Liquid crystal eyebox guidance in a waveguide eyewear display

Abstract

The disclosure herein presents an eyebox expander for a wearable head mounted display, the eyebox expander including a first liquid crystal layer, an electrode arrangement for applying a voltage to the first liquid crystal layer to change an orientation associated with the first liquid crystal layer, and a compensation layer for redirecting light passing through the eyebox expander based on the change in orientation associated with the first liquid crystal layer.

Description

[Background technology]

[0001] background To provide a satisfying experience for a wide population of users, the eyebox associated with a wearable head mounted display (WHMD) device must be large enough to accommodate the variability in user head shapes. For example, the design of the WHMD must take into account the differences in the distance between the eyes (called interpupillary distance or IPD), head width, ear apex, and nose width among different potential users in the general population. Typically, the width of the eyebox of the WHMD is on the order of at least about 10 mm to accommodate these different head shapes, and the IPD distribution itself can be in the range of ±8 mm, for example, within about two standard deviations of the mean IPD. Conventional waveguide-based WHMDs typically take such distributions into account by sizing the out-coupler grid of the WHMD's waveguide to accommodate different user head sizes. For example, a larger out-coupler size is used to accommodate a wider range of user head shapes. Summary of the Invention [Problem to be solved by the invention]

[0002] However, having one outcoupler size for a wide range of user head shapes reduces efficiency and color uniformity in the projected light that is outcoupled to the user, in addition to manufacturing challenges and increased costs. [Means for solving the problem]

[0003] overview This disclosure describes embodiments of an eyebox expander for a wearable head mounted display (WHMD).

[0004] In one exemplary embodiment, an eyebox expander for a WHMD includes a first liquid crystal layer, an electrode arrangement for applying a voltage to the first liquid crystal layer to change an orientation associated with the first liquid crystal layer, and a compensation layer for redirecting light passing through the eyebox expander based on the change in orientation associated with the first liquid crystal layer.

[0005] In some embodiments, the eyebox expander includes an electrode array including a patterned electrode. In some embodiments, the patterned electrode is disposed between a first electrode and a second electrode. In some embodiments, the first liquid crystal layer is disposed between the patterned electrode and the second electrode. In some embodiments, the second electrode receives light from the first liquid crystal layer and transmits light toward an eyebox associated with the WHMD based on a change in orientation associated with the first liquid crystal layer. In some embodiments, the patterned electrode includes a plurality of electrode sections arranged to form an aperture. In some embodiments, the electrode array applies a first voltage as a plurality of voltages across the plurality of electrode sections of the patterned electrode. In some embodiments, the electrode array is configured to apply the first voltage between the second electrode and the patterned electrode. In some embodiments, a compensation layer is disposed between the first electrode and the patterned electrode. In some embodiments, the compensation layer is a second liquid crystal layer. In some embodiments, the electrode array is configured to apply a second voltage to the second liquid crystal layer based on the first voltage applied to the first liquid crystal layer. In some embodiments, the change in orientation associated with the first liquid crystal layer is based on a condition associated with an eyebox of the WHMD. For example, the condition associated with the eyebox is based on at least one of a variation in interpupillary distance of a user of the WHMD, a variation in eye relief between the WHMD and the user, or a movement of the user's eyes. In some embodiments, light input to the eyebox expander from outside the WHMD (e.g., ambient light) and light output from the eyebox expander toward the user have the same angle within a predetermined margin of difference.

[0006] In another exemplary embodiment, a lens for a WHMD includes a first substrate, a second substrate, and an eyebox expander between the first substrate and the second substrate, the eyebox expander including a first liquid crystal layer, an electrode arrangement for applying a voltage to the first liquid crystal layer to change an orientation associated with the first liquid crystal layer, and a compensation layer for redirecting light passing through the eyebox expander based on the change in orientation associated with the first liquid crystal layer.

[0007] In some embodiments, a lens for a WHMD includes a waveguide including an in-coupler, an exit pupil expander, and an out-coupler, the waveguide being disposed between a first substrate and a second substrate, for example, an eyebox expander is integrated into or partially disposed on each of the in-coupler, the exit pupil expander, and the out-coupler.

[0008] Another exemplary embodiment describes a method of directing a light beam in an eyebox of a wearable head mounted display (WHMD), the method including applying a first voltage to a first liquid crystal layer to change an orientation associated with the first liquid crystal layer to direct a light beam in the eyebox of the WHMD, and applying a second voltage to a second liquid crystal layer to redirect light passing through a lens of the WHMD based on the change in orientation associated with the first liquid crystal layer.

[0009] In some embodiments, the method further includes applying a first voltage in a series of segmented voltages to the first liquid crystal layer via an electrode array including a first electrode, a patterned electrode, and a second electrode. In some embodiments, the first liquid crystal layer is disposed between the patterned electrode and the second electrode, and the second liquid crystal layer is disposed between the first electrode and the patterned electrode, and the first liquid crystal layer is disposed closer to a direction of a user of the WHMD than the second liquid crystal layer.

