Waveguide with dynamically addressable diffractive optical element

Abstract

A waveguide includes a waveguide body including an optically transmissive material having a different refractive index than a surrounding medium and defining an output surface. The waveguide body is configured to propagate light by total internal reflection in one or more directions substantially tangential to the output surface. The waveguide includes one or more diffractive optical elements (DOEs), each DOE configured to vary its diffraction efficiency in response to a respective excitation, and a DOE driver configured to independently provide excitation to each of the DOEs.

Description

[0001] Priority Claim

[0002] This application claims the benefit of priority to U.S. Provisional Application Serial No. 63 / 354,821 filed on June 23, 2022 and U.S. Patent Application Serial No. 18 / 305,953 filed on April 24, 2023, each of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to optical structures, and more particularly to waveguides having input and output diffractive optical elements (eg, diffraction gratings). Background Art

[0004] Diffractive optical elements (DOEs), such as diffraction gratings, operate by diffracting light and are used to control the intensity and direction of light when it interacts with the DOE, which is a structure whose size is approximately the wavelength of the light of interest. A typical augmented reality (AR) device includes a waveguide having an input coupler (IC) and an output coupler (OC) formed on the waveguide, each of the IC and the OC being a DOE. A light source (such as a projector or a microdisplay) transmits light to the IC, which diffracts the light at a certain angle within the waveguide so that the light propagates within the waveguide by total internal reflection (TIR). When the light propagating in the waveguide is incident on the output coupler (OC), the light diffracts out of the waveguide and is emitted toward the eyes of a viewer or user of the AR device. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] In the drawings, which are not necessarily drawn to scale, similar reference numerals may describe similar components in different views. To easily identify the discussion of any particular element or action, the highest digit or digits in the reference numeral refer to the figure number in which the element is first introduced. Some non-limiting examples are shown in the figures of the accompanying drawings, in which:

[0006] Figure 1 A cross-sectional view of light entering and reflecting within a waveguide having an input DOE and an output DOE is shown according to some examples.

[0007] Figure 2 A cross-sectional view of light entering and reflecting within a waveguide having an input DOE and multiple output DOEs is shown according to some examples.

[0008] Figure 3 is a block diagram of a waveguide with a controller, a DOE driver, and multiple dynamically addressable output DOEs according to some examples.

[0009] Figure 4A perspective view of a waveguide with multiple folded DOEs and multiple output DOEs is shown according to some examples.

[0010] Figure 5 According to some examples Figure 4 Figure 2. Waveguide showing a single output DOE with a folded DOE and an output DOE being energized to direct light toward the position of the eye.

[0011] Figure 6 According to some examples Figure 4 A waveguide showing a set of multiple output DOEs where the folded DOE and the output DOE are activated to direct light toward the eye.

[0012] Figure 7 A perspective view of a waveguide having multiple adjacent fold DOEs and multiple adjacent output DOEs is shown according to some examples.

[0013] Figure 8 A cross-sectional view of light entering and reflecting within a waveguide having multiple stacked color-specific input DOEs and multiple stacked color-specific output DOEs is shown, showing a first input DOE and a first output DOE corresponding to a first color being energized, according to some examples.

[0014] Fig. 9 shows light entering the Figure 8 A cross-sectional view of a waveguide and reflections within the waveguide showing that a second input DOE and a second output DOE corresponding to a second color are excited.

[0015] Fig.10 shows light entering the Figure 8 A cross-sectional view of a waveguide and reflections within the waveguide showing that a third input DOE and a third output DOE corresponding to a third color are excited.

[0016] Fig.11 is a diagrammatic representation of a machine in the form of a computer system according to some examples within which a set of instructions may be executed for causing the machine to perform any one or more of the methodologies discussed herein.

[0017] Fig.12 is a block diagram illustrating a software architecture in which examples may be implemented.

[0018] Fig.13 Methods according to some examples are shown. DETAILED DESCRIPTION

[0019] Examples of providing a waveguide with a DOE having a dynamically adjustable diffraction efficiency distribution are described herein. A dynamically addressable DOE (also referred to herein as an "adjustable DOE") can be used to implement a dynamically controllable waveguide for use in various light projection or light redirection systems (e.g., AR display systems). In various examples, the adjustable DOE can be used as a spatial modulator, a color selector, or both.

[0020] The position of the user's eyes may change, and therefore an AR device that creates a single image at a specific position via the OC will have limited practicality. The user's eyes must be precisely located at the required position, otherwise there is a risk of not being able to see the image formed by the light from the OC. Due to this limitation, AR devices are usually formed so that the light propagating in the waveguide is incident on the OC multiple times at different positions of the OC. The light incident at each of these positions is diffracted out of the waveguide to provide a corresponding image, and the user can perceive the image when the user's eyes are correctly positioned relative to the position (the position where the light is coupled out of the waveguide, which can be called the "pupil" or "exit pupil" of the waveguide). In this way, the user's eyes can be positioned in multiple positions within the eye range defined in the space above the viewer's eyes, and still be able to perceive the image. The eye range must be expanded to allow different eye positions and different facial shapes and sizes. However, in this method, since the light is directed to the area where the user's eyes do not exist in the eye range, a large amount of light or even most of the light may be wasted.

[0021] In some examples, the dynamically adjustable DOE is configured to direct light out of the OC only where needed given the position of the user's eye or another target area where light needs to be projected. Eye tracking technology can be used to detect the position of the user's eye, and the diffraction efficiency of one or more DOEs, such as the output DOE (i.e., the OC), can be controlled so that only the output DOE directed to the target area is made efficient. This causes light to be diffracted out of the waveguide toward the position of the user's eye. In some examples, the efficiency of other DOEs (such as a folding DOE used to redirect light within a planar waveguide) can also be adjusted to direct a larger amount of light traveling within the waveguide toward the desired output DOE.

[0022] Some examples described herein may attempt to solve one or more technical problems by providing a waveguide with an adjustable DOE configured to direct light toward a target area, such as the position of an eye. By sending light only to the portion of the eye range where the eye actually resides, the efficiency of the image projection system can be improved, and the intensity of the light projected toward the user's eye can be increased. Since the entire large eye range no longer needs to be illuminated at full power, the optical power requirements of such a projection system can be reduced. In addition, some examples can reduce stray light caused by diffraction from areas in the output surface of the waveguide that are not required for imaging at the user's eye position; this can have the effect of presenting a clearer, clearer image to the user's eye.

[0023] In another set of examples, adjustable DOEs can be used to implement a stacked arrangement of color-specific input and / or output DOEs, each of which can be selectively activated (i.e., increased in diffraction efficiency by applying excitation) or deactivated (i.e., decreased in diffraction efficiency by removing or reducing excitation) during a corresponding time period (e.g., a color subframe of a color sequential display frame time).

[0024] Some examples described herein may attempt to address one or more technical issues by providing an adjustable DOE configured to selectively diffract light based on time-varying conditions (e.g., during different color subframes). Relative to conventional color-specific stacked DOE approaches, the use of stacked adjustable DOEs may reduce light loss, artifacts, and / or stray lighting effects caused by light interacting with the wrong color-specific DOE (e.g., green light interacting with red and blue DOEs). Since each color-specific DOE is activated to diffract light only for a portion of the frame time rather than the entire frame time (e.g., for a 30-color system, each color-specific DOE is activated only 1 / 3 of the time), some examples may reduce the brightness of ambient stray light artifacts (e.g., rainbow effects). In addition, some examples may eliminate the need to manufacture a waveguide with an air gap inserted between each pair of adjacent stacked color-specific DOEs.

[0025] Other technical features will be readily apparent to those skilled in the art from the following drawings, descriptions and claims.

[0026] Figure 1A cross-sectional diagram of light entering and reflecting within a waveguide with an input DOE and an output DOE is shown. As described above, DOEs operate by diffracting light. Light propagation typically occurs in isotropic media (vacuum, air, plastic, glass) where non-conductivity and absorption are equal and constant regardless of the direction of the light. The DOE presents a non-isotropic medium to the propagating light, which effectively changes the direction of the light as it scatters the light. Non-isotropic media consist of periodic media with regions of different refractive indices, resulting in a situation where light waves scatter in certain directions and add in phase (i.e., cause constructive interference). In this way, a non-isotropic DOE enables the direction of light propagation to be controlled or manipulated.

