3D printing method and light guide made thereby

Abstract

The present disclosure relates to a method of 3D printing a light guide optical element, comprising: 3D printing a chassis comprising a first surface and at least one holding means formed on a second surface opposite the first surface and angled relative to the first surface using at least one ultra-transparent liquid resin; bringing the at least one translucent beam splitter into contact with the at least one holding device; and contacting the at least one ultra-transparent liquid resin over the at least one translucent beam splitter and curing the at least one ultra-transparent liquid resin so as to form the light guide optical element. The present disclosure also relates to light guide optical elements made thereby.

Description

Technical Field

[0001] This invention generally relates to 3D printing methods and optical guide elements produced therefrom. Background Technology

[0002] A light-guiding optical element (LOE) is a waveguide that directs electromagnetic waves from a light source to the user's eye. LOEs can be used in augmented reality displays.

[0003] Augmented reality (AR) display technology enables users to perceive virtual images superimposed on the real world. AR integrates and overlays virtual information onto the user's physical world in real time. Optical see-through near-eye displays are commonly used in AR display systems, typically employing light-guiding optics (LOEs) to guide light emitted from the display panel to the user's eyes.

[0004] Based on publicly announced business plans from leading technology companies in the Augmented Reality (AR) field, AR possesses enormous market potential and could become the next-generation computing platform. This could lead to a shift in consumer spending away from traditional mobile devices. Compared to conventional smart glasses that simply overlay content onto a head-mounted display, AR enables viewers to interact with virtual information in a more vivid way without affecting their natural vision. To date, AR has been progressively used in navigation, entertainment, healthcare, manufacturing, education, and the military. With its widespread adoption in industry, driving, and education, AR has the potential to become the next-generation computing platform.

[0005] One of the key components in near-eye displays used in AR applications is the optical waveguide or optical combiner. Commercially available optical combiners can be broadly categorized into two types based on their operating principles: geometric and diffractive. Geometric waveguide structures were initially proposed by Lumus and have been continuously optimized over the past two decades. In this approach, incident light first enters the waveguide through a reflective surface. After multiple rounds of total internal reflection, the light encounters a semi-transmissive semi-reflective mirror array, which couples the light out. Diffractive waveguide structures, on the other hand, utilize diffractive optical elements such as surface relief gratings or volume holographic gratings to couple light into and out of the waveguide. Similar to geometric waveguide structures, using surface relief gratings also provides an effective method. This method involves introducing an incident grating to couple light into the waveguide and replacing the mirror array with an exit grating. Companies such as Microsoft, Vuzix, Magic Leap, and Waveoptics have commercialized devices using this technology. Another type of diffractive waveguide structure is based on the use of volume holographic gratings, employing different grating manufacturing techniques closely related to hologram fabrication. While products based on this technology are currently limited in the market, Digilens and Sony have demonstrated prototypes showcasing the potential of this approach. Table 1 provides an overview of these AR glasses.

[0006] Table 1. AR glasses available on the market. Due to the challenges of manufacturing AR waveguides, most AR glasses require long delivery times.

[0007]

[0008] In addition to these methods, the literature also reports many alternative optical waveguides using different approaches, such as holographic optics, needle-beam configurations, metasurfaces, and polarization devices. However, these technologies have not yet been commercialized due to various challenges in the manufacturing process.

[0009] Both geometric waveguides and diffractive waveguides exhibit advantages and disadvantages. Diffractive waveguide technology relies on depositing thin films on a glass substrate, eliminating the need for glass slicing and bonding processes used in manufacturing geometric waveguides. This offers advantages in terms of design and manufacturing flexibility. However, a significant drawback is the presence of chromatic aberration or rainbow effects. Furthermore, diffractive waveguides can have limitations in their field of view. These issues primarily stem from the inherent selectivity of the diffraction grating relative to the light input angle and wavelength. Additionally, the refractive index of the waveguide also plays a role in these limitations. In contrast, geometric waveguide structures can provide a large field of view, excellent image quality, and are dispersion-free. However, the commercialization of both methods faces challenges due to limitations in mass production capabilities. Consequently, most AR glasses on the market are expensive.

[0010] Traditional LOE manufacturing methods are costly, time-consuming, unable to produce curved or other shapes, and often result in poor image quality. Currently, there are two main LOE manufacturing methods. The first method involves depositing multiple layers of material exhibiting different refractive indices onto a glass surface using techniques such as photolithography, physical vapor deposition, and electron beam evaporation, followed by layer-by-layer lamination, cutting, and further optical or air-bonding processes. The second method traditionally relies on injection molding or thermoforming, which is difficult to mass-produce due to its time-consuming and costly nature. Furthermore, these manufacturing techniques are prone to deficiencies in the precision and uniformity of any microstructures used, which can lead to a decline in the displayed image quality.

[0011] The aim is to overcome or improve at least one of the above-mentioned problems. The aim is to overcome or improve the manufacturing challenges arising from high optical performance requirements, miniaturization, and lightweight limitations. The aim is to overcome or improve the problem of insufficient production capacity in its mass production. Summary of the Invention

[0012] This disclosure provides a method for 3D printing optical guide components, including:

[0013] a) 3D printing a base structure using at least one ultra-transparent liquid resin, the base structure including a first surface and at least one holding means formed on a second surface opposite to the first surface and at an angle relative to the first surface.

[0014] b) bringing at least one semi-transparent beam splitter into contact with the at least one holding device; and

[0015] c) Contact the at least one ultra-transparent liquid resin above the at least one semi-transparent beam splitter and cure the at least one ultra-transparent liquid resin to form a light guide optical element.

[0016] In some embodiments, the base structure is 3D printed on a substrate.

[0017] In some embodiments, step a) includes: depositing and at least partially curing the at least one ultra-transparent liquid resin in a slice-by-slice manner. This prevents the formation of air pockets during the curing process by 3D printing the underlying structure.

[0018] In some embodiments, the infrastructure is 3D printed using a liquid crystal display (LCD) 3D printer.

[0019] In some embodiments, step a) includes: changing the refractive index of the at least one ultra-transparent liquid resin such that at least one 3D-printed slice of the base structure has a different refractive index relative to adjacent 3D-printed slices. This allows for optical path compensation in cases where the total internal reflected optical path is offset due to curvature or thickness variations caused, for example, by bending light guide optics.

[0020] In some embodiments, step a) includes: at least partially curing the at least one 3D printed slice of the base structure under conditions different from those of adjacent 3D printed slices.

[0021] In some embodiments, the at least one 3D printed slice is at least partially cured under a different light pattern relative to adjacent 3D printed slices.

[0022] In some embodiments, the at least one 3D printed slice is at least partially cured under a different light intensity relative to adjacent 3D printed slices.

[0023] In some embodiments, step a) includes: 3D printing the base structure using a second ultra-transparent liquid resin with a different refractive index, such that at least one 3D printed slice of the base structure has a different refractive index relative to an adjacent 3D printed slice.

[0024] In some embodiments, step a) includes: 3D printing a base structure using a mixture of the at least one ultra-transparent liquid resin and a second ultra-transparent liquid resin having a different refractive index, such that at least one 3D printed slice of the base structure has a different refractive index relative to an adjacent 3D printed slice.

[0025] In some embodiments, step a) includes:

[0026] i) 3D printing slices of the basic structure;

[0027] ii) Mixing a portion of the second ultra-transparent liquid resin into the at least one ultra-transparent liquid resin;

[0028] iii) 3D printing subsequent slices of the basic structure; and

[0029] iv) Repeat steps ii) and iii) iteratively until the basic structure is formed.

[0030] In some embodiments, the refractive index difference between 3D printed slices is from about 0.001 to about 0.1.

[0031] In some embodiments, the ultra-transparent liquid resin is a UV-curable resin.

[0032] In some embodiments, the ultra-transparent liquid resin is an acrylic resin.

[0033] In some embodiments, step a) is performed at ambient temperature, or preferably at about 20°C to about 40°C.

