Systems and methods for eye tracking

Abstract

Systems may include an eye-tracking illumination source, a waveguide optically coupled to the eye-tracking illumination source, and an optical sensor positioned to detect light from the eye-tracking illumination source. The waveguide may include at least one optical element for directing light from the eye-tracking illumination source toward an eye of a user. Various other related systems, devices, and methods are also disclosed.

Description

SYSTEMS AND METHODS FOR EYE TRACKING CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of and priority to U.S. provisional patent application Ser. No. 63 / 635,178 filed April 17, 2024.TECHNICAL FIELD

[0002] The present disclosure relates generally to systems and methods for eye tracking and finds particular, although not exclusive, utility in providing an eye-tracking system that may be smaller, lighter, more efficient, and more readily incorporated in commercially feasible industrial designs than traditional eye-tracking systems.BACKGROUND

[0003] Eye tracking and facial expression tracking have significant potential to be used in a variety of ways in augmented reality devices. To be implemented in such devices, eye tracking components may need to be positioned within limited space (e.g., on the frame of a head-mountable device, such as augmented-reality glasses, a virtual-reality headset, etc.), may need to meet industrial design requirements, and may need to be as lightweight and low power as possible. Traditional eye-tracking systems may fail to meet some or all of these design goals.SUMMARY

[0004] According to a first aspect, there is provided a system comprising: an eye-tracking illumination source; a waveguide optically coupled to the eye-tracking illumination source, wherein the waveguide comprises at least one optical element for directing light from the eyetracking illumination source toward an eye of a user; and an optical sensor positioned to detect light from the eye-tracking illumination source.

[0005] The eye-tracking illumination source may comprise a near-infrared illumination source.

[0006] The near-infrared illumination source may comprise at least one of: a collimated laser; or a light-emitting diode.

[0007] The eye-tracking illumination source may comprise a display eye-tracking illumination source such that illumination for eye tracking is delivered through a display engine of the system.

[0008] Alternatively or additionally, the system may further comprise a display illumination source that provides illumination to be displayed to a user separately from the eye-tracking illumination source.

[0009] The optical sensor may be positioned along a rim that holds the waveguide in place.

[0010] The optical sensor may be positioned under a display engine.

[0011] The optical sensor may be positioned on a nose pad of a head-mountable device.

[0012] The optical sensor may be positioned on a nose bridge of a head-mountable device.

[0013] The system may comprise a head-mountable device.

[0014] The system may further comprise a prism. The waveguide may be optically coupled to the eye-tracking illumination source via the prism such that light from the eye-tracking illumination source passes through the prism into the waveguide.

[0015] The waveguide may comprise a display geometric reflective waveguide.

[0016] The eye-tracking illumination source and waveguide may be configured to project a pattern of dots in an eye box of the system when light from the eye-tracking illumination source is directed through the waveguide.

[0017] The pattern of dots may comprise a plurality of uniformly spaced dots.

[0018] The pattern of dots may be sufficiently large to be projected on the eye and eyelids of the user. The eyebox of the system may be at least 30mm by 30mm in cross-section, to cover the size of a typical human eye. The pattern of dots may be projected from an emission point or region of the optical element within 70mm, 60mm, 50mm, 40mm, 30mm, 20mm or 10mm of the eyebox of the system.

[0019] According to a second aspect, there is provided a method of fabricating a system, the method comprising: optically coupling a waveguide to an eye-tracking illumination source, wherein the waveguide comprises at least one optical element for directing light from the eyetracking illumination source toward an eye of a user; and positioning an optical sensor to detect light from the eye-tracking illumination source.

[0020] Optically coupling the waveguide to the eye tracking illumination source may comprise optically coupling the waveguide to a display eye-tracking illumination source such that illumination for eye tracking is delivered through a display engine.

[0021] The method may further comprise optically coupling the waveguide to a display illumination source separate from the eye tracking illumination source.

[0022] Positioning an optical sensor to detect light from the eye-tracking illumination source may comprise positioning the optical sensor on at least one of: a nose pad of a head- mountable device; a rim that holds the waveguide in place; a nose bridge of the head- mountable device; or under a display engine of the head-mountable device.

[0023] Optically coupling the waveguide to the eye tracking illumination source may comprise positioning a prism optically between the waveguide and the eye tracking illumination source such that light from the eye-tracking illumination source passes through the prism into the waveguide.

[0024] Optically coupling the waveguide to the eye tracking illumination source may comprise configuring the waveguide and the eye tracking illumination source to project a pattern of dots in an eye box of the system when light from the eye-tracking illumination source is directed through the waveguide.BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings illustrate a number of examples and are a part of thespecification. Togetherwith the following description, these drawings demonstrate and explain various principles of the present disclosure.

[0026] FIG. 1 is an illustration of an eye-tracking system.

[0027] FIG. 2 is an illustration of exemplary illumination patterns provided by eye-tracking systems discussed herein.

[0028] FIG. 3 is a flowchart diagram illustrating a method of fabricating a system.

[0029] FIG. 4 is an illustration of exemplary augmented-reality glasses that may be used in connection with embodiments of this disclosure.

[0030] FIG. 5 is an illustration of an exemplary virtual-reality headset that may be used in connection with embodiments of this disclosure.

[0031] FIG. 6 an illustration of an exemplary system that incorporates an eye-tracking subsystem capable of tracking a user’s eye(s).

[0032] FIG. 7 is a detailed illustration of various aspects of the eye-tracking subsystem illustrated in FIG. 6.

[0033] Throughout the appendices and drawings, identical reference characters and descriptions indicate similar, but not necessarily identical, elements. Specific examples have been shown by way of example in the appendices and will be described in detail herein. However, the scope of the invention is not intended to be limited to the particular examples disclosed. Rather, the scope of the present invention is set out in the claims appended hereto.DETAILED DESCRIPTION

[0034] Examples of this disclosure provide an eye-tracking system that leverages one or more components of an augmented-reality display (e.g., a waveguide) to create an eye-tracking system that may be smaller, lighter, more efficient, and more readily incorporated in commercially feasible industrial designs than traditional eye-tracking systems. Examples of this disclosure may also accommodate users having different inter-pupillary distances, different eye and face shapes, different eye-relief (i.e., eye to glass distances), and different prescription requirements.

