Light guide member

Abstract

To provide a light guide member that can reduce color unevenness without degrading other performance aspects. [Solution] The light guide member comprises a first layer 10 that guides light L2, a first region 14A on which a first hologram having a first interference fringe interval is arranged, and a second region 14B on which a second hologram having a second interference fringe interval different from the first interference fringe interval is arranged and which does not overlap with the first region 14A when viewed from the stacking direction, and a second layer 11 stacked on the first layer 10 in the stacking direction.

Description

Technical Field

[0001] The present invention relates to a light guide member.

Background Art

[0002] It is known to use a hologram having interference fringes in a light guide member for guiding light. Since the hologram has high wavelength selectivity, the diffraction angles of lights with different wavelengths are different, resulting in color unevenness. Patent Document 1 discloses laminating a plurality of layers for diffracting lights with different wavelengths.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By laminating a plurality of layers for diffracting lights with different wavelengths and diffracting lights with different wavelengths for each layer, color unevenness and the like can be reduced. However, when a plurality of layers are laminated, the light guide member becomes thick. In addition, the light transmittance of the light guide member becomes low. Multiple recording is considered as a method of not laminating a plurality of layers. Multiple recording is a method of forming interference fringes for diffracting different wavelengths in one layer. However, in multiple recording, it is difficult to control the diffraction efficiency, and it is difficult to provide a layer having a desired diffraction efficiency.

[0005] An object of the present disclosure is to provide a light guide member capable of reducing color unevenness without degrading other performances.

Means for Solving the Problems

[0006] Embodiments of the present disclosure are light-guiding members comprising: a first layer that guides light; a first region on which a first hologram having a first interference fringe spacing is arranged; and a second region on which a second hologram having a second interference fringe spacing different from the first interference fringe spacing is arranged, and which does not overlap with the first region when viewed from the stacking direction, and which is stacked on the first layer in the stacking direction. [Effects of the Invention]

[0007] According to this disclosure, color unevenness can be reduced without degrading other performance aspects. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing a light guide member according to the first embodiment. [Figure 2] Figure 2 is an enlarged cross-sectional view of the light guide member according to the first embodiment. [Figure 3] Figure 3 is an enlarged cross-sectional view of the light guide member according to the first embodiment. [Figure 4] Figure 4 is a schematic diagram showing the first, second, and third regions in the first embodiment. [Figure 5] Figure 5 is a plan view showing an example of the arrangement of the first, second, and third regions in the second layer of the first embodiment. [Figure 6] Figure 6 is a plan view showing an example of the arrangement of the first, second, and third regions in the second layer of the first embodiment. [Figure 7] Figure 7 is a plan view showing example 3 of the arrangement of the first, second, and third regions in the second layer of the first embodiment. [Figure 8] Figure 8 is a plan view showing another example of the planar shapes of the first, second, and third regions in the second layer of the first embodiment. [Figure 9] Figure 9 shows examples of spectra illustrating the diffraction efficiency for the first, second, and third regions with respect to wavelengths in the first embodiment. [Modes for carrying out the invention]

[0009] The embodiments for implementing this disclosure will be described in detail below with reference to the drawings. The embodiments described below are examples for embodying the technical concept of the invention and do not limit this disclosure to the configurations and numerical values ​​described. In each drawing, the same reference numerals are used for the same components, and redundant explanations may be omitted as appropriate. The size, positional relationships, etc., of each component shown in each drawing may be exaggerated to facilitate understanding of the invention.

[0010] (First Embodiment) Figure 1 is a cross-sectional view showing a light guide member according to the first embodiment. The stacking direction of the third layer 12, the second layer 11, and the first layer 10 is defined as the Z direction. The direction from hologram region 20A to hologram region 20B is defined as the X direction. The direction perpendicular to the Z direction and the X direction is defined as the Y direction.

