Dynamic extension of the eyebox for maxwellian view ar waveguides

Abstract

In an embodiment of the invention, a Maxwellian view augmented reality waveguide display includes a metasurface optical element (MOE) waveguide having an inMOE and an outMOE, a lens, a lens adjustment system having an adjustable angle in X and Y orthogonal directions, and an optical engine configured to provide an input beam to the MOE waveguide through the lens.

Description

Dynamic Extension of the Eyebox for Maxwellian View AR WaveguidesGOVERNMENT SUPPORT

[0001] This invention was made with government support under 2015151 awarded by NationalScience Foundation. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The current application claims priority to U.S. Provisional Application No. 63 / 626,430, filed January 29, 2024, the disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION

[0003] The present invention relates to digital displays and more specifically to Maxwellian view waveguide displays.BACKGROUND OF THE INVENTION

[0004] Augmented reality (AR) waveguide displays have revolutionized the way we interact with virtual content overlaid in the real world. These systems offer incredible potential for a wide range of applications, including gaming, education, healthcare, and industrial training. A crucial aspect of AR displays is the concept of the eyebox, which refers to the region within the waveguide where users can observe virtual images with optimal clarity and brightness. The size, position, and adaptability of the eyebox greatly influence the user experience and play a pivotal role in achieving comfortable and immersive visual interactions.

[0005] Maxwellian view displays, originally devised by James Clerk Maxwell in 1860, offer several advantages for 3D augmented reality (AR) and mixed reality (MR) applications, particularly in head-mounted displays (HMDs). By removing the focus cue from the display, these systems eliminate the conflict between vergence (eye convergence) and accommodation (eye focus) that often leads to discomfort and fatigue in traditional displays. As a result, the image appears focused at all distances, providing a more comfortable viewing experience. One key benefit of Maxwellian view displays is the preservation of temporal information bandwidth. Since these displays do not provide accommodation information, the refresh rates can be determined solely by the speed of the display engine, allowing for high-speed and responsive visual content.SUMMARY OF THE INVENTION

[0006] In an embodiment of the invention, a Maxwellian view augmented reality waveguide display includes a metasurface optical element (MOE) waveguide having an inMOE and an outMOE, a lens, a lens adjustment system having an adjustable angle in X and Y orthogonal directions, and an optical engine configured to provide an input beam to the MOE waveguide through the lens.

[0007] A further embodiment of the invention includes an eye-tracking subsystem.

[0008] Another embodiment of the invention also includes an eyebox region where an eye may observe an image created by the input beam.

[0009] In yet another embodiment of the invention, a center-to-center (CTC) distance between metasurfaces of the waveguide is determined based on shift of the input beam while minimizing beam spread.

[0010] In a still further embodiment of the invention, beam spread is determined to offset the determined CTC to achieve image quality.

[0011] In several additional embodiments of the invention, input MOE size is determined to enlarge an eyebox region and input beam angle is determined to offset beam spread caused by the determined input MOE size to achieve image quality.

[0012] In some additional embodiments of the invention, thickness of the waveguide is calculated to a minimum dimension to enlarge the eyebox region while remaining mechanically stable.

[0013] In yet more embodiments of the invention, the waveguide is 3.5mm thick.

[0014] In yet another embodiment of the invention, the CTC is 30 mm.

[0015] In a still further embodiment of the invention, the MOE waveguide is constructed by deposition of nitride thin films and deepultraviolet lithography.

[0016] In several additional embodiments of the invention, the beam angle of the input beam is x 20 degrees and y 0 degrees.

[0017] In some additional embodiments of the invention, a Gaussian spread of rMM values are applied from the center of the OutMOE.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A illustrates an optical setup for eyebox position modulation of an augmented reality waveguide in accordance with an embodiment of the invention.

[0019] Figure IB illustrates a numerically obtained optimization map for the metasurface with optical diffraction efficiency in accordance with an embodiment of the invention.

[0020] Figure 1C illustrates a wafer with metasurfaces fabricated via cleanroom (inset: SEM with scale bar 2 um) in accordance with an embodiment of the invention.

[0021] Figure ID illustrates display results from a metasurface waveguide display in accordance with an embodiment of the invention.

[0022] Figure IE illustrates a Maxwellian view augmented reality (AR) waveguide with dynamically extended eye box in accordance with embodiments of the invention.