[0010] The present disclosure may be better understood, and its numerous features and advantages may become apparent to those skilled in the art by referencing the accompanying drawings, in which: The use of the same reference symbols in different drawings refers to similar or identical items. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 illustrates an exemplary display system having a support structure housing a projection system configured to project images toward a user's eyes, according to some embodiments. [Diagram 2] FIG. 2 shows an example block diagram of a projection system that projects light representing an image to a user's eye via a display system, such as the display system of FIG. 1, in accordance with some embodiments. [Diagram 3] FIG. 2 illustrates an example of a WHMD with an eyebox expander, according to some embodiments. [Figure 4] FIG. 1 illustrates an example of a diagram demonstrating eye-box considerations for liquid crystal beam steering, according to some embodiments. [Diagram 5] FIG. 2 illustrates an example of a schematic diagram showing an eyebox expander, according to some embodiments. [Figure 6] FIG. 1 illustrates an example of patterned electrodes in an electrode array of an eyebox expander, according to some embodiments. [Figure 7] 1A-1C show examples of world side and perspective views of an eyebox expander integrated with a waveguide according to some embodiments. [Figure 8] FIG. 13 illustrates an example of the compensation effect of a compensation layer on see-through light from the real world, according to some embodiments. [Figure 9] 1 is a flowchart illustrating a method for an eyebox expander to direct light to an eyebox of a WHMD, according to some embodiments. [Figure 10]11 is a flow chart illustrating a method for an eyebox expander to determine a first voltage and / or a second voltage to apply to a first liquid crystal layer and / or a compensation layer, respectively, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Detailed Description In WHMD design for augmented reality (AR) applications, challenges include sizing the eyebox to accommodate a wide variety of different user head shapes and designing an optical see-through display to effectively guide the projected image to the user while minimizing distortion of the real-world view from the user's viewpoint. Figures 1-10 show techniques for eyebox expansion in a WHMD by directing light rays to a target location, e.g., the user's pupil. In addition, Figures 1-10 show techniques for attenuating the distorting effect of eyebox expansion on the real-world see-through view, such as by using a liquid crystal layer to further direct the light rays. Thus, the techniques described herein provide a WHMD device that provides improved projected image quality while minimizing distortion of the real-world view, thereby improving the overall user experience.

[0013] To illustrate, the lens element of the WHMD includes an eyebox expander. The eyebox expander includes a first liquid crystal layer having a first plurality of crystals. The eyebox expander further includes an electrode array for applying a first voltage to the first liquid crystal layer to change an orientation associated with the first liquid crystal layer based on a condition associated with the eyebox of the WHMD. For example, this includes changing the orientation of the first plurality of liquid crystals. In some embodiments, the applied voltage changes the orientation of the first plurality of crystals to direct a light beam generated at a light source of the WHMD. In some embodiments, the condition associated with the eyebox is a target position corresponding to a detected pupil position of a user of the WHMD. Thus, the change in the orientation of the first plurality of liquid crystals directs the light beam to the target position based on the electrically adjustable properties of the first liquid crystal layer. In some cases, the change in the orientation of the first plurality of crystals can distort see-through light (also called incident light or ambient light) from the real world passing through the lens of the WHMD. To counteract this distortion effect, the eyebox expander also includes a compensation layer. The compensation layer includes, for example, a second liquid crystal layer having a second plurality of liquid crystals. In some embodiments, the electrode array applies a second voltage to the second liquid crystal layer based on the first voltage applied to the first liquid crystal layer, which changes the second plurality of crystals to reduce the distortion effect on the real world light passing through the eyebox expander. In this way, the eyebox expander steers the light beam to a target position and reduces the distortion effect on the real world light caused by the steering of the light beam. The result is a higher projected image quality and a more realistic depiction of the real world scene, thereby improving the overall user experience on multiple levels.

[0014] 1-10 show an embodiment of an exemplary eyebox expander and corresponding technique for eyebox guidance utilizing a liquid crystal layer, thereby providing an expandable eyebox for a WHMD without the need to change or increase the size of the outcoupler grid to accommodate different user head shapes. However, it will be appreciated that the apparatus and techniques of the present disclosure are not limited to implementation in this particular display system, but instead may be implemented in any of a variety of display systems using the guidelines provided herein.

[0015] FIG. 1 illustrates an exemplary display system 100 having a support structure 102 including an arm 104 housing a projection system configured to project an image toward a user's eye such that the user perceives the projected image as being displayed in the display's field of view (FOV) at one or both of the lens elements 108, 110. In the illustrated embodiment, the display system 100 is a WHMD including a support structure 102 configured to be worn on a user's head and having the general shape and appearance of an eyeglass (e.g., sunglasses) frame. The support structure 102 including the lens elements 108, 110 encompasses or otherwise includes various components to facilitate the projection of such images toward the user's eye, such as a laser projector, an optical scanner, a wave guide, and an eyebox expander. In some embodiments, the support structure 102 further includes various sensors, such as one or more front-facing cameras, rear-facing cameras, other optical sensors, motion sensors, accelerometers, etc. In some embodiments, the support structure 102 further includes one or more radio frequency (RF) interfaces or other interfaces, such as a Bluetooth™ interface, a WiFi interface, etc. Additionally, in some embodiments, the support structure 102 further includes one or more batteries or other portable power sources for powering the electrical components of the display system 100. In some embodiments, some or all of these components of the display system 100 are contained completely or partially within an interior volume of the support structure 102, such as within an arm 104 in region 112 of the support structure 102. It should be noted that while an exemplary form factor is shown, it will be appreciated that in other embodiments, the display system 100 may have a different shape and appearance than the eyeglass frames shown in FIG.

[0016] One or both of the lens elements 108, 110 may be used by the display system 100 to provide an augmented reality (AR) display, in which rendered graphical content may be superimposed on or otherwise provided in relation to a real-world view perceived by a user through the lens elements 108, 110. For example, a projected light beam used to form a perceivable image or series of images may be projected by a laser projector of the display system 100 to a user's eye via a series of optical elements, such as a waveguide, one or more scanning mirrors, one or more optical relays, and an eyebox expander, formed at least partially in a corresponding lens element. Thus, one or both of the lens elements 108, 110 may include at least a portion of a waveguide that transmits display light received by a waveguide in-coupler to a waveguide out-coupler that outputs the display light toward the eye of a user of the display system 100. The display light is modulated and scanned toward the user's eye such that the user perceives the display light as an image. In addition, each of the lens elements 108, 110 is sufficiently transparent to allow a user to see through the lens element, thereby providing a view of the user's real-world environment, such that the image appears superimposed on at least a portion of the real-world environment. In some embodiments, the lens elements 108, 110 include an eyebox expander for redirecting projected light rays from the projector to a target location, e.g., the user's pupil. Furthermore, in some embodiments, the eyebox expander is configured to reduce distortion effects in the real-world view resulting from redirecting the projected light rays, as described further herein.

