Patent Publication Number: US-2022229290-A1

Title: Color-selective waveguides for augmented reality/mixed reality applications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/065,905 filed on Oct. 8, 2020, which claims the benefit of U.S. Patent Application Nos. 62/912,305 filed Oct. 8, 2019; 62/912,949 filed Oct. 9, 2019; and 63/057,412 filed Jul. 28, 2020, all of which are hereby incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to color-selective waveguides and implementation of color-selective waveguides for augmented reality (AR)/mixed reality (MR) applications. 
     BACKGROUND 
     Typically, augmented reality (AR)/mixed reality (MR) eyepiece stacks are composed of separate red (R), green (G), blue (B) waveguide layers stacked together with gaps of a few tens of microns between the successive layers. Multi-pupil liquid crystal on silicon (LCOS) projectors are designed to direct light from each color into the respective incoupling grating (ICG) (e.g., green light into the ICG of the green waveguide layer). However, stray light (often from diffraction at the LCOS) from the wrong color can propagate into a neighboring ICG due to the necessary close proximity of the ICGs in the super-pupil. The stray light can induce ghost images or reduce optical properties such as contrast. 
     SUMMARY 
     Embodiments of the present disclosure are generally directed to color-selective waveguides, methods for fabricating color-selective waveguides, and augmented reality (AR)/mixed reality (MR) applications including color-selective waveguides. In particular, color-selective waveguides described herein can advantageously reduce or block stray light entering a waveguide (e.g., red, green, or blue waveguide), thereby reducing or eliminating back-reflection or back-scattering into the eyepiece. 
     In a first general aspect, forming a polymer waveguide includes dispensing a first polymerizable material on a first region of a first mold, dispensing a second polymerizable material on a second region of the first mold, contacting the first polymerizable material and the second polymerizable material with a second mold, polymerizing the first polymerizable material and the second polymerizable material to yield a patterned polymer layer between the first mold and the second mold, and separating the patterned polymer layer from the first mold and the second mold to yield a polymer waveguide having an undoped region formed by the first polymerizable material and a doped region formed by the second polymerizable material. The first polymerizable material includes a first resin, and the second polymerizable material includes a second resin and a chromatic component. The first mold, the second mold, or both include protrusions, recessions, or both. 
     Implementations of the first general aspect may include one or more of the following features. 
     In one implementation, the chromatic component is selected to allow transmission of a selected wavelength of light. A concentration of the chromatic component in the second polymerizable material can be in a range of 3-3000 parts per million by weight. The selected wavelength of light typically corresponds to red, green, or blue light. The chromatic component includes one or more dyes. In some cases, the chromatic component includes a nano-particulate material, and optionally one or more dyes. In some implementations, the first resin and the second resin are the same. The polymer waveguide can include more than one doped region, more than one undoped region, or more than one doped region and more than one undoped region. 
     A second general aspect includes a polymer waveguide formed by the first general aspect. 
     In a third general aspect, a polymer waveguide includes an undoped region including a first resin, and a doped region including a second resin and a chromatic component. The undoped region and the doped region have substantially the same index of refraction. In some implementations of the third general aspect, the chromatic component is selected to absorb red light, green light, blue light, or any combination thereof. 
     In a fourth general aspect, forming a polymer waveguide includes dispensing a polymerizable material on a first mold, contacting the polymerizable material with a second mold, polymerizing the polymerizable material to yield a patterned polymer layer between the first mold and the second mold, and separating the patterned polymer layer from the first mold and the second mold to yield a doped polymer waveguide. The polymerizable material includes a resin and a chromatic component. The first mold, the second mold, or both include protrusions, recessions, or both. The chromatic component is selected to absorb red light, green light, blue light, or any combination thereof. 
     Implementations of the fourth general aspect may include one or more of the following features. 
     In some implementations, the doped polymer waveguide is free of one or more undoped regions. The doped polymer waveguide typically absorbs at least 90% of one or more of red light, green light, and blue light traveling through the polymer waveguide. In certain cases, the chromatic component is selected to absorb at least 90% of only red light, only green light, or only blue light. In some cases, the polymerizable material is a homogeneous mixture. A thickness of the doped polymer waveguide is typically in a range of about 200 μm to about 1000 μm. A total internal reflection path length of the doped polymer waveguide is typically in a range of about 2 cm to about 15 cm. A refractive index of the doped polymer waveguide is usually greater than about 1.45. 
     The fourth general aspect can include casting or molding. Polymerizing the polymerizable material can include irradiating the polymerizable material with ultraviolet radiation. 
     In a fifth general aspect, a polymer waveguide includes one or more patterned regions and one or more unpatterned regions. The one or more patterned regions and one or more unpatterned regions include a doped polymer having a chromatic component selected to absorb at least 90% of one or more of red light, green light, and blue light traveling through the polymer waveguide. 
     Implementations of the fifth general aspect may include one or more of the following features. 
     The one of the one or more patterned regions can be an incoupling grating, an exit pupil expander, or an orthogonal pupil expander. The doped polymer waveguide is typically free of one or more undoped regions. The absorb at least 90% of only red light, only green light, or only blue light. The doped polymer waveguide can absorb at least 90% of one or more of red light, green light, and blue light traveling through the polymer waveguide, or at least 90% of only red light, only green light, or only blue light. The doped polymer can be a homogeneous material. A thickness of the doped polymer waveguide is typically in a range of about 200 μm to about 1000 μm. A total internal reflection path length of the doped polymer waveguide is typically in a range of about 2 cm to about 15 cm. A refractive index of the doped polymer waveguide is typically greater than about 1.45. 
     An additional aspect includes an eyepiece including the polymer waveguide of the fifth general aspect. 
     In a sixth general aspect, coating a waveguide includes dispensing one or more portions of a polymerizable material on a first surface of a waveguide, and polymerizing the polymerizable material to yield a doped coating on the first surface of the waveguide. The polymerizable material includes a resin and a chromatic component. The waveguide can be formed of glass or polymer. The doped coating is selected to absorb at least 90% of one or more of red light, green light, and blue light traveling through the polymer waveguide. 
     Implementations of the sixth general aspect may include one or more of the following features. 
     In some cases, the doped coating can be a continuous coating. In certain cases, the doped coating forms two or more discontinuous regions on the first surface of the waveguide. The doped coating typically covers the first surface of the waveguide. The first surface of the waveguide can include one or more patterned regions and one or more unpatterned regions, with the polymerizable material is dispensed on one of the one or more unpatterned regions of the first surface of the waveguide. The waveguide and the doped coating can have substantially the same index of refraction. 
     The sixth general aspect may further include dispensing one or more additional portions of the polymerizable material on a second surface of the waveguide, and polymerizing the one or more additional portions of the polymerizable material to yield a second doped coating on the second surface of the waveguide. The second surface is opposite the first surface, and the second doped coating is selected to absorb at least 90% of one or more of red light, green light, and blue light traveling through the polymer waveguide. 
