Light guide plate and display device

Abstract

[Problem] To provide a light guide plate with good color balance. [Solution] This light guide plate comprises a light guide substrate and at least one light-deflecting part formed on the light guide substrate. The light-deflecting part has a light entry part that in-couples light having a prescribed viewing angle to the light guide plate, a light exit part that allows the light in-coupled by the light entry unit to exit the light guide plate, and a splitting deflection part disposed between the light entry part and the light exit part to split the light into at least a first light portion and a second light portion. The first light portion has a greater proportion of blue light and a smaller proportion of red light than the second light portion. The propagation angle of blue light at the center of the viewing angle of the first light portion is equal to or greater than the propagation angle of green light at the center of the viewing angle of the second light portion, or is equal to or greater than the propagation angle of red light at the center of the viewing angle of the second light portion.

Description

Light guide plate and display device

[0001] The present disclosure relates to a light guide plate and a display device.

[0002] BACKGROUND ART Conventionally, in display devices such as AR (Augmented Reality) glasses and VR (Virtual Reality) glasses, a light guide plate that guides light having a predetermined viewing angle that forms an image has been known.

[0003] For example, U.S. Pat. No. 1,130,7429 discloses a technology for guiding different color components in two directions in a light guide plate having a single-layer light guide substrate and guiding red, green, and blue light having a viewing angle, in order to widen the viewing angle.

[0004] Furthermore, International Publication No. 2022 / 147866 discloses a configuration in which a light guide plate has a single-layer light guide substrate and guides red, green, and blue light having a viewing angle, and a light-shielding region is provided between two intermediate diffraction gratings that guide different color components in two directions to prevent light mixing.

[0005] However, U.S. Pat. No. 1,307,429 and WO 2022 / 147866 do not disclose the color balance of the light guided by the light guide plate.

[0006] The present disclosure aims to provide a light guide plate with good color balance.

[0007] In one aspect of the present disclosure, there is provided a light guide plate having a light guide substrate and one or more light deflection units formed on the light guide substrate, wherein the light deflection units include a light incident unit that incouples light having a predetermined viewing angle into the light guide plate, a light exit unit that causes the light incoupled by the light incident unit to exit the light guide plate, and a separation deflection unit disposed between the light incident unit and the light exit unit that separates the light into at least a first light portion and a second light portion, wherein the first light portion has a higher proportion of blue light and a lower proportion of red light than the second light portion, and the propagation angle of the blue light at the center of the viewing angle of the first light portion is equal to or greater than the propagation angle of the green light at the center of the viewing angle of the second light portion, or is equal to or greater than the propagation angle of the red light at the center of the viewing angle of the second light portion.

[0008] The present disclosure makes it possible to provide a light guide plate with good color balance.

[0009] 1 is a schematic diagram showing a display device having a light guide plate according to an embodiment; FIG. 1 is a schematic cross-sectional view along line II-II in FIG. 1; FIG. 2 is a diagram for explaining an NA diagram; FIG. 3 is a diagram showing the relationship between the critical angle and the propagation angle; FIG. 4 is a diagram showing an NA diagram of light guided by the light guide plate according to an embodiment; FIG. 5 is a diagram showing how blue light is guided in the light guide plate according to an embodiment; FIG. 6 is a diagram showing an NA diagram of blue light in the light guide plate according to an embodiment; FIG. 7 is a diagram showing how green light is guided in the light guide plate according to an embodiment; FIG. 8 is a diagram showing an NA diagram of green light in the light guide plate according to an embodiment; FIG. 9 is a diagram showing how red light is guided in the light guide plate according to an embodiment; FIG. 10 is a diagram showing an NA diagram of red light in the light guide plate according to an embodiment; FIG. 11 is a schematic diagram showing a diffraction grating of a light entrance portion of the light guide plate according to an embodiment; FIG. 12 is a schematic diagram showing a diffraction grating of a light exit portion of the light guide plate according to an embodiment; FIG. 13 is a schematic diagram showing a diffraction grating of a separation deflection portion of the light guide plate according to an embodiment; FIG. 14 is a schematic diagram showing a diffraction grating of an intermediate deflection portion of the light guide plate according to an embodiment; FIG. 15 is a schematic diagram showing a diffraction grating of an optical duplication portion of the light guide plate according to an embodiment; FIG. 16 is a schematic diagram showing a reference two-dimensional diffraction grating of a light deflection portion of the light guide plate according to an embodiment. FIG. 1 is a diagram showing the configuration of a light guide plate according to Example 2. FIG. 2 is a diagram showing how blue light is guided in the light guide plate according to Example 2. FIG. 3 is a diagram showing an NA diagram of blue light in the light guide plate according to Example 2. FIG. 4 is a diagram showing how green light is guided in the light guide plate according to Example 2. FIG. 5 is a diagram showing an NA diagram of green light in the light guide plate according to Example 2. FIG. 6 is a diagram showing how red light is guided in the light guide plate according to Example 2. FIG. 7 is a diagram showing an NA diagram of red light in the light guide plate according to Example 2. FIG. 8 is a diagram showing the light guide efficiency of blue light by the light guide plates according to Examples 1 and 2. FIG. 9 is a diagram showing the light guide efficiency of green light by the light guide plates according to Examples 1 and 2. FIG. 10 is a diagram showing the light guide efficiency of red light by the light guide plates according to Examples 1 and 2. FIG. 11 is a diagram showing the light guide efficiency of blue light by the light guide plate according to Example 1. FIG. 12 is a diagram showing the light guide efficiency of blue light by the light guide plate according to Example 2. FIG. 13 is a schematic diagram showing a reference two-dimensional diffraction grating of a light deflection unit in the light guide plate according to Example 2. FIG. 14 is a diagram showing the configuration of a light guide plate according to Example 3. FIG. 15 is a diagram showing an NA diagram of blue light in the light guide plate according to Example 3.FIG. 10 is a diagram showing an NA diagram of green light in the light guide plate according to Example 3. FIG. 11 is a diagram showing an NA diagram of red light in the light guide plate according to Example 3. FIG. 12 is a schematic diagram showing a diffraction grating of a light entrance portion in the light guide plate according to Example 3. FIG. 13 is a schematic diagram showing a diffraction grating of a light exit portion in the light guide plate according to Example 3. FIG. 14 is a schematic diagram showing a diffraction grating of a separation deflection portion in the light guide plate according to Example 3. FIG. 15 is a schematic diagram showing a diffraction grating of an intermediate deflection portion in the light guide plate according to Example 3. FIG. 16 is a schematic diagram showing a diffraction grating of an optical duplication portion in the light guide plate according to Example 3. FIG. 17 is a schematic diagram showing a reference two-dimensional diffraction grating of an optical deflection portion in the light guide plate according to Example 3. FIG. 18 is a diagram showing the configuration of a light guide plate according to Example 4. FIG. 19 is a diagram showing an NA diagram of blue light in the light guide plate according to Example 4. FIG. 19 is a diagram showing an NA diagram of green light in the light guide plate according to Example 4. FIG. 19 is a diagram showing an NA diagram of red light in the light guide plate according to Example 4. FIG. 19 is a diagram showing the configuration of a light guide plate according to Example 5. FIG. 20 is a diagram showing how blue light is guided in the light guide plate according to Example 5. FIG. 21 is a diagram showing an NA diagram of blue light in the light guide plate according to Example 5. FIG. 10 is a diagram showing how green light is guided in the light guide plate according to Example 5. FIG. 11 is a diagram showing an NA diagram of green light in the light guide plate according to Example 5. FIG. 12 is a diagram showing how red light is guided in the light guide plate according to Example 5. FIG. 13 is a diagram showing an NA diagram of red light in the light guide plate according to Example 5. FIG. 14 is a schematic diagram showing a diffraction grating of a light incident portion in the light guide plate according to Example 5. FIG. 15 is a schematic diagram showing a diffraction grating of a light exit portion in the light guide plate according to Example 5. FIG. 16 is a schematic diagram showing a diffraction grating of an intermediate deflection portion in the light guide plate according to Example 5. FIG. 17 is a schematic diagram showing a diffraction grating of an optical duplication portion in the light guide plate according to Example 5. FIG. 18 is a diagram showing the configuration of a light incident portion in the light guide plate according to Example 6. FIG. 19 is a diagram showing how blue light is guided in the light guide plate according to Example 6. FIG. 19 is a first diagram showing an NA diagram of blue light in the light guide plate according to Example 6. FIG. 20 is a second diagram showing an NA diagram of blue light in the light guide plate according to Example 6. FIG. 21 is a diagram showing how green light is guided in the light guide plate according to Example 6. FIG. 22 is a diagram showing an NA diagram of green light in the light guide plate according to Example 6. 10A and 10B are diagrams illustrating how red light is guided in the light guide plate according to Example 6. FIG. 10A is a diagram illustrating an NA diagram of red light in the light guide plate according to Example 6.FIG. 10 is a schematic diagram showing a diffraction grating of a first light incident portion in a light guide plate according to Example 6. FIG. 11 is a schematic diagram showing a diffraction grating of a second light incident portion in a light guide plate according to Example 6. FIG. 12 is a schematic diagram showing a diffraction grating of a light output portion in a light guide plate according to Example 6. FIG. 13 is a schematic diagram showing a diffraction grating of a first intermediate deflection portion in a light guide plate according to Example 6. FIG. 14 is a schematic diagram showing a diffraction grating of a second intermediate deflection portion in a light guide plate according to Example 6. FIG. 15 is a schematic diagram showing a diffraction grating of a light duplication portion in a light guide plate according to Example 6. FIG. 16 is a diagram showing an example of the configuration of a light guide plate according to Example 7. FIG. 17 is a diagram showing how blue light is guided in a light guide plate according to Example 7. FIG. 18 is a diagram showing an NA diagram of blue light in a light guide plate according to Example 7. FIG. 19 is a diagram showing how green light is guided in a light guide plate according to Example 7. FIG. 19 is a diagram showing an NA diagram of green light in a light guide plate according to Example 7. FIG. 19 is a diagram showing how red light is guided in a light guide plate according to Example 7. FIG. 19 is a diagram showing an NA diagram of red light in a light guide plate according to Example 7. FIG. 19 is a diagram showing another example of the configuration of a light guide plate according to Example 7. FIG. 19 is a diagram showing how green light is guided in a light guide plate according to another example of Example 7. FIG. 10 is a diagram showing an NA diagram of green light in a light guide plate according to another example of Example 7. FIG. 11 is a diagram showing the configuration of a light guide plate according to Example 8. FIG. 12 is a diagram showing how blue light is guided in the light guide plate according to Example 8. FIG. 13 is a diagram showing an NA diagram of blue light in the light guide plate according to Example 8. FIG. 14 is a diagram showing how green light is guided in the light guide plate according to Example 8. FIG. 15 is a diagram showing an NA diagram of green light in the light guide plate according to Example 8. FIG. 16 is a diagram showing how red light is guided in the light guide plate according to Example 8. FIG. 17 is a diagram showing the configuration of a light guide plate according to Example 9. FIG. 18 is a diagram showing how blue light is guided in the light guide plate according to Example 9. FIG. 19 is a diagram showing an NA diagram of blue light in the light guide plate according to Example 9. FIG. 19 is a diagram showing how green light is guided in the light guide plate according to Example 9. FIG. 19 is a diagram showing how red light is guided in the light guide plate according to Example 9. FIG. 19 is an NA diagram of green light in the light guide plate according to Example 9. FIG. 19 is a diagram showing how red light is guided in the light guide plate according to Example 9.

[0010] Hereinafter, embodiments for carrying out the present disclosure will be described in detail with reference to the drawings. However, the embodiments shown below are examples of light guide plates and display devices for embodying the technical ideas of the embodiments of the present disclosure, and are not limited to the following. Note that the size, positional relationship, etc. of components shown in each drawing may be exaggerated for clarity. In each drawing, the same components are assigned the same reference numerals, and duplicate explanations will be omitted as appropriate.

[0011] In the drawings shown below, directions may be expressed using a Cartesian coordinate system having an X-axis, a Y-axis, and a Z-axis. In the X direction along the X-axis, the direction in which the arrow points is referred to as the +X direction, and the direction opposite to the +X direction is referred to as the -X direction. In the Y direction along the Y-axis, the direction in which the arrow points is referred to as the +Y direction, and the direction opposite to the +Y direction is referred to as the -Y direction. In the Z direction along the Z-axis, the direction in which the arrow points is referred to as the +Z direction, and the direction opposite to the +Z direction is referred to as the -Z direction. In the description of the specification, the surface on which the light deflection section is formed on the light guide substrate of the light guide plate according to the embodiment is referred to as the XY plane, and the normal direction to the surface on which the light deflection section is formed is referred to as the Z direction. However, the above directional expressions merely describe the relationship between relative positions, orientations, directions, etc., and do not necessarily coincide with the relationship between the light guide plate according to the embodiment and the display device when in use.

[0012] In the NA diagrams used in the description of the embodiments, only the minimum number of arrows representing numerical aperture transitions are shown to clarify the description of the embodiments. Therefore, numerical aperture transitions other than those indicated by the arrows shown in each NA diagram are also possible. For example, in the light output section of the waveguide plate according to the embodiment, there are many numerical aperture transitions, so only the minimum number of arrows representing numerical aperture transitions are shown, and other arrows are omitted.

[0013] In the present specification and claims, the term "planar view" refers to viewing a target object from the normal direction of the surface on which the light deflection unit is formed on the light guide substrate of the light guide plate according to the embodiment. However, the surface is not limited to being flat and may have irregularities or curvature, and the normal direction of the surface may be a direction facing the entire surface. "Along the axis" includes not only a state parallel to the axis but also a state tilted at ±10 degrees or less from the axis. Furthermore, "perpendicular" includes not only a state at 90 degrees but also a state deviated at ±10 degrees or less from 90 degrees. Furthermore, "arranged" is not limited to direct contact, but also includes indirect arrangement, for example, via another member.

[0014] [Embodiments] <Display Device Having Light Guide Plate According to Embodiment> A light guide plate according to an embodiment and a display device having the light guide plate will be described with reference to FIGS. 1 to 11 .

