Increased Depth of Field for Mixed Reality Displays

Abstract

An optical system and a method of operation thereof are disclosed. A demarcation zone is defined as a function of distance from the optical system based on VAC limits, the demarcation zone having at least one distance threshold. A virtual distance of a virtual depth plane from the optical system at which a virtual object will be displayed is determined. Whether the virtual distance is outside the demarcation zone is determined by comparing the virtual distance to the at least one distance threshold. A collimated pixel beam associated with the virtual object is generated by a projector of the optical system. The collimated pixel beam is modified to generate a modified pixel beam if the virtual distance is outside the demarcation zone.

Description

Technical Field

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 946,291, filed on December 10, 2019, entitled "INCREASED DEPTH OF FIELD FOR MIXED-REALITY DISPLAY", the entire content of which is incorporated herein by reference for all purposes.

Background Art

[0002] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that they appear or can be perceived as if they were real. Virtual reality, i.e., "VR" scenarios, typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, and augmented reality, i.e., "AR" scenarios, typically involve the presentation of digital or virtual image information as an augmentation to the visualization of the actual world around the user.

[0003] Despite the progress made in these display technologies, there remains a need in the art for improved methods, systems, and devices related to augmented reality systems, particularly display systems.

Summary of the Invention

Means for Solving the Problems

[0004] The present disclosure generally relates to techniques for improving the performance and user experience of optical systems. More specifically, embodiments of the present disclosure use a microdisplay and a leakage grating light-induced pupil expansion eyepiece element that, in a compact form factor, employs a scheme for preventing human visual system depth-of-field cues by dynamically extending the depth of field of the system to operate a fixed focal plane optical system. The present invention is described with reference to optical systems such as augmented reality (AR) devices, but the present disclosure is applicable to various applications in computer vision and image display systems.

[0005] An overview of the present invention is provided below with reference to a series of examples. As used below, any reference to a series of examples is to be understood as referring to each of those examples separately (e.g., "Examples 1-4" should be understood as "Examples 1, 2, 3, or 4").

[0006] Example 1 is a method of operating an optical system, comprising the steps of: defining a separation zone as a function of the distance from the optical system based on the vergence - accommodation conflict (VAC) limit, the separation zone having at least one distance threshold; determining a virtual distance of a virtual depth plane from the optical system at which a virtual object will be displayed; determining whether the virtual distance is outside the separation zone by comparing the virtual distance to at least one distance threshold; generating a collimated pixel beam associated with the virtual object by a projector of the optical system; modifying the collimated pixel beam and generating a modified pixel beam based on determining that the virtual distance is outside the separation zone, the step of modifying the collimated pixel beam including at least one of the steps of converging the collimated pixel beam or reducing the diameter of the collimated pixel beam; injecting the modified pixel beam into an eyepiece lens of the optical system; and outputting the modified pixel beam from the eyepiece lens towards the user's eye.

[0007] Example 2 is an optical system, comprising: a projector configured to generate a collimated pixel beam associated with a virtual object; an optical modification device configured to modify the collimated pixel beam and generate a modified pixel beam; an eyepiece lens configured to output the modified pixel beam; a processing module configured to perform operations including: determining a virtual distance of a virtual depth plane from the optical system at which a virtual object will be displayed; comparing the virtual distance to at least one distance threshold; and causing the optical modification device to modify the collimated pixel beam and generate a modified pixel beam based on comparing the virtual distance to at least one distance threshold.

[0008] Example 3 is the optical system according to Example 2, wherein the step of modifying the collimated pixel beam includes the step of converging the collimated pixel beam.

[0009] Example 4 is the optical system according to Examples 2-3, wherein the step of modifying the collimated pixel beam includes the step of reducing the diameter of the collimated pixel beam.

[0010] Example 5 is the optical system according to Examples 2-4, wherein the operation further includes the step of defining a delimited zone as a function of the distance from the optical system, the delimited zone including at least one distance threshold.

[0011] Example 6 is the optical system according to Example 5, wherein the step of comparing the virtual distance with at least one distance threshold includes the step of determining whether the virtual distance is outside the delimited zone.

[0012] Example 7 is the optical system according to Examples 5-6, wherein the delimited zone is defined based on the VAC limit.

[0013] Example 8 is the optical system according to Example 7, wherein the VAC limit is defined by the user of the optical system.

[0014] Example 9 is the optical system according to Examples 2-8, wherein at least one distance threshold includes an upper distance threshold.

[0015] Example 10 is the optical system according to Example 9, wherein the step of comparing the virtual distance with at least one distance threshold includes the step of determining whether the virtual distance exceeds the upper distance threshold.

[0016] Example 11 is the optical system according to Example 10, wherein the step of modifying the collimated pixel beam based on comparing the virtual distance with at least one distance threshold includes causing the optical modification device to modify the collimated pixel beam in response to a determination that the virtual distance exceeds the upper distance threshold.

[0017] Example 12 is the optical system according to Examples 2-11, wherein at least one distance threshold includes a lower distance threshold.

[0018] Example 13 is the optical system according to Example 12, wherein the step of comparing the virtual distance with at least one distance threshold includes determining whether the virtual distance is less than the lower distance threshold.

[0019] Example 14 is the optical system according to Example 13, wherein the step of modifying the collimated pixel beam based on comparing the virtual distance with at least one distance threshold includes causing the optical modification device to modify the collimated pixel beam in response to a determination that the virtual distance is less than the lower distance threshold.

[0020] Example 15 is the optical system according to Examples 2-14, wherein the eyepiece is configured to receive the modified pixel beam from the optical modification device.

[0021] Example 16 is the optical system according to Examples 2-15, wherein the optical modification device is positioned within the optical path between the projector and the eyepiece.

[0022] Example 17 is a method of operating an optical system, the method including: determining a virtual distance of a virtual depth plane from the optical system at which a virtual object is to be displayed; comparing the virtual distance with at least one distance threshold; generating, by a projector of the optical system, a collimated pixel beam associated with the virtual object; and modifying the collimated pixel beam and generating a modified pixel beam based on the comparison of the virtual distance with the at least one distance threshold.

[0023] Example 18 is the method according to Example 17, wherein the step of modifying the collimated pixel beam includes converging the collimated pixel beam.

[0024] Example 19 is the method according to Examples 17-18, wherein the step of modifying the collimated pixel beam includes reducing the diameter of the collimated pixel beam.

