Adjustable attenuation of light transmission artifacts in wearable displays

Abstract

A method for displaying an image using a wearable display system includes guiding display light from the display toward a user through an eyepiece to project an image into the user's field of vision, determining the relative position between an ambient light source and the eyepiece, and adjusting the attenuation of ambient light from the ambient light source through the eyepiece according to the relative position between the ambient light source and the eyepiece.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Patent Application No. 63 / 044,013, filed June 25, 2020, entitled “Tunable Attenuation of Light Transmission Artifacts in Wearable Displays”, under 35 U.S.SC §119(e), which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to techniques for adjustable attenuation of light transmission artifacts in wearable displays. Background Technology

[0004] Optical imaging systems, such as wearable display systems (e.g., wearable display head-mounted viewers), may include one or more eyepieces that present a projected image to a user. The eyepieces may be constructed from thin layers of one or more highly refractive materials. As an example, an eyepiece may be constructed from one or more layers of highly refractive glass, silicon, metal, or polymer substrates.

[0005] Multiple eyepieces can be used in combination to project simulated 3D images. For example, multiple eyepieces—each with a different pattern—can be stacked on top of each other, and each eyepiece can project different depth layers of the volumetric image. Thus, the eyepieces can present a volumetric image to the user across three dimensions. This can be useful, for example, when presenting a "virtual reality" environment to a user.

[0006] Optical components in wearable display systems can also interact with ambient light, which is light from the user's surroundings. For example, diffraction structures in wearable display systems can diffract ambient light incident on the wearable display (which typically does not enter the user's field of vision) at high angles into the field of vision, thereby producing visible artifacts that degrade the user experience. Summary of the Invention

[0007] A wearable display system is described, comprising an angle-selective film to mitigate artifacts associated with high incident angles of ambient light. For example, the angle-selective film may utilize a polarizer combined with a polarization adjustment element, the amount of adjustment of which varies according to the incident angle of light to reduce light transmission at certain angles of incidence. In some embodiments, the angle-selective film may include a dynamic element in which transmission characteristics can be altered in response to certain stimuli, such as an electric field.

[0008] The various aspects of this invention are summarized below.

[0009] Generally, in a first aspect, the present invention is characterized by a method for displaying images using a wearable display system, comprising: guiding display light from a display towards a user through an eyepiece to project an image into the user's field of vision; determining the relative position between an ambient light source and the eyepiece; and adjusting the attenuation of ambient light from the ambient light source through the eyepiece according to the relative position between the ambient light source and the eyepiece.

[0010] Embodiments of a method for displaying images using a wearable display system may include one or more of the following features. For example, determining the relative position includes determining the angle of incidence of ambient light from an ambient light source on the eyepiece and adjusting the attenuation based on the angle of incidence. The attenuation may be adjusted to reduce the transmission of ambient light at a lower angle of incidence compared to the attenuation at a lower angle of incidence.

[0011] Attenuating ambient light can include polarizing the ambient light to provide polarized light, and modulating the polarization state of the polarized light as a function of the incident angle of the ambient light. Attenuation can be altered by changing the modulation of the polarization state of the polarized light. Modulation can be altered by changing the delay provided by a birefringent material layer along the path of the polarized light. The birefringent material can include a liquid crystal. The delay can be altered by changing the electric field applied to the liquid crystal. The liquid crystal can be a blue phase liquid crystal or a vertically aligned liquid crystal.

[0012] Attenuation of ambient light can also include guiding modulated polarized light through a second polarizer. The attenuation can be altered using liquid crystal elements.

[0013] Determining the relative position between an ambient light source and the eyepiece can include monitoring ambient light intensity and determining the relative position based on changes in the monitored ambient light intensity. Ambient light intensity can be monitored by acquiring images of the surrounding environment and analyzing the acquired images to determine the position of the ambient light source within the images.

[0014] In a second aspect, the invention is characterized by a wearable display system comprising: an eyepiece stack having a world side and a user side opposite to the world side, wherein, during use, a user located on the user side views a display image delivered by the wearable display system via the eyepiece stack, the display image enhancing the user's field of vision of the user's environment; an adjustable attenuator disposed on the world side of the eyepiece stack, the adjustable attenuator including an electro-optic unit disposed between a pair of linear polarizers; a camera module facing the world side; and an electronic processing module communicating with the adjustable attenuator and the camera module, the electronic processing module being programmed to determine information about the relative position of the eyepiece stack with respect to an ambient light source based on images captured by the camera module, and to change the attenuation of the adjustable attenuator based on the information about the relative position.

[0015] Embodiments of the wearable display system may include one or more of the following features. An adjustable attenuator can reduce the transmission of visible light incident on the adjustable attenuator within a first incident angle range, without significantly reducing the transmission of light incident on the adjustable attenuator at incident angles outside the first range.

[0016] The electro-optic unit may include a layer of liquid crystal material, and the adjustable attenuator may further include a voltage source arranged to apply a variable voltage to the liquid crystal material. The liquid crystal material may be a blue phase liquid crystal material or a vertically aligned liquid crystal material. In addition to the liquid crystal material layer, the adjustable attenuator may further include at least one birefringent material layer.

[0017] At least one layer of birefringent material may include a pair of quarter-wave plates disposed on opposite sides of the liquid crystal material layer. Each quarter-wave plate may be arranged relative to a corresponding linear polarizer in a linear polarizer to form a circular polarizer. At least one layer of birefringent material may further include a C-plate.

[0018] In some embodiments, the through axes of the two linear polarizers may intersect.

[0019] An electro-optic unit can rotate the polarization state of light transmitted by the first linear polarizer, located on the world side of an adjustable attenuator in a pair of linear polarizers. The amount of polarization state rotation can be varied depending on the state of the electro-optic unit and the angle of incidence of the light transmitted by the first linear polarizer in the pair. Transmitted light with a large angle of incidence can be rotated less than that with a small angle of incidence.

[0020] Adjustable attenuators can have an area greater than 50mm x 50mm.

[0021] The electro-optic unit may be a first electro-optic unit, and the adjustable attenuator may further include a second electro-optic unit and a third linear polarizer, the second electro-optic unit being disposed between a pair of linear polarizers and the third linear polarizer. Each of the first and second electro-optic units may include a corresponding liquid crystal material layer. The adjustable attenuator may further include one or more birefringent material layers disposed on opposite sides of the respective liquid crystal material layers.

[0022] An adjustable attenuator may include two or more stages, each stage comprising an electro-optic unit arranged between a pair of linear polarizers. Adjacent stages may share linear polarizers.

[0023] Among other advantages, embodiments of the present invention can reduce unwanted optical artifacts (e.g., rainbow effect) associated with stray ambient light in certain wearable displays, where stray ambient light interacts with grating structures in the display. For example, waveguide-based wearable displays employing relief gratings (e.g., for AR / MR applications) may diffract stray ambient light into the display's eyebox, resulting in unwanted artifacts in the user's field of vision and thus degrading the user experience. Embodiments of the present invention can significantly reduce such artifacts without significantly affecting the user's viewing field of vision.

[0024] Implementation methods can attenuate the transmission of ambient light based on the angle of incidence of ambient light. For example, a film that selectively attenuates light with an angle of incidence greater than the user's field of vision can reduce the visibility of artifacts caused by diffraction near-eye displays without sacrificing the transmission of the user's world view.

[0025] Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features and advantages will be apparent from the description and drawings, as well as from the claims. Attached Figure Description

[0026] Figure 1 An example of a wearable display system is shown.

[0027] Figure 2A A conventional display system for simulating three-dimensional image data for a user is shown.

[0028] Figure 2B Aspects of a method for simulating three-dimensional image data using multiple depth planes are shown.

[0029] Figures 3A-3C The relationship between the radius of curvature and the focal radius is shown.

[0030] Figure 4 An example of a waveguide stack used in an AR eyepiece to output image information to the user is shown.

[0031] Figure 5 and 6 An example of an outgoing beam output from a waveguide is shown.

[0032] Figure 7A and 7B This is a schematic diagram illustrating the light path through a display combiner with a surface-embossed grating.

[0033] Figure 8A and 8B This is a schematic diagram comparing light transmission through display assemblies with and without angle-selective films.

[0034] Figure 9This is a schematic diagram of an eyepiece with an adjustable attenuator that displays a combiner and an example.

[0035] Figure 10 This is a graph showing the transmission of an adjustable attenuator as a function of the incident light angle for three different wavelengths.