[0034] In some embodiments, the ultra-transparent liquid resin is characterized by a viscosity of about 400 MPa to about 700 MPa, or preferably about 450 MPa to about 600 MPa.

[0035] In some embodiments, the ultra-transparent liquid resin is characterized by a volume shrinkage rate of less than 8%, or preferably less than 1%.

[0036] In some embodiments, 3D printing is further performed in the presence of a release liner and / or a hydrophobic material.

[0037] In some embodiments, the at least one retaining device is a ramp cut into a second surface of the base structure.

[0038] In some embodiments, the at least one holding device is at an angle of about 20° to about 40°.

[0039] In some embodiments, the at least one holding device is three holding devices, and the at least one semi-transparent beam splitter is three semi-transparent beam splitters.

[0040] In some embodiments, the at least one semi-transparent beam splitter is selected from dielectric reflectors, metal reflectors, or combinations thereof.

[0041] In some embodiments, the at least one semi-transparent beam splitter is characterized by having a transparency of at least 85%.

[0042] In some embodiments, the at least one semi-transparent beam splitter is characterized by a reflectivity of about 8% to about 20%, or preferably about 10%.

[0043] In some embodiments, the semi-transparent beam splitter is characterized by a root mean square (RMS) roughness of about 1.1 nm to about 1.8 nm.

[0044] In some embodiments, step c) includes: immersing the 3D-printed base structure into a tank comprising an ultra-transparent liquid resin, and immersing the at least one translucent beam splitter into the tank such that the at least one translucent beam splitter contacts a holding device of the base structure.

[0045] In some embodiments, the method further includes a step of 3D printing a top structure separately, the top structure including a third surface and a fourth surface opposite to the third surface, wherein the fourth surface includes a morphology complementary to the second surface relative to the base structure and the at least one translucent beam splitter.

[0046] In some embodiments, the method further includes the step of mating the base structure and the at least one semi-transparent beam splitter with the top structure to form a light-guiding optical element.

[0047] In some embodiments, the base structure and the at least one translucent beam splitter are fitted with the top structure in a tank comprising an ultra-transparent liquid resin and cured.

[0048] In some embodiments, step c) includes: contacting the transparent substrate and the at least one ultra-transparent liquid resin above the holding device of the base structure and the second surface to form a covered groove; curing the at least one ultra-transparent liquid resin such that the transparent substrate is bonded to the second surface; and filling the covered groove with a transparent liquid to form a light guide optical element.

[0049] In some embodiments, the transparent liquid is characterized by a refractive index of about 1.4 to about 1.8.

[0050] In some embodiments, the transparent liquid is silicone oil, mineral oil, polydimethylsiloxane (PDMS), or a combination thereof.

[0051] In some embodiments, step c) includes: 3D printing an ultra-transparent liquid resin over the at least one translucent beam splitter. In some embodiments, step c) includes: depositing and at least partially curing the ultra-transparent liquid resin in a slice-by-slice manner. In this way, any gaps or spaces adjacent to the at least one translucent beam splitter can be filled layer by layer.

[0052] In some embodiments, step c) includes: changing the refractive index of the ultra-transparent liquid resin such that at least one 3D printed slice has a different refractive index relative to adjacent 3D printed slices.

[0053] In some embodiments, the infrastructure further includes prism structures at its ends.

[0054] In some embodiments, the prism is a triangular prism positioned at an angle of about 40° to about 60° relative to a first surface of the base structure.

[0055] In some embodiments, the method further includes, after step a), a step of cleaning and further curing the base structure of step a).

[0056] In some embodiments, the method further includes: changing the refractive index of the light guide optical element such that at least one 3D printed slice of the light guide optical element has a different refractive index relative to an adjacent 3D printed slice.

[0057] In some embodiments, the method further includes: thermally annealing the optical element.

[0058] In some embodiments, the light-guiding optical element is characterized by a transparency of more than about 85%.

[0059] This disclosure also provides 3D-printed light guide optical elements formed by methods as disclosed herein.

[0060] This disclosure also provides 3D-printed light-guiding optical elements, including:

[0061] a) An ultra-transparent body with a first surface; and

[0062] b) At least one semi-transparent beam splitter within the ultra-transparent body and at an angle relative to the first surface;

[0063] The 3D printed optical guide element is characterized in that at least one 3D printed slice has a different refractive index relative to the adjacent 3D printed slice.

[0064] This disclosure also provides 3D-printed light-guiding optical elements, including:

[0065] a) An ultra-transparent body with a first surface; and

[0066] b) At least one semi-transparent beam splitter within the ultra-transparent body and at an angle relative to the first surface;

[0067] Among them, the cross-section of the 3D printed optical guide element is characterized by one part of the cross-section having a different refractive index relative to another part. Attached Figure Description

[0068] Embodiments of the invention will now be described by way of non-limiting example with reference to the accompanying drawings, in which:

[0069] Figure 1 (Left) A 2D schematic diagram of the waveguide showing the reflector orientation, image formation direction, and optical coupling direction. (Right) A 3D representation of the waveguide.

[0070] Figure 2 Ray tracing illustrates the optical path, image composition, and pupil expansion as light travels from the coupled optics to the end-user's eye.

[0071] Figure 3(Left) Loading an object (bitmap file) into the model so that the spatial density of the light rays emitted from the object's surface is proportional to the values ​​in the imported bitmap. (Right) An enlarged, perfectly stitched image (rotated for easier viewing) is shown, reconstructed using 23,000 rays on the image plane.

[0072] Figure 4 The foundation of 3D printing of optical components.

[0073] Figure 5 A 3D-printed AR waveguide display prototype and its perspective image. The image is coupled from an LCOS-based light engine. A camera captures the floating image.

[0074] Figure 6 A side view of an optical guide element with layers of different refractive indices to compensate for total internal refraction (TIR) ​​imaging offset in the case of a bent waveguide.

[0075] Figure 7 Ray tracing illustrates the optical path, image composition, and pupil expansion as light travels from the coupled optics to the user's eye. The object (bitmap file) is loaded into the model in such a way that the spatial density of rays emitted from the object's surface is proportional to the values ​​in the imported bitmap. A reconstructed image generated on the image plane using 23,000 rays shows a magnified, perfectly stitched, and inverted image. A 2D schematic of the waveguide illustrates the key angles and dimensions of the combiner.

[0076] Figure 8 Adapted printing platform and manufacturing process. A schematic diagram illustrates the improved 3D printing platform. To enhance light distribution uniformity, a diffuser and absorber are placed in front of the light source. Additionally, another diffuser is positioned on top of the LCD screen. The top and bottom components of the waveguide are printed separately on a glass printing bed and then integrated with the dielectric reflector.

[0077] Figure 9 Illumination uniformity and LCD pixel gap issues. (Left) A comparative example shows illumination uniformity with and without a light source diffuser. Due to excessive light source intensity causing camera sensor saturation, an optical filter was used to reduce LED intensity, revealing the illumination pattern depicted in the lower right subfigure. (Right) Without an LCD diffuser, the printed sample shows numerous fine lines within the body, as indicated by the arrows. However, these lines disappear after applying the diffuser. To enhance the visibility of the lines, a transparent sample was placed on a piece of black paper and observed under a microscope.

[0078] Figure 10Surface roughness and transmittance of the reflector and a 3D-printed sample with a thickness of 3 mm. (Left) 2D surface roughness maps of the reflector and the printed resin block were measured over a small area (5 µm × 2.5 µm). (Right) Transmittance of the reflector was measured at incident angles of 0° and 65°. Transmittance of the 3D-printed resin block was measured at an incident angle of 0°, showing an average transmittance of 92.3% above 420 nm.

[0079] Figure 11 Experimental results. (a) A printed prototype of a waveguide integrating three reflectors. (b) The prototype is placed at an angle to show the reflectors. (c) Projected image. (d) Overlap of the virtual image with the real world. Due to the design of the combiner, the virtual image is horizontally mirrored.