[0025] Example 20 is the method according to Examples 17-19, further including defining a delimiting zone as a function of the distance from the optical system, the delimiting zone including at least one distance threshold.

[0026] Example 21 is the method according to Example 20, wherein the step of comparing the virtual distance with at least one distance threshold includes determining whether the virtual distance is outside the delimiting zone.

[0027] Example 22 is the method according to Examples 20-21, wherein the delimiting zone is defined based on a VAC limit.

[0028] Example 23 is the method according to Example 22, wherein the VAC limit is defined by a user of the optical system.

[0029] Example 24 is the method according to Examples 17 - 23, wherein at least one distance threshold includes an upper distance threshold.

[0030] Example 25 is the method according to Example 24, wherein the step of comparing the virtual distance with at least one distance threshold includes the step of determining whether the virtual distance exceeds the upper distance threshold.

[0031] Example 26 is the method according to Example 25, wherein the step of modifying the collimated pixel beam based on comparing the virtual distance with at least one distance threshold includes the step of modifying the collimated pixel beam in response to a determination that the virtual distance exceeds the upper distance threshold.

[0032] Example 27 is the method according to Examples 17 - 26, wherein at least one distance threshold includes a lower distance threshold.

[0033] Example 28 is the method according to Example 27, wherein the step of comparing the virtual distance with at least one distance threshold includes the step of determining whether the virtual distance is less than the lower distance threshold.

[0034] Example 29 is the method according to Example 28, wherein the step of modifying the collimated pixel beam based on comparing the virtual distance with at least one distance threshold includes the step of modifying the collimated pixel beam in response to a determination that the virtual distance is less than the lower distance threshold.

[0035] Example 30 is the method according to Examples 17 - 29, further including the step of introducing the modified pixel beam into the eyepiece of the optical system.

[0036] Example 31 is the method according to Examples 17 - 30, further including the step of outputting the modified pixel beam from the eyepiece of the optical system towards the user's eye.

[0037] Example 32 is the method described in Examples 17 - 31, in which the collimated pixel beam is modified by an optical modification device positioned within the optical path between the projector and the eyepiece of the optical system.

[0038] A number of advantages over conventional techniques are achieved by the methods of the present disclosure. For example, embodiments enable a single focal plane system to have some of the same advantages as a two - focal plane system, such as reduced VAC in both the near - field and far - field virtual depth planes. Additionally, since the pixel beam can be modified prior to entry into the eyepiece, embodiments are compatible with existing eyepieces that employ pupil - expanding combiner eyepiece technology. Embodiments also often eliminate the need to clip planes, which are employed for the near - field depth plane, thereby reducing the inconvenience to the user due to virtual content disappearance. Other advantages of the present disclosure will be readily apparent to those skilled in the art.

Brief Description of the Drawings

[0039] The accompanying drawings, which are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the detailed description, serve to explain the principles of the present disclosure. It is not intended to show the structural details of the present disclosure in more detail than is necessary for a fundamental understanding of the present disclosure and the various ways in which it may be practiced.

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[0056] In the accompanying drawings, like components and / or features may have the same numerical reference labels. Further, various components of the same type may be distinguished among like components and / or features by a second numerical reference label that follows a reference label with a letter or that follows a reference label with a dash. When only the first numerical reference label is used herein, the description is applicable to any one of the like components and / or features having the same first numerical reference label, regardless of the subscript. DETAILED DESCRIPTION OF THE INVENTION

[0057] Mixed reality (MR) and augmented reality (AR) wearable displays are capable of presenting virtual content to a user over a wide depth range. For many displays, the user can experience variable levels of vergence-accommodation conflict (VAC) at different depths, which occurs when the user's brain receives inconsistent cues between the distance from the user's eye to a virtual object and the focusing distance required for the eye to focus on that virtual object. VAC leads to visual fatigue, headaches, nausea, and eye strain, leaving a significant source of discomfort for the user. Thus, in order to maintain user comfort, modern MR and AR wearable displays may consider a VAC budget allowance when delivering virtual content over a depth range that can result in a significantly reduced depth range.

[0058] Various approaches for reducing VAC have been implemented. One approach involves adding a variable focus switch based on a second depth plane and eye tracking to the optical system. Another approach is to add a variable focus element with the ability to sweep across a wide range of the eyepiece focal plane. These approaches come with increased volume due to the integration of additional eyepiece lens layers and / or liquid-fillable adjustable lens pairs spanning the eyepiece, and increased complexity due to complex illumination schemes.

[0059] Some embodiments of the present invention provide a partitioning zone in the optical system within which a limited amount of VAC is tolerated by the user and outside of which an extended depth of field can be switched on to interfere with the human visual system vergence cues. In some embodiments, the partitioning zone can be defined based on single or multiple fixed focal planes or single or multiple variable focal planes. Virtual content having an associated virtual depth plane within the partitioning zone can be projected to the user in a normal manner, while virtual content outside the partitioning zone is modified by an optical correction device to reduce the reliability of the vergence cues.

[0060] In some instances, the light modification device can cause the collimated light generated by the projector to converge when it enters the eyepiece lens. This also converges the virtual image light (i.e., the light associated with the virtual image) that is externally coupled from the leakage grating of the eyepiece lens. However, the chief ray of each beamlet results in a virtual image that does not change direction, but with a very weak focusing cue along with the convergence / divergence motion cue. Such a virtual image can interfere with the convergence / divergence motion - focusing response within the depth of field area where the VAC will exceed the threshold tolerance. Therefore, the embodiments disclosed herein can extend the depth of field of the optical system because the user's eye may not be able to focus on the pixels in the virtual depth plane. Additionally, or alternatively, the light modification device can reduce the diameter of each collimated pixel beam generated by the projector. This causes the light externally coupled from the leakage grating of the eyepiece lens to also have a pixel beam with a reduced diameter, thereby being able to interfere with the focusing cue associated with the externally coupled light.

[0061] In some instances, an optical see - through (OST) AR device can improve the virtual content presented to the user by applying refractive power to the virtual image light using one or more lens assemblies arranged within the optical stack. Embodiments of the present invention are compatible with existing systems that utilize lens assemblies to vary the virtual depth plane of virtual objects.

