CN119816775A

CN119816775A - Output coupling gratings for waveguide-based displays

Info

Publication number: CN119816775A
Application number: CN202380066430.0A
Authority: CN
Inventors: 塞巴斯蒂安·德·康塞尔; 清水一恵; 克里斯托夫·佩洛兹
Original assignee: Sony Group Corp
Current assignee: Sony Group Corp
Priority date: 2022-09-22
Filing date: 2023-09-14
Publication date: 2025-04-11
Also published as: WO2024063005A1

Abstract

An OCG for a waveguide-based display includes a base substrate and a plurality of unit cells arranged in groups on the base substrate. The unit cells of the first group each include a first photonic structure in a first orientation and having a first size and a first shape, and the unit cells of the second group each include a second photonic structure in a second orientation and having a second size and a second shape. One or more of the first orientation, the first dimension, and the first shape of the first photonic structure are different from the second orientation, the second dimension, and the second shape of the second photonic structure.

Description

Output coupling grating for waveguide-based displays

Technical Field

Example embodiments relate to an out-coupling grating (OCG) for a waveguide-based display.

Background

Waveguide-based displays may be used in near-eye display devices, such as head-mounted display (HMD) devices in Augmented Reality (AR) and/or Mixed Reality (MR) applications. The optical coupling at the input and output of the waveguide affects the image quality seen by the user of the HMD.

Disclosure of Invention

The illustrative embodiments relate to an OCG for a waveguide-based display. The OCG includes a base substrate and a plurality of unit cells arranged in groups on the base substrate. The unit cells of the first group each include a first photonic structure in a first orientation and having a first size and a first shape, and the unit cells of the second group each include a second photonic structure in a second orientation and having a second size and a second shape. One or more of the first orientation, the first dimension, and the first shape of the first photonic structure are different from the second orientation, the second dimension, and the second shape of the second photonic structure.

In another illustrative embodiment, a waveguide includes a base substrate, an in-coupling grating (ICG) to receive light from a light source, and an out-coupling grating (OCG) to output light. The OCG includes a plurality of unit cells arranged in groups on a base substrate at regular intervals. The unit cells of the at least one group of unit cells each include a first photonic structure having an even number of sides greater than six when viewed in plan, and each side of the first photonic structure is parallel to at least two other sides of the first photonic structure.

In yet another illustrative embodiment, a system includes a light source and a waveguide including an in-coupling grating (ICG) that receives light from the light source and an out-coupling grating (OCG) that outputs light. The OCG includes a base substrate and a plurality of unit cells arranged in groups on the base substrate, wherein the unit cells of the first group each include a first photonic structure in a first orientation and having a first size and a first shape, and wherein the unit cells of the second group each include a second photonic structure in a second orientation and having a second size and a second shape, wherein one or more of the first orientation, the first size, and the first shape of the first photonic structure are different from the second orientation, the second size, and the second shape of the second photonic structure.

Drawings

FIG. 1 is a block diagram of a system according to at least one example embodiment.

Fig. 2 shows a schematic diagram of a display device and an example of a k-space design of the display device according to at least one example embodiment.

Fig. 3 shows a k-space design defining a unit cell in accordance with at least one example embodiment.

Fig. 4 illustrates an example structure of an OCG including a plurality of unit cells according to at least one example embodiment.

Fig. 5 illustrates four example photonic structures in accordance with at least one example embodiment.

Fig. 6 illustrates diffraction characteristics of two different photonic structures in accordance with at least one example embodiment.

Fig. 7 illustrates diffraction characteristics of three different unit cells, each having a multi-layer photonic structure, in accordance with at least one example embodiment.

Fig. 8 illustrates another example design of a photonic structure within a unit cell in accordance with at least one example embodiment.

Fig. 9 shows a schematic diagram of a Head Mounted Display (HMD) in accordance with at least one example embodiment.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Photonic waveguides are promising optical building blocks for developing Augmented Reality (AR)/Mixed Reality (MR) displays. Photonic waveguides employ a variety of diffractive optical elements to replicate an image generated by an optical engine (light source) and display the image to the user's eye. Light from an optical engine propagates via a waveguide by Total Internal Reflection (TIR) and can be schematically divided into three main functions, input pupil coupling, pupil replication (or expansion) and output pupil coupling. The development of efficient AR/MR displays requires optimization of these three functions by photonic micro/nanostructure combinations. The photonic structure is used to control the path of the TIR light within the waveguide and outcouple the light towards the user's eye with the best possible image quality. Some photonic structures include one-dimensional linear gratings that can be blazed (blazed), multi-stepped (multi-stepped), or slanted (slanted), and the height and orientation of the grating affects diffraction efficiency. Two-dimensional gratings have been proposed to control TIR light propagation and achieve higher pattern quality, in particular uniformity and output efficiency. These structures have limited tunability of the diffraction orders and limit the overall performance of the waveguide.

Embodiments of the present disclosure propose photonic structures for high tunability of diffraction orders in order to achieve high optical image quality, in particular high brightness and high uniformity, in e.g. AR displays. A photonic structure (also referred to as a photonic element) is included in a particular unit cell that is periodically repeated in two axes at defined pitches Λ _PC1 and Λ _PC2 to form a photonic crystal. The shape of the photonic element may be based on a reference shape, such as a parallelogram, and may be tailored according to certain rules. The photonic elements may be stacked to provide a multilayer structure with enhanced functionality. The shape of the photonic element may be varied across the output coupling region of the waveguide to improve image quality.

