Method for coating optical reflecting layer on waveguide and screen printing device

Abstract

A method (500) for coating an optically reflective layer on a waveguide having an in-coupler grating, the method comprising:-depositing (502) an ink on the in-coupler grating of the waveguide by screen printing.

Description

Technical Field

[0001] Embodiments described herein relate to methods for coating an optically reflective layer on a waveguide having an optical grating within a coupler and to screen printing devices for use therein. Embodiments described herein further relate to a waveguide having an optical grating within a coupler and to a lens comprising an optical waveguide. Background Art

[0002] Virtual reality is generally considered to be a computer-generated simulated environment that a user has their perception / experience. The virtual reality experience can be generated in 3D and viewed through a head-mounted display (HMD), such as glasses or other wearable display devices with near-eye display panels acting as lenses to display the experienced virtual reality environment rather than the actual environment.

[0003] Augmented reality (AR) enables an experience in which the user still sees their surroundings through the display lenses of glasses or other HMDs, but also sees images of virtual objects generated for display and appearing to be superimposed on the environment. AR can include any type of input, such as audio and tactile input, as well as virtual images, graphics, and video of the environment that enhance or augment the user's experience. As an emerging technology, AR presents many challenges and design constraints.

[0004] To allow computer-generated virtual images to be combined with real-world images of an environment to provide an augmented reality experience, an optical combiner may be used. Such an optical combiner may include a waveguide comprising a substrate having a plurality of optical structures formed thereon.

[0005] An optical combiner may involve the use of a lens with a waveguide, specifically, a waveguide with input and / or output couplers, and configured such that, for example, light from a computer-generated image incident on the input coupler is transmitted through the waveguide to, for example, the output coupler, where the light is then ultimately directed toward the eyes of a human user to be superimposed with light from the physical world that has passed through the lens.

[0006] The efficiency of the input coupler is related to the efficiency of the optical combiner and / or the quality of the superimposed image. Therefore, there is a need for improved input couplers and / or waveguides and lenses for augmented reality for virtual reality applications. Summary of the Invention

[0007] The present invention is defined by the independent clauses. The dependent clauses define further embodiments of the present invention.

[0008] According to one aspect, the present disclosure discloses a method for coating an optical reflective layer on a waveguide having a grating within a coupler, the method comprising:

[0009] - Ink is deposited on the grating inside the coupler of the waveguide by screen printing.

[0010] The present disclosure further discloses a waveguide having an intra-coupler grating, wherein the intra-coupler grating has a particle-free optical reflective layer produced by depositing and sintering a particle-free ink adhered to the intra-coupler grating, wherein the optical reflective layer of the intra-coupler grating adhered to the waveguide is obtained by the method of the present disclosure.

[0011] The present disclosure further discloses a lens including the optical waveguide of the present disclosure, which has a length from 40 mm to 80 mm and a width from 20 mm to 60 mm.

[0012] According to another aspect, the present disclosure discloses a screen printing apparatus comprising:

[0013] - Waveguide loading and unloading system;

[0014] a transport system configured to transport the waveguides loaded by the loading and unloading system;

[0015] - one or more alignment systems and one or more actuators configured to align and move the waveguide transported by the transport system; and

[0016] - one or more screen printing heads, each comprising a screen, one or more squeegees and one or more flood plates, configured to apply ink on the waveguide aligned and moved by one or more alignment systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A Detail of a top view of a lens including a waveguide according to an embodiment of the present disclosure is shown.

[0018] Figure 1B Detail of a side view of a waveguide according to an embodiment of the present disclosure is shown.

[0019] Figure 1C Propagation of light within and / or through a waveguide is shown in accordance with an embodiment of the present disclosure.

[0020] Figure 2A Shown is a side view of a waveguide having a grating within a coupler with an optically reflective layer, in accordance with an embodiment of the present disclosure.

[0021] Figure 2B A side view of a waveguide having a grating within a coupler with an optically reflective layer is shown, and further illustrates the presence of a protective coating, in accordance with an embodiment of the present disclosure.

[0022] Figure 2CDetail of a grating within a coupler of a waveguide according to an embodiment of the present disclosure is shown.

[0023] Figure 2D Shown is a detail of a reflective layer on a grating within a coupler of a waveguide according to an embodiment of the present disclosure.

[0024] Figure 3A A screen-printed protective mask having a negative pattern of a grating within a coupler is shown, according to an embodiment of the present disclosure.

[0025] Figure 3B A screen-printed protective mask having a negative pattern of a grating in a coupler according to an embodiment of the present disclosure is shown, and an optical reflective layer on a waveguide having a grating in a coupler according to an embodiment of the present disclosure is further shown.