[0023] Figure 2A illustrates input beam angle conditions on InMOE (Input Meta-Optical Element) of an input beam on different sections of metasurface in accordance with an embodiment of the invention.

[0024] Figure 2B illustrates resulting metasurface conditions from different input beam angles in accordance with an embodiment of the invention.

[0025] Figure 3 illustrates eye position variations from different input beam angles (Center of MOE) in accordance with an embodiment of the invention.

[0026] Figure 4 illustrates eye position variations from different input beam angles. (Full area of MOE) in accordance with an embodiment of the invention.

[0027] Figure 5A illustrates eyebox positions with CTC 24mm (Full area of MOE) from different input beam angles in accordance with an embodiment of the invention.

[0028] Figure 5B illustrates eyebox positions with CTC 26mm (Full area of MOE) from different input beam angles in accordance with an embodiment of the invention.

[0029] Figure 5C illustrates eyebox positions with CTC 28mm (Full area of MOE) from different input beam angles in accordance with an embodiment of the invention.

[0030] Figure 5D illustrates eyebox positions with CTC 30mm (Full area of MOE) from different input beam angles in accordance with an embodiment of the invention.

[0031] Figure 6A illustrates eyebox area with CTC 24mm from different input beam angles in y direction (Full area of MOE) in accordance with an embodiment of the invention.

[0032] Figure 6B illustrates eyebox area with CTC 26mm from different input beam angles in y direction (Full area of MOE) in accordance with an embodiment of the invention.

[0033] Figure 6C illustrates eyebox area with CTC 28 from different input beam angles in y direction (Full area of MOE) in accordance with an embodiment of the invention.

[0034] Figure 7A illustrates eye box area with CTC 24mm from different input beam angles in x direction with different CTC (Full area of MOE) in accordance with an embodiment of the invention.

[0035] Figure 7B illustrates eyebox area with CTC 26mm from different input beam angles in x direction with different CTC (Full area of MOE) in accordance with an embodiment of the invention.

[0036] Figure 7C illustrates eyebox area with CTC 28mm from different input beam angles in x direction with different CTC (Full area of MOE) in accordance with an embodiment of the invention.

[0037] Figure 7D illustrates eyebox area with CTC 30mm from different input beam angles in x direction with different CTC (Full area of MOE) in accordance with an embodiment of the invention.

[0038] Figure 8 illustrates maximum eye position shifts from different input beam angles in x direction with different CTC (Full area of MOE) from different input beam angles in x direction with different CTC (Full area of MOE) in accordance with an embodiment of the invention.

[0039] Figure 9 A illustrates second derivatives of area increase from different input beam angles with different CTC (Full area of MOE) in x direction in accordance with an embodiment of the invention.

[0040] Figure 9B illustrates second derivatives of area increase from different input beam angles with different CTC (Full area of MOE) in y direction in accordance with an embodiment of the invention.

[0041] Figure 10A illustrates minimum of area from different input beam angles with different CTC. (Full area of MOE) in x direction in accordance with an embodiment of the invention.

[0042] Figure 10B illustrates minimum of area from different input beam angles with different CTC. (Full area of MOE) in y direction in accordance with an embodiment of the invention.

[0043] Figure 11A illustrates effect on maximum eye position shifts of different input beam angles with different InMOE size (Full area of MOE) in accordance with an embodiment of the invention.

[0044] Figure 1 IB illustrates effect on minimum of area in x direction (inset: in y direction) of different input beam angles with different InMOE size (Full area of MOE) in accordance with an embodiment of the invention.

[0045] Figure 11C illustrates effect on second derivatives of area increase in x in accordance with an embodiment of the invention.

[0046] Figure 1 ID illustrates effect on second derivatives of area increase in y in accordance with an embodiment of the invention.

[0047] Figure 12A illustrates effect on maximum eye position shifts of different input beam angles with different thickness of waveguide (Full area of MOE) in accordance with an embodiment of the invention.

[0048] Figure 12B illustrates effect on minimum of area in x direction (inset: in y direction) in accordance with an embodiment of the invention.

[0049] Figure 12C illustrates effect on second derivatives of area increase in x in accordance with an embodiment of the invention.

[0050] Figure 12D illustrates effect on second derivatives of area increase in y in accordance with an embodiment of the invention.