[0062] FIG. 1 illustrates an AR scene 100 as viewed through a wearable AR device, according to some embodiments. The AR scene 100 is depicted in which the user of the AR technology sees a real-world park-like setting 106 featuring various real-world objects 130 such as people, trees, buildings in the background, and a real-world concrete platform 120. In addition to these items, the user of the AR technology also "sees" various virtual objects 102 such as a robotic figure 102-2 standing on the real-world concrete platform 120 and a flying, cartoon-like avatar character 102-1 that appears to be an anthropomorphized honeybee, although these elements (character 102-1 and figure 102-2) do not exist within the real world. Due to the extreme complexity of human vision and the nervous system, it is difficult to produce virtual reality (VR) or AR technology that facilitates a comfortable and natural, rich presentation of virtual image elements among other virtual or real-world image elements.

[0063] FIG. 2A illustrates an AR device 200A having a single fixed focal plane, according to some embodiments. During operation, the projector 214 of the AR device 200A may project virtual image light 223 (i.e., light associated with virtual content) onto the eyepiece lens 202-1, which may project a light field (i.e., an angular representation of the virtual content) onto the user's retina in a manner such that the user perceives the corresponding virtual content to be located at a location within the user's environment. For example, the virtual image light 223 externally coupled by the eyepiece lens 202-1 may cause the user to perceive the character 102-1 to be located at a first virtual depth plane 210-1 and the figure 102-2 to be located at a second virtual depth plane 210-2. The user perceives the virtual content together with world light 232 corresponding to one or more world objects 230 such as the platform 120.

[0064] In some embodiments, the AR device 200A includes a first lens assembly 205-1 positioned on the user side of the eyepiece lens 202-1 (the side of the eyepiece lens 202-1 closest to the user's eye) and a second lens assembly 205-2 positioned on the world side of the eyepiece lens 202-1. The lens assemblies 205-1, 205-2 may each be configured to apply a refractive power to light passing therethrough.

[0065] FIG. 2B illustrates an AR device 200B having two fixed focal planes, according to some embodiments. During operation, the projector 214 may project virtual image light 223 onto the first eyepiece lens 202-1 and the second eyepiece lens 202-2, which may project a light field onto the user's retina in a manner such that the user perceives the corresponding virtual content to be located at a location within the user's environment. For example, the virtual image light 223 externally coupled by the first eyepiece lens 202-1 may cause the user to perceive the character 102-1 to be positioned at the first virtual depth plane 210-1, and the virtual image light 223 externally coupled by the second eyepiece lens 202-2 may cause the user to perceive the image 102-2 to be positioned at the second virtual depth plane 210-2.

[0066] FIG. 3 illustrates the relationship between the VAC and the distance to the virtual depth plane for each of the AR devices 200A and 200B described with reference to FIGS. 2A and 2B, respectively. For the AR device 200B, the two focal plane system provides switchable focal planes at 1.95 diopters (0.51 m) and 0.65 diopters (1.54 m) with a switching point at 1.3 diopters (0.77 m), a near content limit (clipping plane) at 2.7 diopters (0.37 m), and the ability to provide an image that never exceeds 1.0 diopter VAC between that plane and infinity. For the AR device 200A, the single fixed focal plane system has a focal plane location at 1.5 diopters (0.6 m), a near content limit of 2.5 diopters (0.4 m), and a far content limit of 0.31 diopters (3.2 m), assuming a maximum allowable VAC of 1.0 diopter. Such a configuration has a usable range of 0.4 to 3.2 m, and content falling outside that range requires a solution to mitigate VAC limit exceedance.

[0067] Figure 4 illustrates a schematic diagram of an exemplary wearable AR device 400 according to some embodiments of the present invention. The AR device 400 may include a left eyepiece lens 402A and a left lens assembly 405A arranged in a juxtaposed configuration, and the right eyepiece lens 402B and the right lens assembly 405B are also arranged in a juxtaposed configuration. In some embodiments, the AR device 400 includes one or more sensors including, but not limited to, a left front-facing world camera 406A directly attached to or near the left eyepiece lens 402A, a right front-facing world camera 406B directly attached to or near the right eyepiece lens 402B, a left side-facing world camera 406C directly attached to or near the left eyepiece lens 402A, and a right side-facing world camera 406D directly attached to or near the right eyepiece lens 402B. In some embodiments, the AR device 400 includes one or more image projection devices such as a left projector 414A optically linked to the left eyepiece lens 402A and a right projector 414B optically linked to the right eyepiece lens 402B.

[0068] Some or all of the components of the AR device 400 may be head-mounted so that the projected image can be visually recognized by the user. In one particular implementation, all of the components of the AR device 400 shown in FIG. 4 are mounted on a single device (e.g., a single headset) that can be worn by the user. In another implementation, one or more components of the processing module 450 are physically separate from the other components of the AR device 400 and are communicatively coupled thereto by one or more wired and / or wireless connections. For example, the processing module 450 may include a local module 452 on the head-mounted portion of the AR device 400 and a remote module 456 that is physically separate from the local module 452 and is communicatively linked thereto. The remote module 456 may be mounted in various configurations, such as fixed to a helmet or hat worn by the user, fixed to a frame, built into headphones, or otherwise removably attached to the user (e.g., in a backpack configuration, in a belt attachment configuration, etc.).

[0069] The processing module 450 may include a processor and an associated digital memory such as non-volatile memory (e.g., flash memory), both of which can be utilized to assist in data processing, caching, and storage. The data may include data captured from sensors such as camera 406, ambient light sensor, eye tracker, microphone, inertial measurement unit, accelerometer, compass, GPS unit, wireless device, and / or gyroscope (e.g., operatively coupled to the AR device 400 or alternatively, attachable to the user). For example, the processing module 450 may receive an image 420 from the camera 406. Specifically, the processing module 450 may receive a left front image 420A from the world camera 406A facing the left front, a right front image 420B from the world camera 406B facing the right front, a left side image 420C from the world camera 406C facing the left side, and a right side image 420D from the world camera 406D facing the right side. In some embodiments, the image 420 may include a single image, a pair of images, a video comprising a stream of images, a video comprising a stream of paired images, and the like. The image 420 may be periodically generated and transmitted to the processing module 450 while the AR device 400 is powered on, or may be generated in response to an instruction transmitted by the processing module 450 to one or more of the cameras. As another example, the processing module 450 may receive ambient light information from the ambient light sensor. As another example, the processing module 450 may receive gaze information from one or more eye trackers. As another example, the processing module 450 may receive image information (e.g., image brightness values) from one or both of the projectors 414.