[0080] Figure 12 (a) Design of the optical system. (b) The left image shows the target bitmap image, and the right image shows the reconstructed image stitched together at the retina. (c) Illustration of the manufacturing process.

[0081] Figure 13 (a) A prototype of a liquid light combiner. (b) An example of a virtual image captured by the liquid light combiner, overlaid with a laboratory environment. The projection source image is shown in the lower left corner. Detailed Implementation

[0082] This disclosure is based on the understanding that the mass production of augmented reality (AR) waveguides has always been challenging due to the complex nature of the manufacturing technology and the high precision required for their optical properties.

[0083] Without being bound by theory, the inventors believe that ultra-transparent liquid resin can be used in 3D printing technology to additively or synergistically address the aforementioned problems by facilitating the production of 3D-printed optics with quality comparable to conventional optical components. This specialized resin is formulated to minimize turbidity and exhibits low shrinkage after UV curing, enabling the fabrication of AR light combiners that offer superior clarity and transparency. Additive manufacturing (or 3D printing) involves the continuous layer-by-layer deposition of material to generate three-dimensional objects. This method facilitates the production of complex and customized geometries that may be difficult to achieve using conventional manufacturing techniques. Moreover, 3D printing allows for simplified mass production and reduced production costs. Accordingly, this paper discloses a 3D printing method suitable for manufacturing optically high-quality AR displays.

[0084] This paper presents a low-cost method for fabricating geometric light guide optics (or waveguides) designed for AR applications using 3D printing technology. To achieve a balance between optical performance and fabrication feasibility, conventional geometric waveguide designs are optimized to facilitate easier manufacturing. The waveguide integrates at least three dielectric reflectors. This method eliminates the need for molding, dicing, and post-printing surface polishing. The waveguide's fabrication cost is approximately $5. Prototypes based on this method have been successfully fabricated, demonstrating immersion between virtual images and real-world scenes. This method has significant potential for large-scale production adaptable to a wide range of AR applications.

[0085] Accordingly, this disclosure relates to a method for 3D printing light guide optical elements, comprising:

[0086] a) 3D printing a base structure using at least one ultra-transparent liquid resin, the base structure including a first surface and at least one holding device formed on a second surface opposite to the first surface and at an angle relative to the first surface;

[0087] b) bringing at least one semi-transparent beam splitter into contact with the at least one holding device; and

[0088] c) Contact the at least one ultra-transparent liquid resin above the at least one semi-transparent beam splitter and cure the at least one ultra-transparent liquid resin to form a light guide optical element.

[0089] This disclosure relates to a 3D printing technique for manufacturing light guide optical elements (LOEs) for augmented reality displays. This disclosure enables efficient mass production and is particularly useful in near-eye displays. The LOE is designed to manipulate the direction and intensity of light.

[0090] 3D printing, or additive manufacturing, is the process of constructing three-dimensional objects from CAD or digital 3D models. It can be accomplished through a variety of processes in which materials are deposited, bonded, or solidified under computer control. Materials are typically added together layer by layer, such as plastics, liquids, or powder particles being melted.

[0091] In 3D printing, stereolithography (SLA) and digital light processing (DLP) can be used for resin printing. Both technologies rely on the controlled emission of UV radiation onto a liquid resin tank, transforming it into a solid polymer based on a predefined model loaded into slicing software. In SLA, a laser at a UV frequency is directed into the liquid resin tank. The emission point is controlled by a mirror galvanometer. The laser moves point-by-point along a single layer of resin until that layer is complete, after which the build platform moves to allow fresh resin to be exposed to UV radiation. In DLP, the process is similar, except that the UV radiation is projected onto the entire layer at once using a micron-scale array of mirrors (each mirror can be rotated to control the emission point of the UV radiation). LED light panels can also be used. For both SLA and DLP printers, printing can be performed from bottom to top or top to bottom. The main difference between the two lies in the position of the light source.

[0092] In some embodiments, 3D printing is resin-based 3D printing. This is an additive manufacturing method that cures a liquid photosensitive polymer layer by layer onto a solid object. For example, 3D printing can be stereolithography (SLA) 3D printing. The print bed or platform can be immersed in a transparent resin tank and exposed to UV light emitted from the bottom or top by an LED array. A UV screen can be used to shield the UV light to enable the printing of appropriate 3D structures. The screen can provide a pixel resolution of approximately 22 µm, and bilinear guides provide a stable z-axis step size of 10 µm.

[0093] The 3D printing process for light-guiding optical elements (LOEs) can involve first designing the basic structure using computer-aided design (CAD) software, such as... Figure 4 As shown in the diagram. Other software can also be used. Therefore, the base structure is printed slice by slice according to the template. The template can be designed to include at least one holding device. By changing the template, and thus the base structure to be printed, the light guide optics can be configured for different augmented reality displays.

[0094] The basic structure can be printed using a liquid crystal display (LCD) 3D printer. An LCD 3D printer is configured to provide an LCD screen that is generated based on layers of the 3D structural model to be printed. UV light can be transmitted through the LCD screen, which cures the resin. In this way, the entire layer can be irradiated with UV light at once. This means that 3D printing using an LCD 3D printer may be faster and more accurate than using other 3D printers.

[0095] The difference between LCD 3D printers and other types of 3D printers, such as DLP or SLA printers, lies in their light source. LCD 3D printers use a UV LCD array as their light source. Therefore, light from the LCD panel shines directly onto the work area in a parallel manner. Because this light does not spread, LCD printing suffers from significantly less pixel distortion.

[0096] At least one type of ultra-transparent liquid resin can be slowly poured into the 3D printer to avoid generating air bubbles.

[0097] In some embodiments, the basic structure is 3D printed on a substrate. The substrate may have a smooth surface, such as glass. To further improve the smoothness of the surface, and thus the smoothness of the resulting 3D printed product, the surface of the substrate may be polished or etched with ozone water. The substrate may be temporarily held on the print bed using an adhesive such as glue or double-sided tape.

[0098] In some embodiments, step a) includes: depositing and at least partially curing at least one ultra-transparent liquid resin in a slice-by-slice manner. Air pockets are prevented from forming during the curing process by 3D printing the base structure.

[0099] In some embodiments, step a) includes: changing the refractive index of at least one ultra-transparent liquid resin such that at least one 3D-printed slice of the base structure has a different refractive index relative to adjacent 3D-printed slices. This allows for optical path compensation in cases where the overall internal reflected light path is offset due to curvature or thickness variations caused, for example, by bending a light guide optics. Certain regions of the light guide optics may also be thickened for additional structural support. However, differences in thickness can cause deflection and divergence of the light path within the light guide optics, thus producing a blurred virtual image for the user. This can be compensated for by changing the refractive index of certain regions within the light guide optics.

[0100] In some embodiments, step a) includes: changing the curing duration of the ultra-transparent liquid resin such that at least one 3D printed slice of the base structure has a different refractive index relative to adjacent 3D printed slices.

[0101] In some embodiments, step a) includes: at least partially curing (or polymerizing) at least one 3D printed slice of the underlying structure under conditions different from those of adjacent 3D printed slices.

[0102] In some embodiments, at least one 3D printed slice is at least partially cured under a different light pattern relative to adjacent 3D printed slices. In some embodiments, at least one 3D printed slice is at least partially cured under a different light intensity relative to adjacent 3D printed slices. The light intensity can be adjusted in the range of 0 W / cm²–3 W / cm². Thus, for example, one 3D printed slice can be cured using light at about 2.1 W / cm², while adjacent slices can be cured using light at about 2.2 W / cm².

[0103] In some embodiments, step a) includes: 3D printing a base structure using a second ultra-transparent liquid resin with a different refractive index, such that at least one 3D-printed slice of the base structure has a different refractive index relative to adjacent 3D-printed slices. In this regard, at least one ultra-transparent liquid resin can be used to form the 3D-printed slices, and a second ultra-transparent liquid resin can be used to form adjacent slices.

