Viewing optics for microdisplays

Abstract

A head-wearable display system (300, 400) includes an optical stack (100) and an image source (100) to project light comprising an image. The optical stack includes a plano-convex lens (108), a first double convex lens (102), a plano-concave lens (106), and second double convex (104). The plano-concave lens is disposed between the plano-convex lens and the first double convex lens. The second double convex lens is disposed between the plano-concave lens and the first double convex lens.

Description

VIEWING OPTICS FOR MICRODISPLAYSBACKGROUND

[0001] The field of virtual reality (VR) and mixed reality (MR) head-wearable displays is undergoing significant advancements, driven by the growing demand for more immersive and realistic visual experiences. These technologies are rapidly gaining popularity across various sectors, including gaming, entertainment, education, healthcare, and industrial applications. As users seek increasingly immersive experiences, there is a corresponding need to improve the quality and performance of the visual components of these devices, all while maintaining or even reducing their size and weight.SUMMARY OF EMBODIMENTS

[0001] According to one aspect, an apparatus includes a plano-convex lens, a first double convex lens, a plano-concave lens disposed between the plano-convex lens and the first double convex lens, and a second double convex lens disposed between the plano-concave lens and the first double convex lens.

[0002] In at least some embodiments, the apparatus further includes a gap between the plano-convex lens and the plano-concave lens. The gap, in at least some embodiments, has a meniscus shape. In at least some embodiments, the gap includes an inert gas or a vacuum.

[0003] In at least some embodiments, the apparatus further includes at least one of a linear polarizer or a quarter-wave plate between the plano-concave lens and the second double convex lens.

[0004] In at least some embodiments, the first double convex lens has a diameter that is smaller than a diameter of the second double convex lens.

[0005] In at least some embodiments, the apparatus further includes a beam splitting component disposed between the plano-convex lens and the plano-concave lens. The beam splitting component, in at least some embodiments, is a layer formed on a curved portion of the plano-convex lens.

[0006] In at least some embodiments, the apparatus further includes at least one of a quarter-wave plate, a linear polarizer, or a polarization beam splitter disposed at an eye-facing side of the plano-convex lens. The at least one of the quarter-wave plate, the linear polarizer, or the polarization beam splitter, in at least some embodiments, is disposed on the plano-convex lens.

[0007] In at least some embodiments, the apparatus further includes a display device configured to emit an image through the first double convex lens. In at least some embodiments, the display device is a microdisplay device.

[0008] In another aspect, a head-wearable display system includes an optical stack comprising the apparatus described above and herein.

[0009] In a further aspect, a method includes converging, by a first double convex lens, light rays emitted from a display device. A second double convex lens focuses the light rays converged by the first double convex lens. A plano-concave lens diverges the light rays focused by the second double convex lens. A plano-convex lens converges the light rays diverged by the plano-concave lens. A polarization beam splitter redirects the light rays converged by the plano-convex lens back into the plano-convex lens. A beam-splitting coating on the plano-convex lens reflects the redirected light rays back out of the plano-convex lens.BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items.

[0003] FIG. 1 is a diagram illustrating an exploded view of an optical stack for correcting chromatic aberrations and expanding the eyebox in a head-wearable display system in accordance with some embodiments.

[0004] FIG. 2 is a diagram of an optical path of light rays traveling through the optical stack of FIG. 1 in accordance with some embodiments.

[0005] FIG. 3 is a diagram of a head-wearable display (HWD) system in accordance with some embodiments.

[0006] FIG. 4 is a diagram of another HWD system in accordance with some embodiments.

[0007] FIG. 5 and FIG. 6 together are a flow diagram illustrating an example of an overall process for managing and optimizing the light path within an optical stack of a head-wearable display to deliver a high-quality, distortion-free visual experience with optically corrected lateral color and an expanded eyebox in accordance with some embodiments.DETAILED DESCRIPTION

[0008] The advancement of VR and MR technologies has created a growing demand for head-wearable display systems that can deliver highly immersive visual experiences while maintaining a compact and lightweight form factor. Achieving this balance poses technical challenges, particularly in designing and integrating viewing optics and display systems that can provide high-resolution images, wide fields of view, and low-latency performance. The trade-off between optical performance and device compactness is a consideration in this design process, as larger optics can enhance visual quality but often result in bulkier and heavier devices, which may be uncomfortable for prolonged use.

[0009] One approach to addressing these challenges involves using aspheric lenses combined with large liquid-crystal displays (LCDs) or organic light-emitting diode (OLED) displays on glass, where the display size typically exceeds 3 inches. This configuration can offer reasonable display quality and an adequate eyebox size, contributing to a satisfying visual experience. However, the significant lateral color aberration is a major drawback, which can detract from image clarity and color fidelity. Correcting this aberration often requires substantial computational power, leading to increased system complexity and power consumption. Furthermore, the large size of the optical module, driven by the dimensions of the display and lens, can impose constraints on the overall product design, making it difficult to achieve a compact form factor.

[0010] Another configuration leverages pancake optics paired with relatively small LCDs, typically ranging between 2.1 and 3 inches. Pancake optics are known for their ability to correct lateral color aberration effectively, resulting in improved image quality and a more compact optical module, often around 25 millimeters (mm) in thickness. Despite these advantages, this approach is primarily limited to LCDs, which may not be ideal for high-end VR / MR applications. LCDs in this size range tend to have limited contrast ratios, suboptimal color performance, and relatively high power consumption. Additionally, due to the inherent limitations in LCD pixel structure, achieving a 4K resolution at these display sizes is challenging, thereby hindering the ability to provide an eye-limiting viewing experience that meets the highest visual fidelity standards.