[0011] As shown in Figure 1, the light guide member 100 according to the first embodiment comprises a first layer 10, a second layer 11, and a third layer 12. The second layer 11 has hologram regions 20A and 20B. The first layer 10 is located on the second layer 11. The third layer 12 is located below the second layer 11.

[0012] Light L1 incident on the light guide member 100 from the +Z direction is transmitted through the first layer 10 and diffracted in the second layer 11. The diffracted light L2 undergoes repeated total internal reflection between the upper surface of the first layer 10 and the lower surface of the second layer 11, guiding it through the first layer 10 and the second layer 11 in the X direction. Light L2 may be guided through the first layer 10 but not through the second layer 11 and the third layer 12. In this case, the second layer 11 between the hologram regions 20A and 20B may not be present.

[0013] Light L2 guided into the hologram region 20B is diffracted in the hologram region 20B and emitted as light L3 in the -Z direction. By lowering the diffraction efficiency in the hologram region 20B, the undiffracted light L2' is guided through the first layer 10, diffracted in the hologram region 20B, and emitted as light L3' in the -Z direction. The undiffracted light L2'' is guided through the first layer 10, diffracted in the hologram region 20B, and emitted as light L3'' in the -Z direction. The undiffracted light L2'''' is guided through the first layer 10, diffracted in the hologram region 20B, and emitted as light L3'''' in the -Z direction.

[0014] When the light guide member 100 is used in a head-mounted display, the projector irradiates the light guide member 100 with light L1. Light L3~L3'''' is irradiated into the user's eyes. The hologram region 20A can efficiently diffract light L1 by having a high diffraction efficiency, for example, 80% or more. In the hologram region 20B, by having a low diffraction efficiency, for example, 30% or less, light L3~L3'''' can be emitted over a wide area when viewed from the -Z direction. This allows for a wider tolerance range for the eye position in the XY plane. As a result, the width W20B in the X direction of the hologram region 20B is greater than the width W20A in the X direction of the hologram region 20A. The width W20B is, for example, more than twice and less than or equal to 10 times the width W20A.

[0015] Figures 2 and 3 are enlarged cross-sectional views of the light guide member according to the first embodiment. Figure 2 is an enlarged view of the area around the hologram region 20A, and Figure 3 is an enlarged view of the area around the hologram region 20B. Note that the third layer 12 is not shown.

[0016] As shown in FIG. 2, the hologram region 20A has a plurality of first regions 14A, a plurality of second regions 14B, and a plurality of third regions 14C. The plurality of first regions 14A, the plurality of second regions 14B, and the plurality of third regions 14C do not overlap with each other when viewed from the Z direction. The light L1 includes lights LA1, LA2, and LA3 having different peak wavelengths from each other. The incident angles of the lights LA1, LB1, and LC1 to the hologram region 20A are approximately equal and are 0°. The incident angles of LA1, LB1, and LC1 may be other than 0°.

[0017] The first region 14A, the second region 14B, and the third region 14C diffract the lights LA1, LB1, and LC1, respectively. The diffracted lights LA2, LB2, and LC2 guide the lights L2 through the first layer 10 and the second layer 11. The diffraction angles of the lights LA2, LB2, and LC2 are approximately equal and are angles θA2, θB2, and θC2, respectively. The first region 14A, the second region 14B, and the third region 14C transmit lights other than the corresponding lights LA1, LB1, and LC1. The transmitted light is transmitted, absorbed, or reflected by the region of the third layer 12 corresponding to the hologram region 20A.

[0018] As shown in FIG. 3, the hologram region 20B has a plurality of first regions 14A, a plurality of second regions 14B, and a plurality of third regions 14C. The plurality of first regions 14A, the plurality of second regions 14B, and the plurality of third regions 14C do not overlap with each other when viewed from the Z direction. The lights LA2, LB2, and LC2 that have guided through the first layer 10 and the second layer 11 reach the hologram region 20B. The incident angles of the lights LA2, LB2, and LC2 to the hologram region 20B are approximately equal and are angles θA2, θB2, and θC2, respectively. The first region 14A, the second region 14B, and the third region 14C diffract the lights LA2, LB2, and LC2, respectively. The diffraction angles of the lights LA3, LB3, and LC3 are approximately equal and are approximately 0°. The diffraction of the lights LA3, LB3, and LC3 may be other than 0°. The diffracted lights LA3, LB3, and LC3 pass through the third layer 12 and are emitted in the -Z direction.