Fig. 1 is a block diagram of a system 100 including a display device 102 in accordance with at least one example embodiment. The display device 102 may be a waveguide-based display and includes a waveguide 104, an in-coupling grating (ICG) 108, an out-coupling grating (OCG) 110, and an eye-box (eyebox) 112 that outputs light to a user 116.

The waveguide 104 receives input light incident on a first surface of the waveguide 104 from a light source or image generation device (not shown, but see additional details of the image generation device of fig. 9). The received light is received by an input region of ICG 108 on a first surface of waveguide 104 and redirected (e.g., diffracted) at a propagation angle to internally reflect (e.g., total Internal Reflection (TIR)) within waveguide 104. Internally reflected light may travel within the waveguide 104 before encountering the OCG 110 at the second surface of the waveguide 104. The waveguide 104 may be secured to or on a substrate or base (not shown). The OCG 110 has a structure that diffracts at least some of the internally reflected light to the eye-box 112 of the display device 102 as output light for viewing by the user 116. The region of waveguide 104 between ICG 108 and OCG 110 may correspond to an extended region. The input light may be generated by a light source under the control of an image processing circuit (not shown) or image generating device that controls the light source to output light in a manner that displays still and/or moving images to the user 116 via the eye box 112, thereby providing AR or MR images to the user 116. The eye box 112 may include a region or volume of view in which the user's eyes will receive output light. The light source may include any suitable light source for diffractive waveguide applications, such as one or more Light Emitting Diodes (LEDs) or other light sources coupled with one or more lenses and/or prisms that direct light to the waveguide 104.

The image processing circuit and the image generating device described above may include a memory including executable instructions and a processor (e.g., a microprocessor) executing the instructions on the memory. The memory may correspond to any suitable type or set of memory devices configured to store instructions. Non-limiting examples of suitable memory devices that may be used include flash memory, random Access Memory (RAM), read Only Memory (ROM), variations thereof, combinations thereof, and the like. In some embodiments, the memory and processor may be integrated into a common device (e.g., the microprocessor may include an integrated memory). Additionally or alternatively, the image processing circuitry may comprise hardware, such as an Application Specific Integrated Circuit (ASIC). Other non-limiting examples of image processing circuitry include Integrated Circuit (IC) chips, central Processing Units (CPUs), graphics Processing Units (GPUs), microprocessors, field Programmable Gate Arrays (FPGAs), digital Signal Processors (DSPs), sets of logic gates or transistors, resistors, capacitors, inductors, or diodes, and so forth. Some or all of the image processing circuitry may be disposed on a Printed Circuit Board (PCB) or a collection of PCBs. It will be appreciated that any suitable type or collection of electronic components may be adapted for inclusion in the image processing circuit.

The waveguide 104 may comprise any suitable material for diffractive waveguide applications, such as glass, plastic, polymer, or other suitable organic or inorganic optical materials. The waveguide 104 may be implemented in any suitable manner. For example, the waveguide 104 may include a core and one or more cladding layers, where the core and cladding layers have different dielectric constants. In another example, the waveguide 104 may be implemented with silicon photonics.

As described herein, ICG 108 and/or OCG 110 may include photonic structures (e.g., protrusions and/or recesses) at one or more surfaces of waveguide 104 (see discussion of photonic structures 500 and 800 below). Thus, ICG 108 and OCG 110 may be considered Surface Relief Gratings (SRGs). Fig. 1 shows an example in which ICG 108 and OCG 110 are both located on a single surface of waveguide 104 in the figure (the bottom surface of ICG 108 and the top surface of OCG 110). However, the same or similar photonic structures may additionally or alternatively be located on opposite surfaces of waveguide 104 (i.e., the top surface of ICG 108 and the bottom surface of OCG 110). The photonic structures of each of ICG 108 and OCG 110 may be formed according to suitable methods, such as nanoimprint lithography and/or inkjet printing. The photonic structures of each of ICG 108 and OCG 110 may be formed on the surface of waveguide 104 (i.e., the photonic structures are not part of waveguide 104, but are placed on the surface of waveguide 104) and/or included as part of the surface of waveguide 104. The photonic structure of each of ICG 108 and OCG 110 may take a suitable shape or form. For example, the photonic structure may include one-dimensional structures (e.g., linear structures), two-dimensional structures (struts, holes, and/or the like), supersurfaces, and/or other suitable forms. Regardless, the specific design of the photonic structures of ICG 108 and/or OCG 110 may be based on the desired optical characteristics of the output light of display device 102. As described in more detail below, OCG 110 may include photonic structures arranged into unit cells designed to improve brightness and uniformity of an image output to eye box 112.

The eye box 112 may correspond to a volume of free space in which the eyes of the user 116 receive a view of an image created by light output from the OCG 110. The size and location of this volume may be selected based on the optical architecture, where the designer trades off many constraints, such as field of view (FOV), image quality, and product design.

Fig. 2 shows a schematic diagram of a display device 102 and an example of a k-space design of the display device 102 according to at least one example embodiment. It is understood from the k-space design diagram 200 that IN is the IN-coupling vector of the ICG 108, and that O1 and O2 are the expansion and out-coupling unit vectors for the waveguide and the expansion region of the OCG 110, respectively. As described herein, the photonic structure of the OCG 110 may be divided into unit cells arranged at substantially the same pitch. The term "substantially" is used to explain the variation in value (such as pitch) that may occur as a result of the manufacturing process. In other words, the photonic structures are arranged at substantially the same pitch, wherein the pitch is within manufacturing tolerances. In some cases, the pitch is within other acceptable deviations from the standard pitch value (e.g., within +/-5% of the standard pitch value).