[0035] As shown in FIG. 1 , a system 100 for eye tracking may include an illumination source 110 and a waveguide 120, which may be implemented in a head-mountable device (e.g., augmented-reality glasses, a virtu a I- reality headset, etc.). In some examples, illumination source 110 may provide near-infrared illumination (e.g., light with wavelengths from around 750-1400 nm) or any other illumination (e.g., other wavelength of infrared light) suitable for eye tracking of a user’s eye 130. FIG. 1 also shows that illumination may be delivered from illumination source 110 through waveguide 120, which may be a display geometric reflective waveguide that provides a display for a wearer of system 100. In such a configuration, eyetracking illumination can be provided without added components or space requirements in an eyepiece.

[0036] In some examples, illumination source 1 10 may include a small collimated nearinfrared laser or light-emitting diode (LED) and may be optically coupled into waveguide 120 through a prism 140 in a region 142 where a display engine 143 is located. In some examples, region 142 may be in a temple arm of glasses (e.g., augmented-reality glasses) at or near a lens frame 144 (e.g., a rim that holds waveguide 120 in place). The illumination source 1 10 may also be optically coupled to the waveguide 120 in any other suitable manner. Alternatively, instead of using an illumination source 110 separate from display engine 143, the illumination source 1 10 may be provided through display engine 143 itself (e.g., in or through an image projector of the display engine).

[0037] In some examples, system 100 may include one or more optical sensors for sensing illumination originating from illumination source 1 10, passing through waveguide 120, and reflecting off of the user’s eye 130. For example, the one or more optical sensors may include one or more of eye-tracking cameras 146, 147, 148, 149. For example, an eye-tracking camera 146 may be located at or near a nose bridge 150 of the glasses, an eye-tracking camera 147 may be positioned on a nose pad 152 or adjacent to nose pad 152, an eyetracking camera 148 may be located along a bottom of lens frame 144, an eye-tracking camera 149 may be located below display engine 143, along a top of lens frame 144, and / or in another position along lens frame 144. Eye-tracking cameras 146, 147, 148, 149 may be adapted for sensing light having a wavelength or wavelength range corresponding to light from illumination source 110. For example, eye-tracking cameras 146, 147, 148, 149 may be infrared cameras sensitive to infrared light.

[0038] Illumination through waveguide 120 may generate any suitable light pattern for eye tracking. For example, as shown in FIG. 2, eye-tracking illumination may create a dot pattern 202 within an eye box (e.g., a volume behind a waveguide where an eye is to be placed to view images projected by the waveguide). The dot pattern 202 may be substantially uniform (e.g., including substantially uniformly spaced dots) or may have some other configuration. In some examples, dot pattern 202 may provide uniformity across different eye relief distances in the eye box and may be compatible for prescription lenses. When dot pattern 202 is projected on an eye 204, dot pattern 202 may reflect off eye 204 in a modified configuration, such as depending on where the cornea, iris, pupil, and / or other features of eye 204 are located and / or directed. An eye-tracking camera may sense this reflection and / or modifications in the pattern, which may be analyzed to determine where eye 204 is directed and / or positioned.

[0039] The dot pattern 202 can also be used to extract three-dimensional depth information of an eye region 206 for authentication applications. For example, dot pattern 202 reflected from the eye (e.g., cornea, iris, pupil, and / or other features of eye), upper eyelid, lower eyelid, etc., in eye region 206 may facilitate unique identification of an individual user.

[0040] The eye-tracking systems according to various examples of the present disclosure may include any suitable type or form of optical sensor (e.g., eye-tracking camera) to detect the eye-tracking illumination projected on the eye via the waveguide. In some examples, an eyetracking system may include one direct-view camera per eye. Alternatively, an eye-tracking system may include multiple cameras per eye. The camera or cameras may be located in any suitable position, including within a nose bridge region of eyewear or on a rim (e.g., lens frame) of eyewear. In some examples, the eye-tracking camera or cameras may be positioned under the display engine to minimize the visual conspicuity.

[0041] As discussed herein, an eye-tracking system may include an eye-tracking illumination source and a waveguide optically coupled to the eye-tracking illumination source, where the waveguide includes at least one optical element for directing light from the eye-tracking illumination source toward an eye of a user. The optical element for directing light from the eye-tracking illumination source toward the eye of the user may include any suitable refractive element or other optical component that redirects light passing through the waveguide toward an eye of a wearer.

[0042] As illustrated in FIG. 3, a method 300 of fabricating a system (e.g., an eye-tracking system) may include operation 310 and operation 320.

[0043] At operation 310, a waveguide may be optically coupled to an eye-tracking illumination source. In some examples, the waveguide may include at least one optical element for directing light from the eye-tracking illumination source toward an eye of a user. Operation 310 may be performed in a variety of ways. For example, the waveguide and eye-tracking illumination source may be configured in any of the manners described above. In some examples, the waveguide may be optically coupled to a display illumination source (e.g., projector) such that illumination for eye tracking may be delivered through a display engine. In additional examples, the eye-tracking illumination source may be separate from the display illumination source. In some examples, a prism may be used to optically couple the waveguide to the eye-tracking illumination source such that light from the eye-tracking illumination source passes through the prism into the waveguide. In some examples, the waveguide and the eyetracking illumination source may be configured to project a pattern of dots in an eye box of the system when light from the eye-tracking illumination source is directed through the waveguide.

[0044] At operation 320, an optical sensor may be positioned to detect light from the eyetracking illumination source, such as light passing through the waveguide and reflecting off an eye and / or eye region of a user. Operation 320 may be performed in a variety of ways. For example, the optical sensor may be positioned on a nose pad of a head-mountable device, on a rim that holds the waveguide in place (e.g., on a lens frame), on a nose bridge of the head-mountable device, and / or under a display engine of the head-mountable device.