[0019] Figure 4 is a schematic diagram showing the first, second, and third regions in the first embodiment. As shown in Figure 4, the first region 14A, the second region 14B, and the third region 14C are respectively arranged with the first hologram 16A, the second hologram 16B, and the third hologram 16C. The first hologram 16A, the second hologram 16B, and the third hologram 16C are volume holograms, and are either reflective volume holograms or transmissive volume holograms.

[0020] The first hologram 16A, the second hologram 16B, and the third hologram 16C have interference fringes. The second interference fringe spacing DB in the second hologram 16B is wider than the first interference fringe spacing DA in the first hologram 16A. The third interference fringe spacing DC in the third hologram 16C is wider than the second interference fringe spacing DB. As a result, the wavelengths of the light LB1 and LB2 diffracted by the second hologram 16B are longer than the wavelengths of the light LA1 and LA2 diffracted by the first hologram 16A. The wavelengths of the light LC1 and LC2 diffracted by the third hologram 16C are longer than the wavelengths of the light LB1 and LB2 diffracted by the second hologram 16B.

[0021] When the light guide member 100 is used in an image display device such as a head-mounted display, the peak wavelengths of light LA1, LA2, and LA3 are blue wavelengths (e.g., 400nm to 500nm), the peak wavelengths of light LB1, LB2, and LB3 are green wavelengths (e.g., 500nm to 600nm), and the peak wavelengths of light LC1, LC2, and LA3 are red wavelengths (e.g., 600nm to 700nm). The peak wavelengths of light LA1, LA2, and LA3 may be other wavelengths than blue, the peak wavelengths of light LB1, LB2, and LB3 may be other wavelengths than green, and the peak wavelengths of light LC1, LC2, and LA3 may be other wavelengths than red. The third region 14C may not be provided. There may be two or more regions with different interference fringe spacings.

[0022] The first layer 10 and the third layer 12 are, for example, translucent. The first layer 10 and the third layer 12 may contain, for example, an inorganic material such as glass or an organic material such as a resin. The resin contained in the first layer 10 and the third layer 12 may be a thermosetting resin or a thermoplastic resin, and may be, for example, a poly(meth)acrylate resin, a polycarbonate resin, a polyurethane resin, an epoxy resin, a polyamide resin, a polyimide resin, a polyolefin resin, a (meth)acrylic resin, a cyclic polyolefin resin (norbornene-based resin), a polyarylate resin, a polystyrene resin, a polyvinyl alcohol resin, a cellulose resin such as a triacetylcellulose-based resin film, a polyester resin, a polyethersulfone resin, or a polysulfone resin.

[0023] The second layer 11 is a photopolymer layer, and a hologram is recorded in the hologram regions 20A and 20B. The photopolymer layer is not particularly limited as long as it is composed of a photopolymer capable of recording a hologram. The photopolymer layer may, for example, contain a photopolymerizable monomer, a photopolymerization initiator, and a binder. Alternatively, the photopolymer layer may not contain a binder and may contain a matrix polymer, a writing monomer which is a photopolymerizable monomer, and a photoinitiator. In this case, the matrix polymer may be an amorphous thermoplastic resin. The matrix polymer may be an acrylic polymer, for example, a homopolymer or copolymer containing one or more monomers from among (meth)acrylic acid, (meth)acrylic acid esters, and their derivatives, polybutyl acrylate, polyvinyl acetate, polyvinyl butyrate, gelatin, cellulose ester, cellulose ether, silicone copolymer, polyurethane, polybutadiene, polyisoprene, polyethylene oxide, epoxy resin polyamide, or polycarbonate.

