Out-coupling grating for waveguide-based display

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 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.

Description

Technical Field

[0001] Example embodiments relate to output coupling gratings (OCGs) for waveguide based displays. Background Art

[0002] Waveguide-based displays can 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. Summary of the invention

[0003] 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, first size, and first shape of the first photonic structure are different from the second orientation, second size, and second shape of the second photonic structure.

[0004] In another illustrative embodiment, a waveguide includes a base substrate, an input coupling grating (ICG) receiving light from a light source, and an output coupling grating (OCG) outputting light. The OCG includes a plurality of unit cells arranged in groups at regular intervals on the base substrate. Each of the unit cells in at least one group of unit cells includes a first photonic structure having an even number of sides greater than six when viewed from a plan view, and each side of the first photonic structure is parallel to at least two other sides of the first photonic structure.

[0005] In yet another illustrative embodiment, a system includes a light source and a waveguide, the waveguide including an input coupling grating (ICG) that receives light from the light source and an output coupling grating (OCG) that outputs the 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 a 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 a 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, first size, and first shape of the first photonic structure are different from the second orientation, second size, and second shape of the second photonic structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a block diagram of a system according to at least one example embodiment.

[0007] Figure 2A schematic diagram of a display device and an example of a k-space plan diagram of a display device according to at least one example embodiment are shown.

[0008] Figure 3 A k-space design defining a unit cell according to at least one example embodiment is shown.

[0009] Figure 4 An example structure of an OCG including a plurality of unit cells according to at least one example embodiment is illustrated.

[0010] Figure 5 Four example photonic structures are shown according to at least one example embodiment.

[0011] Figure 6 Diffraction characteristics of two different photonic structures are shown according to at least one example embodiment.

[0012] Figure 7 Diffraction characteristics of three different unit cells, each having a multi-layered photonic structure, according to at least one example embodiment are shown.

[0013] Figure 8 Another example design of a photonic structure within a unit cell according to at least one example embodiment is shown.

[0014] Fig. 9 A schematic diagram of a head mounted display (HMD) is shown according to at least one example embodiment. Specific embodiments

[0015] 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 the image generated by the optical engine (light source) and display the image to the user's eye. Light from the optical engine propagates through the 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 the optimization of these three functions through a combination of photonic microstructures / nanostructures. Photonic structures are used to control the path of TIR light within the waveguide and to couple the light outward toward the user's eye with the best possible image quality. Some photonic structures include one-dimensional linear gratings that can be blazed, multi-stepped, or slanted, and the height and orientation of the grating affect the diffraction efficiency. Two-dimensional gratings have been proposed to control TIR light propagation and achieve higher image quality, especially uniformity and output efficiency. These structures have limited tunability of the diffraction orders and limit the overall performance of the waveguide.

[0016] Embodiments of the present disclosure propose photonic structures for high tunability of diffraction orders in order to achieve high optical image quality, especially high brightness and high uniformity, in, for example, AR displays. The photonic structure (also called a photonic element) is contained in a specific unit cell, which is connected in two axes with a defined spacing Λ PC1 and Λ PC2 Repeat periodically to form a photonic crystal. The shape of the photonic element can be based on a reference shape, such as a parallelogram, and can be tailored according to specific rules. The photonic elements can be stacked to provide a multi-layer structure with enhanced functionality. The shape of the photonic element can vary across the output coupling region of the waveguide to improve image quality.

[0017] Figure 1 is a block diagram of a system 100 including a display device 102 according to at least one example embodiment. The display device 102 may be a waveguide-based display and include a waveguide 104, an input coupling grating (ICG) 108, an output coupling grating (OCG) 110, and an eyebox 112 that outputs light to a user 116.

[0018] The waveguide 104 receives light from a light source or image generating device (not shown, but see Fig. 9 104). The received light is received by an input region of the ICG 108 on the first surface of the waveguide 104 and redirected (e.g., diffracted) at a propagation angle to be internally reflected (e.g., total internal reflection (TIR)) within the waveguide 104. The 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 an eye box 112 of the display device 102 as output light for viewing by a user 116. The region of the waveguide 104 located between the ICG 108 and the OCG 110 may correspond to an expansion region. The input light may be generated by a light source under the control of an image processing circuit (not shown) or an image generating device, which controls the light source to output light in a manner that displays still images and / or moving images to the user 116 via the eye box 112, thereby providing an AR image or an MR image to the user 116. The eye box 112 may include an area or volume of view in which the user's eye will receive the 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 to one or more lenses and / or prisms that direct light to the waveguide 104.

