Method for manufacturing diffractive optical waveguide, diffractive optical waveguide and near-eye display device

Abstract

The application discloses a manufacturing method of a diffractive optical waveguide, the diffractive optical waveguide and a near-eye display device. The manufacturing method of the diffractive optical waveguide comprises the following steps: forming a liquid adhesive layer on a first surface of a cover layer; pre-solidifying the liquid adhesive layer, so that the liquid adhesive layer is changed into a pre-solidified layer; patterning the pre-solidified layer, so as to form a groove on a surface of the pre-solidified layer which is away from the cover layer; adhering a first optical waveguide layer with a grating to the cover layer through the pre-solidified layer, wherein a second surface of the first optical waveguide layer provided with the grating is arranged to face the first surface, and the grating is correspondingly arranged at the position of the groove; and solidifying the pre-solidified layer, so that the pre-solidified layer is changed into a solid adhesive layer and the first optical waveguide layer is adhered to the cover layer. According to the manufacturing method of the diffractive optical waveguide, the relative deformation between layer structures in the diffractive optical waveguide can be reduced, so that the stability of the display effect is improved.

Description

Technical Field

[0001] This application relates to the field of near-eye displays, and in particular to a method for fabricating a diffractive waveguide, the diffractive waveguide, and a near-eye display device. Background Technology

[0002] Augmented Reality (AR) near-eye display devices typically include an optomechanical system and a diffractive waveguide. The diffractive waveguide comprises several waveguide layers and at least one protective layer, with a grating disposed on one side surface of each waveguide layer. Taking a diffractive waveguide consisting of one waveguide layer and one protective layer as an example, in existing technologies, after the waveguide layer and protective layer are assembled, a gap layer exists between them when no external force is applied. When the air pressure in this gap layer is lower than the external air pressure or when the diffractive waveguide is subjected to external force, the waveguide layer and protective layer may undergo relative deformation, affecting the stability of the display effect. Summary of the Invention

[0003] This application provides a method for fabricating a diffractive waveguide, a diffractive waveguide, and a near-eye display device, which can reduce the relative deformation between the layers in the diffractive waveguide to improve the stability of the display effect.

[0004] In a first aspect, embodiments of this application provide a method for fabricating a diffractive optical waveguide, comprising: forming a liquid adhesive layer on a first surface of a capping layer; pre-curing the liquid adhesive layer to transform it into a pre-cured layer; patterning the pre-cured layer to form a groove on the surface of the pre-cured layer opposite to the capping layer; bonding a first optical waveguide layer having a grating to the capping layer through the pre-cured layer, wherein a second surface of the first optical waveguide layer having the grating is disposed facing the first surface, and the grating corresponds to the groove; curing the pre-cured layer to transform it into a solid adhesive layer and bonding the first optical waveguide layer to the capping layer.

[0005] According to any of the foregoing embodiments of the first aspect of this application, forming a liquid adhesive layer on the first surface of the cover layer includes: forming a liquid adhesive layer of uniform thickness on the first surface of the cover layer by electrostatic adsorption coating, electromagnetic adsorption coating or centrifugal force coating.

[0006] According to any of the foregoing embodiments of the first aspect of this application, the pre-curing of the liquid adhesive layer to transform the liquid adhesive layer into a pre-cured layer includes: performing a viscosity-increasing treatment on the liquid adhesive layer to obtain a pre-cured layer that can maintain its shape under external force within a preset range.

[0007] According to any of the foregoing embodiments of the first aspect of this application, the patterning of the pre-cured layer and the formation of a groove on the surface of the pre-cured layer opposite to the cover layer includes: providing a patterned mask on the side of the pre-cured layer opposite to the cover layer, the patterned mask having a mask opening; etching the pre-cured layer using the patterned mask to form a groove in the area of ​​the pre-cured layer corresponding to the mask opening; and peeling off the patterned mask.

[0008] According to any of the foregoing embodiments of the first aspect of this application, the etching depth of the pre-cured layer is less than 200 nm, such that the depth of the groove is less than 200 nm.

[0009] According to any of the foregoing embodiments of the first aspect of this application, in the step of bonding the first optical waveguide layer with a grating to the cover layer through the pre-cured layer, the bonding pressure and bonding time are controlled so that the thickness variation of the pre-cured layer is within 200 nm.

[0010] According to any of the foregoing embodiments of the first aspect of this application, the covering layer is a protective layer; or the covering layer is a second optical waveguide layer.

[0011] Secondly, embodiments of this application provide a diffractive optical waveguide, which is obtained by the fabrication method of a diffractive optical waveguide according to any of the foregoing embodiments of the first aspect of this application.