[0051] Figure 13A illustrates effect engineering metasurface gratings where rMM 1.0 is the degree of engineering (Full area of MOE) in accordance with an embodiment of the invention.

[0052] Figure 13B illustrates effect engineering metasurface gratings where rMM 1.3 is the degree of engineering (Full area of MOE) in accordance with an embodiment of the invention.

[0053] Figure 13C illustrates effect engineering metasurface gratings where rMM 1.6 is the degree of engineering (Full area of MOE) in accordance with an embodiment of the invention.

[0054] Figure 13C illustrates effect engineering metasurface gratings where rMM 1.9 is the degree of engineering (Full area of MOE) in accordance with an embodiment of the invention.

[0055] Figure 14 illustrates eye position variations from different input beam angles with rMM engineering in Gaussian function from center (Full area of MOE) in accordance with an embodiment of the invention.

[0056] Figure 15A illustrates eye box area from different input beam angles after rMM engineering (Full area of MOE) in xdirection in accordance with an embodiment of the invention.

[0057] Figure 15BB illustrates eye box area from different input beam angles after rMM engineering (Full area of MOE) in y direction in accordance with an embodiment of the invention.DETAILED DISCLOSURE OF THE INVENTION

[0058] Turning now to the drawings, Maxwellian view augmented reality (AR) waveguides with dynamically extended eye boxes are disclosed.

[0059] Maxwellian view displays can be designed to be compact and lightweight, making them well-suited for head-mounted applications. They require fewer optical components compared to other displays that address the vergence-accommodation conflict, resulting in a more streamlined and efficient design. The optical efficiency of Maxwellian displays is also noteworthy. As all the light from the display is coupled directly onto the retina, these displays can achieve extremely high optical efficiency, surpassing the efficiency of handheld smartphone displays by a factor of up to 30,000.

[0060] However, it is important to note that Maxwellian view displays have a limited eyebox, meaning that the user must position their eyes within a specific region to perceive the displayed content clearly. This limitation poses challenges in terms of accommodating users with varying eye positions and head movements. Despite the limitations, there are potential applications where a Maxwellian view display can excel. For example, in a sports head mounted display (HMD), displaying critical information such as the current speed in a clear and legible manner regardless of the user's focus distance can enhance user experience and efficiency. Monocular displays that provide easily readable information at all distances, combined with stereoscopic 3D VAC-free imagery, could prove to be a valuable combination for certain use cases.

[0061] In the Maxwellian view of AR waveguides, the eyebox takes on great significance. Maxwellian view systems aim to provide a more natural viewing experience by presenting virtual images that match the eye's entrance pupil. This approach enables a larger field of view, reduced aberrations, and improved visual comfort. However, one of the key challenges in maximizing the benefits of Maxwellian view systems is extending the eyebox to accommodate various user positions and head movements. The ability to dynamically adjust the position and shape of the eyebox is crucial for delivering a seamless and adaptable AR experience.

[0062] Systems and methods in accordance with embodiments of the invention provide a dynamic approach to extend the eyebox in Maxwellian view AR waveguides through input angle modulation. By manipulating the input angles, which determine the light propagation within the waveguide, the position of the eyebox can be effectively shifted to accommodate different user positions and gaze directions. This dynamic extension of the eyebox holds great promise for enhancing the usability and versatility of AR systems.

[0063] Moreover, incorporating eye-tracking technology into the dynamic eyebox extension further enhances the interactive capabilities of AR systems. By continuously monitoring the user'sgaze direction, the eyebox can be dynamically adjusted in real-time to align with the user's current focus point. This personalized and adaptive eyebox extension offers a more intuitive and immersive AR experience, as the virtual content seamlessly aligns with the user's visual attention.

[0064] To achieve dynamic eyebox extension, simulations and experiments can be conducted to identify optimal conditions and parameters. Various factors, including input angles, waveguide geometry, and optical properties, may be systematically explored to determine the most favorable settings for extending the eyebox. Special attention is given to minimizing distortion and preserving high resolution within the extended eyebox region, ensuring a visually pleasing and immersive AR experience. By expanding the capabilities of the eyebox and enabling adaptable viewing parameters, AR systems can provide users with a more comfortable, personalized, and engaging augmented reality experience.