[0019] The above-mentioned image processing circuit and image generating device may include a memory and a processor (e.g., a microprocessor), the memory includes executable instructions, and the processor executes the instructions on the memory. The memory may correspond to any suitable type of memory device or a collection of memory devices configured to store instructions. Non-limiting examples of suitable memory devices that can be used include flash memory, random access memory (RAM), read-only memory (ROM), variants thereof, or combinations thereof, etc. In some embodiments, the memory and the processor may be integrated into a common device (e.g., a microprocessor may include an integrated memory). Additionally or alternatively, the image processing circuit may include hardware, such as an application-specific integrated circuit (ASIC). Other non-limiting examples of image processing circuits include integrated circuit (IC) chips, central processing units (CPUs), graphics processing units (GPUs), microprocessors, field programmable gate arrays (FPGAs), digital signal processors (DSPs), collections of logic gates or transistors, resistors, capacitors, inductors, or diodes, etc. Some or all of the image processing circuits may be provided on a printed circuit board (PCB) or a collection of PCBs. It will be appreciated that any suitable type of electronic component or collection of electronic components may be suitable for inclusion in the image processing circuit.

[0020] The waveguide 104 may include any suitable material for diffractive waveguide applications, such as glass, plastic, polymer, or other suitable organic or inorganic optical material. The waveguide 104 may be implemented in any suitable manner. For example, the waveguide 104 may include a core and one or more claddings, wherein the core and the claddings have different dielectric constants. In another example, the waveguide 104 may be implemented using silicon photonics.

[0021] As described herein, ICG 108 and / or OCG 110 may include photonic structures (e.g., protrusions and / or depressions) 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). Figure 1An example is shown in which both the ICG 108 and the OCG 110 are located on a single surface of the waveguide 104 in the figure (the bottom surface of the ICG 108 and the top surface of the OCG 110). However, the same or similar photonic structures may additionally or alternatively be located on opposite surfaces of the waveguide 104 (i.e., the top surface of the ICG 108 and the bottom surface of the OCG 110). The photonic structure of each of the ICG 108 and the OCG 110 may be formed according to a suitable method, such as nanoimprint lithography and / or inkjet printing. The photonic structure of each of the ICG 108 and the OCG 110 may be formed on a surface of the waveguide 104 (i.e., the photonic structure is not part of the waveguide 104, but is placed on the surface of the waveguide 104) and / or included as part of the surface of the waveguide 104. The photonic structure of each of the ICG 108 and the OCG 110 may take a suitable shape or form. For example, the photonic structure may include a one-dimensional structure (e.g., a linear structure), a two-dimensional structure (pillars, holes, and / or the like), a metasurface, and / or other suitable forms. Regardless, the specific design of the photonic structure of the ICG 108 and / or OCG 110 may be based on the desired optical properties of the output light of the display device 102. As described in more detail below, the OCG 110 may include a photonic structure arranged into a unit cell that is designed to improve the brightness and uniformity of the image output to the eye box 112.

[0022] Eyebox 112 may correspond to a volume of free space in which the eyes of user 116 receive a view of an image created by light output from OCG 110. The size and location of this volume may be selected based on the optical architecture, where the designer weighs a number of constraints, such as field of view (FOV), image quality, and product design.

[0023] Figure 2 A schematic diagram of a display device 102 and an example of a k-space design diagram of the display device 102 according to at least one example embodiment are shown. It can be understood from the k-space design diagram 200 that IN is the in-coupling vector of the ICG 108, while O1 and O2 are the extension and out-coupling unit vectors for the extension region of the waveguide and OCG 110, respectively. As described herein, the photonic structure of the OCG 110 can be divided into unit cells arranged at substantially the same pitch. The term "substantially" is used to explain the changes in values ​​(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, where the pitch is within the manufacturing tolerance. In some cases, the pitch is within other acceptable deviations relative to the standard pitch value (e.g., within + / - 5% of the standard pitch value).

