Patent Description:
This disclosure relates generally to head mounted devices, optical systems, and near-eye optical elements, and in specific embodiments concerns head mounted devices, optical systems, and near-eye optical elements having a transparent illumination layer and a transparent waveguide structure.

A common technique to illuminate a target is to aim one or more light sources such as light emitting diodes (LEDs) toward the target. Yet, conventional light sources have a large enough footprint to introduce significant occlusions into an optical system. In the particular context of head mounted devices, it may be desirable to illuminate an eye region without introducing significant occlusions into an optical system.

<CIT> describes an apparatus including an extraocular device, which includes an eyeglasses frame, which is placed in front of an eye of a subject, and a power source coupled to the eyeglasses frame and configured to emit a beam of light that is outside of <NUM>-<NUM>. A light-guiding element is coupled to the eyeglasses frame and at least one optical coupling-in element and at least one optical coupling-out element are optically coupled to the light-guiding element. The coupling-in element is positioned such that the beam of light is directed into the light-guiding element via the coupling-in element, and the coupling-in and coupling-out elements are positioned such that the beam diverges from a focal point located within <NUM> of the coupling-out element.

<CIT> describes that a head mounted display is used in a state of being mounted on a user's head and includes a convex lens disposed at a position facing the user's cornea when the head mounted display is mounted. An infrared light source emits infrared light toward the convex lens. A camera captures an image including the user's cornea in a subject. A housing houses the convex lens, the infrared light source, and the camera. The convex lens is provided with a plurality of reflection regions that reflects infrared light in an inside of the convex lens. The infrared light source causes a pattern of infrared light to appear on the user's cornea by emitting infrared light to each of the plurality of reflection regions provided in the convex lens.

<CIT> describes a system that includes an emitter configured to emit a light. The system may include a light guide configured to direct the light toward a pupil of an eye. The light guide may include a directing portion configured to propagate the light. The light guide may include a turning portion configured to receive light from the directing portion and direct the light toward the pupil of the eye and configured to receive reflected light directed from the pupil of the eye and direct the reflected light toward the directing portion. The system may include a receiver configured to receive the reflected light from the light guide. The system may include a processor configured to determine a gaze direction of the pupil of the eye based at least in part on the reflected light received by the receiver.

<CIT> describes a near-eye display device.

According to an aspect of the invention, there is provided a head mounted device according to claim <NUM>.

In some embodiments, the transparent waveguide structure has a transparent core and a transparent clad layer.

In some embodiments, the outcoupling elements are less than <NUM> microns across and unnoticeable to observers of the head mounted device.

In some embodiments, a first outcoupling element in the plurality of outcoupling elements is configured to outcouple the near-infrared illumination light as a first light cone having a first divergence angle, and wherein a second outcoupling element in the plurality of outcoupling elements is configured to outcouple the near-infrared illumination light as a second light cone having a second divergence angle that is different than the first divergence angle.

In some embodiments, the waveguide structure follows an indirect curving path between the near-infrared light source and the outcoupling elements.

In some embodiments, at least a portion of the outcoupling elements include a backside reflector configured to outcouple the near-infrared illumination light toward the eye region.

In some embodiments, the backside reflector includes at least one of a metal layer or a Bragg reflector.

In some embodiments, the outcoupling elements include an output grating and a beam-shaping element.

In some embodiments, the outcoupling elements are in a field of view (FOV) of an eye of a user of the optical system.

In some embodiments, the optical system further comprises: an input coupling structure configured to receive the near-infrared light from the near-infrared light source and inject the near-infrared light into the transparent waveguide structure.

In some embodiments, the optical system further comprises: a second near-infrared light source configured to emit second near-infrared light; a second plurality of outcoupling elements positioned across the transparent layer; and a second transparent waveguide structure configured to deliver the second near-infrared light to the second plurality of outcoupling elements, the second plurality of outcoupling elements configured to outcouple the second near-infrared light as the near-infrared illumination light to illuminate the eye region.

It will be appreciated that any features described herein as being suitable for incorporation into the first aspect, the second aspect or the third aspect, are intended to be generalizable across any and all aspects and embodiments of the present disclosure.