[0015] FIG. 1 is a schematic diagram showing a display device 100 having a light guide plate 10 according to an embodiment. In FIG. 1, the lower diagram is a schematic enlarged diagram of region A in the upper diagram. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a diagram illustrating an NA (Numerical Aperture) diagram. Note that an NA diagram is a diagram that visually and easily shows the direction in which light is guided in a light guide plate, or whether or not total reflection occurs. FIG. 4 is a diagram showing the relationship between the critical angle and the propagation angle.

[0016] Fig. 5 is a diagram showing an NA diagram of light guided by the light guide plate 10. Fig. 6 is a diagram showing how blue light LB is guided in the light guide plate 10. Fig. 7 is a diagram showing an NA diagram of blue light LB in the light guide plate 10. Fig. 8 is a diagram showing how green light LG is guided in the light guide plate 10. Fig. 9 is a diagram showing an NA diagram of green light LG in the light guide plate 10. Fig. 10 is a diagram showing how red light LR is guided in the light guide plate 10. Fig. 11 is a diagram showing an NA diagram of red light LR in the light guide plate 10.

[0017] 1, the display device 100 includes a light guide plate 10 and a projector 120. In the example shown in FIG. 1, the display device 100 also includes an eyeglass-type support 110 including a frame 101 and temples 102.

[0018] The light guide plate 10 is disposed inside the frame 101. The projector 120 is disposed inside the temple 102. Light projected from the projector 120 enters the light guide plate 10 and exits from the light exit portion 122. The display device 100 shown in FIG. 1 is a device that displays an image by causing light constituting an image projected from the projector 120 to enter the light guide plate 10 and exit from the light exit portion 122. An observer can observe an image displayed by the display device 100 while wearing the eyeglass-type support body 110. The display device 100 is, for example, so-called see-through AR glasses or VR glasses that display an image superimposed on the observer's field of vision of the outside world.

[0019] 1 , the light guide plate 10 is disposed, in plan view, inside the frame 101 for the viewer's left eye in the eyeglass-type support 110. The projector 120 is disposed inside the left temple 102. However, the light guide plate 10 may also be disposed inside the frame 101 for the viewer's right eye, or may be disposed inside the frames 101 for both the right and left eyes. The projector 120 may also be disposed inside the right temple 102, or inside the frame 101.

[0020] As shown in FIGS. 1 and 2 , the light guide plate 10 includes a light guide substrate 11 and one or more light deflection units 12 formed on the light guide substrate 11. The light deflection unit 12 includes a light incident unit 121 that incouples light L having a predetermined viewing angle into the light guide plate 10 and a light exit unit 122 that causes the light L incoupled by the light incident unit 121 to exit the light guide plate 10. The light deflection unit 12 also includes a separation deflection unit 123 that is disposed between the light incident unit 121 and the light exit unit 122 and separates the light L into a first light portion L1 and a second light portion L2. In the example shown in FIG. 1 , the light deflection unit 12 also includes an intermediate deflection unit 124 that is disposed in the light guide path of the first light portion L1, and a light duplication unit 125 that duplicates the incident light L. The light duplication unit 125 is disposed between the light exit unit 122 and the separation deflection unit 123. The light L is light that constitutes the image projected from the projector 120 .

[0021] The light guide substrate 11 includes a first main surface 111 and a second main surface 112 located opposite the first main surface 111. The light guide substrate 11 guides light L by total reflection by each of the first main surface 111 and the second main surface 112. In the light guide plate 10, blue light LB included in the blue (B) wavelength band, green light LG included in the green (G) wavelength band, and red light LR included in the red (R) wavelength band enter the single-layer light guide substrate 11 and exit from the light guide substrate 11. The blue wavelength band is, for example, 440 nm or more and 480 nm or less. The green wavelength band is, for example, 510 nm or more and 550 nm or less. The red wavelength band is, for example, 610 nm or more and 650 nm or less.

[0022] In the examples shown in FIGS. 1 and 2 , a portion of the red light LR is represented by a solid arrow, a portion of the green light LG is represented by a dashed-dotted arrow, and a portion of the blue light LB is represented by a two-dot dashed arrow. The thickness of the arrow indicates the amount of light of each color. Each arrow represents a light ray at the center of the viewing angle, and the direction of the arrow schematically represents the direction of travel of the light ray. In this embodiment, the first light portion L1 contains a larger proportion of blue light LB and a smaller proportion of red light LR than the second light portion L2. Therefore, in the example shown in FIG. 1 , the first light portion L1 contains blue light LB and green light LG, but does not contain red light LR. The two-dot dashed arrow representing the blue light LB is thicker than the dashed-dotted arrow representing the green light LG. On the other hand, the second light portion L2 contains a larger proportion of red light LR and green light LG and a smaller proportion of blue light LB than the first light portion L1. 1 and 2, the solid arrows indicating red light LR and the dashed-dotted arrows indicating green light LG are thicker than the dashed-two-dotted arrows indicating blue light LB. Note that the relationship between the line type of the arrows representing light and the color of light, as well as the relationship between the thickness of the arrows representing light and the amount of light, is the same in the subsequent figures.

[0023] 1 and 2 , each of the light incident section 121, the light exit section 122, the separating deflection section 123, the intermediate deflection section 124, and the light duplication section 125 is a diffraction grating. These diffraction gratings are formed on the first main surface 111. The light incident section 121 incouples the incident light L into the light-guiding substrate 11 by diffracting all viewing angle components of the incident light L. The light exit section 122 diffracts the light L to emit it out of the light-guiding substrate 11.

[0024] The separating / deflecting unit 123, the intermediate deflecting unit 124, and the optical duplication unit 125 each diffract the light L incoupled by the light input unit 121 and guide it to the light output unit 122. In the example shown in FIG. 1 , the intermediate deflecting unit 124 guides the first-order diffracted light of the first light portion L1 to the light output unit 122. The optical duplication unit 125 guides the zeroth-order diffracted light and the first-order diffracted light of the second light portion L2 to the light output unit 122. On the other hand, the intermediate deflecting unit 124 does not guide the second light portion L2. The optical duplication unit 125 guides the second light portion L2 and the first light portion L1, which is the remaining small amount of light not guided to the intermediate deflecting unit 124. Note that the angle φ shown in FIG. 1 is the angle formed by the light guide directions of the first light portion L1 and the second light portion L2 at the center of the viewing angle of the separated light portion L1 and the second light portion L2.

[0025] 3 shows an NA diagram having an NAx axis and an NAy axis orthogonal to the NAx axis. The NAx axis corresponds to the numerical aperture NA in the X direction. The NAy axis corresponds to the numerical aperture NA in the Y direction. The donut-shaped total internal reflection light-guiding region T between the inner and outer circles is a region where light can be guided by total internal reflection within the light-guiding substrate 11. The inner circle represents the NA at the critical angle. The outer circle represents the NA at the maximum propagation angle.

[0026] FIG. 4 shows the light guiding state within the light-guiding substrate 11. The numerical aperture NA is expressed as n × sin θ. The angle of incidence of light guided by total reflection at the interface is defined as the propagation angle θprop. In this specification, the numerical aperture NA may be simply referred to as "NA." The critical angle at which total reflection begins to occur at the interface is defined as θc. The inner circle in the NA diagram is the NA when θprop = θc. If the numerical aperture NA in this case is 1, i.e., NA = 1, the inner circle has a radius of 1. On the outer circle, θprop is 90 degrees. The radius of the outer circle is determined by the refractive index n of the light-guiding substrate 11. The higher the refractive index of the light-guiding substrate 11 used, the wider the outer circle becomes, and the wider the angular range over which light can be guided by total reflection becomes.

[0027] In this embodiment, the propagation angle θprop of the blue light LB at the center of the viewing angle of the first light portion L1 is equal to or greater than the propagation angle θprop of the green light LG at the center of the viewing angle of the second light portion L2, or equal to or greater than the propagation angle of the red light LR at the center of the viewing angle of the second light portion L2. The propagation angles θprop of the blue light LB, the green light LG, and the red light LR can be adjusted by, for example, adjusting the orientation or pitch of the diffraction grating that constitutes the separation deflection unit 123.

[0028] In FIG. 5 , the approximate squares shown within the inner circles of the NA diagram represent the viewing angle of light L incident on the light guide plate 10 or the viewing angle of light L exiting from the light exit portion. Furthermore, the approximate squares shown within the total reflection light guide region T represent the viewing angle of light guided by the light guide plate 10. The approximate squares shown with thin solid lines represent the viewing angle resulting from the superposition of red light LR, green light LG, and blue light LB. The approximate squares shown with solid lines represent the viewing angle of red light LR. The approximate squares shown with dashed dotted lines represent the viewing angle of green light LG. The approximate squares shown with dashed two dotted lines represent the viewing angle of blue light LB. The positions of the approximate squares representing the viewing angles vary depending on the wavelength. The correspondence between the line types of the approximate squares in the NA diagram and the colors of light is the same in the NA diagrams shown below.

[0029] 5, the center of each of the approximate squares representing the viewing angles corresponds to the center of the viewing angles of the red light LR, the green light LG, and the blue light LB. Ｂ represents the NA at the maximum propagation angle corresponding to the blue light LB. The outer circle MX shown by the solid line R represents the NA at the maximum propagation angle corresponding to the red light LR. This means that in the light guide substrate 11, the refractive index for the blue light LB is higher than the refractive index for the red light LR. It also means that, among the approximate squares representing the viewing angle, light corresponding to part or all of the approximate squares located outside the outer circle of the NA diagram is not guided by the light guide plate 10.

[0030] 5 also shows the transition of the NA state by the reference two-dimensional diffraction grating. The reference two-dimensional diffraction grating is a virtual two-dimensional diffraction grating having a first grating pitch P1 having a length represented by the vector (X, Y) = (p1x, p1y) in a first direction and a second grating pitch P2 having a length represented by the vector (X, Y) = (p2x, p2y) in a second direction different from the first direction. Here, the directions and lengths of the first grating pitch P1 and the second grating pitch P2 correspond to the directions and lengths of two sides of the reference two-dimensional unit cell. When λ is the wavelength and m1o and m2o are integers, ΔNAx, which is the transition of the NA state in the NAx axis direction by the reference two-dimensional diffraction grating, is given by the following equation (1). Also, ΔNAy, which is the transition of the NA state in the NAy axis direction, is given by the following equation (2). ΔNAx=m1o·λ·{p2y / (p1x·p2y-p1y·p2x)}+m2o·λ·{-p1y / (p1x·p2y-p1y·p2x)} (1) ΔNAy=m1o·λ·{-p2x / (p1x·p2y-p1y·p2x)}+m2o·λ·{p1x / (p1x·p2y-p1y·p2x)} (2) m1o and m2o mean the diffraction orders in the reference two-dimensional diffraction grating when the light incident on the light guide plate 10 is used as a reference. In Fig. 5, the NA states transitioned by the reference two-dimensional diffraction grating when the light incident on the light guide plate 10 is used as a reference are represented as (m1o, m2o).

[0031] In the example shown in FIG. 5 , when the first grating pitch P1 has a length and direction of p1x = 355 (nm) and p1y = 0 (nm), and the second grating pitch P2 has a length and direction of p2x = 0 (nm) and p2y = 355 (nm), the direction of the arrow AR along the NAx axis is the direction in NA space corresponding to the first direction in real space, i.e., the reciprocal lattice vector of P1, and corresponds to (ΔNAx, ΔNAy) when (m1o, m2o) = (1, 0). In the example of FIG. 5 , ΔNAy = 0, so the direction is along the NAx axis. Furthermore, the direction of the arrow BR along the NAy axis is the direction in NA space corresponding to the second direction in real space, i.e., the reciprocal lattice vector of P2, and corresponds to (ΔNAx, ΔNAy) when (m1o, m2o) = (0, 1). In the example of FIG. 5 , ΔNAx = 0, so the direction is along the NAy axis. The reference two-dimensional diffraction grating, the first direction, and the second direction in the real space will be described later with reference to FIG.

[0032] In this embodiment, it is preferable that the NA state of the light guided by the light guide plate 10 is only that which has been transitioned by the reference two-dimensional diffraction grating during light guiding. It is also preferable that the NA state of the light guided by the light guide plate 10 is only that which is expressed by m1o=0,±1 and m2o=0,±1 in formulas (1) and (2).

[0033] In this embodiment, the propagation angle θprop of the blue light LB at the center of the viewing angle of the first light portion L1 is equal to or greater than the propagation angle θprop of the green light LG at the center of the viewing angle of the second light portion L2, or equal to or greater than the propagation angle of the red light LR at the center of the viewing angle of the second light portion L2. The propagation angles θprop of the blue light LB, the green light LG, and the red light LR can be adjusted by, for example, adjusting the orientation or pitch of the diffraction grating that constitutes the separation deflection unit 123.

[0034] 6 to 11 are diagrams illustrating in detail how blue light LB, green light LG, and red light LR are guided by the light guide plate 10. Note that in Figs. 6, 8, and 10, which show how light is guided by the light guide plate 10, only the light guide plate 10 arranged inside the frame 101 in the display device 100 shown in Fig. 1 is shown. This also applies to the subsequent diagrams showing how light is guided by the light guide plate.

[0035] As shown in FIG. 6 , blue light LB is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Of the blue light LB that enters the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 enters the intermediate deflection unit 124. Of the blue light LB that enters the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 enters the light exit unit 122. On the other hand, of the blue light LB that enters the separation / deflection unit 123, the light that is transmitted through the separation / deflection unit 123 without being diffracted by the separation / deflection unit 123 enters the optical duplication unit 125. In the example shown in FIG. 6 , the amount of blue light LB that enters the optical duplication unit 125 is less than the amount of blue light LB that enters the intermediate deflection unit 124. Of the blue light LB incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 is incident on the light emitting unit 122. The blue light LB incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and is emitted from the light guide plate 10.

[0036] Figure 7 shows the guiding of blue light LB in the real space shown in Figure 6 in an NA diagram, in other words, in wavenumber space. The arrows in Figure 7 correspond to vectors representing the transition of the NA state due to light guiding in the light deflection unit 12. If the wavelength of light incident on the diffraction grating is λ and the grating pitch of the diffraction grating is d, the length of the arrow corresponding to the grating vector is expressed as λ / d. Furthermore, the direction of the arrow corresponding to the grating vector corresponds to the periodic axis of the diffraction grating. However, strictly speaking, the direction of this arrow corresponds to the periodic axis of the diffraction grating in the case of a one-dimensional diffraction grating, and corresponds to the direction of the reciprocal lattice vector of the two grating vectors that form the sides of the two-dimensional diffraction grating in the case of a two-dimensional diffraction grating, and depends on the diffraction direction.