[0012] Thirdly, embodiments of this application provide a diffractive optical waveguide, comprising: a capping layer having a first surface; a first optical waveguide layer having a second surface, wherein the first optical waveguide layer has a grating on the second surface; and an adhesive layer, wherein the first optical waveguide layer is bonded and adhered to the capping layer via the adhesive layer, the second surface being disposed opposite to the first surface, the adhesive layer being disposed between the first optical waveguide layer and the capping layer or on the outer peripheral surface of the region where the first optical waveguide layer and the capping layer meet, and the adhesive layer being used to bond the first optical waveguide layer and the capping layer in a vacuum environment and to eliminate air in the bonding surface between the first optical waveguide layer and the capping layer.

[0013] Fourthly, embodiments of this application provide a diffractive optical waveguide, comprising: a capping layer having a first surface; a first optical waveguide layer having a second surface, wherein the first optical waveguide layer has a grating on the second surface; and an adhesive layer, wherein the first optical waveguide layer is bonded and adhered to the capping layer via the adhesive layer, the second surface being disposed opposite to the first surface, the adhesive layer being disposed between the first optical waveguide layer and the capping layer, the surface of the adhesive layer facing away from the capping layer having a groove, and the grating being positioned corresponding to the groove, thereby creating a gap between the grating and the surface of the adhesive layer.

[0014] According to the foregoing embodiments of the fourth aspect of this application, the depth of the groove is 0 to 200 nm.

[0015] According to any of the foregoing embodiments of the fourth aspect of this application, the covering layer is a second optical waveguide layer.

[0016] According to any of the foregoing embodiments of the fourth aspect of this application, the cover layer is provided with a first alignment mark, and the first optical waveguide layer is provided with a second alignment mark corresponding to the first alignment mark.

[0017] Fifthly, embodiments of this application provide a diffractive optical waveguide, comprising: a capping layer having a first surface; a first optical waveguide layer having a second surface, wherein the first optical waveguide layer has a grating on the second surface; and an adhesive layer, wherein the first optical waveguide layer is bonded and adhered to the capping layer via the adhesive layer, the second surface being disposed opposite to the first surface, the adhesive layer being disposed at the outer peripheral edge of the region where the first optical waveguide layer and the capping layer meet, and the adhesive layer being used to bond the first optical waveguide layer and the capping layer in a vacuum environment and to eliminate air in the bonding surface between the first optical waveguide layer and the capping layer.

[0018] According to the aforementioned embodiments of the fifth aspect of this application, the adhesive layer is disposed on the outer peripheral edge and outer peripheral side region of the area where the first optical waveguide layer and the cover layer are connected.

[0019] Sixthly, embodiments of this application provide a near-eye display device, comprising: an optomechanism for emitting signal light; and a diffractive waveguide according to any of the foregoing embodiments of this application for transmitting the signal light.

[0020] The fabrication method of the diffractive waveguide according to the embodiments of this application can provide a diffractive waveguide with a specific structure, wherein a solid adhesive layer fully adheres and bonds the first waveguide layer and the cover layer. Under the action of external force, the relative deformation between the first waveguide layer and the cover layer is small, thereby improving the stability and reliability of the display effect after the diffractive waveguide transmits signal light. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a flowchart of an embodiment of the fabrication method of the diffractive optical waveguide of the present invention;

[0023] Figure 2 This is a schematic diagram of a liquid adhesive layer formed on the first surface of a capping layer in one embodiment of the fabrication method of the diffractive waveguide of the present invention. Figure 3 This is a schematic diagram of the structure of a pre-cured liquid adhesive layer in one embodiment of the fabrication method of the diffractive optical waveguide of the present invention, which transforms the liquid adhesive layer into a pre-cured layer. Figure 4 This is a schematic diagram of a patterned pre-cured layer with grooves formed on the surface of the pre-cured layer away from the cover layer in one embodiment of the fabrication method of the diffractive optical waveguide of the present invention. Figure 5 This is a schematic diagram of the structure in one embodiment of the fabrication method of the diffractive waveguide of the present invention, in which a first waveguide layer with a grating is bonded to a cover layer through a pre-cured layer; Figure 6 This is a schematic diagram of a structure in one embodiment of the method for fabricating a diffractive optical waveguide of the present invention, in which a pre-cured layer is cured, so that the pre-cured layer is transformed into a solid adhesive layer and the first optical waveguide layer is bonded to the cover layer. Figure 7 This is a schematic diagram of the structure of an embodiment of the diffractive waveguide of the present invention; Figure 8 This is a schematic diagram of another embodiment of the diffractive waveguide of the present invention; Figure 9 This is a schematic diagram of another embodiment of the diffractive waveguide of the present invention; Figure 10 This is a cross-sectional structural diagram of an embodiment of the near-eye display device of the present invention.