[0045] Embodiments of the present disclosure may include or be implemented in conjunctionwith various types of artificial-reality systems. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, for example, a virtual reality, an augmented reality, a mixed reality, a hybrid reality, or some combination and / or derivative thereof. Artificial-reality content may include completely computer-generated content or computer-generated content combined with captured (e.g., real-world) content. The artificial-reality content may include video, audio, haptic feedback, or some combination thereof, any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional (3D) effect to the viewer). Additionally, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, for example, create content in an artificial reality and / or are otherwise used in (e.g., to perform activities in) an artificial reality.

[0046] Artificial-reality systems may be implemented in a variety of different form factors and configurations. Some artificial-reality- systems may be designed to work without near-eye displays (NEDs). Other artificial-reality systems may include an NED that also provides visibility into the real world (such as, e.g., augmented-reality system 400 in FIG. 4) or that visually immerses a user in an artificial reality (such as, e.g., virtual-reality system 500 in FIG. 5). While some artificial-reality devices may be self-contained systems, other artificial-reality devices may communicate and / or coordinate with external devices to provide an artificialreality experience to a user. Examples of such external devices include handheld controllers, mobile devices, desktop computers, devices worn by a user, devices worn by one or more other users, and / or any other suitable external system.

[0047] Turning to FIG. 4, augmented-reality system 400 may include an eyewear device 402 with a frame 410 configured to hold a left display device 415(A) and a right display device 415(B) in front of a user’s eyes. Display devices 415(A) and 415(B) may act together or independently to present an image or series of images to a user. While augmented-reality system 400 includes two displays, embodiments of this disclosure may be implemented in augmented-reality systems with a single NED or more than two NEDs.

[0048] In some examples, augmented-reality system 400 may include one or more sensors, such as sensor 440. Sensor 440 may generate measurement signals in response to motion of augmented-reality system 400 and may be located on substantially any portion of frame 410. Sensor 440 may represent one or more of a variety of different sensing mechanisms, such as a position sensor, an inertial measurement unit (IMU), a depth camera assembly, a structured light emitter and / or detector, or any combination thereof. In some examples, augmented-reality system 400 may or may not include sensor 440 or may include more than one sensor. In examples in which sensor 440 includes an IMU, the IMU may generate calibration data based on measurement signals from sensor 440. Examples of sensor 440may include, without limitation, accelerometers, gyroscopes, magnetometers, other suitable types of sensors that detect motion, sensors used for error correction of the IMU, or some combination thereof.

[0049] In some examples, augmented-reality system 400 may also include a microphone array with a plurality of acoustic transducers 420(A)-420(J), referred to collectively as acoustic transducers 420. Acoustic transducers 420 may represent transducers that detect air pressure variations induced by sound waves. Each acoustic transducer 420 may be configured to detect sound and convert the detected sound into an electronic format (e.g., an analog or digital format). The microphone array in FIG. 4 may include, for example, ten acoustic transducers: 420(A) and 420(B), which may be designed to be placed inside a corresponding ear of the user, acoustic transducers 420(C), 420(D), 420(E), 420(F), 420(G), and 420(H), which may be positioned at various locations on frame 410, and / or acoustic transducers 420(l) and 420(J), which may be positioned on a corresponding neckband 405.

[0050] In some examples, one or more of acoustic transducers 420(A)-(J) may be used as output transducers (e.g., speakers). For example, acoustic transducers 420(A) and / or 420(B) may be earbuds or any other suitable type of headphone or speaker.

[0051] The configuration of acoustic transducers 420 of the microphone array may vary. While augmented-reality system 400 is shown in FIG. 4 as having ten acoustic transducers 420, the number of acoustic transducers 420 may be greater or less than ten. In some examples, using higher numbers of acoustic transducers 420 may increase the amount of audio information collected and / or the sensitivity and accuracy of the audio information. In contrast, using a lower number of acoustic transducers 420 may decrease the computing power required by an associated controller 450 to process the collected audio information. In addition, the position of each acoustic transducer 420 of the microphone array may vary. For example, the position of an acoustic transducer 420 may include a defined position on the user, a defined coordinate on frame 410, an orientation associated with each acoustic transducer 420, or some combination thereof.

[0052] Acoustic transducers 420(A) and 420(B) may be positioned on different parts of the user’s ear, such as behind the pinna, behind the tragus, and / or within the auricle or fossa. Or, there may be additional acoustic transducers 420 on or surrounding the ear in addition to acoustic transducers 420 inside the ear canal. Having an acoustic transducer 420 positioned next to an ear canal of a user may enable the microphone array to collect information on how sounds arrive at the ear canal. By positioning at least two of acoustic transducers 420 on either side of a user’s head (e.g., as binaural microphones), augmented-reality device 400 may simulate binaural hearing and capture a 3D stereo sound field around about a user’s head. In some examples, acoustic transducers 420(A) and 420(B) may be connected to augmented- reality system 400 via a wired connection 430, and in other examples acoustic transducers420(A) and 420(B) may be connected to augmented-reality system 400 via a wireless connection (e.g., a BLUETOOTH connection). In still other examples, acoustic transducers 420(A) and 420(B) may not be used at all in conjunction with augmented-reality system 400.

[0053] Acoustic transducers 420 on frame 410 may be positioned in a variety of different ways, including along the length of the temples, across the bridge, above or below display devices 415(A) and 415(B), or some combination thereof. Acoustic transducers 420 may also be oriented such that the microphone array is able to detect sounds in a wide range of directions surrounding the user wearing the augmented-reality system 400. In some examples, an optimization process may be performed during manufacturing of augmented- reality system 400 to determine relative positioning of each acoustic transducer 420 in the microphone array.

[0054] In some examples, augmented-reality system 400 may include or be connected to an external device (e.g., a paired device), such as neckband 405. Neckband 405 generally represents any type or form of paired device. Thus, the following discussion of neckband 405 may also apply to various other paired devices, such as charging cases, smart watches, smart phones, wrist bands, other wearable devices, hand-held controllers, tablet computers, laptop computers, other external compute devices, etc.