Fig. 3 and 4 illustrate various details of OCG 110 in accordance with at least one example embodiment. More specifically, fig. 3 shows a k-space design 204 defining a unit cell 300, while fig. 4 shows an example structure of an OCG 110 including a plurality of unit cells 300. As shown in fig. 3, Λ '_PC1 and Λ' _PC2 are defined by grating vectors:

Angles θ ₁ and θ ₂ are derived from the grating vector AndIs defined by the angle of (a).

It will be appreciated that the unit cell 300 is formed by the intersection of two sets of parallel lines, thereby forming a parallelogram shape.

Fig. 4 shows a design of an OCG 110 for spatially tuning TIR light to accommodate deviations in the waveguide and reliefs towards the user's eye, and fig. 5 shows an example photonic structure 500 for use in a unit cell 300. As shown in fig. 4, OCG 110 is divided into a plurality of regions 302, which may be referred to as photonic crystal units 302. Fig. 4 shows an example in which the region 302 is provided in a rectangular shape and in a grid pattern on the OCG 110. However, OCG 110 may be partitioned differently such that regions 302 have different sizes, different shapes, and/or are arranged in different patterns. In some cases, the size, shape, and pattern of the region 302 are selected to optimize image quality (e.g., brightness and uniformity) for the user. Clearly, the area 302 is a virtual partition for mapping each set of unit cells 300, and does not necessarily exist as a physical partition line on the OCG 110.

As further shown in fig. 4, each region 302 includes a plurality of unit cells 300. As shown in fig. 5, each unit cell 300 includes one or more photonic structures 500. Fig. 5 shows four example photonic structures 500 a-500 d. All of the unit cells 300 in a particular region 302 may have photonic structures 500 set to the same shape, size, and orientation, where the shape, size, and orientation of the photonic structures 500 in a particular region 302 are selected to match the diffraction efficiency desired for that particular region 302. Because different diffraction efficiencies are used in different regions 302, the shape, size, and/or orientation of photonic structure 500 may vary between regions 302.

In other words, a plurality of unit cells 300 are arranged in groups on a base substrate of the OCG 110, such as a portion of the waveguide 104. OCG 110 is divided into regions 302. Each region 302 includes a set of unit cells 300 that contain photonic structures that are substantially identical in shape, size, and orientation. However, the shape, size, and/or orientation of the photonic structure may vary between groups of unit cells. For example, the unit cells of the first group (in one of the regions 302) each include a first photonic structure in a first orientation and having a first size and a first shape. Meanwhile, the unit cells of the second group (in the different regions 302) each include a second photonic structure in a second orientation and having a second size and a second shape. According to an embodiment, at least one of the first orientation, the first size, and the first shape of the first photonic structure is different from the second orientation, the second size, and the second shape of the second photonic structure.

It will be apparent that the present disclosure relates to the size, shape and orientation of structures from a plan view perspective of the structure (such as the views shown in fig. 5-8). The dimensions of the photonic structure may be determined by the two-dimensional surface area (or footprint) of the photonic structure when viewed from a plan view, without taking into account any variations in the 3D profile. The size of a photonic structure may be measured by the amount (e.g., in percent) of area occupied by the photonic structure within a unit cell. The size of the unit cell may correspond to the two-dimensional surface area of the unit cell.

The shape of the photonic structure may correspond to a two-dimensional shape when viewed from a plan view, without taking into account any variations in the 3D profile. When each photonic structure has the same size scale (i.e., the only difference between the two structures is the scale), the two photonic structures can be considered to have the same shape. Thus, two parallelograms having different proportions but the same size (each occupying the same amount of area within a unit cell) can be considered to have different shapes. In addition, if the scale of a smaller-sized shape can be enlarged to obtain a structure that matches the size of a larger-sized shape, two photonic structures of different sizes can be considered to have the same shape. For example, photonic structures 500c and 500e in fig. 6 may be considered to have different shapes and dimensions (orientation is not a factor), while photonic structures 800a and 800b may be considered to have the same shape and same dimensions, but different orientations.

The shape of the unit cell may correspond to a two-dimensional shape of the unit cell as viewed from a plan view. Meanwhile, when viewed from a plan view, the orientation of the photonic structure corresponds to a position of the photonic structure in the 2D space with respect to a reference (the reference may correspond to a central axis of the unit cell). The orientation of the unit cell may correspond to the position of the unit cell in 2D space relative to a reference (e.g., the reference may correspond to the direction of light propagation in fig. 1) when viewed from a plan view. In view of the above, it should be appreciated that the two photonic structures of the unit cell from different regions 302 may differ in one or more of shape, size, and orientation.