[0065] Figure 1 A provides an overview of a metasurface AR / MR waveguide glass architecture in accordance with several embodiments of the invention. The overview illustrates the behavior of ray propagation and the absence of the Vergence- Accommodation Conflict (VAC) effect. The metasurface optical element (MOE) waveguide operates within a Maxwellian vision system, ensuring that the image reaching the user's eye is not focused, thus eliminating the VAC issue. This is an important aspect, as it enhances user comfort and reduces visual fatigue.

[0066] To optimize the MOEs, numerical design map optimizations can be performed as shown in Figure IB. This plot demonstrates the high average efficiency achieved within a specific input angle range, while also highlighting the desirable Fill Factor (FF) values. Through coupled- wave analysis, the MOE display can be fine-tuned to minimize unwanted diffraction modes and maximize the efficiencies of the essential modes. As a result, the MOE system can achieve an impressive output efficiency exceeding 1%.

[0067] The fabrication of an MOE waveguide can involve a sophisticated silicon foundry process, as depicted in Figure 1C. This process encompasses the deposition of nitride thin films, deepultraviolet lithography, and precise nanopatterning. Adhering to these fabrication protocols can enable faithfully replicating the design while maintaining the desired parameters such as FoV, full-color capabilities, and refractive index. Additionally, a priority can be to minimize the occurrence of dark crossing lines, ensuring an optimal visual experience for users.

[0068] Figure ID shows an AR waveguide display in accordance with an embodiment of the invention. The image displayed through this prototype was exceptionally sharp and clear, capturedusing a camera and projected using a portable laser beam projector. This early success highlights the potential of our MOE-based waveguide glass system to deliver high-quality visual content in an augmented or mixed-reality environment.

[0069] Figure IE shows another waveguide display in accordance with an embodiment of the invention. The waveguide display 100 includes a lens 102, an optical engine 104, a motor 106 or other system capable of moving the lens 102, and an MOE waveguide 110 having an in-MOE 112 and an out-MOE 114. The optical engine 104 may be configured to direct light rays as an input beam to the in-MOE 112 through the lens 102. The lens 102 can be adjusted as discussed below (e.g., in x and y directions) using the motor 106 or other system capable of moving the lens 102 or adjusting the input beam angle. The out-MOE 114 can provide beam patterns that may be observed by a user’s eye.

[0070] Figures 2A and 2B show the impact of input beam angle variations on the metasurface conditions in the OutMOE. Figure 2A displays the different input beam conditions, while Figure 2B illustrates the corresponding metasurface conditions resulting from those angles. Each condition corresponds to a different portion of the OutMOE, with varying periods and angles (Psi) of the metasurface.

[0071] Figure 3 illustrates the outgoing beam patterns resulting from the variations in the input beam angles depicted in Figure 2A. Specifically, on the beam at the eye position, located 15mm away from the OutMOE. The regular condition (x20-y0), with an input beam angle of 20 degrees in the x direction and 0 degrees in the y direction, aligns with the regular eye position at (0mm, 0mm).

[0072] When the input beam is shifted to different angles, as shown in Figure 3, the position of the beam at the eye plane undergoes a corresponding shift. For instance, a 24-degree x input beam angle results in a positive shift of +1.4mm in the x direction at the eye plane, while a 10- degree x input beam angle leads to a negative shift of -3.4mm in the x direction. Similarly, a 12- degree y input beam angle results in a positive shift of +3.3mm in the x direction, while a -12- degree x input beam angle leads to a negative shift of -3.3mm in the y direction.

[0073] This dynamic shift in the position of the beam at the eye plane enables the increase of the eyebox. In the current conditions, the eyebox can be expanded to 4.8mm in the x direction and 6.8mm in the y direction. Consequently, the dynamic eyebox area reaches 32.64 mm2. Theseresults demonstrate the potential of input beam angle modulation to dynamically extend the eyebox, providing a more flexible and comfortable viewing experience.

[0074] Figure 4 highlights a challenge that may be encountered when simulating the full MOE. In the regular condition, where the input beam angle is set to x 20 degrees and y 0 degrees, the beam from the full MOE converges to a single position, aligning perfectly with the eye pupil. This ensures that the entire beam passes through the pupil, enabling a clear and focused image perception.

[0075] However, complications can arise when the input beam angle deviates from the regular condition. Figure 4 illustrates that as the input beam angle is changed, the beam emitted by the full MOE becomes dispersed and spreads out. This dispersion becomes more pronounced as the beam is tilted at larger angles compared to the regular condition. While the dispersed beam can still fit within the dimensions of the eye pupil (assuming a pupil size of 2mm2), such spreading of the beam leads to image deterioration and distortion of the resolution.

