Attenuation of light transmittance artifacts in wearable displays

Abstract

To provide a suitable wearable display system. [Solution] The wearable display system includes an eyepiece stack having a world side and a user side opposite the world side, positioned on the user side during use, allowing the user to view displayed images that extend the user's view of the user's environment, delivered by the system via the eyepiece stack. The wearable display system also includes an angle-selectable film arranged on the world side of the eyepiece stack. The angle-selectable film includes a polarization-adjusting film arranged between a pair of linear polarizers. The linear polarizers and polarization-adjusting film significantly reduce the transmittance of visible light incident on the angle-selectable film at a large angle of incidence without significantly reducing the transmittance of light incident on the angle-selectable film at a small angle of incidence.

Description

[Technical Field]

[0001] This disclosure relates to a technique for attenuating light transmittance artifacts in wearable displays. [Background technology]

[0002] Optical imaging systems, such as wearable display systems (e.g., wearable display headsets), may include one or more eyepieces that present a projected image to the user. Eyepieces can be constructed using one or more thin layers of a highly refractive material. In examples, eyepieces can be constructed from one or more layers of a highly refractive glass, silicon, metal, or polymer substrate.

[0003] Multiple eyepieces can be used in combination to project a simulated three-dimensional image. For example, multiple eyepieces (each with a different pattern) can be layered, and each eyepiece can project a different depth layer of the stereoscopic image. Thus, the eyepieces can collectively present a stereoscopic image to the user across three dimensions. This could be useful, for example, when presenting a "virtual reality" environment to a user.

[0004] Optical elements within a wearable display system can also interact with ambient light, which is light from the environment in which the user is present. For example, diffractive structures within a wearable display system can diffract ambient light that enters the wearable display at a high angle, which would normally not enter the user's field of view, into the field of view, creating visible artifacts that reduce the user's experience. [Overview of the project] [Means for solving the problem]

[0005] A wearable display system is described that includes an angle-selectable film and reduces artifacts associated with high-angle ambient light incidence. For example, the angle-selectable film can be combined with a polarization adjustment element to utilize a polarizer, the amount of which adjustment varies depending on the angle of incidence of light, thereby reducing the transmittance of light at a given angle of incidence. In one embodiment, the angle-selectable film may include a dynamic element in which the transmittance property can be varied in response to a stimulus, such as in response to an electric field.

[0006] In general, in a first aspect, the present invention features a wearable display system comprising an eyepiece stack having a world side and a user side opposite the world side, the eyepiece stack positioned on the user side during use, the user viewing displayed images that extend the user's field of view of the user's environment, delivered by the wearable display system via the eyepiece stack. The wearable display system also comprises an angularly selectable film arranged on the world side of the eyepiece stack, the angularly selectable film comprising a polarization-adjusting film arranged between a pair of linear polarizers, the linear polarizers and the polarization-adjusting film significantly reduce the transmittance of visible light incident on the angularly selectable film at a large angle of incidence without significantly reducing the transmittance of light incident on the angularly selectable film at a small angle of incidence.

[0007] Embodiments of a wearable display system may include one or more of the following features and / or other features: For example, the passing axes of two linear polarizers may intersect.

[0008] In some embodiments, a polarization-adjusting film rotates the polarization state of light transmitted by a first of a pair of linear polarizers on the world side of the polarization-adjusting film. The amount of rotation of the polarization state can vary depending on the angle of incidence of the light transmitted by the first of the pair of linear polarizers. Light transmitted with a large angle of incidence may be rotated less than light transmitted with a small angle of incidence.

[0009] Unpolarized light with wavelengths in the range of 420nm to 680nm, incident on an angularly selectable film with an incident angle of 35° to 65°, can have a transmittance efficiency of less than 0.5%.

[0010] Unpolarized light with wavelengths in the range of 420nm to 680nm, incident on an angularly selectable film with an incident angle of -32° to +32°, can achieve a transmittance efficiency of over 45%.

[0011] Regarding the D65 source, angularly selectable films can shift the CIE1931 white point by less than (+ / -0.02, + / -0.02) for non-polarized light with incidence angles of -32° to +32°.

[0012] Films that can be selected at an angle exceed 10mm x 10mm (for example, 2,500mm) 2 Or larger (for example, larger than 50mm x 50mm), such as 200mm 2 or greater than that, 500mm 2 or greater than that, 1,000 mm 2 It may have an area (or larger).

[0013] A polarization-adjusting film may include at least one layer of birefringent material. For example, the at least one layer of birefringent material may include a C-plate. In some embodiments, the at least one layer of birefringent material comprises a pair of quarter-wave plates, the quarter-wave plates positioned on the opposite side of the C-plate. Each quarter-wave plate can be aligned with a corresponding linear polarizer to form a circular polarizer.

[0014] At least one layer of the birefringent material may include at least one quarter-wave plate.

[0015] The polarizing film may be a first polarizing film, and the angularly selectable film may further include a second polarizing film and a third linear polarizer, the second polarizing film being arranged between a pair of linear polarizers and the third linear polarizer. The first and second polarizing films may each consist of one or more layers of birefringent material. The one or more layers of birefringent material in the first and second polarizing films may each include a C-plate. The one or more layers of birefringent material in the first and second polarizing films may each include a pair of quarter-wave plates arranged on the opposite side of the corresponding C-plate.

[0016] An angularly selectable film may include two or more stages, each stage including a polarization-adjusting film arranged between a pair of linear polarizers. Adjacent stages may share a linear polarizer.

[0017] An angularly selectable film may further include a switchable element having variable optical properties. The switchable element may include a liquid crystal layer between a pair of polarizers, and the light transmittance through the switchable element is variable. The switchable element may include multiple pixels, and the optical properties of each pixel are independently variable.

[0018] In general, in another aspect, the present invention features a method for displaying an image using a wearable display system, the method comprising directing display light from the display toward the user through an eyepiece to project an image into the user's field of view, and transmitting ambient light from the user's environment through the eyepiece. Transmitting ambient light involves attenuating the light incident on the eyepiece from the environment as a function of the angle of incidence of the ambient light onto the eyepiece, wherein ambient light incident on the eyepiece at an angle of incidence of 35° or greater is attenuated more strongly than ambient light incident on the eyepiece at an angle of incidence of 35° or less.

[0019] Implementations of this method may include one or more of the following features and / or other features. For example, attenuating ambient light may include polarizing ambient light and providing polarization, and modulating the polarization state of the polarization as a function of the angle of incidence of the ambient light. Modulating the polarization state of the polarization may include rotating the polarization state. The amount of rotation of the polarization state may vary depending on the angle of incidence of the ambient light. For example, the amount of rotation may decrease as the angle of incidence increases. In some embodiments, attenuating ambient light may further include directing the polarization through a second polarizer.

[0020] The ambient light transmittance can be 1% or less (e.g., 0.5%, 0.3%, 0.2%, 0.1%) for at least one incident angle greater than 30° (e.g., 35° or greater, 40° or greater, 45° or greater, 50° or greater). In some embodiments, the ambient light transmittance is 1% or less for at least one incident angle greater than 50°. In some embodiments, the ambient light transmittance is 1% or less for at least one incident angle in the range of 60° to 80°.