     In a seventh general aspect, a coated waveguide includes one or more unpatterned regions on a first surface, and one or more patterned regions on the first surface. At least one of the one or more unpatterned regions is coated with a doped polymer coating, and the doped polymer coating is selected to absorb at least 90% of one or more of red light, green light, and blue light traveling through the polymer waveguide. In some implementations of the seventh general aspect, a second surface of the waveguide, opposite the first surface, includes an additional doped polymer coating. 
     In an eighth general aspect, coating a waveguide includes dispensing a portion of a first polymerizable material on a first surface of a waveguide, dispensing a portion of a second polymerizable material on the first surface of the waveguide, and polymerizing the first polymerizable material and the second polymerizable material to yield a first doped coating and a second doped coating on the first surface of the waveguide. The first polymerizable material includes a first resin and a first chromatic component. The second polymerizable material includes a second resin and a second chromatic component. The first doped coating is selected to absorb at least 90% of a first one or more of red light, green light, and blue light traveling through the polymer waveguide, and the second doped coating is selected to absorb at least 90% of a second one or more of red light, green light, and blue light traveling through the polymer waveguide. 
     In a ninth general aspect, fabricating color filters includes dispensing a portion of a first polymerizable material on a surface of a first mold, dispensing a portion of a second polymerizable material on the surface of the first mold, and dispensing a portion of a third polymerizable material on the surface of the first mold. Fabricating color filters further includes contacting the first polymerizable material, the second polymerizable material, and the third polymerizable material with a surface of a second mold, and polymerizing the first polymerizable material, the second polymerizable material, and the third polymerizable material to yield a first color filter, a second color filter, and a third color filter. The first polymerizable material includes a first resin and a first chromatic component, and the second polymerizable material includes a second resin and a second chromatic component. The third polymerizable material includes a third resin and a third chromatic component. The first colored filter is selected to absorb at least 90% of a first one or more of red light, green light, and blue light traveling through the first colored filter; the second colored filter is selected to absorb at least 90% of a second one or more of red light, green light, and blue light traveling through the second colored filter; and the third colored filter is selected to absorb at least 90% of a third one or more of red light, green light, and blue light traveling through the third colored filter. In some implementations, the ninth general aspect further includes adhering the first colored filter, the second colored filter, and the third colored filter to an optical substrate or a waveguide. 
     In a tenth general aspect, a polymer waveguide includes an incoupling grating and a pupil expander. The polymer waveguide includes a polymer doped with a chromatic component. A concentration of the chromatic component in the polymer varies from a first side of the polymer waveguide to a second side of the polymer waveguide. In some implementations of the tenth general aspect, the concentration of the chromatic component increases from a first side of the polymer waveguide to a second side of the polymer waveguide. 
     An eleventh general aspect includes a waveguide formed by any of the above general aspects. 
     A twelfth general aspect includes an eyepiece including two or more of the waveguides of the eleventh general aspect. 
     A thirteenth general aspect includes a device including the eyepiece of the twelfth general aspect. 
     In a fourteenth general aspect, a waveguide structure includes a waveguide configured to transmit light in a visible wavelength range, and a cured adhesive doped with a colorant that absorbs light in the visible wavelength range and transmits ultraviolet light. The cured adhesive is in direct contact with the waveguide. 
     Implementations of the fourteenth general aspect may include one or more of the following features. 
     In some cases, the visible wavelength range can correspond to red, green, or blue light or any combination thereof. In certain cases, the visible wavelength range corresponds to cyan, magenta, or yellow light or any combination thereof. The cured adhesive is typically a single layer having a thickness in a range of about 10 μm to about 1.5 mm. The cured adhesive can be completely cured. The cured adhesive typically forms an edge seal. 
     In a fifteenth general aspect, a waveguide stack includes a multiplicity of waveguide structures, and a cured adhesive doped with a colorant that absorbs light in each of the different visible wavelength ranges and transmits ultraviolet light. Each waveguide structure has a waveguide configured to transmit light in a different visible wavelength range, and the adhesive is in direct contact with adjacent waveguide structures in the multiplicity of waveguide structures. In some implementations of the fifteenth general aspect, the cured adhesive is a single layer having a thickness in a range of about 10 μm to about 1.5 mm. In certain implementations of the fifteenth general aspect, the cured adhesive forms an edge seal. 
     In a sixteenth general aspect, forming a waveguide structure includes selecting a waveguide configured to transmit light in a visible wavelength range, applying to the waveguide an adhesive doped with a colorant that absorbs light in the visible wavelength range and transmits ultraviolet light, and fully curing the adhesive with a single application of ultraviolet light to yield the waveguide structure. The adhesive has a thickness in a range of about 10 μm to about 1.5 mm. In some implementations of the sixteenth general aspect, the adhesive is applied to an edge of the waveguide or to a surface of the layer configured for lamination to another waveguide configured to transmit visible light in another visible wavelength range. 
     The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  depict color filters and optical transmission through these color filters, respectively. 
         FIGS. 2A and 2B  depict dye-doped waveguides for color filtration. 
         FIG. 3A  depicts local dispense of dye-doped resin during waveguide fabrication via casting.  FIG. 3B  depicts a dye-doped polymer waveguide.  FIG. 3C  depicts transmission of a selected light component through a dye-doped polymer waveguide. 
         FIGS. 4A-4D  depict global dispense of dye-doped resin to yield color-selective waveguides. 
         FIGS. 5A-5F  depict local and global coating of dye-doped resin onto glass or polymer waveguides for color selectiveness. 
         FIGS. 6A and 6B  depict direct casting of a color filter onto a surface of an existing waveguide or cover layer. 
         FIG. 7  depicts casting of individual color filters with a dye-doped resin. 
         FIGS. 8A-8H  depict examples of gradients in dye loadings in a waveguide. 
         FIGS. 9A-9C  show examples of suitable absorptivity ranges for red, green, blue (RGB) dyes for color-selective polymer waveguides. 
         FIGS. 10A-10C  shows examples of suitable transmission for red, green, and blue dyes for color-selective polymer waveguides. 
         FIG. 11  shows the UV-visible spectrum of an example UVA enhanced lamp suitable for UV curing of adhesives. 
         FIGS. 12A-12C  show red, green, and blue edge absorbers with colorant absorption spectra tailored directly to color channels in a waveguide. 
         FIG. 13  depicts an edge absorber with green and blue portions. 
         FIG. 14A  shows an example with adhesive and a colorant having tailored absorption in green and blue wavelengths at different dopant levels.  FIG. 14B  is a graph showing percent transmission versus dopant level from  FIG. 14A . 
         FIG. 15  depicts a visible wavelength edge absorber and interlayer lamination adhesive including colorants that absorb wavelengths of every color channel in the eyepiece stack. 
         FIG. 16  shows overlaid absorbance spectra of red, green, and blue colorants. 
         FIG. 17  shows a comparison of a simulation of the absorbance spectra of  FIG. 16  and output of exemplary red, green, and blue light-emitting diodes. 
     
