Patent Description:
Eye tracking may refer to the process of detecting the direction of a user's gaze, which may include detecting the angular orientation of the eye in <NUM>-dimensional (3D) space. Eye tracking may further include detecting the position and movements of the eye (e.g., the center of the eye), the torsion (i.e., the roll of the eye about the pupillary axis) of the eye, the shape of the eye, the current focal distance of the eye, the dilation of the pupil, other features of the eye's state, or some combination thereof.

Eye tracking systems may be utilized in a variety of contexts, such as medical research or diagnosis, human-computer interaction, etc. In some contexts, such as with head mounted displays (HMDs), it may be advantageous for the HMD to determine the location of the eye of the user and/or determine where the eyes of the user are focusing to alter the content being presented to the user.

<CIT> describes a method for providing augmented reality contents to a wearer using a head-mounted display device that includes an eye tracking sensor, a light projector, a beam steerer, and a combiner, the method including determining, with the eye tracking sensor, a position of a pupil of an eye of the wearer. The method also includes projecting, with the light projector, light for rendering images based at least on the augmented reality contents, and changing, with the beam steerer, a direction of the light from the light projector based on the position of the pupil. The light from the beam steerer is directed toward the combiner and the light from the beam steerer and light from an outside of the head-mounted display device are combined, by the combiner, to provide an overlap of a rendered image and a real image that corresponds to the light from the outside of the head-mounted display device.

<CIT> describes a display device including a two-dimensional array of tiles. Each tile includes a two-dimensional array of pixels and a lens of a two-dimensional array of lenses. Each pixel is configured to output light so that the two-dimensional array of pixels outputs a respective pattern of light. Each lens is configured to direct at least a portion of the respective pattern of light from the two-dimensional array of pixels to a pupil of an eye of a user. The display device also includes an array of sensors for determining a location of the pupil of the eye of the user.

<CIT> discloses an eye tracking method. bright pupil tracking is mentioned as one possibility. Infrared illuminators are positioned above or behind a combiner combining a large area low resolution display panel with a low area high resolution display panel, and infrared light. Bright pupil illumination sources and the camera are positioned coaxially with the gaze direction of the user's eye.

Accordingly, the present invention is directed to methods, systems, and head-mounted displays according to the appended claims.

Non-limiting and non-exhaustive aspects of the present disclosure are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

Various aspects and embodiments are disclosed in the following description and related drawings to show specific examples relating to an eye-tracking method and system. Alternate aspects and embodiments will be apparent to those skilled in the pertinent art upon reading this disclosure and may be constructed and practiced without departing from the scope of the disclosure. Additionally, well-known elements will not be described in detail or may be omitted so as to not obscure the relevant details of the aspects and embodiments disclosed herein.

In some implementations of the disclosure, the term "near-eye" may be defined as including an element that is configured to be placed within <NUM> of an eye of a user while a near-eye device is being utilized. Therefore, a "near-eye optical element" or a "near-eye system" would include one or more elements configured to be placed within <NUM> of the eye of the user.

In aspects of this disclosure, visible light may be defined as having a wavelength range of approximately <NUM> - <NUM>. Non-visible light may be defined as light having wavelengths that are outside the visible light range, such as ultraviolet light and infrared light. Infrared light having a wavelength range of approximately <NUM> - <NUM> includes near-infrared light. In aspects of this disclosure, near-infrared light may be defined as having a wavelength range of approximately <NUM> - <NUM>.

<FIG> illustrates an example eye-tracking system 100A, in accordance with aspects of the present disclosure. The illustrated example of eye-tracking system 100A includes an array of light sources 102A-<NUM>, a layer <NUM>, beam shaping optics 106A-<NUM>, an optical element <NUM>, an optical combiner <NUM>, a camera <NUM>, and a computing device <NUM>. Also shown in <FIG> is an eye <NUM> that includes a fundus <NUM>, a pupil <NUM>, and a pupil plane <NUM>.