[0037] In the example shown in Fig. 7, arrow W1 represents the transition of the NA state by the light input unit 121. Arrow W2 represents the transition of the NA state by the light output unit 122. Arrow W3 represents the transition of the NA state by the separation deflection unit 123. Arrow W4 represents the transition of the NA state by the intermediate deflection unit 124. Arrow W5 represents the transition of the NA state by the optical duplication unit 125. The meanings represented by the arrows in the NA diagram shown in Fig. 7 are the same as those in the NA diagrams shown below.

[0038] Of the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to blue light LB incoupled into light guide plate 10 are all located within total internal reflection light guide region T. Therefore, blue light LB corresponding to these approximate squares is guided by light guide plate 10 at all viewing angles.

[0039] As shown in FIG. 8 , the green light LG is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Of the green light LG that enters the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 enters the intermediate deflection unit 124. Of the green light LG that enters the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 enters the light exit unit 122. On the other hand, of the green light LG that enters the separation / deflection unit 123, the light that is transmitted through the separation / deflection unit 123 without being diffracted by the separation / deflection unit 123 enters the optical duplication unit 125. In the example shown in FIG. 8 , the amount of green light LG that enters the optical duplication unit 125 is greater than the amount of green light LG that enters the intermediate deflection unit 124. Of the green light LG incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 is incident on the light emitting unit 122. The green light LG incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and is emitted from the light guide plate 10.

[0040] In the NA diagram shown in Fig. 9, of the multiple approximate squares representing the viewing angles of green light LG, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, light of all viewing angles of green light LG corresponding to these approximate squares is guided by light guide plate 10. On the other hand, portions of the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are each located outside the outer circle of the NA diagram. Therefore, light of some viewing angles of green light LG corresponding to these approximate squares is not guided by light guide plate 10.

[0041] 10 , the red light LR is incoupled by the light incident unit 121 and then incident on the separation / deflection unit 123. In the example shown in FIG. 10 , the red light LR incident on the separation / deflection unit 123 is hardly diffracted by the separation / deflection unit 123 and passes through the separation / deflection unit 123 to enter the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 enters the light exit unit 122. The red light LR incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10.

[0042] In the NA diagram shown in Fig. 11 , of the multiple approximate squares representing the viewing angles of the red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by the light guide plate 10 at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by the light guide plate 10 at all viewing angles.

[0043] <Effects of the Light Guide Plate 10> For example, in a light guide plate utilizing optical deflection such as diffraction, when blue, green, and red light are guided by a single-layer light guide substrate, the propagation angles of the light of each color propagating within the light guide substrate differ depending on the diffraction angle. Specifically, considering the transition of NA states with the same viewing angle and the same diffraction order, the propagation angles of the light of each color are the largest for red, the next largest for green, and the smallest for blue. Furthermore, when the light of each color is guided the same distance in the in-plane direction of the light guide substrate, for example, in the XY plane, the propagation distance of the light of each color is the longest for blue, the next longest for green, and the shortest for red, depending on the propagation angle. The number of total reflections at each of the first and second main surfaces of the light guide plate is also the highest for blue, the second highest for green, and the lowest for red.

[0044] The longer the light propagation distance, the greater the attenuation of the light amount due to light absorption in the light guide plate. Furthermore, the greater the number of times of total reflection at each of the first and second main surfaces of the light guide plate, the greater the attenuation of the light amount due to scattering at each of the first and second main surfaces. Furthermore, in materials that are transmissive to visible light, short-wavelength light is generally more likely to be absorbed and scattered than long-wavelength light. For these reasons, in a light guide plate having a single-layer light guide substrate, the attenuation of blue light is greatest, the attenuation of green light is next greatest, and the attenuation of red light is least.

[0045] On the other hand, light propagating within the light-guiding substrate is output to the outside of the light-guiding substrate by the light output portion. Generally, when light is diffracted by the same diffraction grating in a range where the grating height of the diffraction grating is lower than the perfect diffraction condition, short-wavelength light has a higher diffraction efficiency than long-wavelength light. Therefore, when red, green, and blue light propagate in parallel, the blue light exits the light-guiding substrate in the fastest and largest amount, followed by green light, and red light exits the light-guiding substrate the slowest. Similarly, in the optical duplication portion, short-wavelength light has a higher diffraction efficiency than long-wavelength light. Therefore, when red, green, and blue light propagate in parallel, the blue light transitions in the fastest and largest amount, followed by green light, and red light transitions in the slowest NA state. Therefore, when red, green, and blue light propagate in parallel, the blue light attenuates the fastest, followed by green light, and red light attenuates the slowest. As a result, in a single-layer light guide substrate, when white light incident from a light incident portion is guided and emitted, the color tends to take on blue, green, and red in that order as it moves away from the light incident portion.

[0046] As described above, in a single-layer light guide substrate that guides blue, green, and red light, the difference in the amount of light among the guided colors can cause large intensity variations among the colors, or a difference between the intensity distribution of the incident light and the intensity distribution of the exiting light, resulting in poor color balance. Therefore, a light guide plate with good color balance is desired. Here, "good color balance" means at least one of the following: when the light guide efficiency at a certain viewing angle is defined as the quotient of the incident intensity divided by the intensity emitted from the light exit portion that can be received by the eye, there is little variation in light guide efficiency among the colors at the same viewing angle; and there is little variation in light guide efficiency among the colors at different viewing angles.

[0047] In this embodiment, the propagation angle θprop of the blue light LB at the center of the viewing angle of the first light portion L1 is equal to or greater than the propagation angle θprop of the green light LG at the center of the viewing angle of the second light portion L2, or equal to or greater than the propagation angle θprop of the red light LR at the center of the viewing angle of the second light portion L2. For example, the first light portion L1 separated by the separation deflection unit 123 takes any one of the NA states (m1o, m2o) = (1,1), (-1,1), (1,-1), or (-1,-1) in the above equations (1) and (2). Therefore, the propagation angle θprop of the blue light LB at the center of the viewing angle is equal to or greater than the propagation angle θprop of the green light LG at the center of the viewing angle where the second light portion L2 takes any one of the NA states (m1o, m2o) = (1,0), (-1,0), (0,1), or (0,-1). Alternatively, in the second light portion L2, it is equal to or greater than the propagation angle θprop of the red light LR at the center of the viewing angle in which the NA state (m1o, m2o) is any one of (1, 0), (−1, 0), (0, 1), and (0, −1).

[0048] Because the propagation angle θprop is large, the number of total reflections of the blue light LB at the center of the viewing angle of the first light portion L1 within the light guide substrate 11 is smaller than the number of total reflections of the green light LG at the center of the viewing angle of the second light portion L2 when propagating the same distance in the in-plane direction within the light guide substrate 11. Alternatively, the number of total reflections of the blue light LB at the center of the viewing angle of the first light portion L1 within the light guide substrate 11 is smaller than the number of total reflections of the red light LR. This reduces the attenuation of the blue light LB, and the intensities of the blue light LB, green light LG, and red light LR become closer to each other, resulting in improved color balance. As described above, in this embodiment, each light portion propagates while assuming the NA states of the different diffraction orders of the reference two-dimensional diffraction grating, thereby providing a light guide plate 10 with good color balance. Furthermore, the display device 100, having the light guide plate 10, can display images with good color balance.

[0049] The color balance of the light guide plate 10 can be adjusted, for example, by adjusting the orientation or pitch of the diffraction grating that constitutes the separation deflection section 123, and by adjusting the propagation angle θprop of the blue light LB, the propagation angle θprop of the green light LG, and the propagation angle θprop of the red light LR.

[0050] The angle φ formed by the light guide directions of the first light portion L1 and the second light portion L2 separated by the separation deflection unit 123 at the viewing angle centers is 20 degrees or more and 70 degrees or less, preferably 30 degrees or more and 60 degrees or less, more preferably 35 degrees or more and 55 degrees or less, and even more preferably 40 degrees or more and 50 degrees or less. When the angle φ satisfies this condition, the propagation angle θprop of the blue light LB can be easily increased.

[0051] As described above, the vector representing the first grating pitch P1 is (X, Y) = (p1x, p1y), the vector representing the second grating pitch P2 is (X, Y) = (p2x, p2y), and m is a natural number. Also, m1 = 0, ±1, ±2, and m2 = 0, ±1, ±2. In this embodiment, based on a reference two-dimensional diffraction grating having a first grating pitch P1 in a first direction and a second grating pitch P2 in a second direction, all of the light deflection sections 12 formed on the light guide plate 10 are preferably diffraction gratings that satisfy either the following condition (a) or (b): (a) A one-dimensional diffraction grating having only a grating pitch Pm given by the following formula: Pm = m / [[m1·{p2y / (p1x·p2y-p1y·p2x)}+m2·{-p1y / (p1x·p2y-p1y·p2x)}] ２ +[m1・{-p2x / (p1x・p2y-p1y・p2x)}+m2・{p1x / (p1x・p2y-p1y・p2x)}] ２ 〕 ０．５ (b) a two-dimensional diffraction grating having a first grating pitch m·P1 in the first direction and a second grating pitch m·P2 in the second direction;

[0052] For example, if the grating pitch of the one-dimensional diffraction grating is not the above-mentioned grating pitch Pm, unintended stray light generated during light guide by the light guide plate 10 may cause image blurring due to diffracted light, for example, an image at a shifted angle. When the grating pitch of the one-dimensional diffraction gratings in all light deflection units 12 is the above-mentioned grating pitch Pm, image blurring due to diffracted light is reduced. The same applies when the grating pitch of the two-dimensional diffraction grating is not m·P1 in the first direction and m·P2 in the second direction. In this way, in this embodiment, image blurring can be reduced by propagating light guided by the light guide plate 10 only in the NA state transitioned by the reference two-dimensional diffraction grating.

[0053] Furthermore, in this embodiment, it is preferable that the light incident portion 121 is a diffraction grating that satisfies either the following condition (c) or (d). By satisfying this condition, propagation of light in unintended directions or to unnecessary orders due to diffraction is suppressed. As a result, the waveguiding efficiency is increased. (c) A one-dimensional diffraction grating having a minimum unit grating with a grating pitch Pm that can be expressed as (m1, m2) = (1, 0), (-1, 0), (0, 1), or (0, -1). (d) A two-dimensional diffraction grating having a first grating pitch m·P1 in a first direction and a second grating pitch m·P2 in a second direction.

[0054] In this embodiment, the separating / deflecting unit 123 is preferably a diffraction grating that satisfies either the following condition (e) or (f). By satisfying this condition, propagation of light in unintended directions or to unnecessary orders due to diffraction can be reduced, thereby achieving higher waveguiding efficiency. (e) If the diffraction orders of light incident on the separating / deflecting unit 123 converted to a reference two-dimensional diffraction grating are (m1in, m2in), and the diffraction orders of light output from the separating / deflecting unit 123 converted to a reference two-dimensional diffraction grating are (m1out, m2out), then (m1, m2) = (m1out - m1in, m2out - m2in), and the one-dimensional diffraction grating has a minimum unit grating with a grating pitch Pm given by the combination of (m1in, m2in) = (±1, 0), (0, ±1), and (m1out, m2out) = (±1, -1), (±1, 1). (f) A two-dimensional diffraction grating having a first grating pitch m·P1 in a first direction and a second grating pitch m·P2 in a second direction.

[0055] In this embodiment, the viewing angle of the light L does not change when the light L is guided. For example, in Figures 7, 9, and 11, the approximate squares representing the viewing angle always have the same size regardless of the transition of the NA state, and the viewing angle of the light L does not change when the light L is guided. Since the viewing angle of the light L does not change when the light L is guided, the design of the light guide plate 10 is easier.

[0056] In this embodiment, the light deflection unit 12 includes an intermediate deflection unit 124 disposed on the light guide path of the first light portion L1. The first light portion L1 does not include red light LR at any viewing angle immediately before entering the light output unit 122. For example, in FIGS. 10 and 11 , the first light portion L1 separated by the separation deflection unit 123 does not include red light LR, and therefore the first light portion L1 does not include red light LR at any viewing angle immediately before entering the light output unit 122. Because the first light portion L1 does not include red light LR at any viewing angle, the red light LR in the second light portion L2 and the blue light LB in the first light portion L1 are guided along different paths. This allows the color balance of the red light LR and the blue light LB to be individually adjusted.

[0057] The number of intermediate deflection units 124 is not limited to one, and may be at least one. In the examples shown in Figures 10 and 11, the first light portion L1 separated by the separation deflection unit 123 does not contain the red light LR, but this is not limiting. For example, the first light portion L1 may contain the red light LR when separated by the separation deflection unit 123, and then be deflected by the intermediate deflection unit 124 so that the first light portion L1 does not contain the red light LR at any viewing angle immediately before entering the light emitting unit 122.

[0058] In this embodiment, the light deflection unit 12 has a function of duplicating the incident light L. This allows the eyebox to be enlarged in the display device 100 having the light guide plate 10.

[0059] <Configuration of Light Deflection Unit 12> The configuration of the light deflection unit 12 of the light guide plate 10 will be described in detail with reference to Figs. 12 to 16A and 16B. Fig. 12 is a schematic diagram showing the diffraction grating of the light entrance unit 121 of the light guide plate 10. Fig. 13 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10. Fig. 14 is a schematic diagram showing the diffraction grating of the separation deflection unit 123 of the light guide plate 10. Fig. 15 is a schematic diagram showing the diffraction grating of the intermediate deflection unit 124 of the light guide plate 10. Fig. 16 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10. Fig. 17 is a schematic diagram showing the reference two-dimensional diffraction grating BC of the light deflection unit 12 of the light guide plate 10.

