System and method for an optical system with an exit pupil expander - Patents.com

Abstract

To provide systems and methods for optical systems with an exit pupil expander.SOLUTION: Architectures are provided for expanding the exit pupil of systems including one or more waveguides. Various embodiments include a display device including one or more waveguides. One or more physical / optical parameters of the one or more waveguides and / or a wavelength of light input to the waveguides can be varied as the angle at which incoming light is incident on the waveguide varies in order to maintain phase correlation between different beamlets of an output light beam emitted from the one or more waveguides.SELECTED DRAWING: Figure 8C

Description

[Technical field]

[0001] (Incorporated by reference) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 397,759, filed Sep. 21, 2016, and entitled “SYSTEMS AND METHODS FOR OPTICAL SYSTEMS WITH EXIT PUPIL EXPANDER,” which is incorporated by reference in its entirety herein.

[0002] The present disclosure relates to virtual reality and augmented reality imaging and visualization systems. [Background technology]

[0003] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears or may be perceived as real. Virtual reality or "VR" scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, while augmented reality or "AR" scenarios typically involve the presentation of digital or virtual image information as an augmentation to the visualization of the real world around the user. For example, referring to FIG. 1, an augmented reality scene 1000 is depicted in which a user of the AR technology sees a real-world park-like setting 1100 featuring people, trees, buildings in the background, and a concrete platform 1120. In addition to these items, the user of the AR technology also perceives that they are "seeing" a robotic figure 1110 standing on the real-world platform 1120, and a flying cartoon-like avatar character 1130 that appears to be an anthropomorphic bumblebee, even though these elements do not exist in the real world. In conclusion, the human visual perception system is highly complex, making it difficult to produce VR or AR technologies that facilitate comfortable, natural-feeling, and rich presentation of virtual image elements among other virtual or real-world image elements. The systems and methods disclosed herein address various challenges associated with VR and AR technologies. Summary of the Invention [Means for solving the problem]

[0004] An innovative aspect of the subject matter disclosed herein is implemented in an optical system comprising an image projection system, a waveguide, and a control system. The image projection system is configured to emit a coherent beam of light at a plurality of wavelengths in the visible spectrum. The waveguide comprises a first edge, a second edge, and a pair of reflective surfaces disposed between the first and second edges. The pair of reflective surfaces is separated by a gap having a gap height d. The waveguide includes a material having a refractive index n. The pair of reflective surfaces has a reflectivity r. A beam emitted from the image projection system is coupled into the waveguide at an input angle θ. The input light can be coupled through one of the first or second edges or through one of the reflective surfaces. The control system is configured to vary at least one parameter selected from the group consisting of a wavelength from a plurality of wavelengths, the gap height d, the refractive index n, and the reflectivity r. The variation of the at least one parameter is correlated with the variation of the input angle θ.

[0005] In various embodiments of the optical system, the image projection system can be configured to vary the input angle θ of the emitted beam at a scan rate. The control system can be configured to modulate at least one parameter at a modulation rate approximately equal to the scan rate. The control system can be configured to modulate at least one parameter, the modulation rate being configured such that the equation 2ndsinθ=mλ is satisfied for all values ​​of the input angle θ, where m is an integer and λ is the wavelength of the beam. In various embodiments, the at least one parameter can be a wavelength from a plurality of wavelengths. In some embodiments, the at least one parameter can be a gap height d. In various embodiments, the at least one parameter can be a refractive index n. In some embodiments, the at least one parameter can be a reflectivity r. In various embodiments, the image projection system can comprise a fiber. In various embodiments, the emitted beam can be collimated. The plurality of wavelengths can include wavelengths in the red, green, and blue spectral regions. The waveguide can comprise an acousto-optical material, a piezoelectric material, an electro-optical material, or a microelectromechanical system (MEMS). The waveguide can be configured as an exit pupil expander that expands and increases the emitted beam. The waveguide can be configured to expand the beam to a spot size of greater than 1 mm. Various embodiments of the optical system discussed herein can be integrated into an augmented reality (AR) device, a virtual reality (VR) device, an eyepiece display device, or eyewear that includes at least one of a frame, one or more lenses, or an ear piece.

[0006] An innovative aspect of the subject matter disclosed herein is implemented in an optical system comprising an image projection system, a plurality of stacked waveguides, and a control system. The image projection system is configured to emit a coherent beam of light at a plurality of wavelengths in the visible spectrum. Each waveguide of the plurality of stacked waveguides comprises a first edge, a second edge, and a pair of reflective surfaces disposed between the first and second edges. The pair of reflective surfaces is separated by a gap having a gap height d. The waveguide includes a material having a refractive index n. The pair of reflective surfaces has a reflectivity r. The control system is configured to vary at least one parameter selected from the group consisting of a wavelength from a plurality of wavelengths, the gap height d, the refractive index n, and the reflectivity r. A beam emitted from the image projection system is coupled into the waveguide at an input angle θ. The input light can be coupled through one of the first or second edges or through one of the reflective surfaces. The variation of the at least one parameter is correlated with the variation of the input angle θ.

[0007] In various embodiments, each waveguide of the plurality of stacked waveguides can have an associated depth plane. The beam emitted from each waveguide appears to originate from the associated depth plane of that waveguide. Different waveguides from the plurality of stacked waveguides can have different associated depth planes. Various embodiments of the optical system discussed above can be integrated into an augmented reality (AR) device, a virtual reality (VR) device, an eyepiece display device, or eyewear comprising at least one of a frame, one or more lenses, or an ear piece.

[0008] Details of one or more implementations of the subject matter described herein are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. Neither this summary nor the following detailed description purport to define or limit the scope of the inventive subject matter. The present invention provides, for example, the following: (Item 1) 1. An optical system comprising: an image projection system configured to emit a coherent beam of light at multiple wavelengths within the visible spectrum; a waveguide comprising a first edge, a second edge, and a pair of reflective surfaces disposed between the first edge and the second edge, the pair of reflective surfaces being separated by a gap having a gap height d, the waveguide comprising a material having a refractive index n, the pair of reflective surfaces having a reflectivity r, and a beam emitted from the image projection system being coupled into the waveguide at an input angle θ; a control system configured to vary at least one parameter selected from the group consisting of a wavelength from the plurality of wavelengths, the gap height d, the refractive index n, and the reflectivity r, wherein variation of the at least one parameter is correlated with variation of the input angle θ; and An optical system comprising: (Item 2) 2. The optical system of claim 1, wherein the image projection system is configured to vary the input angle θ of the emitted beam at a scanning rate. (Item 3) 3. The optical system of any of items 1 and 2, wherein the control system is configured to modulate the at least one parameter at a modulation rate substantially equal to the scan rate. (Item 4) 4. The optical system of any of items 1-3, wherein the control system is configured to modulate the at least one parameter, and the modulation rate is configured such that the equation 2ndsinθ=mλ is satisfied for all values ​​of the input angle θ, where m is an integer and λ is the wavelength of the beam. (Item 5) 5. The optical system of any of items 1-4, wherein the at least one parameter is a wavelength from the plurality of wavelengths. (Item 6) 6. The optical system of any of items 1-5, wherein the at least one parameter is the gap height d. (Item 7) 7. The optical system according to any one of items 1 to 6, wherein the at least one parameter is the refractive index n. (Item 8) 8. The optical system according to any one of items 1 to 7, wherein the at least one parameter is the reflectivity r. (Item 9) 9. The optical system of any of items 1-8, wherein the image projection system comprises a fiber. (Item 10) 10. The optical system of any of items 1-9, wherein the emitted beam is collimated. (Item 11) 11. The optical system of any of items 1-10, wherein the multiple wavelengths include wavelengths in the red, green, and blue spectral regions. (Item 12) Item 13. The optical system of any one of items 1-11, wherein the waveguide includes an acousto-optic material. 13. The optical system of any of claims 1-12, wherein the waveguide comprises a piezoelectric material. (Item 14) Item 15. The optical system of any one of items 1-13, wherein the waveguide includes an electro-optic material. 15. The optical system of any of claims 1-14, wherein the waveguide comprises a microelectromechanical system (MEMS). (Item 16) 16. The optical system of any of items 1-15, wherein the waveguide is configured as an exit pupil expander that expands and increases the emitted beam. (Item 17) 17. The optical system of any of claims 1-16, wherein the waveguide is configured to expand the beam to a spot size of greater than 1 mm. (Item 18) 18. The optical system according to any of items 1-17, integrated within an augmented reality (AR) device. (Item 19) 19. The optical system according to any of items 1-18, integrated within a virtual reality (VR) device. (Item 20) 20. The optical system of any of items 1-19, integrated within an eyepiece display device. (Item 21) 21. The optical system of any of items 1-20, integrated into eyewear comprising at least one of a frame, one or more lenses, or an ear piece. (Item 22) 1. An optical system comprising: an image projection system configured to emit a coherent beam of light at multiple wavelengths within the visible spectrum; A plurality of stacked waveguides, each waveguide comprising: a waveguide comprising a first edge, a second edge, and a pair of reflective surfaces disposed between the first edge and the second edge, the pair of reflective surfaces being separated by a gap having a gap height d, the waveguide comprising a material having a refractive index n, and the pair of reflective surfaces having a reflectivity r; a control system configured to vary at least one parameter selected from the group consisting of a wavelength from the plurality of wavelengths, the gap height d, the refractive index n, and the reflectivity r; a beam emitted from the image projection system is coupled into the waveguide at an input angle θ, and a variation in the at least one parameter is correlated with a variation in the input angle θ. (Item 23) 24. The optical system of claim 23, wherein each waveguide has an associated depth plane, and the beam emitted from each waveguide appears to originate from the associated depth plane of the waveguide. 24. The optical system of any of items 22-23, wherein different waveguides from the plurality of stacked waveguides have different associated depth planes. (Item 25) 25. The optical system according to any of items 22-24, which is integrated into an augmented reality (AR) device. (Item 26) 26. The optical system according to any of items 22-25, which is integrated into a virtual reality (VR) device. (Item 27) 27. The optical system of any of items 22-26, integrated within an eyepiece display device. (Item 28) 28. The optical system of any of items 22-27, integrated into eyewear comprising at least one of a frame, one or more lenses, or ear pieces. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 depicts an illustration of an augmented reality scenario with a virtual reality object and a real reality object viewed by a person.

[0010] [Diagram 2] FIG. 2 diagrammatically illustrates an embodiment of a wearable display system.

[0011] [Diagram 3] FIG. 3 diagrammatically illustrates aspects of an approach for simulating a three-dimensional image using multiple depth planes.

[0012] [Figure 4] FIG. 4 diagrammatically illustrates an embodiment of a waveguide stack for outputting image information to a user.

[0013] [Diagram 5] FIG. 5 shows an exemplary output beam that may be output by a waveguide.

[0014] [Figure 6]FIG. 6 is a schematic diagram showing an optical system including a waveguide device, an optical coupler subsystem for optically coupling light to or from the waveguide device, and a control subsystem for use in generating a multifocal volumetric display, image, or light field.