As shown in fig. 4, the unit cells 300 in region 302 repeat periodically along two non-parallel axes in a parallelogram geometry having dimensions Λ _PC1 and Λ _PC2. Λ _PC1 and Λ _PC2 reflect the periodicity of the unit cell 300, and the values of Λ _PC1 and Λ _PC2 may depend on the operating wavelength, material properties and/or design choices. In some examples, Λ _PC1 and Λ _PC2 are between 200nm and 620 nm. In other examples, Λ _PC1 and Λ _PC2 are between 300nm and 550 nm. In some cases, the values of Λ _PC1 and Λ _PC2 are equal to each other across the region 302 or the unit cells 300 in all the regions 302. In other cases, the values of Λ _PC1 and Λ _PC2 are different. Referring to fig. 3, the shape of the unit cell 300 is defined by an angle α _PC, and α _PC is a minimum angle defining a parallelogram of the unit cell 300. The angle alpha _PC may be selected depending on the geometry of the desired field of view (FOV) represented in k-space. The angle α _PC is between 30 ° and 90 °, such as between 40 ° and 80 ° or between 50 ° and 65 °. It is understood that the unit cells 300 in the specific region 302 have the same size, the same shape, and the same orientation. In some examples, the unit cells 300 have the same size, the same shape, and the same orientation for all of the regions 302. As shown in fig. 4, a central axis a (e.g., a longitudinal axis) of the unit cell 300 may be aligned with a direction of light propagation in the waveguide 104 from the ICG 108. In some cases, however, the central axis a of the unit cell may be rotated by an angle (e.g., less than 90 °) compared to the direction of light propagation.

Fig. 5 shows four example photonic structures (also referred to as Photonic Elements (PEs)) 500a through 500d. Each unit cell 300 includes a single photonic structure 500 or a plurality of stacked photonic structures 500. In other words, the unit cell 300 includes m photonic structures, which may be stacked in n layers (also referred to as a TIR direction or a light propagation direction in fig. 1) in a direction perpendicular to the light propagation direction. The photonic structure 500 may be made of one or more materials having a refractive index between 1.2 and 2.6. The photonic structure 500 may exhibit low absorption in the visible wavelength range and may include a polymer, hybrid (organic/inorganic) resist, or an inorganic film, such as glass.

The present disclosure proposes a photonic structure 500 capable of controlling the spatial diffraction efficiency in three dimensions, thereby improving image brightness and uniformity. The photonic structures 500a to 500d follow a set of rules or conditions that 1) the photonic structure 500 has a shape derived from a parallelogram-shaped reference shape and the photonic structure 500 is a parallelepiped, a substantially constant thickness (height) between 1.0nm and 500.0nm or between 5.0nm and 320.0nm, 2) the parallelogram-shaped reference shape has lengths L1 and L2, 3) the area of the parallelogram-shaped reference shape is smaller than the area of the unit cell 300 such that the photonic structure 500 fits within the unit cell 300, 4) the photonic structure 500 can be clipped as compared to the parallelogram-shaped reference shape, 5) clipping is applied to the major or minor angles of the photonic structure 500 (where the major angle is defined as one of the angles of the photonic structure 500a and the minor angle is defined as the angle produced by the major angle as in the photonic structure 500 b), 6) clipping can be applied once or more times as long as the table in FIG. 5 is complied with, 7) the clipped edges are parallel to the edges of the parallelogram-shaped reference shape, and 8) clipping edges 1 and 2 are within the range 1< L <1 and 2< 1< L < 0< 2.

It is understood that photonic structure 500a is uncut and shows a parallelogram-shaped reference shape from which photonic structures 500b through 500d are derived. Accordingly, photonic structure 500a may also be referred to as reference shape 500a. Photonic structure 500c shows a single Crop (Crop 1) of the principal included angle of reference shape 500a. Photon structure 500b shows a clip from 500c and an additional clip (Crop 2) to one of the minor included angles of the shape in 500c produced by the first clip (Crop 1). Meanwhile, photonic structure 500d shows a clip from 500c and an additional clip (loop 2) to the main included angle of reference shape 500a.

The reference shape 500a has two equal angles β. The angle β may be between 30 ° and 90 °, such as between 40 ° and 80 °, or between 50 ° and 65 °. In some examples, angle β within photonic structure 500 and angle α _PC of unit cell 300 having photonic structure 500 are substantially the same, but may also be different. It is appreciated from photonic structures 500b and 500c that the trim of reference shape 500a may form additional included angles with angle β within the remainder of the photonic structure.

The photonic structure shown in the figures is implemented with a post configuration in which the photonic structure protrudes from the base substrate. However, the photonic structure may additionally or alternatively be implemented with a hole configuration, wherein the photonic structure is a recess that is recessed into the base substrate (e.g., composed of resin).

Fig. 6 illustrates diffraction characteristics of two different photonic structures in accordance with at least one example embodiment. More specifically, fig. 6 shows the diffraction characteristics of the photonic structure 500c of fig. 5 and another photonic structure 500e, including a graph of reflected diffraction efficiency versus angle, with the other photonic structure 500e including more cuts than 500 c. Fig. 6 further shows the outline of the unit cell 300, and the unit cell 300 has the same parallelogram shape as the reference shape 500 a. The shaded and unshaded regions beside each unit cell 300 correspond to the photonic structures of adjacent unit cells 300 (recall that the shape of photonic structure 500 is repeated for all unit cells 300 in a particular region 302). The non-shaded region may correspond to a layer below photonic structure 500, such as may include a portion of waveguide 104 or a base substrate corresponding to a portion of waveguide 104.

Fig. 7 shows diffraction characteristics of three different unit cells 300a to 300c, which include graphs of reflection diffraction efficiency versus angle, each of the unit cells 300a to 300c having a multi-layered photonic structure stacked on a base substrate. In particular, FIG. 7 shows a plan view of a unit cell 300 a-300 c having a multi-layer design, wherein a first photonic structure 500-1 is stacked on a base substrate 700 (e.g., waveguide 104) and a second photonic structure 500-2 is stacked on the first photonic structure 500-1. As shown in the cross-sectional view in fig. 7, it is assumed that a first photonic structure 500-1 exists under and completely overlaps a second photonic structure 500-2. In other words, the region belonging to the second photonic structure 500-2 shown in fig. 7 has a region of the same shape and size as the first photonic structure 500-1 under the second photonic structure 500-2. In some examples, however, the second photonic structure 500-2 may include overhanging regions that are devoid of the corresponding photonic structure 500-1 thereunder. In this case, the space between the second photonic structure 500-2 and the base substrate may correspond to an air gap. As in fig. 6, the shaded and unshaded areas beside each unit cell 300a to 300c in fig. 7 correspond to adjacent unit cells 300.