[0021] Directing display light can include waveguide-display light through a waveguide within an eyepiece lens and diffracting the waveguide-display light toward a user.

[0022] The method can include varying attenuation of transmitted ambient light in response to a signal from a wearable display system. For example, the attenuation can be varied by different amounts across the eyepiece lens. In some embodiments, the attenuation is varied using liquid crystal elements.

[0023] Among other advantages, implementations of the present invention can reduce undesirable optical artifacts (e.g., rainbow effects) in a wearable display associated with stray ambient light that interacts with a grating structure in the display. For example, a waveguide-based wearable display (e.g., for AR / MR applications) employing a surface relief grating diffracts stray ambient light into the display's eye box, introducing undesirable artifacts into the user's field of view and degrading the user experience. Implementations of the present invention can significantly reduce such artifacts without significantly affecting the user's field of view.

[0024] Implementations can attenuate the transmittance of ambient light based on its angle of incidence. For example, a film that selectively attenuates light having an angle of incidence greater than the user's field of view can reduce the visibility of artifacts generated by a diffractive eyepiece display without sacrificing the transmittance of the user's view of the world.

[0025] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. This document also provides, for example, the following items. (Item 1) A wearable display system, An eyepiece stack comprising: an eyepiece stack having a world side and a user side facing the world side, wherein during use, a user positioned on the user side views through the eyepiece stack a displayed image that extends the user's field of view of the user's environment delivered by the wearable display system; An angularly selectable film, wherein the angularly selectable film is arranged on the world side of the eyepiece stack, and the angularly selectable film comprises a polarization adjustment film arranged between a pair of linear polarizers. Equipped with, A wearable display system comprising a linear polarizer and a polarization-adjusting film that significantly reduces the transmittance of visible light incident on the angularally selectable film at a large incident angle without significantly reducing the transmittance of light incident on the angularally selectable film at a small incident angle. (Item 2) The axes passing through the two linear polarizers described above intersect in the wearable display system described in item 1. (Item 3) The wearable display system according to item 1 or 2, wherein the polarization-adjusting film rotates the polarization state of light transmitted by the first linear polarizer of the pair of linear polarizers on the world side of the polarization-adjusting film. (Item 4) The wearable display system according to item 3, wherein the amount of rotation of the polarization state varies depending on the angle of incidence of light transmitted by the first linear polarizer of the pair of linear polarizers. (Item 5) The wearable display system according to item 4, wherein the light transmitted with a large angle of incidence is rotated less than the light transmitted with a small angle of incidence. (Item 6) A wearable display system according to any of the above items, wherein unpolarized light with wavelengths in the range of 420 nm to 680 nm incident on the angularly selectable film with an incident angle of 35° to 65° has a transmittance efficiency of less than 0.5%. (Item 7) A wearable display system according to any of the above items, wherein unpolarized light with wavelengths in the range of 420 nm to 680 nm incident on the angularly selectable film with an incident angle of -32° to +32° has a transmittance efficiency of more than 45%. (Item 8) With respect to a D65 source, the angularly selectable film shifts the CIE1931 white point by less than (+ / -0.02, + / -0.02) for non-polarization with an incident angle of -32° to +32°, as described in any of the above items, in a wearable display system. (Item 9) The wearable display system according to any of the above items, wherein the angle-selectable film has an area greater than 50 mm x 50 mm. (Item 10) The wearable display system according to any of the above items, wherein the polarization-adjusting film comprises at least one layer of birefringent material. (Item 11) The wearable display system according to item 10, wherein at least one layer of the birefringent material comprises a C-plate. (Item 12) The wearable display system according to item 11, wherein at least one layer of the birefringent material comprises a pair of quarter-wave plates, the quarter-wave plates being positioned on the opposite side of the C-plate. (Item 13) The wearable display system according to item 12, wherein each of the quarter-wave plates is arranged relative to the corresponding linear polarizer to form a circular polarizer. (Item 14) The wearable display system according to item 11, wherein at least one layer of the birefringent material comprises at least one quarter-wave plate. (Item 15) The wearable display system according to any of the above items, wherein the polarization-adjustable film is a first polarization-adjustable film, and the angularly selectable film further comprises a second polarization-adjustable film and a third linear polarizer, the second polarization-adjustable film being arranged between the pair of linear polarizers and the third linear polarizer. (Item 16) The wearable display system according to item 15, wherein the first and second polarization-adjusting films each consist of one or more layers of birefringent material. (Item 17) The wearable display system according to item 16, wherein one or more layers of the birefringent material of the first and second polarization-adjusting films each comprises a C-plate. (Item 18) The wearable display system according to item 17, wherein one or more layers of the birefringent material of the first and second polarization-adjusting films each comprises a pair of quarter-wave plates arranged on the opposite side of the corresponding C-plate. (Item 19) The wearable display system according to any of the above items, wherein the angularly selectable film comprises two or more stages, each stage comprising a polarization-adjusting film arranged between a pair of linear polarizers. (Item 20) The adjacent stages share a linear polarizer, as described in item 19 of the wearable display system. (Item 21) The wearable display system according to any of the above items, wherein the angle-selectable film further comprises a switchable element having variable optical properties. (Item 22) The wearable display system according to item 21, wherein the switchable element comprises a liquid crystal layer between a pair of polarizers, and the light transmittance through the switchable element is variable. (Item 23) The wearable display system according to item 21, wherein the switchable element comprises multiple pixels, and the optical properties of each pixel are individually variable. (Item 24) A method for displaying an image using a wearable display system, The display light from the display is directed towards the user through the eyepiece, and the image is projected into the user's field of view. The ambient light from the user's environment is transmitted through the eyepiece. Includes, A method wherein transmitting ambient light includes attenuating light incident on the eyepiece from the environment as a function of the angle of incidence of the ambient light onto the eyepiece, wherein ambient light incident on the eyepiece at an angle of incidence of 35° or greater is attenuated more strongly than ambient light incident on the eyepiece at an angle of incidence of 35° or less. (Item 25) The method according to item 24, wherein attenuating the ambient light includes polarizing the ambient light and providing polarization, and modulating the polarization state of the polarization as a function of the angle of incidence of the ambient light. (Item 26) The method according to item 25, wherein modulating the polarization state of the polarization includes rotating the polarization state. (Item 27) The method according to item 26, wherein the amount of rotation of the polarization state varies according to the angle of incidence of the ambient light. (Item 28) The method according to item 27, wherein the amount of rotation decreases as the angle of incidence increases. (Item 29) The method according to item 25, wherein attenuating the ambient light further includes directing the polarization through a second polarizer. (Item 30) The method according to item 24, wherein the transmittance of ambient light is 1% or less with respect to at least one incident angle greater than 35°. (Item 31) The method according to item 30, wherein the transmittance of ambient light is 1% or less with respect to at least one incident angle greater than 50°. (Item 32) The method according to item 30, wherein the transmittance of the ambient light is 1% or less with respect to at least one incident angle in the range of 60° to 80°. (Item 33) The method according to any of items 24-32, wherein directing the display light includes guiding the display light through a waveguide in the eyepiece and diffracting the guided display light toward the user. (Item 34) The method according to any one of items 24-32, further comprising varying the attenuation of the transmitted ambient light in response to a signal from the wearable display system. (Item 35) The method according to item 34, wherein the attenuation is varied by different amounts across the eyepiece. (Item 36) The aforementioned damping is varied using a liquid crystal element, as described in item 34. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 shows an example of a wearable display system.