[0036] Figure 11A-11I These are diagrams showing different simulated rainbow artifacts corresponding to three different eyepiece examples at different incident angles.

[0037] Figure 12A , 12C 12E is a graph showing the perceived color shift at three different delay values.

[0038] Figure 12B , 12D Figures 1 and 12F show the transmission curves for three different wavelengths at three different retardation values.

[0039] Figure 13 This is a schematic diagram of an eyepiece with a display combiner and another example of an adjustable attenuator.

[0040] Figure 14 It is a graph showing the transmission through multiple adjustable attenuators as a function of the incident light angle for three different wavelengths.

[0041] Figure 15 This is a schematic diagram of an eyepiece with a display combiner and, as another example, an adjustable attenuator combined with a static C-plate.

[0042] Figure 16 This is a flowchart detailing an example of a voltage-controlled feedback mechanism used for ambient light attenuation.

[0043] Figure 17A and 17B This is a schematic diagram comparing the light transmission through the display combiner at different incident angles.

[0044] Figure 18 This is a schematic diagram comparing the transmission of multiple light rays through the display combiner at multiple incident angles over time.

[0045] Figures 19A-19C This is a schematic diagram comparing the refractive index ellipses of isotropic media and different blue phase LC materials.

[0046] Figure 20 This is a schematic diagram of an example electro-optic unit with a vertically aligned nematic liquid crystal layer.

[0047] Figures 21A-21C This is a diagram illustrating an example surface alignment pattern in a device using a vertically aligned nematic liquid crystal layer.

[0048] Figure 22 This is a diagram of an example computer system that is useful for wearable display systems.

[0049] In the diagram, similar references represent similar elements.

[0050] In the figure, similar reference numerals indicate similar elements. Detailed Implementation

[0051] Figure 1 An example wearable display system 60 is shown, comprising a display or eyepiece 70, and various mechanical and electronic modules and systems supporting the functionality of the display 70. The display 70 is housed in a frame 80, which is wearable by a user 90 and configured to position the display 70 in front of the user 90's eyes. In some embodiments, the display 70 may be considered as eyeglasses. A world-viewing camera 81 (e.g., facing the user's environment and having a similar field of vision) is mounted in the frame 80. In some embodiments, a speaker 100 is coupled to the frame 80 and positioned near the user 90's ear canal. The display system may also include one or more microphones 110 for sound detection. The microphones 110 may allow the user to provide input or commands to the system 60 (e.g., selection of voice menu commands, natural language questions, etc.), and / or may allow audio communication with others (e.g., with other users of similar display systems). The microphones 110 may also collect audio data from the user's surrounding environment (e.g., sounds from the user and / or the environment). In some embodiments, the display system may further include peripheral sensors 120a, which may be detached from the frame 80 and attached to the body of the user 90 (e.g., head, torso, limbs, etc.). In some embodiments, peripheral sensors 120a may acquire data characterizing the physiological state of the user 90.

[0052] Display 70 is operatively coupled to local data processing module 140 via communication link 130 (e.g., via a wired or wireless connection). Local data processing module 140 can be mounted in various configurations, such as being fixedly attached to frame 80, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or removably attached to user 90 (e.g., in a backpack configuration or a belt-coupled configuration). Similarly, sensor 120a can be operatively coupled to local processor and data module 140 via communication link 120b (e.g., via a wired lead or a wireless connection). Local processing and data module 140 may include a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or hard disk drive), both of which can be used for auxiliary processing, caching, and data storage. This data may include 1) data captured by sensors (which may be operatively coupled to frame 80 or otherwise attached to user 90), such as image capture devices (e.g., cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radios, gyroscopes, and / or other sensors disclosed herein; and / or 2) data (including data concerning virtual content) acquired and / or processed using remote processing module 150 and / or remote data storage 160, which may be transmitted to display 70 after such processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data storage 160 via communication links 170, 180 (e.g., via wired or wireless communication links), such that these remote modules 150, 160 are operatively coupled to each other and available as a resource for local processing and data module 140. In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be attached to the frame 80, or may be a separate device that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0053] Remote processing module 150 may include one or more processors for analyzing and processing data, such as image or audio information. In some embodiments, remote data storage 160 may be a digital data storage facility accessible via the Internet or other network configurations in a "cloud" resource configuration. In some embodiments, remote data storage 160 may include one or more remote servers that provide information (e.g., information for generating augmented reality content) to local processing and data module 140 and / or remote processing module 150. In other embodiments, all data is stored, and all computations are performed in the local processing and data module, thereby allowing for completely autonomous use from the remote module.

[0054] The perception of an image as "three-dimensional" or "3D" can be achieved by providing a slightly different image presentation to each of the user's eyes. Figure 2A A conventional display system for simulating 3D image data for a user is illustrated. Two distinct images 190 and 200 are output to the user—each image targeted at one eye 210 and 220. Images 190 and 200 are spaced apart from the eyes 210 and 220 by a distance 230 along an optical axis or z-axis parallel to the user's line of sight. Images 190 and 200 are flat, and the eyes 210 and 220 can be focused on the images by assuming a single accommodation state. Such a 3D display system relies on the human visual system to combine images 190 and 200 to provide a sense of depth and / or scale in the combined image.

[0055] However, the human visual system is complex, and providing a realistic sense of depth is challenging. For example, many users of traditional “3D” display systems find such systems uncomfortable or completely incapable of perceiving depth. Objects can be perceived as “three-dimensional” due to the combination of convergence and accommodation. The convergence movement of the two eyes relative to each other (e.g., the rotation of the eyes causing the pupils to move toward or away from each other to bring the corresponding lines of sight to the object) is closely related to the focusing (or “accommodation”) of the eye’s lens. Under normal circumstances, changing the focus of the eye’s lens or adjusting the eye to shift focus from one object to another at a different distance, according to a relationship known as the “accommodation-convergence reflex” and pupil dilation or constriction, will automatically result in a matching change in convergence at the same distance. Similarly, under normal circumstances, changes in convergence will trigger matching changes in accommodation of the lens shape and pupil size. As described in this paper, many stereoscopic or “3D” display systems use slightly different presentations (and therefore slightly different images) to display the scene to each eye, allowing the human visual system to perceive three-dimensional perspective. However, such systems may be uncomfortable for some users because they provide image information only in a single accommodation state and operate against the principle of accommodation-convergence. Display systems that provide a better match between accommodation and convergence can create more realistic and comfortable simulations of three-dimensional image data.

[0056] Figure 2B This illustrates various aspects of a method for simulating 3D image data using multiple depth planes. (Reference) Figure 2B Eyes 210 and 220 adopt different accommodation states to focus on objects at different distances along the z-axis. Therefore, a particular accommodation state can be considered associated with a specific one of the illustrated depth planes 240 (which has an associated focal length) such that when the eye is in an accommodation state for a particular depth plane, an object or part of an object in that particular depth plane is in focus. In some embodiments, three-dimensional image data can be simulated by providing different presentations of the image for each eye 210, 220, and also by providing different presentations of the image corresponding to multiple depth planes. Although the respective fields of view of eyes 210 and 220 are shown as separate for clarity, they can overlap, for example, with increasing distance along the z-axis. Furthermore, although the depth planes are shown as flat for ease of illustration, it should be understood that the contours of the depth planes can be curved in physical space such that all features within the depth plane are in focus when the eye is in a particular accommodation state.

[0057] The distance between the object and the eye 210 or 220 can also change the amount of light emanating from the object as seen by the eye. Figures 3A to 3CThe relationship between distance and light divergence is shown. The distances between the object and the eye 210 are represented by R1, R2, and R3 in decreasing order of distance. Figures 3A to 3C As shown, the light rays become more divergent as the distance to the object decreases. As the distance increases, the light rays become more collimated. In other words, the light field generated by a point (the object or part of the object) can be considered to have a spherical wavefront curvature, which is a function of the distance of that point from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. Therefore, the degree of divergence of the light rays varies at different depth planes, increasing as the distance between the depth plane and the user's eye 210 decreases. Although in order to... Figures 3A to 3C As clearly illustrated in other figures in this document, only a single eye 210 is shown; however, it should be understood that the discussion of eye 210 can be applied to both eyes 210 and 220 of the user.

[0058] Highly believable perceptual depth simulation can be achieved by providing the eye with different presentations of images corresponding to each of a finite number of depth planes. These different presentations can be focused individually by the user's eye, thus helping to provide depth cues based on the amount of eye accommodation required to focus different image features of the scene located in different depth planes and / or based on observing different image features defocused on different depth planes.