The unit cell 300a shows a multi-layer structure in which a first photonic structure 500-1 has a reference shape 500a and a second photonic structure 500-2 includes a small cutout (where 100% of the arrow is located) closest to the light input region of the unit cell 300a at the tip of the reference shape 500 a. The unit cell 300a shows a multi-layer structure in which a first photonic structure 500-1 has been tailored to form a V-shape according to a reference shape 500a and a second photonic structure 500-2 has been tailored to form a smaller parallelogram where the portion of the V-shape stops. Meanwhile, the unit cell 300c shows a multi-layered structure in which the first photonic structure 500-1 has been tailored to form a smaller parallelogram according to the reference shape 500a, and the second photonic structure has been tailored to form a smaller parallelogram on the first photonic structure 500-1 according to the reference shape 500 a.

Here, it should be understood that each layer of the photonic structure in the multilayer design may have a different refractive index than one or more other layers of the photonic structure in the multilayer design. In other examples, one or more layers of the photonic structure in the multilayer design have the same refractive index. It should be further understood from fig. 7 that the base substrate 700 is exposed to the regions between the unit cells (see unit cell 300 a) and the regions without the photonic structures 500-1 and/or 500-2 (see unit cells 300b and 300 c). In some cases, one or more layers of photonic structure 500 are not considered to be located between base substrate 700 and first photonic structure 500-1. In this case, the absence of photonic structure 500 exposes one of the layers. In addition, the multi-layer photonic structure for unit cell 300 may include more than two photonic structures 500a and 500b discussed above and shown in fig. 7. Each layer may be formed separately from the other layers.

Fig. 8 shows another example design of a photonic structure within a unit cell. More specifically, fig. 8 shows a photonic structure 800 having a parallelogram shape within a unit cell 804, the unit cell 804 having the same or similar shape, size, and orientation as the unit cell 300 in fig. 3. As with photonic structure 500, photonic structure 800 can provide control over spatial diffraction efficiency in three dimensions, thereby improving image brightness and uniformity. OCG 110 may comprise a plurality of unit cells 804 distributed across area 302 in the same or similar manner as unit cells 300. Each group of unit cells 804 in region 302 may have the same shape, size, and orientation of photonic structure 800. The photonic structure 800 within the unit cell 804 should follow the rules or conditions that 1) the photonic structure 800 is parallelepiped, has a parallelogram shape (e.g., the same or similar to the reference shape 500 a), and has a substantially constant thickness (height) between 1.0nm and 500.0nm or between 5.0nm and 320.0nm, 2) the parallelogram shape defined by the lengths L1 and L2, the two-dimensional area of the photonic structure 800 is smaller than the area of the unit cell 804, and 3) the angle β of the photonic structure 800 is different from the angle α _PC of the unit cell 804. In some cases, and as shown in fig. 8, photonic structure 800 is rotated a selected angle relative to unit cell 804. In contrast to photonic structure 500, photonic structure 800 is not necessarily cut from a reference shape.

Fig. 8 shows two example photonic structures 800a and 800b and their associated diffraction characteristics within various unit cells 804a and 804b, including a graph of reflected diffraction efficiency versus angle. The photonic structure 800a includes a parallelogram shape with an angle β different from the angle α _PC and rotated relative to the unit cell 804 a. Photonic structure 800b includes the same parallelogram shape as 800a, except that photonic structure 800b is rotated 90 deg. compared to 800 a.

Although not explicitly shown, it should be understood that the non-shaded region in fig. 8 may correspond to an exposed base substrate (e.g., base substrate 700) or other layer of waveguide 104, and that the shaded region adjacent to a unit cell 804 is a photonic structure 800 of an adjacent unit cell 804.

Although not explicitly shown, it should be understood that the unit cell 804 may include a multi-layer structure having a plurality of photonic structures 800 stacked on one another in the same or similar manner as described above with reference to fig. 7. Additionally or alternatively, the multi-layer structure within a unit cell may include an uncut but rotated parallelogram shape of photonic structure 800 stacked on or under cut and uncut photonic structure 500.

Fig. 9 shows a schematic diagram of a Head Mounted Display (HMD) 1300 in accordance with at least one example embodiment.

The HMD 1300 may include a wearable frame 10 supporting elements of the HMD 1300, a hinge 11 at an end 10A of the frame 10, an ear bud 13 removably mounted to an ear of the observer 40, a nose pad 14, and wiring 15 connected to external processing circuitry (not shown) that enables movement of a temple portion 12 securing the HMD 1300 to the head of the observer 40, in which external processing circuitry image processing operations are performed, for example based on output from a camera 18. The HMD 1300 may further include headphones 16, headphone wiring 17, an image sensor or camera 18 mounted on the surface 10B of the frame 10 in the central portion 10C of the frame 10, a member 20 mounting the image generation devices 111A and 111B through, for example, a housing 113, and a waveguide 104 placed in front of the pupil 41 of the observer 40 when the HMD 1300 is worn. It will be appreciated that both image generation devices 111A and 111B may include an optical system for providing input light to the respective waveguides 104. The optical system of each image generation device 111A and 111B may include one or more light sources, one or more lenses, one or more prisms or mirrors, one or more light modulators, and/or other suitable elements for generating input light for waveguide 104. Each waveguide 104 takes the form of one or more waveguides 104 discussed above with reference to fig. 1-8, and receives the input light shown in fig. 1 from one of the image generation devices 111A and 111B.

