Virtual image display device and optical unit

Abstract

To improve the light utilization efficiency of a virtual image display device.SOLUTION: A virtual image display device 100A comprises: a display panel 11a that emits video light ML; a projection optical system 20 that collimates the video light ML from the display panel 11a; and a light-guiding member 50 including a light guide plate 51a that guides the video light ML, an input diffraction optical element DI that causes the video light ML to enter the light guide plate 51a, and an output diffraction optical element DO that causes the video light ML to be emitted from the light guide plate 51a. The input diffraction optical element DI is divided into a plurality of regions RR1 to RR3, and inclination angles θ1 to θ3 of a grating in the plurality of regions RR1 to RR3 are different from each other in accordance with angles of incidence AN1 to AN3 of the video light ML.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] As an image display device that enables the observation of a virtual image, there is one that has two light guide plates and a diffractive optical element on the light entrance surface and the light exit surface of each light guide plate (Patent Document 1). In the device of Patent Document 1, a surface relief type diffraction grating is used for the diffractive optical element. The surface relief type diffraction grating has dependency on the wavelength and the incident angle, and the diffraction efficiency changes depending on the wavelength and the incident angle. Therefore, it is easy to cause color unevenness and brightness unevenness in the image. In the device of Patent Document 1, the diffraction efficiency is increased by inclining the grating surface of the diffractive optical element on the light entrance surface. In the two light guide plates, each diffractive optical element on the light entrance surface uses a grating with a different diffraction efficiency, thereby optimizing it for incident light of different wavelengths and reducing color unevenness. In addition, the diffraction efficiency of the diffractive optical element on the light exit side is changed for each region to uniform the amount of emitted light in the eye box. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-49376 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the device of Patent Document 1, image light of all angles of view is incident on the light incident surface, so the diffraction efficiency changes for each angle of view. Therefore, the device of Patent Document 1 does not provide sufficient measures to improve the brightness unevenness that occurs when the image is viewed and the brightness varies depending on the angle of view. [Means for solving the problem]

[0005] A virtual image display device or optical unit in one aspect of the present invention comprises 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 that includes an input diffractive optical element that causes the image light to enter the light guide plate, and an output diffractive optical element that emits the image light from the light guide plate, wherein the input diffractive optical element is divided into a plurality of regions, and the inclination angles of the gratings in the plurality of regions differ from one another depending on the angle of incidence of the image light. [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] 4 is a conceptual diagram illustrating the optical system of the first display driver. FIG. [Figure 6] FIG. 4 is a partial enlarged view of an input diffractive optical element. [Figure 7] FIG. 2 is a conceptual diagram illustrating the relationship between a wave vector and a lattice vector. [Figure 8] FIG. 1 is a conceptual diagram illustrating vectors of an inclined diffraction grating. [Figure 9] 4 is a conceptual diagram illustrating vectors of a diffraction grating of an input diffractive optical element according to the first embodiment. FIG. [Figure 10] FIG. 11 is a conceptual diagram illustrating an optical system in a second embodiment. [Figure 11] FIG. 13 is a conceptual diagram illustrating an optical system in a third embodiment. [Figure 12] FIG. 13 is a conceptual diagram illustrating a modified example of the optical system in the third embodiment. [Figure 13] FIG. 13 is a conceptual diagram illustrating an optical system in a fourth embodiment. [Figure 14] FIG. 13 is a conceptual diagram illustrating an optical system in a fifth embodiment. [Figure 15] FIG. 13 is a partially enlarged rear view illustrating a modified example of the input diffractive optical element. 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 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. 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 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] Referring 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 guides the collimated image light ML from the first display driver 102a (see FIG. 2) into the light guide plate 51a and propagates the image light ML in the lateral direction. The pupil enlargement grating layer 51e propagates the image light ML propagating in the lateral direction in the light guide plate 51a downward while expanding the pupil size of the image light ML. The exit diffraction layer 51c 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] FIG. 5 is a diagram 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 drive 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 a 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, and micro LED, and forms still images or moving images on a two-dimensional display surface parallel to the XY plane. 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 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 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 made of 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] The projection optical system 20 includes a first lens 21a and a second lens 21b as a lens element 21 that collimates, i.e., parallelizes, 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. Although the details will be described later, the incident diffraction layer 51b has a grating with an inclination angle according to the incident angle of the image light ML. Here, the incident angle of the image light ML is the angle of the image light ML corresponding to each angle of view of the image. In other words, the incident angle of the image light ML is the incident angle of the standard incident light from a certain image point, and is the incident angle of the image light ML at which the main ray passes through the center of a predetermined region (specifically, the regions RR1 to RR3 of the incident diffraction layer 51b).