[0017] In some embodiments, the projector is a digital light processing projector, a scanning laser projector, or any combination of a modulating light source, such as a laser or one or more LEDs, and a dynamic reflector mechanism, such as one or more dynamic scanners or digital light processors. In some embodiments, the projector includes multiple laser diodes (e.g., red, green, and / or blue laser diodes) and at least one scanning mirror (e.g., two one-dimensional scanning mirrors, which may be microelectromechanical systems (MEMS) or piezoelectric). The projector is communicatively coupled to a controller and a non-transitory processor-readable storage medium or memory that stores processor-executable instructions and other data that, when executed by the controller, cause the controller to control the operation of the projector. In some embodiments, the controller is communicatively coupled to a processor (not shown) that controls the scan area size and scan area position for the projector and generates the content displayed on the display system 100. The projector scans light over a variable area, a specified FOV area 106, of the display system 100. The scan area size corresponds to the size of the FOV area 106, and the scan area position corresponds to the region of one of the lens elements 108, 110 where the FOV area 106 is visible to the user. In general, it is desirable for a display to have a wide FOV to accommodate outcoupling of light over a wide range of angles. The range of different user eye positions from which the display can be viewed is referred to herein as the eyebox of the display.

[0018] In some embodiments, the projector directs light through the first and second scan mirrors, an optical relay disposed between the first and second scan mirrors, and a waveguide disposed at the output of the second scan mirror. In some embodiments, at least a portion of the waveguide outcoupler may overlap the FOV area 106.

[0019] 2 shows a simplified block diagram of a projection system 200 that projects an image directly to a user's eye via laser light. The projection system 200 includes an optical engine 202, an optical scanner 204, and a waveguide 205. As shown, the optical scanner 204 includes a first scan mirror 206, a second scan mirror 208, and an optical relay 210. The waveguide 205 includes an in-coupler 212 and an out-coupler 214, which in this example is optically aligned with a user's eye 216. In some embodiments, the projection system 200 is implemented in a WHMD or other display, such as the display system 100 of FIG. 1.

[0020] In some embodiments, the optical engine 202 includes one or more laser light sources configured to generate and output laser light 218 (e.g., visible laser light, such as red, blue, and green laser light, and / or non-visible laser light, such as infrared laser light). In some embodiments, the optical engine 202 is coupled to a driver or other control device (not shown) that controls the timing of emission of laser light from the laser light sources of the optical engine 202 according to instructions received by the controller or driver from a computer processor coupled to the controller or driver, to modulate the laser light 218 so as to be perceived as an image when output to the retina of a user's eye 216.

[0021] For example, during operation of the projection system 200, multiple laser beams, each having a different wavelength, are output by the laser light sources of the optical engine 202 and then combined via a beam combiner (not shown) before being directed towards the user's eye 216. The optical engine 202 modulates the intensity of each of the laser beams such that the combined laser beams reflect a series of pixels of an image, with the particular intensity of each laser beam at any given time contributing to a corresponding amount of color content and brightness in the pixel represented by the combined laser beams at that time.

[0022] One or both of the scan mirrors 206 and 208 of the optical scanner 204 are MEMS mirrors in some embodiments. For example, the scan mirrors 206 and 208 are MEMS mirrors driven by respective actuation voltages to oscillate during active operation of the laser projection system 200, causing the scan mirrors 206 and 208 to scan the laser light 218. The oscillation of the scan mirror 206 causes the laser light 218 output by the optical engine 202 to pass through the optical relay 210 and to be scanned across the surface of the second scan mirror 208. The second scan mirror 208 scans the laser light 218 received from the scan mirror 206 toward the incoupler 212 of the waveguide 205. In some embodiments, the scan mirror 206 oscillates along a first scanning axis 219, which causes the laser light 218 to be scanned only in one dimension (i.e., in a line) across the surface of the second scan mirror 208. In some embodiments, the scan mirror 208 oscillates or otherwise rotates along the second scanning axis 221. In some embodiments, the first scanning axis 219 is perpendicular to the second scanning axis 221.

[0023] In some embodiments, the incoupler 212 has a substantially rectangular profile and is configured to receive the laser light 218 and direct the laser light 218 into the waveguide 205. The incoupler 212 is defined by a smaller dimension (i.e., width) and a larger orthogonal dimension (i.e., length). In one embodiment, the optical relay 210 is a line-scan optical relay that receives the laser light 218 scanned in a first dimension by the first scan mirror 206 (e.g., the first dimension corresponds to the smaller dimension of the incoupler 212), sends the laser light 218 to the second scan mirror 208, and introduces a convergence of the laser light 218 in the first dimension beyond the second scan mirror 208 to an exit pupil. Here, "exit pupil" in an optical system refers to a location along an optical path where light rays intersect. For example, following reflection from the first scan mirror 206, the possible optical paths of the laser light 218 initially diverge along the first scanning axis, but later these paths cross the second scan mirror 208 at the exit pupil due to the focusing introduced by the optical relay 210. For example, the width (i.e., smallest dimension) of a given exit pupil corresponds approximately to the diameter of the laser light corresponding to that exit pupil. Thus, the exit pupil can be considered a "virtual aperture." According to various embodiments, the optical relay 210 includes one or more collimation lenses that shape and focus the laser light 218 at the second scan mirror 208, or includes a shaped reflecting relay that includes two or more spherical, aspheric, parabolic, and / or freeform lenses that shape and direct the laser light 218 to the second scan mirror 208. The second scan mirror 208 receives the laser light 218 and scans the laser light 218 in a second dimension, which corresponds to the long dimension of the incoupler 212 of the waveguide 205. In some embodiments, the second scan mirror 208 causes the exit pupil of the laser light 218 to be swept along a line along the second dimension. In some embodiments, the incoupler 212 is positioned at or near the swept line downstream of the second scan mirror 208, such that the second scan mirror 208 scans the laser light 218 as a line or row over the incoupler 212.

