Composite light guide for augmented reality

Abstract

Various examples related to composite light guides that can be used in augmented reality and other augmented display applications are provided. In one example, a composite light guide includes a support substrate including a surface and a light guide layer disposed on the surface of the support substrate. The light guide layer may have a density greater than a density of the support substrate. For example, the density of the light guide layer may be greater than twice the density of the support substrate. The thickness of the light guide layer may be about 25% or less of the thickness of the support substrate.

Description

[0001] This application claims the priority benefit of Dutch Patent Application No. 2035758, filed September 7, 2023, which claims the priority benefit of U.S. Provisional Application No. 63 / 533400, filed August 18, 2023, the contents of which are relied upon and incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present disclosure relates to devices for augmented reality. More specifically, the present disclosure relates to light guides having a composite structure for light coupling in augmented reality devices. BACKGROUND

[0003] Due to recent advances in light projection technology, head-mounted displays have improved in both usability and popularity. Head-mounted displays are now capable of presenting digital virtual images to a user. The virtual images, which can represent objects or other information, look like they exist in the environment around the user. This is typically achieved by projecting light directly from different positions of optical elements (e.g., lenses) to the user’s eyes. Head-mounted displays are also referred to as near-eye devices or near-eye devices. These terms refer to image-forming optical computing that is different from traditional electronic displays (e.g., monitor screens). For a user of a head-mounted display, this visual experience is often referred to as ‘virtual reality’ if the user is isolated from the surrounding environment while still being able to see the virtual images. The term ‘augmented reality’ generally describes a visual experience in which virtual images are presented to a user as an overlay to a real-world environment, thereby augmenting the visual information received by the user. Additionally, this experience is often referred to as ‘mixed reality’ when the visual experience allows the user to interact with virtual objects that appear to be integrated with the user’s real-world environment. BRIEF DESCRIPTION OF DRAWINGS

[0004] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed on clearly illustrating the principles of the present disclosure. Furthermore, in the drawings, like reference numerals designate corresponding parts throughout the several views.

[0005] Figures 1A-1D Examples of flat slab glass light guide optical devices according to various embodiments of the present disclosure are shown.

[0006] Figures 2A-2C Examples of the impact of refractive index on horizontal FOV at different values of R-factor according to various embodiments of the present disclosure are shown.

[0007] Figures 3A-3C Examples of the impact of refractive index on horizontal FOV at different entrance pupil width and light guide thickness dimensions according to various embodiments of the present disclosure are shown.

[0008] Figure 4 Examples of light guide thickness relative to entrance pupil width according to various embodiments of the present disclosure are shown.

[0009] Figure 5 Examples of composite light guide optical devices according to various embodiments of the present disclosure are shown. Detailed Implementation

[0010] This document discloses various examples relating to composite light guides that can be used in augmented reality (AR) and other augmented display applications. A detailed description of embodiments will now be made with reference to the accompanying drawings, in which the same reference numerals indicate the same portions throughout several views.

[0011] AR systems are used to add virtual objects to a real-world visual scene that a user is observing. Example types of AR systems are wearable and utilize eye-worn devices in the form of glasses, goggles, or helmets worn by the user, sometimes referred to as head-mounted display (HMD) systems. AR systems typically include an optical system configured to allow viewing of objects or scenes while simultaneously adding augmented objects to actual objects or directly to the scene being viewed.

[0012] The advantage of using optical guides is that they can provide a compact design that is particularly suitable for AR glasses. Figure 1A An example of a one-dimensional planar light guide pupil expander optical device 100 is shown. The optical device 100 includes a block-shaped glass light guide 103 defining a width... The light guide pupil input (or coupled) grating 106, and the grating defining the width The output (or coupled out) grating 109 of the light-exiting pupil, such as Figure 1B As shown in the figure, the expansion of the exit pupil is achieved by copying the entrance pupil onto the exit pupil, wherein the distance between each copied portion is... Figure 1B Zhongyou Other gratings, such as cross-coupled gratings and cross-output gratings, can also be used in light guides to extend the exit pupil in two dimensions. Gratings 106 and 109 can be positioned on the interface of light guide 103, formed on or within the surface of light guide 103, or located inside light guide 103. Grating types can include, for example, surface relief gratings (SRG), volume Bragg gratings (VBG), or other suitable grating types or combinations thereof. Light 112 can be provided by an image source optics 115, such as a liquid crystal on silicon (LCOS) display, microLED display, laser scanner, etc., combined with suitable optics 118, to be coupled into light guide 103. Light guide 103 can guide light 112 through total internal reflection (TIR) ​​between the interfaces of light guide 103. Light guide 103 has, for example, a total internal reflection (TIR) ​​between the interfaces of light guide 103. Figure 1B The refractive index shown and thickness and the material surrounding the light guide 103 has an index of refraction and is typically air. When light 112 is incident on the top and bottom glass-air interfaces of the light guide at an angle of incidence TIR occurs, such that:

[0013] (1)

[0014] where is the so-called critical angle, while is the diffraction angle and is related to the incident field angle by the well-known grating equation

[0015] (1a)

[0016] where is the wavelength of light, and is the diffraction grating pitch, as shown in Figure 1B After being coupled into the light guide 103 via the input grating 106, the light 112 propagates through the light guide 103, where at least a portion can be coupled out of the light guide 103 by the output grating 109.