[0024] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] It should be noted that all directional indications in the embodiments of this application, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture as shown in the attached figures. If the specific posture changes, the directional indications will also change accordingly. When describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above another layer or region, or that it contains other layers or regions between it and another layer or region. Furthermore, if the component is flipped, the layer or region will be located "below" or "under" another layer or region.

[0027] Furthermore, the descriptions using terms such as "first," "second," etc., in this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on what a person skilled in the art can implement. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0028] Diffractive waveguides can be used in augmented reality (AR) display devices, such as AR glasses. They can be used to transmit signal light emitted from an optical engine.

[0029] In related technologies, taking a diffractive waveguide consisting of a waveguide layer and a protective layer as an example, after the waveguide layer and the protective layer are assembled, there is a gap layer between them when no external force is applied. When the air pressure in this gap layer is lower than the external air pressure or when the diffractive waveguide is subjected to external force, the waveguide layer and the protective layer may undergo relative deformation. After deformation, interference easily occurs in some areas of the diffractive waveguide, generating Newton's rings, which affects the observation effect during user observation. The stability of the display effect of this diffractive waveguide needs to be improved. In order to avoid the generation of Newton's rings, related technologies also fill the space between the waveguide layer and the protective layer with an adhesive layer. However, during the filling process, the adhesive layer also fills into the grating microstructure, thereby reducing the optical performance of the waveguide and resulting in a poor display effect.

[0030] This application provides a method for fabricating a diffractive optical waveguide and a diffractive optical waveguide fabricated according to the method.

[0031] Figure 1 This is a flowchart illustrating an embodiment of the fabrication method of the diffractive optical waveguide of the present invention. The fabrication method of the diffractive optical waveguide includes steps S110 to S160.

[0032] In step S110, a cover layer is provided.

[0033] In some embodiments, the cover layer is a protective layer. The protective layer may be made of resin, glass, or silicon wafers, etc.

[0034] In some embodiments, the cover layer is a second optical waveguide layer, that is, the diffractive optical waveguide may include two or more optical waveguide layers, and the cover layer is another optical waveguide layer that is different from the first optical waveguide layer.

[0035] In this embodiment, the cladding layer is used as the protective layer, and the diffractive waveguide includes one waveguide layer and one protective layer as an example. In other embodiments, the diffractive waveguide may include other numbers of waveguide layers, or may include multiple protective layers.

[0036] In step S120, a liquid adhesive layer is formed on the first surface of the cover layer. Figure 2 This is a schematic diagram illustrating the structure of a liquid adhesive layer formed on the first surface of a capping layer in one embodiment of the fabrication method of the diffractive waveguide of the present invention. In this embodiment, a liquid adhesive is coated on the first surface of the capping layer to form the liquid adhesive layer.

[0037] In some embodiments, step S120 of forming a liquid adhesive layer 120a on the first surface S1 of the cover layer 110 includes forming a liquid adhesive layer 120a of uniform thickness on the first surface S1 of the cover layer 110 by electrostatic adsorption coating, electromagnetic adsorption coating or centrifugal coating.

[0038] In step S130, the liquid adhesive layer 120a is pre-cured, so that the liquid adhesive layer 120a is transformed into a pre-cured layer 120b. Figure 3 This is a schematic diagram of the structure of a pre-cured liquid adhesive layer 120a, which is transformed into a pre-cured layer 120b, in one embodiment of the fabrication method of the diffractive optical waveguide of the present invention.

[0039] In some embodiments, step S130, which pre-cures the liquid adhesive layer 120a to transform it into a pre-cured layer 120b, includes: increasing the viscosity of the liquid adhesive layer 120a to obtain a pre-cured layer 120b that can maintain its shape under external force within a preset range. The specific method for increasing the viscosity of the liquid adhesive layer 120a can be determined based on the physical properties of the liquid adhesive layer. For different types of adhesives (liquid adhesive layer 120a), such as temperature-sensitive adhesives, humidity-curing adhesives, and photosensitive adhesives, the corresponding type of adhesive can be pre-cured by adjusting temperature, humidity, and light exposure. For example, for a UV-sensitive liquid adhesive layer 120a, irradiation with UV light for a preset duration pre-cures the liquid adhesive layer 120a, allowing the pre-cured adhesive to still form under external force.

[0040] In step S140, the pre-cured layer 120b is patterned, and a groove is formed on the surface of the pre-cured layer 120b opposite to the cover layer 110. Figure 4 This is a schematic diagram of a patterned pre-cured layer 120b with a groove formed on the surface of the pre-cured layer 120b away from the cover layer 110, as shown in one embodiment of the fabrication method of the diffractive waveguide of the present invention.

[0041] In some embodiments, step S140 of forming a groove 121 on the surface of the patterned pre-cured layer 120b away from the cover layer 110 includes: providing a patterned mask on the side of the pre-cured layer 120b away from the cover layer 110, the patterned mask having a mask opening; etching the pre-cured layer 120b using the patterned mask to form a groove 121 in the area of ​​the pre-cured layer 120b corresponding to the mask opening; and peeling off the patterned mask.