[0026] Figure 3C and Figure 3D An optically reflective layer on a waveguide with a grating within a coupler is shown according to an embodiment of the present disclosure.

[0027] Figure 4A and Figure 4B A screen printing apparatus according to an embodiment of the present disclosure is shown.

[0028] Figure 5 According to the present disclosure, a method for coating an optically reflective layer on a waveguide having a grating within a coupler is described.

[0029] Figure 6 A waveguide stack comprising several waveguides according to the present disclosure is shown. DETAILED DESCRIPTION

[0030] In the following description, unless otherwise specified, the conjunction "or" is not intended to be an exclusive or (xor). Thus, the word "or" and the word "and / or" are intended to define the same conjunction, specifically, one that evaluates to true if both operands are true.

[0031] The embodiments described herein relate to optical devices. A device may be considered an optical device if its optical properties are relevant to a method or apparatus for using the device. At least a portion of an optical device may be made of a transparent material, such as glass or plastic. Some optical devices may be configured to change the properties of light, such as the direction of propagation. For example, an optical device may include an optical structure for changing the direction of propagation of light. Other optical devices may be unstructured and allow light to pass through them substantially unchanged. An optical device as described herein may be an optical device for use in augmented reality applications. An optical device may also be referred to as an optical element. Examples of optical devices include waveguides and transparent cover elements, such as cover glass, as described herein.

[0032] An optical device (such as a waveguide or a transparent cover element) as described herein can be a thin sheet of material. The optical device can be a plate-like element, including a plate-like element having a flat surface or a plate-like element having a curved surface. The optical device can have a first major surface and a second major surface opposite the first major surface. The optical device can be a substantially two-dimensional device, wherein the thickness of the optical device between the first major surface and the second major surface can be much smaller (e.g., 1% or less) than a dimension (such as a length or width) of the first major surface or the second major surface.

[0033] Figure 1A Detail of a top view of a lens 100 including a waveguide 10 is shown in accordance with an embodiment of the present disclosure.

[0034] The waveguide 10 may include and / or be formed from a substrate 102, which may be a thin sheet of transparent material such as glass or plastic. The waveguide 10 may include an input coupler grating 104 defined by a grating structure that may be disposed on the substrate 102. The waveguide 10 may include an output coupling region defined by an outer coupler grating 108 that may be disposed on the substrate 102. Light (particularly, light corresponding to a virtual, computer-generated image) may be coupled into the waveguide 10 at the input coupling region formed by the inner coupler grating 104. The light may propagate through the waveguide 10 until it reaches the outer coupler grating 108.

[0035] At the coupler outer grating 108, light can exit the waveguide 10. Furthermore, also at the outcoupling region formed by the coupler outer grating 108, light from the external real-world environment can be transmitted through the waveguide 10, allowing the user to see a combination of virtual and real-world images. The waveguide 10 can be a waveguide combiner for providing an augmented reality experience to the user.

[0036] In augmented reality and / or virtual reality devices, images, typically computer-generated, are presented to the eyes of a human user, who perceives the images as superimposed on and / or replacing the physical environment around the user.

[0037] For example, a lens including a waveguide can be used to combine computer-generated imagery with light from a physical environment so that a user effectively sees a superposition of the physical environment and the computer-generated imagery.

[0038] A computer-generated image can include any type of data. For example, a computer-generated image can include images recorded at different locations and / or times. For example, a computer-generated image can display data processed by a computer and / or transmitted via a communication network and / or a cloud computing system and / or via a network and / or the Internet.

[0039] Computer-generated images may include any type of transmission of data / information perceptible to the human eye, including data encoded / presented as text and / or numbers.

[0040] The computer-generated imagery can be updated in real time, allowing the user to experience a sequence of computer-generated imagery that can be part of a video that the user can experience in a virtual reality or superimposed on their surrounding real-world perception.

[0041] Computer-generated images, either as still images or included in a video, may be produced by any suitable projection system or lighting system configured to display images and / or video.

[0042] When the image enters the eyes of a human user located in a physical environment, the image is then combined / superimposed with the light from the physical environment, or replaces the light of the physical environment, and the human user then experiences the resulting augmented reality or virtual reality, respectively.

[0043] This combination can be done using a lens with a waveguide.

[0044] The lens 100 may comprise further waveguides, in particular further waveguides for different wavelengths or wavelength ranges. For example, the lens 100 may comprise three waveguides 10 for each color range of an additive color model, such as an RGB color model (Red Green Blue color model).