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

Embodiments of a transparent layer and transparent layer for illumination are described herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

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>.

Creating an illumination optical system across a transparent layer typically includes disposing light sources across the transparent layer and routing electrical conductors to the light sources. However, even when the light sources are small, they introduce occlusions into the optical system and the electrical traces that are routed to power the light sources may cause unwanted diffraction effects. In the context of a head mounted device such as smart glasses, an augmented reality (AR) head mounted display (HMD), or a virtual reality (VR) HMD, it may be advantageous to illuminate an eye region from a transparent layer in the field of view (FOV) of a user of the head mounted device. In some contexts, the eye region is illuminated with non-visible illumination light (e.g. near-infrared light) to image the eye for eye-tracking purposes, for example.

In aspects of the disclosure, a transparent layer shaped like a lens may be mounted to a frame of a head mounted device. A transparent waveguide structure receives non-visible light from one or more light source such as an LED, a superluminescent light emitting diode (S-LED), or a vertical-cavity surface-emitting laser (VCSEL). The transparent waveguide structure delivers the non-visible light to outcoupling element disposed across the transparent layer. The outcoupling elements direct the received non-visible light toward an eye region as non-visible illumination light. A camera configured to image the non-visible light may then capture eye-tracking images of the eye illuminated with non-visible illumination light. These and other embodiments are described in more detail in connections with <FIG>.

<FIG> illustrates an example head mounted device <NUM>, in accordance with aspects of the present disclosure. A head mounted device, such as head mounted device <NUM>, is one type of smart device. In some contexts, head mounted device <NUM> is also a head mounted display (HMD) 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 head mounted device <NUM> is shown as including a frame <NUM>, temple arms 104A and 104B, and a near-eye optical element 106A and a near-eye optical element 106B. <FIG> also illustrates an exploded view of an example of near-eye optical element 106A. Near-eye optical element 106A is shown as including an illumination layer <NUM> and a display layer <NUM>.

As shown in <FIG>, frame <NUM> is coupled to temple arms 104A and 104B for securing the head mounted device <NUM> to the head of a user. Example head mounted device <NUM> may also include supporting hardware incorporated into the frame <NUM> and/or temple arms 104A and 104B. The hardware of head mounted device <NUM> may include any of processing logic, wired and/or wireless data interfaces for sending and receiving data, graphic processors, and one or more memories for storing data and computer-executable instructions. In one example, head mounted device <NUM> may be configured to receive wired power and/or may be configured to be powered by one or more batteries. In addition, head mounted device <NUM> may be configured to receive wired and/or wireless data including video data.

<FIG> illustrates near-eye optical elements 106A and 106B that are configured to be mounted to the frame <NUM>. The frame <NUM> may house the near-eye optical elements 106A and 106B by surrounding at least a portion of a periphery of the near-eye optical elements 106A and 106B. The near-eye optical element 106A is configured to receive visible scene light <NUM> at a world side <NUM> of the near-eye optical element 106A. The visible scene light <NUM> propagates through optical element 106A to an eye of a user of the head mounted device on an eyeward side <NUM> of optical element 106A. In some examples, near-eye optical element 106A may be transparent or semi-transparent to the user to facilitate augmented reality or mixed reality such that the user can view visible scene light <NUM> from the environment while also receiving display light <NUM> directed to their eye(s) by way of display layer <NUM>. A waveguide <NUM> included in display layer <NUM> may be utilized to direct the display light <NUM> generated by an electronic display in an eyeward direction, although other display technologies may also be utilized in display layer <NUM>. In some implementations, at least a portion of an electronic display is included in the frame <NUM> of the head mounted device <NUM>. The electronic display may include an LCD, an organic light emitting diode (OLED) display, micro-LED display, pico-projector, or liquid crystal on silicon (LCOS) display for generating the display light <NUM>.

In further examples, some or all of the near-eye optical elements 106A and 106B may be incorporated into a virtual reality headset where the transparent nature of the near-eye optical elements 106A and 106B allows the user to view an electronic display (e.g., a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a micro-LED display, etc.) incorporated in the virtual reality headset. In this context, display layer <NUM> may be replaced by the electronic display.