[0017] The use of light guides can reduce the cost of AR glasses while improving image quality and field of view (FOV), enabling viable consumer use cases, improving energy efficiency and battery life, enabling less heat generation for practical use times, and enabling lower weight eyeglass form factors to promote social acceptance and long-term comfort. It is desirable to provide a system that provides a wide FOV and good image quality with small compact image source optics and light-weight single RGB (red-green-blue) light guide eyepieces that have high brightness and good overall energy efficiency and are geometrically rigid and mechanically reliable. However, it is challenging to achieve these attributes simultaneously at the optical system level.

[0018] Light guides currently in use tend to be standalone thick bulk light guides made of high index glass. While thick light guides provide improved mechanical reliability and can preserve image quality, this constraint impacts other desirable features. Ensuring that the light guide is thick enough to preserve a plan-parallel plate geometry to maintain image quality and ensure mechanical reliability limits other features. For example, thin light guides with high index of refraction can provide improved FOV and image quality. Small source optics with small exit pupils and low density light guides can also improve form factor and weight. High blue light transmission light guides can also improve energy efficiency and reduce battery size to further improve form factor and weight.

[0019] The number M of the replicated portion on the light guide pupil is important for improving FOV and image quality. The “replicated portion” corresponds to a point along the output grating 109, at which light from the light guide input grating is diffracted by the output grating 109 into the surrounding environment. Figure 1A M replicated portions at the output grating 109 are schematically depicted. Each replicated portion corresponds to the point where reflected light in the light guide interacts with the output grating 109. The high number M of replicated portions achieves a higher FOV and improved image quality. For thick light guides, a high refractive index is required ( This is achieved by reducing the internal diffraction angle in the optical guide 103. To achieve a high number M of replicated portions. This can be seen from the determination of the maximum and minimum replicated portions. The maximum number M of the entrance pupil replicated portions on the output raster 109. max Determined by the following formula:

[0020] (2)

[0021] This is and the shortest wavelength ( It occurs at ) such as Figure 1C As shown in the figure. This maximum value is based on the exit pupil width dimension ( ), optical refractive index ( ) and optical guide thickness ( The minimum number M of replicated portions on the output raster 109. min It is given by the following formula:

[0022] (3)

[0023] This is and longest wavelength ( It occurs at ) such as Figure 1D As shown in the figure. Considering the R-coefficient defined by T. Levola in his article "Diffractive Optics for Virtual Reality Displays" in the Journal of the SID 14(5), 467-475 (2006) ( A lower R value results in better exit pupil uniformity across the entire FOV, thus improving overall image quality. This can be related to the horizontal FOV (HFOV) and refractive index using the following formula:

[0024] ,and

[0025] (4)

[0026] in It is the maximum field angle limited by R. A higher refractive index ( ) can be used to increase a given The FOV, or can be used to achieve a lower FOV for a given FOV. This is to improve image quality. This FOV / image quality tradeoff is directly related to the number of replicates M on the output raster 109.

[0027] Figures 2A-2C The different values ​​of the R coefficient are shown. Using equation (4) above with values ​​of 3, 5 and 8 respectively, the refractive index ( The effect of ) on horizontal HFOV. The wavelength of all curves is , and . Figures 2A-2C The different traces shown represent optical guides that support different wavelengths of light. Traces labeled "R or G or B" correspond to those supporting λ, respectively. B , λ G and λ R Any one of the optical guides in the array. The trace labeled "B+G" corresponds to simultaneously supporting λ. B and λ G The optical guide. The trace marked "G+R" corresponds to simultaneously supporting λ. G and λ R The optical guide. The trace labeled R+B+G corresponds to simultaneously supporting λ. R , λ G and λ B The optical guide. It can be seen that, for a given R, increasing the refractive index increases the FOV, while for a given refractive index it decreases the FOV. Improving image quality will reduce the field of view (FOV). For example... Figure 2B The image shown ( An optical guide made of glass with a refractive index in the range of 2.0 to 2.2 will require three optical guides (one each for R, G, and B) to achieve a horizontal RGB FOV in the range of approximately 50 to approximately 65 degrees (see traces labeled "R or G or B"). At this time, light guides made of glass with refractive indices in the same range can enable a single RGB light guide to have an HFOV in the range of about 25 degrees to about 35 degrees (see traces labeled "R+G+B"). This is limited by the dispersion mapping from the field angle to the ray angle within the light guide associated with the grating equation (Equation (1a)). Glass with a refractive index ≥2.35 can achieve an HFOV ≥70 degrees with separate R, G, and B light guides.

[0028] Besides considering the R-coefficient, the light-guiding pupil should be in The light guide must be at least just filled by the replicated portion of the light-guided pupil (JF) to achieve satisfactory image quality at a given field of view (FOV). For a given number of replicates, a thicker light guide requires a larger exit pupil (JF). Larger source optics are required, and therefore a larger light-guiding pupil width is needed. In other words, the exact filling condition of the exit pupil needs to be met. and longest wavelength ( )Down This makes the maximum field angle just within the filling condition limit be

[0029] (5)

[0030] in This refers to the just-fill limit HFOV. From this requirement, it can be seen that for a given entrance pupil width, a decrease in the light guide thickness or an increase in the refractive index will cause an increase in the just-fill limit HFOV. To simultaneously satisfy the just-fill condition and provide the required R-coefficient, The thickness of the optical guide ( ), refractive index ( ) and entrance pupil width ( The following constraints apply:

[0031] or (6)

[0032] Therefore, for a given R and refractive index (and HFOV), the minimum entrance pupil width is proportional to the light guide thickness, or the maximum light guide thickness is proportional to the entrance pupil width.