[0059] Figure 4 An example of a waveguide stack in an AR eyepiece for outputting image information to a user is shown. The display system 250 includes a waveguide stack or a stacked waveguide assembly 260, which can be used to provide three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is... Figure 1 The system 60, among which, Figure 4 Some parts of the system 60 are shown schematically in more detail. For example, the waveguide assembly 260 may be... Figure 1 It is part of the display 70. It will be understood that in some embodiments, the display system 250 may be considered as a light field display.

[0060] Waveguide assembly 260 may also include multiple features 320, 330, 340, 350 between waveguides. In some embodiments, features 320, 330, 340, 350 may be one or more lenses. Waveguides 270, 280, 290, 300, 310 and / or multiple lenses 320, 330, 340, 350 may be configured to send image information to the eye at various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a specific depth plane and may be configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 may serve as light sources for the waveguides and may be used to inject image information into waveguides 270, 280, 290, 300, 310, as described herein, each waveguide may be configured to distribute incident light across each respective waveguide for output toward the eye 210. Light exits from the output surfaces 410, 420, 430, 440, and 450 of each respective image injection device 360, 370, 380, 390, and 400, and is injected into the corresponding input surfaces 460, 470, 480, 490, and 500 of the respective waveguides 270, 280, 290, 300, and 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, and 500 may be an edge of the corresponding waveguide or a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces directly facing the world 510 or the user's eye 210). In some embodiments, the light beam (e.g., a collimated beam) may be injected into each waveguide and may be replicated in the waveguide (e.g., sampled into sub-beams by diffraction), and then guided to the eye 210 in an amount corresponding to the refractive power of the depth plane associated with that particular waveguide. In some embodiments, a single image injection device among image injection devices 360, 370, 380, 390, 400 may be associated with multiple (e.g., three) waveguides 270, 280, 290, 300, 310 and inject light into these waveguides.

[0061] In some embodiments, the image injection devices 360, 370, 380, 390, and 400 are discrete displays, each generating image information for injection into a corresponding waveguide 270, 280, 290, 300, and 310, respectively. In some other embodiments, the image injection devices 360, 370, 380, 390, and 400 are the outputs of a single multiplexed display, the output of which can transmit image information to each of the image injection devices 360, 370, 380, 390, and 400 via one or more optical conduits (such as fiber optic cables). It will be understood that the image information provided by the image injection devices 360, 370, 380, 390, and 400 may include light of different wavelengths or colors.

[0062] In some embodiments, light injected into waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes an optical module 530. The optical module 530 may include a light source or light emitter, such as a light-emitting diode (LED). Light from the optical module 530 may be directed via a beam splitter (BS) 550 to an optical modulator 540 (e.g., a spatial light modulator) and modulated by the optical modulator 540. The optical modulator 540 may spatially and / or temporally vary the perceived intensity of light injected into waveguides 270, 280, 290, 300, 310. Examples of spatial light modulators include liquid crystal displays (LCDs) (including liquid crystal on silicon (LCOS) displays) and MEMS micromirror arrays (such as those used in digital light processing (DLP) displays). In some embodiments, the light projector system 520 may include a light-emitting diode (LED) display, such as a microLED display.

[0063] In some embodiments, the light projector system 520 or one or more components thereof may be attached to the frame 80. Figure 1 For example, the light projector system 520 may be part of the temple portion of the frame 80 (e.g., the earpiece 82), or it may be positioned at the edge of the display 70. In some embodiments, the light module 530 may be detached from the BS 550 and / or the light modulator 540.

[0064] In some embodiments, the display system 250 may be a scanning fiber optic display, which includes one or more scanning fibers for projecting light in various patterns (e.g., raster scanning, spiral scanning, Lissajous patterns, etc.) into one or more waveguides 270, 280, 290, 300, 310, and ultimately into the user's eye 210. In some embodiments, the image injection devices 360, 370, 380, 390, 400 shown may schematically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may schematically represent multiple scanning fibers or multiple bundles of scanning fibers, each configured to inject light into an associated waveguide in waveguides 270, 280, 290, 300, 310. One or more fibers may transmit light from optical module 530 to one or more waveguides 270, 280, 290, 300, and 310. Furthermore, one or more intermediate optical structures may be provided between the scanning fibers or multiple fibers and one or more waveguides 270, 280, 290, 300, 310 to, for example, redirect light emanating from the scanning fibers into one or more waveguides 270, 280, 290, 300, 310.

[0065] Controller 560 controls the operation of the stacked waveguide assembly 260, including the operation of image injection devices 360, 370, 380, 390, 400, light source 530, and optical modulator 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 includes programming (e.g., instructions in a non-transitory medium) that regulates the timing and delivery of image information to waveguides 270, 280, 290, 300, 310. In some embodiments, the controller may be a single monolithic device or a distributed system connected via wired or wireless communication channels. In some embodiments, controller 560 may be processing module 140 or 150. Figure 1 Part of ).

[0066] Waveguides 270, 280, 290, 300, and 310 can be configured to propagate light within each respective waveguide via total internal reflection (TIR). Waveguides 270, 280, 290, 300, and 310 can each be planar or have another shape (e.g., curved), having a top main surface and a bottom main surface, and an edge extending between these top and bottom main surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, and 310 can each include coupling-out optics 570, 580, 590, 600, and 610, which are configured to extract light from the waveguide by redirecting light propagating within their respective waveguides to output image information to eye 210. The extracted light can also be referred to as the coupling-out light, and the coupling-out optics light can also be referred to as the light extraction optics. The extracted light beam can be output from the waveguide at the location where light propagating in the waveguide strikes the light extraction optics. As further discussed herein, the coupling optical elements 570, 580, 590, 600, 610 can be, for example, diffractive optical features including diffraction gratings. Although the coupling optical elements 570, 580, 590, 600, 610 are shown disposed on the bottom main surface of waveguides 270, 280, 290, 300, 310, in some embodiments, as further discussed herein, the coupling optical elements 570, 580, 590, 600, 610 can be disposed on the top main surface and / or the bottom main surface, and / or can be disposed directly within the volume of waveguides 270, 280, 290, 300, 310. In some embodiments, the coupling optical elements 570, 580, 590, 600, and 610 may be formed in a material layer attached to a transparent substrate to form waveguides 270, 280, 290, 300, and 310. In some other embodiments, the waveguides 270, 280, 290, 300, and 310 may be a monolithic material, and the coupling optical elements 570, 580, 590, 600, and 610 may be formed on the surface and / or within the monolithic material.

[0067] Each waveguide 270, 280, 290, 300, 310 can output light to form an image corresponding to a specific depth plane. For example, waveguide 270 closest to the eye can deliver a collimated beam to the eye 210. The collimated beam can represent the optical infinity focal plane. The next uplink waveguide 280 can output a collimated beam that has traveled through a first lens 350 (e.g., a negative lens) before reaching the eye 210. The first lens 350 can add a slightly convex wavefront curvature to the collimated beam, such that the eye / brain interprets the light from this waveguide 280 as originating from a first focal plane closer to the eye 210 from optical infinity. Similarly, a third waveguide 290 causes its output light to travel through the first lens 350 and a second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 can add another increment to the wavefront curvature, causing the eye / brain to interpret light from the third waveguide 290 as originating from the second focal plane, which is closer to optical infinity than light from the second waveguide 280.

[0068] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, wherein the highest waveguide 310 in the stack sends its output through all the lenses between itself and the eye to obtain total refractive power representing the focal plane closest to the person. To compensate the stack of lenses 320, 330, 340, 350 when viewing / interpreting light from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 can be provided on top of the stack to compensate for the total refractive power of the lens stack 320, 330, 340, 350 below. This configuration provides as many perceptible focal planes as available waveguide / lens pairs. Both the outgoing optics of the waveguides and the focusing aspects of the lenses can be static (i.e., not dynamic or electrically active). In some alternative embodiments, using electrically active features, either or both of the outgoing optics of the waveguides and the focusing aspects of the lenses can be dynamic.

[0069] In some embodiments, two or more of waveguides 270, 280, 290, 300, and 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, and 310 can output image sets to the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, and 310 can output image sets to the same multiple depth planes, each depth plane corresponding to one set. This can provide an advantage in forming a tiled image to provide an extended field of view at those depth planes.