As shown in <FIG>, the light sources 102A-<NUM> are disposed on layer <NUM>. Layer <NUM> may be a transparent substrate, such as glass or plastic. In one example, the light sources 102A-<NUM> may be encapsulated within the transparent substrate. The transparent substrate may be transmissive to visible light (e.g. <NUM> - <NUM>) and may be configured to be placed on a display plane of an electronic or optical display layer (e.g., a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a micro-LED display, a waveguide, etc.) that is configured to generate display light for presentation to the user. In another example, layer <NUM> is, itself, the electronic or optical display layer, where light sources 102A-<NUM> are disposed on the display layer, interspersed within display light that is generated by the display layer (e.g., within the field of view of the user).

Each light source 102A-<NUM> may be a micro light emitting diode (micro-LED), an edge emitting LED, a vertical cavity surface emitting laser (VCSEL) diode, or a Superluminescent diode (SLED). In addition, each light source 102A-<NUM> may be individually enabled to emit non-visible light <NUM> to illuminate the eye <NUM>. In some examples, non-visible light <NUM> is infrared light or near-infrared light. In some aspects, each light source 102A-<NUM> is arranged on layer <NUM> in a two-dimensional (2D) array of columns and rows. In some examples, each light source 102A-<NUM> may be referred to as a point light source, where only one of the light sources 102A-<NUM> are enabled at a time to emit non-visible light <NUM> (e.g., in the illustrated example of <FIG>, only a single light source <NUM> is currently enabled to emit non-visible light <NUM>).

The illustrated example of <FIG> also illustrates a plurality of beam shaping optics 106A-<NUM>. Each beam shaping optic 106A-<NUM> may be disposed on a corresponding light source 102A-<NUM> to direct the non-visible light emitted by each light source along a respective optical axis. Thus, in some aspects, each light source 102A-<NUM> may be configured, by way of a respective beam shaping optic 106A-<NUM>, to emit non-visible light <NUM> along a different optical axis. For example, beam shaping optic 106A may be configured to direct non-visible light generated by light source 102A along a first optical axis, whereas beam shaping optic 106B may be configured to direct non-visible light generated by light source 102B along a second (i.e., different) optical axis. In some examples, each of the beam shaping optics 106A-<NUM> may also be configured to collimate the non-visible light <NUM> generated by a respective light source 102A-<NUM>.

As shown in <FIG>, the eye-tracking system 100A also includes an optical element <NUM> that is disposed between the beam shaping optics 106A-<NUM> and an eyeward side <NUM> of the eye-tracking system 100A. <FIG> also illustrates an optical combiner <NUM> that is disposed between the light sources 102A-<NUM> and the eyeward side <NUM>, and in particular may be disposed between the optical element <NUM> and the eyeward side <NUM>. In some examples, optical element <NUM> includes one or more lenses that are configured to receive the collimated non-visible light <NUM> and to focus the collimated non-visible light <NUM> through the optical combiner <NUM> to the pupil plane <NUM> of the eye <NUM>. Thus, in some examples, the optical element <NUM> provides a "Maxwellian view" of the non-visible light <NUM>. As shown in <FIG>, the non-visible light <NUM> then expands as it exits the pupil <NUM> towards to back of the eye <NUM> to illuminate a large area of the fundus <NUM>.

In some aspects, the optical combiner <NUM> is configured to receive reflected non-visible light <NUM> (having the wavelength emitted by the light sources 102A-<NUM>) that is reflected/scattered by the fundus <NUM> of eye <NUM> and to direct the reflected non-visible light <NUM> to the camera <NUM>. The camera <NUM> may be located in different positions than the positions illustrated. In some aspects, the optical combiner <NUM> is transmissive to visible light (e.g. approximately <NUM> - <NUM>), such as scene light (e.g., from the environment) that is incident on the backside <NUM> of the eye-tracking system 100A. Even still, in some examples, the optical combiner <NUM> is transmissive to visible light that generated by a display layer (e.g., layer <NUM>). According to the invention, the optical combiner <NUM> is configured as a holographic optical element (HOE) or a volume hologram that may include one or more Bragg gratings for directing the reflected non-visible light <NUM> toward the camera <NUM>. In some examples, the optical combiner <NUM> includes a polarization-selective volume hologram (a. polarized volume hologram) that diffracts (in reflection) a particular polarization orientation of incident light having a particular wavelength toward camera <NUM> while passing other polarization orientations.