[0076] This phenomenon can pose a challenge in maintaining image quality and preserving the intended resolution in AR waveguide displays. The spread of the beam beyond its intended position may not only compromise the sharpness of the image but may also introduce unwanted distortions that can negatively impact the user experience.

[0077] Addressing this issue considers optimization of the MOE design and beam propagation. Techniques such as advanced beam shaping, aberration correction, or adaptive optics may be employed to mitigate the effects of beam spreading and preserve image quality even when the input beam angles deviate from the regular condition.

[0078] Efforts in this direction aim to enhance the performance and capabilities of Maxwellian view AR waveguides, ensuring that users can enjoy immersive and visually pleasing experiences with minimal image degradation and distortion. By overcoming the challenges associated with beam spreading, this dynamic eyebox increase can be adapted using the input beam angle steering.

[0079] In order to optimize the performance of the metasurface in our AR waveguide system, various conditions could impact the eyebox area and beam position. One of the parameters is the center-to-center distance (CTC) between the metasurfaces. Figure 5 illustrates the effect of changing the CTC on the variance of the eyebox area.

[0080] As shown in the figure, different CTC values not only alter the overall area of the eye positions for each input beam angle but also cause a shift in the positions for the same angles.Notably, the largest shift occurs when the CTC is set to 30mm. This significant shift can be advantageous as it leads to a larger dynamic eyebox, allowing for a greater range of eye positions to perceive the augmented content.

[0081] However, it is important to consider the trade-off associated with this larger shift. As demonstrated in the figure, a larger shift in the beam position is accompanied by an increase in beam spread. The beam spread refers to the dispersion of the beam beyond its intended position, which can result in image degradation and reduced resolution. Therefore, in order to achieve an optimal balance, a condition can be identified where the beam shift is substantial while keeping the beam spread to a minimum.

[0082] Finding the right combination of parameters, such as the CTC, input MOE size, and waveguide thickness, can be important to achieving a larger dynamic eyebox while maintaining high image quality. Analyzing and optimizing these parameters can strike a balance between the extent of the eyebox and the sharpness of the displayed content. This optimization process can ultimately contribute to the development of AR waveguide systems with enhanced user experience, offering a wider range of viewing positions without compromising on image clarity and resolution.

[0083] Figure 5 observed that each incoming beam resulted in a spread with a certain area. To further analyze the impact of beam variation on the spread, the areas corresponding to different beam conditions are examined in Figures 6 and 7. In both figures, the lowest area (indicating the smallest spread) is obtained when the beam condition closely matched the regular beam angle of x 20 degrees and y 0 degrees. As the beam condition deviated further from the regular angle, the area increased.

[0084] Notably, Figure 6 shows the areas for different beam conditions in the x direction, while Figure 7 displays the areas in the y direction. In both cases, the plots exhibit a parabolic trend, with the minimum area occurring when the beam condition closely matches the regular angle. The plots provide insights into how the spread varies with beam angle deviation.

[0085] Three key points can be extracted from the analysis of Figures 5 to 7. Firstly, derived from Figure 5, Figure 8 highlights the maximum shifts in the eye positions, which correspond to the largest dynamic eyebox area. These shifts occur when the beam condition is farthest from the regular beam angle, indicating that a greater deviation from the regular angle results in a larger dynamic eyebox.

[0086] Secondly, Figure 9 shows the second derivatives of the plots in Figures 6 and 7 indicating the rate at which the spread increases with beam angle deviation. These derivatives provide valuable information on the sensitivity of the spread to changes in the beam condition. By examining the second derivatives, we can assess the extent to which the spread expands as the beam condition deviates from the regular angle.

[0087] Lastly, Figure the minimum areas in Figures 6 and 7 are of particular importance. These areas represent the smallest beam spreads, which are desirable for maintaining image quality and resolution. Ideally, these minimum areas are aimed to be as small as possible, indicating a minimal spread and reduced distortion.

[0088] Carefully analyzing the key points discussed earlier can gain valuable insights into how variations in the beam condition impact the eyebox area and spread. These insights are critical for optimizing the design of the AR waveguide system, enabling to determine the optimal beam conditions that simultaneously maximize the dynamic eyebox area while minimizing the spread and preserving image quality.