[0024] Figure 3 and Figure 4Various details of OCG 110 are shown according to at least one example embodiment. More specifically, Figure 3 A k-space design 204 defining a unit cell 300 is shown, and Figure 4 1 shows an example structure of an OCG 110 including a plurality of unit cells 300. Figure 3 As shown, Λ' PC1 and Λ' PC2 Defined using raster vectors:

[0025]

[0026] Angle θ 1 and θ 2 From raster to vector and defined by the angle.

[0027] It can be understood that the unit cell 300 is formed by the intersection of two sets of parallel lines, thereby forming a parallelogram shape.

[0028] Figure 4 shows a design of an OCG 110 for spatially tuning the TIR light to accommodate deviations in the waveguide and relief toward the user's eye, and Figure 5 An example photonic structure 500 is shown for use in unit cell 300. Figure 4 As shown, OCG 110 is divided into a plurality of regions 302 , which may be referred to as photonic crystal units 302 . Figure 4 An example is shown in which regions 302 are set to be rectangular in shape and in a grid pattern on OCG 110. However, OCG 110 can be divided differently so that regions 302 have different sizes, different shapes, and / or are arranged in different patterns. In some cases, the size, shape, and pattern of regions 302 are selected to optimize image quality (e.g., brightness and uniformity) for the user. Obviously, regions 302 are virtual divisions used to map groups of unit cells 300 and do not necessarily exist as physical division lines on OCG 110.

[0029] like Figure 4 As further shown, each region 302 includes a plurality of unit cells 300. Figure 5 As shown, each unit cell 300 includes one or more photonic structures 500 . Figure 5Four example photonic structures 500a to 500d are shown. All unit cells 300 in a particular region 302 may have a photonic structure 500 set to the same shape, size, and orientation, wherein the shape, size, and orientation of the photonic structure 500 in a particular region 302 is selected to match the diffraction efficiency required for that particular region 302. Because different diffraction efficiencies are used in different regions 302, the shape, size, and / or orientation of the photonic structure 500 may vary between regions 302.

[0030] In other words, a plurality of unit cells 300 are arranged in groups on a base substrate of the OCG 110, such as on a portion of the waveguide 104. The OCG 110 is divided into regions 302. Each region 302 includes a group of unit cells 300, which contain photonic structures of substantially the same shape, size, and orientation. However, the shape, size, and / or orientation of the photonic structures may vary between groups of unit cells. For example, the unit cells of a 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. At the same time, the unit cells of a second group (in a different region 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, first size, and first shape of the first photonic structure is different from the second orientation, second size, and second shape of the second photonic structure.

[0031] Obviously, the present disclosure relates to the plan view of the structure (such as Figure 5-8 The size, shape, and orientation of the structure as viewed from the perspective of the view shown in FIG. 1A and FIG. 1B . The size of a photonic structure can 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 changes in the 3D profile. The size of a photonic structure can be measured by the amount of area (e.g., as a percentage) that the photonic structure occupies within a unit cell. The size of a unit cell can correspond to the two-dimensional surface area of ​​the unit cell.

[0032] The shape of a photonic structure can correspond to a two-dimensional shape when viewed in plan view, without regard to any changes in the 3D profile. Two photonic structures can be considered to have the same shape when each has the same dimensional ratio (i.e., the only difference between the two structures is the scale). Thus, two parallelograms of the same size (each occupying the same amount of area within the unit cell) with different ratios can be considered to have different shapes. Alternatively, two photonic structures of different sizes can be considered to have the same shape if the scale of the smaller-sized shape can be enlarged to produce a structure that matches the size of the larger-sized shape. For example, Figure 6Photonic structures 500c and 500e in FIG. 5 have different shapes and sizes (orientation is not a factor), while photonic structures 800a and 800b can be considered to have the same shape and the same size, but different orientations.

[0033] The shape of the unit cell may correspond to the two-dimensional shape of the unit cell as viewed from a plan view. At the same time, the orientation of the photonic structure may correspond to the position of the photonic structure in 2D space relative to a reference (the reference may correspond to the central axis of the unit cell) when viewed from a plan view. 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 central axis of the unit cell) when viewed from a plan view. Figure 1 In view of the above, it should be understood that the two photonic structures of the unit cells from different regions 302 may differ in one or more of shape, size and orientation.

