Anti-reflective coatings used in waveguide optical systems and their formation methods

Abstract

An antireflective coating includes a plurality of first layers, each comprising a first material having a relatively high refractive index; and a plurality of second layers, each comprising a second material having a relatively low refractive index. The total thickness of the first layers, composed of the first material, is about 120 nm or less. Furthermore, when light propagates under total internal reflection, the antireflective coating is configured to absorb about 0.25% or less of the light at each wavelength between about 425 nm and about 495 nm to achieve single reflection of the average of the s-polarization and p-polarization of the light.

Description

Technical Field

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 016,406, filed April 28, 2020, the contents of which are incorporated herein by reference in their entirety.

[0002] This invention relates to antireflective coatings, articles comprising antireflective coatings, and methods for forming the same. Specifically, this invention relates to antireflective coatings for use in optical lenses and glass to reduce reflection. Background Art

[0003] Glass covers are commonly used in electronic products to protect critical components and provide a platform for user interfaces and / or displays. These products include augmented and virtual reality devices, mobile devices, night vision systems, and medical imaging devices. Other applications of glass covers include eyeglasses, camera lenses, and laser glass. The performance of these products depends on the optical components used in the design of the glass cover. For example, the glass cover must have sufficient transmittance while minimizing unwanted light reflection. Additionally, some applications require that the color and / or brightness perceived by the user through the glass cover not change significantly with the user's viewing angle. If the user can detect changes in color and / or brightness from different viewing angles, the user may experience a degraded display quality.

[0004] Glass cover products traditionally consist of a substrate and a coating. The substrate is typically formed from a material with high reflectivity, and the coating is usually a series of one or more layers applied to the substrate. For augmented and virtual reality devices, the substrate is an optical waveguide. Summary of the Invention

[0005] The anti-reflective coatings disclosed herein are designed to have low reflectivity and reduce glare, making them highly advantageous in the aforementioned applications. For example, the anti-reflective coatings disclosed herein are particularly beneficial in optical lenses and glasses used in augmented and virtual reality devices. In such devices, the optical path of a virtual image propagates multiple times within an optical waveguide under total internal reflection (TIR). The optical path of the virtual image propagates along the axis of the optical waveguide within the waveguide under TIR until it reaches a diffractive optical element, at which point the optical path is coupled outside the optical waveguide. While the optical path of the virtual image propagates within the optical waveguide under TIR, the optical path of the real image is transmitted through the optical waveguide. Once coupled outside the optical waveguide or transmitted through it, the optical paths of the virtual and real images overlap in the user's eye, creating augmented or virtual reality for the user.

[0006] To provide TIR, the virtual image light path propagating within the optical waveguide bends at an angle greater than the critical angle of the optical waveguide. In other words, when the virtual image light path bounces back within the optical waveguide, it strikes the edge of the optical waveguide at an angle greater than the critical angle of the optical waveguide. The angle of the light path must be greater than the critical angle for the light path to propagate through TIR. The critical angle of the optical waveguide is given by Snell's Law, as provided by Equation (1):

[0007] θ c =sin -1 (n2 / n1) (1)

[0008] Where θ c Let n1 be the critical angle, n2 be the refractive index of the optical medium (e.g., an optical waveguide) in which the virtual image is traveling, and n3 be the refractive index of the medium adjacent to the optical medium in which the virtual image's light path is traveling.

[0009] Anti-reflective coatings are applied to optical waveguides to increase the efficiency of the light path transmitting the real image through the waveguide. Increased transmittance reduces unwanted reflections as light travels backward within the system. However, while conventional anti-reflective coatings benefit transmission, they inadvertently cause some light propagating within the waveguide to be absorbed by the coating. More specifically, some light from the virtual image is absorbed by the coating whenever the light path bounces off the edge of the waveguide. Therefore, more light is emitted at the beginning of the path within the waveguide than at its end. This light loss due to absorption can cause changes in color and / or brightness when the user's viewing angle changes.

[0010] Because light bounces multiple times from the edges of an optical waveguide as it propagates, even small amounts of absorption can significantly contribute to the user's viewing quality. The small amount of absorption from each bounce is synthesized by the large number of bounces encountered along the light path.

[0011] The anti-reflective coating disclosed herein advantageously reduces / prevents any such absorption of light along its path while still maintaining excellent transmittance characteristics. Therefore, the anti-reflective coating disclosed herein provides users with an improved viewing quality.