The camera <NUM> is configured to generate one or more images <NUM> of the eye <NUM>, where the images <NUM> are of the reflected non-visible light <NUM>. In some examples, camera <NUM> may be configured to filter out light that is other than the non-visible light <NUM>/reflected non-visible light <NUM> such that the camera <NUM> only images the wavelength of the reflected non-visible light <NUM>.

In some examples, the computing device <NUM> may be configured to determine eye-tracking information (e.g., location, orientation, gaze angle, etc.) of the eye <NUM> based on images <NUM> captured by the camera <NUM>. As will be described in more detail below, the computing device <NUM> may then process the images <NUM> to detect a bright pupil condition to determine eye-tracking information (e.g., position, orientation, gaze angle, etc. of the eye <NUM>). For example, the computing device <NUM> may determine whether the eye <NUM> is looking in the straight, left, right, upwards, or downwards direction.

In some embodiments, the computing device <NUM> may include a light source control module that is communicatively coupled to the array of light sources 102A-<NUM>. As discussed above, each of the light sources 102A-<NUM> may emit non-visible light <NUM> along a respective optical axis. If the eye <NUM> is misaligned with a currently-enabled light source 102A-<NUM>, then the pupil <NUM> of the eye may vignette the non-visible light <NUM> which may reduce or prevent the light from reaching the fundus <NUM>, which will darken the appearance of the pupil <NUM> in the resultant image <NUM>. However, if the eye <NUM> is aligned with the currently-enabled light source 102A-<NUM> (e.g., along the same optical axis as the non-visible light <NUM> being emitted), then the pupil <NUM> will appear brighter in the resultant image <NUM>.

Accordingly, the control module of computing device <NUM> may generate one or more control signals <NUM> to selectively enable at least one of the light sources 102A-<NUM> and analyze the resultant images <NUM> to detect a bright pupil condition. If an image <NUM> that was captured while a particular light source (e.g., light source <NUM>) was enabled indicates a bright pupil condition, then the computing device <NUM> may then determine a position/gaze angle of the eye <NUM> based on a position of that light source (e.g., light source <NUM>) within the array of light sources.

As mentioned above, the beam shaping optics 106A-<NUM> may be configured to collimate the non-visible light <NUM> that is emitted by the light sources 102A-<NUM>, where optical element <NUM> then focuses the collimated non-visible light onto the pupil plane <NUM>. However, in other examples of the present disclosure, the beam shaping optics 106A-<NUM> that collimate the non-visible light may be omitted. For example, <FIG> illustrates another example eye-tracking system 100B, in accordance with aspects of the present disclosure. In the illustrated example of <FIG>, the non-visible (and non-collimated) light <NUM> emitted by the light source <NUM> is received by optical element <NUM>. In this example, the optical element <NUM> may then collimate the non-visible light and direct the collimated non-visible light to the eye <NUM>. The eye <NUM> then focuses the collimated non-visible light (e.g., by way of the lens of the eye <NUM>) onto the fundus <NUM>. In this example, the fundus <NUM> may act as a retroreflector where the reflected non-visible light is reflected back at an angle that is substantially the same as the angle that the non-visible light is incident upon the fundus <NUM>. Similar to the example of <FIG>, the reflected non-visible light <NUM> is received by the optical combiner <NUM>, which then directs the reflected non-visible light <NUM> to the camera <NUM> to generate the images <NUM>.