[0034] like Figure 4 As shown, the unit cell 300 in the region 302 is arranged along a line having Λ PC1 and Λ PC2 The two non-parallel axes in the parallelogram geometry of the size repeat periodically. PC1 and Λ PC2 reflects the periodicity of the unit cell 300, and Λ PC1 and Λ PC2 The value of may depend on the operating wavelength, material properties, and / or design choices. In some examples, Λ PC1 and Λ PC2 Between 200 nm and 620 nm. In other examples, Λ PC1 and Λ PC2 Between 300nm and 550nm. In some cases, Λ PC1 and Λ PC2 The value of is equal to each other across the region 302 or the unit cells 300 in all regions 302. In other cases, Λ PC1 and Λ PC2 The value of is different. Figure 3 , the shape of the unit cell 300 is determined by the angle α PC Definition, α PC is the minimum angle of the parallelogram defining the unit cell 300. The angle α may be selected depending on the geometry of the desired field of view (FOV) represented in k-space. PC Angle α PC Between 30° and 90°, such as between 40° and 80° or between 50° and 65°. It is understood that the unit cells 300 in a particular region 302 have the same size, shape, and orientation. In some examples, the unit cells 300 have the same size, shape, and orientation for all regions 302. Figure 4 As shown, the central axis A (e.g., the longitudinal axis) of the unit cell 300 can be aligned with the light propagation direction in the waveguide 104 from the ICG 108. In some cases, however, the central axis A of the unit cell can be rotated by an angle (e.g., rotated by less than 90°) compared to the light propagation direction.

[0035] Figure 5 Four exemplary photon structures (also referred to as photon elements (PE)) 500a to 500d are shown. Each unit cell 300 includes a single photon structure 500 or multiple stacked photon structures 500. In other words, the unit cell 300 includes m photon structures, which can be stacked in n layers in a direction perpendicular to the light propagation direction (also referred to as the TIR direction or the light propagation direction in Figure 1 ). The photon structure 500 can be made of one or more materials having a refractive index between 1.2 and 2.6. The photon structure 500 can exhibit low absorption in the visible wavelength range and can include polymers, hybrid (organic / inorganic) resists, or inorganic films such as glass.

[0036] The present disclosure proposes a photon structure 500 capable of controlling the spatial diffraction efficiency in three dimensions, thereby improving image brightness and uniformity. The photon structures 500a to 500d follow the following set of rules or conditions: 1) The photon structure 500 has a shape derived from a parallelogram reference shape, and the photon structure 500 is a parallelepiped with a substantially constant thickness (height) between 1.0 nm and 500.0 nm or between 5.0 nm and 320.0 nm; 2) The parallelogram reference shape has lengths L1 and L2; 3) The area of the parallelogram reference shape is smaller than the area of the unit cell 300 such that the photon structure 500 fits within the unit cell 300; 4) The photon structure 500 can be trimmed in comparison with the parallelogram reference shape; 5) The trimming is applied to the main angle or the secondary angle of the photon structure 500 (where the main angle is defined as one of the angles of the photon structure 500a, and the secondary angle is defined as the angle generated by trimming the main angle as in the photon structure 500b); 6) The trimming can be applied once or multiple times as long as the Figure 5 table in is complied with; 7) The trimmed edges are parallel to the edges of the parallelogram reference shape; and 8) The lengths of the trimmed edges l1 and l2 are in the range of 0 < l1 < L1 and 0 < l2 < L2.

[0037] It will be appreciated that photonic structure 500a is uncropped and shows a parallelogram reference shape from which photonic structures 500b to 500d are derived. Therefore, photonic structure 500a may also be referred to as reference shape 500a. Photonic structure 500c shows a single crop (Crop1) of the primary angle of reference shape 500a. Photonic structure 500b shows a crop from 500c and an additional crop (Crop 2) to one of the secondary angles of the shape in 500c generated by the first crop (Crop1). At the same time, photonic structure 500d shows a crop from 500c and an additional crop (Crop 2) to the primary angle of reference shape 500a.

[0038] Reference shape 500a has two equal angles β. Angle β can 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 of unit cell 300 of photonic structure 500 are equal. PC Substantially the same, but may also be different. It can be understood from the photonic structures 500b and 500c that the cutout of the reference shape 500a may form an additional angle having an angle β within the remainder of the photonic structure.

[0039] The photonic structures shown in the figures are implemented using a pillar configuration, where the photonic structures protrude from the base substrate. However, the photonic structures may additionally or alternatively be implemented using a hole configuration, where the photonic structures are recessed into the base substrate (eg, composed of a resin).