[0027] exist Figure 1 In the example shown, the projector 132 projects light (shown as input ray 102) toward the waveguide body 142 at an incident angle 104 relative to the surface normal of the waveguide body 142. When the light enters the waveguide body 142, which is made of a light-transmitting material having a different refractive index than the surrounding medium (e.g., air), the light is refracted to travel as ray 108 at a waveguide refraction angle 106. The ray 108 encounters the input DOE 134 (e.g., a diffraction grating). The input DOE 134 is configured to refract the light so that the light travels generally toward the right side of the waveguide body 142 along a direction 140 by bouncing between the upper and lower surfaces of the waveguide body 142 via total internal reflection (TIR). In this example, the ray 108 is refracted by the input DOE 134 into a ray 114 that travels at a first angle 112. First angle 112 is an angle sufficient to maintain TIR as light continues to propagate along waveguide body 142 in direction 140 as ray 116 , ray 118 , ray 120 , ray 122 , ray 124 , and ray 126 .

[0028] The direction 140 is substantially parallel to the length of the waveguide body 142 (i.e., from left to right in the illustrated embodiment) and is therefore substantially tangent to the output surface 138 of the waveguide body 142, where light enters the waveguide body 142 and where the light will exit the waveguide body 142 after encountering the output DOE 136, as described below.

[0029] Upon encountering the output DOE 136 (e.g., another diffraction grating), a portion of the light is refracted out of the output surface 138 of the waveguide body 142. The output DOE 136 is configured to refract the light so that the light travels approximately perpendicular to the output surface 138, or at a sufficient angle to avoid TIR. The first encounter with the output DOE 136 outputs a first output ray 128, which represents a portion of the light from the ray 120. The remaining light within the waveguide body 142 as the ray 122, after being reflected by the output surface 138 as the ray 124, encounters the output DOE 136 a second time, which again refracts a portion of the light of the ray 124 out of the waveguide body 142 as the second output ray 130. This pattern continues as the light continues to propagate in the direction 140 via TIR, with a portion of the light refracted out of the output surface 138 at each encounter with the output DOE 136 as an additional output ray.

[0030] In the case of a static, uniform output DOE 136, this reflection and diffraction pattern limits the usefulness of the illustrated device for producing bright, uniform images across the eye range. A uniform output DOE 136 having a fixed diffraction efficiency across its length (i.e., left to right in this example) will result in reduced image brightness at the rightmost portion of the waveguide body 142 because the light loses more power the farther it travels along the direction 140. For example, an output DOE 136 having a uniform diffraction efficiency of 50% will refract 50% of the light as the first output ray 128, then refract 25% of the light (the remaining 50% of the light multiplied by the 50% diffraction efficiency) as the second output ray 130, with the efficiency being further reduced by half with each subsequent encounter with an output DOE 136. Furthermore, when the light encounters the output DOE 136 for the last time at the rightmost end of the waveguide body 142, some light still remains inside the waveguide body 142, which may further reflect off the elements at the right end of the waveguide body 142 and continue to propagate in the opposite direction of direction 140, resulting in stray images that interfere with image clarity.

[0031] Therefore, some approaches use a static DOE whose refractive index is non-uniform along direction 140. If the output DOE 136 has a different refractive index at each point where it encounters the light, then for each output ray, the amount of light refracted out of the output surface 138 can vary based on the distance along direction 140. For example, the output DOE 136 at the first encounter (producing the first output ray 128) can have a diffraction efficiency of 1 / 6 (17%), so that 17% of the light is output as the first output ray 128, while 83% continues to propagate via TIR. The output DOE 136 at the second encounter (producing the second output ray 130) can have a diffraction efficiency of 1 / 5 (20%), so that 20% of the remaining light (83%×20%=17%) is output as the second output ray 130, while 66% of the original light continues to propagate via TIR. This pattern continues so that the third encounter is at 25% diffraction efficiency, the fourth encounter is at 33% efficiency, the fifth encounter is at 50% efficiency, and the sixth and final encounter is at 100% efficiency. Such a non-uniform configuration of the output DOE 136 produces six output rays, each having the same brightness (17% of the original ray), with no light remaining inside the waveguide body 142. It will be appreciated that the diffraction efficiency of the output DOE 136 can be varied by various techniques, for example, by gradually changing the shape of the diffraction grating in different regions along the direction 140.

[0032] Figure 2 Shown with Figure 1 , but where the single output DOE 136 is replaced by a plurality of discrete output DOEs 202, 204. Figure 2 202 and 204 are shown as separate elements, but it will be appreciated that in some examples, the output DOEs 202 and 204 may be implemented as different regions of a continuous single output DOE, or as adjacent discrete output DOEs with no gaps therebetween. Figure 7 describes an example of adjacent DOEs with no gap; however, Figures 2 to 6 In the figures, for visual clarity, the various DOEs will be shown as discrete, spatially separated elements.

[0033] In methods using an output DOE having a non-uniform diffraction efficiency across its length (e.g., using the above-described method of increasing the diffraction efficiency at each encounter along direction 140), Figure 2The first output DOE 202 and the second output DOE 204 shown in the figure can be implemented as DOEs with different diffraction efficiencies (for example, 17% for the first output DOE 202 (thereby producing the first output light 206 accounting for 17% of the total projected light), and 20% for the second output DOE 204 (thereby producing the second output light 208 accounting for 17% of the total projected light)) to form the first two output DOEs of a chain of six output DOEs, which form rows or columns of exit pupils of the eye movement range.

[0034] However, such an approach still exhibits the limitations described above. Since each output DOE in the chain outputs 17% of the available light, each such output ray that the DOE fails to reach the user's eye represents wasted light.

[0035] Thus, in the examples described herein, individual DOEs (e.g., first output DOE 202 and second output DOE 204) can be dynamically configured to independently change their respective diffraction efficiencies in response to a stimulus. This dynamic control of the diffraction efficiency of each of the plurality of DOEs of the waveguide enables the display system to direct light to a target area without wasting light (or generating undesirable ambient light) at locations outside the target area.

[0036] Figure 3 is a block diagram of a waveguide with multiple dynamically addressable output DOEs 302, 304, 306 according to various examples described herein.

[0037] As described herein, a dynamically addressable DOE (also referred to as an adjustable DOE) is a DOE with a variable diffraction efficiency based on an excitation applied to the DOE. A variety of different techniques can be used to manufacture an adjustable DOE. Some examples utilize dynamically addressable diffractive optical elements used in waveguide-based AR systems. In some examples, instead of dividing the light propagating within a waveguide into multiple exit pupils in a fixed pattern of uniform or non-uniform efficiency, the diffraction efficiency of the dynamically addressable DOE is selectively controlled to direct light with maximum power from an exit pupil corresponding to a target area (e.g., the detected position of a user's eyes).

[0038] Figure 3 The waveguide 300 shown in FIG. 3 includes a controller 316 , a DOE driver 318 , and a plurality of dynamically addressable output DOEs 302 , 304 , 306 , each having a dynamically adjustable diffraction efficiency in response to a stimulus provided by the DOE driver 318 , which in turn is controlled by the controller 316 .

[0039] The controller 316 may be implemented using a suitable combination of hardware and software logic suitable for performing the operations described herein, such as a microcontroller, a central processor and memory of a computing device, etc. In some examples, the controller may be implemented as described below with reference to Fig.11 The machine 1100 described herein. In some examples, the controller 316 receives target area data 326, such as eye tracking data indicating the position of an eye. The eye tracking data may be generated using any suitable means for eye tracking. The controller 316 processes the target area data 326 to identify which exit pupils of the waveguide 300 may output light toward the target area, and controls the DOE driver 318 (e.g., by electrical control signals sent via a data bus) to generate and provide a separate and independent stimulus to each adjustable DOE (e.g., a first stimulus 320 provided to the first output DOE 302, a second stimulus 322 provided to the second output DOE 304, and a third stimulus 324 provided to the third output DOE 306). In response to the stimulus, the adjustable DOEs change their respective diffraction efficiencies to achieve a desired configuration of diffraction efficiencies across the waveguide body 142. This causes light (shown as input light 102) projected from the projector 132 and entering the waveguide body 142 (based on received projector control data 314, such as image data) to be refracted out of the waveguide body 142 with a different and dynamically adjustable diffraction efficiency each time it encounters an output DOE (e.g., as a first output light ray 308 after encountering the first output DOE 302, as a second output light ray 310 after encountering the second output DOE 304, or as a third output light ray 312 after encountering the third output DOE 306).