[0011] A further implementation involves using pancake optics with Micro Organic Light Emitting Diode (microOLED) displays on silicon, where the display size is typically less than 2 inches. In at least some configurations, microOLED technology on silicon substrates offers benefits, including superior brightness, lower power consumption, a broader color space, and a significantly reduced display size, making it well-suited for compact HMD designs. However, these advantages come with challenges, particularly in designing and fabricating the viewing optics. The optical systems required to deliver high optical resolution and a wide eyebox with microOLED displays are still under development, and current solutions often involve complex manufacturing processes, such as hard film lamination, which can result in low processing yields and high production costs.

[0012] As such, to address these challenges, the following describes implementations of an optical stack that provides an optimal balance between display quality, compactness, power efficiency, and manufacturability, enabling the creation of VR / MR devices that can deliver truly immersive experiences in a form factor suitable for widespread consumer adoption. As described in greater detail below, one or more embodiments utilize a pancake optics configuration in conjunction with small microdisplays, ranging in size from, for example, 1 to 2 inches with 4K resolution, although other sizes are also applicable. One example of a microdisplay is a microOLED on silicon display. These microdisplays can achieve a field of view of up to, for example, 120 degrees with a large eyebox and optically corrected lateralcolor. However, larger fields of view are also applicable. This architecture, in at least some embodiments, excludes the use of curved film lamination, thereby significantly improving processing yields and reducing manufacturing costs. Additionally, in at least some embodiments, the micro OLEDs or LEDs of the display have a pixel size of approximately 6 microns, although other pixel sizes are also applicable.

[0013] The optical stack described herein combines a plano-convex lens, a planoconcave lens, and two double convex lenses. The plano-convex lens, in at least some embodiments, incorporates one or more elements, such as a linear polarizer, a polarization beam splitter, and a quarter-wave plate. A beam-splitting component, in at least some embodiments, a beam-splitting component is applied to the curved portion of the plano-convex lens or placed between the plano-convex and planoconcave lenses. Similarly, the plano-concave lens, in at least some embodiments, also includes one or both of a linear polarizer and a quarter-wave plate.

[0014] In at least some embodiments, this optical stack corrects chromatic aberrations using the plano-convex and plano-concave lenses while the two double convex lenses correct for field curvature. A gap between the plano-convex and plano-concave lenses, in at least some embodiments, is filled with a substance, such as air or nitrogen, to achieve a desired refractive index. In other embodiments, a vacuum is created within the gap. The gap introduces a degree of freedom that enhances the eyebox size. The shape of the gap, in at least some embodiments, is a meniscus shape. As such, the optical stack described herein eliminates the need for curved film lamination, further streamlining the manufacturing process while delivering high-quality visual output.

[0015] FIG. 1 is a diagram showing an exploded view of an optical stack 100 for use in a virtual reality (VR) or mixed reality (MR) head-wearable display. It should be noted that the dimensions of the components depicted in FIG. 1 are not to scale and may be adjusted for clarity and illustrative purposes. The optical stack includes 100 includes components arranged in a specific configuration that optimizes visual performance and compactness. Starting from the right and moving to the left of FIG. 1 , the optical stack 100 comprises a first double convex lens 102, a second double convex lens 104, a plano-concave lens 106, and a plano-convex lens 108. The first double convex lens 102 is the lens in the optical stack 100 closest to a display device(light source) 110, such as a microdisplay device (e.g., a microOLED on silicon display device). The first double convex lens 102 is curved on both sides 112 (illustrated as the first side or surface 112-1 and the second side or surface 112-2). The first side 112-1 of the lens 102 is a world-facing side that faces the external environment or the display device 110 and is responsible for receiving and initially shaping the light emitted by the display device 110. The second side 112-2 of the lens 102 further shapes the light, helping to focus and direct it towards the subsequent lenses in the optical stack 100.

[0016] The first double convex lens 102, in at least some embodiments, is comprised of one or more materials, such as optical glass (e.g., borosilicate crown glass, fused silica, etc.) having low dispersion and high optical clarity, polymers (e.g., polycarbonate, polymethyl methacrylate (PMMA), etc.), a combination thereof, and the like. In at least some embodiments, the first double convex lens 102 is fabricated using one or more processes, such as glass molding, injection molding, a combination thereof, and the like. During glass molding, heated glass is pressed into a mold to form the desired shape. During injection molding, molten polymer is injected into a mold, cooled, and then ejected to form the lens. In at least some embodiments, the first double convex lens 102 has a diameter that is smaller than the diameter of the second double convex lens 104.

[0017] The second double convex lens 104 is disposed in the optical stack 100 between the plano-concave lens 106 and the first double convex lens 102. In at least some embodiments, the second double convex lens 104 is similar to the first double convex lens 102. For example, in at least some embodiments, the second double convex lens 104 is curved on both sides 114 (illustrated as the first side or surface 114-1 and the second side or surface 114-2). The first side 114-1 of the lens 104 is a world-facing side opposite the second side 112-2 of the first double convex lens 102, and the second side 114-2 is an eye-facing side opposite the first side 114-1 of the lens 104. The second double convex lens 104, in at least some embodiments, includes materials similar to the materials of the first double convex lens 102, although other materials are also applicable. Also, in at least some embodiments, the second double convex lens 104 is fabricated similarly to the first double convex lens 102, although other fabrication techniques are also applicable. In at least someembodiments, the first double convex lens 102 and the second double convex lens 104 are refractive lenses that manipulate light rays through refraction to align and focus them properly.

