed above the cross dichroic prism.

[0075] In a specific embodiment of the virtual image display device, the cross axis of the cross dichroic prism extends parallel to the light guide plate. In this case, when the aspect ratio of the display panel is large in the direction parallel to the cross axis, it is easy to bring the cross dichroic prism close to the light guide plate.

[0076] In a specific embodiment of the virtual image display device, an aperture stop is provided in association with the second transmitting surface of the path bending prism, which makes it easier to suppress the occurrence of stray light.

[0077] In a specific aspect, the optical unit includes a first display panel that emits a first 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, a cross dichroic prism that has a first light incident surface for allowing the first image light to be incident, a second light incident surface for allowing the second image light to be incident, and a third light incident surface for allowing the third image light to be incident, and that combines the first image light, the second image light, and the third image light and emits the combined image light from the light exit surface, a projection optical system including an optical path bending prism that has a first transmitting surface for allowing the image light from the cross dichroic prism to be incident, a first reflecting surface and a second reflecting surface for reflecting the image light transmitted through the first transmitting surface, and a second transmitting surface for exiting the image light reflected at the second reflecting surface, and a light guiding member that guides the image light emitted from the projection optical system to a pupil position where the eye is positioned. [Explanation of symbols]

[0078] 10...image light generating device, 11...image light emitting unit, 11r, 11b, 11g...display panel, 18...cross dichroic prism, 18ia, 18ib, 18ic...light entrance surface, 18o...light exit surface, 18r, 18b...dichroic mirror, 20...projection optical system, 21, 221, 321...light path bending prism, 22c...inclined surface, 23...lens group, 23a, 23b, 23c...lens, 25...aperture stop, 50...light guiding member, 51a...light guiding plate, 51b...incident diffraction layer, 51c ...Emission diffraction layer, 51e...Pupillary expansion grating layer, 71...Holder, 88...Drive circuit member, 90...User terminal, 100...Optical unit, 100A, 100B...Virtual image display device, 100C...Support device, 102a, 102b...Display drive unit, 10 3a,103b...Light guide optical system, AX...Optical axis, CX...Cross axis, ML, MLg, MLr, MLb...Image light, OX...Emission optical axis, PP...Pupillary position, S1...First transmission surface, S2...First reflection surface, S3...Second reflection surface, S4...Second transmission surface, US...Wearer

Claims

1. a first display panel that emits a first 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 having a first light incident surface onto which the first image light is incident, a second light incident surface onto which the second image light is incident, and a third light incident surface onto which the third image light is incident, the cross dichroic prism combining the first image light, the second image light, and the third image light, and emitting the combined image light from a light exit surface; a projection optical system including an optical path bending prism having a first transmitting surface onto which the image light from the cross dichroic prism is incident, a first reflecting surface and a second reflecting surface which reflect the image light transmitted through the first transmitting surface, and a second transmitting surface from which the image light reflected by the second reflecting surface is emitted; a light guiding member for guiding the image light emitted from the projection optical system to a pupil position where an eye is positioned; Equipped with Virtual image display device.

2. The optical path bending prism has a positive power. The virtual image display device according to claim 1 .

3. the first reflecting surface has a positive power; The virtual image display device according to claim 2 .

4. The second reflecting surface has a positive power. The virtual image display device according to claim 3 .

5. the first transmitting surface has a positive power; The virtual image display device according to claim 2 .

6. the first transmitting surface is a plane and is bonded to the light exit surface of the cross dichroic prism; The virtual image display device according to claim 2 .

7. the projection optical system includes a lens disposed between the cross dichroic prism and the optical path bending prism; The virtual image display device according to claim 1 .

8. An optical axis passing through the first transmitting surface of the optical path bending prism and an optical axis passing through the second transmitting surface of the optical path bending prism form a perpendicular or obtuse angle. The virtual image display device according to claim 1 .

9. The light guide member includes a flat light guide plate, an incident diffraction layer provided in association with the light guide plate, and an exit diffraction layer provided in association with the light guide plate at a position different from the incident diffraction layer. The virtual image display device according to claim 1 .

10. an optical axis of the projection optical system on the exit side extends perpendicular to the light guide plate; The virtual image display device according to claim 9 .

11. The optical axis passing through the light exit surface of the cross dichroic prism is The virtual image display device according to claim 10 , extending parallel to the light guide plate.

12. The optical path bending prism is disposed above the cross dichroic prism. The virtual image display device according to claim 11 .

13. The cross axis of the cross dichroic prism extends parallel to the light guide plate. The virtual image display device according to claim 11 .

14. an aperture stop is provided in association with the second transmitting surface of the optical path bending prism; The virtual image display device according to claim 1 .

15. a first display panel that emits a first 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 having a first light incident surface onto which the first image light is incident, a second light incident surface onto which the second image light is incident, and a third light incident surface onto which the third image light is incident, the cross dichroic prism combining the first image light, the second image light, and the third image light, and emitting the combined image light from a light exit surface; a projection optical system including an optical path bending prism having a first transmitting surface onto which the image light from the cross dichroic prism is incident, a first reflecting surface and a second reflecting surface which reflect the image light transmitted through the first transmitting surface, and a second transmitting surface from which the image light reflected by the second reflecting surface is emitted; a light guiding member for guiding the image light emitted from the projection optical system to a pupil position where an eye is positioned; Equipped with Optical unit.

Images