[0024] In some embodiments, the optical engine 202 includes an edge-emitting laser (EEL) that emits laser light 218 having a substantially elliptical, non-circular cross-section, and the optical relay 210 expands or minimizes the laser light 218 along its semimajor or semiminor axis of orbit and circularizes the laser light 218 prior to focusing of the laser light 218 at the second scan mirror 208. In some such embodiments, the surface of the mirror plate of the scan mirror 206 is elliptical and non-circular (e.g., similar in shape and size to the cross-sectional area of ​​the laser light 218). In other such embodiments, the surface of the mirror plate of the scan mirror 206 is circular.

[0025] The waveguide 205 of the laser projection system 200 includes an in-coupler 212 and an out-coupler 214. As used herein, the term "waveguide" is understood to mean a coupler that uses one or more of total internal reflection (TIR), special filters, and / or reflective surfaces to transmit light from an in-coupler (such as in-coupler 212) to an out-coupler (such as out-coupler 214). In some display applications, the light is a collimated image, and the waveguide transmits and replicates the collimated image to the eye. In general, the terms "in-coupler" and "out-coupler" are understood to mean any type of optical grating structure, including, but not limited to, a diffraction grating, a hologram, a holographic optical element (e.g., an optical element that uses one or more holograms), a volume diffraction grating, a volume hologram, a surface relief diffraction grating, and / or a surface relief hologram. In some embodiments, a given in- or out-coupler is configured as a transmission grating (e.g., a transmission grating or a transmission holographic grating) that causes the in- or out-coupler to transmit light and apply a designed optical function to the light during transmission. In some embodiments, a given in- or out-coupler is a reflection grating (e.g., a reflection grating or a reflection holographic grating) that causes the in- or out-coupler to reflect light and apply a designed optical function to the light during reflection. In this example, the laser light 218 received at the in-coupler 212 is relayed to the out-coupler 214 via a waveguide 205 using TIR. The laser light 218 is then output to the user's eye 216 via the out-coupler 214. As described above, in some embodiments, the waveguide 205 is implemented as part of a spectacle lens, such as the lens 108 or the lens 110 (FIG. 1) of a display system having a spectacle form factor and employing the laser projection system 200.

[0026] 2, in some embodiments, additional optical components are included in the optical path between the optical engine 202 and the scan mirror 206, between the scan mirror 206 and the optical relay 210, between the optical relay 210 and the scan mirror 208, between the scan mirror 208 and the incoupler 212, between the incoupler 212 and the outcoupler 214, and / or between the outcoupler 214 and the eye 216 (e.g., to shape the laser light for viewing by the user's eye 216). In some embodiments, a prism is used to direct the light from the scan mirror 208 to the incoupler 212, so that the light is coupled into the incoupler 212 at the proper angle to facilitate propagation of the light in the waveguide 205 by TIR. Also, in some embodiments, an exit pupil expander (EPE), such as a fold grating, is positioned at an intermediate stage between the in-coupler 212 and the out-coupler 214 to receive the light coupled into the waveguide 205 by the in-coupler 212, expand the light, and redirect the light towards the out-coupler 214, which then couples the laser light from the waveguide 205 (e.g., towards the user's eye 216).

[0027] In some embodiments, the projection system 200 also includes an eyebox expander (not shown) that at least partially overlaps the waveguide 205 or is integrated within the waveguide 205. For example, the eyebox expander includes a first liquid crystal layer, an electrode array, and a compensation layer that at least partially overlaps each of the in-coupler 212, the out-coupler 214, and the EPE of the waveguide 205. The eyebox expander directs light rays generated by the projection system 200 to a target location, such as the user's eye 216. Additionally, the eyebox expander directs light rays from the real world that pass through the waveguide 205 to a target location, such as the user's eye 216.

[0028] Figure 3 shows a portion of a WHMD 300 that includes a projection system, such as projection system 200 described above in Figure 2. In some embodiments, WHMD 300 represents display system 100 of Figure 1. Optical engine 202, optical scanner 204, incoupler 212, and a portion of waveguide 205 are included in arm 302 of WHMD 300, in this example.

[0029] The WHMD 300 includes an optical coupler lens 304 including a first substrate 306, a second substrate 308, and a waveguide 205 disposed between the first substrate 306 and the second substrate 308. The projected light 318 emerging through the out-coupler 214 passes through the second substrate 308 (e.g., corresponding to the lens element 100 of the display system 100). In use, the projected light 318 emerging from the second substrate 308 enters the pupil of the eye 216 of a user wearing the WHMD 300, causing the user to perceive a displayed image conveyed by the laser light output by the optical engine 202. The optical combiner lens 304 is substantially transparent such that light 320 (also referred to as incident light or ambient light) from a real-world scene corresponding to the environment surrounding the WHMD 300 passes through the first substrate 306, the second substrate 308, and the waveguide 205 to the user's eye 216. In this manner, an image or other graphical content output by the projection system 200 is combined (e.g., overlaid) with the real-world image of the user's environment when projected to the user's eye 216 to provide the user with an AP experience.

