Waveguide element

Abstract

To provide a waveguide element configured so that the energy can be distributed more evenly during pupil expanding, thereby improving the uniformity of pictures.SOLUTION: A waveguide element includes a substrate and a grating structure. The grating structure is located on a substrate to form a light in-coupling area, a light out-coupling area and a light pupil expanding area, the light pupil expanding area being optically coupled to the light in-coupling area and the light out-coupling area. The light pupil expanding area is configured to receive a light beam from the light in-coupling area and to diffract and to expand the light beam towards the light out-coupling area. The light pupil expanding area has at least two partitions, and has an included angle φ between a border of the partitions of the light pupil expanding area and a horizontal line. The included angle φ satisfies φ=tan-1(β1 / α1) wherein α1=(-λ sin ψ+αd) / nd, β1=(λ cos ψ+βd) / nd, α=sin(θ)×cos ψ, β=sin(θ)×sin ψ, λ is a wavelength of an incident light, θ is a field of view, n is a refractive index of the substrate, ψ is a grating vector direction, and d is a grating periodic distance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a waveguide element.

Background Art

[0002] In an augmented reality (AR) display, one of the important technologies is to expand an image using a waveguide element based on a diffractive optical element. Expanding the image in either the one-dimensional direction or the two-dimensional direction contributes to the comfort of wearing the device.

[0003] However, expanding the image involves dispersing the energy of the image in a two-dimensional space. However, the farther away from the image input position, the more serious the attenuation of the energy of the image becomes, which affects the uniformity of the image.

Summary of the Invention

Means for Solving the Problems

[0004] One technical aspect of the present disclosure is a waveguide element.

[0005] According to an embodiment of the present disclosure, the waveguide element includes a substrate and a grating structure. The grating structure is located on the substrate so as to constitute a light coupling input region, a light coupling output region, and a pupil expansion region. The pupil expansion region is optically coupled to the light coupling input region and the light coupling output region. The pupil expansion region is configured to receive light rays from the light coupling input region and diffract them to the light coupling output region to expand the pupil. The pupil expansion region has at least two divided regions, and has an included angle φ between the boundary of the divided region of the pupil expansion region and the horizontal line, and φ = tan -1 (β1 / α1) is satisfied, where α1 = (-λsinψ + αd) / nd, β1 = (λcosψ + βd) / nd, α = sin(θ)×cosψ, β = sin(θ)×sinψ, λ is the incident light wavelength, θ is the viewing angle, n is the refractive index of the substrate, ψ is the grating vector direction of the light coupling input region, and d is the grating period distance of the light coupling input region.

[0006] In one embodiment of the present disclosure, the included angle φ between the boundary of the divided region of the pupil expansion region and the horizontal line has an offset amount, and the offset amount is 10° or less.

[0007] In one embodiment of the present disclosure, the grating structure includes a plurality of gratings. The gratings in the divided regions of the pupil expansion region each have a grating height, and the grating height increases from the divided region closest to the optical coupling input region to the divided region farthest from the optical coupling input region.

[0008] In one embodiment of the present disclosure, the grating height is in the range of 10 nanometers to 300 nanometers.

[0009] In one embodiment of the present disclosure, each divided region of the pupil expansion region has a filling ratio, and the filling ratio decreases from the divided region closest to the optical coupling input region to the divided region farthest from the optical coupling input region.

[0010] In one embodiment of the present disclosure, the grating structure includes a plurality of gratings. The gratings in the pupil expansion region and the horizontal line each have an inclination angle, and the inclination angle decreases from the divided region closest to the optical coupling input region to the divided region farthest from the optical coupling input region.

[0011] In one embodiment of the present disclosure, the grating period distance is in the range of 300 nanometers to 1200 nanometers.

[0012] In one embodiment of the present disclosure, the refractive index of the substrate is in the range of 1.5 to 2.5, and the refractive index of the grating structure is in the range of 1.2 to 2.5.

[0013] In one embodiment of the present disclosure, the viewing angle is in the range of 0° to 90°.

[0014] In one embodiment of the present disclosure, the incident light wavelength is in the range of 400 nanometers to 700 nanometers.

Advantages of the Invention

[0015] In the above-described embodiment of the present disclosure, the pupil expansion region has at least two divided regions, and the included angle between the boundary of these divided regions and the horizontal line is correlated with parameters such as the incident light wavelength, viewing angle, refractive index of the substrate, grating vector direction of the optical coupling input region, and grating period distance of the optical coupling input region through special calculations. As a result, the energy can be arranged more uniformly during pupil expansion, improving the uniformity of the screen.