[0027] [Figure 2A] Figure 2A shows a conventional display system for simulating a three-dimensional image for the user.

[0028] [Figure 2B] Figure 2B illustrates aspects of an approach to simulating a 3D image using multiple depth planes.

[0029] [Figure 3] Figures 3A-3C show the relationship between the radius of curvature and the radius of focus.

[0030] [Figure 4] Figure 4 shows an example of a waveguide stack for outputting image information to the user within an AR eyepiece.

[0031] [Figure 5] Figures 5 and 6 show examples of the output beam produced by the waveguide. [Figure 6] Figures 5 and 6 show examples of the output beam produced by the waveguide.

[0032] [Figure 7] Figures 7A and 7B are schematic diagrams illustrating the optical paths through a display combiner having a surface relief grating.

[0033] [Figure 8] Figures 8A and 8B are schematic diagrams illustrating the light transmittance through a display combiner with and without an angle-selectable film.

[0034] [Figure 9] Figure 9 is a schematic diagram of an eyepiece lens with a display combiner and an example of an angle-selectable film.

[0035] [Figure 10] Figure 10 is a plot showing the transmittance as a function of the incident light angle through an example of an angularly selectable film.

[0036] [Figure 11] Figure 11 is a schematic diagram of an eyepiece, showing a display combiner and another embodiment of an angle-selectable film.

[0037] [Figure 12]Figure 12 is a plot showing the transmittance as a function of the angle of incident light through another embodiment of an angularly selectable film.

[0038] [Figure 13] Figure 13 is a schematic diagram of an eyepiece lens with an example of an angle-selectable film including a display combiner and a segmented dimmer.

[0039] [Figure 14] Figure 14 is a schematic diagram of an eyepiece, with a display combiner and another embodiment of an angle-selectable film including a segmented dimmer.

[0040] [Figure 15] Figure 15 is a schematic diagram of an eyepiece lens, with a display combiner and a further embodiment of an angle-selectable film including a segmented dimmer.

[0041] [Figure 16] Figure 16 is a schematic diagram of an exemplary computer system that is useful for use in conjunction with a wearable display system. [Modes for carrying out the invention]

[0042] Detailed explanation Figure 1 illustrates an exemplary wearable display system 60, which includes a display or eyepiece 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 may be housed within a frame 80, which is wearable by a display system user 90 and configured to position the display 70 in front of the user's eyes. In some embodiments, the display 70 may be considered eyewear. In some embodiments, a speaker 100 is coupled to the frame 80 and positioned adjacent to the user's ear canal. The display system may also include one or more microphones 110 to detect sound. The microphones 110 can enable the user to provide input or commands to the system 60 (e.g., selection of voice menu commands, natural language questions, etc.) and / or enable audio communication with other persons (e.g., other users of a similar display system). The microphones 110 can also collect audio data (e.g., sounds from the user and / or the environment) from the user's surroundings. In some embodiments, the display system may also include a peripheral sensor 120a, which is separate from the frame 80 and may be mounted on the user 90's body (e.g., on the head, torso, limbs, etc.). In some embodiments, the peripheral sensor 120a may acquire data characterizing the user 90's physiological state.

[0043] The display 70 is operably coupled to the local data processing module 140 by a communication link 130, such as a wired connection or wireless connectivity, which may be mounted in various configurations, such as being fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise detachably attached to the user 90 (e.g., in a backpack configuration or a belt-mounted configuration). Similarly, the sensor 120a may be operably coupled to the local processor and data module 140 by a communication link 120b (e.g., a wired connection or wireless connectivity). The local processing and data module 140 may include a hardware processor and digital memory such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be used to assist in data processing, caching, and storage. The data may include 1) data captured from sensors such as image capture devices (e.g., cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein (e.g., operably coupled to frame 80 or otherwise attached to user 90), and / or 2) data acquired and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content) for passage to display 70 after processing or reading. The local processing and data module 140 may be operably coupled to the remote processing module 150 and the remote data repository 160 by communication links 170, 180 via wired or wireless communication links, etc., so that these remote modules 150, 160 are operably coupled to each other and available as resources to the local processing and data module 140.In some embodiments, the local processing and data module 140 may include one or more of the following: an image acquisition 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 mounted on the frame 80 or be a standalone device communicating with the local processing and data module 140 via a wired or wireless communication path.

[0044] The remote processing module 150 may include one or more processors for analyzing and processing data such as image and audio information. In some embodiments, the remote data repository 160 may be a digital data storage facility, which may be available through the internet or other networking configurations in a “cloud” resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information (e.g., information for generating augmented reality content) to the local processing and data module 140 and / or the remote processing module 150. In other embodiments, all data is stored, and all calculations are performed in the local processing and data module, enabling fully autonomous use from the remote module.

[0045] The perception of an image as "three-dimensional" or "3-D" can be achieved by providing slightly different presentations of the image to each of the user's eyes. Figure 2A illustrates a conventional display system for simulating three-dimensional image data relating to a user. Two distinctly different images 190, 200, one for each eye 210, 220, are output to the user. Images 190, 200 are spaced only 230 units apart from eyes 210, 220 along the optical or z-axis parallel to the user's line of sight. Images 190, 200 are flat, and eyes 210, 220 can focus on the image by taking a single, perspective-accommodated state. Such a 3-D display system relies on the human visual system, combines images 190, 200, and provides a perception of depth and / or scale of the combined image.

[0046] However, the human visual system is complex, and providing a realistic perception of depth is difficult. For example, many users of conventional "3-D" display systems find such systems unpleasant or perceive no sense of depth at all. Objects can be perceived as "three-dimensional" due to a combination of convergence-divergence movements and accommodation. The convergence-divergence movement of two eyes relative to each other (e.g., pupillary rotation such that the pupils move toward or away from each other, converging the individual lines of sight of the eyes and fixing on an object) is closely related to the focusing (or "accommodation") of the eye's lens. Under normal conditions, a change in the focus of the eye's lens or the eye's accommodation to change the focus from one object to another object at a different distance will automatically result in a consistent change in convergence-divergence movements at the same distance, under the relationship known as the "accommodation-convergence-divergence reflex" and pupillary dilation or miosis. Similarly, under normal conditions, changes in convergence and divergence movements will induce changes in the alignment of accommodative lens shape and pupil size. As described herein, many stereoscopic or "3-D" display systems display a scene using slightly different presentations (and therefore slightly different images) to each eye so that the three-dimensional viewpoint is perceived by the human visual system. However, such systems can be uncomfortable for many users because they simply provide image information in a single accommodative state and function against the "accommodative-convergence / divergence reflex." A display system that provides a better match between accommodation and convergence / divergence movements can form a more realistic and comfortable simulation of three-dimensional image data.