[0033] Figures 3A-3C This shows the different entrance pupil widths ( (respectively = 2.0 mm, 2.75 mm and 3.5 mm) and different optical guide thicknesses ( At (0.125 mm, 0.25 mm, 0.5 mm and 1.0 mm), the refractive index ( The impact of HFOV. Figures 3A-3C All curves in the diagram are for single-wavelength optical guides, i.e. It can be seen that reducing the thickness of the optical guide ( The number of copies M is increased, as shown in equations (2) and (3) for a given exit pupil width D. ExP The given information indicates that more copies will achieve the desired result before the number of copies decreases below the minimum required to satisfy the just-fill condition. The larger the entrance pupil, the greater the effect of reducing the light guide thickness, because more replicates are needed to meet the exact fill condition of the exit pupil.

[0034] To realize the opportunity for miniaturization in developing smaller image source optics, a thinner light guide will be required to provide the required image quality for a given HFOV. The maximum allowed light guide thickness required to maintain image quality at a given HFOV is proportional to the light guide entrance pupil width of the light guide, ) which corresponds to the exit pupil width of the image source optics. As the image source optics become smaller, the image source optics exit pupil width decreases and the maximum light guide thickness that can maintain image quality decreases. Figure 4 The change in maximum light guide thickness ( ) relative to the light guide entrance pupil width ( ) is shown for different refractive indices ( ) and HFOVs for image quality corresponding to For example, a 0.5 mm thick light guide results in a minimum exit pupil width of the image source optics of about 2.5 mm to about 3.0 mm, depending on the HFOV, as shown in Figure 4 0.3 mm light guide thickness results in a minimum exit pupil width of the image source optics of about 1.5 mm to about 2.0 mm. A 0.2 mm light guide thickness results in a minimum exit pupil width of the image source optics of about 1.0 mm to about 1.25 mm. A 0.1 mm (or less) light guide thickness enables the smallest image source optics and corresponding exit pupil width and improves image quality by increasing the number of replicated sections for a given HFOV over the entrance pupil width range.

[0035] As discussed, the use of thick light guides ensures a plan-parallel plate geometry to maintain image quality and ensure mechanical reliability. For a given HFOV and image quality level defined by the R coefficient, this drives the need for higher refractive indices and larger source optics. This relationship is independent of the type of gratings 106 and 109 ( Figure 1A ) used (e.g., SRG (surface relief grating), VBG (volume Bragg grating), or a combination of both), the layout of the in-coupling, cross-coupling, and out-coupling gratings in the light guide 103 (FIG. 1), or the type of image source optics (e.g., LCOS, microLED, laser scanner, etc.). By prioritizing these needs, the tradeoffs that result therefrom can be managed to achieve the implementation required for a given application.

[0036] The use of thick light guides drives the need for higher refractive index materials with lower density and high blue light transmission. Because the refractive index ( ), internal transmission ( ), and density ( ) are interdependent for a given glass composition, these three cannot be optimized simultaneously. The density is given by:

[0037] (7)

[0038] in It is the molecular weight, and It is the molar volume; the simplified expression for the refractive index can be given by the following formula:

[0039] (8)

[0040] And internal transmittance ( ) and extinction coefficient ( The simplified expression for ) can be given by the following formula:

[0041] (9)

[0042] (10)

[0043] in It is the strength of the oscillator. It is the resonant wavelength of the oscillator. It is a broadening factor. and It is a constant composed of physical constants, and It is the thickness of the material. Equations (8) and (10) show that the refractive index and extinction coefficient are coupled through the oscillator strength, the oscillator resonant wavelength, and the molar volume. Therefore, increasing the refractive index by changing the glass composition to increase the oscillator strength will cause an increase in the extinction coefficient, and thus a decrease in the transmittance. Similarly, increasing the refractive index by changing the glass composition to decrease the molar volume will cause an increase in the extinction coefficient, and thus a decrease in the transmittance. There is also an indirect relationship between the oscillator strength and the average molecular weight. Generally, the higher the molecular weight, the higher the average molecular weight. Higher oscillator strength can be achieved through larger ionic radii and / or a higher number of available valence electrons. Therefore, current glass-based AR systems are constrained by the material properties and physical dimensions of the light guide itself, which may hinder the simultaneous achievement of the desired HFOV and image quality, form factor and weight, and mechanical properties required for practical applications in augmented reality. Therefore, a novel solution must be considered to overcome these constraints.

[0044] A composite light guide is proposed that allows for greater freedom in separating otherwise interdependent light guide properties. While the refractive index and extinction coefficient of the light guide are inherently coupled and cannot be separated, the density of the light guide is coupled to the refractive index and extinction coefficient only through molar volume, a property that can be separated at the component level. In other words, the thickness required to guide the light can be separated from the thickness required to maintain the planar parallel geometry, enabling high image quality to be achieved with more compact image source optics without compromising the mechanical reliability of the light guide.