[0070] Cameras 406A and 406B may each be positioned to capture images that substantially overlap within the fields of view of the user's left and right eyes. Thus, the cameras 406 may be placed near the user's eyes, but not so close as to obscure the user's field of view. Alternatively or in addition, cameras 406A and 406B may each be positioned to align with the internal coupling locations of virtual image lights 422A and 422B, respectively. Cameras 406C and 406D may be positioned, for example, to capture images with respect to the sides of the user, either within or outside the user's peripheral vision. Images 420C and 420D captured using cameras 406C and 406D need not necessarily overlap with images 420A and 420B captured using cameras 406A and 406B.

[0071] Eyepieces 402A and 402B may each comprise a transparent or translucent waveguide configured to direct and externally couple the light generated by projectors 414A and 414B, respectively. Specifically, processing module 450 may cause left projector 414A to output left virtual image light 422A to left eyepiece 402A and right projector 414B to output right virtual image light 422B to right eyepiece 402B. In some embodiments, eyepieces 402A and 402B may each comprise a plurality of waveguides corresponding to different colors. In some embodiments, lens assemblies 405A and 405B may be coupled to and / or integrated with eyepieces 402A and 402B. For example, lens assemblies 405A and 405B may be incorporated into a multi-layer eyepiece and may form one or more layers that constitute one of eyepieces 402A and 402B.

[0072] In some embodiments, the AR device 400 includes one or more optical modification devices 404A, 404B for modifying the virtual image light 422A, 422B. Specifically, the left optical modification device 404A may be positioned within the optical path between the left projector 414A and the left eyepiece lens 402A to modify the left virtual image light 422A prior to being output onto the left eyepiece lens 402A, and the right optical modification device 404B may be positioned within the optical path between the right projector 414B and the right eyepiece lens 402B to modify the right virtual image light 422B prior to being output onto the right eyepiece lens 402B. In some embodiments, the optical modification devices 404A, 404B may be integrated with the projectors 414A, 414B. In some embodiments, the optical modification devices 404A, 404B may be integrated with the eyepiece lenses 402A, 402B.

[0073] In some embodiments, the projectors 414A, 414B may include microelectromechanical systems (MEMS) spatial light modulator (SLM) scanning devices. In such embodiments, the optical modification devices 404A, 404B may employ a variable focus mirror or lens that can be used within the laser beam prior to the scanning mirror. If a relay optical system is used, one of the optical elements within the relay optical system may be variable focus and switchable to provide the converging pixel light rays onto the ICG formed on the eyepiece lens. If a standard projection system is used in combination with a pixel-based SLM (such as liquid crystal on silicon (LCOS)), the SLM itself may be translated in the z-axis (perpendicular to the array) such that the projection lens produces a finite external focal plane (and thus converging pixel light rays). In some embodiments, a variable focus lens is incorporated between the projection / relay lens of the microdisplay and the ICG of the eyepiece lens itself and can convert the output collimated pixel light rays into a converging state.

[0074] FIG. 5 illustrates an exemplary function of the viewing optical system assembly 500 of the AR device and an object of user visual perception resulting from the output of the present system. The viewing optical system assembly 500 includes a projector 514 and an eyepiece lens 502. The projector 514 generates a collimated pixel beam 516 that is conveyed on the eyepiece lens 502 at an input conjugate grating (ICG) 503 formed on the eyepiece lens 502. After being diffracted by the ICG 503, the collimated pixel beam 516 propagates within the eyepiece lens 502 until an output grating formed on the eyepiece lens 502 diffracts the light towards the user.

[0075] A leakage-mode grating light-induced pupil expansion eyepiece lens without programmed refractive power produces a virtual image at infinity. The object of perception is produced by a plurality of output "beamlets" (replicas of the emitted input pixel wavefronts) that are collected through the pupil and imaged onto the retina of the user's eye. In this case, when the user's eye is focused at infinity, a sharp image of the pixels is formed on the retina. When the eye is focused on another plane (e.g., 1.33 meters from the user), a blurred image of the pixels is formed on the retina.

[0076] FIG. 6 illustrates an exemplary function of the viewing optical system assembly 600 of the AR device and an object of user visual perception resulting from the output of the present system. The viewing optical system assembly 600 includes a projector 614 that generates a collimated pixel beam 616 that is conveyed on the eyepiece lens 602 at an ICG 603 formed on the eyepiece lens 602. After being diffracted by the ICG 603, the collimated pixel beam 616 propagates within the eyepiece lens 602 until an output grating formed on the eyepiece lens 602 diffracts the light towards the user.

[0077] The viewing optical system assembly 600 includes a -0.75 diopter lens assembly 605 that modulates the wavefronts of the emitted beamlets to both focus the pixel light and converge the beamlets to 1.33 meters from the user's eye, diverge them relative to each other, and diverge each ray independently. The lens assembly 605 deflects the chief ray of the emerging beamlets and diverges the collimated output at the focal length of the lens to a single pixel focal position. In this case, when the user's eye is focused at 1.33 meters, a sharp image of the pixel is formed on the retina. When the eye is focused at infinity, the image is blurred.

[0078] In the embodiment illustrated in FIG. 6, the depth of focus of the image is determined by several factors including the beamlet fill density (determined by the beam diameter, eyepiece substrate thickness among several other factors), the size of the user's pupil, the optical quality of the lens assembly 605, and the inherent depth of field of the user's eye. Each of these factors can be considered to determine the acceptable VAC budget value for the system. In some embodiments, 1.0 diopter can be used as the VAC budget value, although this value can be higher or lower in practice.

[0079] FIG. 7 illustrates the exemplary function of the viewing optical system assembly 700 of the AR device and the object of user visual perception resulting from the output of the system. The viewing optical system assembly 700 includes a projector 714 that generates a collimated pixel beam 716 that is modified by an optical modification device 704 to produce a modified pixel beam 752 having a converging wavefront. The modified pixel beam 752 is propagated on the eyepiece 702 at the ICG 703 formed on the eyepiece 702. After being diffracted by the ICG 703, the modified pixel beam 752 propagates within the eyepiece 702 until an output grating formed on the eyepiece 702 diffracts the light towards the user.