[0040] Figure 6 The diffraction characteristics of two different photonic structures according to at least one example embodiment are shown. More specifically, Figure 6 Shows Figure 5 Diffraction characteristics of the photonic structure 500c and another photonic structure 500e, including a graph of the relationship between the reflection diffraction efficiency and the angle, the other photonic structure 500e including more cutouts than 500c. Figure 6 Further shown is the outline of the unit cell 300, which has the same parallelogram shape as the reference shape 500a. The shaded and non-shaded areas next to each unit cell 300 correspond to the photonic structure of the adjacent unit cell 300 (recall that the shape of the photonic structure 500 is repeated for all unit cells 300 in a particular area 302). The non-shaded area can correspond to a layer below the photonic structure 500, such as a base substrate that can include a portion of the waveguide 104 or correspond to a portion of the waveguide 104.

[0041] Figure 71 shows the diffraction characteristics of three different unit cells 300a to 300c, including a graph of the relationship between the reflective diffraction efficiency and the angle, each of which has a multi-layer photonic structure stacked on a base substrate. In particular, Figure 7 1 shows a plan view of a unit cell 300a to 300c having a multi-layer design, wherein a first photonic structure 500-1 is stacked on a base substrate 700 (eg, a waveguide 104), and a second photonic structure 500-2 is stacked on the first photonic structure 500-1. Figure 7 As shown in the cross-sectional view in FIG. 5 , it is assumed that the first photonic structure 500 - 1 exists below the second photonic structure 500 - 2 and completely overlaps with it. In other words, Figure 7 The region shown belonging to the second photonic structure 500-2 has the same shape and size as the region of the first photonic structure 500-1 below the second photonic structure 500-2. In some examples, however, the second photonic structure 500-2 can include an overhanging region without a corresponding photonic structure 500-1 below it. In this case, the space between the second photonic structure 500-2 and the base substrate can correspond to an air gap. Figure 6 Same, Figure 7 The shaded and non-shaded areas beside each of the unit cells 300 a to 300 c correspond to the adjacent unit cells 300 .

[0042] Unit cell 300a shows a multi-layer structure in which the first photonic structure 500-1 has a reference shape 500a and the second photonic structure 500-2 includes a small cutout at the tip of the reference shape 500a closest to the light input area of ​​the unit cell 300a (where the 100% arrow is located). Unit cell 300a shows a multi-layer structure in which the first photonic structure 500-1 has been cut according to the reference shape 500a to form a V-shape, and the second photonic structure 500-2 has been cut according to the reference shape 500a to form a smaller parallelogram at the partial stop of the V-shape. Meanwhile, unit cell 300c shows a multi-layer structure in which the first photonic structure 500-1 has been cut according to the reference shape 500a to form an even smaller parallelogram, and the second photonic structure has been cut according to the reference shape 500a to form an even smaller parallelogram on the first photonic structure 500-1.

[0043] 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. Figure 7It is further understood that the base substrate 700 is exposed in areas between the unit cells (see unit cell 300a) and in areas without photonic structures 500-1 and / or 500-2 (see unit cells 300b and 300c). In some cases, one or more layers of the photonic structure 500 are not considered to be located between the base substrate 700 and the first photonic structure 500-1. In this case, the absence of the photonic structure 500 exposes one of these layers. In addition, the multilayer photonic structure for the unit cell 300 may include the above-discussed and in Figure 7 More than two photonic structures 500a and 500b are shown in FIG. Each layer may be formed separately from the other layers.