[0045] The separation of the thickness required for guiding light and the thickness required for mechanical reliability can be achieved with a composite light guide that includes a thin glass light guide disposed on the surface of a thicker support substrate. The thin glass light guide can be formed of a material with high density and high refractive index, and the thicker support substrate can be formed of a material with low density. This enables the separation of light guide properties from support substrate properties, and enables independent control of the material properties required for guiding light and the material properties required for mechanical reliability. High image quality and HFOV can be achieved by optimizing the refractive index and other properties of the light guide without regard to mechanical stability. Thinner light guides that are compatible with smaller source optics, for example, can be used regardless of density, while mechanical reliability can be provided by the support substrate. The support substrate can be selected to have low density. Since the thickness of the composite light guide is determined by the thickness of the support substrate, the overall density of the composite light guide can be low, enabling a lightweight assembly for an augmented reality system.

[0046] Figure 5 An example of a composite light guide optical device 500 is shown. The composite light guide 500 includes a thin light guide layer 503 disposed on a support substrate 506. The light guide layer 503 can include input (or in-coupling) gratings 106 and output (or out-coupling) gratings 109 positioned on the interface of the light guide layer 503, or can be formed in or integrated into the surface of the light guide layer 503 (e.g., by forming grooves in the surface), or can be located inside the light guide layer 503, or can be formed at the interface between the light guide and the support interface 509. The grating type can include, for example, a surface relief grating (SRG), a volume Bragg grating (VBG), or other suitable grating type or combination of grating types including a metasurface. Light 112 can be provided by an image source optic 115, such as a liquid crystal on silicon (LCOS), microLED, laser scanner, etc., to be coupled into the light guide 103.

[0047] The light guide layer 503 can include a thin layer of glass with a high refractive index n d and high blue light transmission (e.g., 80% or more at a wavelength of 440 nm). The glass can be a high-entropy glass, such as a La2O3-Nb2O5glass or other suitable glass or optical material. The glass with high refractive index includes a significant proportion of components that are capable of increasing the refractive index. Examples of high refractive index glass components include La2O3, TiO2, Nb2O5, WO3, and Bi2O3. The glass with high refractive index includes silicates, borosilicates, tungsten borates, and phosphates that include one or more high refractive index glass components.

[0048] In an embodiment, the glass of the light guide layer may include 10.0 mol% to 40.0 mol% of B2O3, greater than or equal to 0 mol% to 40.0 mol% of WO3, greater than or equal to 0 mol% to 30.0 mol% of Nb2O5, greater than or equal to 0 mol% to 30.0 mol% of TiO2, greater than or equal to 0 mol% to 25.0 mol% of La2O3, and greater than or equal to 0 mol% to 15.0 mol% of ZrO2.

[0049] In embodiments, the glass of the light guide may further comprise greater than or equal to 0 mol% to 20.0 mol% of Bi₂O₃, greater than or equal to 0 mol% to 15.0 mol% of TeO₂, greater than or equal to 0 mol% to 10.0 mol% of PbO, greater than or equal to 0 mol% to 10.0 mol% of GeO₂, 0 mol% to 10.0 mol% of P₂O₅, greater than or equal to 0 mol% to 6.0 mol% of Y₂O₃, greater than or equal to 0 mol% to 5.0 mol% of V₂O₅, greater than or equal to 0 mol% to 10.0 mol% of silicon dioxide (SiO₂), or combinations thereof.

[0050] In an embodiment, the glass of the light guide layer may include WO3, Bi2O3 or both at a concentration of 0.1 mol% or higher.

[0051] In an embodiment, the glass of the light guide layer may include an amount of La2O3 in the range of 5.0 mol%, or greater than 10.0 mol%, or greater than 15.0 mol%, or greater than 20.0 mol%, or greater than 25.0 mol%, or greater than 30.0 mol%, or in the range of 5.0 mol% to 40.0 mol%, or in the range of 10.0 mol% to about 35.0 mol%, or in the range of 15.0 mol% to 30.0 mol%.

[0052] In an embodiment, the glass of the light guide layer may include an amount of B2O3 in the range of 5.0 mol%, or greater than 10.0 mol%, or greater than 15.0 mol%, or greater than 20.0 mol%, or greater than 25.0 mol%, or greater than 30.0 mol%, or in the range of 5.0 mol% to 40.0 mol%, or in the range of 10.0 mol% to 35.0 mol%, or in the range of 15.0 mol% to 30.0 mol%.

[0053] In an embodiment, the glass of the light guide layer may include an amount of WO3 in the range of 5.0 mol%, or greater than 10.0 mol%, or greater than 15.0 mol%, or greater than 20.0 mol%, or greater than 25.0 mol%, or greater than 30.0 mol%, or in the range of 5.0 mol% to 40.0 mol%, or in the range of about 10.0 mol% to 35.0 mol%, or in the range of 15.0 mol% to 30.0 mol%.

[0054] In an embodiment, the glass of the light guide layer may include an amount of Nb2O5 in the range of 5.0 mol%, or greater than 10.0 mol%, or greater than about 15.0 mol%, or greater than 20.0 mol%, or greater than 25.0 mol%, or greater than 30.0 mol%, or in the range of 5.0 mol% to 50.0 mol%, or in the range of 10.0 mol% to 40.0 mol%, or in the range of 15.0 mol% to 30.0 mol%.

[0055] In an embodiment, the glass of the light guide layer may include an amount of TiO2 in the range of 5.0 mol%, or greater than 10.0 mol%, or greater than 15.0 mol%, or greater than 20.0 mol%, or greater than 25.0 mol%, or greater than 30.0 mol%, or in the range of 5.0 mol% to 40.0 mol%, or in the range of 10.0 mol% to 35.0 mol%, or in the range of 15.0 mol% to 30.0 mol%.