<FIG> illustrates an array of light sources <NUM> and the corresponding images 202A-<NUM> of an eye captured when at least one of the light sources are enabled, in accordance with aspects of the present disclosure. The array of light sources <NUM> is one possible example of the array of light sources 102A-<NUM> of <FIG> and <FIG>. Similarly, the images 202A-<NUM> are possible examples of the images <NUM>. As discussed above, each of the light sources of the array of light sources <NUM> may be individually enabled to emit non-visible light to illuminate the eye, where a corresponding image may then be captured of the eye while the light source is enabled. By way of example, <FIG> illustrates an image 202A that was captured when light source 208A was enabled, image 202B is an image of the eye when light source 208B was enabled, image 202C is an image of the eye when light source 208C was enabled, image 202D is an image of the eye when light source 208D was enabled, image 202E is an image of the eye when light source 208E was enabled, image 202F is an image of the eye when light source 208F was enabled, image <NUM> is an image of the eye when light source <NUM> was enabled, and so on. The images captured by the camera (e.g., camera <NUM> of <FIG>) may then be analyzed by a computing device (e.g., computing device <NUM> of <FIG>). In one example, analyzing the images 202A-<NUM> includes determining if any of the images indicate a bright pupil condition. In the illustrated example of <FIG>, image 202E indicates a bright pupil condition of the pupil <NUM>. In response to determining that an image indicates a bright pupil condition, the computing device determines that the eye was aligned with the light source that was enabled when the image was obtained (e.g., the eye was aligned with light source 208E when image 202E was captured). The computing device may then determine the position of the eye based on a known position of the light source 208E within the array <NUM>. In some examples, determining the position of the eye includes translating the position of the light source 208E to a calculated eye position and/or gaze angle.

In some examples, determining whether a bright pupil condition exists includes comparing a brightness of the pupil <NUM> in one image to the brightness of the pupil <NUM> in another image. In some aspects, this may include utilizing one or more computer-vision techniques to identify a pupil region of each image and determining a brightness of the pupil region (e.g., average brightness of all pixels within the pupil region). The determined brightness of the pupil region may then be compared with the brightness determined in other images, where the image with the brightest pupil region is determined to indicate a bright pupil condition.

In other examples, the bright pupil condition may be determined by comparing the brightness of the pupil region of an image with a brightness threshold. That is, in this example, rather than comparing images together, the brightness of the pupil region of one image may be compared against a fixed or dynamically-created threshold that indicates the bright pupil condition.

In some aspects, each light source of the array of light sources <NUM> may be individually enabled and a corresponding image captured. However, in other examples, two or more groupings of light sources may be enabled, where corresponding images are obtained to determine whether the eye is aligned with a particular grouping of light sources. By way of example, <FIG> illustrates the array of light sources <NUM> and the corresponding images 302A and 302B of an eye captured when a grouping of light sources are enabled, in accordance with aspects of the present disclosure. As shown in <FIG>, image 302A is an image of the eye captured when a first grouping <NUM> of light source were enabled, whereas image 302B is an image of the eye captured when a second grouping <NUM> of light sources were enabled. Although <FIG> illustrates only two groupings of light sources, other embodiments may include multiple groupings of the array of light sources <NUM>, including two or more.

In some examples, enabling a grouping of light sources includes simultaneously enabling multiple light sources of the array of light sources <NUM>, where the captured image includes an image of the eye when all of the light sources in the grouping were enabled. The resultant images 302A and 302B may then be analyzed (e.g., by computing device <NUM>) to determine whether a bright pupil condition exists, either by comparing the brightness of the pupil <NUM> of image 302A with the brightness of the pupil <NUM> of image 302B, or by comparing the brightness of the pupil <NUM> in each image with the brightness threshold. In the illustrated example, image 302B indicates the bright pupil condition.

An image that indicates a bright pupil condition when a grouping of light sources were enabled means that one of the light sources included in the grouping of light sources <NUM> is aligned with the eye. Thus, in some examples, each light source of that grouping (e.g., grouping <NUM> of <FIG>) may then be individually enabled (and a corresponding image captured) to determine the particular light source that caused the bright pupil condition.