[0055] As shown, neckband 405 may be coupled to eyewear device 402 via one or more connectors. The connectors may be wired or wireless and may include electrical and / or nonelectrical (e.g., structural) components. In some cases, eyewear device 402 and neckband 405 may operate independently without any wired or wireless connection between them. While FIG. 4 illustrates the components of eyewear device 402 and neckband 405 in example locations on eyewear device 402 and neckband 405, the components may be located elsewhere and / or distributed differently on eyewear device 402 and / or neckband 405. In some examples, the components of eyewear device 402 and neckband 405 may be located on one or more additional peripheral devices paired with eyewear device 402, neckband 405, or some combination thereof.

[0056] Pairing external devices, such as neckband 405, with augmented-reality eyewear devices may enable the eyewear devices to achieve the form factor of a pair of glasses while still providing sufficient battery and computation power for expanded capabilities. Some or all of the battery power, computational resources, and / or additional features of augmented-reality system 400 may be provided by a paired device or shared between a paired device and an eyewear device, thus reducing the weight, heat profile, and form factor of the eyewear device overall while still retaining desired functionality. For example, neckband 405 may allow components that would otherwise be included on an eyewear device to be included in neckband 405 since users may tolerate a heavier weight load on their shoulders than they would tolerate on their heads. Neckband 405 may also have a larger surface area over whichto diffuse and disperse heat to the ambient environment. Thus, neckband 405 may allow for greater battery and computation capacity than might otherwise have been possible on a standalone eyewear device. Since weight carried in neckband 405 may be less invasive to a user than weight carried in eyewear device 402, a user may tolerate wearing a lighter eyewear device and carrying or wearing the paired device for greater lengths of time than a user would tolerate wearing a heavy standalone eyewear device, thereby enabling users to more fully incorporate artificial-reality environments into their day-to-day activities.

[0057] Neckband 405 may be communicatively coupled with eyewear device 402 and / or to other devices. These other devices may provide certain functions (e.g., tracking, localizing, depth mapping, processing, storage, etc.) to augmented-reality system 400. In the example of FIG. 4, neckband 405 may include two acoustic transducers (e.g., 420(1) and 420(J)) that are part of the microphone array (or potentially form their own microphone subarray). Neckband 405 may also include a controller 425 and a power source 435.

[0058] Acoustic transducers 420(1) and 420(J) of neckband 405 may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). In the example of FIG. 4, acoustic transducers 420(1) and 420(J) may be positioned on neckband 405, thereby increasing the distance between the neckband acoustic transducers 420(1) and 420(J) and other acoustic transducers 420 positioned on eyewear device 402. In some cases, increasing the distance between acoustic transducers 420 of the microphone array may improve the accuracy of beamforming performed via the microphone array. For example, if a sound is detected by acoustic transducers 420(C) and 420(D) and the distance between acoustic transducers 420(C) and 420(D) is greater than, e.g., the distance between acoustic transducers 420(D) and 420(E), the determined source location of the detected sound may be more accurate than if the sound had been detected by acoustic transducers 420(D) and 420(E).

[0059] Controller 425 of neckband 405 may process information generated by the sensors on neckband 405 and / or augmented-reality system 400. For example, controller 425 may process information from the microphone array that describes sounds detected by the microphone array. For each detected sound, controller 425 may perform a direction-of-arrival (DOA) estimation to estimate a direction from which the detected sound arrived at the microphone array. As the microphone array detects sounds, controller 425 may populate an audio data set with the information. In examples in which augmented-reality system 400 includes an inertial measurement unit, controller 425 may compute all inertial and spatial calculations from the IMU located on eyewear device 402. A connector may convey information between augmented-reality system 400 and neckband 405 and between augmented-reality system 400 and controller 425. The information may be in the form of optical data, electrical data, wireless data, or any other transmittable data form. Moving the processing of information generated byaugmented-reality system 400 to neckband 405 may reduce weight and heat in eyewear device 402, making it more comfortable to the user.

[0060] Power source 435 in neckband 405 may provide power to eyewear device 402 and / or to neckband 405. Power source 435 may include, without limitation, lithium-ion batteries, lithium-polymer batteries, primary lithium batteries, alkaline batteries, or any other form of power storage. In some cases, power source 435 may be a wired power source. Including power source 435 on neckband 405 instead of on eyewear device 402 may help better distribute the weight and heat generated by power source 435.

[0061] As noted, some artificial -reality systems may, instead of blending an artificial reality with actual reality, substantially replace one or more of a user’s sensory perceptions of the real world with a virtual experience. One example of this type of system is a head-worn display system, such as virtual-reality system 500 in FIG. 5, that mostly or completely covers a user’s field of view. Virtual-reality system 500 may include a front rigid body 502 and a band 504 shaped to fit around a user’s head. Virtual-reality system 500 may also include output audio transducers 506(A) and 506(B). Furthermore, while not shown in FIG. 5, front rigid body 502 may include one or more electronic elements, including one or more electronic displays, one or more inertial measurement units (IMUs), one or more tracking emitters or detectors, and / or any other suitable device or system for creating an artificial-reality experience.

[0062] Artificial -reality systems may include a variety of types of visual feedback mechanisms. For example, display devices in augmented-reality system 400 and / or virtual- reality system 500 may include one or more liquid crystal displays (LCDs), light emitting diode (LED) displays, microLED displays, organic LED (OLED) displays, digital light project (DLP) micro-displays, liquid crystal on silicon (LCoS) micro-displays, and / or any other suitable type of display screen. These artificial -reality systems may include a single display screen for both eyes or may provide a display screen for each eye, which may allow for additional flexibility for varifocal adjustments or for correcting a user’s refractive error. Some of these artificial -reality systems may also include optical subsystems having one or more lenses (e.g., concave or convex lenses, Fresnel lenses, adjustable liquid lenses, etc.) through which a user may view a display screen. These optical subsystems may serve a variety of purposes, including to collimate (e.g., make an object appear at a greater distance than its physical distance), to magnify (e.g., make an object appear larger than its actual size), and / or to relay (to, e.g., the viewer’s eyes) light. These optical subsystems may be used in a non-pupil- forming architecture (such as a single lens configuration that directly collimates light but results in so-called pincushion distortion) and / or a pupil-forming architecture (such as a multi-lens configuration that produces so-called barrel distortion to nullify pincushion distortion).