[0040] Thus, in some examples, a waveguide 300 is provided that includes a waveguide body 142 that includes an optically transmissive material having a different refractive index than a surrounding medium (e.g., air). The waveguide body 142 defines an output surface 138 and is configured to propagate light by total internal reflection along one or more directions (e.g., direction 140) that are substantially tangential to the output surface 138. The waveguide 300 includes one or more diffractive optical elements (e.g., a first output DOE 302, a second output DOE 304, and a third output DOE 306), each of which is configured to change its diffraction efficiency in response to a corresponding stimulus (e.g., a first stimulus 320, a second stimulus 322, and a third stimulus 324, respectively). The waveguide 300 also includes a DOE driver 318 configured to independently provide stimulus to each of the DOEs.

[0041] In various examples, a variety of different techniques can be used to implement a dynamically addressable DOE. In some examples, the DOE can include a liquid crystal material that, in some examples, can respond to excitation in the form of electrical excitation. In some examples, a holographic polymer dispersed liquid crystal (HPDLC) can be used: a diffraction grating can be interferometrically recorded on a photopolymer, with liquid crystal (LC) dispersed within the grating. The formation of the grating promotes LC phase separation. In the absence of an electric field (e.g., in the absence of electrical excitation), the LC is randomly aligned and the diffraction efficiency of the DOE is highest. In the presence of an electric field (e.g., in the presence of electrical excitation), the LC is aligned and the refractive index matches the surrounding environment, so the diffraction efficiency is reduced or minimized. The electric field strength anywhere in between can proportionally affect the diffraction efficiency.

[0042] In some examples, a surface relief DOE with LC can be used: unlike conventional surface relief structures where the gaps between features are filled with air, the LC acts as a filler. As with the HPDLC described above, alignment of the LC can lead to reduced efficiency of the structure.

[0043] In some examples, non-LC materials and / or non-electrical excitation may be used. Elastic physical deformation of a DOE may change its diffraction efficiency. By applying mechanical compression and / or tension, or by applying thermal deformation and / or relaxation due to temperature changes, the diffraction grating may be deformed to a point that is not on Bragg or efficient for incident light. Thus, in some examples, excitation may include physical deformation of at least one DOE and / or temperature change of at least one DOE.

[0044] Depending on the nature of the excitation used to adjust the diffraction efficiency of the DOE, the DOE driver 318 can take different forms and / or can operate according to different principles. In an LC-based system using an electrical signal as an excitation, a conductive channel can be provided through or adjacent to the waveguide body to enable selective electrical excitation of each region or each DOE independently according to known LC control methods. In some examples using mechanical compression and / or tension as an excitation, a mechanical actuator (e.g., a piezoelectric element) can be used to selectively deform different regions (and / or different DOEs) of the DOE. In some examples using thermal excitation to deform parts of the DOE or different DOEs, a heating element (e.g., an electrothermal heating element) can be used to selectively heat the DOE or parts thereof. The DOE driver 318 can be configured to selectively provide power to various electrical, mechanical, and / or thermal components used to provide excitation to various DOEs or regions thereof.

[0045] As described above, the waveguide body 142 is formed of an optically transmissive material. In some examples, the optically transmissive material includes a dielectric material. In some examples, the optically transmissive material includes a plastic material. In some examples, the optically transmissive material includes a glass material.

[0046] Thus far, the examples shown have only addressed light propagating in a single direction 140 within a waveguide body 142. However, some examples will describe waveguides in which light propagating by TIR travels in more than one direction based at least in part on the diffraction efficiency of a folded DOE of the waveguide.

[0047] Figure 4 A two-dimensional waveguide 400 is shown. The two-dimensional waveguide 400 includes a waveguide body 434 implemented as a substantially two-dimensional plate, such as a display surface of an AR display (e.g., a lens of a pair of glasses). The two-dimensional waveguide 400 includes an input DOE 402 for receiving projected light (shown as input light ray 428). Figure 1 In a similar mode as shown, light propagates in a first direction 430 via TIR within the waveguide body 434 .

[0048] However, the two-dimensional waveguide 400 includes a series of fold DOEs configured to redirect, via diffraction, a portion of the light propagating via TIR in a first direction 430 to continue propagating via TIR in a second direction 432 within a waveguide body 434. When the light encounters the first fold DOE 420, a portion of the light (determined by the diffraction efficiency of the first fold DOE 420) is diffracted at an angle sufficient for TIR to propagate in the second direction 432, and thereafter sequentially encounters the first output DOE 404, the second output DOE 406, the third output DOE 408, and the fourth output DOE 410. The remaining light continues to propagate in the first direction 430 until it encounters the second fold DOE 422, the third fold DOE 424, and the fourth fold DOE 426, with some light potentially lost to diffraction at each encounter, resulting in propagation in the second direction 432. Thus, in the example shown, the longest path traveled by light is to encounter the input DOE 402, propagate in the first direction 430, encounter the first fold DOE 420, the second fold DOE 422, the third fold DOE 424 and the fourth fold DOE 426, be diffracted by the fourth fold DOE 426, propagate in the second direction 432, and encounter the 13th output DOE 412, the 14th output DOE 414, the 15th output DOE 416 and the 16th output DOE 418 (at which point the light is diffracted out of the waveguide body 434).

[0049] It will be appreciated that although light propagating by TIR bounces within the waveguide body 434 is shown as traveling in straight lines in the first direction 430 and the second direction 432 for visual clarity, in reality it behaves in a manner similar to Figure 1 The light in the image is reflected in a similar zigzag path.

[0050] A folded DOE is a DOE configured to split and fold propagating light, such as a diffraction grating formed inside the waveguide body 434. Figure 3 The diffraction efficiency at the folded DOE is dynamically adjusted. The diffraction efficiency of the folded DOE is adjusted so that the propagated light is folded and split only at the necessary position and degree. Therefore, in the example shown, each row of output DOEs projected along the second direction 432 can be selectively activated or deactivated so that light is not wasted by directing light to a row that does not include an output DOE directed toward the target area. Figure 5 and Figure 6 An example of such an operation is described.

[0051] Figure 5 Shows Figure 4 4 is a two-dimensional waveguide 400, showing that the fold DOEs and output DOEs are activated to direct light (output light ray 502) out of a single output DOE (12th output DOE 512) toward the location of the eye 504. In this example, the DOE driver activates the various fold DOEs and output DOEs so that the first fold DOE 420 and the second fold DOE 422 have minimum diffraction efficiency, causing most or all of the received light to propagate to the third fold DOE 424. The third fold DOE 424 is activated to have maximum diffraction efficiency, causing most or all of the remaining light to propagate along the third row of output DOEs in the second direction 432. The light encounters the 9th output DOE 506, the 10th output DOE 508, and the 11th output DOE 510, all of which are activated to have minimum diffraction efficiency. Upon encountering the 12th output DOE 512, which is energized to have maximum diffraction efficiency, most or all of the remaining light is diffracted out of the waveguide body 434 as output light rays 502 to travel toward the target area, in this case the location of the eye 504.

[0052] In some examples, this mode of excitation can be achieved by using an eye tracking system to track the position of the eye 504 to generate eye tracking data. The eye tracking data is provided to the controller 316 (with or without pre-processing) as target area data 326. The controller processes the target area data 326 and controls the DOE driver 318 based on the target area data 326 to drive the above-mentioned excitation mode.

[0053] Thus, in some examples, the DOEs include: a first one or more output DOEs (e.g., the 12th output DOE 512) configured to diffract light out of an output surface toward a target area; and a second one or more output DOEs (e.g., all other output DOEs of the device) configured to diffract light out of an output surface toward a location outside the target area. The excitation provided to the DOEs is configured to increase the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs. In some examples, increasing the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs includes increasing the diffraction efficiency of the first one or more output DOEs. In some examples, increasing the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs includes reducing the diffraction efficiency of the second one or more output DOEs. Some examples may perform both operations.

[0054] In some examples, a waveguide (e.g., waveguide 300 or two-dimensional waveguide 400) includes a controller 316 configured to receive target region data 326 and control a DOE driver 318 to provide an excitation based on the target region data 326. In some examples, the excitation provided to the DOE is configured to direct light toward the target region by diffracting the light out of the waveguide body 142 via the output surface 138.

