Light guide plate and display device

Abstract

This light guide plate includes: a light guide substrate; and one or more light deflection parts formed on the light guide substrate. The light deflection parts include: a light incident part for in-coupling light having a predetermined viewing angle into the light guide plate; a light emission part for emitting the light in-coupled by the light incident part from the light guide plate; and a folding deflection part located on an extension line of an optical path of the light transmitted through the light emission part after being in-coupled by the light incident part. The folding deflection part deflects at least blue light toward the light emission part and transmits red light at least at the center of the viewing angle of the light incident from a first incident direction.

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, U.S. Pat. No. 1,130,7429 discloses a light guide plate having a single-layer light guide substrate and guiding red, green, and blue light having a viewing angle, in which 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, US Pat. Nos. 11,307,429 and 11,307,429 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 outputs the light incoupled by the light incident unit from the light guide plate, and a folding deflection unit that is arranged on an extension of the optical path of the light that has been incoupled by the light incident unit and then transmitted through the light exit unit, and the folding deflection unit deflects at least blue light toward the light exit unit and transmits red light, at least at the center of the viewing angle of the light incident from a first incident direction.

[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. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1; FIG. 3 is a diagram for explaining an NA diagram; FIG. 4 is a diagram showing the relationship between the critical angle and the propagation angle; FIG. 5 is a diagram showing an NA diagram of light guided by the light guide plate according to an embodiment; FIG. 6 is a diagram showing how blue light is guided in the light guide plate according to an embodiment; FIG. 7 is a diagram showing an NA diagram of blue light in a first light portion of the light guide plate according to an embodiment; FIG. 8 is a diagram showing an NA diagram of blue light in a second light portion of the light guide plate according to an embodiment; FIG. 9 is a diagram showing how green light is guided in the light guide plate according to an embodiment; FIG. 10 is a diagram showing an NA diagram of green light in the first light portion of the light guide plate according to an embodiment; FIG. 11 is a diagram showing an NA diagram of green light in the second light portion of the light guide plate according to an embodiment; FIG. 12 is a diagram showing how red light is guided in the light guide plate according to an embodiment; FIG. 13 is a diagram showing an NA diagram of red light in the first light portion of the light guide plate according to an embodiment; FIG. 14 is a diagram showing an NA diagram of red light in the second light portion of the light guide plate according to an embodiment; FIG. 1 is a schematic diagram showing a diffraction grating of a separation deflection unit in a light guide plate according to an embodiment. FIG. 2 is a schematic diagram showing a diffraction grating of an intermediate deflection unit in a light guide plate according to an embodiment. FIG. 3 is a schematic diagram showing a diffraction grating of an optical duplication unit in a light guide plate according to an embodiment. FIG. 4 is a schematic diagram showing a diffraction grating of a first folding deflection unit in a light guide plate according to an embodiment. FIG. 5 is a schematic diagram showing a diffraction grating of a second folding deflection unit in a light guide plate according to an embodiment. FIG. 6 is a schematic diagram showing a reference two-dimensional diffraction grating of an optical deflection unit in a light guide plate according to an embodiment. FIG. 7 is a diagram showing the configuration of a light guide plate according to Example 2. FIG. 8 is a diagram showing how blue light is guided in a light guide plate according to Example 2. FIG. 9 is a diagram showing an NA diagram of blue light in a first light portion of a light guide plate according to Example 2. FIG. 10 is a diagram showing an NA diagram of blue light in a second light portion of a light guide plate according to Example 2. FIG. 11 is a diagram showing how green light is guided in a light guide plate according to Example 2. FIG. 12 is a diagram showing an NA diagram of green light in a first light portion of a light guide plate according to Example 2. FIG. 13 is a diagram showing an NA diagram of green light in a second light portion of a light guide plate according to Example 2.1 is a diagram showing how red light is guided in a light guide plate according to Example 2. FIG. 2 is a diagram showing an NA diagram of red light in a first light portion of the light guide plate according to Example 2. FIG. 3 is a diagram showing an NA diagram of red light in a second light portion of the light guide plate according to Example 2. FIG. 4 is a diagram showing the light guiding efficiency of blue light by the light guide plates according to Examples 1 and 2. FIG. 5 is a diagram showing the light guiding efficiency of green light by the light guide plates according to Examples 1 and 2. FIG. 6 is a diagram showing the light guiding efficiency of red light by the light guide plates according to Examples 1 and 2. FIG. 7 is a diagram showing the light guiding efficiency of blue light by the light guide plate according to Example 1. FIG. 8 is a diagram showing the light guiding efficiency of blue light by the light guide plate according to Example 2. FIG. 9 is a diagram showing the configuration of a light guide plate according to Example 3. FIG. 10 is a diagram showing how blue light is guided in a light guide plate according to Example 3. FIG. 11 is a diagram showing an NA diagram of blue light in a first light portion of the light guide plate according to Example 3. FIG. 12 is a diagram showing an NA diagram of blue light in a second light portion of the light guide plate according to Example 3. FIG. 13 is a diagram showing how green light is guided in a light guide plate according to Example 3. FIG. 14 is a diagram showing an NA diagram of green light in the first light portion of the light guide plate according to Example 3. 1 is a diagram showing an NA diagram of green light in a second light portion of a light guide plate according to Example 3. FIG. 2 is a diagram showing how red light is guided in a light guide plate according to Example 3. FIG. 3 is a diagram showing an NA diagram of red light in a first light portion of a light guide plate according to Example 3. FIG. 4 is a diagram showing an NA diagram of red light in a second light portion of a light guide plate according to Example 3. FIG. 5 is a schematic diagram showing a diffraction grating of a light entrance portion of a light guide plate according to Example 3. FIG. 6 is a schematic diagram showing a diffraction grating of a light exit portion of a light guide plate according to Example 3. FIG. 7 is a schematic diagram showing a diffraction grating of a separation deflection portion of a light guide plate according to Example 3. FIG. 8 is a schematic diagram showing a diffraction grating of an intermediate deflection portion of a light guide plate according to Example 3. FIG. 9 is a schematic diagram showing a diffraction grating of an optical duplication portion of a light guide plate according to Example 3. FIG. 10 is a schematic diagram showing a reference two-dimensional diffraction grating of a light deflection portion of a light guide plate according to Example 3. FIG. 11 is a diagram showing the configuration of a light guide plate according to Example 4. FIG. 12 is a diagram showing how blue light is guided in a light guide plate according to Example 4. FIG. 13 is a diagram showing an NA diagram of blue light in a first light portion of a light guide plate according to Example 4. FIG. 14 is a diagram showing an NA diagram of blue light in a second light portion of a light guide plate according to Example 4. 10A and 10B are diagrams illustrating how green light is guided in the light guide plate according to Example 4.FIG. 10 is a diagram showing an NA diagram of green light in a first light portion of a light guide plate according to Example 4. FIG. 11 is a diagram showing an NA diagram of green light in a second light portion of a light guide plate according to Example 4. FIG. 12 is a diagram showing how red light is guided in a light guide plate according to Example 4. FIG. 13 is a diagram showing an NA diagram of red light in a first light portion of a light guide plate according to Example 4. FIG. 14 is a diagram showing an NA diagram of red light in a second light portion of a light guide plate according to Example 4. FIG. 15 is a schematic diagram showing a diffraction grating of a light incident portion of a light guide plate according to Example 4. FIG. 16 is a schematic diagram showing a diffraction grating of a light exit portion of a light guide plate according to Example 4. FIG. 17 is a schematic diagram showing a diffraction grating of an intermediate deflection portion of a light guide plate according to Example 4. FIG. 18 is a schematic diagram showing a diffraction grating of an optical duplication portion of a light guide plate according to Example 4. FIG. 19 is a schematic diagram showing a diffraction grating of a first folding deflection portion of a light guide plate according to Example 4. FIG. 19 is a schematic diagram showing a diffraction grating of a second folding deflection portion of a light guide plate according to Example 4. FIG. 19 is a schematic diagram showing a reference two-dimensional diffraction grating of a light deflection portion of a light guide plate according to Example 4.