[0089] Larger values of CTC (center-to-center distance) allowed for an increased maximum eye position shift. For example, with a larger CTC, the maximum eye position shift could be enlarged to 6.25mm in the x-direction and 6.6mm in the y-direction. This indicates that by carefully engineering the CTC parameter can achieve a greater extent of eyebox movement.

[0090] However, it is important to note that larger CTC values also result in larger beam spreads, as depicted in Figure 9. The second derivatives of the plots become larger for beam conditions further away from the regular condition, especially when using a larger CTC. This implies that the spread increases more rapidly with beam angle deviation for these conditions.

[0091] Similarly, Figure 10 illustrates the minimum area for different beam conditions. It is evident that as the CTC increases, the minimum area also increases. This indicates a larger beam spread, which can negatively impact image quality and resolution.

[0092] Therefore, when engineering the CTC parameter, it is crucial to strike a balance between achieving a sufficient maximum eye position shift and maintaining a small beam spread. This delicate balance ensures that the eyebox can be dynamically extended while minimizing image distortion and preserving visual clarity.

[0093] By considering these findings and optimizing the CTC parameter accordingly, we can design AR waveguide systems that offer a larger dynamic eyebox area, providing users withenhanced viewing experiences while maintaining high image quality and minimizing visual artifacts.

[0094] In addition to the impact of the CTC parameter, the size of the InMOE (Input Meta- Optical Element) also plays a significant role in determining the characteristics of the eyebox area and spread. Figure 11 provides insights into the effects of varying the InMOE size.

[0095] From the figure, it can be observed that increasing the InMOE size leads to a larger maximum eye position shift. This means that a larger InMOE allows for a greater range of eyebox movement, providing more flexibility in terms of the positions from which the display can be viewed.

[0096] However, it is important to consider the trade-offs associated with increasing the InMOE size. As depicted in Figure 11, larger InMOE sizes result in an increased minimum area and larger second derivatives. The minimum area represents the spread of the beam, and a larger minimum area indicates a larger beam spread. This can potentially result in a decrease in image quality and resolution, as well as a decrease in the perceived sharpness of the displayed content.

[0097] Furthermore, the larger second derivatives indicate that the beam spread increases more rapidly with beam angle deviation for larger InMOE sizes. This means that even small variations in the input beam angle can result in significant changes in the spread of the beam. It is crucial to consider this effect in order to minimize distortions and maintain a high-quality viewing experience.

[0098] Therefore, similar to the CTC parameter, the size of the InMOE must be carefully engineered to strike a balance between maximizing the eyebox movement and minimizing the beam spread and associated distortions. Optimal design parameters should be determined based on a comprehensive analysis of these factors, taking into account the specific requirements and constraints of the AR waveguide system.

[0099] The waveguide thickness is another important parameter to consider when designing AR waveguide systems. Figure 12 illustrates the effects of varying waveguide thickness on the eyebox characteristics.

[0100] From the figure, it can be observed that thinner waveguides tend to result in increased maximum eye position shifts. This means that reducing the waveguide thickness allows for a larger range of eyebox movement, providing more flexibility in terms of viewing positions.

[0101] Interestingly, the effect of waveguide thickness on the minimum area and second derivatives is relatively minimal compared to the effects of CTC and InMOE size. The minimum area, which represents the beam spread, and the second derivatives, which indicate the rate of change in the beam spread, are less affected by changes in waveguide thickness.

[0102] This implies that, within certain process engineering limitations, the waveguide thickness can be made thinner without significantly impacting the eyebox characteristics. In an embodiment of the invention, the waveguide thickness is thinned down to 3.5mm, suggesting that a relatively thin waveguide can be used without compromising the eyebox performance.

[0103] However, it is important to note that other factors, such as optical efficiency, fabrication considerations, and mechanical stability, should also be taken into account when determining the optimal waveguide thickness for a specific AR waveguide system.

[0104] By carefully considering the trade-offs and interplay between the CTC, InMOE size, and waveguide thickness, designers can achieve an optimal balance that maximizes the eyebox movement, minimizes the beam spread, and ensures high-quality visual experiences in AR applications.