[0024] As the photopolymer layer, for example, a photopolymer film for holographic recording known in this field can be used. A commercially available photopolymer film for holographic recording is the Bayfol® HX series from Covestro AG, such as the Bayfol HX200.

[0025] (Comparative form) The effects of the first embodiment will be explained in comparison with the comparative embodiment. The first comparative embodiment is an example in which hologram regions 20A and 20B have one type of interference fringe spacing. A hologram with one type of interference fringe spacing has wavelength selectivity. Therefore, in the first comparative embodiment, if hologram regions 20A and 20B diffract light LB1 and LB2 at the diffraction angles specified in the design, the diffraction angles of light LA1, LA2, LC1 and LC3 will differ from the design. As a result, color unevenness occurs.

[0026] The second comparative form is an example in which second layers 11 with different interference fringe spacings are stacked in the Z direction. In the second comparative form, the second layers 11 with different interference fringe spacings each diffract light of different wavelengths. Therefore, the diffraction angles of light of different wavelengths can be made the same. However, because the second layers 11 are stacked, the conductive material becomes thicker in the Z direction. Also, the second layers that are farther from the first layer 10 diffract light that has passed through the other second layers. Therefore, the light transmittance becomes low.

[0027] The third comparative form is an example of multiplex recording in which interference fringes of different spacings are formed within a single region on a single second layer 11. In the third comparative form, since multiple exposures are used to form the interference fringes, it is difficult to design the desired diffraction efficiency. Therefore, it becomes difficult to design a system that increases the diffraction efficiency in the hologram region 20A and decreases the diffraction efficiency in the hologram region 20B.

[0028] (Description of the first embodiment) In the first embodiment, the first region 14A, the second region 14B, and the third region 14C are designed to diffract the light LA1 and LA2, the light LB1 and LB2, and the light LC1 and LC2 at desired angles, respectively. This reduces the color unevenness seen in the first comparative embodiment.

[0029] Furthermore, the first region 14A, the second region 14B, and the third region 14C are arranged so as not to overlap when viewed from the Z direction. This suppresses the increase in thickness of the light guide member, as seen in the second comparative form. In addition, since the light LA1 and LA2, light LB1 and LB2, and light LC1 and LC2 do not transmit light through regions other than the corresponding first region 14A, second region 14B, and third region 14C, the decrease in transmittance can be reduced.

[0030] Furthermore, the first region 14A, the second region 14B, and the third region 14C can be formed separately by masking or other means. This makes it easy to design the diffraction efficiency in the first region 14A, the second region 14B, and the third region 14C to a desired value.

[0031] As described above, according to the first embodiment, as shown in Figure 4, the second layer 11 has a first region 14A on which a first hologram 16A having a first interference fringe spacing DA is arranged, and a second region on which a second hologram 16B having a second interference fringe spacing DB different from the first interference fringe spacing DA is arranged. When viewed from the Z direction, the first region 14A and the second region 14B do not overlap. This reduces the increase in thickness of the light guide member 100 and the decrease in transmittance, makes it easier to design the diffraction efficiency, and reduces color unevenness.

[0032] The second layer 11 has a third region 14C in which a third hologram 16C is arranged, having a third interference fringe spacing DC that is different from the first interference fringe spacing DA and the second interference fringe spacing DB. The third region 14C does not overlap with the first region 14A and the second region 14B when viewed from the Z direction. This makes it possible to reduce color unevenness even when using different light with three or more peak wavelengths.