[0045] The waveguide 10 has a grating 104 within the coupler.

[0046] An exit pupil expander 106 may optionally be included in the waveguide 10 .

[0047] The grating 104 in the coupler receives a light beam, such as a light beam emitted by a projector or any light emitting device for projecting computer generated images, such as light beams of a color channel such as, for example, the RGB color channels.

[0048] The light beam received by the coupler inner grating 104 is then transferred within the waveguide 10 toward the coupler outer grating 108. The light beam travels as light within the waveguide 10, from the coupler inner grating 104 to the coupler outer grating 108. The waveguide 10 can be configured using an exit pupil expander 106 to create an appropriate eyebox area so that the coupler outer grating 108 provides an output light beam that is perceived as focused and sharp by a human user. The function of the eye pupil expander is to spread and expand the size of the light beam to match the output coupler.

[0049] Figure 1B Detail of a side view of a waveguide according to an embodiment of the present disclosure is shown. In particular, Figure 1B A coupler inner grating 104 and a coupler outer grating 108 disposed on a substrate 102 of the waveguide 10 are shown.

[0050] Figure 1C The propagation of light within and / or through the waveguide 10 is shown in accordance with an embodiment of the present disclosure.

[0051] Incident light 120 , typically from a projector or light emitting device (not shown), reaches the grating 104 within the coupler of the waveguide 10 of the lens 100 .

[0052] The incident light 120 is then at least partially reflected by the coupler inner grating 104 of the waveguide 10 and propagates within the waveguide 10 and / or within the exit pupil expander 106 and / or the substrate 102 as propagated light 122. The propagated light 122 then reaches the coupler outer grating 108, which produces an output light beam 124 that typically reaches a human user's eye 130. Alternatively, an animal eye or a video camera may replace the human eye 130.

[0053] In the case of augmented reality applications, another external light beam 126 originating from an external physical environment 132 can also pass through the waveguide 10 in the lens 100, allowing for appropriate combination / superposition of the output light beam 124 and the external light beam 126. In this way, the computer-generated image projected as the incident light 120 is combined with the perception of the physical environment 132, and the user's human eye 130 experiences a visual superposition of the physical environment 132 and the computer-generated image.

[0054] To achieve virtual reality applications, external light beams 126 originating from the physical environment 132 may be blocked so that the user only experiences computer-generated images transmitted by the incident light 120 .

[0055] A properly arranged lens 100 including one or more waveguides 10 can produce smooth color and / or 3D vision for augmented reality and / or virtual reality applications.

[0056] To improve the vision experienced by the user's eye 130 , it is beneficial to maximize the reflection of the incident light 120 at the grating 104 within the coupler to maximize the propagating light 122 .

[0057] The present disclosure provides improved incoupling of incident light 120 into the waveguide 10 .

[0058] Figure 2A A side view of a waveguide 10 having an intra-coupler grating 104 with an optically reflective layer 202 is shown, in accordance with an embodiment of the present disclosure.

[0059] In the present disclosure, an optically reflective layer 202 is coated on the waveguide 10 having the grating 104 within the coupler. According to the method of the present disclosure, ink is deposited on the grating 104 within the coupler of the waveguide 10 by screen printing. The ink can be a particle-free ink. The ink can be a silver ink. The ink can then be treated (e.g., heat treatment, sintering process, or UV curing) to obtain the optically reflective layer 202. The optically reflective layer 202 can be obtained specifically on the grating 104 within the coupler to improve the reflection of the incident light 120 into the waveguide 10, thereby improving or maximizing the propagation of light 122 within the waveguide 10.

[0060] The present disclosure addresses the problem of coating an optically reflective layer in atmosphere on a nanostructure formed by a grating within a coupler.

[0061] The optically reflective layer 202 improves the incoupling of the incident light 120 into the waveguide 10 , thereby improving the propagating light 122 to obtain an improved image presented to the human eye 130 .

[0062] Without the optical reflective layer 202, the first-order diffraction percentage (i.e., light collected in the waveguide for total internal reflection) inside the coupler is, for example, approximately 10%, and similarly, the light collected from the waveguide outside the coupler is, for example, approximately 10%, with an overall efficiency (input to output) of 1%. Adding the reflective layer 202 inside the coupler makes it possible to increase this to, for example, 50%, with an overall coupling efficiency of 5%.