[0105] After carefully considering the engineering aspects, including waveguide thickness, InMOE size, and CTC, specific engineering techniques can be applied to different positions within the metasurface to reduce the beam spread. This engineering can involve modifying the period and angle of the metasurface grating based on the distance from the center of the OutMOE. This modification is quantified as rMM, indicating the degree of engineering applied to each position.

[0106] Figure 13 illustrates the impact of this engineering on the beam spread. It can be observed that as the degree of engineering (rMM) increases, the beam spread is successfully reduced. This indicates that the modified metasurface grating effectively focuses the light and minimizes dispersion, resulting in a narrower and more concentrated beam.

[0107] However, it is important to note that increasing rMM also has some trade-offs. As shown in the figure, as rMM increases, the position of the eyebox becomes compressed. This means that the range of eye positions within the eyebox may become more limited, potentially affecting the flexibility and comfort of the viewing experience.

[0108] Additionally, the areas where the beam condition closely resembles the normal conditions (x 20 degrees, y 0 degrees) and the beam spread is minimal also increase in size with higher rMM values. This indicates that while the engineering reduces the overall spread of thebeam, it may result in a more concentrated area around the normal conditions, potentially limiting the effective eyebox area.

[0109] Therefore, the selection of rMM should be carefully balanced, taking into consideration the desired beam spread reduction, eyebox position flexibility, and overall image quality. By optimizing the engineering parameters, designers can achieve a trade-off that best suits the specific requirements of the AR waveguide system.

[0110] Through further analysis, it can be determined that applying a Gaussian spread of rMM values from the center of the OutMOE yielded the best results in terms of reducing beam spread and minimizing distortions. This engineering approach is depicted in Figure 14, where the rMM value at the center of the OutMOE is 1.03 and gradually increases to 1.08 at further positions following a Gaussian function with a sigma value of 5.5.

[0111] The effectiveness of this engineering can be observed in Figure 15, where the resulting area is significantly reduced compared to before the engineering. The beam area now occupies a smaller region, ensuring that it can enter the pupil of the eye without excessive spread or distortion, even at the highest beam angles. This indicates that the modified metasurface grating, designed with the Gaussian spread of rMM, successfully concentrates the light and maintains image quality within a confined area.

[0112] By implementing this engineering approach, the AR waveguide system achieves a more controlled and precise distribution of the beam, ensuring that the visual information reaches the viewer's eye with minimal distortions. This leads to an enhanced viewing experience, as the images displayed within the eyebox maintain their sharpness, clarity, and fidelity.

[0113] Overall, the application of rMM with a Gaussian spread has proven to be an effective technique in reducing beam spread and optimizing the performance of the AR waveguide system. It enables a more efficient utilization of the eyebox area and ensures that the displayed content remains visually appealing and immersive for the user.

[0114] Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of the invention. Various other embodiments are possible within its scope. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A Maxwellian view augmented reality waveguide display, comprising: a metasurface optical element (MOE) waveguide having an inMOE and an outMOE; a lens; a lens adjustment system having an adjustable angle in X and Y orthogonal directions; and an optical engine configured to provide an input beam to the MOE waveguide through the lens.

2. The waveguide display of claim 1, further comprising an eye-tracking subsystem.

3. The waveguide display of claim 1, further comprising an eyebox region where an eye may observe an image created by the input beam.

4. The waveguide display of claim 1, wherein a center-to-center (CTC) distance between metasurfaces of the waveguide is determined based on shift of the input beam while minimizing beam spread.

5. The waveguide display of claim 4, where beam spread is determined to offset the determined CTC to achieve image quality.

6. The waveguide display of claim 1 wherein input MOE size is determined to enlarge an eyebox region and input beam angle is determined to offset beam spread caused by the determined input MOE size to achieve image quality.

7. The waveguide display of claim 1, wherein thickness of the waveguide is calculated to a minimum dimension to enlarge the eyebox region while remaining mechanically stable.

8. The waveguide display of claim 1, where the waveguide is 3.5mm thick.

9. The waveguide display of claim 1, wherein the CTC is 30 mm.

10. The waveguide display of claim 1, wherein the MOE waveguide is constructed by deposition of nitride thin films and deepultraviolet lithography.

11. The waveguide display of claim 1, wherein the beam angle of the input beam is x 20 degrees and y 0 degrees.

12. The waveguide display of claim 1, wherein a Gaussian spread of rMM values are applied from the center of the OutMOE.

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