[0018] The plano-concave lens 106 is disposed in the optical stack 100 between the plano-convex lens 108 and the second double convex lens 104. In at least some embodiments, the plano-concave lens 106 includes one flat portion or surface 116-1 and one inwardly curved portion or surface 116-2. The flat surface 116-1 is a worldfacing surface disposed opposite the eye-facing side 114-2 of the second double convex lens 104. The inwardly curved surface 116-2 curves inward toward the flat surface 116-1 and is an eye-facing surface disposed opposite the flat surface 116-1. In at least some embodiments, the plano-concave lens 106 is comprised of optical glass (e.g., borosilicate crown glass, fused silica, etc.) having low dispersion and high optical clarity, polymers (e.g., polycarbonate, polymethyl methacrylate (PM MA), etc.), a combination thereof, and the like. The plano-concave lens 106, in at least some embodiments, is fabricated using precision glass molding, injection molding, a combination thereof, and the like. The plano-concave lens 106 slightly diverges the light, which helps to correct chromatic aberrations and prepare the light for further manipulation by the subsequent optical elements. This lens 106 ensures that the light is properly dispersed before it enters the next stage of the optical stack 100, contributing to overall image quality.

[0019] In at least some embodiments, one or both of a linear polarizer 118 or a quarter-wave plate 120 are formed on or adjacent to the flat surface 116-1 of the plano-concave lens 106. The linear polarizer 118, in at least some embodiments, is directly bonded or laminated to the flat surface 116-1 of the plano-concave lens 106 using, for example, an optical adhesive that maintains the optical integrity of the stack 100. In other embodiments, the linear polarizer 118 is implemented as a separate element disposed adjacent to the flat surface 116-1 in the optical path.

[0020] The linear polarizer 118, in at least some embodiments, is comprised of a thin film of polymeric material like polyvinyl alcohol (PVA), treated with, for example, iodine or other polarizing agents. In another example, the linear polarizer 118 comprises stretched polymer films, where the molecular chains are aligned in one direction, creating the polarizing effect, although other materials are also applicable.In at least some embodiments, the linear polarizer 118 is fabricated by coating the polarizing material onto a substrate, such as glass or plastic, and then laminated onto the flat surface 116-1. If the linear polarizer 118 is implemented as a separate element, the linear polarizer 118 is fabricated independently using the same materials and processes. The linear polarizer 118 is positioned adjacent to the flat surface 116-1 of the plano-concave lens 106 in the optical path. The separate polarizer, in at least some embodiments, is held in place using an optical-grade adhesive or a mechanical mount designed to maintain the correct orientation and alignment. The linear polarizer 118 filters the light, allowing only waves vibrating in a specific direction to pass through. This polarization control manages glare and enhances image contrast, improving overall visual clarity.

[0021] The quarter-wave plate 120, in at least some embodiments, is directly bonded or laminated to the flat surface 116-1 of the plano-concave lens 106 using, for example, an optical adhesive that maintains the optical integrity of the stack 100. The quarter-wave plate 120, in at least some embodiments, is comprised of a birefringent material, such as quartz or mica, that is cut and polished to a specific thickness. This thickness controls the phase shift between the two orthogonal polarization components of the light, converting linearly polarized light into circularly polarized light or vice versa. The orientation of the quarter-wave plate 120 relative to the incoming light is configured to achieve the desired polarization conversion.

[0022] In other embodiments, the quarter-wave plate 120 is implemented as a separate element positioned adjacent to the flat surface 116-1 of the plano-concave lens 106 in the optical path. When implemented as a separate element, the quarterwave plate 120 is fabricated independently using the same birefringent materials and processes as when directly bonded. After fabrication, the quarter-wave plate 120 is positioned adjacent to the flat surface 116-1 of the plano-concave lens 106. In this case, the quarter-wave plate 120, in at least some embodiments, is held in place using an optical-grade adhesive or a mechanical mount designed to ensure precise alignment and maintain the correct orientation within the optical path.

[0023] The quarter-wave plate 120 modifies the polarization state of the light. By converting linearly polarized light into circularly polarized light or vice versa, the quarter-wave plate 120 helps to reduce unwanted reflections and ensures that thelight can pass through subsequent optical components in the optical stack 100 with minimal loss or distortion. This precise control of light polarization helps achieve high image quality and overall visual clarity in the VR / MR head-wearable display.

[0024] If both the linear polarizer 118 and the quarter-wave plate 120 are implemented, in at least some embodiments, the linear polarizer 118 and the quarterwave plate 120 are typically stacked in sequence, with the quarter-wave plate 120 disposed after the polarizer 118 when following the light path. For example, the quarter-wave plate 120 is disposed between the flat surface 116-1 of the planoconcave lens 106 and the linear polarizer 118. In this configuration, the linear polarizer 118 and quarter-wave plate 120 work in tandem to control the polarization state of the light as it moves through the optical stack 100. As the light travels from the display device 110 and passes through the first double convex lens 102 and the second double convex lens 104, the light encounters the linear polarizer 118 and the quarter-wave plate 120 on or coupled to the plano-concave lens 106. This configuration ensures that the light is correctly polarized before it enters the planoconvex lens 106 and interacts with a subsequent beam-splitting component 124. By integrating these components directly onto or adjacent to the plano-concave lens 106, the optical stack 100 effectively manages light propagation, corrects distortions, and delivers a high-quality visual experience in the VR / MR head-mounted display. This arrangement also contributes to reducing chromatic aberrations, enhancing overall image clarity and quality, while maintaining the compactness required for such devices.