[0042] In one example, the patterned mask is a patterned photoresist layer. Therefore, the process of forming the patterned mask is, for example, to spin-coat a positive photoresist layer or a negative photoresist layer on the side of the pre-cured layer 120b away from the cover layer 110, and then to expose and develop the positive photoresist layer or the negative photoresist layer under the mask, so that the photoresist layer in a specific area of ​​the positive photoresist layer or the negative photoresist layer is removed, forming a mask opening, thus obtaining a patterned mask with a mask opening.

[0043] In step S150, the first optical waveguide layer 130 with grating 131 is bonded to the cover layer 110 through the pre-cured layer 120b, wherein the second surface S2 of the first optical waveguide layer 130 with grating 131 is arranged facing the first surface S1 of the cover layer 110, and the grating 131 corresponds to the groove 121. Figure 5 This is a schematic diagram of the structure of a first optical waveguide layer 130 with a grating 131 bonded to a cover layer 110 via a pre-cured layer 120b, as described in one embodiment of the fabrication method of the diffractive optical waveguide of the present invention.

[0044] In some embodiments, the grating 131 includes a coupling-in grating 131a and a coupling-out grating 131b spaced apart from each other. The coupling-in grating 131a couples the signal light emitted by the optical engine (or optical engine) into the first optical waveguide layer 130 and causes total internal reflection. The signal light is transmitted to the coupling-out grating 131b after total internal reflection in the first optical waveguide layer 130. The coupling-out grating 131b diffracts the signal light in the first optical waveguide layer 130 into free space. The signal light diffracted into free space enters the human eye and forms a virtual image to be displayed on the retina.

[0045] In some embodiments, the etching depth of the pre-cured layer 120b is less than 200 nm, so that the depth of the groove 121 is less than 200 nm.

[0046] In the above embodiment, a groove 121 is formed on the surface of the pre-cured layer 120b facing away from the cover layer 110. After the first optical waveguide layer 130 is bonded to the cover layer 110, the groove 121 corresponds to the position of the grating 131 on the first optical waveguide layer 130. The groove 121 creates a gap between the grating 131 and the pre-cured layer 120b, or between the grating 131 and the surface of the solid adhesive layer. After the diffraction waveguide is fabricated, this gap creates a thin gap space between the grating 131 and the surface of the solid adhesive layer. According to the Newton's rings formation conditions, when the gap space thickness d < λ / 2 ≈ 200 nm (where λ is the minimum wavelength of visible light, λ ≈ 400 nm), the alternating light and dark Newton's rings cannot be seen visually. In the fabrication method of the diffractive waveguide in this embodiment, the etching depth of the pre-cured layer 120b is less than 200nm, so that the depth of the groove 121 is less than 200nm. This ensures that the adhesive layer (pre-cured layer 120b or solid adhesive layer) will not penetrate into the grating 131, and at the same time avoids the generation of Newton's rings. Thus, under the condition of using any adhesive layer, both the display light effect can be guaranteed and the generation of Newton's rings can be avoided.

[0047] In some embodiments, the step of bonding the first optical waveguide layer 130 with grating 131 to the cover layer 110 via the pre-cured layer 120b may include bonding the first optical waveguide layer 130 with grating 131 to the cover layer 110 via the pre-cured layer 120b in a vacuum environment.

[0048] In the above embodiment, the first optical waveguide layer 130 and the cover layer 110 are bonded together in a vacuum environment (vacuum degree < 30 Pa). Mechanical pressure is used to bond the first optical waveguide layer 130 and the cover layer 110 together. After bonding, the first optical waveguide layer 130 and the cover layer 110 are tightly bonded under atmospheric pressure to obtain a diffractive optical waveguide assembly. This bonding method can reduce or even eliminate air in the gaps of the grating 131, improve the adhesion and optical performance between the first optical waveguide layer 130 and the cover layer 110, and result in lower warpage after bonding, thereby improving the display yield of the diffractive optical waveguide.

[0049] In some embodiments, the cover layer 110 is provided with a first alignment mark, and the first optical waveguide layer 130 is provided with a second alignment mark. The step of bonding the first optical waveguide layer 130 with the grating 131 to the cover layer 110 via the pre-curing layer 120b may include: identifying the positions of the first alignment mark and the second alignment mark using an image acquisition module, and obtaining the positional deviation between the second alignment mark and the first alignment mark; compensating for the relative position of the first optical waveguide layer 130 and the cover layer 110 based on the positional deviation until the second alignment mark coincides with the first alignment mark. By using the image acquisition module to identify the first alignment mark and the second alignment mark, the positions of the first optical waveguide layer 130 and the cover layer 110 can be accurately calibrated, ensuring the alignment accuracy of the bonding between the first optical waveguide layer 130 and the cover layer 110.