[0056] In an embodiment, the glass of the light guide layer may include an amount of ZrO2 in the range of 2.0 mol%, or greater than 4.0 mol%, or greater than 6.0 mol%, or greater than 8.0 mol%, or greater than 10.0 mol%, or greater than 12.0 mol%, or in the range of 2.0 mol% to 15.0 mol%, or in the range of 4.0 mol% to 12.0 mol%, or in the range of 6.0 mol% to 10.0 mol%.

[0057] In an embodiment, the glass of the light guide layer may include an amount of P2O5 in the range of 5.0 mol%, or greater than 10.0 mol%, or greater than about 15.0 mol%, or greater than 20.0 mol%, or greater than 25.0 mol%, or greater than 30.0 mol%, or in the range of 5.0 mol% to 40.0 mol%, or in the range of 10.0 mol% to 35.0 mol%, or in the range of 15.0 mol% to 30.0 mol%.

[0058] The glass of the light guide layer may also contain materials selected from rare earth metal oxides (Re). m O n Al2O3, BaO, CaO, K2O, Li2O, MgO, Na2O, SrO, Ta2O5, ZnO, and one or more combinations thereof.

[0059] Table 1 shows the representative composition of the glass in the optical guide layer. In Table 1, d RT This refers to the density of glass at room temperature, and n d It is the refractive index at 587.5 nm. Glass is prepared by combining glass components in the desired proportions, melting them in a crucible, and cooling them using methods well known in the art.

[0060] Table 1. Exemplary Glass Composition

[0061]

[0062] The refractive index n of the optical guide layer d Greater than 1.60, or greater than 1.70, or greater than 1.80, or greater than 1.90, or greater than 2.00, or greater than 2.10, or greater than 2.20, or in the range of 1.60 to 2.40, or in the range of 1.70 to 2.20, or in the range of 1.80 to 2.10, or in the range of 1.90 to 2.00.

[0063] The density of the optical guide layer is greater than 3.0 g / cm³. 3 or greater than 3.5 g / cm 3 or greater than 4.0 g / cm 3 or greater than 4.5 g / cm 3 or greater than 5.0 g / cm 3 or greater than 5.5 g / cm 3 Or at 3.0 g / cm 3 Up to 6.0 g / cm 3 Within the range, or at 3.5 g / cm 3 Up to 5.5 g / cm 3 Within the range, or at 4.0 g / cm 3 Up to 5.0 g / cm 3 Within the range.

[0064] The thickness of the light guide layer is less than 0.50 mm, or less than 0.40 mm, or less than 0.30 mm, or less than 0.20 mm, or less than 0.10 mm, or in the range of 0.05 mm to 0.50 mm, or in the range of 0.10 mm to 0.45 mm, or in the range of 0.15 mm to 0.40 mm, or in the range of 0.20 mm to 0.35 mm.

[0065] The support substrate 506 may comprise a low-density material (e.g., about 2.5 g / cm³) having a low refractive index (e.g., about 1.60 or less). 3 (or smaller). Low-density materials may include, for example, glass or other suitable materials such as polymers or plastics. Representative glasses used to support the substrate 506 include fused silica, soda-lime glass, alkali metal or alkaline earth metal silica glass, Gorilla glass, etc. ® Glass (available from Corning) and borosilicates. Representative polymers include polyacrylates, polyimides, polyamides, polycarbonates, polyethylene, and cyclic olefins.

[0066] The combination of the glass light guide layer 503 and the support substrate 506 can provide the combination of properties required for AR applications without the limitations imposed by using a bulk glass light guide 103 alone. The light guide layer 503 can provide a high refractive index and a thin light guide, which contributes to a wider HFOV and improved image quality, while also providing high blue light transmittance. It can be seen that reducing the light guide thickness ( This increases the number of replicates M. The thin light guide layer 503 also allows for the use of smaller source optics 115 with a small exit pupil.

[0067] The support substrate 506 provides a low-density assembly with a thickness that ensures the maintenance of the geometry and mechanical reliability of the composite light guide. The support substrate 506 can set the macroscopic properties of the assembly, such as geometric and mechanical properties, weight, and bulk optics for real-world lighting. The cost of the glass light guide layer 503 can also be offset by using cheaper materials for the support substrate.

[0068] The refractive index n of the supporting substrate d Less than 1.60, or less than 1.55, or less than 1.50, or less than 1.45, or in the range of 1.40 to 1.60, or in the range of 1.45 to 1.55.

[0069] The density of the support substrate 506 is less than 3.0 g / cm³. 3 or less than 2.8 g / cm³ 3 or less than 2.6 g / cm³ 3 or less than 2.4 g / cm 3 or less than 2.2 g / cm3 or less than 2.0 g / cm 3 Or at 1.8 g / cm 3 Up to 3.0 g / cm 3 Within the range, or at 2.0 g / cm 3 Up to 2.9 g / cm 3 Within the range, or at 2.1 g / cm 3 Up to 2.8 g / cm 3 Within the range, or at 2.2 g / cm 3 Up to 2.7 g / cm 3 Within the range, or at 2.3 g / cm 3 Up to 2.6 g / cm 3 Within the range.