[0025] The plano-convex lens 108 is disposed in the optical stack 100 after the plano-concave lens 106 when the following the optical path and is the lens closest to the user’s eye. In at least some embodiments, the plano-convex lens 108 includes one outwardly curved portion or surface 122-1 and one flat portion or surface 122-2. The outwardly curved surface 122-1 curves outward away from the flat surface 122-2 and is a world-facing surface disposed opposite the inwardly curved surface 116-2 of the plano-concave lens 106. The flat surface 122-2 is an eye-facing surface disposed closest to the user’s eye. In at least some embodiments, the plano-convex lens 108 is comprised of optical glass (e.g., borosilicate crown glass, fused silica, etc.) having low dispersion and high optical clarity, polymers (e.g., polycarbonate,polymethyl methacrylate (PMMA), etc.), a combination thereof, and the like. The plano-convex lens 108, in at least some embodiments, is fabricated using precision glass molding, injection molding, a combination thereof, and the like. The lens 108 converges the light, focusing the image, and helps correct chromatic aberrations, ensuring that different wavelengths of light are brought to the same focal point, resulting in a sharp and clear image. This lens 108 also helps with the final image formation, ensuring that the light exiting the optical stack 100 is properly focused and free from distortions.

[0026] In at least some embodiments, a beam splitting component 124 is formed on or adjacent to the outwardly curved surface 122-1 of the plano-convex lens 108. The beam-splitting component 124, in at least some embodiments, is a beam-splitting coating or layer, such as a half-mirror coating, applied directly to the curved surface 122-1 of the plano-convex lens 108 using thin-film deposition techniques, such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), which maintain the optical integrity of the stack 100. The half-mirror coating is configured to reflect folded light back toward the user’s eye. In other embodiments, the beam-splitting component 124 is implemented as a separate element disposed between the planoconvex lens 108 and the plano-concave lens 106.

[0027] The beam-splitting component 124, in at least some embodiments, is comprised of thin layers of dielectric materials, such as magnesium fluoride (MgF2) or titanium dioxide (TiO2), that create constructive and destructive interference, which enables the selective reflection and transmission of light. In another example, the beam-splitting component 124 is comprised of multiple layers of dielectric materials, stacked to achieve desired optical properties, such as reflecting specific wavelengths or polarization states while allowing others to pass through. It should be understood that other materials and configurations are also applicable.

[0028] In at least some embodiments, the beam-splitting component 124 is fabricated by depositing the dielectric materials onto a substrate, such as glass, which is then bonded to the plano-convex lens 108. If the beam-splitting component 124 is implemented as a separate element, the beam-splitting component 124, in at least some embodiments, is fabricated independently using the same materials and processes, and then positioned adjacent to the plano-convex lens 108 within theoptical path. The separate component, in at least some embodiments, is held in place using an optical-grade adhesive or a mechanical mount designed to maintain the correct orientation and alignment. The beam-splitting component 124 functions to selectively reflect and transmit different components of the light based on their wavelengths or polarization states. This selective control helps optimize light paths, enhancing image contrast, and improving the overall visual performance of the optical stack 100.

[0029] In at least some embodiments, one or more of a quarter-wave plate 126, a polarization beam splitter 128, and a linear polarizer 130 are formed on or adjacent to the flat surface 122-2 of the plano-convex lens 108. The quarter-wave plate 126, in at least some embodiments, is directly bonded or laminated to the flat surface 122-2 of the plano-convex lens 108 using, for example, an optical adhesive that maintains the optical integrity of the stack 100. The quarter-wave plate 126, in at least some embodiments, is comprised of materials similar to (or different from) the materials described above with respect to the quarter-wave plate 120 implemented with respect to the plano-concave lens 106. Also, in at least some embodiments, the quarterwave plate 126 is fabricated using processes similar to (or different from) the process described above with respect to the quarter-wave plate 120 implemented with respect to the plano-concave lens 106.

[0030] In other embodiments, the quarter-wave plate 126 is implemented as a separate element positioned adjacent to the flat surface 122-2 of the plano-convex lens 108 in the optical path. When implemented as a separate element, the quarterwave plate 126 is fabricated independently using the same birefringent materials and processes as when it is directly bonded. After fabrication, the quarter-wave plate 126 is positioned adjacent to the flat surface 122-2 of the plano-convex lens 122. In this case, the quarter-wave plate 126, in at least some embodiments, is held in place using an optical-grade adhesive or a mechanical mount designed to ensure precise alignment and maintain the correct orientation within the optical path. The quarterwave plate 126 modifies the polarization state of the light. By converting linearly polarized light into circularly polarized light or vice versa, the quarter-wave plate 126 helps to reduce unwanted reflections and ensures that the light can pass through subsequent optical components, such as the polarization beam splitter 128 and linearpolarizer 130, with minimal loss or distortion. This precise control of light polarization is essential for achieving high image quality and overall visual clarity in the VR / MR head-mounted display.