[0015] [Figure 7] FIG. 7 illustrates a waveguide receiving an input light beam that is incident on the waveguide at an angle θ and propagates through the waveguide by multiple total internal reflections.

[0016] [Figure 8A-1] Figure 8A-1 illustrates light output from an embodiment of a waveguide receiving light from an incoherent light source, and Figure 8B-1 illustrates the point spread function of light output from the waveguide depicted in Figure 8A-1.

[0017] [Figure 8A-2] Figure 8A-2 illustrates light output from an embodiment of a waveguide receiving light from a coherent light source, and Figure 8B-2 illustrates the point spread function of light output from the waveguide depicted in Figure 8A-2.

[0018] [Figure 8A-3] Figure 8A-3 illustrates light output from an embodiment of a waveguide receiving light from a coherent light source. Figure 8B-3 illustrates the point spread function of light output from the waveguide depicted in Figure 8A-3. [Figure 8B-1] Figure 8A-1 illustrates light output from an embodiment of a waveguide receiving light from an incoherent light source, and Figure 8B-1 illustrates the point spread function of light output from the waveguide depicted in Figure 8A-1. [Figure 8B-2] Figure 8A-2 illustrates light output from an embodiment of a waveguide receiving light from a coherent light source, and Figure 8B-2 illustrates the point spread function of light output from the waveguide depicted in Figure 8A-2. [Figure 8B-3]Figure 8A-3 illustrates light output from an embodiment of a waveguide receiving light from a coherent light source. Figure 8B-3 illustrates the point spread function of light output from the waveguide depicted in Figure 8A-3.

[0019] [Figure 8C] FIG. 8C illustrates a light beam with a continuous wavefront having a uniform phase output from an embodiment of a waveguide that receives light from a coherent input light source, forming an output light beam, where the optical path length difference between the beams is an integer multiple of the wavelength of the incident light.

[0020] [Figure 9A] FIG. 9A graphically illustrates a graph showing the variation of the refractive index "n" of a waveguide versus the cosine of the input angle.

[0021] [Figure 9B] FIG. 9B diagrammatically illustrates a graph showing the variation of the spacing between the reflective surfaces "d" of a waveguide versus the cosine of the input angle.

[0022] [Figure 9B-1] FIG. 9B-1 illustrates an embodiment of a waveguide that includes three layers, each layer having a variable reflectivity.

[0023] [Figure 9C] FIG. 9C diagrammatically illustrates a graph showing the variation of the wavelength λ of the incident light versus the cosine of the input angle.

[0024] [Figure 10] FIG. 10 illustrates an embodiment of a waveguide comprising a plurality of spatially multiplexed holographic structures configured to output a phase-locked beamlet array for light incident at varying angles of incidence.

[0025] The drawings are provided to illustrate certain example embodiments and are not intended to limit the scope of the present disclosure. Like numbers refer to like parts throughout. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] (overview) In order for a three-dimensional (3D) display to create a true sensation of depth, and more specifically a simulated sensation of surface depth, it may be desirable to generate, for each point in the field of view of the display, an accommodation response that corresponds to that point's virtual depth. If the accommodation response to a display point does not correspond to that point's virtual depth as determined by the binocular depth cues of convergence and stereopsis, the human eye may experience accommodation conflicts, resulting in unstable imaging, deleterious eye strain, headaches, and, in the absence of accommodative information, a near-complete lack of surface depth.

[0027] VR and AR experiences can be provided by a display system having a display in which images corresponding to multiple depth planes are provided to a viewer. The images may be different for each depth plane (e.g., providing slightly different presentations of a scene or object) and may be focused separately by the viewer's eyes, thereby serving to provide depth cues to the user based on the ocular accommodation required to focus on different image features of a scene located on different depth planes and / or based on observing different image features on different depth planes that are out of focus. As discussed elsewhere herein, such depth cues provide a believable perception of depth.

[0028] 2 illustrates an example of a wearable display system 80. The display system 80 includes a display 62 and various mechanical and electronic modules and systems to support the functionality of the display 62. The display 62 may be coupled to a frame 64, which is wearable by a display system user, wearer, or viewer 60 and configured to position the display 62 directly in front of the eye of the user 60. In some embodiments, a speaker 66 is coupled to the frame 64 and positioned adjacent the user's ear canal (in some embodiments, another speaker, not shown, is positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). The display 62 is operably coupled 68, such as by wired leads or wireless connectivity, to a local data processing module 71, which may be mounted in a variety of configurations, such as fixedly attached to the frame 64, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise removably attached to the user 60 (e.g., in a backpack configuration, in a belt-connected configuration), etc.

[0029] The local processing and data module 71 may comprise a hardware processor and digital memory such as non-volatile memory (e.g., flash memory), both of which may be utilized to aid in processing, caching, and storing data. The data may include a) data captured from sensors (e.g., which may be operatively coupled to the frame 64 or otherwise attached to the user 60), such as image capture devices (e.g., cameras), microphones, inertial measurement units, accelerometers, compasses, global positioning system (GPS) units, wireless devices, and / or gyroscopes, and / or b) data obtained and / or processed using the remote processing module 72 and / or remote data repository 74, possibly for passing through the display 62 after processing or readout. The local processing and data module 71 may be operatively coupled to the remote processing module 72 and / or remote data repository 74 by communication links 76 and / or 78, via wired or wireless communication links, etc., such that these remote modules are available as resources to the local processing and data module (71). In addition, the remote processing module 72 and the remote data repository 74 may be operatively coupled to each other.

[0030] In some embodiments, remote processing module 72 may comprise one or more processors configured to analyze and process the data and / or image information. In some embodiments, remote data repository 74 may comprise a digital data storage facility, which may be available through the Internet or other networking configurations in a "cloud" resource configuration. In some embodiments, all data is stored and all calculations are performed in the local processing and data module, allowing for fully autonomous use from the remote module.

[0031] The human visual system is complex and difficult to provide a realistic perception of depth. Without being limited by theory, it is believed that a viewer of an object may perceive the object as three-dimensional due to a combination of vergence and accommodation. Vergence of the two eyes relative to one another (e.g., pupil rotation such that the pupils move toward or away from one another, converging the gaze of the eyes to fixate on an object) is closely linked to the focusing (or "accommodation") of the eye's lenses. Under normal conditions, a change in focus of the eye's lenses or accommodation of the eye to change focus from one object to another at a different distance will automatically produce a matching change in vergence at the same distance, a relationship known as the "accommodation-vergence reflex." Similarly, a change in vergence will induce a matching change in accommodation under normal conditions. Display systems that provide better matching between accommodation and convergence-divergence movements may produce more realistic and comfortable simulations of three-dimensional images.

[0032] FIG. 3 illustrates aspects of an approach for simulating a three-dimensional image using multiple depth planes. With reference to FIG. 3, objects at various distances from the eyes 302 and 304 on the z-axis are accommodated by the eyes 302 and 304 such that the objects are in focus. The eyes 302 and 304 assume a particular accommodated state, focusing objects at different distances along the z-axis. As a result, a particular accommodated state may be said to be associated with a particular one of the depth planes 306 having an associated focal length such that an object or part of an object at a particular depth plane is in focus when the eye is in an accommodated state relative to that depth plane. In some embodiments, a three-dimensional image may be simulated by providing a different presentation of an image for each eye 302 and 304, and by providing a different presentation of an image corresponding to each of the depth planes. Although shown as separate for clarity of illustration, it should be understood that the fields of view of the eyes 302 and 304 may overlap, for example, as the distance along the z-axis increases. In addition, while shown to be flat for ease of illustration, it should be understood that the contours of the depth planes may be curved in physical space such that all features within the depth plane are in focus with the eye in a particular accommodative state. Without being limited by theory, it is believed that the human eye is typically capable of interpreting a finite number of depth planes to provide depth perception. As a result, a highly realistic simulation of perceived depth may be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes.

[0033] (Waveguide Stack Assembly) 4 illustrates an example of a waveguide stack for outputting image information to a user. Display system 100 includes a stack of waveguides or stacked waveguide assembly 178 that may be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 182, 184, 186, 188, 190. In some embodiments, display system 100 may correspond to system 80 shown in FIG. 2, with FIG. 4 diagrammatically illustrating some portions of system 80 in greater detail. For example, in some embodiments, waveguide assembly 178 may be integrated into display 62 of FIG. 2.

[0034] Continuing with reference to FIG. 4, the waveguide assembly 178 may also include a number of features 198, 196, 194, 192 between the waveguides. In some embodiments, the features 198, 196, 194, 192 may be lenses. The waveguides 182, 184, 186, 188, 190 and / or the number of lenses 198, 196, 194, 192 may be configured to transmit image information to the eye with various levels of wavefront curvature or light beam divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image injection devices 200, 202, 204, 206, 208 may be utilized to inject image information into the waveguides 182, 184, 186, 188, 190, which may be configured to distribute incident light across each individual waveguide for output toward the eye 304, respectively. Light exits the output surfaces of the image injection devices 200, 202, 204, 206, 208 and is injected into corresponding input edges of the waveguides 182, 184, 186, 188, 190. In some embodiments, a single beam of light (e.g., a collimated beam) may be injected into each waveguide to output an entire field of cloned collimated beams that are directed towards the eye 304 at a particular angle (and divergence) corresponding to the depth plane associated with the particular waveguide.

[0035] In some embodiments, each of the image input devices 200, 202, 204, 206, 208 is a discrete display that generates image information for input into each corresponding waveguide 182, 184, 186, 188, 190. In some other embodiments, the image input devices 200, 202, 204, 206, 208 are the output of a single multiplexed display that may, for example, send image information to each of the image input devices 200, 202, 204, 206, 208 via one or more optical conduits (such as fiber optic cables).

[0036] A controller 210 controls the operation of the stacked waveguide assembly 178 and the image input devices 200, 202, 204, 206, 208. In some embodiments, the controller 210 includes programming (e.g., instructions in a non-transitory computer readable medium) that coordinates the timing and provision of image information to the waveguides 182, 184, 186, 188, 190. In some embodiments, the controller may be a single integrated device or a distributed system connected by a wired or wireless communication channel. The controller 210 may be part of the processing module 71 or 72 (illustrated in FIG. 2) in some embodiments.

[0037] The waveguides 182, 184, 186, 188, 190 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Each of the waveguides 182, 184, 186, 188, 190 may be planar or have another shape (e.g., curved) with major top and bottom surfaces and edges extending between the major top and bottom surfaces. In the illustrated configuration, the waveguides 182, 184, 186, 188, 190 may each include light extraction optical elements 282, 284, 286, 288, 290 configured to extract light from the waveguides by redirecting the light, propagating it within each individual waveguide, and outputting image information from the waveguides to the eye 304. The extracted light may also be referred to as out-coupled light, and the light extraction optical elements may also be referred to as out-coupling optical elements. The extracted beam of light is output by the waveguide at the location where the light propagating within the waveguide strikes the light redirecting element. The light extraction optical elements 282, 284, 286, 288, 290 may be, for example, reflective and / or diffractive optical features. Although illustrated disposed on the bottom major surfaces of the waveguides 182, 184, 186, 188, 190 for ease of explanation and clarity of drawing, in some embodiments the light extraction optical elements 282, 284, 286, 288, 290 may be disposed on the top and / or bottom major surfaces and / or may be disposed directly within the volume of the waveguides 182, 184, 186, 188, 190. In some embodiments, the light extraction optical elements 282, 284, 286, 288, 290 may be formed in a layer of material that is attached to a transparent substrate and forms the waveguides 182, 184, 186, 188, 190. In some other embodiments, the waveguides 182, 184, 186, 188, 190 may be monolithic pieces of material and the light extraction optical elements 282, 284, 286, 288, 290 may be formed on and / or within that piece of material.