Brief Description of the Drawings

[0016]

Figure 1

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Embodiments for Carrying Out the Invention

[0017] When viewed in conjunction with the drawings, the aspects of the content of the present disclosure are best understood by subsequent embodiments. In accordance with the standard practice in this industry, each feature is not drawn to scale. In fact, for clarity of description, the sizes of various features may be arbitrarily increased or decreased.

[0018] The content of the embodiments disclosed below provides a number of different embodiments or examples for implementing different features of the provided subject matter. The following describes specific examples of elements and arrangements for the sake of simplifying the present invention. Of course, these are merely examples and are not limiting. Also, in each embodiment of this case, element symbols and / or alphabets can be duplicated. This duplication is for the purpose of simplification and clarity and does not itself specify the relationship between each described embodiment and / or arrangement.

[0019] For example, spatial relative terms such as "below ~", "under ~", "lower part", "above ~", "upper part", etc. may be used in this specification for the convenience of explanation to describe the relationship between one element or feature and another element or feature as shown in the drawings. The spatial relative terms are intended to encompass different orientations of the device during use or operation in addition to the orientation shown in the drawings. The device may be oriented in other ways (rotated by 90° or other orientations), and the spatial relative descriptive terms used in this specification may be interpreted accordingly.

[0020] FIG. 1 shows a top view of a waveguide element 100 according to an embodiment of the present disclosure. Referring to FIG. 1, the waveguide element 100 includes a substrate 110 and a grating structure 120. The grating structure 120 is located on the substrate 110 so as to constitute a light coupling input region 122, a pupil expansion region 124, and a light coupling output region 126. The pupil expansion region 124 is optically coupled to the light coupling input region 122 and the light coupling output region 126. In this embodiment, the light coupling input region 122 is located at the upper right of the waveguide element 100, the light coupling output region 126 is located at the upper left of the waveguide element 100, and the pupil expansion region 124 is located below the center of the waveguide element 100.

[0021] The pupil expansion region 124 is configured to receive light rays from the optical coupling input region 122 and diffract them to the optical coupling output region 126 for pupil expansion. In FIG. 1, the pupil expansion region 124 has five divided regions 125a, 125b, 125c, 125d, and 125e, and has an included angle φ between the boundaries of the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124 and the horizontal line, where φ = tan -1 (β1 / α1) is satisfied, where α1 = (-λsinψ + αd) / nd, β1 = (λcosψ + βd) / nd, α = sin(θ)×cosψ, β = sin(θ)×sinψ, λ is the incident light wavelength, θ is the viewing angle, n is the refractive index of the substrate 110, ψ is the grating vector direction of the optical coupling input region 122, and d is the grating period distance of the optical coupling input region 122. Each parameter (incident light wavelength, viewing angle, refractive index of the substrate, grating vector direction of the optical coupling input region, and grating period distance of the optical coupling input region) is determined by each part of the waveguide element 100 and the used light source (described in FIG. 2).

[0022] FIG. 2 shows a side view of the waveguide element 100 and the light source 200 according to an embodiment of the present disclosure. Referring to FIGS. 1 and 2 simultaneously, when the waveguide element 100 is used to receive an image from the light source 200, the wavelength and the field of view of the image are determined by the light source 200. For color display, it can be understood that the incident light wavelength is not a fixed value but a range in order to display images of different colors. For example, in some embodiments, the incident light wavelength is in the range of 400 nanometers to 700 nanometers. With such a design, since the calculated included angle φ is also a range, it can be understood that the included angle φ between the boundaries of the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124 and the horizontal line has an offset amount of 10 degrees or less. Also, in some embodiments, the viewing angle θ of the incident light is in the range of 0 degrees to 90 degrees. The viewing angle θ is also a designed parameter, because if the light rays emitted by the light source 200 do not enter the optical coupling input region 122, the optical coupling input region 122 will not transmit the light source to the pupil expansion region 124 that is optically coupled to the optical coupling input region 122. Also, the refractive index of the substrate 110 also determines the included angle φ, and in some embodiments, the refractive index of the substrate 110 is in the range of 1.5 to 2.5. In the following description, the optical coupling input region 122 of the grating structure 120 will be described in detail.