[0044] Figure 8 Another example design of a photonic structure within a unit cell is shown. More specifically, Figure 8 A photonic structure 800 is shown having a parallelogram shape within a unit cell 804 having a Figure 3 The photonic structure 800 may have the same or similar shape, size, and orientation as the unit cell 300 in the region 302. As with the photonic structure 500, the photonic structure 800 may provide control over spatial diffraction efficiency in three dimensions, thereby improving image brightness and uniformity. The OCG 110 may include a plurality of unit cells 804 distributed over the region 302 in the same or similar manner as the unit cell 300. Each group of unit cells 804 in the region 302 may have a photonic structure 800 of the same shape, size, and orientation. As with the photonic structure 500, the photonic structure 800 may provide control over spatial diffraction efficiency in three dimensions, thereby improving image brightness and uniformity. The OCG 110 may include a plurality of unit cells 804 distributed over the region 302 in the same or similar manner as the unit cell 300. Each group of unit cells 804 in the region 302 may have the same shape, size, and orientation as the photonic structure 800. The photonic structure 800 within the unit cell 804 should comply with the following rules or conditions: 1) the photonic structure 800 is a parallelepiped, has a parallelogram shape (e.g., the same or similar to the reference shape 500a), and has a substantially constant thickness (height) between 1.0 nm and 500.0 nm or between 5.0 nm and 320.0 nm; 2) the two-dimensional area of ​​the photonic structure 800 defined by the parallelogram shape of the lengths L1 and L2 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 of the unit cell 804. PC In some cases, and as Figure 8 As shown, the photonic structure 800 is rotated by a selected angle relative to the unit cell 804. In contrast to the photonic structure 500, the photonic structure 800 is not necessarily cut from a reference shape.

[0045] Figure 8 Two example photonic structures 800a and 800b and their associated diffraction properties within various unit cells 804a and 804b are shown, including a graph of reflective diffraction efficiency versus angle. Photonic structure 800a includes a parallelogram shape with angle β different from angle α. PCand is rotated relative to unit cell 804a. Photonic structure 800b comprises the same parallelogram shape as 800a, except that photonic structure 800b is rotated 90° compared to 800a.

[0046] Although not explicitly shown, it should be understood that Figure 8 The non-shaded areas in may correspond to exposed base substrate (eg, base substrate 700 ) or other layers of the waveguide 104 , and the shaded areas adjacent to the unit cell 804 are the photonic structures 800 of the adjacent unit cell 804 .

[0047] Although not explicitly shown, it should be understood that the unit cell 804 may include a multi-layer structure having the same structure as described above with reference to Figure 7 The plurality of photonic structures 800 stacked on each other in the same or similar manner as described. Additionally or alternatively, the multilayer structure within the unit cell may include an uncropped but rotated parallelogram shape of the photonic structure 800 stacked above or below the cropped and unrotated photonic structure 500.

[0048] Fig. 9 A schematic diagram of a head mounted display (HMD) 1300 is shown according to at least one example embodiment.

[0049] The HMD 1300 may include a wearable frame 10 that supports elements of the HMD 1300, a hinge 11 located at an end 10A of the frame 10, an earplug 13 detachably mounted on the ear of the observer 40, a nose pad 14, and a wiring 15 connected to an external processing circuit (not shown) in which an image processing operation is performed, for example, based on an output from a camera 18. The HMD 1300 may further include an earphone 16, an earphone wiring 17, an image sensor or camera 18 mounted on a surface 10B of the frame 10 in a central portion 10C of the frame 10, a member 20 to which image generating devices 111A and 111B are mounted by, 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 is understood that the image generating devices 111A and 111B may each include an optical system for providing input light to the respective waveguide 104. The optical system of each image generating 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 the waveguide 104. Each waveguide 104 adopts the above reference Figures 1 to 8 The form of one or more waveguides 104 discussed above and receiving from one of the image generating devices 111A and 111B Figure 1The input light is shown in .

[0050] Here, it should be understood that the above details relate to one non-limiting example of the HMD 1300, and the HMD 1300 may include more or fewer elements than shown and described above.

[0051] Reference Figure 1-9 , it should be understood that example embodiments relate to an OCG 110 for a waveguide-based display 102. The OCG 110 may include a base substrate, such as the base substrate 700, which may be a portion of the waveguide 104 (i.e., waveguide material) and / or another suitable layer on the surface of the 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 unit cells 300 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 300 of the second group 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, first size, and first shape of the first photonic structure is different from the second orientation, second size, and second shape of the second photonic structure. In particular, the size, shape, and orientation of the photonic structure in each region are selected to provide the desired diffraction characteristics for a particular region 302 of the OCG 110.

[0052] In some examples, the first shape of the first photonic structure is a parallelogram shape, each unit cell in the first group has a parallelogram shape, and 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 300 (see Figure 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.

[0053] In some examples, such as Figure 5 and Figure 6 As shown, the first shape of the first photonic structure is based on a parallelogram reference shape and has a cropped area, wherein the cropped area includes one or more cropped portions, wherein a portion of the first photonic structure is missing compared to the parallelogram reference shape. As shown, one of the one or more cropped portions defines two intersecting sides of the first photonic structure, and each unit cell in the first group also has a parallelogram shape. The two intersecting sides can have the same length, which is shorter than the length of at least another side of the first photonic structure. As shown Figure 3 and Figure 5 As shown, the two angles of the parallelogram shape of each unit cell 300 are the same as the two angles of the first photonic structure.