[0038] With continued reference to FIG. 4, as discussed herein, each waveguide 182, 184, 186, 188, 190 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 182 closest to the eye may be configured to deliver collimated light to the eye 304 as it is launched into such waveguide 182. The collimated light may represent an optical infinity focal plane. The next upper waveguide 184 may be configured to send collimated light that passes through a first lens 192 (e.g., a negative lens) before it can reach the eye 304. The first lens 192 may be configured to generate a slight convex wavefront curvature such that the eye / brain interprets the light originating from the next upper waveguide 184 as originating from a first focal plane closer inward from optical infinity toward the eye 304. Similarly, the third upper waveguide 186 passes its output light through both the first lens 192 and the second lens 194 before reaching the eye 304. The combined refractive powers of the first and second lenses 192 and 194 may be configured to produce another incremental amount of wavefront curvature such that the eye / brain interprets the light emerging from the third upper waveguide 186 as emerging from a second focal plane that is closer inward from optical infinity towards the person than was the light from the next upper waveguide 184.

[0039] Other waveguide layers (e.g., waveguides 188, 190) and lenses (e.g., lenses 196, 198) are similarly configured, with the highest waveguide 190 in the stack sending its output through all of the lenses between it and the eye for an aggregate focal force that represents the focal plane closest to the person. To compensate for the stack of lenses 198, 196, 194, 192 when viewing / interpreting light originating from the world 144 on the other side of the stacked waveguide assembly 178, a compensating lens layer 180 may be placed on top of the stack to compensate for the aggregate force of the lens stacks 198, 196, 194, 192 below. Such a configuration provides as many perceived focal planes as there are waveguide / lens pairs available. Both the light extraction optical elements of the waveguides and the focusing sides of the lenses may be static (e.g., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0040] Continuing with reference to FIG. 4, the light extraction optical elements 282, 284, 286, 288, 290 may be configured to redirect light from its respective waveguide and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes may have different configurations of light extraction optical elements that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, as discussed herein, the light extraction optical elements 282, 284, 286, 288, 290 may be volumetric or surface features that may be configured to output light at specific angles. For example, the light extraction optical elements 282, 284, 286, 288, 290 may be volume holograms, surface holograms, and / or diffraction gratings. Light extraction optical elements such as diffraction gratings are described in U.S. Patent Publication No. 2015 / 0178939, published June 25, 2015, which is incorporated by reference in its entirety. In some embodiments, features 198, 196, 194, 192 may not be lenses. Rather, they may simply be spacers (e.g., cladding layers and / or structures for forming air gaps).

[0041] In some embodiments, the light extraction optical elements 282, 284, 286, 288, 290 are diffractive features that form a diffraction pattern or "diffractive optical elements" (also referred to herein as "DOEs"). Preferably, the DOEs have a relatively low diffraction efficiency so that only a portion of the light in the beam is deflected toward the eye 304 at each intersection of the DOE, while the remainder continues traveling through the waveguide via total internal reflection. The light carrying the image information is thus split into several related exit beams that exit the waveguide at multiple locations, resulting in a very uniform pattern of exit emission toward the eye 304 for this particular collimated beam bouncing within the waveguide.

[0042] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer dispersed liquid crystal in which microdroplets comprise a diffractive pattern in a host medium, and the refractive index of the microdroplets can be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets can be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0043] In some embodiments, the number and distribution of depth planes and / or depths of field may be dynamically varied based on the pupil size and / or orientation of the viewer's eyes. In some embodiments, a camera 500 (e.g., a digital camera) may be used to capture images of the eye 304 and determine the size and / or orientation of the pupil of the eye 304. The camera 500 may be used to obtain images for use in determining the direction the wearer 60 is looking (e.g., eye pose) or for biometric identification of the wearer (e.g., via iris identification). In some embodiments, the camera 500 may be mounted to the frame 64 (as illustrated in FIG. 2) and may be in electrical communication with processing modules 71 and / or 72, which may process image information from the camera 500 and, for example, determine the pupil diameter and / or orientation of the user 60's eyes. In some embodiments, one camera 500 may be utilized per eye to separately determine the pupil size and / or orientation of each eye, thereby allowing the presentation of image information to each eye to be dynamically tailored to that eye. In some other embodiments, the pupil diameter and / or orientation of only one eye 304 (e.g., using only a single camera 500 per pair of eyes) is determined and assumed to be similar for both eyes of the viewer 60.

[0044] For example, the depth of field may vary inversely with the viewer's pupil size. As a result, as the size of the viewer's eye pupil decreases, the depth of field increases so that one plane that is indistinguishable because its location exceeds the eye's focal depth may become distinguishable and appear more focused with a corresponding increase in the depth of field with a reduction in pupil size and a corresponding increase in the depth of field. Similarly, the number of spaced depth planes used to present different images to the viewer may be reduced with a reduced pupil size. For example, the viewer may not be able to clearly perceive details of both the first and second depth planes at one pupil size without adjusting the eye's accommodation from one depth plane to the other. However, these two depth planes may be sufficient to simultaneously focus the user at another pupil size without changing accommodation.

[0045] In some embodiments, the display system may vary the number of waveguides that receive image information based on a determination of pupil size and / or orientation, or in response to receiving an electrical signal indicative of a particular pupil size and / or orientation. For example, if the user's eye is unable to distinguish between two depth planes associated with two waveguides, the controller 210 may be configured or programmed to stop providing image information to one of those waveguides. Advantageously, this may reduce the processing burden on the system, thereby increasing the responsiveness of the system. In embodiments in which the DOE for a waveguide is switchable between on and off states, the DOE may be switched to the off state when the waveguide receives image information.

[0046] In some embodiments, it may be desirable to have the exit beam meet the condition of having a diameter less than the diameter of the viewer's eye. However, meeting this condition may be difficult in light of the variability in the size of the viewer's pupil. In some embodiments, this condition is met over a wide range of pupil sizes by varying the size of the exit beam in response to a determination of the size of the viewer's pupil. For example, as the pupil size decreases, the size of the exit beam may also decrease. In some embodiments, the exit beam size may be varied using a variable aperture.

[0047] 5 shows an example of an output beam output by a waveguide. Although one waveguide is shown, it will be understood that other waveguides in the waveguide assembly 178 may function similarly and that the waveguide assembly 178 includes multiple waveguides. Light 400 is launched into the waveguide 182 at the input edge 382 of the waveguide 182 and propagates within the waveguide 182 by TIR. At the point where the light 400 strikes the DOE 282, a portion of the light exits the waveguide as an output beam 402. The output beam 402 is shown as approximately parallel, but may also be redirected to propagate to the eye 304 at an angle (e.g., divergent output beam formation) depending on the depth plane associated with the waveguide 182. It will be understood that a nearly collimated exit beam may refer to a waveguide with light extraction optics that outcouples light to form an image that appears to be set at a depth plane at a large distance (e.g., optical infinity) from the eye 304. Other waveguides or other sets of light extraction optics may output a more divergent exit beam pattern, which would require the eye 304 to accommodate to a closer distance and focus on the retina, and would be interpreted by the brain as light from a distance closer to the eye 304 than optical infinity.

[0048] FIG. 6 shows another embodiment of an optical display system 100 including a waveguide device, an optical coupler subsystem for optically coupling light to or from the waveguide device, and a control subsystem. The optical display system 100 can be used to generate multifocal volumes, images, or light fields. The optical system can include one or more primary planar waveguides 1 (only one is shown in FIG. 6) and one or more DOEs 2 associated with each of at least some of the primary waveguides 1. The planar waveguides 1 can be similar to the waveguides 182, 184, 186, 188, 190 discussed with reference to FIG. 4. The optical system may employ a dispersive waveguide device to relay light along a first axis (the vertical or Y-axis in the view of FIG. 6). In various embodiments, the distributed waveguide device may be configured to expand the effective exit pupil of light along a first axis (e.g., the Y-axis) and / or expand the area where a viewer may position their eyes to view the optical display system (also referred to herein as the eyebox). The distributed waveguide device may include, for example, a distributed planar waveguide 3 and at least one DOE 4 (illustrated by a double dashed line) associated with the distributed planar waveguide 3. The distributed planar waveguide 3 may be similar or the same in at least some respects as the primary planar waveguide 1 with a different orientation therefrom. Similarly, the at least one DOE 4 may be similar or the same in at least some respects as the DOE 2. For example, the distributed planar waveguide 3 and / or the DOE 4 may be made of the same material as the primary planar waveguide 1 and / or the DOE 2, respectively. The embodiment of the optical display system 100 shown in FIG. 4 or 6 can be integrated into the wearable display system 80 shown in FIG. 2.

[0049] The relayed, exit pupil expanded light is optically coupled from the dispersive waveguide device into one or more primary planar waveguides 1. The primary planar waveguides 1 preferably relay the light along a second axis (e.g., the horizontal or X-axis in the diagram of FIG. 6) that is orthogonal to the first axis. Notably, the second axis can be a non-orthogonal axis to the first axis. In various embodiments, the primary planar waveguides 1 can be configured to expand the effective exit pupil of the light along its second axis (e.g., the X-axis) and / or expand the eyebox through which a viewer may view the optical display system. For example, the dispersive planar waveguides 3 can relay and expand the light along the vertical or Y-axis and pass the light through a primary planar waveguide 1 that relays and expands the light along the horizontal or X-axis.

[0050] The optical system may include one or more colored light sources (e.g., red, green, and blue laser light) 110 that may be optically coupled into the proximal end of a single mode optical fiber 9. The distal end of the optical fiber 9 may be threaded or received through a hollow tube 8 of piezoelectric material. The distal end protrudes from the tube 8 as an unfixed flexible cantilever 7. The piezoelectric tube 8 may be associated with four quadrant electrodes (not shown). The electrodes may be, for example, plated on the outside, outer surface or outer periphery, or diameter of the tube 8. A core electrode (not shown) is also located in the core, center, inner periphery, or inner diameter of the tube 8.

[0051] Drive electronics 12, electrically coupled, for example, via wires 10, drive opposing pairs of electrodes to bend the piezoelectric tube 8 independently in two axes. The protruding distal tip of the optical fiber 7 has a mechanical resonant mode. The frequency of the resonance may depend on the diameter, length, and material properties of the optical fiber 7. By oscillating the piezoelectric tube 8 near the first mechanical resonant mode of the fiber cantilever 7, the fiber cantilever 7 may be caused to oscillate and sweep through a large deflection.