[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] As used herein, 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; it 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 relative to 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 5. FIG.

[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. FIG. 5 is a diagram showing an NA diagram of light guided by the light guide plate 10.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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 outputs the light L incoupled by the light incident unit 121 from the light guide plate 10. The light deflection unit 12 also includes a return deflection unit 126 that is disposed on an extension of the optical path of the light L that has been incoupled by the light incident unit 121 and then transmitted through the light exit unit 122. 1 , the light deflection unit 12 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, an intermediate deflection unit 124 that is disposed on 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 an image projected from the projector 120.

[0020] 1 , the folded deflection unit 126 includes, in plan view, a first folded deflection unit 126-1 arranged on the opposite side of the light emitting unit 122 from the side on which the intermediate deflection unit 124 is located, and a second folded deflection unit 126-2 arranged on the opposite side of the light emitting unit 122 from the side on which the optical duplication unit 125 is located. However, the number of folded deflection units 126 is not limited to two, and may be at least one.

[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 indicating the blue light LB in the first light portion L1 is thicker than the dashed-dotted arrow indicating 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 the red light LR and the dashed-dotted arrows indicating the green light LG in the second light portion L2 are thicker than the dashed-dotted arrows indicating the 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, the light duplication section 125, and the folding deflection section 126 is a diffraction grating. These diffraction gratings are formed on the first main surface 111. The light incident section 121 diffracts all viewing angle components of the incident light L to incouple it into the light-guiding substrate 11. The light exit section 122 diffracts the light L to emit it out of the light-guiding substrate 11.

[0024] The separating deflection unit 123, the intermediate deflection 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 deflection 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 deflection 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 deflection unit 124.

[0025] In this embodiment, the first folding deflection unit 126-1 and the second folding deflection unit 126-2 each deflect the blue light LB toward the light output unit 122 and transmit the red light LR at the center of the viewing angle of the light L incident from the first incident direction D1. Furthermore, the first folding deflection unit 126-1 and the second folding deflection unit 126-2 each deflect the blue light LB, the red light LR, and the green light LG toward the light output unit 122 at the center of the viewing angle of the light L incident from a second incident direction D2 different from the first incident direction D1. In the example shown in FIG. 1 , the first incident direction D1 corresponds to the direction in which the first light portion L1 is guided toward the light output unit 122, and the second incident direction D2 corresponds to the direction in which the second light portion L2 is guided toward the light output unit 122.

[0026] In this embodiment, the second deflection unit 126-2 deflects the blue light LB incident on the second deflection unit in a direction opposite to the direction of incidence. In the example shown in Fig. 1, the second deflection unit 126-2 deflects the blue light LB incident from the second incident direction D2 in a direction opposite to the second incident direction D2.

[0027] In this embodiment, the second deflection unit 126-2 deflects the blue light LB incident on the second deflection unit 126-2 in a direction non-parallel to the direction of incidence. In the example shown in Fig. 1, the second deflection unit 126-2 deflects the blue light LB incident from the first incident direction D1 in a direction that is mirror-symmetrical to the first incident direction D1 with respect to the normal to the second deflection unit 126-2.

[0028] 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.

[0029] 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.

[0030] In this embodiment, it is preferable that the propagation angle θprop at the center of the viewing angle of the blue light LB deflected by the folding deflection unit 126 is equal to or greater than the propagation angle θprop of the red light LR or green light LG guided to the light emitting unit 122 without passing through the folding deflection unit 126. Note that 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 can be adjusted by adjusting, for example, the orientation or pitch of the diffraction grating that constitutes the separation deflection unit 123.

[0031] In this embodiment, the viewing angle of the blue light LB deflected by the folding deflection unit 126 is preferably equal to the viewing angle of the light L incident on the light incident unit 121. The propagation angle θprop of the blue light LB at the center of the viewing angle of the first light portion L1 is preferably 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.

[0032] In FIG. 5 , the approximate squares shown within the inner circles of the NA diagram represent the field of view of light L having a predetermined field of view incident on the light guide plate 10, or the field of view of light L exiting from the light exit portion. The approximate squares shown within the total internal reflection light guide region T represent the field of view of light guided by the light guide plate 10. The approximate squares shown with thin solid lines represent the field of view resulting from the superposition of red light LR, green light LG, and blue light LB. The approximate squares shown with solid lines represent the field of view of red light LR. The approximate squares shown with dashed dotted lines represent the field of view of green light LG. The approximate squares shown with dashed two dotted lines represent the field of view of blue light LB. The positions of the approximate squares representing the field of view vary depending on the wavelength. Note that the correspondence between the line types of the approximate squares in the NA diagram and the color of light is the same in the NA diagrams shown below.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] 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).

[0037] The manner in which blue light LB, green light LG, and red light LR are guided by the light guide plate 10 will be described in detail with reference to FIGS. 6 to 14 . FIG. 6 is a diagram showing the manner in which blue light LB is guided by the light guide plate 10. FIG. 7 is a diagram showing an NA diagram of blue light LB in the first light portion L1 of the light guide plate 10. FIG. 8 is a diagram showing an NA diagram of blue light LB in the second light portion L2 of the light guide plate 10. FIG. 9 is a diagram showing the manner in which green light LG is guided by the light guide plate 10. FIG. 10 is a diagram showing an NA diagram of green light LG in the first light portion L1 of the light guide plate 10. FIG. 11 is a diagram showing an NA diagram of green light LG in the second light portion L2 of the light guide plate 10. FIG. 12 is a diagram showing the manner in which red light LR is guided by the light guide plate 10. FIG. 13 is a diagram showing an NA diagram of red light LR in the first light portion L1 of the light guide plate 10. FIG. 14 is a diagram showing the NA diagram of the red light LR in the second light portion L2 of the light guide plate 10. As shown in FIG.

[0038] 6, 9, and 12, 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 drawings showing how light is guided by the light guide plate.

[0039] 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 incident on 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 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 that is not diffracted by the separation / deflection unit 123 and passes through the separation / deflection unit 123 enters the optical duplication unit 125. In the example shown in FIG. 6 , 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 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.

[0040] A portion of the blue light LB incident on the light emitting unit 122 is transmitted through the light emitting unit 122 without being diffracted by the light emitting unit 122 and is incident on the folding deflection unit 126. In this embodiment, the folding deflection unit 126 deflects the blue light LB toward the light emitting unit 122 at the center of the viewing angle of the blue light LB incident from the first incident direction D1. The folding deflection unit 126 also deflects the light at the center of the viewing angle of the blue light LB incident on the folding deflection unit 126 in the direction opposite to the incident direction. The folding deflection unit 126 also deflects the light at the center of the viewing angle of the blue light LB incident on the folding deflection unit 126 non-parallel to the incident direction.

[0041] 6, the second fold-back deflection unit 126-2 deflects the blue light LB incident on the second fold-back deflection unit 126-2 from the first incident direction D1 toward the light emitting unit 122. The second fold-back deflection unit 126-2 also deflects the blue light LB incident on the second fold-back deflection unit 126-2 from the second incident direction D2 in the direction opposite to the second incident direction D2. The second fold-back deflection unit 126-2 also deflects the blue light LB incident on the second fold-back deflection unit 126-2 from the first incident direction D1 non-parallel to the incident direction, for example, in a direction mirror-symmetrical to the first incident direction D1 with respect to the normal to the second fold-back deflection unit 126-2. Furthermore, of the blue light LB folded back by the second folding deflection unit 126-2 to the light emitting unit 122, the light that is not diffracted by the light emitting unit 122 and passes through the light emitting unit 122 is incident on the first folding deflection unit 126-1. The first folding deflection unit 126-1 deflects the incident light non-parallel to the incident direction, for example, in a direction mirror-symmetrical to the incident direction with respect to the normal to the second folding deflection unit 126-2.