[0054] 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 uncropped area of ​​the first photonic structure is at a second end of the parallelogram shape of each unit cell opposite to the first end (e.g., see Figure 5 ). For each unit cell 300 in the first group, the first end corresponds to a point where the first side and the second side of the unit cell 300 intersect, and the second end corresponds to a point where the third side and the fourth side of the unit cell intersect. In some cases, the direction from the first end to the second end corresponds to the direction of light propagation in the waveguide-based display 102. In at least one example, the cutout 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).

[0055] In some cases, each of the plurality of unit cells has the same size and the same shape. In addition, in each unit cell 300 of the first group, the thickness of the first photonic structure may be the same and constant, and in each unit cell 300 of the second group, the thickness of the second photonic structure may be the same and constant.

[0056] like Figure 7 As shown, the third photonic structure can be stacked on the first photonic structure (e.g., 500-2 is stacked on 500-1). In a plan view, the third photonic structure and the first photonic structure can have different numbers of sides. Figure 5-Figure 7 It is understood that the first photonic structure has at least six sides in a plan view and has at least three identical angles between 30° and 90°. Any details described above with reference to the first photonic structure may also be applied to the second photonic structure and any other photonic structure of the OCG 110. In addition, it is understood that the system may include a light source (111A / 111B) and a waveguide 104 including the above-described OCG 110.

[0057] Still refer to Figure 1-Figure 9Example embodiments relate to a waveguide including a base substrate (e.g., 700), an input coupling grating (ICG) 108 receiving light from a light source (e.g., 111A / 111B), and an output coupling grating (OCG) 110 outputting light. The OCG 110 may include a plurality of unit cells 300 arranged in groups at regular intervals (e.g., at regular pitches) on the base substrate. When viewed from a plan view, each of the unit cells 300 in at least one group of unit cells includes a first photonic structure having an even number of sides greater than six, each side of the first photonic structure being parallel to at least two other sides of the first photonic structure. Each of the unit cells 300 in at least one group of unit cells includes a second photonic structure stacked on the first photonic structure, the second photonic structure having a shape different from the first photonic structure. Each of the plurality of unit cells 300 may have a parallelogram shape.

[0058] Reference Figure 1-Figure 9 The described embodiments may be combined with each other in any suitable way.

[0059] Although the technology has been described in conjunction with a number of embodiments, it is apparent that many alternatives, modifications and variations are apparent to those skilled in the art. Therefore, it is intended to encompass all such alternatives, modifications, equivalents and variations within the spirit and scope of the present disclosure.

[0060] It should be understood that the inventive concept covers any embodiment combined with any other embodiment or embodiments, any one or more features disclosed herein, any one or more features substantially disclosed herein, any one or more features substantially disclosed herein combined with any one or more features substantially disclosed herein, any aspect or feature or embodiment combined with any one or more other aspects or features or embodiments, and the use of any one or more embodiments or features disclosed herein. It should be understood that any feature described herein may be claimed in combination with any other feature described herein, regardless of whether these features are from the same described embodiment.

[0061] Any processing device, control unit, processing unit, 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, which are configured to execute an instruction set stored in a memory.

[0062] The above discussion is presented for the purpose of illustration and description. The above content is not intended to limit the present disclosure to one or more forms disclosed herein. For example, in the above detailed description, in order to simplify the present disclosure, various features of the present disclosure are grouped together in one or more aspects, embodiments and / or configurations. The features of the aspects, embodiments and / or configurations of the present disclosure can be combined in alternative aspects, embodiments and / or configurations other than those discussed above. This method of the present disclosure should not be interpreted as reflecting the intention that the claims require more features than those explicitly cited in each claim. On the contrary, as reflected in the following claims, the inventive aspects are less than all the features of the above-mentioned single disclosed aspects, embodiments and / or configurations. Therefore, the following claims are hereby and incorporated into this detailed description, and each claim exists independently as an embodiment of the present disclosure.