    
    
     DETAILED DESCRIPTION 
     Current incoupling grating (ICG) designs have limited wavelength selectivity, such that stray light of an undesired wavelength is sometimes injected into the waveguide. In one example, a green ICG diffracts some portion of blue and red light, which gets coupled into the waveguide as “stray light.” The presence of stray light in a waveguide can degrade its optical performance. In some cases, light at the edge of a waveguide is back-reflected or back-scattered into an eyepiece, thereby eroding contrast. 
     One way to mitigate the coupling of stray light into a waveguide is to use a color filter that selectively lets a single color pass through and blocks other colors that would otherwise end up as unwanted light in the waveguide.  FIG. 1A  depicts an exploded view of glass-based eyepiece stack  100  with red, green, and blue color filters  102 ,  104 ,  106 , respectively, on eye side cover layer  108 . Red, green, and blue color filters  110 ,  112 ,  114 , respectively are typically used to selectively transmit RGB light into corresponding red, green, and blue waveguides  102 ,  104 ,  106 , respectively, while absorbing other colors. RGB waveguides include incoupling gratings (ICG)  116 , exit pupil expanders (EPE)  118 , and orthogonal pupil expanders (OPE)  120 , respectively. Red, green, and blue waveguides  102 ,  104 ,  106  are positioned between eye side cover layer  108  and world side cover layer  122 .  FIG. 1B  depicts the spectral response  130 ,  132 ,  134  of red, green, and blue color filters, respectively, shown in  FIG. 1A . Due at least in part to differences in thermal expansion and high-precision alignment requirements of certain optical designs, however, it can be difficult to integrate a glass color filter with a polymer eyepiece. Doing so can introduce complexity and cost that is not present in glass eyepieces. 
     Color-selective polymer waveguide eyepieces that mitigate coupling of stray light into waveguides are described herein. In some cases, the polymer of a specific color eyepiece layer is doped with one or more dyes or particles with selected chromatic properties to attenuate undesired wavelengths of coupled light (e.g., a green eyepiece layer is doped with green dye on the optical path). In one example, a high refractive index (R.I.) resin used for polymer waveguide fabrication is loaded with a desired color dye to allow light of a certain wavelength range to pass through and block all other wavelengths. As used herein, “high refractive index” generally refers to a R.I. at 587.56 nm (R.I., nd) greater than about 1.45 or greater then about 1.5. The amount of light of a specific color that gets blocked by a specific dye is based at least in part on the concentration of the dye in the polymer. 
     Typically, waveguide thicknesses described herein are on the order of a few hundred microns (about 200 μm to about 1000 μm) and are typically smaller than the total internal reflection (TIR) path lengths, which can be several centimeters (about 2 cm to about 15 cm). The longer optical path length in a waveguide facilitates effective absorption of the stray light even with low concentration dye loadings in a polymer waveguide.  FIG. 2A  depicts orange dye-doped waveguide  200  (e.g., with a thickness of about 200 μm to about 500 μm) and transmission of blue light  202  through orange-doped waveguide  200 .  FIG. 2B  depicts attenuation of blue light  202  that occurs as the light travels a total internal reflection (TIR) path (e.g., about 3 cm to about 5 cm) through orange dye-doped waveguide  200 . The suitability of a dye for dye loading into a specific polymer waveguide for color selectivity can depend at least in part on factors including chemical compatibility, process compatibility, and solubility of the dye in a base high index resin. 
     Color-selective waveguides described herein can be fabricated in a variety of methods, including various molding and casting methods, other appropriate methods including lithography methods (e.g., imprint lithography methods), etching methods, deposition methods, and any combination thereof. Fabrication may include a single process or two or more different processes. In one example, fabricating a color-selective waveguide includes casting a waveguide with a chromatic component to yield a doped waveguide (e.g., a dye-doped waveguide), and modifying the doped waveguide to include features (e.g., gratings, pillars, spacers, and the like). The doped waveguide may be flat or patterned, or have any combination of flat and patterned regions. Modifying the doped waveguide can include an imprint lithography process or an etching process to create appropriate features. 
     One aspect includes local dispense of dye-doped high index resin along with dispense of a base resin for waveguide fabrication. Using this approach, the dye doping can be achieved at a single or multiple locations in the bulk of the polymer waveguide depending at least in part on the concentration of the dye used and or the extent of light that needs to be attenuated. In one example, the dye-doped high index resin is dispensed in a controlled fashion around the ICG area.  FIG. 3A  depicts steps in a process for fabricating a dye-doped polymer waveguide. Base (un-doped) high-index resin  300  is dispensed onto patterned surface  302  (e.g., around a center area) of bottom mold  304 . Dye-doped resin  306  is dispensed onto another area of bottom mold  304  and allowed to spread between top mold  308  and bottom mold  304  spaced apart at a selected distance. After casting, the resins are cured (e.g., with UV radiation), and the resulting waveguide is demolded to yield dye-doped polymer waveguide  310  with un-doped polymer region  312  and doped polymer region  314 . Dye-doped polymer waveguide  310 , with ICG area  316  formed of doped polymer and diffractive areas  318  formed of un-doped polymer, is highly selective for a chosen color. As depicted in  FIG. 3B , doped polymer waveguide  310  includes un-doped polymer regions  312  (diffractive areas  316 ) and doped polymer regions  314  (ICG area  318  and areas  320  between diffractive areas  316 ).  FIG. 3C  shows light with RGB components  322 ,  324 ,  326 , respectively, entering dye-doped polymer waveguide  310 , and only the selected component (e.g., red component  322 ) demonstrating TIR through dye-doped polymer waveguide  310 . 
     Example 1. Two different resin samples were prepared based on LUMIPLUS 1.71 index resin supplied by Mitsubishi Gas Chemicals (MGC), Japan. 50 ml of pure LUMIPLUS formulation was prepared using MGC&#39;s protocol without adding any dye in the base resin to yield a resin batch. 25 ml of the resin batch was taken in a separate glass vial and 1 wt % of VIS 484 (supplied by Adam Gates &amp; Company) was added to the vial. The resulting dye loaded resin was then subjected to ultrasonic waves for mixing for about 5 minutes to yield a homogeneous dye-doped resin. A polymer waveguide was fabricated by dispensing about 3 ml of pure resin in the center and about 1 ml of dye-doped resin around the ICG area onto a nano-patterned mold with diffractive patterns. The resin then spread between two molds spaced apart with a distance of about 350 μm and was exposed to UV light (wavelength of about 365 nm) for curing followed by a post anneal step at 100° C. for 20 minutes. The resulting dye-doped polymer waveguide has two different zones as depicted in  FIG. 3A : a first zone around the ICG area that has a color selective dye, with the rest of the waveguide being free of dye. 
     In a manner similar to that described in Example 1, various color dyes (Red, Green, Blue, Cyan, Magenta, Yellow and Infrared dye) that have selective transmission and absorption can be used to fabricate color selective polymer waveguides. Example base resin/dye combinations are listed in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Various combinations of dyes and base resins for color selective polymer waveguides. 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Absorbing 
                   