[0047] Figure 2B illustrates aspects of an approach for simulating three-dimensional image data using multiple depth planes. Referring to Figure 2B, eyes 210, 220 take on different accommodated states, focusing objects at various distances along the z-axis. As a result, a particular accommodated state can be associated with one of the illustrated depth planes 240, each having an associated focal length such that an object or part of an object in a particular depth plane is in focus when the eye is accommodated to that depth plane. In some embodiments, the three-dimensional image data may be simulated by providing a different presentation of the image for each eye 210, 220, and by providing different presentations of the image corresponding to multiple depth planes. The individual fields of view of eyes 210, 220 are shown as distinct for clarity in the illustration, but they may overlap, for example, as the distance along the z-axis increases. Furthermore, for the sake of illustration, the depth plane is shown as flat, but it should be understood that the contour of the depth plane can be curved in physical space so that all features within the depth plane are in focus with the eye in a particular state of focus adjustment.

[0048] The distance between an object and the eye 210 or 220 can also change the amount of light diverging from that object as visible to that eye. Figures 3A-3C illustrate the relationship between distance and ray divergence. The distances between the object and the eye 210 are expressed in the order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, rays diverge more as the distance to the object decreases. As the distance increases, rays become more collimated. In other words, the light field generated by a point (object or part of an object) can be said to have a spherical wavefront curvature, which is a function of the distance the point is from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. Consequently, in different depth planes, the ray divergence is also different, and the divergence increases with decreasing distance between the depth plane and the user's eye 210. Only a single eye 210 is illustrated in Figures 3A–3C and other figures herein for illustrative purposes, but it should be understood that the discussion relating to eye 210 may apply to both eyes 210 and 220 of the user.

[0049] A highly realistic simulation of perceived depth can be achieved by providing the eye with different presentations of images corresponding to each of a limited number of depth planes. These different presentations may be individually focused by the user's eye and thereby help provide the user with depth cues based on the amount of eye accommodation required to focus on different image features for scenes located on different depth planes, and / or on observations of different image features on different depth planes that are out of focus.

[0050] Figure 4 illustrates an embodiment of a waveguide stack for outputting image information to the user within an AR eyepiece. The display system 250 includes a waveguide stack or stacked waveguide assembly 260, which may be used to provide three-dimensional perception to the eye / brain using a plurality of waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is the system 60 of Figure 1, and Figure 4 shows some parts of that system 60 in more detail. For example, the waveguide assembly 260 may be part of the display 70 of Figure 1. It should be understood that the display system 250 may be considered a light field display in some embodiments.

[0051] Waveguide assembly 260 may also include several features 320, 330, 340, 350 between the 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 transmit image information to the eye using varying 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 input devices 360, 370, 380, 390, and 400 may function as light sources for the waveguides and may be used to input image information into the waveguides 270, 280, 290, 300, and 310, and each may be configured to disperse incident light across each individual waveguide for output toward the eye 210, as described herein. The light exits from the output surfaces 410, 420, 430, 440, and 450 of each individual image input device 360, 370, 380, 390, and 400 and is input into the corresponding input surfaces 460, 470, 480, 490, and 500 of the individual waveguides 270, 280, 290, 300, and 310. In some embodiments, the input surfaces 460, 470, 480, 490, and 500 may each be the edge of the corresponding waveguide or a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the user's eye 210). In some embodiments, a beam of light (e.g., a collimated beam) may be injected into each waveguide, replicated by refraction within the waveguide, such as by sampling into a beamlet, and then directed toward the eye 210 with an amount of refractive force corresponding to the depth plane associated with that particular waveguide. In some embodiments, one of the image input devices 360, 370, 380, 390, and 400 may be associated with a plurality (e.g., three) of waveguides 270, 280, 290, 300, and 310, into which light may be injected.

[0052] In some embodiments, the image input devices 360, 370, 380, 390, and 400 are discrete displays, each generating image information for input into the corresponding waveguides 270, 280, 290, 300, and 310, respectively. In some other embodiments, the image input devices 360, 370, 380, 390, and 400 are output terminals of a single multiplexed display, which can transmit image information to each of the image input devices 360, 370, 380, 390, and 400 via one or more optical conduits (such as fiber optic cables). It should be understood that the image information provided by the image input devices 360, 370, 380, 390, and 400 may include light of different wavelengths or colors.

[0053] In some embodiments, the light introduced into waveguides 270, 280, 290, 300, and 310 is provided by an optical projector system 520, which includes an optical module 530, which may include a light source or optical emitter such as a light-emitting diode (LED). The light from the optical module 530 may be directed and modulated by an optical modulator 540 (e.g., a spatial light modulator) via a beam splitter (BS) 550. The optical modulator 540 may spatially and / or temporally vary the perceived intensity of the light introduced into waveguides 270, 280, 290, 300, and 310. Embodiments of the spatial light modulator include liquid crystal displays (LCDs) and digital light processing (DLP) displays, including liquid crystal displays on silicon (LCOS).

[0054] In some embodiments, the optical projector system 520 or one or more components thereof may be mounted on the frame 80 (Figure 1). For example, the optical projector system 520 may be part of the temple portion (e.g., the ear hook portion 82) of the frame 80, or positioned on the edge of the display 70. In some embodiments, the optical module 530 may be separate from the BS550 and / or the optical modulator 540.

[0055] In some embodiments, the display system 250 may be a scanning fiber display, comprising one or more scanning fibers for projecting light in various patterns (e.g., raster scanning, helical 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 illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to input light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a plurality of scanning fibers or a plurality of bundles of scanning fibers, each configured to input light into one of the associated waveguides 270, 280, 290, 300, 310. One or more optical fibers may transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, and 310. In addition, one or more intervening optical structures may be provided between the scanning fiber or multiple fibers and one or more waveguides 270, 280, 290, 300, and 310 to, for example, redirect light emanating from the scanning fiber into one or more waveguides 270, 280, 290, 300, and 310.

[0056] The controller 560 controls the operation of the stacked waveguide assembly 260, including the operation of the image input devices 360, 370, 384, 390, 400, the light source 530, and the optical modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transient medium) to coordinate the timing and delivery of image information to the waveguides 270, 280, 290, 300, 310. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 may be part of the processing module 140 or 150 (Figure 1).

[0057] Waveguides 270, 280, 290, 300, and 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Waveguides 270, 280, 290, 300, and 310 may each be planar or have another shape (e.g., curved), with major upper and lower surfaces and edges extending between their major upper and lower surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, and 310 may each include external coupling optical elements 570, 580, 590, 600, and 610, respectively, configured to extract light from the waveguide by redirecting the light propagating within each individual waveguide outwards from the waveguide and outputting image information to the eye 210. The extracted light may also be referred to as externally coupled light, and the optical elements that externally couple the light may also be referred to as light extraction optical elements. The extracted beam of light can be output by a waveguide at the point where light propagating within the waveguide strikes the light extraction optical element. The external coupling optical elements 570, 580, 590, 600, 610 may be diffractive optical features, including, for example, a diffraction grating, as further discussed herein. The external coupling optical elements 570, 580, 590, 600, 610 are shown positioned on the bottom main surface of the waveguides 270, 280, 290, 300, 310, but in some embodiments they may be positioned on the top and / or bottom main surface, and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be mounted on a transparent substrate and formed within a layer of material that forms the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material, and the external coupling optical elements 570, 580, 590, 600, 610 may be formed on and / or inside the material piece.