[0104] In some embodiments, step a) includes: 3D printing a base structure using a mixture of at least one ultra-transparent liquid resin and a second ultra-transparent liquid resin having a different refractive index, such that at least one 3D-printed slice of the base structure has a different refractive index relative to adjacent 3D-printed slices. In this respect, the refractive index of the resulting 3D slice is varied by the ratio of the at least one ultra-transparent liquid resin to the second ultra-transparent liquid resin. By giving the 3D slices different ratios, the refractive index can be changed or gradiented.

[0105] In some embodiments, step a) includes:

[0106] i) 3D printing slices of the basic structure;

[0107] ii) Mixing a portion of the second ultra-transparent liquid resin into at least one ultra-transparent liquid resin;

[0108] iii) 3D printing subsequent slices of the basic structure; and

[0109] iv) Repeat steps ii) and iii) iteratively until the basic structure is formed.

[0110] This method, which involves sequentially pouring a second type of ultra-transparent liquid resin into a resin tank, such that the ratio of the second type of ultra-transparent liquid resin to at least one type of ultra-transparent liquid resin increases sequentially, can be performed in a single 3D printer. Alternatively, multiple 3D printers can be used, each comprising a resin tank with different resin ratios.

[0111] In some embodiments, the difference in refractive index between 3D printed slices is from about 0.001 to about 0.1. In other embodiments, the difference in refractive index is from about 0.002 to about 0.1, from about 0.004 to about 0.1, from about 0.006 to about 0.1, from about 0.008 to about 0.1, from about 0.01 to about 0.1, from about 0.02 to about 0.1, from about 0.04 to about 0.1, from 0.06 to about 0.1, or from about 0.08 to about 0.1.

[0112] In some embodiments, the ultra-transparent liquid resin is a UV-curable resin. In some embodiments, the ultra-transparent liquid resin is an epoxy-based resin. In some embodiments, the ultra-transparent liquid resin is an acrylate-based resin. The liquid resin may include acrylate monomers, methacrylate monomers, or combinations thereof. When exposed to UV radiation, these monomers rapidly form molecular bonds with each other and transform into a solid polymer. In some embodiments, the ultra-transparent liquid resin is NOVA3D ultra-transparent resin, Stratasys VeroClear resin, variants thereof, or combinations thereof.

[0113] In some embodiments, step a) is performed at ambient temperature, or preferably at about 20°C to about 40°C.

[0114] In some embodiments, the ultra-transparent liquid resin is characterized by a refractive index of about 1.5 to about 2. In other embodiments, the refractive index is about 1.5 to about 1.9, about 1.5 to about 1.8, about 1.5 to about 1.7, or about 1.5 to about 1.6. For example, NOVA3D ultra-transparent resin with a refractive index of about 1.53 can be used.

[0115] In some embodiments, the ultra-transparent liquid resin is characterized by a viscosity of about 400 MPa to 700 MPa, or preferably about 450 MPa to about 600 MPa.

[0116] In some embodiments, the ultra-transparent liquid resin is characterized by a volume shrinkage rate of less than 8%, or preferably less than 1%. In other embodiments, the volume shrinkage rate is less than 7%, 6%, 5%, 4%, 3%, or 2%. For example, NOVA3D ultra-transparent resin can be used, which has a volume shrinkage rate of 3.6% when cured at 25°C.

[0117] In some embodiments, the method further includes, prior to step a), a step of treating the ultra-transparent liquid resin. This allows for a change in the refractive index.

[0118] In some embodiments, 3D printing is further performed in the presence of a release liner. The release liner can form a film on the surface of the ultra-clear liquid resin when the resin is contained in a liquid tank. The release liner can be a perfluoroalkoxyalkane (PFA).

[0119] In some embodiments, 3D printing is further performed in the presence of a hydrophobic material. The hydrophobic material provides the 3D-printed structure with non-stick properties. The hydrophobic material can form a film on top of the release liner. The hydrophobic material can be polytetrafluoroethylene (PTFE).

[0120] In some embodiments, 3D printing is performed in the presence of a light diffuser. The diffuser disperses light and softens bright or glaring light over a larger area, thereby eliminating unwanted glare. The diffuser can be positioned in the optical path between the light source and the LCD screen. Alternatively, a second diffuser can be positioned in the optical path between the LCD screen and the 3D-printed structure.

[0121] In some embodiments, 3D printing is performed in the presence of a light absorber. The light absorber can be positioned parallel to and outside the light path to remove stray light from the light source to the LCD screen.

[0122] In some embodiments, 3D printing is performed using anti-aliasing. Anti-aliasing is a computer graphics technique that smooths jagged edges on curves and diagonals. By eliminating the “staircase” effect that often appears on curves or diagonals, it helps make digital images look more realistic.

[0123] The basic structure includes a first surface. During 3D printing, the first surface can contact the substrate. In use, the first surface is close to the user's eye. The function of the first surface is to transmit light traveling along the optical path in the light-guiding optics out of the light-guiding optics. In this respect, the optical path of the light is changed after being reflected by the semi-transparent beam splitter and exits from the light-guiding optics.

[0124] The base structure includes at least one retaining device. The retaining device is formed on a second surface opposite to the first surface. Each retaining device may be used to contain a translucent beam splitter. The retaining device may be a ramp cut into the second surface of the base structure, or it may be a groove. In some embodiments, the retaining device is a triangular recess.

[0125] In some embodiments, at least one retaining device is at an angle of about 20° to about 40°, or preferably about 25°, relative to the first surface. In other embodiments, the angle is about 20° to about 35°, or about 20° to about 30°. The angles of the retaining devices may all be the same, or may increase sequentially to allow for optical path compensation in the bent light guide optics.

[0126] Depending on the size of the translucent beam splitter and the eyebox design, multiple translucent beam splitters can be used for pupil expansion. In some embodiments, the infrastructure includes at least two retaining devices for contacting at least two translucent beam splitters. In some embodiments, at least one retaining device is three retaining devices. In some embodiments, at least one retaining device is six retaining devices.

[0127] In some embodiments, the method further includes, after step a), a step of cleaning and further curing the substrate from step a). The substrate may be cleaned using isopropanol in an ultrasonic cleaner. In some embodiments, alcohol is not used. The substrate may be cured using UV light. These actions may be performed individually or as a single step together.

[0128] In some embodiments, the base structure is characterized by a refractive index of about 1.5 to about 2. In other embodiments, the refractive index is about 1.5 to about 1.9, about 1.5 to about 1.8, about 1.5 to about 1.7, or about 1.5 to about 1.6. For example, NOVA3D ultra-transparent resin can be used.

[0129] The translucent beam splitter can be placed on the holding device using a pick-and-place machine or by a jig assembly molded according to the base structure. In this sense, the translucent beam splitter is inserted into the holding device. The translucent beam splitter can be bonded to the holding device and the base structure. Alternatively, the translucent beam splitter can be deposited via deposition methods such as chemical vapor deposition or vacuum deposition.

[0130] Transparent beam splitters can also be 3D printed. Different materials can be used for 3D printing of translucent beam splitters. For example, metal wires, metal powders, metal threads, or metal-impregnated resins can be used. Available techniques include fused deposition modeling (FDM), laser bed fusion (LPBF), electron beam bed fusion (also known as electron beam melting (EBM)), metal binder jetting, arc additive manufacturing (WAAM), laser-directed energy deposition (Laser DED), electron beam directed energy deposition (eBeam DED), micro-metal 3D printing, cold spraying, and fused deposition modeling (FDM).

[0131] In some embodiments, at least one semi-transparent beam splitter is selected from dielectric reflectors, metallic reflectors, or combinations thereof. At least one semi-transparent beam splitter may have a flat or curved shape. A curved shape may follow the gradient of the optical path to direct light to the user.

[0132] A semi-transparent beam splitter can be a dielectric reflector. A dielectric reflector can be a mirror composed of a single thin layer or multiple thin layers of dielectric material, typically deposited on a substrate of glass or some other optical material. By carefully selecting the type and thickness of the dielectric layer, optical coatings with specific reflectivities for different wavelengths of light can be designed. Unreflected light is transmitted through the dielectric reflector. The percentage of reflected and transmitted light can be controlled, for example, by the thickness and number of thin layers.