[0042] 7 and 8 show the guiding of blue light LB in the real space shown in FIG. 6 in NA diagrams, in other words, in wavenumber space. FIG. 7 is an NA diagram showing the guiding of the first light, i.e., the light corresponding to the first incident direction D1, and FIG. 8 is an NA diagram showing the guiding of the second light, i.e., the light corresponding to the second incident direction D2. The arrows shown in FIGS. 7 and 8 correspond to vectors representing the transition of the NA state due to the guiding of light in the light deflection unit 12. If the wavelength of the 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 this vector is expressed as λ / d. The direction of the arrow corresponding to this vector corresponds to the periodic axis of the diffraction grating. However, strictly speaking, the direction of the 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 forming the sides of the two-dimensional diffraction grating in the case of a two-dimensional diffraction grating, and depends on the diffraction direction. When the arrow corresponding to the vector representing this transition is represented by a solid line, it means that there is light that is deflected by the light deflection unit 12 and further guided. When the arrow corresponding to the vector representing this transition is represented by a dashed line, it means that there is no light that is deflected by the light deflection unit 12 and further guided, or that there is no light that is guided.

[0043] In the examples shown in Figures 7 and 8, arrow W1 represents the transition of the NA state by the light incident section 121. Arrow W3 represents the transition of the NA state by the separation deflection section 123. Arrow W4 represents the transition of the NA state by the intermediate deflection section 124. Arrow W5 represents the transition of the NA state by the optical duplication section 125. Arrow W6-1 represents the transition of the NA state by the first return deflection section 126-1. Arrow W6-2 represents the transition of the NA state by the second return deflection section 126-2. The meanings represented by the arrows in the NA diagrams in Figures 7 and 8 are the same in the NA diagrams shown below.

[0044] 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.

[0045] The arrows W1, W3, W4, W5, W6-1, and W6-2 are all represented by solid lines, and therefore, blue light LB exists that is guided in accordance with each arrow.

[0046] As shown in FIG. 9 , 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 not diffracted by the separation / deflection unit 123 and passes through the separation / deflection unit 123 enters the optical duplication unit 125. In the example shown in FIG. 9 , 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.

[0047] A portion of the green light LG incident on the light emitting portion 122 is not diffracted by the light emitting portion 122 but passes through the light emitting portion 122 and is incident on the folding deflection portion 126. The folding deflection portion 126 deflects the green light LG toward the light emitting portion 122 at the center of the viewing angle of the green light LG incident from the first incident direction D1. Furthermore, the folding deflection portion 126 deflects the green light LG toward the light emitting portion 122 at the center of the viewing angle of the green light LG incident from the second incident direction D2.

[0048] 10 is an NA diagram showing the guiding of the first light, i.e., the light corresponding to the first incident direction D1, and FIG. 11 is an NA diagram showing the guiding of the second light, i.e., the light corresponding to the second incident direction D2. In the NA diagrams shown in FIGS. 10 and 11 , among the multiple approximate squares representing the viewing angles of the 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, the green light LG 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 each have a portion located outside the outer circle of the NA diagram. Therefore, the green light LG corresponding to these approximate squares has light at some viewing angles that is not guided by the light guide plate 10.

[0049] 10 and 11, arrows W1, W3, W4, W5, and W6-2 are all represented by solid lines. Therefore, there is green light LG guided in accordance with each arrow. On the other hand, arrow W6-1 is represented by a dashed line. Therefore, there is no green light LG guided in accordance with arrow W6-1.

[0050] 12 , 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. 12 , the red light LR incident on the separation / deflection unit 123 is not diffracted by the separation / deflection unit 123, but passes through the separation / deflection unit 123 and enters 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.

[0051] A portion of the red light LR incident on the light emitting unit 122 is transmitted through the light emitting unit 122 without being diffracted by the light emitting unit 122, and is then incident on the folding deflection unit 126. The folding deflection unit 126 transmits the red light LR at the center of the viewing angle of the red light LR incident from the first incident direction D1. The folding deflection unit 126 also deflects the red light LR toward the light emitting unit 122 at the center of the viewing angle of the red light LR incident from the second incident direction D2.

[0052] FIG. 13 is an NA diagram showing the guiding of the first light, i.e., the light corresponding to the first incident direction D1, and FIG. 14 is an NA diagram showing the guiding of the second light, i.e., the light corresponding to the second incident direction D2. In the NA diagrams shown in FIGS. 13 and 14 , among 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.

[0053] In the example shown in FIG. 13, the arrow W1 is represented by a solid line. Therefore, there is red light LR that is guided in accordance with the arrow W1. On the other hand, the arrows W3, W4, W6-1, and W6-2 are represented by dashed lines. Therefore, there is no red light LR that is guided in accordance with these. In the example shown in FIG. 14, the arrows W1, W5, and W6-2 are represented by solid lines. Therefore, there is red light LR that is guided in accordance with these.

[0054] <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.

[0055] 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.

[0056] 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 the green light, and the 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 the green light, and the red light transitions in the slowest NA state. Therefore, when red, green, and blue light propagate in parallel, the blue light attenuates the fastest, the green light attenuates the next fastest, and the 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.

[0057] 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.

[0058] In this embodiment, the folding deflection unit 126 is disposed on an extension of the optical path of the light L that is incoupled by the light incident unit 121 and then transmitted through the light output unit 122. The folding deflection unit 126 deflects at least the blue light LB toward the light output unit 122 and transmits the red light LR, at least at the center of the viewing angle of the light L incident from the first incident direction D1. By deflecting at least the blue light LB of the light L that has transmitted through the light output unit 122 toward the light output unit 122 by the folding deflection unit 126, the blue light LB can be made to re-enter the light output unit 122 and be emitted from the light guide plate 10 by the light output unit 122. This reduces the amount of blue light LB that transmits through the light output unit 122 and cannot contribute to the light emitted from the light guide plate 10, and increases the amount of blue light LB that contributes to the light emitted from the light guide plate 10. On the other hand, the folded deflection unit 126 transmits the red light LR of the light L that has passed through the light output unit 122, and does not allow the red light LR to contribute to the light output from the light guide plate 10. As a result, in the light guide plate 10, the amount of red light LR can be reduced while compensating for the amount of blue light LB, which is attenuated more than the red light LR and the green light LG, and the light guide efficiencies of the blue light LB, the green light LG, and the red light LR can be made closer to each other. Furthermore, by modulating the diffraction efficiency within the folded deflection unit 126, it is possible to adjust the light amount distribution of the blue light LB, of the blue light LB and the red light LR, that is selectively deflected toward the light output unit 122, and therefore it is possible to adjust the unevenness in the light guide efficiency for blue independently.

[0059] There is a correlation between the amount of light and its intensity. As the ratios of the amount of emitted light to the amount of incident light of the blue light LB, the green light LG, and the red light LR approach each other, the ratios of the amount of emitted light to the amount of incident light of the blue light LB, the green light LG, and the red light LR approach each other. This brings the light guide efficiencies of the blue light LB, the green light LG, and the red light LR closer to each other, improving color balance. As described above, this embodiment can provide a light guide plate 10 with good color balance. Furthermore, by including the light guide plate 10, the display device 100 can display an image with good color balance.

[0060] 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.