[0031] The polarization beam splitter 128, in at least some embodiments, is directly bonded or laminated to the flat surface 122-2 of the plano-convex lens 108 using an optical adhesive that preserves the optical properties of the stack 100. The polarization beam splitter 128, in at least some embodiments, is comprised of birefringent crystals (e.g., calcite, glass substrates with specialized coatings, etc.), although other materials are also applicable. In at least some embodiments, the polarization beam splitter 128 is fabricated by bonding or coating materials with different refractive indices onto a glass substrate, although other fabrication techniques are also applicable. The polarization beam splitter 128 functions to split the light into two orthogonal polarization states, reflecting one polarization while transmitting the other. In at least some embodiments, the polarization beam splitter 128 redirects (e.g., reflects or folds) light from the plano-convex lens 108 back into the plano-convex lens 108. In other embodiments, the polarization beam splitter 128 is implemented as a separate element, fabricated independently using the same materials and processes, and then positioned adjacent to the flat surface 122-2 in the optical path. The separate polarization beam splitter 128 is held in place using an optical-grade adhesive or a mechanical mount, ensuring precise alignment and functionality.

[0032] The linear polarizer 130, in at least some embodiments, is directly bonded or laminated to the flat surface 122-2 of the plano-convex lens 122 using, for example, an optical adhesive that maintains the optical integrity of the stack 100. In other embodiments, the linear polarizer 130 is implemented as a separate element positioned adjacent to the flat surface 122-2 in the optical path. The linear polarizer 130, in at least some embodiments, is comprised of materials similar to (or different from) the materials described above with respect to the linear polarizer 118 implemented with respect to the plano-concave lens 106. Also, in at least some embodiments, the linear polarizer 130 is fabricated using processes similar to (or different from) the process described above with respect to the linear polarizer 118 implemented with respect to the plano-concave lens 106. Once fabricated, the linearpolarizer 118 is bonded or laminated onto the flat surface 122-2 of the plano-convex lens 108.

[0033] If the linear polarizer 130 is implemented as a separate element, the linear polarizer 130 is fabricated independently using the same materials and processes, and is then positioned adjacent to the flat surface 122-2 of the plano-convex lens 108 in the optical path. The separate polarizer, in at least some embodiments, is held in place using an optical-grade adhesive or a mechanical mount designed to maintain the correct orientation and alignment. The linear polarizer 130 functions to filter the light, allowing only waves vibrating in a specific direction to pass through, which is helps manage glare and enhancing image contrast, thereby contributing to overall visual clarity.

[0034] If the quarter-wave plate 126, the polarization beam splitter 128, and the linear polarizer 130 are implemented together, in at least some embodiments, these components are stacked in sequence, with the quarter-wave plate 126 positioned first in the optical path, followed by the polarization beam splitter 128, and finally, the linear polarizer 130 as the last layer that the light passes through before exiting the optical stack 100. This configuration allows the quarter-wave plate 126 to further modify the polarization state of the light, ensuring it is correctly aligned for interaction with the polarization beam splitter 128. The polarization beam splitter 128 then directs the light based on its polarization state, either reflecting or transmitting it. For example, the polarization beam splitter 128 folds light back into the plano-convex lens 108, directing it toward the half-mirror coating of the beam-splitting component 124. The beam-splitting component 124 then reflects the folded light rays back out of the optical stack 100 toward the user's eye. Finally, the linear polarizer 130 filters the light, allowing only light waves vibrating in a specific direction to pass through, thereby managing glare and enhancing image contrast. By integrating these components directly onto or adjacent to the plano-convex lens 108, the optical stack 100 effectively manages light propagation, corrects distortions, and delivers a high- quality visual experience in the VR / MR head-mounted display. This arrangement also contributes to reducing chromatic aberrations and enhancing overall image clarity and quality while maintaining the compactness required for such devices.

[0035] In at least some embodiments, there is a gap 132 disposed between the plano-concave lens 106 and the plano-convex lens 108. The gap 132 introduces a degree of freedom in configuring the optical stack 100, allowing for fine-tuning of the optical path. This fine-tuning allows for the size of the eyebox, which is the area within which the viewer can move their eyes while still seeing the full field of view clearly, to be increased. The gap 132, in at least some embodiments, has a meniscus shape, which further aids in optimizing the light’s trajectory as it passes through the optical stack 100.

[0036] The gap 132, in at least some embodiments, is filled with a substance such as air, nitrogen, or another inert gas. These substances have transparency and non- reactive properties, which ensures they do not interfere with the light path or introduce additional optical distortions. In other embodiments, the gap 132 is a vacuum, which eliminates any material-related refractive index changes and reduces potential distortions, contributing to the overall optical clarity and performance. In embodiments implementing a gas within the gap 132, the gap 132 is sealed to maintain the correct gas composition and pressure to ensure consistent optical performance over time. If a vacuum is implemented, the gap 132 is evacuated and hermetically sealed to prevent air ingress, maintaining the vacuum state. In at least some embodiments, the gap 132 helps manage the refractive index transition between the plano-concave lens 106 and the plano-convex lens 108. By controlling the conditions within the gap 132, the optical stack 100 minimizes distortions such as chromatic aberrations and field curvature, leading to a sharper and clearer final image.