               
               
                   
                   
                 wavelength 
                 Transmitting 
               
               
                 Dye 
                 Base Resin/monomer 
                 (nm) 
                 wavelength (nm) 
               
               
                   
               
               
                 VIS 484 from 
                 High refractive index resins (LUMIPLUS) 
                 420-550 
                 600-900 
               
               
                 Adam Gates &amp; 
                 1.72 and 1.75 index resins (MGC Advanced 
                 Blue and 
                 Red 
               
               
                 Company 
                 Polymers, Inc.), UV curable low index 
                 Green 
                   
               
               
                   
                 polymers such as acrylates, thiol-ene 
                   
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
                   
                   
               
               
                 VIS 606 from 
                 High refractive index resins-LUMIPLUS 
                 530-650 
                 400-500 
               
               
                 Adam Gates &amp; 
                 1.72 and 1.75 index resins (MGC Advanced 
                 Green and 
                 Blue 
               
               
                 Company 
                 Polymers, Inc.), UV curable low index 
                 Red 
                   
               
               
                   
                 polymers such as acrylates, thiol-ene 
                   
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
                   
                   
               
               
                 VIS 682 from 
                 High refractive index resins-LUMIPLUS 
                 600-750 
                 400-610 
               
               
                 Adam Gates &amp; 
                 1.72 and 1.75 index resins from (MGC 
                 Red 
                 Blue &amp; Green 
               
               
                 Company 
                 Advanced Polymers, Inc.), UV curable low 
                   
                   
               
               
                   
                 index polymers such as acrylates, thiol-ene 
                   
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
                   
                   
               
               
                 SR-4000L from 
                 High refractive index resins-LUMIPLUS 
                 400-570 
                 570-700 
               
               
                 Fujifilm 
                 1.72 and 1.75 index resins from (MGC 
                 Blue and 
                 Red 
               
               
                   
                 Advanced Polymers, Inc.), UV curable low 
                 Green 
                   
               
               
                   
                 index polymers such as acrylates, thiol-ene 
                   
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
                   
                   
               
               
                 SG-4000L from 
                 High refractive index resins-LUMIPLUS 
                 400-475 &amp; 
                 500-575 
               
               
                 Fujifilm. 
                 1.72 and 1.75 index resins from (MGC 
                 600-700 
                 Green 
               
               
                   
                 Advanced Polymers, Inc.), UV curable low 
                 Blue and 
                   
               
               
                   
                 index polymers such as acrylates, thiol-ene 
                 Red 
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
                   
                   
               
               
                 SB-4000L from 
                 High refractive index resins-LUMIPLUS 
                 525-700 
                 400-500 
               
               
                 Fuji-film 
                 1.72 and 1.75 index resins from (MGC 
                 Green and 
                 Blue 
               
               
                   
                 Advanced Polymers, Inc.), UV curable low 
                 Red 
                   
               
               
                   
                 index polymers such as acrylates, thiol-ene 
                   
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
                   
                   
               
               
                 VIS 575 from 
                 High refractive index resins-LUMIPLUS 
                 400-650 
                     700 
               
               
                 Adam Gates &amp; 
                 1.72 and 1.75 index resins from (MGC 
                 Most visible 
                     Infrared 
               
               
                 Company 
                 Advanced Polymers, Inc.), UV curable low 
                 wavelengths 
                   
               
               
                 (Black dye) 
                 index polymers such as acrylates, thiol-ene 
                   
                   
               
               
                   
                 polymers, polydimethoxysilane (PDMS), 
                   
                   
               
               
                   
                 OrmoStamp (micro resist technology GmbH) 
               
               
                   
               
            
           
         
       
     
     In addition to the resin-dye combinations listed in Table 1, two or more dyes can be incorporated into the same base resin to achieve specific color selectivity. Examples of dye combinations are listed in Table 2. This approach can be helpful when a single dye cannot achieve the desired color selectivity. In one example, a pseudo black dye formulated to absorb RGB light is doped around an ICG toward the anti-launch side to absorb RGB light. Such pseudo black dye can also be applied around the periphery of a glass or polymer waveguide to absorb RGB light reflected or refracted from the edges. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Combinations of dyes for desired color 
               
               
                 selectivity in polymer waveguides 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Location in a 
                   
               
               
                 Color 
                 Dye(s) 
                 waveguide 
                 Expected outcome 
               
               
                   
               
               
                 Red 
                 Blue and green light 
                 Local or global 
                 Block blue and 
               
               
                   
                 absorbing dyes 
                   
                 green light; allow 
               
               
                   
                   
                   
                 only red light 
               
               
                 Green 
                 Blue and red light 
                 Local or global 
                 Block blue and red 
               
               
                   
                 absorbing dyes 
                   
                 light; allow only 
               
               
                   
                   
                   
                 green light. 
               
               
                 Blue 
                 Green and red light 
                 Local or global 
                 Block green and  
               
               
                   
                 absorbing dyes 
                   
                 red light; allow 
               
               
                   
                   
                   
                 only green light 
               
               
                   
                   
                   
                 to do TIR. 
               
               
                 Pseudo 
                 Red, green, 
                 Local around 
                 Block RGB light 
               
               
                 Black 
                 and blue light 
                 ICG area 
                 colors 
               
               
                 (R + G + B) 
                 absorbing dyes 
                 (anti-launch side) 
                   
               
               
                 Infrared 
                 Infrared dye 
                 Local or global 
                 Helps with eye 
               
               
                   
                   
                   
                 tracking 
               
               
                   
               
            
           
         
       
     