[0061] In this embodiment, the light guide plate 10 has the separation deflection unit 123, so that the first light portion L1 has a higher proportion of blue light LB and a lower proportion of red light LR than the second light portion L2, and is incident on the return deflection unit 126 from the first incident direction D1. This increases the amount of blue light LB deflected by the separation deflection unit 123 toward the light output unit 122, thereby efficiently compensating for the amount of blue light LB. As a result, the light guide efficiencies of the blue light LB, green light LG, and red light LR become closer to each other, improving the color balance of the light guide plate 10.

[0062] In this embodiment, the folding deflection unit 126 deflects blue light LB, red light LR, and green light LG toward the light emitting unit 122 at the center of the viewing angle of light L incident from the second incident direction D2. This reduces the amounts of blue light LB, red light LR, and green light LG that pass through the light emitting unit 122 and cannot contribute to the light emitted from the light guide plate 10, and increases the amounts of blue light LB, red light LR, and green light LG that contribute to the light emitted from the light guide plate 10. As a result, the light utilization efficiency of the light guide plate 10 is improved.

[0063] In this embodiment, the blue light LB incident from the first incident direction D1 and deflected by the return deflection unit 126 has an NA state of (m1o, m2o) = (1,1), (-1,1), (1,-1), or (-1,-1) in the above equations (1) and (2), and the red light LR or green light LG incident from the second incident direction D2 and guided to the light output unit 122 without passing through the return deflection unit 126 has an NA state of (m1o, m2o) = (1,0), (-1,0), (0,1), or (0,-1). For this reason, the propagation angle θprop at the center of the viewing angle of blue light LB, which is incident from the first incident direction D1 and deflected by the folding deflection unit 126, is equal to or greater than the propagation angle θprop of red light LR or green light LG, which is incident from the second incident direction D2 and guided to the light output unit 122 without passing through the folding deflection unit 126. As a result, the number of total reflections within the light guide substrate 11 of the light at the center of the viewing angle of blue light LB is less than the number of total reflections of the light at the center of the viewing angle of red light LR or the light at the center of the viewing angle of green light LG, when propagating the same distance in the in-plane direction within the light guide substrate 11. As a result, attenuation of blue light LB is reduced.

[0064] In this embodiment, the viewing angle of the blue light LB deflected by the folding deflection section 126 is equal to the viewing angle of the light L incident on the light incident section 121. This makes it easier to design the light guide plate 10.

[0065] In this embodiment, the folding deflection section 126 deflects the light at the center of the viewing angle of the incident blue light LB in the direction opposite to the incident direction, which makes it easier to design the light guide plate 10.

[0066] The number of intermediate deflection units 124 is not limited to one, and may be at least one. In the example shown in Fig. 1, the first light portion L1 separated by the separation deflection unit 123 does not include the red light LR, but this is not limiting. For example, the first light portion L1 may include 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 include the red light LR at any viewing angle immediately before entering the light emitting unit 122.

[0067] <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. 15 to 22. FIG. 15 is a schematic diagram showing the diffraction grating of the light entrance unit 121 of the light guide plate 10. FIG. 16 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10. FIG. 17 is a schematic diagram showing the diffraction grating of the separation deflection unit 123 of the light guide plate 10. FIG. 18 is a schematic diagram showing the diffraction grating of the intermediate deflection unit 124 of the light guide plate 10. FIG. 19 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10. FIG. 20 is a schematic diagram showing the diffraction grating of the first folding deflection unit 126-1 of the light guide plate 10. FIG. 21 is a schematic diagram showing the diffraction grating of the second folding deflection unit 126-2 of the light guide plate 10. FIG. 22 is a schematic diagram showing the reference two-dimensional diffraction grating BC of the light deflection unit 12 in the light guide plate 10. As shown in FIG.

[0068] In the example shown in FIG. 15 , the light incident portion 121 is a diffraction grating with a one-dimensional lattice shape having a plurality of line-and-space patterns extending in the Y direction. For ease of explanation, a diffraction grating with a one-dimensional lattice shape will hereinafter be referred to as a one-dimensional lattice. 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 of 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.

[0069] In the example shown in FIG. 16 , the light emitting portion 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 be referred to as a two-dimensional lattice hereinafter. 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 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. A portion of the light L incident on the light emitting portion 122 is converted into first-order diffracted light in its light guide direction.

[0070] 17, the separating / deflecting unit 123 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 separating / deflecting unit 123. The second grating pitch P2 is the pitch of the diffraction grating of the separating / deflecting unit 123 in the Y direction. The second grating pitch P2 in the separating / deflecting unit 123 is, for example, 355.0 nm. The light guide direction of part of the light L incident on the separating / deflecting unit 123 is converted as first-order diffracted light.

[0071] 18 , 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 second grating pitch P2 is the pitch of the diffraction grating of the intermediate deflection unit 124 in the Y direction. The second grating pitch P2 in the intermediate deflection unit 124 is, for example, 177.5 nm. The light guide direction of part of the light L incident on the intermediate deflection unit 124 is converted into first-order diffracted light.

[0072] In the example shown in FIG. 19 , 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 that constitutes 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 X direction. The second grating pitch P2 is the pitch of the diffraction grating of the optical duplication unit 125 in the Y direction. 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 guided direction converted into first-order diffracted light.

[0073] In the example shown in FIG. 20 , the first folding deflection unit 126-1 is a one-dimensional grating having a plurality of line-and-space patterns extending in the X direction. The minimum unit cell UC represents the smallest unit cell constituting the first folding deflection unit 126-1. The second grating pitch P2 is the pitch of the diffraction grating of the first folding deflection unit 126-1 in the Y direction. The second grating pitch P2 in the first folding deflection unit 126-1 is, for example, 177.5 nm. The light L incident on the first folding deflection unit 126-1 has a portion of its light guide direction converted into first-order diffracted light.

[0074] In the example shown in FIG. 21 , the second deflection unit 126-2 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 deflection unit 126-2. The first grating pitch P1 is the pitch of the diffraction grating of the second deflection unit 126-2 in the X direction. The first grating pitch P1 in the second deflection unit 126-2 is, for example, 177.5 nm. The light L incident on the first deflection unit 126-1 has a portion of its light guide direction converted into first-order diffracted light.

[0075] Here, 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), m is a natural number, and m1 and m2 are m1 = 0, ±1, ±2, and m2 = 0, ±1, ±2. In this embodiment, based on a reference two-dimensional diffraction grating BC shown in FIG. 22 that has 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...(3)(b) 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.

[0076] For example, if the grating pitch of the diffraction grating does not satisfy the above condition (a) or (b), unintended stray light may be generated during light guide by the light guide plate 10, causing the diffracted light to blur the image, for example, to produce an image at a shifted angle. When the grating pitches of the diffraction gratings in all light deflection units 12 satisfy the above condition, image blurring caused by the 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 the light guided by the light guide plate 10 only in the NA state transitioned by the reference two-dimensional diffraction grating.

[0077] 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.

[0078] 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) A one-dimensional diffraction grating having a minimum unit grating with a grating pitch Pm given by the combination of (m1in, m2in) = (m1out - m1in, m2out - m2in) where m1 and m2 are (m1, m2) = (m1out - m1in, m2out - m2in) and (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.

[0079] In the example shown in Fig. 22 , 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. 22 , to indicate that the first direction A is a direction along the reference two-dimensional diffraction grating pitch PS1, the symbols for the first direction A and the reference two-dimensional diffraction grating pitch PS1 are written together. To indicate that the second direction B is a direction along the reference two-dimensional diffraction grating pitch PS2, the symbols for the second direction B and the reference two-dimensional diffraction grating pitch PS2 are written together.