[0070] The thickness of the support substrate 506 is greater than 0.20 mm, or greater than 0.30 mm, or greater than 0.40 mm, or greater than 0.50 mm, or in the range of 0.20 mm to 1.0 mm, or in the range of 0.25 mm to 0.90 mm, or in the range of 0.30 mm to 0.80 mm, or in the range of 0.35 mm to 0.70 mm, or in the range of 0.40 mm to 0.60 mm.

[0071] In one example of the composite light guide 500, the light guide layer 503 comprises La2O3-Nb2O5 glass, and the support substrate 506 comprises Gorilla glass. ® Glass 3. The following references provide selected refractive index and density data for the La2O3-Nb2O5 glass system: A. Masuno, H. Inoue, K. Yoshimoto and Y. Watanabe, “Thermal and optical properties of La2O3-Nb2O5 high refractive index glasses”, Optical Materials Express 4(4), 710-718 (2014). The properties of the photoconductive layer can be set by adjusting the stoichiometry of (1-x)La2O3-xNb2O5 glass. For x=0.6, the refractive index ( The value is 2.175, and the density is ( The concentration was 5.8 g / cm³. 3 La2O3-Nb2O5 glass also offers high blue light transmittance. The properties of the glass support substrate include a refractive index of 1.5 (…). ) and 2.4 g / cm 3The density. Consider a 5 cm × 5 cm composite substrate sample with a support substrate thickness of 0.5 mm and a photoconductor layer thickness of 0.1 mm. The weight of the photoconductor layer 503 is (0.01 cm)(5 cm). 2 × 5.8 g / cm 3 = 1.45 g is given, and the weight of the supporting substrate 506 is (0.05 cm)(5 cm). 2 × 2.4 g / cm 3 = 3.0 g given, total weight 4.45 g. Sample volume is (0.06 cm²)(5 cm²). 2 In this case, the effective density becomes It is significantly smaller than that of (La2O3). 0.4 (Nb2O5) 0.6 The density of the fabricated bulk glass optical guide. Therefore, the composite optical guide 500 still provides a high refractive index ( It has high blue light transmittance while providing significantly reduced density.

[0072] In a second example of the composite light guide 500, the light guide layer 503 includes the exemplary glass 8 of Table 1, and the support substrate 506 includes Gorilla Glass 8. ® Glass 3. Refractive index of exemplary glass 8 ( The value is 2.013, and the density is ( The value was 5.162 g / cm³. 3 Exemplary glass 8 also provides high blue light transmittance. The properties of the glass support substrate include a refractive index of 1.5 (…). ) and 2.4 g / cm 3 The density was determined. A 5 cm × 5 cm composite substrate sample with a support substrate thickness of 0.5 mm and an optical guide layer thickness of 0.1 mm was prepared. The weight of the optical guide layer 503 was determined by (0.01 cm)(5 cm). 2 × 5.162 g / cm 3 = 1.29 g is given, and the weight of the supporting substrate 506 is (0.05 cm)(5 cm). 2 × 2.4 g / cm 3 = 3.0 g given, total weight 4.29 g. Sample volume (0.06 cm²)(5 cm²) 2 In this case, the effective density becomes Its density is significantly lower than that of a block glass optical guide made of exemplary glass 8. Therefore, the composite optical guide 500 still provides a high refractive index ( It exhibits high blue light transmittance (>96% / mm at 460 nm) while providing significantly reduced density. A surface-embossed grating is formed within the layers of exemplary glass 8 to provide both input and output gratings. The waveguide is tested by guiding red, green, and blue light to the input grating. For each color of light, transmission and diffraction of the output grating are demonstrated.

[0073] The thickness of the composite light guide 500 is less than 1.00 mm, or less than 0.90 mm, or less than 0.80 mm, or less than 0.70 mm, or less than 0.60 mm, or less than 0.50 mm, or less than 0.40 mm, or less than 0.30 mm, or in the range of 0.30 mm to 1.00 mm, or in the range of 0.35 mm to 0.90 mm, or in the range of 0.40 mm to 0.85 mm, or in the range of 0.45 mm to 0.70 mm.

[0074] The ratio of the thickness of the light guide layer to the thickness of the supporting substrate is less than 0.70, or less than 0.60, or less than 0.50, or less than 0.40, or less than 0.30, or less than 0.20, or less than 0.10, or in the range of 0.10 to 0.70, or in the range of 0.15 to 0.60, or in the range of 0.20 to 0.55, or in the range of 0.25 to 0.50, or in the range of 0.30 to 0.45.

[0075] The density of the composite optical guide 500 is less than 4.0 g / cm³. 3 or less than 3.8 g / cm³ 3 or less than 3.6 g / cm³ 3 or less than 3.4 g / cm 3 or less than 3.2 g / cm 3 or less than 3.0 g / cm 3 or less than 2.8 g / cm 3 or less than 2.6 g / cm³ 3 or less than 2.4 g / cm 3 or less than 2.2 g / cm 3 Or at 1.8 g / cm 3 Up to 4.0 g / cm 3 Within the range, or at 2.0 g / cm 3 Up to 3.8 g / cm 3 Within the range, or at 2.2 g / cm 3 Up to 3.6 g / cm 3 Within the range, or at 2.4 g / cm 3 Up to 3.4 g / cm 3 Within the range, or at 2.6 g / cm3 Up to 3.2 g / cm 3 Within the range, or at 2.7 g / cm 3 Up to 3.1 g / cm 3 Within the range.