[0037] FIG. 2 illustrates the light path from the display device 110, which in this example is a microdisplay, such as a microOLED on silicon display device. The light is emitted as light rays 202 (illustrated as light rays 202-1 to light rays 202-5) having different wavelengths. These rays 202 then travel sequentially through each component of the optical stack 100. Each component of the optical stack 100 is configured to manipulate these light rays 202, ensuring they converge correctly and contribute to an expanded eyebox, which produces a clear and vibrant image for the user and allows the user greater freedom of eye movement.

[0038] The path of the light rays 202 begins as they are emitted from the display device 110. The display device 110 emits light across various wavelengths, with each wavelength corresponding to a specific color, such as red, green, blue, yellow, and the like. The emitted light rays 202 spread out as they travel away from the display device 110. In at least some embodiments, the first optical element that these light rays 202 encounter is the first double convex lens 102. As described above, the first double convex lens 102, which is situated closest to the display device 110, has two outwardly curved sides or surfaces 112, configured to begin shaping and focusing the diverging light rays 202. As the light rays 202 enter the first side 112-1 of this lens 102, which faces the display device 110, the curvature of the lens 102 causes the rays 202 to start converging. The second side 112-2 of the lens 102 continues this process, further refining the focus of the light rays 202 and directing them toward the next component in the optical stack 100, which is the second double convex lens 104.

[0039] As the light rays 202 pass through the second double convex lens 104, the focus of the light is further refined. This lens 104, similar to the first double convex lens 102, has two outwardly curved surfaces 114 that correct for field curvature, which is a distortion that would otherwise cause the edges of the image to blur. The second double convex lens 104 ensures that the rays of different wavelengths remain properly aligned and focused as they proceed through the optical stack 100, helping to maintain a consistent image quality across a larger eyebox.

[0040] The focused light rays 202 then encounter the linear polarizer 118. The linear polarizer 118 filters the light by allowing only the rays 202 vibrating in a specific direction to pass through. This polarization control manages glare and ensures that the subsequent optical elements can interact with the light in a predictable manner. After the light rays 202 have been filtered by the linear polarizer 118, they pass through the quarter-wave plate 120. This component modifies the polarization state of the light rays 202, converting linearly polarized light into circularly polarized light or vice versa. This conversion minimizes reflections and ensures that the light rays 202 can be further manipulated without significant loss or distortion.

[0041] Following polarization control, the light rays 202 enter the plano-concave lens 106. This lens 106, with one flat surface 116-1 and one inwardly curved surface116-2, diverges the light rays 202. The divergence helps to optically correct lateral color (chromatic aberrations), which is a common issue where different wavelengths of light are refracted by different amounts, leading to color fringing at the edges of the image. By ensuring that the light rays are evenly dispersed, the plano-concave lens 106 prepares the light rays for the next stage in the optical path, contributing to the enlargement of the eyebox by allowing the image to remain clear over a wider range of eye positions.

[0042] After passing through the plano-concave lens 106, the light rays travel through a gap 132 disposed between the plano-concave lens 106 and the planoconvex lens 108. This gap 132 introduces a degree of freedom in the configuration of the optical stack 100, allowing for fine-tuning of the light’s trajectory. As described above, the gap 132, in at least some embodiments, is filled with air, nitrogen, or another inert gas, or it is a vacuum. The presence of the gap 132 helps manage the transition of refractive indices between the plano-concave lens 106 and the planoconvex lens 108. This further minimizes distortions, such as chromatic aberrations, and ensures that the light rays 202 remain on the correct path toward the final image formation.

[0043] Upon exiting the gap 132, the light rays 202 encounter the beam-splitting component 124. This component 124 is configured to selectively reflect or transmit light based on its polarization state or wavelength. By controlling which rays 202 are reflected and which are transmitted, the beam-splitting component 124 optimizes the light paths for the subsequent stages of the optical stack 100. This ensures that the rays 202 are correctly aligned for final image formation.

[0044] The light rays 202 then enter the plano-convex lens 108, which converges the light further and focuses the multi-wavelength image. This lens 108 corrects any remaining chromatic aberrations, bringing different wavelengths of light to the same focal point. The plano-convex lens 108 ensures that the light rays 202 exiting the optical stack 100 are sharp, clear, and free from distortions, ready to be viewed by the user.

[0045] As the light rays 202 exit the plano-convex lens 108, they interact with another quarter-wave plate 126. This quarter-wave plate 126 further adjusts thepolarization state of the light, ensuring it is correctly aligned for interaction with the polarization beam splitter 128. The polarization beam splitter 128 then folds the light rays 202 back into the plano-convex lens 108, directing them toward the half-mirror coating of the beam-splitting component 124, which then reflects the light rays 202 toward the user’s eye.

[0046] Finally, the light rays 202 pass through the linear polarizer 130, which further filters. By allowing only light waves vibrating in a specific direction to pass through, this polarizer 130 manages glare and enhances contrast, ensuring that the light reaching the user’s eye is optimized for clarity and visual quality. After passing through all these optical components, the light rays 202 exit the optical stack 100, delivering a high-quality, distortion-free visual experience to the user with an expanded eyebox and optically corrected lateral color. In at least some embodiments, through optical stack 100 described herein, the microdisplay image is magnified from its original size (e.g., 1 ,5-inch display) to appear much larger (e.g., a several hundred-inch display) in front of the user’s eye.