[0060] In the example shown in Figure 12, the light incident section 121 is a diffraction grating with a one-dimensional lattice shape having a plurality of line-and-space patterns extending in the Y direction. The grating pitch of the light incident section 121 is, for example, 355 nm in a direction parallel to the X axis. For ease of explanation, a diffraction grating with a one-dimensional lattice shape will be referred to as a one-dimensional grating hereinafter. The minimum unit grating UC represents the smallest unit grating that constitutes the light incident section 121. The reference two-dimensional diffraction grating BC is a diffraction grating having two sides with the reference two-dimensional diffraction grating pitch PS1 and the reference two-dimensional diffraction grating pitch PS2.

[0061] In this embodiment, the light entrance portion 121 is a one-dimensional grating. With this configuration, the light guide plate 10 can reduce the propagation of light in unintended directions due to diffraction, compared to when a two-dimensional diffraction grating is used, and therefore can achieve higher waveguiding efficiency.

[0062] In the example shown in Fig. 13, the light emitting section 122 is a diffraction grating with a two-dimensional lattice shape in which the unit lattice is a square lattice. For ease of explanation, a diffraction grating with a two-dimensional lattice shape will hereinafter be referred to as a two-dimensional lattice. The minimum unit lattice UC represents the smallest unit lattice that constitutes the light emitting section 122. Because it is a two-dimensional lattice, it has two lattice pitches, for example, a square lattice with a pitch of 355 nm in the direction parallel to the X axis and 355 nm in the direction parallel to the Y axis, forming an angle of 90 degrees.

[0063] 14, the separation deflection unit 123 is a one-dimensional grating having a plurality of line-and-space patterns extending in the X direction. The minimum unit lattice UC represents the smallest unit lattice that constitutes the separation deflection unit 123. As it is a one-dimensional grating, it has one grating pitch, and is, for example, a one-dimensional grating having a pitch of 355 nm in the direction parallel to the Y axis.

[0064] 15, the intermediate deflection unit 124 is a one-dimensional lattice having a plurality of line-and-space patterns extending in the X direction. The minimum unit lattice UC represents the smallest unit lattice that constitutes the intermediate deflection unit 124. As it is a one-dimensional lattice, it has one lattice pitch, and is, for example, a one-dimensional lattice having a pitch of 177.5 nm in the direction parallel to the Y axis.

[0065] 16, the optical duplication unit 125 is a diffraction grating in which a two-dimensional lattice with a square unit lattice is tilted at 45 degrees with respect to the X-axis. The minimum unit lattice UC represents the smallest unit lattice that constitutes the optical duplication unit 125. As it is a two-dimensional lattice, it has two grating pitches, for example, 355 / √2 nm in a direction tilted at +45 degrees from the X-axis and 355 / √2 nm in a direction tilted at -45 degrees from the X-axis, forming a square lattice with an angle of 90 degrees.

[0066] The light output unit 122, the separating deflection unit 123, the intermediate deflection unit 124, and the optical duplication unit 125 can also be expressed as follows using the reference two-dimensional diffraction grating BC shown in Fig. 17. That is, the reference two-dimensional diffraction grating BC is a square lattice with a grating pitch of 355 nm in the direction parallel to the X axis and 355 nm in the direction parallel to the Y axis, forming an angle of 90 degrees. Using the coordinate axes shown in Fig. 17, they can be expressed as vectors: P1: (p1x, p1y) = (355 nm, 0 nm) and P2: (p1x, p1y) = (0 nm, 355 nm).

[0067] 12, the light incident portion 121 is a one-dimensional diffraction grating, and the diffraction orders of the light incident portion 121 correspond to, for example, m = 1, m1 = -1, and m2 = 0. Substituting these into equation (3), Pm = 355 (nm), which matches the grating pitch of the light incident portion 121, and the light L incident on the light incident portion 121 has a part of its light guide direction converted into first-order diffracted light.

[0068] 13, the light emitting portion 122 is a two-dimensional diffraction grating, and the diffraction orders of the light emitting portion 122 correspond to m=1, m1=1, and m2=0 in the +X direction, for example, and to m=1, m1=0, and m2=1 in the +Y direction. The pitch of the two-dimensional diffraction grating obtained from this is 355 nm in all cases, which matches the grating pitch of the light emitting portion 122.

[0069] 14, the separation deflection unit 123 is a one-dimensional diffraction grating, and the diffraction orders of the separation deflection unit 123 correspond to, for example, m=1, m1=0, and m2=-1. Substituting these into equation (3), Pm=355 (nm), which matches the grating pitch of the separation deflection unit 123.

[0070] 15 , the intermediate deflection unit 124 is a one-dimensional diffraction grating, and the diffraction orders of the intermediate deflection unit 124 correspond to, for example, m = 1, m1 = 0, and m2 = 2. Substituting these into equation (3), Pm = 355 / 2 = 177.5 (nm), which matches the grating pitch of the intermediate deflection unit 124.

[0071] In the example shown in FIG. 16 , the optical duplication unit 125 is a two-dimensional diffraction grating, and the diffraction orders of the optical duplication unit 125 correspond to m = 1, m1 = 1, and m2 = 1 in the +Y direction. In the -Y direction, they correspond to m = 1, m1 = 1, and m2 = -1. The pitch of the two-dimensional diffraction grating obtained from this is 355 nm, which does not match the grating pitch of the minimum unit lattice UC of the optical duplication unit 125. On the other hand, the two-dimensional diffraction grating of the optical duplication unit 125 can also be considered as a diffraction grating having the same grating pitch as the reference two-dimensional diffraction grating. Therefore, the pitch of the two-dimensional diffraction grating obtained from the above relationship matches the grating pitch of the optical duplication unit 125.

[0072] In the example shown in Fig. 17 , the first direction A is the X direction along the reference two-dimensional diffraction grating pitch PS1. The second direction B is the Y direction along the reference two-dimensional diffraction grating pitch PS2. In Fig. 17 , the symbols for the first direction A and the reference two-dimensional diffraction grating pitch PS1 are shown together to indicate that the first direction A is the direction along the reference two-dimensional diffraction grating pitch PS1. The symbols for the second direction B and the reference two-dimensional diffraction grating pitch PS2 are shown together to indicate that the second direction B is the direction along the reference two-dimensional diffraction grating pitch PS2.

[0073] In the example shown in Figure 17, the angle between the first direction A and the second direction B is the angle between two intersecting sides of the reference two-dimensional diffraction grating BC. In the example shown in Figure 17, the angle between the two sides of the reference two-dimensional diffraction grating BC is 90 degrees, and the angle between the first direction A and the second direction B is also 90 degrees. However, the angle between the first direction A and the second direction B is not limited to 90 degrees. For example, the angle between the first direction A and the second direction B may be 90 degrees ± 20 degrees or less. By making the angle between the first direction A and the second direction B 90 degrees ± 20 degrees or less, the viewing angle of the light guide plate 10 can be increased.

[0074] The type of the light deflection unit 12 is not limited to the example in which the light entrance unit 121, the separation deflection unit 123, and the intermediate deflection unit 124 are each one-dimensional lattices, and the light exit unit 122 and the light duplication unit 125 are two-dimensional lattices. The type of the light deflection unit 12 can be changed as appropriate depending on the specifications of the light guide plate 10, etc. In the case of a two-dimensional lattice, the minimum unit lattice UC is not limited to a square lattice (the angle formed by the equal lattice pitch in two directions is 90 degrees), but may be a rectangular lattice (the angle formed by the different lattice pitch in two directions is 90 degrees), a rhombic lattice (the angle formed by the equal lattice pitch in two directions is not 90 degrees), or a parallelogram lattice (the angle formed by the different lattice pitch in two directions is not 90 degrees).

[0075] The reference two-dimensional diffraction grating BC is not limited to one in which the unit lattice is a square lattice, but may be a rectangular lattice, a rhombic lattice, or a parallelogram lattice.

[0076] <Materials of the Light Guide Substrate 11 and the Light Deflector 12> The light guide substrate 11 is, for example, a glass substrate. ２ O ３ -TeO ２ La-based glass or La ２ O ３ -B ２ O ３ Here, the term "composition" refers to an assembly of elements or components that are designed to total 100% in percent (mol%, wt%, etc.), excluding unavoidable impurities and intentionally added impurities or additives in ppm (parts per million) units.

[0077] The light guide substrate 11 may be a single crystal substrate. A single crystal is a crystal in which the direction of the arrangement of atoms or molecules is the same throughout the crystal. As the single crystal light guide substrate 11, TiO ２ , SrTiO ３ , KTaO ３ , LiNbO ３ The light-guiding substrate 11 may be an isotropic single-crystal substrate whose optical properties do not depend on direction, or a uniaxial or biaxial single-crystal substrate whose crystal axis faces a predetermined direction.

[0078] The light deflection unit 12 is made of, for example, ZrO ２ , HfO ２ , Ta ２ O ５ , Nb ２ O ５ , TeO ２ , MoO ３ , W.O. ３ , TiO ２ , SiN, SiON, SnO, ITO, Al ２ O ３ , Y ２ O ３ , AlN, MgO, or a mixture of two or more of these. Alternatively, the light deflection unit 12 may be formed of a glass material containing three or more inorganic elements. The light deflection unit 12 can be formed on the surface of the light-guiding substrate 11 by vapor deposition, sputtering, or the like. By forming a desired pattern, such as a line-and-space pattern or a square lattice pattern, in the light deflection unit 12 by etching, the light entrance unit 121, the light exit unit 122, the separating deflection unit 123, the intermediate deflection unit 124, and the light duplication unit 125 can be formed.

[0079] In addition, in the light deflection unit 12, a desired pattern may be formed by directly etching the light guide substrate material. ２ and TiO ２ A desired pattern may be formed by nanoimprinting, photolithography, or interference exposure of an organic material containing fine particles or an organic material consisting only of organic components without fine particles. In addition, a desired periodic structure may be formed by patterning a photo-alignment film by interference exposure and aligning a polymer liquid crystal material along the alignment film.

[0080] [Examples and Comparative Examples] Examples and comparative examples will be described below. However, the present disclosure is not limited to these examples. Note that the same names and symbols as those in the already described embodiments indicate the same or similar components or configurations, and detailed explanations will be omitted as appropriate. Furthermore, the numerical values ​​in parentheses represent (m1o, m2o) in the above formulas (1) and (2).

[0081] Examples 1, 3, 4, 7, 8, and 9 shown below are working examples. Examples 2, 5, and 6 are comparative examples. The wavelengths and refractive indices of blue light LB, green light LG, and red light LR are shown in Table 1. The wavelengths and refractive indices of blue light LB, green light LG, and red light LR are common to each example.

[0082]

[0083] Example 1 Example 1 corresponds to the light guide plate 10 according to the above-described embodiment, and embodies the specifications of the light guide plate 10. Table 2 shows the main specifications of the light guide plate 10 according to Example 1. Table 3 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the separation deflection unit 123.

[0084] In Table 2, the incoupling direction (-1, 0) represents, for example, the +X direction. The reference two-dimensional diffraction grating pitch PS1 refers to the pitch of the diffraction grating in a direction along one of the two sides of the reference two-dimensional diffraction grating. The reference two-dimensional diffraction grating pitch PS2 refers to the pitch of the diffraction grating in a direction along the other of the two sides of the reference two-dimensional diffraction grating. In Table 3, the NA state (-1, -1) represents, for example, the state of light diffracted in a direction corresponding to the period of the reference two-dimensional diffraction grating pitch PS1 and in a direction corresponding to the period of PS2, when the NA state of the light projected from the projector, i.e., the diffraction order, is (0, 0). In Example 1, PS1 and PS2 are both 355 nm, the angle between the reference two-dimensional diffraction grating pitches PS1 and PS2, i.e., the angle between two sides of the reference two-dimensional diffraction grating, is 90 degrees, and the reference unit lattice is a square lattice, so the NA state (-1, -1) represents a direction tilted at 45 degrees with respect to the X axis, and the closer it is to the -X direction, the closer it is to the -Y direction. (-1, 0) in the NA state represents, for example, the -X direction.

[0085]

[0086]

[0087] <Example 2> A light guide plate according to Example 2 will be described with reference to Figures 18 to 23, Figures 24A, 24B, 24C, 24D, 24E, 24F, and 25. Figure 18 is a diagram showing the configuration of a light guide plate 10a according to Example 2. Figure 19 is a diagram showing how blue light LB is guided in the light guide plate 10a. Figure 20 is a diagram showing an NA diagram of blue light LB in the light guide plate 10a. Figure 21 is a diagram showing how green light LG is guided in the light guide plate 10a. Figure 22 is a diagram showing an NA diagram of green light LG in the light guide plate 10a. Figure 23 is a diagram showing how red light LR is guided in the light guide plate 10a. Figure 24A is a diagram showing an NA diagram of red light LR in the light guide plate 10a. Figure 24B is a diagram showing the light guide efficiency of blue light by the light guide plate 10 according to Example 1 and the light guide plate 10a according to Example 2. Fig. 24C is a diagram showing the light guide efficiency of green light by the light guide plate 10 according to Example 1 and the light guide plate 10a according to Example 2. Fig. 24D is a diagram showing the light guide efficiency of red light by the light guide plate 10 according to Example 1 and the light guide plate 10a according to Example 2. Fig. 24E is a diagram showing the light guide efficiency of blue light by the light guide plate 10 according to Example 1. Fig. 24F is a diagram showing the light guide efficiency of blue light by the light guide plate 10a according to Example 2. Fig. 25 is a schematic diagram showing the reference two-dimensional diffraction grating BC of the light deflection unit 12 in the light guide plate 10a.

[0088] As shown in FIG. 18, a light guide plate 10a differs from the light guide plate 10 according to Example 1 in that the light deflection section 12 does not have a separation deflection section and an intermediate deflection section.

[0089] Table 4 shows the main specifications of the light guide plate 10a. Table 5A shows the propagation angles and NA states of blue light LB, green light LG, and red light LR at the center of the viewing angle.

[0090]

[0091]

[0092] 19, blue light LB is incoupled by light incident unit 121 and then incident on optical duplication unit 125. Of the blue light LB incident on optical duplication unit 125, the light that is transmitted through optical duplication unit 125 or diffracted by optical duplication unit 125 is incident on light exit unit 122. The blue light LB incident on light exit unit 122 is diffracted by light exit unit 122 and exits from light guide plate 10a.