[0030] In some embodiments, the eyebox expander 330 (described in further detail below) at least partially overlaps or is integrated with the waveguide 205. For example, typically, the eyebox expander 330 is disposed between the first substrate 306 and the second substrate 308 of the optical combiner lens 304. The eyebox expander 330 includes a first liquid crystal layer that achieves a "prismatic" phase based on a first applied voltage to direct light rays to an eyebox corresponding to the WHMD 300 on demand, e.g., based on a detected position of the pupil of the user's eye 216. The first applied voltage, in other words, changes the orientation of a first plurality of liquid crystals in the first liquid crystal layer, and the change in orientation directs the light rays to a target position. In some embodiments, the eyebox expander 330 further includes a compensation layer, which counteracts the distortion effect on the light 320 from the real-world scene caused by the change in the orientation of the first plurality of liquid crystals in the first liquid crystal layer. For example, the compensation layer is a second liquid crystal layer to which a second voltage is applied to change the orientation of the second plurality of liquid crystals disposed in the second liquid crystal layer. Thus, the eyebox expander 330 further includes an electrode arrangement for applying the first and second voltages to the first liquid crystal layer and the compensation layer, respectively.

[0031] 4 shows an example diagram 400 demonstrating eyebox considerations for liquid crystal beam steering. In some embodiments, the projection system 402 corresponds to the projection system 200 of the WHMD shown in the previous figure. Two eyeboxes 404 are shown, each corresponding to a volume in which the projection system 402 can display an image to a user. In addition, two exemplary pupil positions 406 are shown.

[0032] As shown in FIG. 400, the projection system 402 projects light, for example from an out-coupler, in the form of a radiation cone to the eyebox 404. Generally speaking, the eyebox is a volume in front of the display where the display content can be observed with a relatively small amount of distortion or other visual artifacts. For example, outside the eyebox, the display content may be distorted or the colors may be inaccurately displayed. Although shown as a two-dimensional box for clarity, the eyebox can also be described as a cone-shaped three-dimensional volume that becomes thinner as the distance to the projection system 402 increases. In some embodiments, the etendue of the radiation cone is matched to, for example, a 10 mm pupil and a 10×10 degree field. Furthermore, in some embodiments, there is a continuous number of steering states of the projection system 402, for example, with steering angles ranging from ±15 degrees. The eye relief 412 (the distance from the projection system 402 to the pupil position 402) and the IPD distance 414 are also shown in FIG. 400. Thus, the eyebox 404 for a WHMD display can be defined as a function of a number of variables, including eye relief 412, IPD distance 414, other user head shape variables (e.g., ear tip, nose width), and the area of ​​the out-coupler in the projection system 402.

[0033] The techniques described herein allow a projection system of a WHMD, such as that shown in the previous figures, to direct light rays in a manner that expands the size of the eyebox associated with the WHMD, thereby enabling the WHMD to effectively display images to a wider range of users. Thus, smaller outcoupler sizes can be used to outcouple images to display light to a wider eyebox range, thereby allowing increased efficiency and color uniformity for a broad user base while reducing manufacturing costs.

[0034] Figure 5 shows a cross-sectional view of a schematic diagram of an eyebox expander 500 according to some embodiments. In some embodiments, the eyebox expander 500 corresponds to the eyebox expander 330 of Figure 3. As shown in Figure 5, the positive z-direction points in the direction of the eyebox corresponding to the user's eyes 216.

[0035] In some embodiments, the eyebox expander 500 includes a first liquid crystal layer 502 and a compensation layer 504. The first liquid crystal layer 502 includes a first plurality of liquid crystals. For example, the first plurality of liquid crystals is a first set of nematic liquid crystals. The compensation layer 504, in some embodiments, is a second liquid crystal layer including a second plurality of liquid crystals, for example a second set of nematic liquid crystals. In some embodiments, the liquid crystals in the first plurality of liquid crystals are of the same type as those in the second plurality of liquid crystals. In other embodiments, the types of liquid crystals are different. In some embodiments, each of the first liquid crystal layer 502 and the compensation layer 504 is at least partially optically transparent to allow light rays to pass through.

[0036] In some embodiments, the eyebox expander 500 includes an electrode array 510 including a first electrode 512, a patterned electrode 514, and a second electrode 516. Each of the electrodes in the electrode array 510 is formed from an at least partially optically transparent material to pass light. In addition, each of the electrodes in the electrode array 510 is formed from an at least partially conductive material to apply a first voltage to the first liquid crystal layer 504 and / or a second voltage to the compensation layer 504. For example, in some embodiments, each of the first electrode 512, the patterned electrode 514, and the second electrode 516 in the electrode array is formed from an at least partially optically transparent metal oxide, such as a transparent conductive oxide film.

[0037] 5, the first liquid crystal layer 502, in some embodiments, is disposed between a patterned electrode 514 and a second electrode 516. The compensation layer 504, in some embodiments, is disposed between the first electrode 512 and the patterned electrode 514.

[0038] In some embodiments, the electrode array 510 is coupled to a controller 560. The controller 560 is configured to control voltages across different electrodes in the electrode array 510. For example, a first power supply 532 is disposed between the patterned electrode 514 and the second electrode 516. In some embodiments, a second power supply 534 is disposed between the first electrode 512 and the second electrode 516. The controller 560 is configured to control one or both of the first power supply 532 and the second power supply 534 to vary the voltages applied to the first liquid crystal 502 and / or the compensation layer 504, respectively. In this manner, the controller 560 controls the voltages applied to each of the first liquid crystal layer 502 and the compensation layer 504 to change their respective structures to affect the manner in which light passes through the respective layers. For example, a first voltage is applied via the first power supply 532 to change the orientation of a first plurality of crystals in the first liquid crystal layer 502 to direct a light beam, e.g., output light 554, towards a target location, such as a detected pupil of the user's eye 216. Based on the first voltage, the controller 560 is further configured in some embodiments to apply a second voltage via the second power supply 534 to the compensation layer 504 to change a structure of the compensation layer 504 and redirect light passing through the compensation layer 504. For example, where the compensation layer 504 is a second liquid crystal layer, this may include changing the orientation of the crystals in the second liquid crystal layer.