[0012] The embodiments disclosed herein include an antireflective coating comprising a plurality of first layers, each first layer comprising a first material having a relatively high refractive index; and a plurality of second layers, each second layer comprising a second material having a relatively low refractive index. The total thickness of the first layers, composed of the first material, is about 120 nm or less. Furthermore, when light propagates under total internal reflection, the antireflective coating is configured to absorb about 0.25% or less of the light at each wavelength between about 425 nm and about 495 nm to achieve single reflection of the average of the s-polarization and p-polarization of the light.

[0013] The embodiments disclosed herein also include an antireflective waveguide comprising an optical waveguide configured to propagate an optical path via total internal reflection and an antireflective coating on the surface of the optical waveguide. The antireflective coating comprises a plurality of first layers, each comprising a first material having a relatively high refractive index; and a plurality of second layers, each comprising a second material having a relatively low refractive index. The total thickness of the first layers composed of the first material is about 120 nm or less. Furthermore, when light propagates under total internal reflection, the antireflective coating is configured to absorb about 0.25% or less of the light at each wavelength between about 425 nm and about 495 nm to achieve a single reflection of the average of the s-polarized and p-polarized light.

[0014] The embodiments disclosed herein also include a method for propagating an optical path within an antireflective waveguide comprising an optical waveguide and an antireflective coating on the surface of the optical waveguide, the method comprising propagating an optical path within the optical waveguide at each wavelength between about 425 nm and about 495 nm by total internal reflection with an absorption loss of about 0.25% or less, to achieve single reflection of the average values ​​of the s-polarization and p-polarization of the light.

[0015] It should be understood that the foregoing general description and the following detailed description are merely exemplary and intended to provide an overview or framework for understanding the nature and features of the claims. Drawings are included to provide further understanding and are incorporated in and form a part of this specification. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operation of the various embodiments. Attached Figure Description

[0016] Figure 1 A cross-sectional view of an article having an anti-reflective coating according to an embodiment of the present invention;

[0017] Figure 2 A cross-sectional view of an article having a multilayer antireflective coating according to an embodiment of the present invention;

[0018] Figure 3 The graph shows the number of light bounces versus the reflection of blue and violet wavelengths of light.

[0019] Figure 4A Another cross-sectional view of an article having a multilayer antireflective coating according to an embodiment of the present invention;

[0020] Figure 4B Another cross-sectional view of an article having a multilayer antireflective coating according to an embodiment of the present invention;

[0021] Figure 4CA cross-sectional view of an article having a detailed view of multiple anti-reflective coatings; and

[0022] Figure 5A-8C The graph shows the angle versus percentage of reflectivity for both exemplary and comparative coatings. Detailed Implementation

[0023] Additional features and advantages of the invention will be set forth in the following detailed description, and these features and advantages will be apparent to those skilled in the art from the description, or will be recognized by practice of the invention as described below, as well as by the claims and drawings.

[0024] As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B, and / or C, then the composition may contain only A; only B; only C; a combination containing both A and B; a combination containing both A and C; a combination containing both B and C; or a combination containing both A, B, and C.

[0025] In this document, relational terms such as first and second, top and bottom are used only to distinguish one entity or action from another, and do not necessarily require or imply any actual such relationship or order between such entities or actions.

[0026] Those skilled in the art will understand that the construction and other components of the described disclosure are not limited to any particular material. Unless otherwise described herein, other exemplary embodiments of the invention disclosed herein can be formed from a wide variety of materials.

[0027] It is equally important to note that the construction and configuration of the elements of the present invention, as shown in the exemplary embodiments, are merely illustrative. Although only a few embodiments are described in detail in this invention, those skilled in the art will readily understand that many modifications are possible (e.g., variations in the size, dimensions, structure, shape and proportions, parameter values, mounting configurations, use of materials, color, orientation, etc.) of various elements without substantially departing from the novel and non-significant teachings and advantages of the subject matter. For example, an element shown as integrally formed may be composed of multiple parts, or elements shown as multiple parts may be integrally formed; interface operation may be altered in the opposite or other manner; the structure of the system and / or the length or width of components or connectors or other elements may be changed; and the nature or number of adjustment positions provided between the elements may be changed. It should be noted that the elements of the system and / or components may be constructed from any of a wide variety of materials providing sufficient strength or durability, and from any of a wide variety of colors, textures, and combinations thereof. Therefore, all such modifications are intended to be included within the scope of the invention. Other substitutions, modifications, alterations, and omissions may be made to the design, operating conditions, and configuration of the desired and other exemplary embodiments without departing from the spirit of the invention.