[0055] In some examples, one or more DOEs include a folded DOE (e.g., third folded DOE 424) configured to diffract light propagating in the first direction 430 to propagate in the second direction 432. Light propagating in the second direction 432 is more likely to reach the target area than light propagating in the first direction 430, and the excitation provided to the DOE is configured to increase the diffraction efficiency of the folded DOE (e.g., third folded DOE 424) so ​​that the amount of light diffracted to propagate in the second direction 432 is increased.

[0056] In some examples, the target area includes the location of eye 504 , and target area data 326 includes eye tracking data representing the location of eye 504 .

[0057] Figure 6 Shows Figure 4 4, a two-dimensional waveguide 400 is shown, showing a set of multiple output DOEs where the folded DOE and the output DOE are activated to direct light toward the location of the eye 504. In some cases, the location of the eye may not be sufficiently certain, or may span more than one exit pupil, making it desirable to project light from multiple exit pupils to ensure that the image is optimally presented to the eye.

[0058] In this example, the eye 504 defines a target area spanning four output DOEs: the 11th output DOE 510, the 12th output DOE 512, the 15th output DOE 416, and the 16th output DOE 418. Therefore, in an ideal case (e.g., a case where the diffraction efficiency is fully controllable), the diffraction efficiency of the various DOEs can be configured as follows: all folded DOEs except the third folded DOE 424 and the fourth folded DOE 426 are at minimum diffraction efficiency; the third folded DOE 424 is at 50% diffraction efficiency; and the fourth folded DOE 426 is at 100% diffraction efficiency. Since (in an ideal case) no light is diffracted toward the output DOEs in the first two rows, the output DOEs in the first two rows are unrelated; however, in real-world non-ideal cases, it may be preferable to minimize the diffraction efficiency of these output DOEs to avoid stray light leaving the waveguide body 434. In the last two rows of output DOEs, the first two output DOEs in series are excited to have minimum diffraction efficiency; the third output DOE in each row (i.e., the 11th output DOE 510 and the 15th output DOE 416) is set to 50% diffraction efficiency; and the last output DOE in each row (i.e., the 12th output DOE 512 and the 16th output DOE 418) is set to 100% diffraction efficiency. Ideally, this excitation pattern will produce four outputs of equal brightness at each of the four output DOEs (the 11th output DOE 510, the 12th output DOE 512, the 15th output DOE 416, and the 16th output DOE 418). It will be appreciated that real-world implementations will likely have non-ideal optical properties and may need to be adjusted accordingly; furthermore, it will be appreciated that in some intended applications, it may be desirable to have non-uniform brightness at different locations.

[0059] Figure 7 A continuous DOE waveguide 700 is shown with a continuous DOE, which can be viewed as a plurality of adjacent fold DOEs and a plurality of adjacent output DOEs, each defining an area of ​​a single continuous DOE. In other examples, the output DOEs may be adjacent but the fold DOEs may not be adjacent, or vice versa. In some examples, the various areas may be dynamically reconfigured such that a given diffraction efficiency may be applied to an area of ​​a dynamically defined shape and / or size via actuation, or a continuously varying diffraction efficiency may be applied over an area of ​​a continuous DOE.

[0060] Thus, the continuous DOE waveguide 700 includes a continuous DOE divided into regions, such as a first folding DOE 710 defining a first folding region, a second folding DOE 712 defining a second folding region, a third folding DOE 714 defining a third folding region, and a fourth folding DOE 716 defining a fourth folding region, and a 13th output DOE 702 defining a first output region, a 14th output DOE 704 defining a second output region, a fourth folding DOE 716 defining a third output region, and a 16th output DOE 708 defining a fourth output region. The components of the continuous DOE waveguide 700 are otherwise similar to those of the two-dimensional waveguide 400.

[0061] Although the above examples are of waveguides involving DOEs with spatially modulated diffraction efficiency, the techniques described herein can also be applied to provide DOEs that selectively propagate light according to time-varying conditions. For example, a waveguide can provide multiple color-specific DOEs that can be activated during different color subframes of a color sequence display.

[0062] A color sequence display cycles through temporally separated subframes of each of two or more colors (such as red, green, and blue). The persistence of vision of the human eye fuses the sequence of color subframes together into one image containing a mixture of colors.

[0063] Figure 8 A cross-sectional view is shown of light entering and reflecting within a color sequential waveguide 810 having multiple stacked color-specific input DOEs and multiple stacked color-specific output DOEs. The DOE corresponding to each color may be activated during a corresponding color subframe that defines a time period during which light of the corresponding color is projected into the waveguide.

[0064] Figure 8 The example shown in shows a first input DOE 802 and a first output DOE 804, both corresponding to a first color (e.g., blue). The first input DOE 802 and the first output DOE 804 are configured to optimize the diffraction of light of the first color (e.g., blue light having a wavelength below 495 nm). The projector 132 is configured to sequentially project light of each of three colors (e.g., red, green, and blue) during three corresponding color subframes spanning three time periods. The projector control data 314 that controls the timing and color of the light projected by the projector 132 can be synchronized with the control data provided to the controller (not shown) so that the controller drives the DOE driver 318 to appropriately excite each color-specific DOE during each time period.

[0065] During a first time period (eg, a blue subframe), the DOE driver drives the first input DOE 802 and the first output DOE 804 to have high diffraction efficiency relative to the other color-specific DOEs in the stack (as described below with reference to Fig. 9 and Fig.10 This causes the light of the first color (e.g., blue light) projected by the projector 132 to be diffracted at the first input DOE 802, thereby optimizing the amount of light propagating via TIR. Upon encountering the first output DOE 804, the light of the first color is again optimally diffracted as a first output ray 806, and then as a second output ray 808.

[0066] Fig. 9 Shows Figure 8 810, showing an activated second input DOE 902 and an activated second output DOE 904, both of which are optimized to diffract light of a second color (e.g., green) during a second time period (e.g., a green subframe). In this example, when light of a second color (e.g., green light having a dominant wavelength of 510 nm or close to 510 nm) is projected by the projector 132, the first input DOE 802 and the first output DOE 804 are deactivated (e.g., have minimal diffraction efficiency), while the second input DOE 902 and the second output DOE 904 are activated, causing the light of the second color to be optimally diffracted into TIR when encountering the second input DOE 902, and optimally diffracted out of the waveguide as a first output ray 906 when encountering the second output DOE 904, and then as a second output ray 908.

[0067] Fig.10 Shows Figure 8 810, showing an activated third input DOE 1002 and an activated third output DOE 1004, both of which are optimized to diffract light of a third color (e.g., red) during a third time period (e.g., red subframe). In this example, when light of a third color (e.g., red light having a wavelength above 620 nm) is projected by the projector 132, the first input DOE 802, the first output DOE 804, the second input DOE 902, and the second output DOE 904 are deactivated (e.g., with minimal diffraction efficiency), while the third input DOE 1002 and the third output DOE 1004 are activated, so that the light of the third color is optimally diffracted into TIR when encountering the third input DOE 1002, and optimally diffracted out of the waveguide as a first output ray 1006 when encountering the third output DOE 1004, and then as a second output ray 1008.

[0068] Thus, in some examples, the DOEs selectively propagate light according to a time-varying condition, and the time-varying condition includes a temporal sequence of color-specific time periods, the color-specific time periods including a first time period during which light of a first color propagates within the waveguide body, and a second time period during which light of a second color propagates within the waveguide body. The one or more DOEs include: a first one or more DOEs configured to diffract light of the first color (e.g., a first input DOE 802 and a first output DOE 804), and a second one or more DOEs configured to diffract light of the second color (e.g., a second input DOE 902 and a second output DOE 904). The excitation is configured to increase the diffraction efficiency of the first one or more DOEs relative to the diffraction efficiency of the second one or more DOEs during the first time period, and to increase the diffraction efficiency of the second one or more DOEs relative to the diffraction efficiency of the first one or more DOEs during the second time period.