[0063] In addition, although the description includes descriptions of one or more aspects, embodiments and / or configurations and certain variations and modifications, other variations, combinations and modifications are also within the scope of the present disclosure after understanding the present disclosure, for example, within the skill and knowledge of those skilled in the art. It is intended that the rights to include alternative aspects, embodiments and / or configurations, including alternative, interchangeable and / or equivalent structures, functions, ranges or steps as claimed, whether or not such alternative, interchangeable and / or equivalent structures, functions, ranges or steps are disclosed herein, without the need to disclose any patentable subject matter, are obtained to the extent permitted.

[0064] As used herein, the phrases "at least one," "one or more," "or," and "and / or" are open-ended expressions that are both conjunctions and transitional conjunctions 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" refers to A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together.

[0065] Various aspects of the disclosure are described herein with reference to drawings that may be schematic illustrations of idealized configurations.

[0066] Unless otherwise specified, 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 the present disclosure belongs. It will be further understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure.

[0067] 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 is further understood that when used in this specification, the terms "include", "contain" and / or "comprise" indicate the presence of stated features, integers, steps, operations, elements and / or components, but do not exclude 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 and all combinations of one or more of the associated listed items.

[0068] Example embodiments may be configured as follows: (1)

[0070] An output coupling grating (OCG) for a waveguide-based display comprising:

[0071] a base substrate; and

[0072] A plurality of unit cells are arranged in groups on a base substrate, wherein each of the unit cells of a 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 a 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. (2)

[0074] The OCG according to (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 so that the parallelogram shape of the first photonic structure is rotated relative to the parallelogram shape of each unit cell. (3)

[0076] 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)

[0078] An OCG according to one or more of (1) to (3), wherein the first shape of the first photonic structure is based on a parallelogram reference shape and has a cropping region, wherein the cropping region includes one or more cropping portions, wherein a portion of the first photonic structure is missing compared to the parallelogram reference shape. (5)

[0080] The OCG of one or more of (1) to (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)

[0082] The OCG according to one or more of (1) to (5), wherein the two intersecting sides have the same length, which is shorter than the length of at least another side of the first photonic structure. (7)

[0084] The OCG according to 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)

[0086] An OCG according to one or more of (1) to (7), wherein the cutting region of the first photonic structure is at a first end of the parallelogram shape of each unit cell, and wherein the non-cutting 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)

[0088] An OCG according to one or more of (1) to (8), 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 shape 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)

[0090] The OCG of one or more of (1) to (9), wherein the cut-out region exposes a layer below the first photonic structure. (11)

[0092] 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)

[0094] An OCG according to 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)

[0096] The OCG of one or more of (1) to (12), wherein the base substrate comprises a waveguide material. (14)

[0098] The OCG according to one or more of (1) to (13), further comprising:

[0099] A third photonic structure is stacked on the first photonic structure. (15)

[0101] The OCG according to one or more of (1) to (14), wherein in a plan view, the third photonic structure and the first photonic structure have different numbers of sides. (16)

[0103] The OCG according to one or more of (1) to (15), wherein in a plan view, the first photonic structure has at least six edges and at least three identical angles between 30° and 90°. (17)

[0105] A waveguide comprising:

[0106] base substrate;

[0107] an input coupling grating (ICG) that receives light from a light source; and

[0108] An output coupling grating (OCG) for outputting light, the OCG comprising:

[0109] A plurality of unit cells are arranged in groups at regular intervals on a base substrate, wherein each of the unit cells in at least one group of unit cells comprises a first photonic structure having an even number of sides greater than six when viewed from a plan view, wherein each side of the first photonic structure is parallel to at least two other sides of the first photonic structure. (18)

[0111] The waveguide according to (17), wherein each unit cell in the at least one group of unit cells comprises a second photonic structure stacked on the first photonic structure, and wherein the second photonic structure has a different shape from the first photonic structure. (19)

[0113] The waveguide according to one or more of (17) to (18), wherein each of the plurality of unit cells has a parallelogram shape. (20)

[0115] A system comprising:

[0116] Light source; and

[0117] A waveguide, the waveguide comprising:

[0118] an input coupling grating (ICG) receiving light from the light source; and

[0119] An output coupling grating (OCG) for outputting light, the OCG comprising:

[0120] a base substrate; and

[0121] 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.

Claims

1. An output coupling grating (OCG) for a waveguide-based display, comprising: base substrate; as well as 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; as well as 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; as well as 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.

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