[0052] By stimulating resonant vibrations in two axes, the tip of the fiber cantilever 7 is scanned biaxially within an area filling a two-dimensional (2-D) scan. By modulating the intensity of the light source 11 synchronously with the scanning of the fiber cantilever 7, the light emitted from the fiber cantilever 7 forms an image. A description of such a setup is provided in U.S. Patent Publication No. 2014 / 0003762, which is incorporated herein by reference in its entirety.

[0053] An optical coupler subsystem component 6 collimates the light emanating from the scanning fiber cantilever 7. The collimated light is reflected by a mirrored surface 5 into a narrow dispersive planar waveguide 3, which contains at least one diffractive optical element (DOE) 4. The collimated light propagates perpendicularly (with respect to the view of FIG. 6) along the dispersive planar waveguide 3 by total internal reflection, and in so doing repeatedly intersects with the DOE 4. The DOE 4 preferably has a low diffraction efficiency. This causes a portion of the light (e.g., 10%) to diffract toward the edge of the larger primary planar waveguide 1 at each point of intersection with the DOE 4, and a portion of the light to continue on its original trajectory down the length of the dispersive planar waveguide 3 via TIR.

[0054] At each point of intersection with the DOE 4, additional light is diffracted towards the entrance of the primary planar waveguide 1. By splitting the incoming light into multiple outcoupled sets, the exit pupil of the light can be vertically expanded by the DOE 4 in the dispersive planar waveguide 3 and / or the eyebox can also be expanded. This vertically expanded light outcoupled from the dispersive planar waveguide 3 enters the edge of the primary planar waveguide 1.

[0055] Light entering the primary waveguide 1 propagates horizontally (with respect to the view of FIG. 6) along the primary waveguide 1 via TIR. The light propagates horizontally along at least a portion of the length of the primary waveguide 1 via TIR as it intersects with DOE2 at multiple points. DOE2 advantageously has a phase profile that is the sum of a linear diffraction pattern and a radially symmetric diffraction pattern, and may be designed or configured to produce both deflection and focusing of the light. DOE2 advantageously may have a low diffraction efficiency (e.g., 10%) such that only a portion of the light in the beam is deflected towards the viewer's eye at each intersection of DOE2, while the remainder of the light continues to propagate through the waveguide 1 via TIR.

[0056] At each point of intersection between the propagating light and DOE2, a portion of the light is diffracted towards the exit surface of the primary waveguide 1, allowing the light to escape the TIR and emerge from the exit surface of the primary waveguide 1. In some embodiments, the radially symmetric diffraction pattern of DOE2 additionally imparts divergence to the diffracted light such that it appears to result from the focal depth, thereby shaping (e.g., imparting curvature) the optical wavefronts of the individual beams and steering the beams to angles that match the designed focal depth.

[0057] Thus, these different paths can couple light out of the primary planar waveguide 1 by resulting in different fill patterns at the exit pupil, focal depth, and / or multiplicity of the DOE 2 at different angles. Different fill patterns at the exit pupil can be advantageously used to generate light field displays with multiple depth planes. Each layer or set of layers (e.g., three layers) in the waveguide assembly or stack may be employed to generate individual colors (e.g., red, blue, green). Thus, for example, a first set of three layers may be employed to generate red, blue, and green light, respectively, at a first focal depth. A second set of three layers may be employed to generate red, blue, and green light, respectively, at a second focal depth. Multiple sets may be employed to generate full 3D or 4D color image light fields with various focal depths.

[0058] (Other components of the AR system) In many implementations, the AR system may include other components in addition to the wearable display system 80 (or optical system 100). The AR device may include, for example, one or more tactile devices or components. The tactile devices or components may be operable to provide a sense of touch to the user. For example, the tactile device or component may provide a sense of pressure and / or texture upon touching the virtual content (e.g., a virtual object, virtual tool, other virtual structure). The haptics may replicate the sensation of a physical object that the virtual object represents, or may replicate the sensation of an imaginary object or character (e.g., a dragon) that the virtual content represents. In some implementations, the tactile device or component may be worn by the user (e.g., a user-wearable glove). In some implementations, the tactile device or component may be held by the user.

[0059] An AR system may include, for example, one or more physical objects that can be manipulated by a user to allow input to or interaction with the AR system. These physical objects may be referred to herein as totems. Some totems may take the form of inanimate objects, such as, for example, pieces of metal or plastic, walls, the surface of a table, etc. Alternatively, some totems may take the form of animate objects, such as a user's hand. As described herein, a totem may not actually have any physical input structures (e.g., keys, triggers, joysticks, trackballs, rocker switches). Instead, a totem may simply provide a physical surface, and the AR system may render a user interface to appear to the user on one or more surfaces of the totem. For example, the AR system may render images of a computer keyboard and trackpad to appear to reside on one or more surfaces of the totem. For example, the AR system may render a virtual computer keyboard and virtual trackpad to appear on the surface of a thin rectangular plate of aluminum that serves as the totem. The rectangular plate itself does not have any physical keys or trackpad or sensors, however, the AR system may detect user manipulation or interaction or touch with the rectangular plate as a selection or input made via a virtual keyboard or virtual trackpad.

[0060] Examples of tactile devices and totems usable with the AR devices, HMDs, and display systems of the present disclosure are described in U.S. Patent Publication No. 2015 / 0016777, which is incorporated by reference in its entirety herein.

[0061] (Optical system with exit pupil expander) An optical system (e.g., wearable display system 80 or optical system 100) comprising a waveguide (e.g., planar waveguide 1) configured to output in-coupled light propagating through the waveguide via total internal reflection can be associated with an exit pupil configured such that light rays exiting the system through the exit pupil can be viewed by a user. An exit pupil larger than the pupil size of the user's eye wastes some light but allows some tolerance in lateral movement of the user's head or eye. The optical system can also be associated with an eyebox, which corresponds to a volume in which a user may place their eye without sacrificing the full field of view (FOV) and / or full resolution of the optical system.

[0062] Various embodiments of an optical system (e.g., wearable display system 80 or optical system 100) can include additional waveguides (e.g., a dispersive waveguide device 3 illustrated in FIG. 6) configured to increase the size of the light beam exiting the optical system. Increasing the size of the light beam exiting the optical system can advantageously expand the size of the exit pupil of the optical system. Expanding the size of the exit pupil can be useful when the optical system is configured to be viewed directly by a user and / or in eyepiece display applications. Expanding the size of the exit pupil can also be advantageous in reducing eye strain when viewing the optical system.

[0063] Various embodiments of the optical system (e.g., wearable display system 80 or optical system 100) may include a waveguide (e.g., planar waveguide 1) having two reflective surfaces, i.e., a first reflective surface and a second reflective surface. An incident light beam incident on the first reflective surface at an angle θ may be coupled into the waveguide to propagate through the waveguide via total internal reflection at the first and second reflective surfaces. Each occurrence of total internal reflection at the first and second reflective surfaces may be considered to produce a copy of the incident light beam. Thus, multiple copies of the incident light beam may be produced as the light beam propagates through the waveguide. An incident light beam propagating through the waveguide may be outcoupled from the waveguide through the second reflective surface. Each copy of the incoupled light beam may be considered a kaleidoscope-like copy or mirror image of the incoupled light beam. Thus, the light coupled out of the second reflective surface of the waveguide can be considered to include a beamlet array, which includes multiple light beams that are copies of the internally coupled light beam. Each of the multiple light beams can have a beam diameter equal to the beam diameter of the internally coupled light beam. Each of the multiple light beams of the beamlet array can appear to originate from a virtual source, which is located on one side of the reflective surface where the internally coupled light beam is totally internally reflected. Thus, each reflective surface of the waveguide produces a set of mirror copies of the input light source that emits an incident light beam. The set of mirror copies appears to be on one side of the respective reflective surface. This is further described below with reference to FIG. 7, which illustrates an internally coupled light beam 701 incident on a first reflective surface 712b of the waveguide 710 at an angle θ and propagating through the waveguide 710 by multiple total internal reflections at the first reflective surface 712b and the second reflective surface 712a opposite the first reflective surface 712b of the waveguide 710. Reflected light beams 702, 703, 704, 705, and 706 are reflected from surfaces 712a and / or 712b at an angle θ with respect to a normal to surfaces 712a and / or 712b. As discussed above, each reflected beam 702, 703, 704, 705, and 706 can be considered a copy of incombined light beam 701.A portion of each reflected beam 702, 703, 704, 705, and 706 may exit the waveguide 710 through the second reflective surface 712a to form a beamlet array including a plurality of light beams, each light beam in the plurality of light beams being a copy of the incombined light beam. For example, each light beam in the plurality of light beams may comprise the same image information. In various embodiments, the portion of each reflected beam 702, 703, 704, 705, and 706 in the beamlet array may have a size equal to the size of the incombined light beam 701. FIG. 7 illustrates a simplified one-dimensional version of a two-dimensional beamlet array produced by an optical system (e.g., wearable display system 80 or optical system 100) that includes a waveguide (e.g., planar waveguide 1). This two-dimensional beamlet array may extend, for example, along the plane of the first / second reflective surfaces of the waveguide (e.g., planar waveguide 1).

[0064] For example, a pivotable optical system, such as a human eye, viewing one of the two surfaces of waveguide 710 (e.g., second reflective surface 712a as illustrated in FIG. 7 ) can receive a portion of one or more of reflected beams 702, 703, 704, 705, and 706 exiting waveguide 710. In some such embodiments, the pivotable optical system can perceive (i) other reflected beams propagating in a parallel direction to the incoupling beam 701 (e.g., reflected beams 703 and 705) towards surface 712a as emitted from sources (e.g., 701p, 703p, 705p) located on a plane 715 perpendicular to the incoupling light beam 701 and the waveguide 710, and (ii) reflected beams propagating in a parallel direction to the reflected beam 702 (e.g., reflected beams 704 and 706) towards surface 712b as emitted from sources (e.g., 702p, 704p, 706p) located on the plane 715. The multiple sources 701p, 702p, 703p, 704p, 705p, and 706p are mirror copies of the input source from which the incoupling light beams are emitted. 7, sources 701p, 703p, and 705p can be perceived as being located below the waveguide 710, and sources 702p, 704p, and 706p can be perceived as being located above the waveguide 710. Sources 701p, 703p, and 705p can be equidistant from each other. Sources 702p, 704p, and 706p can also be equidistant from each other. If the input light sources are coherent, the optical wavefronts produced by the multiple mirrored sources 701p, 702p, 703p, 704p, 705p, and 706p can interact with each other to produce angle-selective interference patterns that may be similar to interference patterns produced by Fabry-Perot interferometers, Bragg gratings, and thin film optics. The distance s between the continuous point sources 701p, 703p, and 705p (or 702p, 704p, and 706p) can be equal to twice the product of the waveguide thickness "d" corresponding to the distance between surfaces 712a and 712b and the refractive index "n" of the waveguide 710.Therefore, the distance s between the successive point sources 701p, 703p, and 705p (or 702p, 704p, and 706p) can be calculated using the equation s=2nd. As depicted in FIG. 7, the distance b between two adjacent light beams in the beamlet array (also referred to herein as inter-beamlet spacing) propagating along the same direction and produced by multiple virtual sources 701p, 703p, and 705p (or 702p, 704p, and 706p) is given by the equation b=2ndsinθ, where the angle θ is the angle of incidence of the internally coupled light beams. Without any loss of generality, light from an input light source can be coupled into the waveguide 710 through one of the reflective surfaces 712a or 712b, or through one of the edges between the reflective surfaces 712a or 712b. In various embodiments where the incoupled light beam is introduced into the waveguide 710 by a projector (e.g., a projection system including a fiber cantilever 7 as illustrated in FIG. 6), the angle θ can be a scan angle. The optical path length, Γ, between adjacent light beams of the beamlet array is given by the equation Γ=2ndcosθ.