[0017] 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.

[0018] The exit pupil Lx of the projection optical system 20 is disposed at a position shifted from the grating plane SS corresponding to the surface of the incident diffraction layer 51b. This causes the input position of the image light ML to the incident diffraction layer 51b to change according to the incident angle of the image light ML. In this embodiment, the exit pupil Lx is disposed between the lens element 21 of the projection optical system 20 and the incident diffraction layer 51b.

[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 entrance diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are formed on the first total reflection surface 51i of the light guiding plate 51a.

[0021] The incident diffraction layer 51b is an input diffractive optical element DI that folds back the image light ML emitted from the display panel 11a of the image light generating device 10 and incident via the lens element 21 of the projection optical system 20 so as to propagate inside the light guide member 50. The image light ML 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 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. The pupil enlargement grating layer 51e does not substantially lose 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 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 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 DS1 direction parallel to the XY plane and repeats periodically in the DS2 direction parallel to the XY plane and perpendicular to the DS1 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 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 entrance diffraction layer 51b, and 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 DO, which 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 exited. The image light ML exited from the exit diffraction layer 51c is 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°. The exit diffraction layer 51c is formed of a diffraction pattern that extends linearly in the horizontal X direction and repeats periodically 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 or diffraction grating. The surface relief type diffraction grating 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 or diffraction grating 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] FIG. 6 is a partially enlarged view of the incident diffraction layer 51b. In FIG. 6, the region AR1 is a partially enlarged perspective view of the incident diffraction layer 51b. The region AR2 is a partially enlarged rear view of the incident diffraction layer 51b. The region AR3 is a partially enlarged side view of the incident diffraction layer 51b. Here, in a cross section of the incident diffraction layer 51b passing through an orthogonal axis perpendicular to the surface of the light guide plate 51a, a rotation in a first direction with respect to the orthogonal axis is a positive angle, and a rotation in a second direction opposite to the first direction with respect to the orthogonal axis is a negative angle. Specifically, in the region AR3, the inclination angles θ1 to θ3 of the grating DG are set to 0° with respect to the z-axis corresponding to the orthogonal axis, and a rotation in the +x direction is a + direction, and a rotation in the -x direction is a - direction (the same applies to the following figures). The positive and negative angles are defined similarly for the angles of incidence AN1 to AN3 of the image light ML. The inclination angles θ1 to θ3 of the grating DG of the incident diffraction layer 51b are expressed in a range of -90° to +90°. The inclination angle with respect to the incident angle of 0° may or may not be 0°.

[0026] The incident diffraction layer 51b has an inclined grating structure. The incident diffraction layer 51b is divided into a plurality of regions RR1 to RR3, and the inclination angles θ1 to θ3 of the grating DG in the plurality of regions RR1 to RR3 are different from each other according to the incident angles AN1 to AN3 of the image light ML. The inclination angles θ1 to θ3 change according to the position of the exit pupil Lx with respect to the incident diffraction layer 51b. In the example of FIG. 5, when the exit pupil Lx is disposed inside the incident diffraction layer 51b, the inclination angles θ1 and θ3 of the grating DG in the outer regions RR1 and RR3 in the incident diffraction layer 51b as seen from the projection optical system 20 are inwardly inclined with respect to the center of the incident diffraction layer 51b. That is, the inclination angles θ1 and θ3 of the grating DG in the outer regions RR1 and RR3 are different in positive and negative. Moreover, the inclination angles θ1 to θ3 of the grating DG increase from the incident diffraction layer 51b side toward the exit diffraction layer 51c side in the horizontal direction or the X direction.