     Another aspect includes global dispense of dye-doped high-index resin for waveguide fabrication. Since the waveguide is uniformly doped, a low concentration of the dye can effectively attenuate the unwanted light as the light undergoes TIR over a path length of a few centimeters.  FIG. 4A  depicts global dispense of dye-doped high-index resin, in which dye-doped resin  406  is dispensed on patterned surface  402  of bottom mold  404  and undergoes a casting and curing process between bottom mold  404  and top mold  408  similar to that depicted in  FIG. 3A  to fabricate color selective waveguide  410  with only dye-doped polymer  414  in ICG area  416  and diffractive areas  418 .  FIGS. 4B-4D  depict ray diagrams for waveguides doped with dyes that allow only red, green, and blue light  422 ,  424 , and  426 , respectively. In  FIG. 4B , red polymer-doped waveguide  410   r  allows TIR of only red light  422 . In  FIG. 4C , green polymer-doped waveguide  410   g  allows TIR of only green light  424 . In  FIG. 4D , blue polymer-doped waveguide  410   b  allows TIR of only blue light  426 . 
     Example 2. 25 ml of LUMIPLUS 1.72 index resin was prepared in a glass vial per MGC&#39;s POR mix ratio of individual monomers. To this, a VIS484 dye from Adam Gates &amp; Company was added in a low concentration. The resulting dye-doped resin was then subjected to ultrasonic waves for mixing for about 5 minutes to yield a homogeneous dye-doped resin. The dye-doped resin formulation was dispensed onto a mold surface for waveguide fabrication. 
     In a manner similar to that described in Example 2, various color dyes (Red, Green, Blue, Cyan, Magenta, Yellow, and Infrared) as shown in Table 1 that have selective transmission and absorption can be used to fabricate color-selective polymer waveguides. 
     Another aspect includes local and global coating of the dye-doped high-index resin on a waveguide surface. The waveguide to be coated can be formed of glass or polymer. In this approach, a waveguide surface can be coated locally or globally with dye-doped high-index resin to achieve a desired light attenuation.  FIGS. 5A-5F  depict various implementations of such coatings and example locations on the waveguide where such coatings can be applied. In  FIG. 5A , dye-doped polymer waveguide  510  includes waveguide  512  and dye-doped polymer coating  514  between ICG area  516  and diffractive areas  518 . In  FIG. 5B , dye-doped polymer waveguide  520  includes waveguide  522  and dye-doped coating  524  around ICG area  526 . In  FIG. 5C , dye-doped polymer waveguide  530  includes waveguide  532 , dye-doped coating  534  around ICG area  536  and diffractive area  538 . In  FIG. 5D , dye-doped polymer waveguide  540  includes waveguide  542 , first dye-doped coating  544  on a side of ICG area  546 , as well as second dye-doped coating  544 ′ on a surface of waveguide  542  opposite ICG area  546  and diffractive areas  548 . Second dye-doped coating  544 ′ can be the same as or different than (e.g., in one or more of thickness, color, composition, concentration, transmission) first dye-doped coating  544 . In  FIG. 5E , dye-doped polymer waveguide  550  includes waveguide  552 , first dye-doped coating  554  on waveguide  552  surrounding ICG area  556 , as well as second dye-doped coating  554 ′ on a surface of waveguide  552  opposite ICG area  556  and diffractive areas  558 . Second dye-doped coating  554 ′ can be the same as or different than (e.g., in one or more of thickness, color, composition, concentration, transmission) first dye-doped coating  554 , each of which can be the same or different (e.g., in one or more of thickness, color, composition, composition). In  FIG. 5F , dye-doped polymer waveguide  560  includes waveguide  562 , first dye-doped coating  564  around ICG area  566  and diffractive areas  568 , as well as second dye-doped coating  564 ′ on a surface of waveguide  562  opposite ICG area  566  and diffractive areas  568 . Second dye-doped coating  564 ′ can be the same as or different than (e.g., in one or more of thickness, color, composition, composition) first dye-doped coating  564 , each of which can be the same or different (e.g., in one or more of thickness, color, composition, composition). 
     Referring to  FIGS. 5A-5F , waveguides  512 ,  522 ,  532 ,  542 ,  552 , and  562  can be glass or polymer. In locations where the dye-doped polymer might interfere with a user&#39;s vision, a low concentration of the dye can be used such that the color tint is not detectable. In locations where the dye-doped polymer will not interfere with a user&#39;s vision, a higher concentration dye can be introduced to achieve greater light attenuation as the light propagates with TIR through the waveguide, and thereby achieving higher color selectivity. 
     Another aspect includes casting a color filter directly onto a surface of a waveguide or a cover layer. In this approach, local high-pigmented areas of a specific dye are deposited onto a glass or polymer waveguide or cover layer surface using a UV curable composition loaded with desired dye pigments.  FIGS. 6A and 6B  illustrate color filter fabrication for a waveguide and a cover layer, respectively.  FIG. 6A  depicts casting of dye-doped resin  606  in ICG area  616  on patterned surface  602  between top mold  608  and substrate  604 . Substrate  604  is waveguide  612  (e.g., a glass waveguide or a polymer waveguide). After casting and UV curing, dye-doped waveguide  610  includes dye-doped regions  614  around ICG area  616 .  FIG. 6B  depicts casting of dye-doped resin  626  between substrate  624  (e.g., a cover glass or polymer layer) and top mold  628 , followed by UV curing and demolding of doped polymer waveguide  630  with colored filters  634  on a surface of doped polymer waveguide  630 . Dye-doped resins  626  may be the same or different (e.g., in thickness, color, composition, concentration, transmission), such that colored filters  634  are similarly the same or different. 
     Another aspect includes casting individual color filters separately. The resulting color filters can be fabricated separately in multiple numbers via casting of UV-curable dye-doped high-index resin, as depicted in  FIG. 7 . The color filters then can be picked and placed onto a polymer or glass substrate for use in a selected device.  FIG. 7  depicts dye-doped resin on bottom mold  704 , and casting of dye-doped resin  706  between bottom mold  704  and top mold  708 . The dye-doped resins  716  can be different colors (e.g., RGB). Dye-doped resins  706  are cured (e.g., with UV light) and demolded to yield colored filters  714  on bottom mold  704 . Colored filters  714  (e.g., one each of RGB) can be removed (picked) from bottom mold  704  and positioned (placed) on substrate  720  (e.g., a cover layer). 
     Another aspect includes doping polymer waveguides with infrared dye. Polymer waveguides doped with infrared dye can assist with eye tracking. A waveguide doped with infrared dye can be fabricated in a manner similar to that described in Example 1 or Example 2. 
     Another aspect includes doping polymer waveguides with one or more dyes having a selected concentration gradient.  FIGS. 8A-8H  depict a top view of various implementations in which a waveguide is doped with a dye having a selected concentration gradient over all or a portion of the waveguide to yield a dye-doped waveguide. Dye concentration, doping location, and gradient pattern can be selected based on the application. The dye-doped gradient can be achieved by dispensing dye-doped resin droplets with varying dye concentrations and spreading the droplets to cover the desired areas of the waveguide before curing the resin. 
       FIG. 8A  depicts dye-doped waveguide  810  with a dye concentration gradient decreasing from a perimeter of dye-doped waveguide  810  proximate ICG area  816  toward the perimeter of dye-doped waveguide  810  proximate diffraction (e.g., EPE/OPE) areas  818 .  FIG. 8B  depicts dye-doped waveguide  820  with a dye concentration gradient increasing from a perimeter of dye-doped waveguide  820  proximate ICG area  816  toward the perimeter of dye-doped waveguide  820  proximate diffraction areas  818 .  FIG. 8C  depicts dye-doped waveguide  830  with a dye concentration gradient increasing from perimeter proximate a first side of both the ICG area  816  and diffraction areas  818  (e.g., closer to ICG area  816 ) toward the perimeter on a second side of ICG area  816  and diffraction areas  818  (e.g., closer to diffraction areas  818 ).  FIG. 8D  depicts dye-doped waveguide  840  with a dye concentration gradient increasing from a perimeter of dye-doped waveguide  840  proximate the second side of ICG area  816  and diffraction areas  818  (e.g., closer to diffraction areas  818 ) toward the perimeter on the first side of ICG area  816  and diffraction areas  818  (e.g., closer to diffraction areas  818 ).  FIG. 8E  depicts dye-doped waveguide  850  having a dye concentration gradient similar to that of dye-doped waveguide  810  in  FIG. 8A , together with a dye-doped ICG area  816 ′. Dye-doped ICG area  816 ′ can include a dye the same as or different than (e.g., thickness, color, composition, concentration, transmission) the dye in the dye concentration gradient.  FIG. 8F  depicts dye-doped waveguide  860  similar to that of dye-doped waveguide  850  in  FIG. 8E , together with dye-doped polymer  814  encircling ICG area  816 . Dye-doped polymer  814  can include a dye the same as or different than (e.g., thickness, color, composition, concentration, transmission) the dye in the dye concentration gradient, ICG region  816 , or both.  FIG. 8G  depicts dye-doped waveguide  870  similar to that of dye-doped waveguide  850  in  FIG. 8E , together with dye-doped polymer  814  partially encircling ICG area  816 . One of the diffraction areas  818  (e.g., EPE or OPE) is doped with a dye that is the same as or different than (e.g., thickness, color, composition, concentration, transmission) the dye in dye-doped polymer  814  partially encircling ICG region  816 . Dye-doped polymer  814  is doped with a dye that is the same as or different than (e.g., thickness, color, composition, concentration, transmission) any other dye in dye-doped waveguide  870  (e.g., dye in the dye concentration gradient, dye in ICG area  816 , or both).  FIG. 8H  depicts dye-doped waveguide  880  similar to that of dye-doped waveguide  870  in  FIG. 8G , together with dye-doped region  814 ′ about a perimeter of dye-doped waveguide  880 . Dye-doped region  814 ′ is doped with a dye that is the same as or different than (e.g., thickness, color, composition, concentration, transmission) one or more of the dye in the dye concentration gradient, the ICG area  816 , and the diffraction area  818 . 
     In some aspects, the dye-doped polymer of a polymer waveguide has a refractive index that is substantially the same as, or within a selected range (Δn≤0.5) of, the refractive index of an un-doped polymer of the polymer waveguide. Thus, in some implementations, dye-doped polymer in a polymer waveguide is formed from the same resin as an undoped polymer in the polymer waveguide. In certain implementations (e.g., for a glass waveguide), the refractive index of a dye-doped polymer coating may be selected to be substantially the same as the refractive index of the coated substrate (e.g., a glass substrate). 
     Table 3 lists optical and chemical properties (e.g., solubility, concentration, relative transmission) of suitable chromatic components for doped polymer waveguides and coatings, including components for red, blue, and green layer dyes. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Properties of suitable chromatic components for doped polymer waveguides and coatings. 
               