[0058] Each waveguide 270, 280, 290, 300, and 310 may output light and form an image corresponding to a specific depth plane. For example, waveguide 270, closest to the eye, may deliver a collimated beam of light to the eye 210. The collimated beam of light may represent the optical infinity focal plane. The next upper waveguide 280 may output a collimated beam of light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. The first lens 350 may add some convex wavefront curvature to the collimated beam so that the eye / brain interprets the light emanating from its waveguide 280 as emanating from a first focal plane that is closer and inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may have an additional gradually increasing wavefront curvature added so that the eye / brain interprets the light emanating from the third waveguide 290 as emanating from a second focal plane that is even closer inward from optical infinity than the light emanating from the second waveguide 280.

[0059] Other waveguide layers 300, 310 and lenses 330, 320 are configured similarly, with the highest waveguide 310 in the stack emitting its output through all the lenses between it and the eye for a concentrated focal force representing the focal plane closest to the person. When viewing / interpreting light originating from the other side world 510 of the stacked waveguide assembly 260, a compensating lens layer 620 may be positioned on top of the stack to compensate for the stack of lenses 320, 330, 340, 350 and to compensate for the concentrated refractive force of the lower lens stacks 320, 330, 340, 350. Such a configuration provides the same number of perceived focal planes as there are available waveguide / lens pairs. Both the external coupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0060] In some embodiments, two or more of the waveguides 270, 280, 290, 300, and 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, and 310 may output images set to the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, and 310 may output images set to the same multiple depth planes, with one set for each depth plane. This may offer the advantage of forming tiled images that provide an extended field of view in those depth planes.

[0061] External coupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from their respective waveguides for specific depth planes associated with the waveguides and to output the light with an appropriate amount of divergence or collimation. As a result, waveguides with different associated depth planes may have different configurations of the external coupling optical elements 570, 580, 590, 600, 610, which output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 may be three-dimensional or surface features, which may be configured to output light at specific angles. For example, the light extraction optical elements 570, 580, 590, 600, 610 may be three-dimensional holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (e.g., cladding layers and / or structures for forming voids).

[0062] In some embodiments, the external coupling optical elements 570, 580, 590, 600, and 610 are diffraction features with sufficiently low diffraction efficiency such that only a portion of the refractive power of the light in the beam is redirected toward the eye 210 with each interaction, while the remainder continues to travel through the waveguide via TIR. Thus, the exit pupil of the optical module 530 is replicated across the waveguide, creating multiple output beams that carry image information from the light source 530, effectively expanding the number of locations where the eye 210 can capture the replicated light source exit pupil. These diffraction features may also have variable diffraction efficiency across their geometry, improving the uniformity of the light output by the waveguide.

[0063] In some embodiments, one or more diffraction features 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, the switchable diffraction feature may include a layer of polymer-dispersed liquid crystal in which microdroplets have a diffraction pattern in a host medium, and the refractive index of the microdroplets may 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 refractive index of the microdroplets may be switched to one that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0064] In some embodiments, a camera assembly 630 (e.g., a digital camera including a visible light and IR light camera) is provided to capture images of the eye 210, a portion of the eye 210, or at least a portion of the tissue surrounding the eye 210, and may perform, for example, detecting user input, extracting biometric information from the eye, estimating and tracking the direction of the eye's gaze, monitoring the user's physiological state, etc. In some embodiments, the camera assembly 630 may include an image capture device and a light source for projecting light (e.g., IR or near-IR light) onto the eye (the light is then reflected by the eye and can be detected by the image capture device). In some embodiments, the light source includes a light-emitting diode ("LED") that emits IR or near-IR. In some embodiments, the camera assembly 630 may be mounted on a frame 80 (Figure 1) and may communicate with a processing module 140 or 150, which can process image information from the camera assembly 630 and make various decisions, for example, regarding the user's physiological state, the wearer's gaze direction, iris identification, etc. In some embodiments, one camera assembly 630 may be used for each eye, monitoring each eye separately.

[0065] Figure 5 illustrates an embodiment of an output beam produced by a waveguide. One waveguide is shown (using a perspective view), but other waveguides in the waveguide assembly 260 (Figure 4) can function similarly. Light 640 is introduced into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates through the waveguide 270 by TIR. Through interaction with diffraction features, the light exits the waveguide as an output beam 650. The output beam 650 replicates the exit pupil from a projector device that projects an image into the waveguide. Any one of the output beams 650 contains a sub-portion of the total energy of the input light 640. Also, in a perfectly efficient system, the sum of the energies in all the output beams 650 will be equal to the energy of the input light 640. The outgoing beam 650 is illustrated as substantially parallel in Figure 6, but as discussed herein, a certain amount of refractive force may be imparted depending on the depth plane associated with the waveguide 270. A parallel outgoing beam may represent a waveguide with an externally coupled optical element that externally couples the light and forms an image that appears set on the depth plane at long distances from the eye 210 (e.g., optical infinity). Other waveguides or other sets of externally coupled optical elements may output a more divergent outgoing beam pattern, as shown in Figure 6, which would require the eye 210 to adjust 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 210 than optical infinity.

[0066] Further information relating to wearable display systems (including, for example, optical elements used within a wearable display system) can be found in U.S. Patent Publication No. US2019 / 0187474A1, filed on 14 December 2018 and titled "EYEPIECES FOR AUGMENTED REALITY DISPLAY SYSTEM" (the contents of which are incorporated in whole by reference).

[0067] As described above, the wearable display system 60 includes one or more optical elements having one or more lattice structures that improve the optical performance of the wearable display system. For example, referring to Figures 7A and 7B, a lattice 710, which is a diffraction relief structure, is used in conjunction with an eyepiece display combiner 700 (e.g., a stacked waveguide assembly as described above) as an exit pupil expander (EPE) to increase the size of the exit pupil of the wearable display system. As shown in Figure 7A, 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 the lattice 710 diffracts incident stimulated light such that at least a portion of the light is extracted from the optical guide 710 toward the user of the display system.

[0068] Referring specifically to 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 a portion of this light may be diffracted into the user's field of view. When viewed by the user through the EPE, the light diffracted from the world may appear as undesirable image artifacts. The angle of incidence that generates artifacts in the user's field of view generally depends on the design on the display combiner. With respect to diffraction waveguide-based display combiners, a large angle of incidence often brings the stray light path closest to the center of the user's field of view of the world.