[0027] The image light ML having the incident angles AN1 to AN3 is incident on the regions RR1 to RR3, respectively. In each of the regions RR1 to RR3, the inclination angles θ1 to θ3 of the grating DG are set so as to efficiently diffract the image light ML having the incident angles AN1 to AN3 inputted to the regions RR1 to RR3, that is, so as to optimize the diffraction efficiency of the diffracted light of a predetermined order (for example, +1st order diffracted light). Here, with respect to the grating vector K of the grating DG in each of the regions RR1 to RR3, the component in the propagation direction of the light guide plate 51a (specifically, the x component) is the same. That is, the components of the grating vector K along the surface of the light guide plate 51a in each of the regions RR1 to RR3 are equal to each other. Therefore, the components of the grating period (pitch) P along the surface of the light guide plate 51a in each of the regions RR1 to RR3 are equal to each other. The grating height of the pattern formed on the incident diffraction layer 51b is constant or approximately constant. The inclined lattice structure may include, in a part of its region, a binary lattice structure in which the inclination angle is 0°.

[0028] It is preferable that the boundaries between the regions RR1 to RR3 are adjusted so that the diffraction efficiency of the diffracted light of a predetermined order, the diffraction efficiency of which is optimized in the regions RR1 to RR3, is not reduced.

[0029] As described above, the exit pupil Lx of the projection optical system 20 is disposed at a position shifted from the grating surface SS of the incident diffraction layer 51b (see FIG. 5). In this embodiment, the position of the exit pupil Lx of the projection optical system 20 is disposed in front of the light guide plate 51a, so that the input position of the image light ML to the light guide plate 51a varies depending on the incident angles AN1 to AN3. In other words, the projection optical system 20 has an exit pupil Lx such that the input position to the light guide plate 51a varies depending on the incident angles AN1 to AN3. The incident diffraction layer 51b is divided into a plurality of regions RR1 to RR3 according to the input positions corresponding to the incident angles AN1 to AN3, and is an inclined diffraction grating in which different grating conditions corresponding to the incident angles AN1 to AN3 are set for each of the regions RR1 to RR3.

[0030] When the incidence angles AN1 to AN3 of the image light ML have the relationship AN3>NA2>AN1, the inclination angles θ1 to θ3 of the grating DG have the relationship θ3>θ2>θ1. In other words, as the incidence angle of the image light ML increases, the optimal inclination angle of the corresponding grating DG, i.e., the inclination angle at which the diffraction efficiency is high, also increases.

[0031] Hereinafter, the principle of optimizing the diffraction efficiency of the incident diffraction layer 51b will be described with reference to Figs. 7 to 9. Fig. 7 is a conceptual diagram for explaining the relationship between wave vectors and grating vectors. Fig. 8 is a conceptual diagram for explaining the vectors of an inclined diffraction grating. Fig. 9 is a conceptual diagram for explaining the vectors of the diffraction grating of the incident diffraction layer 51b of this embodiment. Note that, for convenience of explanation, in Fig. 9, the gratings DG of all of the regions RR1 to RR3 are inclined, but there may be regions that are not inclined (see Fig. 6).

[0032] As shown in FIG. 7, when considering the diffraction angle α of the grating DG formed on the substrate BK, the explanation will be given using the incident light wave vector k and the grating vector K. Each vector is expressed by the wave number k (k=2π / λ) of light with wavelength λ and the grating vector K (K=2π / P) of the grating DG with grating period P. Here, the wavelength λ is the wavelength of the incident light IL in air. The refractive index of the substrate BK is N. The diffracted light wave vector Nk of the diffracted light DL corresponds to a line segment that is connected by the intersection VX of the x component of the grating vector K and the circumference CC2 in the substrate BK with the wave number Nk as the radius, and the incident reference point AO of the incident light IL, when the grating vector K is drawn from the incident light wave vector k of the incident light IL in air on the circumference CC1 with the radius of the wave number k. The direction of the diffracted light wave vector Nk starts from the incident reference point AO. The above explanation was given for the +1st order diffraction DD1, but the same applies to the -1st order diffraction DD2 and other orders of diffraction.