[0065] The point spread function (PSF) of the beamlet array output from the waveguide may depend on the characteristics of the input light source that outputs the in-coupled light beam 701. This is described herein with reference to Figures 8A-1, 8A-2, 8A-3, 8B-1, 8B-2, and 8B-3. Figure 8A-1 illustrates an embodiment of a waveguide 710 configured to receive light output from an incoherent input light source, such as an LCOS projector. The incoherent input light source illuminating the embodiment of the waveguide 710 outputs an incoherent beam of light having a beam diameter "a". The beamlet array output from the waveguide 710 includes light beams 801a, 801b, and 801c. Because the input light source is incoherent, the light beams 801a, 801b, and 801c are mutually incoherent with respect to each other such that the phase relationship between the light beams 801a, 801b, and 801c exiting the waveguide cannot be determined. In addition, for the embodiment illustrated in FIG. 8A-1, the inter-beamlet spacing b between two adjacent light beams (e.g., between 801a and 801b or between 801b and beam 801c) exceeds the beam diameter of each light beam in the output beamlet array, which is approximately the same as the beam diameter "a" of the input light beam. FIG. 8B-1 illustrates a diffraction pattern 805a of an individual beam of the beamlet array output from an embodiment of the waveguide 710 illustrated in FIG. 8A-1 that receives light from an incoherent input light source. The diffraction pattern 805a illustrated in FIG. 8B-1 has a central peak and two side lobes. Each side lobe also includes a peak. The width θ between the maxima of the first side lobe of the diffraction pattern 805a a can provide a measure of the aperture size of an optical system including a waveguide 710 driven by an incoherent light source and is proportional to the ratio λ / a, where λ is the wavelength of the incident light and "a" is the beam diameter. The point spread function (PSF) for a beamlet array output from an embodiment of a waveguide 710 receiving light from an incoherent input light source as illustrated in FIG. 8A-1 is the width θ of the diffraction pattern 805a. aand is comparable to the wide diffraction envelope produced by a single beam with a beam diameter equal to "a". The PSF represents the image that the optical system forms of a point source. The PSF of a perfect optical system is an Airy pattern, which consists of a central spot or peak or bright region surrounded by concentric annulus of reduced intensity. The space between the central spot and successive concentric annulus has reduced intensity. At large distances from the aperture or pupil with size d, the angle θ between the axis intersecting the center of the central spot and the region of reduced intensity between the central spot and the first concentric annulus is given by the equation [ka] where λ is the wavelength of light. Thus, as the size of the central spot becomes smaller, the pupil size becomes larger. Thus, the Airy pattern (or PSF) can provide a measure of the pupil size of an optical system. Without being bound to any theory, systems with larger pupil sizes have narrower PSFs.

[0066] 8A-2 illustrates an embodiment of a waveguide 710 configured to receive light output from a coherent input light source. The coherent input light source illuminating the embodiment of the waveguide 710 outputs a coherent beam of light having a beam diameter "a". The beamlet array exiting the waveguide 710 includes light beams 802a, 802b, and 802c. Because the input light source is coherent, the light beams 802a, 802b, and 802c are mutually coherent with respect to one another such that the phase relationship between the light beams 802a, 802b, and 802c exiting the waveguide is deterministic. In addition, for the embodiment illustrated in FIG. 8A-2, the inter-beamlet spacing b between two adjacent light beams (e.g., between 802a and 802b or between 802b and beam 802c) exceeds the beam diameter of each light beam in the output beamlet array, which is approximately the same as the beam diameter "a" of the input light beam. FIG. 8B-2 illustrates an interference pattern 805b produced by optical interference between coherent light beams 802a, 802b, and 802c. The interference pattern 805b illustrated in FIG. 8B-2 has a central peak and four side lobes. Each side lobe also includes a peak. The width θ between the maxima of the first side lobe of the interference pattern 805b is approximately 1 / 2. bis proportional to the ratio λ / b, where λ is the wavelength of the incident light and b is the inter-beamlet spacing. The point spread function (PSF) for the beamlet array output from the embodiment of the waveguide 710 illustrated in FIG. 8A-2 receiving light from a coherent input light source is the product of the interference pattern and the diffraction envelope of the individual beams of the array, which is depicted by pattern 805a. Thus, the PSF for the beamlet array output from the embodiment of the waveguide 710 illustrated in FIG. 8A-2 receiving light from a coherent input light source corresponds to the diffraction envelope produced by a single beam having a beam diameter equal to "a" that is angularly filtered by the interference pattern produced by the mutual interaction between the coherent beams of the beamlet array. The spacing between the filter points of the interference pattern produced by the mutual interaction between the coherent beams of the beamlet array is directly proportional to the optical wavelength λ of the beam and inversely proportional to the inter-beamlet spacing b. The aperture size for the beamlet array output from the embodiment of waveguide 710 illustrated in FIG. 8A-2 that receives light from a coherent input light source may exceed the aperture size of the optical system, including the waveguide 710 driven by an incoherent input light source.

[0067] 8A-3 illustrates an embodiment of a waveguide 710 configured to receive light output from a coherent input light source. The coherent input light source illuminating the embodiment of the waveguide 710 outputs a coherent beam of light having a beam diameter "a". The beamlet array exiting the waveguide 710 is a composite beam including light beams 803a, 803b, and 803c. Because the input light source is coherent, light beams 803a, 803b, and 803c are mutually coherent with respect to one another such that the phase relationship between light beams 803a, 803b, and 803c exiting the waveguide is deterministic. In addition, for the embodiment illustrated in Figure 8A-3, the inter-beamlet spacing b between two adjacent light beams (e.g., between 803a and 803b or between 803b and beam 803c) is adjusted to be approximately equal to the beam diameter of each light beam in the output beamlet array, which is approximately the same as the beam diameter "a" of the input light beam, and the optical path length difference Γ = 2ndcosθ is an integer multiple of the wavelength λ. For this embodiment of waveguide 710 driven by a coherent light source, where the angle of incidence and the thickness and refractive index of waveguide 710 are an integer multiple of the wavelength λ, the various coherent beams of the beamlet array merge to form a continuous wavefront with a uniform phase. The corresponding PSF, obtained by multiplying the interference pattern 805c shown in FIG. 8B-3 with the diffraction envelope of an individual beam illustrated by curve 805a, is comparable to the narrower diffraction envelope produced by a single beam with diameter “A” equal to the product of the number of beamlets in the composite beam and the beam diameter “a” of each individual beam in the beamlet array.

[0068] FIG. 8C illustrates a light beam 810 with a continuous wavefront 815 having uniform phase output from an embodiment of a waveguide 710 receiving light from a coherent input light source, where the optical path length difference Γ=2ndcosθ is an integer multiple of the wavelength λ. As discussed above, the beam diameter "A" of the light beam 810 exceeds the beam diameter "a" of the input light beam. In an optical system where light from a coherent input light source is incident at an angle θ on a waveguide having a refractive index "n" and a thickness "d" such that the optical path length difference Γ=2ndcosθ is an integer multiple of the wavelength λ of the incident light, the waveguide can be configured to function as an exit pupil expander (EPE). An optical system where the optical path length difference Γ=2ndcosθ is not an integer multiple of the wavelength λ of the incident light does not necessarily have to expand the exit pupil of the system, but instead can expand the eyebox of the system. Expanding the eyebox can advantageously increase the tolerance of a system (eg, wearable display system 80 or optical system 100) to lateral movement of the user's head or eyes.

[0069] In embodiments of an optical system (e.g., optical system 100) in which light from a scanning projector (e.g., a projection system including a fiber cantilever 7 illustrated in FIG. 6) is in-coupled into a light guide (e.g., a planar waveguide 1), the aperture size of the projector can be small. For example, the output aperture size of the projector can be 25 microns or more and 50 microns or less, 35 microns or more and 75 microns or more, 50 microns or more and 100 microns or less, or values ​​therebetween. Various embodiments of such optical systems employ complex lens-based optical systems to expand the input aperture, which corresponds to the aperture size of the projector. For example, an optical system employed to expand the exit pupil may be configured to achieve an output aperture of about 200 microns or more and about 1 mm or less, about 250 microns or more and about 950 microns or less, about 300 microns or more and about 900 microns or less, about 350 microns or more and about 850 microns or less, about 400 microns or more and about 800 microns or less, about 450 microns or more and about 750 microns or less, about 500 microns or more and about 700 microns or less, about 550 microns or more and about 650 microns or less, about 600 microns or more and about 650 microns or less, or values ​​therebetween.

[0070] While lens-based exit pupil expander systems can achieve the desired output aperture size, they can be bulky and heavy, making them impractical for integration with eyepiece display systems. As discussed above, a waveguide, having a refractive index "n" and a thickness "d", can function as an EPE when the optical path length difference Γ=2ndcosθ between adjacent beams of a beamlet array output from the waveguide, which is an integer multiple of the wavelength λ of the incident light, can expand the exit pupil. Thus, a waveguide can provide a compact way of increasing the exit pupil of an optical system without contributing weight or bulk.

[0071] However, an optical system including a waveguide, as described in Figures 8A-1 to 8C, can function as an exit pupil expander only when the incidence angle at which the input light is incoupled into the waveguide, the refractive index "n" of the waveguide, and the thickness "d" of the waveguide are configured such that the optical path length difference Γ=2ndcosθ between adjacent beams of the beamlet array output from the waveguide is an integer multiple of the wavelength λ. Light from a scanning projector (e.g., a light source including a fiber cantilever 7 as illustrated in Figure 6) is incident on an optical system employing a waveguide as an exit pupil expander, and the incidence angle θ at which the input light is incoupled into the waveguide varies with the scan angle of the scanning projector, which sweeps a solid angle Θ corresponding to the field of view (FOV) of the optical system. For example, the input angle θ can vary from about 30 degrees to about 50 degrees of solid angle Θ. When the scanning projector includes a fiber (e.g., a light source including a fiber cantilever 7 as illustrated in FIG. 6), the frequency at which the input angle θ varies can be equal to the frequency at which the fiber turns. In various embodiments of a scanning projector including a fiber, the fiber can turn 11,000 to 30,000 times per second. Thus, the input angle θ in such embodiments can vary at a frequency from about 0.1 MHz to about 10 MHz.