For example, <FIG> illustrates the array of light sources <NUM> and the corresponding images 302x-302z of an eye captured when individual light sources of grouping <NUM> are enabled, in accordance with aspects of the present disclosure. Image 302x is an image of the eye that was captured when light source 308A was enabled, image 302y is an image of the eye when light source 308B was enabled, and image 302z is an image of the eye when light source 308C was enabled. Although <FIG> only illustrates three images 302x-302y, as mentioned above, aspects of the present disclosure may include individually enabling each of the light sources included in the grouping <NUM>. As shown in <FIG>, image 302y indicates a bright pupil condition, where the computing device may then determine a position of the eye based on the position of light source 308B within the array of light sources <NUM>.

<FIG> illustrates a computing device <NUM>, in accordance with aspects of the present disclosure. The illustrated example of computing device <NUM> is shown as including a communication interface <NUM>, one or more processors <NUM>, hardware <NUM>, and a memory <NUM>. The computing device <NUM> of <FIG> is one possible implementation of the computing device <NUM> of <FIG>.

The communication interface <NUM> may include wireless and/or wired communication components that enable the computing device <NUM> to transmit data to and receive data from other devices/components. The hardware <NUM> may include additional hardware interface, data communication, or data storage hardware. For example, the hardware interfaces may include a data output device, and one or more data input devices.

The memory <NUM> may be implemented using computer-readable media, such as computer storage media. In some aspects, computer-readable media may include volatile and/or non-volatile, removable and/or non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer-readable media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD), high-definition multimedia/data storage disks, or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device.

The processors <NUM> and the memory <NUM> of the computing device <NUM> may implement a light source control module <NUM>, a camera interface module <NUM>, a bright pupil detection module <NUM>, and a position determination module <NUM>. The light source control module <NUM>, camera interface module <NUM>, bright pupil detection module <NUM>, and the position determination module <NUM> may include routines, program instructions, objects, and/or data structures that perform particular tasks or implement particular abstract data types. The memory <NUM> may also include a data store (not shown) that is used by the light source control module <NUM>, camera interface module <NUM>, bright pupil detection module <NUM>, and/or the position determination module <NUM>.

The light source control module <NUM> may be configured to generate one or more control signals (e.g., control signals <NUM> of <FIG>) to enable and/or disable one or more of the light sources included in the array of light sources 102A-<NUM>. The camera interface module <NUM> may be configured to receive images (e.g., images <NUM> of <FIG>). The camera interface module <NUM> may optionally be configured to trigger the camera <NUM> to capture one or more images in response to the light source control module <NUM> enabling a light source of the array of light sources. The bright pupil detection module <NUM> is configured to analyze one or more images to determine whether an image indicates the bright pupil condition. As mentioned above, the bright pupil detection module <NUM> may implement one or more computer-vision techniques to identify a pupil region and to determine a corresponding brightness of the pupil region. The bright pupil detection module <NUM> may detect the bright pupil condition by comparing the brightness of the pupil region among two or more images or, alternatively, may detect the bright pupil condition by comparing the brightness of the pupil region on an image with the brightness threshold. In response to the bright pupil detection module <NUM> detecting the bright pupil condition, the position determination module <NUM> may determine a position of the eye based on a position of the light source that was enabled for the image that indicates such a bright pupil condition. As mentioned above, the position of the eye may be determined by translating the position of the light source to a calculated eye-position and/or gaze angle.

<FIG> is a flow chart illustrating a process <NUM> of eye-tracking, in accordance with aspects of the present disclosure. Process <NUM> is one possible process of eye-tracking performed by the eye-tracking system 100A of <FIG>. In a process block <NUM>, the computing device <NUM> of <FIG> may generate a control signal <NUM> to enable at least one light source <NUM> of the array of light sources 102A-<NUM> to emit non-visible light <NUM> to illuminate an eye <NUM>. In a process block <NUM>, the computing device <NUM> may obtain (e.g., receive) at least one image <NUM> of the eye <NUM> that was captured by the camera <NUM> while the at least one light source <NUM> was enabled. Next, in a process block <NUM>, the computing device <NUM> determines a position of the eye <NUM> based on a position of the at least one light source <NUM> within the array of light sources 102A-<NUM> in response to determining that the image <NUM> indicates a bright pupil condition.