[0039] In some embodiments, the second voltage depends on a first voltage applied by the controller 560. For example, the first voltage is based on a condition associated with an eyebox corresponding to the eyebox expander 500. The condition is, for example, a detected position of a pupil of the user's eye 216. The controller 506, in some embodiments, includes a processing circuit that includes or is communicatively coupled to a memory that stores a look-up table (LUT) having entries for different positions and a first voltage corresponding to each of the different positions. For example, the different positions include (x,y) coordinates corresponding to the position of the detected pupil of the user's eye 216. Thus, the LUT stores entries for different possible positions of the pupil in the eyebox associated with the eyebox expander 500. Each position entry in the LUT includes a corresponding first voltage for changing the orientation of the first plurality of liquid crystals in the first liquid crystal layer 502 to direct light rays to the respective position. In some embodiments, the LUT also includes information for a second voltage that depends on the first voltage. For example, if the first voltage is zero, the second voltage may also be zero. If the first voltage is a first voltage value, the second voltage may be a second voltage value different from the first voltage value. In some embodiments, the second voltage is a predetermined amount based on the first voltage to change the structure of the compensation layer 504 to reduce the effect of the first liquid crystal layer 502 on light passing through the eyebox expander 500 (described in further detail in FIG. 9). An exemplary LUT is shown below in Table 1. In some embodiments, the number of entries is expandable to provide the eyebox expander 500 with complete coverage covering a wide range of possible target positions in the eyebox corresponding to the eyebox expander 500.

[0040] [Table 1]

[0041] In some embodiments, the eyebox expander 500 implements the following technique for directing light rays to a target location, such as the pupil of the user's eye 216. First, a target location is determined. For example, the target location is determined utilizing eye tracking hardware and / or software in a WHMD, e.g., WHMD 300. The target location is then sent to the controller 560, which looks up the target location coordinates from a LUT, such as those shown above in Table 1. Based on the set of target location coordinates in the LUT that best correlates with the detected target location, a first voltage is retrieved from the corresponding LUT entry. This first voltage is applied to the first liquid crystal layer 502 via the first power supply 532, causing an orientation change of the first plurality of liquid crystals in the first liquid crystal layer 502. A corresponding second voltage is then retrieved from the LUT. The second voltage is applied to the compensation layer 504 via the second power supply 534, causing a change in the structure of the compensation layer 504, e.g., by changing the orientation of the liquid crystals in the compensation layer 504.

[0042] Thus, when incident (or ambient) light 552 enters the eyebox expander 500, the light 552 passes through the first electrode 512, is redirected by the compensation layer 504 based on a second voltage applied to the compensation layer 504 by the second power supply 534, passes through the patterned electrode 514, and then is redirected by the first liquid crystal layer 502 towards the target position based on the first voltage applied by the first power supply 532 before finally exiting the eyebox expander 500 through the second electrode 516.

[0043] In some embodiments, the first voltage applied by the electrode array 510 to the first liquid crystal layer 502 includes multiple voltages applied by patterned electrodes 514. Application of the multiple voltages to the first liquid crystal layer 502 causes the first multiple liquid crystals to change orientation, thereby modulating light passing through the first liquid crystal layer 502 and converting the light into a wavefront of output light 554. In other words, the output light 554 exhibits modulated, electrically adjustable focusing and beam steering properties.

[0044] FIG. 6 illustrates a word side view of the patterned electrode 514. As shown, the patterned electrode 514 includes a plurality of geometric segments 602 (one shown for clarity) forming an aperture 604 in the center, and a voltage can be applied to each of the plurality of different geometric segments 602 individually. The size of the aperture 604 is, for example, in the range of about 5 mm to 20 mm in diameter, e.g., about 10 mm. In this example, the patterned electrode 514 includes four geometric segments 602 forming a circular aperture 604. However, the four geometric segments 602 shown in FIG. 4 are an exemplary configuration, and other quantities (e.g., five or more) and other shapes for the geometric segments 602 are similarly contemplated. By applying a voltage (e.g., V1-V4) to the first liquid crystal layer via the plurality of geometric segments 602, the patterned electrode 514 changes the orientation of the plurality of first liquid crystals in the first liquid crystal layer, effectively directing an output light beam. Thus, an eyebox expander including patterned electrodes 514 can expand the eyebox by directing a beam to a target location, such as a location corresponding to a detected pupil of a user.

[0045] 7 shows a first view 700 and a second view 750 of a waveguide 702 with an integrated eyebox expander according to some embodiments. The first view 700 corresponds to a world side view and the second view 750 corresponds to a perspective view with a partial view of a user's eye 752.

[0046] In some embodiments, the eyebox expander is fully integrated into the waveguide 702 with a set of three gratings: in-coupler (IC) 714, exit pupil expander (EPE) 712, and out-coupler (OC) 710. The orientation and period of these three gratings are designed such that the photon K vector sums to zero. Applying the eyebox expander across the entire waveguide as shown in FIG. 8 provides uniformity to the incoming (or ambient) light from the real world passing through the lenses of the WHMD, thereby providing a more accurate view of the real world and enhancing the overall user experience.

[0047] 8 shows a schematic plan view of an eyebox expander 800 demonstrating the compensation effect on see-through light from a real-world scene according to some embodiments. In some embodiments, the eyebox expander 800 corresponds to the eyebox expander 300 in FIG. 3, the eyebox expander 500 in FIG. 5, and / or the integrated eyebox expander described with respect to FIG. 7. For clarity and this description, the first liquid crystal layer 802 and the compensation layer 804 are featured in the following description, although it will be appreciated that in some embodiments the eyebox expander includes other components, such as the electrode array described in FIG. 5.