            
           
           
               
               
               
               
               
            
               
                 Material 
                 Category 
                 Number 
                 Parameter Name 
                 Specification 
               
               
                   
               
               
                 Blue Layer Dye 
                 Optical 
                 OP01 
                 Relative Transmission @455 nm 
                 &gt;60% 
               
               
                 Blue Layer Dye 
                 Optical 
                 OP02 
                 Relative Transmission @511 nm- 
                 &lt;10% 
               
               
                   
                   
                   
                 640 nm 
                   
               
               
                 Blue Layer Dye 
                 Optical 
                 OP03 
                 Relative Transmission @630 nm 
                  &lt;2% 
               
               
                 Blue Layer Dye 
                 Optical 
                 OP04 
                 Relative Transmission @511 nm- 
                 &lt;55% 
               
               
                   
                   
                   
                 700 nm 
                   
               
               
                 Green Layer 
                 Optical 
                 OP05 
                 Relative Transmission @400 nm- 
                 &lt;10% 
               
               
                 Dye 
                   
                   
                 464 nm 
                   
               
               
                 Green Layer 
                 Optical 
                 OP06 
                 Relative Transmission @525 nm 
                 &gt;85% 
               
               
                 Dye 
                   
                   
                   
                   
               
               
                 Green Layer 
                 Optical 
                 OP07 
                 Relative Transmission @621 nm- 
                 &lt;10% 
               
               
                 Dye 
                   
                   
                 680nm 
                   
               
               
                 Green Layer 
                 Optical 
                 OP08 
                 Relative Transmission @621 nm- 
                 &lt;16% 
               
               
                 Dye 
                   
                   
                 700 nm 
                   
               
               
                 Red Layer Dye 
                 Optical 
                 OP09 
                 Relative Transmission @400 nm- 
                 &lt;12% 
               
               
                   
                   
                   
                 576 nm 
                   
               
               
                 Red Layer Dye 
                 Optical 
                 OP10 
                 Relative Transmission @450 nm- 
                 &lt;10% 
               
               
                   
                   
                   
                 576 nm 
                   
               
               
                 Red Layer Dye 
                 Optical 
                 OP11 
                 Relative Transmission @620 nm- 
                 AVG &gt;90% 
               
               
                   
                   
                   
                 640 nm 
                   
               
               
                 All Dye 
                 Chemical 
                 CH01 
                 Solubility in Acetone 
                 Initial screening conditions: 
               
               
                   
                   
                   
                   
                 0.03 g in 2 ml (room temperature,  
               
               
                   
                   
                   
                   
                 3-4 min ultrasonic) 
               
               
                 All Dye 
                 Chemical 
                 CH02 
                 Solubility in IPA 
                 Initial screening conditions: 
               
               
                   
                   
                   
                   
                 0.03 g in 2 ml (room temperature, 
               
               
                   
                   
                   
                   
                 3-4 min ultrasonic) 
               
               
                 All Dye 
                 Chemical 
                 CH03 
                 Solubility in Hexane 
                 No requirement 
               
               
                 All Dye 
                 Chemical 
                 CH04 
                 Solubility in Water 
                 No requirement 
               
               
                 All Dye 
                 Chemical 
                 CH05 
                 Concentration in 
                 up to 3000 ppm 
               
               
                   
                   
                   
                 High Index Resin 
               
               
                   
               
            
           
         
       
     
     Table 4 lists suitable ranges related to doping of chromatic components in high R.I. resins used for polymer waveguides. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Absorption and Transmission bands, 
               
               
                 absorptivity, and solubility for RGB polymer waveguides. 
               