[0033] Consider the case where the grating DG is inclined with respect to the light guide plate 51a as shown in FIG. 8. In this case, the grating vector K' has an inclination. Consider the diffracted light DL in this inclined grating DG. The diffraction angle α is determined by the x-component K'x of the grating vector K'. Therefore, when the x-component K'x of the grating vector K' shown in FIG. 8 is the same as the x-component Kx of the grating vector K shown in FIG. 7, the diffraction angle α shown in FIG. 8 coincides with the diffraction angle α shown in FIG. 7. Since the grating vector K' is inclined, the end point EN1 of the diffracted light wave vector Nk of the +1st order diffraction DD1 and the end point EN2 of the grating vector K' approach each other. This phenomenon means that the phase mismatch amount PN1 becomes smaller, which means that the diffraction efficiency becomes higher. On the other hand, for the -1st order diffraction DD2, the phase mismatch amount PN2 becomes larger, so the diffraction efficiency becomes lower. In other words, when the inclined grating DG is used, the diffraction efficiency can be increased only for a predetermined order. In addition, the phase mismatch amounts PN1 and PN2 change depending on the incident angle of the incident light IL. Therefore, by changing the inclination angle of the grating DG according to the incident angle, the diffraction efficiency for the incident angle of the image light ML can be optimized. Here, since the only component that affects the diffraction angle α is the x-component K'x of the grating vector K', even if the inclination angles θ1 to θ3 are changed by the regions RR1 to RR3 of the incident diffraction layer 51b shown in Fig. 4, as long as the x-component K'x of the grating vector K' is consistent, the grating vectors of the incident diffraction layer 51b, pupil enlargement grating layer 51e, and exit diffraction layer 51c are closed as a whole, and a compensation relationship can be maintained.

[0034] As shown in FIG. 9, the grating DG of this embodiment has different inclination angles θ1 to θ3 in the regions RR1 to RR3. In this embodiment, based on the above principle, the x-components K1'x to K3'x of the grating vectors K1' to K3' of the regions RR1 to RR3 are matched to optimize the inclination angles θ1 to θ3 of the grating DG so that the diffraction efficiency is improved for the angles of incidence AN1 to AN3. This increases the diffraction efficiency of each of the regions RR1 to RR3, improving the light utilization efficiency. Furthermore, the grating DG of this embodiment has uniform brightness of the images corresponding to the regions RR1 to RR3, compared to a binary type diffraction grating (see FIG. 7) having a uniform concave-convex structure, and therefore improves brightness unevenness.

[0035] 9, in consideration of optimizing the diffraction efficiency, the absolute value of the difference PN between a resultant vector GK, which is the sum of the incident light wave vector k (k1 to k3) of the incident light IL to the incident diffraction layer 51b and the lattice vector K' (K1' to K3') of the incident diffraction layer 51b, and the diffracted light wave vector Nk (Nk1 to Nk3) of the diffracted light DL of the incident diffraction layer 51b, is a predetermined value or less. The difference PN corresponds to the amount of phase mismatch shown in FIG.

[0036] Hereinafter, the light guide of the image light ML and the formation of a virtual image using the light guide member 50 will be described with reference to FIG. 4 and the like. The image light ML from the image light generating device 10 is incident on the incident diffraction layer 51b through the light guide plate 51a, and is diffracted in an angular direction corresponding to the grating period P of the pattern formed on the incident diffraction layer 51b, and is propagated while being totally reflected in the light guide plate 51a, and proceeds in the +X direction as a whole. At this time, the incident diffraction layer 51b diffracts diffracted light of a predetermined order in each of the regions RR1 to RR3. The image light ML propagated in the +X direction in the light guide plate 51a is diffracted by the pupil enlargement grating layer 51e, and the overall optical path is bent in the -Y direction, and shifted to a position in the +X direction that reflects the number of reflections until it is diffracted by the pupil enlargement grating layer 51e. In other words, the pupil enlargement grating layer 51e has a role of enlarging the horizontal pupil size, which corresponds to the width of the light beam in the horizontal or X direction in which the image light ML is incident on the eye EY. The image light ML propagating through the light guide plate 51a in the −Y direction as a whole via the pupil enlargement lattice layer 51e is diffracted by the exit diffraction layer 51c and exits toward the eye EY. The image light ML exiting from the exit diffraction layer 51c reproduces the angular state before it is exited from the image light generating device 10 and enters the light guide member 50 in the X and Y directions, while the pupil size is expanded in the X and Y directions. In other words, the light guide member 50 expands the pupil size vertically and horizontally while maintaining the image information. This allows the wearer US to observe a virtual image generated by the image light ML even if the position of the eye EY is shifted.

[0037] The virtual image display devices 100A, 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, and a light-guiding member 50 that includes a light-guiding plate 51a that guides the image light ML, an input diffractive optical element DI that causes the image light ML to enter the light-guiding plate 51a, and an output diffractive optical element DO that emits the image light ML from the light-guiding plate 51a, where the input diffractive optical element DI is divided into a plurality of regions RR1 to RR3, and the inclination angles θ1 to θ3 of the gratings in the plurality of regions RR1 to RR3 differ from one another depending on the incidence angles AN1 to AN3 of the image light ML.