[0080] For example, the separating / deflecting unit 123 is a one-dimensional diffraction grating, and the light L has (m1in, m2in) = (-1, 0) when it enters the separating / deflecting unit 123, and (m1out, m2out) = (-1, -1) when it exits the separating / deflecting unit 123. Therefore, (m1, m2) = (m1out - m1in, m2out - m2in) = (0, -1), which matches the diffraction order of the separating / deflecting unit 123. Satisfying such conditions makes it easier to design the light guide plate 10.

[0081] The light incident portion 121 is a one-dimensional diffraction grating, and the diffraction orders of the light incident portion 121 correspond to m = 1, m1 = -1, and m1 = 0. The grating pitch Pm obtained by substituting these into equation (3) matches the grating pitch of the light incident portion 121.

[0082] 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. In the Y direction, they correspond to m=1, m1=0, and m2=1. The pitch of the two-dimensional diffraction grating obtained from these corresponds to the grating pitch of the light emitting portion 122.

[0083] The intermediate deflection unit 124 is a one-dimensional diffraction grating, and the diffraction orders of the intermediate deflection unit 124 correspond to m = 1, m1 = 0, and m2 = 2. The grating pitch Pm obtained by substituting these into equation (3) matches the grating pitch of the intermediate deflection unit 124.

[0084] 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 = 0 in the +Y direction. In the -Y direction, they correspond to m = 1, m1 = 0, and m2 = -1. The pitch of the two-dimensional diffraction grating obtained from these is 355.0 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.

[0085] In this embodiment, the return deflection unit 126 is preferably a diffraction grating that satisfies either the following condition (g) or (h). 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. (g) A one-dimensional diffraction grating having a grating pitch Pm given by the combination of (m1in, m2in) = (m1out - m1in, m2out - m2in), where (m1in, m2in) = (±1, 0), (0, ±1), and (m1out, m2out) = (±1, -1), (±1, 1). (h) 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.

[0086] The first deflection unit 126-1 is a one-dimensional diffraction grating, and the diffraction orders of the first deflection unit 126-1 correspond to m = 1, m1 = 0, and m2 = -2. The grating pitch Pm obtained by substituting these into equation (3) matches the grating pitch of the first deflection unit 126-1.

[0087] The second deflection unit 126-2 is a one-dimensional diffraction grating, and the diffraction orders of the second deflection unit 126-2 correspond to m = 1, m1 = 2, and m2 = 0. The grating pitch Pm obtained by substituting these into equation (3) matches the grating pitch of the second deflection unit 126-2.

[0088] The light deflection unit 12 is not limited to an 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 light deflection unit 12 can be changed as appropriate depending on the specifications of the light guide plate 10. In the case of a two-dimensional lattice, the minimum unit lattice UC is not limited to a square lattice (where the lattice pitch in two directions is equal and the angle formed by the lattice is 90 degrees), but may be a rectangular lattice (where the lattice pitch in two directions is different and the angle formed by the lattice is not 90 degrees), a rhombic lattice (where the lattice pitch in two directions is equal and the angle formed by the lattice is not 90 degrees), or a parallelogram lattice (where the lattice pitch in two directions is different and the angle formed by the lattice is not 90 degrees). Furthermore, the reference two-dimensional diffraction grating BC is not limited to a square lattice, but may be a rectangular lattice, a rhombic lattice, or a parallelogram lattice.

[0089] In this embodiment, it is preferable that the return deflection unit 126 is a one-dimensional diffraction grating. By using the return deflection unit 126 as a one-dimensional diffraction grating, the return deflection unit 126 can be easily processed and the generation of unnecessary light in the return deflection unit 126 can be reduced.

[0090] <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.

[0091] 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 ３The 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.

[0092] 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 separation deflection unit 123, the intermediate deflection unit 124, the light duplication unit 125, the first folding deflection unit 126-1, and the second folding deflection unit 126-2 can be formed.

[0093] 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.

[0094] [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).

[0095] Examples 1, 3, and 4 shown below are working examples. Example 2 is a comparative example. 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.

[0096]

[0097] 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.

[0098] In Table 2, (-1, 0) in the incoupling light guide direction represents, for example, the +X direction. The reference two-dimensional diffraction grating pitch PS1 means 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 means 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, (-1, 1) in the NA state represents, for example, a direction tilted 45 degrees with respect to the X axis, and a direction that approaches the +Y direction as it approaches the -X direction. The (-1, 0) in the NA state represents, for example, the -X direction.

[0099]

[0100]

[0101] <Example 2> A light guide plate according to Example 2 will be described with reference to Figs. 23 to 32A, 32B, 32C, 32D, 32E, and 32F. Fig. 23 is a diagram showing the configuration of a light guide plate 10a according to Example 2. Fig. 24 is a diagram showing how blue light LB is guided in the light guide plate 10a. Fig. 25 is a diagram showing an NA diagram of blue light LB in the first light portion L1 of the light guide plate 10a. Fig. 26 is a diagram showing an NA diagram of blue light LB in the second light portion L2 of the light guide plate 10a. Fig. 27 is a diagram showing how green light LG is guided in the light guide plate 10a. Fig. 28 is a diagram showing an NA diagram of green light in the first light portion L1 of the light guide plate 10a. Fig. 29 is a diagram showing an NA diagram of green light LG in the second light portion L2 of the light guide plate 10a. Fig. 30 is a diagram showing how red light LR is guided in the light guide plate 10a. Fig. 31 is a diagram showing an NA diagram of red light LR in the first light portion L1 of light guide plate 10a. Fig. 32A is a diagram showing an NA diagram of red light LR in the second light portion L2 of light guide plate 10a.

[0102] Fig. 32B 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. 32C 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. 32D 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. 32E is a diagram showing the light guide efficiency of blue light by the light guide plate 10 according to Example 1. Fig. 32F is a diagram showing the light guide efficiency of blue light by the light guide plate 10a according to Example 2.

[0103] As shown in FIG. 23, 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 folded deflection section.

[0104] 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.

[0105]

[0106]

[0107] 24 , blue light LB is incoupled by the light incident unit 121 and then incident on 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 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, of the blue light LB incident on the separation / deflection unit 123, the light that has passed through the separation / deflection unit 123 is incident on the optical duplication unit 125. In the example shown in FIG. 24 , 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 10a.

[0108] 25 and 26 , among 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.

[0109] 27, the green light LG is incoupled by the light incident unit 121 and then incident on the separation / deflection unit 123. Of the green light LG incident on the separation / deflection unit 123, the light diffracted by the separation / deflection unit 123 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, of the green light LG incident on the separation / deflection unit 123, the light that has passed through the separation / deflection unit 123 is incident on the optical duplication unit 125. In the example shown in FIG. 27, 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 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 10a.

[0110] 28 and 29 , among 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, light of the green light LG corresponding to these approximate squares at all viewing angles is guided by light guide plate 10a. On the other hand, multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx axis each have a portion located outside the outer circle of the NA diagram. Therefore, light of some viewing angles of the green light LG corresponding to these approximate squares is not guided by light guide plate 10a.

[0111] 30 , 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. 30 , the red light LR incident on the separation / deflection unit 123 is not diffracted by the separation / deflection unit 123 but passes through the separation / deflection unit 123 and is 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 is output from the light guide plate 10 a.

[0112] In the NA diagrams shown in Figures 31 and 32, among the multiple approximate squares representing the viewing angles of the red light LR, the multiple approximate squares located 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 10a 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 10a at all viewing angles. Furthermore, as shown in Figure 31, there is no red light LR guided in the directions indicated by arrows W3 and W4.

[0113] 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 separation deflection section 123 in Example 2 is the same as the diffraction order of the separation deflection section 123 in Example 1. The diffraction order of the intermediate deflection section 124 in Example 2 is the same as the diffraction order of the intermediate deflection section 124 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.