[0070] The coupling optical elements 570, 580, 590, 600, and 610 can be configured to both redirect light outside their respective waveguides and output the light with appropriate divergence or collimation to a specific depth plane associated with the waveguide. As a result, waveguides with different associated depth planes can have coupling optical elements 570, 580, 590, 600, and 610 with different configurations, and these different configurations output light with different divergence amounts depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, and 610 can be volumetric or surface features that can be configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, and 610 can be volumetric holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, and 350 may not be lenses; rather, they may simply be spacers (e.g., cladding and / or structures for forming air gaps).

[0071] In some embodiments, the coupling optical elements 570, 580, 590, 600, and 610 have diffraction characteristics with sufficiently low diffraction efficiency such that, at each interaction, only a portion of the power of the light is redirected to the eye 210, while the remainder continues to travel through the waveguide via TIR. Thus, the exit pupil of the replica optical module 530 is replicated across the entire waveguide to generate multiple output beams carrying image information from the light source 530, thereby effectively expanding the number of positions of the replica light source's exit pupil that the eye 210 can explain. These diffraction characteristics can also have diffraction efficiencies that vary across their geometry to improve the uniformity of the light output from the waveguide.

[0072] In some embodiments, one or more diffraction features can be switchable between an "on" state where they actively diffract and an "off" state where they do not significantly diffract. For example, the switchable diffraction element may include a polymer-dispersed liquid crystal layer, wherein droplets form diffraction patterns in a host medium, and the refractive index of the droplets can be switched to a refractive index substantially matching that of the host material (in which case the pattern does not significantly diffract incident light) or the droplets can be switched to a refractive index mismatched with that of the host medium (in which case the pattern actively diffracts incident light).

[0073] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible light and infrared cameras) may be provided to capture images of eye 210, portions of eye 210, or at least a portion of tissue surrounding eye 210 for purposes such as detecting user input, extracting biometric information from the eye, estimating and tracking the gaze direction of the eye, monitoring the user's physiological state, etc. In some embodiments, the camera assembly 630 may include an image capturing device and a light source to project light (e.g., infrared or near-infrared light) onto the eye, which may then be reflected by the eye and detected by the image capturing device. In some embodiments, the light source includes a light-emitting diode (“LED”) that emits infrared or near-infrared light. In some embodiments, the camera assembly 630 may be attached to a frame 80 ( Figure 1 It can also be electrically communicated with processing module 140 or 150, which can process image information from camera assembly 630 to make various determinations about, for example, the user's physiological state, the wearer's gaze direction, iris recognition, etc. In some embodiments, one camera assembly 630 can be used for each eye to monitor each eye separately.

[0074] Figure 5 An example of an outgoing beam output from a waveguide is shown. (Perspective view) A waveguide is shown, but waveguide assembly 260 ( Figure 4 Other waveguides in the waveguide can function similarly. Light 640 is injected into waveguide 270 at input surface 460 and propagates within waveguide 270 via TIR. Through interaction with diffraction features, the light exits the waveguide as an outgoing beam 650. The outgoing beam 650 replicates the exit pupil from the projector device that projects an image into the waveguide. Each of the outgoing beams 650 comprises a sub-part of the total energy of the input light 640. In a fairly efficient system, the sum of the energies of all outgoing beams 650 equals the energy of the input light 640. The outgoing beams 650 are shown as substantially parallel, however, in Figure 6 In this context, as discussed herein, a certain amount of refractive force can be assigned based on the depth plane associated with waveguide 270. A parallel outgoing beam can indicate a waveguide having coupled optics that couple light out to form an image that appears to be positioned at a distant distance (e.g., optical infinity) on a depth plane from eye 210. Other waveguides or other sets of coupled optics can output more divergent outgoing beam patterns, such as... Figure 6 As shown, this would require the eye 210 to adjust to a closer distance so that the more divergent outgoing beam pattern is focused on the retina and will be interpreted by the brain as light coming from a distance closer to the eye 210 than optical infinity.

[0075] Additional information regarding wearable display systems (e.g., including optical elements used in wearable display systems) can be found in U.S. Patent Publication No. 2019 / 0187474A1, filed December 14, 2018, entitled “EYEPIECES FOR AUGMENTED REALITY DISPLAYSYSTEM,” the contents of which are incorporated herein by reference in their entirety.

[0076] As described above, the wearable display system 60 includes one or more optical elements having one or more grating structures that enhance the optical performance of the wearable display system. For example, refer to... Figure 7A and 7B The diffraction relief structured grating 710, together with the near-eye display combiner 700 (e.g., a stacked waveguide assembly as described above), serves as an exit pupil expander (EPE), increasing the size of the exit pupil of the wearable display system. Figure 7A As shown, the combiner 700 includes a waveguide 720 (e.g., a glass substrate) that guides edge-coupled light along its length via total internal reflection (TIR), while a grating 710 diffracts the incident guided light, such that at least some light is extracted from the waveguide 710 to the user of the display system.

[0077] Specific reference Figure 7B Ambient light from the user's environment also enters the display combiner 700 from the "world" side. This light interacts with the grating 710, and at least some of this light can be diffracted into the user's field of view. When the user views through the EPE, the light diffracted from the world can manifest as unwanted image artifacts. The angle of incidence that produces artifacts in the user's field of view typically depends on the design of the display combiner. For display combiners based on diffractive waveguides, a large angle of incidence often results in stray light paths closest to the center of the user's world field of view.

[0078] This effect is Figure 8A The text further explains that, Figure 8A Display combiner 800 is shown. Ambient light at an incident angle θ inc The incident light is incident on the front surface of the display combiner 800. As shown, at least some of the incident light is transmitted through the grating and the combiner. However, the display combiner 800 supports a grating (not shown) that diffracts at least some of the incident light toward the user. This light, labeled as stray light, travels at an angle θ. stray diffraction.

[0079] Reference Figure 8BAn adjustable attenuator 810 can be applied (e.g., bonded to) a display combiner 800 to variably reduce stray light artifacts associated with ambient light. Typically, the transmission of light through the attenuator 810 depends on the angle of incidence of the light on the film and the optical state of one or more adjustable layers of the attenuator. As shown, the attenuator 810 attenuates (e.g., reduces or blocks) light with an angle of incidence θ. inc The transmission of light at a relatively high angle of incidence (e.g., 30° or higher, 35° or higher, 40° or higher, 45° or higher, such as what a user experiences from overhead lighting in an indoor environment), but the attenuator 810 allows for a lower angle of incidence θ. a Light (e.g., "world light" as seen by the wearer in the core field of view of the device) is transmitted. As discussed in more detail below, the attenuator 810 can vary the degree of attenuation at different incident angles, for example, in response to changes in ambient lighting conditions, such as changing the relative orientation of the ambient light source with respect to the display. The attenuator can perform this function over a wide wavelength range, for example, within the operating wavelength range of the display system, such as from 420 nm to 680 nm.

[0080] Under a given optical condition, the transmission efficiency of incident light typically varies from relatively high (e.g., 40% or more, 45% or more) to relatively low (e.g., less than 1%, less than 0.5%) depending on the angle of incidence. Transmission efficiency refers to the relative intensity of light transmitted at a specific wavelength. In some embodiments, unpolarized light with wavelengths in the range of 420 nm to 680 nm incident at an angle of incidence between 25° and 85° has a transmission efficiency of less than 0.5%. The exact angle within this angular range can be adjusted to achieve the minimum transmission efficiency.

[0081] Adjustable attenuators can also have a relatively small effect on the color of the image viewed through the film. For example, for a D65 source, an adjustable attenuator can make the (0.33, 0.33) CIE 1931 white point shift less than (+ / -0.02, + / -0.02) (e.g., (+ / -0.01, + / -0.01) or less) for unpolarized light with an incident angle within a specified angular range (e.g., ±40°).

[0082] Transmission of an adjustable attenuator can also be characterized by attenuation, which may be high for at least some relatively high incident angles (e.g., 10 dB or greater, 15 dB or greater, 20 dB or greater, 25 dB or greater, 30 dB or greater). Light at lower incident angles, such as 25° or less (e.g., 20° or less, 15° or less, 10° or less), may experience very low levels of attenuation (e.g., 2 dB or less, 1 dB or less).

[0083] Typically, the adjustable attenuator 810 can be relatively thin. For example, the film 810 can have a total thickness ranging from 500 micrometers to 5,000 micrometers. Therefore, the benefits of using an adjustable attenuator can be realized without significantly increasing the volume of the wearable display system.