[0063] In addition to or instead of using display screens, some of the artificial -reality systems described herein may include one or more projection systems. For example, display devicesin augmented-reality system 400 and / or virtual-reality system 500 may include micro-LED projectors that project light (using, e.g., a waveguide) into display devices, such as clear combiner lenses that allow ambient light to pass through. The display devices may refract the projected light toward a user’s pupil and may enable a user to simultaneously view both artificial -reality content and the real world. The display devices may accomplish this using any of a variety of different optical components, including waveguide components (e.g., holographic, planar, diffractive, polarized, and / or reflective waveguide elements), lightmanipulation surfaces and elements (such as diffractive, reflective, and refractive elements and gratings), coupling elements, etc. Artificial -reality systems may also be configured with any other suitable type or form of image projection system, such as retinal projectors used in virtual retina displays.

[0064] The artificial -reality systems described herein may also include various types of computer vision components and subsystems. For example, augmented-reality system 400 and / or virtual-reality system 500 may include one or more optical sensors, such as two- dimensional (2D) or 3D cameras, structured light transmitters and detectors, time-of-flight depth sensors, single-beam or sweeping laser rangefinders, 3D LiDAR sensors, and / or any other suitable type or form of optical sensor. An artificial -reality system may process data from one or more of these sensors to identify a location of a user, to map the real world, to provide a user with context about real-world surroundings, and / or to perform a variety of other functions.

[0065] The artificial -reality systems described herein may also include one or more input and / or output audio transducers. Output audio transducers may include voice coil speakers, ribbon speakers, electrostatic speakers, piezoelectric speakers, bone conduction transducers, cartilage conduction transducers, tragus-vibration transducers, and / or any other suitable type or form of audio transducer. Similarly, input audio transducers may include condenser microphones, dynamic microphones, ribbon microphones, and / or any other type or form of input transducer. In some examples, a single transducer may be used for both audio input and audio output.

[0066] In some examples, the artificial -reality systems described herein may also include tactile (i.e., haptic) feedback systems, which may be incorporated into headwear, gloves, body suits, handheld controllers, environmental devices (e.g., chairs, floormats, etc.), and / or any other type of device or system. Haptic feedback systems may provide various types of cutaneous feedback, including vibration, force, traction, texture, and / or temperature. Haptic feedback systems may also provide various types of kinesthetic feedback, such as motion and compliance. Haptic feedback may be implemented using motors, piezoelectric actuators, fluidic systems, and / or a variety of other types of feedback mechanisms. Haptic feedback systems may be implemented independent of other artificial-reality devices, within otherartificial— reality devices, and / or in conjunction with other artificial— reality devices.

[0067] By providing haptic sensations, audible content, and / or visual content, artificial— reality systems may create an entire virtual experience or enhance a user’s real-world experience in a variety of contexts and environments. For instance, artificial— reality systems may assist or extend a user’s perception, memory, or cognition within a particular environment. Some systems may enhance a user’s interactions with other people in the real world or may enable more immersive interactions with other people in a virtual world. Artificial— reality systems may also be used for educational purposes (e.g., for teaching or training in schools, hospitals, government organizations, military organizations, business enterprises, etc.), entertainment purposes (e.g., for playing video games, listening to music, watching video content, etc.), and / or for accessibility purposes (e.g., as hearing aids, visual aids, etc.). The examples disclosed herein may enable or enhance a user’s artificial-reality experience in one or more of these contexts and environments and / or in other contexts and environments.

[0068] In some examples, the systems described herein may also include an eye-tracking subsystem designed to identify and track various characteristics of a user’s eye(s), such as the user’s gaze direction. The phrase “eye tracking” may, in some examples, refer to a process by which the position, orientation, and / or motion of an eye is measured, detected, sensed, determined, and / or monitored. The disclosed systems may measure the position, orientation, and / or motion of an eye in a variety of different ways, including through the use of various optical-based eye-tracking techniques, ultrasound-based eye-tracking techniques, etc. An eye-tracking subsystem may be configured in a number of different ways and may include a variety of different eye-tracking hardware components or other computer-vision components. For example, an eye-tracking subsystem may include a variety of different optical sensors, such as two-dimensional (2D) or 3D cameras, time-of-flight depth sensors, single-beam or sweeping laser rangefinders, 3D LiDAR sensors, and / or any other suitable type or form of optical sensor. In this example, a processing subsystem may process data from one or more of these sensors to measure, detect, determine, and / or otherwise monitor the position, orientation, and / or motion of the user’s eye(s).

[0069] FIG. 6 is an illustration of an exemplary system 600 that incorporates an eye-tracking subsystem capable of tracking a user’s eye(s). As depicted in FIG. 6, system 600 may include a light source 602, an optical subsystem 604, an eye-tracking subsystem 606, and / or a control subsystem 608. In some examples, light source 602 may generate light for an image (e.g., to be presented to an eye 601 of the viewer). Light source 602 may represent any of a variety of suitable devices. For example, light source 602 can include a two-dimensional projector (e.g., a LCoS display), a scanning source (e.g., a scanning laser), or other device (e.g., an LCD, an LED display, an OLED display, an active-matrix OLED display (AMOLED), a transparent OLED display (TOLED), a waveguide, or some other display capable of generating light forpresenting an image to the viewer). In some examples, the image may represent a virtual image, which may refer to an optical image formed from the apparent divergence of light rays from a point in space, as opposed to an image formed from the light ray’s actual divergence.

[0070] In some examples, optical subsystem 604 may receive the light generated by light source 602 and generate, based on the received light, converging light 620 that includes the image. In some examples, optical subsystem 604 may include any number of lenses (e.g., Fresnel lenses, convex lenses, concave lenses), apertures, filters, mirrors, prisms, and / or other optical components, possibly in combination with actuators and / or other devices. In particular, the actuators and / or other devices may translate and / or rotate one or more of the optical components to alter one or more aspects of converging light 620. Further, various mechanical couplings may serve to maintain the relative spacing and / or the orientation of the optical components in any suitable combination.