[0028] The preferred embodiments of the present invention will now be described in detail, examples of which are shown in the accompanying drawings.

[0029] refer to Figure 1 Article 1 according to one or more embodiments includes a substrate 10 and an anti-reflective coating 20 disposed on the substrate. The substrate 10 includes opposing surfaces 12, 14, such that the anti-reflective coating 20 is disposed on surface 12.

[0030] However, it is also envisioned that the anti-reflective coating 20 be applied only to surface 14, or to both surfaces 12 and 14. Figure 1 In this embodiment, surface 14 can be positioned closer to the user's eyes than surface 12. Additionally, the anti-reflective coating 20 can be applied along surface 12 and / or surface 14 across the entire or less of the substrate 10. The anti-reflective coating 20 can be in direct or indirect contact with the substrate 10. For example, one or more materials, such as adhesive materials, can be disposed between the anti-reflective coating 20 and the substrate 10. Figure 1 In one embodiment, a diffractive optical element (not shown) is disposed on a surface 14 at one or more locations.

[0031] The substrate 10 may be an optical waveguide as described above and may comprise glass or glass-ceramic, such as, for example, silicate glass, aluminosilicate glass, alkali metal aluminosilicate glass, alkaline aluminosilicate glass, borosilicate glass, borosilicate glass, alkali metal aluminoborosilicate glass, alkaline aluminoborosilicate glass, soda-lime glass, fused silica (fused silica), or other types of glass. Exemplary glass substrates include, but are not limited to, those sold by Corning Incorporated of Corning, New York under glass codes 7980, 7979, and 8655. Fused silica, and the same EAGLE sold by Corning Incorporated of Corning, New York. Borosilicate glass. Other glass substrates include, but are not limited to, Lotus glass sold by Corning Incorporated of Corning, New York. TM NXT Glass, Iris TM Glass, Glass, Glass, glass or Glass. In other embodiments, substrate 10 comprises one or more transparent polymers, such as, for example, thermoplastics, including polystyrene (PS) (including styrene copolymers and blends), polycarbonate (PC) (including copolymers and blends), polyesters (including copolymers and blends, including polyethylene terephthalate and polyethylene terephthalate copolymers), polyolefins (PO) and cyclic polyolefins (cyclic PO), polyvinyl chloride (PVC), acrylic polymers (including polymethyl methacrylate (PMMA) (including copolymers and blends)), thermoplastic ethyl carbamate (TPU), polyetherimide (PEI), and blends of these polymers with each other. Other exemplary polymers include epoxy resins, styrene resins, phenolic resins, melamine resins, and silicone resins. The material of the antireflective coating 20 is further discussed below.

[0032] like Figure 1As shown, light 30 from the virtual image propagates along axis A of substrate 10. As light 30 propagates, it bounces off the side of substrate 10 at an angle θ. As described above, angle θ must be greater than the critical angle of substrate 10 (calculated according to Snell's law) for light 30 to propagate via TIR. In the embodiments disclosed herein, angle θ is greater than about 35 degrees, or greater than about 40 degrees, or about 35 degrees to 80 degrees, or about 40 degrees to about 80 degrees, or about 35 degrees to about 70 degrees, or about 40 degrees to about 70 degrees, or about 50 degrees to about 60 degrees.

[0033] As discussed above regarding conventional coatings, some absorption loss may occur, thus reducing the amount of light 30 that continues to propagate along axis A. For example, some light 35 may be absorbed by a conventional coating applied to substrate 10. The absorbed light 35 may be absorbed with each bounce experienced by the light 30 as it propagates along axis A. Therefore, for a conventional coating, the amount of light at position C is less than the amount of light at position B. The antireflective coating of the present invention reduces the amount of absorbed light 35 compared to a conventional coating. In some embodiments of the present invention, and as further discussed below, the amount of absorbed light 35 is 0.0%, such that the amount of light at position C is equal to the amount of light at position B.

[0034] like Figure 2 As shown, the anti-reflective coating 20 comprises multiple layers of material. For example, the anti-reflective coating 20 comprises layers 21-24. Although Figure 2 The disclosed implementation discloses four layers, but it is also contemplated that more or fewer layers may be used. For example, the antireflective coating 20 may comprise one, two, three, five, six, seven, eight, nine, ten, eleven, twelve, or more than twelve layers. In some embodiments, the antireflective coating 20 comprises seven or fewer layers to achieve the desired thickness, as further discussed below.