[0050] In step S160, the pre-cured layer 120b is cured, so that the pre-cured layer 120b is transformed into a solid adhesive layer 120c and the first optical waveguide layer 130 is bonded to the cover layer 110. Figure 6 This is a schematic diagram of a structure in one embodiment of the method for fabricating a diffractive optical waveguide of the present invention, in which a pre-cured layer 120b is cured, so that the pre-cured layer 120b is transformed into a solid adhesive layer 120c and the first optical waveguide layer 130 is bonded to the cover layer 110.

[0051] In one example, a UV-sensitive liquid adhesive layer 120a is used. Correspondingly, the step of curing the pre-cured layer 120b specifically involves: degassing the bonded diffractive waveguide (i.e., the assembly obtained by bonding the first waveguide layer 130 to the cover layer 110 via the pre-cured layer 120b) under high temperature and high pressure, followed by exposure to UV light, causing the pre-cured layer 120b to transform into a solid adhesive layer 120c, thereby curing the liquid adhesive between the first waveguide layer 130 and the cover layer 110. This treatment increases the bonding strength between the first waveguide layer 130 and the cover layer 110, and increases the stability of the diffractive waveguide and lens assembly.

[0052] In some embodiments, in step S160, where the first optical waveguide layer 130 with grating 131 is bonded to the cover layer 110 via the pre-cured layer 120b, the bonding pressure and bonding time are controlled so that the thickness variation of the pre-cured layer 120b is within 200 nm.

[0053] According to the fabrication method of the diffractive waveguide according to the embodiments of this application and the diffractive waveguide obtained by the fabrication method, the solid adhesive layer 120c fully adheres the first waveguide layer 130 and the cover layer 110 together. The solid adhesive layer 120c fills most of the area between the first waveguide layer 130 and the cover layer 110, eliminating most of the gaps between them. Therefore, even when the diffractive waveguide is subjected to external force, the relative deformation between the first waveguide layer 130 and the cover layer 110 is small due to the filling effect of the solid adhesive layer 120c, thereby improving the stability and reliability of the display effect after the diffractive waveguide transmits signal light. During the fabrication process of the diffractive waveguide, the pre-cured layer 120b obtained by the transformation is patterned by pre-curing the liquid adhesive layer 120a. By patterning the pre-cured layer 120b, a groove 121 can be formed on the surface of the pre-cured layer 120b away from the cover layer 110. After the first optical waveguide layer 130 is bonded to the cover layer 110, the groove 121 corresponds to the position of the grating 131 on the first optical waveguide layer 130. The groove 121 makes a gap between the grating 131 and the pre-cured layer 120b or between the grating 131 and the surface of the solid adhesive layer 120c. In this way, during the fabrication of the diffractive waveguide, the adhesive layer (pre-cured layer 120b or solid adhesive layer 120c) will not penetrate into the grating 131 on the first optical waveguide layer 130, thus avoiding the influence of the adhesive layer penetrating into the grating 131 and ensuring that the duty cycle of the grating 131 remains consistent with the design value. Since the pre-cured layer 120b does not penetrate into the grating 131, the refractive index of the liquid adhesive layer 120a is no longer restricted when selecting materials, thus reducing the material requirements for the liquid adhesive layer 120a.

[0054] This application also provides a diffractive optical waveguide, such as... Figure 7 or Figure 8 or Figure 9 The diffractive waveguide 100 includes a capping layer 110, a first waveguide layer 130, and an adhesive layer 120x. The capping layer 110 has a first surface S1. The first waveguide layer 130 has a second surface S2, and a grating 131 is provided on the second surface S2. The first waveguide layer 130 is bonded to the capping layer 110 via the adhesive layer 120x, with the second surface S2 facing the first surface S1. The adhesive layer 120x is disposed between the first waveguide layer 130 and the capping layer 110 or on the outer peripheral surface of the area where the first waveguide layer 130 and the capping layer 110 meet. The adhesive layer 120x is used to bond the first waveguide layer 130 and the capping layer 110 in a vacuum environment and to eliminate air in the bonding surface between the first waveguide layer 130 and the capping layer 110.

[0055] like Figure 7 In some embodiments, an adhesive layer 120x is disposed between the first optical waveguide layer 130 and the cover layer 110. The adhesive layer 120x has a groove 121 on its surface facing away from the cover layer 110, and a grating 131 corresponds to the groove 121, creating a gap between the grating 131 and the surface of the adhesive layer 120x. In some embodiments, the depth of the groove 121 is less than 200 nm. Simultaneously, the diffractive waveguide assembly is designed to achieve tight bonding by mechanically pressing the first optical waveguide layer 130 and the cover layer 110 together in a vacuum environment (vacuum degree < 30 Pa). This eliminates air in the gaps of the grating 131, improves the adhesion and optical performance between the first optical waveguide layer 130 and the cover layer 110, reduces warping after bonding, and improves the display yield of the diffractive waveguide.