[0133] In some embodiments, at least one semi-transparent beam splitter is characterized by having a transparency of at least about 85%, or preferably at least about 90%.

[0134] In some embodiments, at least one semi-transparent beam splitter is characterized by a transmittance of at least about 85%, or preferably at least about 90%. Transmittance is the fraction of incident light that is transmitted. In other words, it is the amount of light that "successfully" passes through the material and emerges from the other side.

[0135] In some embodiments, at least one semi-transparent beam splitter is characterized by a reflectivity of about 8% to about 20%, or preferably about 10%.

[0136] In some embodiments, the semi-transparent beam splitter is characterized by a root mean square (RMS) roughness of about 1.1 nm to about 1.8 nm. In other embodiments, the RMS roughness is about 1.1 nm to about 1.7 nm, about 1.1 nm to about 1.6 nm, about 1.1 nm to about 1.5 nm, or about 1.1 nm to about 1.4 nm.

[0137] In some embodiments, the semi-transparent beam splitter is characterized by an average roughness of about 1 nm to about 1.5 nm. In other embodiments, the average roughness is about 1 nm to about 1.4 nm, about 1 nm to about 1.3 nm, about 1 nm to about 1.2 nm, or about 1 nm to about 1.1 nm.

[0138] Optical components can be formed from a base structure in several ways. The base structure with a semi-transparent beam splitter can be brought into contact with an additional ultra-transparent liquid resin, thereby covering the semi-transparent beam splitter. The ultra-transparent liquid resin can then be cured to completely encapsulate the semi-transparent beam splitter. For example, the contact and curing steps can be performed as a single step, or they can be performed layer-by-layer using a micro-assembly machine.

[0139] For example, an ultra-transparent liquid resin can be added sufficiently to submerge at least one ramp. An ultra-transparent liquid resin can be added to completely submerge the translucent beam splitter. Upon curing, the second surface of the base structure forms a flat surface for the light-guiding optics. This surface allows light to pass through the light-guiding optics, enabling the user to see a true image through them.

[0140] Accordingly, in some embodiments, at least one ultra-transparent liquid resin in step c) originates from a different stock solution. In other words, at least one ultra-transparent liquid resin in step c) is not 3D printed on top of the second surface. At least one ultra-transparent liquid resin can be poured onto the second surface. By changing the type of at least one ultra-transparent liquid resin, the refractive index of the light guide optical element can be adjusted.

[0141] Alternatively, in some embodiments, the method further includes, after step a), immersing the 3D-printed substrate in a container comprising an ultra-transparent liquid resin. At least one translucent beam splitter may contact at least one holding device within the container.

[0142] In some embodiments, the method further includes immersing the translucent beam splitter in a container comprising an ultra-clear liquid resin. The translucent beam splitter can contact the substrate in the container comprising the ultra-clear liquid resin. This effectively prevents the formation of air bubbles during placement. It also allows the resin to act as an adhesive for bonding the translucent beam splitter to the substrate during curing.

[0143] In some embodiments, step c) includes: bringing at least one ultra-transparent liquid resin into contact with a second surface of the base structure and the holding device, and at least one translucent bundle splitter and / or above and in contact with them, and curing at least one ultra-transparent liquid resin. In this manner, at least one translucent bundle splitter is bonded to the holding device.

[0144] In some embodiments, the method further includes the step of separately 3D printing a top structure. The top structure includes a third surface adjacent to the printer platform and a fourth surface opposite to the third surface. The fourth surface may have a complementary morphology to the second surface of the base structure and at least one translucent beam splitter. The top structure may be 3D printed on a separate substrate. The top structure can then be coupled with the second surface of the base structure and at least one translucent beam splitter to form a light-guiding optical element. For example, at least one translucent beam splitter may be contacted with a holding device of the second surface of the base structure, and the top structure may be contacted with at least one translucent beam splitter and the second surface in a container comprising an ultra-transparent liquid resin. The assembly can then be cured to form the light-guiding optical element. This effectively prevents the formation of bubbles during placement.

[0145] As another example, in some embodiments, step c) includes: contacting a transparent substrate and at least one ultra-transparent liquid resin above the holding device of the base structure and the second surface to form a covered groove, and curing the at least one ultra-transparent liquid resin such that the transparent substrate is bonded to the second surface. The transparent substrate may be a glass substrate. In this respect, the at least one ultra-transparent liquid resin acts as an adhesive. The covered groove can then be filled with the transparent liquid to form a light-guiding optical element. Therefore, the covered groove is air-free.

[0146] In some embodiments, the transparent liquid is characterized by a refractive index of about 1.4 to about 1.8. In other embodiments, the refractive index is about 1.4 to about 1.7, about 1.4 to about 1.6, or about 1.4 to about 1.5.

[0147] In some embodiments, the transparent liquid is silicone oil, mineral oil, polydimethylsiloxane (PDMS), or a combination thereof.

[0148] In some embodiments, step c) further includes: applying pressure to at least one translucent beam splitter during curing such that it makes uniform contact with the holding device and / or the second surface. For example, pressure may be applied between the base structure and the top structure. For example, pressure may be applied between the transparent substrate and the base structure.

[0149] In some embodiments, at least one ultra-transparent liquid resin is cured under inert conditions in the presence of UV radiation. The inert conditions may be a nitrogen gas flow. At least one ultra-transparent liquid resin may be cured in a nitrogen chamber.

[0150] Alternatively, in some embodiments, step c) includes: 3D printing an ultra-transparent liquid resin over at least one translucent beam splitter. In some embodiments, step c) includes: depositing and at least partially curing the ultra-transparent liquid resin in a slice-by-slice manner. In this way, any gaps or spaces adjacent to at least one translucent beam splitter can be filled layer by layer.

[0151] In some embodiments, step c) includes: changing the refractive index of the ultra-transparent liquid resin such that at least one 3D printed slice has a different refractive index relative to adjacent 3D printed slices.

[0152] In some embodiments, the method further includes a step of heat-treating the optical element. This heat treatment may place the optical element at about 40°C to about 80°C for about 20 minutes to about 60 minutes. This helps to alleviate internal stresses accumulated in the optical element during the curing stage. In some embodiments, the temperature is about 40°C to about 70°C, about 40°C to about 60°C, or about 40°C to about 50°C. In some embodiments, the duration is about 20 minutes to about 50 minutes, about 20 minutes to about 40 minutes, or about 20 minutes to about 30 minutes.

[0153] In some embodiments, the method further includes the step of removing a substrate from the light-guiding optics. For example, the substrate may be glass, which can be separated from the light-guiding optics using a sharp blade.

[0154] In some embodiments, the base structure further includes a prism structure at its ends. The prism structure facilitates efficient coupling of light into the waveguide. The prism can be 3D printed together with the base structure. The prism can be a triangular prism. The prism can be positioned at an angle of approximately 40° to approximately 60° relative to a first surface of the base structure and the corresponding light-guiding optics element. This angle ensures total internal reflection within the light-guiding optics element, enabling optimal light transmission along its path. In some embodiments, this angle is 50°.

[0155] In some embodiments, the method further includes a step of cleaning the light guide optical element after step c).

[0156] For prints made of resin, a degree of post-printing curing may be required to achieve optimal durability. This can be achieved via a specific UV chamber or simply by exposing the finished print to sunlight. In some embodiments, the method further includes a step of curing the light-guiding optics after step c).

[0157] In some embodiments, the method further includes: changing the refractive index of the light guide optical element such that at least one 3D printed slice of the light guide optical element has a different refractive index relative to an adjacent 3D printed slice.

[0158] In some embodiments, the method further includes thermally annealing the optical element to change its refractive index. A refractive index gradient can be created by controlling the temperature and duration of the annealing process.