[0114] 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. FIG. 32B shows the simulation results of 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 in the X direction from the design center position. FIG. 32C shows the simulation results of 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 in the X direction from the design center position. FIG. 32D shows the simulation results of 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 in the X direction from the design center position. Note that in FIGS. 32B, 32C, and 32D, 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.

[0115] Fig. 32E shows the simulation results of calculations for the light guide efficiency of blue light LB by light guide plate 10 when the eye position is shifted within a range of ±2.2 mm in the X and Y directions from the design center position. Fig. 32F shows the simulation results of calculations for the light guide efficiency of blue light LB by light guide plate 10a when the eye position is shifted within a range of ±2.2 mm in the X and Y directions from the design center position.

[0116] 32B to 32F , because the light guide plate 10 has the first folded deflection section 126-1 and the second folded deflection section 126-2, the light guide efficiency of the blue light LB by the light guide plate 10 is greater than the light guide efficiency of the blue light LB by the light guide plate 10a. On the other hand, there is almost no difference in the light guide efficiency of the green light LG and the red light LR between the light guide plate 10 and the light guide plate 10a.

[0117] 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.

[0118]

[0119] As shown in Table 5B, by having the first folded deflection section 126-1 and the second folded deflection section 126-2 in the light guide plate 10, the light guide efficiency of the blue light LB by the light guide plate 10 was approximately 1.2 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.

[0120] <Example 3> A light guide plate according to Example 3 will be described with reference to Figs. 33 to 42. Fig. 33 is a diagram showing the configuration of a light guide plate 10b according to Example 3. Fig. 34 is a diagram showing how blue light LB is guided in the light guide plate 10b. Fig. 35 is a diagram showing an NA diagram of blue light LB in the first light portion L1 of the light guide plate 10b. Fig. 36 is a diagram showing an NA diagram of blue light in the second light portion L2 of the light guide plate 10b. Fig. 37 is a diagram showing how green light LG is guided in the light guide plate 10b. Fig. 38 is a diagram showing an NA diagram of green light LG in the first light portion L1 of the light guide plate 10b. Fig. 39 is a diagram showing an NA diagram of green light LG in the second light portion L2 of the light guide plate 10b. Fig. 40 is a diagram showing how red light LR is guided in the light guide plate 10b. Fig. 41 is a diagram showing an NA diagram of red light in the first light portion L1 of the light guide plate 10b. FIG. 42 is a diagram showing an NA diagram of red light LR in the first light portion L1 of the light guide plate 10b.

[0121] 33 , light guide plate 10b 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 and deflected by light incident section 121 is tilted at 45 degrees with respect to the X axis. Furthermore, in light guide plate 10b, folded deflection section 126 transmits light L that is incident from second incident direction D2. Note that in light guide plate 10b, intermediate deflection section 124 also functions as an optical duplication section, and optical duplication section 125 also functions as an intermediate deflection section.

[0122] In the light guide plate 10b, the folding deflection section 126 transmits light incident from the second incident direction D2. For example, the folding deflection section 126 acts as a folding grating for blue light LB incident from the second incident direction D2, while transmitting green light LG. This allows the amount of blue light LB that contributes to the output light from the light guide plate 10b to be selectively adjusted, thereby adjusting the intensity of the blue light LB according to the amount of light, thereby improving the unevenness of the light guide efficiency of the blue light LB. Furthermore, since the amount of blue light LB that contributes to the output light from the light guide plate 10b can be increased only for blue light LB, which is easily attenuated, the intensity of the blue light LB can be increased according to the amount of light, thereby improving the unevenness of the light guide efficiency for each color. As a result, the color balance of the light guide plate 10b can be improved.

[0123] 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.

[0124]

[0125]

[0126] As shown in FIG. 34 , blue light LB is incoupled by the light incident unit 121 and then incident on 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 is incident on the intermediate deflection unit 124. Of the blue light LB incident on the intermediate deflection unit 124, the light that passes through the intermediate deflection unit 124 or is diffracted by the intermediate deflection unit 124 is incident on the light exit unit 122. On the other hand, of the blue light LB incident on the separation / deflection unit 123, the light that passes through the separation / deflection unit 123 is incident on the optical duplication unit 125. In the example shown in FIG. 34 , 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 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 10b.

[0127] 35 and 36, the blue light LB 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 the arrow W1. The blue light LB is then split into a first light portion L1 and a second light portion L2 by the splitting / deflecting unit 123.

[0128] 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 10b 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 10b at all viewing angles. Also, in Figure 36, there is no blue light LB guided in the direction indicated by arrow W6.

[0129] 37 , green light LG is incoupled by the light incident unit 121 and then incident on the separation / deflection unit 123. Of the green light LG incident on the separation / deflection unit 123, light diffracted by the separation / deflection unit 123 is incident on the intermediate deflection unit 124. Of the green light LG incident on the intermediate deflection unit 124, light that passes through the intermediate deflection unit 124 or is diffracted by the intermediate deflection unit 124 is incident on the light exit unit 122. Meanwhile, of the green light LG incident on the separation / deflection unit 123, light that passes through the separation / deflection unit 123 is incident on the optical duplication unit 125. Of the green light LG incident on the optical duplication unit 125, light 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 10b.

[0130] 38 and 39, the green light LG 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 the arrow W1. The green light LG is then split into a first light portion L1 and a second light portion L2 by the splitting / deflecting unit 123.

[0131] Of the multiple approximate squares representing the viewing angles of the green light LG, multiple approximate squares located in a diagonal direction tilted 45 degrees with respect to the NAx 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 10b at all viewing angles. On the other hand, portions of the multiple approximate squares located along the NAx axis and the NAy axis are each 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 10b at some viewing angles. Furthermore, there is no green light LG guided in the direction indicated by arrow W6.

[0132] As shown in Fig. 40 , 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. 40 , the red light LR incident on the separation / deflection unit 123 is not diffracted by the separation / deflection unit 123, passes through the separation / deflection unit 123, and is incident on the optical duplication unit 125. Of the red light LR incident on the optical duplication unit 125, the light 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 is output from the light guide plate 10b.

[0133] In the NA diagrams shown in FIGS. 41 and 42 , the red light LR incoupled by the light incident unit 121 transitions to an NA state located in a direction tilted 45 degrees with respect to the NAx axis, as indicated by arrow W1. Of the multiple approximate squares representing the viewing angles of the red light LR, multiple approximate squares located in diagonal directions tilted 45 degrees with respect to the NAx 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 10b across the entire viewing angle. Meanwhile, the multiple approximate squares located 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 10b across the entire viewing angle. Furthermore, there is no red light LR guided in the directions indicated by arrows W3, W4, and W6.

[0134] The configuration of the light deflection unit 12 of the light guide plate 10b will be described with reference to Figs. 43 to 48. Fig. 43 is a schematic diagram showing the diffraction grating of the light entrance unit 121 of the light guide plate 10b. Fig. 44 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10b. Fig. 45 is a schematic diagram showing the diffraction grating of the separation deflection unit 123 of the light guide plate 10b. Fig. 46 is a schematic diagram showing the diffraction grating of the intermediate deflection unit 124 of the light guide plate 10b. Fig. 47 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10b. Fig. 48 is a schematic diagram showing the reference two-dimensional diffraction grating BC of the light deflection unit 12 of the light guide plate 10b.

[0135] In the example shown in FIG. 43 , the light incidence 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 incidence portion 121. The first grating pitch P1 is the pitch of the diffraction grating of the light incidence portion 121 in a direction tilted 45 degrees with respect to the X direction. The first grating pitch P1 in the light incidence portion 121 is, for example, 355.0 nm. A portion of the light L incident on the light incidence portion 121 is converted into first-order diffracted light in its light guide direction. Because the grating pitch of the light incidence portion 121 is tilted in this way, the transition from the approximately square NA state located in the NAy direction toward the -NAx direction corresponds to (-1, 0).