[0063] The present disclosure relates to methods for coating, for example, nanostructures formed from glass, high refractive index surfaces, or a combination of both (e.g., glass or SiC substrates coated with nanostructured metal oxides), such as gratings within a coupler of a waveguide. In some embodiments, the waveguide 10 is comprised of or includes a glass substrate or a substrate having a refractive index greater than 1.8.

[0064] Embodiments of the present disclosure relate to specialty materials that are nanostructured and optically reflective and adhere to a substrate.

[0065] Figure 2B A side view of a waveguide 10 having an intra-coupler grating 104 with an optically reflective layer 202 is shown, in accordance with an embodiment of the present disclosure, and further depicts the presence of a protective coating 210 in accordance with an embodiment of the present disclosure.

[0066] In some embodiments, the material forming the optical reflective layer 202 is obtained from ink (specifically, a particle-free ink) and deposited by screen printing on top of the grating 104 structure within the lens / waveguide coupler. The optical reflective layer can then be protected by a resist to prevent oxidation and tarnishing effects.

[0067] The optically reflective layer 202 may be obtained by ink deposition via an additive process based on screen printing.

[0068] In some embodiments, the protective coating 210 is applied over the optically reflective layer 202, for example, over the ink, after the ink has been processed, for example, by a heat treatment or sintering process or UV curing.

[0069] The problem addressed by the present disclosure is to deposit a material that, when processed, acts as an optical mirror in the visible wavelength range, which material forms an optically reflective layer 202. A substrate is processed to obtain the optically reflective layer 202. The substrate may consist of a waveguide 10 with a grating 104 in a coupler.

[0070] The present disclosure addresses the problem of coating nanostructures on substrates using additive or subtractive deposition methods in atmosphere. A pattern is deposited on top of a grating within a coupler. The pattern can involve the use of a particle-free ink, specifically a particle-free Ag ink (silver ink). The pattern forms an optically reflective layer 202. The pattern / optically reflective layer 202 is deposited on top of the grating 104 within the coupler to improve coupling efficiency due to the high optical reflectivity of the treated material.

[0071] The particle-free silver ink can achieve a higher reflectivity than deposited aluminum, thereby providing an improved optical reflective layer 202 on the grating 104 within the coupler of the waveguide, thereby improving the reflection of the incident light 120 and providing better incoupling into the waveguide 10.

[0072] The present disclosure further overcomes limitations in depositing aluminum, particularly limitations related to expensive and slow masking and sputtering or physical vapor deposition of aluminum.

[0073] The objects of the present disclosure may be combined with other processes to, for example, define circuits.

[0074] The optically reflective layer 202 provides an optical reflector obtained, for example, by screen printing with a particle-free ink.

[0075] The substrate to be processed (e.g., the waveguide 10 with the grating 104 in the coupler) may be, for example:

[0076] a glass substrate having a refractive index (RI) greater than 1.45 (RI>1.45), with a flat coating or a nanostructured coating forming, for example, the substrate 102 and / or the grating 104 in the coupler,

[0077] - a high refractive index substrate (RI>1.8) with a flat coating or nanostructured coating forming, for example, the substrate 102 and / or the grating 104 within the coupler, or

[0078] - A plastic substrate with a planar coating or a nanostructured coating forming, for example, the substrate 102 and / or the grating 104 within the coupler.

[0079] Screen printing can be performed on:

[0080] - a circular wafer of 150 mm to 300 mm and 0.3 mm to 0.8 mm thickness, comprising a plurality of waveguides 10, or

[0081] - A single waveguide / lens (after the wafer has been diced) with typical dimensions of 40-80 mm length by 20-60 mm width.

[0082] The deposition material used to form the optical reflective layer 202 may be:

[0083] - particle-free ink, or

[0084] -Metallic particle ink.

[0085] The wafer may be a glass substrate in which one or more waveguides are present, eg, a plurality of waveguides that have not yet been cut / singulated.

[0086] Figure 2C Detail of the grating 104 within the coupler of the waveguide 10 is shown in accordance with an embodiment of the present disclosure.

[0087] For example, the coupler inner grating 104 may be formed by a set of gratings having the shape of tilted fins placed on the substrate 102 (e.g., Figure 2C ) and / or any other suitable shape to implement the in-coupling functionality into the substrate 102 of the waveguide.

[0088] like Figure 2C The grating shown can be the grating structure of the coupler inner grating 104 or the grating structure of the coupler outer grating 108, and can be used to provide the input coupling region or the output coupling region of the waveguide 10, respectively. The grating structure can be formed on the main surface of the substrate 102. The grating structure can include multiple optical structures. The optical structures can be configured to change the propagation direction of light incident on the grating structure. The optical structures can have dimensions in the submicron or even nanometer range, such as width and / or height. The optical structures can be arranged adjacent to each other with gaps between them. The optical structures can be shaped as, for example, tilted fins.