[0069] This effect is further illustrated in Figure 8A, which shows the display combiner 800. The ambient light is at an incident angle θ. inc In this configuration, light is incident on the front surface of the display combiner 800. At least a portion of the incident light is transmitted through the grating and combiner, as shown in the figure. However, the display combiner 800 supports a grating (not shown) that diffracts at least a portion of the incident light toward the user. Labeled as stray light, this light is directed toward the user at an angle θ stray It diffracts at this point.

[0070] Referring to Figure 8B, the angle-selectable film 810 can be applied to (e.g., laminated over) the display combiner 800 to reduce stray light artifacts associated with ambient light. Generally, the transmittance of light through the film 810 depends on the angle of incidence of light onto the film. As illustrated, the film 810 has a relatively high transmittance (e.g., 30° or greater, 35° or greater, 40° or greater, 45° or greater, as a user might be exposed to overhead lighting in an indoor environment), and the angle of incidence θ inc It has the ability to reduce (e.g., block) light transmittance, but at a lower incident angle θ. a The film has the ability to transmit light (for example, "world light" as seen by the wearer within the core field of view of this device). The angularly selectable film can perform this function over a wide wavelength range, for example, over the operating wavelength range of the display system, such as 420 nm to 680 nm.

[0071] The transmittance efficiency with respect to incident light generally varies as a function of the angle of incidence, ranging from relatively high transmittance efficiency (e.g., 40% or more, 45% or more) to relatively low transmittance efficiency (e.g., less than 1%, less than 0.5%). Transmittance efficiency refers to the relative intensity of light transmitted at a particular wavelength. In some embodiments, unpolarized light in the range of 420nm to 680nm incident on an angularly selectable film with an angle of incidence of 35° to 65° has a transmittance efficiency of less than 0.5%. In some embodiments, unpolarized light in the range of 420nm to 680nm incident on an angularly selectable film with an angle of incidence of -32° to +32° has a transmittance efficiency greater than 45%.

[0072] Angularly selectable films can also have only a relatively slight effect on the colors of the image viewed through the film. For example, with respect to a D65 source, an angularly selectable film can shift the CIE1931 white point (0.33, 0.33) by less than (+ / -0.02, + / -0.02) (e.g., (+ / -0.01, + / -0.01) or less) due to unpolarized light with an incidence angle of -32° to +32°.

[0073] The transmittance of angle-selectable films can also be characterized by attenuation, which can be high at relatively high angles of incidence (e.g., 10 dB or above, 15 dB or above, 20 dB or above, 25 dB or above, 30 dB or above). Light at lower angles of incidence, such as 25° or below (e.g., 20° or below, 15° or below, 10° or below), may suffer very low levels of attenuation (e.g., 2 dB or below, 1 dB or below).

[0074] Generally, angle-selectable films 810 can be relatively thin. For example, film 810 can have a total thickness in the range of 500 microns to 2,000 microns. Therefore, the advantages of using angle-selectable films can be achieved without adding significant bulk to the wearable display system.

[0075] In some embodiments, the angularly selectable film 810 is a film stack including a polarization adjustment film arranged between a pair of polarizer films (e.g., a linear polarizer). The polarizer films and polarization adjustment film significantly reduce the transmittance of visible light incident on the angularly selectable film 810 at a large incident angle without significantly reducing the transmittance of light incident on the angularly selectable film at a small incident angle.

[0076] In general, the configuration of two polarizers and a polarization-adjusting film can be varied to provide a desired level of transmittance variation over the angle of interest incidence range (e.g., -75° to +75°). In some embodiments, the polarizers are linear polarizers, and the passing axes of the two linear polarizers can intersect (e.g., at 90°).

[0077] Generally, a polarization-adjusting film includes one or more birefringent layers designed to rotate the polarization state of light transmitted by the first of a pair of linear polarizers, incident from the world side. The birefringent layers may include A-plates (e.g., quarter-wave plates (QW)) in which the anomalous axis of the birefringent material is parallel to the plane of the layer, and / or C-plates in which the anomalous axis of the birefringent material is perpendicular to the plane of the layer; exemplary arrangements are shown below. More generally, the birefringent layers may include uniaxial (e.g., A-plates or C-plates) or biaxial birefringent materials.

[0078] Typically, the amount by which a polarization-modulating layer rotates the polarization state varies depending on the configuration of the polarization-modulating layer and the angle of incidence of the light transmitted by the first of a pair of linear polarizers. In some embodiments, light transmitted with a large angle of incidence (e.g., 35° or greater) is rotated less than light transmitted with a small angle of incidence (e.g., less than 35°). For example, when a polarizer intersects a linear polarizer, a larger amount of rotation up to 90° results in greater transmittance efficiency of the film. In such cases, a larger rotation with respect to on-axial light is desirable compared to light at larger angles of incidence. Conversely, in some embodiments, the polarizer axes are parallel, and the polarization-modulating film rotates on-axial light less than light at larger angles of incidence.

[0079] Generally, angle-selectable films are appropriately sized to cover at least a portion of the eyepiece of a wearable display system. For example, in some embodiments, angle-selectable films can have an area larger than 50 mm × 50 mm.

[0080] Turning to a specific embodiment of the angularly selectable film, referring to FIG. 9, the eyepiece 900 of the wearable display system includes a display combiner 800 and a film stack 910 that operates as an angularly selectable film. 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 (QW) 930a and 930b on both sides of a C-plate 940.

[0081] The fast axes of the wave plates 930a and 930b are each oriented at about 45° with respect to the transmission axes of the linear polarizers 920a and 920b such that the combination of the 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 chirality of each circular polarizer is the same.

[0082] The C-plate 940 has a zero retardation with respect to normal incident light, but has a non-zero retardation with respect to obliquely incident light. Although not wishing to be bound by theory, the retardation of the C-plate as a function of the angle of incidence is

Chemical formula

[0083] An example of transmittance as a function of the angle of incidence for stack 910 is shown in Figure 10. Here, the transmittance as a function of the angle of incidence is given for the C-plate example at n at three different wavelengths. o = 1.5236, n e This is shown with =1.52 and d=153μm. The transmittance is normalized to 1 with respect to axial light here, remains 1 or close to 1 up to about 20°, and then monotonically decreases to zero in the 60°–80° range depending on the wavelength. For shorter wavelengths (e.g., 460nm–525nm), the transmittance increases as the incident angle increases up to 90°.

[0084] Figure 9 shows an embodiment of an angularly selectable film containing a birefringent layer between two linear polarizers, although implementations with additional layers are also possible. For example, Figure 10 shows an eyepiece 100 including a film stack 1010 applied to the world side of a display combiner 800. The film stack 1010 includes three linear polarizers 1020a, 1020b, and 1020c. The first polarization adjustment stack is arranged between polarizers 1020a and 1020b. This stack includes a pair of QWs 1030a and 130b on both sides of the C-plate 1040a. The second polarization adjustment stack is arranged between polarizers 1020b and 1020c. This stack includes QWs 1030c and 1030d on both sides of the C-plate 1040b. In effect, stack 1010 is implemented like two stacks 910 stacked together.

[0085] Stack 910 can be considered a single-stage array, and stack 1010 can be considered a double-stage array. In general, additional stages can be added. Although we do not wish to be constrained by theory, some stages can be used in series to achieve different transmittance responses. [ka] They may provide Γ n This represents the delay of the nth stage.