[0076] The ratio of the density of the light guide layer to the density of the supporting substrate is greater than 1.40, or greater than 1.50, or greater than 1.60, or greater than 1.70, or greater than 1.80, or greater than 1.90, or greater than 2.00, or greater than 2.10, or in the range of 1.40 to 2.30, or in the range of 1.40 to 2.20, or in the range of 1.40 to 2.00, or in the range of 1.50 to 1.90, or in the range of 1.60 to 1.80.

[0077] The ratio of the density of the composite optical guide to the density of the optical guide layer is less than 0.80, or less than 0.70, or less than 0.60, or less than 0.50, or less than 0.40, or less than 0.30, or in the range of 0.20 to 0.80, or in the range of 0.25 to 0.75, or in the range of 0.30 to 0.70, or in the range of 0.35 to 0.65, or in the range of 0.40 to 0.60.

[0078] In addition to a single-material light guide layer 503, in some embodiments, the light guide layer 503 may include combinations of materials to provide a variety of refractive index distributions. For example, the light guide layer 503 may have, for instance, a graded refractive index distribution, a recessed cladding graded refractive index distribution, a stepped refractive index distribution, a double-cladding stepped refractive index distribution, a recessed cladding stepped refractive index distribution, a double-recessed cladding stepped refractive index distribution, an Anderson index distribution, or a recessed cladding Anderson refractive index distribution, or other suitable refractive index distributions. A composite light guide can be formed by separately manufacturing a support substrate and a light guide layer, and then bonding them together using known adhesives, optical, thermal, or other bonding processes. The support substrate and light guide layer are produced using known methods for manufacturing and finishing sheet materials such as glass and polymers. Another method for forming a composite light guide includes forming the light guide layer directly on the support substrate. In this case, a support substrate is formed using known methods for manufacturing and finishing sheet materials, and a light guide layer is formed directly on the formed substrate using methods such as sol-gel, vapor deposition, deposition, and sintering, followed by finishing if necessary. The method for manufacturing composite light guides described herein is intended to be exemplary in nature; other methods for preparing composite light guides are also possible.

[0079] refer to Figures 1A to 5In light of the foregoing discussion, the following is a description of various embodiments of this disclosure. It should be understood that the following embodiments are not an exhaustive description of possible embodiments of this disclosure, and other embodiments are described herein.

[0080] Aspect 1 is a composite light guide. The composite light guide includes a supporting substrate and a light guide layer disposed on a surface of the supporting substrate, the supporting substrate including a surface, such as a flat surface or a curved surface. The light guide layer includes an input grating and an output grating. The light guide layer has a refractive index n greater than 1.60. d The ratio of the density of the light guide layer to the density of the supporting substrate is greater than 1.40, and the ratio of the thickness of the light guide layer to the thickness of the supporting substrate is less than 0.50.

[0081] Aspect 2 is a composite light guide of aspect 1, wherein the ratio of the density of the light guide layer to the density of the supporting substrate is greater than 1.70.

[0082] Aspect 3 is a composite optical guide of aspect 1, wherein the ratio of the density of the composite optical guide to the density of the optical guide layer is less than 0.80.

[0083] Aspect 4 is a composite optical guide of aspect 3, wherein the ratio of the density of the composite optical guide to the density of the optical guide layer is less than 0.60.

[0084] Aspect 5 is a composite optical guide of aspect 4, wherein the ratio of the density of the composite optical guide to the density of the optical guide layer is less than 0.40.

[0085] Aspect 6 is a composite optical guide of aspect 1, wherein the density of the optical guide layer is greater than 3.5 g / cm³. 3 .

[0086] Aspect 7 is a composite optical guide of aspect 6, wherein the density of the optical guide layer is greater than 4.0 g / cm³. 3 .

[0087] Aspect 8 is a composite optical guide of aspect 7, wherein the density of the optical guide layer is greater than 5.0 g / cm³. 3 .

[0088] Aspect 9 is a composite optical guide of aspect 1, wherein the density of the supporting substrate is less than 3.0 g / cm³. 3 .

[0089] Aspect 10 is a composite optical guide of aspect 9, wherein the density of the supporting substrate is less than 2.6 g / cm³. 3 .

[0090] Aspect 11 is a composite light guide of aspect 1, wherein the ratio of the thickness of the light guide layer to the thickness of the supporting substrate is less than 0.30.

[0091] Aspect 12 is a composite light guide of aspect 1, wherein the thickness of the light guide layer is less than 0.20 mm.

[0092] Aspect 13 is a composite light guide of aspect 12, wherein the thickness of the light guide layer is less than 0.10 mm.

[0093] Aspect 14 is a composite light guide of aspect 13, wherein the thickness of the supporting substrate is greater than 0.30 mm.

[0094] Aspect 15 is a composite optical guide of aspect 14, wherein the thickness of the supporting substrate is greater than 0.50 mm.

[0095] Aspect 16 is a composite optical guide of aspect 1, wherein the optical guide layer has a refractive index n greater than 1.8. d .

[0096] Aspect 17 is a composite optical guide of aspect 16, wherein the optical guide layer has a refractive index n greater than 2.0. d .

[0097] Aspect 18 is a composite optical guide of aspect 1, wherein the supporting substrate has a refractive index n of less than 1.50. d .