[0033] Lights L1 and L2 include light LA1 and LA2 (first light) having a first peak wavelength, light LB1 and LB2 (second light) having a second peak wavelength different from the first peak wavelength, and light LC1 and LC2 (third light) having a third peak wavelength different from the first and second peak wavelengths. As shown in Figures 2 and 3, the diffraction angle at the first peak wavelength in the first region 14A, the diffraction angle at the second peak wavelength in the second region 14B, and the diffraction angle at the third peak wavelength in the third region 14C are equal. By designing the first hologram 16A, the second hologram 16B, and the third hologram 16C in this way, color unevenness can be reduced. Note that equal diffraction angles and equal incident angles do not mean strictly equal, and a difference of about ±10° is allowed. That is, equal incident angles mean that the difference between the maximum and minimum incident angles is 0.05 times or less of the average incident angle. Equal diffraction angles mean that the difference between the maximum and minimum diffraction angles is less than or equal to 0.05 times the average diffraction angle.

[0034] When the first peak wavelength is λA, the second peak wavelength is λB, and the third peak wavelength is λC, |λA-λB| / (λA+λB) is preferably 0.05 or greater, and more preferably 0.1 or greater. |λB-λC| / (λB+λC) is preferably 0.05 or greater, and more preferably 0.1 or greater. Thus, when the difference between λA and λB, and the difference between λB and λC are large, color unevenness is likely to occur. Therefore, it is preferable to provide a first region 14A, a second region 14B, and a third region 14C.

[0035] As shown in Figure 2, the first region 14A, the second region 14B, and the third region 14C of the hologram region 20A are inlet couplers (incouplings) that diffract light L1 irradiated from outside the first layer 10 and the second layer 11 into the first layer 10. If the inlet coupler has the structure shown in Figure 2, the outlet coupler may have a structure other than that shown in Figure 3.

[0036] As shown in Figure 3, the first region 14A, the second region 14B, and the third region 14C of the hologram region 20B are exit couplers (also called out-couplings) that diffract the light L2 guiding the first layer 10 to the outside of the first layer 10 and the second layer 11. This reduces color unevenness of the light L3. When the light guide member 100 is used in a head-mounted display, it is desirable to reduce color unevenness of the exit coupler. Therefore, it is preferable to have the structure of the exit coupler as shown in Figure 3. When the exit coupler has the structure of Figure 3, the inlet coupler may have a structure other than that shown in Figure 2.

[0037] In the example described, light L3 is emitted in the -Z direction within the hologram region 20B. However, light L3 may also be emitted in the +Z direction within the hologram region 20B.

[0038] (Example 1 of the arrangement of the first, second, and third regions) Figure 5 is a plan view showing an example of the arrangement of the first region 14A, the second region 14B, and the third region 14C in the second layer of the first embodiment. As shown in Figure 5, in the hologram regions 20A and 20B, the planar shapes of the first region 14A, the second region 14B, and the third region 14C are strip-shaped and extend in the Y direction. Multiple instances of each of the first region 14A, the second region 14B, and the third region 14C are arranged in the X direction. The first region 14A and the second region 14B are arranged alternately in the X direction, and the third region 14C is provided between the second region 14B and the first region 14A. That is, sets of the first region 14A, the second region 14B, and the third region 14C are arranged in order in the X direction and are repeated.

[0039] The widths of the first region 14A, the second region 14B, and the third region 14C in the X direction are WAx, WBx, and WCx, respectively. The preferred ranges of widths WAx, WBx, and WCx will be explained using the hologram region 20B as an example. In the hologram region 20B, from the viewpoint of interfering the optical LA2, LB2, and LC2, respectively, the widths WAx, WBx, and WCx are preferably 1 or more times the peak wavelength of the optical LA2, LB2, and LC2, and more preferably 5 or more times. If the number of first region 14A, second region 14B, and third region 14C is small, the image quality will deteriorate. From this viewpoint, it is preferable that 10 or more first region 14A, second region 14B, and third region 14C are provided in the X direction, and it is preferable that 100 or more are provided. Therefore, the widths WAx, WBx, and WCx are preferably 1 / 30 or less of the width W20Bx in the X direction of the hologram region 20B, and more preferably 1 / 300 or less. For example, the width W20Bx is 20 mm, and the widths WAx, WBx, and WCx are 10 μm each.