[0093] 20 , of the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to the NA states of blue light LB guided by light guide plate 10a are all located within total internal reflection light guide region T. Therefore, blue light LB corresponding to these approximate squares is guided by light guide plate 10a at all viewing angles.

[0094] 21, green light LG is incoupled by the light incident unit 121 and then incident on the optical duplication unit 125. Of the green light LG incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The green light LG incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10a.

[0095] 22 , of the multiple approximate squares representing the viewing angles of green light LG, the multiple approximate squares located in directions along the NAx axis and the NAy axis are located within the total internal reflection light-guiding region T. Therefore, the green light LG corresponding to these approximate squares is guided by light guide plate 10 a at all viewing angles.

[0096] 23, the red light LR is incoupled by the light incident unit 121 and then incident on the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The red light LR incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10a.

[0097] 24A , among the multiple approximate squares representing the viewing angles of red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by light guide plate 10 a at all viewing angles.

[0098] The diffraction order of the light incident section 121 in Example 2 is the same as the diffraction order of the light incident section 121 in Example 1. The diffraction order of the light exit section 122 in Example 2 is the same as the diffraction order of the light exit section 122 in Example 1. The diffraction order of the optical duplication section 125 in Example 2 is the same as the diffraction order of the optical duplication section 125 in Example 1.

[0099] Here, the light guide efficiency of the light guide plate 10 according to Example 1 and the light guide plate 10a according to Example 2 will be described. Figure 24B shows the simulation results for the light guide efficiency of blue light LB by the light guide plate 10 and the light guide plate 10a, calculated within a range of ±2.2 mm deviation in the X direction from the design center position. Figure 24C shows the simulation results for the light guide efficiency of green light LG by the light guide plate 10 and the light guide plate 10a, calculated within a range of ±2.2 mm deviation in the X direction from the design center position. Figure 24D shows the simulation results for the light guide efficiency of red light LR by the light guide plate 10 and the light guide plate 10a, calculated within a range of ±2.2 mm deviation in the X direction from the design center position. Note that in Figures 24B, 24C, and 24D, the solid line graphs indicate the light guide efficiency of the light guide plate 10 according to Example 1. The dashed line in the graph indicates the light guide efficiency of the light guide plate 10a according to Example 2.

[0100] Fig. 24E shows the simulation results of the light guide efficiency of blue light LB by light guide plate 10, calculated within a range of eye position deviation of ±2.2 mm in the X and Y directions from the design center position. Fig. 24F shows the simulation results of the light guide efficiency of blue light LB by light guide plate 10a, calculated within a range of eye position deviation of ±2.2 mm in the X and Y directions from the design center position.

[0101] 24B to 24F , since light guide plate 10 has separation deflection unit 123, the light guide efficiency of blue light LB by light guide plate 10 is greater than the light guide efficiency of blue light LB by light guide plate 10a. On the other hand, there is almost no difference in the light guide efficiency of green light LG and red light LR between light guide plate 10 and light guide plate 10a.

[0102] Table 5B shows the simulation results of the average light guide efficiency when the eye position is shifted within a range of ±2.2 mm in each of the X and Y directions from the design center position.

[0103]

[0104] As shown in Table 5B, by having the separate deflection section in the light guide plate 10, the light guide efficiency of the blue light LB by the light guide plate 10 was about 5.4 times higher than the light guide efficiency of the blue light LB by the light guide plate 10a. On the other hand, there was almost no difference in the light guide efficiency for the green light LG and the red light LR between the light guide plate 10 and the light guide plate 10a. As a result, it can be seen that the difference in the light guide efficiency for the blue light LB, the green light LG, and the red light LR is smaller in the light guide plate 10 than in the light guide plate 10a, and the color balance is improved.

[0105] <Example 3> A light guide plate according to Example 3 will be described with reference to Fig. 26 to Fig. 29. Fig. 26 is a diagram showing the configuration of a light guide plate 10b according to Example 3. Fig. 27 is a diagram showing an NA diagram of blue light LB in the light guide plate 10b. Fig. 28 is a diagram showing an NA diagram of green light LG in the light guide plate 10b. Fig. 29 is a diagram showing an NA diagram of red light LR in the light guide plate 10b.

[0106] As shown in FIG. 26, the light guide plate 10b differs from the light guide plate 10 according to Example 1 in that the light at the center of the viewing angle of the light L that is incident on the light incident portion 121 and deflected is tilted by 45 degrees with respect to the X axis.

[0107] Table 6 shows the main specifications of the light guide plate 10b. Table 7 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the separation / deflection unit 123.

[0108]

[0109]

[0110] In the NA diagram shown in FIG. 27 , the blue light LB incoupled by the light incident unit 121 transitions to an NA state tilted at 45 degrees with respect to the NAx axis, as indicated by arrow W1. In Example 3, the NA state at this time is (-1, 0). The blue light LB is then separated into a first light portion L1 and a second light portion L2 by the separation / deflection unit 123. The first light portion L1 transitions to an NA state of (1, 1), as indicated by arrow W3, and is further transitioned by the intermediate deflection unit 124 to an NA state of (-1, 1), as indicated by arrow W4. The second light portion L2 transitions to an NA state of (0, 1), as indicated by arrow W5, by the light duplication unit 125. Of the multiple approximate squares representing the viewing angles of the blue light LB, the approximate squares corresponding to the blue light LB incoupled into the light guide plate 10b are all located within the total reflection light-guiding region T. Therefore, the blue light LB corresponding to these approximately squares is guided by the light guide plate 10b over the entire viewing angle.

[0111] In the NA diagram shown in FIG. 28 , the green light LG incoupled by the light incident unit 121 transitions to an NA state tilted 45 degrees with respect to the NAx axis, as indicated by arrow W1. In Example 3, the NA state at this time is (-1, 0). The green light LG then passes through the separation / deflection unit 123 as the second light portion L2. The light duplication unit 125 then transitions to an NA state of (0, 1), as indicated by arrow W5. Of the multiple approximate squares representing the viewing angle of the green light LG, multiple approximate squares located diagonally at 45 degrees with respect to the NAx axis are each located within the total reflection light-guiding region T. Therefore, the green light LG corresponding to these approximate squares is guided by the light guide plate 10b as light of the entire viewing angle. Meanwhile, multiple approximate squares located along the NAx axis and the NAy axis each have a portion located outside the outer circle of the NA diagram. Therefore, the green light LG corresponding to these approximately squares has some viewing angles that are not guided by the light guide plate 10b, and most of the light is transmitted through the separation deflection unit 123 without being diffracted.

[0112] In the NA diagram shown in FIG. 29 , the red light LR incoupled by the light incident unit 121 transitions to an NA state inclined at 45 degrees with respect to the NAx axis, as indicated by arrow W1. In Example 3, the NA state at this time is (-1, 0). The red light LR then passes through the separation / deflection unit 123 as the second light portion L2. The light duplication unit 125 then transitions to an NA state of (0, 1), as indicated by arrow W5. Of the multiple approximate squares representing the viewing angle of the red light LR, multiple approximate squares located diagonally inclined at 45 degrees with respect to the NAx axis are each located within the total reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by the light guide plate 10b as light of the entire viewing angle. Meanwhile, the multiple approximate squares located in directions along the NAx axis and the NAy axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximately squares is not guided by the light guide plate 10b at all viewing angles, and therefore the light passes through the separation deflection unit 123 without being diffracted.

[0113] The configuration of the light deflection unit 12 of the light guide plate 10b will be described with reference to Figures 30 to 35. Figure 30 is a schematic diagram showing the diffraction grating of the light entrance unit 121 of the light guide plate 10b. Figure 31 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10b. Figure 32 is a schematic diagram showing the diffraction grating of the separation deflection unit 123 of the light guide plate 10b. Figure 33 is a schematic diagram showing the diffraction grating of the intermediate deflection unit 124 of the light guide plate 10b. Figure 34 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10b. Figure 35 is a schematic diagram showing the reference two-dimensional diffraction grating BC of the light deflection unit 12 of the light guide plate 10b.

[0114] In the example shown in FIG. 30 , the light incident portion 121 is a one-dimensional grating having a plurality of line-and-space patterns extending in a direction tilted 45 degrees with respect to the Y direction. The minimum unit cell UC represents the smallest unit cell constituting the light incident portion 121. The first grating pitch P1 is the pitch of the diffraction grating of the light incident portion 121 in a direction tilted 45 degrees with respect to the X direction. The first grating pitch P1 in the light incident portion 121 is, for example, 355.0 nm. The diffraction orders of the light incident portion 121 correspond to m=1, m1=−1, and m2=0. The light L incident on the light incident portion 121 is converted into first-order diffracted light in a part of its light guide direction.

[0115] In the example shown in FIG. 31 , the light emitting portion 122 is a two-dimensional lattice with a square unit lattice. The minimum unit lattice UC represents the smallest unit lattice constituting the light emitting portion 122. The first grating pitch P1 is the pitch of the diffraction grating of the light emitting portion 122 in a direction tilted 45 degrees with respect to the X direction. The second grating pitch P2 is the pitch of the diffraction grating of the light emitting portion 122 in a direction tilted 45 degrees with respect to the Y direction. In the light emitting portion 122, the first grating pitch P1 and the second grating pitch P2 are, for example, 355.0 nm each. The diffraction orders of the light emitting portion 122 correspond to m=1, m1=1, and m2=0 in the direction from the +X direction toward the +Y direction to the +X direction. The diffraction orders correspond to m=1, m1=0, and m2=-1 in the direction from the +X direction toward the -Y direction to the -Y direction. The light L incident on the light emitting portion 122 has a part of its guide direction converted into first-order diffracted light.

[0116] In the example shown in Figure 32, the separating / deflecting unit 123 is a one-dimensional grating having a plurality of line-and-space patterns extending in a direction tilted at approximately 70 degrees with respect to the Y direction. The minimum unit grating UC represents the smallest unit grating constituting the separating / deflecting unit 123. The first grating pitch P1 is, for example, 355.0 / (√5) nm. The diffraction orders of the separating / deflecting unit 123 correspond to m = 1, m1 = 2, and m2 = 1. The light L incident on the separating / deflecting unit 123 has a portion of its light guide direction converted into first-order diffracted light.

[0117] In the example shown in FIG. 33 , the intermediate deflection unit 124 is a one-dimensional grating having a plurality of line-and-space patterns extending in a direction tilted 45 degrees with respect to the Y direction. The minimum unit grating UC represents the smallest unit grating constituting the intermediate deflection unit 124. The first grating pitch P1 is the pitch of the diffraction grating of the intermediate deflection unit 124 in a direction tilted 45 degrees with respect to the X direction. The first grating pitch P1 in the intermediate deflection unit 124 is, for example, 177.5 nm. The diffraction orders of the intermediate deflection unit 124 correspond to m=1, m1=−2, and m2=0. The light L incident on the intermediate deflection unit 124 has a portion of its light guide direction converted into first-order diffracted light.

[0118] In the example shown in FIG. 34 , the optical duplication unit 125 is a one-dimensional lattice having a plurality of line-and-space patterns extending in the X direction. The minimum unit lattice UC represents the smallest unit lattice constituting the optical duplication unit 125. The first lattice pitch P1 is, for example, 355.0 / (√2) nm. The diffraction orders of the optical duplication unit 125 correspond to m=1, m1=1, and m2=1. The light L incident on the optical duplication unit 125 has a portion of its guide direction converted into first-order diffracted light.

[0119] The light entrance unit 121, the light exit unit 122, the separating deflection unit 123, the intermediate deflection unit 124, and the optical duplication unit 125 are all considered to be diffraction gratings whose unit lattices are two-dimensional diffraction gratings having two sides with the same reference two-dimensional diffraction grating pitches PS1 and PS2 as the reference two-dimensional diffraction grating BC shown in Fig. 35. In this case, the angle formed by the two sides of the reference two-dimensional diffraction grating BC is, for example, 90 degrees ± 20 degrees or less.

[0120] <Example 4> A light guide plate according to Example 4 will be described with reference to Fig. 36 to Fig. 39. Fig. 36 is a diagram showing the configuration of a light guide plate 10c according to Example 4. Fig. 37 is a diagram showing an NA diagram of blue light LB in the light guide plate 10c. Fig. 38 is a diagram showing an NA diagram of green light LG in the light guide plate 10c. Fig. 39 is a diagram showing an NA diagram of red light LR in the light guide plate 10c.

[0121] 36 , light guide plate 10c differs from light guide plate 10 according to Example 1 in that the light at the center of the viewing angle of light L that is incident on light incident portion 121 and deflected is tilted by 51 degrees with respect to the X axis. Light guide plate 10c also differs from light guide plate 10b according to Example 3 in that the shape of the unit lattice is a rhombuses.

[0122] Table 8 shows the main specifications of the light guide plate 10c. Table 9 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the separation deflection unit 123.

[0123]

[0124]

[0125] In the NA diagram shown in FIG. 37 , the blue light LB incoupled by the light incident unit 121 transitions to an NA state tilted 51 degrees with respect to the NAx axis, as indicated by arrow W1. In Example 4, the NA state at this time is (-1, 0). The blue light LB is then separated into a first light portion L1 and a second light portion L2 by the separation / deflection unit 123. The first light portion L1 transitions to an NA state of (1, 1), as indicated by arrow W3, and is further transitioned to an NA state of (-1, 1) by the intermediate deflection unit 124, as indicated by arrow W4. The second light portion L2 transitions to an NA state of (0, 1), as indicated by arrow W5, by the light duplication unit 125. Of the multiple approximate squares representing the viewing angles of the blue light LB, the approximate squares corresponding to the blue light LB incoupled into the light guide plate 10c are all located within the total reflection light-guiding region T. Therefore, the blue light LB corresponding to these approximately squares is guided by the light guide plate 10c over the entire viewing angle.