[0035] The term "layer" may include a single layer or may include one or more sublayers. Such sublayers may be in direct contact with each other. Sublayers may be formed of the same material or two or more different materials. In one or more alternative embodiments, sublayers may have intervening layers of different materials disposed therebetween. In one or more embodiments, a layer may include one or more continuous and uninterrupted layers and / or one or more discontinuous and interrupted layers (i.e., layers of different materials formed adjacent to each other). Furthermore, each layer (e.g., each layer 21-24) may be in direct or indirect contact with its adjacent layers.

[0036] Layers or sublayers can be formed using any method known in the art, including discrete or continuous deposition processes. In one or more embodiments, layers may be formed using only continuous deposition processes or alternatively using only discrete deposition processes.

[0037] As further discussed below, the number of layers, the thickness of each layer, and the material of each layer are optimized to provide a coating with minimal or zero light absorption. Therefore, the coating disclosed herein exhibits increased reflectivity under TIR. Additionally, the coating disclosed herein increases transmittance to real images.

[0038] Individual layers of the antireflective coating 20 may contain the same or different materials and may have the same or different refractive indices as other layers. For example, each layer may contain a first material with a relatively high refractive index or a second material with a relatively low refractive index. Thus, for example, layers 21 and 23 may contain a first material with a relatively high refractive index, and layers 22 and 24 may contain a second material with a relatively low refractive index. In this embodiment, it is also contemplated that the specific material of layer 21 may be the same as or different from the specific material of layer 23, as long as both layers contain materials with relatively high refractive indices. Similarly, the specific material of layer 22 may be the same as or different from the specific material of layer 24, as long as both layers contain materials with relatively low refractive indices.

[0039] The refractive index of the first material may be higher than that of the substrate 10. In some embodiments, the refractive index of the first material at 850 nm is about 1.6 or greater, or about 1.7 or about 1.8 or greater, or about 1.9 or greater, or about 2.0 or greater, or about 2.1 or greater, or about 2.2 or greater, or about 2.3 or greater, or about 2.4 or greater, or about 2.5 or greater, or about 2.6 or greater. Exemplary materials include, for example, Nb2O2, TiO2, Ta2O5, HfO2, Sc2O3, SiN, and SiO2. x N and AlO x N.

[0040] The refractive index of the second material may be lower than that of the substrate 10. In some embodiments, the refractive index of the second material at 850 nm is about 1.6 or less, or about 1.5 or less, or about 1.4 or less, or about 1.3 or less, or about 1.2 or less. Exemplary materials include, for example, SiO2, MgF2, and AlF3.

[0041] In some embodiments, the substrate 10 comprises glass having a refractive index of about 1.5, about 1.6, or about 1.7 at 850 nm, a first material having a refractive index greater than about 1.5, about 1.6, or about 1.7 at 850 nm, and a second material having a refractive index less than about 1.5, about 1.6, or about 1.7 at 850 nm.

[0042] The ratio of the refractive index of the first material to the refractive index of the second material is about 1.3 or greater, or about 1.4 or greater, or about 1.5 or greater, or about 1.6 or greater, or about 1.7 or greater. A higher ratio advantageously provides higher transmittance while reducing the total number of layers, and thus advantageously reduces the total thickness of the coating.

[0043] The anti-reflective coating 20 may comprise an alternating layer of a first material and a second material. The layer of the anti-reflective coating 20 directly adjacent to the substrate 10 (e.g., layer 21) may comprise the first material.

[0044] Additionally, the layer of the antireflective coating 20 furthest from the substrate 10 (e.g., layer 24) may contain a second material.

[0045] The total thickness of the antireflective coating 20 may be about 300 nm or less, or about 250 nm or less, or about 200 nm or less. Alternatively, the total thickness of the antireflective coating 20 may be about 50 nm or more, or about 75 nm or more, or about 80 nm or more, or about 90 nm or more, or about 100 nm or more, or about 125 nm or more, or about 150 nm or more. In some embodiments, the total thickness of the coating is in the range of about 75 nm to about 300 nm, or about 100 nm to about 250 nm, or about 200 nm to about 250 nm, or about 125 nm to about 225 nm.

[0046] The total thickness of the antireflective coating 20 can be customized and optimized depending on the material chosen for the layer. Furthermore, the total thickness must be thick enough to properly propagate light 30, but also thin enough to provide sufficient flexibility and reduce manufacturing costs. In some embodiments, the total thickness of the antireflective coating 20 is less than about 250 nm to provide the desired light propagation while still maintaining flexibility and reducing manufacturing costs.