[0069] In some examples, the first one or more DOEs include a first one or more output DOEs (e.g., first output DOE 804) configured to diffract light of a first color out of an output surface. The second one or more DOEs include a second one or more output DOEs (e.g., second output DOE 904) configured to diffract light of a second color out of an output surface. The first one or more output DOEs and the second one or more output DOEs may be arranged in a stacked configuration such that during a first period of time, relatively more light enters the first one or more output DOEs and is diffracted out of the output surface by the first one or more output DOEs, and during a second period of time, relatively more light passes through the first one or more output DOEs, enters the second one or more output DOEs, and is diffracted out of the output surface by the second one or more output DOEs.

[0070] In some examples, the first one or more DOEs further include a first one or more input DOEs (e.g., first input DOE 802) configured to diffract light of the first color into the waveguide body at an angle sufficient to achieve total internal reflection. The second one or more DOEs further include a second one or more input DOEs (e.g., second input DOE 902) configured to diffract light of the second color into the waveguide body at an angle sufficient to achieve total internal reflection. The first one or more input DOEs and the second one or more input DOEs can be arranged in a stacked configuration such that during a first period of time, relatively more light enters the first one or more input DOEs and is diffracted into the waveguide body by the first one or more input DOEs, and during a second period of time, relatively more light passes through the first one or more input DOEs, enters the second one or more input DOEs, and is diffracted into the waveguide body by the second one or more output DOEs.

[0071] In some examples, the stacked arrangement does not include an air gap between the first one or more output DOEs and the second one or more output DOEs (e.g., between the first output DOE 804 and the second output DOE 904), or between the first one or more input DOEs and the second one or more input DOEs (e.g., between the first input DOE 802 and the second input DOE 902).

[0072] Machine Architecture

[0073] Fig.111100 within which instructions 1102 (e.g., software, programs, applications, applet, app, or other executable code) may be executed for causing the machine 1100 to perform any one or more of the methodologies discussed herein. For example, the instructions 1102 may cause the machine 1100 to perform any one or more of the methodologies described herein. The instructions 1102 transform a general purpose, unprogrammed machine 1100 into a specific machine 1100 that is programmed to perform the functions described and illustrated in the manner described. The machine 1100 may operate as a standalone device or may be coupled (e.g., networked) to other machines. In a networked deployment, the machine 1100 may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine 1100 may include, but is not limited to, a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a personal digital assistant (PDA), an entertainment media system, a cellular phone, a smart phone, a mobile device, a wearable device (e.g., a smart watch, a pair of augmented reality glasses), a smart home device (e.g., a smart appliance), other smart devices, a web appliance, a network router, a network switch, a network bridge, or any machine capable of sequentially or otherwise executing instructions 1102 specifying actions to be taken by the machine 1100. In addition, while only a single machine 1100 is shown, the term "machine" should also be taken to include a collection of machines that individually or jointly execute instructions 1102 to perform any one or more of the methods discussed herein. In some examples, the machine 1100 may include both a client system and a server system, wherein certain operations of a particular method or algorithm are performed on the server side, and certain operations of the particular method or algorithm are performed on the client side.

[0074] The machine 1100 may include a processor 1104, a memory 1106, and an input / output I / O component 1108, which may be configured to communicate with each other via a bus 1110. In an example, the processor 1104 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a radio frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor 1112 that executes instructions 1102 and a processor 1114. The term "processor" is intended to include multi-core processors, which may include two or more independent processors (sometimes referred to as "cores") that can execute instructions simultaneously. Although Fig.11 Multiple processors 1104 are shown, but the machine 1100 may include a single processor with a single core, a single processor with multiple cores (e.g., a multi-core processor), multiple processors with a single core, multiple processors with multiple cores, or any combination thereof.

[0075] The memory 1106 includes a main memory 1116, a static memory 1118, and a storage unit 1120, which are all accessible by the processor 1104 via the bus 1110. The main memory 1106, the static memory 1118, and the storage unit 1120 store instructions 1102 that implement any one or more of the methods or functions described herein. The instructions 1102 may also reside, completely or partially, within the main memory 1116, within the static memory 1118, within the machine-readable medium 1122 within the storage unit 1120, within at least one of the processors 1104 (e.g., within a cache memory of a processor), or within any suitable combination thereof during execution thereof by the machine 1100.

[0076] I / O components 1108 may include various components for receiving input, providing output, generating output, sending information, exchanging information, capturing measurements, etc. The specific I / O components 1108 included in a particular machine will depend on the type of machine. For example, a portable machine such as a mobile phone may include a touch input device or other such input mechanism, while a headless server machine will be less likely to include such a touch input device. It will be appreciated that I / O components 1108 may include Fig.111108. In various examples, the I / O components 1108 may include a user output component 1124 and a user input component 1126. The user output component 1124 may include a visual component (e.g., a display (e.g., a waveguide and / or projector as described herein, a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)), an acoustic component (e.g., a speaker), a tactile component (e.g., a vibration motor, a resistance mechanism), other signal generators, etc. The user input component 1126 may include an alphanumeric input component (e.g., a keyboard, a touch screen configured to receive alphanumeric input, an optical keyboard, or other alphanumeric input component), a point-based input component (e.g., a mouse, a touch pad, a trackball, a joystick, a motion sensor, or other pointing instrument), a tactile input component (e.g., a physical button, a touch screen or other tactile input component that provides the location and force of a touch or touch gesture), an audio input component (e.g., a microphone), etc.

[0077] In other examples, the I / O component 1108 may include a biometric component 1128, a motion component 1130, an environmental component 1132, or a positioning component 1134, as well as various other components. For example, the biometric component 1128 includes components for detecting expressions (e.g., hand expressions, facial expressions, voice expressions, body postures, or eye tracking), measuring biosignals (e.g., blood pressure, heart rate, body temperature, sweat, or brain waves), identifying people (e.g., voice recognition, retinal recognition, facial recognition, fingerprint recognition, or EEG-based recognition), etc. The motion component 1130 includes an acceleration sensor component (e.g., an accelerometer), a gravity sensor component, and a rotation sensor component (e.g., a gyroscope).

[0078] Environmental components 1132 include, for example, one or more cameras (with still image / photo and video capabilities), lighting sensor components (e.g., photometers), temperature sensor components (e.g., one or more thermometers that detect ambient temperature), humidity sensor components, pressure sensor components (e.g., barometers), acoustic sensor components (e.g., one or more microphones that detect background noise), proximity sensor components (e.g., infrared sensors that detect nearby objects), gas sensors (e.g., gas detection sensors that detect concentrations of hazardous gases for safety or measure pollutants in the atmosphere), depth sensors (e.g., one or more LIDAR arrays), or other components that can provide indications, measurements, or signals corresponding to the surrounding physical environment.

[0079] With respect to cameras, the machine 1100 may have a camera system including, for example, a front camera on the front surface of the machine 1100 and a rear camera on the rear surface of the machine 1100. The front camera may, for example, be used to capture still images and videos of a user of the machine 1100 (e.g., a "selfie"), which may then be enhanced with the enhancement data (e.g., filters) described above. The rear camera may, for example, be used to capture still images and videos in a more traditional camera mode, where the images are similarly enhanced using the enhancement data. In addition to the front camera and the rear camera, the machine 1100 may also include a 360° camera for capturing 360° photos and videos.

[0080] In addition, the camera system of the machine 1100 may include dual rear cameras (e.g., a main camera and a depth sensing camera), or even triple, quad, or quintuple rear camera configurations on the front and back sides of the machine 1100. For example, these multiple camera systems may include a wide-angle camera, an ultra-wide-angle camera, a telephoto camera, a macro camera, and a depth sensor. For example, the system may additionally include an infrared camera to allow for gesture tracking, eye position tracking, or night vision.

[0081] The positioning component 1134 includes a position sensor component (e.g., a GPS receiver component), an altitude sensor component (e.g., an altimeter or barometer that detects air pressure, from which the altitude can be obtained), an orientation sensor component (e.g., a magnetometer), and the like.

[0082] A variety of technologies may be used to achieve communication. The I / O components 1108 also include a communication component 1136 that is operable to couple the machine 1100 to a network 1138 or device 1140 via a corresponding coupling or connection. For example, the communication component 1136 may include a network interface component or another suitable device that interfaces with the network 1138. In other examples, the communication component 1136 may include a wired communication component, a wireless communication component, a cellular communication component, a satellite communication, a near field communication (NFC) component, Components (e.g. Low energy consumption), Components, Zigbee, Ant+, and other communication components that provide communication via other modalities. Device 1140 can be another machine or any peripheral device among various peripheral devices (e.g., a peripheral device coupled via USB).