[0056] This application also provides a diffractive optical waveguide. Figure 7 This is a schematic diagram of a diffractive waveguide according to an embodiment of the present invention. The diffractive waveguide 100 includes a capping layer 110, a first waveguide layer 130, and an adhesive layer 120x. The capping layer 110 has a first surface S1. The first waveguide layer 130 has a second surface S2. The first waveguide layer 130 has a grating 131 on the second surface S2. The first waveguide layer 130 is bonded to the capping layer 110 via the adhesive layer 120x. The second surface S2 is disposed facing the first surface S1. The surface of the adhesive layer 120x facing away from the capping layer 110 has a groove 121, and the grating 131 is positioned corresponding to the groove 121, such that there is a gap between the grating 131 and the surface of the adhesive layer 120x. In this embodiment, the adhesive layer 120x is a solid adhesive layer, obtained by curing a liquid adhesive layer.

[0057] According to the diffractive waveguide 100 of this application embodiment, the adhesive layer 120x fully bonds the first waveguide layer 130 and the cover layer 110 together. The adhesive layer 120x fills most of the area between the first waveguide layer 130 and the cover layer 110, eliminating most of the gaps between them. Therefore, even when the diffractive waveguide 100 is subjected to external force, the relative deformation between the first waveguide layer 130 and the cover layer 110 is small due to the filling effect of the adhesive layer 120x, thereby improving the stability and reliability of the display effect after the diffractive waveguide 100 transmits signal light. A gap exists between the grating 131 and the surface of the adhesive layer 120x. This prevents the adhesive layer used to form the adhesive layer 120x from penetrating into the grating 131 on the first waveguide layer 130 during the fabrication of the diffractive waveguide 100. This avoids the adhesive layer penetrating into the grating 131 and affecting it, ensuring that the duty cycle of the grating 131 remains consistent with the design value. Since the adhesive layer does not penetrate into the grating 131, the refractive index of the adhesive layer is no longer restricted, reducing the material requirements for the adhesive layer.

[0058] In some embodiments, the depth of the groove 121 is 0 to 200 nm, that is, the depth of the groove 121 is less than 200 nm. In the above embodiments, the groove 121 creates a gap between the grating 131 and the pre-cured layer 120b, or between the grating 131 and the surface of the adhesive layer 120x. This gap is equivalent to a thin gap space maintained between the grating 131 and the surface of the adhesive layer 120x. According to the Newton's rings formation conditions, when the gap space thickness d < λ / 2 ≈ 200 nm (where λ is the minimum wavelength of visible light, λ ≈ 400 nm), the alternating light and dark Newton's rings cannot be seen visually. Since the depth of the groove 121 is less than 200 nm, it ensures that the adhesive layer does not penetrate into the grating 131, while also preventing the formation of Newton's rings.

[0059] like Figure 8 In some other embodiments, the adhesive layer 120x is disposed on the outer peripheral edge of the area where the first optical waveguide layer 130 and the cover layer 110 meet. The adhesive layer 120x is used to bond the first optical waveguide layer 130 and the cover layer 110 in a vacuum environment and to eliminate air in the bonding surface of the first optical waveguide layer 130 and the cover layer 110.

[0060] Specifically, the diffractive waveguide 100 includes a capping layer 110, a first waveguide layer 130, and an adhesive layer 120x. The capping layer 110 has a first surface S1. The first waveguide layer 130 has a second surface S2, and a grating 131 is provided on the second surface S2. The first waveguide layer 130 is bonded to the capping layer 110 via the adhesive layer 120x. The second surface S2 is disposed facing the first surface S1. The adhesive layer 120x is disposed at the outer peripheral edge of the area where the first waveguide layer 130 and the capping layer 110 meet. The adhesive layer 120x is used to bond the first waveguide layer 130 and the capping layer 110 in a vacuum environment and to eliminate air in the bonding surface between the first waveguide layer 130 and the capping layer 110.

[0061] In another embodiment described above, no adhesive layer 120x is provided or filled between the first optical waveguide layer 130 and the cover layer 110, and the first optical waveguide layer 130 and the cover layer 110 can be directly bonded together in a vacuum environment.

[0062] Specifically, under high vacuum conditions (vacuum degree < 30 Pa), the first optical waveguide layer 130 and the cover layer 110 are directly bonded together without using adhesive on the bonding surface. This ensures tight contact between the first optical waveguide layer 130 and the cover layer 110, while also preventing the location of the grating 131 from being filled with adhesive, thus not affecting the optical properties. After bonding, an adhesive layer 120x is used to bond the perimeter of the bonded component under vacuum conditions to ensure that no gas permeates between the first optical waveguide layer 130 and the cover layer 110.