Illumination layer <NUM> includes a transparent layer that may be formed of optical polymers, glasses, transparent wafers (such as high-purity semi-insulating SiC wafers) or any other transparent materials used for this purpose. A waveguide structure <NUM> is configured to receive non-visible light from a non-visible light source coupled with frame <NUM>. Waveguide structure <NUM> is configured to deliver the non-visible light from the non-visible light source to outcoupling element <NUM>, in <FIG>. Only one waveguide structure <NUM> and one outcoupling element <NUM> are illustrated in <FIG>, although there may be a plurality of outcoupling elements in some implementations. The one or more outcoupling elements <NUM> are configured to outcouple the non-visible light propagating in waveguide structure <NUM> as non-visible illumination light <NUM> to illuminate an eye region.

The non-visible illumination light <NUM> may be near-infrared light, in some aspects. The non-visible light source that generates the non-visible light for waveguide structure <NUM> may include one or more of light emitting diode (LED), a micro light emitting diode (micro-LED), an edge emitting LED, a vertical cavity surface emitting laser (VCSEL), on-chip integrated laser, hybrid integrated laser, or a Superluminescent diode (S-LED). Depending on the architecture, a single light source or a light source array can be used. When a single light source is used, waveguide splitters can be used to distribute the light into multiple outputs. The light source may be buried in the frame so that is out of a FOV (field of view) of a user. When an array of light sources is used, each light source can supply one output so that no waveguide splitter is needed. A waveguide splitter may be used to split the power in one waveguide into multiple waveguides. For example, a Y shaped splitter can divide a single waveguide into two channels with balanced power or designed unbalanced power. A 1x2 MMI (multimode interferometer) coupler can function similarly to a Y splitter, a 1x4 MMI splitter can divide a single waveguide into <NUM> channels, and so on. A Mach-Zehnder interferometer can also be used for splitting optical power of a waveguide.

In some implementations, a combiner layer (not illustrated) is optionally disposed between display layer <NUM> and illumination layer <NUM> to direct reflected non-visible illumination light that has reflected from an eye region to a camera (e.g. camera <NUM>) to capture eye-tracking images. In some implementations, camera <NUM> is positioned to image the eye directly by imaging the reflected non-visible illumination light reflecting from the eye region. Camera <NUM> may include a complementary metal-oxide semiconductor (CMOS) image sensor. When non-visible illumination light <NUM> is infrared light, an infrared filter that receives a narrow-band infrared wavelength may be placed over the image sensor so it is sensitive to the narrow-band infrared wavelength while rejecting wavelengths outside the narrow-band, including visible light wavelengths.

As shown in <FIG>, outcoupling element <NUM> and waveguide structure <NUM> are disposed within the field-of-view (FOV) of a user provided by the near-eye optical element 106A. While outcoupling element <NUM> may introduce minor occlusions or non-uniformities into the near-eye optical element 106A, outcoupling element(s) <NUM> and waveguide structure <NUM> may be so small as to be unnoticeable or insignificant to a wearer of head mounted device <NUM>. Additionally, any occlusion from outcoupling element <NUM> and waveguide structure <NUM> may be placed so close to the eye as to be unfocusable by the human eye and therefore outcoupling element <NUM> and waveguide structure <NUM> will not be noticeable to a user of device <NUM>. Waveguide structure <NUM> includes a transparent (to visible light) dielectric material, in some implementations. Furthermore, outcoupling element <NUM> and waveguide structure <NUM> may be so small that even an observer (a person not wearing device <NUM> but viewing device <NUM>) may not notice outcoupling element <NUM> and waveguide structure <NUM>. Outcoupling element <NUM> may be smaller than <NUM> microns at it widest/longest dimension. In an implementation, outcoupling element <NUM> may be smaller than <NUM> microns at its widest/longest dimension and waveguide structure <NUM> may be approximately <NUM>-<NUM> microns wide and formed with transparent materials. Waveguide structure <NUM> may be approximately <NUM> to <NUM> micron, in some implementations. Outcoupling element <NUM> may be approximately <NUM> microns at its widest/longest dimension, in some implementations. In contrast, actual light sources positioned in illumination layer <NUM> would have a footprint of approximately <NUM> x <NUM> microns or larger.