[0048] In some embodiments, the first liquid crystal layer 802 includes a first plurality of crystals 802a (one shown for clarity) and the compensation layer 804 includes a second plurality of crystals 804a (one shown for clarity). The orientation of the plurality of crystals 802a in the first liquid crystal layer 802 is changed by application of a first voltage (V1) 822 via an electrode array (not shown). Based on the application of the first voltage (V1) 822 to the first liquid crystal layer 802, the electrode array applies a second voltage (V2) 824 to the compensation layer 804, changing the orientation of the second plurality of crystals 804a. In this way, the eyebox expander can direct light to a target location 830, such as a detected pupil of a user, while improving distortion effects on light passing through the eyebox expander.

[0049] To illustrate, input beam 810 represents a ray of light from an external real-world scene received by eyebox expander 800. Input beam 810 first passes through compensation layer 804, which includes a second plurality of liquid crystals 804a. Upon passing through compensation layer 804, input ray 810 is directed in a direction corresponding to ray 812. The ray then impinges on die 1 liquid crystal layer 802, which includes a first plurality of liquid crystals 802a. Upon passing through first liquid crystal layer 802, ray 812 is redirected in a direction corresponding to ray 814. Upon exiting first liquid crystal layer 802, the ray is redirected in a direction corresponding to output ray 820. In this manner, compensation layer 804 ensures that the angle of output ray 820 and the angle of input ray 810 are the same or within a predetermined margin of difference compared to when eyebox expander 800 does not include compensation layer 804. This margin of difference is, for example, an acceptable margin of difference such that the effect of eyebox expander 800 on see-through light resulting from a real-world scene is not apparent to a user. For example, this acceptable margin of difference between input beam 810 and output beam 820 is approximately 0.33 diopters.

[0050] Thus, the compensation layer 804 counteracts the subsequent effect the first liquid crystal layer 802 has on the see-through light by changing the orientation of the second plurality of liquid crystals 804a based on the change in the first plurality of crystals 802a in the first liquid crystal layer 802. For example, the eyebox expander applies a second voltage (V2) 824 to the compensation layer 804 based on a first voltage (V1) 822 applied to the first liquid crystal layer 802. Thus, the input beam 810 and the output beam 820 have substantially the same angle (i.e., points in the same direction), providing a more accurate depiction of the real world to the user, thereby improving the overall user experience.

[0051] 9 shows a flow chart 900 detailing a method for an eyebox expander to direct light rays in an eyebox of a WHMD housing the eyebox expander. At 902, the method includes applying a first voltage to a first liquid crystal layer of the eyebox expander to change an orientation associated with the first liquid crystal layer to direct light rays in the eyebox of the WHMD. For example, the change associated with the first liquid crystal layer includes changing an orientation of a first plurality of crystals in the first liquid crystal layer. At 1004, the method includes applying a second voltage to a second liquid crystal layer of the eyebox expander based on the change in orientation associated with the first liquid crystal layer to redirect light passing through the eyebox expander.

[0052] For example, an eyebox expander in a WHMD performs step 902 in response to determining that a pupil of a user's eye has moved from a first position to a second position. The eyebox expander applies a voltage to a first liquid crystal layer via an electrode array to change the orientation of liquid crystals in the first liquid crystal layer and direct light from the first position to the second position. Thus, the WHMD displays an image adjusted based on the movement and / or rotation of the user's eyes. In addition, the eyebox expander performs step 904 to redirect light passing through the eyebox expander (e.g., light originating from a real-world scene outside the WHMD) based on the change in orientation of the first plurality of crystals in step 902.

[0053] FIG. 10 shows a flow chart 1000 detailing a method for an eyebox expander to determine a first voltage and / or a second voltage to apply to a first liquid crystal layer and / or a compensation layer, respectively. At 1002, the method includes identifying a target position. The target position corresponds, for example, to a detected pupil position to which the eyebox expander dynamically directs light. In some embodiments, the target position is detected utilizing eye tracking hardware and / or software in the WHMD. In some embodiments, the target position is detected by a component separate from the eyebox expander (e.g., where the eye tracking feature is part of a separate processing component of the WHMD) and then communicated to the eyebox expander. At 1004, the method looks up a target position coordinate corresponding to the identified target position. For example, a LUT table storing multiple entries of target position coordinates is utilized, and the entry having the closest target position coordinate to the identified target position is used. In some embodiments, two target position coordinates are used to linearly interpolate data for the identified target position. At 1006, the method includes retrieving the first voltage and / or the second voltage. For example, the first voltage and / or the second voltage are retrieved from the LUT at an entry corresponding to the respective target position coordinate from 1004. The first voltage is a voltage applied to the first liquid crystal layer, and the second voltage is a voltage applied to the compensation layer based on the first voltage applied to the first liquid crystal layer. At 1008, the method includes applying one or both of the first voltage or the second voltage to the first liquid crystal layer and / or the compensation layer via an electrode arrangement, such as electrode arrangement 510 in FIG. 5. In some embodiments, if the first voltage and / or the second voltage are zero, this includes removing any voltage applied to the first liquid crystal layer and / or the compensation layer.

[0054] In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system executing software. The software includes one or more sets of executable instructions stored or otherwise tangibly embodied in a non-transitory computer-readable storage medium. The software may include instructions and data that, when executed by one or more processors, operate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer-readable storage medium may include, for example, magnetic or optical disk storage, solid-state storage, such as flash memory, cache, random access memory (RAM), or one or more other non-volatile memory devices. The executable instructions stored on the non-transitory computer-readable storage medium may be source code, assembly language code, object code, or other instruction formats that are interpreted or otherwise executable by one or more processors.