[0159] In some embodiments, the method further includes: rapidly cooling the light guide optical element.

[0160] Once formed, the surface of the LOE can be polished or laminated with the same or different optical materials to ensure smoothness and clarity. In some embodiments, the method further includes a polishing step on the surface of the light guide optical element after step c).

[0161] In some embodiments, the light-guiding optical element is characterized by a transparency greater than about 85%.

[0162] In some embodiments, the light-guiding optical element is characterized by a transmittance of at least about 85% from 420 nm to 700 nm, or preferably at least about 90%.

[0163] In some embodiments, the light guide optical element is characterized by a length of about 20 mm to about 50 mm. In one embodiment, the light guide optical element is characterized by a length of about 20 mm to about 45 mm, about 20 mm to about 40 mm, about 25 mm to about 40 mm, or about 30 mm to about 40 mm.

[0164] In some embodiments, the light guide optical element is characterized by a width of about 20 mm to about 50 mm. In some embodiments, the light guide optical element is characterized by a width of about 20 mm to about 45 mm, about 20 mm to about 40 mm, about 20 mm to about 35 mm, or about 20 mm to about 30 mm.

[0165] In some embodiments, the light-guiding optical element is characterized by a thickness of about 2 mm to about 15 mm. In some embodiments, the light-guiding optical element is characterized by a thickness of about 2 mm to about 10 mm, or about 2 mm to about 5 mm. In some embodiments, the light-guiding optical element is characterized by a thickness of about 3 mm or about 7.5 mm.

[0166] This disclosure also provides 3D-printed light-guiding optical elements formed by the methods disclosed herein. In this respect, if the same resin material is used, the 3D-printed resin portion and the resin portion filling the grooves in the base structure (non-3D-printed) can have the same refractive index.

[0167] This disclosure also provides 3D-printed light-guiding optical elements, including:

[0168] a) An ultra-transparent body with a first surface; and

[0169] b) At least one semi-transparent beam splitter within the ultra-transparent body and at an angle relative to the first surface;

[0170] The 3D printed optical guide element is characterized in that at least one 3D printed slice has a different refractive index relative to the adjacent 3D printed slice.

[0171] This disclosure also provides 3D-printed light-guiding optical elements, including:

[0172] a) An ultra-transparent body with a first surface; and

[0173] b) At least one semi-transparent beam splitter within the ultra-transparent body and at an angle relative to the first surface;

[0174] The cross-section of a 3D-printed optical guide element is characterized by one part of the cross-section having a different refractive index relative to another part.

[0175] In some embodiments, the 3D-printed light-guiding optical element also includes a projector.

[0176] In some embodiments, the 3D-printed light-guiding optical element further includes a lens. The lens may be adjacent to a prism. The focal length of the lens may be about 20 mm to about 50 mm, about 20 mm to about 45 mm, about 20 mm to about 40 mm, about 20 mm to about 35 mm, about 20 mm to about 30 mm, or about 20 mm to about 25 mm.

[0177] In some embodiments, the 3D-printed light guide optical element is characterized by a magnification of about 1.1 to about 1.8. In some embodiments, the magnification is about 1.1 to about 1.7, about 1.2 to about 1.7, about 1.3 to about 1.7, or about 1.4 to about 1.7. In some embodiments, the magnification is about 1.4.

[0178] In some embodiments, the 3D-printed light-guiding optical element is characterized by a root mean square (RMS) surface roughness of about 1.1 nm to about 1.8 nm. In other embodiments, the RMS roughness is about 1.1 nm to about 1.7 nm, about 1.1 nm to about 1.6 nm, about 1.1 nm to about 1.5 nm, or about 1.1 nm to about 1.4 nm.

[0179] In some embodiments, the 3D-printed light guide optical element is characterized by an average surface roughness of about 1 nm to about 1.5 nm. In other embodiments, the average roughness is about 1 nm to about 1.4 nm, about 1 nm to about 1.3 nm, about 1 nm to about 1.2 nm, or about 1 nm to about 1.1 nm. In other embodiments, the average roughness is about 1.1 nm to about 1.5 nm, about 1.2 nm to about 1.5 nm, about 1.3 nm to about 1.5 nm, or about 1.4 nm to about 1.5 nm.

[0180] Figure 1The diagram illustrates a waveguide or LOE. Light from a light source or optical engine can be coupled into the waveguide via a prism and then directed to the user's eye using a reflector. Figure 1 A waveguide with three reflectors is shown.

[0181] like Figure 2 As shown, a simulation was performed to demonstrate the effectiveness of the waveguide. Figure 2 A simulated optical path is presented. Due to the combined effect of the reflector and the micropatterns on the first surface, the resulting image is combined at the retina of the eye.

[0182] Figure 3 An example of a reconstructed image generated by the waveguide of this disclosure is shown.

[0183] Figure 5 The image shows a waveguide prototype and images captured using a camera placed next to the waveguide.

[0184] Example

[0185] Simulation results

[0186] We optimized our geometric waveguide design using the finite element method implemented in COMSOL Multiphysics to achieve a balance between optical performance and fabrication feasibility. For example, if the waveguide is too thin, it may break when removing the printed sample from the glass printing bed. An exemplary geometric AR waveguide has dimensions of 31 mm x 26 mm x 7.6 mm. A 3D-printed triangular prism is used to facilitate efficient coupling of light into the waveguide. The prism is positioned at a 50-degree angle relative to the bottom surface of the waveguide. This specific angle ensures total internal reflection within the waveguide, enabling optimal light transmission along its path. For simplicity, the design incorporates three dielectric reflectors integrated at a 25-degree angle relative to the bottom surface, as shown below. Figure 1 , Figure 2 and Figure 7 As shown in the diagram. These reflectors are used to direct light towards the observer's eye. The projector used in our design is a general-purpose LCOS projector with a 40° field of view, whose emission is then coupled to a virtual image in the waveguide via a triangular prism. We then used COMSOL simulations to evaluate the effectiveness of the design. Simulation parameters included a refractive index of 1.53 for the resin material used in the waveguide. Additionally, propagation loss was considered, and based on actual measurements, the dielectric reflectors used in the waveguide were assigned 90% transmittance, and wall boundary conditions were applied. Furthermore, we used an ideal lens with a focal length of 25 mm and applied optimal lens boundary conditions to simulate the human eye. Figure 2 and Figure 7The simulated ray tracing results are shown, illustrating the propagation of light rays through the waveguide, their convergence at the retina, and the formation of the final image. An example of the computationally reconstructed University of Melbourne emblem is also shown. To achieve this, an object (a bitmap file of the emblem) is loaded into the model, where the spatial distribution of rays emitted from the object's surface is scaled to the values ​​of the bitmap. With 23,000 rays emitted, we achieved a magnified and perfectly stitched image at the image plane, achieving a magnification of 1.4. This waveguide design not only demonstrates its effectiveness in providing high-quality image reconstruction but also considers its fabrication feasibility.

[0187] Manufacturing process—3D printed waveguide

[0188] Optimized geometric AR waveguides were fabricated using a semi-custom 3D printer. Our platform is built upon the PhrozenSonic mini 8K resin 3D printer, a custom-grade liquid crystal display (LCD) 3D printer. In short, the print bed is immersed in a transparent resin tank and exposed to UV light emitted by an LED array at the bottom. The UV light passes through an LCD screen that acts as a masking element. This reveals the image pattern on the print bed and selectively cures the corresponding pixels. This layering process is repeated for subsequent layers. The LCD screen provides an impressive ultra-high resolution of 22µm, and the dual linear guides provide a stable Z-axis step size of 10µm.