[0023] FIG. 3 shows a partially enlarged top view of the optical coupling input region 122 of the waveguide element 100 in FIG. 1. Referring to FIG. 3, when determining the included angle φ between the boundaries of the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124 and the horizontal line, two parameters, namely, the grating vector direction ψ of the optical grating in the optical coupling input region 122 and the grating period distance d of the optical grating in the optical coupling input region 122, are determined by the optical coupling input region 122. Here, the grating vector direction ψ is the included angle between the extension direction of the gap of the grating and the horizontal line, and the period distance d is the distance of one repetition of the grating. In some embodiments, the grating period distance d is in the range of 300 nanometers to 1200 nanometers. Also, in some embodiments, the grating vector direction ψ is in the range of 0 degrees to 360 degrees. Different from the incident light wavelength, the grating vector direction ψ and the grating period distance d of the optical coupling input region 122 become fixed values after the design of the optical coupling input region 122 is completed. In the following description, the pupil expansion region 124 of the grating structure 120 will be described in detail.

[0024] FIG. 4 shows a partially enlarged top view of the pupil expansion region 124 of the waveguide element 100 in FIG. 1. FIGS. 5 and 6 show partially enlarged cross-sectional views of the divided regions 125a and 125b in the grating structure 120 of the waveguide element 100 in FIG. 1. Referring to FIGS. 4, 5, and 6, when dividing the region, the divided regions 125a, 125b, 125c, 125d, and 125e can be divided in several forms so that the optical properties of the divided regions 125a, 125b, 125c, 125d, and 125e are different. It should be explained first that the included angle φ between the boundaries of the divided regions 125a, 125b, 125c, 125d, and 125e and the horizontal line and the angle θ2 between the grating and the horizontal line are two independent parameters. In some embodiments, the gratings of the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124 each have a grating height H, and the grating height H increases from the divided region 125a closest to the optical coupling input region 122 to the divided region 125e farthest from the optical coupling input region 122.

[0025] In some embodiments, each of the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124 has a filling ratio, and the filling ratio decreases from the divided region 125a closest to the optical coupling input region 122 to the divided region 125e farthest from the optical coupling input region 122. Here, the "filling ratio" is the optical grating width W divided by the optical grating period distance d, that is, the wider the width of the optical grating line, the higher the filling ratio. In some embodiments, the grating structure 120 includes a plurality of gratings, the gratings in the pupil expansion region 124 and the horizontal line each have an inclination angle θ1, and the inclination angle θ1 decreases from the divided region 125a closest to the optical coupling input region 122 to the divided region 125e farthest from the optical coupling input region 122. With such a design, in order to make the refractive index distribution of each of the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124 discontinuous, the energy of the incident light can be emitted to the optical coupling output region 126 in several portions. In some embodiments, the refractive index of the grating structure 120 is in the range of 1.2 to 2.5.

[0026] The pupil expansion region 124 has divided regions 125a, 125b, 125c, 125d, and 125e, and the included angle between the boundaries of these divided regions 125a, 125b, 125c, 125d, and 125e and the horizontal line is correlated with parameters such as the incident light wavelength, the viewing angle θ, the refractive index of the substrate 110, the grating vector direction ψ of the optical coupling input region 122, and the grating period distance d of the optical coupling input region 122 through special calculations, whereby the energy can be arranged more uniformly during pupil expansion, improving the uniformity of the screen.

[0027] FIG. 7 shows a top view of the waveguide element 100a and the light source 200 according to another embodiment of the present disclosure. Referring to FIG. 7, the waveguide element 100a includes a substrate 110 and a grating structure 120a. The grating structure 120a is positioned on the substrate 110 so as to constitute a light coupling input region 122, a light coupling output region 126, and a pupil expansion region 124a. The pupil expansion region 124a is optically coupled to the light coupling input region 122 and the light coupling output region 126. The difference between this embodiment and the embodiment of FIG. 1 lies in the arrangement of the positions of the light coupling output region 126 and the pupil expansion region 124a of the grating structure 120a. The light coupling output region 126 is located at the lower left and the lower center of the waveguide element 100a, and the pupil expansion region 124a is located at the upper left and the upper center of the waveguide element 100a. Also, the light source 200 in this embodiment is a single-wavelength light source, and the wavelength is fixed at 550 nanometers. The wavelength and other parameters are shown in Table 1.

Table 1

[0028] In this embodiment, the divided regions 125a, 125b, 125c, 125d, and 125e of the pupil expansion region 124a are divided by the grating height H of the grating in each of the divided regions 125a, 125b, 125c, 125d, and 125e. In this embodiment, the grating heights of the five divided regions 125a, 125b, 125c, 125d, and 125e are 5 nanometers, 15 nanometers, 60 nanometers, 90 nanometers, and 120 nanometers, respectively.