[0040] (Example of arrangement of the first, second, and third regions 2) Figure 6 is a plan view showing an example of arrangement 2 of the first region 14A, second region 14B, and third region 14C in the second layer of the first embodiment. As shown in Figure 6, in the hologram regions 20A and 20B, the planar shapes of the first region 14A, second region 14B, and third region 14C are strip-like, extending in the X direction. Multiple instances of each of the first region 14A, second region 14B, and third region 14C are arranged in the Y direction.

[0041] The widths of the first region 14A, the second region 14B, and the third region 14C in the Y direction are WAy, WBy, and WBy, respectively. The preferred ranges for widths WAy, WBy, and WBy are the same as the preferred ranges for widths WAx, WBx, and WBx in Figure 5 for the same reasons. That is, widths WAy, WBy, and WCy are preferably 1 or more times the peak wavelength of optical LA2, LB2, and LC2, and more preferably 5 or more times. The first region 14A, the second region 14B, and the third region 14C are each preferably provided with 10 or more elements in the Y direction, and more preferably 100 or more elements. Therefore, widths WAy, WBy, and WCy are preferably 1 / 30 or less of width W20By, and more preferably 1 / 300 or less. As an example, width W20By is 20 mm, and widths WAy, WBy, and WCy are 10 μm.

[0042] (Example 3 of the arrangement of the first, second, and third regions) Figure 7 is a plan view showing arrangement example 3 of the first, second, and third regions in the second layer of the first embodiment. As shown in Figure 7, in the hologram regions 20A and 20B, the planar shapes of the first region 14A, the second region 14B, and the third region 14C are dot-like and rectangular. Multiple instances of each of the first region 14A, the second region 14B, and the third region 14C are arranged in the X and Y directions.

[0043] The widths of the first region 14A, the second region 14B, and the third region 14C in the X direction are WAx, WBx, and WBx, respectively, and the widths in the Y direction are WAy, WBy, and WBy, respectively. The preferred ranges of widths WAy, WBy, and WBy are the same as those in Figures 5 and 6.

[0044] An example is shown in which the same regions from the first region 14A, the second region 14B, and the third region 14C are arranged in the Y direction, but the same regions from the first region 14A, the second region 14B, and the third region 14C may also be arranged in the X direction. The same regions from the first region 14A, the second region 14B, and the third region 14C may also be arranged in directions that are inclined in both the X and Y directions.

[0045] As shown in Figures 5 and 6, the planar shapes of the first region 14A, the second region 14B, and the third region 14C may be rectangular. The first region 14A, the second region 14B, and the third region 14C may extend in directions that are inclined in the X and Y directions. As shown in Figure 7, the planar shapes of the first region 14A, the second region 14B, and the third region 14C may be dot-shaped.

[0046] (Another example of the planar shape of the first, second, and third regions) Figure 8 is a plan view showing another example of the planar shapes of the first region 14A, the second region 14B, and the third region 14C in the second layer of the first embodiment. As shown in Figure 8, in the hologram regions 20A and 20B, the planar shapes of the first region 14A, the second region 14B, and the third region 14C are dot-shaped and circular. The planar shapes of the first region 14A, the second region 14B, and the third region 14C may be other than strip-shaped, rectangular, and circular, for example, elliptical or polygonal other than rectangular. In addition, the first region 14A, the second region 14B, and the third region 14C may be a mixture of different planar shapes.

[0047] Figures 5 to 8 illustrate an example where the planar shapes of the first region 14A, the second region 14B, and the third region 14C are the same in hologram regions 20A and 20B. However, the planar shapes of the first region 14A, the second region 14B, and the third region 14C may be different in hologram regions 20A and 20B.

[0048] As shown in Figures 5 to 8, multiple first regions 14A are arranged in the arrangement direction such as the X or Y direction, multiple second regions 14B are arranged in the arrangement direction, and multiple third regions 14C are arranged in the arrangement direction. The first regions 14A and the second regions 14B are arranged alternately in the arrangement direction, and the second regions 14B and the third regions 14C are arranged alternately in the arrangement direction. This improves image quality. From the viewpoint of improving image quality, the number of first regions 14A, second regions 14B, and third regions 14C arranged in the arrangement direction is preferably 10 or more, more preferably 100 or more, and even more preferably 500 or more.