[0038] In the virtual image display devices 100A and 100B, the grating inclination angles θ1 to θ3 in the regions RR1 to RR3 of the input diffractive optical element DI are different from each other according to the incidence angles AN1 to AN3 of the image light ML, so that the diffraction efficiency of a predetermined order is optimized in the regions RR1 to RR3, and the light utilization efficiency can be improved. Also, the luminance uniformity can be improved in the images corresponding to the regions RR1 to RR3.

[0039] 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.

[0040] 10, in the virtual image display device 100A of this embodiment, the exit pupil Lx of the projection optical system 20 is disposed on the opposite side of the projection optical system 20 across the light guide member 50, that is, outside the incident diffraction layer 51b. That is, the position of the exit pupil Lx may be disposed behind the light guide plate 51a, and the input position may be changed for each of the incidence angles AN1 to AN3. In this embodiment, although the incidence angles AN1 to AN3 become smaller, the virtual image display device 100A can be made smaller.

[0041] In this embodiment, since the position of the exit pupil Lx is disposed deeper than the light guide plate 51a, the gratings of the regions RR1 to RR3 of the incident diffraction layer 51b are inverted with respect to the center of the grating from the gratings shown in FIG. 5 and the like. In this embodiment, the image light ML with the incident angle AN3 is incident on the region RR1, the image light ML with the incident angle AN2 is incident on the region RR2, and the image light ML with the incident angle AN1 is incident on the region RR3. In this case, the size of each region RR1 to RR3 and the inclination angle of the grating are adjusted according to the incident angles AN3 to AN1 of the image light ML. In the example of FIG. 10, when the exit pupil Lx is disposed outside the incident diffraction layer 51b, the inclination angles of the gratings of the outer regions RR1 and RR3 are inclined outward with respect to the center of the incident diffraction layer 51b in the incident diffraction layer 51b as viewed from the projection optical system 20. In addition, the inclination angle of the grating becomes smaller from the incident diffraction layer 51b side to the exit diffraction layer 51c side in the horizontal direction or X direction.

[0042] 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 the common parts will be omitted.

[0043] 11, in a virtual image display device 100A of the present embodiment, the image light generation device 10 of a first display drive unit 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.

[0044] 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 parallel to the YZ plane, and emits red image light MLr.

[0045] 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 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.

[0046] 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 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. That is, the red image light MLr, which is the first image light, and the blue image light MLb, which is the second image light, have different wavelength ranges. That is, the green image light MLg, which is the third image light, and the red image light MLr, which is the first image light, and the blue image light MLb, which is the second image light, have different wavelength ranges.

[0047] 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.

[0048] 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.

[0049] The cross dichroic prism 18 is formed by joining four right-angled triangular prisms made of glass or the like so that the edges of the right angles 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 entrance 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 entrance 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.

[0050] 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 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 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 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 entrance surface 18ia of the cross dichroic prism 18 from the third display panel 11g for green passes through the dichroic mirrors 18r and 18b toward the projection optical system 20 without being reflected, 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.

[0051] 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.

[0052] 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 rays of the image light MLg, MLr, and MLb emitted from each part of the light emitting element 14a, which is 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 axis AX, thereby entering the cross dichroic prism 18 and being 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.

[0053] The arrangement of the display panels 11b, 11r, and 11g can be changed as appropriate.

[0054] 12, the virtual image display device 100A of this embodiment may have the same configuration as that of the second embodiment. Specifically, the exit pupil Lx is disposed outside the entrance diffraction layer 51b located opposite the projection optical system 20.

[0055] [Fourth embodiment] Hereinafter, a virtual image display device according to a fourth embodiment of the present invention will be described. Note that the virtual image display device of the fourth embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of common parts will be omitted.

[0056] As shown in FIG. 13, in the virtual image display device 100A of this embodiment, the incident diffraction layer 51b is disposed on the external side, that is, the +Z side, of the light guide plate 51a. Specifically, the incident diffraction layer 51b is disposed on the surface of the light guide plate 51a opposite to the projection optical system 20, that is, on the second total reflection surface 51o which is the back surface 51p of the light guide plate 51a. In this case, although not shown, the exit diffraction layer 51c and the pupil enlargement grating layer 51e are also disposed on the external side of the light guide 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. The more the incident diffraction layer 51b is separated from the exit pupil Lx, the easier it becomes to divide the regions RR1 to RR3. In this case, the number of divided regions can be increased.