[0047] FIG. 3 illustrates an example apparatus, such as a head-wearable display (HWD) system 300, for implementing an optical stack, such as the optical stack 100 of FIG. 1 and FIG. 2. In the illustrated implementation, the HWD system 300 utilizes an eyeglasses form factor. However, the HWD system 300 is not limited to this form factor and, thus, may have a different shape and appearance from the eyeglasses frame depicted in FIG. 3, such as headsets or goggles shown in FIG. 4. The HWD system 300 includes a support structure 302 (e.g., a support frame) to mount to a head of a user and that includes an arm 304 that houses an image source, such as light projection system, including a micro-display (e.g., micro-light emitting diode (LED) display) or other light engine, configured to project display light representative of images or imagery toward the eye of a user, such that the user perceives the projected display light as a sequence of images displayed in a field of view (FOV) area 306 at one or both of lens elements 308, 310 supported by the support structure 302. In at least some embodiments, the support structure 302 further includes various sensors, such as one or more front-facing cameras, rear-facing cameras, other light sensors, motion sensors, accelerometers, and the like. The support structure 302, in at least some embodiments, further includes one or more radiofrequency (RF) interfaces or other wireless interfaces, such as a Bluetooth (TM) interface, a Wi-Fi interface, and the like.

[0048] The support structure 302, in at least some embodiments, further includes one or more batteries or other portable power sources for supplying power to the electrical components of the HWD system 300. In at least some embodiments, some or all of these components of the HWD system 300 are fully or partially contained within an inner volume of support structure 302, such as within the arm 304 in region 312 of the support structure 302. In the illustrated implementation, the HWD system 300 utilizes an eyeglasses form factor. However, the HWD system 300 is not limited to this form factor and, thus, may have a different shape and appearance from the eyeglasses frame depicted in FIG. 3.

[0049] One or both of the lens elements 308, 310 are used by the HWD system 300 to provide an immersive display in which rendered graphical content can be superimposed over or otherwise provided in conjunction with a real-world view as perceived by the user through the lens elements 308, 310. For example, microOLED light, micro LED light, laser light, or other display light is used to form a perceptible image or series of images projected onto the user's eye via one or more optical elements, including a waveguide, formed at least partially in the corresponding lens element. One or both of the lens elements 308, 310 thus include at least a portion of a waveguide that routes display light received by an incoupler (not shown in FIG. 3) of the waveguide to an outcoupler (not shown in FIG. 3) of the waveguide, which outputs the display light toward an eye of a user of the HWD system 300.Additionally, the waveguide employs an exit-pupil-expander (not shown in FIG. 3) in the light path between the incoupler and outcoupler or in combination with the outcoupler to increase the dimensions of the display exit pupil. Each lens element 308, 310 is sufficiently transparent to allow a user to see through the lens elements to provide a field of view of the user’s real-world environment such that the image appears superimposed over at least a portion of the real-world environment.

[0050] FIG. 4 illustrates another example HWD system 400 (e.g., an extended reality (XR) HWD) for implementing an optical stack, such as the optical stack 100 of FIG. 1 and FIG. 2. In this example, the HWD has a headset or goggle form factor and includes a housing 502 coupled to a frame 404. In at least some embodiments,the HWD system 400 includes an audio output device 406 including, for example, speakers mounted in headphones, also coupled to or separate from the frame 404. A display (not shown), in at least some embodiments, is mounted on an interior facing side of the front portion 408 of the housing 402. Lenses (not shown), in at least some embodiments, are mounted in the housing 402 between the user's eyes and the display.

[0051] In some implementations, the HWD system 400 includes a sensing system 410 including various sensors such as, for example, audio sensor(s), image / light sensor(s), positional sensors / tracking device (e.g., inertial measurement unit including gyroscope and accelerometer), camera(s), and the like. The HWD system 400, in at least some embodiments, also includes a control system 412, including a processor and various control system devices to facilitate the operation of the HWD system 400.

[0052] FIG. 5 and FIG. 6 together are a diagram illustrating an example method 500 of an overall process for managing and optimizing the light path within an optical stack of a head-wearable display to deliver a high-quality, distortion-free visual experience with optically corrected lateral color and an expanded eyebox. It should be understood that the processes described below with respect to method 500 have been described above in greater detail with reference to FIG. 1 to FIG. 4. The method 500 is not limited to the sequence of operations shown in FIG. 5 and FIG. 6, as at least some of the operations can be performed in parallel or in a different sequence. Moreover, in at least some implementations, the method 500 can include one or more different operations than those shown in FIG. 5 and FIG. 6.

[0053] At block 502, a display device 110 generates and emits light rays 202 towards an optical stack 100. At block 504, these emitted light rays 202 enter a first double convex lens 102 where they begin to converge, aligning the different wavelengths and starting the correction of lateral color. At block 506, the light rays 202 pass through the second double convex lens 104, which continues to focus and refine the alignment of the wavelengths, further maintaining consistent lateral color correction across the entire image. At block 508, the light rays 202 encounter a first linear polarizer 118, which filters the light to allow only rays 202 with the desired polarization direction to pass through. At block 510, a first quarter-wave plate 120modifies the polarization state of the light rays 202, converting linearly polarized light into circularly polarized light (or vice versa), which minimizes reflections and preserves the quality of the optical corrections applied thus far.