[0049] Figure 9 shows the diffraction efficiency with respect to wavelength for the first region 14A, the second region 14B, and the third region 14C in the first embodiment. In Figure 9, the horizontal axis represents wavelength, and the vertical axis represents diffraction efficiency. Using the hologram region 20B in Figure 2 as an example, the diffraction efficiency is the value obtained by dividing the light intensity of light LA3, LB3, and LC3 by the intensity of light LA2, LB2, and LC2 for each wavelength. The first curve S1, the second curve S2, and the third curve S3 in the first region 14A, the second region 14B, and the third region 14C in Figure 9, respectively, show the diffraction efficiency with respect to wavelength. The first curve S1, the second curve S2, and the third curve S3 schematically represent the case when light is incident on the first region 14A, the second region 14B, and the third region 14C at the same angle of incidence (for example, angles θA2, θB2, and θC2 in Figure 3), and the diffracted light from the first region 14A, the second region 14B, and the third region 14C is measured at the same diffraction angle (for example, 0° in Figure 3).

[0050] As shown in Figure 9, the wavelength difference between the peak wavelength λ1 of the first curve S1 and the peak wavelength λ3 of the second curve S2 is Δ12, and the wavelength difference between the peak wavelength λ2 and the peak wavelength λ3 of the third curve S3 is Δ23. The full widths at half maximum (FMAX) of the first curve S1, the second curve S2, and the third curve S3 are W1, W2, and W3, respectively. A wavelength difference of Δ12 is greater than or equal to the FMAX W1 and FMAX W2. A wavelength difference of Δ23 is greater than or equal to the FMAX W2 and FMAX W3. As a result, the first region 14A, the second region 14B, and the third region 14C can efficiently diffract the light LA2, LB2, and LC2, respectively. Preferably, the wavelength difference Δ12 is 1.5 times or more the FMAX W1 and W2, and the wavelength difference Δ23 is 1.5 times or more the FMAX W2 and W3.

[0051] The incident angle is defined as the incident angle of light LA1, LB2, and LC2 incident from the first layer 10 to the second layer 11 in the hologram region 20B, and the diffraction angle is defined as the diffraction angle of light LA3, LB3, and LC3 in the hologram region 20B. In this case, it is preferable that the peak wavelength λA of light LA2 is located within the wavelength range of the full width at half maximum W1 of the first curve S1, the peak wavelength λB of light LB2 is located within the wavelength range of the full width at half maximum W2 of the second curve S2, and the peak wavelength λC of light LC2 is located within the wavelength range of the full width at half maximum W3 of the third curve S3. As a result, the first region 14A, the second region 14B, and the third region 14C can efficiently diffract light LA2, LB2, and LC2.

[0052] The light guide member of the first embodiment can be used not only in display devices such as head-mounted displays but also in optical devices such as lighting devices.