[0047] The total thickness of all layers containing the first material may be less than the total thickness of all layers containing the second material in order to reduce the amount of absorbed light 35. The first material, having a relatively high refractive index, begins to absorb light 30 before the second material, having a relatively low refractive index.

[0048] Therefore, the total thickness of the first material layer can be reduced in order to provide reduced absorption.

[0049] The ratio of the total thickness of the first material layer to the total thickness of the second material layer is in the range of about 0.2 to about 0.8, or about 0.3 to about 0.7, or about 0.4 to about 0.6, or about 0.5. The total thickness of the first material layer may be about 120 nm or less, or about 110 nm or less, or about 100 nm or less, or about 90 nm or less, or about 80 nm or less, or about 70 nm or less, or about 60 nm or less, or about 50 nm or less. In some embodiments, the total thickness of the first material layer is in the range of about 20 nm to about 70 nm, or about 30 nm to about 60 nm, or about 40 nm to about 55 nm. For example, the total thickness of the first material layer is about 31 nm, or about 35 nm, or about 38 nm, or about 50 nm, or about 54 nm, or about 55 nm. The total thickness of the second material layer can be about 100 nm or more, or about 120 nm or more, or about 130 nm or more, or about 140 nm or more, or about 150 nm or more, or about 160 nm or more, or about 170 nm or more. In some embodiments, the total thickness of the second material layer is in the range of about 100 nm to about 180 nm, or about 115 nm to about 165 nm, or about 130 nm to about 150 nm. For example, the total thickness of the second material layer is about 130 nm, or about 140 nm, or about 149 nm, or about 155 nm.

[0050] Within the scope of this invention, one or more first material layers may have a different thickness than one or more other first material layers. Similarly, one or more second material layers may have a different thickness than one or more other second material layers. For example, refer to... Figure 2 Layers 21 and 23 may both contain the first material, but layer 21 may have a different thickness than layer 23. Alternatively, layers 22 and 24 may both contain the second material, but layer 22 may have a different thickness than layer 24. It is also conceivable that all layers 21-24 have different thicknesses from each other.

[0051] For example, the anti-reflective coating 20 layer directly adjacent to the substrate 10 ( Figure 2 The thickness of layer 21 in the antireflective coating 20 may be in the range of about 5 nm to about 60 nm, or about 10 nm to about 50 nm, or about 15 nm to about 45 nm, or about 20 nm to about 40 nm, or about 25 nm to about 35 nm. As described above, the layer of the antireflective coating 20 directly adjacent to the substrate 10 may have a reduced thickness to provide reduced absorption. In some embodiments, the thickness of the layer of the antireflective coating 20 is about 15 nm, or about 17 nm, or about 20 nm, or about 23 nm, or about 25 nm, or about 27 nm. The layer of the antireflective coating 20 may comprise a first material and may have a thickness less than that of each of the remaining layers composed of the first material.

[0052] When moving away from substrate 10 (i.e., when in) Figure 2 As the material moves upwards from the substrate 10, the thickness of each first material layer can increase. Therefore, in embodiments where layers 21 and 23 contain the first material, layer 23 can have a greater thickness than layer 21. As the material moves away from the substrate 10, the thickness of each second material layer can also increase. Therefore, in embodiments where layers 22 and 24 contain the second material, layer 24 can have a greater thickness than layer 22.

[0053] As described above, the number of antireflective coating layers, the thickness of each layer, and the material of each layer are optimized to provide reduced absorption of light 30 under TIR. Therefore, the antireflective coating 20 allows light at each wavelength within the red wavelength range (e.g., 625 nm to 740 nm) to propagate within the substrate 10 with an absorption loss of approximately 0.0%, thus achieving single reflection (i.e., bounce). Alternatively, the antireflective coating 20 allows light at each wavelength within the green wavelength range (e.g., 500 nm to 565 nm) to propagate within the substrate 10 with an absorption loss of approximately 0.0%, thus achieving single reflection (i.e., bounce). Alternatively, the antireflective coating 10 allows light at each wavelength in the blue and violet wavelength range (e.g., 425 nm to 495 nm) to propagate within the substrate 10 with the following absorption loss: about 6.0% or less, or about 5.0% or less, or about 4.0% or less, or about 3.0% or less, or about 2.0% or less, or about 1.5% or less, or about 1.0% or less, or about 0.75% or less. Less, or about 0.60% or less, or about 0.50% or less, or about 0.40% or less, or about 0.25% or less, or about 0.20% or less, or about 0.10% or less, or about 0.05% or less, or about 0.04% or less, or about 0.03% or less, or about 0.02% or less, or about 0.01% or less, or about 0.0%, to perform single reflection (i.e., bounce) of light. It should be noted that light in the blue / violet wavelength range has a shorter wavelength and therefore more energy than light in the red and green wavelength range. Therefore, conventionally, antireflective coatings absorb a greater amount of blue / violet wavelength light compared to red or green wavelength light. However, the antireflective coating of the present invention reduces not only the absorption of red and green wavelength light but also the absorption of blue / violet wavelength light.