[0086] Using multiple stages in series can enable stronger attenuation of light from large incident angles. For example, referring to Figure 11, the transmittance as a function of incident angle for a two-stage C-plate array such as stack 1010 is shown. In this embodiment, no=1.5236, ne=1.52, the thickness of the C-plate in the first stage (i.e., 1040b) is d1=111μm, and the thickness of the C-plate in the second stage (i.e., 1040a) is d2=111μm. Compared to the single-stage film depicted in Figure 10, the transmittance at high incident angles up to 90° does not increase from the minimum value in the 60°~80° range, but remains low in the 460nm~525nm range.

[0087] Various suitable different materials can be used for each layer in the angularly selectable film. Linear polarizers can be formed from stretched polymer materials (e.g., PVA) that are stained with a chromophore (e.g., iodine). Commercially available linear polarizers, such as those available from Sanritz Co. (Japan) or Nittto Denko (Japan), can be used. QW can be made from stretched polymer films or liquid crystal polymer films, for example. C-plates can be formed from cast polymer films, such as cast cellulose triacetate. Liquid crystal polymer C-plates are also possible.

[0088] Generally, each layer is represented as a homogeneous layer, but composite layers are also possible. For example, a C-plate can be formed from multiple stacked layers, each having different optical properties from its adjacent layers. Similarly, multilayer QW can also be used.

[0089] In general, a film stack may include additional layers other than those described above. For example, the stack may include additional layers that provide mechanical functions rather than optical functions. These may include adhesive layers and / or layers for mechanical strength and / or environmental protection. 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, these may include anti-reflective films and / or hard coating layers.

[0090] The aforementioned embodiments of angle-selectable films include optically passive elements, but more generally, the implementation may also feature optically active elements. Such elements can change their optical properties in response to electrical signals or some other physical stimulus, and thus change the transmittance properties of the angle-selectable film. For example, Figure 13 shows an eyepiece 1100 including a stack 1110 on a display combiner 800, which includes several passive optical films, as well as a segmented liquid crystal (LC) dimmer 1150. The film stack 1110 includes polarizers 1120a, 1120b, and 1120c (e.g., linear polarizers). A polarization adjustment stack, consisting of a C-plate 1140 between two A-plates 1130a and 1130b, is arranged between polarizers 1120b and 1120c on the world side of the dimmer 1150, which is arranged between polarizers 1120a and 1120b. In effect, stack 1110 corresponds to a single-stage attenuator stacked with the LC dimmer 1150 (as shown in Figure 9).

[0091] The segmented LC dimmer 1150 is a pixelated device that enables variable control of light transmittance across the area of ​​the eyepiece 1100. In some embodiments, the LC dimmer 1150 includes a layer of liquid crystal material (e.g., nematic LC material) between two transparent electrodes (e.g., formed from indium tin oxide). The electrodes are patterned and can form pixels, each individually addressable by a drive signal, which can control the orientation of LC molecules within the LC layer. The transmittance through each pixel will generally vary as a function of the voltage applied to the pixel electrode. The LC dimmer 1150 can operate as a variable neutral density filter, for example, the transmittance through the dimmer is constant across its area but varies over time. For example, the transmittance through the dimmer can be reduced in bright ambient environments, for example, when the system is used directly in sunlight. In darker environments, the transmittance can be increased.

[0092] The LC dimmer 1150 can also vary the transmittance through a stack spanning the eyepiece area. For example, in areas with substantial overhead illumination, the LC dimmer 1150 can reduce the transmittance in the upper half of the eyepiece while leaving the transmittance in the lower half relatively high.

[0093] Using spatial control of an LC dimmer across the eyepiece area can also be used as a method of artifact suppression, but this function should be balanced with preserving the user's view of the world. The dimmer darkens in front of the eyepiece area, which generates stray light paths, and therefore can reduce the magnitude of associated artifacts.

[0094] A dimmer can also be included within a multi-stage stack. For example, referring to Figure 14, the eyepiece 1200 includes a stack 1210 mounted on a display combiner 800, which includes a segmented dimmer 1250 in addition to two stages of angularly selectable film. Specifically, the stack 1210 includes polarizers 1220a, 1220b, 1220c, and 1220d. The dimmer 1250 is located between polarizers 1220a and 1220b, closest to the display combiner 800. One stage of the angularly selectable film includes QW1230a and 1230b, arranged on both sides of C-plate 1240a. The other stage includes QW1230c and 1230d, arranged on both sides of C-plate 1240b.

[0095] In some embodiments, dimmers may be included between stages of angularly selectable film. For example, Figure 15 shows an eyepiece 1300 including a stack 1310 on the world side of the display combiner 800, the stack including an LC-segmented dimmer 1350 between two stages of angularly selectable film. The stack 1310 includes polarizers 1320a, 1320b, 1320c, and 1320d. The dimmer 1350 is located between polarizers 1320a and 1320b, closest to the display combiner 800. One stage of angularly selectable film includes QW1330a and 1330b, arranged on both sides of the C-plate 1340a. The other stage includes QW1330c and 1330d, arranged on both sides of the C-plate 1340b.

[0096] As shown in Figure 15, placing single-stage angle-selectable films on both sides of the dimmer may be more advantageous than having two-stage angle-selectable films on one side of the dimmer, as shown in Figure 14, from a mechanical standpoint, for example, saving space in the stack of optical components used in an augmented reality display.

[0097] Some implementations described herein may be implemented as one or more groups or modules of digital electronic networks, computer software, firmware, or hardware, or within a combination of one or more of these. Different modules may be used, but each module does not need to be distinctly different, and multiple modules may be implemented on the same digital electronic network, computer software, firmware, or hardware, or a combination thereof.

[0098] Some implementations described herein may be implemented as one or more modules of computer program instructions encoded on a computer storage medium for execution by a data processing device or to control its operation. The computer storage medium may be, or be contained within, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of these. Furthermore, although the computer storage medium is not a propagating signal, it may be the source or destination of computer program instructions encoded within an artificially generated propagating signal. The computer storage medium may also be, or be contained within, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

[0099] The term "data processing device" encompasses all types of devices, machines, and equipment for processing data, including, for example, programmable processors, computers, systems on a chip, or a combination of the aforementioned. A device may include special-purpose logic networks, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits). In addition to hardware, a device may also include code that constitutes the execution environment for the computer program, such as processor firmware, protocol stacks, database management systems, operating systems, cross-platform runtime environments, virtual machines, or a combination of one or more of these. Devices and execution environments can realize various different computing model infrastructures, such as web services, distributed computing, and grid computing infrastructures.

[0100] 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. Computer programs may, but do not, correspond to files in a file system. A program may be stored in part of a file that holds other programs or data (e.g., one or more scripts stored within a markup language document), in a single file dedicated to the program, or in multiple collaborative files (e.g., files storing one or more modules, subprograms, or parts of code). Computer programs may be deployed to run on one or more computers located in a single facility or distributed across multiple facilities and interconnected by a communication network.