            
           
           
               
               
               
               
            
               
                   
                 Absorption Band (nm) 
                 Transmission Band (nm) 
                 Solubility 
               
               
                   
                 Absorptivity 
                 Absorptivity 
                 with no  
               
               
                 Color 
                 (Lg −1  cm −1 ) 
                 (Lg −1  cm −1 ) 
                 particulates 
               
               
                   
               
               
                 Red 
                 400-560  
                 600-650  
                 &gt;3 ppm 
               
               
                   
                 &gt;10 
                 &lt;0.1 
                   
               
               
                 Green 
                 440-480, 600-650  
                 500-550 nm  
                 &gt;3 ppm 
               
               
                   
                 &gt;10 
                 &lt;0.1 
                   
               
               
                 Blue 
                 500-700 nm  
                 440-480  
                 &gt;3 ppm 
               
               
                   
                 &gt;10 
                 &lt;0.1 
               
               
                   
               
            
           
         
       
     
     Assuming that diffraction efficiency from LCOS is 60:1, and that all of this light is incident upon an ICG of a color other than the color of interest, it is estimated that &gt;5:1 (&lt;20% transmission) color filter performance is needed to achieve &gt;300:1 performance. Using an estimated average path length in the waveguide of 50 mm, this equates to an absorptivity of ≥0.14 cm −1 . For the color of interest, a transmission of &gt;95% is advantageous. Using an estimated average path length in the waveguide of 50 mm, this equates to an absorptivity of ≤0.004 cm −1 .  FIGS. 9A-9C  show examples of suitable absorptivity ranges for RGB dye wavelength ranges for color-selective polymer waveguides. In  FIG. 9A  (blue dye), the absorptivity for blue dye  900  is typically about 0.004 cm −1  or less, and the absorptivity for green dye  902  and red dye  904  is typically about 0.14 cm −1  or greater. In  FIG. 9B  (green dye), the absorptivity for green dye  902  is typically about 0.004 cm −1  or less, and the absorptivity for blue dye  900  and red dye  904  is typically about 0.14 cm −1  or greater. In  FIG. 9C  (red dye), the absorptivity for red dye  904  is typically about 0.004 cm −1  or less, and the absorptivity for blue dye  900  and green dye  902  is typically about 0.14 cm −1  or greater. 
     While a final concentration of a colorimetric component at casting may correspond to the levels depicted in  FIGS. 9A-9C , these ranges would correspond to &lt;72% transmission (absorbing regions) and &gt;99% transmission (transmission regions) for a 1 cm path length. It may be advantageous to consider an absorbance range between &gt;0.7 and &lt;0.02 at a 1 cm path length, which corresponds to &lt;20% transmission (absorbing region) and &gt;95% transmission (transmission regions). 
       FIGS. 10A-10C  show examples of suitable transmission for RGB dyes for color-selective polymer waveguides. In  FIG. 10A  (blue dye), the transmission for blue dye  900  is typically about 95% or greater, and the transmission for green dye  902  and red dye  904  is typically about 20% or less. In  FIG. 10B  (green dye), the absorptivity for green dye  902  is typically about 95% or greater, and the transmission for blue dye  900  and red dye  904  is typically about 20% or less. In  FIG. 9C  (red dye), the transmission for red dye  904  is typically about 95% or greater, and the absorptivity for blue dye  900  and green dye  902  is typically about 20% or less. 
     In another aspect, colorant-doped (e.g., dye- or pigment-doped) UV-curable adhesives are implemented to retain light-absorbing or light-attenuating properties of an edge seal adhesive or interlayer adhesive, thereby allowing for efficient UV curing at a wide range of applied thicknesses. UV-cured adhesives are typically used for interlayer adhesive and edge seal applications, but if excessive UV light is absorbed at the adhesive surface during UV curing, a UV-cured skin and un-cured center can result. This imposes a thickness limitation on the applied adhesive, increasing processing time (cycles) in order to achieve increased thickness or limiting maximum thickness of the applied adhesive if the processing time is held constant. This effect is even more apparent for “black-edging adhesives,” which typically include carbon black and broadly absorb UV-Visible light. 
       FIG. 11  shows the UV-visible (200-400 nm 400-700 nm, respectively) spectrum of an example UVA enhanced lamp (Uvitron 600 W UVA Enhanced Lamp Spectral Distribution UV0834) suitable for UV curing of adhesives. The relative intensity of UVC radiation (200 nm to 280 nm—depicted as 250 nm to 280 nm)  1100 , UVB radiation (280 nm to 315 nm)  1102 , UVA radiation (315 nm to 400 nm)  1104 , and visible radiation (400 nm to 700 nm)  1106 . Carbon black absorption spectra have a broad absorption across UV and visible wavelengths. This broad absorption, especially in the UV, decreases the depth of cure of a black edging adhesive, and the UV radiation typically only penetrates to a limited depth of the layer (e.g., 120 μm to 200 μm), leaving the rest of the layer partially cured or completely uncured in the absence of thermal curing. When an edge seal is partially un-cured, the adhesive can phase separate during reliability test conditions, with clear resin wicking into the grating areas. While repeated application of thinner coatings followed by UV-curing after each coating can be implemented to achieve thicker coatings, adhesive dispensing uniformity and increased processing times (cycles) can be problematic. 
     Colorant-doped adhesives described herein are suitable for high-throughput manufacturing of waveguide based eyepieces including polymer or glass waveguides. The absorption spectra of these color-absorbing adhesives can be selectively tuned (RGB, CMYK, etc.) to match the color channel and visible light absorption specifications of each waveguide. Colorants (e.g., pigments or dyes) with tailored spectra can be added to an adhesive to absorb the specific operating single or multiple wavelengths of light of the waveguides while not absorbing UV light, thereby allowing for efficient curing of the adhesive material with limited effect of its thickness. This method allows for fabrication of a customized wavelength-absorbing adhesive. 
     Colorant-doped adhesives are prepared by combining a base adhesive and a colorant. As provided by the Beer-Lambert law, concentration of the colorant in the base adhesive can be selected based on the absorptivity of the colorant at the wavelength of interest, the amount of light to be attenuated, and the optical path-length available to achieve this attenuation. The colorant can be selected to absorb the specific wavelength(s) carried by waveguide while not absorbing UV light. Suitable colorant concentrations are typically in a range of 0.1 mg/L to 100 g/L. Table 5 lists examples of commercially available UV curable adhesive materials, and Table 6 lists examples of commercially available colorants. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Examples of UV-curable adhesives 
               
            
           
           
               
               
               
            
               
                 Manufacturer 
                 Product Name 
                 Viscosity (cP) 
               
               
                   
               
               
                 ThreeBond 
                 TB3042B 
                    500 cP 
               
               
                 ThreeBond 
                 TB3114 
                 26,000 cP 
               
               
                 Dexerials 
                 SA1641SN 
                 35,000 cP 
               
               
                 Dexerials 
                 SA1801SN 
                 33,000 cP 
               
               
                 Dymax 
                 3069 
                    450 cP 
               
               
                 Dymax 
                 4-20418-GEL 
                 35,000 cP 
               
               
                 Dymax 
                 6-630-T 
                  6,000 cP 
               
               
                 Dymax 
                 OP-4-20632-GEL 
                 70,000 cP 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Examples of colorants 
               