Here, it should be understood that the above details relate to one non-limiting example of the HMD 1300, and that the HMD 1300 may include more or fewer elements than those shown and described above.

Referring now to fig. 1-9, it should be appreciated that the exemplary embodiments relate to an OCG 110 for a waveguide-based display 102. OCG 110 may comprise a base substrate, such as base substrate 700, which may be part of waveguide 104 (i.e., waveguide material) and/or another suitable layer on the surface of waveguide 104. The OCG 110 may include a plurality of unit cells 300 arranged in groups on the base substrate 700. Each group of unit cells 300 may correspond to one of the regions 302. In some examples, the first group of unit cells 300 each include a first photonic structure in a first orientation and having a first size and a first shape, and the second group of unit cells 300 each include a second photonic structure in a second orientation and having a second size and a second shape. As described herein, one or more of the first orientation, the first dimension, and the first shape of the first photonic structure are different from the second orientation, the second dimension, and the second shape of the second photonic structure. In particular, the size, shape, and orientation of the photonic structures in each region are selected to provide the desired diffraction characteristics for a particular region 302 of OCG 110.

In some examples, the first shape of the first photonic structure is a parallelogram shape, each unit cell in the first group having a parallelogram shape, the first orientation being different from the second orientation such that the parallelogram shape of the first photonic structure rotates relative to the parallelogram shape of each unit cell 300 (see fig. 8). In addition, the angle of the parallelogram shape of the first photonic structure may be different from the angle of the parallelogram shape of each unit cell 300 in the first group.

In some examples, as shown in fig. 5 and 6, the first shape of the first photonic structure is based on a parallelogram-shaped reference shape and has a clipping region including one or more clipping portions, wherein a portion of the first photonic structure is missing compared to the parallelogram-shaped reference shape. As shown, one of the one or more trim portions defines two intersecting edges of the first photonic structure, each unit cell in the first group also having a parallelogram shape. The two intersecting edges may have the same length, which is shorter than the length of at least the other edge of the first photonic structure. As shown in fig. 3 and 5, two angles of the parallelogram shape of each unit cell 300 are the same as two angles of the first photonic structure.

In some examples, the cropped area of the first photonic structure is at a first end of the parallelogram shape of each unit cell 300 and the unclamped area of the first photonic structure is at a second end of the parallelogram shape of each unit cell opposite the first end (see, e.g., fig. 5). For each unit cell 300 in the first group, the first end corresponds to the point at which the first and second sides of the unit cell 300 intersect, and the second end corresponds to the point at which the third and fourth sides of the unit cell intersect. In some cases, the direction from the first end toward the second end corresponds to the direction of light propagation in the waveguide-based display 102. In at least one example, the trim area exposes a layer below the first photonic structure (which may correspond to the base substrate or a layer between the base substrate and the first photonic structure).

In some cases, each of the plurality of unit cells has the same size and the same shape. In addition, the thickness of the first photonic structure may be the same and constant in each unit cell 300 of the first group, and the thickness of the second photonic structure may be the same and constant in each unit cell 300 of the second group.

As shown in fig. 7, a third photonic structure may be stacked on the first photonic structure (e.g., 500-2 stacked on 500-1). In plan view, the third photonic structure and the first photonic structure may have a different number of edges. As can be appreciated from fig. 5-7, the first photonic structure has at least six sides in plan view and at least three identical angles between 30 ° and 90 °. Any of the details described above with reference to the first photonic structure may also be applied to the second photonic structure of OCG 110 and any other photonic structure. Additionally, it should be appreciated that the system may include a light source (111A/111B) and a waveguide 104 including the OCG 110 described above.

Still referring to fig. 1-9, an example embodiment relates to a waveguide that includes a base substrate (e.g., 700), an in-coupling grating (ICG) 108 that receives light from a light source (e.g., 111A/111B), and an out-coupling grating (OCG) 110 that outputs light. The OCG 110 may include a plurality of unit cells 300 arranged in groups on a base substrate at regular intervals (e.g., at regular intervals). The unit cells 300 in the at least one group of unit cells each include a first photonic structure having even sides greater than six when viewed in plan, each side of the first photonic structure being parallel to at least two other sides of the first photonic structure. Each unit cell 300 in the at least one group of unit cells includes a second photonic structure stacked on the first photonic structure, the second photonic structure having a different shape than the first photonic structure. Each of the plurality of unit cells 300 may have a parallelogram shape.

The embodiments described with reference to fig. 1-9 may be combined with each other in any suitable manner.

While the technology has been described in conjunction with a number of embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the applicable arts. Accordingly, it is intended to embrace all such alternatives, modifications, equivalents and variations as fall within the spirit and scope of the disclosure.

It is to be understood that the inventive concept encompasses any embodiment in combination with any one or more other embodiments, any one or more features disclosed herein in essence, any one or more features disclosed herein in combination with any one or more features disclosed herein in essence, any aspect or feature or embodiment in combination with any one or more other aspects or features or embodiments, and any one or more embodiments or uses of features disclosed herein. It should be understood that any feature described herein may be claimed in combination with any other feature described herein, whether or not such feature is from the same described embodiment.