[0126] In the NA diagram shown in FIG. 38 , the green light LG incoupled by the light incident unit 121 transitions to an NA state tilted 51 degrees with respect to the NAx axis, as indicated by arrow W1. In Example 4, the NA state at this time is (-1, 0). The green light LG then passes through the separation / deflection unit 123 as the second light portion L2. The light duplication unit 125 then transitions to an NA state of (0, 1), as indicated by arrow W5. Of the multiple approximate squares representing the field of view of the green light LG, the multiple approximate squares positioned diagonally tilted 51 degrees with respect to the NAx axis and the multiple approximate squares positioned along the NAx axis are each located within the total reflection light-guiding region T. Therefore, the green light LG corresponding to these approximate squares is guided by the light guide plate 10c as light of the entire field of view. On the other hand, the multiple approximate squares positioned along the respective NAy axes are all located outside the outer circle of the NA diagram. Therefore, the green light LG corresponding to these approximate squares has some viewing angles that are not guided by the light guide plate 10c.

[0127] In the NA diagram shown in FIG. 39 , the red light LR incoupled by the light incident unit 121 transitions to an NA state inclined at 51 degrees with respect to the NAx axis, as indicated by arrow W1. In Example 4, the NA state at this time is (-1, 0). The red light LR then passes through the separation / deflection unit 123 as the second light portion L2. The light duplication unit 125 then transitions to an NA state of (0, 1), as indicated by arrow W5. Of the multiple approximate squares representing the viewing angle of the red light LR, multiple approximate squares located diagonally inclined at 51 degrees with respect to the NAx axis are each located within the total reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by the light guide plate 10c as light of the entire viewing angle. Meanwhile, the multiple approximate squares located in directions along the NAx axis and the NAy axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by the light guide plate 10c over the entire viewing angle.

[0128] <Example 5> A light guide plate according to Example 5 will be described with reference to Figs. 40 to 46. Fig. 40 is a diagram showing the configuration of a light guide plate 10d according to Example 5. Fig. 41 is a diagram showing how blue light LB is guided in the light guide plate 10d. Fig. 42 is a diagram showing an NA diagram of blue light LB in the light guide plate 10d. Fig. 43 is a diagram showing how green light LG is guided in the light guide plate 10d. Fig. 44 is a diagram showing an NA diagram of green light LG in the light guide plate 10d. Fig. 45 is a diagram showing how red light LR is guided in the light guide plate 10d. Fig. 46 is a diagram showing an NA diagram of red light LR in the light guide plate 10d.

[0129] As shown in Figure 40, light guide plate 10d differs from light guide plate 10 of Example 1 in that the light deflection section 12 does not have a separation deflection section, and the light incident section 121 separates light L into at least a first light portion L1 and a second light portion L2.

[0130] The light L is incoupled and split into a first light portion L1 and a second light portion L2 by the light incident unit 121. The first light portion L1 is incident on the intermediate deflection unit 124. The second light portion L2 is incident on the light duplication unit 125.

[0131] Table 10 shows the main specifications of the light guide plate 10d. Table 11 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the light incident portion 121.

[0132]

[0133]

[0134] As shown in FIG. 41 , the blue light LB is incoupled and separated into a first light portion L1 and a second light portion L2 by the light incident unit 121. In the example shown in FIG. 41 , the amount of blue light LB in the first light portion L1 is greater than the amount of blue light LB in the second light portion L2. The blue light LB in the first light portion L1 is incident on the intermediate deflection unit 124. Of the blue light LB incident on the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 is incident on the light exit unit 122. On the other hand, the blue light LB in the second light portion L2 is incident on the optical duplication unit 125. Of the blue light LB incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The blue light LB incident on the light emitting portion 122 is diffracted by the light emitting portion 122 and is emitted from the light guide plate 10d.

[0135] 42 , among the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to blue light LB incoupled into light guide plate 10d are all located within total internal reflection light guide region T. Therefore, blue light LB corresponding to these approximate squares is guided by light guide plate 10d at all viewing angles.

[0136] As shown in FIG. 43 , the green light LG is incoupled and separated into a first light portion L1 and a second light portion L2 by the light incident unit 121. In the example shown in FIG. 43 , the amount of green light LG in the second light portion L2 is greater than the amount of green light LG in the first light portion L1. The green light LG in the first light portion L1 is incident on the intermediate deflection unit 124. Of the green light LG incident on the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 is incident on the light exit unit 122. On the other hand, the green light LG in the second light portion L2 is incident on the optical duplication unit 125. Of the green light LG incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The green light LG incident on the light emitting portion 122 is diffracted by the light emitting portion 122 and is emitted from the light guide plate 10d.

[0137] In the NA diagram shown in Fig. 44, of the multiple approximate squares representing the viewing angles of green light LG, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, light of all viewing angles of green light LG corresponding to these approximate squares is guided by light guide plate 10d. On the other hand, portions of the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are each located outside the outer circle of the NA diagram. Therefore, light of some viewing angles of green light LG corresponding to these approximate squares is not guided by light guide plate 10d.

[0138] As shown in Fig. 45, the red light LR is incoupled and separated into a first light portion L1 and a second light portion L2 by the light incident portion 121. In the example shown in Fig. 45, the red light LR is not included in the first light portion L1. The red light LR in the second light portion L2 is incident on the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The red light LR incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10d.

[0139] In the NA diagram shown in Fig. 46, of the multiple approximate squares representing the viewing angles of the red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by light guide plate 10d at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by light guide plate 10d at all viewing angles.

[0140] The configuration of the optical deflection unit 12 of the light guide plate 10d will be described with reference to Fig. 47 to Fig. 50. Fig. 47 is a schematic diagram showing the diffraction grating of the light entrance unit 121 of the light guide plate 10d. Fig. 48 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10d. Fig. 49 is a schematic diagram showing the diffraction grating of the intermediate deflection unit 124 of the light guide plate 10d. Fig. 50 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10d.

[0141] In the example shown in FIG. 47 , the light incident portion 121 is a two-dimensional lattice including a parallelogram in which the unit lattice has a side extending in a direction tilted 45 degrees with respect to the X axis and a side extending in the Y direction. The minimum unit lattice UC represents the smallest unit lattice constituting the light incident portion 121. The first grating pitch P1 is the pitch of the diffraction grating of the light incident portion 121 in the X direction. The first grating pitch P1 in the light incident portion 121 is, for example, 355.0 nm. The second grating pitch P2 is the pitch of the diffraction grating of the light incident portion 121 in the Y direction. The second grating pitch P2 in the light incident portion 121 is, for example, 355.0 nm. The light L incident on the light incident portion 121 has a portion of its guided direction converted into first-order diffracted light.

[0142] In the example shown in FIG. 48 , the light emitting portion 122 is a two-dimensional lattice in which the unit lattice is a square lattice. The minimum unit lattice UC represents the smallest unit lattice that constitutes the light emitting portion 122. The first grating pitch P1 is the pitch of the diffraction grating of the light emitting portion 122 in the X direction. The second grating pitch P2 is the pitch of the diffraction grating of the light emitting portion 122 in the Y direction. In the light emitting portion 122, the first grating pitch P1 and the second grating pitch P2 are, for example, 355.0 nm each. The light L incident on the light emitting portion 122 has a portion of its guided direction converted into first-order diffracted light.

[0143] 49 , the intermediate deflection unit 124 is a one-dimensional grating having a plurality of line-and-space patterns extending in the X direction. The minimum unit grating UC represents the smallest unit grating constituting the intermediate deflection unit 124. The first grating pitch P1 is the pitch of the diffraction grating of the intermediate deflection unit 124 in the Y direction, and is, for example, 177.5 nm. The light L incident on the intermediate deflection unit 124 has a portion of its light guide direction converted into first-order diffracted light.

[0144] In the example shown in FIG. 50 , the optical duplication unit 125 is a diffraction grating in which a two-dimensional lattice with a square unit lattice is tilted 45 degrees with respect to the X-axis. The minimum unit lattice UC represents the smallest unit lattice constituting the optical duplication unit 125. The first grating pitch P1 is the pitch of the diffraction grating of the optical duplication unit 125 in the direction in which the Y direction becomes more positive as the X direction becomes more positive. The second grating pitch P2 is the pitch of the diffraction grating of the optical duplication unit 125 in the direction in which the Y direction becomes more negative as the X direction becomes more positive. In the optical duplication unit 125, the first grating pitch P1 and the second grating pitch P2 are, for example, 355.0 / (√2) nm each. The light L incident on the optical duplication unit 125 has a portion of its light guide direction converted into first-order diffracted light.

[0145] The light entrance section 121, the light exit section 122, the intermediate deflection section 124, and the light duplication section 125 can all be considered as diffraction gratings in which a two-dimensional diffraction grating having the same reference two-dimensional diffraction grating pitches PS1 and PS2 as two sides is a reference two-dimensional diffraction grating BC, and the angle between the two sides of the reference two-dimensional diffraction grating BC is, for example, 90 degrees ± 20 degrees or less.

[0146] <Example 6> A light guide plate according to Example 6 will be described with reference to Figs. 51 to 59. Fig. 51 is a diagram showing the configuration of a light guide plate 10e according to Example 6. Fig. 52 is a diagram showing the configuration of a light incident portion 121-1 in the light guide plate 10e. Fig. 53 is a diagram showing how blue light LB is guided in the light guide plate 10e. Fig. 54 is a first diagram showing an NA diagram of blue light LB in the light guide plate 10e. Fig. 55 is a second diagram showing an NA diagram of blue light LB in the light guide plate 10e. Fig. 56 is a diagram showing how green light LG is guided in the light guide plate 10e. Fig. 57 is a diagram showing an NA diagram of green light LG in the light guide plate 10e. Fig. 58 is a diagram showing how red light LR is guided in the light guide plate 10e. Fig. 59 is a diagram showing an NA diagram of red light LR in the light guide plate 10e.

[0147] As shown in FIG. 51, the light guide plate 10e differs from the light guide plate 10 of Example 1 in that the light deflection section 12 does not have a separation deflection section, and the light incident section 121-1 separates the light L into at least a first light portion L1 and a second light portion L2, and in that the light deflection section 12 has a first intermediate deflection section 124A and a second intermediate deflection section 124B.

[0148] The light incident unit 121-1 includes a first light incident unit 121A and a second light incident unit 121B. The light L is incoupled and separated into a first light portion L1 and a second light portion L2 by the first light incident unit 121A and the second light incident unit 121B. The first light portion L1 enters the first intermediate deflection unit 124A and is diffracted by the first intermediate deflection unit 124A. The first light portion L1 then enters the second intermediate deflection unit 124B and is diffracted by the first intermediate deflection unit 124A before entering the light exit unit 122. The second light portion L2 enters the optical duplication unit 125.

[0149] Table 12 shows the main specifications of the light guide plate 10e. Table 13 shows the propagation angles and NA states of the blue light LB at the center of the viewing angle after separation by the first light incident portion 121A. Table 14 shows the propagation angles and NA states of the blue light LB, green light LG, and red light LR at the center of the viewing angle after separation by the second light incident portion 121B.

[0150]

[0151]

[0152]

[0153] As shown in FIG. 53, the blue light LB is incoupled and separated into a first light portion L1 and a second light portion L2 by the light incident unit 121-1. In the example shown in FIG. 53, the amount of blue light LB in the first light portion L1 is greater than the amount of blue light LB in the second light portion L2. The blue light LB in the first light portion L1 is incident on the first intermediate deflection unit 124A. Of the blue light LB incident on the first intermediate deflection unit 124A, the light diffracted by the first intermediate deflection unit 124A is incident on the second intermediate deflection unit 124B. Of the blue light LB incident on the second intermediate deflection unit 124B, the light diffracted by the second intermediate deflection unit 124B is incident on the light exit unit 122. On the other hand, the blue light LB in the second light portion L2 is incident on the optical duplication unit 125. Of the blue light LB incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light emitting unit 122. The blue light LB incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and is emitted from the light guide plate 10e.

[0154] 54 , the NA state of blue light LB that is incoupled and separated by first light incident portion 121A transitions as indicated by arrows W4A and W4B. Of the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to blue light LB incoupled into light guide plate 10e are all located within total internal reflection light guide region T. Therefore, blue light LB corresponding to these approximate squares is guided by light guide plate 10e at all viewing angles.

[0155] 55 , the NA state of blue light LB that is incoupled and separated by second light incident portion 121B transitions as indicated by arrow W5. Of the multiple approximate squares that represent the viewing angles of blue light LB, the approximate squares that correspond to blue light LB incoupled into light guide plate 10e are all located within total internal reflection light guide region T. Therefore, blue light LB corresponding to these approximate squares is guided by light guide plate 10e at all viewing angles.

[0156] 56, the green light LG is incoupled by the light incident portion 121. In the example shown in FIG. 56, the first light portion L1 does not include the green light LG. The green light LG in the second light portion L2 is incident on the optical duplication portion 125. Of the green light LG incident on the optical duplication portion 125, the light that is transmitted through the optical duplication portion 125 or diffracted by the optical duplication portion 125 is incident on the light exit portion 122. The green light LG incident on the light exit portion 122 is diffracted by the light exit portion 122 and exits from the light guide plate 10e.

[0157] In the NA diagram shown in Fig. 57, of the multiple approximate squares representing the viewing angles of green light LG, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, light of all viewing angles of green light LG corresponding to these approximate squares is guided by light guide plate 10e. On the other hand, portions of the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are each located outside the outer circle of the NA diagram. Therefore, light of some viewing angles of green light LG corresponding to these approximate squares is not guided by light guide plate 10e.

[0158] As shown in Fig. 58, the red light LR is incoupled by the light incident portion 121. In the example shown in Fig. 58, the first light portion L1 does not include the red light LR. The red light LR in the second light portion L2 is incident on the optical duplication portion 125. Of the red light LR incident on the optical duplication portion 125, the light that is transmitted through the optical duplication portion 125 or diffracted by the optical duplication portion 125 is incident on the light exit portion 122. The red light LR incident on the light exit portion 122 is diffracted by the light exit portion 122 and exits from the light guide plate 10e.

[0159] In the NA diagram shown in Fig. 59, of the multiple approximate squares representing the viewing angle of red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by light guide plate 10e at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by light guide plate 10e at all viewing angles.

[0160] The configuration of the optical deflection unit 12 of the light guide plate 10e will be described with reference to Fig. 60 to Fig. 65. Fig. 60 is a schematic diagram showing the diffraction grating of the first light incident unit 121A of the light guide plate 10e. Fig. 61 is a schematic diagram showing the diffraction grating of the second light incident unit 121B of the light guide plate 10e. Fig. 62 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10e. Fig. 63 is a schematic diagram showing the diffraction grating of the first intermediate deflection unit 124A of the light guide plate 10e. Fig. 64 is a schematic diagram showing the diffraction grating of the second intermediate deflection unit 124B of the light guide plate 10e. Fig. 65 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10e.