[0089] This disclosure is not limited to Figures 1A to 2D For example, a waveguide may have more than two grating structures (e.g., a waveguide may have one or more intermediate regions defined by additional grating structures), and the arrangement and shape of the optical structures may be different from Figure 2C In the example shown, the waveguide may be provided with grating structures on both sides of the waveguide, and so on.

[0090] The waveguide 10 described herein may include a substrate 102. The waveguide may include a plurality of optical structures formed on the substrate. The optical structures may have submicron dimensions, for example, nanometer dimensions. The plurality of optical structures may form one or more grating structures on the substrate. The waveguide may be a waveguide combiner. The waveguide combiner may be configured to combine virtual computer-generated images with real-world images of a surrounding environment. The waveguide may be an augmented reality waveguide combiner.

[0091] In optical systems such as augmented reality devices, several waveguides can be stacked on top of each other to form a waveguide stack. For example, each waveguide in the waveguide stack can be configured to manipulate light of a corresponding wavelength range, which is beneficial for providing color images.

[0092] Figure 2D Detail of the optically reflective layer 202 on the grating 104 within the coupler of the waveguide 10 is shown in accordance with an embodiment of the present disclosure.

[0093] The optical reflective layer 202 is formed over and / or between the inclined fins disposed on the substrate 102 of the waveguide 10 , thereby improving reflection of the incident light 120 .

[0094] The deposition method can be any one of the following processes or any combination thereof:

[0095] - additive processes based on screen printing, inkjet, dispensing, aerosol using conformal patterns to obtain the optically reflective layer 202 by screen printing,

[0096] - subtractive processes based on a protective mask with a negative pattern of the mirror / grating inside the coupler, combined with screen printing, inkjet, dispensing, aerosol or spin coating,

[0097] - the protective mask may be a screen-printed protective mask and / or may be a water-soluble polymer material deposited by inkjet with a thickness of 2 to 5 μm and a resolution of 10 to 20 μm, or

[0098] - A combination of the aforementioned methods.

[0099] Figure 3A A screen-printed protective mask 302 is shown having a negative pattern of the grating 104 within the coupler, in accordance with an embodiment of the present disclosure.

[0100] Figure 3BA screen-printed protective mask 302 having a negative pattern of the grating 104 within the coupler according to an embodiment of the present disclosure is shown, and further an optical reflective layer 202 on the waveguide 10 having the grating 104 within the coupler according to an embodiment of the present disclosure is shown.

[0101] The reflective layer 202 can be obtained by screen printing.

[0102] Figure 3C and Figure 3D An optically reflective layer 202 is shown on a waveguide with a grating within a coupler according to an embodiment of the present disclosure. The optically reflective layer 202 may be obtained after removing the screen-printed protective mask 302, or after removing a water-soluble polymer material deposited by inkjet to form an alternative protective mask.

[0103] The method of alignment of the screen can be based, for example, on:

[0104] - fiducial marks on the wafer or single waveguide,

[0105] - the edge of the wafer (notch) or single waveguide,

[0106] - patterned nanostructures on a wafer or a single waveguide, or

[0107] - A combination of the above methods.

[0108] The treatments applied to the deposited material may be:

[0109] - thermal treatment, application of conduction, convection, radiation (photon, laser) heating or a combination thereof,

[0110] -UV curing,

[0111] - a two-step process comprising a step of evaporation of the solvent present in the deposited material and a step of realising the optical properties, for example by sintering or curing, or

[0112] - A combination of the above methods.

[0113] The protective coating 210 applied to the material acting as the encapsulant may be deposited by one of the following methods:

[0114] - the protective coating can be deposited by the same method as the optical material or by a different method (e.g., screen printing, inkjet, aerosol, spin coating),

[0115] - the curing method can be the same as the optical material or different (thermal or UV),

[0116] - coatings to protect optical materials from oxidation and / or corrosion, and / or

[0117] -Coatings can improve adhesion and durability of optical materials.

[0118] Printing may be screen printing, for example, silk screen printing.

[0119] In case of screen printing in any of the previously described methods, for example for coating an optically reflective layer on a waveguide with an inner coupler and / or for a protective coating, the screen may be:

[0120] - traditional screens with silk screen and flat emulsion,

[0121] - a stepped screen with a screen and two emulsion layers, where the lower emulsion thickness helps to reduce the effective forces acting on the substrate during the printing process, or

[0122] - Metal stencils with stepped thickness, where the metal thickness of the emulsion helps to reduce the effective forces acting on the substrate during the printing process.