[0101] Some of the processes and logic flows described herein can be implemented by one or more programmable processors that execute one or more computer programs and perform actions by acting on input data and producing outputs. Processes and logic flows can also be implemented by special-purpose logic networks, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits), and devices can also be implemented as such.

[0102] Processors suitable for executing computer programs include, as an example, both general-purpose and special-purpose microprocessors and processors of any kind of digital computer. Generally, a processor will receive 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 for storing data, e.g., magnetic, magneto-optical disks, or optical disks, or may be operably coupled thereto to receive data from there, or transfer data thereto, or both. However, a computer is not required to have such devices. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, as an example, semiconductor memory devices (e.g., EPROM, EEPROM, flash memory devices, and others), magnetic disks (e.g., internal hard disks, removable disks, and others), magneto-optical disks, and CD-ROM and DVD-ROM disks. Processors and memory can be complemented by or incorporated into special-purpose logic networks.

[0103] To provide user interaction, the operation can be implemented on a computer having a display device (e.g., a monitor or another type of display device) for displaying information to the user, and a keyboard and pointing device (e.g., a mouse, trackball, tablet, touch-sensitive screen, or another type of pointing device) through which the user can provide input to the computer. Other types of devices can also be used to provide user interaction; for example, the feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or haptic feedback, and input from the user can be received in any form, including acoustic, verbal, or haptic input. In addition, the computer can interact with the user by sending and receiving documents to and from devices used by the user, for example, by sending a web page to a web browser on the user's client device in response to a request received from a web browser.

[0104] A computer system may include a single computing device or multiple computers operating in close proximity to each other, or generally at a distance, and typically interacting through a communication network. Examples of communication networks include local area networks ("LANs") and wide area networks ("WANs"), inter-network networks (e.g., the Internet), networks with satellite links, and peer-to-peer networks (e.g., ad-hoc peer-to-peer networks). Client-server relationships may arise from computer programs running on individual computers that have client-server relationships with each other.

[0105] Figure 16 shows an exemplary computer system 1600, which includes a processor 1610, memory 1620, storage device 1630, and input / output device 1640. Components 1610, 1620, 1630, and 1640 can each be interconnected, for example, by a system bus 1650. The processor 1610 is capable of processing instructions for execution within the system 1600. In some implementations, the processor 1610 is a single-threaded processor, a multi-threaded processor, or another type of processor. The processor 1610 is capable of processing instructions stored in memory 1620 or on storage device 1630. Memory 1620 and storage device 1630 can store information within the system 1600.

[0106] The input / output device 1640 provides input / output operation for system 1600. In some implementations, the input / output device 1640 may include one or more of the following: a network interface device, e.g., an Ethernet® card; a serial communication device, e.g., an RS-232 port; and / or a wireless interface device, e.g., an 802.11 card, a 3G wireless modem, a 4G wireless modem, etc. In some implementations, the input / output device may include a driver device configured to receive input data and transmit output data to another input / output device, e.g., a wearable display device 1660. In some implementations, mobile computing devices, mobile communication devices, and other devices may also be used.

[0107] This specification contains many details, which should be interpreted not as limitations on the scope of what can be claimed, but rather as descriptions of features specific to particular embodiments. Certain features described herein in the context of separate implementations can also be combined. Conversely, various features described in the context of a single implementation can also be implemented separately or in any preferred secondary combination within multiple embodiments.

[0108] Several implementations are described. However, it should be understood that various modifications may be made without departing from the spirit and scope of the invention. Therefore, other implementations are also within the scope of the following claims.

Claims

1. A wearable display system, An eyepiece stack comprising: an eyepiece stack having a world side and a user side facing the world side, wherein during use, a user positioned on the user side views through the eyepiece stack a displayed image that extends the user's field of view, delivered by the wearable display system; An angle-selectable film, wherein the angle-selectable film is arranged on the world side of the eyepiece stack, and the angle-selectable film comprises a liquid crystal layer having variable optical properties arranged between a pair of linear polarizers. Equipped with, A wearable display system in which, with respect to non-polarization in the wavelength range of 420 nm to 680 nm, the angularly selectable film has a transmittance efficiency of 40% or more at incident angles less than 35° and a transmittance efficiency of 1% or less at at least one incident angle greater than 35°.

2. The wearable display system according to claim 1, wherein, with respect to non-polarization in the wavelength range of 420 nm to 680 nm, the angularly selectable film has a transmittance efficiency of more than 45% at incident angles of -32° to +32°.

3. The wearable display system according to claim 1, wherein the passing axes of the pair of linear polarizers intersect.

4. The wearable display system according to claim 1, wherein the polarization-adjusting film rotates the polarization state of light transmitted by the first linear polarizer of the pair of linear polarizers on the world side of the polarization-adjusting film.

5. The amount of rotation of the polarization state varies according to the angle of incidence of light transmitted by the first linear polarizer of the pair of linear polarizers, according to claim 4.

6. The wearable display system according to claim 5, wherein the light transmitted with an incident angle of 35° or more is rotated less than the light transmitted with an incident angle of less than 35°.

7. The wearable display system according to claim 1, wherein unpolarized light with wavelengths in the range of 420 nm to 680 nm incident on the angularly selectable film with an incident angle of 35° to 65° has a transmittance efficiency of less than 0.5%.

8. With respect to a D65 source, the angularly selectable film shifts the CIE 1931 white point by less than (+ / -0.02, + / -0.02) for non-polarization with an incident angle of -32° to +32°, according to claim 1, the wearable display system.

9. The wearable display system according to claim 1, wherein the polarization-adjusting film comprises at least one layer of birefringent material.

10. The wearable display system according to claim 9, wherein at least one layer of the birefringent material comprises a C-plate.

11. The wearable display system according to claim 10, wherein at least one layer of the birefringent material comprises a pair of quarter-wave plates, the quarter-wave plates being positioned on the opposite side of the C-plate.

12. The wearable display system according to claim 11, wherein each of the pair of quarter-wave plates is arranged relative to the corresponding linear polarizer to form a circular polarizer.

13. The wearable display system according to claim 10, wherein at least one layer of the birefringent material comprises at least one quarter-wave plate.

14. The wearable display system according to claim 1, wherein the polarization-adjusting film is a first polarization-adjusting film, and the angularly selectable film further comprises a second polarization-adjusting film and a third linear polarizer, the second polarization-adjusting film being arranged between the pair of linear polarizers and the third linear polarizer.

15. The wearable display system according to claim 14, wherein each of the first and second polarization-adjusting films comprises one or more layers of birefringent material.

16. The wearable display system according to claim 15, wherein one or more layers of the birefringent material of the first and second polarization-adjusting films each comprises a C-plate.

17. The wearable display system according to claim 16, wherein one or more layers of the birefringent material of the first and second polarization-adjusting films each comprises a pair of quarter-wave plates arranged on the opposite side of the corresponding C-plate.

18. The wearable display system according to claim 1, wherein the angularly selectable film comprises two or more steps, each step comprising a polarization-adjusting film arranged between a pair of linear polarizers.

19. The wearable display system according to claim 18, wherein adjacent stages share a linear polarizer.

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