[0057] Fifth embodiment Hereinafter, a virtual image display device according to a fifth embodiment of the present invention will be described. Note that the virtual image display device of the fifth embodiment is a partial modification of the virtual image display device of the first embodiment, and a description of common parts will be omitted.

[0058] 14, in the virtual image display device 100A of the present embodiment, the first light guiding optical system 103a has a plurality of light guiding plates 51a stacked in parallel. Specifically, the first light guiding optical system 103a includes a first light guiding member 151 and a second light guiding member 152 that diffracts image light ML in a wavelength range different from that of the first light guiding member 151. The first and second light guiding members 151 and 152 each include a light guiding plate 51a, an incident diffraction layer 51b, an exit diffraction layer 51c, and a pupil enlargement grating layer 51e.

[0059] The first light guiding member 151 and the second light guiding member 152 are optimized according to the wavelength range of the image light ML. The first and second light guiding members 151 and 152 can correspond to three colors, for example, RBG. The diffraction efficiency and uniformity of the brightness can be further improved by allocating the colors to the light guiding plates 51a of the first and second light guiding members 151 and 152. Specifically, the first light guiding member 151 has a grating period or the like of the incident diffraction layer 51b set so that blue light and green light propagate therethrough. The second light guiding member 152 has a grating period or the like of the incident diffraction layer 51b set so that red light propagates therethrough. The first light guiding member 151 has an incident diffraction layer 51b divided into regions RR1 to RR3. The second light guiding member 152 has an incident diffraction layer 51b divided into regions RR4 to RR6. The regions RR1 to RR6 of the first light guiding member 151 and the second light guiding member 152 have different inclination angles, etc. The regions RR1 to RR6 may have different sizes or positions. The incident diffraction layer 51b may have the boundaries of the regions RR1 to RR6 shifted or may have other regions added.

[0060] Alternatively, three light guide members may be provided corresponding to the three colors.

[0061] [Other matters] The above-described structure is merely an example, and various modifications can be made within the scope of achieving the same function.

[0062] As shown in FIG. 15, the entrance diffraction layer 51b is not limited to a circular shape, but can be appropriately changed to another shape, such as a rectangular shape.

[0063] The inclination angles θ1 to θ3 of the grating DG in each of the regions RR1 to RR3 of the incident diffraction layer 51b can be adjusted appropriately. Also, the order of the diffracted light DL that increases the diffraction efficiency can be adjusted appropriately.

[0064] The grating structure of the incident diffraction layer 51b is not limited to an inclined grating, and may include a binary grating having no inclination as described above, or may include a blade grating.

[0065] The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e may be formed of 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 made by laminating a plurality of functional layers adapted to the wavelength of the image light ML, etc.

[0066] 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.

[0067] 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).

[0068] 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, an input diffractive optical element that causes the image light to enter the light guide plate, and a light guide member that includes an output diffractive optical element that emits the image light from the light guide plate, wherein the input diffractive optical element is divided into a plurality of regions, and the inclination angles of the gratings in the plurality of regions differ from one another depending on the angle of incidence of the image light.

[0069] In the virtual image display device, the inclination angles of the gratings in the multiple regions of the input diffractive optical element are different from each other depending on the incident angle of the image light, so that the diffraction efficiency of a predetermined order in the region is optimized, thereby improving the light utilization efficiency and the luminance uniformity in the image corresponding to the region.

[0070] In a virtual image display device according to a specific embodiment, the components of the lattice vector in each of the multiple regions along the surface of the light guide plate are equal to each other.

[0071] In a specific embodiment of a virtual image display device, in a cross section of the input diffractive optical element passing through an orthogonal axis perpendicular to the surface of the light guide plate, rotation in a first direction relative to the orthogonal axis is a positive angle, and rotation in a second direction opposite to the first direction relative to the orthogonal axis is a negative angle, and in multiple regions, the tilt angle becomes larger as the incident angle becomes larger.

[0072] In a specific embodiment of the virtual image display device, the exit pupil of the projection optical system is disposed at a position shifted from the grating surface of the input diffractive optical element, and in this case, the input position of the image light to the input diffractive optical element changes according to the angle of incidence of the image light.