[0123] If the deposited material is conductive when processed, it can be used to create an electrical circuit along the contours of each lens.

[0124] The deposited material can be deposited and processed simultaneously in the mirror area (eg, the lens within the coupler) and in other areas of the lens.

[0125] Figure 4A and Figure 4B A screen printing apparatus 400 according to an embodiment of the present disclosure is shown.

[0126] The screen printing device 400 includes:

[0127] -Waveguide loading and unloading system,

[0128] a transport system configured to transport the waveguides loaded by the loading and unloading system,

[0129] - one or more alignment systems 408 and one or more actuators configured to align and move the waveguide transported by the transport system, and

[0130] One or more screen printing heads 402, each comprising a screen 406, one or more squeegees 404 and / or one or more flood plates, configured to apply ink on the waveguide aligned and moved by one or more alignment systems.

[0131] The screen printing device and in particular the loading and unloading system of the screen printing device can deliver waveguides in glass wafers, for example, about 20 waveguides in a 300 mm wafer, or separate and already cut waveguides that can be arranged in a specific printing chuck through precise alignment and multiple printing processes, or alternatively separate and print one waveguide at a time.

[0132] In some embodiments, the waveguide is a plurality of waveguides in a glass wafer, or a plurality of separate and already cut waveguides arranged in a printing chuck, or a single waveguide.

[0133] A single screen can be used for screen printing on a glass wafer or on multiple waveguides separated and arranged in a print chuck. A conveyor system 410 can bring wafers / lenses / waveguides to and from the transport system for processing. The wafers / lenses / waveguides forming the substrate to be processed can be moved in a direction 420 generally parallel to the movement of the screen 406.

[0134] More specifically, in the case of application by screen printing, the apparatus may, for example, consist of:

[0135] - manual or automatic loading and unloading systems for wafers, single waveguides / lenses or waveguide / lens trays,

[0136] - one or more alignment systems 408 based on an optical camera, a dedicated lighting system and a set of actuators in X, Y and angular directions, wherein the alignment system is capable of detecting substrate edges, fiducials or patterned nanostructures, and wherein the actuators move the substrate, the printing screen or both,

[0137] one or more screen printing heads 402, which consist of a screen 406, one or more squeegees 404 and one or more overflow plates,

[0138] -Optional air filtration system (FFU) for use in cleanrooms of Class 1,000 or higher,

[0139] - optional treatment stations, which can be built-in in the printing module (thermal or UV),

[0140] - a transport system (i.e., rotary table, linear shuttle, ...) for carrying the wafer / lens onto the processing station and holding the wafer / lens during the process (i.e., printing), and / or

[0141] - A conveyor system 410 for bringing wafers / lenses to and / or out of the transport system for processing.

[0142] The screen printing device 400 can deliver one or more waveguides in parallel. For example, Figure 4A The screen printing device 400 includes a printing head 402, and the Figure 4B The screen printing system 400 shown in the alternative embodiment specifically includes two print heads 402, thereby allowing parallel printing on a substrate.

[0143] Other embodiments may include one, two, or more print heads 402 and / or different numbers and arrangements of components to print on multiple substrates in parallel.

[0144] Figure 5 A method 500 for coating an optically reflective layer 202 on a waveguide 10 having an intra-coupler grating 104 is shown in accordance with the present disclosure.

[0145] The method 500 for coating an optical reflective layer 202 on a waveguide 10 having a grating 104 within a coupler includes:

[0146] - Depositing 502 ink on the grating 104 inside the coupler of the waveguide 10 by screen printing.

[0147] Figure 6 A waveguide stack 600 including several waveguides according to the present disclosure is shown. The waveguide stack 600 may, for example, be included in the lens 100.

[0148] The waveguide stack 600 may include a cover glass 602a (e.g., bottom cover glass), a waveguide 10a, a waveguide 10b, a waveguide 10c, and a cover glass 602b (top cover glass) stacked in this order. An adhesive 604a may be disposed between the cover glass 602a and the waveguide 10a. Adhesives 604b, 604c, and 604d may be disposed between the waveguides 10a and 10b, between the waveguides 10b and 10c, and between the waveguide 10c and the cover glass 602b, respectively. Each of the waveguides 10a-c may be a waveguide as described herein, such as the waveguide 10.

[0149] The cover glass (e.g., multiple cover glasses) may be protective glass. The cover glass may shield the surface of the waveguide adjacent to the cover glass, for example, to prevent contact or contamination of the grating formed on the surface. The cover glass itself may not have optical structures, such as gratings.