[0084] In some embodiments, the adjustable attenuator 810 includes a multilayer stack comprising an electro-optic unit (e.g., a liquid crystal electro-optic unit) disposed between a pair of polarizer films (e.g., linear polarizers). The polarizer films and electro-optic units significantly reduce the transmission of visible light incident on the adjustable attenuator 810 within a certain incident angle range, without significantly reducing the transmission of light incident on the adjustable attenuator at incident angles outside that range.

[0085] Typically, the configuration of the two polarizers and the electro-optic unit can be varied to provide a desired level of transmission variation over the range of angular incidence of interest (e.g., from -75° to +75°). In some embodiments, the polarizers are linear polarizers and the through axes of the two linear polarizers can intersect (e.g., at 90°).

[0086] Typically, an electro-optic unit includes one or more variable birefringence layers designed to switch between different optical states, wherein, in at least one state, these layers rotate the polarization state of light incident from the world side and transmitted by the first linear polarizer in the pair of linear polarizers. The variable birefringence layers may include a liquid crystal material (e.g., a nematic liquid crystal material) that can be aligned such that, in at least one state, the anomalous axis of the liquid crystal material is parallel to the plane of the layer (e.g., providing a quarter-wave (QW) delay) and / or arranged isotropically, wherein the anomalous axis of the liquid crystal material is perpendicular to the plane of the layer.

[0087] Typically, the amount by which the electro-optic unit rotates the polarization state varies depending on the configuration and phase of the liquid crystal material and the angle of incidence of the light transmitted by the first linear polarizer in the pair of linear polarizers. In some embodiments, transmitted light with a large angle of incidence (e.g., 35° or greater) rotates less than transmitted light with a small angle of incidence (e.g., less than 35°). For example, in the case where the polarizers are crossed linear polarizers, the greater the rotation, up to 90°, the higher the transmission efficiency of the film. In this case, a greater rotation of the on-axis light compared to light with a larger angle of incidence is desirable. Conversely, in some embodiments, the polarizer axes are parallel, and the polarization adjustment film rotates the on-axis light less compared to light with a larger angle of incidence.

[0088] Typically, the size of the adjustable attenuator is appropriately determined to cover at least a portion of the eyepiece of the wearable display system. For example, in some embodiments, the adjustable attenuator may have an area of ​​20mm × 20mm or larger (e.g., an area with a minimum dimension of 2mm).

[0089] Now turn to a specific example of an adjustable attenuator and refer to... Figure 9 An eyepiece 900 for a wearable display system includes a display combiner 800 and a stack 910 serving as an adjustable attenuator. The stack 910 includes a pair of linear polarizers 920a and 920b. Between the linear polarizers, the stack 910 includes a pair of quarter-wave plates (QWs) 930a and 930b located on either side of an adjustable birefringent layer 940 (e.g., a liquid crystal layer).

[0090] In some embodiments, the fast axes of waveplates 930a and 930b are oriented at approximately 45° to the transmission axes of linear polarizers 920a and 920b, respectively, such that the combination of linear polarizer 920b and QW 930b converts unpolarized light incident from the world side into substantially circularly polarized light (i.e., the combination behaves as a circular polarizer). The combination of QW 930a and linear polarizer 920a behaves similarly. Note that the rotatability of each circular polarizer is the same.

[0091] In at least one state, the tunable birefringent layer 940 can have zero delay for orthogonally incident light, but a non-zero delay for obliquely incident light. Without being bound by theoretical constraints, the delay of the tunable birefringent layer as a function of the incident angle can be given by the following formula: Where n o It is the ordinary refractive index of the tunable birefringent layer, n e It is the anomalous refractive index of the tunable birefringent layer, θ is the angle of incidence relative to the interface normal of the tunable birefringent layer, and k o =2π / λ is the wavenumber of the incident light, λ is the wavelength of the incident light, and d is the thickness of the tunable birefringent layer. Furthermore, the effective refractive index n of the tunable birefringent layer... o and n e This can be altered by applying a non-zero voltage to the tunable birefringent layer. By using circularly polarized light, the excitation of ordinary and anomalous modes in the tunable birefringent layer is approximately equal for all incident angles. This results in the transmission from the input circularly polarized state to the birefringent layer at T = cos... 2 The same circularly polarized state at the output of (Γ / 2).

[0092] Typically, the transmission characteristics of the stack 910 vary depending on the characteristics of the tunable birefringent layer 940 (e.g., the thickness and birefringence of the material forming the layer) and the applied voltage. Figure 10 The example shown is a transmission as a function of the incident angle for a sample implementation of stack 910. Here, for an example implementation configured as n o =1.5236, n eAn adjustable attenuator for a C-plate with a wavelength of 1.52 and a thickness of d = 153 μm is used to demonstrate transmission as a function of the incident angle at three different wavelengths. Simulations were generated. Figure 10 The adjustable attenuator has the same characteristics as Figure 9 The same configuration, for example, two linear polarizers, two quarter-wave plates, and a tunable birefringent layer. Here, on-axis transmission is normalized and remains at or near 1 within approximately 20°, then monotonically decreases to zero between 60° and 80°, depending on the wavelength. For shorter wavelengths (such as 460 nm and 525 nm), after a narrow peak attenuation window at 1010 and 1020 nm, transmission increases as the incident angle increases outward to 90°.

[0093] In the tunable birefringent layer, n o and n e The value depends on the voltage applied to the tunable birefringent layer. This means that the transmission, as a function of the angle of incidence, also depends on the voltage applied to the tunable birefringent layer. Furthermore, the minimum values ​​associated with transmission at different wavelengths, at 1010, 1020, and 1030, can be adjusted to match the angle of incidence of a specific light source (e.g., a ceiling light or the sun), such as a specific light source detected using a world-side sensor.

[0094] exist Figures 11A to 11I The graphs shown illustrate the effect of using an adjustable attenuator. These graphs compare the effect with no attenuator ( Figure 11A , 11D 11G), with a static attenuator ( Figure 11B , 11E , 11H) and with adjustable attenuator ( Figure 11C , 11F The eyepiece grating of (11I) addresses rainbow artifacts formed when light from an ambient light source strikes the lens at three different non-zero incident angles. Rainbow artifacts are caused by the dispersion of different wavelengths of white light from the ambient light source, resulting from diffraction (as discussed above) through the grating structure in the display combiner at non-zero incident angles. Figure 7B (as shown in the image).

[0095] exist Figure 11A-11I In the middle, targeting 70° ( Figure 11A-11C ), 60° Figure 11D-11F ) and 50° Figure 11G-11IAn optical rainbow artifact is shown when a white light source with a 5800K blackbody spectrum is incident on the device from above at an angle of incidence of 390 nm. A grating with a pitch of 390 nm was used to calculate the diffraction angle of the artifact. The image in column 1110 shows the rainbow artifact perceived without a filter. The image in column 1120 shows the reduction in the intensity of the rainbow artifact when a static C-plate filter with a peak delay at 550 nm is used. The image in column 1130 shows a further reduction in artifact intensity than in column 1110 when the voltage controlling the delay of the tunable birefringent layer in the film stack is selected relative to the incident angle of the light source. Figure 11C In this study, the transmission of an adjustable attenuator with a peak delay at 450 nm is modeled; Figure 11F In the study, transmission of an adjustable attenuator with a peak delay at 660 nm is modeled; and in Figure 11I In this study, transmission with a peak delay at 900 nm is modeled.

[0096] When using an adjustable attenuator in a film stack (e.g., stack 910), there may be a trade-off with the color shift in the world view seen by the user through eyepiece 900. As the angle of incidence of light from the ambient light source decreases, the peak delay of the adjustable attenuator should be adjusted to attenuate any artifacts seen by the user, such as... Figure 11A-11I As described.

[0097] However, as the peak delay of the adjustable attenuator is modified, a perceptible color shift may appear in the transmitted light. Figure 12A-12F The illustration depicts this effect, which is set at 550 nm ( Figure 12A and 12B ), 660nm ( Figure 12C and 12D ) and 900nm ( Figure 12E and 12F Transmission characteristics of an adjustable attenuator with optimal peak delay. Figure 12A , 12C The simulated apertures for these three optical peak delays are depicted in 12E and 12E, respectively, spanning a 100° field of view (from -50° to 50°) vertically and horizontally. The simulated apertures reduce transmission to zero at incident angles greater than 45°.