[0073] In a specific embodiment of the virtual image display device, the exit pupil is disposed between the projection optical system and the input diffractive optical element, and the inclination angle of the grating in the outer region of the input diffractive optical element as seen from the projection optical system is inwardly inclined with respect to the center of the input diffractive optical element. In this case, it is possible to handle a large angle of incidence.

[0074] In a specific embodiment of the virtual image display device, the exit pupil is disposed outside the input diffractive optical element located opposite the projection optical system, and the inclination angle of the grating in the outer region of the input diffractive optical element as seen from the projection optical system is inclined outward with respect to the center of the input diffractive optical element. In this case, the angle of incidence becomes smaller, but the device can be made smaller.

[0075] 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.

[0076] In a specific embodiment, the virtual image display device includes a first light guide member that is a light guide member, and a second light guide member that diffracts image light in a wavelength range different from that of the first light guide member. In this case, it is possible to optimize the diffraction efficiency according to the wavelength range of the image light.

[0077] In a specific embodiment of the virtual image display device, the display panel is an organic light emitting diode.

[0078] In a specific embodiment, the optical unit comprises 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, an input diffractive optical element that causes the image light to enter the light guide plate, and a light guide member that includes an output diffractive optical element that emits the image light from the light guide plate, wherein the input diffractive optical element is divided into a plurality of regions, and the inclination angles of the gratings in the plurality of regions differ from one another depending on the angle of incidence of the image light. [Explanation of symbols]

[0079] 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...drive circuit member, 90...user terminal, 100...optical unit, 100A, 100B...virtual image display device, 100C ...Support device, 102a, 102b...Display drive unit, 103a, 103b...Light guide optical system, AX...Optical axis, DE...Pupil expansion diffractive optical element, DG...Grating, DI...Input diffractive optical element, DL...Diffracted light, DO...Output diffractive optical element, EY...Eye, IL...Input light, ML...Image light, OX...Emitted optical axis, P...Grating period, PN1, PN2...Amount of phase mismatch, PP...Pupil position, RR1 to RR6...Area, SS...Grating surface, 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 guiding member including a light guiding plate that guides the image light, an input diffractive optical element that causes the image light to enter the light guiding plate, and an output diffractive optical element that causes the image light to exit from the light guiding plate; Equipped with the input diffractive optical element is divided into a plurality of regions, and the inclination angles of the gratings in the plurality of regions are different from one another depending on the angle of incidence of the image light; Virtual image display device.

2. In the plurality of regions, components of the lattice vector in each region along the surface of the light guide plate are equal to each other. The virtual image display device according to claim 1 .

3. In a cross section of the input diffractive optical element passing through an orthogonal axis perpendicular to a surface of the light guide plate, a rotation in a first direction with respect to the orthogonal axis is defined as a positive angle, and a rotation in a second direction opposite to the first direction with respect to the orthogonal axis is defined as a negative angle, In the plurality of regions, the inclination angle is larger as the incidence angle is larger. The virtual image display device according to claim 1 .

4. an exit pupil of the projection optical system is disposed at a position shifted from a grating surface of the input diffractive optical element; The virtual image display device according to claim 1 .

5. the exit pupil is disposed between the projection optical system and the input diffractive optical element; In the input diffractive optical element as viewed from the projection optical system, the inclination angle of the grating in the outer region is inclined inward with respect to the center of the input diffractive optical element. The virtual image display device according to claim 4 .

6. the exit pupil is disposed outside the input diffractive optical element opposite the projection optical system; When viewed from the projection optical system, the inclination angle of the grating in the outer region is inclined outward with respect to the center of the input diffractive optical element. The virtual image display device according to claim 4 .

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. A first light guiding member which is the light guiding member; A second light guiding member that diffracts the image light in a wavelength range different from that of the first light guiding member. The virtual image display device according to claim 1 .

9. The display panel is an organic light emitting diode. 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 guiding member including a light guiding plate that guides the image light, an input diffractive optical element that causes the image light to enter the light guiding plate, and an output diffractive optical element that causes the image light to exit from the light guiding plate; Equipped with the input diffractive optical element is divided into a plurality of regions, and the inclination angles of the gratings in the plurality of regions are different from one another depending on the angle of incidence of the image light; Optical unit.

Images