Any of the processing devices, control units, processing units, etc. discussed above may correspond to one or more computer processing devices, such as a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), any other type of Integrated Circuit (IC) chip, an IC chipset, a microcontroller, a set of microcontrollers, a microprocessor, a Central Processing Unit (CPU), a Digital Signal Processor (DSP), or multiple microprocessors configured to execute a set of instructions stored in a memory.

The foregoing discussion has been presented for purposes of illustration and description. The foregoing is not intended to limit the disclosure to one or more of the forms disclosed herein. For example, in the foregoing detailed description, various features of the disclosure are grouped together in one or more aspects, embodiments, and/or configurations for the purpose of streamlining the disclosure. Features of aspects, embodiments, and/or configurations of the present disclosure may be combined in alternative aspects, embodiments, and/or configurations than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed aspect, embodiment, and/or configuration. Thus, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as an embodiment of this disclosure.

Moreover, while the description includes descriptions of one or more aspects, embodiments and/or configurations, as well as certain variations and modifications, other variations, combinations, and modifications are within the scope of the disclosure, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. The claims are intended to cover alternative aspects, embodiments, and/or configurations, including alternative, interchangeable and/or equivalent structures, functions, ranges, or steps, to the extent permitted, whether or not such alternative, interchangeable and/or equivalent structures, functions, ranges, or steps are disclosed herein without requiring any patentable subject matter to be disclosed.

As used herein, the phrases "at least one," "one or more," "or" and/or "are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B or C", "one or more of A, B and C", "one or more of A, B or C", "A, B and/or C", and "A, B or C" means a alone, B alone, C, A and B together, a and C together, B and C together, or A, B and C together.

Various aspects of the disclosure are described herein with reference to the accompanying drawings, which may be schematic illustrations of idealized configurations.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this disclosure.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The term "and/or" includes any one of the one or more of the associated listed items and all combinations thereof.

Example embodiments may be configured as follows:

(1)

An out-coupling grating (OCG) for a waveguide-based display, comprising:

A base substrate, and

A plurality of unit cells arranged in groups on a base substrate, wherein a first group of unit cells each include a first photonic structure in a first orientation and having a first size and a first shape, wherein a second group of unit cells each include a second photonic structure in a second orientation and having a second size and a second shape, and wherein one or more of the first orientation, the first size, and the first shape of the first photonic structure are different from the second orientation, the second size, and the second shape of the second photonic structure.

(2)

The OCG of (1), wherein the first shape of the first photonic structure is a parallelogram shape, wherein each unit cell in the first group has a parallelogram shape, and wherein the first orientation is different from the second orientation such that the parallelogram shape of the first photonic structure rotates relative to the parallelogram shape of each unit cell.

(3)

The OCG of one or more of (1) to (2), wherein an angle of the parallelogram shape of the first photonic structure is different from an angle of the parallelogram shape of each unit cell in the first group.

(4)

The OCG of one or more of (1) to (3), wherein the first shape of the first photonic structure is based on a parallelogram-shaped reference shape and has a clipping region comprising one or more clipping, wherein a portion of the first photonic structure is missing compared to the parallelogram-shaped reference shape.

(5)

The OCG of one or more of (1) through (4), wherein each of the one or more trim portions defines two intersecting edges of the first photonic structure, and wherein each unit cell in the first group also has a parallelogram shape.

(6)

The OCG of one or more of (1) to (5), wherein the two intersecting edges have the same length that is shorter than a length of at least another edge of the first photonic structure.

(7)

The OCG of one or more of (1) to (6), wherein two angles of the parallelogram shape of each unit cell are the same as two angles of the first photonic structure.

(8)

The OCG of one or more of (1) to (7), wherein the clipping region of the first photonic structure is at a first end of the parallelogram shape of each unit cell, and wherein a non-clipping region of the first photonic structure is at a second end of the parallelogram shape of each unit cell opposite the first end.

(9)

The OCG of one or more of (1) to (8), wherein for each unit cell in the first group, the first end corresponds to a point at which a first side and a second side of the unit cell intersect, wherein the second end shape corresponds to a point at which a third side and a fourth side of the unit cell intersect, and wherein a direction from the first end toward the second end corresponds to a light propagation direction.

(10)

The OCG of one or more of (1) to (9), wherein the clipping region exposes a layer under the first photonic structure.

(11)

The OCG of one or more of (1) to (10), wherein each of the plurality of unit cells has the same size and the same shape.

(12)

The OCG of one or more of (1) to (11), wherein in each unit cell of the first group, the thickness of the first photonic structure is the same and constant, and wherein in each unit cell of the second group, the thickness of the second photonic structure is the same and constant.

(13)

The OCG of one or more of (1) to (12), wherein the base substrate comprises a waveguide material.

(14)

The OCG of one or more of (1) to (13), further comprising:

and a third photonic structure stacked on the first photonic structure.

(15)

The OCG of one or more of (1) to (14), wherein the third photonic structure and the first photonic structure have different numbers of edges in plan view.

(16)

The OCG of one or more of (1) to (15), wherein in plan view the first photonic structure has at least six sides and at least three identical angles between 30 ° and 90 °.

(17)

A waveguide, comprising:

A base substrate;

an in-coupling grating (ICG) receiving light from the light source, and

An Output Coupling Grating (OCG) for outputting light, the OCG comprising:

A plurality of unit cells arranged in groups on a base substrate at regular intervals, wherein each unit cell of at least one group of unit cells comprises a first photonic structure having even sides greater than six when viewed in plan, wherein each side of the first photonic structure is parallel to at least two other sides of the first photonic structure.