[0080] In the embodiment illustrated in FIG. 7, modifying the wavefront of the imaged pixels involves introducing refractive power into the projection system and converting an infinity-focusing system into a system that produces a finite image position in front of the projector. In such a configuration, a single pixel produces a converging (curved) wavefront at the pupil plane of the projector. When the converging pixel rays are incident on the eyepiece lens, the exiting beamlets maintain this convergence, however, the chief ray of each beamlet does not change direction. In this case, when the user's eye is focused either at 1.33 meters or at infinity, a blurred image of the pixel is formed on the retina. Additionally, the pixels perceived when the user's eye is focused at 1.33 meters can be different from the pixels perceived when the user's eye is focused at infinity, as depicted by the different types of blur in FIG. 7.

[0081] FIG. 8 illustrates an exemplary function of the viewing optics assembly 800 of the AR device and the object of user visual perception resulting from the output of the system. The viewing optics assembly 800 includes a projector 814 that generates a collimated pixel beam 816 which is modified by an optical modification device 804 to produce a modified pixel beam 852 having a converging wavefront. The modified pixel beam 852 is conveyed on the eyepiece lens 802 at an ICG 803 formed on the eyepiece lens 802. After being diffracted by the ICG 803, the modified pixel beam 852 propagates within the eyepiece lens 802 until an output grating formed on the eyepiece lens 802 diffracts the light towards the user. The viewing optics assembly 800 further includes a -0.75 diopter lens assembly 805 positioned between the eyepiece lens 802 and the user's eye that modulates the wavefront of the emitted beamlets.

[0082] In the embodiment illustrated in FIG. 8, the lens assembly 805 collimates each beamlet output while simultaneously redirecting the chief ray of each beamlet and pivoting it around a point on the focal plane of the lens. As a result, when the user's eye is focused at 1.33 meters, a blurred image of the pixels is formed on the retina. When the user's eye is focused at infinity, an object of perception is produced that has a repeated structure of the blurred image. The user's eye cannot be focused on the blurred image, thereby preventing the user's physiological convergence / divergence motion - accommodation cue and reducing the unpleasant effects of convergence / divergence motion - accommodation conflict. The object of this perception having a repeated structure allows the virtual content to exist on a plane outside the VAC threshold. As a result, the depth of field of the optical system can extend beyond the VAC threshold without discomfort because the user's eye will not be able to focus on the pixels in the virtual depth plane.

[0083] FIG. 9 illustrates the exemplary function of the viewing optical system assembly 900 of the AR device and the object of user visual perception resulting from the output of the system. The viewing optical system assembly 900 includes a projector 914 that generates a collimated pixel beam 916 that is modified by a light modification device 904 such as a spatial light modulator (SLM), relay optics, polarizer, beam splitter, lens, or combinations thereof to produce a modified pixel beam 952 having a reduced diameter. The modified pixel beam 952 is propagated on the eyepiece lens 902 at the ICG 903 formed on the eyepiece lens 902. After being diffracted by the ICG 903, the modified pixel beam 952 propagates through the eyepiece lens 902 until the output grating formed on the eyepiece lens 902 diffracts the light towards the user. The viewing optical system assembly 900 further includes a lens assembly 905 that includes a -1 diopter component positioned between the eyepiece lens 902 and the user's eye and a +1 diopter component positioned on the world side of the eyepiece lens 902.

[0084] In the embodiment illustrated in FIG. 9, the convergence / divergence movement - focus adjustment queue is blocked, and the depth of field of the system is extended not through the divergence / convergence of the image light but by modulating the diameter of the laser beam. This may be performed by the optical modification device 904 prior to introducing the light into the ICG903. In this case, the object of perception is driven by the fact that the lens assembly between the eyepiece 902 and the user's eye cannot provide a small focal spot due to the reduced size of the pixel beam.

[0085] FIGS. 10A - 10C illustrate exemplary optical modification devices for reducing the diameter of a collimated pixel beam according to some embodiments of the present invention. By varying the position of the second lens 1004 with respect to the first lens 1002 and the third lens 1006, the diameter of the input collimated pixel beam can be expanded, reduced, or left unmodified. Referring to FIG. 10A, the second lens 1004 is positioned closer to the first lens 1002 than the third lens 1006 (e.g., adjacent to the first lens 1002) and is adjusted to expand the diameter of the collimated pixel beam upon exit from the optical modification device. Referring to FIG. 10B, the second lens 1004 is positioned at the midpoint between the first lens 1002 and the third lens 1006 and is adjusted to leave the diameter of the collimated pixel beam unmodified upon exit from the optical modification device. Referring to FIG. 10C, the second lens 1004 is positioned closer to the third lens 1006 than the first lens 1002 (e.g., adjacent to the third lens 1006) and is adjusted to reduce the diameter of the collimated pixel beam upon exit from the optical modification device.

[0086] In some embodiments, the optical modification device illustrated in FIGS. 10A - 10C is used to dynamically vary the diameter of the MEMS laser beam. In some instances, the optical modification device may be positioned prior to the MEMS mirror to modify the laser beam as it impinges on the MEMS mirror.

[0087] FIG. 11 illustrates an exemplary control scheme for an optical modification device and the corresponding user perception target of the output of the system, according to some embodiments of the present invention. In some embodiments, the VAC segmentation zone 1102 is defined based on a desired VAC limit such as 1 diopter. The VAC segmentation zone 1102 may include a lower distance threshold 1104 below which the VAC covered by the user exceeds the VAC limit, and an upper distance threshold 1106 above which the VAC covered by the user exceeds the VAC limit.

[0088] Under the control scheme, when it is determined that the distance to the virtual depth plane (from the AR device or the user) is less than the lower distance threshold 1104, the optical modification device is caused to modify the wavefront of the collimated pixel beam. When it is determined that the distance to the virtual depth plane is greater than the lower distance threshold 1104 and less than the upper distance threshold 1106 (i.e., within the VAC segmentation zone 1102), the optical modification device is caused to output the collimated pixel beam without modification. When it is determined that the distance to the virtual depth plane is greater than the upper distance threshold 1106, the optical modification device is caused to modify the wavefront of the collimated pixel beam.