[0054] At block 512, the light rays 202 enter a plano-concave lens 106, where divergence is introduced to correct chromatic aberrations and ensure even dispersion of the light. This also contributes to the expansion of the eyebox, allowing for greater eye movement while maintaining image clarity. At block 514, the light rays 202 pass through a gap 132 between the plano-concave lens 106 and a plano-convex lens 108 that allows for precise fine-tuning of their trajectory, further optimizing lateral color correction and enhancing the eyebox size. At block 516, the light rays 202 encounter a beam-splitting component 124, which, in at least some embodiments, is a halfmirror coating, where selective reflection and transmission occur based on the polarization state and wavelength of the light. At block 518, the light rays 202 enter the plano-convex lens 108, which performs the final convergence, ensuring the image is sharply focused and free from distortions, with all wavelengths properly aligned.

[0055] At block 520, the light rays 202 pass through a second quarter-wave plate (126, which further adjusts the polarization state to prepare the rays for the upcoming beam-splitting process. At block 522, the polarization beam splitter 128 directs the light rays 202 based on their polarization state, either reflecting or transmitting them as needed, preserving image contrast and maintaining lateral color correction. For example, the polarization beam splitter 128 folds at least some of the light rays 202 back into the plano-convex lens 108. At block 524, the light rays are reflected toward the user’s eye(s) by the beam-splitting component 124. At block 526, these reflected light rays 202 pass through the second quarter-wave plate 126 and the polarization beam splitter 128 to the second linear polarizer 130, which filters the light one last time, managing glare and enhancing contrast to ensure that the visual output is clear and color-accurate. Finally, at block 528, the light rays 202 exit the optical stack 100 and are delivered to the user’s eye, providing a high-quality, distortion-free visual experience with optically corrected lateral color and an expanded eyebox.

[0056] In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system executingsoftware. The software comprises one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer readable storage medium. The software can include the instructions and certain data that, when executed by the one or more processors, manipulate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer readable storage medium can include, for example, a magnetic or optical disk storage device, solid state storage devices such as Flash memory, a cache, random access memory (RAM) or other non-volatile memory device or devices, and the like. The executable instructions stored on the non-transitory computer readable storage medium may be in source code, assembly language code, object code, or other instruction format that is interpreted or otherwise executable by one or more processors.

[0057] A computer readable storage medium may include any storage medium, or combination of storage media, accessible by a computer system during use to provide instructions and / or data to the computer system. Such storage media can include, but is not limited to, optical media (e.g., compact disc (CD), digital versatile disc (DVD), Blu-Ray disc), magnetic media (e.g., floppy disc , magnetic tape, or magnetic hard drive), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or Flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer readable storage medium may be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g, a magnetic hard drive), removably attached to the computing system (e.g., an optical disc or Universal Serial Bus (USB)-based Flash memory), or coupled to the computer system via a wired or wireless network (e.g., network accessible storage (NAS)).

[0058] Note that not all of the activities or elements described above in the general description are required, that a portion of a specific activity or device may not be required, and that one or more further activities may be performed, or elements included, in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed. Also, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can bemade without departing from the scope of the present disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0059] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. Moreover, the particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below.

Claims

WHAT IS CLAIMED IS:

1. An apparatus (300, 3400), comprising: a plano-convex lens (108); a first double convex lens (102); a plano-concave lens (106) disposed between the plano-convex lens (108) and the first double convex lens (102); and a second double convex lens (104) disposed between the plano-concave lens (106) and the first double convex lens (102).

2. The apparatus of claim 1 , further comprising a gap (132) between the planoconvex lens and the plano-concave lens.

3. The apparatus of any one of claims 1 or 2, wherein a gap has a meniscus shape.

4. The apparatus of claim 2, wherein the gap comprises an inert gas or a vacuum.

5. The apparatus of any one of claims 1 to 4, further comprising at least one of a linear polarizer (118) or a quarter-wave plate (120) between the plano-concave lens and the second double convex lens.

6. The apparatus of claim 5, wherein the at least one of the linear polarizer or the quarter-wave plate is disposed on a flat portion (116-1) of the plano-concave lens.

7. The apparatus of any one of claims 1 to 6, wherein the first double convex lens has a diameter that is smaller than a diameter of the second double convex lens.

8. The apparatus of any one of claims 1 to 7, wherein the apparatus further comprises: a beam splitting component (124) disposed between the plano-convex lens and the plano-concave lens.

9. The apparatus of claim 8, wherein the beam splitting component is a layer formed on a curved portion (122-1) of the plano-convex lens.

10. The apparatus of any one of claims 1 to 9, further comprising at least one of a quarter-wave plate (126), a linear polarizer (130), or a polarization beam splitter (128) disposed at an eye-facing side of the plano-convex lens.11 . The apparatus of claim 10, wherein the at least one of the quarter-wave plate, the linear polarizer, or the polarization beam splitter is disposed on the planoconvex lens.

12. The apparatus of any one of claims 1 to 11 , further comprising: a display device (110) configured to emit an image through the first double convex lens.

13. The apparatus of claim 12, wherein the display device is a microdisplay device.

14. A head-wearable display system (300, 400), comprising: an optical stack (100) comprising the apparatus of any of the preceding claims; and an image source (110) to project light comprising an image.

15. A method, comprising: converging, by a first double convex lens (102), light rays emitted from a display device (100); focusing, by a second double convex lens (104), the light rays converged by the first double convex lens; diverging, by a plano-concave lens (106), the light rays focused by the second double convex lens; converging, by a plano-convex lens (108), the light rays diverged by the planoconcave lens; redirecting, by a polarization beam splitter (128), the light rays converged by the plano-convex lens back into the plano-convex lens; andreflecting, by a beam-splitting coating (124) on the plano-convex lens, the redirected light rays back out of the plano-convex lens.

Images