[0054] As described above, since light 30 propagates multiple times within substrate 10, even a small amount of absorption is synthesized after multiple reflections (i.e., bounces) of light. Therefore, even if only a small amount of light is absorbed in each reflection of light 30 within substrate 10, after, for example, 20 or 25 reflections within substrate 10, the small amount of absorbed light rapidly increases. For example, such as... Figure 3As shown, optical path D has a reflectivity of 99% per light bounce (corresponding to a 1% absorption loss per light bounce), and optical path H has a reflectivity of 99.9% per light bounce (corresponding to a 0.1% absorption loss per light bounce). It should be noted that in TIR, light is either absorbed by the coating or reflected from the coating. Therefore, in TIR, A + R = 100%, where A is the amount of light absorbed and R is the amount of light reflected. Again, it is desirable to have a higher percentage of reflectivity (equivalent to a lower percentage of absorptivity) in order to reduce the amount of light lost during propagation in TIR.

[0055] Similarly, Figure 3 As shown, after 5 bounces, the difference in reflected light within the blue / violet wavelength range of optical paths D and H is small (approximately 95% for optical path D and approximately 99% for optical path H). However, after 20 bounces, the difference in reflected light within the blue / violet wavelength range of optical paths D and H becomes larger (approximately 81% for optical path D and approximately 98% for optical path H). After 30 bounces, the difference in reflected light within the blue / violet wavelength range of optical paths D and H becomes even larger (approximately 75% for optical path D and approximately 97% for optical path H). The absorption loss of optical paths D and H differs only slightly with each bounce. However, this small difference increases significantly when the light undergoes multiple bounces under TIR. As described above, even after multiple bounces under TIR, the antireflective coating disclosed herein is optimized to provide minimal or zero light absorption.

[0056] The antireflective coating disclosed herein also exhibits transmittance of approximately 95.0% or greater, or approximately 96.0% or greater, or approximately 97.0% or greater, or approximately 98.0% or greater, or approximately 98.5% or greater, or approximately 99.0% or greater, or approximately 99.2% or greater, or approximately 99.5% or greater, or approximately 99.6% or greater, or approximately 99.7% or greater, or approximately 99.8% or greater, or approximately 99.9% or greater, or 100% for each of the red, green, and blue / violet wavelengths. These disclosed transmittance values ​​are referenced to a direction orthogonal to the longitudinal length of the antireflective waveguide. As described above, the optical paths of the virtual and real images are coupled or transmitted through the optical waveguide and overlap in the user's eye to create augmented or virtual reality for the user. Therefore, the antireflective coating of the present invention advantageously provides high transmittance, which improves the quality of the image produced for the user.

[0057] Figure 4AIn an exemplary embodiment of article 100, layers 210 and 230 of the antireflective coating 200 both contain Nb₂O₂ (a first material layer), and layers 220 and 240 of the antireflective coating 200 both contain MgF₂ (a second material layer). In this embodiment, layer 210 is directly adjacent to the substrate 10 and its thickness is less than that of layer 230. More specifically, layer 210 has a thickness of 17.50 nm, and layer 230 has a thickness of 21.20 nm. Additionally, layer 220 has a thickness of 38.23 nm, which is less than the thickness of layer 240 (111.70 nm). The total thickness of the first material layers (layers 210 + 230) is 38.70 nm, and the total thickness of the second material layers (layers 220 + 240) is 149.93 nm. In this embodiment, the total thickness of the antireflective coating 200 is 188.63 nm.

[0058] Figure 4B In a second exemplary embodiment of the article 1000, layers 2100 and 2300 of the antireflective coating 2000 both contain Ta2O5 (a first material layer), and layers 2200 and 2400 of the antireflective coating 2000 both contain MgF2 (a second material layer). In this embodiment, layer 2100 is directly adjacent to the substrate 10 and has a thickness less than that of layer 2300. More specifically, layer 2100 has a thickness of 25.17 nm, and layer 2300 has a thickness of 28.85 nm. Additionally, layer 2200 has a thickness of 31.91 nm, which is less than the 108.94 nm thickness of layer 2400. The total thickness of the first material layers (layers 2100 + 2300) is 54.02 nm, and the total thickness of the second material layers (layers 2200 + 2400) is 140.85 nm. In this embodiment, the total thickness of the antireflective coating 2000 is 194.87 nm.