[0098] Figure 12B , 12D Figure 12F shows the transmission curves of transmitted light at 460 nm, 525 nm, and 630 nm as a function of the angle of incidence. Figure 12A , 12C In 12E, the dashed line drawn at a 45° incident angle is presented as representing the point where the simulated aperture reduces transmission to zero. Figure 12B , 12DIn the 12F, between incident angles of 0° and 45°, the transmission curves for 630nm (e.g., red) light show higher transmittance than for 460nm (e.g., blue) light, indicating lower attenuation at the 630nm wavelength. The relative ratio of red to blue light causes the color perceived through the adjustable attenuator to shift towards a reddish hue, depending on the incident angle. Figure 12A , 12C This effect can be observed in the simulated field of view of 12E. For example, in Figure 12F In the study, at an incident angle of 45°, the transmission curve of 460nm light is approximately zero, while light with a wavelength of 630nm still has a relative transmission value of approximately 0.2. This is achieved through... Figure 12E The reddish hue around the edge of the field of vision serves as evidence.

[0099] Usually, although Figure 9 An example of an adjustable attenuator is shown, comprising a single tunable birefringent layer 940 between two linear polarizers 920, but implementations with additional layers are possible. For example, Figure 13 An eyepiece 1300 is shown, comprising a film stack 1310 applied to the world side of a display combiner 800. The film stack 1310 includes three linear polarizers 1320a, 1320b, and 1320c. A first polarization adjustment stack is arranged between polarizers 1320a and 1320b. This stack includes a pair of QW layers 1330a and 130b on either side of an tunable birefringent layer 1340a. A second polarization adjustment stack is arranged between polarizers 1320b and 1320c. This stack includes QW layers 1330c and 1330d on either side of the tunable birefringent layer 1340b. In practice, the performance of stack 1310 is similar to that of two stacks 910 placed together.

[0100] Stack 910 can be considered a "single-stage" arrangement, while stack 1310 is a two-stage arrangement. Typically, additional stages can be added. When it is not desirable to be bound by theory, several stages can be used in series to provide different transmission responses. Where Γ n It is the delay of the nth stage and varies depending on the applied voltage.

[0101] The use of multiple cascaded stages can result in greater attenuation of light from large incident angles. For example, reference... Figure 14 This illustrates a two-stage tunable attenuator arrangement, such as stack 1310, where the transmission of three different wavelengths varies according to the incident angle. In this example, the n-wavelengths of the tunable birefringent layers 1340a and 1340b... o =1.5236, n e =1.52, the thickness of the tunable birefringent layer in the first stage 1340b is d1 = 111 μm, and the thickness of the tunable birefringent layer in the second stage 1340a is d2 = 111 μm. (And...) Figure 10 Compared to the single-stage membranes depicted in the text, Figure 14 This indicates that the transmission for all three wavelengths is normalized to the on-axis light and remains at or near 1 within approximately 20°, after which they gradually decrease at wavelengths around 460 nm, and monotonically decrease to a peak at longer wavelengths (e.g., 525 nm and 630 nm), with a non-zero attenuation value at 90° incident angle. At high incident angles reaching 90° outwards, the transmission at 460 nm and 525 nm remains low, rather than increasing from a minimum between 60° and 80°. After the peak attenuation angle, the transmission no longer increases, which is consistent with... Figure 10 The transmission at these wavelengths described in the text is different.

[0102] When multiple layers are used in a film stack, the second layer can be a layer that is not an adjustable birefringent layer, that is, it can be a static layer. Figure 15 An example adjustable attenuator 1510 is shown using an adjustable birefringent layer 1550 in conjunction with a static C-plate 1540. The C-plate 1540 has zero delay for normal incident light but a static, non-zero delay for oblique incident light. When the adjustable birefringent layer 1550 is used in conjunction with the static C-plate 1540, the C-plate 1540 provides the initial delay, while the adjustable birefringent layer provides an additional and variable amount of delay to provide the total delay required by the environment, Γ. Increasing the static C-plate layer 1540 can help reduce the driving voltage and the thickness of the adjustable birefringent layer.

[0103] Typically, wearable display systems using adjustable attenuators can detect and attenuate ambient light sources to eliminate optical artifacts (e.g., optical rainbows). Wearable display systems can control the adjustable attenuator by applying a differential voltage to an adjustable birefringent layer to attenuate ambient light sources at different incident angles. Figure 16 An example method for specifically attenuating light from ambient light sources is illustrated. For example, image data from a frame-mounted camera can be sent to a local data processing module, which can be programmed to detect the presence of ambient light sources 1610. In some embodiments, high-brightness areas in the image data can be used by the local data processing module to distinguish ambient light sources from the background image.

[0104] After detecting the presence of an ambient light source in the user's field of vision, the incident angle of the ambient light source can be calculated by the local data processing module of the wearable display system (1620). Then, the wearable display system can send a command to the display to control the voltage applied to the liquid crystal layer of the adjustable attenuator (1630). The modified voltage can modify the liquid crystal layer in a way that attenuates the detected ambient light source. Subsequently, if the user's field of vision changes (e.g., the user is moving, or there is more than one ambient light source), the system can return to step 1610 for further determination.

[0105] Figure 16 The example application of ambient light source detection and attenuation described in the figure is depicted in Figure 17A and 17B In. Figure 17A In this process, ambient light source 1710 emits light 1720 that strikes an adjustable attenuator at a first incident angle 1730. By applying a voltage to the adjustable attenuator 1750, the ambient light can be attenuated 1770. Figure 17B In this configuration, ambient light source 1710 emits light 1720 that strikes an adjustable attenuator at different incident angles 1740. By applying different voltages to the adjustable attenuator 1750, the ambient light can be attenuated 1770 for its specific incident angle 1740. In this way, the transmission minimums (1010, 1020, and 1030) associated with different wavelengths of light can be adjusted to attenuate a specific ambient light source at a unique incident angle.

[0106] Furthermore, multiple ambient light sources at their respective incident angles and intensities can be attenuated within the user's field of vision. Figure 18 Three ambient light sources are shown incident on an adjustable attenuator 1850 with a first intensity S1 1810, a second intensity S2 1820, and a third intensity S3 1830. In a time-sequential operating mode, these ambient light sources can be attenuated with respect to their respective intensities and angles of incidence. Some adjustable birefringent layers have a time response (≤1 ms) faster than the frequency (<~0.03 s) of displaying new visual image frames to the user. If the total time between frames displayed to the user is given as t... total This can be further subdivided based on n ambient light sources within the user's field of vision. The total subdivision is t. total =Δt1+Δt2+…+Δt n After the intensity of each ambient light source is determined, a subframe time is calculated, during which a specific light source will be primarily attenuated. If the intensities of the three ambient light sources S1 1810, S2 1820, and S3 1830 are related in the following manner: S2 > S3 > S1, then a subframe time can be calculated such that Δt2 1880 > Δt3 1890 > Δt1 1870, as follows. Figure 18 As shown in the diagram. By implementing this function, each ambient light source at its respective intensity level n can be positioned at its respective subframe time interval t. n Light from multiple ambient light sources can be attenuated within a single user display frame based on their respective intensity and angle of incidence.

[0107] Typically, various applicable LC phases and modes can be used in tunable birefringent layers. For example, in some embodiments, blue phase liquid crystal (BPLC) can be used as a tunable birefringent layer. BPLC displays are optically isotropic when no voltage is applied. In other words, the refractive index of the BPLC medium is equal in the three principal directions of the birefringent layer (e.g., n...). z =n x =n y When a voltage is applied, for liquid crystal molecules with positive dielectric anisotropy, the liquid crystal molecules align with the generated electric field, inducing birefringence in the layer. With appropriate electrode geometry, the BPLC layer can act as a tunable C-plate, which induces positive or negative birefringence depending on the birefringence of the liquid crystal material. For example, in a BPLC material with positive dielectric anisotropy and positive birefringence, the refractive index ellipse describing the refractive index orientation becomes n... o =n x =n y n z =n e And n o <n e , where n e Alignment along the electric field. In BPLC materials with negative birefringence, the refractive index ellipse describing the refractive index orientation is defined as n o >n e n o Aligned orthogonally with the applied electric field. Figures 19A-19C The diagram illustrates this effect. Specifically, Figure 19A The refractive index ellipse of an isotropic optical medium is shown, i.e., in the zero-voltage state of the BPLC layer. Figure 19B The refractive index ellipse of a positive birefringent LC material with positive dielectric anisotropy is shown when a sufficient voltage is applied to the layer to align the LC molecules with the corresponding electric field E. Figure 19C The refractive index ellipse of a negative birefringent LC material with positive dielectric anisotropy is shown when a sufficient voltage is applied to the layer to align the LC molecules with the electric field.