[0189] To enhance the uniformity of light distribution, a diffuser and an absorber were placed in front of the light source. Additionally, another diffuser was placed on top of the LCD screen to address the issue of inter-pixel gaps and ensure seamless display of image patterns. Figure 8 In fact, we found that the second diffuser had no significant impact on the xy-plane resolution, especially when the z-axis step size was less than 20µm. This observation remains true, particularly for objects lacking complex details. The resin tank contained a thin perfluoroalkoxy (PFA) film as a release liner, designed to form a non-adhesive surface that facilitates removal of the printed object after printing. To enhance the non-stick properties, a thin layer of polytetrafluoroethylene (PTFE) was coated on the PFA film. We used NOVA3D ultra-clear resin, which has a relatively stable refractive index of approximately 1.53 in the visible light wavelength range. After curing at 25°C, it exhibited a volume shrinkage rate of 3.6%. Unlike professional inkjet printers that achieve smooth surface finishes without additional post-processing, LCD printers cannot provide comparable surface roughness. A strategy to mitigate this problem is to print the top and bottom waveguide components separately on a glass print bed and then integrate them with a dielectric reflector (such as...). Figure 8(As shown in the diagram). This method improves the overall surface finish of the waveguide and potentially enhances its performance. Regarding the tilted surface of the prism, achieving a smooth finish is not necessary since it will be glued to the projector in a later stage.

[0190] We first bonded a plain glass slide to a metal printing bed. Using a z-axis step size of 10µm, the top and bottom components of the waveguide were printed, with the flat side facing down towards the glass slide. To improve print quality, anti-aliasing was applied to the image pattern during the printing process. This technique effectively blurred the image pattern, reducing the presence of jagged edges and thus enhancing the subpixel resolution of the final product. The total printing time was approximately 2 hours, and we did not add any supports to the model. Once the printing process was complete, the printed portion, along with the glass slide, was removed from the printing bed and immersed in a shallow resin tank. The sample was examined under a microscope to assess its quality. Any debris on the surface could be removed by gently blowing it off using nitrogen. It is crucial to avoid using isopropyl alcohol during this cleaning process, as it can potentially reduce the transparency level. The dielectric reflector was then carefully placed into its corresponding slot within the resin, effectively preventing the formation of air bubbles during placement. Subsequently, the assembled sample was removed and cured under UV light in a nitrogen chamber, with appropriate pressure applied to the top glass. The sample is then transferred to a hot plate at 40°C and allowed to undergo a 30-minute heat treatment to relieve internal stresses that may have accumulated during the curing phase. Finally, the glass slide is removed using a sharp blade.

[0191] Experimental Results—3D Printed Waveguides

[0192] The integration of diffusers significantly enhances print quality. The use of a first diffuser placed in front of the light source substantially improves light uniformity. Including a second diffuser at the top of the LCD screen further enhances illumination uniformity, effectively mitigating the inter-pixel gap problem. Without this diffuser, printed samples exhibit numerous fine lines within their structure. Figure 9 ).

[0193] In the design, we utilized a dielectric thin-film interference filter as a reflector. The surface roughness of the reflector was evaluated using atomic force microscopy (AFM), and the corresponding results are as follows: Figure 10 As shown in the figure. According to the standard definition of surface roughness, the measured RMS roughness of the reflector is Rq = 1.40 nm, and the average roughness is Ra = 1.09 nm. In addition to the surface roughness measurements, we also evaluated the transmittance of the reflector at various angles in the visible light wavelength range. The reflector exhibits approximately 90% transmittance at angles of 0 degrees and 65 degrees, corresponding to real-world light transmission scenarios (reflector; Figure 10 ).

[0194] The combined printed waveguide has a thickness of 3 mm. The planar surface printed on the glass slide exhibits good roughness characteristics. Its RMS roughness is 1.49 nm, and the average roughness is 1.38 nm (resin block); Figure 10 Regarding transmittance, the waveguide exhibits low transmittance from 400 nm to 420 nm. However, above 420 nm up to 700 nm, the transmittance remains consistently high, hovering around 90%, making it well-suited for a wide range of optical applications in this particular spectral region. Figure 10 ).

[0195] To verify the effectiveness of the design, a prototype of a printed AR waveguide containing three dielectric reflectors was successfully fabricated, such as... Figure 11 a- Figure 11 The AR waveguide was illustrated in section b. Furthermore, it was tested using a commercial micro-projector. Figure 11 c- Figure 11 Example d shows a projected image and an image captured through a waveguide.

[0196] Manufacturing process and experimental results—3D printed liquid waveguide

[0197] Alternatively, low-cost liquid reflective optical combiners that use silicone oil as a waveguide can be manufactured. Figure 12 c illustrates the manufacturing process. We first 3D printed the waveguide frame using a Stratasys J826 PolyJet 3D printer. The resin we chose was Stratasys VeroClear, known for its strong resistance to deformation, exhibiting a flexural strength of at least 75 MPa. For the support material, we opted for a water-soluble support using Stratasys SUP707. The frame was printed using a high-quality print mode with a z-axis step size of 14µm. The total printing time was approximately 2 hours. Next, three dielectric reflectors were inserted into the slots. Then, three thin glass sheets were glued to the frame. Finally, silicone oil was injected into the frame to fill air gaps, and the filling holes were sealed with UV adhesive. While mineral oils typically have a higher refractive index, which is desirable for waveguide design, we chose silicone oil because of its better chemical inertness, superior temperature stability, and lower viscosity. Figure 13 a and Figure 13 b demonstrates a prototype of a liquid light combiner.

[0198] Essentially, a virtual image projected from a microdisplay is coupled into a waveguide via a prism and exits to the human eye through three reflectors (based on measurements, T=90%). The prism has a 50-degree incline, and the reflectors are tilted at 25 degrees. The combiner is filled with silicone oil (n=1.41) as the waveguide and protected by a thin glass (n=1.50). The effective area of ​​the combiner has dimensions of 30mm x 26mm x 3.2mm. Figure 12 b presents an example of COMSOL simulation results, demonstrating a mushroom image reconstructed on the retina using the proposed combiner design.

[0199] Next, we evaluated the optical performance of the combiner using a commercial LCOS microdisplay. Figure 13 b demonstrates an example of overlaying a virtual image captured via a waveguide onto a laboratory environment. The total cost of the prototype is approximately $18. However, the cost can be further reduced during mass production. Furthermore, samples can be assembled using automated assembly machines such as those from Ficontech. This eliminates the need for dicing, bonding, and polishing required by traditional manufacturing methods.

[0200] in conclusion

[0201] In this paper, we present a method for fabricating geometric AR light combiners required for augmented reality applications. Instead of relying on high-cost inkjet 3D printers known for their superior surface smoothness, we developed a strategy focused on utilizing cost-effective LCD 3D printers. These printers are custom-modified to achieve significantly improved surface roughness without molding, dicing, and post-polishing. Inkjet printers, on the other hand, require extremely low-viscosity resins, which limits the selection of available photoinitiators, stabilizers, and UV absorbers. This constraint can, in turn, raise concerns about resin yellowing. In contrast, LCD printers offer a much wider range of resin options. In the current design, for simplicity, we integrate only three dielectric reflectors. However, additional reflectors can be integrated to expand the eyebox and field of view. Finally, we successfully fabricated a prototype of the proposed light combiner, creating a virtual image that seamlessly overlaps with the real world. This achievement demonstrates the system's potential for low-cost, high-volume production.

[0202] It will be appreciated that many further modifications and arrangements may be possible with respect to the various aspects of the described embodiments. Accordingly, the described aspects are intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims.

[0203] Throughout this specification and the following claims, unless the context otherwise requires, the word "comprise (comprise, comprise, comprising, etc.)" shall be understood to imply the inclusion of the stated integer or step or group of integers or steps, but does not exclude any other integer or step or group of integers or steps.

[0204] Throughout this specification and the following claims, unless the context otherwise requires, the phrase "consisting essentially of, consists essentially of, etc." will be understood to indicate that the listed element(s) is essential to the invention, i.e., a necessary element. This phrase allows for the presence of other unlisted elements that do not substantially affect the characteristics of the invention, but excludes additional unspecified elements that would affect the fundamental and novel characteristics of the defined method.