[0059] Figure 4C Comparative examples of articles having an anti-reflective coating 3000 with six layers of material are provided. For example... Figure 4C As shown, the comparative coating 3000 has more layers and a greater total thickness than the exemplary coatings in Figures 4A and 4B. Specifically, the total thickness of the comparative coating 3000 is 261.70 nm, which is greater than the thickness of the exemplary coating 200 (188.63 nm) and greater than the thickness of the exemplary coating 200 (194.87 nm). Furthermore, Figure 4C The comparative coating 3000, made of a high-refractive-index material (Ta2O5), has a total thickness of 126.25 nm, which is significantly greater than the thickness of coating 200 (38.70 nm) and coating 2000 (54.02 nm). Because the comparative examples contain a larger amount of material with a high refractive index, they exhibit higher absorptivity (and therefore lower reflectivity), as shown below.

[0060] Figures 5A-5C A comparison of the percentage of reflectance of exemplary coatings 200 and 2000 with that of comparative coating 3000 is provided for a 425nm optical path. It should be noted that... Figures 5A-5C In the TIR, light propagates at an angle of approximately 40 to approximately 70 degrees to be greater than the critical angle of the optical waveguide. As mentioned above, the optical path must propagate within the optical waveguide at an angle greater than the critical angle in order to propagate in the TIR.

[0061] It should also be noted that polarized light includes two orthogonal linear polarization states: s-polarization (perpendicular to the incident plane) and p-polarization (parallel to the incident plane). Figures 5A-5C This section depicts the percentage of reflectance for S-polarized light, P-polarized light, and average S-polarized and P-polarized light. For comparative purposes, the average S-polarization and P-polarization diagrams are discussed below. Average S-polarization and P-polarization diagrams with higher reflectance percentages reduce color shift and brightness inhomogeneity in the image viewed by the user. This also reduces streaks or banding in the image, thereby improving the user's viewing quality.

[0062] Compared with the use of coating 3000 ( Figure 5C Compared to using the exemplary coating 200 () Figure 5A ) and exemplary coating 2000 ( Figure 5B When using the exemplary coating 200, the average s-polarization and p-polarization patterns show a higher percentage of reflectance. For example, when using the exemplary coating 200... Figure 5A ) or exemplary coating 2000 ( Figure 5B When using the s-polarization and p-polarization patterns, the average reflectance exceeds 99.75% in the angular range of 40 to 70 degrees. Conversely, when using the comparative coating 3000 ( Figure 5C When the average s-polarization and p-polarization patterns drop to below 99.75% reflectivity within the stated angular range, the comparison coating 3000 exhibits a lower percentage of reflectivity (and therefore a higher percentage of absorptivity) when using 425nm light.

[0063] Figures 6A-6C A comparison of the percentage of reflectance of exemplary coatings 200 and 2000 with that of comparative coating 3000 is provided for a 435nm optical path. Similar to... Figures 5A-5C Compared with the use of coating 3000 ( Figure 6C Compared to using the exemplary coating 200 () Figure 6A ) and exemplary coating 2000 ( Figure 6B When using the exemplary coating 200, both the average s-polarization and p-polarization patterns exhibit higher percentages of reflectance. For example, when using the exemplary coating 200... Figure 6A ) or exemplary coating 2000 ( Figure 6BWhen using the coating 3000, the average s-polarization and p-polarization patterns exhibit reflectivity of 99.85% or higher in the angular range of 40 to 70 degrees. Conversely, when using the comparative coating 3000... Figure 6C When the average s-polarization and p-polarization patterns drop to below 99.85% reflectivity within the stated angular range, the comparison coating 3000 exhibits a smaller percentage of reflectivity (and therefore a higher percentage of absorptivity) when using 435nm light.