[0089] The control scheme may optionally implement a gradual correction to the collimated pixel beam at or near the distance threshold. For example, the optical correction device may apply a partial correction just before the distance threshold, a greater correction at the distance threshold, and a full correction well past the distance threshold to the collimated pixel beam for the virtual distance. As one example, for an upper distance threshold of 3.2 meters, the collimated pixel beam converges 0% for a virtual distance of 2.8 meters, 25% for a virtual distance of 3.0 meters, 50% for a virtual distance of 3.2 meters, 75% for a virtual distance of 3.4 meters, and 100% for a virtual distance of 3.6 meters, and a control scheme may be implemented. In the same or different embodiments, for a lower distance threshold of 0.4 meters, the collimated pixel beam converges 0% for a virtual distance of 0.6 meters, 25% for a virtual distance of 0.5 meters, 50% for a virtual distance of 0.4 meters, 75% for a virtual distance of 0.3 meters, and 100% for a virtual distance of 0.2 meters, and a control scheme may be implemented. Control schemes with longer or shorter transition bands than the above embodiments may also be implemented. Those skilled in the art will envision various variations, alternatives, and modifications.

[0090] Figure 12 illustrates an exemplary method for defining a VAC cut zone 1202 according to some embodiments of the present invention. First, the VAC covered by the user is plotted as a function of the distance from the AR device to the virtual depth plane (alternatively referred to as a "VAC plot"). In some embodiments, the VAC plot is determined based on the focal plane design of the AR device. For the VAC plot illustrated in Figure 12, a 0.75-meter focal plane is utilized. Next, the VAC limit is plotted along with the VAC covered by the user. Next, the intersection points 1204, 1206 between the two plots are identified, and the corresponding distances are used as the lower and upper distance thresholds of the VAC zone 1202, respectively.

[0091] FIG. 13 illustrates various embodiments of a VAC segmentation zone that can be defined based on a VAC plot for various single focal plane systems. As the focal plane of the AR device increases, both the lower and upper distance thresholds of the VAC segmentation zone increase, presenting a trade-off between near-field and far-field performance. An additional depth plane can also be added to the system to increase the VAC segmentation zone.

[0092] FIG. 14 illustrates an exemplary method 1400 for operating an optical system (e.g., AR device 400) according to some embodiments of the present invention. One or more steps of method 1400 may be performed in a different order than illustrated, and one or more steps of method 1400 may be omitted during the implementation of method 1400. Additionally, two or more steps of method 1400 may be performed simultaneously or in parallel with each other.

[0093] In step 1402, a VAC segmentation zone (e.g., VAC segmentation zones 1102, 1202) is defined. In some embodiments, the VAC segmentation zone is defined based on the number of focal planes of the optical device and / or their corresponding focal plane locations. For example, the VAC associated with a single focal plane system with a focal plane location at 1.5 diopters is estimated and can be used to determine the VAC segmentation zone, which can be significantly smaller than the VAC segmentation zone determined using the VAC associated with a multi-focal plane system, such as a two-focal plane system with focal plane locations at 1.95 diopters and 0.65 diopters. In some embodiments, the VAC segmentation zone is additionally (or alternatively) defined based on VAC limits, which may be defined by the user or predefined for the system. In some embodiments, the VAC segmentation zone is defined by finding the intersection (e.g., intersections 1204, 1206) between the VAC associated with the optical system and the VAC limits, as described with reference to FIGS. 3, 12, and 13.

[0094] In some embodiments, the VAC separation zone is defined as a function of the distance from the optical system, and the distance inside the VAC separation zone corresponds to a virtual depth plane where the virtual content causes the user to experience a VAC below the VAC limit, and the distance outside the VAC separation zone corresponds to a virtual depth plane where the virtual content causes the user to experience a VAC above the VAC limit. In some embodiments, the VAC separation zone includes at least one distance threshold. For example, the VAC separation zone may include a lower distance threshold (e.g., lower distance threshold 1104) and / or an upper distance threshold (e.g., upper distance threshold 1106), and the lower distance threshold is less than the upper distance threshold.

[0095] In step 1404, the virtual distance from the optical system to the virtual depth plane (e.g., virtual depth plane 210) at which a virtual object (e.g., virtual object 102) will be displayed is determined. The virtual distance may be expressed in meters, diopters, or some other unit that indicates a physical displacement. In some embodiments, the virtual distance is determined by a processing module (e.g., processing module 450). In some embodiments, the virtual distance is determined before, during, or after a collimated pixel beam associated with the virtual object is generated by the optical system.

[0096] In step 1406, the virtual distance is compared with a lower distance threshold and / or an upper distance threshold. In some embodiments, it is determined whether the virtual distance is less than the lower distance threshold, greater than the lower distance threshold, less than the upper distance threshold, or greater than the upper distance threshold. For example, in some embodiments, step 1406 may include determining whether the virtual distance is less than the lower distance threshold. As another example, in some embodiments, step 1406 may include determining whether the virtual distance is greater than the upper distance threshold. As another example, in some embodiments, step 1406 may include determining whether the virtual distance is less than the lower distance threshold or greater than the upper distance threshold. In some embodiments, step 1406 is comparable to determining whether the virtual distance is outside the VAC delimited zone.

[0097] In step 1408, collimated pixel beams (e.g., collimated pixel beams 516, 616, 716, 816, 916) associated with the virtual object are generated by the optical system. In some embodiments, the collimated pixel beams are generated by a projector (e.g., projectors 214, 414, 514, 614, 714, 814, 914) of the optical system. The collimated pixel beams may contain color, brightness, and size information for displaying the virtual object. For example, the collimated pixel beams may include light from a single LED color source (e.g., red) or multiple LED color sources (e.g., red, green, and blue).

[0098] In step 1410, the collimated pixel beam is modified to generate a modified pixel beam (e.g., modified pixel beams 752, 852, 952). In some embodiments, the collimated pixel beam is modified by an optical modification device (e.g., optical modification devices 404, 704, 804, 904) of the optical system. In some embodiments, whether step 1410 is performed may depend on the comparison performed in step 1406. For example, in some embodiments, step 1410 is performed only when it is determined that the virtual distance is outside the VAC section zone. For example, step 1410 may be performed only in response to a determination that the virtual distance is less than a lower distance threshold or in response to a determination that the virtual distance exceeds an upper distance threshold. In some embodiments, the optical modification device is integrated with the projector. In some embodiments, the optical modification device is separate from the projector.

[0099] In some embodiments, step 1410 includes step 1412 and / or step 1414. In step 1412, the collimated pixel beam is converged. In some embodiments, the collimated pixel beam is converged by an optical modification device. In step 1414, the diameter of the collimated pixel beam is reduced. In some embodiments, the diameter of the collimated pixel beam is reduced by an optical modification device.