            
           
           
               
               
               
            
               
                   
                   
                 Absorbing wavelength 
               
               
                   
                 Dye 
                 (nm) 
               
               
                   
                   
               
               
                   
                 VIS 484 
                 420-550 
               
               
                   
                 Adam Gates &amp; Company 
                 Blue and Green 
               
               
                   
                 VIS 606 
                 530-650 
               
               
                   
                 Adam Gates &amp; Company 
                 Red and Green 
               
               
                   
                 VIS 682 
                 600-750 
               
               
                   
                 Adam Gates &amp; Company 
                 Red 
               
               
                   
                 VIS461B 
                 400-500 
               
               
                   
                 QCR Solutions Corp 
                 Blue 
               
               
                   
                 VIS548B 
                 450-600 
               
               
                   
                 QCR Solutions Corp 
                 Green 
               
               
                   
                 VIS637A 
                 500-700 
               
               
                   
                 QCR Solutions Corp 
                 Red and Green 
               
               
                   
                   
               
            
           
         
       
     
     In one example, a green light source with FWHM between 1 nm and 35 nm is paired with a colorant that absorbs in the same wavelength range. For certain architectures and light sources, a 1:1 match in spectra is favorable. For other architectures and light sources, the colorant absorption spectrum is focused on the peak wavelength of light source. 
     In a single color absorption example, a red channel waveguide is paired with an adhesive doped with red-absorbing colorant used as an edge absorber.  FIGS. 12A-12C  show RGB edge absorbers with colorant absorption spectra tailored directly to the color channel carried in the waveguide. The waveguide can be made of glass or polymer.  FIG. 12A  shows blue channel waveguide  1200  with spacer  1202  having adhesive  1204  doped with UV-pass blue-absorbing colorant (e.g., VIS461B).  FIG. 12B  shows green channel waveguide  1210  with spacer  1212  having adhesive  1214  doped with UV-pass green-absorbing colorant (e.g., VIS548B).  FIG. 12C  shows red channel waveguide  1220  having spacer  1222  having adhesive  1224  doped with UV-pass red-absorbing colorant (e.g., VIS637A). 
     In a multi-color absorption example, a blue and green channel waveguide is paired with an adhesive doped with blue and green wavelength absorbing colorant used as an edge absorber. The blue and green channel waveguide can be made of glass or polymer.  FIG. 13  depicts blue and green channel waveguide  1300  with spacer  1302  having adhesive  1304  doped with UV-pass blue- and green-absorbing colorant (e.g., Adam Gates VIS484 or QCR Solutions VIS461B+QCR Solutions VIS548B). 
       FIG. 14A  shows transmission (%) versus wavelength (nm) of various compositions, including air (plot  1400 ), a comparative example with adhesive (LPB-224) only (plot  1402 ), and examples including adhesive (LPB-224) and various colorant (Adam Gates VIS484) concentrations (plots  1404 ,  1406 ,  1408 ,  1410 ) showing tailored absorption in blue and green wavelengths. Plot  1404  corresponds to 1 mL LPB-224/20 μL dye standard. Plot  1406  corresponds to 1 mL LPB-224/40 μL dye standard. Plot  1408  corresponds to 1 mL LPB-224/80 μL dye standard. Plot  1410  corresponds to 1 mL LPB-224/160 μL dye standard. The dye standard included 0.0177 g of VIS484 dissolved in 20.58 g (or 20.58 mL) base monomer (LPB). Plots  1420 ,  1422 ,  1424  in  FIG. 14B  show percent transmission (% T) versus dopant level at 640 nm, 520 nm, and 450 nm, respectively, taken from  FIG. 14A . 
     In another example, a visible wavelength edge absorber and interlayer lamination adhesive is prepared by adding colorants that absorb wavelengths of every color channel in the eyepiece stack.  FIG. 15  shows red, green, and blue channel waveguides  1500 ,  1502 ,  1504  between cover layers  1506  and supported by visible wavelength edge absorbers  1508  and integrated spacers  1510  and  1512 . Waveguides  1500 ,  1502 , and  1504  can be made of polymer or glass. Visible wavelength edge absorbers  1508  are RGB absorbing, UV-pass. Integrated spacers  1510  and  1512  include visible wavelength inter-lamination glue that is RGB absorbing, UV pass. Any mixture of RGB, CMY, or the like can be used, depending on the wavelength(s) of waveguide channel light that are advantageously absorbed, while leaving the adhesive with UV-transparency. 
     Plots  1600 ,  1602 ,  1604  in  FIG. 16  shows overlaid absorbance spectra (absorbance versus wavelength) of individual QCR Solutions Dye VIS637A (red), VIS548B (green), and VIS461B (blue), respectively, exhibiting little absorption in the UV band. Plot  1700  in  FIG. 17  shows optical output versus wavelength for a combination of QCR Solutions Dyes (33% VIS461, 33% VIS548, and 33% VIS637) from  FIG. 16 . Plots  1702 ,  1704 ,  1706  show optical output versus wavelength for example RBG light emitting diode output. Plot  1708  shows optical output versus wavelength for phototropic transmission illustrating absorption in RGB bands (RGB=0.735, 0.797, and 0.727, respectively). 
     Customized color-absorbing adhesive can be applied on an edge (e.g., as depicted in  FIGS. 12A-12C and 13 ) or on any horizontal surface of a waveguide layer, inclusive of integrated spacers (e.g., as depicted in  FIG. 15 ). 
     Refractive index matching of the adhesive (whether for inter-layer adhesive or edge absorber) can be obtained by utilizing a high index component along with methods described herein or by using a high refractive index UV cure adhesive and a matching colorant as described herein. Closer refractive index matching between the adhesive and waveguide layer can be achieved to reduce back reflections at an interface. 
     Colorants can be incorporated into a wide range of adhesives without limiting or restricting the dispensed thickness, dispensed area, or viscosity of the adhesive. A viscosity of the adhesive can be selected as appropriate for an intended application. A suitable viscosity range for edge seals is typically in a range of about 300 cP to about 3000 cP at application temperature (e.g., at room temperature). A suitable viscosity range for interlayer lamination without integrated spacers is typically in a range of about 27,000 cP to about 70,000 cP. A suitable viscosity range for interlayer lamination with adhesive dispensed on integrated spacers is typically less than about 20 cP. A thickness range of the adhesive also depends on intended applications. A suitable thickness for edge seals is typically in a range of about 50 μm to about 150 μm. A suitable thickness for interlayer lamination with integrated spacers is typically in a range of about 25 μm to about 250 μm. A suitable thickness for interlayer lamination with integrated spacers is typically in a range of about 1 μm to about 10 μm. 
     While this specification contains many specific details, these should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as examples of features that are associated with particular embodiments. Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some examples be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, various structures shown above may be used, with elements rearranged, positioned differently, oriented differently, added, and/or removed. Accordingly, other embodiments are within the scope of the following claims.