[0071] In one example, eye-tracking subsystem 606 may generate tracking information indicating a gaze angle of an eye 601 of the viewer. In this example, control subsystem 608 may control aspects of optical subsystem 604 (e.g., the angle of incidence of converging light 620) based at least in part on this tracking information. Additionally, in some examples, control subsystem 608 may store and utilize historical tracking information (e.g., a history of the tracking information over a given duration, such as the previous second or fraction thereof) to anticipate the gaze angle of eye 601 (e.g., an angle between the visual axis and the anatomical axis of eye 601). In some examples, eye-tracking subsystem 606 may detect radiation emanating from some portion of eye 601 (e.g., the cornea, the iris, the pupil, or the like) to determine the current gaze angle of eye 601 . In other examples, eye-tracking subsystem 606 may employ a wavefront sensor to track the current location of the pupil.

[0072] Any number of techniques can be used to track eye 601 . Some techniques may involve illuminating eye 601 with infrared light and measuring reflections with at least one optical sensor that is tuned to be sensitive to the infrared light. Information about how the infrared light is reflected from eye 601 may be analyzed to determine the position(s), orientation(s), and / or motion(s) of one or more eye feature(s), such as the cornea, pupil, iris, and / or retinal blood vessels.

[0073] In some examples, the radiation captured by a sensor of eye-tracking subsystem 606 may be digitized (i.e., converted to an electronic signal). Further, the sensor may transmit a digital representation of this electronic signal to one or more processors (for example, processors associated with a device including eye-tracking subsystem 606). Eye-tracking subsystem 606 may include any of a variety of sensors in a variety of different configurations. For example, eye-tracking subsystem 606 may include an infrared detector that reacts to infrared radiation. The infrared detector may be a thermal detector, a photonic detector, and / or any other suitable type of detector. Thermal detectors may include detectors that react tothermal effects of the incident infrared radiation.

[0074] In some examples, one or more processors may process the digital representation generated by the sensor(s) of eye-tracking subsystem 606 to track the movement of eye 601 . In another example, these processors may track the movements of eye 601 by executing algorithms represented by computer-executable instructions stored on non-transitory memory. In some examples, on-chip logic (e.g., an application-specific integrated circuit or ASIC) may be used to perform at least portions of such algorithms. As noted, eye-tracking subsystem 606 may be programmed to use an output of the sensor(s) to track movement of eye 601. In some examples, eye-tracking subsystem 606 may analyze the digital representation generated by the sensors to extract eye rotation information from changes in reflections. In one example, eye-tracking subsystem 606 may use corneal reflections or glints (also known as Purkinje images) and / or the center of the eye’s pupil 622 as features to track over time.

[0075] In some examples, eye-tracking subsystem 606 may use the center of the eye’s pupil 622 and infrared or near-infrared, non-collimated light to create corneal reflections. In these examples, eye-tracking subsystem 606 may use the vector between the center of the eye’s pupil 622 and the corneal reflections to compute the gaze direction of eye 601. In some examples, the disclosed systems may perform a calibration procedure for an individual (using, e.g, supervised or unsupervised techniques) before tracking the user’s eyes. For example, the calibration procedure may include directing users to look at one or more points displayed on a display while the eye-tracking system records the values that correspond to each gaze position associated with each point.

[0076] In some examples, eye-tracking subsystem 606 may use two types of infrared and / or near-infrared (also known as active light) eye-tracking techniques: bright-pupil and dark-pupil eye tracking, which may be differentiated based on the location of an illumination source with respect to the optical elements used. If the illumination is coaxial with the optical path, then eye 601 may act as a retroreflector as the light reflects off the retina, thereby creating a bright pupil effect similar to a red-eye effect in photography. If the illumination source is offset from the optical path, then the eye’s pupil 622 may appear dark because the retroreflection from the retina is directed away from the sensor. In some examples, bright-pupil tracking may create greater iris / pupil contrast, allowing more robust eye tracking with iris pigmentation, and may feature reduced interference (e.g., interference caused by eyelashes and other obscuring features). Bright-pupil tracking may also allow tracking in lighting conditions ranging from total darkness to a very bright environment.

[0077] In some examples, control subsystem 608 may control light source 602 and / or optical subsystem 604 to reduce optical aberrations (e.g., chromatic aberrations and / or monochromatic aberrations) of the image that may be caused by or influenced by eye 601. In some examples, as mentioned above, control subsystem 608 may use the tracking informationfrom eye-tracking subsystem 606 to perform such control. For example, in controlling light source 602, control subsystem 608 may alter the light generated by light source 602 (e.g., by way of image rendering) to modify (e.g., pre-distort) the image so that the aberration of the image caused by eye 601 is reduced.

[0078] The disclosed systems may track both the position and relative size of the pupil (since, e.g., the pupil dilates and / or contracts). In some examples, the eye-tracking devices and components (e.g., sensors and / or sources) used for detecting and / or tracking the pupil may be different (or calibrated differently) for different types of eyes. For example, the frequency range of the sensors may be different (or separately calibrated) for eyes of different colors and / or different pupil types, sizes, and / or the like. As such, the various eye-tracking components (e.g., infrared sources and / or sensors) described herein may need to be calibrated for each individual user and / or eye.

[0079] The disclosed systems may track both eyes with and without ophthalmic correction, such as that provided by contact lenses worn by the user. In some examples, ophthalmic correction elements (e.g., adjustable lenses) may be directly incorporated into the artificial reality systems described herein. In some examples, the color of the user’s eye may necessitate modification of a corresponding eye-tracking algorithm. For example, eye-tracking algorithms may need to be modified based at least in part on the differing color contrast between a brown eye and, for example, a blue eye.