[0029] FIG. 8 shows a top view of the waveguide element 100b and the light source 200 according to another embodiment of the present disclosure. Referring to FIG. 8, the waveguide element 100a includes a substrate 110 and a grating structure 120b. The grating structure 120 is positioned on the substrate 110 so as to constitute a light coupling input region 122, a light coupling output region 126, and a pupil expansion region 124b. The pupil expansion region 124b is optically coupled to the light coupling input region 122 and the light coupling output region 126. The difference between this embodiment and the embodiment of FIG. 1 is that in this embodiment, the pupil expansion region 124b has only four divided regions 125a, 125b, 125c, and 125d. Further, the light source 200 in this embodiment is a light source 200 capable of emitting a plurality of wavelengths, and the design parameters of this embodiment are shown in Table 2.

Table 2

[0030] In this embodiment, the divided regions 125a, 125b, 125c, and 125d of the pupil expansion region 124b are divided by the grating height H of the grating in each of the divided regions 125a, 125b, 125c, and 125d. In this embodiment, the grating heights of the four divided regions 125a, 125b, 125c, and 125d are 20 nanometers, 40 nanometers, 60 nanometers, and 80 nanometers, respectively.

[0031] As described above, in order for those skilled in the art to better understand the aspects of the present disclosure, the features of some embodiments have been described. Those skilled in the art should understand that the present disclosure can be easily used as a basis for designing or modifying other processes and structures so as to achieve the same objectives and / or the same advantages as the embodiments described in this specification. Further, those skilled in the art will recognize that such equivalent structures can make various changes, substitutions, and modifications without departing from the spirit and scope of the present disclosure and without departing from the spirit and scope of the present disclosure.

Description of Reference Numerals

[0032] 100, 100a, 100b Waveguide element 110 Substrate 120, 120a, 120b Lattice Structure 122 Optical Coupling Input Region 124, 124a, 124b Pupil Expansion Region 125a, 125b, 125c, 125d, 125e Division Region 126 Optical Coupling Output Region 200 Light Source φ Angle ψ Vector Direction d Periodic Distance H Height W Width θ Viewing Angle θ1 Inclination Angle θ2 Angle

Claims

1. A waveguide element, A substrate; an optical grating structure located on the substrate to define an optical coupling input region, an optical coupling output region, and an optical pupil expansion region; The optical pupil expansion region is optically coupled to the optical coupling input region and the optical coupling output region, and the optical pupil expansion region is configured to receive light rays from the optical coupling input region and diffract them to the optical coupling output region to expand the pupil, and the optical pupil expansion region has at least two divided regions, and an included angle φ between the boundary of the divided region of the optical pupil expansion region and a horizontal line, where φ=tan -1 (β 1 / α 1 ), where α 1 = (-λsinψ+αd) / nd, β 1 = (λ cos ψ + β d) / nd, α = sin(θ) × cos ψ, β = sin(θ) × sin ψ, λ is the wavelength of incident light, θ is the viewing angle, n is the refractive index of the substrate, ψ is the optical grating vector direction of the optical coupling input region, and d is the optical grating periodic distance of the optical coupling input region.

2. 2. The waveguide element of claim 1, wherein the included angle φ between a boundary of the divided regions of the optical pupil expansion region and the horizontal line has an offset of 10° or less.

3. 2. The waveguide element of claim 1, wherein the optical grating structure includes a plurality of optical gratings, the optical gratings in the split regions of the optical pupil expansion region each having an optical grating height, the optical grating height increasing from the split region closest to the optical coupling input region to the split region furthest from the optical coupling input region.

4. The waveguide element of claim 3 , wherein the optical grating height is in the range of 10 nanometers to 300 nanometers.

5. 2. The waveguide element of claim 1, wherein each of the split regions of the optical pupil expansion region has a fill fraction, and the fill fraction decreases from the split region closest to the optical coupling input region to the split region furthest from the optical coupling input region.

6. 2. The waveguide element of claim 1, wherein the optical grating structure includes a plurality of optical gratings, the optical gratings and the horizontal line of the optical pupil expansion region each have a tilt angle, and the tilt angle decreases from the split region closest to the optical coupling input region to the split region farthest from the optical coupling input region.

7. The waveguide element of claim 1 , wherein the optical grating periodic distance is in the range of 300 nanometers to 1200 nanometers.

8. 2. The waveguide element of claim 1, wherein the refractive index of the substrate is in the range of 1.5 to 2.5, and the refractive index of the optical grating structure is in the range of 1.2 to 2.

5.

9. The waveguide element of claim 1 , wherein the viewing angle is in the range of 0° to 90°.

10. 2. The waveguide element of claim 1, wherein the incident light wavelength is in the range of 400 nanometers to 700 nanometers.

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