[0108] In some embodiments, vertically aligned nematic liquid crystal (VAN) material may be used between two circular polarizers in the film stack 910. The vertically aligned liquid crystal (VALC) layer is optically equivalent to a positive C-plate compensation film, which has the added advantage of allowing the delay to be adjusted by applying a voltage, as is done with conventional liquid crystal displays (LCDs).

[0109] A typical VALC device 2000 is as follows: Figure 20As shown. A typical VALC device includes a vertically aligned LC material layer 2040 between two substrates 2010. Each substrate 2010 is supported on a transparent electrode 2020 on a surface facing the LC layer 2040, and an alignment layer 2030 on the transparent electrode.

[0110] A voltage source (not shown) is connected to each electrode 2020 to apply a voltage across the LC layer 2040. An alignment layer 2030 controls the alignment of LC molecules at the boundaries of the LC layer 2040, thereby controlling the zero-voltage orientation of LC molecules within the LC layer 2040. Typically, the alignment layer 2030 controls alignment by introducing a pretilt angle 2050 (α), which ensures that the molecules are uniformly oriented when the applied voltage is removed, thereby reducing the introduction of misalignment or other orientation defects in the LC layer. This pretilt angle is typically between 1° and 5° (e.g., 2°, 3°, 4°) relative to the surface normal of the substrate 2010 and can be established by physically rubbing the polymer layer with a cloth or by exposure to linearly polarized ultraviolet light (the process depends on the material and is known in the art).

[0111] In such a device, if a single electrode 2020 is used, the delay can be uniformly adjusted within the active region of the device. In some embodiments, the electrode 2020 can be patterned so that the delay can be adjusted in a spatially varying manner. The electrode can be a general rectangular shape and configured as a Cartesian grid (like a conventional LCD) to define an arbitrary delay distribution, or a series of concentric circles with fixed or varying widths to define a rotationally symmetric delay distribution.

[0112] Although the pretilt angle 2050 is generally uniform and unidirectional across the entire surface of the substrate 2010, such as in Figure 21A As depicted, the pretilt angle can be spatially varied in some cases. Spatially varying the pretilt angle can be used regardless of whether uniform or patterned electrodes are used. This can be used to achieve delay distributions that are not achievable using patterned electrode structures, or delay distributions that do not require patterned electrodes. While any suitable pattern of the pretilt angle 2050 can be achieved, in some embodiments, the pretilt angle 2050 can be purely radial (e.g., radially away from the central z-axis), such as... Figure 21B The depicted, or purely directional (e.g., circular around the central z-axis), such as Figure 21C What is depicted.

[0113] Various suitable materials can be used for each layer in the angle-selective film. For example, the linear polarizer can be formed from a stretched polymer material (e.g., PVA) stained with a chromophore (e.g., iodine). Commercially available linear polarizers, such as those available from Sanritz Co. (Japan) or Nitto Denko (Japan), can be used. For example, the QW can be made from a stretched polymer film or a liquid crystal polymer film. The C-plate can be formed from a cast polymer film, such as, for example, cellulose triacetate. A liquid crystal polymer C-plate is also possible.

[0114] Typically, while each layer is represented as a homogeneous layer, composite layers are possible. For example, a C-plate can be formed from multiple stacked layers, each with different optical properties than its neighboring layers. Similarly, multilayer QWs can be used.

[0115] Typically, film stacks may include additional layers beyond those described above. For example, the stack may include extra layers to provide mechanical functions rather than optical functions. Adhesive layers and / or layers for mechanical strength and / or environmental protection may be included. Such layers may be optically isotropic so as not to significantly affect the polarization of transmitted light. In some embodiments, the stack includes one or more layers on the world side of the outermost linear polarizer. For example, antireflective films and / or hard coatings may be included.

[0116] Some of the embodiments described in this specification can be implemented as a group or more of digital electronic circuits, computer software, firmware or hardware, or one or more combinations thereof, or as modules. Although different modules can be used, each module does not need to be different, and multiple modules can be implemented on the same digital electronic circuits, computer software, firmware or hardware, or combinations thereof.

[0117] Some embodiments described in this specification can be implemented as one or more computer programs, i.e., one or more computer program instruction modules encoded on a computer storage medium for execution by a data processing apparatus or for controlling the operation of the data processing apparatus. The computer storage medium may be a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or apparatus, or a combination thereof, or may be contained in a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or apparatus, or a combination thereof. Furthermore, although the computer storage medium is not a propagating signal, it may be a source or destination of computer program instructions encoded in an artificially generated propagating signal. The computer storage medium may also be in one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices) or contained in one or more separate physical components or media.

[0118] The term "data processing apparatus" encompasses all kinds of devices, apparatuses, and machines used for processing data, including, for example, programmable processors, computers, systems-on-a-chip, or a combination thereof. The apparatus may include special-purpose logic circuitry, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits). In addition to hardware, the apparatus may also include code that creates an execution environment for the computer program in question, such as code constituting processor firmware, protocol stacks, database management systems, operating systems, cross-platform runtime code environments, virtual machines, or combinations thereof. The apparatus and execution environment can implement a variety of different computing model infrastructures, such as network services, distributed computing, and grid computing infrastructures.

[0119] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages. A computer program may, but does not necessarily, correspond to a file in a file system. A program may be stored as a part of a file that supports other programs or data (e.g., one or more scripts stored in a markup language document), a single file dedicated to the program in question, or multiple coordination files (e.g., a file storing one or more modules, subroutines, or portions of code). Computer programs can be deployed to execute on a single computer or on multiple computers located at a site or distributed across multiple sites and interconnected via a communication network.

[0120] Some of the processes and logic flows described in this specification can be executed by one or more programmable processors that execute one or more computer programs to perform actions by manipulating input data and generating output. Processes and logic flows can also be executed by special-purpose logic circuitry (e.g., FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits)), and the devices can also be implemented as special-purpose logic circuitry.

[0121] Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, as well as processors of any kind of digital computer. Typically, a processor receives instructions and data from read-only memory or random access memory, or both. A computer includes a processor for performing actions according to instructions and one or more memory devices for storing instructions and data. A computer may also include one or more mass storage devices (e.g., magneto-optical, magneto-optical, or optical disc) for storing data or operatively coupled to receive data from or transfer data to such mass storage devices, or both. However, a computer does not necessarily have to have such devices. Suitable storage media for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, such as semiconductor memory devices (e.g., EPROM, EEPROM, flash memory devices, etc.), magnetic disks (e.g., internal hard disks, removable disks, etc.), magneto-optical disks, and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by or integrated into dedicated logic circuitry.

[0122] To provide interaction with the user, operation can be implemented on a computer having a display device for displaying information to the user (e.g., a monitor or another type of display device) and a keyboard and pointing device (e.g., a mouse, trackball, tablet, touchscreen, or other type of pointing device) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; input from the user can be received in any form, including sound, speech, or tactile input. Furthermore, the computer can interact with the user by sending and receiving documents to and from the device used by the user; for example, by sending a webpage to a web browser on the user's client device in response to a request received from a web browser.

[0123] A computer system may include a single computing device, or multiple computers operating nearby or typically far from each other and generally interacting via a communication network. Examples of communication networks include local area networks (“LANs”) and wide area networks (“WANs”), interconnected networks (e.g., the Internet), networks including satellite links, and peer-to-peer networks (e.g., ad hoc peer-to-peer networks). Client-server relationships can be created by computer programs running on the respective computers and having client-server relationships with each other.

[0124] Figure 22An example computer system 2200 is shown, including a processor 2210, a memory 2220, a storage device 2230, and an input / output device 2240. Each of components 2210, 2220, 2230, and 2240 may be interconnected, for example, via a system bus 2250. The processor 2210 is capable of processing instructions for execution within the system 2200. In some embodiments, the processor 2210 is a single-threaded processor, a multi-threaded processor, or other type of processor. The processor 2210 is capable of processing instructions stored in the memory 2220 or the storage device 2230. The memory 2220 and the storage device 2230 may store information within the system 2200.