[0098] Aspect 19 is a composite light guide of aspect 1, wherein the light guide layer comprises glass, and the glass comprises one or more of TiO2, Nb2O5, WO3, La2O3 and Bi2O3.

[0099] Aspect 20 is a composite optical guide of aspect 19, wherein the glass further includes P2O5.

[0100] Aspect 21 is a composite optical guide of aspect 1, wherein the refractive index n of the optical guide layer is... d The composite optical guide has a g / cm² value greater than 1.80 and a g / cm² value less than 4.0 g / cm². 3 The density.

[0101] Aspect 22 is a composite optical guide of aspect 21, wherein the composite optical guide has a density of less than 3.6 g / cm. 3 The density.

[0102] Unless otherwise explicitly stated, disjunctive language such as the phrase “at least one of X, Y, or Z” is understood in the context to generally indicate that an item, term, etc., can be X, Y, or Z or any combination thereof (e.g., X, Y, and / or Z). Therefore, such disjunctive language is generally not intended and should not imply that certain embodiments require the presence of at least one of X, at least one of Y, or at least one of Z.

[0103] It should be emphasized that the above embodiments of this disclosure are merely possible examples of implementations set forth for the purpose of clearly understanding the principles of this disclosure. Many variations and modifications can be made to the above embodiments without substantially departing from the spirit and principles of this disclosure. All such modifications and variations are intended to be included within the scope of this disclosure and protected by the appended claims.

[0104] The term "substantially" refers to a deviation in descriptive terminology that does not negatively impact the intended purpose. Descriptive terms are implicitly understood to be modified by the word "substantially," even if the term is not explicitly modified by the word "substantially."

[0105] It should be understood that ratios, concentrations, amounts, and other numerical data may be expressed in range format herein. It should be understood that such range format is used only for convenience and brevity, and therefore should be interpreted flexibly as including not only the numerical values ​​explicitly stated as the limits of the range, but also all individual numerical values ​​or subranges covered within said range, as if each numerical value and subrange were explicitly stated. For example, the concentration range “about 0.1% to about 5%” should be interpreted as including not only the explicitly listed concentrations of about 0.1 wt% to about 5 wt%, but also the individual concentrations (e.g., 1%, 2%, 3%, and 4%) and subranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. The term “about” may include conventional rounding based on the significant figures of the numerical value. Furthermore, the phrase “about 'x' to 'y'” includes “about 'x' to about 'y'”.

Claims

1. A composite optical guide, comprising: Support substrate, including a surface; and A light guide layer is disposed on the surface of the supporting substrate, the light guide layer including an input grating and an output grating, and the light guide layer having a refractive index n greater than 1.

60. d ; The ratio of the density of the light guide layer to the density of the supporting substrate is greater than 1.40, and the ratio of the thickness of the light guide layer to the thickness of the supporting substrate is less than 0.

50.

2. The composite light guide according to claim 1, wherein the ratio of the density of the light guide layer to the density of the supporting substrate is greater than 1.

70.

3. The composite optical guide according to claim 1 or 2, wherein the ratio of the density of the composite optical guide to the density of the optical guide layer is less than 0.

80.

4. The composite optical guide according to claim 3, wherein the ratio of the density of the composite optical guide to the density of the optical guide layer is less than 0.

60.

5. The composite optical guide according to any one of claims 1 to 4, wherein the density of the optical guide layer is greater than 3.5 g / cm³. 3 .

6. The composite optical guide according to claim 5, wherein the density of the optical guide layer is greater than 5.0 g / cm³. 3 .

7. The composite optical guide according to any one of claims 1 to 6, wherein the density of the supporting substrate is less than 3.0 g / cm³. 3 .

8. The composite optical guide according to claim 7, wherein the density of the supporting substrate is less than 2.6 g / cm³. 3 .

9. The composite light guide according to any one of claims 1 to 8, wherein the ratio of the thickness of the light guide layer to the thickness of the supporting substrate is less than 0.

30.

10. The composite light guide according to any one of claims 1 to 9, wherein the thickness of the light guide layer is less than 0.20 mm.

11. The composite light guide according to claim 10, wherein the thickness of the light guide layer is less than 0.10 mm.

12. The composite light guide according to claim 11, wherein the thickness of the supporting substrate is greater than 0.30 mm.

13. The composite light guide according to claim 12, wherein the thickness of the supporting substrate is greater than 0.50 mm.

14. The composite optical guide according to any one of claims 1 to 13, wherein the optical guide layer has a refractive index n greater than 1.

8. d .

15. The composite optical guide according to claim 14, wherein the optical guide layer has a refractive index n greater than 2.

0. d .

16. The composite optical guide according to any one of claims 1 to 15, wherein the supporting substrate has a refractive index n of less than 1.

50. d .

17. The composite light guide according to any one of claims 1 to 16, wherein the light guide layer comprises glass, and the glass comprises one or more of TiO2, Nb2O5, WO3, La2O3 and Bi2O3.

18. The composite optical guide according to claim 17, wherein the glass further comprises P2O5.

19. The composite optical guide according to any one of claims 1 to 18, wherein the refractive index n of the optical guide layer is... d The value is greater than 1.80, and the composite optical guide has a value of less than 4.0 g / cm. 3 The density.

20. The composite optical guide according to claim 19, wherein the composite optical guide has a content of less than 3.6 g / cm³. 3 The density.

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