[0072] As the angle of incidence at which the input light is in-coupled into the waveguide varies within the solid angle Θ, the beamlet array output from the waveguide is angularly filtered by a discrete two-dimensional (2D) grid of focused spots, as described above with reference to Figures 8A-2 and 8B-2. The focused spots may correspond to a set of angles that satisfy the phase-locking condition that the optical path length difference between adjacent beams is an integer multiple of the wavelength of light. Angular filtering of the beamlet array by a discrete two-dimensional (2D) grid of focused spots can produce interference maxima corresponding to bright, tightly focused pixels and interference minima corresponding to dark or blank pixels as the angle of incidence varies within the solid angle Θ, if the optical and mechanical properties of the waveguide (e.g., refractive index "n" and thickness "d") do not vary correspondingly such that the optical path length difference between adjacent beams of the beamlet array is an integer multiple of the wavelength of light. Thus, the intensity of the beamlet array output from the waveguide may vary intermittently as the angle of incidence varies within the solid angle Θ between maximum and minimum brightness if the optical and mechanical properties (e.g., refractive index "n" and thickness "d") of the waveguide do not vary correspondingly such that the optical path length difference between adjacent beams of the beamlet array is an integer multiple of the wavelength of light. Thus, an image projected through an embodiment of an optical system in which the angle of incidence varies but the mechanical properties of the waveguide and / or the wavelength of the incident light remain the same such that the optical path length difference between adjacent beams of the beamlet array is not an integer multiple of the wavelength of light for all angles of incidence may appear as if the image has been sieved by a black mesh.

[0073] In an optical system including a scanning projector with a small aperture size as an optical signal source and a waveguide as an exit pupil expander, it is advantageous to control one or more of the optical and / or mechanical properties of the display system and / or the input beam to maintain the intensity of the projected image at an intensity level above a threshold. The optical and / or mechanical properties may include the spacing between the reflective surfaces of the waveguide (also referred to as the thickness "d"), the refractive index "n" of the waveguide, or the wavelength λ of the input optical signal. The optical and / or mechanical properties of the display system and / or the input beam can be controlled to be synchronized with the variation of the scan angle of the input beam in such a manner that a discrete two-dimensional (2D) grid of focused spots can be angularly shifted and all the scan angles of the projector will produce a beamlet array with a compact tightly focused PSF (similar to the PSF depicted in FIG. 8B-3).

[0074] An output beam produced by an optical system comprising a waveguide that splits a scanning input beam into a regular two-dimensional beamlet array containing multiple light beams can have a beam diameter that exceeds the beam diameter of an individual one of the multiple light beams of the beamlet array when one or more of the physical or optical properties of the waveguide and / or the wavelength of the scanning input beam are varied at a frequency approximately equal to the scan rate. Varying one or more of the physical or optical properties of the waveguide and / or the wavelength of the scanning input beam at a frequency approximately equal to the scan rate can advantageously control the relative phase shift between the light beams in the beamlet array such that the output beam has a continuous wavefront with a uniform phase. Such an embodiment of the optical system can be considered to function as an optical phase array capable of forming and steerable an output beam with a larger beam diameter. In such optical systems, the scanning technique of the projector can steer the input beam between preferred angles of the angular filter grid of the waveguide (corresponding to a 2D grid of focused spots), and the modulation technique employed to vary one or more of the physical or optical properties of the waveguide and / or the wavelength of the scanning input beam at the frequency of the scan rate is responsible for steering the angular filter grid between different angles of the input beam. In various embodiments, the waveguide can be configured such that the beamlet array output from the waveguide forms a light beam having a continuous wavefront with uniform phase and a beam diameter larger than the beam diameter of the individual beams in the beamlet array without dynamically varying one or more of the physical or optical properties of the waveguide and / or the wavelength of the scanning input beam at the frequency of the scan rate (e.g., by utilizing one or more holographic structures). Systems and methods that can dynamically or non-dynamically achieve phase synchronization between the various light beams of the beamlet array for different scan angles of the input light beam are discussed below.

[0075] (1. Dynamic Phase Synchronization) Various techniques and methods can be used to vary one or more of the physical or optical properties of the waveguide and / or the wavelength of the scanning input beam at the frequency of the scan rate to dynamically achieve phase synchronization between the various light beams of the beamlet array for different scan angles of the input light beam, as discussed below. In various embodiments, the optical system can include a control system configured to control one or more of the physical or optical properties of the waveguide (e.g., refractive index, distance between reflective surfaces of the waveguide) and / or the wavelength of the input beam. The control system can include a feedback loop to continuously maintain phase synchronization between the individual light beams of the beamlet array.

[0076] (1.1. Refractive Index) As discussed above, to maintain phase lock between the individual light beams of the beamlet array, the optical path length difference Γ=2ndcosθ should be an integer multiple of the wavelength λ. Thus, if the refractive index of the material of the waveguide is varied at the frequency of the scan rate (or at the frequency at which θ is varied) such that the optical path length difference Γ=2ndcosθ is an integer multiple of the wavelength λ for all input angles θ, then phase lock between the individual light beams of the beamlet array can be maintained for all input angles θ. FIG. 9A graphically illustrates a graph showing the variation of the refractive index "n" of the waveguide versus the cosine of the scan angle θ. Points 901a, 901b, and 901c in FIG. 9A are plotted against the term 2n 0 dcosθ m , 2n 0 dcosθ m+1 , and 2n 0 dcosθ m+2 are equal to mλ, (m+1)λ, and (m+2)λ, respectively, where m is an integer; m , θ m+1 , and θ m+2 Refractive index value n 0 Point 901d in FIG. 9A refers to the term [ka] The scan angle θ such that is equal to mλ, where m is an integer. m+1 Refractive index value at [ka] has. Point 901e in FIG. 9A corresponds to the term [ka] The scan angle θ such that is equal to (m+1)λ, where m is an integer. m+2 Refractive index value at [ka] In FIG. 9A, m is [ka] but [ka] Only some of the possible values ​​of the refractive index "n" for which 2ndcosθ is an integer multiple of the wavelength λ are depicted in FIG. 9A. Other values ​​of the refractive index "n" for which 2ndcosθ is an integer multiple of the wavelength λ are also possible. m and θ m+1 (or θ m+1 and θ m+2 ), the value of the refractive index can be changed such that 2ndcosθ remains an integer multiple of the wavelength λ. For small changes in the value of the refractive index "n", the scan angle θ m and θ m+1 (or θ m+1 and θ m+2 The variation in refractive index "n" between the refractive index "n" and the refractive index "n" can be linear, as depicted in FIG. 9A. In various embodiments, the refractive index can be varied by an amount Δn of about 25% or less of the base refractive index. The base refractive index is the refractive index value n discussed above. 0For example, the refractive index can be varied by an amount Δn of about 10% or less, about 15% or less, or about 20% or less of the base refractive index. As discussed above, the variation of the refractive index can be synchronized with the variation of the scan angle θ. As another example, the refractive index can be varied by an amount Δn of approximately 0.001 to about 0.01. The variation of the refractive index can be periodic, as depicted in FIG. 9A.

[0077] The refractive index of the waveguide material can be varied by a variety of techniques, including, but not limited to, varying the parameters of an electric or optical field, varying the temperature of the waveguide material, varying the chemical composition and / or concentration of various materials contained within the waveguide, piezo-optical effects, and the like. For example, the waveguide can include crystalline and / or liquid crystal materials, whose refractive index can be varied with the application of an electric field through a number of different electro-optical effects. As another example, the waveguide can include a liquid solution, whose refractive index can be varied by controlling the mixture and relative concentration of the solution. As another example, the waveguide can include a chemically active substrate, whose refractive index can be varied by controlling the rate and / or results of a chemical reaction within the material comprising the waveguide. For example, in some embodiments, the rate and / or results of a chemical reaction within the material comprising the waveguide can be controlled by the application of an electric field, the application of an optical field, or both. As another example, in some embodiments, the rate and / or results of a chemical reaction within the material comprising the waveguide can be controlled through the use of a chemical pump. A change in optical wavelength can also produce a change in refractive index. Thus, in various embodiments, the change in refractive index can be correlated to the wavelength λ of the light incident on the waveguide. For example, the wavelength λ of the incident light can vary due to various factors, including, but not limited to, modulation, nonlinearity, and / or dispersion of the light incident on the waveguide. For example, in various embodiments, the wavelength λ of the incident light can vary due to modulation, but not limited to, the wavelength λ of the non-modulated incident light. opticalThe controller can vary Δλ by an amount of about 1% to 10% of the refractive index of the optical material. Thus, the controller configured to vary the refractive index of the optical material can be configured to take into account the change in wavelength λ of the incident light when calculating the amount Δn by which the refractive index is to be changed. In various embodiments, the controller can include a feedback loop configured to dynamically calculate the change in wavelength λ of the incident light and calculate the amount Δn by which the refractive index is to be changed based on the change in wavelength λ of the incident light such that phase synchronization between various light beams of the beamlet array for different scan angles of the input light beam can be achieved.

[0078] (1.2.Reflector plane spacing) Various embodiments of the waveguide can be configured such that the space (also referred to as the thickness of the waveguide) between the reflective surfaces (e.g., the reflective surfaces 712a and 712b of the waveguide 710) need not be fixed, but can instead be varied. For example, in various embodiments of the waveguide, the space between the reflective surfaces (e.g., the reflective surfaces 712a and 712b of the waveguide 710) can be occupied by a fluid or air. The waveguide can be equipped with a controller that moves one or both of the reflective surfaces relative to each other, varying the distance and / or thickness of the space between the reflective surfaces, including the fluid or air, at the frequency of the scan rate (or at which θ varies) such that the optical path length difference Γ=2ndcosθ is an integer multiple of the wavelength λ for all input angles θ. FIG. 9B graphically illustrates a graph showing the variation of the spacing "d" between the reflective surfaces of the waveguide versus the cosine of the scan angle θ. Points 905a, 905b, and 905c in FIG. 9B are the same as the term 2nd 0 cosθ m , 2nd 0 cosθ m+1 , 2nd 0 cosθ m+2 are equal to mλ, (m+1)λ, and (m+2)λ, respectively, where m is an integer. m , θ m+1 , and θ m+2 The distance d between the reflecting surfaces of the waveguide at 0The spacing between the reflecting surfaces of the waveguide at point 905d in FIG. 9B is given by the term [ka] is equal to mλ, where m is an integer, and the scan angle θ m+1 In [ka] The spacing between the reflecting surfaces of the waveguide at point 905e in FIG. [ka] is equal to (m+1)λ, where m is an integer, and the scan angle θ m+2 In [ka] In FIG. 9B, m is [ka] but [ka] θ is considered to have a large value such that θ is approximately equal to θ. Only some of the possible values ​​of the spacing "d" between the reflective surfaces of the waveguides for which 2ndcosθ is an integer multiple of the wavelength λ are depicted in FIG. 9B. Other values ​​of the spacing "d" between the reflective surfaces of the waveguides for which 2ndcosθ is an integer multiple of the wavelength λ are also possible. m and θ m+1 (or θ m+1 and θ m+2 ), the value of the spacing "d" between the reflective surfaces of the waveguide can be varied such that 2ndcosθ remains an integer multiple of the wavelength λ. For small changes in the value of the spacing "d" between the reflective surfaces of the waveguide, the scan angle θ m and θ m+1 (or θm+1 and θ m+2 The variation in the spacing "d" between the reflective surfaces of the waveguides between the reflective surfaces (between the reflective surfaces (a) and (b)) can be linear, as depicted in FIG. 9B. The spacing "d" between the reflective surfaces of the waveguides can be varied by an amount Δd of about 25% or less of the fundamental spacing between the reflective surfaces of the waveguides. For example, the spacing "d" between the reflective surfaces of the waveguides can be varied by an amount Δd of about 10% or less, about 15% or less, about 20% or less of the fundamental spacing between the reflective surfaces of the waveguides. As another example, the spacing "d" between the reflective surfaces of the waveguides can be varied by an amount Δd of about 1 micron or less. In various embodiments, the fundamental spacing between the reflective surfaces of the waveguides can be varied by an amount Δd of about 1 micron or less. 0 It can correspond to.