[0161] 60, the first light incident portion 121A is a one-dimensional lattice having a plurality of line-and-space patterns extending in the X direction. The minimum unit lattice UC represents the smallest unit lattice constituting the first light incident portion 121A. The first grating pitch P1 is the pitch of the diffraction grating of the first light incident portion 121A in the Y direction and is, for example, 235.0 nm. The light L incident on the first light incident portion 121A has a portion of its light guide direction converted into first-order diffracted light.

[0162] 61 , the second light incident portion 121B is a one-dimensional grating having a plurality of line-and-space patterns extending in the Y direction. The minimum unit cell UC represents the smallest unit cell constituting the second light incident portion 121B. The first grating pitch P1 is the pitch of the diffraction grating of the second light incident portion 121B in the X direction, and is, for example, 355.0 nm. The light L incident on the second light incident portion 121B has a portion of its light guide direction converted into first-order diffracted light.

[0163] In the example shown in FIG. 62 , the light emitting portion 122 is a two-dimensional lattice in which the unit lattice is a square lattice. The minimum unit lattice UC represents the smallest unit lattice that constitutes the light emitting portion 122. The first grating pitch P1 is the pitch of the diffraction grating of the light emitting portion 122 in the X direction. The second grating pitch P2 is the pitch of the diffraction grating of the light emitting portion 122 in the Y direction. In the light emitting portion 122, the first grating pitch P1 and the second grating pitch P2 are, for example, 355.0 nm each. The light L incident on the light emitting portion 122 has a portion of its guided direction converted into first-order diffracted light.

[0164] In the example shown in Figure 63, the first intermediate deflection unit 124A is a one-dimensional grating having a plurality of line-and-space patterns extending in a direction tilted at approximately 45 degrees with respect to the X-axis. The minimum unit grating UC represents the smallest unit grating constituting the first intermediate deflection unit 124A. The first grating pitch P1 is the pitch of the diffraction grating of the first intermediate deflection unit 124A, and is, for example, 235 / (√2) nm. The light L incident on the first intermediate deflection unit 124A has a portion of its light guide direction converted into first-order diffracted light.

[0165] In the example shown in Figure 64, the second intermediate deflection unit 124B is a one-dimensional grating having a plurality of line-and-space patterns extending in a direction tilted at approximately 34 degrees with respect to the Y axis. The minimum unit grating UC represents the smallest unit grating constituting the second intermediate deflection unit 124B. The first grating pitch P1 is the pitch of the diffraction grating of the second intermediate deflection unit 124B, and is, for example, 195.96 nm. The light L incident on the second intermediate deflection unit 124B has a portion of its light guide direction converted into first-order diffracted light.

[0166] In the example shown in FIG. 65 , the optical duplication unit 125 is a diffraction grating in which a two-dimensional lattice with a square unit lattice is tilted 45 degrees with respect to the X-axis. The minimum unit lattice UC represents the smallest unit lattice constituting the optical duplication unit 125. The first grating pitch P1 is the pitch of the diffraction grating of the optical duplication unit 125 in the direction in which the Y direction becomes more positive as the X direction becomes more positive. The second grating pitch P2 is the pitch of the diffraction grating of the optical duplication unit 125 in the direction in which the Y direction becomes more negative as the X direction becomes more positive. In the optical duplication unit 125, the first grating pitch P1 and the second grating pitch P2 are, for example, 355.0 / (√2) nm each. The light L incident on the optical duplication unit 125 has a portion of its light guide direction converted into first-order diffracted light.

[0167] <Example 7> A light guide plate according to Example 7 will be described with reference to Fig. 66 to Fig. 72A, Fig. 72B, Fig. 7C, and Fig. 72D. Fig. 66 is a diagram showing an example of the configuration of a light guide plate 10f according to Example 7. Fig. 67 is a diagram showing how blue light LB is guided in the light guide plate 10f. Fig. 68 is a diagram showing an NA diagram of blue light LB in the light guide plate 10f. Fig. 69 is a diagram showing how green light LG is guided in the light guide plate 10f. Fig. 70 is a diagram showing an NA diagram of green light LG in the light guide plate 10f. Fig. 71 is a diagram showing how red light LR is guided in the light guide plate 10f. Fig. 72A is a diagram showing an NA diagram of red light LR in the light guide plate 10f. Fig. 72B is a diagram showing another example of the configuration of the light guide plate according to Example 7. Fig. 72C is a diagram showing how green light is guided in a light guide plate according to another example of Example 7. FIG. 72D is a diagram showing an NA diagram of green light in a light guide plate according to another example of Example 7.

[0168] As shown in Fig. 66 , light guide plate 10f differs from light guide plate 10 according to Example 1 in that light deflection unit 12 has first recovery deflection unit 126. Note that in Fig. 66 , the reference numerals for light deflection unit 12 and first recovery deflection unit 126 are shown together to indicate that light deflection unit 12 has first recovery deflection unit 126. In the drawings shown later, the reference numerals may also be shown together for the same purpose.

[0169] In the example shown in Figure 66, the first recovery deflection unit 126 is positioned on the opposite side of the intermediate deflection unit 124 in the separation deflection unit 123, and deflects the light L deflected by the separation deflection unit 123 to the side opposite to the side where the intermediate deflection unit 124 is located, in the direction where the light emission unit 122 is located or the direction where the intermediate deflection unit 124 is located.

[0170] In Example 7, the light L deflected by the separation deflection unit 123 in the direction opposite to the side where the intermediate deflection unit 124 is located is deflected by the first recovery deflection unit 126 toward the direction where the intermediate deflection unit 124 is located. This makes it possible to use the light L deflected in the opposite direction. This makes it possible to increase the light utilization efficiency of the light guide plate 10f in Example 7.

[0171] Table 15 shows the main specifications of the light guide plate 10f. Table 16 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the separation / deflection unit 123.

[0172]

[0173]

[0174] As shown in FIG. 67 , blue light LB is incoupled by light incident unit 121 and then incident on separation / deflection unit 123. Of the blue light LB incident on separation / deflection unit 123, the light diffracted by separation / deflection unit 123 is incident on intermediate deflection unit 124. Of the blue light LB incident on intermediate deflection unit 124, the light diffracted by intermediate deflection unit 124 is incident on light exit unit 122. Furthermore, of the blue light LB incident on separation / deflection unit 123, the light diffracted by separation / deflection unit 123 to the side opposite to the side where intermediate deflection unit 124 is located is incident on first recovery / deflection unit 126. Of the blue light LB incident on first recovery / deflection unit 126, the light diffracted by first recovery / deflection unit 126 passes through optical duplication unit 125 and incident on intermediate deflection unit 124. On the other hand, of the blue light LB incident on the separating / deflecting unit 123, the light that passes through the separating / deflecting unit 123 enters the optical duplication unit 125. In the example shown in Fig. 67, the amount of blue light LB incident on the optical duplication unit 125 is less than the amount of blue light LB incident on the intermediate deflection unit 124. Of the blue light LB incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 enters the light emitting unit 122. The blue light LB incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and exits from the light guide plate 10f.

[0175] In the NA diagram shown in Fig. 68, arrow W6 represents the transition of the NA state by the first recovery deflection unit 126. Of the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to blue light LB incoupled into light guide plate 10f are all located within the total internal reflection light guide region T. Therefore, the blue light LB corresponding to these approximate squares is guided by light guide plate 10f at all viewing angles.

[0176] As shown in FIG. 69 , green light LG is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Of the green light LG that enters the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 enters the intermediate deflection unit 124. Of the green light LG that enters the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 enters the light exit unit 122. Furthermore, of the green light LG that enters the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 to the side opposite to the side where the intermediate deflection unit 124 is located enters the first recovery / deflection unit 126. Of the green light LG that enters the first recovery / deflection unit 126, the light diffracted by the first recovery / deflection unit 126 passes through the optical duplication unit 125 and enters the intermediate deflection unit 124. On the other hand, of the green light LG incident on the separation deflection unit 123, the light that passes through the separation deflection unit 123 enters the optical duplication unit 125. In the example shown in Fig. 69, the amount of green light LG incident on the optical duplication unit 125 is greater than the amount of green light LG incident on the intermediate deflection unit 124. Of the green light LG incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 enters the light exit unit 122. The green light LG incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10f.

[0177] In the NA diagram shown in FIG. 70 , among the multiple approximate squares representing the viewing angles of the green light LG, the multiple approximate squares positioned along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the green light LG corresponding to these approximate squares is guided by the light guide plate 10f at all viewing angles. On the other hand, the multiple approximate squares positioned diagonally at 45 degrees to the NAx axis each have portions located outside the outer circle of the NA diagram. Therefore, the green light LG corresponding to these approximate squares is not guided by the light guide plate 10f at some viewing angles. Therefore, only a portion of the green light LG at all viewing angles is deflected by the separation deflection unit 123 toward the first recovery deflection unit 126, and only a portion of that portion of the viewing angles is deflected in the direction of the intermediate deflection unit 124.

[0178] 71 , red light LR is incoupled by the light incident unit 121 and then incident on the separation / deflection unit 123. In the example shown in FIG. 71 , the red light LR incident on the separation / deflection unit 123 is hardly diffracted by the separation / deflection unit 123 and passes through the separation / deflection unit 123, and then incident on the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The red light LR incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10f.

[0179] In the NA diagram shown in Figure 72A, of the multiple approximate squares representing the viewing angle of red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by light guide plate 10f at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by light guide plate 10f at all viewing angles.

[0180] The light guide plate 10f according to another example of Example 7 shown in Figures 72B, 72C, and 72D differs from the light guide plate 10f according to the one example of Example 7 in that an additional recovery deflection section 126B is arranged to surround the first recovery deflection section 126a.

[0181] The additional recovery deflection unit 126B recovers the green light LG that is not recovered by the first recovery deflection unit 126a, particularly the green light LG at a field angle that is not diffracted toward the separation deflection unit 123, by deflecting it toward the optical duplication unit 125. This makes it possible to further increase the light utilization efficiency of the light guide plate 10f in another example of Example 7.

[0182] <Example 8> A light guide plate according to Example 8 will be described with reference to Figs. 73 to 79. Fig. 73 is a diagram showing the configuration of a light guide plate 10g according to Example 8. Fig. 74 is a diagram showing how blue light LB is guided in the light guide plate 10g. Fig. 75 is a diagram showing an NA diagram of blue light LB in the light guide plate 10g. Fig. 76 is a diagram showing how green light LG is guided in the light guide plate 10g. Fig. 77 is a diagram showing an NA diagram of green light LG in the light guide plate 10g. Fig. 78 is a diagram showing how red light LR is guided in the light guide plate 10g. Fig. 79 is a diagram showing an NA diagram of red light LR in the light guide plate 10g.

[0183] As shown in FIG. 73, a light guide plate 10 g differs from the light guide plate 10 according to Example 1 in that the light deflection section 12 has a folded deflection section 127 .

[0184] 73 , the return deflection unit 127 is disposed in the optical path between the separation deflection unit 123 and the intermediate deflection unit 124, and deflects the light L deflected by the separation deflection unit 123 in the direction of the intermediate deflection unit 124. The light L deflected by the return deflection unit 127 is incident on the intermediate deflection unit 124.

[0185] In Example 8, the light L deflected by the separation deflection unit 123 is incident on the intermediate deflection unit 124 via the return deflection unit 127. This reduces the amount of light that does not enter the intermediate deflection unit 124 compared to when the light L deflected by the separation deflection unit 123 is incident on the intermediate deflection unit 124 without passing through the return deflection unit 127. As a result, in Example 8, the light utilization efficiency of the light guide plate 10g can be increased.

[0186] Table 17 shows the main specifications of the light guide plate 10g. Table 18 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the separation / deflection unit 123.

[0187]

[0188]

[0189] As shown in FIG. 74 , blue light LB is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Of the blue light LB incident on the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 enters the return deflection unit 127. Of the blue light LB incident on the return deflection unit 127, the light diffracted by the return deflection unit 127 enters the intermediate deflection unit 124. Of the blue light LB incident on the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 enters the light exit unit 122. On the other hand, of the blue light LB incident on the separation / deflection unit 123, the light transmitted through the separation / deflection unit 123 enters the optical duplication unit 125. In the example shown in FIG. 74 , the amount of blue light LB incident on the optical duplication unit 125 is less than the amount of blue light LB incident on the intermediate deflection unit 124. Of the blue light LB incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light emitting unit 122. The blue light LB incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and is emitted from the light guide plate 10g.

[0190] 75 , arrow W7 represents the transition of the NA state by the folded deflection unit 127. Of the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to blue light LB incoupled into light guide plate 10g are all located within the total internal reflection light guide region T. Therefore, the blue light LB corresponding to these approximate squares is guided by light guide plate 10g at all viewing angles.

[0191] As shown in FIG. 76 , the green light LG is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Of the green light LG that enters the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 enters the folding deflection unit 127. Of the green light LG that enters the folding deflection unit 127, the light diffracted by the folding deflection unit 127 enters the intermediate deflection unit 124. Of the green light LG that enters the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 enters the light exit unit 122. On the other hand, of the green light LG that enters the separation / deflection unit 123, the light that passes through the separation / deflection unit 123 enters the optical duplication unit 125. In the example shown in FIG. 76 , the amount of green light LG that enters the optical duplication unit 125 is greater than the amount of green light LG that enters the intermediate deflection unit 124. Of the green light LG incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light emitting unit 122. The green light LG incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and is emitted from the light guide plate 10g.

[0192] In the NA diagram shown in FIG. 77 , among the multiple approximate squares representing the viewing angles of green light LG, the multiple approximate squares positioned along the NAx axis and the NAy axis are located within the total internal reflection light-guiding region T. Therefore, the green light LG corresponding to these approximate squares is guided by the light guide plate 10g at all viewing angles. On the other hand, the multiple approximate squares positioned diagonally at 45 degrees to the NAx axis each have portions located outside the outer circle of the NA diagram. Therefore, the green light LG corresponding to these approximate squares is not guided by the light guide plate 10g at some viewing angles. Therefore, only a portion of the green light LG at a certain viewing angle is deflected by the separation deflection unit 123 toward the return deflection unit 127, and only a portion of that portion of the viewing angle is deflected in the direction of the intermediate deflection unit 124.