[0063] The fabrication process of the diffractive waveguide in the above embodiments may further include a bonding step, an adhesive coating step, and a curing step.

[0064] In the bonding step: Under high vacuum conditions (vacuum degree < 30 Pa), the first optical waveguide layer 130 and the cover layer 110 are bonded together by mechanical pressure. After bonding, the first optical waveguide layer 130 and the cover layer 110 are tightly bonded under atmospheric pressure to obtain a diffractive optical waveguide assembly. The bonding environment is a high vacuum environment, such as a high vacuum environment less than -10 Pa, where the bonding surfaces of the first optical waveguide layer 130 and the cover layer 110 have low surface roughness.

[0065] In the adhesive application step: After the lens assembly is bonded together, the outer periphery of the area where the first optical waveguide layer 130 and the cover layer 110 meet is sealed in a vacuum environment using an adhesive layer 120X formed by liquid adhesive to ensure that air does not seep into the space between the first optical waveguide layer 130 and the cover layer 110, thereby preventing the lens assembly from cracking.

[0066] In the curing step: the liquid adhesive coating on the lens assembly is cured by UV and / or heating to obtain an adhesive layer 120x disposed on the outer peripheral edge of the area where the first optical waveguide layer 130 and the cover layer 110 meet, thereby increasing the reliability of the diffractive waveguide and the lens assembly.

[0067] like Figure 9 In some other embodiments, the adhesive layer 120x is disposed on the outer peripheral edge and outer peripheral side region of the area where the first optical waveguide layer 130 and the cover layer 110 meet. The adhesive layer 120x is used to bond the first optical waveguide layer 130 and the cover layer 110 in a vacuum environment and to eliminate air in the bonding surface of the first optical waveguide layer 130 and the cover layer 110.

[0068] According to the diffractive waveguide 100 of this application embodiment, the adhesive layer 120x fully adheres and bonds the first waveguide layer 130 to the cover layer 110. Therefore, when the diffractive waveguide 100 is subjected to external force, the relative deformation between the first waveguide layer 130 and the cover layer 110 is small, thereby improving the stability and reliability of the display effect after the diffractive waveguide 100 transmits signal light.

[0069] In the above embodiments, the cover layer 110 is a protective layer. The protective layer can be made of resin, glass, or silicon wafers, etc.

[0070] In the above embodiments, the cover layer 110 is a second optical waveguide layer, that is, the diffractive optical waveguide may include two or more optical waveguide layers, and the cover layer 110 is another optical waveguide layer that is different from the first optical waveguide layer 130.

[0071] In the above embodiment, the cover layer 110 is provided with a first alignment mark, and the first optical waveguide layer 130 is provided with a second alignment mark corresponding to the first alignment mark. When the first optical waveguide layer 130 and the cover layer 110 are bonded together, the positions of the first alignment mark and the second alignment mark are identified by an image acquisition module, and the positional deviation between the second alignment mark and the first alignment mark is obtained. Based on the positional deviation, the relative position of the first optical waveguide layer 130 and the cover layer 110 is compensated until the second alignment mark coincides with the first alignment mark. By using the image acquisition module to identify the first alignment mark and the second alignment mark, the position of the first optical waveguide layer 130 and the cover layer 110 can be accurately calibrated, ensuring the alignment accuracy of the bonding between the first optical waveguide layer 130 and the cover layer 110.

[0072] This application also provides a diffractive optical waveguide. Figure 9This is a schematic diagram of another embodiment of the diffractive waveguide of the present invention. The diffractive waveguide 100 includes a capping layer 110, a first waveguide layer 130, and an adhesive layer 120x. The capping layer 110 has a first surface S1. The first waveguide layer 130 has a second surface S2, and a grating 131 is provided on the second surface S2. The first waveguide layer 130 is bonded to the capping layer 110 by the adhesive layer 120x. The second surface S2 is disposed facing the first surface S1. The adhesive layer 120x is disposed at the outer peripheral edge of the area where the first waveguide layer 130 and the capping layer 110 meet. The adhesive layer 120x is used to bond the first waveguide layer 130 and the capping layer 110 in a vacuum environment and to eliminate air in the bonding surface of the first waveguide layer 130 and the capping layer 110.

[0073] like Figure 9 In this embodiment, the adhesive layer 120x is disposed on the outer peripheral edge and outer peripheral side region of the area where the first optical waveguide layer 130 and the cover layer 110 meet. In some embodiments, the outer contour shape and size of the first optical waveguide layer 130 and the cover layer 110 are the same, and the adhesive layer 120x is disposed on the outer peripheral edge and outer peripheral side region of the area where the first optical waveguide layer 130 and the cover layer 110 meet, which can further improve the sealing performance between the first optical waveguide layer 130 and the cover layer 110 and improve the bonding strength of the obtained lens assembly.