[0100] In step 1416, the modified pixel beam is introduced into an eyepiece (e.g., eyepieces 202, 402, 502, 602, 702, 802, 902) of the optical system. In some embodiments, the modified pixel beam is introduced into an ICG (e.g., ICGs 503, 603, 703, 803, 903) formed on the eyepiece.

[0101] In step 1418, the modified pixel beam is output from the eyepiece lens of the optical system. In some embodiments, the modified pixel beam is output from a leakage grating formed on the eyepiece lens. In some embodiments, the modified pixel beam is output from the eyepiece lens towards the user's eye.

[0102] FIG. 15 illustrates a simplified computer system 1500 according to an embodiment described herein. The computer system 1500 as illustrated in FIG. 15 may be incorporated within a device described herein. FIG. 15 provides a simplified illustration of one embodiment of a computer system 1500 that may perform some or all of the steps of a method provided by various embodiments. Note that FIG. 15 is intended only to provide a generalized illustration of various components and that any or all of them may be utilized as desired. FIG. 15 thus illustrates, in a broad sense, situations in which individual system elements may be implemented in a relatively separated manner or in a relatively more integrated manner.

[0103] The computer system 1500 is shown to include hardware elements that can be electrically coupled via a bus 1505 or communicate otherwise as desired. The hardware elements may include one or more processors 1510 including, but not limited to, one or more general-purpose processors and / or one or more special-purpose processors such as digital signal processing chips, graphics acceleration processors, and / or the like, and one or more input devices 1515 including, but not limited to, a mouse, keyboard, camera, and / or the like, and one or more output devices 1520 including, but not limited to, a display device, printer, and / or the like.

[0104] The computer system 1500 can further include, but is not limited to, local and / or network-accessible storage devices, and / or can include, but is not limited to, disk drives, drive arrays, optical storage devices, solid state storage devices such as random access memory (“RAM”), and / or read-only memory (“ROM”) that can be programmable, flash updatable, and / or the like, and / or can communicate with one or more non-transitory storage devices 1525. Such storage devices can be configured to implement any suitable data storage, including, but not limited to, various file systems, database structures, and / or the like.

[0105] The computer system 1500 can also include, but is not limited to, a communication subsystem 1519 that includes, for example, Bluetooth® devices, 802.11 devices, WiFi devices, WiMax devices, cellular communication facilities, and / or the like, and / or modems, network cards (wireless or wired), infrared communication devices, wireless communication devices, and / or chip sets. The communication subsystem 1519 can include one or more input and / or output communication interfaces and can enable data to be exchanged with a network, such as the networks described below by way of example in one embodiment, namely, other computer systems, televisions, and / or any other devices described herein. Depending on the desired functionality and / or other implementation concerns, a portable electronic device or similar device can communicate images and / or other information via the communication subsystem 1519. In other embodiments, a portable electronic device, such as a first electronic device, can be incorporated into the computer system 1500, such as an input device 1515, within the electronic device. In some embodiments, the computer system 1500 can further include a working memory 1535, which will include a RAM or ROM device as described above.

[0106] The computer system 1500 may also include computer programs provided by various embodiments and / or implement the methods provided by other embodiments as described herein and / or be designed to configure the system, including an operating system 1540, device drivers, executable libraries, and / or other code, such as one or more application programs 1545, shown as currently located within the working memory 1535. Merely by way of example, one or more procedures described with respect to the methods discussed above may be implemented as code and / or instructions executable by a computer or a processor within a computer, and in some aspects, such code and / or instructions may then be used to configure and / or adapt a general-purpose computer or other device to perform one or more operations in accordance with the methods described.

[0107] These sets of instructions and / or code may be stored on a non-transitory computer-readable storage medium, such as the storage device 1525 described above. In some cases, the storage medium may be incorporated within a computer system, such as the computer system 1500. In other embodiments, the storage medium is separate from the computer system, for example, a removable medium such as a compact disk, and / or may be provided within an installation package such that the storage medium can be used to program, configure, and / or adapt a general-purpose computer with the instructions / code stored thereon. These instructions may take the form of executable code executable by the computer system 1500 and / or may take the form of source and / or installable code that, upon compilation and / or installation on the computer system 1500 using, for example, any of a variety of generally available compilers, installation programs, compression / decompression utilities, etc., then takes the form of executable code.

[0108] It will be apparent to those skilled in the art that substantial variations may be made and yet remain within the scope of the invention, and that such variations are contemplated as being covered by the appended claims. For example, customized hardware may also be used and / or particular elements may be implemented in software, or both, including portable software such as applets, and / or other computing devices such as network input / output devices may be employed.

[0109] As described above, in one aspect, some embodiments may employ a computer system, such as computer system 1500, to perform methods according to various embodiments of the present technology. According to one set of embodiments, some or all of the procedures of such methods may be performed by computer system 1500 in response to one or more sequences of one or more instructions that may be incorporated within operating system 1540, and / or other code, such as application program 1545, contained within working memory 1535, where processor 1510 may execute the instructions. Such instructions may be read into working memory 1535 from another computer-readable medium, such as one or more of storage devices 1525. Merely by way of example, execution of a sequence of instructions contained within working memory 1535 may cause processor 1510 to perform one or more procedures of the methods described herein. Additionally, or alternatively, some of the methods described herein may be performed through special purpose hardware.

[0110] As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any medium involved in providing data that causes a machine to operate in a specific manner. In certain embodiments implemented using computer system 1500, various computer-readable media may be involved in providing instructions / code for execution to processor 1510 and / or may be used to store and / or carry such instructions / code. In many implementations, the computer-readable medium is a physical and / or tangible storage medium. Such a medium may take the form of a non-volatile medium or a volatile medium. Non-volatile media includes, for example, optical and / or magnetic disks such as storage device 1525. Volatile media includes, but is not limited to, dynamic memory such as work memory 1535.

[0111] Common forms of physical and / or tangible computer-readable media include, for example, a floppy (registered trademark) disk, a flexible disk, a hard disk, a magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, a punch card, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other memory chip or cartridge, or any other medium from which a computer can read instructions and / or code.

[0112] Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions for execution to processor 1510. Merely by way of example, the instructions may first be carried on a magnetic disk and / or optical disk of a remote computer. The remote computer may load the instructions into its dynamic memory and transmit the instructions as a signal via a transmission medium that is received and / or executed by computer system 1500.