[0193] 78 , red light LR is incoupled by the light incident unit 121 and then incident on the separation / deflection unit 123. In the example shown in FIG. 78 , the red light LR incident on the separation / deflection unit 123 is hardly diffracted by the separation / deflection unit 123 and passes through the separation / deflection unit 123, and then incident on the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 is incident on the light exit unit 122. The red light LR incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10g.

[0194] In the NA diagram shown in Fig. 79, of the multiple approximate squares representing the viewing angle of the red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by light guide plate 10g at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by light guide plate 10g at all viewing angles.

[0195] In Example 8, by arranging a separation deflection unit 123 and a return deflection unit 127 and increasing the NA transition amount in the separation deflection unit, it is possible to suppress the generation of light deflected in the direction opposite to the direction deflected from the separation deflection unit 123 toward the return deflection unit 127, thereby increasing the light utilization efficiency.

[0196] <Example 9> A light guide plate according to Example 9 will be described with reference to Fig. 80 to Fig. 86. Fig. 80 is a diagram showing the configuration of a light guide plate 10h according to Example 9. Fig. 81 is a diagram showing how blue light LB is guided in the light guide plate 10h. Fig. 82 is a diagram showing an NA diagram of blue light LB in the light guide plate 10h. Fig. 83 is a diagram showing how green light LG is guided in the light guide plate 10h. Fig. 84 is a diagram showing an NA diagram of green light LG in the light guide plate 10h. Fig. 85 is a diagram showing how red light LR is guided in the light guide plate 10h. Fig. 86 is a diagram showing an NA diagram of red light LR in the light guide plate 10h.

[0197] As shown in FIG. 80, a light guide plate 10 h differs from the light guide plate 10 according to Example 1 in that the light deflection section 12 has a second recovery deflection section 128 .

[0198] 80 , the second recovery deflection unit 128 is disposed on the opposite side of the light incident unit 121 from the separation deflection unit 123. The second recovery deflection unit 128 deflects the light L deflected by the light incident unit 121 in the direction opposite to the direction in which the separation deflection unit 123 is located, toward the direction in which the intermediate deflection unit 124 is located. The light L deflected by the second recovery deflection unit 128 is incident on the intermediate deflection unit 124.

[0199] In Example 9, the light L deflected by the light incident section 121 in the direction opposite to the direction in which the separation deflection section 123 is located is deflected by the second recovery deflection section 128 and made incident on the intermediate deflection section 124. This makes it possible to use the light L deflected in the opposite direction. As a result, in Example 9, the light utilization efficiency of the light guide plate 10h can be increased.

[0200] Table 19 shows the main specifications of the light guide plate 10h. Table 20 shows the propagation angles and NA states of the blue light LB, the green light LG, and the red light LR at the center of the viewing angle after separation by the separation / deflection unit 123.

[0201]

[0202]

[0203] As shown in FIG. 81 , blue light LB is incoupled by light incident unit 121 and then enters separation / deflection unit 123. Of the blue light LB incident on separation / deflection unit 123, the light diffracted by separation / deflection unit 123 enters intermediate deflection unit 124. Furthermore, a portion of the blue light LB incident on light incident unit 121 is diffracted in the direction opposite to the direction in which separation / deflection unit 123 is located, and enters second recovery / deflection unit 128. Of the blue light LB incident on second recovery / deflection unit 128, the light diffracted by second recovery / deflection unit 128 enters intermediate deflection unit 124. Of the blue light LB incident on intermediate deflection unit 124, the light diffracted by intermediate deflection unit 124 enters light exit unit 122. On the other hand, of the blue light LB incident on the separating / deflecting unit 123, the light that passes through the separating / deflecting unit 123 enters the optical duplication unit 125. In the example shown in Fig. 81 , the amount of blue light LB incident on the optical duplication unit 125 is less than the amount of blue light LB incident on the intermediate deflection unit 124. Of the blue light LB incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 enters the light emitting unit 122. The blue light LB incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and exits from the light guide plate 10h.

[0204] 82, arrow W8 represents the transition of the NA state by the second recovery deflection unit 128. Of the multiple approximate squares representing the viewing angles of blue light LB, the approximate squares corresponding to blue light LB incoupled into light guide plate 10h are all located within the total internal reflection light guide region T. Therefore, the blue light LB corresponding to these approximate squares is guided by light guide plate 10h at all viewing angles.

[0205] As shown in FIG. 83 , green light LG is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Of the green light LG that enters the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 enters the intermediate deflection unit 124. Furthermore, a portion of the green light LG that enters the light incident unit 121 is diffracted in the direction opposite to the direction in which the separation / deflection unit 123 is located, and enters the second recovery / deflection unit 128. Of the green light LG that enters the second recovery / deflection unit 128, the light diffracted by the second recovery / deflection unit 128 enters the intermediate deflection unit 124. Of the green light LG that enters the intermediate deflection unit 124, the light diffracted by the intermediate deflection unit 124 enters the light exit unit 122. On the other hand, of the green light LG incident on the separation deflection unit 123, the light that passes through the separation deflection unit 123 enters the optical duplication unit 125. In the example shown in Fig. 83, the amount of green light LG incident on the optical duplication unit 125 is greater than the amount of green light LG incident on the intermediate deflection unit 124. Of the green light LG incident on the optical duplication unit 125, the light that passes through the optical duplication unit 125 or is diffracted by the optical duplication unit 125 enters the light emitting unit 122. The green light LG incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and exits from the light guide plate 10h.

[0206] In the NA diagram shown in FIG. 84 , among the multiple approximate squares representing the viewing angles of the green light LG, the multiple approximate squares positioned along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the green light LG corresponding to these approximate squares is guided by the light guide plate 10h at all viewing angles. On the other hand, the multiple approximate squares positioned diagonally at 45 degrees to the NAx axis each have portions located outside the outer circle of the NA diagram. Therefore, the green light LG corresponding to these approximate squares is not guided by the light guide plate 10h at some viewing angles. Therefore, only a portion of the green light LG at all viewing angles is deflected by the separation deflection unit 123 toward the second recovery deflection unit 128, and only a portion of that portion of the viewing angles is deflected in the direction of the intermediate deflection unit 124.

[0207] As shown in Figure 85, the red light LR is incoupled by the light incident unit 121 and then enters the separation / deflection unit 123. Furthermore, a portion of the green light LG incident on the light incident unit 121 is diffracted in the direction opposite to the direction in which the separation / deflection unit 123 is located, and enters the second recovery / deflection unit 128. In the example shown in Figure 85, the red light LR incident on the separation / deflection unit 123 is not diffracted by the separation / deflection unit 123 and passes through the separation / deflection unit 123. Furthermore, the red light LR incident on the second recovery / deflection unit 128 is not deflected by the second recovery / deflection unit 128. Of the red light LR incident on the separation / deflection unit 123, the light that passes through the separation / deflection unit 123 enters the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light that is transmitted through the optical duplication unit 125 or diffracted by the optical duplication unit 125 is incident on the light emitting unit 122. The red light LR incident on the light emitting unit 122 is diffracted by the light emitting unit 122 and is emitted from the light guide plate 10h.

[0208] In the NA diagram shown in Fig. 86, of the multiple approximate squares representing the viewing angle of the red light LR, the multiple approximate squares located in directions along the NAx axis and the NAy axis are each located within the total internal reflection light-guiding region T. Therefore, the red light LR corresponding to these approximate squares is guided by the light guide plate 10h at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis are all located outside the outer circle of the NA diagram. Therefore, the red light LR corresponding to these approximate squares is not guided by the light guide plate 10h at all viewing angles.

[0209] Although the preferred embodiments have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments of the present disclosure without departing from the scope of the claims.

[0210] All numbers such as ordinal numbers and quantities used in the description of the embodiments of the present disclosure are provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated numbers. Furthermore, the connection relationships between components are provided as examples to specifically explain the technology of the present disclosure, and do not limit the connection relationships that realize the functions of the present disclosure.

[0211] Although the present disclosure has been described based on specific configuration examples, the present disclosure is not limited to the above-described configuration examples. A display device using a light guide plate according to the embodiment may be linked to a smartphone, a notebook personal computer (PC), or the like.

[0212] The disclosure of Japanese Patent Application No. 2024-150966, filed on September 2, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0213] 10, 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h Light guide plate 11 Light guide substrate 12 Light deflection section 121 Light entrance section 122 Light exit section 123 Separation deflection section 124 Intermediate deflection section 125 Light duplication section 126 First recovery deflection section 127 Return deflection section 128 Second recovery deflection section 100 Display device 101 Frame 102 Temple 110 Glasses-type support 111 First main surface 112 Second main surface A First direction B Second direction L Light L1 First light portion L2 Second light portion LB Blue light LG Green light LR Red light P1 First grating pitch P2 Second grating pitch PS1, PS2 Reference two-dimensional diffraction grating pitch S1 First side S2 Second side T Total internal reflection light-guiding region BC Reference two-dimensional diffraction grating UC Minimum unit grating W1, W2, W3, W4, W4A, W4B, W5, W6, W7, W8 Arrow θprop Propagation angle φ Angle

Claims

1. A light guide plate having a light guide substrate and one or more light deflection units formed on the light guide substrate, wherein the light deflection units have: a light incident unit that incouples light having a predetermined viewing angle into the light guide plate; a light exit unit that causes the light incoupled by the light incident unit to exit the light guide plate; and a separation deflection unit that is disposed between the light incident unit and the light exit unit and separates the light into at least a first light portion and a second light portion, wherein the first light portion has a higher proportion of blue light and a lower proportion of red light than the second light portion, and the propagation angle of the blue light at the center of the viewing angle of the first light portion is equal to or greater than the propagation angle of the green light at the center of the viewing angle of the second light portion, or is equal to or greater than the propagation angle of the red light at the center of the viewing angle of the second light portion.

2. The light guide plate according to claim 1, wherein the light incident portion is a one-dimensional diffraction grating.

3. The light guide plate according to claim 1, wherein the angle formed by the light guide directions of the light at the center of the viewing angle of the first light portion separated by the separation deflection unit and the light at the center of the viewing angle of the second light portion is between 20 degrees and 70 degrees.

4. Let the vector representing the first grating pitch P1 be (X, Y) = (p1x, p1y), let the vector representing the second grating pitch P2 be (X, Y) = (p2x, p2y), let m be a natural number, let m1 = 0, ±1, ±2, and let m2 = 0, ±1, ±2, then, using a reference two-dimensional diffraction grating having the first grating pitch P1 in a first direction and the second grating pitch P2 in a second direction different from the first direction as a reference, all of the light deflection sections formed on the light guide plate are diffraction gratings that satisfy either the following condition (a) or (b): (a) a one-dimensional diffraction grating having only a grating pitch Pm given by the following formula: Pm = m / [[m1·{p2y / (p1x·p2y-p1y·p2x)} + m2·{-p1y / (p1x·p2y-p1y·p2x)}] ２ +[m1・{-p2x / (p1x・p2y-p1y・p2x)}+m2・{p1x / (p1x・p2y-p1y・p2x)}] ２ 〕 ０．５ (b) a two-dimensional diffraction grating having a first grating pitch m·P1 in the first direction and a second grating pitch m·P2 in the second direction.

5. The light entrance portion is a diffraction grating that satisfies either of the following conditions (c) or (d): (c) a one-dimensional diffraction grating having a minimum unit grating with the grating pitch Pm that can be expressed as (m1, m2) = (1, 0), (-1, 0), (0, 1), or (0, -1); (d) a two-dimensional diffraction grating having a first grating pitch m·P1 in the first direction and a second grating pitch m·P2 in the second direction. The light guide plate according to claim 4.

6. The separating / deflecting unit is a diffraction grating that satisfies either the following condition (e) or (f): (e) where the diffraction orders of light incident on the separating / deflecting unit converted to the reference two-dimensional diffraction grating are (m1in, m2in) and the diffraction orders of light exiting the separating / deflecting unit converted to the reference two-dimensional diffraction grating are (m1out, m2out), then (m1, m2) = (m1out - m1in, m2out - m2in), and the one-dimensional diffraction grating has a minimum unit grating with the grating pitch Pm given by a combination of (m1in, m2in) = (±1, 0), (0, ±1) and (m1out, m2out) = (±1, -1), (±1, 1); (f) a two-dimensional diffraction grating having a first grating pitch m·P1 in the first direction and a second grating pitch m·P2 in the second direction. The light guide plate of claim 4.

7. The light guide plate of claim 1, wherein the viewing angle of the light does not change as the light is guided.

8. The light guide plate according to claim 4, wherein the angle between two sides of the reference two-dimensional unit cell that constitutes the light deflection section is 90 degrees ±20 degrees or less.

9. The light guide plate according to claim 1, wherein the light deflection section further has at least one intermediate deflection section arranged in the light guide path of the first light portion, and the first light portion immediately before entering the light emitting section does not contain red light at any of the viewing angles.

10. The light guide plate according to claim 1, wherein the light deflection section has a light duplication section that duplicates the incident light.

11. A light guide plate as described in claim 9, wherein the light deflection section is arranged on the opposite side of the separation deflection section from the intermediate deflection section, and has a first recovery deflection section that deflects light deflected by the separation deflection section in the direction opposite to the side where the intermediate deflection section is located, in the direction where the light output section is located.

12. The light guide plate according to claim 9, wherein the light deflection section has a return deflection section that is disposed in the optical path between the separation deflection section and the intermediate deflection section and deflects the light deflected by the separation deflection section in the direction where the intermediate deflection section is located.

13. The light guide plate according to claim 9, wherein the light deflection section is disposed on the opposite side of the light incident section from the separation deflection section, and has a second recovery deflection section that deflects light deflected by the light incident section in the direction opposite to the direction in which the separation deflection section is located, in the direction in which the intermediate deflection section is located.

14. A display device comprising: a light guide plate according to any one of claims 1 to 13; and a projector, wherein light projected from the projector enters the light guide plate and is emitted from the light emitting section.

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