In some implementations, optical element 106A may have a curvature for focusing light (e.g., display light <NUM>) to the eye of the user. The curvature may be included in the transparent layer of illumination layer <NUM>. Thus, optical element 106A may be referred to as a lens. In some aspects, optical element 106A may have a thickness and/or curvature that corresponds to the specifications of a user. In other words, optical element 106A may be considered a prescription lens.

<FIG> illustrates an example optical element <NUM> including illumination layer <NUM> having a transparent layer <NUM>, a waveguide structure <NUM>, and an outcoupling element <NUM>, in accordance with aspects of the disclosure. Transparent layer <NUM> may be made from glass or optical polymer. Non-visible light source <NUM> emits non-visible light into waveguide structure <NUM> and waveguide structure <NUM> is configured to receive non-visible light from non-visible light source <NUM> coupled with frame <NUM>. Non-visible light source <NUM> may include a laser source, a superluminescent light emitting diode (S-LED), or a vertical-cavity surface-emitting laser (VCSEL), for example.

Waveguide structure <NUM> confines the non-visible light emitted by non-visible light source <NUM> and the non-visible light propagates toward outcoupling element <NUM>. As in <FIG>, only one waveguide structure <NUM> and one outcoupling element <NUM> are illustrated in <FIG>, although there may be a plurality of outcoupling elements in some implementations. The one or more outcoupling elements <NUM> are configured to outcouple the non-visible light propagating in waveguide structure <NUM> as non-visible illumination light <NUM> to illuminate an eye <NUM> in the eye region. Outcoupling element <NUM> may be configured to generate cone-shaped non-visible illumination light <NUM>. The outcoupling element(s) <NUM> may be configured differently to output non-visible illumination light <NUM> in different divergence angles and/or different shapes to form patterned non-visible illumination light. The patterned non-visible illumination light may assist in processing and analyzing eye-tracking images that include reflected non-visible illumination light <NUM> that is captured by a camera, for example.

<FIG> illustrates a functional diagram of an input coupler <NUM>, waveguide structure <NUM>, and outcoupling element 311A, in accordance with aspects of the disclosure. Taken together, the components of <FIG> may be referred to as a photonic integrated circuit (PIC). Input coupler <NUM> may be a grating or other conversion structure such as a prism, tapered waveguide, or otherwise. Input coupler <NUM> can include a single component or multiple components, for example, a grating coupler may be formed by a single grating layer or a dual grating layer. A grating may be curved for a compact input coupler. Input coupler <NUM> may include a coupler that has a tapered waveguide for coupling to fiber, a surface grating with a back reflector, a grating with micro optics coupled to an edge emitting laser diode, or a flat waveguide end-face coupled to a lensed fiber. Input coupler <NUM> is configured to receive non-visible light <NUM> from non-visible light source <NUM> and incouple the non-visible light <NUM> into waveguide structure <NUM>. <FIG> illustrates a side view of an example input coupler <NUM>. Input coupler <NUM> may be specifically designed to incouple a narrow-band wavelength of non-visible light <NUM> into waveguide structure <NUM>. Input coupler <NUM> may have a footprint that is approximately the size of the non-visible light source <NUM>. For example, for a fiber coupled source, this is the size of the mode profile of a single mode fiber (e.g. approximately <NUM> microns).

Outcoupling element 311A is configured to generate a particular illumination pattern of the non-visible illumination light in the far field (approximately where the non-visible illumination light will become incident on an eye region). In the illustrated embodiment of <FIG>, outcoupling element 311A is configured to direct non-visible illumination light <NUM> in an eyeward direction in a cone-shape having a divergence angle of θ 381A. Other outcoupling elements <NUM> may have different divergence angles and/or different shapes. The size of outcoupling element <NUM>/<NUM>/<NUM> may be approximately <NUM> microns, which is invisible to an unaided human eye. In some aspects, outcoupling element 311A includes a main output grating. A refractive or diffractive optical element may also be used to provide beam shaping to the non-visible illumination light outcoupled by the main output grating. The outcoupling element 311A may utilize both sides of transparent layer <NUM> to distribute its components.