[0053] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0054] Examples of the present invention are as follows: <1> A light guide member comprising: a first layer that guides light; a first region on which a first hologram having a first interference fringe spacing is arranged; a second region on which a second hologram having a second interference fringe spacing different from the first interference fringe spacing is arranged, and which does not overlap with the first region when viewed from the stacking direction; and a second layer stacked on the first layer in the stacking direction. <2> The light includes a first light having a first peak wavelength and a second light having a second peak wavelength different from the first peak wavelength. <1> The light guide member described above. <3> The diffraction angle of the first peak wavelength in the first region and the diffraction angle of the second peak wavelength in the second region are equal, <2> The light guide member described above. <4> When incident light is incident on the first region and the second region at the same incident angle, and the diffracted light diffracted from the first region and the second region is measured at the same diffraction angle, the difference between the peak wavelength of the first curve showing the diffraction efficiency with respect to wavelength in the first region and the peak wavelength of the second curve showing the diffraction efficiency with respect to wavelength in the second region is greater than or equal to the full width at half maximum of the first curve and greater than or equal to the full width at half maximum of the second curve, <1> from the above <3> A light guide member as described in any one of the items. <5> The first hologram and the second hologram are volume holograms. <1> from the above <4> A light guide member as described in any one of the items. <6> The first region and the second region diffract the light guiding the first layer to the area outside the first and second layers. <1> from the above <5> A light guide member as described in any one of the items. <7> The first region and the second region diffract light irradiated from outside the first and second layers into the first layer. <1> from the above <6> A light guide member as described in any one of the items. <8> Multiple first regions are arranged in the direction of arrangement, multiple second regions are arranged in the same direction of arrangement, and the first and second regions are arranged alternately in the direction of arrangement, <1> from the above <7> A light guide member as described in any one of the items. <9> The number of the plurality of first regions arranged in the arrangement direction and the number of the plurality of second regions arranged in the arrangement direction are both 10 or more. <8> The light guide member described above. <10> The second layer has a third hologram having a third interference fringe spacing different from the first and second interference fringe spacings, and has a third region that does not overlap with the first and second regions when viewed from the stacking direction, <1> from the above <9> A light guide member as described in any one of the items. [Explanation of Symbols]

[0055] 10 1st layer 11 2nd layer 12 3rd layer 14A 1st area 14B 2nd area 14C 3rd area 16A First Hologram 16B Second Hologram 16C Third Hologram 20A, 20B Hologram area DA 1st Interference Fringe Spacing DB 2nd Interference Fringe Spacing DC 3rd Interference Fringe Spacing S1 1st curve S2 2nd curve S3 3rd curve

Claims

1. The first layer guides light, A second layer comprising a first region on which a first hologram having a first interference fringe spacing is arranged, and a second region on which a second hologram having a second interference fringe spacing different from the first interference fringe spacing is arranged, and which does not overlap with the first region when viewed from the stacking direction, and which is stacked on the first layer in the stacking direction, A light guide member comprising:

2. The light guide member according to claim 1, wherein the light includes a first light having a first peak wavelength and a second light having a second peak wavelength different from the first peak wavelength.

3. The light guide member according to claim 2, wherein the diffraction angle of the first peak wavelength in the first region is equal to the diffraction angle of the second peak wavelength in the second region.

4. The light guide member according to any one of claims 1 to 3, wherein when light is incident on the first region and the second region at the same incident angle, and the diffracted light diffracted from the first region and the second region is measured at the same diffraction angle, the difference between the peak wavelength of the first curve showing the diffraction efficiency with respect to wavelength in the first region and the peak wavelength of the second curve showing the diffraction efficiency with respect to wavelength in the second region is greater than or equal to the full width at half maximum of the first curve and greater than or equal to the full width at half maximum of the second curve.

5. The light guide member according to any one of claims 1 to 3, wherein the first hologram and the second hologram are volume holograms.

6. The light guide member according to any one of claims 1 to 3, wherein the first region and the second region diffract the light guiding the first layer to the outside of the first and second layers.

7. The light guide member according to any one of claims 1 to 3, wherein the first region and the second region diffract light irradiated from outside the first layer and the second layer into the first layer.

8. The light guide member according to any one of claims 1 to 3, wherein the first region is arranged in multiple locations in the arrangement direction, the second region is arranged in multiple locations in the arrangement direction, and the first region and the second region are arranged alternately in the arrangement direction.

9. The light guide member according to claim 8, wherein the number of the plurality of first regions arranged in the arrangement direction and the number of the plurality of second regions arranged in the arrangement direction are both 10 or more.

10. The light guide member according to any one of claims 1 to 3, wherein the second layer has a third hologram having a third interference fringe spacing different from the first and second interference fringe spacings, and has a third region that does not overlap with the first and second regions when viewed from the stacking direction.

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