[0079] As discussed above, the variation of the spacing "d" between the reflective surfaces of the waveguide can be synchronized with the variation of the scan angle θ. The variation of the spacing between the reflective surfaces of the waveguide can be periodic, as depicted in FIG. 9B. The spacing between the reflective surfaces of the waveguide can be varied by various techniques, including, but not limited to, mechanical, electromechanical, acousto-optical, electromagnetic, piezoelectric, and the like. For example, the waveguide can be configured as a microelectromechanical (MEMS) device comprising a pair of reflective surfaces and a controller configured to control the distance between the reflective surfaces. As another example, the waveguide can include an acousto-optical material bounded by two surfaces. The two surfaces of the waveguide can be configured to be reflective due to density variations in the acousto-optical material induced by an acoustic standing wave generated by an acoustic driver. In such an embodiment, the spacing between the two surfaces can be varied by changing the frequency of the acoustic driver that generates the acoustic standing wave.

[0080] In another embodiment, the waveguide can comprise multiple layers spaced apart from each other. Each of the multiple layers can be configured to be switched between a reflective state and a transmissive state. A pair of reflective surfaces with any desired spacing between them can be obtained by selectively configuring two of the multiple layers to be in a reflective state and the remaining multiple layers to be in a transmissive state. In such an embodiment, each of the multiple layers can be switched between a reflective state and a transmissive state using an electromagnetic control system. This is described in more detail below with reference to FIG. 9B-1, which depicts a waveguide 907 comprising three layers 907a, 907b, and 907c. The third layer 907c is disposed between the first layer 907a and the second layer 907b. The first layer 907a can be maintained in a reflective state. By configuring the second layer 907b in a transmissive state and the third layer 907c in a reflective state, the spacing between the reflective surfaces of the pair of waveguides 907 can be selected to be d1. By configuring the second layer 907b in a reflective state and the third layer 907c in a transmissive state, the spacing between the reflective surfaces of a pair of waveguides 907 can be selected to be d1+d2. In this manner, the spacing between the reflective surfaces of the waveguides can be varied. Additional layers can be included within the waveguides to provide a larger range of spacing variation.

[0081] In some embodiments of the waveguide, the reflective surfaces can include a piezoelectric material, in which the spacing between the reflective surfaces can be varied by inducing a mechanical expansion or contraction of the waveguide via application of an electric field.

[0082] (1.3.Wavelength) Various embodiments of the waveguide can be configured such that the wavelength of the incident light (e.g., light beam 701) can be varied at the frequency of the scan rate (or the frequency at which θ varies) such that the optical path length difference Γ=2ndcosθ is an integer multiple of the wavelength λ for all input angles θ. FIG. 9C graphically illustrates a graph showing the variation of the wavelength λ of the incident light versus the cosine of the scan angle θ. Points 910a, 910b, and 910c in FIG. 9C are plotted against the term 2ndcosθ m , 2ndcosθ m+1 , and 2ndcosθ m+2 are mλ 0 , (m+1)λ 0 , and (m+2)λ 0 where m is an integer and the scan angle θ is m , θ m+1 , and θ m+2 Wavelength λ 0 The wavelength λ at point 910d in FIG. 9C is expressed by the term 2ndcosθ m+1 But, mλ 0 where m is an integer and the scan angle θ is m+1 In [ka] The wavelength λ at point 910e in FIG. [ka] But (m+1)λ 0 where m is an integer and the scan angle θ is m+2 In [ka] In FIG. 9C, m is [ka] but [ka] Only some of the possible values ​​of the wavelength λ of the incident light for which 2ndcosθ is an integer multiple of the wavelength λ are depicted in FIG. 9C. Other values ​​of the wavelength λ of the incident light for which 2ndcosθ is an integer multiple of the wavelength λ are also possible. m and θ m+1 (or θ m+1 and θ m+2 ), the value of the wavelength λ of the incident light can be changed such that 2ndcosθ remains an integer multiple of the wavelength λ. For small changes in the value of the wavelength λ of the incident light, the scan angle θ m and θ m+1 (or θ m+1 and θ m+2 ) can be linear, as depicted in FIG. 9C. The wavelength λ of the incident light can be varied by an amount Δλ of about 25% or less of the fundamental wavelength. For example, the wavelength λ of the incident light can be varied by an amount Δλ of about 10% or less, about 15% or less, or about 20% or less of the fundamental wavelength. As another example, the wavelength λ of the incident light can be varied by an amount Δλ of about 1 nm to about 10 nm. In various embodiments, the fundamental wavelength can be any of the wavelengths λ discussed above. 0 It can correspond to.

[0083] As discussed above, the variation of the wavelength λ of the incident light can be synchronized with the variation of the scan angle θ. The variation of the wavelength λ of the incident light can be periodic, as depicted in FIG. 9C. The wavelength λ of the incident light can be varied by employing a tunable laser. For example, the optical source (e.g., the light source / image source 11 in FIG. 6) can include a tunable laser, such as a distributed feedback (DFB) laser, a distributed Bragg reflector (DBR) laser, etc., in which the wavelength λ of the laser can be varied by application of a current and / or a voltage. As another example, the wavelength λ of the light output from the optical source (e.g., the light / image source 11 in FIG. 6) can be varied by varying the temperature of the optical source.

[0084] As discussed above, a change in optical wavelength can also produce a change in refractive index. Thus, in various embodiments, a change in the wavelength λ of the light incident on the waveguide can be correlated with a change in the refractive index "n". For example, a controller configured to vary the wavelength λ of the incident light can be configured to take into account the change in the refractive index of the material of the waveguide. In various embodiments, the controller can include a feedback loop configured to dynamically calculate a change in the wavelength λ of the incident light based on a change in the refractive index Δn of the waveguide such that phase synchronization between various light beams of the beamlet array for different scan angles of the input light beam can be achieved.

[0085] In general, for dynamic phase locking, the angular spacing (in radians) between angles that satisfy the phase locking condition is approximately equal to the wavelength of light divided by the width of the waveguide. For a waveguide width and beam diameter of approximately 100 to 1000 microns, the angular shift can be approximately 0.001 to 0.01 radians (or a percentage change of approximately 0.1% to 1%). To maintain phase locking, the angular shift can be compensated for by decreasing the refractive index of the waveguide by an amount in the range of approximately 0.001 to approximately 0.01, increasing or decreasing the spacing between the reflecting surfaces (or the width of the waveguide) by approximately 1 micron, or increasing or decreasing the wavelength of the incident light within the range of approximately 1 to approximately 10 nm.

[0086] (2. Non-dynamic phase synchronization) Phase locking can also be achieved without using any of the dynamic approaches discussed above. For example, a waveguide can be provided with multiple holographic structures, each providing a phase-locked output for each angle of incidence. Thus, phase-locked outputs can be obtained as the angle of incidence of the input beam is varied without actively simultaneously modulating the spacing between the reflective surfaces of the waveguide, the refractive index of the waveguide, or the wavelength of the incident light at the scan rate of the input beam.

[0087] A first of the plurality of holographic structures providing a phase-locked output for a first angle of incidence can be recorded on the thick holographic medium by interfering with a first reference beam incident on the holographic medium from a first side of the holographic medium at the first angle of incidence and a second reference beam incident on the holographic medium from a second side of the holographic medium opposite the first side. The first reference beam can be configured to have characteristics of a light beam output from a scanning projector. For example, the first reference beam can be collimated in some embodiments. The first reference beam can have a beam diameter of about 100 microns or less (e.g., 90 microns or less, 80 microns or less, 70 microns or less, 60 microns or less, 50 microns or less, 40 microns or less, 30 microns or less, 25 microns or less, 20 microns or less, or values ​​therebetween). The second reference beam can be configured to have characteristics of a phase-locked beamlet array output from the waveguide when the first reference beam is incident on the waveguide at the first angle of incidence. For example, the second reference beam can be a collimated beam having a continuous wavefront with uniform phase similar to the beamlet array depicted in Figure 8A-3 and / or Figure 8C. The beam diameter of the second reference beam can be about 200 microns or more and about 10 mm or less. For example, the beam diameter of the second reference beam can be about 250 microns or more and about 950 microns or less, about 300 microns or more and about 900 microns or less, about 350 microns or more and about 850 microns or less, about 400 microns or more and about 800 microns or less, about 450 microns or more and about 750 microns or less, about 500 microns or more and about 700 microns or less, about 550 microns or more and about 650 microns or less, about 600 microns or more and about 650 microns or less, or a value therebetween.

[0088] A plurality of holographic structures are recorded on the same holographic medium by varying the incidence angle of the first reference beam. For example, the incidence angle of the first reference beam can be varied continuously between about ±30 degrees. As another example, the incidence angle of the first reference beam can be varied between about ±30 degrees in discrete steps of about 1 degree or less (e.g., 0.9 degrees or less, 0.8 degrees or less, 0.7 degrees or less, 0.6 degrees or less, 0.5 degrees or less, 0.4 degrees or less, 0.3 degrees or less, 0.2 degrees or less, 0.1 degrees or less, 0.05 degrees or less, or values ​​therebetween). The incidence angle of the second reference beam can also be varied corresponding to the variation of the incidence angle of the first reference beam.

[0089] Thus, at least one holographic structure is recorded on the holographic medium for each combination of the incidence angle of the first reference beam and the incidence angle of the second reference beam. With a plurality of holographic structures thus recorded, the waveguide can be configured to output a phase-locked beamlet array for an input beam incident at different angles θ within the solid angle Θ swept by the scanning projector. Furthermore, the diameter of the output beamlet array can exceed the diameter of the input beam. In such an embodiment, angular selectivity is built into the waveguide such that it is not necessary to dynamically synchronize the phase between the various beams of the beamlet array as the incidence angle of the input light is varied. Thus, in such an embodiment, one or more parameters of the waveguide (e.g., refractive index, spacing between the reflective surfaces of the waveguide) and / or the wavelength λ of the incident light do not need to be varied at the frequency of the scan rate to achieve phase lock between the various light beams of the beamlet array output from the waveguide.