<FIG> illustrate example waveguide designs that may be utilized in waveguide structure <NUM>, in accordance with aspects of the disclosure. <FIG> illustrates a ridge waveguide structure <NUM> having a first refractive material <NUM> surrounding a second refractive material <NUM>. First refractive material <NUM> has a refractive index n<NUM> that is less than a second refractive index n<NUM> of second refractive material <NUM>. The illustrated cross section of second refractive material <NUM> may be approximately <NUM> by <NUM> and the illustrated cross section of first refractive material <NUM> may be approximately <NUM> microns by <NUM> microns. <FIG> illustrates a rib waveguide structure <NUM> having a first refractive material <NUM> surrounding a second refractive material <NUM>. First refractive material <NUM> has a refractive index n<NUM> that is less than a second refractive index n<NUM> of second refractive material <NUM>.

<FIG> illustrates an example outcoupling element 311B generating non-visible illumination light 313B in an eyeward direction, in accordance with aspects of the disclosure. Outcoupling element 311B is configured to direct non-visible illumination light 313B in a different direction and at a different divergence angle θ 381B than outcoupling element 311A. <FIG> also illustrates that a backside reflector layer <NUM> may be used to increase optical efficiency by reflecting any non-visible light <NUM> that is not incoupled into waveguide structure <NUM> on the first encounter back to input coupler <NUM> to be incoupled into waveguide structure <NUM>. Additionally, backside reflector layer <NUM> is disposed below outcoupling element 311B to reflect any stray non-visible illumination light back to outcoupling element 311B. Backside reflector layer <NUM> or <NUM> may be a metallic layer of a Distributed Bragg Reflector (DBR), for example. Backside reflector layer <NUM> or <NUM> may be disposed on a world side of the transparent layer <NUM>. Backside reflectors <NUM> and <NUM> may also be utilized in the PIC of <FIG>.

<FIG> illustrate example outcoupling elements having a grating, a reflector, and a beam shaping element, in accordance with aspects of the disclosure. Outcoupling elements may have a single component or multiple components. The outcoupling element may have a single grating coupler, a grating coupler paired with a back reflector, a grating coupler that has curved gratings, a grating coupler that has a dual grating layer, or a grating coupler with a back reflector and a third layer for beam shaping. The beam shaping layer may include a diffractive optical element (DOE) or a refractive microlens.

<FIG> illustrates an outcoupling element 311F including a grating <NUM>, a reflector <NUM>, and a diffractive optical element (DOE) <NUM> as the beam shaping layer. Grating <NUM> is configured to receive the non-visible light from waveguide <NUM> and illuminate DOE <NUM>. Reflector <NUM> may recycle any stray light back toward DOE <NUM>. Grating <NUM> and reflector <NUM> are illustrated as being included in transparent layer <NUM>. DOE <NUM> may be configured with particular beam shaping features to control the divergence angle of θ 381F and the direction of non-visible illumination light 313F. The beam-shaping layer may include a metasurface formed by nanostructures or a holographic surface, for example. The DOE may be designed for specific far field illumination.

<FIG> illustrates an outcoupling element <NUM> including a grating <NUM>, a reflector <NUM>, and a microlens <NUM> as the beam shaping layer. Grating <NUM> is configured to receive the non-visible light from waveguide <NUM> and illuminate microlens <NUM>. Reflector <NUM> may recycle any stray light back toward microlens <NUM>. Grating <NUM> and reflector <NUM> are illustrated as being included in transparent layer <NUM>. Microlens <NUM> may be configured with particular beam shaping features to control the divergence angle of θ <NUM> and the direction of non-visible illumination light <NUM>. The beam-shaping layer may include a microlens with a free-form surface. Microlens <NUM> may be designed for specific far field illumination. Microlens <NUM> may include a dielectric material.

A distance between the beam shaping layer and the (<NUM> in <FIG> or <NUM> in <FIG>) may be greater than one micron. The beam shaping layer may be fabricated with lithography and etch processes or by nanoimprint process, for example.

<FIG> illustrates an outcoupling element <NUM>. Outcoupling element <NUM> is a mirror configured to outcouple the non-visible light from waveguide <NUM> as non-visible illumination light <NUM> having divergence angle of θ <NUM>.