[0083] In addition, the communication component 1136 can detect an identifier or include a component that is operable to detect an identifier. For example, the communication component 1136 can include a radio frequency identification (RFID) tag reader component, an NFC smart tag detection component, an optical reader component (e.g., for detecting a one-dimensional barcode such as a Universal Product Code (UPC) barcode, a multi-dimensional barcode such as a Quick Response (QR) code, an Aztec code, a Data Matrix, a Dataglyph, or a similar barcode). TM , MaxiCode, PDF417, Ultra Code, UCC RSS-2D barcode and other optical codes) or acoustic detection components (e.g., microphones for audio signals to identify tags). In addition, various information can be obtained via communication component 1136, such as location obtained via Internet Protocol (IP) geolocation, location obtained via Location derived from signal triangulation, location derived via detection of NFC beacon signals that can indicate a specific location, etc.

[0084] Various memories (e.g., main memory 1116, static memory 1118, and memory of processor 1104) and storage unit 1120 may store one or more sets of instructions and data structures (e.g., software) implemented or used by any one or more of the methods or functions described herein. When executed by processor 1104, these instructions (e.g., instructions 1102) cause various operations to implement the disclosed examples.

[0085] The instructions 1102 may be sent or received over the network 1138 using a transmission medium via a network interface device (e.g., a network interface component included in the communication component 1136) and using any of a number of well-known transmission protocols (e.g., the Hypertext Transfer Protocol (HTTP)). Similarly, the instructions 1102 may be sent or received via a coupling (e.g., a peer-to-peer coupling) with the device 1140 using a transmission medium.

[0086] Software Architecture

[0087] Fig.121200 is a block diagram illustrating a software architecture 1202 that may be installed on any one or more of the devices described herein. The software architecture 1202 is supported by hardware such as a machine 1204, which includes a processor 1206, a memory 1208, and an I / O component 1210. In this example, the software architecture 1202 can be conceptualized as a stack of layers, where each layer provides specific functionality. The software architecture 1202 includes layers such as an operating system 1212, a library 1214, a framework 1216, and an application 1218. In operation, the application 1218 invokes an API call 1220 through the software stack and receives a message 1222 in response to the API call 1220.

[0088] The operating system 1212 manages hardware resources and provides public services. The operating system 1212 includes, for example, a kernel 1224, services 1226, and drivers 1228. The kernel 1224 serves as an abstraction layer between the hardware and other software layers. For example, the kernel 1224 provides functions such as memory management, processor management (e.g., scheduling), component management, networking, and security settings. Services 1226 can provide other public services to other software layers. Drivers 1228 are responsible for controlling or interfacing with the underlying hardware. For example, drivers 1228 may include display drivers, camera drivers, or Low-power drivers, Flash drivers, Serial communication drivers (e.g., USB drivers), Drivers, audio drivers, power management drivers, etc.

[0089] The libraries 1214 provide a common low-level infrastructure used by the applications 1218. The libraries 1214 may include a system library 1230 (e.g., a C standard library) that provides functions such as memory allocation functions, string manipulation functions, mathematical functions, etc. In addition, the libraries 1214 may include an API library 1232, such as a media library (e.g., a library for supporting presentation and manipulation of various media formats such as Moving Picture Experts Group-4 (MPEG4), Advanced Video Coding (H.264 or AVC), Moving Picture Experts Group Layer-3 (MP3), Advanced Audio Coding (AAC), Adaptive Multi-Rate (AMR) audio codec, Joint Photographic Experts Group (JPEG or JPG), or Portable Network Graphics (PNG)), a graphics library (e.g., an OpenGL framework for rendering in two dimensions (2D) and three dimensions (3D) in graphics content on a display), a database library (e.g., SQLite providing various relational database functions), a web library (e.g., WebKit providing web browsing functions), etc. The library 1214 may also include various other libraries 1234 to provide many other APIs to the application 1218 .

[0090] The framework 1216 provides a common high-level infrastructure used by the applications 1218. For example, the framework 1216 provides various graphical user interface (GUI) functions, advanced resource management, and advanced location services. The framework 1216 can provide a wide range of other APIs that can be used by the applications 1218, some of which can be specific to a specific operating system or platform.

[0091] In an example, applications 1218 may include home applications 1236, location applications 1238, and a variety of other applications, such as third-party applications 1240. Applications 1218 are programs that execute functions defined in the program. Various programming languages ​​may be used to create one or more of the applications 1218 structured in various ways, such as object-oriented programming languages ​​(e.g., Objective-C, Java, or C++) or procedural programming languages ​​(e.g., C language or assembly language). In a specific example, third-party applications 1240 (e.g., provided by an entity other than the vendor of a particular platform using ANDROID TM or IOS TM Software Development Kit (SDK) can be used to develop applications on platforms such as IOS TM ANDROID TM , Mobile software running on the mobile operating system of the phone or other mobile operating systems. In this example, the third-party application 1240 can activate the API call 1220 provided by the operating system 1212 to facilitate the functions described in this article.

[0092] Fig.13 The steps of an example method 1300 of controlling an adjustable DOE of a waveguide as described above are shown.

[0093] At operation 1302 , light is propagated within the waveguide body 142 in one or more directions (eg, direction 140 , or directions 430 , 432 ) that are substantially tangential to the output surface 138 of the waveguide body 142 .

[0094] At operation 1304, method 1300 independently provides a respective stimulus to each of one or more diffractive optical elements (DOEs). Each DOE is configured to change its diffraction efficiency in response to the respective stimulus such that at least a portion of light propagating in waveguide body 142 is diffracted by one or more DOEs.

[0095] in conclusion

[0096] As described above, examples described herein can solve one or more technical problems associated with diffractive waveguides. The efficiency of an image projection system can be improved. The intensity of light projected toward a user's eyes can be increased. The optical power requirements of such a projection system can be reduced. Stray light can be reduced, thereby improving image quality. Light loss, artifacts, and / or stray lighting effects caused by color-specific DOEs can be reduced. The brightness of ambient stray light artifacts (e.g., rainbow effects) can be reduced. The need to insert an air gap between each pair of adjacent stacked color-specific DOEs can be eliminated.

[0097] Thus, according to examples described herein, a waveguide, a method, and a computer readable medium may be provided.

[0098] Example 1 is a waveguide comprising: a waveguide body comprising an optically transmissive material having a refractive index different from that of a surrounding medium and defining an output surface, the waveguide body being configured to cause light to propagate by total internal reflection along one or more directions substantially tangential to the output surface; one or more diffractive optical elements (DOEs), each DOE being configured to change its diffraction efficiency in response to a corresponding excitation; and a DOE driver configured to independently provide the corresponding excitation to each of the DOEs.

[0099] In Example 2, the subject matter of Example 1 includes, wherein: the stimulus provided to the DOE is configured to direct light toward a target area by diffracting light out of the waveguide body via the output surface.

[0100] In Example 3, the subject matter of Example 2 includes, wherein: the one or more DOEs include: a first one or more output DOEs configured to diffract light out of the output surface toward the target area; and a second one or more output DOEs configured to diffract light out of the output surface toward a location outside the target area; and the excitation provided to the DOEs is configured to increase the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs.

[0101] In Example 4, the subject matter of Example 3 includes, wherein increasing the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs includes: increasing the diffraction efficiency of the first one or more output DOEs.

[0102] In Example 5, the subject matter of Examples 3-4 includes, wherein increasing the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs includes: decreasing the diffraction efficiency of the second one or more output DOEs.

[0103] In Example 6, the subject matter of Examples 3 to 5 includes a controller configured to: receive target region data; and control the DOE driver to provide the stimulus based on the target region data.

[0104] In Example 7, the subject matter of Example 6 includes, wherein: the target area includes the position of an eye; and the target area data includes eye tracking data representing the position of the eye.

[0105] In Example 8, the subject matter of Examples 2 to 7 includes, wherein: the one or more DOEs include: a folded DOE configured to diffract light propagating along a first direction among the one or more directions to propagate along a second direction among the one or more directions; light propagating along the second direction is more likely to reach the target area than light propagating along the first direction; and the excitation provided to the DOE is configured to increase the diffraction efficiency of the folded DOE so that the amount of light diffracted to propagate along the second direction is increased.