[0090] FIG. 10 illustrates an embodiment of a waveguide 1010 in which angular selectivity is built into the waveguide such that it is not necessary to dynamically synchronize the phase between the various beams of the beamlet array as the angle of incidence of the input light is varied. The waveguide 1010 comprises a stack of layers 1012a, 1012b, 1012c, 1012d. Each stack of layers can include one or more holographic structures. The holographic structures can comprise volume holograms and / or spatially multiplexed Bragg gratings. In various embodiments, multiple holograms can be superimposed or multiplexed within the volume of the waveguide. In such an embodiment, the waveguide need not comprise a stack of layers. Each holographic structure can be configured to output a beamlet array that is phase-locked with respect to an input beam incident at an angle θ within the solid angle Θ swept by the scanning projector, as discussed above. Although FIG. 10 depicts a phase-locked beamlet array 1015 output by the waveguide 1010 for an input light beam 1001 incident at an angle close to the normal to the surface of the waveguide 1010, the waveguide 1010 can also be configured to emit a beamlet array that is phase-locked for an input beam incident at an angle other than close to the normal to the surface of the waveguide 1010.

[0091] Each of the processes, methods, and algorithms described herein and / or depicted in the accompanying figures may be embodied in code modules executed by one or more physical computing systems, hardware computer processors, application-specific circuits, and / or electronic hardware configured to execute specific and particular computer instructions, and may be fully or partially automated thereby. For example, the computing systems may include general-purpose computers (e.g., servers) or special-purpose computers programmed with specific computer instructions, special-purpose circuits, etc. The code modules may be written in a programming language that may be compiled and linked into an executable program, installed in a dynamic link library, or interpreted. In some implementations, certain operations and methods may be performed by circuitry specific to a given function.

[0092] Furthermore, certain implementations of the functionality of the present disclosure may be sufficiently mathematically, computationally, or technically complex that special purpose hardware (utilizing appropriate specialized executable instructions) or one or more physical computing devices may be required to implement the functionality, e.g., due to the amount or complexity of the calculations involved, or to provide results in substantially real-time. For example, a video may contain many frames, each frame may have millions of pixels, and specifically programmed computer hardware may be required to process the video data to provide the desired image processing task or application in a commercially reasonable amount of time.

[0093] The code modules or any type of data may be stored on any type of non-transitory computer readable medium, such as physical computer storage devices, including hard drives, solid state memory, random access memory (RAM), read only memory (ROM), optical disks, volatile or non-volatile storage devices, combinations of the same, and / or the like. The methods and modules (or data) may also be transmitted as data signals (e.g., as part of a carrier wave or other analog or digital propagated signal) generated over a variety of computer readable transmission media, including wireless-based and wired / cable-based media, and may take a variety of forms (e.g., as part of a single or multiplexed analog signal, or as multiple discrete digital packets or frames). The results of the disclosed processes or process steps may be stored persistently or otherwise in any type of non-transitory tangible computer storage device, or communicated via a computer readable transmission medium.

[0094] Any process, block, state, step, or functionality in the flow diagrams described herein and / or depicted in the accompanying figures should be understood as potentially representing a code module, segment, or portion of code that includes one or more executable instructions for implementing a specific function (e.g., logical or arithmetic) or step in the process. Various processes, blocks, states, steps, or functionality can be combined, rearranged, added, deleted, modified, or otherwise altered from the illustrative examples provided herein. In some embodiments, additional or different computing systems or code modules may perform some or all of the functionality described herein. The methods and processes described herein are also not limited to any particular sequence, and the blocks, steps, or states associated therewith can be performed in other sequences as appropriate, e.g., serially, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed exemplary embodiments. Furthermore, the separation of various system components in the implementations described herein is for illustrative purposes and should not be understood as requiring such separation in all implementations. It should be understood that the described program components, methods, and systems may generally be integrated together in a single computer product or packaged into multiple computer products. Many implementation variations are possible.

[0095] The process, method, and system may be implemented in a network (or distributed) computing environment. Network environments include enterprise-wide computer networks, intranets, local area networks (LANs), wide area networks (WANs), personal area networks (PANs), cloud computing networks, crowdsourced computing networks, the Internet, and the World Wide Web. The network may be a wired or wireless network or any other type of communication network.

[0096] The systems and methods of the present disclosure each have several innovative aspects, none of which is solely responsible for or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of the present disclosure. Various modifications of the implementations described in the present disclosure may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of the present disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but should be accorded the widest scope consistent with the present disclosure, the principles, and novel features disclosed herein.

[0097] Certain features described herein in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented separately in multiple implementations or in any suitable subcombination. Furthermore, although features may be described above as acting in a combination and may even be initially claimed as such, one or more features from the claimed combination may in some cases be deleted from the combination and the claimed combination may be directed to a subcombination or variation of the subcombination. No single feature or group of features is required or essential to every embodiment.

[0098] In particular, conditional statements used herein, such as "can," "could," "might," "may," "eg," and the like, are generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not, unless specifically stated otherwise or understood otherwise within the context as used. Thus, such conditional statements are generally not intended to suggest that features, elements, and / or steps are in any way required for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether or not those features, elements, and / or steps should be included or performed in any particular embodiment, with or without authorial input or prompting. The terms "comprise," "include," "have," and the like, are synonymous and used inclusively in a non-limiting manner and do not exclude additional elements, features, acts, operations, etc. Also, the term "or" is used in its inclusive sense (and not its exclusive sense), so that, for example, when used to connect a list of elements, the term "or" means one, some, or all of the elements in the list. In addition, the articles "a," "an," and "the," as used in this application and the appended claims, unless otherwise specified, should be interpreted to mean "one or more" or "at least one."

[0099] As used herein, a phrase referring to a list of items "at least one of" refers to any combination of those items, including single elements. As an example, "at least one of A, B, or C" is intended to cover A, B, C, A and B, A and C, B and C, and A, B, and C. Transitive phrases such as "at least one of X, Y, and Z" are generally understood differently in the context in which they are used to convey that an item, term, etc. may be at least one of X, Y, or Z, unless specifically stated otherwise. Thus, such transitive phrases are generally not intended to suggest that an embodiment requires that at least one of X, at least one of Y, and at least one of Z, respectively, be present.

[0100] Similarly, although operations may be depicted in the figures in a particular order, it should be appreciated that such operations need not be performed in the particular order depicted, or in sequential order, or that all of the depicted operations need not be performed to achieve desirable results. Additionally, the figures may diagrammatically depict one or more exemplary processes in the form of a flow chart. However, other operations not depicted may be incorporated within the diagrammatically depicted exemplary methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or during any of the depicted operations. Additionally, operations may be rearranged or reordered in other implementations. In some circumstances, multitasking and parallel processing may be advantageous. Additionally, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged in multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

Claims

1. 1. An optical system, comprising: an image projection system comprising a fiber configured to emit a coherent beam of light at multiple wavelengths in the visible spectral range; a waveguide including a first edge, a second edge, and a pair of surfaces disposed between the first edge and the second edge, the pair of surfaces being separated by a fluid-filled gap having a variable gap height d, the waveguide including a material having a refractive index n, at least one of the pair of surfaces having a reflectivity r, and a beam emitted from the image projection system being coupled into the waveguide at an input angle θ; a control system configured to vary the input angle θ of a beam emitted from the image projection system at a scan rate, the control system configured to vary at least one parameter selected from the group consisting of a wavelength from the plurality of wavelengths, the gap height d, the refractive index n, and the reflectivity r, the variation of the at least one parameter being correlated with the variation of the input angle θ based on an equation 2ndcosθ=mλ, where the equation is satisfied for all values ​​of the input angle θ, where m is an integer and λ is a wavelength of the beam, the control system configured to modulate the at least one parameter at a modulation rate approximately equal to the scan rate, and the control system further configured to cause at least one of the pair of surfaces to move relative to a second of the pair of surfaces; An optical system comprising:

2. The optical system of claim 1 , wherein the at least one parameter is a wavelength from the plurality of wavelengths.

3. The optical system of claim 1 , wherein the at least one parameter is the gap height d.

4. The optical system of claim 1 , wherein the at least one parameter is the refractive index n.

5. The optical system of claim 1 , wherein the at least one parameter is the reflectivity r.

6. The optical system of claim 1 , wherein the emitted beam is collimated.

7. The optical system of claim 1 , wherein the plurality of wavelengths includes wavelengths in the red spectral region, wavelengths in the green spectral region, and wavelengths in the blue spectral region.

8. The optical system of claim 1 , wherein the waveguide comprises an acousto-optic material.

9. The optical system of claim 1 , wherein the waveguide comprises a piezoelectric material.

10. The optical system of claim 1 , wherein the waveguide comprises an electro-optic material.

11. The optical system of claim 1 , wherein the waveguide comprises a microelectromechanical system (MEMS).

12. The optical system of claim 1 , wherein the waveguide is configured as an exit pupil expander to expand and multiply the emitted beam.

13. The optical system of claim 1 , wherein the waveguide is configured to expand the beam to a spot size greater than 1 mm.

14. The optical system of claim 1 , wherein the optical system is integrated within an augmented reality (AR) device.

15. The optical system of claim 1 , wherein the optical system is integrated within a virtual reality (VR) device.

16. The optical system of claim 1 , wherein the optical system is integrated within an eyepiece display device.

17. The optical system of claim 1 , wherein the optical system is integrated into eyewear comprising at least one of a frame or one or more eyepieces or ear pieces.

18. 1. An optical system, comprising: an image projection system comprising a fiber configured to emit a coherent beam of light at multiple wavelengths in the visible spectral range; a plurality of stacked waveguides, each waveguide including a first edge, a second edge, and a pair of surfaces disposed between the first edge and the second edge, the pair of surfaces being separated by a gap having a gap height d, the waveguides including a material having a refractive index n, and at least one of the pair of surfaces having a reflectivity r; a control system configured to vary an input angle θ of a beam emitted from the image projection system at a scan rate, the control system configured to vary at least one parameter selected from the group consisting of a wavelength from the plurality of wavelengths, the gap height d, the refractive index n, and the reflectivity r, the variation of the at least one parameter being correlated with the variation of the input angle θ based on an equation 2ndcosθ=mλ, where the equation is satisfied for all values ​​of the input angle θ, where m is an integer and λ is a wavelength of the beam, the control system configured to modulate the at least one parameter at a modulation rate approximately equal to the scan rate, and the control system further configured to cause at least one of the pair of surfaces to move relative to a second of the pair of surfaces; An optical system comprising:

19. 20. The optical system of claim 18, wherein each waveguide has an associated depth plane, and the beam emitted from each waveguide appears to originate from that waveguide's associated depth plane.

20. 20. The optical system of claim 18, wherein different waveguides from the plurality of stacked waveguides have different associated depth planes.

21. The optical system of claim 18 , wherein the optical system is integrated within an augmented reality (AR) device.

22. The optical system of claim 18 , wherein the optical system is integrated within a virtual reality (VR) device.

23. The optical system of claim 18 , wherein the optical system is integrated within an eyepiece display device.

24. 20. The optical system of claim 18, wherein the optical system is integrated into eyewear comprising at least one of a frame or one or more eyepieces or ear pieces.

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