[0150] An adhesive, such as adhesives 604a-604d, can be configured to attach adjacent optical devices of a waveguide stack to each other. For example, adhesive 604a can be configured to attach cover glass 602a to waveguide 10a. The adhesive can be a pressure sensitive adhesive (PSA). The adhesive can be a preformed adhesive, such as a preformed PSA. The adhesive can have an elongated shape. For example, the adhesive can be a tape. The adhesive can act as a spacer, providing a gap, specifically an air gap, between adjacent optical devices of a waveguide stack. Due to the adhesive, the adjacent optical devices may not contact each other.

[0151] Figure 6The waveguide stack 600 shown in FIG. 5 includes a total of three waveguides. The present disclosure is not limited in this regard. A waveguide stack may include one or more, two or more, or three or more waveguides. For example, a waveguide stack may include a total of two waveguides stacked between cover glass 602 a and cover glass 602 b.

[0152] Furthermore, instead of a cover glass, a transparent cover element made of materials other than glass may be used in the waveguide stack.Throughout the present disclosure, the cover glass may be replaced by a transparent cover element.

[0153] In some embodiments of method 500 , the ink may be a particle-free ink. The ink and / or the ink after a treatment is applied to the ink forms the optically reflective layer 202 .

[0154] Hereinafter, relevant embodiments of the present disclosure are briefly summarized.

[0155] In some embodiments of method 500, the ink is a particle-free ink. In some embodiments, the particle-free ink can be a silver ink.

[0156] In some embodiments, the waveguide 10 includes a glass substrate or a substrate having a refractive index greater than 1.8.

[0157] In some embodiments, the waveguide can be included in a lens having a length of from 40 mm to 80 mm and a width of from 20 mm to 60 mm. For example, a single screen can be used to screen print on a single lens, on multiple single lenses, or on a substrate where lenses are present but not yet singulated.

[0158] In some embodiments, a single screen is used to screen print on a single waveguide, on multiple cleaved waveguides, or on a wafer / glass substrate where waveguides are present but not cleaved.

[0159] In some embodiments, ink deposition is performed by a screen printing based additive process.

[0160] The additive process creates an optically reflective layer 202 on the grating 104 within the coupler of the waveguide 10 .

[0161] In some embodiments, ink deposition is performed by a subtractive process based on a screen-printed resist mask 302 having a negative pattern of the grating 104 within the coupler combined with screen printing.

[0162] In some embodiments, the method 500 further includes applying a treatment to the ink, wherein the treatment is a heat treatment or a sintering process or UV curing; and applying a protective coating 210 on the treated ink.

[0163] The present disclosure further discloses a waveguide 10 having an intra-coupler grating 104, wherein the intra-coupler grating 104 has a particle-free optical reflective layer 202 produced by depositing and sintering a particle-free ink adhered to the intra-coupler grating, wherein the optical reflective layer 202 of the intra-coupler grating adhered to the waveguide is obtained by the method of the present disclosure.

[0164] The particle-free ink is a particle-free ink that forms the optical reflective layer 202 according to the present disclosure.

[0165] The present disclosure further discloses a lens comprising the optical waveguide 10 according to the present disclosure and having a length from 40 mm to 80 mm and a width from 20 mm to 60 mm.

[0166] The present disclosure further discloses a screen printing device 400, comprising:

[0167] - Waveguide loading and unloading system;

[0168] a transport system configured to transport the waveguides loaded by the loading and unloading system;

[0169] - one or more alignment systems 408 and one or more actuators configured to align and move the waveguide transported by the transport system, and

[0170] One or more screen printing heads 402, each comprising a screen 406, one or more squeegees 404 and one or more flood plates, configured to apply ink on a substrate aligned and moved by one or more alignment systems.

[0171] The conveyor system 410 may bring wafers / lenses / waveguides to and / or out of the transport system for processing / printing.

[0172] In some embodiments, the ink is a particle-free ink and a silver ink.

[0173] In some embodiments, the screen printing apparatus further comprises an air filtration system for use in a Class 1000 or higher clean room.

[0174] Screen printing of particle-free inks according to the present disclosure provides higher throughput and lower cost, and provides improved reflectivity of the waveguide 10 and improved intercouplers.

[0175] The method of the present disclosure specifically provides an improved coating of an improved optical reflective layer 202 on a waveguide 10 having a grating 104 within a coupler. Deposition by screen printing provides higher throughput and lower cost compared to waveguides without such a coating, thereby improving the method of coating an optical reflective layer on a waveguide having a grating within a coupler.