[0106] In Example 9, the subject matter of Examples 1 to 8 includes, wherein: the stimulus provided to the DOE is configured to selectively propagate light based on a time-varying condition.

[0107] In Example 10, the subject matter of Example 9 includes, wherein: the time-varying conditions include a time series of color-specific time periods, the color-specific time periods including: a first time period in which light of a first color propagates within the waveguide body; and a second time period in which light of a second color propagates within the waveguide body; the one or more DOEs include: a first one or more DOEs configured to diffract the first color of light; and a second one or more DOEs configured to diffract the second color of light; and the excitation is configured to: during the first time period, increase the diffraction efficiency of the first one or more DOEs relative to the diffraction efficiency of the second one or more DOEs; and during the second time period, increase the diffraction efficiency of the second one or more DOEs relative to the diffraction efficiency of the first one or more DOEs.

[0108] In Example 11, the subject matter of Example 10 includes, wherein: the first one or more DOEs include a first one or more output DOEs, which are configured to diffract light of the first color out of the output surface; the second one or more DOEs include a second one or more output DOEs, which are configured to diffract light of the second color out of the output surface; and the first one or more output DOEs and the second one or more output DOEs are arranged in a stacked configuration so that: during the first time period, relatively more light enters the first one or more output DOEs and is diffracted out of the output surface by the first one or more output DOEs; and during the second time period, relatively more light passes through the first one or more output DOEs, enters the second one or more output DOEs, and is diffracted out of the output surface by the second one or more output DOEs.

[0109] In Example 12, the subject matter of Example 11 includes, wherein: the first one or more DOEs also include a first one or more input DOEs, which are configured to diffract light of the first color into the waveguide body at an angle sufficient to achieve the total internal reflection; the second one or more DOEs also include a second one or more input DOEs, which are configured to diffract light of the second color into the waveguide body at an angle sufficient to achieve the total internal reflection; and the first one or more input DOEs and the second one or more input DOEs are arranged in a stacked configuration so that: during the first time period, relatively more light enters the first one or more input DOEs and is diffracted into the waveguide body by the first one or more input DOEs; and during the second time period, relatively more light passes through the first one or more input DOEs, enters the second one or more input DOEs, and is diffracted into the waveguide body by the second one or more output DOEs.

[0110] In Example 13, the subject matter of Example 12 includes, wherein: the stacked arrangement does not include an air gap between the first one or more output DOEs and the second one or more output DOEs or between the first one or more input DOEs and the second one or more input DOEs.

[0111] In Example 14, the subject matter of Examples 1 to 13 includes, wherein: the stimulus comprises a physical deformation of at least one DOE.

[0112] In Example 15, the subject matter of Examples 1 to 14 includes, wherein: the stimulus comprises a temperature change of at least one DOE.

[0113] In Example 16, the subject matter of Examples 1 to 15 includes, wherein: the excitation comprises electrical excitation of at least one DOE.

[0114] In Example 17, the subject matter of Example 16 includes, wherein: the at least one DOE comprises a liquid crystal material.

[0115] In Example 18, the subject matter of Examples 1 to 17 includes, wherein: the optically transmissive material comprises a dielectric material.

[0116] In Example 19, the subject matter of Examples 1 to 18 includes, wherein: the optically transmissive material comprises a plastic material.

[0117] In Example 20, the subject matter of Examples 1 to 19 includes, wherein: the optically transmissive material comprises a glass material.

[0118] Example 21 is a method comprising: causing light to propagate within a waveguide body along one or more directions substantially tangential to an output surface of the waveguide body; and independently providing a corresponding excitation to each of one or more diffractive optical elements (DOEs), each DOE being configured to change its diffraction efficiency in response to the corresponding excitation so that at least a portion of the light propagating in the waveguide body is diffracted by the one or more DOEs.

[0119] Example 22 is a non-transitory computer-readable storage medium, which includes instructions that, when executed by a computer, cause the computer to perform operations, the operations including: independently providing a corresponding excitation to each of one or more diffractive optical elements (DOEs), each DOE being configured to change its diffraction efficiency in response to the corresponding excitation, so that at least a portion of light propagating in a waveguide body is diffracted by the one or more DOEs.

[0120] Example 23 is at least one machine-readable medium comprising instructions that, when executed by a processing circuit system, cause the processing circuit system to perform operations to implement any one of Examples 1 to 22.

[0121] Example 24 is an apparatus comprising means for implementing any one of Examples 1-22.

[0122] Example 25 is a system implementing any one of Examples 1 to 22.

[0123] Example 26 is a method of implementing any one of Examples 1 to 22.

[0124] It will be appreciated that various aspects of the above-described examples may be combined in various combinations or sub-combinations.

[0125] Glossary

[0126] "Augmented reality" (AR) refers to an interactive experience, such as a real-world environment, in which physical objects residing in the real world are "augmented" or enhanced by computer-generated digital content (also called virtual content or synthetic content). AR may also refer to a system that enables the combination of the real and virtual worlds, real-time interaction, and 3D registration of virtual and real objects. Users of AR systems perceive virtual content that appears to be attached to or interacting with real-world physical objects.

[0127] "Component" refers to a logic or device, a physical entity, for example, with the following boundaries, which are defined by functions or subroutine calls, branch points, APIs, or other technical definitions that provide partitioning or modularization for specific processing or control functions. Components can be docked with other components via their interfaces to perform machine processing. Components can be part of a packaged functional hardware unit designed for use with other components, and a program that generally performs a specific function in a related function. Components can constitute software components (e.g., codes implemented on machine-readable media) or hardware components. "Hardware components" are tangible units that can perform certain operations and can be configured or arranged in a certain physical manner. In various examples, one or more computer systems (e.g., independent computer systems, client computer systems, or server computer systems) or one or more hardware components (e.g., processors or processor groups) of a computer system can be configured by software (e.g., applications or application parts) to operate to perform certain operations described herein. Hardware components can also be implemented mechanically, electronically, or any suitable combination thereof. For example, a hardware component may include a dedicated circuit system or logic that is permanently configured to perform certain operations. The hardware component may be a dedicated processor, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). The hardware component may also include a programmable logic or circuit system that is temporarily configured to perform certain operations by software. For example, the hardware component may include software executed by a general-purpose processor or other programmable processor. Once configured by such software, the hardware component becomes a specific machine (or a specific component of a machine) that is uniquely customized to perform the configured function, and is no longer a general-purpose processor. It will be recognized that it can be determined for cost and time considerations whether to mechanically implement the hardware component in a dedicated and permanently configured circuit system or in a temporarily configured (e.g., configured by software) circuit system to implement the hardware component. Therefore, the phrase "hardware component" (or "hardware-implemented component") should be understood to include a tangible entity, that is, an entity that is physically constructed, permanently configured (e.g., hardwired) or temporarily configured (e.g., programmed) to operate in some way or perform certain operations described herein. Considering an example where a hardware component is temporarily configured (e.g., programmed), it is not necessary to configure or instantiate each hardware component in the hardware component at any one time. For example, in the case where a hardware component includes a general-purpose processor that is configured by software to become a special-purpose processor, the general-purpose processor can be configured as different special-purpose processors (e.g., including different hardware components) at different times. Therefore, the software configures one or more specific processors to constitute a specific hardware component at one time, for example, and to constitute different hardware components at different times. Hardware components can provide information to other hardware components and receive information from other hardware components. Therefore, the described hardware components can be considered to be communicatively coupled.In the case of multiple hardware components being present at the same time, communication can be achieved by signal transmission (e.g., by appropriate circuits and buses) between or among two or more hardware components in the hardware components. In an example where multiple hardware components are configured or instantiated at different times, communication between such hardware components can be achieved, for example, by storing information in a memory structure to which multiple hardware components have access rights and retrieving information in the memory structure. For example, a hardware component can perform an operation, and the output of the operation is stored in a memory device coupled to it in communication. Then, other hardware components can access the memory device at a subsequent time to retrieve the stored output and process it. The hardware component can also initiate communication with an input device or an output device, and can operate on resources (e.g., a collection of information). The various operations of the example methods described herein can be performed at least in part by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform related operations. Whether it is temporarily configured or permanently configured, such a processor can constitute a processor-implemented component that operates to perform one or more operations or functions described herein.