(18)

The waveguide of (17), wherein each unit cell of the at least one set of unit cells includes a second photonic structure stacked on the first photonic structure, and wherein the second photonic structure has a different shape than the first photonic structure.

(19)

The waveguide of one or more of (17) to (18), wherein each of the plurality of unit cells has a parallelogram shape.

(20)

A system, comprising:

A light source, and

A waveguide, the waveguide comprising:

an in-coupling grating (ICG) receiving light from the light source, and

An Output Coupling Grating (OCG) for outputting light, the OCG comprising:

A base substrate, and

A plurality of unit cells arranged in groups on the base substrate, wherein a first group of unit cells each include a first photonic structure in a first orientation and having a first size and a first shape, wherein a second group of unit cells each include a second photonic structure in a second orientation and having a second size and a second shape, and wherein one or more of the first orientation, the first size, and the first shape of the first photonic structure are different from the second orientation, the second size, and the second shape of the second photonic structure.

Claims

1. An output coupling grating (OCG) for a waveguide-based display, comprising:

a base substrate; and

A plurality of unit cells are arranged in groups on a base substrate,

wherein each of the unit cells of the first group comprises a first photonic structure in a first orientation and having a first size and a first shape, wherein each of the unit cells of the second group comprises a second photonic structure in a second orientation and having a second size and a second shape, and wherein one or more of the first orientation, the first size and the first shape of the first photonic structure are different from the second orientation, the second size and the second shape of the second photonic structure.

2. The OCG of claim 1 , wherein the first shape of the first photonic structure is a parallelogram shape, wherein each unit cell in the first group has a parallelogram shape, and wherein the first orientation is different from the second orientation such that the parallelogram shape of the first photonic structure is rotated relative to the parallelogram shape of each unit cell.

3 . The OCG of claim 2 , wherein an angle of the parallelogram shape of the first photonic structure is different from an angle of the parallelogram shape of each unit cell in the first group.

4. The OCG of claim 1 , wherein the first shape of the first photonic structure is based on a parallelogram reference shape and has a clipping region comprising one or more clippings wherein a portion of the first photonic structure is missing compared to the parallelogram reference shape.

5 . The OCG of claim 4 , wherein each of the one or more cutouts defines two intersecting sides of the first photonic structure, and wherein each unit cell in the first group also has a parallelogram shape.

6. The OCG of claim 5, wherein the two intersecting sides have the same length, which is shorter than a length of at least another side of the first photonic structure.

7 . The OCG of claim 5 , wherein two angles of the parallelogram shape of each unit cell are the same as two angles of the first photonic structure.

8. The OCG of claim 5, wherein the clipping region of the first photonic structure is at a first end of the parallelogram shape of each unit cell, and wherein the non-clipping region of the first photonic structure is at a second end of the parallelogram shape of each unit cell opposite to the first end.

9. The OCG of claim 7 , wherein for each unit cell in the first group, the first end corresponds to a point where a first side and a second side of the unit cell intersect, wherein the second end corresponds to a point where a third side and a fourth side of the unit cell intersect, and wherein a direction pointing from the first end to the second end corresponds to a light propagation direction.

10. The OCG of claim 5, wherein the cut-out region exposes layers beneath the first photonic structure.

11. The OCG of claim 1, wherein each of the plurality of unit cells has the same size and the same shape.

12. The OCG of claim 1, wherein in each unit cell of the first group, a thickness of the first photonic structure is the same and constant, and wherein in each unit cell of the second group, a thickness of the second photonic structure is the same and constant.

13. The OCG of claim 1, wherein the base substrate comprises a waveguide material.

14. The OCG of claim 1, further comprising:

A third photonic structure is stacked on the first photonic structure.

15. The OCG of claim 14, wherein in plan view, the third photonic structure and the first photonic structure have different numbers of sides.

16. The OCG of claim 1, wherein in a plan view, the first photonic structure has at least six sides and at least three identical angles between 30° and 90°.

17. A waveguide comprising:

base substrate;

an input coupling grating (ICG) that receives light from a light source; and

An output coupling grating (OCG) for outputting light, the OCG comprising:

A plurality of unit cells are arranged in groups at regular intervals on the base substrate, wherein each of the unit cells in at least one group of unit cells comprises a first photonic structure, and when viewed from a plan view, the first photonic structure has an even number of sides greater than six, wherein each side of the first photonic structure is parallel to at least two other sides of the first photonic structure.

18. The waveguide of claim 17, wherein each unit cell of the at least one set of unit cells comprises a second photonic structure stacked on the first photonic structure, and wherein the second photonic structure has a different shape than the first photonic structure.

19. The waveguide of claim 17, wherein each of the plurality of unit cells has a parallelogram shape.

20. A system comprising:

Light source; and

A waveguide, the waveguide comprising:

an input coupling grating (ICG) receiving light from the light source; and

An output coupling grating (OCG) for outputting light, the OCG comprising:

a base substrate; and

A plurality of unit cells are arranged in groups on the base substrate, wherein each of the unit cells of the first group includes a first photonic structure in a first orientation and having a first size and a first shape, wherein each of the unit cells of the second group includes a second photonic structure in a second orientation and having a second size and a second shape, and wherein one or more of the first orientation, the first size and the first shape of the first photonic structure are different from the second orientation, the second size and the second shape of the second photonic structure.