[0055] A computer-readable storage medium may include any storage medium, or combination of storage media, accessible by a computer system during use to provide instructions and / or data to the computer system. Such storage media may include, but are not limited to, optical media (e.g., compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs), magnetic media (e.g., floppy disks, magnetic tapes, or magnetic hard drives), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (read-only memory (ROM) or flash memory), or microelectromechanical system (MEMS)-based storage media. A computer-readable storage medium may be embedded in a computing system (e.g., system RAM or ROM), fixedly attached to a computing system (e.g., magnetic hard drives), removably attached to a computing system (e.g., optical disks or Universal Serial Bus (USB)-based flash memory), or coupled to a computer system via a wired or wireless network (e.g., network-accessible storage (NAS)).

[0056] It should be noted that not all of the operations or elements described above in the summary are required, some of the specific operations or devices may not be required, and one or more additional operations may be performed or elements may be included in addition to those described. Furthermore, the order in which the operations are listed is not necessarily the order in which they are performed. Also, the concepts have been described with reference to specific embodiments. However, those skilled in the art will recognize that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the appended claims. Thus, the specification and drawings should be regarded in an illustrative rather than restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0057] Benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, the benefits, advantages, solutions to problems, any benefits, and any features that may cause or make the advantages or solutions more prominent should not be construed as critical, necessary, or essential features of any or all claims. Moreover, the specific embodiments disclosed above are exemplary only, as the disclosed subject matter may be modified and embodied in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to the details of construction or design shown herein, other than as set forth in the appended claims. It is therefore apparent that the specific embodiments disclosed above may be altered or modified, and all such variations are considered to be within the scope of the disclosed subject matter. The protection sought herein is therefore set forth in the appended claims.

Claims

1. 1. An eyebox expander for a wearable head mounted display (WHMD), comprising: a first liquid crystal layer; an electrode array for applying a first voltage to the first liquid crystal layer to change an orientation associated with the first liquid crystal layer based on at least one of variations in interpupillary distance of a user of the WHMD, variations in distance between the WHMD and the user's pupil, or eye movement of the user; a compensation layer for redirecting light passing through the eyebox expander based on the change in orientation associated with the first liquid crystal layer.

2. The eyebox expander of claim 1 , wherein the electrode array comprises patterned electrodes.

3. the electrode array includes a first electrode and a second electrode; The eyebox expander of claim 2 , wherein the patterned electrode is disposed between the first electrode and the second electrode.

4. 4. The eyebox expander of claim 3, wherein the first liquid crystal layer is disposed between the patterned electrode and the second electrode.

5. 4. The eyebox expander of claim 3, wherein the second electrode receives light from the first liquid crystal layer and transmits light toward an eyebox associated with the WHMD based on the change in orientation associated with the first liquid crystal layer.

6. The eyebox expander of claim 2 , wherein the patterned electrode includes a plurality of electrode sections arranged to form an aperture.

7. The eyebox expander of claim 6 , wherein the electrode array applies the first voltage as multiple voltages across the multiple electrode sections of the patterned electrode.

8. The eyebox expander of claim 3 , wherein the electrode array is configured to apply the first voltage between the second electrode and the patterned electrode.

9. The eyebox expander of claim 3 , wherein the compensation layer is disposed between the first electrode and the patterned electrode.

10. The eyebox expander of claim 1 , wherein the compensation layer is a second liquid crystal layer.

11. 11. The eyebox expander of claim 10, wherein the electrode array is configured to apply a second voltage to the second liquid crystal layer based on the first voltage applied to the first liquid crystal layer.

12. An eyebox expander as described in any one of claims 1 to 11, wherein light input to the eyebox expander from outside the WHMD and light output from the eyebox expander toward the user have the same angle within a predetermined margin of difference.

13. 1. A lens for a wearable head mounted display (WHMD), comprising: a first substrate; a second substrate; an eyebox expander between the first substrate and the second substrate; The eyebox expander comprises: a first liquid crystal layer; an electrode array for applying a voltage to the first liquid crystal layer to change an orientation associated with the first liquid crystal layer based on at least one of variations in interpupillary distance of a user of the WHMD, variations in distance between the WHMD and the user's pupil, or eye movement of the user; a compensation layer for redirecting light passing through the eyebox expander based on the change in orientation associated with the first liquid crystal layer.

14. 14. The lens of claim 13, further comprising a waveguide including an in-coupler, an exit pupil expander, and an out-coupler, the waveguide being disposed between the first substrate and the second substrate.

15. 15. The lens of claim 14, wherein the eyebox expander is integral with or partially disposed on each of the in-coupler, the exit pupil expander, and the out-coupler.

16. 1. A method for directing light rays in an eyebox of a wearable head mounted display (WHMD), the method comprising: applying a first voltage to a first liquid crystal layer to change an orientation associated with the first liquid crystal layer and direct a light beam in an eyebox of the WHMD; applying a second voltage to a second liquid crystal layer to redirect light passing through a lens of the WHMD based on the change in orientation associated with the first liquid crystal layer; The change in orientation relative to the first liquid crystal layer comprises: The method is based on at least one of the following: variation in interpupillary distance of a user of the WHMD, variation in distance between the WHMD and the user's pupils, or eye movements of the user.

17. 17. The method of claim 16, further comprising applying the first voltage in a series of segmented voltages to the first liquid crystal layer via an electrode array including a first electrode, a patterned electrode, and a second electrode.

18. 18. The method of claim 17, wherein the first liquid crystal layer is disposed between the patterned electrode and the second electrode, the second liquid crystal layer is disposed between the first electrode and the patterned electrode, and the first liquid crystal layer is disposed closer to a direction of a user of the WHMD than the second liquid crystal layer.

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