[0064] Figures 7A-7C A comparison of the percentage of reflectance of exemplary coatings 200 and 2000 with that of comparative coating 3000 is provided for a 445nm optical path. Similar to... Figures 5A-5C Compared with the use of coating 3000 ( Figure 7C Compared to using the exemplary coating 200 () Figure 7A ) and exemplary coating 2000 ( Figure 7B When using the exemplary coating 200, both the average s-polarization and p-polarization patterns exhibit higher percentages of reflectance. For example, when using the exemplary coating 200... Figure 7A ) or exemplary coating 2000 ( Figure 7B When using the coating 3000, the average s-polarization and p-polarization patterns exhibit reflectivity exceeding 99.85% over an angular range of 40 to 70 degrees. Conversely, when using the comparative coating 3000... Figure 7C When the average s-polarization and p-polarization patterns drop to below 99.85% reflectivity within the stated angular range, the comparison coating 3000 exhibits a smaller percentage of reflectivity (and therefore a higher percentage of absorptivity) when using 445nm light.

[0065] Figures 8A-8C A comparison of the percentage of reflectance of exemplary coatings 200 and 2000 with that of comparative coating 3000 is provided for a 448nm optical path. Similar to... Figures 5A-5C Compared with the use of coating 3000 ( Figure 8C Compared to using the exemplary coating 200 () Figure 8A ) and exemplary coating 2000 ( Figure 8B When using the exemplary coating 200, both the average s-polarization and p-polarization patterns exhibit higher percentages of reflectance. For example, when using the exemplary coating 200... Figure 8A ) or exemplary coating 2000 ( Figure 8B When using the coating 3000, the average s-polarization and p-polarization patterns exhibit reflectivity exceeding 99.85% over an angular range of 40 to 70 degrees. Conversely, when using the comparative coating 3000... Figure 8CWhen the average s-polarization and p-polarization patterns drop to below 99.85% reflectivity within the stated angular range, the comparison coating 3000 exhibits a smaller percentage of reflectivity (and therefore a higher percentage of absorptivity) when using 448nm light.

[0066] The exemplary coatings disclosed herein optimize the number of layers, the thickness of each layer, and the specific materials of each layer in order to reduce reflectivity, reduce glare, increase transmittance, and reduce color shift when viewing images from different angles.

[0067] The present invention also includes a method for propagating an optical path within an antireflective waveguide, such that the waveguide comprises the optical waveguide and antireflective coating of the present invention. Therefore, as described above, the method includes propagating an optical path via TIR with reduced absorption loss (increased reflection) and increased transmittance.

[0068] The description of embodiments of the present invention is not intended to be exhaustive or limiting. Although specific embodiments and examples of the invention have been described herein for illustrative purposes, various equivalent modifications can be made within the scope of the invention, as will be recognized by those skilled in the art. Such modifications may include, but are not limited to, changes in dimensions and / or materials as shown in the disclosed embodiments.

Claims

1. An anti-reflective coating, comprising: Multiple first layers, each comprising a first material having a relatively high refractive index, the first material including Nb2O5, TiO2, Ta2O5, HfO2, Sc2O3, SiN, SiO x N and AlO x At least one of N; and Multiple second layers, each containing a second material with a relatively low refractive index. in: The total thickness of the first layer, composed of the first material, is approximately 120 nm or less, and When light is propagated under total internal reflection, the antireflective coating is configured to absorb about 0.05% or less of the light at each wavelength between about 425 nm and about 495 nm to achieve single reflection of the average of the s-polarization and p-polarization of the light.

2. The antireflective coating of claim 1, wherein when light is propagated under total internal reflection, the antireflective coating is configured to absorb about 0.04% or less of the light at each wavelength between about 425 nm and about 495 nm to perform single reflection of the average values ​​of the s-polarization and p-polarization of the light.

3. The antireflective coating of claim 1, wherein when light is propagated under total internal reflection, the antireflective coating is configured to absorb about 0.03% or less of the light at each wavelength between about 425 nm and about 495 nm to perform single reflection of the average values ​​of the s-polarization and p-polarization of the light.

4. The antireflective coating as described in any one of claims 1-3, wherein the antireflective coating comprises an alternating layer of the first material and the second material.

5. The antireflective coating as described in any one of claims 1-3, wherein the refractive index of the first material is about 1.8 or greater at 850 nm.

6. The antireflective coating according to any one of claims 1-3, wherein the refractive index of the second material is about 1.5 or less at 850 nm.

7. The antireflective coating according to any one of claims 1-3, wherein the second material comprises at least one of SiO2, MgF2 and AlF3.

8. The antireflective coating as described in any one of claims 1-3, wherein the total thickness of the first layer is less than the total thickness of the second layer.

9. The antireflective coating of any one of claims 1-3, wherein the transmittance percentage of the antireflective coating is about 98.0% or greater.

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