[0136] In the example shown in FIG. 44 , 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 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 light L incident on the light emitting portion 122 has a portion of its guided direction converted into first-order diffracted light.

[0137] In the example shown in Figure 45, the separating deflection 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 deflection unit 123. The first grating pitch P1 is the pitch of the diffraction grating of the separating deflection unit 123 in a direction tilted at approximately 70 degrees with respect to the X direction and perpendicular to the line and space patterns. The first grating pitch P1 in the separating deflection unit 123 is, for example, 355.0 / (√5) nm. The light guide direction of part of the light L incident on the separating deflection unit 123 is converted as first-order diffracted light.

[0138] 46, 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 cell UC represents the smallest unit cell 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 light L incident on the intermediate deflection unit 124 has a portion of its light guide direction converted into first-order diffracted light.

[0139] 47 , the optical duplication unit 125 is a one-dimensional grating having a plurality of line-and-space patterns extending in the X direction. The minimum unit cell UC represents the smallest unit cell 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 Y direction. The first grating pitch P1 is, for example, 355.0 / (√2) nm. The light L incident on the optical duplication unit 125 has a portion of its guided direction converted into first-order diffracted light.

[0140] In the example shown in FIG. 45 , the reference two-dimensional diffraction grating BC is a two-dimensional diffraction grating having a reference two-dimensional diffraction grating pitch PS1 in a direction tilted 45 degrees with respect to the X direction and a reference two-dimensional diffraction grating pitch PS2 in a direction tilted 45 degrees with respect to the Y direction. The reference two-dimensional diffraction grating pitch PS1 is, for example, 355.0 nm. The reference two-dimensional diffraction grating pitch PS2 is, for example, 355.0 nm. In this reference two-dimensional diffraction grating BC, the transition to the approximately square NA state in FIG. 43 corresponds to the numbers shown in FIG. 35 . The reference two-dimensional diffraction grating pitch PS1 of the reference two-dimensional diffraction grating BC is tilted 45 degrees with respect to the X axis. Therefore, the transition state in which the light L diffracted by the light incident portion 121 is guided is also (−1, 0) in the direction going in the −NAy direction as it goes in the −NAx direction.

[0141] <Example 4> A light guide plate according to Example 4 will be described with reference to Figs. 49 to 58. Fig. 49 is a diagram showing the configuration of a light guide plate 10c according to Example 4. Fig. 50 is a diagram showing how blue light LB is guided in the light guide plate 10c. Fig. 51 is a diagram showing an NA diagram of blue light LB in the first light portion L1 of the light guide plate 10c. Fig. 52 is a diagram showing an NA diagram of blue light LB in the second light portion L2 of the light guide plate 10c. Fig. 53 is a diagram showing how green light LG is guided in the light guide plate 10c. Fig. 54 is a diagram showing an NA diagram of green light LG in the first light portion L1 of the light guide plate 10c. Fig. 55 is a diagram showing an NA diagram of green light LG in the second light portion L2 of the light guide plate 10c. Fig. 56 is a diagram showing how red light LR is guided in the light guide plate 10c. Fig. 57 is a diagram showing an NA diagram of red light LR in the first light portion L1 of the light guide plate 10c. FIG. 58 is a diagram showing the NA diagram of the red light LR in the second light portion L2 of the light guide plate 10c.

[0142] 49 , light guide plate 10c differs from light guide plate 10 according to Example 1 in that light incident portion 121 separates incident light L into at least a first light portion L1 and a second light portion L2. In other words, because light incident portion 121 functions as a separating / deflecting portion, light deflection portion 12 of light guide plate 10c does not have separating / deflecting portion 123 of light guide plate 10.

[0143] In light guide plate 10c, first light portion L1 separated by light incident portion 121 has a higher proportion of blue light LB and a lower proportion of red light LR than second light portion L2, and enters folding deflection portion 126 from first incident direction D1. This increases the amount of blue light LB deflected by light incident portion 121 toward light exit portion 122, thereby efficiently compensating for the amount of blue light LB. As a result, the light guide efficiencies of blue light LB, green light LG, and red light LR approach each other depending on the light amount of each color, improving the color balance of light guide plate 10.

[0144] Furthermore, in the light guide plate 10c, similarly to the light guide plate 10 according to Example 1, the folding deflection unit 126 deflects the light at the center of the viewing angle of the blue light LB that is incident on the folding deflection unit 126 in the direction opposite to the incident direction. This makes it easier to design the light guide plate 10.

[0145] 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.

[0146]

[0147]

[0148] As shown in FIG. 50 , 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. 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. In the example shown in FIG. 50 , 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 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 10c.

[0149] In the NA diagram shown in Fig. 51, the blue light LB in the first light portion L1 incoupled by the light incident portion 121 transitions to an NA state located in a direction tilted at -45 degrees with respect to the NAx axis, as indicated by the arrow W1. In the NA diagram shown in Fig. 52, the blue light LB in the second light portion L2 incoupled by the light incident portion 121 transitions to an NA state located in a direction along the NAx axis, as indicated by the arrow W1.

[0150] 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 10c 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 10c at all viewing angles.

[0151] As shown in FIG. 53 , 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. 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. In the example shown in FIG. 53 , 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 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 10c.

[0152] In the NA diagram shown in Fig. 54, the green light LG in the first light portion L1 incoupled by the light incident unit 121 transitions to an NA state located in a direction tilted at -45 degrees with respect to the NAx axis, as indicated by the arrow W1. In the NA diagram shown in Fig. 55, the green light LG in the second light portion L2 incoupled by the light incident unit 121 transitions to an NA state located in a direction along the NAx axis, as indicated by the arrow W1.

[0153] In the NA diagrams shown in Figures 54 and 55, 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, the green light LG corresponding to these approximate squares is guided by light guide plate 10c at all viewing angles. On the other hand, the multiple approximate squares located in diagonal directions tilted 45 degrees from 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 light guide plate 10c at all viewing angles. Also, in Figure 54, there is no green light LG guided in the direction indicated by arrow W6-1.

[0154] As shown in Fig. 56, 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. 56, the red light LR is almost absent in the first light portion L1, and therefore most of the red light LR is incident on the optical duplication unit 125. Of the red light LR that is 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 that is incident on the light exit unit 122 is diffracted by the light exit unit 122 and exits from the light guide plate 10c.

[0155] In the NA diagram shown in Fig. 57, the red light LR in the first light portion L1 incoupled by the light incident unit 121 transitions to an NA state located in a direction tilted at -45 degrees with respect to the NAx axis, as indicated by the arrow W1. In the NA diagram shown in Fig. 58, the red light LR in the second light portion L2 incoupled by the light incident unit 121 transitions to an NA state located in a direction along the NAx axis, as indicated by the arrow W1.

[0156] In the NA diagrams shown in Figures 57 and 58, 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 10c 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 10c at all viewing angles. Also, in Figure 57, there is no red light LR guided in accordance with arrows W1, W4, W6-1, and W6-2.