<FIG> is a flow chart illustrating another process <NUM> of eye-tracking that includes enabling a first and a second light source, in accordance with aspects of the present disclosure. Process <NUM> is described with reference to <FIG>. In a process block <NUM> a first light source 208A of the array of light sources <NUM> is enabled to emit non-visible light to illuminate an eye. In a process block <NUM>, a first image 202A is obtained that is an image of the eye captured when the first light source 208A was enabled. Next, in a process block <NUM> a second light source 208E is enabled to emit non-visible light to illuminate the eye (e.g., and the first light source 208A is disabled). Process block <NUM> includes obtaining the image 202E that was captured by the camera (e.g., camera <NUM>) while the second light source 208E was enabled.

In a decision block <NUM>, the computing device (e.g., computing device <NUM>) determines whether the pupil <NUM> in the first image 202A is brighter than the pupil <NUM> in the second image 202E. If the pupil <NUM> in the first image 202A is determined to be brighter than the pupil <NUM> in the second image 202E, then process <NUM> proceeds to process block <NUM>, where the computing device determines the position of the eye based on the position of the first light source 208A within the array of light sources <NUM>. If, however, in decision block <NUM>, it is determined that the pupil <NUM> in the first image 202A is not brighter than the pupil <NUM> in the second image 202E (i.e., the pupil <NUM> in the second image 202E is brighter), then process <NUM> proceeds to process block <NUM> where the position of the eye is determined based on the position of the second light source 208E with the array of light sources <NUM>.

Although process <NUM> is described above with reference to the enabling of only two of the light sources (and obtaining a corresponding two images), as described above, aspects of the present disclosure may include individually enabling two or more of the light sources included in the array of light sources 102A-<NUM>, where the brightness's of each of the obtained images are compared to one another to determine which image indicates the bright pupil condition.

<FIG> is a flow chart illustrating a process <NUM> of eye-tracking that includes enabling a first and a second grouping of light sources, in accordance with aspects of the present disclosure. Process <NUM> is described with reference to <FIG> and <FIG>.

In a process block <NUM> a first grouping <NUM> of light sources is enabled to emit non-visible light to illuminate an eye. In a process block <NUM>, a first image 302A is obtained that is an image of the eye while all light sources included in the first grouping <NUM> were simultaneously enabled. In a process block <NUM>, a second grouping <NUM> of light sources is enabled to emit the non-visible light. Process block <NUM> includes obtaining the second image 302B that is an image of the eye while all light sources included in the second grouping <NUM> were simultaneously enabled (e.g., and light sources of the first grouping <NUM> were disabled).

Next, in decision block <NUM>, the computing device (e.g., computing device <NUM>) determines whether the pupil <NUM> in the first image 302A is brighter than the pupil <NUM> in the second image 302B. If the pupil <NUM> in the first image 302A is determined to be brighter than the pupil <NUM> in the second image 302B, then process <NUM> proceeds to process block <NUM>, where each light source withing the first grouping <NUM> are individually enabled and respective images of the eye are obtained (e.g., captured by camera <NUM>). In a process block <NUM>, the computing device then determines a position of the eye based on a position of a light source of the first grouping <NUM> that corresponds to an image (i.e., obtained in process block <NUM>) that indicates a bright pupil condition.

Returning to decision block <NUM>, if the pupil <NUM> in the first image 302A is not brighter than the pupil <NUM> in the second image 302B, then process <NUM> proceeds to process block <NUM> where each of the light sources included in the second grouping <NUM> are individually enabled and respective images of the eye are obtained. In a process block <NUM>, the computing device may then determine the position of the eye based on a position of a light source of the second grouping <NUM> that corresponds to an image (i.e., obtained in process block <NUM>) that indicates the bright pupil condition.

In some implementations, aspects of the present disclosure may be utilized in a head mounted device, such as a virtual reality (VR) or augmented reality (AR) device. In some aspects, a head mounted device may incorporate an eye-tracking system to enhance a user's viewing experience. Eye-tracking, may in some instances, be aided by determining the position and/or movement of the eye. For example, when the gaze angle is determined, a virtual image presented to a user by a display of a head mounted device may be adjusted in response to the determined gaze angle.