[0205] Any prior publications (or information derived therefrom) or any known matters mentioned in this specification shall not be construed as, and should not be construed as, an acknowledgment or endorsement, or in any way imply that such prior publications (or information derived therefrom) or known matters constitute part of the well-known knowledge in the technical field to which this specification pertains.

Claims

1. A method of 3D printing a light guide optical element, comprising: a) 3D printing a base structure using at least one ultra-clear liquid resin, the base structure comprising a first surface and at least one holding device formed on a second surface opposite the first surface and at an angle relative to the first surface; b) contacting at least one semi-transparent beam splitter with the at least one holding device; and c) contacting the at least one ultra-clear liquid resin over the at least one semi-transparent beam splitter and curing the at least one ultra-clear liquid resin so as to form a light guide optical element. The base structure is 3D printed on a substrate.

2. The method of claim 1, wherein, Step a) comprises depositing and at least partially curing the at least one ultra-clear liquid resin in a slice-by-slice manner.

3. The method of claim 1 or 2, wherein, The base structure is 3D printed using liquid crystal display (LCD) 3D printing.

4. The method of any one of claims 1 to 3, wherein, Step a) comprises varying the refractive index of the at least one ultra-clear liquid resin such that at least one 3D printed slice of the base structure has a different refractive index relative to an adjacent 3D printed slice.

5. The method of any one of claims 1 to 4, wherein, Step a) comprises at least partially curing the at least one 3D printed slice of the base structure under different conditions relative to an adjacent 3D printed slice.

6. The method of claim 5, wherein, The at least one 3D printed slice is at least partially cured under a different light pattern relative to an adjacent 3D printed slice.

7. The method of claim 5 or 6, wherein, The at least one 3D printed slice is at least partially cured under a different light intensity relative to an adjacent 3D printed slice.

8. The method of any one of claims 5-7, wherein, Step a) comprises 3D printing the base structure using a second ultra-clear liquid resin having a different refractive index such that at least one 3D printed slice of the base structure has a different refractive index relative to an adjacent 3D printed slice.

9. The method of any one of claims 5 to 8, wherein, Step a) comprises 3D printing the base structure using a mixture of the at least one ultra-clear liquid resin and a second ultra-clear liquid resin having a different refractive index such that at least one 3D printed slice of the base structure has a different refractive index relative to an adjacent 3D printed slice.

10. The method of any one of claims 5 to 9, wherein, Step a) comprises:

11. The method of claim 10, wherein, i) 3D printing a slice of the base structure; ii) mixing a portion of a second ultra-clear liquid resin into the at least one ultra-clear liquid resin; iii) 3D printing a subsequent slice of the base structure; and iv) iteratively repeating steps ii) and iii) until the base structure is formed. The refractive index difference between 3D printed slices is about 0.001 to about 0.

1.

12. The method of any one of claims 1 to 11, wherein, The ultra-clear liquid resin is a UV-curable resin.

13. The method of any one of claims 1 to 12, wherein, The ultra-clear liquid resin is an acrylic-based resin.

14. The method of any one of claims 1 to 13, wherein, Step a) is performed at ambient temperature, or preferably at about 20 °C to about 40 °C.

15. The method of any one of claims 1 to 14, wherein, The ultra-clear liquid resin is characterized by a viscosity of about 400 MPa to about 700 MPa, or preferably about 450 MPa to about 600 MPa.

16. The method of any one of claims 1 to 15, wherein, The ultra-clear liquid resin is characterized by a volume shrinkage of less than 8%, or preferably less than 1%.

17. The method of any one of claims 1 to 16, wherein, The 3D printing is further performed in the presence of a release liner and / or a hydrophobic material.

18. The method of any one of claims 1 to 17, wherein, The at least one holding device is a ramp cut into the second surface of the base structure.

19. The method of any one of claims 1 to 18, wherein, ​ 20. The method of any one of claims 1 to 19, wherein, The at least one holding device is angled at about 20° to about 40°.

21. The method of any one of claims 1 to 20, wherein, The at least one holding device is three holding devices and the at least one semi- transparent beam splitter is three semi-transparent beam splitters.

22. The method of any one of claims 1 to 21, wherein, The at least one semi-transparent beam splitter is selected from a dielectric reflector, a metallic reflector, or a combination thereof.

23. The method of any one of claims 1 to 22, wherein, The at least one semi-transparent beam splitter is characterized by a transparency of at least 85%.

24. The method of any one of claims 1 to 23, wherein, The at least one semi-transparent beam splitter is characterized by a reflectivity of about 8% to about 20%.

25. The method of any one of claims 1 to 24, wherein, The semi-transparent beam splitter is characterized by a root mean square (RMS) roughness of about 1.1 nm to about 1.8 nm.

26. The method of any one of claims 1 to 25, wherein, Step c) includes immersing the 3D printed base structure in a vat comprising an ultra- transparent liquid resin and immersing the at least one semi-transparent beam splitter in the vat such that the at least one semi-transparent beam splitter is in contact with the holding devices of the base structure.

27. The method of any one of claims 1 to 26, wherein, The method further includes the step of separately 3D printing a top structure comprising a third surface and a fourth surface opposite the third surface, wherein the fourth surface comprises a complementary morphology to the second surface of the base structure and the at least one semi-transparent beam splitter.

28. The method of claim 27, wherein, The method further includes the step of mating the base structure and the at least one semi- transparent beam splitter with the top structure to form the light guide optical element.

29. The method of claim 27 or 28, wherein, The base structure and the at least one semi-transparent beam splitter are mated with the top structure in a vat comprising an ultra-transparent liquid resin and are cured.

30. The method of any one of claims 1 to 25, wherein, Step c) includes contacting a transparent substrate and the at least one ultra- transparent liquid resin over the holding devices and the second surface of the base structure to form a covered trench; curing the at least one ultra-transparent liquid resin such that the transparent substrate is bonded to the second surface; and filling the covered trench with a transparent liquid to form the light guide optical element.

31. The method of claim 30, wherein, The transparent liquid is characterized by a refractive index of about 1.4 to about 1.

8.

32. The method of claim 30 or 31, wherein, The transparent liquid is a silicone oil, a mineral oil, a polydimethylsiloxane (PDMS), or a combination thereof.

33. The method of any one of claims 1 to 25, wherein, Step c) includes 3D printing the ultra-transparent liquid resin over the at least one semi- transparent beam splitter.

34. The method of claim 33, wherein, Step c) includes varying the refractive index of the ultra-transparent liquid resin such that at least one 3D printed slice has a different refractive index relative to an adjacent 3D printed slice.

35. The method of any one of claims 1 to 34, wherein, The base structure further includes a prism structure at an end thereof.

36. The method of claim 35, wherein, The prism is a triangular prism positioned at an angle of about 40° to about 60° relative to the first surface of the base structure.

37. The method of any one of claims 1 to 36, wherein, The method further includes, after step a), the step of cleaning and further curing the base structure of step a).

38. The method of any one of claims 1 to 37, wherein, The method further includes varying the refractive index of the light guide optical element such that at least one 3D printed slice of the light guide optical element has a different refractive index relative to an adjacent 3D printed slice.

39. The method of any one of claims 1 to 38, wherein, The method further includes thermally annealing the light guide optical element.

40. The method of any one of claims 1 to 39, wherein, The light guide optical element is characterized by a transparency of greater than about 85%.

41. A 3D printed light guide optical element formed by the method of any of claims 1 to 40.

42. A 3D printed light guide optical element comprising: a) an ultra-transparent body having a first surface; and b) at least one semi-transparent beam splitter within the ultra-transparent host and at an angle relative to the first surface; wherein the 3D-printed light guide optical element is characterized in that at least one 3D-printed slice has a different refractive index relative to an adjacent 3D-printed slice.

43. A 3D-printed light guide optical element comprising: a) an ultra-transparent host having a first surface; and b) at least one semi-transparent beam splitter within the ultra-transparent host and at an angle relative to the first surface; wherein a cross-section of the 3D-printed light guide optical element is characterized in that one portion of the cross-section has a different refractive index relative to another portion.

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