<FIG> illustrates an outcoupling element 311I. Outcoupling element 311I is a curved mirror configured to outcouple the non-visible light from waveguide <NUM> as non-visible illumination light 313I having divergence angle of θ 381I. Divergence angle θ 381I may be larger than the divergence angle of θ <NUM> due to the curvature of the curved mirror of outcoupling element 311I compared to a planar mirror of outcoupling element <NUM>.

<FIG> illustrates an outcoupling element 311J including a curved mirror <NUM> and a refractive microlens <NUM>. Outcoupling element 311J is configured to outcouple the non-visible light from waveguide <NUM> as non-visible illumination light 313J having divergence angle of θ 381J. Refractive microlens <NUM> may function as the beam-shaping layer to control the divergence of θ 381J and direction of non-visible illumination light 313J.

<FIG> illustrates an example optical element <NUM> including an illumination layer <NUM> having a plurality of outcoupling elements <NUM> distributed across transparent layer <NUM>, in accordance with aspects of the disclosure. <FIG> includes twelve outcoupling elements 411A-<NUM> having corresponding waveguide structures 408A-<NUM>. Each waveguide structure <NUM> is configured to receive non-visible light from a non-visible light source and provide the non-visible light to its respective outcoupling element <NUM>. Each outcoupling element <NUM> is configured to outcouple the received non-visible light as non-visible illumination light to illuminate an eye region. Outcoupling elements 411A-<NUM> are approximately positioned on an outside ring and outcoupling elements <NUM>-<NUM> are approximately positioned on an inside ring. Of course, other arrangements and numbers of outcoupling elements <NUM> are possible in other implementations.

<FIG> illustrates an example one-to-one relationship between non-visible light sources, waveguide structures <NUM>, and outcoupling elements <NUM>. That is, a non-visible light source illuminates a single waveguide structure <NUM> to provide light to a corresponding outcoupling element.

<FIG> illustrates an optical element <NUM> that is configured to receive non-visible light into waveguide structure <NUM> from a single non-visible light source (not illustrated) and waveguide structure <NUM> distributes the non-visible light to a plurality of outcoupling elements <NUM>. <FIG> illustrates an example optical element <NUM> including an illumination layer <NUM> having a plurality of outcoupling elements 511A-<NUM> distributed across transparent layer <NUM>, in accordance with aspects of the disclosure. In the example illustration, the optical path length in waveguide structure <NUM> is roughly the same for each outcoupling element <NUM>. This may homogenize a brightness output of each outcoupling element <NUM>. In other implementations, the optical path lengths from the non-visible light source to the outcoupling elements <NUM> of waveguide structure <NUM> may be adjusted to increase or decrease brightness of a particular outcoupling element <NUM> due to optical losses in waveguide structure <NUM> according to the length of waveguide structure <NUM>. Each outcoupling element <NUM> is configured to outcouple the received non-visible light as non-visible illumination light to illuminate an eye region.

The waveguides described in this disclosure may follow an indirect curving path between a non-visible light source and an outcoupling element. The waveguides may be randomly curved so that, over a variety of viewing angles, any light scattering associated with the waveguides are visually less conspicuous compared to more straight line waveguide paths. Any of the features described in <FIG> may be used in the implementations of optical elements <NUM> and <NUM>. For example, optical fibers may be utilized for waveguide structures <NUM> and <NUM>.

Claim 1:
A head mounted device (<NUM>) comprising:
a frame (<NUM>, <NUM>);
a near-infrared light source (<NUM>, <NUM>) coupled with the frame, wherein the near-infrared light source is configured to emit near-infrared light; and
an optical element secured to the frame, the optical element including:
a transparent layer (<NUM>, <NUM>);
a plurality of outcoupling elements (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) distributed across the transparent layer; and
a transparent waveguide structure (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to receive the near-infrared light from the near-infrared light source coupled with the frame, wherein the transparent waveguide structure is configured to deliver the near-infrared light from the near-infrared light source to the outcoupling elements, wherein the outcoupling elements are configured to outcouple the near-infrared light as near-infrared illumination light to
illuminate an eye region with near-infrared illumination light
characterized in that
said near-infrared illumination light is patterned.