[0157] The configuration of the light deflection unit 12 of the light guide plate 10c will be described with reference to FIGS. 59 to 65. FIG. 59 is a schematic diagram showing the diffraction grating of the light entrance unit 121 of the light guide plate 10c. FIG. 60 is a schematic diagram showing the diffraction grating of the light exit unit 122 of the light guide plate 10c. FIG. 61 is a schematic diagram showing the diffraction grating of the intermediate deflection unit 124 of the light guide plate 10c. FIG. 62 is a schematic diagram showing the diffraction grating of the optical duplication unit 125 of the light guide plate 10c. FIG. 63 is a schematic diagram showing the diffraction grating of the first folding deflection unit 126-1 of the light guide plate 10c. FIG. 64 is a schematic diagram showing the diffraction grating of the second folding deflection unit 126-2 of the light guide plate 10c. FIG. 65 is a schematic diagram showing the reference two-dimensional diffraction grating BC of the light deflection unit 12 of the light guide plate 10c.

[0158] In the example shown in Figure 59, the light incident section 121 is a two-dimensional lattice including a parallelogram in which the unit lattice has sides extending in a direction tilted 45 degrees with respect to the X axis and sides extending in the Y direction. The minimum unit lattice UC represents the smallest unit lattice constituting the light incident section 121. The first grating pitch P1 is the pitch of the diffraction grating of the light incident section 121 in the X direction. The second grating pitch P2 is the pitch of the diffraction grating of the light incident section 121 in the Y direction. In the light incident section 121, 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 incident section 121 has a portion of its light guide direction converted into first-order diffracted light.

[0159] In the example shown in FIG. 60 , 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.

[0160] In the example shown in Figure 61, 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 that constitutes 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. The first grating pitch P1 in the intermediate deflection unit 124 is, for example, 177.5 nm. The light guide direction of part of the light L incident on the intermediate deflection unit 124 is converted as first-order diffracted light.

[0161] In the example shown in FIG. 62 , 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 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 a direction tilted at 45 degrees with respect to the X direction. The second grating pitch P2 is the pitch of the diffraction grating of the optical duplication unit 125 in a direction tilted at 45 degrees with respect to the Y direction. 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. On the other hand, although the two-dimensional diffraction grating of the optical replication unit 125 is not the minimum unit grating, it can also be considered as a diffraction grating having a two-dimensional grating with a first grating pitch P1 in the X direction and a second grating pitch P2 in the Y direction, each pitch being 355.0 nm, as its unit grating.

[0162] In the example shown in Figure 63, the first folding deflection unit 126-1 is a one-dimensional grating having a plurality of line-and-space patterns extending in the X direction. The minimum unit cell UC represents the smallest unit cell constituting the first folding deflection unit 126-1. The first grating pitch P1 is the pitch of the diffraction grating of the first folding deflection unit 126-1 in the Y direction. The first grating pitch P1 in the first folding deflection unit 126-1 is, for example, 177.5 nm. The light L incident on the first folding deflection unit 126-1 has a portion of its light guide direction converted into first-order diffracted light.

[0163] In the example shown in Figure 64, the second folding deflection unit 126-2 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 folding deflection unit 126-2. The first grating pitch P1 is the pitch of the diffraction grating of the second folding deflection unit 126-2 in the X direction. The first grating pitch P1 in the second folding deflection unit 126-2 is, for example, 177.5 nm. The light L incident on the first folding deflection unit 126-1 has a portion of its light guide direction converted into first-order diffracted light.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] The disclosure of Japanese Patent Application No. 2024-150967, 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.

[0168] 10, 10a, 10b, 10c Light guide plate 11 Light guide substrate 12 Light deflection section 121 Light incident section 122 Light exit section 123 Separation deflection section 124 Intermediate deflection section 125 Light duplication section 126 Folding deflection section 100 Display device 101 Frame 102 Temple 110 Glasses-type support 111 First main surface 112 Second main surface D1 First incident direction D2 Second incident 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 T Total internal reflection light guide region BC Reference two-dimensional diffraction grating UC Minimum unit grating W1, W2, W3, W4, W5, W6, W6-1, W6-2 Arrows θprop Propagation angle

Claims

A light guide plate having a light guide substrate and one or more light deflection units formed on the light guide substrate, The optical deflection unit a light incident portion for incoupling light having a predetermined viewing angle into the light guide plate; a light exit portion that outputs the light incoupled by the light entrance portion from the light guide plate; a return deflection unit disposed on an extension of an optical path of the light that has been incoupled by the light incident unit and then transmitted through the light exit unit, The light guide plate, wherein the folding deflection section deflects at least blue light toward the light exit section and transmits red light at least at the center of the viewing angle of the light incident from a first incident direction. 　 a separation deflection unit disposed between the light entrance unit and the light exit unit, the splitting and deflecting unit splits the incident light into at least a first light portion and a second light portion; 2. The light guide plate according to claim 1, wherein the first light portion has a larger proportion of blue light and a smaller proportion of red light than the second light portion, and is incident on the folded deflection portion from the first incident direction. 　 the light incident unit separates the incident light into at least a first light portion and a second light portion; 2. The light guide plate according to claim 1, wherein the first light portion has a larger proportion of blue light and a smaller proportion of red light than the second light portion, and is incident on the folded deflection portion from the first incident direction.

2. The light guide plate according to claim 1, wherein the folding deflection section further deflects the blue light, the red light, and the green light toward the light output section at a center of the viewing angle of the light incident from a second incident direction different from the first incident direction. 　 The light guide plate according to claim 1 , wherein the folding deflection section further transmits the light incident from a second incident direction different from the first incident direction. 　 A vector representing the first grating pitch P1 is (X, Y) = (p1x, p1y), A vector representing the second grating pitch P2 is (X, Y) = (p2x, p2y), Let m be a natural number, If m1 = 0, ±1, ±2 and m2 = 0, ±1, ±2, then With respect to 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 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. 　 The light incident 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 by (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 6. 　 a separation deflection unit disposed between the light entrance unit and the light exit unit, the splitting and deflecting unit splits the incident light into at least a first light portion and a second light portion; the first light portion has a larger proportion of blue light and a smaller proportion of red light than the second light portion, and is incident on the folding deflection unit from the first incident direction; The separating / deflecting unit is a diffraction grating that satisfies either the condition (e) or (f) below: (e) where (m1in, m2in) is a diffraction order of light incident on the separating / deflecting unit, converted to the reference two-dimensional diffraction grating, and (m1out, m2out) is a diffraction order of light output from the separating / deflecting unit, converted to the reference two-dimensional diffraction grating, 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 return deflection unit is a diffraction grating that satisfies either of the following conditions (g) or (h): (g) where (m1in, m2in) is a diffraction order of light incident on the return deflection unit converted to the reference two-dimensional diffraction grating, and (m1out, m2out) is a diffraction order of light output from the return deflection unit converted to the reference two-dimensional diffraction grating, then (m1, m2) = (m1out - m1in, m2out - m2in), and the one-dimensional diffraction grating has the grating pitch Pm given by a combination of (m1in, m2in) = (±1, 0), (0, ±1), and (m1out, m2out) = (±1, -1), (±1, 1); (h) 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.

2. The light guide plate according to claim 1, wherein a propagation angle at the center of the viewing angle of the blue light deflected by the folding deflection section is equal to or greater than a propagation angle of the red light or green light guided to the light output section without passing through the folding deflection section. 　 The light guide plate according to claim 1 , wherein the viewing angle of the blue light deflected by the folding deflection section is equal to the viewing angle of the light incident on the light incident section. 　 The light guide plate according to claim 1 , wherein the folding deflection section deflects the blue light incident on the folding deflection section at the center of the viewing angle in a direction opposite to the direction of incidence. 　 The light guide plate according to claim 1 , wherein the folding deflection section deflects the blue light incident on the folding deflection section at the center of the viewing angle in a direction non-parallel to the direction of incidence. 　 The light guide plate according to claim 1 , wherein the folded deflection portion is a one-dimensional diffraction grating. 　 The light guide plate according to any one of claims 1 to 14; a projector; The display device, wherein light projected from the projector enters the light guide plate and is emitted from the light emitting portion.

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