[0125] Input / output device 2240 provides input / output operations for system 2200. In some embodiments, input / output device 2240 may include one or more of the following: network interface device (e.g., Ethernet card), serial communication device (e.g., RS-232 port), and / or wireless interface device (e.g., 802.11 card), 3G wireless modem, 4G wireless modem, etc. In some embodiments, input / output device may include driver device configured to receive input data and send output data to other input / output devices, such as wearable display system 2260. In some embodiments, mobile computing devices, mobile communication devices, and other devices may be used.

[0126] Although this specification contains numerous details, these should not be construed as limiting the scope of claims, but rather as descriptions of specific features of particular examples. Certain features described in the context of individual embodiments in this specification may also be combined. Conversely, the various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0127] Many embodiments have been described. However, it should be understood that various modifications can be made without departing from the spirit and scope of the invention. Therefore, other embodiments are within the scope of the appended claims.

Claims

1. A wearable display system, comprising: a frame to be worn by a user as eyewear, the frame housing an eyepiece stack having a world side and a user side opposite the world side, wherein, during use, the user, located at the user side, views display images delivered by the wearable display system via the eyepiece stack, the display images augmenting a user’s view of a user’s environment; an adjustable attenuator disposed at the world side of the eyepiece stack, the adjustable attenuator including a first electro-optical cell and a second electro-optical cell separated from the first electro-optical cell by a first linear polarizer, and the first electro-optical cell, the second electro-optical cell, and the first linear polarizer disposed between a pair of linear polarizers; a camera module mounted to the frame and facing the world side; and an electronic processing module in communication with the adjustable attenuator and the camera module, the electronic processing module programmed to determine information about an angle of incidence of light from an ambient light source based on images captured by the camera module and to vary an attenuation of the adjustable attenuator based on the angle of incidence, wherein, for at least one state of the first electro-optical cell and the second electro-optical cell, the adjustable attenuator attenuates incident light such that light having wavelengths at 460 nm, 525 nm, and 630 nm transmitted through the adjustable attenuator has a transmittance greater than 10% compared to the transmittance of on-axis light for angles of incidence less than 50° and a transmittance less than 10% compared to the transmittance of on-axis light for angles of incidence greater than 70°.

2. The wearable display system of claim 1, wherein, the electronic processing module programmed to vary the attenuation of the adjustable attenuator by controlling optical states of the first electro-optical cell and the second electro-optical cell to reduce transmission of visible light incident on the adjustable attenuator by an amount dependent on the angle of incidence within a first range of angles of incidence.

3. The wearable display system of claim 2, wherein, the electronic processing module programmed to control the adjustable attenuator to reduce transmission of visible light incident on the adjustable attenuator within the first range of angles of incidence without significantly reducing transmission of light incident on the adjustable attenuator at angles of incidence outside the first range.

4. The wearable display system of claim 1, wherein, the first electro-optical cell and the second electro-optical cell each include a layer of liquid crystal material, and the adjustable attenuator further includes a voltage source arranged to apply a voltage to each of the liquid crystal materials.

5. The wearable display system of claim 4, wherein, the adjustable attenuator further includes at least one birefringent material layer in addition to the layers of liquid crystal material of the first electro-optical cell and the second electro-optical cell.

6. The wearable display system of claim 5, wherein, the at least one birefringent material layer includes a pair of quarter-wave plates disposed on opposite sides of the layers of liquid crystal material of the first electro-optical cell and the second electro-optical cell.

7. The wearable display system of claim 6, wherein, each quarter-wave plate of the pair of quarter-wave plates of the first electro-optical cell and the second electro-optical cell is arranged relative to a respective one of the linear polarizers to form a circular polarizer.

8. The wearable display system of claim 6, wherein, the at least one birefringent material layer further includes a C-plate.

9. The wearable display system of claim 1, wherein, One of the first electro-optical cell or the second electro-optical cell rotates a polarization state of light transmitted by a first linear polarizer of the pair of linear polarizers that is on the world side of the tunable attenuator.

10. The wearable display system of claim 9, wherein, An amount of rotation of the polarization state varies according to a state of the first electro-optical cell or the second electro-optical cell and an angle of incidence of light transmitted by the first linear polarizer of the pair of linear polarizers.

11. The wearable display system of claim 10, wherein, Transmitted light having a large angle of incidence is rotated less than transmitted light having a small angle of incidence.

12. The wearable display system of claim 1, wherein, The tunable attenuator has an area greater than 50 mm x 50 mm.

13. The wearable display system of claim 1, wherein, The first electro-optical cell and the second electro-optical cell each include a respective layer of liquid crystal material.

14. The wearable display system of claim 13, wherein, The tunable attenuator further includes one or more birefringent material layers disposed on opposite sides of each of the respective layers of liquid crystal material of the first electro-optical cell and the second electro-optical cell.

15. A method for displaying images using a wearable display system, comprising: directing display light from a display through an eyepiece toward a user to project an image in a field of view of the user; determining a relative position between an ambient light source and the eyepiece; and adjusting attenuation of ambient light from the ambient light source through the eyepiece according to the relative position between the ambient light source and the eyepiece to cause ambient light having wavelengths at 460 nm, 525 nm, and 630 nm to have a transmittance greater than 10% compared to an on-axis light transmittance for angles of incidence less than 50° and a transmittance less than 10% compared to the on-axis light transmittance for angles of incidence greater than 70°, wherein the adjusting comprises, in order: polarizing the ambient light to provide polarized light, retarding the polarized light by a first retardance to provide once-retarded polarized light, polarizing the once-retarded polarized light to provide twice-polarized light, retarding the twice-polarized light to provide twice-retarded polarized light, and polarizing the twice-retarded polarized light to provide thrice-polarized light, the thrice-polarized light having an intensity attenuated relative to the ambient light.

16. The method of claim 15, wherein, Determining the relative position includes determining an angle of incidence of the ambient light from the ambient light source on the eyepiece and adjusting the attenuation based on the angle of incidence.

17. The method of claim 16, wherein, The attenuation is adjusted to reduce transmission of the ambient light at the angle of incidence compared to the attenuation at low angles of incidence.

18. The method of any one of claims 15-17, wherein, The adjusting further includes modulating a polarization state of the polarized light as a function of the angle of incidence of the ambient light.

19. The method of claim 18, wherein, The attenuation is changed by changing the modulation of the polarization state of the polarized light.

20. The method of claim 19, wherein, The modulation is changed by changing a retardance provided by a layer of birefringent material in a path of the polarized light.

21. The method of claim 20, wherein, The birefringent material includes liquid crystal.

22. The method of claim 21, wherein, The retardance is changed by changing an electric field applied to the liquid crystal.

23. The method of claim 22, wherein, The liquid crystal is a blue phase liquid crystal or a homeotropically aligned liquid crystal.

24. The method of claim 19, wherein, The adjusting further includes directing the modulated polarized light through a second polarizer.

25. The method of claim 24, wherein, The attenuation is changed using a liquid crystal element.

26. The method of any one of claims 15-17, wherein, Determining the relative position between the ambient light source and the eyepiece includes monitoring ambient light intensity and determining the relative position based on changes in the monitored ambient light intensity.

27. The method of claim 26, wherein, The ambient light intensity is monitored by acquiring an image of the surrounding environment and analyzing the acquired image to determine a location of the ambient light source in the image.

28. A wearable display system comprising: a frame to be worn by a user as eyewear, the frame housing an eyepiece stack having a world side and a user side opposite the world side, wherein, during use, the user, located at the user side, views display images delivered by the wearable display system via the eyepiece stack, the display images augmenting a user's view of a user's environment; an adjustable attenuator disposed at the world side of the eyepiece stack, the adjustable attenuator including an electro-optical cell disposed between a pair of linear polarizers, wherein the electro-optical cell includes a layer of blue phase liquid crystal material; a camera module mounted to the frame and facing the world side; and an electronic processing module in communication with the adjustable attenuator and the camera module, the electronic processing module programmed to determine information about an angle of incidence of light from an ambient light source based on images captured by the camera module and to vary an attenuation of the adjustable attenuator based on the angle of incidence, wherein, for at least one state of the electro-optical cell, the adjustable attenuator attenuates incident light such that light transmitted through the adjustable attenuator at 460 nm, 525 nm, and 630 nm has a transmittance greater than 10% compared to the transmittance of on-axis light for angles of incidence less than 50° and a transmittance less than 10% compared to the transmittance of on-axis light for angles of incidence greater than 70°.

Images