[0128] As used herein, "processor-implemented components" refer to hardware components implemented using one or more processors. Similarly, the method described herein may be implemented at least in part by a processor, wherein a specific one or more processors are examples of hardware. For example, at least some of the operations of the method may be performed by one or more processors or components implemented by the processor. In addition, one or more processors may also operate to support the execution of related operations in a "cloud computing" environment or as a "software as a service" (SaaS) operation. For example, at least some operations may be performed by a group of computers (as an example of a machine including a processor), wherein these operations may be accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., application programming interface (API)). The execution of certain operations in the operation may be distributed among the processors, not only residing in a single machine, but also deployed across multiple machines. In some examples, a processor or a component implemented by a processor may be located in a single geographic location (e.g., in a home environment, an office environment, or a server cluster). In other examples, a processor or a component implemented by a processor may be distributed across multiple geographic locations.

[0129] "Computer-readable storage media" refers to both, for example, machine storage media and transmission media. Thus, the term includes both storage devices / media as well as carrier / modulated data signals. The terms "machine-readable medium," "computer-readable medium," and "device-readable medium" mean the same thing and may be used interchangeably in this disclosure.

[0130] "Machine storage media" refers to, for example, a single or multiple storage devices and media (e.g., centralized or distributed databases, and associated caches and servers) that store executable instructions, routines, and data. Thus, the term should be considered to include, but is not limited to, solid-state memory and optical and magnetic media, including memory internal or external to the processor. Specific examples of machine storage media, computer storage media, and device storage media include: non-volatile memory, including, for example, semiconductor memory devices, such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), FPGA, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; USB flash drives; and CD-ROM and DVD-ROM disks. The terms "machine storage media", "device storage media", and "computer storage media" mean the same thing and may be used interchangeably in this disclosure. The terms "machine storage media", "computer storage media", and "device storage media" expressly exclude carrier waves, modulated data signals, and other such media, at least some of which are encompassed by the term "signal media".

[0131] “Non-transitory computer-readable storage medium” refers to a tangible medium that is capable of storing, encoding, or carrying instructions to be executed by a machine, for example.

[0132] "Signal medium" refers to any intangible medium that is capable of storing, encoding or carrying instructions to be executed by a machine, for example, and includes digital or analog communication signals or other intangible media that facilitate the communication of software or data. The term "signal medium" should be deemed to include any form of modulated data signals, carrier waves, etc. The term "modulated data signal" refers to a signal that has one or more of its various characteristics set or changed in such a manner as to encode information in the signal. The terms "transmission medium" and "signal medium" mean the same thing and are used interchangeably in this disclosure.

[0133] "User device" refers to a device that is, for example, accessed, controlled, or owned by a user and with which the user interacts to perform actions or interactions on the user device, including interactions with other users or computer systems.

Claims

1. A waveguide comprising: a waveguide body comprising an optically transmissive material having a different refractive index than a surrounding medium and defining an output surface, the waveguide body being configured to cause light to propagate by total internal reflection in one or more directions substantially tangential to the output surface; one or more diffractive optical elements (DOEs), each configured to change its diffraction efficiency in response to a respective stimulus; as well as A DOE driver is configured to independently provide the respective stimulus to each of the DOEs.

2. The waveguide according to claim 1, wherein: The stimulus provided to the DOE is configured to direct light toward a target area by diffracting the light out of the waveguide body via the output surface.

3. The waveguide according to claim 2, wherein: The one or more DOEs include: a first one or more output DOEs configured to diffract light out of the output surface toward the target area; and a second one or more output DOEs configured to diffract light out of the output surface toward a location outside of the target area; and The excitation provided to the DOE is configured to increase the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs.

4. The waveguide according to claim 3, wherein: Increasing the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs comprises: The diffraction efficiency of the first one or more output DOEs is increased.

5. The waveguide according to claim 3, wherein: Increasing the diffraction efficiency of the first one or more output DOEs relative to the diffraction efficiency of the second one or more output DOEs comprises: The diffraction efficiency of the second one or more output DOEs is reduced.

6. The waveguide according to claim 3, further comprising: A controller, the controller being configured to: receiving target area data; as well as The DOE driver is controlled based on the target region data to provide the stimulus.

7. A waveguide according to claim 6, wherein: The target area includes the location of the eyes; and The target area data includes eye tracking data representing the position of the eye.

8. The waveguide according to claim 2, wherein: The one or more DOEs include: a folded DOE configured to diffract light propagating in a first direction of the one or more directions to propagate in a second direction of the one or more directions; light propagating in the second direction is more likely to reach the target area than light propagating in the first direction; and The excitation provided to the DOE is configured to increase the diffraction efficiency of the folded DOE such that an amount of light diffracted to propagate along the second direction is increased.

9. The waveguide according to claim 1, wherein: The stimulus provided to the DOE is configured to selectively propagate light based on a time-varying condition.

10. The waveguide according to claim 9, wherein: The time-varying condition includes a time series of a color-specific period, and the color-specific period includes: a first period of time during which light of a first color propagates within the waveguide body; and a second period of time during which light of a second color propagates within the waveguide body; The one or more DOEs include: a first one or more DOEs configured to diffract light of the first color; and a second one or more DOEs configured to diffract light of the second color; and The stimulus is configured to: During the first time period, increasing the diffraction efficiency of the first one or more DOEs relative to the diffraction efficiency of the second one or more DOEs; and During the second time period, the diffraction efficiency of the second one or more DOEs is increased relative to the diffraction efficiency of the first one or more DOEs.

11. The waveguide according to claim 10, wherein: The first one or more DOEs include first one or more output DOEs configured to diffract light of the first color out of the output surface; the second one or more DOEs comprising a second one or more output DOEs configured to diffract light of the second color out of the output surface; as well as The first one or more output DOEs and the second one or more output DOEs are arranged in a stacked configuration such that: During the first time period, relatively more light enters the first one or more output DOEs and is diffracted out of the output surface by the first one or more output DOEs; as well as During the second period, relatively more light passes through the first one or more output DOEs, enters the second one or more output DOEs, and is diffracted out of the output surface by the second one or more output DOEs.

12. The waveguide according to claim 11, wherein: The first one or more DOEs further include first one or more input DOEs configured to diffract light of the first color into the waveguide body at an angle sufficient to achieve the total internal reflection; The second one or more DOEs further include a second one or more input DOEs configured to diffract light of the second color into the waveguide body at an angle sufficient to achieve the total internal reflection; as well as The first one or more input DOEs and the second one or more input DOEs are arranged in a stacked configuration such that: During the first time period, relatively more light enters the first one or more input DOEs and is diffracted into the waveguide body by the first one or more input DOEs; as well as During the second time period, relatively more light passes through the first one or more input DOEs, enters the second one or more input DOEs, and is diffracted into the waveguide body by the second one or more output DOEs.

13. The waveguide of claim 12, wherein: The stacked arrangement does not include an air gap between the first one or more output DOEs and the second one or more output DOEs or between the first one or more input DOEs and the second one or more input DOEs.

14. The waveguide of claim 1, wherein: The excitation comprises a physical deformation of at least one DOE.

15. The waveguide of claim 1, wherein: The stimulus comprises a temperature change of at least one DOE.

16. The waveguide of claim 1, wherein: The excitation includes electrical excitation of at least one DOE.

17. A waveguide according to claim 16, wherein: The at least one DOE includes a liquid crystal material.

18. The waveguide of claim 1, wherein: The optically transmissive material includes a dielectric material.

19. The waveguide of claim 1, wherein: The optically transmissive material comprises a plastic material.

20. The waveguide of claim 1, wherein: The optically transmissive material includes a glass material.

21. A method comprising: causing light to propagate within a waveguide body in one or more directions substantially tangential to an output surface of the waveguide body; as well as A respective excitation is independently provided to each of the one or more diffractive optical elements (DOEs), each DOE being configured to change its diffraction efficiency in response to the respective excitation such that at least a portion of light propagating in the waveguide body is diffracted by the one or more DOEs.

22. A non-transitory computer-readable storage medium comprising instructions that, when executed by a computer, cause the computer to perform operations comprising: A respective excitation is independently provided to each of the one or more diffractive optical elements (DOEs), each DOE being configured to change its diffraction efficiency in response to the respective excitation such that at least a portion of light propagating in the waveguide body is diffracted by the one or more DOEs.

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