[0113] The communication subsystem 1519 and / or its components generally receive signals, and the bus 1505 can then convey the signals and / or the data, instructions, etc. carried by the signals to the working memory 1535, from where the processor 1510 reads and executes the instructions. The instructions received by the working memory 1535 may optionally be stored on the non-transitory memory device 1525 either before or after execution by the processor 1510.

[0114] The methods, systems, and devices discussed above are examples. Various configurations may omit, substitute, or add various procedures or components as necessary. For example, in alternative configurations, the method may be performed in a different order than that described, and / or various steps may be added, omitted, and / or combined. Also, the features described with respect to one configuration may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. Also, technology is advancing, and thus many of the elements are examples and do not limit the scope or claims of the present disclosure.

[0115] Specific details are given in the description to provide a complete understanding of the exemplary configurations, including implementations. However, the configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques are shown without unnecessary detail to avoid obscuring the configurations. This description provides only exemplary configurations and does not limit the scope, usability, or configurations of the claims. Rather, the foregoing description of the configurations will provide an effective description for those skilled in the art to implement the techniques described. Various changes may be made to the functions and arrangements of the elements without departing from the spirit or scope of the present disclosure.

[0116] Also, the architecture can be described as a process, depicted as a schematic flowchart or block diagram. Each can be described as operating as a sequential process, although many of the operations may be performed in parallel or simultaneously. Additionally, the order of the operations may be rearranged. The process may have additional steps not included in the figures. Further, embodiments of the present method may be implemented by hardware, software, firmware, middleware, microcode, a hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments for performing the required tasks may be stored in a non-transitory computer-readable medium such as a storage medium. The processor may perform the described tasks.

[0117] Although several exemplary architectures have been described, various modifications, alternative structures, and equivalents may be used without departing from the spirit of the present disclosure. For example, the elements described above may be components of a larger system, and other rules may take precedence over or otherwise modify the use of this technology. Also, some steps may be performed before, during, or after the elements described above are considered. Thus, the foregoing description does not limit the scope of the claims.

[0118] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to "a user" includes a reference to one or more such users, and a reference to "the processor" includes a reference to one or more processors and equivalents thereof known to those skilled in the art.

[0119] Also, the words "comprise", "comprising", "contains", "containing", "include", "including", and "includes", when used in this specification and the following claims, are intended to specify the presence of the stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.

[0120] Also, the examples and embodiments described herein are for illustrative purposes only, and in light of this, it should be understood that various modifications or changes may be suggested to those skilled in the art and are included within the spirit and scope of the present application and the appended claims.

Claims

1. 1. A method of operating an optical system, the method comprising: defining a demarcation zone as a function of distance from the optical system based on vergence-accommodation collision (VAC) limits, the demarcation zone having at least one distance threshold; determining a virtual distance of a virtual depth plane from said optical system at which a virtual object will be displayed; determining whether the virtual distance is outside the demarcation zone by comparing the virtual distance to the at least one distance threshold; generating, by a projector of the optical system, a collimated pixel beam associated with the virtual object; modifying the collimated pixel beam based on determining that the virtual distance is outside the demarcation zone to generate a modified pixel beam, the modifying of the collimated pixel beam comprising: converging the collimated pixel beam; or Reducing the diameter of the collimated pixel beam. and injecting the modified pixel beam into an eyepiece of the optical system; outputting the modified pixel beam through the eyepiece towards a user's eye; A method comprising:

2. 1. An optical system comprising: a projector configured to generate a collimated pixel beam associated with a virtual object; and a light modifying device configured to modify the collimated pixel beam to generate a modified pixel beam; and an eyepiece configured to output the modified pixel beam; A processing module, the processing module comprising: determining a virtual distance of a virtual depth plane from the optical system at which the virtual object will be displayed; comparing the virtual distance to at least one distance threshold; causing the light modifying device to modify the collimated pixel beam based on comparing the virtual distance to the at least one distance threshold to generate the modified pixel beam; a processing module configured to perform operations including: Equipped with the eyepiece is configured to receive the modified pixel beam from the light modifying device; Optical system.

3. Modifying the collimated pixel beam comprises: The optical system of claim 2 including converging the collimated pixel beam.

4. Modifying the collimated pixel beam comprises: The optical system of claim 2 including reducing a diameter of the collimated pixel beam.

5. The operation further comprises: The optical system of claim 2 , further comprising: defining a delimitation zone as a function of distance from the optical system, the delimitation zone including the at least one distance threshold.

6. Comparing the virtual distance to the at least one distance threshold comprises: The optical system of claim 5 , further comprising determining whether the virtual distance is outside the demarcation zone.

7. The optical system of claim 5 , wherein the demarcation zones are defined based on vergence-accommodation collision (VAC) limits.

8. The optical system of claim 7 , wherein the VAC limit is defined by a user of the optical system.

9. The optical system of claim 2 , wherein the light modifying device is positioned in the optical path between the projector and the eyepiece.

10. 1. A method of operating an optical system, the method comprising: determining a virtual distance of a virtual depth plane from said optical system at which a virtual object will be displayed; comparing the virtual distance to at least one distance threshold; generating, by a projector of the optical system, a collimated pixel beam associated with the virtual object; modifying the collimated pixel beam based on comparing the virtual distance to the at least one distance threshold to generate a modified pixel beam; Including, The method further includes injecting the modified pixel beam into an eyepiece of the optical system. method.

11. Modifying the collimated pixel beam comprises: The method of claim 10 comprising converging the collimated pixel beam.

12. Modifying the collimated pixel beam comprises: The method of claim 10 comprising reducing a diameter of the collimated pixel beam.

13. The method of claim 10 , further comprising: defining a delimitation zone as a function of distance from the optical system, the delimitation zone including the at least one distance threshold.

14. Comparing the virtual distance to the at least one distance threshold comprises: The method of claim 13, comprising determining whether the virtual distance is outside the demarcation zone.

15. The method of claim 13, wherein the demarcation zones are defined based on vergence-accommodation conflict (VAC) limits.

16. The method of claim 15 , wherein the VAC limit is defined by a user of the optical system.

17. The method of claim 10 , further comprising outputting the modified pixel beam from the eyepiece of the optical system towards an eye of a user.

18. The method of claim 10 , wherein the collimated pixel beam is modified by a light modifying device positioned in an optical path between the projector and the eyepiece of the optical system.

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