[0080] FIG. 7 is a more detailed illustration of various aspects of the eye-tracking subsystem illustrated in FIG. 6. As shown in this figure, an eye-tracking subsystem 700 may include at least one source 704 and at least one sensor 706. Source 704 generally represents any type or form of element capable of emitting radiation. In one example, source 704 may generate visible, infrared, and / or near-infrared radiation. In some examples, source 704 may radiate non-collimated infrared and / or near-infrared portions of the electromagnetic spectrum towards an eye 702 of a user. Source 704 may utilize a variety of sampling rates and speeds. For example, the disclosed systems may use sources with higher sampling rates in order to capture fixational eye movements of a user’s eye 702 and / or to correctly measure saccade dynamics of the user’s eye 702. As noted above, any type or form of eye-tracking technique may be used to track the user’s eye 702, including optical-based eye-tracking techniques, ultrasound-based eye-tracking techniques, etc.

[0081] Sensor 706 generally represents any type or form of element capable of detecting radiation, such as radiation reflected off the user’s eye 702. Examples of sensor 706 include, without limitation, a charge coupled device (CCD), a photodiode array, a complementary metal-oxide-semiconductor (CMOS) based sensor device, and / or the like. In one example, sensor 706 may represent a sensor having predetermined parameters, including, but not limited to, a dynamic resolution range, linearity, and / or other characteristic selected and / ordesigned specifically for eye tracking.

[0082] As detailed above, eye-tracking subsystem 700 may generate one or more glints. As detailed above, a glint 703 may represent reflections of radiation (e.g., infrared radiation from an infrared source, such as source 704) from the structure of the user’s eye. In various examples, glint 703 and / or the user’s pupil may be tracked using an eye-tracking algorithm executed by a processor (either within or external to an artificial reality device). For example, an artificial reality device may include a processor and / or a memory device in order to perform eye tracking locally and / or a transceiver to send and receive the data necessary to perform eye tracking on an external device (e.g., a mobile phone, cloud server, or other computing device).

[0083] FIG. 7 shows an example image 705 captured by an eye-tracking subsystem, such as eye-tracking subsystem 700. In this example, image 705 may include both the user’s pupil 708 and a glint 710 near the same. In some examples, pupil 708 and / or glint 710 may be identified using an artificial-intelligence-based algorithm, such as a computer-vision-based algorithm. In one example, image 705 may represent a single frame in a series of frames that may be analyzed continuously in order to track the eye 702 of the user. Further, pupil 708 and / or glint 710 may be tracked over a period of time to determine a user’s gaze.

[0084] In one example, eye-tracking subsystem 700 may be configured to identify and measure the inter-pupillary distance (IPD) of a user. In some examples, eye-tracking subsystem 700 may measure and / or calculate the IPD of the user while the user is wearing the artificial reality system. In these examples, eye-tracking subsystem 700 may detect the positions of a user’s eyes and may use this information to calculate the user’s IPD.

[0085] As noted, the eye-tracking systems or subsystems disclosed herein may track a user’s eye position and / or eye movement in a variety of ways. In one example, one or more light sources and / or optical sensors may capture an image of the user’s eyes. The eye-tracking subsystem may then use the captured information to determine the user’s inter-pupillary distance, interocular distance, and / or a 3D position of each eye (e.g., for distortion adjustment purposes), including a magnitude of torsion and rotation (i.e., roll, pitch, and yaw) and / or gaze directions for each eye. In one example, infrared light may be emitted by the eye-tracking subsystem and reflected from each eye. The reflected light may be received or detected by an optical sensor and analyzed to extract eye rotation data from changes in the infrared light reflected by each eye.

[0086] The eye-tracking subsystem may use any of a variety of different methods to track the eyes of a user. For example, a light source (e.g., infrared light-emitting diodes) may emit a dot pattern onto each eye of the user. The eye-tracking subsystem may then detect (e.g., via an optical sensor coupled to the artificial reality system) and analyze a reflection of the dot pattern from each eye of the user to identify a location of each pupil of the user. Accordingly, the eye-tracking subsystem may track up to six degrees of freedom of each eye (i.e. , 3D position, roll, pitch, and yaw) and at least a subset of the tracked quantities may be combined from two eyes of a user to estimate a gaze point (i.e., a 3D location or position in a virtual scene where the user is looking) and / or an IPD.

[0087] In some cases, the distance between a user’s pupil and a display may change as the user’s eye moves to look in different directions. The varying distance between a pupil and a display as viewing direction changes may be referred to as "pupil swim” and may contribute to distortion perceived by the user as a result of light focusing in different locations as the distance between the pupil and the display changes. Accordingly, measuring distortion at different eye positions and pupil distances relative to displays and generating distortion corrections for different positions and distances may allow mitigation of distortion caused by pupil swim by tracking the 3D position of a user’s eyes and applying a distortion correction corresponding to the 3D position of each of the user’s eyes at a given point in time. Thus, knowing the 3D position of each of a user’s eyes may allow for the mitigation of distortion caused by changes in the distance between the pupil of the eye and the display by applying a distortion correction for each 3D eye position. Furthermore, as noted above, knowing the position of each of the user’s eyes may also enable the eye-tracking subsystem to make automated adjustments for a user’s IPD.

[0088] In some examples, a display subsystem may include a variety of additional subsystems that may work in conjunction with the eye-tracking subsystems described herein. For example, a display subsystem may include a varifocal subsystem, a scene-rendering module, and / or a vergence-processing module. The varifocal subsystem may cause left and right display elements to vary the focal distance of the display device. In one example, the varifocal subsystem may physically change the distance between a display and the optics through which it is viewed by moving the display, the optics, or both. Additionally, moving or translating two lenses relative to each other may also be used to change the focal distance of the display. Thus, the varifocal subsystem may include actuators or motors that move displays and / or optics to change the distance between them. This varifocal subsystem may be separate from or integrated into the display subsystem. The varifocal subsystem may also be integrated into or separate from its actuation subsystem and / or the eye-tracking subsystems described herein.

[0089] In one example, the display subsystem may include a vergence-processing module configured to determine a vergence depth of a user’s gaze based on a gaze point and / or an estimated intersection of the gaze lines determined by the eye-tracking subsystem. Vergence may refer to the simultaneous movement or rotation of both eyes in opposite directions to maintain single binocular vision, which may be naturally and automatically performed by the human eye. Thus, a location where a user’s eyes are verged is where the user is looking andis also typically the location where the user’s eyes are focused. For example, the vergenceprocessing module may triangulate gaze lines to estimate a distance or depth from the user associated with intersection of the gaze lines. The depth associated with intersection of the gaze lines may then be used as an approximation for the accommodation distance, which may identify a distance from the user where the user’s eyes are directed. Thus, the vergence distance may allow for the determination of a location where the user’s eyes should be focused and a depth from the user’s eyes at which the eyes are focused, thereby providing information (such as an object or plane of focus) for rendering adjustments to the virtual scene.