By way of example, <FIG> illustrates a head-mounted display (HMD) <NUM>, in accordance with aspects of the present disclosure. An HMD, such as HMD <NUM>, is one type of head mounted device, typically worn on the head of a user to provide artificial reality content to a user. Artificial reality is a form of reality that has been adjusted in some manner before presentation to the user, which may include, e.g., virtual reality (VR), augmented reality (AR), mixed reality (MR), hybrid reality, or some combination and/or derivative thereof. The illustrated example of HMD <NUM> is shown as including a viewing structure <NUM>, a top securing structure <NUM>, a side securing structure <NUM>, a rear securing structure <NUM>, and a front rigid body <NUM>. In some examples, the HMD <NUM> is configured to be worn on a head of a user of the HMD <NUM>, where the top securing structure <NUM>, side securing structure <NUM>, and/or rear securing structure <NUM> may include a fabric strap including elastic as well as one or more rigid structures (e.g., plastic) for securing the HMD <NUM> to the head of the user. HMD <NUM> may also optionally include one or more earpieces <NUM> for delivering audio to the ear(s) of the user of the HMD <NUM>.

The illustrated example of HMD <NUM> also includes an interface membrane <NUM> for contacting a face of the user of the HMD <NUM>, where the interface membrane <NUM> functions to block out at least some ambient light from reaching to the eyes of the user of the HMD <NUM>.

Example HMD <NUM> may also include a chassis for supporting hardware of the viewing structure <NUM> of HMD <NUM> (chassis and hardware not explicitly illustrated in <FIG>). The hardware of viewing structure <NUM> may include any of processing logic, wired and/or wireless data interface for sending and receiving data, graphic processors, and one or more memories for storing data and computer-executable instructions. In one example, viewing structure <NUM> may be configured to receive wired power and/or may be configured to be powered by one or more batteries. In addition, viewing structure <NUM> may be configured to receive wired and/or wireless data including video data.

Viewing structure <NUM> may include a display system having one or more electronic displays for directing light to the eye(s) of a user of HMD <NUM>. The display system may include one or more of a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a micro-LED display, etc. for emitting light (e.g., content, images, video, etc.) to a user of HMD <NUM>. The viewing structure <NUM> may also include an optical assembly that is configured to receive the image light from the display system and generate a virtual image (e.g., by collimating the image light) for viewing by an eye of a wearer of the HMD <NUM>.

In some examples, viewing structure includes an eye-tracking system <NUM> for tracking movements and/or determining a position of the user's eye. The eye-tracking system <NUM> may be implemented by way of any of the embodiments discussed herein, including eye-tracking system 100A of <FIG>.

Embodiments of the invention may include or be implemented in conjunction with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, e.g., a virtual reality (VR), an augmented reality (AR), a mixed reality (MR), a hybrid reality, or some combination and/or derivatives thereof. Artificial reality content may include completely generated content or generated content combined with captured (e.g., real-world) content. The artificial reality content may include video, audio, haptic feedback, or some combination thereof, and any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional 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, e.g., create content in an artificial reality and/or are otherwise used in (e.g., perform activities in) an artificial reality. The artificial reality system that provides the artificial reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

The above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed.

Claim 1:
An eye-tracking method (<NUM>), comprising:
enabling (<NUM>) at least one light source of an array of light sources to emit non-visible light to illuminate an eye, wherein the non-visible light emitted by the at least one light source propagates through an optical combiner disposed between the array of light sources and the eye, wherein the optical combiner is configured to receive non-visible light reflected by a fundus of the eye and direct the non-visible light reflected by the fundus to a camera, and wherein the optical combiner is configured as a holographic optical element or a volume hologram;
generating (<NUM>) at least one image of the eye with the camera while the at least one light source is enabled, wherein the at least one image is of the non-visible light reflected by the fundus; and
determining (<NUM>) a position of the eye based on a position of the at least one light source within the array of light sources in response to determining that the at least one image indicates a bright pupil condition when the at least one light source was enabled.