[0176] For example, in a typical printing process and configuration, screen printing and, for example, printing on top of each other, may require, for example, a range of 2 to 5 seconds for each printing step. In comparison, a typical inkjet head with one nozzle would require, for example, approximately 20-30 minutes to produce the same pattern. Even if a large number of nozzles are used in parallel, the screen printing time will be at least comparable and / or still advantageous.

[0177] Because the viscosity of inkjet inks is relatively low (which can be measured in orders of magnitude), there is significant spreading on the grating structure, and thicker materials can provide significantly improved pattern fidelity. Therefore, the present application generally provides significantly improved pattern fidelity and / or improves the time required to generate a pattern.

[0178] The particle-free ink, specifically silver ink, improves the optical reflective layer 202 on the waveguide 10 having the grating 104 within the coupler, providing better reflectivity, which improves light coupling into the waveguide 10 and / or propagating light 122, thereby providing improved incoupling.

[0179] Depositing 502 the ink by screen printing further provides an improved and more uniform optical reflective layer 202 , thereby further helping to improve reflectivity within the coupler and further improving incoupling of incident light 120 into the waveguide 10 and / or into the substrate 102 of the waveguide 10 .

[0180] Screen printing improves process time. For example, if an inkjet system can produce a specific pattern in minutes, screen printing can typically produce the same pattern in seconds.

[0181] The patterning capability of screen printing and / or the quality of the resulting optically reflective layer is generally improved because the paste / ink has a higher viscosity and stays in place better than when using an inkjet method. The patterning capability and / or the quality of the resulting reflective layer are evaluated, for example, taking into account the placement accuracy and precision when reproducing the pattern / optically reflective layer.

[0182] Furthermore, when screen printing is used, the adhesion of the ink to the substrate and / or the grating within the coupler is improved due to the effect of the pressure applied during transfer of the paste / ink during screen printing.

Claims

1. A method for coating an optical reflective layer on a waveguide having a grating within a coupler, the method comprising: - Depositing ink by screen printing on the grating inside the coupler of the waveguide. The method of claim 1 , wherein the ink is a particle-free ink. The method of claim 2 , wherein the particle-free ink is a silver ink.

4. The method of any one of claims 1 to 3, wherein the waveguide comprises a glass substrate or a substrate having a refractive index greater than 1.

8.

5. The method of any one of claims 1 to 4, wherein the waveguide is included in a lens having a length from 40 mm to 80 mm and a width from 20 mm to 60 mm.

6. The method of any one of claims 1 to 5, wherein the screen printing is performed using a single screen on a single waveguide, on a plurality of cut waveguides, or on a glass substrate where waveguides are present but have not been cut.

7. Method according to any one of claims 1 to 6, wherein the depositing of the ink is performed by an additive process based on screen printing.

8. Method according to any one of claims 1 to 6, wherein said depositing of said ink is performed by a subtractive process based on a screen-printed protective mask having a negative pattern of the grating in said coupler combined with screen printing.

9. The method according to any one of claims 1 to 8, further comprising: applying a treatment to the ink, wherein the treatment is a heat treatment, a sintering process, or UV curing; and applying a protective coating over the treated ink.

10. A waveguide having a grating within a coupler, the grating within the coupler having a particle-free optical reflective layer produced by depositing and sintering a particle-free ink adhered to the grating within the coupler, wherein the optical reflective layer adhered to the grating within the coupler of the waveguide is obtained by the method of any one of claims 1 to 9.

11. A lens comprising the optical waveguide according to claim 10, the lens having a length from 40 mm to 80 mm and a width from 20 mm to 60 mm.

12. A screen printing device comprising: - a loading and unloading system for the waveguide; a transport system configured to transport the waveguides loaded by the loading and unloading system; - one or more alignment systems and one or more actuators configured to align and move the waveguide transported by the transport system; as well as - one or more screen printing heads, each comprising a screen, one or more squeegees and one or more flood plates, configured to apply ink on the waveguide aligned and moved by the one or more alignment systems.

13. The screen printing apparatus according to claim 12, wherein the ink comprises particle-free ink and silver ink.

14. The screen printing apparatus according to any one of claims 12 to 13, wherein the waveguide is a plurality of waveguides in a glass wafer, or a plurality of separate and cut waveguides arranged in a printing chuck, or a single waveguide.

15. The screen printing apparatus according to any one of claims 12 to 14, further comprising an air filtration system for a Class 1000 or higher clean room.

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