[0090] The vergence-processing module may coordinate with the eye-tracking subsystems described herein to make adjustments to the display subsystem to account for a user’s vergence depth. When the user is focused on something at a distance, the user’s pupils may be slightly farther apart than when the user is focused on something close. The eye-tracking subsystem may obtain information about the user’s vergence or focus depth and may adjust the display subsystem to be closer together when the user’s eyes focus or verge on something close and to be farther apart when the user’s eyes focus or verge on something at a distance.

[0091] The eye-tracking information generated by the above-described eye-tracking subsystems may also be used, for example, to modify various aspect of how different computer-generated images are presented. For example, a display subsystem may be configured to modify, based on information generated by an eye-tracking subsystem, at least one aspect of how the computer-generated images are presented. For instance, the computergenerated images may be modified based on the user’s eye movement, such that if a user is looking up, the computer-generated images may be moved upward on the screen. Similarly, if the user is looking to the side or down, the computer-generated images may be moved to the side or downward on the screen. If the user’s eyes are closed, the computer-generated images may be paused or removed from the display and resumed once the user’s eyes are back open.

[0092] The above-described eye-tracking subsystems can be incorporated into one or more of the various artificial reality systems described herein in a variety of ways. For example, one or more of the various components of system 600 and / or eye-tracking subsystem 700 may be incorporated into augmented-reality system 400 in FIG. 4 and / or virtual-reality system 500 in FIG. 5 to enable these systems to perform various eye-tracking tasks (including one or more of the eye-tracking operations described herein).

[0093] The process parameters and sequence of the steps described and / or illustrated herein are given by way of example only and can be varied as desired. For example, while the steps illustrated and / or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various exemplary methods described and / or illustrated herein may also omit one or more ofthe steps described or illustrated herein or include additional steps in addition to those disclosed.

[0094] The preceding description has been provided to enable others skilled in the art to best utilize various aspects of the examples disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible without departing from the scope of the present disclosure. The examples disclosed herein should be considered in all respects illustrative and not restrictive. Reference should be made to any claims appended hereto and their equivalents in determining the scope of the present disclosure.

[0095] Unless otherwise noted, the terms “connected to” and “coupled to” (and their derivatives), as used in the specification and / or claims, are to be construed as permitting both direct and indirect (i.e., via other elements or components) connection. In addition, the terms “a” or “an,” as used in the specification and / or claims, are to be construed as meaning “at least one of.” Finally, for ease of use, the terms “including" and “having” (and their derivatives), as used in the specification and / or claims, are interchangeable with and have the same meaning as the word “comprising.”

Claims

CLAIMS1 . A system comprising: an eye-tracking illumination source; a waveguide optically coupled to the eye-tracking illumination source, wherein the waveguide comprises at least one optical element for directing light from the eye-tracking illumination source toward an eye of a user; and an optical sensor positioned to detect light from the eye-tracking illumination source.

2. The system of claim 1 , wherein the eye-tracking illumination source comprises a near-infrared illumination source; preferably wherein the near-infrared illumination source comprises at least one of: a collimated laser; or a light-emitting diode.

3. The system of claim 1 or 2, wherein the eye-tracking illumination source comprises a display eye-tracking illumination source such that illumination for eye tracking is delivered through a display engine of the system.

4. The system of any preceding claim, further comprising a display illumination source that provides illumination to be displayed to a user separately from the eye-tracking illumination source.

5. The system of any preceding claim, wherein the optical sensor is positioned: on a nose pad of a head-mountable device; along a rim that holds the waveguide in place; on a nose bridge of a head-mountable device; and / or under a display engine.

6. The system of any preceding claim, further comprising a prism, wherein the waveguide is optically coupled to the eye-tracking illumination source via the prism such that light from the eye-tracking illumination source passes through the prism into the waveguide.

7. The system of any preceding claim, wherein the waveguide comprises a display geometric reflective waveguide.

8. The system of any preceding claim, wherein the eye-tracking illumination source and waveguide are configured to project a pattern of dots in an eye box of the system when light from the eye-tracking illumination source is directed through the waveguide.

9. The system of claim 8, wherein: the pattern of dots comprises a plurality of uniformly spaced dots; and / or the pattern of dots is sufficiently large to be projected on the eye and eyelids of the user.

10. A method of fabricating a system, the method comprising: optically coupling a waveguide to an eye-tracking illumination source, wherein the waveguidecomprises at least one optical element for directing light from the eye-tracking illumination source toward an eye of a user; and positioning an optical sensor to detect light from the eye-tracking illumination source.

11. The method of claim 10, wherein optically coupling the waveguide to the eye-tracking illumination source comprises optically coupling the waveguide to a display eye tracking illumination source such that illumination for eye tracking is delivered through a display engine.

12. The method of claim 10 or 11 , further comprising optically coupling the waveguide to a display illumination source separate from the eye-tracking illumination source.

13. The method of any of claims 10 to 12, wherein positioning an optical sensor to detect light from the eye-tracking illumination source comprises positioning the optical sensor on at least one of: a nose pad of a head-mountable device; a rim that holds the waveguide in place; a nose bridge of the head-mountable device; or under a display engine of the head-mountable device.

14. The method of any of claims 10 to 13, wherein optically coupling the waveguide to the eye-tracking illumination source comprises positioning a prism optically between the waveguide and the eye-tracking illumination source such that light from the eye-tracking illumination source passes through the prism into the waveguide.

15. The method of any of claims 10 to 14, wherein optically coupling the waveguide to the eye-tracking illumination source comprises configuring the waveguide and the eye-tracking illumination source to project a pattern of dots in an eye box of the system when light from the eye-tracking illumination source is directed through the waveguide.

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