[0074] This application also provides a near-eye display device. Figure 10 This is a cross-sectional structural schematic diagram of an embodiment of the near-eye display device of the present invention. The near-eye display device includes an optomechanical system 200 and a diffractive waveguide 100 of any of the aforementioned embodiments. The optomechanical system 200 is used to emit signal light. The diffractive waveguide 100 is used to transmit signal light.

[0075] In one example, the diffractive waveguide 100 includes a capping layer 110, a first waveguide layer 130, and an adhesive layer 120x. The capping layer 110 has a first surface S1. The first waveguide layer 130 has a second surface S2. A grating 131 is formed on the second surface S2 of the first waveguide. The first waveguide layer 130 is bonded to and adhered to the capping layer 110 via the adhesive layer 120x. The second surface S2 is disposed facing the first surface S1. The surface of the adhesive layer 120x facing away from the capping layer 110 has a groove 121, and the grating 131 is positioned corresponding to the groove 121, such that there is a gap between the grating 131 and the surface of the adhesive layer 120x.

[0076] Near-eye display devices are, for example, augmented reality (AR) glasses or part of AR glasses.

[0077] According to an embodiment of this application, a near-eye display device includes a diffractive waveguide 100, wherein an adhesive layer 120x fully adheres and bonds a first waveguide layer 130 to a cover layer 110. Therefore, when the diffractive waveguide 100 is subjected to external force, the relative deformation between the first waveguide layer 130 and the cover layer 110 is small, thereby improving the stability and reliability of the display effect after the diffractive waveguide 100 transmits signal light.

[0078] According to the near-eye display device of the above example, the adhesive layer 120x of the diffractive waveguide 100 fully bonds the first waveguide layer 130 and the cover layer 110 together. The adhesive layer 120x fills most of the area between the first waveguide layer 130 and the cover layer 110, eliminating most of the gap between them. Therefore, even when the diffractive waveguide 100 is subjected to external force, the relative deformation between the first waveguide layer 130 and the cover layer 110 is small due to the filling effect of the adhesive layer 120x, thereby improving the stability and reliability of the display effect after the diffractive waveguide 100 transmits signal light. A gap exists between the grating 131 and the surface of the adhesive layer 120x. This prevents the adhesive layer used to form the adhesive layer 120x from penetrating into the grating 131 on the first waveguide layer 130 during the fabrication of the diffractive waveguide 100, thus avoiding any impact on the grating 131 due to adhesive penetration. Since the adhesive layer does not penetrate into the grating 131, the refractive index of the adhesive layer is no longer restricted, reducing the material requirements for the adhesive layer.

[0079] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A diffractive optical waveguide, characterized in that, include: A covering layer having a first surface; A first optical waveguide layer has a second surface, and the first optical waveguide layer has a grating on the second surface; An adhesive layer is provided, wherein the first optical waveguide layer is bonded and adhered to the cover layer through the adhesive layer, the second surface is disposed facing the first surface, the adhesive layer is disposed between the first optical waveguide layer and the cover layer, the surface of the adhesive layer away from the cover layer has a groove, the grating is positioned corresponding to the groove, so that there is a gap between the grating and the surface of the adhesive layer.

2. The diffractive waveguide as described in claim 1, characterized in that, The depth of the groove is 0 to 200 nm.

3. The diffractive waveguide as described in claim 1, characterized in that, The covering layer is a second optical waveguide layer.

4. The diffractive waveguide as described in claim 1, characterized in that, The cover layer is provided with a first alignment mark, and the first optical waveguide layer is provided with a second alignment mark corresponding to the first alignment mark.

5. A diffractive optical waveguide, characterized in that, include: A covering layer having a first surface; A first optical waveguide layer has a second surface, and the first optical waveguide layer has a grating on the second surface; An adhesive layer is provided, wherein the first optical waveguide layer is bonded to the cover layer through the adhesive layer, the second surface is disposed facing the first surface, and the adhesive layer is disposed at the outer peripheral edge of the area where the first optical waveguide layer and the cover layer meet. The adhesive layer is used to bond the first optical waveguide layer and the cover layer in a vacuum environment and to eliminate air in the bonding surface of the first optical waveguide layer and the cover layer.

6. The diffractive waveguide as described in claim 5, characterized in that, The adhesive layer is disposed on the outer peripheral edge and outer peripheral side region of the area where the first optical waveguide layer and the cover layer meet.

7. A near-eye display device, characterized in that, include: Optical engines are used to transmit signal light; as well as The diffractive waveguide as described in any one of claims 1 to 6 is used to transmit the signal light.

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